retention of the orthodontic bands.....in vitro study - dr. priya k

RETENTION OF THE ORTHODONTIC

BANDS FOLLOWING

SANDBLASTING USING THREE

DIFFERENT LUTING CEMENTS –

A COMPARATIVE IN VITRO STUDY

DR. PRIYA. K

RETENTION OF THE ORTHODONTIC BANDS

FOLLOWING SANDBLASTING USING THREE

DIFFERENT LUTING CEMENTS –

A COMPARATIVE IN VITRO STUDY

BY

DR. PRIYA. K,

MDS

2006.

Rajiv Gandhi University of Health Sciences, Bangalore, Karnataka.

ACKNOWLEDGEMENTS

I am extremely t hankful to my renowned teachers D r . G a n es h P , M DS , Dr. Silju Matthew,

MDS, and Dr. Anil Kumar Rai, MDS, professors, department of orthodont ics and dentofacial

orthop edics, for their keen interest and their valuable suggest ions whenever sought for and

their coop eration in the completion of t his stu dy.

I sincerely thank Dr. Shaik Hyder Ali. H.K MDS, Principal, for allowing me to avail the facilit ies

and his invaluable guida nce and encouragement during the course of my study.

My sincer e thanks to Mr. Suresh, chief manager, HAL Fou ndr y and Forge

Department for providing me the testing facilities and excellent gu idance wit hout which

t his study would not have been possible. I am also grateful to Mr. Dutta, Mr. Padmanabia h,

and Mr. Madhavan who help ed me conduct the study. I am also grateful to Mr. Ravi for

helping me with the SEM facilities.

I am extremely obliged to Mr. Paul Gange, President, Reliance Orthodontic Products for being

kind enough to send the material required for my stud y.

I am thankful to Dr. Ramesh Hegde, MDS, Dept. of Oral Pathology and Dr. Sreenivasa Murthy,

MDS, Dept. of Conservative Dentistry for providing their department facilit ies.

I also thank Dr. Kyshap and Mr. Reji George Professors, Department of M echa nica l engineer

ing M. S. Ramaiah Engineering College who helped me wit h the surface area of the bands.

My heartfelt thanks to Mr. Jaganath, statisticia n for his immense help in statist ica l analysis

for this study.

I revere the suggestions and help offered to me b y my collea gu es Dr. Rajesh. R.N.G, Dr. Dinesh

Samuel Reddy. I am also thankful to my postgraduate juniors Dr. Sukhpreet Mangat, Dr. Maheen

Ali Fathima, Dr. Chetan Kumar, Dr. Sumit Bansal, Dr. Rishi S eth, Dr. Kiran. H, Dr.

Shrish, Dr Mahendra. S and Dr. Gunasheela.B for their ever-read y help and assistance during my

study. I am also thankful to Dr. Deepa, my dear friends and postgraduate colleagu es. I thank

them all sincer ely.

I sincerely thank Mr. Trimurthy and Mr. Reddy, of my department for their sincer e co- operation

during my course. I also thank Mr. Shashidhara, Librarian and Mr. Yeshwantraj Urs,

Assista nt lbrarian and ot her staff memb ers for their support during my entire course.

My sincere and heartfelt thanks to my beloved parents, without whose endless love, trust,

advice, constant inspiration, patience and sacrifice I wou ld not have reached this far. I am

thankful to my brothers and all my family members for their support and encouragement during

all these years of my life.

Above all, it is the blessings of the Almighty and to him, I offer my sincer e prayers.

Dr.Priya. K

ORTHODONTIC BANDS – INVITRO STUDY

LIST OF ABBREVIATIONS USED

ANOVA –

ARI –

Analys is Of Var iance

Adhesive Remna nt Index

EBA

GIC

MP a

PMCR

RMGIC

SEM

SS

– Ethoxy Benzoic Acid

– Glass Ionomer C ement

– Mega Pascal

– Polyacid Modified Composite R es in

– Resin-M odified Glass Ionomer C ement

– Scanning Electron Microscope

– Stainless Steel

DR. PRIYA K, MDS

Background and Objectives: T he purpose of this in vitro study was to explore and

emp hasize the possibilities of increasing bond strength wit h newer hybrid cements and

subsequently sandblasting the inner surface of the bands to deter mine if this procedure

of increasing the surface area helps in enhancing bond strengt h.

Methods: Forty-five non-carious, unrestored human mandibular molars, which were

freshly extracted b ecause of severe periodontal disease, were used for this

investigation. T he teet h wer e mount ed in P VC sleeves and prefor med stainless steel

orthodontic bands wer e selected for each sp ecimen. The teet h were randomly divided

into 3 groups. The teeth specimens were cemented with one RMGIC and one PMCR

and the conventional GIC as t he control. The bond strengt h was tested after 24 hours

using T IRA.

The second part of the study involved measuring the force required to deband after the

luting surface was sandblasted. T he bands wer e treated with aluminum oxide (50µ m)

particles dir ected from the sandblaster under 60 psi of air pressure. The force recorded

during debanding was chosen from the stress-strain curve for each specimen and were

measured in Newtons and fina l readings were tabulated in MPa.

Results: The sandblasted bands showed statistically higher results than non sandb lasted

bands. Among the groups, Group B exhib ited higher retentive valu es. Statistically,

ANOVA test indicated that non-sandblasted bands had significantly less retent ion than

sandblasted bands. (P<0.05), with a mean of 1.117 for non sandblasted bands and 1.860

for sandblasted bands. Among groups RMGIC had the highest mean value.


Interpretation and co nclusio n: The RMGIC luting cement gives ever y indication of

becoming t he material of choice for cementation of crowns, space maintainers and

orthodontic bands. In-office Sandblasting appears to be a convenient method to increase

the retention of loose bands.

Key words: (In-office Sandb lasting, RMGIC, PMCR, Prefor med Bands)

DR. PRIYA K, MDS

1.

INTRODUCTION

Page No.

1-3

2.

AIMS & OBJECTIVES

4-5

3.

REVIEW OF LITERATURE

6-23

4.

METHODOLOGY

24-41

5.

RESULTS

42-50

6

DISCUSSION

51-60

7.

SUMMARY & CONCLUSION

61-63

8.

BIBLIOGRAPHY

64-74


Table No. Title Page no

I Retentive bond strengt h valu es obtained from the study in

MPa

42

II Comparison of mean values of bond strengt h b etween

non-sandb lasted and sandb lasted bands, also among

differ ent luting cements.

43

III Comparison of the mea n valu es of bond strengt h between

non-sandb lasted bands and sandblasted bands.

45

IV Comparison of the mea n valu es of bond strengt h a mong

different luting cements in the Non Sandblasted met ho d.

45

V Comparison of the mea n valu es of bond strengt h a mong

different luting cements in the Sandb lasted method.

46

DR. PRIYA K, MDS

Figure No. Title Page no

1. Armamentarium 29

2. Ultrasonic Cleaner 29

3. Incubator 30

4. TIR A 31

5. Scanning Electron Microscope 31

6. Mounting of the tooth specimen 32

7. Enlarged view of the lingual surface of the

tooth, being parallel to the analyzing rod of the

surveyor

32

8. Tooth held in the same position with PVC in

place.

32

9. Group A – Conventional GIC 33

10. Group B – Resin Modified GIC 33

11. Group C – Compomer 34

12. Mounted Specimens – Group A 35

13. Mounted Specimens – Group B 35

14. Mounted Specimens – Group C 36

15. Specimen before debanding 37

16. Specimen after debanding 37

17. Bands placed in bottles after debanding 38

18. Teeth specimens after debanding 38

19. Procedure of sandblasting 39

20. Non sandblasted band 40

21. Sandblasted band 40

22. Non sandblasted band under SEM 41


23. Sandblasted band under SEM 41

24. Distribution of values of bond strength among

Group A

47

25. Minimum and maximum bond strength values

between groups using group A bonding agent

47


Group B

48


between groups using group B bonding agent

48


Group C

49


between groups using group C bonding agent

49

30. Comparison of mean values of bond strength

between the two methods

50

DR. PRIYA K, MDS

Ort hodont ic band has been in clinical use for mo re t han 100 years. In spit e o f t he

wide spread use o f direct bonded bracket s and t ubes in clinical ort hodont ics, t he co nvent iona l

band st ill plays an import ant role in fixed appliance t herapy.

Alt hough bonding o f ort hodont ic t ubes t o t he t eet h is receiving much current

int erest in t he for m o f indirect bonding, t he vast majo r it y o f buccal att achment s are st ill being

cement ed using st ainless st eel bands and co nvent io nal cement s, consider ing t he force levels

in t he post erior regio n.

Enamel demineralizat ion under ort hodont ic bands is a ser ious, but a co mmo n

problem to all ort hodont ist s. Whit e spot formatio n or enamel decalcificat ion can occur

whenever bact erial plaque is ret ained on enamel sur face for a prolonged per iod.1,2 By t he

presence o f fixed appliance t he efficiency o f ho me pro phylact ic procedure is great ly reduced

and t here is a need for prot ect ion o f adjacent enamel sur face.3 Inadequat e bonding st rengt h o f

dent al cement , seal break down, so lu bilit y o f t he current ly used dent al cement s in oral fluids

and poor oral hygiene all cont r ibut e to t he init iat ion o f decalcificat ion. 1, 4-6

Several st udies in t he past have invest igat ed t he chemical co mpo sit io n o f var ious

cement s, t heir phys ical and chemical propert ies and t heir app licat ion as well as use in

restorat ive dent ist ry.7,8

The ret ent ion of ort hodont ic bands to t he toot h surface is import ant to ensure fixed

appliance t herapy. Numerous agent s have been used to ret ain ort hodont ic bands. Gutt a

percha, zinc oxide eugeno l, zinc po lyacr ylat e cement , zinc po lycar boxylat e cement , resin

based cement s, zinc silicophosphat e and black copper cement have all been invest igat ed.

More recent ly att ent ion has been focused on glass io no mer cement (GIC).2,9

1


Zinc phosphat e cement and glass io no mer cement have been more ext ensively

t est ed bot h in laboratory and clinical t rials.10,11 In vit ro invest igat ions have shown t hat GIC

have great er ret ent ive capacit y t han ot her cement s and t his has been support ed by a reduced

failure rat e in vivo.12,13

In 1972, Wilson and Kent 14 int roduced glass io nomer cement . Experiment ally it

has been demo nst rat ed t hat GIC chemically adheres to t he toot h enamel, dent in as well as to

st ainless st eel15 and t he laboratory t est s on ort hodont ic bands cement ed wit h t his mat eria l

showed t hat t hey had improved ret ent io n relat ive to t heir predecessors.3 It was shown t hat

GIC released fluor ide fro m t he set cement . The fluoride can be elut ed as a simp le io n or as a

complex such as fluoro phosphat e and is considered to be of clinical benefit s.

Ort hodont ist s have used t he for med bands for near ly half a cent ur y. Ear ly st ainless

st eel bands were anatomically crude and d iffic ult to adapt to t he t eet h wit hout creat ing

cement lines. Their po pular it y grew as manufact urers developed, improved chro me allo ys t

hat allowed bett er adapt at ion. In t he lat e 1960s, Washbon int roduced a mo lar band design t

hat has remained t he indust r y st andard.16

The advent of acid et ching17 has confined t he use of bands mainly t o t he t eet h in t he

post erior regions o f t he dent al arches. Ret ent io n of t he co nvent ional ort hodont ic bands is

t hrough mechanical means via it s close adapt at ion to t he toot h surface assist ed by t he lut ing

act ion o f t he cement . This pr inciple remains valid today in sp it e o f development s t hat have

t aken place wit h regard to bot h dent al cement s and ort hodont ic bands.

A review o f lit erat ure however reveals t hat t he mo st frequent sit e of failure is at t he

band-cement int erface9,12 and t he cement remaining on t he toot h surface. Hence, it warrant ed

2

DR. PRIYA K, MDS

add it ional invest igat ion on t he met hods to enhance bond st rengt h at t he met al-cement

int er face to improve ret ent io n.

Increasing t he bond st rengt h at t his int er face should reduce t he r isk o f band

lo osening dur ing t reat ment . Recent research has focused on t he t reat ment of met als to

increase t he ret ent ive area of t he bands and improve chemical and mechanical bonding.

Several met hods have been descr ibed one such st udy was w it h elect ron micrographs o f t he

met al sur face roughened wit h d iamo nd bur or green stone has shown t o provide less micro

mechanical ret ent ion when co mpared to sandblast ing.

Sand blast ing o f t he met al sur face improves ret ent ion by roughening, t hereby

increasing t he sur face area and providing a pot ential for a degree o f mechanical att achment .

It not only increases t he ret ent ive area o f t he band lut ing sur face, but also remo ves

cont aminant s and t hins t he st ainless st eel oxide layer leaving a more fir mly att ached layer for

bonding.

This t echnique o f air abrasio n or sand blast ing was int roduced in 1950’s. It uses a

high-speed st ream o f aluminum o xide part icles propelled by co mpressed air. 18-20 Alt hough

in it ially reint roduced as a met hod to roughen the sur face of any dent al mat er ials before

cement at ion, it is ro ut inely used in cast met al rest o rat ion to enhance t he bond st rengt h, more

recent market ing includes it s app licat ion to ort hodont ics to roughen t he int ernal sur face o f t he

bands and bracket bases.

3


A sur vey o f lit erat ure unraveled a large number of co nt ribut io ns on t he subject of

cement s and cement ing procedures in t he field of ort hodont ics. Yet , of all t he rout ine

operat ions, which we as ort hodont ist s are called upon to perform, pro bably no ne is more

fundament al or fraught wit h great er pot ent ialit ies t han t he seemingly simple act of

cement at ion o f bands. The unplanned debanding is a co mmo n occurrence amo ng t he

pat ient s, which is ver y frust rat ing to recement t he loose bands as it o ft en goes undet ect ed.

Loose bands t end to while away significant amount of clinical t ime.

Despit e t he increased po pular it y o f bonded appliance in ort hodont ics, t he use o f

bands st ill prevails which is pr incipally confined to t he posterior segment wherein t he

mo lars play a pr ime ro le in serving as an anchor unit .

One o f t he major, but a basic problem confro nt ing t he clinicians is band fa ilure.

The pr inciple sit e o f band failure usually being t he band-cement int er face. Severa l

met hods are emp lo yed to enhance ret ent ion o f bands by roughening t he inner sur face

wit h d iamo nd or carbide burs or wit h green stone et c. One such met hod of roughening t he

lut ing sur face in order to secure t he bands in place is by sand blast ing, which also aids in

add it io nal ret ent ion by increasing t he surface area.

Thus, t his in vit ro st udy is under t aken to explore and emphasize t he po ssibilit ies o f

increasing bond st rengt h wit h newer hybr id cement s and su bsequent ly sand blast ing t he

inner sur face o f t he bands to det ermine if t his procedure of increasing t he sur face area he lps

in enhancing bond st rengt h.

4

DR. PRIYA K, MDS

OB JECTIVES

� To det ermine t he increase in bo nd st rengt h fo llowing sandblast ing.

� Compar ison o f t he bond st rengt h wit h t hree different lut ing cement s.

� Effect of in-o ffice sandblast ing procedure on t he retent ion o f ort hodont ic bands

using different cement s.

� To correlat e t he effect iveness of t his procedure of sandblast ing in a clinica l

sit uat ion fo llowing t he use of a plain bands init ially.

5


DEFINITION

Dental cements are subst ances t hat harden t o act as a base, liner, filling mat eria l, or

adhesive and prost heses to toot h struct ure or to each ot her. Cement s set by acid- base

react ion.21

Ret ent ion o f t he convent ional ort hodont ic bands is t hrough mechanical means via

it s close adapt at ion to t he toot h surface assist ed by t he lut ing act ion o f t he cement . 11 Thus, in

spit e of t he develo pment s in t he field o f cement s as well bands t his pr incip le is st ill valid.

One o f t he aims o f ort hodont ic t reat ment is to reduce t he incidence o f car ies by

br inging malposed t eet h int o correct po sit io n. This aim is part ly de feat ed because o f t he

appearance o f t he areas o f decalcificat ion and car ies on t he banded t eet h, which ma y

accompany ort hodont ic t reat ment .

Gibbon22 po int ed out t hat much unfavorable cr it icism was direct ed at ort hodont ic

services by bot h t he lait y and t he pro fessio n and t hat many be lieved t hat excessive toot h

dest ruct ion was t he penalt y paid for having “t eet h st raight ened”.

Numerous agent s have been used to ret ain o rt ho dont ic bands. Gutt a percha (LOWE

YOUNG, 1912)23, zinc oxide eugeno l (WILLIAMS et al, 1965)24, zinc po lyacr ylat e

cement (RICH et al, 1975)25, zinc po lycarboxylat e cement (RICH et al, 1975)25, resin

based cement s (LEE et al, 197326; SADOWSK Y AND RETIEF, 1976)22; zinc

silicophosphat e (CLARK et al, 1977)27 and red copper cement (RICH et al, 1975)25 have

all been invest igat ed.

6

DR. PRIYA K, MDS

Zinc phosphat e and silico phosphat e cement s, t he che mical and p hysica l

charact er ist ic o f which have been well document ed over a number of years and have lo ng

been t he accept ed mat erials for cement ing o rt ho dont ic bands to t he t eet h.21

Zinc phosphat e cement was int roduced in 1878,3 the cement soon became t he go ld

st andard by which ot her cement s are co mpared because o f it s lo ng and well document ed

history o f clinical use in band cement at ion.

A st udy by BERK SON (1950)28 invest igat ed t he adhesive propert ies o f zinc

phosphat e cement and claimed t hat some adhesio n to enamel occurred.

According t o ADAMS (1955),29 who st udied t he mechanical propert ies o f zinc

phosphat e cement and had provided useful in fo rmat ion on t he mixing t echnique, liquid

powder rat io and adhesive propert ies under var ying cond it io ns concluded, t hat t here was no

difference whet her t he sur face was cleaned wit h alcohol or dist illed wat er and also st at ed t hat

if t he powder was exposed to air for a long per iod gave a poor mix consist ency.

The co mparat ive in vit ro t est by WILLIAMS et al (1965)24 had report ed t he fo rces

required, for removing bands cement ed to ext ract ed t eet h wit h different cement s namely-

zinc phosphat e, silico phosphat e, and EBA reinfo rced zinc oxide eugeno l cement s. Using

solder reinforced bands, he demo nst rat ed t hat zinc phosphat e and silico phosphat e were

similar in t heir abilit y t o ret ain ort hodont ic bands and t hat t he ret ent ive st rengt hs o f t hese t wo

cement s were slig ht ly more t han twice t hat of t he EBA cement . The possible har mful effect

of zinc phosphat e cement on surface enamel was anot her aspect t hat has also been

report ed.30,31

7


According t o NORRIS et al3 in t he 1960s, fluoride was added t o zinc phosphat e

cement to reduce t he acid so lu bilit y and to impart ant icar iogenic propert ies to toot h enamel t o

which st ainless st eel bands were cement ed. There were cert ain drawbacks inherent to t he use

of zinc phosphat e cement . It was br itt le, had a relat ively high so lu bilit y in t he mout h, and it

did not adhere to toot h subst ance. Zinc phosphat e cement relied on mechanical int er locking

for it s ret ent ive e ffect and on close physical adapt at ion for sealing restorat ion margins, but it

did not provide any chemical bonding to toot h or metal sur faces. Researchers have developed

ot her dent al cement s to overcome t hese drawbacks.

However, WISTH JOHAN (1970)30 st udied t he effect of zinc phosphat e cement

on t he enamel sur face and t he difference in t he rat e of demineralizat ion and he concluded t

hat t he cement , of t he consist ency rout inely used in t he clinic is not of any import ance in t he

development of decalcificat io n. Under cert ain co nd it io ns it prot ect s t he enamel fro m

demineralizat io n.

Wit h t he development of po ly car boxylat e cement by Smit h in 1968, anot her group

of cement s became available for cement ing ort hodont ic bands. He has descr ibed carbo xylat e

cement as t he first dent al cement , which does not solely rely upon irregu lar it ies o f t he

ad jo ining sur faces for mechanical ret ent io n. He also noted t he po lyacr ylic acid mo lecules

have t he abilit y to chemica lly bo nd to calcium io ns on t he calcified enamel t oot h surface as

well as t o st ainless st eel. Also carboxylat e cement achieved a chemical bo nd w it h t oot h

enamel and it was proven to be super ior to zinc phosphat e cement .

According t o NORRIS et al,3 one disadvant age of t his cement was short sett ing

and working t imes t hat made t he cement at ion o f more t han t wo bands fro m a single mix

8

DR. PRIYA K, MDS

difficult . In add it io n t he mixed cement s viscosit y could make band cement at ion d ifficu lt .

Different fluo ride preparat ions had been added to polycar boxylat e cement to le nd

ant icar iogenic propert ies and alt er t he mechanical propert ies.

The development of t he orig inal glass io no mer cement by Wilson and Kent in 1972

was significant , as it made available, for t he first t ime a restorat ive dent al mat er ial t hat had

lo ng-t erm ad hesio n to toot h st ruct ure and also possessed car iost at ic propert ies due t o

sust ained release o f fluor ide. Mc Lean and Wilso n lat er developed it during t he 1970s. This

class o f mat erial has achieved wide spread use as a translucent mat er ial.32 True adhesio n to

enamel and met al 15 probably occurs via io nic or polar mo lecular int eract ions.

A t hree- mo nt h st udy was conduct ed by CRISP and WILSON (1976)33 on t he

chemist r y o f wat er erosion o f t he t wo for ms o f GIC t hat was made. The st udy invest igat ed t

he effect of var ying t he consist ency and cur ing time. The result was descr ibed in t er ms o f

chemistr y and st ructure of t he cement . It also compared t he chemistry o f dent al silicat es, zinc

polycar boxylat e wit h glass io no mer.

According t o M.H REISBICK (1981),34 glass io no mer o ffered several advant ages,

which were good flow, adherence t o t eet h, ample working t ime and t he cast ing seat ed

readily. The drawbacks obser ved were d ifficu lt y in remo ving fro m t eet h and cast ing, if left

for a lo ng per iod, lacked o pacit y, adhered t o dry gingiva and caused slight pain for 2-5min in

unanaest het ized t eet h.

Alt hough GIC has de mo nst rat ed high levels o f fluoride release, t hey have shown t o

have poor bond st rengt h and great er bond failure rat es t han co mposit e resins. 35,36 In an

9


att empt to provide great er fluor ide release and obt ain adequat e bond st rengt h, combinat ion o f

composit es and GIC had been developed. Resin- modified glass io no mer (RMGIC) are such

co mbinat ions, consist ing of 2 component s, term originally used by ANTONUCCI.32

Polyacid modified co mposit e resins (PMCR) or co mpo mer consist of similar co mbinat ions

t hat behave pr imar ily like resins.32

S ince t he int roduct ion o f s ilicat e cement s, fluoride release fro m restorat ive

mat er ials has been advocat ed as having t he abilit y to prevent secondary or cont act surface

car ies. Glass io no mer and t heir mo dified fo r mu lat ions are t he main fluoride releasing

mat er ials used today.37

In t he search o f ideal cement for lut ing purpose several co mparat ive st udies have

been undert aken over t he last few years.

According t o t he st udy by CAMERON et al (1963),38 on t he physical propert ies o f

dent al cement s t hat were commerc ially available, concluded t hat t he best physical propert y is

possessed by silico phosphat e cement and t hose cement s wit h higher liquid powder rat io did

not have bett er physical propert ies.

A review by SAMUEL T. SAK AMAK I and ARTHUR N. BAHU (1969),39

report ed t he effect of banding on t he localized lactobacilli count , which increased fo llo wing

banding and it ret urned to t he original level aft er t he bands were removed. The

microorganisms were increased at t he gingival margins t hus increasing t he suscept ibilit y to

car ies.

10

DR. PRIYA K, MDS

According t o WISTH JOHAN (1972),31 who compared t he sealing abilit y o f zinc

phosphat e and hydro phosphat e cement under band spaces, report ed t hat no difference

exist ed bet ween t he t wo groups. The result also sust ained t he hypot hesis t hat t he cement

layer could be penet rat ed by fluoride io ns, which possibly act as a fluor ide depot and

increased t he enamel resist ance to demineralizat ion.

A reliable met hod to t est t he ret ent ion of cement s was invest igat ed by RICH et al

(1975)25 and co mpared t he ret ent ive charact erist ics o f zinc phosphat e, polycarboxylat e and

red copper cement . They conc luded t hat t he st rengt h required t o init ially fract ure t he cement

bond ho lding t he bands, was used as a measure of ret ent ion and zinc phosphat e had t he

highest ret ent ive value fo llowed by red copper and t hen po lycar boxylat e.

A co mparat ive st udy by SADOWSK Y and RETIEF (1976)22 on so me cement s

used in ort hodont ics inferred t hat composit e cement had great er ret ent ion t o enamel as we ll

as to bands t han zinc phosphat e, silico phosphat e and po lycarbo xylat e.

MIZRAHI (1977)11 st at ed t hat, t wo major factors affect ed t he ret ent io n o f bands,

t hose relat ed to t he operator and t hose relat ed to the pat ient . He concluded t hat t here was no

difference in recement at ion rat es bet ween bo ys and gir ls, however, Class II div 2 and Klo ehn

cervical face bow t herapy had more rat es of recement at ion.

Furt her MIZRAHI (1979),40 in a clinical st udy including t wo prospect ive groups

and t wo ret rospect ive groups concluded t hat ret rospect ive groups cement ed wit h zinc

phosphat e had more failure rat es t han prospect ive groups cement ed wit h zinc

11


polycar boxylat e which could have been due to different t ypes o f bands, cement s, cement ing

procedures of different operators.

In anot her st udy MIZRAHI et al (1981),41 report ed t he effect of toot h sur face

co nt aminat ion on band ret ent ion w it h different cement s. The result s showed t hat no

significant difference was seen wit h bands cement ed by eit her zinc phosphat e or silico

phosphat e on sur face co nt aminat ion. Wit h po lycarboxylat e t he ret ent ion decreased fo llowing

co nt aminat ion. They also concluded po lishing t eeth wit h pu mice pr ior to cement at ion did not

appear to benefit band ret ent ion.

On t he incidence o f whit e spot fo rmat io n aft er bonding and banding GORELICK

LEONARD et al (1982)1 concluded t hat no significant difference occurred bet ween t he t wo

procedures.

Furt her MIZRAHI (1983)5 had st udied t he enamel o pacit ies fo llowing ort hodont ic

t reat ment . The st udy revealed, t here was st at ist ically significant increase in t he prevalence o f

enamel opacit ies on t he vest ibular and lingual sur face o f t he dent it ion. The increase was seen

great est at t he cervical and middle t hirds of t he crowns.

A co mpar ison st udied by EINAR K VAM and MEYER (1983),42 bet ween zinc

phosphat e and GIC concluded t hat glass io no mer was a bett er lut ing medium in ort hodont ics.

A report by COPENHAVER (1986),43 on co mpar ing zinc phosphat e and GIC for

it s abilit y t o inhibit decalc ificat io n st at ed t hat GIC had bett er abilit y t o inhibit decalcificat ion.

12

DR. PRIYA K, MDS

Ret ent ive bo nd st rengt h of t he ort hodont ic band cement s surveyed by NORRIS

STEPHEN et al (1986)3 using zinc phosphat e, polycar boxylat e and GIC, inferred t hat bot h

poly carbo xylat e and GIC were as effect ive as orthodont ic lut ing cement as zinc phosphat e.

GIC was more favorable because o f t he prot ect ion against decalc ificat io n.

An updat e on GIC was provided by MIZRAHI (1988)12 in ort hodont ics t hat

det ermined t he failure rat es of t he bands cement ed wit h GIC. The failure rat e was muc h

lesser t han t hat recorded for polycarboxylat e.

Bond st rengt h o f light cure and chemical cure GIC for ort hodont ic bonding was

compared by COMPTON et al (1992).44 They concluded t hat light cure GIC was superior to

chemical cure dur ing t he first t went y- four hours and for bot h t he bond st rengt h increased

fro m t he first one to t went y four hours but light cure was t he more preferred mat er ial.

Mechanical propert ies o f light cure and chemical cure GIC as bonding agent were

compared by Mc CARTHY and HONDRUM (1994).45 They concluded t hat light cure was

bett er t han self cure.

An invest igat io n by DURNING et al (1994)46 on cement s used to ret ain

ort hodont ic bands concluded t hat in vivo simu lat io n yields less in fo r mat ion and GIC was a

bett er alt ernat ive t han phosphat e; t he band ret ent ive abilit y o f bot h reduced wit h t ime.

Furt her, WRIGHT et al (1996)47 evaluat ed t he clinical per for mance of resin-

modified GIC for bonding and also it s effect on cert ain microorganisms. T hey conc luded t hat

resin- mo dified GIC bonded bracket s effect ively, decreased t he proport ion o f t he S. mut ans

and Lacto bacilli when co mpared to resin adhesive.

13


MILLET et al (1998)48 compared dual cure compo mer and convent ional GIC fo r

band cement at ion and concluded t hat dual cure showed sig nificant ly higher bond st rengt h t

han convent ional GIC and t he failure was at t he enamel ce ment int erface for co mpo mer a nd

t he cement band int erface for convent ional GIC.

RMGIC was st udied under different surface co nd it io ns by ANNE BERESS et al

(1998).49 They inferred t hat et ched enamel had t he highest st rengt h. No significant difference

was not iced in mo ist and dr y fields.

Anot her co mparat ive st udy by STEPHEN M.COHEN et al (1998),50 on t he bond

st rengt h of chemical cure and light cure resin- mo dified GIC concluded t hat t he et ched light

cure had t he highest bond st rengt h.

Compar ison o f t wo RMGIC to porcelain by CH UN- HIS CHUNG et al (1999)51

concluded t hat silane increased t he bo nding t o porcelain in bot h cases and t hat composit e as

well as resin- modified GIC had co mparable bond st rengt h.

The effect of t he enamel co nd it io ner on t he bond st rengt h of resin-reinforced GIC

evaluat ed by SAMIR BISHARA et al (2000)52 concluded t hat acid et ching wit h 37%

proved to be bett er t han 10% poly acr ylic acid.

Var ious ort hodont ic banding cement s have been descr ibed by NICOLA

JOHNSON (2000).53

In a clinical ret rospect ive st udy by MILLET et al (2001)54 on t wo different band

cement s namely modified co mposit e and convent io nal GIC concluded t hat no significant

14

DR. PRIYA K, MDS

difference was not ed in t he t reat ment t ime and t he band failure w it h eit her o f t he t wo

cement s.

According t o TJ Gillgrass et al (2001),55 in t heir st udy on co mpar ison o f t he t ime

of first fa ilure, t he po sit io n o f band failure and t he change in whit e spot enamel lesio n dur ing

fixed ort hodont ic t reat ment wit h modified composit e and convent ional GIC for band

cement at ion fo und t hat t here was no significant difference in t he failure. They not ed t hat t he

band fa ilure was at t he enamel-cement int er face for modified co mposit e and band-cement

int er face for convent ional GIC.

Fluoride release by resin- mod ified GIC and polyacid modified co mposit e was

st udied by DOUGLAS RIX et al (2001)56 and t hey demo nst rat ed t hat init ial fluoride release

was more fro m po lyacid modified co mposit e and lat er it was fro m resin- modified GIC.

The shear bond st rengt h to enamel was st udied by TOLEDANO et al (2003)57

using self and light cure GIC and a co mposit e as cont rol used for direct bonding. The y

inferred t hat resin modified GIC should be st rongly reco mmended as a mode of direct

bonding.

However, YOSHITAK A K ITAYAMA et al (2003)58 measured t he t ensile

st rengt h and t he shear bond st rengt h o f resin-reinforced GIC to porcelain and concluded t hat

resin adhesive had higher bond st rengt h to porcelain t han resin-reinforced GIC. They also

st at ed t hat resin-reinforced GIC could serve as an advant ageous alt ernat ive.

Furt her COUPS SMITH et al (2003)59 have assessed t he shear bond st rengt h o f

resin-re inforced GIC, bot h self and light cur ing. They concluded t hat self cure had higher

15


st rengt h t han light cure under all enamel preparat ions. The st udy also st at ed t hat GIC had

sufficient bond st rengt h to ret ain ort hodont ic bracket s and served as a reservo ir of fluor ide

io ns.

An in vivo st udy to det ermine t he effect of resin- modified GIC on t he ename l

demineralizat ion by RENATA CORREA PASCOTTO et al (2004)60 concluded t hat glass

io no mer was a suit able alt ernat ive to adhesive for bracket placement .

A co mpar ison by K NOX et al (2004)61 on resin- mod ified GIC and po lyacid

modified co mposit e inferred t hat resin- modified GIC had higher bond st rengt h. The failure

was at t he band-cement int er face for GIC and for polyacid modified co mposit e it was at t he

enamel-cement int erface.

16

DR. PRIYA K, MDS

DEFINITION

An O rthodontic Band is defined as “A r ing, usually made o f a t hin st rip o f st

ainless st eel t hat serves to secure ort hodont ic att achment s to a toot h”.62

The var ious mat er ials used for band const ruct ion are base mat erials like Ger ma n

silver or Nickel silver, precious met als like go ld, irid io p lat inum et c.

PULLEN (1921)63 descr ibed t he var ious qualit ies a band mat er ial should possess

and co mment ed on t he direct met hods of mak ing mo lar bands.

POLLOCK (1923)64 described t he var ious st eps invo lved in fit t ing a band to t he

mo lars or ancho r t eet h.

He quot ed “Like unt o t he house built upon t he shift ing sands, t hese bands are t he

fo undat ion o f a fixed ort hodont ic appliance. If t hey are not st rong, durable and at t he same t

ime well fitt ed an o rt ho do nt ic appliance cannot be efficient , regardless o f how beaut iful a

piece o f jewelr y it may be”. He also point s out t he var ious requirement s in choosing an idea l

band mat erial.

ALLAN BRODIE (1932)65 described t he t echnique of band pinching.

According to SHELDON FRIEL (1935),66 a compar ison bet ween plain and cla mped bands

demonst rat ed t hat plain band was as good as t he clamped one if well fabr icat ed and adapt ed

to t he t eet h.

17


HERBERT PASK OW (1950)67 described an easy way o f fabr icat ing t apered

mo lar bands.

According to SIDNEY BRANDT (1968)68 t he bands have cert ainly been improved

over t he years. The advent of t he prefor med band was a major st ep forward. The saving in t

ime and effo rt to t he pro fessio n was enor mous. It made fit t ing o f difficult and inco mplet e ly

erupt ed teet h easier and possible, ear lier t han before. Preformed bands made t he pro fessio n

aware of t he frequency o f mis mat ches in t oot h size. When bands were well fitt ed, well placed

and well cared for t hey made possible a high level of ort hodont ic achievement .

In t he era of bonded ort hodont ic appliance, prefo rmed st ainless st eel bands re ma in

import ant for ort hodont ic t herapy.

GEORGE V. NEWMAN (1974)69 comment ed that prefor med mo lar bands were

so well adapt ed t hat t he fr ict ional forces alo ne could almost ret ain t hem on t he t eet h.

The preformed bands o ffered several advant ages as descr ibed by WARREN

HAMULA et al (1996).16 He also descr ibed a new band design.

Bonded mo lar t ubes were st udied by MILLET (1999)70 who found t he mean

survival rat e was 699 days and t hat t he gender and malocc lusio n had no significant role but t

he age at t he st art of t he t reat ment and t he operator were determined to be useful predict ors

of t he bonded mo lar t ube.

18

DR. PRIYA K, MDS

The evo lut ion fro m pinching go ld - p lat inum or chro me allo y st raight , flat st rips t o

fit toot h for m, to pinching pre for med st rips, to having an invent ory o f preformed band s

cont aining fully-shaped sizes has been an amazing ser ies of advances.

Wit h t he coupling o f prefor med bands, appliance placement and t he philosophy o f

light force toot h movement , ort hodont ics has reached a new plat eau.

19


DEFINITION

it .71

Sandblasting is a procedure to clean or roughen a sur face by a iming a jet of sand at

The most frequent sit e of band failure is at t he band-cement int er face9,12 and t he

laboratory st udies support t his finding.3

According to HODGES et al (2001)72 increasing t he bond st rengt h at t his int er face

would decrease t he risk o f band loosening dur ing treat ment .

The current focus is on t reat ment of t he met al to increase t he ret ent ive sur face area

of t he band and enhance t he chemical and mechanical bo nding.

Early in 1943, DR. ROBERT BLACK 20 began his pio neer ing st udies using air

abrasive t echno logy in dent ist r y. The t echnique int roduced in t he 1950s, used a high-speed

st ream of aluminum o xide part icles propelled by compressed air. 18,19 In 1951 air abrasive

inst rument was int roduced.20

Air abrasives were init ially used for modifying the sur face of enamel, dent in and

restorat ive mat er ials,20 before cement at ion and t o enhance t he bond st rengt h. More recent ly

market ing includes it s app licat ion t o ort hodont ics to roughen t he int ernal sur face o f bands

and bracket bases.73

A st udy by ZACHRISSON AND BUYUK YILMK AZ (1993)74 on elect ron

micrographs of t he met al sur face t hat has been roughened wit h d iamo nd bur or green stone

demonst rat ed t hat t he apparent roughness was caused by per iodic r idges and grooves, whic h

20

DR. PRIYA K, MDS

provide lit t le micro mechanical ret ent ion and concluded t hat t he micro mechanical ret ent io n

provided by sand blast ing was more advant ageous.

Furt her WOOD et al (1996)75 co mpared t he bond st rengt h of zinc phosphat e, zinc

po lycar bo xylat e and GIC before and aft er sandblast ing and inferred t hat sandblast ing

improved t he ret ent ion and t hat GIC was a bett er lut ing agent .

Compar ison o f failed bracket s by SONIS L. ANDREW (1996)73 t reat ed wit h air

abrasio n and t he unt reat ed bracket s inferred t hat t he fa iled air abraided bracket s, had t he

same bond st rengt h as an unt reat ed new bracket. Air abrasio n increased t he mechanica l

ret ent ion.

Anot her st udy by STANLEY MILLER, JOSEPH H. ZERNIK (1996),76

compared t he effect of sand blast ing on t he bo nd st rengt h and concluded t hat sand blast ing

increased t he bond st rengt h and, when co mbined wit h glass io no mer decreased t he failure

rat e.

Different met hods o f sur face roughening descr ibed by ENIS GURAY, ALI IHYA

K ARAMAN (1997)77 concluded all t he met hods increased t he ret ent ion but micro -et ching

provided ho mogenous microscopic undercut s.

They roughened t he maxillar y first premo lar bands by micro -et ching wit h

alum inum oxide, and a low speed micro motor wit h t ungst en carbide and green stone. The y

21


concluded t hat t he t reat ed bands had sig nificant ly great er ret ent io n t han unt reat ed and no

st at ist ically significant difference was found bet ween t he different met hods emp lo yed.

A st udy was conduct ed by MILLET et al (1999)78 using co mpo mer and resin

modified GIC under laboratory co nd it io ns for bonding. The resu lt s showed no significant

difference in debonding force bet ween t he t wo convent ional adhesive. The ARI inde x

indicat ed no cement was seen on t he toot h sur face aft er debonding wit h RMGIC; half t he

cement was on t he toot h, wit h co nvent ional GIC. For co mpo mer and co mposit e most of t he

adhesive was on t he toot h aft er debonding. They also suggest ed micro et ching t he base to

minimize t he amount of cement on t he toot h surface.

Bond st rengt h st udied by MUI et al (1999),79 on t he bonded and rebonded

ort hodont ic bracket base t reat ed wit h different co nd it io ning met hods also compar ing t he light

cure and t he self-cure syst ems, concluded t hat the best reco ndit ioning met hod fo llowing

debonding appeared t o be removal o f t he residual co mposit e wit h t ungst en carbide bur and

acid et ching t he enamel. The rebonding procedure was done using t he self cure s yst em and

new bracket s. If t he bracket s were to be reused t hen t he base could be micro -et ched.

A co mpar ison by MENNEMEYER et al (1999)80 evaluat ed t he use o f hybr id

io no mer, resin cement s and GIC cont rol, bonded to photo-et ched and st andard band mat eria ls

t est ed in as received and air abraded co nd it io ns, they inferred t hat air abrasio n increased t he

bond st rengt h o f bot h cement s.

MANISH AGGARWAL et al (2000)81 compared t he shear peel st rengt h o f five

different cement s using factory and in-o ffice mic ro-et ched bands and concluded t hat t here

22

DR. PRIYA K, MDS

was no difference bet ween RMGIC and PMCR and amo ng t he t wo RMGIC but st at ist ically

significant difference was seen w it hin PMCR. There was low bo nd st rengt h wit h t he in

pract ice-sand blast ing group.

However, CANAY et al (2000)82 co mpared acid et ching wit h air abrasio n for

sur face preparat ion t echnique on enamel. The st udy inferred t hat sandblast ing fo llowed by

acid et ching had t he highest bond st rengt h and t hat sandblast ing alo ne proved to have lo w

bond st rengt h and should not be advocat ed as enamel co nd it io ner.

Anot her compar ison by HODGES et al (2001)72 on t reat ed and unt reat ed bands

concluded t hat t he t reat ed bands had bett er ret ent ion.

The vert ical loading o f t he micro-et ched bands cement ed wit h modified co mposit e,

RMGIC and co nvent ional GIC was co mpared by MILLET et al (2003).83 They concluded

t he ret ent ive st rengt h was lower for modified co mposit e fo llowed by convent ional GIC t ha n

RMGIC wit h micro-et ched bands.

Recent ly METE OZER and SELIM ARICI (2005)84 st udied clinical per formance

of sandblast ed met al bracket s bonded wit h self cure RMGIC. They however concluded t hat

no difference bet ween sandblast ed and non sandblast ed bracket wit h RMGIC aft er 20-mo nt h

o bservat ion.

23


SELECTION AND GROUPING OF TEETH

Fort y- five non-car ious, unrestored human mandibular mo lars, which were freshly ext ract ed

because o f severe per iodont al disease, were used for t his invest igat ion. The ext ract ed t eet h

were stored in 10% for malin at room t emperat ure pr ior to use.

INSTRUM ENTS AND M ATERIALS USED (Fig. 1, 2,3,4 and 5)

� P.V.C. SLEEVES

� AUTO POLYMERISING ACRYLIC RESIN

� CONVENTIONAL GIC (FUJI, TYPE I)

� DUAL CURE COMPOMER (RELIANCE ORTHODONTIC PRODUCT)

� RESIN-MODIFIED GIC (3M, MULTI CURE)

� PREFORMED ORTHODONTIC BANDS (3M Unit ek)

� BUCCAL TUBES [NIBHA, � ROUND, int ernal diamet er of 0.9mm (0.036'')

lengt h 6.3mm (0.25'')� ]

� LINGUAL BUTTONS (NIBHA)

� 0.9mm (0.036'') SS WIRE AND 0.5mm (0.020'' SS) WIRE (LEONE)

� INCUBATOR (YORCO, INDIA)

� INSTRON MACHINE (TIRA 2820S, GERMANY)

� ULTRASONIC TANK (Dent aurum)

� SANDBLASTER (Bio-art , Brasil. ALUMINA - 50� SIZE)

� SEM (LEO 440 I)

� WELDER (Dent aurum)

� LIGHT CURE UNIT (Spect rum 800, Dent sply)

24

DR. PRIYA K, MDS

SPECIM EN PREPARATION

A per fo rat io n was made t hrough t he cent er of each t oot h near t he furcat ion area

and a 0.9mm (0.036'') SS wire was placed in t he ho le to aid in t he ret ent ion of t he t eet h

wit hin t he acr ylic. The t eet h were t hen mo unt ed wit h auto-polymer izing acr ylic resin in

custom- made P.V.C sleeves of appro ximat ely 30mm (1.18'') in lengt h and 25.6mm

(1.00'') dia met er. The lingual sur faces o f t he t eet h were kept parallel t o t he analyz ing rod

of t he Ney’s surve yor and were mount ed (Fig. 6, 7 and 8). Root s wit h t he ret ent ive wire

in place were fully encapsulat ed by t he resin. T he exposed crowns were c leaned wit h

non- fluor idat ed pro phylact ic past e for 1 minut e to remove any fo reign debr is.

Prefor med st ainless st eel ort hodont ic bands were select ed for each specimen and checked

for size and fit on each mo lar. The buccal t ubes and lingual buttons were welded at

3.5mm fro m t he occlusal sur face at 4 Amps wit h five spot welds.

The t eet h were rando mly divided int o 3 groups of 15 specimens each t o t est t hree

commercially available lut ing cement s. The t eeth spec imens were numbered and t he

bands were placed in numbered bott les respect ively as t hey were t o be recement ed.

» GROUP A – Co nvent ional Glass Ionomer Cement (GIC) (Fig.9 and 12).

» GROUP B – Resin-Modified Glass Ionomer Cement (RMGIC) (Fig 10 and 13).

» GROUP C– Dual cure Co mpo mer / Polyacid Modified Co mposit e Resin (PMCR) (Fig.11

and 14).

The convent ional cement was manipu lat ed on t he mixing pad as per t he

manufact urers reco mmendat ions. Aft er mixing each cement , t hey were loaded int o t he

ort hodont ic bands. Each band was seat ed on t he select ed t eet h wit h hand pressure and t he n

25


wit h t he band seat er. The excess cement was remo ved fro m t he occlusal and cer vical margins

of t he bands w it h dr y cotton roll so t hat it would not int erfere wit h t he t est result s. The

RMGIC and co mpo mer were t hen light cured wit h t he dent al cur ing light , for 40 seconds in

case o f RMGIC and 20 seconds in case o f PMCR fro m t he occlusal aspect of t he band, as

direct ed by t he manufact urer. Pet roleum jelly was applied around t he band per ipher y.

Aft er wait ing for t en minut es, t he specimens were stored in saline at 37º C and

100% hu mid it y for 24 hours in an incubat or. The bond st rengt h was t est ed aft er 24 hours

using TIRA.

The mo unt ed t eet h were clamped to t he ho lding device w it h a large diamet er ho le

allowing each mo lar crown t o protrude and sit direct ly below t he att achment apparat us o f

TIRA. This arrangement allowed all t he fo rces t o be direct ed parallel t o t he lo ng axis o f t he

toot h during band remo val. T he ort hodont ic bands were att ached wit h 0.5mm (0.020'') SS

wire s ling, t he loop of which engaged t he buccal t ube and t he lingual button of each ba nd

(Fig.15 and 16).

Using TIRA in t he t ensile mode wit h t he crosshead speed o f 0.5mm (0.02'') per

minut e, t he maximum force recorded during debanding was chosen fro m t he st ress-st rain

curve for each specimen and was measured in Newtons, which was used t o calculat e t he

bond st rengt h wit h t he band sur face area dat a, and final readings were t abulat ed in MPa.

Aft er debanding t he bands were placed int o t he respect ive numbered bott les (Fig.

17). The debanded t eet h were stored back in wat er and cleaned wit h scaler and pumice. The

bands were cleaned in an ult rasonic cleaner for 20 minut es to remo ve any residual cement .

26

DR. PRIYA K, MDS

The second part of t he st udy invo lved measur ing t he force required t o deband aft er

t he lut ing surface was sandblast ed.

The bands were t reated wit h alu minum oxide (50µ m) part ic les direct ed fro m t he

sandblast er under 60 psi o f air pressure at a dist ance of 10mm fro m t he band u nt il a unifo r m

frost y appearance was visible (Fig.19). Typically t his required 15-20 seconds. Any residua l

sand was remo ved using t he air syr inge. The sandblast ed band sur face was obser ved under a

magnifying lens. The sandblast ed bands were recement ed to t heir respect ive t eet h. The

cement at ion was carr ied out according t o t he manufact urer’s reco mmendat io n as ment ioned

above.

One non sandblast ed (Fig. 20 and 22) and one sandblast ed band (Fig. 21 and 23)

was photographed under SEM at 25KV, magnificat ion of 1000X.

Method of Statistical Analysis:

The dat a were co llect ed on for ms and ent ered into a Microso ft Excel Worksheet and

analyzed using SPSS (ver 7.5) st at ist ical package.

The result s were averaged ( mean + st andard deviat ion) for bond st rengt h bet ween t he

met hods and t he lut ing agent s. Two -way analys is o f var iance t est used to find a

significant difference bet ween t wo means.

27


Analysi s of Variance:

In t his st udy, t wo independent var iables namely met hod and lut ing cement s were

compared w it h respect to bond st rengt h. This exper iment al design is called a t wo -way

analys is o f var iance.

If F value is significant , t here is a significant difference bet ween group means.

Tukey’s t est was t hen used to det ect significant difference bet ween group means.

In above t est “p” value o f < 0.05 was accept ed as ind icat ing st at ist ica l

significance.

28

DR. PRIYA K, MDS

29


30

DR. PRIYA K, MDS

31


32

DR. PRIYA K, MDS

33


34

DR. PRIYA K, MDS

35


36

DR. PRIYA K, MDS

37

DR. PRIYA K, MDS

DR. PRIYA K, MDS

40


41

DR. PRIYA K, MDS

The st udy was conduct ed in t he Depart ment of Ort hodont ics and Dent ofacia l

Ort hopedics, M.S.R.D.C, Bangalore and HAL - Foundr y and Forge Depart ment ,

Bangalore. The st udy was conduct ed to evaluat e t he effect of in-o ffice sand blast ing on t

he ret ent ion o f ort hodont ic bands w it h t hree different lut ing cement s. The shear bond

st rengt h was t est ed on a universal t est ing machine. (TIRA). The values were recorded in

Newton and convert ed int o MPa for st at ist ical analysis (Table I).

Table I: Retentive bond strength values obtained from the study in MPa

Sl Group A Group A Group B Group B Group C Group C

No. Non- sandblast ed

Sandblast ed Non- sandblast ed


Sandblast ed

1. 0.8650 1.8464 1.2431 1.9501 1.1153 1.5768 2. 0.9106 1.9499 1.4490 2.1865 1.0373 1.4916 3. 0.8265 1.8918 1.4080 2.2035 1.1466 1.6654 4. 0.9744 1.9352 1.4129 2.1557 1.0110 1.4746 5. 0.9721 1.9082 1.4265 2.1827 0.9922 1.4350 6. 0.9123 1.9048 1.4150 2.1750 1.0356 1.4834 7. 0.8662 1.8312 1.3067 2.1348 1.0856 1.5455 8. 0.8321 1.7438 1.3599 2.0672 1.1003 1.5820 9. 0.9300 1.9897 1.3331 2.1929 1.1251 1.6099 10. 0.9544 1.9762 1.4308 2.2321 0.9962 1.4456 11. 0.9076 1.9454 1.4406 2.1869 1.0360 1.4909 12. 0.9409 1.9970 1.4202 2.1607 1.0678 1.4424 13. 0.9156 1.9781 1.3877 2.1353 1.1714 1.6567 14. 0.9224 1.9434 1.4617 2.2341 1.0180 1.4487 15. 0.8714 1.8791 1.3380 2.0404 0.9314 1.4221

The dat a fro m t he st udy was subject ed to ANOVA t est.

The Mean values and St andard Deviat ions o f shear bond st rengt hs o f non

sandblast ed and sandblast ed bands are present ed in Table II.

42


Table II: Comparison of mean values of bond strength between non-

sandblasted and sandblasted bands, also among different luting ce ments.

Method Group N Mean Median Std Dev Minimum Maximum

GROUP A 15 0.907 0.912 0.046 0.827 0.974

GROUP B 15 1.389 1.413 0.061 1.243 1.462

Non Sandblasted Bands

GROUP C 15 1.058 1.037 0.066 0.931 1.171

GROUP A 15 1.915 1.935 0.069 1.744 1.997

GROUP B 15 2.149 2.175 0.077 1.950 2.234

Sandblasted Bands

GROUP C 15 1.518 1.491 0.082 1.422 1.665

Class Level Informatio n

Class Levels Values

Method 2 Non Sandblasted and Sandblasted

Band

Group 3 GROUP A, GROUP B & GROUP C

Number o f observatio ns 90

The result s were st at ist ically analyzed. “ANOVA” test was used for ana lyzing t he

significance bet ween t he ret ent ion of non sandblast ed and sandblast ed bands.

The result s o f analys is o f var iance in co mpar ison amo ng non sandblast ed and

sandblast ed bands showed t hat t here was st at ist ically significant difference bet ween t he

t wo met hods (Table III, Fig. 30)

The Test revealed t hat t here was Significant Mean difference in bo nd st rengt h

bet ween group A, B and C.

43

DR. PRIYA K, MDS

Group A

ANOVA t est indicat ed t hat non-sandblast ed bands had sig nificant ly less ret ent io n

t han sandblast ed bands. (P<0.05). Range fro m a minimum o f 0.827 to maximum o f 0.974

for t he no n sandblast ed group wit h a mean o f 0.0907 and for t he sandblast ed group

minimum being 1.744 and maximum o f 1.997 and a mean o f 1.915 (Table.IV and V,

Fig.24 and 25).

Group B



and a mean o f 1.389 for t he no n sandblast ed group and for t he sandblast ed group

minimum being 1.950 and maximum o f 2.234 wit h mean of 2.149 (Table IV and V, Fig.

26 and 27).

Group C


t han sandblast ed bands. (P<0.05). Range fro m a minimum o f 0.931to maximum o f 1.171

wit h a mean o f 1.058 for t he non sandblast ed group and for t he sandblast ed group

minimum being 1.422 and maximum o f 1.665 wit h mean of 1.518 (Table IV and V,

Fig.28 and 29).

44


Table III: Co mparison of the mean values of bond strength between non

sandblasted bands and sandblasted bands.

Methods

N

Mean

F value

P value

Non-Sandblast ed

45

1.117

Sandblast ed

45

1.860

2707.62

<0.05

S ince t here was also st at ist ically significant value exist ing amo ng t he t hree

groups, Tukey’s t est was perfor med.

Table IV: Co mparison of the mean values of bond strength among different

luting ce ments in the Non Sandblasted method.

Cement groups

N

Mean

F value

P value

Group A (Red)

Convent ional GIC

15

0.907

Group B (Yello w) RMGIC

15

1.389

Group C (Green) Compo mer

15

1.058

269.16

<0.05

45

DR. PRIYA K, MDS

Table V: Co mparison of the mean values of bond strength among different

luting cements in the Sandblasted method.

Cement groups

N

Mean

F value

P value

Group A

15

1.915

Group B

15

2.149

Group C

15

1.518

264.09

<0.05

Thus in co mpar iso n, t he sandblast ed bands showed st at ist ically higher result s t han

non sandblast ed ones. Amo ng t he groups Group B exhibit ed higher ret ent ive values

st at ist ically.

46


Ob

se

rved

Va

lue

s

Bo

nd

Str

en

gth

(M

Pa

)

0. 8

65

0. 9

10

6

0. 8

26

5 0

. 97

44

0. 9

72

1

0. 9

12

3

0. 8

66

2

0. 8

32

1

0. 9

3

0. 9

54

4

0. 9

07

6

0. 9

40

9

0. 9

15

6

0. 9

22

4

0. 8

71

4

1. 8

46

4

1. 9

49

9

1. 8

91

8

1. 9

35

2

1. 9

08

2

1. 9

04

8

1. 8

31

2

1. 7

43

8

1. 9

89

7

1. 9

76

2

1. 9

45

4

1. 9

97

1. 9

78

1

1. 9

43

4

1. 8

79

1

F ig . 2 4 : D is t r i b u t io n o f V a l u e s o f B o n d s t r e n g th a m o n g G r o u p A

2 .5

S a n d b la s t e d m e th o d

2

N o n - s a n d b la s t e d m e th o d

1 .5

1

0 .5

0

1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3

1 4 1 5

S a m p le N u m b e r

Fig. 25 : Minimum and Maximum Bond Strength values between Groups using Group A

bonding agent

2.5

1.997

2

1.7438

1.5

1 0.8265

0.9744

0.5

0

Minimum Maximum Minimum Maximum

Non-sandblasted method Sandblasted method

47

DR. PRIYA K, MDS

Ob

se

rve

d V

alu

es

B

on

d S

tre

ng

th (

M P

a)

1.2

43

1

1.4

49

1.4

08

1.4

12

9

1.4

26

5

1.4

15

1.3

067

1.3

59

9

1.3

33

1

1.4

30

8

1.4

40

6

1.4

20

2

1.3

87

7

1.4

61

7

1.3

38

1.9

50

1

2.1

86

5

2.2

03

5

2.1

55

7

2.1

82

7

2.1

75

2.1

34

8

2.0

672

2.1

92

9

2.2

32

1

2.1

86

9

2.1

60

7

2.1

35

3

2.2

34

1

2.0

404

Fig. 26: Distribution of Valu es of Bond strength among Group B

2.7 Sandblasted method

2.2

Non-sandblasted method

1.7

1.2

0.7

0.2

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

-0.3

Sa mple Nu mber

F i g . 2 7 : M i n i m u m a n d M a x i m u m B o n d S t r e n g t h v a l u e s b e t w e e n G r o u

p s u s in g

G r o u p B b o n d in g a g e n t

2 . 5

2 .2 3 4 1

2 1 .9 5 0 1

1 .5 1 .4 6 1 7

1 .2 4 3

1

1

0 . 5

0

M in im u m M a x im u m M in im u m M a x im u m

N o n -s a n db la s te d m e th o d S a n d b la s t e d m e t ho d

48


Ob

se

rve

d V

alu

es

B

on

d S

tren

g th

(M

Pa )

1.1

15

3

1.0

37

3 1.1

46

6

1.0

11

0.9

92

2

1.0

35

6

1.0

85

6

1.1

00

3

1.1

25

1

0.9

96

2

1.0

36

1.0

67

8 1.1

71

4

1.0

18

0.9

31

4

1.5

76

8

1.4

91

6

1.6

65

4

1.4

74

6

1.4

35

1.4

83

4

1.5

45

5

1.5

82

1.6

09

9

1.4

45

6

1.4

90

9

1.4

42

4

1.6

56

7

1.4

48

7

1.4

22

1

Fig. 28: Distribution of Values of Bond strength among Group C

2

Sandblasted method

1.8

1.6


1.4

1.2

1

0.8

0.6

0.4

0.2

0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2 3 4 5 6 7 8 9 10

11 12 13 14 15

Sample Nu mber

F i g . 2 9 : M i n i mu m a n d M a x i m u m B o n d S tr e n g th v a lu e s b e tw e e n G r o u p s u s i n g

G r o u p C b o n d i n g a g e n t

1 .8

1 . 6 6 5 4

1 .6

1 . 4

1 . 4 2 2 1

1 . 2 1 . 1 7 1 4

1

0 . 9 3 1 4

0 .8

0 .6

0 .4

0 .2

0

M i n i m u m M a x im u m M in i m u m M a x im u m

N o n - s a n d b l a s te d m e th o d S a n d b l a s te d m e t h o d

DR. PRIYA K, MDS

49


Me

an

Va

lues o

f B

on

d S

tre

ng

th (

Mp

a)

Fig. 30: Comparision of M ean values of Bond strength b et ween two methods

2.500

Non-sandblasted m ethod

Sandblasted method

2. 149

2.000

1.915

1.500

1.389

1.518

1.058

1.000 0.907

0.500

0.000 Group A Group B Group C

50

DR. PRIYA K, MDS

Int egrit y o f an ort hodont ic appliance is essent ial to t he co nt inu it y o f t reat ment

mechanics. Alt hough direct bond ing of fixed ort hodont ic appliance att achment , is a

rout ine pract ice for ant er ior t eet h, mo lars are o ft en banded because t he failure rat es t end

to be lower t han t hat of bonded attachment s.70 Improved ret ent ion is mainly due to

increase in sur face area of t he bands.

Unlike a cast crown or inlay, an ort hodont ic band is not in int imat e cont act wit h

enamel. There are areas, part icular ly around t he cervical margin, where t he band does not

cont act t he enamel sur face. Space bet ween band and enamel are filled w it h cement . Band

ret ent ion is a co mplex p heno menon and may be influenced t o a var ying ext ent by t he fit

of t he band, t he t ype o f band mat erial, band widt h, band po sit ion and cement ing

procedures.

Zinc phosphat e was in wide spread use for mo lar band ce ment at io n u nt il 1980s

but due to t he incidence o f increased so lu bilit y and enamel de mineralizat ion under loose

bands, Glass io no mer cement (GIC) has beco me a more attract ive alt ernat ive especially

due to it s propert y o f fluor ide release.3

COMPOSITION AND SETTING REACTION OF GIC

GI cement has t wo co mponent s: a powder calcium aluminum fluorosilicat e glass;

and a carbo xylic acid copolymer, which exist s eit her in dr ied for m or as hydrous so lut ion.

It capit alizes on t he carboxyl chelat ion to enamel, dent in and most met als by emp lo ying

var ious mixt ures of carbo xyl cont aining acids (po lyalkeno ic acids) react ing wit h

alumino silicat e glass. Alu mino silicat e glass fused in t he presence of fluoride fluxes result

51


in an alkaline co mpo sit io n t hat releases fluor ide io ns when react ed wit h acids. Mixing

process occurs in hydrous phase.

The fluoride co mplexes o f calc ium and aluminum react wit h carboxylic acid

copolymer. In t his acid- base react ion a po lysalt gel is for med in which t he glass part icles

are embedded. Sett ing process t akes place in t wo st eps:85

1. In t he first , rapid st ep, t he calcium io ns (which may t ake t he for m o f fluoride co mple x

io ns, CaF+) are incorporat ed bet ween t he polycarboxylic acid mo lecules.

2. In t he fo llo w ing, slower st ep, a co mplet e int er lacing occurs by t he react io n o f

aluminum io ns wit h t he carboxylic acid groups t hat have not yet react ed.

Ad hesio n probably resu lt s fro m io nic or polar mo lecular int eract ions.15 The fluid

past e wet s t he sur face and is att ached by hydrogen bo nds, which are progressively

replaced by io nic ones, as t he react ion proceeds. This is so met imes called “chemica l

adhesio n”. Alt hough a chemical react io n may be invo lved in for ming t he adhesive bo nd,

it is not ent irely correct. It is almost cert ainly t he result of secondar y fo rces o f mo lecular

att ract ion rat her t han pr imar y chemical bonds. The t erms “specific adhesio n” or a

“phys ico-chemical adhesio n” is a more accurat e t erm, which serves t o dist inguish t his t

ype o f att achment fro m mechanical ad hesio n, which relies on mechanical int er locking.

It was seen t hat a st rong polar bo nd bet ween t he toot h, cement and t he met al

restorat ion reduces micro leakage patt erns arising fro m fau lt y ce ment margins. Fluor ide

release has been measured dur ing t he GIC sett ing react ion, as well as aft er sett ing86

Add it io nal fluor ide is released when GIC is exposed to acids. However, GIC is more

prone to early mo ist ure cont aminat ion and t akes 24 hours to reach maximum st rengt h.44

52

DR. PRIYA K, MDS

St ephen and Wilso n87,88 had obser ved similar findings in t heir st udy o f sett ing

react ion of GIC. The phys ical propert ies o f GIC had also been evaluat ed and st udied by

var ious aut hors.89,90,91 The so lu bilit y o f t his cement had been evaluat ed by Mit chem.92

HYBRID CEMENTS

In an att empt to provide great er fluor ide release and obt ain adequat e bond

st rengt h comparable to composit es, co mbinat ion of GIC and co mposit e resin has bee n

developed t o creat e “Hybr id cement s”, which allowed snap set , decreases mo ist ure

co nt aminat io n and increases rat e of st rengt h development . Resin- modified glass io no mer

cement s (RMGIC) are such co mbinat io n, consist ing of t wo component s; t hey self cure by

acid- base react ion o f GIC. They have a diffusio n-based ad hesio n bet ween t he cement and

toot h surface and co nt inuously release fluor ide. Po lyacid modified co mposit e res ins

(PMCR) also consist of similar co mbinat ion. They are essent ially resin mat r ix co mposit es

in which filler is replaced by io n leachable aluminosilicat e glass t hat will not self-cure by

acid- base react io ns of GIC and behave pr imar ily like resins,32 which set s by

polymer izat ion of met hacr ylat e group (oft en light act ivat ed).

The first mo lars st ill show highest incidence o f band fa ilure. One reason is t he

convergence o f t he t hree st rongest muscles o f mast icat io n – masset er, t emporalis and

int er nal pt er ygo id in t he area of first mo lar and second bicuspid. Mandibu lar mo lars have

a great er t endency t o have loose bands; hence, t hey were chosen for t his st udy.

According to Mat asa,93 t he st rongest bonding is achieved when t he bond is

“cohesive” t hat is, t he adhesive remains aft er debonding in almost equal proport ion on

53


bot h t he subst rat es. To achieve t his goal, t here have been var ious met hods t hat have bee n

t est ed such as development of cement s, t reat ment of t he inner sur face o f t he bands and

t he t eet h surface.

RMGIC have been int roduced to restorat ive dent ist r y dur ing t he mid 1990s and t

hen su bsequent ly int o ort hodont ics. Several studies have been carr ied out on t his

mat er ial and t he resu lt s have been ver y encouraging. Mu lt iple uses and handling

charact er ist ics have been discussed in dept h on it s clinical imp licat ion by S. K S idhu.94

Thus, t his in vit ro st udy was undert aken at t he Depart ment of Ort hodont ics and

Dentofacial Ort hopedics, M.S.Rama iah Dent al College, Bangalore to evaluat e t he effect

of in-o ffice sand blast ing on t he ret ent ive st rength of used plain bands wit h different

lut ing agent s. Fort y- five ext ract ed human mo lars were used for t he st udy. The t eet h were

in it ially cement ed wit h t he hybr id cement s namely one RMGIC and one Po lyacid

modified co mposit e resin, wit h t he co nvent ional GIC act ing as t he cont rol.

The pr imar y goal was to det ermine t he effic iency of t hese newer hybr id cement s

and to det ect if t he in-o ffice sand blast ing o f t he used pla in bands would aid in add it io na l

ret ent ion simu lat ing a clinical sit uat ion.

The present st udy co mpared t he different lut ing cement s and inferred t hat RMGIC

has great er bo nd st rengt h t han t he PMCR and co nvent io nal GIC, bot h, before and aft er

sandblast ing, which is in accordance t o Menneme yer et al, Sadiq and Hodges. 80,95 The

mean values before sand blast ing were 1.389 MPa for RMGIC, 1.058 MPa for co mpo mer

and 0.907MPa for t he co nvent io nal GIC, where as Millet 54 had found t hat no significant

difference exist ed bet ween RMGIC and PMCR.

54

DR. PRIYA K, MDS

The mean value o f 2.149 MPa for RMGIC and t he value o f 1.518 MPa for

co mpo mer and1.915 MPa for convent ional GIC respect ively were t abulat ed aft er

sandblast ing.

Fro m our st udy, we also inferred t hat t he procedure of sand blast ing increased t he

ret ent io n, which was in accordance w it h t he find ings of Wood et al,75 Hodges et al72 and

ot hers.73,76 Millet et al96 has also emphasized t hat t he sand blast ing procedure had almost

increased t he mean survival t ime of t he ort hodont ic bands by t hree fo lds.

SETTING REACTION OF RMGIC

RMGIC has a sett ing mechanism by t hree react ions, when t he powder and liquid

are mixed; an acid base react ion similar t o t hat of convent ional GIC is in it iat ed. In

add it io n, t his mat erial can be cured quickly by light act ivat ion fro m t he visible lig ht -

cur ing device. T he light act ivat es free radical po lymer izat ion o f HEMA and ot her 2

mo no mers t o form a po ly HEMA mat rix t hat hardens t he mat erial. T he t hird react io n is

self-cur ing o f resin mo no mers. It is t he light init iat ed react ion t hat allows for t he ear ly

placement of t he arch wires, while t he acid base react ion occurs simult aneously and

co nt inues for a per iod aft er t he mass has been cured by light act ivat ion. It is believed t hat

poly HEMA and polyacr ylic met al salt u lt imat ely for ms a ho mogenous mat rix t hat

surrounds t he glass part icles. As a result , light act ivat ed po lymer izat io n react ion is well

har mo nized wit h acid base react ion in t his fo r mat ion.

The advant ages o f t he hybr id io no mer and t he resin cement over t he t radit iona l

GIC include t he fo llowing- improved sett ing t ime, lo nger working t ime due to snap set by

photo curing and a rapid development of early increase in st rengt h, which makes t he set

55


mat r ix more tolerant to t he effect s o f mo ist ure and t hese superior propert ies, account ing

for increase in bo nd st rengt h.

Anot her o bservat ion t hat was made, inferred t hat , pr ior to sandblast ing t he cement

remained on t he toot h wit h respect to RMGIC and co nvent ional GIC whereas, wit h

PMCR, t he cement remained on t he band. Aft er sandblast ing t he fa ilure sit e was wit hin t

he cement , which is more advant ageous in t he two GI groups and at t he band-cement

int er face in case o f t he co mpo mer group.53

Co mpo mer as ment ioned earlier behaves pr imar ily like co mposit es, t hough

sandblast ing procedure had increased t he ret ent ion, it is not significant enough whe n

compared to RMGIC and PMCR. It was cat egorized as t he least effect ive group in our

st udy as co mposit e requires t he sur face of enamel to be et ched to aid in micro ret ent io n

which has been demo nst rat ed, where t he highest bond st rengt h to enamel is att ained w it h

phosphor ic acid, primer and a mo ist bonding sur face.97

The current st udy did not include any sur face t reatment of ename l.

However, in t he st udy by Gillgrass55 it was obser ved t hat t here was no significant

difference bet ween convent ional GIC and co mpomer used for band cement at ion. S imilar

co nclusio ns were drawn by Aggarwal et al.81

SETTING REACTION OF PMCR

Co mpo mer or PMCR are co mposed of io n leachable alumino silicat e glass in a

po lymeric mat rix o f carboxyl modified resin mo no mer. They set by light cured resin

react ion and not acid base and rely upon wat er diffusio n int o t he set polymer which is

56

DR. PRIYA K, MDS

post ulat ed to allow a delayed acid base react ion t hat may release fluoride and ot her

remineralis ing io ns fro m aluminosilicat e glass.98 There are dual past e syst ems, which set

by dual cure and single past e syst ems t hat are light cure. They do not chemically adhere

since t hey do not contain any po lyacid but adhesio n, inst ead, is a resin t ype.53

In t he search of an ideal restorat ive mat er ial, a st udy co mpared var ious mat er ials

t hat were rout inely used, which concluded t hat co mpo mers had sig nificant ly higher

hardness and co mpress ive st rengt h t han RMGIC, but composit e had t he super ior

propert ies.99

The fluoride releasing abilit y bet ween PMCR and RMGIC concluded t hat t he

fluoride levels increased dur ing t he first t hree mont hs and lat er decreased when co mpared

to RMGIC.56 However, Ko mori100 and Karant akis37 showed t hat co mpo mer has less

fluoride release t han RMGIC and convent ional GI C fro m t he init ial per iod it self.

In order to det ermine a suit able lut ing media for ceramic restorat ion Begazo et

al101 concluded t hat sandblast ing, et ching and silanizing showed increased bond st rengt h

for RMGIC fo llowed by co nvent ional GIC but highest bond st rengt h was obt ained wit h

composit e resin.

Gladys102 has ext ensively st udied physico -mechanical charact erist ics o f new

hybr id cement wit h co nvent io nal GIC and co mposit e and inferred t hat t he bond st rengt h

in t he decreasing order as composit e fo llo wed by PMCR, RMGIC and t he least being

co nvent io nal GIC.

The lat est int roduct ion has been t he past e-past e t ype o f RMGIC, which makes

clinical hardening safe and easy and had per formed well w it hout clinical failure over a

57


21- mont h per io d103, it is easy t o handle and is more consist ent since t he need for

measur ing and mixing is eliminat ed.100

Sand blast ing has been regarded as a for m o f macro etching, which cleans and

roughens t he sur face.82 It has beco me t he preferred surface t reat ment in met al bonding

today. This procedure invo lves spraying a st ream of aluminum oxide part icles under hig h

pressure against t he met al sur face int ended for bonding. 80-100 psi o f air pressure is

required and aluminum oxide part icle o f 50�m has been found t o be most desirable for

use in sand blast ing and resu lt ing in excellent bond st rengt h.75

The failure rat es of 2% for t he co mmercially sandblast ed bands co mpares

favorably w it h t hat found by Millet et al96 who carried out t heir own sand blast ing

process.

Anot her st udy was conduct ed by M illet 54 compar ing t wo band cement s. They

concluded no significant difference bet ween RMGIC and PMCR. Debonded bracket s,

which were rebonded fo llowing sandblast ing, showed comparable st rengt h to t hat of a

new bracket .73

A half mout h clinical t rial co mpar ing non sandblast ed and sandblast ed bands by

Hodges72 had also demo nst rat ed t hat sandblast ing sig nificant ly increases bo nd st rengt h

and reduced t he clinical failure rat es.

However, in a recent clinical st udy report ed by Ozere84 on t he self-cur ing

RMGIC concluded no significant difference bet ween sandblast ed and non sandblast ed

bracket s during a 20 mo nt h observat ion per iod.

58

DR. PRIYA K, MDS

Mc Coll and Rossouw,104 conduct ed an invest igat ion to det ermine t he

relat io nship bet ween shear bond st rengt h and base sur face area for t he st andard and fo il

mesh bracket bases, also to assess t he effect of sandblast ing t he bracket s at chair side and

compared it wit h micro et ched bracket s. They fo und significant increase in shear bond

st rength associat ed w it h sand blast ing o f fo il mesh bases for all base sizes but t here was

no difference bet ween t hese t wo groups. They co ncluded t hat to maximize t he shear bond

st rengt h, t here is no need t o increase base sur face area and t hat sand blast ing t he bases

should be carr ied out rout inely just before bonding.

Sand blast ing increases t he ret ent ion by roughening t he sur face o f all met als

including st ainless st eel and as a result , increases sur face area for bot h chemical and

mechanical bo nding. It remo ves t he cont aminant s and decreases t he t hickness o f oxide

layer, leaving a more fir mly att ached layer for bonding. A t hin o xide layer is needed for

good wett ing and bonding t o t he met al. Bot h the procedure of sand blast ing whet her

carr ied out commercially or at t he chair side affects t he bond st rengt h.

Grabouski105 has po int ed out t hat among co nvent ional bracket , a newly et ched

bracket , a debonded and sandblast ed bracket t here was no significant difference bet ween

t he bond st rengt hs. Thus advocat ing in-o ffice sand blast ing.

In our st udy fo llowing sand blast ing we not ed a stat ist ically significant increase in

force value for deband ing. However, t he great est increase was seen in t he RMGIC group.

It must be not ed t hat t he process o f sand blast ing may also enhance t he chemical bonding

capabilit y o f t he cement s. Alt hough, as wit h no n sand blast ing, mechanical bonding

capabilit y is t he pr imary det er minant for increased adhesio n o f sand blast ed bands.

59


The non sandblast ed and sandblast ed bands were photo graphed using a Scanning

Elect ron Microscope (SEM) direct ed at t he lut ing sur face o f t he band. The photographs

were t aken at 20KV and a mag nificat ion o f 1000X. The SEM photograph illust rat es t he

relat ively smoot h lut ing sur face o f t he non sandblast ed bands, in co mpar iso n wit h t he

corrugat ed surface o f sandblast ed bands; t he increase in t he sur face area was seen to

enhance t he pro babilit y o f mechanical and che mical bonding t hat took place wit h t he

var ious cement s used and t hereby reducing t he failure rat es.

EFFECT OF OTHER EXPLANATORY VARIABLES

�Sand blast ing procedure has been carr ied out at 60psi as t he levels can be increased

only t o t his ext ent wit h t he in-o ffice sandblast ing.

�There could be a furt her increase in bond st rengt h if t he t eet h surfaces were et ched for

co mpo mers because t hese cement s do not cont ain any acid and ad hesio n is, inst ead a

resin t ype. The ot her lut ing agent s can be cement ed, subsequent to cond it ioning t he t eet h

sur face.

� Last ly, t his was an in vit ro st udy and would not be able to complet ely simu lat e an oral

environment where t he t eet h are const ant ly subject ed to occlusal forces.

Furt her invest igat ions int o t his field o f hybr id cement s would provide a

meaningful insight int o t hese upcoming and pro mising mat erials.

60

DR. PRIYA K, MDS

This in vit ro st udy was aimed at evaluat ing t he increase in bond st rengt h

fo llo wing sand blast ing w it h different hybr id cement s namely one RMGIC and one

PMCR and t he convent ional GIC as t he cont rol and to correlat e t he effect iveness o f t his

procedure of sand blast ing in a clinical sit uat ion fo llowing t he use o f a plain prefor med

bands and sandblast ing in o ffice.

Fort y- five ext ract ed human mo lars were used for t he st udy t hat was conduct ed at

t he Depart ment of Ort hodont ics and Dento facial Ort hopedics, M. S. Ramaiah Dent al

College. The t eet h were banded using prefor med ort hodont ic plain bands t hat were used

in it ially to det ermine t he bond st rengt h o f different hybr id cement s and t hen su bsequent ly

sandblast ing t he same bands to det ermine t he effect of t his procedure on bond st rengt h.

The resu lt s inferred t hat t here was a st at ist ically significant increase in t he bo nd

st rengt h fo llowing t he procedure of sand blast ing. It also demonst rat ed t hat RMGIC has

great er bond st rength t han t he PMCR and co nvent ional GIC. The mean values before

sandblast ing were 1.389MPa for RMGIC, 1.058MPa for co mpo mer and 0.907MPa for

t he co nvent ional GIC, where as Millet 63 has found t hat no significant difference exist ed

bet ween RMGIC and PMCR.

The mean value o f 2.149MPa for RMGI and t he va lue o f 1.518MPa for

co mpo mer and1.915MPa for convent ional GI respect ively were t abulat ed aft er

sandblast ing.

ANOVA revealed st at ist ically significant difference bet ween t he met hods and

among t he lut ing cement s.

The RMGIC lut ing cement gives ever y ind icat ion o f beco ming t he mat er ial o f

cho ice for cement at ion o f crowns, space maint ainers and ort hodont ic bands. Alt hough

61


more lo ng-t erm dat a is needed concer ning RMGIC, t hey show remarkable pro mise for

mat er ials at t his st age of development .

Wit h all t his development on RMGIC, it might be t empt ing t o conclude t hat

original self hardening GIC is obso let e. However t his is far fro m t he case. These

mat er ials t oo are indulg ing in excit ing development s o f t heir own for eg. Ket ac mo lar in

case o f crowns and br idges, which set s by neut ralizat ion react ion and has propert ies t hat

r ival or exceeds t hose of RMGIC. Sett ing is rapid, early mo ist ure sensit iv it y is

considerably reduced and so lu bilit y in oral fluids is slow.

Alo ng wit h t he increase in bond st rengt h o f RMGIC, t he fluo ride release fro m t he set

cement is also comparable w it h t hat of co nvent io nal GIC providing a similar ant i

car iogenic effect . The sett ing react ion is in it iat ed in t he po ly HEMA mat r ix o f RMGIC

by photo act ivat ion, since t he sett ing of GIC is seen t o be t he most crit ical dur ing t he first

one hour due to t he for mat ion o f a weak mat rix complex o f calcium io ns and subsequent

vu lnerabilit y to mo ist ure cont aminat io n, RMGIC has proven to be t he current chosen

mat er ial.

Wit h t he use o f pre-adjust ed edgewise syst ems, which are more popular today

wherein t he placement o f att achment is more cr it ical, a light act ivat ed GIC will st ret ch t

he luxur y and over co me t he hurdles, ort hodont ist s face wit h bonding o f bracket s to t he

post erior region also. The advent of t his mat er ial has ext ended it s use for sp lint

cement at ion and bands t hat receive a face bow.

Over all GIC are import ant mat erials for modern clinical dent ist ry. Development

of RMGIC has opened a new d imensio n in restorat ive dent ist ry as well as in

ort hodont ics.

62

DR. PRIYA K, MDS

No mat erial is per fect , but wit h current levels of int ensive research on GIC,

deficiencies t hat exist s seems t o be eliminat ed or at least reduced, result ing in an ever

improving range of mat erial o f t his t ype.

The research is be ing direct ed towards t he impro vement of RMGIC in order to

use it in t he post erior as well as ant erior segment s for bonding bracket s.

63

Create PDF files without this message by purchasing novaPDF printer (http://www.novapdf.com)

29

DR. PRIYA K, MDS

30


31

DR. PRIYA K, MDS

32


33

DR. PRIYA K, MDS

34


35

DR. PRIYA K, MDS

36


37

DR. PRIYA K, MDS

39


DR. PRIYA K, MDS

40


41

DR. PRIYA K, MDS

The st udy was conduct ed in t he Depart ment of Ort hodont ics and Dent ofacia l

Ort hopedics, M.S.R.D.C, Bangalore and HAL - Foundr y and Forge Depart ment ,

Bangalore. The st udy was conduct ed to evaluat e t he effect of in-o ffice sand blast ing on t

he ret ent ion o f ort hodont ic bands w it h t hree different lut ing cement s. The shear bond

st rengt h was t est ed on a universal t est ing machine. (TIRA). The values were recorded in

Newton and convert ed int o MPa for st at ist ical analysis (Table I).

Table I: Retentive bond strength values obtained from the study in MPa

Sl Group A Group A Group B Group B Group C Group C

No. Non- sandblast ed



Sandblast ed

1. 0.8650 1.8464 1.2431 1.9501 1.1153 1.5768 2. 0.9106 1.9499 1.4490 2.1865 1.0373 1.4916 3. 0.8265 1.8918 1.4080 2.2035 1.1466 1.6654 4. 0.9744 1.9352 1.4129 2.1557 1.0110 1.4746 5. 0.9721 1.9082 1.4265 2.1827 0.9922 1.4350 6. 0.9123 1.9048 1.4150 2.1750 1.0356 1.4834 7. 0.8662 1.8312 1.3067 2.1348 1.0856 1.5455 8. 0.8321 1.7438 1.3599 2.0672 1.1003 1.5820 9. 0.9300 1.9897 1.3331 2.1929 1.1251 1.6099 10. 0.9544 1.9762 1.4308 2.2321 0.9962 1.4456 11. 0.9076 1.9454 1.4406 2.1869 1.0360 1.4909 12. 0.9409 1.9970 1.4202 2.1607 1.0678 1.4424 13. 0.9156 1.9781 1.3877 2.1353 1.1714 1.6567 14. 0.9224 1.9434 1.4617 2.2341 1.0180 1.4487 15. 0.8714 1.8791 1.3380 2.0404 0.9314 1.4221

The dat a fro m t he st udy was subject ed to ANOVA t est.

The Mean values and St andard Deviat ions o f shear bond st rengt hs o f non

sandblast ed and sandblast ed bands are present ed in Table II.

42

Results ORTHODONTIC BANDS – INVITRO STUDY

Table II: Comparison of mean values of bond strength between non-

sandblasted and sandblasted bands, also among different luting ce ments.

Method Group N Mean Median Std Dev Minimum Maximum

GROUP A 15 0.907 0.912 0.046 0.827 0.974

GROUP B 15 1.389 1.413 0.061 1.243 1.462

Non Sandblasted Bands

GROUP C 15 1.058 1.037 0.066 0.931 1.171

GROUP A 15 1.915 1.935 0.069 1.744 1.997

GROUP B 15 2.149 2.175 0.077 1.950 2.234

Sandblasted Bands

GROUP C 15 1.518 1.491 0.082 1.422 1.665

Class Level Informatio n

Class Levels Values

Method 2 Non Sandblasted and Sandblasted

Band

Group 3 GROUP A, GROUP B & GROUP C

Number o f observatio ns 90

The result s were st at ist ically analyzed. “ANOVA” test was used for ana lyzing t he

significance bet ween t he ret ent ion of non sandblast ed and sandblast ed bands.

The result s o f analys is o f var iance in co mpar ison amo ng non sandblast ed and

sandblast ed bands showed t hat t here was st at ist ically significant difference bet ween t he

t wo met hods (Table III, Fig. 30)

The Test revealed t hat t here was Significant Mean difference in bo nd st rengt h

bet ween group A, B and C.

43

DR. PRIYA K, MDS

Group A



for t he no n sandblast ed group wit h a mean o f 0.0907 and for t he sandblast ed group

minimum being 1.744 and maximum o f 1.997 and a mean o f 1.915 (Table.IV and V,

Fig.24 and 25).

Group B



and a mean o f 1.389 for t he no n sandblast ed group and for t he sandblast ed group

minimum being 1.950 and maximum o f 2.234 wit h mean of 2.149 (Table IV and V, Fig.

26 and 27).

Group C


t han sandblast ed bands. (P<0.05). Range fro m a minimum o f 0.931to maximum o f 1.171

wit h a mean o f 1.058 for t he non sandblast ed group and for t he sandblast ed group

minimum being 1.422 and maximum o f 1.665 wit h mean of 1.518 (Table IV and V,

Fig.28 and 29).

44


Table III: Co mparison of the mean values of bond strength between non

sandblasted bands and sandblasted bands.

Methods

N

Mean

F value

P value

Non-Sandblast ed

45

1.117

Sandblast ed

45

1.860

2707.62

<0.05

S ince t here was also st at ist ically significant value exist ing amo ng t he t hree

groups, Tukey’s t est was perfor med.

Table IV: Co mparison of the mean values of bond strength among different

luting ce ments in the Non Sandblasted method.

Cement groups

N

Mean

F value

P value

Group A (Red)

Convent ional GIC

15

0.907

Group B (Yello w) RMGIC

15

1.389

Group C (Green) Compo mer

15

1.058

269.16

<0.05

45

DR. PRIYA K, MDS

Table V: Co mparison of the mean values of bond strength among different

luting cements in the Sandblasted method.

Cement groups

N

Mean

F value

P value

Group A

15

1.915

Group B

15

2.149

Group C

15

1.518

264.09

<0.05

Thus in co mpar iso n, t he sandblast ed bands showed st at ist ically higher result s t han

non sandblast ed ones. Amo ng t he groups Group B exhibit ed higher ret ent ive values

st at ist ically.

46


Ob

se

rved

Va

lue

s

Bo

nd

Str

en

gth

(M

Pa

)

0. 8

65

0. 9

10

6

0. 8

26

5 0

. 97

44

0. 9

72

1

0. 9

12

3

0. 8

66

2

0. 8

32

1

0. 9

3

0. 9

54

4

0. 9

07

6

0. 9

40

9

0. 9

15

6

0. 9

22

4

0. 8

71

4

1. 8

46

4

1. 9

49

9

1. 8

91

8

1. 9

35

2

1. 9

08

2

1. 9

04

8

1. 8

31

2

1. 7

43

8

1. 9

89

7

1. 9

76

2

1. 9

45

4

1. 9

97

1. 9

78

1

1. 9

43

4

1. 8

79

1

F ig . 2 4 : D is t r i b u t io n o f V a l u e s o f B o n d s t r e n g th a m o n g G r o u p A

2 .5

S a n d b la s t e d m e th o d

2

N o n - s a n d b la s t e d m e th o d

1 .5

1

0 .5

0

1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3

1 4 1 5

S a m p le N u m b e r

Fig. 25 : Minimum and Maximum Bond Strength values between Groups using Group A

bonding agent

2.5

1.997

2

1.7438

1.5

1 0.8265

0.9744

0.5

0

Minimum Maximum Minimum Maximum

Non-sandblasted method Sandblasted method

47

DR. PRIYA K, MDS

Ob

se

rve

d V

alu

es

B

on

d S

tre

ng

th (

M P

a)

1.2

43

1

1.4

49

1.4

08

1.4

12

9

1.4

26

5

1.4

15

1.3

067

1.3

59

9

1.3

33

1

1.4

30

8

1.4

40

6

1.4

20

2

1.3

87

7

1.4

61

7

1.3

38

1.9

50

1

2.1

86

5

2.2

03

5

2.1

55

7

2.1

82

7

2.1

75

2.1

34

8

2.0

672

2.1

92

9

2.2

32

1

2.1

86

9

2.1

60

7

2.1

35

3

2.2

34

1

2.0

404

Fig. 26: Distribution of Valu es of Bond strength among Group B

2.7 Sandblasted method

2.2


1.7

1.2

0.7

0.2

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

-0.3

Sa mple Nu mber

F i g . 2 7 : M i n i m u m a n d M a x i m u m B o n d S t r e n g t h v a l u e s b e t w e e n G r o u

p s u s in g

G r o u p B b o n d in g a g e n t

2 . 5

2 .2 3 4 1

2 1 .9 5 0 1

1 .5 1 .4 6 1 7

1 .2 4 3

1

1

0 . 5

0

M in im u m M a x im u m M in im u m M a x im u m

N o n -s a n db la s te d m e th o d S a n d b la s t e d m e t ho d

48


Ob

se

rve

d V

alu

es

B

on

d S

tren

g th

(M

Pa )

1.1

15

3

1.0

37

3 1.1

46

6

1.0

11

0.9

92

2

1.0

35

6

1.0

85

6

1.1

00

3

1.1

25

1

0.9

96

2

1.0

36

1.0

67

8 1.1

71

4

1.0

18

0.9

31

4

1.5

76

8

1.4

91

6

1.6

65

4

1.4

74

6

1.4

35

1.4

83

4

1.5

45

5

1.5

82

1.6

09

9

1.4

45

6

1.4

90

9

1.4

42

4

1.6

56

7

1.4

48

7

1.4

22

1

Fig. 28: Distribution of Values of Bond strength among Group C

2

Sandblasted method

1.8

1.6


1.4

1.2

1

0.8

0.6

0.4

0.2

0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2 3 4 5 6 7 8 9 10

11 12 13 14 15

Sample Nu mber

F i g . 2 9 : M i n i mu m a n d M a x i m u m B o n d S tr e n g th v a lu e s b e tw e e n G r o u p s u s i n g

G r o u p C b o n d i n g a g e n t

1 .8

1 . 6 6 5 4

1 .6

1 . 4

1 . 4 2 2 1

1 . 2 1 . 1 7 1 4

1

0 . 9 3 1 4

0 .8

0 .6

0 .4

0 .2

0

M i n i m u m M a x im u m M in i m u m M a x im u m

N o n - s a n d b l a s te d m e th o d S a n d b l a s te d m e t h o d

DR. PRIYA K, MDS

49


Me

an

Va

lues o

f B

on

d S

tre

ng

th (

Mp

a)

Fig. 30: Comparision of M ean values of Bond strength b et ween two methods

2.500

Non-sandblasted m ethod

Sandblasted method

2. 149

2.000

1.915

1.500

1.389

1.518

1.058

1.000 0.907

0.500

0.000 Group A Group B Group C

50

DR. PRIYA K, MDS

Int egrit y o f an ort hodont ic appliance is essent ial to t he co nt inu it y o f t reat ment

mechanics. Alt hough direct bond ing of fixed ort hodont ic appliance att achment , is a

rout ine pract ice for ant er ior t eet h, mo lars are o ft en banded because t he failure rat es t end

to be lower t han t hat of bonded attachment s.70 Improved ret ent ion is mainly due to

increase in sur face area of t he bands.

Unlike a cast crown or inlay, an ort hodont ic band is not in int imat e cont act wit h

enamel. There are areas, part icular ly around t he cervical margin, where t he band does not

cont act t he enamel sur face. Space bet ween band and enamel are filled w it h cement . Band

ret ent ion is a co mplex p heno menon and may be influenced t o a var ying ext ent by t he fit

of t he band, t he t ype o f band mat erial, band widt h, band po sit ion and cement ing

procedures.

Zinc phosphat e was in wide spread use for mo lar band ce ment at io n u nt il 1980s

but due to t he incidence o f increased so lu bilit y and enamel de mineralizat ion under loose

bands, Glass io no mer cement (GIC) has beco me a more attract ive alt ernat ive especially

due to it s propert y o f fluor ide release.3

COMPOSITION AND SETTING REACTION OF GIC

GI cement has t wo co mponent s: a powder calcium aluminum fluorosilicat e glass;

and a carbo xylic acid copolymer, which exist s eit her in dr ied for m or as hydrous so lut ion.

It capit alizes on t he carboxyl chelat ion to enamel, dent in and most met als by emp lo ying

var ious mixt ures of carbo xyl cont aining acids (po lyalkeno ic acids) react ing wit h

alumino silicat e glass. Alu mino silicat e glass fused in t he presence of fluoride fluxes result

51

Discussion ORTHODONTIC BANDS – INVITRO STUDY

in an alkaline co mpo sit io n t hat releases fluor ide io ns when react ed wit h acids. Mixing

process occurs in hydrous phase.

The fluoride co mplexes o f calc ium and aluminum react wit h carboxylic acid

copolymer. In t his acid- base react ion a po lysalt gel is for med in which t he glass part icles

are embedded. Sett ing process t akes place in t wo st eps:85

1. In t he first , rapid st ep, t he calcium io ns (which may t ake t he for m o f fluoride co mple x

io ns, CaF+) are incorporat ed bet ween t he polycarboxylic acid mo lecules.

2. In t he fo llo w ing, slower st ep, a co mplet e int er lacing occurs by t he react io n o f

aluminum io ns wit h t he carboxylic acid groups t hat have not yet react ed.

Ad hesio n probably resu lt s fro m io nic or polar mo lecular int eract ions.15 The fluid

past e wet s t he sur face and is att ached by hydrogen bo nds, which are progressively

replaced by io nic ones, as t he react ion proceeds. This is so met imes called “chemica l

adhesio n”. Alt hough a chemical react io n may be invo lved in for ming t he adhesive bo nd,

it is not ent irely correct. It is almost cert ainly t he result of secondar y fo rces o f mo lecular

att ract ion rat her t han pr imar y chemical bonds. The t erms “specific adhesio n” or a

“phys ico-chemical adhesio n” is a more accurat e t erm, which serves t o dist inguish t his t

ype o f att achment fro m mechanical ad hesio n, which relies on mechanical int er locking.

It was seen t hat a st rong polar bo nd bet ween t he toot h, cement and t he met al

restorat ion reduces micro leakage patt erns arising fro m fau lt y ce ment margins. Fluor ide

release has been measured dur ing t he GIC sett ing react ion, as well as aft er sett ing86

Add it io nal fluor ide is released when GIC is exposed to acids. However, GIC is more

prone to early mo ist ure cont aminat ion and t akes 24 hours to reach maximum st rengt h.44

52