Relationship of nasal and skeletal landmarks in lateral cephalograms of preschool children

Forensic Science International 191 (2009) 111.e1–111.e4

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Forensic Anthropology Population Data

Relationship of nasal and skeletal landmarks in lateral cephalograms of preschool children Emi Inada a, Issei Saitoh a,*, Haruaki Hayasaki a, Yoko Iwase b, Naoko Kubota a, Yoshihiko Tokemoto a, Chiaki Yamada a, Youichi Yamasaki a a

Department of Pediatric Dentistry, Field of Developmental Medicine, Course for Health Sciences, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima-shi, Kagoshima, Japan Department of Dental Anesthesia, Kagoshima University Medical and Dental Hospital, Kagoshima, Japan

b

A R T I C L E I N F O

A B S T R A C T

Article history: Received 29 December 2008 Received in revised form 6 June 2009 Accepted 27 June 2009 Available online 3 August 2009

The purpose of this study was to investigate the relationship between cephalometric nasal and skeletal landmarks in preschool children. Lateral cephalograms of 80 Japanese preschool children (40 boys, mean age 5.4  0.3 years; 40 girls, mean age 5.2  0.1 years; total mean age 5.3  0.3 years) were traced, and 22 skeletal and 3 soft-tissue nasal points were digitized. The coordinates from each subject were transformed to a standardized plane using a custom-made program written in Microsoft Visual C++1. In this standard plane, sella was the origin, Frankfort Horizontal (FH) plane was parallel to the X-axis, and all 25 points were rotated to match this reference plane. The three nasal landmarks used in this investigation were: (1) rhi’, the intersection point of a line parallel to the FH plane at rhinion and the facial line; (2) pronasale (Prn), the most anterior point on the nose; and (3) subnasale (Sn), the most posterior–superior point where the columella met the upper lip. An independent-groups t-test was used to test for sex differences of coordinates of the nasal landmarks and their related skeletal landmarks. Significance was set at p < 0.05. A stepwise regression analysis determined how combinations of skeletal landmarks explained the location of the nasal landmarks. Only one skeletal coordinate (NX) and no nasal coordinates showed a significant difference between boys and girls. The coordinates of rhi contributed significantly to the location of rhi’ and Prn (except for the Ycoordinate of girls). Moreover A-point and ANS contributed to the location of Prn and Sn. For Sn, the X- and Ycoordinates of girls and the Y-coordinate of boys were related to lower incisor or dentoalveolar structure of the mandible. It appears that the nasal landmarks in preschool children can be predicted from selected skeletal landmarks, and there are no sex differences for the nasal landmarks in children. ß 2009 Elsevier Ireland Ltd. All rights reserved.

Keywords: Nose Skeletal landmark Preschool children Gender difference Prediction

1. Introduction The nose is an important facial feature when individualized facial reconstruction is performed [1–3]. Nasal morphology is also of scientific interest in many disciplines because it is a prominent characteristic of individual human faces [4,5]. For example, nasal deformity in patients with cleft lips and palates is improved by restoring nasal morphology to standard forms that match the individual [6,7]. On the other hand, there was a strong relationship between the facial soft-tissue profile and underlying bony structures [8–10] or environmental factors like body build and weight [11]. Especially, morphological changes of the nose and lip that occur with growth, clinical orthodontic treatment and orthognathic surgery are often evaluated [12–15]. Because the facial soft-tissue profile is influenced by several skeletal factors,

* Corresponding author. Tel.: +81 99 275 6262; fax: +81 99 275 6268. E-mail address: [email protected] (I. Saitoh). 0379-0738/$ – see front matter ß 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.forsciint.2009.06.015

accurate forensic facial reconstruction, especially identifying a subject’s sex, depends on a strong interrelationship between the soft and hard tissues [16–19]. Although sex differences in adults’ noses are known [20–22], no articles have described sex differences in children’s noses. The purposes of this study were to determine whether (1) the location of nasal cephalometric landmarks are predicted by the skeletal landmarks in preschool children, and (2) nasal landmark positions differ between preschool boys and girls. 2. Materials and methods 2.1. Human subjects Cephalograms from Japanese preschool children (40 boys, mean age 5.4  0.3 years; 40 girls, mean age 5.2  0.1 years; total mean age 5.3  0.3 years) who had visited in the Pediatric Dental Clinic at the Kagoshima University Medical and Dental Hospital (Kagoshima city, Kagoshima prefecture, Japan) from 1983 to 1994 were selected for study. They were healthy children. None had obvious signs or symptoms of temporomandibular joint dysfunction, and their occlusions were normal. They had symmetric faces, as determined from clinical and radiographic examinations. None had a history of orthodontic treatment.

E. Inada et al. / Forensic Science International 191 (2009) 111.e1–111.e4

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Fig. 1. The soft-tissue nasal and skeletal landmarks used in this investigation [2].

The lateral cephalograms were taken with the subject’s head immobilized in a wall-mounted cephalostat with the Frankfort Horizontal (FH) plane parallel to the floor at rest while they maintained an intercuspal position. Informed consent to participate in this study was obtained from the parents of all children, prior to their entering the study. Approval of the study was obtained from the clinical ethics committee of Kagoshima University Hospital (No. 19-65).

anterior point of the nose was determined by sliding a vertical line anteriorly along the FH plane until it was tangent to the anterior curve of the nose [2]. The X- and Y-coordinates of each landmark (X-coordinates; Xrhi’, XPrn, XSn: Y-coordinates; Yrhi’, YPrn, YSn) were analyzed. Only the skeletal landmarks that were significantly related to these nasal landmarks are shown in Table 1. 2.3. Error of the method

2.2. Data preparation The system used in this study has been described in detail elsewhere, however, a brief description follows [23]. Lateral cephalograms were traced on standard acetate paper with a mechanical pencil using 0.5 mm lead. Twenty-two skeletal points and three soft-tissue nasal points were marked on each subject’s lateral cephalogram (Fig. 1). All points for each subject were systematically digitized and the coordinates were transformed to a standardized plane using a custom-made program written in Microsoft Visual C++1 (Microsoft, Redmond, Seattle, USA). In this standard plane, sella was the origin, FH plane was parallel to the X-axis, and all 25 points were rotated to match this reference plane. A single investigator (N.K) performed traces and measurements of the lateral cephalograms. The soft-tissue nasal landmarks used in this investigation were (Fig. 1 and Table 1): (1) rhi’, the soft-tissue counterpart of the skeletal landmark rhi, located at the intersection point of a line parallel to the FH plane at rhinion and the facial line; (2) pronasale (Prn), the most anterior point on the nose; and (3) subnasale (Sn), the most posterior–superior point where the columella meets the upper lip. The most

Table 1 Definition of soft-tissue nasal and skeletal landmarks [2]. Explanatory variable rhi’

Prn Sn S N rhi ANS A Md1(A) B

The soft-tissue counterpart of the skeletal landmark rhi which was located at the intersection point of a line parallel to the FH plane at rhinion and the facial line. The most anterior point on the nose. The most posterior–superior point where the columella met the upper lip. Sella: a constructed point in the middle of the sella turcica. Nasion: V notch of frontal and nasal bone. Rhinion: the most anterior margin of the nasal bones. Tip of the anterior nasal spine. A-point: deepest point between ANS and prosthion. Tip of the crown of the mandibular central incisor. B-point: deepest point between pogonion and the lower incisal alveolus.

All measurements were repeated after 1 week by the same investigator, and Dahlberg’s formula was used for the calculation of the measurement error: sffiffiffiffiffiffiffiffiffiffiffi P 2 d measurement error ¼ 2n where (d) is the difference between first and second measurements and (n) is the number of subjects. The errors ranged from 0.20 mm to 0.48 mm (mean error 0.34 mm), indicating that these errors were negligible. 2.4. Statistical analysis An independent-group t-test was used to test for sex differences of coordinates of the nasal landmarks and their related skeletal landmarks. Significance was set at p < 0.05. A forward stepwise regression analysis determined how combinations of skeletal landmarks explained the location of the nasal landmarks. In this analysis a skeletal landmark was entered and retained in the regression model at each step if it significantly contributed to nasal landmark location (p < 0.05). Addition of skeletal landmarks to the model was stopped when no other skeletal landmarks met the p < 0.05 criterion. Statistical analysis was performed using the Statistical Package for Social Science (SPSS1 15.0J: SPSS Inc., Chicago, IL, USA).

3. Results Means and standard deviations of the coordinates of each of the skeletal landmarks that were related to the nasal landmarks are shown in Table 2. Only one skeletal coordinate (NX), and no nasal coordinates, showed a significant difference between boys and girls. The best skeletal landmarks for predicting the location of the nasal landmarks are shown in Table 3. The landmarks rhi’ and Sn were predictable by the same skeletal landmarks in boys and girls. The standard partial regression coefficients (b) in boys and girls were 0.84–0.99, respectively.

E. Inada et al. / Forensic Science International 191 (2009) 111.e1–111.e4

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Table 2 Comparison of means and standard deviations of the coordinates of related skeletal and nasal landmarks of boys and girls. Variable

X

Y

Boy

Girl

p-Value

Boy

Girl

p-Value

Skeletal

N rhi ANS A Md1(A) B

63.78(2.79) 69.53(2.82) 65.52(2.80) 62.27(3.30) 59.02(3.79) 54.68(3.97)

62.40(2.51) 68.89(2.64) 64.67(2.95) 61.43(2.92) 57.83(3.89) 54.46(3.90)

0.02* 0.29 0.19 0.23 0.17 0.80

7.66(2.66) 13.82(2.94) 37.43(3.07) 41.54(3.05) 61.33(4.27) 75.03(5.04)

8.05(3.45) 13.92(3.42) 36.84(3.27) 40.98(3.29) 60.60(3.39) 73.82(3.55)

0.57 0.89 0.41 0.43 0.40 0.22

Nasal

rhi’ Prn Sn

73.33(2.96) 82.18(3.13) 73.03(3.19)

72.73(2.92) 81.46(2.91) 71.72(2.99)

0.36 0.29 0.06

13.81(2.93) 30.78(3.52) 41.20(3.38)

13.94(3.39) 30.43(3.24) 40.89(3.01)

0.85 0.64 0.67

Standard deviation in parenthesis. S.D.: Standard deviation. * p < 0.05. Table 3 The best skeletal landmark predictors of nasal landmarks. Nasal point

Boy

4. Discussion Many studies have used lateral cephalograms to examine the craniofacial region because they can be obtained and analyzed using almost the same methods throughout the world [24–27]. Our method for the combined analysis of skeletal and soft-tissue has been verified by Inada et al. [23]. Our results indicate that, of the three soft-tissue nasal points studied, rhi’ and rhi have the strongest correlation. This may be because the location of rhinion on the midface is quite variable [28]. Therefore, coordinates of rhi’ might be the ones most predictable in children. The skeletal landmarks highly related to the coordinates of Prn were rhi or ANS, and Prn was also significantly associated with rhi and the dentoalveolar structure of the maxilla (ANS and A). The Xcoordinate of Prn was correlated with ANS in boys and rhi in girls (Table 3). For the Y-coordinate of Prn these relationships were reversed. Although these relationships differed between boys and girls, the individual coordinates showed no sex differences. Stephan et al. reported that pronasal projection can be predicted from nasal bone angle and nasal bone length [29]. It might be possible to predict the coordinates of Prn from more than one skeletal landmark in children. In both boys and girls the skeletal landmark most related to the X-coordinate of Sn was AX, and the skeletal landmark related to the Y-coordinate of Sn was ANSY. The R2 of Sn was from 0.81 to 0.86, which was lower than that of rhi’ and Prn. Others have reported that upper incisor inclination and A-point position contribute to the position of Sn [8,30,31]. Although the coordinates of Sn did not

Girl

Skeletal point

b

Skeletal point

b

X-Coordinate

rhi’ Prn Sn

rhiX ANSX AX

0.96 0.91 0.93

rhiX rhiX AX

0.91 0.84 0.87

Y-Coordinate

rhi’ Prn Sn

rhiY rhiY ANSY

0.99 0.88 0.87

rhiY ANSY ANSY

0.99 0.90 0.94

b: standard partial regression coefficient.

The results of the stepwise regression analysis are shown in Table 4. The multiple regression equations for the prediction model were of the form: Y ¼ a þ b1  X1 þ b2  X2 þ    þ bn  Xn; where Y is the predicted value, (a) denotes constant, and b1, b2, . . ., bn are the standard partial regression coefficients of the independent variables X1, X2, . . ., Xn. This resulted in 12 specific equations (not shown). Multiple correlation coefficients (R2) in boys and girls were 0.81–0.99, respectively, and all p-values were less than 0.001. The landmarks rhi’ and Prn, except for the Ycoordinate of Prn in girls, were strongly associated with the skeletal landmark rhi in the prediction formula. Moreover, either A-point or ANS was a strong predictor of the location of Prn and Sn. For Sn, the X- and Y-coordinates of girls and the Y-coordinate of boys were associated with the locations of B-point and Md1.

Table 4 The relationships between the nasal and skeletal landmarks by forward stepwise regression. Nasal point

X-Coordinate

Y-Coordinate

Boy

Girl R2

p-Value

Skeletal point

b

Constant

R2

p-Value

3.27

0.95

<0.001

rhiX NX

0.64 0.34

0.67

0.87

<0.001

0.51 0.49

7.87

0.90

<0.001

rhiX AX

0.53 0.47

11.46

0.85

<0.001

AX

0.93

17.03

0.86

<0.001

AX rhiX BX

0.48 0.28 0.24

8.61

0.83

<0.001

rhi’

rhiY

0.99

0.09

0.99

<0.001

rhiY

0.99

0.15

0.99

<0.001

Prn

rhiY ANSY

0.48 0.48

2.11

0.85

<0.001

ANSY

0.90

2.51

0.81

<0.001

Sn

ANSY Md1

0.59 0.37

1.01

0.82

<0.001

ANSY Md1

0.70 0.20

3.41

0.81

<0.001

Skeletal point

b

rhi’

rhiX AX

0.77 0.23

Prn

ANSX rhiX

Sn

Constant

b: standard partial regression coefficient, R2: coefficient of determination.

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E. Inada et al. / Forensic Science International 191 (2009) 111.e1–111.e4

differ between boys and girls, the skeletal predictors of Sn location did differ between boys and girls. The Y-coordinate of Sn in boys and the X- and Y-coordinates of Sn in girls were related to maxillary and lower incisor position or dentoalveolar structure of the mandible. It is interesting that the prediction of Sn is connected with mandibular landmarks (Md1 and Bx), since Sn is in the upper facial region. Soft-tissue profiles and the nasolabial angle can be changed by orthodontic treatment of Class III malocclusions [13,32], suggesting that mandibular form and maxillary soft-tissue form have a close relationship. We conclude that the location of nasal cephalometric landmarks in preschool children can be predicted from skeletal cephalometric landmarks. We found no sex differences in the location of the nasal landmarks, but different skeletal landmarks in boys and girls predicted the position of each nasal landmark. 5. Conclusion We evaluated the relation between nasal and skeletal landmarks in preschool children. These results support the following: 1. Cephalometric soft-tissue nasal landmarks can be predicted from skeletal cephalometric landmarks in preschool children. 2. The Y-coordinate of Sn in boys and the X- and Y-coordinates of Sn in girls are related to maxillary and lower incisor position or dentoalveolar structure of the mandible. 3. Although the location of nasal cephalometric landmarks did not differ between boys and girls, different skeletal landmarks in boys and girls predicted the position of nasal landmarks. Acknowledgements This study was supported in part from the Japanese Society for the Promotion of Science (No. 19390532) and the Research Grant for Young Scientists in Oral Biology (No. 70080025). References [1] T. Miyashita, E. Takahashi, Stature and nose height of Japanese, Hum. Biol. 43 (1971) 327–339. [2] J.S. Genecov, P.M. Sinclair, P.C. Dechow, Development of the nose and soft tissue profile, Angle Orthod. 60 (1990) 191–198. [3] L.G. Farkas, J.C. Posnick, T.M. Hreczko, Growth patterns of the face: a morphometric study, Cleft Palate Craniofac. J. 29 (1992) 308–315. [4] R.T. Bergman, Cephalometric soft tissue facial analysis, Am. J. Orthod. Dentofac. Orthop. 116 (1999) 373–389. [5] H.S. Baik, J.M. Jeon, H.J. Lee, Facial soft-tissue analysis of Korean adults with normal occlusion using a 3-dimensional laser scanner, Am. J. Orthod. Dentofac. Orthop. 131 (2007) 759–766. [6] M.I. Siegel, M.P. Mooney, K.R. Kimes, J. Todhunter, Developmental correlates of midfacial components in a normal and cleft lip and palate human fetal sample, Cleft Palate Craniofac. J. 28 (1991) 408–412. [7] S. Sarukawa, Y. Sugawara, K. Harii, Cephalometric long-term follow-up of nasal augmentation using iliac bone graft, J. Craniomaxillofac. Surg. 32 (2004) 233–235. [8] V.F. Ferrario, C. Sforza, Size and shape of soft-tissue facial profile: effects of age, gender, and skeletal class, Cleft Palate Craniofac. J. 34 (1997) 498–504.

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