Linear photogrammetric analysis of the soft tissue facial profile

ORIGINAL ARTICLE

Linear photogrammetric analysis of the soft tissue facial profile Paula Ferna´ndez-Riveiro, DDS, PhD,a David Sua´rez-Quintanilla, DDS, PhD,b Ernesto Smyth-Chamosa, DDS, PhD,c and Mercedes Sua´rez-Cunqueiro, DDS, PhDd Santiago, Spain This study digitally analyzes the soft tissue facial profile of a European white population of young adults by means of linear measurements made on standardized photographic records taken in natural head position. The application of the Student t test showed sexual dimorphism in most parameters of the labial, nasal, and chin areas. In general, males had greater heights and lengths as well as greater prominences of these 3 areas. They also had greater nasal and facial depths at the level of the tragus point. (Am J Orthod Dentofacial Orthop 2002;122:59-66)

T

he analysis of the soft tissue profile of the face was a concern for the pioneers of orthodontics such as Angle and Case at the end of the 19th century and the beginning of the 20th. Angle took the sculpture of Apollo Belvedere as his canon of corporal and facial beauty. However, its straight, almost concave, profile would be difficult to attain orthodontically with Angle’s nonextraction theory; he claimed that the correct occlusion of all teeth in both jaws was necessary to reach an optimum facial appearance. Case, a contemporary of Angle, did not try to follow a single canon representing the ideal of beauty and thus the treatment objective. He tried to individualize the facial esthetic goal of treatment. He looked for the best facial appearance of each person, according to his or her own morphological features and tried to integrate the occlusal and facial objectives into the orthodontic treatment plan. After the standardization of the radiographic technique in 1931 by Broadbent and Hofrath, the importance of soft tissue facial analysis was downplayed, and dentoskeletal relationships became the deciding factor in diagnosis and treatment planning. However, some authors such as Downs1 began to incorporate measurements of the soft tissue facial profile into their cephalometric analyses, introducing filters that allowed the visualization of soft tissues. The From the University of Santiago de Compostela, Santiago, Spain. a Research associate, Department of Orthodontics. b Professor and Chairman, Department of Orthodontics. c Professor, Department of Oral Health. d Assistant professor, Department of Oral Health. Reprint requests to: Paula Ferna´ndez-Riveiro, DDS, PhD, Lo´pez Mora 86, 1° 36211 Vigo, Spain; e-mail, [email protected]. Submitted, August 2001; revised and accepted, December 2001. Copyright © 2002 by the American Association of Orthodontists. 0889-5406/2002/$35.00 ⫹ 0 8/1/125236 doi:10.1067/mod.2002.125236

objective was to obtain information about the relationship between the soft tissue facial profile and the underlying dentoskeletal profile, as they realized that possible anomalies in the hard tissues could be masked or exaggerated by the soft tissues. In other words, soft tissues did not always follow the underlying dentoskeletal profile. In a longitudinal growth study, Subtelny2 used linear measurements of the soft tissue facial profile, such as nasal length (measured perpendicular to the palatine plane), length of the upper lip, thickness of the upper lip at A-point, and the chin at pogonion (Pg). Steiner3 described the S-line (S-Pg) as tangent to the upper and lower lips. Ricketts4 established what he called the law of the labial relationship according to the esthetic E-plane (nasal tip-pogonion). The upper and lower lips should be slightly behind the E-line, with the lower lip closer to it (2 mm). Burstone5,6 carried out an exhaustive esthetic analysis of the facial profile. Within the linear parameters, he defined the position of the upper (Ls) and lower (Li) lips regarding the Sn-Pg line, the nasal length (measured perpendicular to the palatine plane), the length of the upper (Sn-Sto) and lower (Sto-Me) lips, and the interlabial gap (Stos-Stoi). In the 1980s, Ricketts7,8 used the golden divider in his morphologic dentofacial analysis; ie, he established divine or golden proportions (␴ ⫽ 1.618) among the different parts of the face (width of the nose/width of the mouth, length of the upper lip/nasal length, facial height). Holdaway9 defined the H-line (Ls-Pg) with which he evaluated the subnasal position (Sn-H), and the positions of the superior labial sulcus (Sls-H), the inferior labial sulcus (Sli-H), and the inferior lip (Li-H). 59

60 Ferna´ndez-Riveiro et al

He also defined the nasal prominence and the thickness of the upper lip at the level of A-point and the chin at Pg. In 1991, Bass10 introduced the position of the upper incisor as a key for orthodontic treatment. He took the records in natural head position (NHP), using the true horizontal (TH) as a reference line. He defined the ideal position of the upper incisor, Pg, and the upper lip using a perpendicular line to the TH. He also established the exhibition of 2 to 3 mm of the upper incisor below the interlabial gap. In Canut’s 1996 esthetic analysis,11 he studied the interrelationship of nasal, labial, and chin prominences with regard to the Sn-Sm line (facial esthetic triad) and the depth of the nasolabial sulcus that he called the nasolabial esthetic sigma and measured between 2 perpendicular lines to the Frankfort plane through Sn and Ls. Parallel to the development of radiographic cephalometrics, the linear analysis of the soft tissue facial profile on photographic records was developed. In 1981, Farkas,12 using a sample of young people (6-18 years old) of both sexes, standardized the photographic technique and the taking of records in NHP. Included in his linear measurements were nasal length (N-Sn), height of the middle and inferior third of the face (Sn-Me), and length of the upper lip (Sn-Sto). In 1985, he observed that the measurements in his studies on young white subjects were different from the Neoclassical canons13 of facial esthetics used as the norm for orthodontic facial esthetic objectives. The surgeons Powell and Humphreys14 defined their esthetic triangle between the planes N-G/nasal dorsum/G-Pg/E-plane/cervical plane C-Me. In their analysis, they also defined the position of the lips, the exposure of the incisor edge at rest (2 mm with an interlabial gap of 3 mm), and the incisor exposure at broadest smile (two thirds of the clinical crown) Epker15 took his records in NHP, using the true vertical (TV) as the reference line on which he defined proportional measures as the following: the upper lip (Sn-Sto) is 30% of the inferior third of the face (Sn-Gn), the inferior lip (Sto-Sm) is 28% of the inferior third of the face, the height of the chin is 42% of the inferior third, the nasal depth (Sn-Prn) is 40% of the nasal length (N-Sn). Arnett and Bergman16 described an analysis of the soft tissue facial profile on photographic records in NHP. Their analyses of the symmetry, both vertical and horizontal, the contour of the smile line, the facial middle lines, and the facial contour were important. In their linear measurements, they analyzed the position of the upper and lower lips in relation to the Sn-Pg line

American Journal of Orthodontics and Dentofacial Orthopedics July 2002

(previously used by Burstone), the length of the upper (Sn-Ls) and lower (Li-Me) lips, the upper incisor exposure at rest (1-5 mm), and the interlabial gap. The authors defended the equality in the facial thirds TriG/G-Sn/Sn-Me (55-65 mm). On the other hand, all the factors that influence the normality criteria when making a facial analysis should be taken into account, including age, sex, and race.17,18 It has been proven that most facial changes occur before age 18, although growth and reshaping continue throughout life. Through the years, the profile becomes more concave, the nose and the chin grow, the lips become more retrusive, and the nasolabial angle increases.11,17,19-21 These changes are significantly greater in males than in females.22 In general, the existence of sexual dimorphism in the facial features and their remodelling throughout life has been proved. According to this, males experience a greater change, in both hard and soft tissues.21,23 In this study, we tried to determine the linear measurements that define the average soft tissue profile of a young adult white sample. We used a standardized photogrammetric analysis of the profile in NHP. MATERIAL AND METHODS

Our subjects were students from the Faculty of Medicine and Dentistry of the University of Santiago de Compostela, Santiago, Spain. A sample of 212 people, 50 males and 162 females (23.6% male, 76.4% female) between 18 and 20 years old, was randomly selected. All of them were white Galician, which we defined as having 4 grandparents of Galician origin. The photographic setup (Fig 1) consisted of a tripod that held a 35-mm camera with a 100-mm macro lens and a primary flash. The 100-mm macro lens was chosen to avoid facial deformations. The stability of the elements and the easy adjustment of the tripod height allowed us to keep the optic axis of the lens horizontal during the recording. Levelling devices at the base of the tripod and on the camera controlled its correct horizontal position. The primary flash was attached to the tripod by a lateral arm, at a distance of 27 cm from the optic axis to avoid the “red-eye effect” on the records. A secondary flash was placed behind the subject to light the background and eliminate undesirable shadows from the contours of the facial profile. The primary and secondary flashes were synchronized. The camera was used in its manual position, the shutter speed was 1/125 second, and the opening of the diaphragm was f/11. The film was Agfachrome 100 ISO developed with the E-6 process in the same laboratory to ensure that the processing was identical throughout the study.

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Fig 2. Landmarks and reference lines used in this analysis. Fig 1. Photographic setup. ●

Each subject stood on a line on the floor, framed by a vertical scale divided in 5-cm segments. From the scale hung a plumbline held by a thick black thread that indicated the TV. The scale allowed measurements at life size (1:1). On the opposite side of the scale and outside the frame was a vertical mirror, approximately 110 cm from the subject. The records were taken in NHP. Each subject was shown where to stand and asked to relax, and then told to walk a few steps, stand at rest facing the camera, and look into his or her own eyes in the mirror. The lips were also relaxed, adopting their normal position during the day. Glasses were removed, and the patient’s forehead, neck, and ears were clearly visible during the recording. The photographic records, 35-mm slide format, were digitized and analyzed with the Nemoceph 2.0 (Nemotec Dental Systems, Madrid, Spain) software program for Windows. The program was previously customized with the landmarks defined in the analysis of this work. The landmarks were located on a digitized image to obtain all the measurements by the computer. The following landmarks are shown in Figure 2: ● ● ● ●

Trichion (Tri), the sagittal midpoint of the forehead that borders the hairline Glabella (G), the most anterior point of the middle line of the forehead Nasion (N), the point in the middle line located at the nasal root Pronasal (Prn), the most prominent point of the tip of the nose

● ● ● ● ● ● ● ● ● ● ● ● ●

Columella (Cm), the most inferior and anterior point of the nose Subnasal (Sn), the point where the upper lip joins the columella Labial superior (Ls), the point that indicates the mucocutaneous limit of the upper lip Stomion superior (Sts), the most inferior point of the upper lip Stomion inferior (Sti), the most superior point of the lower lip Labial inferior (Li), the point that indicates the mucocutaneous limit of the lower lip Supramental (Sm), the deepest point of the inferior sublabial concavity Pogonion (Pg), the most anterior point of the chin Menton (Me), the most inferior point of the inferior edge of the chin Tragus (Trg), the most posterior point of the auricular tragus Alar (Al), the most lateral point of the alar contour of the nose Superior point of the TV (sTV) Inferior point of the TV (iTV) Ort, the point joining the TV and the TH

The following reference lines are also shown in Figure 2: ● ● ● ●

TV, sTV-iTV TV in N (N-Ort), parallel to TV through N TH, Trg-Ort, perpendicular to TV through Trg Canut line (Juanita Line),22 Sn-Sm

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Fig 3. Vertical measurements (measured parallel to TV line).

American Journal of Orthodontics and Dentofacial Orthopedics July 2002

Fig 4. Horizontal measurements (measured parallel to TH line).

The following vertical linear measurements (parallel to TV) are shown in Figure 3: ● ● ● ● ● ● ● ● ● ● ●

Superior facial third, Tri-G Middle facial third, G-Sn Inferior facial third, Sn-Me Nasal length, N-Sn Length of upper lip, Sn-Sts Interlabial gap, Sts-Sti Length of lower lip, Sti-Sm Vermilion of upper lip, Ls-Sts Vermilion of lower lip, Li-Sti Height of chin, Sm-Me Height of nasal tip, Sn-Prn

The following linear horizontal measurements (parallel to TH) are shown in Figure 4: ● ● ● ● ● ● ● ●

Facial depth, Trg-Sn Nasal depth, Al-Prn Nasal prominence, Prn to N-Ort line Subnasal depth, Sn to N-Ort line Mentolabial depth, Sm to N-Ort line Prominence of upper lip, Ls to N-Ort line Prominence of lower lip, Li to N-Ort line Prominence of chin, Pg to N-Ort line

The following Canut’s linear measurements (perpendicular to Sn-Sm line) are shown in Figure 5: ● ● ● ●

Canut’s Canut’s Canut’s Canut’s

nasal prominence, Prn to Sn-Sm prominence of upper lip, Ls to Sn-Sm prominence of lower lip, Li to Sn-Sm prominence of pogonion, Pg to Sn-Sm

Fig 5. Measurements related to Sn-Sm line.

STATISTICAL ANALYSIS

A descriptive statistics analysis of the linear measurements was carried out, with the results presented in Table I. Sexual dimorphism was evaluated by the Student t test (Table II). The reliability of the method was analyzed by using Dalhberg’s formula, ME ⫽ 公⌺(x1-x2)2/2n, to determine the difference between 2 measurementes made at least a month apart. For this purpose, 54 randomly selected records were retraced and redigitized (Table III).

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Table I.

Application of Student t test relating to sex

Variable Tri-G N-Sn Prn/TV(N) Prn/Sn-Sm Sn-Prn al-Prn Sn-Sts Sti-Sm Sts-Sti Ls-Sts Li-Sti Ls/TV(N) Ls/Sn-Sm Li/TV Li/Sm-Sn Sm-Me Pg/TV(N) Pg/Sn-Sm G-Sn Sn-Me T-Sn Sn/TV(N) Sm/TV(N)

P*

Inferior limit of confidence interval (95%)

Superior limit of confidence interval (95%)

.92 .000* .000* .002* .13 .000* .000* .000* .04* .52 .36 .000* .27 .000* .65 .000* .000* .000* .000* .000* .003* .000* .013*

⫺2.02 ⫺3.88 ⫺4.55 ⫺1.71 ⫺1.19 ⫺3.48 ⫺2.39 ⫺2.29 0.009 ⫺0.31 ⫺0.27 ⫺4.36 ⫺0.98 ⫺5.07 ⫺0.36 ⫺4.06 ⫺7.03 ⫺2.19 ⫺4.89 ⫺7.77 ⫺6.71 ⫺3.90 ⫺6.77

1.83 ⫺1.44 ⫺2.23 ⫺0.38 0.16 ⫺1.80 ⫺0.78 ⫺0.75 0.64 0.61 0.73 ⫺1.46 0.28 ⫺1.47 0.57 ⫺2.40 ⫺2.39 ⫺1.07 ⫺1.88 ⫺4.27 ⫺1.41 ⫺1.39 ⫺0.79

*Statistically significant differences, P ⬍.05.

RESULTS AND DISCUSSION

In the study of facial heights (Tri-G, G-Sn, Sn-Me), the similarity between the inferior facial third (Sn-Me: males 71.4 ⫾ 5.7 mm and females 65.4 ⫾ 4.3 mm) and the middle facial third (G-Sn: males 72.1 ⫾ 5 mm and females 68.7 ⫾ 4.5 mm) was observed, as Powell and Humphreys14 pointed out. Epker,15 however, found that the inferior third was slightly larger (38%) than the middle third (32%). In both cases, males showed more similarity between the facial thirds and significantly larger absolute values than did females; this coincides with the findings of other authors.19,24 However, in the superior third (Tri-G: males 45.3 ⫾ 6 mm and females 45.2 ⫾ 6 mm), sexual dimorphism was not found nor were the facial thirds proportional with the other thirds. Farkas12 published sexual differences (males 58 ⫾ 6 mm and females 51 ⫾ 6 mm) in which the heights were also larger in males. Facial depth (Trg-Sn) was also shown to be significantly larger in males (106.5 ⫾ 8 mm) than in females (102.5 ⫾ 8 mm). Nanda and Ghosh17 studied the facial depth in nasal tip (Trg-Prn), observing significant sexual differences (males 122 ⫾ 4 mm and females 113 ⫾ 5 mm). On the other hand, the great individual variability, with high standard deviations (SDs), and the difficulty of measuring the Trg and the Tri points should be mentioned. This was reflected

in the high method error at the facial superior height and the facial depth. On analyzing the nose, it was observed that males had greater length (N-Sn: males 52.5 ⫾ 4 mm and females 49.8 ⫾ 4 mm) and nasal prominence (Prn/SnSm: males 13.4 ⫾ 2.5 mm and females 12.39 ⫾ 1.9 mm; Prn/TV: males 25.3 ⫾ 3.75 mm and females 21.69 ⫾ 3.1 mm; al-Prn: males 30 ⫾ 3 mm and females 27.4 ⫾ 2.5 mm) than females, with statistically significant differences. The height of the nasal tip (Sn-Prn: males 11.6 ⫾ 2.2 mm and females 11.1 ⫾ 1.7 mm) was the only nasal measurement that did not show sexual dimorphism. This finding coincides with those of Nanda and Ghosh.17 With regard to the reliability of the parameters, we can say that, in most measurements, variability was not excessive (SD ⫽ 2-4 mm), as was the case with the error, which ranged from 1 to 1.5 mm. The labial area should be thoroughly evaluated because the appearance of the lips and the smile can be modified by orthodontic treatment. The length of both lips was larger in males than females (P ⬍ .01) (Sn-Sts: males 23 ⫾ 2.6 mm and females 21.4 ⫾ 2 mm; Sti-Sm: males 19 ⫾ 2.5 mm and females 17.5 ⫾ 2 mm). Park and Burstone25 and Yuen and Hiranaka24 also found a larger length of the upper lip in males (Park and Burstone: males 22 ⫾ 2 mm and females 18 ⫾ 2 mm;

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Table II.

American Journal of Orthodontics and Dentofacial Orthopedics July 2002

Average values for measurements in males and females

Parameter

Sex

n

Min

Max

Mean

SD

95% Confidence interval

Tri-G

M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F M F

50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162 50 162

33.2 28.9 45 40.6 19.2 16.1 5.9 8.5 7.6 7 23.6 21.3 18.3 16.8 13.6 12.6 ⫺0.69 ⫺0.6 3.7 3.6 5.3 4.9 ⫺2.8 ⫺4.8 ⫺1 ⫺1.4 ⫺9.3 ⫺10.5 0.0 ⫺0.6 22.7 20.6 ⫺14.3 ⫺19.3 3.1 1.1 63.3 56.8 62.1 53.1 88.9 84.6 ⫺0.89 ⫺1.4 ⫺15.3 ⫺14.3

71.7 58.1 61.8 59.2 35.1 34.9 19.3 17.2 16.8 16.7 35.5 34.2 28.4 25.5 24 23.1 3.3 9.3 10.5 11 14.1 14.5 18.6 23.5 8.4 6.8 19.4 21.1 8.1 8.5 37.2 32.2 26 20.2 12.3 10 82.2 84 87.3 77.6 121.7 122.2 17.6 20.6 14.6 15.8

45.33 45.24 52.53 49.86 25.29 21.89 13.44 12.39 11.6 11.1 30.06 27.41 23 21.43 19.01 17.48 0.29 0.62 7.27 7.43 8.36 8.59 8.85 5.93 4.03 3.69 5.05 1.77 4.08 4.18 29.09 25.85 1.95 ⫺2.75 6.69 5.05 72.1 68.7 71.4 65.4 106.5 102.4 8.6 5.9 ⫺1.8 ⫺1.2

6.46 5.91 4.12 3.7 3.75 3.1 2.52 1.9 2.21 1.7 3 2.5 2.6 1.83 2.49 1.93 0.76 1.5 1.65 1.39 1.78 1.52 4.83 4.45 2.1 1.41 6.31 5.41 1.59 1.42 2.93 2.48 8.56 6.82 2.0 1.66 4.88 4.66 5.69 4.33 8.1 8.36 4.33 3.79 7.17 7.2

32.4, 58.2 33.4, 57 44.2, 60.7 42.4, 57.2 17.7, 32.7 15.6, 28 8.4, 18.4 8.5, 16.1 7.18, 16 7.7, 14.5 24, 36 22.4, 32.4 17.6, 28.3 17.8, 25 14, 23.9 13.6, 21.3 ⫺1.2, 1.81 ⫺2.3, 3.6 3.9, 10.5 4.6, 10.2 4.8, 11.9 5.5, 11.6 ⫺0.8, 18.5 ⫺2.9, 14.8 ⫺0.1, 8.23 0.8, 6.5 ⫺7.5, 17.6 ⫺9, 12.5 0.9, 7.2 1.3, 7 23.2, 34.9 20.8, 30.8 ⫺15.1, 19 ⫺16.3, 10.8 2.6, 10.6 1.7, 8.3 62.3, 81.9 59.4, 78 60, 82.8 57.6, 74 90.3, 122.7 85.7, 119.1 ⫺0.03, 17.2 ⫺1.6, 13.56 ⫺16.1, 12.5 ⫺15.6, 13.2

N-Sn* Prn/TV* Prn/Sn-Sm* Sn-Prn al-Prn* Sn-Sts* Sti-Sm* Sts-Sti* Ls-Sts Li-Sti Ls/TV(N)* Ls/Sn-Sm Li/TV(N)* Li/Sm-Sn Sm-Me* Pg/TV(N)* Pg/Sn-Sm* G-Sn* Sn-Me* T-Sn* Sn/TV(N)* Sm/TV(N)*

*Statistically significant differences. M, Male; F, female; Min, Minimum; Max, maximum; SD, standard deviation.

Yuen and Hiranaka: males 22 ⫾ 2 mm and females 20.7 ⫾ 2 mm). Differences in the lower lip were not significant (Park and Burstone: 18 ⫾ 2 mm, Yuen and Hiranaka: 17 ⫾ 2 mm). The interlabial gap (Sts-Sti) at rest, however, was larger in females (males 0.29 and females 0.62). Legan and Burstone26 and Bishara et al19

observed a space of 2.5 to 3 mm at rest. In this study, the length of the vermilion did not show sexual differences (superior vermilion: Ls-Sts 7.5 ⫾ 1.5 mm, inferior vermilion: Li-Sti 8.5 ⫾ 2 mm) as in the work of Bishara et al19 (Ls-Sts: 6.5 mm, Li-Sts: 7.5 mm), but it was observed that the inferior vermilion (Li-Sti) was 1

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Table III.

Method error according to Dalhberg’s

formula Parameter Tri-G N-Sn* Prn/TV* Prn/Sn-Sm* Sn-Prn al-Prn* Sn-Sts* Sti-Sm* Sts-Sti* Ls-Sts Li-Sti Ls/TV(N)* Ls/Sn-Sm Li/TV(N)* Li/Sm-Sn Sm-Me* Pg/TV(N)* Pg/Sn-Sm* G-Sn* Sn-Me* T-Sn* Sn/TV(N)* Sm/TV(N)*

Method error (mm) 2.92 1.31 0.58 1.23 0.90 2 0.83 0.78 0.6 0.8 1 0.58 0.47 0.5 0.46 1.3 0.84 0.66 0.95 0.77 2.38 0.66 0.76

*Statistically significant differences.

mm larger than the superior one (Ls-Sts) in both studies. The size of the vermilion causes the exposure of more or less mucocutaneous lip. Its volume is also a reflection of the muscular tension of that lip. The more vermilion that is exposed, the smaller the muscular tension of the same lip. On analyzing the labial prominence with regard to the Sn-Sm line, it was observed that both the upper lip (Ls/Sn-Sm: males 4 ⫾ 2 mm and females 3.69 ⫾ 1.4 mm) and the lower lip (Li/Sn-Sm: males 4 ⫾ 1.6 mm and females 4 ⫾ 1.4 mm) protruded 4 mm beyond the reference line, without noticeable sexual differences. Regarding the TV in N, however, both the upper lip (Ls-TV: males 8.8 ⫾ 5 mm and females 6 ⫾ 4.5 mm) and the lower lip (Li-TV: males 5 ⫾ 6 mm and females 1.7 ⫾ 5.4 mm) showed a different prominence, which was significantly more evident in males. In both cases, the upper lip was more forward than the lower one. The different prominence of the lips with regard to the reference lines could possibly be explained by the different NHP in males and females, but this hypothesis needs further research. The subnasal point with regard to the TV in N (Sn-TV: males 8.6 ⫾ 4 mm and females 6 ⫾ 4 mm) was more prominent in males. The great variability of the measurements obtained by using the TV should be

considered in the analysis of the results. The error committed in the localization of the points was acceptable (⬍1-1.5 mm) and similar in the different parameters of the labial area. The height of the chin (Sm-Me), analyzed by Park and Burstone,25 measured 30 to 35 mm with no sexual differences. In this study, all measurements of the analysis in the area of the chin showed sexual dimorphism characterized by greater length (Sm-Me: males 29 ⫾ 3 mm and females 26 ⫾ 2.5 mm) and greater prominence (P ⬍ .01) in males than in females (Pg-TV: males 2 ⫾ 8.5 mm and females ⫺2.7 ⫾ 7 mm; Pg/Sn-Sm: 6.7 ⫾ 2 mm and females 5 ⫾ 1.6 mm). The mentolabial sulcus regarding the TV was also deeper in males than in females (Sm-TV: males ⫺1.8 ⫾ 7 and females ⫺1.2 ⫾ 7.2 mm). It was quite surprising that the position of this point is located in both sexes behind the TV (through N). The same is true with the prominence of Pg relative to the TV in females, which was located behind the TV line. Again, these measurements relative to the TV showed great variability. CONCLUSIONS

The labial, nasal, and chin areas showed sexual dimorphism in most of the parameters we used. Males have larger faces in general, with greater facial heights; longer nasal, labial, and chin lengths; larger nasal, labial, and chin prominences; and a greater nasal and facial depth in the tragus point. In facial heights, a proportion of 1:1 between the middle and the inferior facial thirds was observed. In the height of the vermilions, sexual dimorphism was not observed. The inferior vermilion was 1 mm larger than the superior. A great variability and a greater sexual dimorphism in the relative measurements to the TV were observed. In particular, the differences were very marked in the prominence of the lower lip and the chin with regard to the TV. The highest errors were found in facial superior height and facial depth, mainly due to the difficulty in the localization of trichion and tragus points. REFERENCES 1. Downs WB. Analysis of the dentofacial profile. Angle Orthod 1956;26:191-212. 2. 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. 3. Steiner C. The use of cephalometrics as an aid to planning and assessing orthodontic treatment. Am J Orthod 1960;46:721-35. 4. Ricketts RM. Esthetic, environment and the law of lip relation. Am J Orthod 1968;54:272-89. 5. Burstone CJ. The integumental profile. Am J Orthod 1958;44:125.

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