Interproximal Enamel Reduction in Orthodontics

JOURNAL CLUBBy – Parag S. Deshmukh

INTRODUCTION

Interproximal reduction is clinical procedure involving the reduction, anatomic recontouring and

protection of proximal enamel surfaces of permanent teeth. (Peck and Peck 1972)

This clinical act is normally referred to as stripping although other names can be found, such as-

slicing, Hollywood trim, selective grinding, mesiodistal reduction, reapproximation,

interproximal wear and coronoplastia.

Interproximal reduction is one of the 6 keys to eliminate lower retention by Raleigh Williams.

The use of this procedure has increased in recent years by orthodontists

With the desire to treat variety of malocclusions with less of extractions slicing provide space to

correct malocclusions

IPR is also being used to help in stabilizing the occlusion that have been produced after

orthodontic treatment

It have also been used to help retreat any relapse that may have occurred after the therapy.

INTERPROXIMAL STRIPPING

in 1944, Ballard advocated

stripping of the proximal surfaces of the mandibular anterior segment

to correct a lack of harmony in tooth

size.

(Ballard ML. Asymmetry in tooth size: A factor in the etiology, diagnosis, and treatment of malocclusion.

Angle Orthod 1944; 14: 67-71.)

A few years later, Hudson in 1956

described in detail a stripping

technique utilizing metallic strips,

followed by polishing and

fluoride preventive measures.

(Hudson AL. A study of the effects of mesio-distal reduction of mandibular anterior teeth. Am J Orthod1956; 42: 615-24.)

Peck and Peck observed that well-aligned mandibular

incisors have significantly lower

mesiodistal/ faciolingual indices

than those of crowded incisors, and

recommended stripping for

addressing tooth shape deviation.

(Peck H, Peck S. An index for assessing tooth shape deviations asapplied to the mandibular incisors. Am J Orthod 1972; 61: 384- 401.)

HISTORY:

In two consecutive studies in 1980’s by Sheridan, grinding

of interdental enamel was presented as an alternative to extraction or expansion procedures in cases of mild

to moderate crowding.

(Sheridan JJ. Air-rotor stripping. J ClinOrthod 1985; 19 :43-59.

Sheridan JJ. Air-rotor stripping update. J Clin Orthod 1987; 21:

781-88.)

Zachrisson recommended enamel reshaping to

improve anterior esthetics, i.e. to prevent or reduce

interdental gingival retraction (black triangles) that becomes evident after

alignment of crowded anterior segments

(Zachrisson BU. Interdental papilla reconstruction in adult orthodontics.

World J Orthod 2004; 5: 67-73.)

PURPOSEOrthodontics

• Increase amount of available space to eliminate tooth crowding, facilitate tooth movement and alignment

• Effectively increase leeway space to allow eruption of permanent premolars (IPR distal of lower canines)

Periodontics

• Reduce interproximal gingival retraction (reduce appearance of black triangles)

• Maintain or improve gingival papillae

ARCH PERIMETER ANLYSIS:

Calculation of space required:Mesiodistal measurement of all teeth mesial

to first molar are measured and summed up.

Calculation of space available: Arch perimeter is measured using brass wire.

Difference between these two will give arch length discrepancy.

Arch length discrepancy

Inference

O to 2.5 mm Proximal stripping can be carried out to reduce minimal tooth material excess

2.5 to 5 mm Extraction of 2nd premolar is indicated.

Greater than 5 mm Extraction of first premolar is usually indicated.

Peck and Peck index :

Proportion of mesiodistal width of each tooth to the labiolingual thickness is calculated using the formula:

Mesiodistal width X 1oo / Labiolingual width

Mean value for lower central incisor should be 88% to 92%

Mean value for lower lateral incisor should be 90% to 95%

If calculated value is greater than mean value then it indicates more mesiodistal width than labiolingual width and hence proximal stripping is indicated.

Guidelines

According to Fillion reduction, maximum of 0.3 mm for maxillary incisors, 0.2 mm for mandibular incisors and 0.6 mm for premolars

and molars.

Sheridan and Ledoux contemplated the possibility of gaining 6.4 mm of space by enamel reduction of the eight proximal surfaces of

the premolars and molars.

Stroud et al considered it possible to achieve 9.8 mm by means of the same procedure

As a rule of thumb, various author consider a reduction of the original enamel by 50% to be acceptable.

• Bellard in 1944 found a left right tooth discrepancy in one or more pairs of teeth, in his study of 500 cases. These discrepancy if not corrected, could be responsible for rotations and slipped contacts. He advocated careful stripping of proximal stripping of anterior teeth.

Tooth size discrepancy:

• Kesling in 1945 stresses the importance of favorable interarch tooth size relationship for the establishment of stable occlusion.

Inter arch size

discrepancies

Indication

• Striiping can and should be used for the reshaping of the enamel on some teeth, thus contributing to an improved finishing of orthodontic treatment and dental esthetics. Peck and Peck in 1972 indicate that a substantial relationship exists between mandibular incisor shape and the presence and absence of mandibular incisor crowding.(Peck H., Peck S. crown dimensions and mandibular incisor alignment. Angle orthodontist 1972; 42: 148-53)

Tooth shape and dental esthetics :

• in cases where tooth are crowded and larger than normal proximal stripping should be considered.

Macrodontiasize

discrepancies:

• stripping was first used to obtain space for correction and prevention of crowding. (Hudson AL Study of effects of mesio-distal reduction of mandibular anterior teeth. Am J Ortho 1956;42:615-24)

Crowding of

mandibular incisors:

• In cases where there are tooth material- arch length discrepancies not only is it necessary to reduce these discrepancies so that the teeth are aligned properly but also,so that the teeth will remain stable after orthodontic therapy and retention has been completed.

To enhance retention

and stability:

• Begg and Kesling in 1977 believed that attritional occlusion is of great benefit to man, and that proximal stripping simulates this if carried out regularly throughout life. (Begg PR, Kesling PC. Begg orthodontic theory and technique, Philadelphia: W.B. Saunder, 1977)

To simulate stone age man

proximal attrition:

Normalization of gingival contour and elimination of triangular spaces above the papilla thus greatly improving esthetic and

smile

Reduced expansion and premolar extraction

• IPR allowed space to be obtained for the correction of moderate dental crowding; up to 8 mm per arch could be achieved without the need for extraction or excessive expansion.

Moderate dentomaxillary

disharmony:

• In slight to moderate Class III condition and overjet. In orthodontic treatment to camouflage Class II with the extraction of 2 maxillary premolars, correcting the crowding and inclination of the mandibular incisors with stripping

Camouflage of Class II and

Class III malocclusions:

• It is necessary to creat a few millimeters of space in the arch.

Correcting curve of spee:

CONTRAINDICATIONS

Severe crowding ( if crowding is more than 8 mm)

Poor oral hygiene and poor oral environment

Small teeth and hypersensitivity to cold.

Small teeth.

Suceptibility to decay.

Multiple restorations.

Shape of teeth

ADVANTAGES

• Increased available space in the mandibular anterior area

• Provide broader contact point areas and thereby greater contact stability

• Increase overbite in cases where it may be beneficial

• Prevent or reduce interdental gingival retraction (reduce appearance of black triangles)

ADVANTAGES

• Maintain or improve gingival papillae

• No major changes in arch shape anticipated

• Reduce proclination of incisors

• Create exact amount of space

• Avoid dentoalveolar expansion in cases where itis contraindicated

• Reduced treatment time

DISADVANTAGES

• Increased caries risk controversial: conflicting evidence of increased caries risk (recent studies suggest that modern techniques result in enamel roughness comparable with unprepared enamel leading to no increased caries risk)

• Increased risk of periodontal disease Reduced interproximal bone widths may predispose patients with inflammation to more rapid progression of periodontal disease. However, in periodontal health, the reduced interproximal bone does not cause greater susceptibility to bone loss

DISADVANTAGES

• Inappropriate use of armamentarium may cause ledge formation which promotes adherence of plaque bacteria and induces iatrogenic damage

• Increased sensitivity due to excessive enamel reduction Treat with fluoride rinses

Instructions to patients

Informed consent needed since…

• Possibility of increased sensitivity – treat with fluoride varnish or rinse

• Irreversible changes to teeth

• Removal of sound tooth structure

Enamel Reduction Techniques in

Orthodontics: A Literature Review (The Open

Dentistry Journal, 2013, 7, 146-151)

Dr Christos Livas, Dr Albert Cornelis Jongsma and Prof.

Yijin Ren

Department of Orthodontics, University Medical Centre Groningen, University of Groningen,

Groningen, The Netherlands

INTERPROXIMAL ENAMEL REDUCTION (IER) IN SIX

STEPS:

Comprehensive planning: Study cast measurements can determine the required amount of

correction. (Zhong M, Jost-Brinkmann PG, Zellmann M, Zellmann S, Radlanski RJ. Clinical evaluation of a

new technique for interdental enamel reduction. J Orofac Orthop 2000; 61: 432-9).

• Ideally, a diagnostic set-up will supplement treatment planning

and visualize the final position and morphology of teeth.

• The use of calibrated radiographic images to determine the exact

amount of enamel that can be removed, though recommended by

various authors, might not be feasible for routine clinical

application.

STEP 1

Access to the interproximal areas:As a general rule, placement of fixed appliances and correction of rotations are recommended prior stripping. (Pinheiro MLR. Interproximal Enamel Reduction. World J Orthod 2002; 3: 223-32.)• An initial phase of levelling and aligning will establish

proper contact points.

• Visibility and mechanical access to the proximal surfaces will be further improved by means of a coil-spring, separator or wooden wedge.

STEP 2

Protection of the soft

tissues:

• An .020-.030" brass or steel indicator wire should be placed gingival to the contact point to protect interdental tissue.(Sheridan JJ. Guidelines for contemporary air-rotor stripping. J Clin Orthod2007; 41: 315-20.)

• The interference of a metal separator or a wedge will also minimize the risk for interproximal gingival lesions.

• Zachrisson endorses a four-handed approach for tongue protection when a revolving diamond disc is used without a tongue and lip retractor in place. (Zachrisson BU. Actual damage to teeth and

periodontal tissue with mesiodistal enamel reduction ("stripping"). World J Ortho 2004; 5: 178-83.)

STEP 3

Zhong et al. observed no soft tissue lesions during the stripping procedure apart from minor

papillary incisions that were not described as painful by the patients.

These authors concluded that the use of an oscillating perforated

diamond-coated disc for enamel reduction eliminates the need for

lip or cheek protectors.

Interproximal enamel removal:Mesiodistal enamel reduction is performed by either manual or mechanical methods

Step 4

The early use of handheld abrasive strips has been criticized as time consuming process, hardly applicable in the posterior teeth, and producing irreversible residual furrows on the treated surfaces.

Nowadays hand-operated strips are reserved for minor enamel removal cases and as either introductory or finishing stripping procedure.

In an update of the ARS technique, Chudasama and Sheridan suggested the use of a safe-tipped ARS bur to reduce interproximal enamel and prevent scarring of the proximal walls.

Alternatively, metallic strip systems , diamond discs or the most recently developed, segment discs adapted to a shuttle head with oscillation movement have become increasingly popular.

Segment disc systems enhance further visual and geometric access in relation to full 360° discs

Disc guards that fit over the handpiece or

contra-angle mounted diamond coated

stripping discs can be used to protect the

adjacent tooth that is not being slenderized.

Smallenamel amounts should be ground

symmetrically from all contact areas before

maximum acceptable removal per site is

reached.

The progress of interproximal reduction can

be quantified by means of commercially

available thickness/leaf gauges

• The interproximal corners are rounded with a cone-shaped triangular diamond bur with fine sand and cuttle discs. and finishing diamonds, proximal walls can be contoured to an acceptable morphology and texture. Final smoothing may be performed with even finer finishing instruments or 37% phosphoric acid gel as substantiated by Joseph and colleagues.(Joseph VP, Rossouw PE, Basson NJ. Orthodontic microabrasivereproximation. Am J Orthod

Dentofacial Orthop 1992; 102: 351-9)• However, other authors have expressed

their concerns regarding chemical stripping due to the susceptibility of the etched enamel to demineralization.

Finishing and

polishing of

enamel surfaces:

STEP 5

Furthermore, though in vitro studies have confirmed a smoother surface of proximal sealants compared with intact and stripped enamel the use of

sealants after stripping is clinically seldom possible.(Grippaudo C, Cancellieri D, Grecolini ME, Deli R. Comparison between different interdental stripping methods and evaluation of abrasive

strips: SEM analysis. Prog Orthod 2010; 11: 127-37.)

Lastly, technical difficulties in maintaining a dry working field, delay of the intraoral remineralization process, and cytoxicityeffects have been used against sealing of the proximal enamel surfaces.(Zhong M, Jost-Brinkmann PG, Zellmann M, Zellmann S, Radlanski RJ. Clinical evaluation of a

new technique for interdental enamel reduction. J Orofac Orthop 2000; 61: 432-9.)

Topical fluoride treatment: To amplify the remineralization capacity of the

abraded proximal surfaces, it is prudent to prescribe a fluoride gel after ARS.

On the other hand, Zachrisson considers unnecessary a special topical fluoride application on ground and polished tooth surfaces, and recommends it only in the presence of tooth thermal sensitivity when a twice-daily mouth rinsing with weak fluoride solution is used.

STEP 5

potential gain of 2.5 mm and 6.4 mm of space may be anticipated by enamel removal from five anterior contacts and eight buccal contacts in an arch respectively. (Sheridan JJ. Air-rotor stripping. J Clin Orthod 1985; 19 :43-59.)

Stroud et al. estimated that enamel reduction of mandibular premolars and molars may provide 9.8 mm of additional space. (Stroud JL, English J, Buschang PH. Enamel thickness of the posterior dentition: its implications for nonextractiontreatment. Angle Orthod 1998; 68: 141-6.)

How much of the interproximal enamel can be safely removed?

Following the latest update , a measured 1 mm (.5 mm per proximal surface) can be removed from the contact points of the buccal section, while stripping of the lower incisors should not exceed .75 mm at each contact point due to the thinner proximal walls. (Sheridan JJ. Guidelines for contemporary air-rotor stripping. J Clin Orthod 2007; 41: 315-20.)

It is also useful to relate the amount of enamel that can be removed to the actual shapes of teeth, restorations and crowns. The amount of gained space can be substantial in teeth with deviating morphology, and especially triangular-shaped teeth.

HOW CAN THE EFFECTS OF STRIPPING-INDUCED HEAT

BE PREVENTED?

It is known from fundamental research

that temperature increases more than 5.5°C

in the dental pulp may lead to irreversible

structural changes.(Zach L,

Cohen G. Pulp response to externally applied heat. Oral Surg Oral Med Oral Pathol 1965; 19:

515-30.)

Other studies on remodeling of teeth showed that

extensive grinding of enamel, even to the extent that dentin is exposed, can be done safely, if two prerequisites are taken care of; water and air cooling

are used and the prepared tooth surfaces are smooth and

self-cleansing.(Zachrisson BU, Mjör IA.

Remodeling of teeth by grinding. Am J

Orthod 1975; 68: 545-53.)

Sheridan suggests in particular the use of water spray with the ARS technique, proximal walls can be contoured to an acceptable morphology and texture.

Final smoothing may be performed with even finer finishing instruments or 37% phosphoric acid gel as substantiated by Joseph and colleagues.

However, other authors have expressed their concerns regarding chemical stripping due to the susceptibility of the etched enamel to demineralization.(Pinheiro MLR.

Interproximal Enamel Reduction. World J Orthod 2002; 3: 223-32.)

• It has been proven by Scanning Electron Microscopic (SEM) observations that all stripping methods dramatically affect the enamel morphology by producing rougher surfaces and furrows compared with untreated surfaces.

• Preparation with abrasive strips, tungsten carbide burs or oscillating perforated diamond coated discs, followed by finishing with Sof-Lexdiscs might result in polished enamel surfaces which are smoother than intact enamel.

• The finer the grain size used for removing enamel, the easier and less time-consuming is the subsequent finishing. (Hein C. et al.)

ARE THERE MORPHOLOGIC DIFFERENCES

BETWEEN STRIPPED AND

INTACT ENAMEL?

DOES STRIPPING INCREASE THE SUSCEPTIBILITY OF TEETH TO CARIES AND PERIODONTAL DISEASE?

The findings that the iatrogenic enamel furrows of stripping procedures may facilitate plaque accumulation, and persist one year after appliance removal.(Radlanski RJ, Jäger A, Schwestka R, Bertzbach F. Plaque

accumulation caused by interdental stripping. Am J Orthod Dentofacial Orthop 1988; 94: 416-20.)

Accidentally introduced proximal steps during grinding have been also claimed to cause future cavities.(Zachrisson BU, Mjör IA. Remodeling of teeth

by grinding. Am J Orthod 1975; 68: 545-53.)

Zachrisson and colleagues used detailed clinical and radiographic methods to evaluate soft and hard tissue complications in 61 subjects that received mesio-distal enamel reduction more than 10 years previously observed no signs of gingival recession or thinning of the labial gingivae in 93% of the patients, an insignificant 0.2 mm difference in crestal bone height between study and control group, and no reduction of mesio-distal bone widths between the roots in the mandibular anterior region.

The difference between teeth subjected to enamel reduction and control teeth was not statistically significant. It is likely that in clinical conditions remineralization from regular fluoride intake, and the natural interproximal enamel abrasion will restore the affected surfaces in the long term.

SHOULD THE CLINICIAN APPLY MEASURES TO PREVENT POSTSTRIPPING

INTERPROXIMAL ENAMEL CARIES?

Plaque control methods, topical use of concentrated fluoride mouth rinses and dentifrices, and part-time wear of a thermoformed retainer containing fluoridating solution have been recommended to avoid possible detrimental effects of enamel reduction.

Exposure of chemically stripped enamel surfaces to low concentrations of calcium-fluoride solution for 5- and 10-hour periods have been found to produce marked crystal growth in vitro. (Joseph VP, Rossouw PE, Basson NJ. Orthodontic microabrasive reproximation. Am J

Orthod Dentofacial Orthop 1992; 102: 351-9.)

CONCLUSION

The available literature indicates that reduction of interproximal enamel surfaces represents a valid therapeutic modality in the hands of the orthodontist. This technique, when carried out properly, and in specific circumstances, may assist achievement of treatment objectives without compromisingintegrity of the dental and periodontal tissues.

Enamel Surfaces Following Interproximal Reduction with

Different MethodsGholamreza Danesha; Andreas Hellakb; Carsten Lippolda; Thomas Zieburac; Edgar

Schafer. (Angle Orthodontist, Vol 77, No 6, 2007)

To assess the surface roughness resulting after application of currently available interproximal polishing.

Objective

MATERIALS AND METHODS

• Fifty-five freshly extracted, caries-free, intact human lower front teeth

that had been extracted because of periodontal involvement were

included in this study.

• The soft tissues and the calculus were removed.

• The teeth were rinsed with water and stored in distilled water.

• Five systems for enamel reduction were used on five groups containing 10 randomly chosen teeth.

The proximal surfaces of 5 teeth (control group) were not treated and

served as a control for the profilometry.

METHOD:- A preparation time of at least 5 seconds or- An interproximal enamel reduction of at least 0.25 mm.

Each tooth was ground on both interproximal enamel surfaces with additional polishing on only one side. Thus, one side of each tooth always had a rough surface while the other side’s surface was smooth, allowinga direct comparison of the results of grinding with and without additionalpolishing. Polishing was always accomplished in the limited time frame of 20seconds.

Each tooth was ground on both interproximal enamel surfaces with additional polishing on only one side. Thus, one side of each tooth always had a rough surface while the other side’s surface was smooth, allowing a direct comparison of the results of grinding with and without additional polishing.

Digital Subtraction Radiography:

To estimate the substance loss, each tooth was embedded in a rectangular

Plexiglas form filled with silicon.

A digital subtraction analysis was conducted.

(a) Radiograph of a specimen before treatment.

(b) Radiograph of a specimen after grinding/polishing.

(c) Example of a subtraction image.

Enamel Reduction (mm) After Grinding and Subsequent Polishing

PROFILOMETRY: The profilometric examination was conducted by

means of interferometry. A specimen is illuminated by white or monochromatic

light through a beam splitter.The computer analysis of the surface characteristics

permitted a numeric and graphical description of the surface.

For every surface that was analyzed by means of profilometry, the arithmetic average of the roughness of the profile’s deviance from the average (Ra) was calculated.

Profilometry :

Ra Values After Grinding and Subsequent Polishing of the Five Experimental

Groups and of the Control Teeth as Assessed by Profilometry

Scanning Electron Microscopy:

• Scanning electron microscopy (SEM) was used to

visualize the surface structure after treatment.

CONCLUSIONS:

• The use of coarse strips or burs left irregular surfaces that

cannot be smoothed effectively by subsequent polishing.

• Automatic oscillating systems presented by Profin, Ortho-Strips, and O-Drive D30 attained the best results.

Temperature Rise in the Pulp Chamber during Different Stripping Procedures - An In Vitro StudyAsli Baysala; Tancan Uysalb; Serdar UsumezcAngle Orthodontist, Vol 77, No 3, 2007

AIM:To measure the temperature changes in the pulpal chamber during different stripping procedures without any type of coolant.

MATERIAL AND METHODS:

RESULTS:

CONCLUSIONS

• Mean temperature changes exceeded the critical level of 5.5C only when the incisor teeth were stripped with a tungsten carbide bur with a high speed hand piece. A metal strip used on premolar teeth seems to be the safest procedure for thermal changes in the pulp chamber.

• There were also individual samples with critical temperature increases almost in all other test groups. This finding calls for caution during stripping of premolars and canines by other methods as well.

• Stripping procedure done with a tungsten carbide bur showed greater temperature rise among all the procedures.

• Clinicians must be aware of the detrimental effect of heat during stripping, and air cooling should be preferred because of greater visibility than with air water sprays.

CONCLUSION

Interproximal enamel reduction has been suggested as apreventive and therapeutic measure.

It is a valuable clinical technique that increases theorthodontic armamentarium.

To eliminate the disadvantages that have been described, testing and development of various techniques are imperative to ensure that the procedure yields a smooth enamel surface and not other significant problems arising from the procedure.

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