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Clinical Management of Tooth Size Discrepanciesjerd_520
155..159Guest Experts
DAN GRAUER, DDS, PhD*
GAVIN C. HEYMANN, DDS, MS
Associate Editor
EDWARD J. SWIFT, JR., DMD, MS
Esthetic anterior dental appearance depends on thealignment,
occlusion, and exposure of anterior teeth.13In order to establish
adequate alignment and occlusion,the upper and lower incisors need
to be proportional insize. Interarch tooth size discrepancy (ITSD)
is denedas a disproportion in the mesiodistal dimensions ofteeth of
opposing dental arches. In the absence of aproportional match in
size of upper and lower teeth, anormal occlusion is
impossible.4
The prevalence of clinically signicant ITSD amongorthodontic
patients has been reported to rangebetween 17% and 30%.5,6 Although
the prevalence ofITSD is higher in patients with malocclusion than
inpatients with normal occlusion,7 in general, there seemsto be no
dierence among malocclusion groups,ethnicities, and gender.7,8 It
is important to note thatmost studies comparing groups with regard
to ITSDhave been conducted in orthodontic populations.
DIAGNOSIS
The following clinical ndings are associated with butnot
exclusive to ITSD: crowding or spacing of incisors,canines in
dental Class II without skeletal Class II,excessive or decient
overjet, excessive or decientoverbite, vertical compensation of
ITSD, wear andcompensatory eruption of anterior teeth,
excessiveprominence of the marginal ridges of upper incisorsand
canines, and abnormal angulation/inclination ofincisors and
canines.
Given that these clinical ndings are not specic to thepresence
of ITSD and that they are common ndings inmany types of
malocclusion, a specic diagnosis ofITSD is needed. The gold
standard for identication ofa tooth size discrepancy is a
diagnostic setup, but otherdiagnostic methods are available. The
ratio of summedmesiodistal widths of the mandibular to maxillary
teeth(either from rst molar to rst molar, or just theanterior
teeth) can be compared with standardizedvalues in order to identify
and quantify a discrepancy.9According to Bolton:
overall ratio
summed mesiodistal widthsof mandibular 12 te
=
eethsummed mesiodistal widthsof maxillary 12 teeth
100 91. = 33%
anterior ratio
summed mesiodistal widthsof mandibular 6 te
=
eethsummed mesiodistal widthsof maxillary 6 teeth
100 77.2 = %%
As with any proportion, the result of the comparisoncould be
higher or lower than the ideal percentage. Forinstance, in regards
to the anterior proportion, if theratio is less than 77.2%, it
means that either the lowerteeth are too narrow, the upper teeth
are too wide, or acombination of both. If the ratio is higher than
77.2%,either the lower teeth are too wide, the upper teeth aretoo
narrow, or both. It has been suggested that ITSD
*Assistant Professor, University of Southern California and
Private Practice, Los Angeles, CA, USAPrivate Practice, Chapel Hill
and Durham, NC, USA
CONTEMPORARY ISSUES
2012 Wiley Periodicals, Inc. DOI
10.1111/j.1708-8240.2012.00520.x Journal of Esthetic and
Restorative Dentistry Vol 24 No 3 155159 2012 155
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must be greater than 1.5 to 2 mm to aect treatmentplanning and
be deemed clinically signicant.4,10,11 In acontinuous spectrum of
discrepancy between widths ofupper and lower teeth, four discrete
descriptionsemerge; each discrepancy might present in a localizedor
generalized way (Figure 1).
CLINICAL DECISION MAKING
Regardless of the clinical continuum of ITSD, treatmentoptions
are discrete. For small ITSD (less than 2 mm),orthodontic
compensation in the alignment andocclusion of the anterior teeth
might be acceptablewithout altering the mesiodistal width of
anterior teeth.For example, to compensate for a small ITSD in
cases
FIGURE 1. General classification of interarch tooth
sizediscrepancy.
A
B
FIGURE 2. A,This patient was referred to the orthodontist for
space distribution prior to veneer restoration of her upperincisor
to address an apparent interarch tooth size discrepancy (ITSD).At
the beginning of treatment, mesiodistal teeth widths weremeasured
and the ITSD was quantified as less than 1 mm. B,With orthodontic
treatment only, we were able to compensate for thesmall ITSD.
Patient did not require additive or reductive procedures, only
orthodontic space closure and refining of occlusion. Thebottom
line: diagnose first and trust your measurements.
CONTEMPORARY ISSUES
Vol 24 No 3 155159 2012 Journal of Esthetic and Restorative
Dentistry DOI 10.1111/j.1708-8240.2012.00520.x 2012 Wiley
Periodicals, Inc.156
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where the upper anterior teeth are too wide or thelower anterior
teeth are too narrow, the orthodontistcould nish the case with
larger overjet and/or overbite,more inclination of lower incisor or
less inclination ofupper incisors. Conversely, in cases where the
upper
teeth are too narrow or the lower teeth are too wide,the
orthodontist can establish an occlusion with smalleroverjet and/or
overbite, less inclination of lower incisorsand/or more inclination
of upper incisors, or even inideal overjet and overbite, but with
canines in dentalClass II relationship (Figure 2).
When the ITSD is greater than 2 mm, clinicalmanagement of tooth
size discrepancy requires eitherthe reduction of tooth width by
means of interproximalenamel removal or the addition of tooth width
bymeans of restorative dental techniques. When changesin
mesiodistal widths are required, the orthodontist andrestorative
dentist must make two decisions (Figure 3):
1 Whether the discrepancy will be addressed in bothupper and
lower dental arches or in one arch only;and in the latter case,
which dental arch will betreated.
FIGURE 3. Usual therapeutic approach for each category
ofinterarch tooth size discrepancy.
A B
C D
FIGURE 4. A,This patient had a localized ITSD. The upper left
lateral incisor was disproportionally small in comparison
withneighboring teeth and opposing dental arch. B,Through
orthodontic treatment, the incisor was positioned in the
appropriate space;1/3 of the space was mesial and 2/3 of the space
distal to the lateral incisor. C,This position allowed for
restoration of optimaltooth contour.At the end of treatment, a
composite buildup was used to restore to acceptable anatomy. D, The
patient and herfamily were pleased with the esthetic result.
CONTEMPORARY ISSUES
2012 Wiley Periodicals, Inc. DOI
10.1111/j.1708-8240.2012.00520.x Journal of Esthetic and
Restorative Dentistry Vol 24 No 3 155159 2012 157
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2 Whether the discrepancy will be solved by addingmesiodistal
width to the teeth of one dental arch,reducing mesiodistal widths
of the opposite dentalarch, or both.
ITSD TREATMENT APPROACHES
The additive approach will often be used in ITSD caseswith
localized (small maxillary lateral incisor) orextreme generalized
mesiodistal deciencies (all incisorsare undersized). The diagnosis
of localized mesiodistaldeciency is relative to the adjacent teeth
and can beassessed in anthropometric norms, in comparison witha
normal-size contralateral tooth or determining theideal mesiodistal
width in proportion to the adjacentteeth (Figure 4).
When mesiodistal widths of adjacent teeth areproportional and no
localized deciency is found, a
reduction approach is more appropriate. For example, ifmaxillary
anterior teeth display normal proportionamong themselves, but are
small overall, the correctionof the ITSD will likely involve
mesiodistal reduction ofthe mandibular anterior teeth. This
reduction approachis normally used in cases with generalized
deciency orexcess or cases with localized extreme excess.
Interproximal reduction can be accomplished with theaid of
slow-speed rotary discs, abrasive strips, orhigh-speed diamonds
(Figure 5). Care should be takennot to remove so much enamel as to
completelyeliminate it from the proximal surfaces of the teeth.This
is of particular concern in the mandibular anteriorarea, where
periapical radiographs may be helpful inquantifying the enamel
thickness. Standardizedreduction gauges that are accurate to the
nearest tenthof a millimeter are helpful in quantifying the amount
ofreduction achieved. Interproximal enamel reductionrendering
smooth self-cleansing surfaces has been
A B
C D
FIGURE 5. Reduction approach: clinical sequence of interproximal
reduction.A,Teeth are separated and gingival tissues areprotected
with WedJet (Coltne Whaledent,Alstatten, Switzerland). B,A
honeycomb-type disc in a reduced slow-speed handpieceis used to
reduce the mesiodistal widths of the teeth, removing 0.2 to 0.5 mm
of enamel. C,A cone-shaped diamond rotaryinstrument is used to
create smooth and round line angles, restoring anatomical contours.
D,After the procedure, spaces areevident between all incisors.
CONTEMPORARY ISSUES
Vol 24 No 3 155159 2012 Journal of Esthetic and Restorative
Dentistry DOI 10.1111/j.1708-8240.2012.00520.x 2012 Wiley
Periodicals, Inc.158
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shown to pose no long-term negative prognosis to theteeth
involved.12
CONCLUSION
Diagnosis and quantication of ITSD are essential forachieving
optimum occlusion and esthetics. It isimportant to measure,
diagnose, and make decisionsprior to the initiation of treatment.
The patient and allmembers of the treatment team should be
informedabout the problem, possible solutions, sequence,
andtiming.
REFERENCES
1. Kokich VO, Kiyak HA, Shapiro PA. Comparing theperceptions of
dentists and lay people to altered dentalesthetics. J Esthet Dent
1999;11:31124.
2. Kokich VO, Kokich VG, Kiyak HA. Perceptions of
dentalprofessionals and laypersons to altered dental
esthetics:asymmetric and symmetric situations. Am J
OrthodDentofacial Orthop 2006;130:14151.
3. Flores-Mir C, Silva E, Barriga MI, et al.
Laypersonssperceptions of visible anterior occlusion. J Can
DentAssoc 2005;71:84953.
4. Prot WR. Contemporary orthodontics. 4th ed. St. Louis(MO):
Mosby Elsevier; 2007.
5. Othman S, Harradine N. Tooth size discrepancies in
anorthodontic population. Angle Orthod 2007;77:66874.
6. Freeman JE, Maskeroni AJ, Lorton L. Frequency of
Boltontooth-size discrepancies among orthodontic patients. AmJ
Orthod Dentofacial Orthop 1996;110:247.
7. Uysal T, Sari Z, Basciftci FA, Memili B. Intermaxillarytooth
size discrepancy and malocclusion: is there arelation? Angle Orthod
2005;75:20813.
8. Johe RS, Steinhart T, Sado N, et al. Intermaxillarytooth-size
discrepancies in dierent sexes, malocclusiongroups, and
ethnicities. Am J Orthod Dentofacial Orthop2010;138:599607.
9. Bolton WA. Disharmony in tooth size and its relation tothe
analysis and treatment of malocclusion. Angle
Orthod1958;28:11330.
10. Bolton W. The clinical application of tooth size analysis.Am
J Orthod 1962;48:50429.
11. Bernab E, Major PW, Flores-Mir C. Tooth-width
ratiodiscrepancies in a sample of Peruvian adolescents. Am JOrthod
Dentofacial Orthop 2004;125:3615.
12. Zachrisson BU, Nyygaard L, Mobarak K. Dental healthassessed
more than 10 years after interproximal enamelreduction of
mandibular anterior teeth. Am J OrthodDentofacial Orthop
2007;131:1629.
CONTEMPORARY ISSUES
2012 Wiley Periodicals, Inc. DOI
10.1111/j.1708-8240.2012.00520.x Journal of Esthetic and
Restorative Dentistry Vol 24 No 3 155159 2012 159