I.A. Nashashibi, BDS, D.Ortho., RCS,
H.S. Shaikh, LDSCPS, BDS, MDS,
O.A. Sarhan, BDS, PhD
Department of Preventive Dental Sciences, King Saud University College of Dentistry, P.O. Box 60169, Riyadh 11545, Saudi Arabia

The present study was conducted to establish cephalometric norms of Saudi boys based on the Steiner's analysis, and to compare the results of the present study with similar studies conducted on other racial or ethnic groups. For this purpose, fifty-five healthy Saudi boys, with a mean age of 12.04 years, were selected from different schools of Riyadh. Female Saudis were not used for this study due to social restrictions with respect to the Kingdom's customs and traditions. Selection was made on the basis of normal occlusion, balanced and pleasing profile with no obvious facial asymmetry. None of the boys have undergone orthodontic treatment prior to this study. Lateral skull cephaiograms were taken and traced using a standar­ dized technique. Each cephalogram was traced twice with a one week interval by the authors. All angular and linear measurements were calculated to the nearest 0.5 degree and 0.5 mm, respectively. Steiner's method of cephalometric analysis was used to establish cephalometric norms. The result of the study demonstrated that the Saudi boys differed from other racial and ethnic groups in some skeletal and dental measurements. Generally, the Saudi boys revealed a more protrusive maxillary apical base and double dental protrusion.

Numerous studies have been conducted to establish cephalometric norms of different races1-15 utilizing Down's,3 Tweed's,16 Steiner's,17,18 Sas-souni's,13 and other various analyses. Differences in the measurements for various craniofacial structures motivated researchers from many countries to investigate anthropometric and cephalometric norms of different racial and ethnic groups9,3-8.10,11 Results  of these  investigations have shown that the nature of basic differences in the configuration of the dentofacial structures were so marked that the ethnic or racial norms of one group, applied to individuals of another group, is an inadequate basis for treatment planning and may lead to unstable treatment results. A perusal of the available Arabic and foreign literatures revealed that very few cephalometric studies have been carried out on the Arab population and none on the Saudi boys.The purpose of this investigation was to establish cephalometric norms for Saudi boys using Steiner's analysis and to compare it with similar norms of other racial or ethnic groups.

Fiftyfive Saudi boys ranging in age from 10 -14 years, with mean age of 12.04 years, were selected from the different schools of Riyadh, the capital of the Kingdom of Saudi Arabia.The Riyadh sample was selected on the basis that they all must be Saudis, fulfilling several criteria. The criteria for selection were Class I molar relationship, no crowding or spacing of the man dibular and maxillary dental arches, overbite not exceeding one third of the clinical crown of the mandibular incisors, overjet not exceeding three millimeters, balanced and pleasing profile, no obvious facial asymmetry, and no history of previous orthodontic treatment.Comparison of the Saudi boys were made with other ethnic groups, Iranian boys (Caucasian) with mean age of 12.4 years,7 Indian boys (Caucasian) with mean age of 13 years,11, American (Caucasian) adolescents,17 Japanese with mean age of 11.8 years,10 and African Bantu (black) adults.1Lateral skull cephalometric radiographs were taken using a standardized technique. Each cephalogram was traced twice with a one week interval by the authors. In the case of bilateral structures, an average of the two was recorded. All linear and angular measurements were calculated to the nearest 0.5 mm and 0.5 degree, respectively. The cephalometric analysis was based on Steiner's method of analyses [Fig. 1]

The means, standard deviations, minimum and maximum values, and standard error of the means of the Steiner's measurements of the 55 Saudi boys are illustrated in Table 1 and polygon 1. The standard measurement of other ethnic and racial groups compared to the results of this study are illustrated in Table 2 and polygons 2, 3, and 4.

An analytic look at the data on different racial and ethnic groups suggests differences in the means, indicating differences in craniofacial traits. The magnitude of the differences can be judged by comparing norms of various ethnic groups.

Skeletal Measurements

Angle SNA:

The SNA angie locates the anterior limit of maxillary apical base to the cranial base. In the Saudis, the mean SNA angle is 83.77° ± 4.37°, which is significantly greater than that of the American and South African Caucasians, Iranians, Indians, and Japanese (Polygon 2). The maxilla, which is central to the midface, is one of the factors which has contributed towards midfacial prominence in Saudi boys as compared to the above ethnic groups. In comparison with American and South African Bantu (blacks), the maxilla is less prominent.

Angle SNB:

The angle SNB locates the anterior limit of the mandibular apical base to the crania! base. The Saudi boys show a mean SNB angle of 80.50° ± 3.97", which differs significantly from other ethnic groups. It is greater than the Caucasians, Iranians, Indians, Japanese, and American blacks but lesser than the South African blacks (Bantu). This is contrary to the genral belief that the mandibular apical base is retropositioned in Saudis (Arabs) contributing to a greater facial convexity in this ethnic group. Polygon 2 shows that the SNB angle is very close to that of the American Caucasians.

Angle ANB:

Angle ANB indicates the relationship of the mandibular and maxillary apical bases to each other and the cranial base. The mean ANB angle of the Saudis is 3.27° ± 1.39°. Comparison of this angle with other groups reveals that although this angle differs significantly from American Caucasians and blacks, it is close to the Caucasians (American and South African), Iranians, and Indians who all show skeletal Class l relationship,

Angle SND:

Angle SND locates the center of the symph-yseal mass to the cranial base. The Saudi boys have a mean SND angle of 77.12° ± 3.89°, which is greater than all other ethnic groups except the South African Bantu (blacks). It confirms the find­ ings of the present study that the Saudis ha ve a well-positioned mandible as seen from the angle SNB and GoGn-SN. The American Caucasians have a forward positioned mandibular apical base and slightly better vertical development of the ramus as compared to the Saudis. However, the center of the symphyseal mass in Saudis is placed more anteriorly than the American Caucasians.

PO-NB Distance (Linear):

The linear distance between PO and NB indi- cates the anterior relationship of the bony chin to the mandibular apical base. The Saudi boys with a PO-NB mean distance of 0.52 mm ±1.13 mm dif­ fer from South African blacks, Japanese, Iranians, and Indians. They are closer to African blacks and Japanese. The Iranians and Indians have a better developed chin button as compared to the Saudis.

Angle GoGn-SN:

This angle reflects the vertical growth vector of the mandible which is dependent on the growth of the vertical ramus. The Saudi norm for this angle is 33.84° ± 5.4°. Vertical development of the ramus of the Saudi boys is better than for the American blacks, Japanese and Iranians but less than for the Caucasians, African blacks, and Indians.

The hard tissue measurements of the Saudi boys can be interpreted as indicating significant dif­ ferences from other ethnic groups. Generally, the Saudis revealed a more protrusive maxillary apical base, a well developed and well positioned man dible, and a Class I skeletal relationship. The greater convexity of the face, as compared to Steiner's American Caucasian, is probably due to the midfacial prominence caused by a forward positioning of maxillary apical base and a well-developed nose. Another contributary feature which may need further study is the position of the temporomandibular joint, the sadle angle, and the soft tissue covering of the face and the slant of the forehead.

Dental Measurements

Location of Maxillary Incisor (I to NA in mm and degrees):

The mean linear measurement for the maxil­lary incisor in Saudi boys is 4.86 mm ± 1.40 mm with an inclination of 25.40° ± 4.76°.

Compared to all ethnic groups, with the exception of the American Caucasians and South African blacks, the maxillary incisor of Saudis is placed closer to the NA plane but is more protrusive than the American Caucasians, South African blacks, and Chinese. The South African blacks and American Caucasians are very close to each other in this respect.

The inclination of maxillary incisors differs in that it is more inclined than for the American and South African Caucasians, American blacks, and Japanese. The Iranians and Indians have more labially inclined maxillary incisors as compared to the Saudis.

In the American blacks and Japanese, the maxillary incisors had the same inclination of 24.1° and the Iranians and Indian Saraswats had almost equal inclination of 27.00°.

Location of Mandibular Incisor (1 to NB in mm and degree):

The mean linear and angular measurements of the Saudi boys are 6.56 mm ± 1.86 mm and 28.73° ± 4.99°, respectively. Compared to the American and South African Caucasians, the mandibular incisors of the Saudis are placed more anteriorly. Compared to American and South African blacks, Japanese, Iranians, and Indian Saraswats, they are placed closer to the NB plane. In comparison to the Caucasians, the Saudi boys show more protrusive lower incisors.

Location of Maxillary and Mandibular Incisors (I to I angle or interincisal angle):

The interincisal angle of the Saudis has a mean of 122.65° ± 6.76° indicating double protrusion of incisors compared to Steiner's Caucasian norms.

Only the American and South African Cauca­ sians show a greater interincisal angle indicating more upright position of incisors than the Saudis. All ethnic groups show a lesser interincisal angle (more protrusive incisors) than the Saudis except the Iranians who have almost similar inclination as the Saudis.

The Saudi boys show a double dental protru­ sion of the incisors and more anterior positioning of the maxillary apical base as compared to Caucasians, which makes the facial profile more convex even though the mandible is normally positioned. Lack of good growth at the chin button may be another contributing factor towards facial convexity.

The authors acknowledge the support of the College of Dentistry Research Center, King Saud University for funding this research  Grant No. 1003. Thanks is also extended to Ms. Millet A. Rendon for organizing and preparing the manu­ script.