IER, or interproximal enamel reduction, involves reducing the mesial-distal width of teeth by removing interproximal enamel in controlled increments. It is used for several orthodontic purposes, including improving microaesthetics and smile appearance, correcting dental midlines, creating additional space, addressing Bolton's discrepancies, and as an adjunct to clear aligner treatment. IER can also be performed prior to taking impressions for retainers to address minor crowding or relapses. Long-term, IER may assist with post-treatment stability by reproximating teeth to minimize future crowding as the arch size decreases.

1. Interproximal Enamel
Reduction
Mohammed Almuzian

2. Page 2
Table of Contents
1 Introduction. ................................................................................................................................... 3
2 Definition........................................................................................................................................ 3
3 What is IER used for?....................................................................................................................... 3
3.1 Improvement of microaesthetics and smile appearance ........................................................... 3
3.2 Correction of dental midlines.................................................................................................. 4
3.3 Retraction of upper anteriors where there is lack of overjet and overbite .................................. 5
3.4 Providing additional space requirements ................................................................................. 5
3.5 Bolton’s discrepancies ............................................................................................................ 5
3.6 As an adjunct to clear aligner treatment for space gain in non-extraction cases, minor crowding
and rotations ...................................................................................................................................... 6
3.7 IER & retainers for mild relapse or as adjunct to finishing.......................................................... 6
3.8 Reproximation to assist in post-treatment stability................................................................... 7
3.9 IER in deciduous teeth ............................................................................................................ 8
4 Methods of IER................................................................................................................................ 8
4.1 Enamel assessment ................................................................................................................ 8
4.2 Air rotor stripping................................................................................................................... 9
4.3 Diamond Coated Stripping Discs in Handpiece/Contra-angle....................................................11
4.4 Handheld or motor-driven abrasive strips...............................................................................12
4.4.1 Handheld..........................................................................................................................12
4.4.2 Reciprocating saws............................................................................................................12
4.5 Post IER desensitising agents..................................................................................................13
5 Long term effects of IER..................................................................................................................14
5.1 IER & periodontal disease/caries ............................................................................................14
5.2 IER and pulp damage .............................................................................................................15
6 References:....................................................................................................................................16

3. Page 3
1 Introduction.
Interproximalenamel reduction(“IER”or“IPR”) is a useful tool forspace creation,achievingideal aesthetics
for tooth size discrepancies (Bolton’s) for maxillary to mandibular dental arch compatibility in Class I
occlusion and interdigitation of teeth during orthodontic finishing.
IER can be used as an option where extractions or overexpansion in non-extractioncases are unwanted.It
can assist with increasing treatment efficiency, conservation of transverse arch widths and ideal incisor
inclinations. IER is also useful in preventionof gingival papilla retraction commonly known as the “black
triangles” of particular relevance to adult patients.2
2 Definition
Interproximal enamel reduction has many aliases such as interdental “stripping”, proximal reduction,
reproximation, enamoplasty, keystoning, enamel approximation and slenderising3-5
_ENREF_3. IER is the
reductionof MDwidthof teethbyremovalof interproximal enamelincontrolledincrements5, 6
.Peck&Peck3
use the term reproximation as it is “the act of ‘redoing’ the approximal surfaces”. They define tooth
reproximation as involving the reduction, anatomic recontouring and protection of the mesial and or distal
enamel surfaces of a permanent tooth (where protection refers to the post procedural topical cariostatic
agents)3
.IERhowevercanbe performedindeciduousandpermanentteeth. KeystoningreferstoobliqueIER
of the lower incisors to “lock” them together to prevent rotational relapse5
.
3 What is IER used for?
3.1 Improvement of microaesthetics and smile appearance
Sarver (2011) describes the importance of including tooth shape and form assessment in the diagnosis and
treatment of orthodontic problems and how enamoplasty is a key component to achieving ideal
microaesthetic characteristics in orthodontic finishing1
. Microaesthetics refers to tooth morphology, ideal
ratios for dimensions, shape and contour, contacts, connectors embrasures, gingival margin form etc.
Enamoplasty can be used to an advantage when one understands the principles of ideal tooth shape and
morphology.
Figure 1: Tooth microaesthetics1, 7
Contact points are where the teeth touch and the connector is defined as the interdental contact area 8
.
‘Black triangles’ or open gingival embrasures is a lack of interdental papilla 9
. The papilla height is 49% of
crown height and contact point to incisal edge is 51%. Prevalence in treated adolescents is 42% 10
and in
treated adults approximately 38%11
. Possible contributing factors include contact points located incisally,
interdentalpapillaandalveolarboneheightloss(e.g.relatedtoperiodontaldisease),triangularcrownshape,
divergent roots and severely maligned incisors. However, rather than crowding it is more to do with

4. Page 4
undetectedincisal attritionleadingtoincorrect bracket positioning11
.The presence of interproximal papilla
isshowntobe relatedtothe distance fromthe contactpointtothe alveolarcrest.A distance 5mmresulted
in 98% presence of papilla, 6mm resulted in 56% papilla presence and >7mm resulted in 27% papilla
presence12
. Thus IER may be used to move incisal contact points to a better position for correct tooth
proportions and improved interdental papilla.
Ensure thatthe teethare well alignedpriortoreshapingasrotationscanconceal the true height:widthratio.
Sarver lists the steps as follows1
:
1. Establish ideal root divergence13
2. Establish Height
The gingival margins should be corrected (with confirmation of
periodontal probing) whether gingivectomy is required to correct
the tooth height
3. Address Width
Aftergingival marginhealingtofinal position,the widthof the teeth
can be reducedwithafine carbide bur(withrounded“safe tip”that
avoids gouging a ledge) first recontouring the connectors in short
vertical motion.
4. Check Connector Length
Squeeze the teeth together to show any interferences and contact
length, adjust accordingly.
5. Round Line Angles
Once the carbide burhasclearedfromLa-Pa/Li,use discsorhandheld
strips (better suited for interpoximal polishing) or cone-shaped
diamond and follow the connector to round the line angles.
6. Close Space From IER
Powerchainoverthe fixedappliancescanbe usedtoclose the space.
7. Create & Refine Embrasures
Usingthe cone shapeddiamondasabove refine emabrasuresandline
angles once spaces closed.
8. Polish
A carbide long flame followedbyrubberpolishingtipisusedto finish
and polish the enamel.
It is thismicroaestheticfeature of IER that may initiallynotseema significant
complimentaryorthodonticfinishingtool,butinfactcantransformacase that
may look average to one with optimal aesthetic and finishing outcomes.
3.2 Correction of dental midlines
IER can assist in correction of midlines to establish symmetry of the anterior
dentition and achievement of perfect Class I canine relationship.
Achievingacoincident dentalmidline tothe true vertical (facialmidline)allows
any deviation <4mm to be unnoticeable14
. When midlines deviate from the
true vertical,thendentalmidlinediscrepancies >2mmare noticed. Thusdental
midline discrepanciesof 2-4mmmay be correctedwithIER ratherthan having
to resort to extraction (>4mm deviation).
Figure 2: Steps to correct microaesthetics1

5. Page 5
3.3 Retraction of upper anteriors where there is lack of overjet and overbite
IER can assistinmore favourableoverbiteandoverjetresultinginimprovedanteriorfunctionandamutually
protectedocclusion15
.IERcan assistinretractionof upper incisorswhenthere isnot enoughoverjetforthe
retraction to occur, thus via lower incisor IER this can create the overjet required for further upper incisor
retraction.There isa positivecorrelationbetweenanincrease inoverbite withincreaseof IER16
.Sometimes,
the occlusion may provide “Class I” relationships but with the
face the aesthetics don’t appear correct. Sarver mentions the
importance of the ¾ profile smile photo as this can identify
smile aestheticsandincisorproclination.If the incisorsappear
overproclined with no spaces remaining and retraction is
required but there is no overjet for this i.e. the lower incisors
are contacting the marginal ridges and cingulum of the upper
incisors,IERin the upperandlowerwill assistinattainingideal
incisorangulations13
.Inadditionduringspace closure afterIER
with powerchain, stainless steel round wire can be used to
allow retroclination of the incisors with some extrusion for
improved tooth display on smiling, increasing a minimal
overbite and for consonance to the lower lip.
Figure 3: Space closure with power chain on round wire13
3.4 Providing additional space requirements
IER can also be used as an adjunctive tool to proclination, expansion, extraction, distallisation and use of
Leeway space for space creation.
Sheridan uses 50% of interproximal enamel reduction as a guide from other references16, 17
and quantifies
this as18
:
Posterior segment IER available: 0.8mm/contact x 8 Buccal contacts = 6.4mm space
Anterior segment IER available: 0.5mm/contact x 5 anterior contacts = 2.5mm space
Total space available from conservative IER = 8.9mm.
More conservative amounts include recommendations of <4mm thus in cases with mild crowding where
extractionsare unwarrantedIERcanassistincorrecting slightarchlengthdiscrepanciesandreduce the need
for extractions or canine expansion15, 19
.
With large ranges of enamel reduction reportedin the literature, Zachrisson et al2
finds mm values useless
clinically due to the wide variation in enamel morphology and thickness for each tooth. Clinically relevant
judgementsinvolve removingenamel conformingtothe shape of the teeth15
.Thusthose teeththatdeviate
from the norm may have more enamel available for removal compared to “screw-driver” shaped teeth,
round premolars and incisors with parallel M-D surfaces which may be non-ideal candidates for IER.
3.5 Bolton’s discrepancies
IER is useful for achieving ideal aesthetics for tooth size (MD) discrepancies (Bolton’s) for maxillary to
mandibular dental arch compatibility in Class I occlusion and interdigitation of teeth during orthodontic
finishing. There may be a maxillary excess +/ mandibular deficiency, maxillary deficiency +/ mandibular
excess.ItiscommonfororthodonticpatientstoexhibitaBolton’stoothsize discrepancy.A Bolton’sanalysis
(deviations from an ideal anterior ratio 77.2%; posterior ratio 91.3%) would identify this prior to starting
treatment so that plans are in place for final modifications. Mandibular incisor IER will affect maxillary
anteriortooth size relationships,howeveritisoftenrequiredincaseswithunfavourablylarge lowerincisor

6. Page 6
MD/FL ratios with Bolton’s discrepancies involving anterior mandibular excess16
. IER can correct Bolton’s
discrepancies and allow for well aligned and ideally occluding teeth.4, 20
3.6 As an adjunct to clear aligner treatment for space gain in non-extraction cases, minor
crowding and rotations
IER isusedmore frequentlyduringclearalignertreatmentthanfixedappliances.Inmildrelapsecaseswhere
space is required,technicianswouldrecommendIERtoassistalignmentastheywere instructedtomaintain
lowerintercanine widthandnotto flare the lowerincisors6
.“Virtual collisions”where the setupcausesone
tooth’sinterproximal surface tovirtuallypassthroughtheadjacenttooth’sinterproximalsurfacewasanother
reasonforIERso thatdesiredtoothmovementcouldoccurwithoutphysical interference.Collisions<0.5mm
are consideredinsignificantasthe aligner“stretches”thisamount,howeverif there are multiple collisions,
although align would recognise this as insignificant this could be clinically significant as the tooth mass is
greaterthan the space allowedforthe alignerandteethwill be intrudedtoreduce arch lengthoftenat the
last molar. 6
The clinician should choose the best IER option for the patient as the options available are
“primarily”, “if needed” and “none”. “If needed” may not be the best as it gives the technician freedomto
control the amount of IER, thus thisshouldonlybe selectedif the orthodontistgivesspecificinstructionson
the conditions IER is allowed. You can also request “no collisions” to ensure there are no insignificant
collisions so that treatment imitates fixed appliance treatment6
.
3.7 IER & retainers for mild relapse or as adjunct to finishing
Custom-made positioners can correct minor corrections in tooth position and occlusal
relationship.Positioners are made on articulatedmodels where the teethare sectioned,
alignedandwaxedintoideal and elastomericorrubbermaterial is contoured around the
teeth and the coronal portion of the gingiva.
Whendebanding,IERcan be performedpriortotakingan impressionforapositioner(for
minimal crowding),ordocumentthe precise amountof IERforthe techniciantocomplete
on the set-up and clinically repeat when inserting positioner.21
Positioners are worn full
time forthe first2 days,followedby4hrs/dayplusnightly.Patientsshouldbite andclench
cyclicallyfor20sec followedby20sec restintervalsduringthe first4hrs to enable desired
toothmovementin3wks,where itsuse becomesa passive rather than active appliance.
Figure 4: Positioner
The Essix appliance is a 0.5mm think removable plastic device that
lock into position without needing adjustments intra-orally. A
modified3-3Essix retainer(.015”thickness)tocover3-5mmoverthe
gingivae faciallyandbuccallywithcutoutsforbracketsatthe 3’swas
usedin10 patientswithmoderate 4-6mmlowerincisorcrowdingby
Ballard& Sheridan22
toprovide anterioranchorage toresistanterior
forcesresultingafterARS.Theirappliance waswornfull time except
for eating and cleaning. The appliance boosted anterior anchorage
via:
1) 6 anterior roots in bone
2) Superior aspects of the lingual and facial cortical plate
3) Anterior unit pitted against the distal movement of
individual posterior teeth.

7. Page 7
TheirresultsfoundtheEssixretainerreinforcedanchorage,
was aesthetic and treatment ranged from 3.5-4.5months.
Figure 5: Modified Essix retainer to provide anterior anchorage with ARS22
3.8 Reproximation to assist in post-treatment stability
“Stripping” mesial +/ distal enamel along with orthodontic treatment to minimise postretention crowding
has a longhistory.IER of the lowerincisorsisoftenthe last resortat maintainingalignmentandoftenused
afterotherconventional methodshave failed16
.Withreductionsinintercaninewidth,archlengthanddepth
continuouslydecreasingthroughoutlife,crowdingoftenensuesandIERcanassistinlong-termmaintenance
of lower incisor alignment4
.
Peckand Peck(1972) proposeda methodforevaluatingtoothshape deviationscontributingtomandibular
incisorcrowdingfromastudyof 45 “perfect”lowerincisoralignmentcasescomparedto70 control subjects.
Theyuse the MD/FL index asa numerical representationof lowerincisorcrownshape viewedincisally.Well
alignedmandibularincisorsare smallerMD&largerFL comparedtocontrols.Theirstandardssuggestideally
shaped lower centrals have MD/FL index = 88-92%, lower laterals = 90-95%. Concluding that well aligned
mandibularincisorshave siginificantlylowerMD/FLindicescomparedtocrowdedincisorsandreproximation
recommendedtocorrect unfavourable incisor shapes3
.
Boese (1980) suggestserial reproximationtocompensatefornatural archlengthreductionwhichappearsto
be commonduringincreasedhorizontalmandibulargrowth.Theystate twomainbenefitsof reproximation;
first providing a broader contact point Fig. 6 harnessing greater contact stability and secondly increasing
space available in the lower anterior region particularly
useful seeing as the biological framework limitsincreases
in arch length or arch form16
. Three phases of IER are
possible: 1) Early in treatment after initial alignment to
provide good LI shape & OB correction (most IER is
performed at this phase), 2) When no lower retention
used, IER shortly after removal of fixed appliances, some
IER performed serially over 4-6months post treatment
recall checking if contact points tight or movement
occurred then IER as required, 3) Depends on changes in
mandibular anterior arch form and amount and direction
of mandibular growth (particularly horizontal growth).
Usually little IER required after 6months post treatment,
however CCW growers exhibit lower incisor uprighting
leading to secondary crowding16
.
Figure 6: Interproximal contacts & stability in arch form15
Boese studied 40 patients with crowded mandibular arches orthodontically treated with premolar
extractionswithoutretention4-9yearspost-treatment.Intercanine widthwasmaintainedasmuchpossible
and all cases had CSF and IER. The mean reproximation of lower incisors at the completion of treatment
(phase I & II total 61.5% of cases IER, remainder in phase III) was 1.69mm SD 0.64mm. Conservative and
precise IER increasedlongtermstabilityof the mandibularanteriorsegment.The periodontiumshowedno
significant increases in probing depth, gingival recession or loss of alveolar crestal bone 4-9yrs post
treatment.23

8. Page 8
3.9 IER in deciduous teeth
IER canbe usedonoccasionsforinterceptiveguidance where noextractionsof permanentteethare planned
and a local interference causesa shift leading to an anterior crossbite or rotation of a lateral incisor where
the mesial of deciduouscaninecanbe reduced6
.Caseswithprolongedretentionof deciduoussecondmolars
can have their mesial and distal surfaces reduced, for example where the lower E forces the lower first
premolar in a mesial position crowding out the canine, the mesial surface of the E can be reduced by the
amount of the leeway space to allow space for the 1st
premolar to move distally and allow space for the
canine to eruptintothe arch6
. A flushterminal plane canbe convertedtomesial stepbyIER on the distal of
the lowerE aimingfora ClassI molarrelationship6
.Congenitallymissinglower2nd
premolarcaseswhere the
future planisforimplantreplacementcanhaveIERof the lowerE’s(dependingonpulpproximity) tosimulate
the space maintenanceneededfora2nd
premolarwhilstholdingboneuntil thechildisofideal age forimplant
replacement.
4 Methods of IER
The mostcommonmethodsof IERreportedbyZacchrisson2
include1) the air-rotorstripping(ARS)technique
withfine tungsten-carbide ordiamondbursanddiamond-coatedstrips(mostlyposteriorIER),2) hand-piece
or contra-angle handpiece with diamond-coated stripping discs and 3) handheld or motor-driven abrasive
strips. The finer the grit, the more efficient and easier it is to complete polishing. Polishing is important to
remove scratches, furrows and steps in enamel which promote plaque retention and increased risk to
caries24
.
4.1 Enamel assessment
IER is irreversible, so careful assessment and reduction amounts must be considered, once enamel is
removed it cannot be replaced. Excessive IER must be avoided, Boese (1980) recommend less than 50% of
interproximal enamel (per side of tooth), any greater increases the risk of caries,sensitivity, discolouration
and possibly reduce transeptal bone between the lower incisors predisposing to periodontal disease16
.
[Referto section3.4 for IER recommendedamounts].IERshouldonlybe performedafteralignmentdue to
inabilitytobe conservativeandestablishidealbroadcontactareasif theteethare malposed.Obviouslyselect
cases carefully, those with poor OH, high caries susceptibility, small teeth, severe crowding and tooth
hypersensitivity,hypoplasticteethwithreducedenamel whereIERcouldcause dentinalinvolvementshould
not be candidates for IER2, 25
.
IER is limited to the enamel thickness at its contact point, this varies, thus bitewing films can be used to
estimate thisbyprojectinga line verticallyfromthe cervical line of the toothto the occlusal/incisal plane18
.
Jarvis recommends 0.5mm per tooth surface as any greater IER will increase the risk of exposing dentine25
.
Consider the extent of any prior stripping, amount of enamel remaining,colour of tooth, shape of lower
incisor or tooth to be reduced, degree of overbite and predicted amount and direction of mandibular
growth16
. Remember to record tooth surfaces and amount of IER to prevent over IER at future
appointments15
.

9. Page 9
4.2 Air rotor stripping
The use of tungsten carbide burs in an air-rotor handpiece
(air-rotor stripping (ARS)) under water was introduced by
Sheridan (1985)18
and updated by Chudasama & Sheridan
(2007)26
. The IER is completed via a lateral approach.
Guidelinesfor contemporary ARS in posterior segments26
:
1) Remove only1mm(0.5mm perproximal surface) of
enamel fromanybuccal interproximalarea,theydo
not recommend 50% reduction due to lack of
scientific basis. Measure the IER performed with a
gauge [Fig. 7] to within1/10th
mm. The 1mm limitis
conservative representing1/3ratherthan½enamel
thickness. For upper laterals incisors and lower
incisors remove only 0.5mm of enamel from any
interproximal area retaining enamel morphology
rather than leaving flat.
Figure 7: Gauges measure amount of IER & separator prior to IER
2) Use coil spring or separator prior to ARS to establish open contact to
enhance visual and mechanical access.
3) Correct rotationspriorto ARS thuslevel andalignfirstto enable IERto
position contact point in improved position.
4) Use .020-.030” brass or steel indicator wire gingival to contact to
protect interdental tissue during ARS. Place the bur beneath the
contact and beginIER withlightand occlusallydirected wipingmotion
movingbur fromBu-Li.The taperedburresultsingood morphologyto
create parallel proximal surfaces.
Figure 8: Indicator wire for protection prior to ARS
5) Use safe-tipped ARS burs to prevent unwanted enamel ledging.
Figure 9:Safe-tipped ARS bur to prevent notching26 Figure
10: Sof-lex discs for finishing26
6) Use IntensivOrtho Strips as an alternative to a rotating bur in a handpiece. This can efficiently
perform IER via hand-piece powered abrasive strips with reciprocating action 0.8mm. They are
available inarange of grit sizes,forcontouringandsmoothinginterproximally.Althoughmore time
consuming the result may be improved.

10. Page 10
7) Finish surfaces to maintain morphology and texture using a 699L tapered fissure carbide bur and
fine-mediumgritdiamondtocontour proximal surfaces.Use Sof-Lex
discs for smooth texture.
8) Complete final smoothingwithafine abrasive stripcoatedwith35%
phosphoric acid gel4
. Rinse with water spray.
9) IER sequentiallyfromposteriortoanteriorinthe posteriorsegments
to maximise control,consolidate space andrepeatatnextvisitsuntil
enough space is created as needed. I.e. move each posterior tooth
distally one at a time like pearls on a string.
10) Establish anchorage when consolidating ARS space e.g. Li arch,
Nance, headgear, miniscrews, stopped arch etc.
Figure 11: Fine abrasive strip coated in etch26
11) Avoid pre-emptive IER to balance tooth mass ratios between arches. Compensatory IER can be
performed in the opposing arch during finishing for sound occlusal and incisal finish.
12) Use F gel/rinses to assist remineralisation.
13) Don’tuse ARSasa stand-alonetechnique,itcanbe anadjuncttoextractiontreatmentorforBolton’s
discrepancies to adjust tooth widths for ideal occlusion.
Ideal orthodonticreproximationshouldresultinproximal surfaceswithcontinuedinterproximal morphology
including marginal ridge height, contact points and embrasures; the only difference being reduced mesio-
distal toothdimension25
.Thisallowsforcontinuedocclusalfunctionwithpreventionof periodontal problems
(e.g. food impaction from reducing the occlusal height of the contact area). Jarvis believed the lateral
approach was disadvantageous as notching occurs, with lack of control for a smooth enamel finish. Jarvis
describesanocclusalapproachforIERintheposterior regions(distal canines
to mesial 1st
molars) using with an ultrafine 0.9mm diameter diamond bur
[Fig. 12] used for his stepwise IER technique25
:
1) Align posterior arch form – resolve rotations and correct marginal
ridge heights
2) Separators plased 3-4 days prior
3) IER with occlusal approach using bur (2.5mm or 4mm length) [Fig.
12] in a high speed air-rotor with water, with bur shoulder against
marginal ridge to maintain its form thus contact is not relocated
gingivally.Eithercomplete one contactarea per visitor all at once.
Move burfromBu toLi,recontourBuand Pasurfaces.Use 4mmbur
for Di canines and do not seat against marginal ridge, a straight
diamond can be used for this. Refine enamel with soflex discs
4) Orthodontic space closure
5) Further recontouring of Bu & Li surfaces at deband if required
Figure 12: IER bur occlusal approach25
Germec & Taner in their study of 26 Cl I borderline exo/non-exo patients with balanced facial profile and
moderate dental crowding found that both extractionand non-exo with ARS produced effective treatment
results with the latter group having an 8month shorter treatment duration. The main soft tissue profile
differences was 1-1.5mm more retrudedUL & LL positions in the exo group, however both groups finished
within normal limits and had desirable facial aesthetics.27
The maindisadvantage of the ARS approach isthat the surfacesare roughercomparedto fine gritdiamond
coated discs28
.

11. Page 11
4.3 Diamond Coated Stripping Discs in Handpiece/Contra -angle
Figure
13: Modified Tuverson Technique2
Zachrisson promotes the use of the modified Tuverson15
technique:2
1) Initial levelling 1-2months.
2) Use Elliot anterior straight separator [Fig 13A]
tightenedshortof theamountof space requiredfor
the IER, 30-45s allows the PD membrane to
compressprovidingadequatediscingspacestarting
at the leastcrowdedteethrequiringlessseparation
that subsequently provides more space for the
crowded teeth.
Figure 14: Separation crucial for IER15
3) Extra-fine (8-10m) diamond-coated perforated
strippingdiscs(Komet8934A.220) ina contra-angle
handpiece at medium speed (30,000 rpm) and
reduce toamountcalculated. Use 4 handedapproach,assistantmustprovideaircoolingwithtriplex
and retraction of tongue with mouth mirror.
4) Roundinterproximalcornerswithfriction-grip,cone-shapedtriangulardiamond burs (Komet 8833)
5) Polish with sof-lex discs (3M)
6) Close spaces

12. Page 12
Figure 15: Example of disc stripping2
While the rotation of the discs can cause trauma to the patient, Zhong et al29
used discs in an oscillating
handpiece which eliminated the need for retractors and risk of damage to the lips, cheeks and tongue.
Moreoverthe discscan be used insegmentsratherthanfull 360 andthe additionof perforationsincreases
visual access. They demonstrated in SEM studies on 32 patients that perforated diamond-coated (<30m
grit) discsinanoscillatinghandpiece followedbytwosof-lex discs(fineandultra-fine) forpolishingminimises
scratches and furrows in the enamel with 90% of the surfaces smoother than untreated enamel and each
surface was completed in 2.2minutes29
.
4.4 Handheld or motor-driven abrasive strips
4.4.1 Handheld
Metal strips can be manipulated with the fingers, however a pair of Matthiews
forcepseithersideof aninterproximal abrasive striporcustom“saw”like handle
that allows insertion of sections of strips provide a means for control of hand
stripping.Thesecanbe useful togaininitial patencyinterproximallyasanadjunct
to motor runstripsor for minorreductionsandrefinementwithfinergritstrips.
Hand-pulledabrasive stripscanbe rather awkwardand tediousthusair-turbine
handpiece methods are more efficient26
.
Figure 16: Metal strips for IER4
4.4.2 Reciprocating saws
Various motor driven contra-angle handpieces which drive a reciprocating or oscillating abrasive strip are
available.Theseare safer(don’trequire extensiveretractionlikethe rotatingdiscs), userfriendly,canprovide
IER to variousthicknessesdependentonthe size striputilisedandthe stripsare flexible toallow contouring

13. Page 13
the interproximal surfaces. They range from polyester strips coated with ultra-fine corundum abrasives to
leave a polishedfinish to diamond coated strips and strips with regions or single sides without diamond
abrasive to prevent unwanted enamel removal.
Figure 17: Example of commercially available reciprocating IER30
4.5 Post IER desensitising agents
Topical desensitisingandremineralisingagentsmostcommonlyusedare caseinphosphopeptide-amorphous
calcium phosphate (CPP-ACP) e.g. Tooth Mousse and concentrated topical fluoride e.g. Duraphat varnish.
The new exposed enamel surface after IER will absorb topical agents and could penetrate undetected
subsurface lesions unidentifiable on bitewings, this will enhance remineralisation and prevent
demineralisation25
.
The theoryisIER resultsinremoval of the outermostFA rich enamel layer,hence the recommendationsfor
use of topical agents, however, recent findings by Zachrisson et al2
suggest this may be unnecessary in
patientswithgoodOH and regularuse of F toothpastesandrinses.The keyisthe balance inthe biofilmand
the cariostatic mechanism of F on this rather than a high F content on the apatite lattice. Thus caries risk
assessmentandFexposure candeterminethe choiceforFsupplementationpostIER.2
Jarjouraetal31
intheir
studyon40 patients1-6yrspostIERwithARSandnotopical FapplicationimmediatelypostIERsupportthese
findingssuggestingpatientsexposedtoFwaterandFtoothpastemaynotreceiveanyadditional benefitfrom
topical F post IER.

14. Page 14
5 Long term effects of IER
5.1 IER & periodontal disease/caries
Boese analysedPA filmstocorrelate fiberotomyandreproximationonthe periodontium,he measured
proportionof crownsize to toothlength23
:
Andperformedperiodontal probing onthe mandibularincisorswithresultingpocketdepthsranging0.5-
1.5mm and foundIER didnot influence anysignificantdecrease inalveolarcrestheightorlossof
interdental bone,withAI/TLratiosall veryclose.Notone of his40 IER casesshowedcariesnorrestorations
on the posttreatmentradiographs23
.
IERinposteriorteethmustbe controlledandresultincontactareas1mmabovethe gingival papillaotherwise
if thisspace isencroachedupon,the papillaispushedfromthe embrasure arearesultinginanoversizedcol
resultinginadeepinterproximal col (nonkeratinisedplaquesusceptiblegingiva)andrisktopocketformation
and periodontal disease.25
There wassome thoughtthat IER couldreduce transeptal bone betweenteethbecause the rootswould
finishincloserproximityandpredispose themtoperiodontal disease,Artunetal ina studyof 400 adult
patients16yrs postorthodontictreatment,foundnosignificantdifferencesininflammation,level of
attachment,andalveolarbone level betweenrootproximityvscontrol sitesandindicate anteriorteeth
aren’tpredisposedtoincreasedperiodontaldestructionwithrootsinclose proximity32
.Jarvisinfersfrom
studiessuchas thisthatthin alveolarbone betweenteeththathave hadIERand closerroot proximity
doesn’tpredispose toincreasedriskof periodontaldisease25
.
Zachrissonetal (2007)33
studied61 patients10yrs postIER withfine diamonddiscsunderaircooling
followedbypolishgingonthe six loweranteriorsandfoundnonew cariouslesionswere present,noroot
pathologyandonly3 adultshad minorlabial gingival recession.Interestinglythe patientswhohadIER
showedrootswithgreaterseparationdistance thanthose thathadnot.59/61 patientsdidnotreport
sensitivitytothermal changes.TheyconcludedthatIERdidn’tresultiniatrogenicdamage,dentalcaries,
gingival problems,bone loss,norreducedinterradiculardistances of the roots.Overall incisorirregularity
was small.33
Zachrissonetal (2011)2
investigatedthe effectsof careful IERwithextrafine diamonddiscswithaircooling,
followedbytriangulardiamondsforcontouringandpolishingoncariesriskinpremolarsandmolarson 43
patients4-6yrspost IER.IER didnotincrease the riskof caries inposteriorteethandconcludedthatcorrect
MD IER withinlimitsandappropriate casescausednoharmto teethandtheirperiodontium.Overall
patientshadsounddentitionswithgoodocclusionandonly2.5% new carieslesions(grade 1- outerhalf of
enamel only),comparedtothe contralateral ungroundreference toothsurfaceswhere 2.4% of new caries
lesionswere found.Nopatientsreportedsensitivitytothermal changes.
Jarjouraet al (2006)31
intheirstudyof 40 patients1-6years postIER withARS andno topical F or sealant
applicationfoundARSdoesnotincrease the cariesrisk.IERinthe anteriorregioncouldalsoassistin
reductionof gingival recessionasthe teethcanbe retractedoverbasal bone15
.

15. Page 15
5.2 IER and pulp damage
Zachrisson advises enamel IER does not result in pulp damage provided the IER doesn’t cause a notched
surface inaccessibletocleaningwhichallowsplaqueretention,cariesanddamage todentinal tubulesleading
to pulpal irritation34
.
Sheridan states grinding enamel surface is not harmful, the amount of enamel needed for adequate
protectionof teethagainstcaries,thermal or chemical change is indeterminate andeach toothhas various
enamel thicknessdependingonthe region,the thinnerBuandLi enamel comparedtointerproximalsuggests
there’s no advantage in having thicker enamel in this region so that careful IER with smooth cleanable
surfaces is not harmful18
.
Studieshave demonstratedthatmarkedgrindingof teethevenintodentine,if donecarefullywithadequate
waterandaircoolingwithresultantsmoothselfcleansingsurfacescanbe performedwithoutadverseeffects,
but if there is no cooling, extensive odontoblast aspirationinto the dentinal tubules is a sign of irreversible
damage2, 34
_ENREF_1.Unintentionalstepsplacedin enamel canleadtopulpal inflammatorycellinfiltration34
.
Cosmeticrecontouringforexampleincasesof canine substitutionformissinglateralincisorswasstudied10-
15yrs posttreatmentindicatingfavourablelongtermresultswithnosignificantcolourdifferences,mobility,
TTP, thermal sensitivity, or negative electric pulp testing results.35

16. Page 16
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