space regain thro pr.slic.pdf

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IInterproximal enamel reduction (IER) is understoodto be the clinical act of removing part of the dental

enamel from the interproximal contact area. The aimof this reduction is to create space for orthodontictreatment and to give teeth a suitable shape when-ever problems of shape or size require attention. Inthe literature, this clinical act is normally referred to as“stripping,” although other names can be found, suchas “slandering,” “slicing,” “Hollywood trim,” “selectivegrinding,” “mesiodistal reduction,” “reapproximation,”“interproximal wear,” and “coronoplastia.”1–3

IER is a critical procedure. Therefore, planningand execution need to be carefully assessed. Thistreatment should be considered as an exact reduc-tion of interproximal enamel and not just as a simplemethod to solve problems.

HISTORHISTORY OF INTERPROXIMALY OF INTERPROXIMALENAMEL REDUCTIONENAMEL REDUCTION

Interproximal dental stripping has been used byorthodontists for many years.2,3 It was initially usedto gain space when correcting mandibular incisorcrowding or to prevent such crowding.

In 1944, Ballard4 recommended a careful strip-ping of the interproximal surfaces, mainly from theanterior segment, when a lack of balance is present.In 1954, Begg5 published his study of Stone Ageman’s dentition, where he referred to the shorteningof the dental arch over time, which occurred throughabrasion. Although the degree of shortening of thedental arch found by Begg was contested, the exis-tence of this natural reduction led to the publicationand development of the technique for interproximalenamel reduction.

In 1956, Hudson6 stated that mesiodistal reduc-tion of the mandibular incisors is only occasionallyreferred to in the literature, and listed just three pre-vious articles with direct reference to the mesiodistalreduction of mandibular incisors. In his study, Hud-son stated that stripping should be carried out withmedium and fine metallic strips, followed by finalpolishing and topical application of fluoride (to theauthor’s knowledge, this is the first description of astripping technique). He stated that it was possibleto gain 3 mm of space between mandibular canines,and presented an enamel thickness table for incisorand mandibular canine contact points.

In 1958, Bolton7 published his seminal studytitled “Disharmony in tooth size and its relation tothe analysis and treatment of malocclusion.” Thisstudy, together with Ballard’s study, supported theneed, in dental dimension discrepancy problems, touse interproximal stripping to correct problems ofdental balance.

IntInterprerprooximal Enamel Rximal Enamel ReductioneductionMartinho L. R. Moreno Pinheiro, DMD1

Aim: To describe in detail the stripping technique, or interproximal enamel reduction. Mate-

rial and Methods: Following a careful literature review, this article discusses the interproxi-mal enamel reduction techniques currently available and presents two clinical cases. Theindications, contraindications, advantages, disadvantages, and precautions of interproximalenamel reduction are discussed. Results and Conclusion: Orthodontists can effectively useinterproximal enamel reduction techniques in many aspects of clinical practice. There is noevidence that, when utilized correctly and in selected clinical situations, interproximalenamel reduction causes harm to the dental hard tissues or soft tissues. World J Orthod2002;3:223–232.

1Private Practice of Orthodontics, Portalegre, Portugal.

REPRINT REQUESTS/CORRESPONDENCEDr Martinho Pinheiro, Av. Pio XII nº2 r/c DTO, 7300-073 Portale-gre, Portugal. E-mail: [email protected]

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Pinheiro WORLD JOURNAL OF ORTHODONTICS

In 1969, Kelsten8 recommended the use ofmechanical means to carry out stripping and recom-mended prior alignment of teeth. He posited thatonly after alignment could stripping be simply andaccurately achieved. That same year, Rogers andWagner9 described an in vitro study that used teethextracted for orthodontic reasons. These extractedteeth were subjected to stripping and polishing. Itwas found that if the extracted teeth were treatedwith fluoride after stripping, they offered greaterresistance to acid attacks, mainly in the 48 to 96hours after the procedure. This scientifically justi-f ied the impor tance, already highl ighted byHudson,6 of topical fluoride application after strip-ping and polishing.

In 1971, Paskow10 published an article that rec-ommended the use of mechanical methods of IER.In 1973, Shillingbourg and Grace11 wrote an articleentitled “Thickness of enamel and dentin,” whichwas an important study on enamel and dentin thick-ness. The results of this study later served as the sci-entific basis for work on stripping and allowed theamount of enamel that could be safely removedfrom each dental face to be accurately determined.Also in the ‘70s, Peck and Peck published arti-cles12,13 on crowding of the mandibular incisors andpresented the Peck index. They advised strippingwhenever the mesiodistal dimension of themandibular incisors did not fall within acceptable fig-ures calculable from their index. They claimed thatanything in excess would constitute predispositiontoward crowding.

In 1980, Tuverson14 published “Anterior interoc-clusal relations: Part 1,” which presented a highlydetailed description of the stripping technique usinga back angle and abrasive disks. In 1981, Doris,Bernard, and Kuftinec15 concluded that one of thestrongest determining factors for dental crowding isthe dimension of teeth in the arch. In 1981, Bet-teridge16 presented the results of stripping on theanterior and inferior segment after 1 year withoutretention. She observed some relapse, but con-cluded that esthetics were clearly acceptable afterobservation by a panel of three dentists, three ortho-dontists, and three non-dentists.

In 1985, Sheridan published his article “Air-rotorstripping”17 and, in 1987, “Air-rotor strippingupdate.”18 These articles totally revolutionized thetechnique and aims of interproximal enamel reduc-tion. He recommended:

1. Use of a turbine with carbide drill, instead of dia-mond disks and strips.

2. Stripping on buccal sectors; in other words, dis-tally on canines or mesially on the second molars

on both arches. This achieves greater space andallows the preservation of incisors.

3. Use of stripping procedures to achieve space (upto 8 mm per arch) for the correction of moderatedentomaxillary disharmony, without recourse toextraction or excessive expansion.

In 1986, Zachrisson19 proposed a new directionfor stripping: improvement of the shape of the teeth,mainly for incisors and reduction of the black trian-gular space above the papilla.

INDICAINDICATIONSTIONS

The IER technique has evolved over the years; it wasfirst used only for stripping mandibular incisors, withthe aim of preventing and correcting crowding. Areasof application have continued to grow:

1. Tooth size discrepancy. In 1944, Ballard recom-mended careful stripping of the proximal surfacesof the anterior teeth when there was imbalance.4

2. Crowding of mandibular incisors. Stripping wasfirst used6 to obtain space for the correction andprevention of crowding.

3. Tooth shape and dental esthetics. Stripping canand should be used for the reshaping of enamel onsome teeth, thus contributing to an improved finish-ing of orthodontic treatment and dental esthetics.19

4. Normalization of gingival contour and eliminationof triangular spaces above the papilla, thusgreatly improving esthetics and smile.19,20

5. Moderate dentomaxillary disharmony. This is a pri-mary area of application for interproximal enamelreduction in the technique developed by Sheridanin 1985 and 1987, which allowed space to beobtained for the correction of moderate dentalcrowding; up to 8 mm per arch could be achievedwithout the need for extraction or excessiveexpansion.17,18

6. Reduced expansion and premolar extraction. 7. Camouflage of Class II and III malocclusions. The

use of mandibular stripping can be beneficial incamouflaging slight to moderate Class III condi-tions and overjet. In orthodontic treatment to cam-ouflage Class II with the extraction of two maxillarypremolars, correcting the crowding and inclinationof the mandibular incisors with stripping is anideal solution.

8. Correction of the curve of Spee. For the correctionof an exaggerated curve of Spee, it is necessary tocreate a few millimeters of space in the arch. Thiscan be achieved through moderate stripping.

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CONTRAINDICACONTRAINDICATIONSTIONS

There are several contraindications for the approxi-mation technique:

1. Severe crowding (more than 8 mm per arch). Withapplication of IER, it would be hazardous to carryout orthodontic correction. There would be risk ofexcessive loss of enamel and all of the ensuingconsequences.

2. Poor oral hygiene and/or poor periodontal envi-ronment. IER should not be used when there isactive periodontal disease or lack of dental stabil-ity. Although little scientific evidence exists linkingIER and increased dental mobility, it is prudent toavoid this technique in these situations. In addi-tion, IER should not be used when there is poororal hygiene; the orthodontist could be heldresponsible for all subsequent iatrogenic activity.Vanarsdall has called attention to the potentialdeleterious consequences.20

3. Small teeth and hypersensitivity to cold. Strippingshould not be used in these situations, as the riskof the appearance of or an increase in dental sen-sitivity is great.

4. Susceptibility to decay or multiple restorations.There is a risk of causing imbalance in unstableoral situations, although the stripping of restora-tions, instead of enamel surfaces, is an option toconsider.

5. Shape of teeth. Stripping should not be carried outon “square” teeth—teeth with straight proximal sur-faces and wide bases—as these shapes producebroad contact surfaces, and could potentially causefood impaction and reduced interseptal bone.

MAMATERIAL AND METHODSTERIAL AND METHODS

Correct IER is composed of four stages: reduction,reshaping, polishing, and protection of the enamel.There are two main techniques for IER, depending onwhether manual or mechanical methods are used.

Manual method

This method consists of metallic strips, impregnatedwith abrasive metal oxides, and numerous holdingdevices (Fig 1). This method was first described in theliterature by Hudson.6 The technique is seldom used forthree reasons: (1) it is time consuming; (2) there is tech-nical difficulty in working on posterior teeth; and (3) itcauses much deeper grooves on the abraded enamelthan those caused by mechanical instrumentation.22,23

Mechanical method

This technique greatly reduces working time. Thetools for its use mainly consist of disks for hand-pieces or contra-angles8,10,14,19 (Fig 2a), high-speedhandpieces,17 and mechanical files for contra-angleheads with shuttle movement (Figs 2b and 2c)

A new generation of perforated disks was recentlytested by Zhong and colleagues24 (Fig 3). In Zurich,van Waes and Matter have developed an “ortho-strips system” (Intensiv; GAC International, York, PA,USA) of flexible strips for contra-angle shuttle headscomposed of four small metallic strips of decreasinggrain size (Fig 4).

Techniques

Initially, stripping was done as described by Hudson,6

with metallic strips (Fig 5). Hand disk contra-angleswere introduced later, and are recommended by anumber of authors8,14,19,23 (Fig 6).

In 1985, Sheridan17 advised the use of carbidefissure drills for turbines, cutting from a horizontalposition and parallel to a 0.022-inch wire, called an“indicator wire,” which was previously positioned atthe gingival margin (Fig 7). For the shaping and fin-ishing of the tooth, Sheridan recommended a fine-grain diamond drill.18

Other authors have recommended very fine dia-mond drills, used vertically, which facilitate the shap-ing movement and reduce the risk of causing the for-mation of steps (Fig 8).

Zhong and colleagues24 have concluded thatstripping executed with perforated disks, followed bypolishing with fine and ultra-fine Sof-Lex disks (3M-Unitek, St Paul, MN, USA), proved to be efficient andprovided good results in final polishing (Fig 9).

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VOLUME 3, NUMBER 3, 2002 Pinheiro

Fig 1 Holding device with metallic stripsused for the manual method of IER.

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Fig 2 Tools for the mechanical method of IER. (a) Disks for handpieces, (b,c) mechanical files for contra-angleheads with shuttle movement.

Fig 3 Perforated disks for IER. Fig 4 The “ortho-strips system”developed by van Maes and Matter.(a) Metallic strips of decreasing grainsize for (b) contra-angle shuttle head.

Fig 5 (Left) Manual stripping withsmall metallic strips.

Fig 6 (RIght) Stripping with disks.

Fig 7 (a) Indicator wire and (b) theSheridan stripping technique.

Fig 8 Stripping technique with avery fine diamond drill, used vertically.

Fig 9 (a) Stripping with perforated disks, followed by (b) polishing withSof-Lex disks.

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The four metallic strips in the van Waes and Matterortho-strips system, with grains between 15 and 90µm for cutting and polishing, can be adapted to a 36-position shuttle head with oscillation movement of 0.8mm. They have the advantage of being flexible andadapt well to the shape and convexity of the tooth,especially at the contour of cervical area (Fig 10).

Files for use with shuttle heads are available in sev-eral different grains (15 to 125 µm) for cutting and pol-ishing, They are also practical for shaping teeth (Fig 11).

Treatment sequence

The following treatment steps are described in moredetail below.

1. Complete treatment planning, with accuratemeasurement of study casts.

2. Ensure that no contraindications to IER exist.3. Place orthodontic appliances and correct rota-

tion. 4. Place elastic or spring separators.5. Carefully do the IER (carried out sequentially).6. Shape and polish the stripped surface.7. Measure and control the obtained space.8. Check posterior anchorage.9. Reduce friction and perform the progressive dis-

talization.10. Apply fluoride.11. Align anterior teeth.12. Retain properly to maintain optimal results.

For sound practice of this technique, the first stepshould be to plan the treatment and accurately mea-sure, on the study casts, the amount of spacerequired18 for the desired correction (Fig 12). No con-traindications to stripping should exist for the patient.

A few days before stripping, separators are placedin position (Fig 13a) or, as Sheridan18 recommends,a spring is placed (Fig 13b) to separate each tooth atthe contact area. This has the advantage of allowingstripping to be carried out individually on each tooth.

However, this also necessitates the prior measure-ment of the space opened up by the elastic (orspring) for optimal reduction (Fig 13c).

Using one or more of the techniques previouslydescribed, IER and polishing are then carried out onthe mesial surface of the last tooth to be strippedand on the distal surface of the penultimate tooth.

The space obtained is measured with the instru-ment recommended by Sheridan25,26 or with cali-brated wires, as recommended by Philippe27 (Figs14a and 14b). Anchorage of the posterior teeth isthen prepared, which can be done with stops (Fig14c), bends in the arch, or through the prior fitting ofpalatal and lingual bars.

Distalization should be carried out tooth by toothto avoid any loss of space.18 The archwire shouldslide freely in the brackets, so round steel arches arerecommended (Fig 15a). Brackets with a ball hookcan also be used, which allows the fitting of a metal-lic ligature to the bracket and force application atthat point (Fig 15b).

At the end of each stripping and polishing ses-sion, a topical application of fluoride should be per-formed6,9,17,23,28 (Fig 16). Initially, Sheridan recom-mended the use of sealants,29 but he later withdrewthese recommendations because remineralizationmight spontaneously occur.22

When distalization of the tooth is finished, thewhole process is repeated in the next contiguousspace (Fig 17). When the stripping and distalizationstages are complete, a nickel-titanium or thermoac-tive arch is placed, followed by alignment of theanterior teeth.

Figures 18 and 19 illustrate, with pre- and post-treatment photographs, the results achieved withproper IER technique in two patients with Class Imalocclusion and moderate crowding.

Advantages of IER

The following are the main advantages of the IERtechnique:

Fig 11 Files for use with shuttleheads.

Fig 10 (a) Ortho-strips system technique and (b) its adaptation to theshape and convexity of the tooth.

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Fig 12 Measurement of the teethon the cast.

Fig 13 A few days before stripping (a) separators are placed in position or (b) spring is used to separate teeth, and(c) measurement of the space is obtained with the spring or separator.

Fig 14 (a) Calibrated wires, as recommended by Julien Philippe. (b) Instrument recommended by Sheridan (Rain-tree Essix, Metairie, LA, USA). (c) Anchorage of the posterior teeth with stops.

Fig 15 (a) Distalization elastic placed on bracket and (b) distalization elasticplaced on a ball hook.

Fig 16 Fluoride ready for topicalapplication.

Fig 17 Treatment progress.

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•The space obtained can be continuously monitoredto adjust it to the space needed to achieve thetreatment goals.

•Overexpansion of the dental arch is avoided.•Extraction of teeth is greatly reduced.•The need for excessive tooth movement, as well as

the possible loss of bone and of root cementum, isreduced due to the fact that the iatrogenic poten-tial is considered less than with extraction.

•Treatment time is reduced.

•The quality of treatment is significantly improved inpatients with crowding and contraindications forextraction, as in the case of closed bites.

•Esthetics are improved, as is the final health of thegingival papilla, which adapts better to a reduction ofinterdental space than to the space left by extraction.

•Treatment of adults with slight or moderate crowd-ing is possible, without the need for extraction.

•Greater posttreatment stability is possible.

Fig 18 Young adult female patient with Class I malocclusion and moderate crowding, treated with IER. (a to e)Pretreatment and (f to j) posttreatment.

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Disadvantages of IER

•It is a time-consuming treatment.

RESERRESERVVAATIONS OR POTENTIALTIONS OR POTENTIALIAIATROGENIC SEQUELAETROGENIC SEQUELAE

In 1956, Hudson already questioned whether IERcould have adverse consequences on oral health. Itis legitimate that some issues arise:

•Does stripping increase the risk of decay?•Does stripping cause periodontal damage?•How much enamel can be stripped?

A perusal of the literature offers some answers.Radlanski and colleagues30,31 demonstrated thateven with thorough polishing it was impossible tototally remove grooves left by stripping and that after1 year, such grooves are still microscopically visibleat the contact point, where there is natural abrasion.They also found that even after careful cleaning,

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Fig 19 Young adult male patient with a Class I malocclusion and moderate crowding, treated with IER. (a to e) Pre-treatment and (f to j) posttreatment.

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including flossing, bacterial plaque was evident.They concluded, however, that no study has demon-strated that this roughness suggested predispositionto decay. In 1980, Boese,32 in a 9-year retrospectivestudy, concluded that it was not possible to findadverse effects. Zachrisson,19 in 1986, consideredpolishing and treatment of the stripped surfaceunnecessary. In 1990, Crane and Sheridan,33 in aretrospective study conducted on patients who hadbeen subjected to stripping between 1985 and1988, found 4.6% of new caries lesions on strippedareas and 4.1% of new caries lesions on unstrippedareas. This difference was statistically insignificant.In 1991, El-Mangoury et al,28 in an in vivo study, con-cluded that the roughness produced by strippingdoes not increase propensity to decay, and that after9 months, the natural remineralization of thestripped area is complete. However, the applicationof fluoride is advised. In 1991, Joseph et al23 recom-mended a mixed technique of polishing with stripsand treatment with 37% phosphoric acid. This pro-vided an excellent polish, which was then followedby topical application of fluoride. It can be concludedfrom these studies that stripping itself is not a factorthat enhances the decay process.

In addition, the preponderance of evidence sug-gests that stripping does not predispose patients toperiodontal deterioration. In 1980, Boese,32 in a 9-year retrospective study carried out on patients sub-jected to stripping and fiberotomy, concluded thatthere was no significant reduction of the osseouscrest in these patients. Sadowsky and BeGole,34 in astudy conducted in 1981 comparing a group ofpatients that received orthodontic treatment duringadolescence with a control group, concluded that thistreatment did not have any effect on long-term peri-odontal health. In 1981, Årtun et al35 concluded thatthe approximation of roots through orthodontic treat-ment did not predispose patients to faster periodontaldestruction. In 1990, Crain and Sheridan,33 in a studyon premolars and molars in patients subjected tostripping, found no alterations of the osseous crestwhen comparing stripped areas to non-stripped areas.

Finally, several authors have conducted studieson the thickness of dental enamel (Fig 20, see WJOwebsite at www.quintpub.com).6,11,36 On the basis ofthese studies, several possibilities regarding theamount of enamel that can be stripped weredescribed, but it is now widely accepted that 50% ofexisting enamel is the maximum amount that can bestripped without causing risk to dental and periodon-tal health.17 In most situations, this corresponds to amaximum of 0.5 mm per dental surface or, in otherwords, 1 mm33,37 per mesial contact area of secondmolars to the distal of the canines.

ADMONITIONSADMONITIONS

•Always carry out IER with new instruments.•Carefully protect soft tissues.•Never carry out IER until dental rotation has been

corrected, so that it can be done at the correct con-tact areas.

•In cases of Class I malocclusions, without tooth sizediscrepancy, always carry out IER on both arches.

•Take into consideration that IER on anterior teethmay detract from their esthetic appearance.

•When using IER in adolescents, consider extractionof third molars, since many clinicians feel that theycould cause new crowding and need for additionaltreatment.

KEY POINTSKEY POINTS

•Carry out stripping sequentially.•Limit stripping to 0.5 mm per contact surface or, in

other words, 1 mm per mesial contact area of sec-ond molars to the distal of the canines.

•Measure space accurately.•Parallel stripped contact areas.•Shape dental surfaces to their original configura-

tion, without abraded grooves.•Carefully polish the stripped surface.•Topically apply fluoride after stripping.•Reduce, as much as possible, inadvertent loss of

space obtained, by using anchorage on posteriorteeth and reducing friction through the use ofround arch and metallic ligatures.

CONCLUSIONCONCLUSION

It has been shown that orthodontists can effectivelyuse the IER technique in many aspects of their prac-tices. There is no evidence that IER conducted withinrecognized limits and in appropriate situationscauses harm to teeth or gingiva.

REFERENCESREFERENCES

1. Fillion D. Apport de la sculpture amélaire irterproximal àl’orthodontie de l’adulte (prémiere partie). Rev Orthop DentoFacial 1992;26:279–293.

2. Ritto AK. Remodelação Dentária Interproximal. Revista deSaúde Oral 1997;2:107–118.

3. Ritto AK. Remodelação Dentária Interproximal. Revista deSaúde Oral 1998;3:33–44.

4. Ballard ML. Asymmetry in tooth size: A factor in the etiology,diagnosis, and treatment of malocclusion. Angle Orthod1944;14:67–71.

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WEB ONLWEB ONLYY

Average Greatest Least

Total Mesial Distal Total Mesial Distal Total Mesial Distal

Tooth mm mm mm

Central incisor 5.00 0.544 0.522 5.88 0.88 0.70 4.40 0.37 0.36Lateral incisor 5.83 0.650 0.683 6.50 1.05 0.98 4.95 0.47 0.50Canine 6.58 0.763 0.900 8.53 1.11 1.80 5.27 0.38 0.55

Fig 20a Hudson’s enamel thickness table.6

Central Lateral First Second FirstIncisor incisor Canine premolar premolar molar

M D M D M D M D M D M D

Maxillary 0.85 0.91 0.96 0.80 1.19 1.31 1.48 1.54 1.27 1.21 1.34 1.41Mandibular 0.75 0.77 0.75 0.77 0.88 1.16 1.41 1.51 1.38 1.80 1.46 1.47

Fig 20b Shillingbourg’s and Grace’s enamel thickness table; contact point values selected by Didier Fillion.11,22

Mesial

Distal

1.291.48

1.281.41

1.181.22

0.981.07

M2

M1

PM2

PM1

0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6

Fig 20c Stoud, English, and Buschang’s enamelthickness table.38

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