REVIEW
Stomatologija, Baltic Dental and Maxillofacial Journal, 16: 19-24, 2014

Interproximal enamel reduction as a part of orthodontic
treatment
Egle Lapenaite, Kristina Lopatiene

SUMMARY
Objective. Interproximal enamel reduction is a part of orthodontic treatment for gaining amodest amount of space in the treatment of crowding. Today interproximal enamel reduction has
become a viable alternative to the extraction of permanent teeth, and helps to adjust the Bolton
Index discrepancy. The aim of the study is to evaluate various interproximal enamel reduction techniques, its indications, contraindications and complications presented in recent scientific studies.
Material and methods. Papers published in English language between 2003 and 2012 weresearched in PubMed, ScienceDirect and The Cochrane Library databases, as well as the Web
search Google Scholar. Initial searches were made to find peer-reviewed systematic reviews,
meta-analyses, literature reviews, clinical trials, which analysed at least one interproximal enamel
reduction method. 31 published data fulfilled the inclusion criteria.
Results. According to the study, abrasive metal strips, diamond-coated stripping disks, andair-rotor stripping are the main interproximal enamel reduction techniques. Indications for use are
mild or moderate crowding in dental arches, Bolton Index discrepancy, changes in tooth shapeand dental esthetics within the enamel, enhancement of retention and stability after orthodontic
treatment, normalization of gingival contour, elimination of black gingival triangles, and correction of the Curve of Spee. Complications of interproximal enamel reduction are hypersensitivity,
irreversible damage of dental pulp, increased formation of plaque, the risk of caries in the stripped
enamel areas and periodontal diseases.
Conclusion. Interproximal enamel reduction is an important part of orthodontic treatment for
gaining space in the dental arch, and for the correction of the Bolton index discrepancy.
Key words: interdental stripping, interproximal enamel reduction, mesiodistal reduction,
reproximation, air-rotor stripping.

INTRODUCTION

Address correspondence to Dr. Kristina Lopatiene, Clinic ofOrthodontics, Lithuanian University of Health Sciences, LuksosDaumanto str. 6, LT-50106, Kaunas, Lithuania.
E-mail address: klopatiene@zebra.lt

prevalence for the anterior region. There are several
methods of relieving dental crowding - transverse
arch expansion, proclination of the anterior teeth,
distalization of the teeth in the arch, extraction of
the tooth, or interproximal enamel reduction. The
amount of crowding, facial profile, and patients’ age
determine the choice of the treatment strategy. Since
1944, when Ballard first used interproximal enamel
reduction for the anterior segment (1), there havebeen many different techniques created for gaining
space in the dental arch: Hudson (1956), Paskow(1971), Peck and Peck (1972), Sheridan air-rotor
stripping (ARS) (1985), and Zachrisson’s method(1986). Interproximal enamel reduction (IER) isa clinical procedure involving the reduction, anatomic re-contouring, and protection of interproximal
enamel surfaces of permanent teeth. For patientswith mild or moderate crowding (4-8 mm), this is

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19

The main goals of orthodontic treatment areto create the best balance among occlusal relationships, dental and facial esthetics, and long-term
treatment stability. Reaching these ideals is difficult
in many patients because the excess tooth structuresoften interfere with the correct alignment of theteeth in the dental arch. Dental crowding is one of
the most common findings in orthodontic patients.
Many cases of dental crowding show a higher*

Clinic of Orthodontics, Academy of Medicine, Lithuanian
University of Health Sciences, Kaunas,
Lithuania

Egle Lapenaite* – D.D.S.
Kristina Lopatiene* – D.D.S., PhD, assoc. prof.

Egle Lapenaite, Kristina Lopatiene
an alternative to dental extraction. However, it isirreversible (2), and therefore careful examination
before the procedure is mandatory. IER cannot be
considered as an independent treatment, but rather
only as a part of orthodontic treatment (3-5). The
aim of the study is to evaluate various interproximal enamel reduction techniques, its indications,contraindications and complications presented inrecent scientific studies.
MATERIAL AND METHODS
A systematic literature review was carried out
to identify, appraise, select and synthesize all highquality relevant studies reporting data on interproximal enamel reduction. Initial searches were carriedout on these databases: PubMed, ScienceDirect and
The Cochrane Library, as well as the Web search
Google Scholar, to find systematic reviews, metaanalyses, literature reviews, randomized controlled
trials and clinical trials. The following MeSH terms
or/and word combinations were used: “interdental
stripping”, “interproximal enamel reduction”, “mesiodistal reduction”, “reproximation”, and “air-rotor
stripping”. It was found 3630 articles during theinitial searches. Irrelevant articles were discardedon the basis of the title, abstract and the original
language (only English language was acceptable).
Articles were included in the study if they compiled
with the following inclusion criteria:• Papers published between 2003 and 2012.
IER articles were searched up to 10 years old, because it was insufficient data following the 5 year
old criteria.
• Peer-reviewed systematic reviews, metaanalyses, literature reviews, clinical trials, whichanalysed at least one IER method.
• Clinical trials including more than 40 patients (or extracted teeth).
• Human subjects.
• Extracted teeth.
Exclusion criteria. From the titles and abstracts
derived from searches, studies were excluded if they
were non peer-reviewed publications, case reports
or clinical trials including less than 40 patients (orextracted teeth), but we read them to identify any
potential studies.
Full texts of the selected articles were independently analyzed by two authors. In reading thearticles, we checked the reference lists to identify
any other articles that may have been relevant to theresearch question. After removing duplicates andnon-english articles, 31 published data fulfilled theinclusion criteria.

20

REVIEWRESULTSIER is a common clinical procedure in orthodontic therapy for gaining a modest amount of
space and has become a viable alternative to theextraction of permanent teeth in the treatment ofcrowding.
Indications for interproximal enamel reduction
The main indications for IER in the treatment of
adults are crowding (1, 4-13), when the lack of spacein the dental arch is 4 to 8 mm (2, 6, 8, 14), Bolton
Index discrepancy (2, 4-9, 12, 14-16), changes in
tooth shape and dental esthetics within the enamel(17), the ability to safely obtain sufficient space for
tooth movement without the need for extractions (2,6, 9, 10, 16, 18, 19), macrodontia (4, 6), enhancement of retention and stability after orthodontic
treatment (5, 6, 8-10, 12, 16, 17), normalization of
gingival contour and elimination of black gingival
triangles (2, 4-6, 10, 15, 20, 21), and correction of
the Curve of Spee (6, 8). IER should be carried out
only in patients with a low risk for caries and goodoral hygiene (2, 6, 10) to avoid increased susceptibility to caries. After creating proper interdental
contacts, the risk of tooth mobility or loss of alveolarbone or root cement is decreased. Lastly, one of theadvantages of IER is short performance time (2).
The most recent methods of interproximal
enamel reduction
Before performing IER it is important to evaluate how much of enamel can be reduced. This canbe made by projecting a line from the cervical line
vertically to the occlusal plane because dentin is
projected in a straight line from the cervical line
(6). Hudson, Gillings and Buonocore, and Shillingburg and Grace in Fillion in their studies showedthat enamel thickness is less than 1 mm, althoughstarting with the distal surface of the canine, thethickness is greater (2). Also, these studies revealed
that the enamel is slightly thinner in the distal thanin the mesial surfaces, and there is no relationshipbetween dental shape and enamel thickness (19).
Another way of measuring enamel thickness is using
special gauges, up to the accuracy of one-tenth of amillimeter (14). Only knowing the thickness of theinterdental enamel, an orthodontist can decide howmuch of it can be removed. Fillion recommends
never to remove more than 0.3 mm of the enamel
from the upper incisors, 0.6 mm – from the upper
posterior teeth, 0.2 mm – from the lower incisors,and 0.6 mm – from the mesial surface of the lower
posterior teeth (2). Chudasama and Sheridan claim

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REVIEW
that interdental enamel is thinner on the upper lateralincisors and lower incisors, and therefore only 0.5mm should be removed from these contact points(14). Sheridan and Ledoux claim that 6.4 mm ofspace can be gained by interproximal enamel reduction of eight proximal surfaces of the premolars
and molars (22). Stroud et al. considered that it ispossible to achieve 9.8 mm by applying the sameprocedure.
First of all, before the IER procedure, rotatedteeth must be fully aligned (2, 3, 23). It is after leveling and aligning the teeth or in the finishing stage
that it becomes clear whether correct occlusion canbe achieved or not (2). After the alignment, separators or a single-sided diamond-coated disk should
be used to make space between the teeth, which
improves visibility and access to the contact point(24). Not all the teeth should be stripped during asingle appointment (2). IER is performed with water or air cooling. During the IER, the anatomy of
the teeth is changed, and thus it is very importantto place the contact point between the teeth in thecorrect anatomical location, and to restore tooth
contours to the original form to the greatest possible
extent. After the IER, the enamel must be polishedusing finishing disks or strips (1, 2, 4, 6, 14, 20,
22, 23, 25, 26), and a fluoride solution should beprescribed (27). Research indicates that fl uoride

Egle Lapenaite, Kristina Lopatiene
increases remineralization of the abraded enamelsurfaces (2, 4-6, 9, 10, 14, 23, 28).
When choosing materials for IER, it is important to decide what instruments and soft tissue
guards are going to be used. IER materials are divided into manual and rotary instruments (2). Eachof them has advantages and disadvantages (Table 1).
Currently, there are 3 most common IER techniques (1, 4, 5, 9, 25):
1. The air-rotor stripping technique with finetungsten-carbide or diamond burs and diamondcoated strips;
2. Hand-piece or contra-angle-mounted diamond-coated disks;
3. Handheld or motor-driven abrasive metal
strips.
The technique of IER depends on the severity of crowding and the segments of the teeth. A
metal abrasive strip is a manual instrument foranterior teeth enamel reduction. The strip can beused in an operator’s hand, the Mathew hemostat,or in special strip holder (7, 8). Diamond disks areabrasive diamond-coated disks available in varying
thicknesses and grits, similar to strips. They can besingle- or double-sided, and can be used in a handpiece or in accordance with the method proposed by
Tuverson (2) (Figure 1). The third most popular IER
technique is air-rotor stripping (ARS). ARS was first

Table 1. Comparison of interproximal stripping techniques
Instruments
Manual/Rotary Advantages
used for IER
instruments
Thin metal strip Manual
Can be used when the teeth arewith an abrasive
so rotated that a disk is not apmaterial
propriate.
Can be used for re-contouring
teeth after IER.
Diamond discs
Rotary instru- The smoothest enamel surface is
mentachieved when using with polishing after IER.

Disadvantages
Impractical, unproductive, and time-consumingwhen used for buccal teeth.
Leaves bits of the strip lodged between the teeth.

Dangerous using on a high speed rotating instrument in close proximity to a patient’s tongue,
cheeks and lips.
Using a disc guard to the hand piece to guard against
the possibility of cutting into soft tissues reduces
visibility.
Unpredictable results.
Leaves deep cuts on the enamel.
Burs
Rotary instru- Have deactivated points that will Leave the roughest enamel surface after IER comment
not create ridges in the proximal pared to diamond discs and metal strips.
enamel.
Diamond and carbide burs do not provide enoughPainless and precise.
flexibility.
Ortho strip sys- Manual
No risk of cutting into the soft Longer procedure time compared to ARS.
temtissue.
Enamel surface is smoother thanafter ARS.
Predictable results. One sidecoated only to protect the adjacent
tooth.

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Egle Lapenaite, Kristina Lopatiene

REVIEW

Fig. 1. Separator and air cooling during interproximal
enamel reduction with the modified Tuverson technique,using a diamond disk in 4-handed approach [5].

Fig. 2. Bur with a “deactivated” point [2]described more than 20 years ago by Sheridan as analternative to extraction or expansion in borderline
cases (14, 28). It generates space primarily in buccal
segments. Using the ARS technique, one can easily
create as much space as needed, and thus there isno need to close the gaps between the teeth - which
always appear after tooth extraction. The applicationof extraction or expansion is difficult when treating
patients who more and more often choose clear plastic appliances such as Invisalign. An alternative tothe treatment of mild-to-moderate crowding is ARS(23, 29). When applying ARS, the recommendation
is to use burs with safety-tipped non-cutting areas
to prevent furrows of the proximal walls, which canoccur when using conventional burs with squaredoff tips (2) (Figure 2). “Intensive Ortho-Strips” is
one more method of IER, which is currently gaining
in popularity. It is used as an alternative to ARS.
Ortho-strips are thin, semi-flexible strips used in a
special holder (Figure 3). Intensive Proxo shapes are
flexible thinner blades that can remove very small
amounts of the intermolar enamel to provide banding space if separation has not been effective (14).
This technology takes more time than ARS, but theresults are more predictable, and the enamel surface
will be smoother than that achieved when using burs

(22). To protect the interdental tissues during IER, arubber dam (6), a disk guard, an indicator wire (14),or wooden wedges should be used (2).
Contraindications for interproximal enamel
reduction
Contraindications for IER are the following:
crowding more than 8 mm per arch (4, 6), poor oral
hygiene, active periodontal diseases (4, 6), enamelhypoplasia (19), hypersensitivity to cold (4, 6), highcaries index, and multiple restorations – because
there is a risk of causing imbalance in an unstableoral situation (the treatment outcomes and possible complications are difficult to predict) (6-8);
rectangular-shaped front teeth (4, 6, 19) – because
it is difficult to create appropriate contact points(7); round-shaped premolars (4); and young patientswith large pulp chambers (7, 8, 19). If the technique
is utilized correctly, there is no evidence that it canbe harmful to the hard tissues or soft tissues of theteeth (4, 6).
Complications of interproximal enamel
reduction
Excessive IER can lead to hypersensitivity (7,8), irreversible damage of the dental pulp (10, 11),

Table 2. Complications of interproximal stripping in vivo
Authors of the article
Number of patients
Zachrisson BU, Minster L, 43
Ogaard B, Birkhed D (2011) [4]Complications
2.5% of new caries lesions (all grade 1) were found during
clinical and radiographic assessments of 278 mesial or distal
surfaces following enamel reduction. These lesions were
found in 3 of 43 patients.
Kanoupakis PM, Peneva MD, 53 patients studied after 18- 4.7% of stripped surfaces registered via DIAGOdent showed
Moutaftchiev VY (2011) [10] 24 months following IER initial enamel change after interproximal enamel reduction.
Zachrisson BU, Nyoygaard L, 61
One patient had generally sensitive teeth, and 1 complained
Mobarak K (2007) [5]of increased sensitivity of the mandibular incisors.
Jarjoura K, Gagnon G, Nieberg 40 patients studied after 1-6 3 of 376 surfaces after IER had new interproximal lesions.
L (2006) [28]years following IER

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REVIEW

Fig. 3. “Ortho-strip” with a special holder

increased formation of plaque (4, 5, 7, 15, 22), caries (7, 8, 15), and the risk of periodontal diseases
in the stripped enamel areas (Table 2).
Hypersensitivity to temperature changes depends on the age of the patient (6-8), the severityof crowding (6 ,8 ,15), pathological tooth wear(8), hypersensitivity before treatment (6), and theamount of the removed enamel (14, 15, 23). Iatrogenic injuries to the proximal enamel surface canbe predisposing factors for periodontal diseases andcaries (30) because interdental enamel becomes
more sensitive to demineralization. The risk of irreversible pulp damage is the highest when a tungsten
carbide bur is used for IER for the lower incisors(30). Trauma to the pulp and dentin results from therevolutions per minute, bur design, and the type of
coolant used during IER (30). Air or water spray
are the most effective cooling techniques. They
limit temperature elevation in the pulp chamber(30). After IER, many more furrows are left on theinterdental enamel - even after polishing (25), andtherefore plaque accumulation is more intensive (2).
After IER, patients have to follow a good oral hygiene regimen, and to undergo regular prophylactic
checkups for caries. The lowest amount of plaqueand the smoothest enamel surface were achieved

Egle Lapenaite, Kristina Lopatiene
when the enamel was stripped by a diamond-coateddisk followed by polishing with the Sof-lex (3M
ESPE), while the roughest enamel surface was observed after chemical stripping and ARS without
polishing (1, 31). After IER, there was a minimal
detection of new carious lesions in the interdental enamel (4, 5, 10, 15, 28). Studies have shownthat hard and soft tissues of the teeth can adapt tochanges made during the IER procedure without
unfavorable consequences; moreover, the stripped
enamel surface is more resistant to caries than intact
enamel is (14, 23). Crain and Sheridan (15), andZachrisson, Nyoygaard and Mobarak (5) deny therisk of periodontal diseases after IER. Frindel (2)claims that periodontal diseases might be causedby damage to the cemento-enamel junction during
IER in a non-triangular-shaped tooth. Moreover,Fillion concluded that “the removal of interproximal
enamel has no negative effect on the periodontium
and it might, in fact, have the beneficial effect, undercertain conditions, of improving the resistance ofbone to disease” (2).
CONCLUSIONS
1. Interproximal enamel reduction is a part oforthodontic treatment for gaining a modest amountof space and adjusting the Bolton Index discrepancy,
and is a viable alternative to the extraction of permanent teeth. The main interproximal enamel reduction
techniques are abrasive metal strips, diamond-coateddisks, and air-rotor stripping.
2. Indications for interproximal enamel reduction are mild or moderate crowding in dental arches,
the Bolton Index discrepancy, changes in tooth shapeand dental esthetics within the enamel, enhancementof retention and stability after orthodontic treatment,
normalization of gingival contour, elimination of
black gingival triangles, and correction of the Curveof Spee.
3. Possible complications of interproximal
enamel reduction are hypersensitivity, irreversible
damage to the dental pulp, increased formation ofplaque, the risk of caries in the stripped enamel areasand periodontal diseases.

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Accepted for publishing: 21 03 201424

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