The relationship between maxillary central incisor proportions and facial proportions

ABSTRACT

Statement of Problem: Despite the numerous tooth selection studies undertaken, there is no

universally accepted parameter for the selection of maxillary central incisor proportions in

relation to facial proportions.

Purpose: To determine the relationship between height and width of the maxillary central

incisor (MCI) and height and width of the face in adults and to assess the inter-gender

difference. To assess measurement differences between right and left MCI.

Materials & Methods: A prospective study of 149 Caucasian dental students (F:76;M:73)

aged 18-30 (sample size after power calculation was 120).  MCI width and height

measurements were taken.  Horizontal (Ft’-Ft’, Zy’-Zy’, Go’-Go’) and vertical facial

measurements (Tr-Me’, G’-Me’, N’-Me’) were recorded directly with digital calipers by one

operator.  2 sample and paired t-tests, and Pearson correlation coefficient analyses were

performed to evaluate the data (α = 0.05). Intra-examiner reliability was tested by re-

measuring 25 volunteers and applying Bland-Altman and Lin’s Concordance Correlation

analyses.

Results:  Mean MCI height was 10.28mm (right and left) and mean tooth width was 8.65mm

(right) and 8.66mm (left). Inter-gender differences existed for tooth measurements (height

differences M:F 0.54mm (right), 0.46mm (left); width differences M:F 0.26mm) but not for

tooth width-to-height ratios (F:0.85; M:0.84). A mean ratio of 15.56 was found between

bizygomatic width and tooth width (M=15.75, F=15.37), and a mean ratio of 17.93 between

total face height (Tr-Me’) and MCI height (M=17.97, F=17.89). Correlation coefficients were

low for all tooth:face measurements.  Intra-examiner reliability was clinically acceptable.

Conclusions: Males have larger teeth and faces but similar width:height ratios. There is no

significant size difference between right and left MCI. There is little individual relationship

between tooth and face proportions, with little influence of gender. The Biometric ratio of

1:16 for MCI width to bizygomatic width was not confirmed but a ratio of 1:18 and 1:12 is

proposed for MCI height to total face height (Tr-Me’) and face height (N’-Me’) respectively.

CLINICAL IMPLICATIONS

This study provides information regarding maxillary central incisor tooth dimensions in

relation to facial proportions. The results can be clinically applied when planning restorative,

implant, periodontal or orthodontic therapies to achieve a favourable balance of teeth to the

surrounding facial structures and therefore harmonious facial aesthetics.

INTRODUCTION

The shape, size and color of the teeth are a starting point in the clinical evaluation of

dentogingival and smile aesthetics. It is important to correlate these factors to individuals’

facial proportions to achieve a favorable balance of teeth to the surrounding facial structures

and therefore harmonious facial aesthetics. The maxillary central incisor (MCI) is considered

to be the most dominant element in anterior dental aesthetics. Many authors have undertaken

research into the relationship between differing anthropometric facial measurements and

certain intraoral measurements with much of the research focused to aid denture tooth

selection in edentulous patients.1

MCI width has been compared to bizygomatic width (BZY),2–5 as well as inter-pupillary

distance,5,6 inter-commisural width,7 inter-alar width,4,8 philtrum width,4 cranial

circumference,9 and even standing height.10 Berry proposed a ‘Biometric Ratio’ of 1:16 of

MCI width to BZY.2 This 1:16 ratio formed the basis for the Trubyte Tooth Selector

instrument (Dentsply/York Division, Denstsply International, York, Pa.) used to select

anterior prosthetic teeth for complete dentures, but with poor reported accuracy.11,12 The

biometric ratio has been repeatedly investigated with differing conclusions. Kern found no

consistency between BZY measurements and MCI widths on dry skulls with only 31% of 92

skulls demonstrating a 1:16 ratio and the majority (42%) a ratio of 1:15.13 The clinical

applicability of measurements taken on dry skulls is questionable. Other authors verified this

ratio,3,4 but concluded that the correlation was not of sufficient magnitude to justify the

selection of prosthetic teeth based on the ratio.4 One author reported a sex difference with

MCI:BZY 1:16 ratio only present in their female subjects.5

MCI height in relation to facial height is less investigated than width. Berry and House and

Loop proposed a relationship of 1:20 and 1:16 respectively of MCI height to face height

measured from the hairline to the lower edge of the symphysis.2,3 However, House and Loop

found that only 15% of measured subjects’ tooth height correlated with the height determined

by the 1:16 relationship with up to 2mm variation which was thought to be related to incisal

wear. Kern found no relationship between tooth height and skull height (measured from

bregma to menton) with a range between 1:18 and 1:21. However, he found a ‘significant’

percentage (81%) of skulls to have a ratio of 1:11 of tooth height to nasio-menton.13 Tooth

height has also been compared to upper, middle and lower facial heights but with inaccurate

correlations.7

‘Average’ dimensions of maxillary central incisors in the Caucasian population have been

defined as: Crown width: 8-9mm; Crown height: 10-11mm; Width-to-height ratio: 0.75:0.8.14

When comparing right and left MCI dimensions, there are inconsistencies in findings with

some authors reporting discrepancies in horizontal15 and vertical measurements,16 and others

finding no significant differences in mesio-distal diameters.17 Gender variations in anterior

teeth dimensions have been reported for most ethnic groups, with men exhibiting larger

anterior teeth than women, and black subjects tending to have larger teeth than white

subjects,18–21 but with consistent width-to-height ratios.10,22 Few studies compare ethnic

groups23 and others are limited by unequal distribution of sexes7 and poorly stated inclusion

and exclusion criteria3 discounting important factors such as incisal wear and gingival

alteration that impact on crown height measurements.24 Tooth measurements are often

calculated with digital calipers either intra-orally or on gypsum diagnostic casts of the

subjects’ teeth. However, the quality of the hydrocolloid impression or cast or the materials

and mixing protocol are not always reported.7,25

Many previous studies that investigated the relationship between tooth and facial proportions

did not report confidence intervals, standard deviations or sufficient statistical analysis to

draw reliable conclusions. Much of this research is aimed specifically at horizontal

relationships.

The objectives of this study therefore were to determine the relationship between height and

width of the MCI and the height and width of the face in adults. As well as to assess the inter-

gender difference and to assess measurement differences between right and left MCI.

The null hypothesis was that for the population of subjects measured, there is no relationship

between tooth size and face size, with no differences between genders. In addition there is no

difference between right and left MCI proportions.

MATERIALS AND METHODS

This was a prospective study involving measurements of the width and height of the right and

left maxillary central incisors as well as horizontal and vertical facial measurements. Subjects

were dental students at King’s and Guy’s Hospitals, London.

Of the 170 subjects (90F:80M) who wished to participate in the study, 21 subjects (14F:7M)

were excluded, leaving 149 subjects (76F:73M) completing the study. The sample size

calculation performed before commencement of the study indicated a sample size of 111 for

the comparison of correlation coefficients based on a significance with an alpha level of 0.05

and Power at 0.8. On this basis a sample size of 120 was required to allow for drop outs.

Sample size was calculated using G*Power version 3.1.4.26 The sample consisted of

Caucasian dental students between the ages of 18 and 30 with a mean age of 25 years and 4

months. The upper age limit was restricted to 30 in order to reduce the probability of incisal

edge alteration by incisal wear and to reduce the probability of extensive periodontal disease

and extensive gingival recession. The lower age limit of 18 was justified to ensure complete

maturation of gingival tissues. The majority of subjects were Caucasian with insufficient non-

Caucasians to allow appropriate comparison; these 13 non-Caucasian subjects were therefore

excluded.

All subjects had well aligned natural maxillary central incisors with marginal gingival tissues

that were coral pink in colour, firm and knife-edged in form. Subjects were excluded if there

was i) Evidence of gingival alteration- involving gingival overgrowth, hyperplasia,

inflammation, attachment loss or history of periodontal surgery ii) evidence or history of

alteration to incisal edge or proximal surfaces of tooth by restorative intervention, caries,

trauma, or incisal wear, iii) Crowding of anterior maxillary teeth that prevents accurate

measurement of the width of teeth at their largest diameter, iv) ongoing orthodontic

treatment, or v) facial alterations or history of congenital facial anomalies or surgery. Eight

subjects were excluded due to tooth or gingival anomalies including restoration (n=2), tooth

anomaly (n=3), incisal wear (n=1), crowding (n=1) and gingival anomalies (n=1). The study

was approved by King’s College London College Research Ethics Committee and all subjects

provided written consent to participate.

Clinical measurements involved i) Vertical facial measurements; ii) Horizontal facial

measurements and iii) Tooth Measurements. (Table 1) The vertical facial measurements

were: (1) Trichion to Soft Tissue Menton (Tr-Me’) (Total facial height), (2) Soft Tissue

Glabella to Soft Tissue Menton (Gl’-Me’), and (3) Soft Tissue Nasion to Soft Tissue Menton

(N’-Me’) (Facial Height). The horizontal facial measurements were: (1) Soft tissue

Bitemporal width (Ft’-Ft’), (2) Soft tissue Bizygomatic width (Zy’-Zy’) (Maximum facial

width), and (3) Soft tissue Bigonial Width (Go’-Go’). The tooth measurements were (1)

Right and left MCI width (maximum distance between the mesial and distal contact points of

the right and left maxillary central incisors on a line perpendicular to the long axis), and (2)

Right and left MCI height (distance between the gingival margin and the incisal edge on a

line parallel to the long axis). In cases where mild gingival recession was present the distance

between the cemento-enamel junction and the incisal edge was measured.

Facial measurements were taken with spreading and sliding digital calipers whilst the subject

was seated upright in natural head position with the head unsupported, lips at rest and teeth in

light occlusion (Fig 1 and 2). Sliding digital calipers (manufactured by Universal Supplies,

Measurement range: 1-300mm; Graduations of 0.01mm) were used to take vertical facial

measurements. Spreading digital calipers (manufactured by Moore & Wright, Measurement

range: 1-150mm; Graduations of 0.1mm; Accuracy ± 0.01”) were used to take horizontal

facial measurements. Horizontal and vertical tooth measurements were taken with sliding

digital calipers (manufactured by TESA, Measurement range: 1-150mm, graduations

0.01mm). The subject was supine in a dental chair with adequate light. The outer aspect of

the beaks of the calipers were ground down to tapered points to allow precise positioning on

the mesial and distal contact points of the teeth. The internal edges remained unaltered (Fig

1). They were barrier wrapped to comply with cross-infection guidelines. All measurements

were taken by the same operator (SR). The data was recorded on a data collection sheet and

then transferred to an Excel® spreadsheet.

Intra-examiner clinical measurement repeatability was assessed by taking measurements on

25 volunteers (16F:9M) who were not participating in the main study and who were not

undergoing any treatment that could affect the position or shape of their soft tissues or their

maxillary incisors between the two time points; T1, and T2 (2 weeks later). All were of

Caucasian origin (n=25). The measurements were taken by one examiner (SR) with the same

digital calipers and methodology used for the main study.

Bland-Altman and Lin’s Concordance Correlation were used to assess the single operator

repeatability. The mean, standard deviation, range and 95% confidence intervals were

calculated for all facial and tooth measurements. Gender differences were calculated with 2

sample t-Tests and differences between right and left maxillary central incisors calculated

with a paired t-Test. Tooth-to-face ratios were calculated along with their 95% confidence

intervals. Pearson correlation coefficients were calculated to assess the correlation between

absolute tooth and facial measurements.

RESULTS

There was clinically acceptable operator repeatability for all values when clinical

measurements were retaken after a 2-week interval as demonstrated by Bland- Altman plots

and Lin’s Concordance Correlation graph. Soft Tissue Nasion-Soft Tissue Menton (N’-Me’)

demonstrated slightly increased bias (0.427) and increased limits of agreement (-

2.1693.022) in comparison to other vertical facial measurements (Tr-Me’, G’-Me’). Of the

horizontal facial measurements, Bi-gonial width (Go’-Go’) demonstrated slightly increased

bias (0.408) and increased limits of agreement (-2.7483.564) in comparison to other

horizontal facial measurements (Ft’-Ft’, Zy’-Zy’). Of the tooth measurements the height

measurements demonstrated increased bias and limits of agreement than corresponding width

measurements for right and left incisors.

The descriptive statistics (mean, standard deviation, range and 95% confidence intervals) of

the recorded measurements are listed in Table 2. In relation to tooth measurements, the mean

MCI height was 10.28 mm (for both right and left incisors) and the mean MCI width was

8.65mm (right) and 8.66 mm (left). Inter-gender comparisons were made with two sample t-

tests. The values for tooth and facial measurements are greater for men than for women, with

effect size and statistically significant inter-gender differences (P<0.05) shown in Table 2.

Tooth height displayed greater inter-gender differences than tooth width with a mean height

difference of 0.54mm (right) and 0.46mm (left) and a mean width difference of 0.26mm

(right and left). While being statistically significantly different (P<0.05), the clinical

significance of a tooth width difference of 0.26 mm is unlikely.

The MCI width-to-height ratio is an important additional relationship. The mean ratio for

right and left MCI width-to-height was 0.85. Despite the increased width and height of both

right and left maxillary central incisors in males, there was minimal difference between

genders with respect to tooth width-to-height ratios (male 0.84, female 0.85), which is

unlikely to be clinically significant. Similarly, despite larger face measurements in males than

females, the proportions of face width and face height were nearly identical between sexes.

Facial width (Zy’-Zy’) was in a ratio of 0.73 to the Physiognomical Facial Height (Tr’-Me’)

in both females and males.

Comparison of right and left MCI was made with a Paired t-test. No statistically significant

difference was found overall between right and left maxillary central incisors, even when

height and width were compared separately and by gender (Table 3).

The tooth width–to- face width and tooth height -to- face height ratios are compared in Table

4. The right MCI was used to represent both right and left MCI due to their minimal reported

differences. In relation to horizontal ratios, a mean ratio of 14.92 exists between MCI width

and bitemporal width (males 15.14, females 14.71) and 15.56 between MCI width and

bizygomatic width (males 15.75, females 15.37). Vertical ratios show a mean ratio of 17.93

between MCI and total face height (Tr-Me’) (males 17.97, females 17.89) and 11.85 between

MCI height and N’-Me’ (males 11.93, females 11.78). Statistically significant inter-gender

differences were present for horizontal ratios but not for vertical ratios using a 2 sample t-test

with equal variances (Table 4).

Pearson correlation coefficients for horizontal and vertical tooth-to-face measurements

demonstrated a positive but weak relationship when all subjects were included (Table 5). In

relation to horizontal proportions, there was a negative correlation between bitemporal and

bigonial facial measurements and right MCI width in female subjects. The 95% confidence

intervals for nearly all horizontal proportions included 0. Despite this, p-values indicated a

statistically significant relationship between bizygomatic width and right MCI width in males

and females combined and also in the male subset (α = 0.05). Comparison of vertical tooth

and face measurements also revealed weak correlations particularly in males. Correlation

coefficients were below 0.1 in males, with Tr-Me’ : Right MCI demonstrating negative

correlation at -0.06. However, p-values indicate sufficient evidence to reject the null

hypothesis demonstrating statistically significant relationships between all vertical facial

measurements and right tooth height in the total dataset (males and females). When

subdivided, only the G’-Me’ was statistically significant in females.

DISCUSSION

The measured tooth values in this investigation could help in planning treatment and

executing clinical procedures to restore ideal clinical crown dimensions based on individual

patients.

The mean MCI width (right 8.65 mm and left 8.66mm, Table 2) recorded in the present study

compares favourably with measurements reported by Abdullah (8.77mm), Al Wazzan (8.48

mm) and Hasanreisoglu et al (8.6mm, s.d 0.5).5,28,29 Earlier studies that recorded

measurements on extracted teeth such as Magne et al found width and height measurements

increased by approximately 1mm (mean width 9.10mm, length 11.69mm).24 When the

subjects were separated by gender, a higher mean incisor width was found for males than for

females (8.78 versus 8.52 mm). Variation based on gender has also been reported by Garn et

al (males 8.78 mm, females 8.50 mm) and Lavelle (males 8.79, females 8.54 mm).17,19

In relation to MCI height (right and left 10.28mm), there were greater differences when

compared to studies by Tsukiyama et al21 (11.93mm) and Magne et al24 (11.69mm). However,

these authors studied extracted teeth and measured height consistently to the cervico-enamel

junction (CEJ). The difference in height measurements could be accounted for by the

stability and level of the gingival level. In this study, tooth height was recorded as the

distance between the unworn and unrestored incisal edge to the gingival crest or the CEJ.

Morrow demonstrated that the process of passive eruption, when the gingiva migrates up the

labial surface of the anatomical crown stabilizing 1-2mm from the CEJ, may not be complete

even at age 18-19 in males. 30 When separated by gender (female 10.02mm, male 10.52mm),

MCI height was comparable to measurements by Gillen et al.22 (female 9.80mm, male

10.68mm) but larger than those by Sterrett et al. 10(female 9.39mm, male 10.19mm).

This study confirmed similar measurements for right and left maxillary central incisors with

statistically insignificant differences. This is in agreement with Gillen et al22 but dissimilar to

other studies. 15,16

The mean tooth width-to-height ratio of 0.85 is consistent with findings of Sterrett 10 (0.85)

but different to other studies that confirmed a ratio of 0.75 which has been reported as the

ideal crown proportion. 21,24 A ratio of 0.85 has been suggested to produce shorter wider

crowns. 31 All these studies confirmed similar inter-gender tooth ratios as was found in this

study.

The mean facial width/bizyomatic width (females 130.51mm, males 137.94mm) compares

favourably to Farkas’ anthropometric studies (females 130mm, males 140mm) (Table 2).32

However, both the bitemporal (females 124.86mm, males 132.49mm) and bigonial width

(females 104.36mm, males 112.38mm) were larger than Farkas’ reports (bitemporal: F

110mm, M 115mm; bigonial: F 95mm, M 105mm). The differences could be accounted by

measurement error particularly in areas with excess soft tissue such as soft tissue gonion, or

differing facial forms.

Tooth size to face size ratios have commonly been used to aid denture tooth selection in

edentulous patients. The 1:16 maxillary central incisor width: bizygomatic width ratio

proposed by Berry and confirmed by House and Loop, was not found in this study 2,3. Instead

a mean ratio of 1:15.56 (right) and 1:15.53 (left) was found, with 1:15.75 (right) and 1:15.72

(left) for males and 1:15.37 (right) and 1:15.72 (left) for females. This does not correlate with

findings by Hasanreisoglu et al5 who found the 1:16 biometric ratio in only their female

subjects. In relation to other horizontal facial measurements, this study found an approximate

1:15 proportional relationship between MCI width and bitemporal width (mean 1:14.92,

female 14.71, male 15.14) (Table 4), which has not been reported in the literature previously.

However, bitemporal width values in this study were found to be larger than other guides. 32

Vertical proportions between MCI height and facial height have been less investigated.

Berry22 and House and Loop3 projected a 1:20 and 1:16 ratio between incisor height and total

face height (Tr-’Me’). The results of this study suggest an approximate proportion of 1:18

for MCI to total face height (mean 17.93, female 17.89, male 17.97) and 1:12 for MCI to face

height (M’-Me’) (mean 11.85, female 11.78 and male 11.93). This could be a useful

customized guide for appropriate maxillary crown restoration or crown lengthening in

individual restorative patients.

When assessing absolute measurement values, poor correlation was found between tooth

width and height when compared to face width and height as indicated by the low correlation

coefficients shown in Table 5. Other authors also found similar correlation coefficient

values4, suggesting that the ratios of tooth-to-face therefore have little predictive value.

Many studies fail to report P-values associated with correlation coefficients or the confidence

intervals. Those that report P-values, rely on the demonstrated ‘significance’ to draw

conclusions of the relationship between face and tooth, despite having correlation coefficients

of a maximum of 0.37.29 In this study, although P-values indicate some ‘significant’

relationships between face and tooth, a mathematical relationship between tooth proportions

and face proportions appears doubtful. The tooth:face ratios could be a useful clinical tool to

aid in rough estimates of ‘average’ patient tooth size but care must be taken as they have a

questionable predictive value.

In general, tooth and face measurements and their comparisons had small standard deviations

and 95% confidence intervals indicating a relatively low margin of prediction error.

Reliability assessments indicated clinically acceptable operator repeatability. There were

however discrepancies between certain measurements when compared with other studies;

tooth height measurements and bitemporal, bigonial and N’-Me’. It is these particular

measurements that also had increased bias and Limits of Agreement when tested for

repeatability. However, these differences were small and therefore operator reliability is

unlikely to fully account for measurement error. Inaccurate landmark identification could be

a contributory factor. Soft tissue gonion is a difficult landmark to identify particularly in

patients with excessive soft tissue. Marking the skin overlying the points has been suggested

to aid accurate landmark identification. 33 Precise determination of soft tissue nasion can also

be challenging to accurately and consistently identify due to it being a constructed rather than

anatomical landmark. Measuring technique and the measuring instrument can also contribute

as sources of error. In this study we used a method of direct facial and tooth measurement

rather than indirect diagnostic casts and 3D computer software. Favorable reliability and

accuracy has been demonstrated through the use of digital models for indirect tooth

measurements and Cone Beam Computed Tomography reproduced images for indirect facial

measurements.34,35 However, a direct method reduced the chance of sources of error such as

linear distortion of impressions and the impact of skin texture, color and facial line angles on

CBCT facial analyses.35,36 Hunter and Priest only found a 0.1mm difference between intra-

oral and cast-derived tooth measurements.25 Measurements with digital calipers have also

been found to produce accurate and reliable results.37 Direct measurements therefore offered

a simple reliable method, allowing a larger sample size.

A checklist for aesthetic success should encompass the objective analysis of the proportions

of anterior teeth as well as the more subjective aesthetic integration into the frame of the face

and individual. Further research into perceptions of attractiveness of different size anterior

teeth would therefore be useful.

CONCLUSIONS

Within the limitations of the present study, the following conclusions were drawn:

There is little individual relationship between tooth proportions and face proportions.

The Biometric ratio of 1:16 for maxillary central incisor width to bizygomatic width

is not confirmed

A ratio of 1:18 and 1:12 is proposed for maxillary central incisor height to total face

height (Tr-Me’) and face height (N’-Me’) respectively.

Gender has little influence on tooth-to-face proportions.

All tooth and face measurements were larger for males than females, but width:height

ratios were similar.

No statistically significant difference between right and left maxillary central incisors

was found.

REFERENCES

1. Young HA. Selecting the Anterior Tooth Mold. J Prosthet Dent. 1954;4:748–760.

2. Berry FH. Is the theory of temperaments the foundation of the study of prosthetic art?

Dent Mag. 1905:405.

3. House MM, Loop JL. Form and Color Harmony in the Dental Art. Whittier; 1939.

p.16-22

4. Scandrett FR, Kerber PE, Umrigar ZR. A clinical evaluation of techniques to

determine the combined width of the maxillary anterior teeth and the maxillary central

incisor. J Prosthet Dent. 1982;48:15–22.

5. Hasanreisoglu U, Berksun S, Aras K, Arslan I. An analysis of maxillary anterior teeth:

facial and dental proportions. J Prosthet Dent. 2005;94:530–8.

6. Cesario V a, Latta GH. Relationship between the mesiodistal width of the maxillary

central incisor and interpupillary distance. J Prosthet Dent. 1984;52:641–3.

7. Zlatarić DK, Kristek E, Čelebić A. Analysis of Width / Length Ratios of Normal

Clinical Crowns of the Maxillary Anterior Dentition : Correlation Between Dental

Proportionsand Facial Measurements. Int J Prosthodont. 2007;20:313–315.

8. Isa ZM, Tawfiq OF, Noor NM, Shamsudheen MI, Rijal OM. Regression methods to

investigate the relationship between facial measurements and widths of the maxillary

anterior teeth. J Prosthet Dent. 2010;103:182–8.

9. Sears VH. Selection of Anterior Teeth for Artificial Dentures. J Am Dent Assoc.

1941;28:928–935.

10. Sterrett JD, Oliver T, Robinson F, Fortson W, Knaak B, Russell CM. Width/length

ratios of normal clinical crowns of the maxillary anterior dentition in man. J Clin

Periodontol. 1999;26:153–7.

11. LaVere AM, Marcroft KR, Smith RC, Sarka RJ. Denture tooth selection: An analysis

of the natural maxillary central incisor compared to the length and width of the face.

Part I. J Prosthet Dent. 1992;67:661–663.

12. LaVere A, Marcroft KR, Smith RC, J SR. Denture tooth selection : An analysis of the

natural maxillary central incisor compared to the length and width of the face : Part II.

J Prosthet Dent. 1992;67:810–812.

13. Kern BE. Anthropmetric parameters of tooth selection. J Prosthet Dent. 1967;17:431–

437.

14. Naini FB. Facial Aesthetics: Concepts and Clinical Diagnosis. 1st ed. Wiley-Blackwell;

2011. p 389–393.

15. Ballard M. Asymmetry in tooth size a factor in etiology, diagnosis and treatment of

malocclusion. Angle Orthod. 1944;14:67–71.

16. Mavroskoufis F, Ritchie GM. Variation in size and form between left and right

maxillary central incisor teeth. J Prosthet Dent. 1980;43:254–257.

17. Garn S, Lewis A, Swindler D, RS K. Genetic control of sexual dimorphism in tooth

size. J Dent Res. 1967;46:963–72.

18. Altemus LA. A comparison of cephalofacial relationships. Angle Orthod.

1960;30:223–240.

19. Lavelle C. Maxillary and mandibular tooth size in different racial groups and in

different occlusal categories. Am J Orthod. 1975;61:29–37.

20. Richardson ER, Malhotra SK. Mesiodistal crown dimension of the permanent dentition

of American Negroes. Am J Orthod. 1975;68:157–64.

21. Tsukiyama T, Marcushamer E, Griffin TJ, Arguello E, Magne P, Gallucci GO.

Comparison of the anatomic crown width/length ratios of unworn and worn maxillary

teeth in Asian and white subjects. J Prosthet Dent. 2012;107:11–6.

22. Gillen R, Schwartz R, Hilton T, DB E. An analysis of selected normative tooth

proportions. Int J Prosthodont. 1994;7:410–7.

23. Varjão FM, Nogueira SS. Nasal width as a guide for the selection of maxillary

complete denture anterior teeth in four racial groups. J Prosthodont. 2006;15:353–8.

24. Magne P, Gallucci GO, Belser UC. Anatomic crown width/length ratios of unworn and

worn maxillary teeth in white subjects. J Prosthet Dent. 2003;89:453–61.

25. Hunter WS, Priest WR. Errors and discrepancies in measurement of tooth size. J Dent

Res. 1959;39:405–14.

26. Erdfelder E, Faul F, Buchner A. A general power analysis program. sample size

calculated using G*Power version 3.1.4. GPOWER A Gen power Anal program Behav

Res Methods, Instruments, Comput. 1996;28:1–11.

27. Cohen J. Statistical power analysis for the behavioral sciences. New Jersey: Lawrence

Eribaum; 1988.

28. Abdullah MA. Inner canthal distance and geometric progression as a predictor of

maxillary central incisor width. J Prosthet Dent. 2002;88:16–20.

29. Al Wazzan KA. The relationship between intercanthal dimension and the widths of

maxillary anterior teeth. J Prosthet Dent. 2001;86:608–12.

30. Morrow L a, Robbins JW, Jones DL, Wilson NH. Clinical crown length changes from

age 12-19 years: a longitudinal study. J Dent. 2000;28:469–73.

31. Ahmad I. Anterior dental aesthetics: Dental perspective. Br Dent J. 2005;199:135–41.

32. Farkas L. Anthropometry of the head and face in medicine. Elsevier; 1981.

33. Mollov N, Bosio JA, Pruszynski J, Wirtz T. Intra- and inter-examiner reliability of

direct facial soft tissue measurements using digital calipers. J World Fed Orthod.

2012;1:e157–e161.

34. Nalcaci R, Topcuoglu T, Ozturk F. Comparison of Bolton analysis and tooth size

measurements obtained using conventional and three-dimensional orthodontic models.

Eur J Dent. 2013;7:66–70.

35. Kook M-S, Jung S, Park H-J, et al. A comparison study of different facial soft tissue

analysis methods. J Cranio-Maxillofacial Surg. 2014:42:648-656.

36. Hollinger J, Lorton L, Krantz W, Connelly M. A clinical and laboratory comparison of

irreversible hydrocolloid impression techniques. J Prosthet Dent. 1984;51:304–309.

37. Zilberman O, Huggare J a V, Parikakis K a. Evaluation of the validity of tooth size and

arch width measurements using conventional and three-dimensional virtual orthodontic

models. Angle Orthod. 2003;73:301–6.

TABLES

Table 1

Description of the points used for facial soft tissue measurements

Vertical

Trichion (Tr) The midline point at the junction of the hairline and

forehead. In subjects with receding hairlines, trichion

can be determined by raising eyebrows and noting the

most superior aspect of contraction of the frontalis

muscle

Soft Tissue Glabella (Gl’) The most prominent midline point of the forehead

between the brow ridges

Soft Tissue Nasion (N’) The point in the midline of the nasal radix and

nasofrontal region

Soft Tissue Menton (Me’) The most inferior midline point of the soft tissue chin

Horizontal

Frontotemporale (Ft’) The most medial point on the temporal crest of the

frontal bone

Zygion (Zy’) The most lateral point of the soft tissue overlying each

zygomatic arch

Gonion (Go’) The most lateral point on the mandibular (gonion)

angle.

Table 2

The mean, standard deviation, range and 95% confidence intervals for the horizontal and

vertical facial and tooth measurements subdivided by gender (mm)

All (n=149) Females (n=76) Males (n=73) F:MP-value

Variable (mm)

Mean (SD) Range 95% CI Mean

(SD) Range 95% CI Mean (SD) Range 95% CI

Vertical Facial

Tr-Me’ 183.16(9.58)

156.27 to 202.43

181.61 to 184.71

178.19(8.06)

156.27 to 197.85

176.35 to 180.03

188.34(8.24)

164.34 to 202.43

186.41 to 190.26

-10.150.00

G’-Me’ 127.06(7.71)

109.09 to 44.15

125.81 to 28.31

122.78 (6.21)

109.09 to 137.79

121.36 to 124.20

131.51(6.52)

114.60 to 144.15

129.99 to 133.03

-8.730.00

N’-Me’ 121.16(7.01)

104.86 to 136.6

120.03 to 122.30

117.40(5.93)

104.86 to 131.16

116.04 to 118.76

125.08(5.82)

111.13 to 136.60

123.72 to 126.44

-7.680.00

Horizontal Facial

Ft’-Ft’ 128.6(7.05)

109.30 to 148.8

127.46 to 129.74

124.86(4.83)

109.30 to 137.00

123.76 to 125.97

132.49(6.92)

114.20 to 148.80

130.88 to 134.10

-7.630.00

Zy’-Zy’ 134.15(6.89)

115.40 to 154.10

133.04 to 135.27

130.51(4.89)

115.90 to 142.40

129.39 to 131.63

137.94(6.64)

115.40 to 154.10

136.39 to 139.49

-7.430.00

Go’-Go’ 108.29(8.20)

88.60 to 139.3

106.96 to 109.61

104.36(6.78)

88.60 to 126.10

102.80 to 105.91

112.38(7.56)

96.50 to 139.30

110.61 to 114.14

-8.020.00

Tooth

RH 10.28(0.89)

8.05 to 12.72

10.14 to 10.43

10.02(0.80)

8.05 to 11.97

9.84 to 10.20

10.56(0.90)

8.69 to 12.72

10.35 to 10.77

-0.540.001

LH 10.28(0.86)

8.05 to 12.45

10.14 to 10.42

10.06(0.52)

8.05 to 12.05

9.87 to 10.24

10.52(0.86)

8.63 to 12.45

10.32 to 10.72

-0.460.002

RW 8.65(0.52)

7.49 to 9.84

8.56 to 8.73

8.52(0.51)

7.53 to 9.68

8.40 to 9.63

8.78(0.51)

7.49 to 9.84

8.66 to 8.90

-0.260.001

LW 8.66(0.53)

7.49 to 9.77

8.58 to 8.75

8.54(0.52)

7.57 to 9.76

8.42 to 8.66

8.80(0.51)

7.49 to 9.77

8.68 to 8.92

-0.260.002

Tr-Me’=Trichion to Soft Tissue Menton; G’-Me’=Soft Tissue Glabella to Soft Tissue

Menton; N’-Me’=Soft Tissue Nasion to Soft Tissue Menton; Ft’-Ft’=Soft Tissue Bitemporal

Width; Zy’-Zy’=Soft Tissue Bizygomatic Width; Go’-Go’=Soft Tissue Bigonial Width;

RH=Right maxillary central incisor Height; LH=Left maxillary central incisor Height;

RW=Right maxillary central incisor Width; LW=Left maxillary central incisor Width;

F:M=Mean difference between female and male face and tooth measurements (mm)

Statistically significant at p<0.05

Table 3

A comparison of right and left maxillary central incisor tooth measurements (mm)

Height Width

RH LH RH:LHP value RW LW RW:LW

P value

All(n-149)

Mean 10.28 10.28 0.001P=0.96

8.65 8.66 -0.18P=0.18

S.D 0.89 0.86 0.52 0.53

95% CI 10.14 to 10.43 10.14 to 10.42 8.56 to 8.73 8.58 to 8.75

Female (n=76)

Mean 10.02 10.06 -0.40P=0.21

8.52 8.54 -0.2P=0.34

S.D 0.80 0.28 0.51 0.52

95% CI 9.84 to 10.20 9.87 to 10.24 8.40 to 9.63 8.42 to 8.66

Male(n=73)

Mean 10.56 10.52 0.42P=0.17

8.78 8.80 -0.17P=0.34

S.D 0.90 0.42 0.51 0.51

95% CI 10.35 to 10.77 10.32 to 10.72 8.66 to 8.90 8.68 to 8.92

RH=Right maxillary central incisor Height; LH=Left maxillary central incisor Height;

RW=Right maxillary central incisor Width; LW=Left maxillary central incisor Width;

RH:LH=Mean difference between right and left maxillary central incisor height;

RW:LW=Mean difference between right and left maxillary central incisor height

Statistically significant gender difference at p<0.05

Table 4

Tooth Size to Face Size Ratios for all subjects using measurements for right maxillary central

incisor, subdivided by gender

Tr-Me’=Trichion to Soft Tissue Menton; G’-Me’=Soft Tissue Glabella to Soft Tissue

Menton; N’-Me’=Soft Tissue Nasion to Soft Tissue Menton; Ft’-Ft’=Soft Tissue Bitemporal

Width; Zy’-Zy’=Soft Tissue Bizygomatic Width; Go’-Go’=Soft Tissue Bigonial Width;

RH=Right maxillary central incisor Height; LH=Left maxillary central incisor Height;

RW=Right maxillary central incisor Width; LW=Left maxillary central incisor Width;

F:M=Mean difference between female and male face-to-tooth ratios

Statistically significant gender difference at p<0.05

Face(F)

Tooth (T)

All (n=149) Females (n=76) Males (n=73) F:MP-value

Mean (s.d) 95% CI Mean

(s.d) 95% CI Mean (s.d) 95% CI

WidthFt’-Ft’

RW

14.92(1.13)

14.74 to 15.10

14.71(1.06)

14.47 to 14.95

15.14(1.17)

14.86 to 15.41

-0.43(P=0.02)

Zy’-Zy’ 15.56(1.04)

15.39 to 15.73

15.37(1.02)

15.14 to 15.61

15.75(1.03)

15.51to 15.99

-0.38(P=0.03)

Go’-Go’ 12.56(1.15)

12.38 to 12.75

12.30(1.12)

12.04 to 12.55

12.84(1.13)

12.56 to 13.10

-0.54(P<0.001)

HeightTr-Me’

RH

17.93(1.67)

17.66 to 18.20

17.89(1.56)

17.54 to 18.25

17.97(1.79)

17.55 to 18.39

-0.79(P=0.77)

G’-Me’ 12.42(1.13)

12.25 to 12.61

12.32(1.00)

12.09 to 12.55

12.54(1.24)

12.26 to 12.83

-0.22(P=0.22)

N’-Me’ 11.85(1.07)

11.68 to 12.03

11.78(0.99)

11.56 to 12.01

11.93(1.15)

11.66 to 12.20

-0.15(P=0.40)

Table 5

Pearson correlation coefficients with P values for face-to-tooth relationships in both

Horizontal and Vertical Planes

Face(F)

Tooth (T)

All (n=149) Females (n=76) Males (n=73)

Mean (95% CI) P value Mean

(95% CI)P value

Mean (95% CI) P value

WidthFt’-Ft’

RW

0.15-0.02 to 0.30 0.08 -0.06

-0.3 to 0.17 0.60 0.06-0.17 to 0.29 0.61

Zy’-Zy’0.290.14 to 0.43 0.0003 0.10

-0.13 to 0.32 0.39 0.260.03 to 0.46 0.03

Go’-Go’0.11-0.05 to 0.27 0.18 -0.08

-0.30 to 0.15 0.51 0.04-0.19 to 0.27 0.74

HeightTr-Me’

RH

0.190.03 to 0.34 0.02 0.14

-0.09 to 0.35 0.23 -0.06-0.28 to 0.18 0.64

G’-Me’ 0.310.16 to 0.45 0.0001 0.30

0.08 to 0.49 0.01 0.07 -0.17 to 0.29 0.58

N’-Me’ 0.290.14 to 0.43 0.0003 0.24

0.02 to 0.44 0.03 0.07 -0.16 to 0.30 0.52

Tr-Me’=Trichion to Soft Tissue Menton; G’-Me’=Soft Tissue Glabella to Soft Tissue

Menton; N’-Me’=Soft Tissue Nasion to Soft Tissue Menton; Ft’-Ft’=Soft Tissue Bitemporal

Width; Zy’-Zy’=Soft Tissue Bizygomatic Width; Go’-Go’=Soft Tissue Bigonial Width;

RH=Right maxillary central incisor Height; LH=Left maxillary central incisor Height;

RW=Right maxillary central incisor Width; LW=Left maxillary central incisor Width;

Statistically significant gender difference at p<0.05