The Importance Of Width And Length Ratios In Anterior Pemanent Dentition.pdf

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The Importance of Ratios of Maxillary Anterior Permanent Teeth in Esthetic Rehabilitation

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Sillas Duarte, Jr, DDS, MS, PhD Associate Professor, Department of Comprehensive Care Case School of Dental Medicine, Case Western Reserve University Cleveland, Ohio, USA

Patrick Schnider, CDT Oral Design Montreux Montreux, Switzerland

Ana Paula Lorezon, DDS Private Practice Campinas, São Paulo, Brazil

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].

224 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 3 • NUMBER 3 • AUTUMN 2008

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CASE REPORT

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Abstract The aim of this study was to investigate the

and length measurements varied between

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

maxillary anterior teeth in the following or-

of maxillary anterior permanent teeth in an-

der: central incisors > canines > lateral in-

terior esthetic rehabilitation. Digital photo-

cisors. Maxillary central incisors displayed

graphs were taken of the anterior teeth for

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

each participant (approximately 20 years

al incisors (LI) displayed the smallest W/L

old). A maxillary impression was taken with

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

irreversible hydrocolloid and cast in die

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

stone under vacuum. The widest mesiodis-

sions have a positive effect on the final

tal width and incisogingival length of the

restoration; therefore, it is suggested that

tested teeth were measured. The data were

the specific width, length, and W/L ratio

submitted to analysis of variance, which

should be used in esthetic rehabilitations of

showed significant statistical differences

maxillary anterior teeth.

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

(Eur J Esthet Dent 2008;3:224–234.)

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225 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 3 • NUMBER 3 • AUTUMN 2008

CASE REPORT

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thetic rehabilitation is establishing a harmo-

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One of the most challenging tasks in esnious distribution of teeth shapes, sizes,

Undergraduate dental students (approxi-

and proportions. Maxillary anterior teeth

mately 20 years old) of São Paulo State

are considered to be the key elements for

University at Araraquara volunteered for

a pleasant smile.

1

Some studies have

this study. The students were selected

shown differences in the widths, lengths,

based on the following inclusion criteria: (1)

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

healthy marginal tissue with no evidence of

anterior teeth.2–6 For this reason, under-

gingival alteration, (2) presence of all ante-

standing the relationship between the

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

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

gery or orthodontics, (4) no noticeable in-

would be helpful to achieve natural esthet-

cisal wear or anterior restorations, and (5)

ic restorations.3,6 In addition, more and

absence of anterior restorations.

more aged patients are searching for an

A digital camera (Fujifilm FinePix S2 Pro,

opportunity to reverse the signs of aging

Fuji Film) was used to produce standard-

and to restore a youthful appearance.7,8

ized photographs of the facial surfaces of

Thus, an analysis was carried out to in-

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

vestigate the mean width, length, and W/L

up photographs (2:1) of central incisors

ratio in unworn maxillary anterior teeth of

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

young patients. The parameters found will

Subsequently, a maxillary impression was

be applied to restore the dimensions of

taken of each participant with irreversible

maxillary anterior teeth.

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.

Fig 1

Measuring the mesiodistal width and incisogin-

gival length of the maxillary central incisor.

226 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 3 • NUMBER 3 • AUTUMN 2008

Fig 2

Measuring the mesiodistal width and incisogin-

gival length of the maxillary lateral incisor and canine.

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Table 1

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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)

7.4 (0.9)

9.01 (0.97)

0.82 (0.10)

Total

102

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DUARTE ET ALopyrig No C t fo rP ub lica tio n Mean (SD) widths, lengths, and W/L ratios of maxillary anterior teeth t e s se nc e

Table 2 Multiple comparisons of maxillary anterior W/L ratios*

Results

n

The mean, standard deviation, and range

Subset 1 a

Subset 2

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

Lateral incisors

34

.790

–

sented in Table 1. ANOVA revealed statisti-

Canines

34

.834a,b

.834b

Central incisors

34

–

.853b

.064

.423

cally significant differences in each category: width (P < .0001), length (P < .0001), and

P

*Same superscript letters indicate no statistically significant difference.

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 following 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 subsets of W/L ratios were found. Maxillary central incisor width corresponded to 85% of the length, resulting in the largest W/L ratio of the three maxillary anterior teeth. The

Fig 3

Preoperative view of the maxillary central incisors.

Fig 4

All crowns were sectioned and removed.

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 allceramic crowns (maxillary right central and lateral incisors) that showed inappropriate width/length ratios (Fig 3). The old crowns

227 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 3 • NUMBER 3 • AUTUMN 2008

CASE REPORT

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Cast metal post and core after crown removal.

Fig 6

Esthetic post and core used to improve light

transmission.

a Fig 7

b

Fig 8

b

c

b

c

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

a Fig 9

c

(a to c) Waxup of the maxillary incisors.

a

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

228 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 3 • NUMBER 3 • AUTUMN 2008

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Fig 5

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a

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b

Fig 10

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

traction cord in place.

were sectioned (Fig 4), and the existing

tions, the provisional crowns had a W/L

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

ratio similar to the data displayed in Table 1.

improve light transmission, the metallic

After 6 months, the soft tissues had sta-

post and core was substituted with a zirco-

bilized (Fig 10), and the final impression

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

was taken with polyvinyl siloxane (Figs 11a

same appointment, cosmetic soft tissue re-

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

contouring was performed for the right

production, a Geller master cast was pro-

central and lateral incisors. Provisional

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

crowns were carefully crafted to assist in

feldspathic crowns were fabricated based

the physiologic remodeling of the soft tis-

on individual tooth proportion (ITP). The

sue complex.

concept of ITP depends on the available

After 6 months of healing, an impression

space for tooth width. Therefore, to main-

of the abutment teeth was taken and a wax-

tain the correct ITP, some modifications of

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

anterior teeth arrangement may be re-

ation previous reports of an optimal 80%

quired. For instance, in situations with re-

3,10

ratio of maxillary anterior teeth.

The wax-

duced interdental space, maxillary teeth

up was clinically tried-in to allow for correc-

could be rotated to produce a satisfactory

tions of tooth shape and proportion by

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

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

not symmetrical; instead, it should be ac-

ical try-in, the waxup was duplicated using

centuated more on side than the other. Fig-

polymethyl methacrylate resin (New Out-

ure 12 shows teeth that were rotated to fit

line, Anaxdent) and cemented in place with

reduced interdental space. The final restorations were then bonded

non-eugenol cement (Fig 9). The provisional crowns were evaluated

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

by the patient for 30 consecutive days. In-

come showed a satisfactory esthetic result,

traoral

mainly due to the incorporation of the prop-

adjustments

of

the

provisional

restorations were performed to meet the 11

patient’s expectations.

er ITP for the restored teeth (Fig 14).

After final correc-

229 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 3 • NUMBER 3 • AUTUMN 2008

CASE REPORT

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d Fig 11

b

c

e

f

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a

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

produced for all abutments.

a

Fig 12

(a and b)

Examples of modified

anterior

teeth

arrangement for reduced interproximal space. The concept of

individual

tooth

proportions depends on the space availb

230 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 3 • NUMBER 3 • AUTUMN 2008

able for tooth width.

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(a) Preoperative and

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Fig 13

(b) postoperative photographs of

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the central incisors.

a Fig 14

a

b

b

c

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

lateral incisors = 79%.

Case 2

maxillary teeth.13 After 1.5 years of treatment, some deficiencies in the soft tissue

A 41-year-old female patient presented

were observed. Loss of interdental papillae

with advanced periodontal disease with

resulting in large black triangles was evi-

attachment loss and mobility of the maxil-

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

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

tive cast post and core were removed. An

derwent intense periodontal therapy asso-

impression was taken, a waxup was made

ciated with orthodontic extrusion of the

as described in case 1, and provisional

Fig 15

Fig 16

Preoperative view of the maxillary anterior

After periodontal treatment, large interdental

sextant with advanced periodontal disease and defec-

black triangles were evident due to the loss of interdental

tive porcelain-fused-to-metal crowns.

papillae.

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CASE REPORT

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17

A

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Fig

slight

mesial rotation of the central incisors was required

to

over-

come the excess interproximal space.

a Fig 18

b (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.

crowns were fabricated based on the wax-

wings17; Fig 18) was utilized to overcome

up and relined every 2 weeks to stimulate

the excess interproximal space. The areas

14,15

interdental papillae formation.

However,

alongside

the

defined

ITP

were

also

after 6 months no interdental papillae had

shaped to generate areas of shadow to

formed between the maxillary central inci-

contribute a more pleasant arrangement

sors. This was due to the reduced vertical

of the anterior teeth. Porcelain-fused-to-

distance from the crest of bone to the

metal crowns were fabricated with a re-

height of the interproximal contact.16 To

duced framework and cemented on the

achieve a better esthetic outcome, the

prepared teeth. The final restorations met

concept of ITP was applied to the final

the patient’s approval (Fig 19).

restorations.

However,

the

interdental

space available was larger than the required mean width of the individual teeth.

Discussion

Minor rotation of the maxillary central incisors (Fig 17) associated with slight inter-

The findings of the present study show the

dental extension of the restorations (mini-

importance of tooth width, length, and W/L

232 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 3 • NUMBER 3 • AUTUMN 2008

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Fig 19

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Final results achieved using the concept of individual tooth proportion.

ratio when creating an esthetic rehabili-

tively.5 These differences in perception

tation. The mean tooth width and length

may explain why patients sometimes dis-

data in this study are consistent with the

approve of the final outcome. To avoid this

data found in the literature for permanent

situation, knowledge of width, length, and

dentition.

3,4,6

Determining the width and

W/L ratio is imperative.

length measurements facilitates the fabri-

Studies of patient judgment of smiles

cation process of an esthetic restoration.

report a tendency for acceptance of W/L

Therefore, to achieve a better distribution

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

of the maxillary teeth into the sextant, the

is in accordance with the present findings.

W/L ratio should be carefully evaluated

It was believed that W/L ratio is homoge-

before the delivery of the restorations.

neous for the three anterior maxillary tooth

Variations in the optimal W/L ratio are 2,3,5,6

present in the literature.

groups.2,3 However, the data show that

In addition, the

each maxillary anterior tooth has its own

perception of the optimal W/L ratio varies

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

greatly between professionals and pa-

ranked as follows: central incisors > ca-

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

nines > lateral incisors. If these dimen-

233 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 3 • NUMBER 3 • AUTUMN 2008

CASE REPORT

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Conclusions

bilitation, the final outcome will show supe-

n

sions are reproduced in an anterior reharior esthetics and a more natural appear-

Each maxillary anterior tooth has its own

ance. Therefore, it is strongly suggested

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

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

dictable restoration of the maxillary anteri-

tios should be used in the esthetic rehabil-

or region can be achieved using the prop-

itation of maxillary anterior teeth.

er dimensions.

Acknowledgments The authors thank Dr Bernard Tandler for editorial assistance.

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