DOI: 10.1051/odfen/2013405 J Dentofacial Anom Orthod 2013;16:105 RODF / EDP Sciences

Quantitative management of morphological problems of the incisor-canine group

Jacques FAURE

ABSTRACT The maxillary incisor-canine group above all, plays a crucial role both in the esthetics of the smile as well as in mastication. The most frequent morphological problems, agenesis, stunted, or peg-shaped maxillary lateral incisors will hinder the anterior guidance and have an adverse impact on the smile (‘‘fang’’ shaped teeth, spaces/overlapping teeth, anomalies in size in relation to neighboring teeth). The satisfactory reconstruction of the upper six anterior teeth requires first and foremost a proportional relationship between the lateral and central incisors and between the upper and lower six front teeth. A study of the esthetic indices (L/C: lateral/central) and functional (I/S: inferior/superior – mandibular anterior teeth/maxillary anterior teeth) can be a decision aid and can measure the effectiveness of different treatments (adding composites, stripping, ceramic cap, single implant-supported crown).

KEY WORDS

Lateral maxillary incisors, Stunted teeth, Peg-shaped teeth, Arch length discrepancy (ALD) Anterior Bolton Index (ABI), Lateral/central esthetic index.

Problems of number and/or morphology The most classic scenario consists of con- of the front teeth are frequent, and are genitally missing or stunted upper lateral in- most often characterized by a discrepancy cisors. But this dental deformity is often not in the morphology of the maxillary anterior isolated; the practitioner will simultaneously teeth. see undersized central incisors, impacted

Conflicts of interest declared by the author: NONE Address for correspondence: Article received: 10-2011 J. FAURE Accepted for publication: 01-2012 10, place Lannes 1 32021 Auch [email protected]

Article available at http://www.jdao-journal.org or http://dx.doi.org/10.1051/odfen/2013405 JACQUES FAURE

canines with atypical morphology struction, implant-supported (spear-shaped, false...) etc. prosthesis or bonded bridge, will be The diagnosis and the choices of based on two types of data: therapy include prosthetic substitutes • Subjective data based on an over- for the missing or peg-shaped teeth, all esthetic evaluation by the practi- either by closing the spaces, or by tioner which will include the hue, preserving or even (re)opening discoloration and possible spotting, spaces by using prosthetic devices, status of the tooth surface, transpar- or possibly reconstructing the dys- ency of the incisor border, corona morphic teeth by enlarging them with morphology and root morphology composite resin or ceramic crowns. (the size of the root will inform its an- Whatever therapeutic choice the chorage value and the cervical dia- practitioner makes, he will have to meter will inform the possibility of manage difficult problems related to making an augmented crown, period- arch length discrepancy (ALD). For ex- ontal context; ample, when faced with peg-shaped • Objective data that are mainly the lateral incisors the first idea is usually mesio-distal dimensions of the teeth to recreate the crowns of the lateral and especially the relationships be- incisors to fill the space that is natu- tween these dimensions. rally theirs (assuming that the canines The goal of this article is to take and the central incisors are in perfect into consideration the numerical cri- anterior class I ). Alas, the teria involved in the choices and in central incisors are often also stunted the management of the treatment of or small, and reconstructing only the these cases. These data are not in- laterals will throw off the harmony of tended to be indisputable directives the incisor group by making the lat- but rather as a diagnostic aid for clini- erals excessively large in relationship cal decision making. The final deci- to the central incisors! sion is made by the practitioners The initial decision for treatment after they quantify the problem and and then, management and order of evaluate the esthetic context that, in the treatment procedures – orthodon- fact, can only be assessed by them. tic, coronoplasty, composite recon-

2 – NUMERICAL CRITERIA

2 – 1 – Anterior occlusion must criteria (anterior guidance slope deter- of course be esthetic mined by the condylar path: absence and functional of posterior contacts in lateral excur- sion assured by a group guidance or better still by secure canine gui- Functional criterion: Anterior dance). Bolton Index We tend to forget the primary Gnathology has taught us about statistical criteria: a perfect Class I occlusal dynamics, the recognized canine, an incisor overjet close to

2 Faure J. Quantitative management of morphological problems of the incisor-canine group QUANTITATIVE MANAGEMENT OF MORPHOLOGICAL PROBLEMS OF THE INCISOR-CANINE GROUP

2 mm in both the anteroposterior 2 – 2 – Esthetic criteria: direction as well as the vertical di- lateral/central rection (overjet and ) and relationship incisor inclination (torque) close to normal. The esthetics of the buccal-dental We certainly cannot make a diag- smile essentially depends, as each of nosis based on an examination of the us knows, on the upper 6 front teeth. casts, but casts that are perfectly re- But in the usual evaluation of the gistered in the anterior zone are a ne- smile, in this case, a head-on view, cessary prerequisite in order for the canines play a lower-profile role, correct functioning to be possible. than the four incisors (they only have Harmony in size between the a three quarters profile). In the same upper and lower six front teeth, will way, overlapping teeth and spaces make it possible to simultaneously would be much more unsightly be- achieve perfect class I canine and tween centrals and between centrals ideal incisor overbite. As soon as a and laterals rather than between lat- relative mandibular excess appears, erals and canines. for example, compensatory maxillary If it is assumed that perfect align- defects spontaneously occur: ment can be obtained and closing – maxillary diastemas; the spaces can be achieved, what will differentiate the unsightly from – overlapping mandibular teeth; the correct positioning will be the re- – diminished overjet. lationship of size between the lateral The accepted criterion for evalua- incisors and the central incisors. tion here is, of course, the Anterior The two extremes for results Bolton Index (Ra = 6I/6S). would be: The values found in research litera- – either an obvious major micro- ture are: dontia of the lateral incisor, exceed- – Bolton (55 subjects)1,2 ;77.2 ingly small in relationship to the (± 1.65); central; – Freeman et al. (157 subjects)5; – or incisors that look like piano 77.8 (± 3.07); keys, in other words, of equal size. – Faure et al. (62 subjects)3,6,7;76.4 The criterion used is the lateral/ (± 2.16). central relationship (RL/C = (12 + 22)/ We will use 77% as a reference (11 + 21)). value. According to Dallow (62 sub- jects)3,7, the mean value is:

RL/C = 0.79 (± 0.04).

3 – USING THE CRITERIA

The numerical criteria will make it phia, and next to help determine and possible to first quantify the dysmor- quantify therapy.

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3 – 1 – The Anterior Bolton Maxillary excess: Index: functional Es =S-Sth = S - I / 0.77. criterion Notice : these two values are dif- ferent: The deviation of the patient value Ei =-Es · 0.77. in relationship to the reference value plus the thresholds that make up the mean ± the type deviation will be used to assess the extent of the dis- 3 – 2 The lateral/central crepancy. relationship: esthetic When several treatment options criterion are feasible, the Anterior Bolton In- dex must be calculated for each of Once again, the comparison of the the possible options. index to the mean value, and taking For example, in the case of into consideration the standard-devia- stunted teeth, the dentist can opt for: tion can determine the gravity of the discrepancy. • preserving the stunted teeth 12- 22 When various options of treatment 43+42+41+31+32+33 are feasible, the lateral/central rela- RA = 13+12n+11+21+22n+23 tionship must be calculated for each of them individually and respectively substitution of 13-23 for 12-22 • in relation to the others. In cases of and 14-24 for 13-23 stunted teeth, the orthodontist could 43+42+41+31+32+33 RA = plan on: 14+13+11+21+23+24 The Anterior Bolton Index makes it • preserving the stunted teeth 12- possible to calculate which ‘‘retouch- 22 12n+22n ing’’ to make: RL/C = – if the maxillary arch is consid- 11+21 ered to be correct, it serves as the • substitution of 13-23 for 12-22 point of reference: and of 14-24 for 13-23 13+23 I either theoretical or ideal (in rela- RL/C = tionship to the point of reference S): 11+21 Ith = S x 0.77. The lateral/central relationship also – Mandibular excess: requires the calculation of how many ‘‘alterations’’ to perform: Ei =I–Ith =I–S· 0.77. – if the centrals are to be main- A positive value expresses how tained as is ; they serve as a point much stripping is required; of reference: – if the mandibular arch is con- Theoretical or ideal L (in relation- sidered to be correct, it serves as ship to point of reference C): the point of reference: Lth =C· 0.79. S either theoretical or ideal (in rela- – Excess of the lateral incisors: tionship to the reference I): EL =L–Lth =L–C· 0.79. Sth = I/0.77.

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A negative value expresses how Theoretical or ideal C (in relation- much stripping is required. ship to point of reference L): Cth =L/ A positive value expresses the 0.79. number of spaces to preserve (possi- – Maxillary excess: bly for a composite filling); EC =C–Cth = C – L/0.79. – if the lateral incisors are to be Notice: these two values are dif- maintained as is , they will serve ferent: EL=-EC x 0.79. as a point of reference:

4 – THE TREATMENT SOLUTIONS

4 – 1 – Management of overall reduce the overjet any more, to an maxillary deficiency / edge to edge incisor relationship and excess (augmented we never find it feasible to increase the overjet to manage an upper ex- Anterior Bolton Index) cess for fear of disturbing the ante- Four solutions are feasible. rior guidance. • Reduction in size of the lower • Management of spaces (upper incisor-canine group: incisor-ca- lateral-canine or inter-centrals) nine stripping We find that the management of We are limited to 2 to 2.5 mm: gaps between lateral and central is 0.2 mm per proximal face, or approxi- mostly a temporary solution, because mately 2.4 mm on the 6 front teeth. patients are in no rush to use a pros- thetic solution. We have to be cogni- If the practitioner decides to do zant of the fact that when the gaps stripping, it should be done at the be- are no greater than 1.5 mm or 2 mm, ginning of treatment. they are inconspicuous and only visi- If there is generalized ble from a three quarters view of the complicated by ALD or arch length smile (usually, when someone smiles discrepancy (the anterior maxillary at someone else, the person who is group is even smaller than the lower smiling is facing the other person). anterior group), then stripping is con- The management of an inter-incisal tra-indicated. gap can be maintained for certain cul- The indication to ‘‘sacrifice’’ a low- tural and ethnic groups for whom this er incisor can only be considered is acceptable or even preferred. where there is a mandibular excess • Enlargement of the upper six greater than 6-7 mm. teeth • Reduction of the incisor overbite Enlarging the upper six teeth A reduction of the incisor overbite should be avoided whenever possible from 2 to 1 mm, decreases the ante- especially because of the fragility (of rior perimeter of the maxillary arch by the resin composite) and the disfig- 2 mm. We may be able to use this urement if a prosthetic solution is decrease in perimeter but we cannot used (we should remember that we

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are generally dealing with adolescent sion for example 1.5 mm), so that me- patients for whom prosthetic solu- sialization of the canines can close a tions should be avoided or delayed space between the lateral and canine, as long as possible). To the extent which can remain or be reconstructed that it is possible, decreasing the size later with composite filler, the occlu- of the lower front teeth is preferable. sion is unstable. After removing the When performing an enlargement braces, the lateral occlusion will inevi- procedure using composites, there tably be shifted in an obvious class I are two conflicting imperatives: the (slight retraction of the upper canine/ dentist should try to treat as few premolar or slight mandibular protru- teeth as possible (limiting the risk of sion) with of course the risk of random composite fracture) and avoiding lat- and uncontrollable reopening spaces eral veneers that are excessively among the upper six front teeth. large on certain teeth (generally 12- • Increase in upper incisor torque 22), once again in order to not weak- We have shown the lack of effect en the coronal reconstruction. of additional torque, whereas crowd- To continue this line of thought, ing is determined by the line joining 4 when an upper enlargement is the the inter-dental contact points . treatment of choice, it is preferable • Increase in upper incisor tipping that the practitioner restrict treatment Once again, we have shown the to only the incisor group: when smil- futility of excessive tipping of the ing, the canines are not as conspicu- front teeth in order ‘‘to fill up’’ space, ous and they are more involved in because there is no substantial in- mastication. When dealing with six crease in the filled space since of front teeth that are significantly under- course it is not stable4. sized, where the defect is most evi- dent on the lateral incisors, the orthodontist must first consider enlar- ging 12-22 therefore creating lateral 4 – 2 – Management of lateral central harmony. Then the practi- deficiency/excess tioner, if it is still necessary, should (augmented Anterior uniformly enlarge the four incisors all Bolton Index) the while being very careful not to make the enlargement too big on the Re-proportionalizing the laterals in laterals and therefore more breakable. relationship to the centrals can once There are also three treatments of- again go through several different ten recommended by veteran ortho- stages: dontists which, in our view, do not – enlargement of the laterals; solve the problem. – reduction of the centrals; • Closing spaces with orthodontic – substitution of the canines for the treatment and accepting a minor upper laterals: this will generally class II canine relation result in an inverted disharmony If a lateral upper/lower relationship that requires a reduction of the has resulted in a minor class II occlu- widths of the ‘‘pseudo-laterals’’.

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Table I Table showing the problem. The dimensions of the front teeth and the calculation of the indices RL/C and RA, in the hypothetical cases of saving or substituting for 12-22. The deficiencies and excesses of the compared groups are also quantified.

5 – QUANTIFICATION OF PROCEDURES

Improving the two indices is a by proportionally applied maxillary complex theoretical process given enlargement, at least of the inci- that the incisors are involved differ- sors. ently in the two indices. In our opi- We find the assistance of an Ex- nion, the priority must be given to cel spreadsheet that automatically the esthetic index (R ). L/C calculates the indices (RL/C and RA) Therefore, the first procedure is along with the necessary corrections either the enlargement or reduction either by enlargement or reduction of the laterals. absolutely indispensable. After doing this, the practitioner The table-valued parameters auto- must evaluate the anterior ALD (RA) matically display the indices RL/C and and recalculate by proportionally ap- RA) for both the hypothetical case of plied mandibular reduction (stripping substitution and preservation of the on all six front teeth) or once again stunted teeth.

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Table II Harmonization of the L/C has been established by enlargement of 12-22 with values of 5.9 mm to 6 mm. The index RA remains uncorrected.

The spreadsheet quantifies the dis- arches: enlargement of the laterals crepancy for the esthetic index as (or reduction of the centrals) then well as for the functional Bolton In- anterior maxillary enlargement or dex, and therefore indicates the mor- anterior mandibular reduction. phological correction that is required Since the spreadsheet is dynamic, (grinding and reduction using corono- it is immediately possible to evaluate plasty or the degree of enlargement). the impact on the indices of a 1 mm Of course, the corrective proce- enlargement for a lateral incisor for dures involve both the upper/lower example.

6 – A CLINICAL EXAMPLE SHOWING THE CALCULATIONS

The clinical case analyzed below The orthodontist has to first decide deals with generalized microdontia whether to save or to extract the (tooth size far below the mean va- peg-shaped teeth. lues), with ALD disorder (Tab. I). As you can see, the substitution/ – The superior dentition is very small sacrifice solution is functionally the in relationship to the lower teeth. best (Bolton at 79% as opposed to – Stunted peg-shape teeth (12-22). 87% with no substitution). However, – Less prominent stunted teeth (11-21). substitution/sacrifice is the worst de- Table I deals with this disorder. cision for the L/C relationship.

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Table III The normalization of the Bolton Index has been established with composites installed on the incisor group, re- specting the value established for the L/C relationship. The orthodontist must enlarge the upper incisor group by 2.52 mm (0.7 mm/central and 0.56 mm/lateral: 0.56/0.71 = 0.79).

The first therapeutic approach is in- 6-5 (+0.7 on the centrals and 0.56 on tended to harmonize the lateral/cen- the laterals). tral relationship: an enlargement of Overall, the centrals were enlarged 2.65 mm, (1.325 mm/tooth). 12-22 at- 0.77 mm, the laterals 1.9 mm; com- tain diameters of 5.9 to 6 mm; the posites will most likely be used on Bolton Index has slightly improved the centrals, whereas on the laterals from 87% to 81% (Tab. II). (depending on the status of the root The second approach is intended and its diameter, the shape of the to harmonize the overall maxillary de- crown, etc), the practitioner can opt ficiency in relationship to the lower for either an implant-supported or teeth. teeth-supported prosthetic device or If the practitioner prefers not to a composite. use the stripping solution for the The orthodontist might feel inclined mandible, because of generalized to only redo the laterals, but that stunted teeth, then the incisor group would require an even more substan- must be enlarged (Tab. III) by propor- tial enlargement (in all: 5.2/2 – tionally performing the necessary en- 2.6 mm per tooth, to comply with largement of 2.52 mm for the L/C = Bolton’s functional imperative), which 0.79 relationship. The centrals have a would leave us with teeth that look 8.2/8.2 diameter and the laterals 6.5/ like ‘‘piano keys’’ (Tab. IV).

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Table IV A significant procedure solely for 12-22 (implant-supported prosthesis) is impossible: the practitioner would have to enlarge the size of the lateral incisors by 1.25 mm; as a result, the teeth in the maxillary incisor-canine group would be almost identical in size.

REFERENCES

1. Bolton WA. Disharmony in tooth size and its relation to the analysis and treatment of . Angle Orthod 1958;28:113-30. 2. Bolton WA. The clinical application of tooth size analysis. Am J Orthod 1962;48(2):504-29. 3. Dallow A. Dysharmonie dento-dentaire : e´ tude quantifie´ e. Me´ moire DUO UPS Tou- louse III 7/2007. 4. Faure J, Baron P. Troubles morphologiques du bloc incisif supe´ rieur. J Edge 1997;36:78-88. 5. Freeman JE, Maskeroni AJ, Lorton L. Frequency of Bolton tooth size discrepancies among orthodontic patients. Am J Orthod Dentofacial Orthop 1996;110(1):24-7. QUES FAURE. 6. Nabbout F, Faure J, Baron P, Braga J, Treil J. Anatomie dentaire et orthodontie. L’ap- port du scanner 3D/ Dental anatomy and . The benefit of the 3D scanner. Revue d’Orthope´ die Dento-Faciale 2003;37(3):59-73. 7. Oueiss A, Marchal-Sixou Ch, Dallow A, Baron P, Faure J. Dysharmonie dento-den- taire poste´ rieure. Rev Orthop Dento Faciale 2008,42(1):9-26.

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