The importance of width and length ratios in anterior pemanent dentition.pdf

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Sillas Duarte, Jr, DDS, MS, PhDAssociate Professor, Department of Comprehensive Care

Case School of Dental Medicine, Case Western Reserve University

Cleveland, Ohio, USA

Patrick Schnider, CDTOral Design Montreux

Montreux, Switzerland

Ana Paula Lorezon, DDSPrivate Practice

Campinas, So Paulo, Brazil

CASE REPORT

THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY

VOLUME 3 NUMBER 3 AUTUMN 2008

224

The Importance of Width/LengthRatios of Maxillary Anterior Perma-nent Teeth in Esthetic Rehabilitation

Correspondence to: Dr Sillas Duarte, Jr

Department of Comprehensive Care, Case School of Dental Medicine, Case Western Reserve University, 10900 Euclid Avenue,

Cleveland, OH 44106-4905; phone: 216 368 67367; e-mail: [email protected].

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DUARTE ET AL

and length measurements varied between

maxillary anterior teeth in the following or-

der: central incisors > canines > lateral in-

cisors. Maxillary central incisors displayed

the largest W/L ratio (85%), maxillary later-

al incisors (LI) displayed the smallest W/L

ratio (79%), and canines displayed the in-

termediate W/L ratio (83%). These dimen-

sions have a positive effect on the final

restoration; therefore, it is suggested that

the specific width, length, and W/L ratio

should be used in esthetic rehabilitations of

maxillary anterior teeth.

(Eur J Esthet Dent 2008;3:224234.)

Abstract

The aim of this study was to investigate the

importance of the width/length (W/L) ratio

of maxillary anterior permanent teeth in an-

terior esthetic rehabilitation. Digital photo-

graphs were taken of the anterior teeth for

each participant (approximately 20 years

old). A maxillary impression was taken with

irreversible hydrocolloid and cast in die

stone under vacuum. The widest mesiodis-

tal width and incisogingival length of the

tested teeth were measured. The data were

submitted to analysis of variance, which

showed significant statistical differences

within each parameter (P < .05). The width



225

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CASE REPORT



226

Method and materials

Undergraduate dental students (approxi-

mately 20 years old) of So Paulo State

University at Araraquara volunteered for

this study. The students were selected

based on the following inclusion criteria: (1)

healthy marginal tissue with no evidence of

gingival alteration, (2) presence of all ante-

rior teeth, (3) no history of periodontal sur-

gery or orthodontics, (4) no noticeable in-

cisal wear or anterior restorations, and (5)

absence of anterior restorations.

A digital camera (Fujifilm FinePix S2 Pro,

Fuji Film) was used to produce standard-

ized photographs of the facial surfaces of

the maxillary teeth sextant (1:1) and close-

up photographs (2:1) of central incisors

(Fig 1), lateral incisors, and canines (Fig 2).

Subsequently, a maxillary impression was

taken of each participant with irreversible

hydrocolloid (Orthoprint, Zhermack) and

vacuum-poured in type IV synthetic die

stone (GC Fujirock EP). The widest

mesiodistal width and incisogingival length

of the tested teeth were measured with a

digital caliper (Mitutoyo). The data were

submitted to analysis of variance (ANOVA)

with a 5% level of significance.

One of the most challenging tasks in es-

thetic rehabilitation is establishing a harmo-

nious distribution of teeth shapes, sizes,

and proportions. Maxillary anterior teeth

are considered to be the key elements for

a pleasant smile.1 Some studies have

shown differences in the widths, lengths,

and width/length (W/L) ratios of maxillary

anterior teeth.26 For this reason, under-

standing the relationship between the

width, length, and W/L ratio of anterior teeth

would be helpful to achieve natural esthet-

ic restorations.3,6 In addition, more and

more aged patients are searching for an

opportunity to reverse the signs of aging

and to restore a youthful appearance.7,8

Thus, an analysis was carried out to in-

vestigate the mean width, length, and W/L

ratio in unworn maxillary anterior teeth of

young patients. The parameters found will

be applied to restore the dimensions of

maxillary anterior teeth.

Fig 1 Measuring the mesiodistal width and incisogin-

gival length of the maxillary central incisor.

Fig 2 Measuring the mesiodistal width and incisogin-

gival length of the maxillary lateral incisor and canine.

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DUARTE ET AL



227

Results

The mean, standard deviation, and range

of the width, length, and W/L ratio are pre-

sented in Table 1. ANOVA revealed statisti-

cally significant differences in each catego-

ry: width (P < .0001), length (P < .0001), and

W/L ratio (P = .026) of maxillary anterior

teeth. Multiple comparisons for width and

length showed that for maxillary anterior

teeth these dimensions fall into the follow-

ing sequence: central incisors > canines >

lateral incisors (P > .05). Duncan multiple

comparisons were performed to rank the

W/L ratios of maxillary anterior teeth

(Table 2). Two statistically significant sub-

sets of W/L ratios were found. Maxillary

central incisor width corresponded to 85%

of the length, resulting in the largest W/L ra-

tio of the three maxillary anterior teeth. The

smallest W/L ratio was in maxillary lateral

incisors (79%), while canines showed an

intermediate W/L ratio (83%).

Case 1

A 45-year-old male patient presented for

treatment because he was dissatisfied with

his smile. The clinical exam revealed

porcelain-fused-to-metal crowns (maxillary

left central and lateral incisors) and all-

ceramic crowns (maxillary right central and

lateral incisors) that showed inappropriate

width/length ratios (Fig 3). The old crownsFig 4 All crowns were sectioned and removed.

Fig 3 Preoperative view of the maxillary central incisors.

Table 1 Mean (SD) widths, lengths, and W/L ratios of maxillary anterior teeth

n Width (mm) Length (mm) W/L ratio

Central incisors 34 8.14 (0.56) 9.57 (0.60) 0.85 (0.09)

Lateral incisors 34 6.54 (0.54) 8.38 (1.01) 0.79 (0.10)

Canines 34 7.52 (0.74) 9.08 (0.88) 0.83 (0.10)

Total 102 7.4 (0.9) 9.01 (0.97) 0.82 (0.10)

Table 2 Multiple comparisons of max-illary anterior W/L ratios*

n Subset 1 Subset 2

Lateral incisors 34 .790a

Canines 34 .834a,b .834b

Central incisors 34 .853b

P .064 .423

*Same superscript letters indicate no statistically significant difference.

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CASE REPORT



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Fig 5 Cast metal post and core after crown removal.

Fig 7 (a to c) Waxup of the maxillary incisors.

Fig 8 (a to c) Try-in of the waxup.

Fig 9 (a to c) Provisional crowns fabricated from the waxup.

Fig 6 Esthetic post and core used to improve light

transmission.

a b c

a b c

a b c

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tions, the provisional crowns had a W/L

ratio similar to the data displayed in Table 1.

After 6 months, the soft tissues had sta-

bilized (Fig 10), and the final impression

was taken with polyvinyl siloxane (Figs 11a

to 11c). To ensure accurate soft tissue re-

production, a Geller master cast was pro-

duced (Figs 11d to 11f).12 Four all-ceramic

feldspathic crowns were fabricated based

on individual tooth proportion (ITP). The

concept of ITP depends on the available

space for tooth width. Therefore, to main-

tain the correct ITP, some modifications of

anterior teeth arrangement may be re-

quired. For instance, in situations with re-

duced interdental space, maxillary teeth

could be rotated to produce a satisfactory

W/L ratio. It is important that the rotation is

not symmetrical; instead, it should be ac-

centuated more on side than the other. Fig-

ure 12 shows teeth that were rotated to fit

reduced interdental space.

The final restorations were then bonded

to the abutment teeth (Fig 13). The final out-

come showed a satisfactory esthetic result,

mainly due to the incorporation of the prop-

er ITP for the restored teeth (Fig 14).

DUARTE ET AL



229

were sectioned (Fig 4), and the existing

cast post and core was removed (Fig 5). To

improve light transmission, the metallic

post and core was substituted with a zirco-

nia post and composite core (Fig 6).9 In the

same appointment, cosmetic soft tissue re-

contouring was performed for the right

central and lateral incisors. Provisional

crowns were carefully crafted to assist in

the physiologic remodeling of the soft tis-

sue complex.

After 6 months of healing, an impression

of the abutment teeth was taken and a wax-

up was made (Fig 7), taking into consider-

ation previous reports of an optimal 80%

ratio of maxillary anterior teeth.3,10 The wax-

up was clinically tried-in to allow for correc-

tions of tooth shape and proportion by

adding or removing wax (Fig 8). After clin-

ical try-in, the waxup was duplicated using

polymethyl methacrylate resin (New Out-

line, Anaxdent) and cemented in place with

non-eugenol cement (Fig 9).

The provisional crowns were evaluated

by the patient for 30 consecutive days. In-

traoral adjustments of the provisional

restorations were performed to meet the

patients expectations.11 After final correc-

Fig 10 Soft tissues after removal of the provisionals. (a) The first retraction cord was packed in. (b) Second re-

traction cord in place.

a b

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CASE REPORT



230

Fig 11 (a to c) Final impressions showing adequate soft tissue deflection. (d to f) A Geller master cast was

produced for all abutments.

Fig 12 (a and b)

Examples of modi-

fied anterior teeth

arrangement for re-

duced interproximal

space. The concept

of individual tooth

proportions depends

on the space avail-

able for tooth width.

a

b

a b c

d e f

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DUARTE ET AL



231

maxillary teeth.13 After 1.5 years of treat-

ment, some deficiencies in the soft tissue

were observed. Loss of interdental papillae

resulting in large black triangles was evi-

dent (Fig 16). The old crowns and defec-

tive cast post and core were removed. An

impression was taken, a waxup was made

as described in case 1, and provisional

Case 2

A 41-year-old female patient presented

with advanced periodontal disease with

attachment loss and mobility of the maxil-

lary anterior teeth (Fig 15). The patient un-

derwent intense periodontal therapy asso-

ciated with orthodontic extrusion of the

Fig 14 (a to c) Final restorations were fabricated using the following W/L ratios: central incisors = 85% and

lateral incisors = 79%.

Fig 13 (a) Preoperative and

(b) postoperative photographs of

the central incisors.

Fig 15 Preoperative view of the maxillary anterior

sextant with advanced periodontal disease and defec-

tive porcelain-fused-to-metal crowns.

Fig 16 After periodontal treatment, large interdental

black triangles were evident due to the loss of interdental

papillae.

a b

a b c

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CASE REPORT



232

wings17; Fig 18) was utilized to overcome

the excess interproximal space. The areas

alongside the defined ITP were also

shaped to generate areas of shadow to

contribute a more pleasant arrangement

of the anterior teeth. Porcelain-fused-to-

metal crowns were fabricated with a re-

duced framework and cemented on the

prepared teeth. The final restorations met

the patients approval (Fig 19).

Discussion

The findings of the present study show the

importance of tooth width, length, and W/L

crowns were fabricated based on the wax-

up and relined every 2 weeks to stimulate

interdental papillae formation.14,15 However,

after 6 months no interdental papillae had

formed between the maxillary central inci-

sors. This was due to the reduced vertical

distance from the crest of bone to the

height of the interproximal contact.16 To

achieve a better esthetic outcome, the

concept of ITP was applied to the final

restorations. However, the interdental

space available was larger than the re-

quired mean width of the individual teeth.

Minor rotation of the maxillary central inci-

sors (Fig 17) associated with slight inter-

dental extension of the restorations (mini-

Fig 18 (a) Gingival view of the porcelain-fused-to-metal crowns before the mini-wings were fabricated.

(b) Delicate mini-wings were produced to close the interproximal black triangles.

Fig 17 A slight

mesial rotation of the

central incisors was

required to over-

come the excess in-

terproximal space.

a b

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DUARTE ET AL



233

tively.5 These differences in perception

may explain why patients sometimes dis-

approve of the final outcome. To avoid this

situation, knowledge of width, length, and

W/L ratio is imperative.

Studies of patient judgment of smiles

report a tendency for acceptance of W/L

ratios ranging from 75% to 85%,2,5 which

is in accordance with the present findings.

It was believed that W/L ratio is homoge-

neous for the three anterior maxillary tooth

groups.2,3 However, the data show that

each maxillary anterior tooth has its own

W/L ratio (Tables 1 and 2), and can be

ranked as follows: central incisors > ca-

nines > lateral incisors. If these dimen-

ratio when creating an esthetic rehabili-

tation. The mean tooth width and length

data in this study are consistent with the

data found in the literature for permanent

dentition.3,4,6 Determining the width and

length measurements facilitates the fabri-

cation process of an esthetic restoration.

Therefore, to achieve a better distribution

of the maxillary teeth into the sextant, the

W/L ratio should be carefully evaluated

before the delivery of the restorations.

Variations in the optimal W/L ratio are

present in the literature.2,3,5,6 In addition, the

perception of the optimal W/L ratio varies

greatly between professionals and pa-

tients, ranging from 66% to 80%, respec-

Fig 19 Final results achieved using the concept of individual tooth proportion.

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14. Bichacho N. Papilla regenera-tion by noninvasive prostho-dontic treatment: Segmentalproximal restorations. PractPeriodontics Aesthet Dent1998;10:75, 7778.

15. Bichacho N, Eylat Y, Dadi M,Jacoby Y, Weiss E. Restorationmodalities of severely injuredanterior teethGingival inte-gration, papillae support, andpredictable imperfections.Compend Contin Educ Dent2003;24:891894, 896898,900894.

16. Tarnow D, Elian N, Fletcher P,et al. Vertical distance from thecrest of bone to the height of theinterproximal papilla betweenadjacent implants. J Periodontol2003;74:17851788.

17. Magne P, Magne M, Belser U.The esthetic width in fixedprosthodontics. J Prosthodont1999;8:106118.

8.Morley J. The role of cosmeticdentistry in restoring a youthfulappearance. J Am Dent Assoc1999;130:11661172.

9.Raptis NV, Michalakis KX,Hirayama H. Optical behaviorof current ceramic systems. IntJ Periodontics Restorative Dent2006;26:3141.

10. Snow SR. Esthetic smile analy-sis of maxillary anterior toothwidth: The golden percentage.J Esthet Dent 1999;11:177184.

11. Magne P, Magne M. Use ofadditive waxup and directintraoral mock-up for enamelpreservation with porcelainlaminate veneers. Eur J EsthetDent 2006;1:1019.

12. Kopp FR. Esthetic principlesfor full crown restorations. PartII: Provisionalization. J EsthetDent 1993;5:258264.

13. Salama H, Salama M. The roleof orthodontic extrusiveremodeling in the enhance-ment of soft and hard tissueprofiles prior to implant place-ment: A systematic approachto the management of extrac-tion site defects. Int J Periodon-tics Restorative Dent 1993;13:312333.

References

1. Rufenacht C. Fundamentals ofEsthetics. Chicago: Quintes-sence, 1990.

2.Brisman AS. Esthetics: A com-parison of dentists andpatients concepts. J Am DentAssoc 1980;100:345352.

3. Sterrett JD, Oliver T, RobinsonF, Fortson W, Knaak B, RussellCM. Width/length ratios of nor-mal clinical crowns of themaxillary anterior dentition inman. J Clin Periodontol 1999;26:153157.

4.Magne P, Gallucci GO, BelserUC. Anatomic crown width/length ratios of unworn andworn maxillary teeth in whitesubjects. J Prosthet Dent 2003;89:453461.

5.Wolfart S, Thormann H, FreitagS, Kern M. Assessment of den-tal appearance followingchanges in incisor proportions.Eur J Oral Sci 2005;113:159165.

6.Chu SJ. Range and mean dis-tribution frequency of individ-ual tooth width of maxillaryanterior dentition. Pract ProcedAesthet Dent 2007;19:209215.

7. Davis BK. Dental aestheticsand the aging patient. FacialPlast Surg 2006;22:154160.

CASE REPORT



234

Conclusions

Each maxillary anterior tooth has its own

width, length, and W/L ratio. A more pre-

dictable restoration of the maxillary anteri-

or region can be achieved using the prop-

er dimensions.

AcknowledgmentsThe authors thank Dr Bernard Tandler for editorial as-

sistance.

sions are reproduced in an anterior reha-

bilitation, the final outcome will show supe-

rior esthetics and a more natural appear-

ance. Therefore, it is strongly suggested

that specific widths, lengths, and W/L ra-

tios should be used in the esthetic rehabil-

itation of maxillary anterior teeth.

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