The facial soft tissue profile of the southern Chinese: Prosthodontic considerations

ial soft tissue profile odontic considerations Connie S. W. Chiu, BDS, MDS,a and Robert K. F. Clark, BDS, FDSRCPS, University of Hong Kong, Hong Kong

of the southern

Chinese:

PhDb

A simple photographic setup was established to produce standardized life-sized black and white prints of Southern Chinese adults. Facial soft tissue profile analysis was performed on 28 men and 31 women aged 19 to 30, dentate Chinese, having class I occlusion and originating from Guangdong province. The facial profile values studied included the profile convexity, the interlabial contour, the nasolabial contour, the columella and upper lip inclination angles to the true horizontal, and the relative positions of upper and lower lips from the Esthetic plane. Data obtained were compared with those from previous Caucasian studies and other accepted empirical values. The lower third of the face presented the greatest ethnic difference: the interlabial contour was more convex and the upper and lower lips were more protrusive among the Southern Chinese. The widely-used standard of a right-angled nasolabial contour proved to be applicable among the Southern Chinese adult males. However, a more obtuse nasolabial angle, almost 100 degrees, occurred among the women. (J PROSTHET DENT 1992;68:839-50.)

he standards of appreciation of beauty, based on proportion, symmetry, and balance, have long been formulated by artists and painters.l However, the criteria of ideal form are by no means universally accepted and are subject to change with time and according to individual, racial, and cultural variations. Moreover, analysis of the hard and soft tissue profile with a view to improving facial appearance has been a focus of interest among dentists, especially orthodontists. Before the midnineteenth century, research was directed more toward the development of cephalometry and the establishment of skeletal and dental norms. The soft tissues overlying the dentoskeletal framework, however, vary among individual patients in thickness, length, elasticity, and postural tone. Hence, prediction of integumental contour purely from the dentoskeletal pattern becomes difficult if not impossible.’ Diverse profile contours have been demonstrated among people with similar malocclusions; not all patients whose treatment results in a class I dentoskeletal relationship show satisfactory profiles. 2-1oSoft tissue profile analysis is necessaryto assess facial harmony and provide a visual objective for subsequent treatment. 11-r3Changes in lip contour contribute most to the overall improvement in the facial profile after treatment.6* i4-17 Facial profile changes resulting from growth and treatment have been described qualitatively* and quantitative-

Submitted in partial fulfillment for the degree of Master of Dental Surgery, University of Hong Korg. aLecturer, Department of Prosthetic Dentistry hProfessor and Head, Department of Prosthetic Dentistry. *References 3, 4, 6, 11, 12, 18-20.

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existing

Caucasian soft tissue profile

values to denture

construction for the Southern Chinese population. MATERIAL

AND

METHODS

A group of volunteers, including dental students and dental surgery assistants from the Prince Philip Dental Hospital, Hong Kong, originating from Guangdong province in Southern China were recruited. The criteria for selection were a stable natural dentition in class I occlusion with no history of orthodontic or orthognathic intervention, no congenital or acquired defects in the head region, no loss of anterior teeth, and no anterior crowns or bridges. S-References2, 7-9, 14, 16, 17, 21-6.

10/1/41052

THE

lyt by orthodontists. Oral and maxillofacial surgeons have concentrated on the overall facial convexity and the facial proportion.27-2gData on soft tissue profile from the prosthodontic viewpoint 30-34have been more empirical but are nevertheless employed widely without much questioning. Moreover, these data have been nearly all derived from Caucasian samples except for a few data derived from Filipinos,35 North American Blacks,36 Thais, and Thai Chinese.37 Data available from various studies are difficult to compare directly because of the nonstandardized soft tissue points used, the different reference planes or lines used, and the different settings for obtaining profile views. In addition, becauseof the racial variations, direct application of data from one ethnic group to another may not be valid. Some of the available data are shown in Table I. The purpose of the present study is to establish some of the facial soft tissue profile norms of dentate Southern Chinese adults and to investigate the applicability of the

OF PROSTHETIC

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839

CHIU

Table

CLARK

I. Values for soft tissue profile analyses in previous studies Brown and MeDowel12’ 1951

Sample

Unknown

Facial convexity (degrees) Interlabial angle (degrees) Nasolabial 90-120 angle (degrees) Upper lip position

Lower lip position

Burstone* 1958

Subtelnyzl 1959

Ricketts43 1968

Mack3s 1971

Watt and MacGregor34 1976

Caucasian Unknown Unknown 40 Caucasian 15 Male young adults and 15 female Caucasian aged 6-18 yr Both sexes Male 162 Female 161 169 F 4

worms et a1.2g 1976

Linesz4 1978

Unknown

Unknown

Both sexes 169-188

Satravaha and Schlege137 1987

70 Chinese female 180 Thai aged 16-21 yr Chinese 166 i 6 Thai 166 + 5

Male 1’70 Female 160

Both sexes 168 k 6 Both Both sexes sexes 90 90

Both sexes go-110

4mm*3 Behind Esthetic plane

2mm?3 behind Esthetic plane

The teeth present, the molar relationship, the incisal relationship, and horizontal overlap were recorded for each subject. Standardized black and white life-sized photographic prints of the lateral profile view were obtained from each subject by use of a Canon AE-1 camera and a Canon FD-100 mm f/2.& lens (Canon Incorporation, Tokyo, Japan) with shutter speed l/60 second and aperture f8, mounted on a tripod, An electronic flash was directed upwards and reflected from the matt-tile false ceiling to eliminate shadovv formation. Exposure was made with a remote shutter control against a matt-white background. Kodak 135T-MAX ASAlOO black and white film (Eastman Kodak Co., Inc., Rochester, N.Y.) was used and processed under standardized conditions. Each subject stood 1 meter in front of a full-length mirror (Fig. 1). A plumb line was suspended in front of the subject and a meter ruler was suspended immediately behind. Both the plumb line and the meter ruler were set in the same plane perpendicular to the mirror. The subject was positioned with the midsagittal plane coincident with the plane formed by the plumb line and the meter ruler and parallel to the plane of the photographic film. The perpendicular distance between the subject’s sagittal plane and the plane of the photographic film was set at 1.50 m. The

840

AND

Male 88 Chinese 94 +- 14 Female 98 Thai 98 i- 9 Chinese 56% Thai 70% on or behind Esthetic plane Chinese 29% Thai 33% on or behind Esthetic plane

subject was asked to relax the whole body with teeth occluding into maximum intercuspation and the lips relaxed. Walking slightly on the spot and tilting the head backward and forward with decreasing amplitude, before standing still, helped the subject assume the natural head position.38 Two photographs were taken, the first with the mirror covered and the second with the subject looking into his own eyes in the mirror. The reproducibility of the natural head position was assessedby repeating these procedures 4 to 6 hours later on the same day. Life-sized profile views were produced by magnification according to the meter ruler in the film image and the plumb line was included to serve as the external vertical reference. From each photograph, 13 anatomic landmarks (Fig. 2 and Table II) were located and transferred to acetate paper by pricking on the acetate paper with a sharp pointer exactly over each landmark. Each point was then accentuated with an HB pencil to produce a halo mark, the centre of which corresponded to the exact location of the landmark. A Grafbar GP-7 sonic digitizer (Science Accessories Corporation, Southport, Conn.) together with a one-button cross-hair cursor were employed for location and registration of the points on each photograph. Data from all registered points, the corresponding subject’s particulars, and

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SOFT

Table

II.

TISSUE

PROFILE

The 13 anatomic landmarks

Point

subject

used (Figs. 2-8)

Landmark

meter

ruler

Any two points on the plumb line Most posterior point of the tragus The outer corner of the right eye The frontal point-the most prominent point of the forehead The soft tissue nasion-the deepest concavity of the bridge of the nose The point at which the tangent from the “soft tissue chin” touches the nose The point at which tangent from the “soft tissue subnasale” touches the base of the columella The soft tissue subnasale-the turning point between the base of the columella and the upper lip The vermilion border of the upper lip in the midsagittal plane The vermilion border of the lower lip in the midsagittal plane The soft tissue chin-the point touching the tangent from lower lip vermilion border to the chin The most inferior point of the ala of the nose

l&2 3 4

5 6

7 8

9

10 II 12

13

mirror

Fig. 1. Photographic setup.

the photographic conditions were entered into the computer (IBM PC, IBM Incorporation, Armonk, N.Y.). All

linear and angular measurements (Figs. 3 through 8 and Table III) were determined from the recorded coordinates and were then analyzed by the SPSS-X system (Asia Pacific PTE Limited, Singapore). The reproducibility of landmark location was assessed by repeating the tracing 4 months later on 20 randomly selected photographs. The difference between the two recordings from each pair of tracings was assessedfor statistical significance by use of Dahlberg’s formula.3g RESULTS There were 28 men and 31 women with a mean age of 22.5 years (age range 19 to 30 years). The mean incisal overlap was 2.4 mm (standard deviation 1.0 mm). Profile

convexity

The profile convexity of both sexes showed normal distribution

from 148 to 179 degrees, with a mean of 163.4 de-

grees and standard deviation of 5.9 degrees. There was no significant difference in profile convexity between men (163.3 degrees) and women (163.4 degrees) (Table IV and Fig. 9). Bnterlabial

contour

The interlabial contour showed a range of 120 to 172 degrees,with a mean of 140.4 degreesand standard deviation

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Fig. 2. Anatomic landmarks for profile analysis. 1 and 2, True vertical line; 3, tragus; 4, lateral corner of the eye; 5, glabella; 6, nasion; 7, nose tip; 8, base of columella; 9, subnasale; 10, vermilion border of upper lip; 12, vermilion border of lower Iip; 12, chin point; 13, base of ala.

of 10.3 degrees and no significant difference between male (141.9 degrees) and female (139 degrees) (Table V and Fig. 10). Nasolabial

angle

The nasolabial angle was distributed over a range of 64 to 124 degrees, with an average of 93.9 degrees and a stan-

dard deviation of 13 degrees.The mean nasolabial angle of the women (97.4 degrees) was found to be significantly greater than that of the men (90.1 degrees). However, the statistical

significance should be interpreted

with caution

841

CHIU AND CLARK

Fig.

Table III.

Angular measurements

Interlabial contour Nasolabial contour Columella inclination Upper lip inclination Esthetic plane Upper and lower lip positions

included

Angle formed between the line joining points 6 and 9 and the line joining points 9 and 12 (Fig. 3) Angle formed between the line joining points 9 and 10 and the line joining points 11 and 12 (Fig. 4) Angle formed between points 8,9, and 10 (Fig. 5) Angle formed between the line joining points 8 and 9 and the true horizontal line (Fig. 6) Angle formed between the line joining points 9 and 10 and the true horizontal line (Fig. 7) Line formed by the tangent touching the soft tissue chin and the tip of the nose (Fig. 8) Perpendicular distance from the vermilion border of the upper and lower lips with respect to the Esthetic plane (Fig. 8)

as this is the result of one of a number of t-tests used, increasing the chance of significant difference (Table VI and Figs. 11 and 12).

Cohnella

inclination

The columella inclination to the true horizontal plane ranged from 0 to as much as 40 degrees, with an average of 22.7 degrees and standard deviation of 9 degrees. A significant difference between the men (20.0 degrees) and the women (25.2 degrees) was demonstrated. This difference may also be attributed to the inflated type I error arising from the use of multiple t-tests (Table VII and Figs. 13 and 14). 842

contour.

Table IV. Profile convexity t-Test on sample means

Description

Parameter Profile convexity

Fig. 4. Interlabial

3. Profile convexity.

Mixed Male Female

Mean (degrees)

SD

SE (t)

163.4 163.3 163.4

5.9 6.6 5.3

1.27 0.95

t Value

p Value

0.06

>>0.2*

*Where p = 0.05, t = 2, and p = 0.2, t = 1.3; :. p > 0.2.

Table

V. Interlabial

contour t-Test on sample means

Mixed Male

Female

Mean (degrees)

SD

SE

t Value

p Value

140.4 141.9 139.0

10.3 10.9 9.7

2.10 1.74

1.06

>0.2*

*Where p = 0.05, t = 2, and p = 0.2, t = 1.3; :. p > 0.2.

Upper

lip inclination

The upper lip inclination to the true horizontal plane ranged from 52 to 85 degrees with a mean of 70.8 degrees and standard deviation of 6 degrees. No significant difference was found between the men (69.2 degrees) and women (72.2 degrees) (Table VIII and Fig. 15).

Upper

and lower

lip positions

The upper and lower lips were on average 0.6 mm posterior to and 1.5 mm anterior respectively to the Esthetic plane. The position of the upper lip ranged from 3.1 mm behind to 2.3 mm in front of the Esthetic plane, with no significant difference between sexes, whereas that of the NOVEMBER

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FACIALSOFTTISSUEPROFILE

Fig.

5. Nasolabial

contour.

Fig. 7. Upper plane.

lip

inclination

to the true

horizontal

3

Fig.

6. Columella inclination

to the true horizontal

plane. Fig. 8. Position plane.

lower lip ranged from 1.8 mm behind to 7 mm in front, with a significant difference between the men (1 mm) and women (1.9 mm). However, the latter difference may have arisen from the exaggerated type I error possible with the use of multiple t-tests and should be interpreted with caution (Tables IX and X, and Figs. 16 through 18). Orientation of the natural head position with reference to the true vertical plane, obtained with or without the subject looking in the mirror in two separate sittings, revealed no significant difference (Table XI). The landmark location in two different tracings also showed no significant difference (Table XII). THE

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Table

VI.

of upper and lower lip from Esthetic

Nasolabial

angle t-Test on sample means

Mean (degrees)

Mixed Male Female

93.9 90.1 97.4

SD

SE

t Value

p Value

2.16

<0.05*

13.0

14.6 2.81 10.5 1.89

*Wherep = 0.05,t = 2, and p = 0.02,t = 2.39;:. p < 0.05. 843

CHILI

AND

CLARK

Frequency I,---12 10 8 6 4 2

160

150

Profile m

Fig.

Convexity

(degree)

-~?- Norma.1 distribution

Null1hel~

9. Distribution

of subjects by profile convexity.

Freauencv

5

A

6

l3! d 20

1 140

130

Interlabial m Fig.

Number

10. Distribution

Contour i-

distribution

of subjects by interlabial

DISeUSSION Methodology The photographic technique used in this study is noninvasive and simple. Standardized, life-sized, shadow-free and sharp profile views can be readily obtained. The subject-to-film distance (1.5 m), set at approximately 10 times the maximum breadth of the subject image (approximately 15 cm from ear to nose) reduces photographic distortion to less than 1% .40 Furthermore, the incorporation of the meter scale in the photographs can virtually eliminate the magnification error inherent to photography. In posing the subjects, natural head position is a logical orientation adopted for assessing facial profile as it relates to patient’s head posture in daily life. An external reference 844

Normal

(degree)

contour.

plane, the true horizontal plane, is defined with reference to the vertical plane as indicated by the plumb line. In this study, the natural head positions obtained with and without the mirror were found to be reproducible, which is consistent with previous studies. 38,41Hence, the data obtained from analysis using the natural head position can be used as a convenient and practical clinical reference. With respect to the angular and linear measurements from a two-dimensional image of a three-dimensional object, three types of errors may arise,42 namely: errors of projection, mechanical errors in drawing lines between points on tracing and in measuring with ruler or protractor, and errors of landmark location. Complete control over projection errors is not possible unless the position of the landmarks is known in three dimensions. Projection error NOVEMBER

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Frequency 10 [ 8

100

90

Nasolabial m Fig. Table VII.

Columella

11.

Mixed Male Female

22.7 20.0 25.3

Distribution

A

SD

SE

9.0 9.1 8.3

1.75 1.49

VIII.

on sample

t Value

Mixed Male Female

70.8 69.2 72.2

‘Where p = 0.05,

t=

SE

6.2 6.8 5.4

1.31 0.97

<0.05*

on sample

t Value

1.84

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t-Test

Mixed Male Female

DENTISTRY

-0.6 -0.7 -0.4

SD

SE

t Value

means p Value

1.3

0.21 0.23

0.96

t=

>>0.2*

1.30; :. p > 0.2.

X. Lower lip position from Esthetic plane t-Test Mean (mm)

p Value

>0.05*

on sample

1.2 1.1

means

2, and p = 0.10, t = 1.67, .: p > 0.05.

OF PROSTHETIC

Upper lip position from Esthetic plane

*Where p = 0.05, t = 2 and p = 0.20,

is conventionally reduced, at least in part, by the use of angular instead of linear measurement whenever feasible,42 because the values of angular measurement remain constant regardless of the enlargement factor. Errors introduced in drawing and measuring lengths and angles by hand can easily be eliminated by machine computation, provided that the reproducibility of digitization of individual points is high. Precise positioning of the subjects, especially with no external device, is very difficult, resulting in a situation in which the true anatomic midsagittal plane coincides with the nominal midsagittal plane at the focusing plane only rarely and by chance. This source of error always makes the angle between objects in the true midsagittal plane appear more obtuse than it really is.42 However, these errors are difficult to evaluate and the more acute the true angle is, the more sensitive the system will THE

IX.

Mean (mm)

Table t-Test

SD

distribution

p Value

2.26

120

means

Upper lip inclination Mean (degrees)

Normal

Table

*Where p = 0.05, t = 2, and p = 0.02, t = 2.39; .: p < 0.05.

Table

110

(degree)

of subjects by nasolabial contour.

inclination t-Test

Meal% (degrees)

Number

Contour

Mixed Male Female

+1.5 +1.0 +1.9

SD

SE

1.7 1.5 1.8

0.29 0.32

on sample

t Value

2.08

means p Value

<0.05*

*Where p = 0.05, t = 2, and p = 0.02, t = 2.39; :. p < 0.05.

be to the malpositioning error. Superimposition of landmarks of a three-dimensional object is one of the inherent problems associated with landmark location from a twodimensional view. The soft tissue nasion may be overlapped by the eye and the subnasale may be covered by the ala of the nose in the profile view. Hence, the exact position of these landmarks can only be guessed from the general contour above and below the overlapped area. Nevertheless, each landmark has been clearly defined to minimize both the intraexaminer location error in this study and the interexaminer errors in future studies.

Profile

assessment

The results obtained from the profile analysis generally reveal a normal distribution. The mean profile convexity of the present group (163 degrees rt 6) is similar to that of 845

CHIU

AND

CLARK

Frequency

00

m

Fig.

It ‘)

Male

--t

12. Distribution

110

100

90

Nasolabial

Contour

Male

m

120

(degree)

Female

-e-

Female

of nasolabial contour of both sexes.

Frequency i

10

a

i-

6

I1 I Nasal m

Fig.

13. Distribution

Number

Inclination -t

Normal

40

(degree) distribution

of subjects by columella inclination

Subtelny’s Caucasian sample’l (females 161 degrees and males 162 degrees). However, Satravaha’s Thai Chinese female sample 37 (166 degrees + 5) represents a significantly less convex profile (t 2.67, p < 0.01). In Burstone’s Caucasian group,2 the profile is even less convex at 169 degrees. Nevertheless, he used the glabella instead of the nasion as the superior reference point and the glabella is always more anterior and superior than the nasion. Hence, a greater angular measurement is expected and direct comparison cannot be made. The interlabial contour (140 degrees t 10) in this Chinese sample is significantly more convex than that of the Caucasian norms’ (168 degrees I 6) (t 17.4, p << 0.001). When compared with the Caucasian preference standard24 (male 170 degrees and female of 160 degrees), the current 846

Angle

30

to horizontal.

group (male 142 degrees and female 139 degrees) also appears to have a more protrusive interlabial contour. Moreover, only 5% of the sample subjects have an interlabial contour greater than 160 degrees with the highest value 172 degrees. Hence, this Southern Chinese sample reveals a more convex lower facial contour with no sexual dimorphism. The nasolabial contour of 37-Satravaha’s Thai Chinese female sample (94 degrees t 14) is not significantly different from that of the present study (97 degrees t 10) (t 1.19, p > 0.2). The Caucasian preference standardz4 (88 degrees for male and 98 degrees for female) seems to correspond to that of this sample group (90 degrees for male and 97 degrees for female). Sexual difference was obvious in the current study and the Caucasian preference standard also has NOVEMBER

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Frequency

r

Nasal Inclination m Fig.

Male

+

14. Distribution

Male

n

Angle (degree) Female

of columella inclination

*

Female of both sexes.

Table XI. Analysis of variance on orientation of the natural head position with reference to the true vertical plane, obtained with or without the subject looking into the mirror in two separate sittings Sources of variation

DF

Gender Subjects within gender Mirror Gender x mirror Mirror x subjects within gender Occasion Gender x occasion Occasion x subjects within gender Mirror x occasion Gender x mirror x occasion Mirror X occasion X subject within gender Total

1 51 1 1 51 1 1 57 1 1 57 235

Sum of squares

(degrees)

762.17 5,478.32 33.56 25.69 1,680.05 0.84 0.10 207.47 0.0011 13.59 248.60 8,450.39

Mean

square

762.17 96.11 33.56 25.69 29.47 0.84 0.10 3.64 0.0011 13.59 4.36

Variance

ratio

7.93


1.14 0.87

>0.05 >0.05

0.23 0.03

>0.05 >0.05

0.0002 3.11

>0.05 >0.05

Whenp = 0.05,F = 4; whenp = 0.01, F = 7.08.

a tendency to prefer a more obtuse nasolabial angle in women than in men.24 Fifty percent of the men and 81% of the women had nasolabial contour greater than 90 degrees, and 42 % of the women had a measurement greater than 100 degrees. The widely accepted standard of 90 degrees for the nasolabial angle35, 37 in denture construction appears to fit well with the observed values for the dentate male in different ethnic groups. However, a greater angle, closer to 100 degrees, seems to be preferred for the Chinese female. No report concerning the columella and upper lip inclinations to the true horizontal plane appears in the literature. However, the upper lip contour and the configuration of columella dictate the nasolabial angle. In the present study, significant (difference between sexes was found in the columella inclination but not in the upper lip inclination. The columella inclination may be responsible for the sexTHE

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ual difference in the nasolabial angle. Moreover, the significant differences of these two measurements may reveal a true sexual divergence instead of a consequence of the exaggerated type I errors. When compared with Ricketts’s standard,43 where upper and lower lips are respectively 4 mm and 2 mm posterior to the Esthetic plane, the present sample apparently demonstrates a more protrusive lip contour with none of the subjects reaching Rickett’s standard. The most retrusive upper and lower lips were 3.1 mm and 1.8 mm behind the Esthetic plane respectively. Only 25 % of the men and 16 % of the women had both upper and lower lips posterior to the Esthetic plane. However, when the Esthetic plane is used as a reference, the degree of prominence of the nose and the chin has to be considered. With a less prominent nose or chin or both, the lips become relatively more protrusive. Hence, consideration of another reference line, such as 847

CBIU

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CLARK

Frequency

r

I;

60

50

Labial m

Angle (degree)

Inclination

Number

-k

Normal

distribution

Fig. 15. Distribution of subjects by upper lip inclination to horizontal.

Freouencv

10

r

.

”

8

6

111111 li I; 111I; 0

-1

Distance m

Number

from +

E-plane Normal

(mm) distribution

Fig. 16. Distribution of subjects by upper lip position from Esthetic plane.

from the subnasale to the soft tissue B point, may reveal a truer picture. Clinical

implications

The present study demonstrated that differences in the soft tissue profile between the Southern Chinese and the Caucasian populations lie mainly in the lower third of the face. Both the upper and lower lips of the Southern Chinese are more protrusive and they show a more convex lower facial contour. Becauseprosthetic intervention imposes most of its influence on soft tissue contour of the lower third of the face, consideration of ethnic differences during complete denture construction cannot be overlooked. A number of factors must be considered in the restoration of facial form. Forsberg44 showed that, even after 848

adulthood is attained, a forward growth of the nose and a retrusion of the upper and lower lips is recorded in the soft tissue. The effect of aging contributes to loss of elasticity of the skin, reduction of size of fat cells, loss of elasticity, or decrease of connective tissue and inefficient neuromuscular control.** Continuous resorption of the residual ridge also contributes to change in the soft tissue profile because of reduced lower facial height and increased mandibular prognathism.46 Other factors include sex, race, general health, inherited characteristics, the length of time since teeth were extracted, the ratio of the rate of tissue change of the lips and cheeks to the rate of change in other regions and the degree of tension of the oral musculature. A longitudinal study47 of perioral muscle tone after insertion of complete dentures demonstrated progressive lowering of NOVEMBER

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Frequency

Distance m Fig.

from -

Number

17. Distribution

4 (mm)

E-plane Normal

6

distribution

of subjects by lower lip position from Esthetic plane.

requency

2 from E-plane

0 Distasnce --t

Male

m

Male

Fig.

18. Distribution

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Female

+

Female

of lower lip position of both sexes.

tissue tension after regular denture wearing and an increase in tissue stiffness subsequent to a period without dentures. Therefore, denture wearing experience also has to be taken into account. Soft tissue profile analysis data only apply to the ethnic group from which they were obtained. Data from one ethnic group may be misIeading when applied to other ethnic groups. Different racial groups have facial characteristics and tooth characteristics that are normal for them. Therefore, care must be taken when the norms found in standard textbooks are applied to non-Caucasian racial groups. Moreover, relying solely on the average soft tissue profile as the clinical guideline in complete denture construction will result in stereotyped faces. However, for each soft tissue profile characteristic, there exists a range of values distributed along a normal distribution curve. This reveals the THE

n

6

4 (mm)

importance of individualization in complete denture construction. Strictly following the soft tissue profile norms may require denture teeth to be placed out of the muscle balance zone or located in a mechanically unfavourable position; both conditions can jeopardize the denture stability, especially in the lower denture. Hence, considerations in conjunction with other available clinical guidelines (such as phonetics, freeway space, smile line) as well as evaluation of patients’ various biological characteristics and denture experience are useful in constructing dentures. In the present study, only the dentate subjects with a class I incisal relationship were considered. Further investigations on subjects with bimaxillary protrusion and class II and class III incisal relationships can provide a more complete picture for diverse clinical application. In addition, soft tissue profile analysis of edentulous patients with 849

CHIU AND CLARK

Table XII. Relationship of the mean difference between each pair of tracings and the method error Landmark coordinates Xl Yl

x2 Y2 x3 Y3 x4 Y4 X5 Y5 X6 Y6 x7 Y7

d2 3.95 2.56 2.23 4.49 3.33 6.23 3.32 2.45 2.20 3.10 4.46 6.40 4.04 5.68

Method error e

Mean difference d

0.31

0.365 0.900 0.175 0.375 0.345 0.465 0.305 0.240 0.260 0.245 0.400 0.395 0.380 0.400

0.80 0.24 0.34 0.29 0.39 0.29 0.25 0.23 0.28 0.33 0.32 0.32 0.38

<2e <2e <2e <2e <2e <2e <2e <2e <2e <2e <2e <2e <2e <2e

or without denture wearing, when compared with that on the dentate population, may reveal valuable information for assessingthe outcome of prosthetic rehabilitation. Significant differences between natural and artificial tooth arrangement that may have imposed differences between the soft tissue profile of the edentulous and the dentate populations have been demonstrated.47,4g REFERENCES 1. Patterson CN, Powell DC. Facial analysis in patient evaluation for physiologic and cosmetic surgery. Laryngoscope 1974;84:1004-19. 2. Burstone CL. The integumental profile. Am J Orthod 1958;44:1-25. 3. Case CS. A practical treatise in the technics and principles of dental orthopedia and prosthetic correction of cleft palate. 2nd ed. Chicago: CS Case Co, 1922:486. 4. Tweed CH. Indications for the extraction of teeth in orthodontic procedures. Am J Orthod 1944;30:405-28. 5. Downs WB. Variations in facial relationships-their significance in treatment and prognosis. Am J Orthod 1948;34:812-40. 6. Riedel RA. Esthetics and its relation to orthodontic therapy. Angle Orthod 1950;20:168-78. 7. Stoner MM. A photometric analysis of the facial profile-a method of assessing facial change induced by orthodontic treatment. Am J Orthod 1955;41:543-69. 8. Neger M. A quantitative method for the evaluation of the soft-tissue facial profile. Am J Orthod 1959;45:738-51. 9. Park UC, Burstone CJ. Soft-tissue profile-fallacies of hard-tissue standards in treatment planning. Am J Orthod Dentofacial Orthop 1986;90:52-62. 10. Wallen T, Bloomquist D. The clinical examination: is it more important than cephalometric analysis in surgical orthodontics? Int J Adult Orthodon Orthognath Surg 1986;1:179-91. 11. Tweed CH. The Frankfort-mandibular incisor angle in orthodontic diagnosis, treatment planning and prognosis. Angle Orthod 1954;24:12169. 12. Downs WB. Analysis of the dentofacisl profile. Angle Orthod 1956; 26191-212. 13. Holdaway RA. A soft-tissue cephalometric analysis and its use in orthodontic treatment planning. Part II. Am J Orthod 1984;85:1-28. 14. Stoner MM, Hanes RA, Hepak FM. A cephalometric evaluation fiftyseven consecutive cases treated by Dr. Charles H. Tweed. Angle Orthod 1956;26:68-98. 15. Subtelny JD. The soft tissue profile, growth and treatment changes. Angle Orthod 1961;31:105-22. 16. Ricketts RM. Planning treatment on the basis of the facial pattern and an estimate of its growth. Angle Orthod 1957;27:14-37. 17. Lo FD, Hunter WS. Changes in nasolabial angle related to maxillary incisor retraction. Am J Orthod 1982;82:384-91.

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18. Angle EN. Treatment of malocclusion of the teeth. 7th ed. Philadelphia: SS White Dental Mfg Co, 1907;60-87. 19. Simon PW. Fundamental principles of systemic diagnosis of dental anomalies. Boston: Stratford Co, 1926;64-76. 20. Wuerpel EH. On facial balance and harmony. Angle Orthod 1937;7:81-9. 21. Subtelny JD. A longitudinal study of soft-tissue facial structures and their profile characteristics, defined in relation to underlying skeletal structures. Am J Orthod 1959;45:481-507. 22. Merrifield LL. The profile line as an aid in critically evaluating facial esthetics. Am 3 Orthod 1966;52:804-22. 23. Peck H, Peck S. A concept of facial esthetics. Angle Orthod 1970;40:284318. 24. Lines PA, Lines RR, Lines CA. Profilemetrics and facial esthetics. Am J Orthod 1978;73:648-57. 25. Spradley FL, Jacobs JD, Crowe DP. Assessment of the anteroposterior soft-tissue contour of the lower facial third in the ideal young adult. Am J Orthod 1981;79:316-25. 26. Holdaway RA. A soft-tissue cephalometric analysis and its use in orthodontic treatment planning. Part I. Am J Orthod 1983;84:1-28. 27. Brown JB, McDowell F. Plastic surgery of the nose. St. Louis: Mosby co, 1951:30. 28. Gonzalez-Ulloa M. Quantitative principles in cosmetic surgery of the face (profileplasty). Plastic Reconstr Surg, 1962;29:186-96. 29. Worms FH, Isaacson RJ, Speidel TM. Surgical orthodontic treatment planning: profile analysis and mandibular surgery. Angle Orthod 1976; 76~1.25. 30. Apfel DA. A radiographic cephalometric study of the facial profile in individuals with complete dental prostheses. Am J Orthod 1959;45:711. 31. Silverman SI. Physiologic factors in complete denture esthetics. Dent Clin North Am 1967;March:115-22. 32. Mack A. The registration of occlusion. Full dentures. 2nd ed. Bristol: John Wright & Sons Ltd, 1978; chap 5. 33. Ismail YH. Changes in soft-tissue profile following extraction and complete denture treatment. J PROSTHET DENT 1971;26:11-20. 34. Watt DM, MacGregor AR. Biometric guides to the design of complete dentures. Designing complete dentures. Philadelphia: Saunders, 1976; chap 2. 35. Wang PNC, Camara CG. A soft tissue profile analysis of young adult Filipino dental students population with normal occlusion. J Philippine Dent Assoc 1975;27:21-42. 36. Sushner NI. A photographic study of the soft-tissue profile of Negro population. Am J Orthod 1977;72:373-85. 37. Satravaha S, Schlegel KD. The significance of the integumentary profile. Am J Orthod Dentofacial Orthop 1987;92:422-6. 38. Solow B, Tallgren A. Natural head position in standing subjects. Acta Odont Stand 1971;29:591-607. 39. Dahlberg G. Statical methods for medical and biological students. London: George Allen & Unwin Lid., 1940:97-8, 122-32. 40. Gavan JA, Washburn SL, Lewis PH. Photography: an anthropometric tool. Am J Phys Anthropol 1952;10:331-53. 41. Moorrees CFA, Kean MR. Natural head position, a basic consideration in the interpretation of cephalometric radiographs. Am J Phys Anthopol 1958;16:213-34. 42. Braumrind S, Frantz R. The reliability of head film measurements. 1. Landmark identification. Am J Orthod 1971;60:111-27. 43. Ricketts RM. Esthetics, environment and the law of lip relation. Am J Orthod 1968;54:272-89. 44. Forsberg CM. Facial morphology and aging: a longitudinal cephalometric investigation of young adults. Eur J Orthod 1979;1:15-23. 45. Massler M. Oral aspects of aging. Postgrad Med 1971;49:179-83. 46. Tallgren A. The effect of denture wearing on facial morphology. A 7-year longitudinal study. Acta Odontol Stand 1967;25:563-92. 47. Jacobs RM. Accommodation of perioral tonus after insertion of complete dentures. J Am Dent Assoc 1967;74:420-2. 48. Rayson JH, Rahn AO, Wesley RC, et al. Placement of teeth in a complete denture: a cephalometric study. J Am Dent Assoc 1970;81:420-4. 49. Watson RM, Bhatia SN. Tooth positions in the natural and complete artificial dentitions, with special reference to the incisor teeth: an interactive on-line computer analysis. J Oral Rehahil 1989;16:139-53. Reprint requests to: DR. CONNIE S. W. CHIU DEPARTMENT OF PROSTHETIC DENTISTRY PRINCE PHILIP DENTAL HOSPITAL 34 HOSPITAL ROAD HONG KONG

NOVEMBER

1992

VOLUME 68

NUMBER 5