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Cephalometric norms of Nigerian children
SHORT COMMUNICATION
Cephalometric norms of Nigerian children Emmanuel Olubusayo Ajayi Benin City, Nigeria Introduction: The purpose of this study was to develop cephalometric standards for Nigerian children. Methods: The average values of 7 dentoskeletal angles were determined from standardized lateral head radiographs of 100 schoolchildren (aged 11 to 13 years; mean, 12.6 years) in Enugu, a city in southeastern Nigeria. The children, born to Nigerian parents of Igbo ancestry (Igbo is 1 of the 3 major ethnic groups in Nigeria), were selected on the basis of a well-balanced face and acceptable profile, Class I occlusion with normal overjet and overbite, minor or no crowding or spacing, and no history of orthodontic treatment. Results: There were no statistically significant differences in cephalometric measurements between boys and girls; thus, the data were combined for analysis. The mean values and standard deviations obtained for the measured variables were: SNA, 85.5° (⫾ 4.3°); SNB, 81.2° (⫾ 4.0°); ANB, 4.3° (⫾ 2.5°); UI-FP, 122.8° (⫾ 7.5°); Ll-MP, 98.8° (⫾ 5.8°); Ul-LI, 109.1° (⫾ 8.0°); and FMA, 26.1° (⫾ 5.0°). Conclusions: Compared with the norms for other ethnic groups, Igbo children have a prognathic relationship of the maxilla and the mandible to the anterior cranial base with a tendency toward a protrusive skeletal pattern. The children also exhibited prominent bimaxillary proclination with procumbent and protrusive maxillary and mandibular incisors and a steep Frankfort-mandibular plane angle. The findings emphasize the need for group-specific norms for orthodontic diagnosis and treatment planning, and provide cephalometric standards for Igbo children. (Am J Orthod Dentofacial Orthop 2005;128:653-6)
R
adiographic cephalometry has been used extensively to study facial form and develop norms to aid in orthodontic diagnosis and treatment planning. It is also used to assess treatment progress and craniofacial growth, to predict growth for individual patients, and for other tasks in orthodontic research. Many cephalometric analyses have been made to establish norms for ideal facial proportions and occlusion, presenting average measurements of skeletal or dental patterns and their ranges.1-8 The cephalometric norms of different ethnic and racial groups established in various studies show that normal measurements for 1 group are not necessarily normal for another group; each racial group must be treated according to its own characteristics. A number of standards have been developed for various racial and ethnic groups.9-20 It is important to compare a patient’s cephalometric findings with the norms for his or her ethnic group for an accurate diagnostic evaluation, while considering his or her treatment goals and needs. Miyajima et al19 also noted that a patient might seek a treatment plan that is based in part on norms for his or her racial or ethnic group. Lecturer and consultant orthodontist, Orthodontic Unit, Department of Preventive Dentistry, College of Medical Sciences, University of Benin, Benin City, Nigeria. Reprint requests to: Dr Emmanuel O. Ajayi, PO Box 7272, Surulere, Lagos, Nigeria; e-mail, [email protected]. Submitted, February 2005; revised and accepted, May 2005. 0889-5406/$30.00 Copyright © 2005 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2005.07.002
Attempts to establish cephalometric norms for the Nigerian population have been made. Nigeria has the largest population of blacks in the world—about 120 million people. Isiekwe and Sowemimo21 published cephalometric values for adult Nigerians based on a study of 15 men and 5 women, aged 18 to 25 years, with ideal occlusions. Isiekwe22,23 also assessed anteroposterior skeletal jaw relationships and incisor angulations in a Nigerian sample. Nigeria has 3 major ethnic groups: Yoruba, Hausa, and Igbo. Variations in their craniofacial morphologies were evaluated by Durosinmi-Etti24 and Utomi,25 using samples of 12- to 14-year-olds in Lagos and 11- to 13-year-olds in Kaduna, respectively. These studies evaluated similar cephalometric parameters and showed variations in the cephalometric standards. The purposes of this study were (1) to establish cephalometric standards of children from the largest ethnic group of southeastern Nigeria, the Igbo, that can be used as baseline data for diagnostic purposes and planning orthodontic treatment; (2) to identify sex differences between Igbo boys and girls; and (3) to compare Igbo norms to the published standards of related Nigerian ethnic groups and other similar studies. MATERIAL AND METHODS
The material consisted of standardized lateral cephalometric radiographs of 100 volunteer Igbo children from public and private secondary schools in Enugu in 653
654 Ajayi
American Journal of Orthodontics and Dentofacial Orthopedics November 2005
Table I.
Comparison of mean and standard deviation of cephalometric measurements between Nigerian Igbo boys and girls Boys (n ⫽ 66)
Girls (n ⫽ 34)
Measurement (°)
Mean
SD
Mean
SD
P
SNA SNB ANB UI-FP LI-MP UI-LI FMA
85.63 81.30 4.35 123.08 99.21 108.10 26.14
4.30 4.14 2.50 7.68 5.53 8.36 4.74
85.35 81.07 4.28 122.38 98.03 111.03 25.99
4.33 3.81 2.42 7.22 6.36 7.10 5.58
NS NS NS NS NS NS NS
NS, Not significant. *Significant difference at P ⬍ .05. Table II.
Figure. Landmarks, planes, and angles measured in Igbo children. SNA, sella-nasion-A-point; SNB, sellanasion-B-point; ANB, A-point-nasion-B-point; UI-FP, upper incisor axis to Frankfort plane angle; LI-MP, lower incisor axis to mandibular plane angle; UI-LI, interincisal angle; FMA, Frankfort mandibular plane angle.
southeastern Nigeria. There were 66 boys and 34 girls, aged 11 to 13 years (mean, 12.6 ⫾ 0.6 years). Attempts were made to select children with balanced faces and acceptable profiles, Class I occlusions with normal overjet and overbite, minor or no crowding or spacing, and no history of orthodontic treatment, and born of Nigerian parents of Igbo ancestry from any of the 5 states of defunct Eastern Nigerian (presently southeastern Nigeria). Authorization and consent were obtained from the principals of the schools and the parents of the children. Lateral cephalograms of 100 children were taken. Each subject was positioned in the cephalostat with the head oriented to the Frankfort horizontal plane and the teeth in centric occlusion with the lips relaxed. The cephalometric radiographs were traced onto 0.003-in matte finish acetate sheets over an illuminated viewing box by using a standard technique. All radiographs were traced by the author, and angular measurement were made with a protractor and recorded to the nearest 0.5°. The following landmarks were identified on each cephalogram (Figure): sella turcica (S), nasion (N), orbitale (O), porion (P), gnathion (Gn), pogonion (Pog), gonion (Go), menton (M), anterior nasal spine (ANS), posterior nasal spine (PNS), A-point, B-point, maxillary incisor apex (MxIA), mandibular incisor apex
Cephalometric norms of Igbo children
Measurement (°)
Mean
SD
Minimum
Maximum
SNA SNB ANB UI-FP LI-MP UI-LI FMA
85.54 81.22 4.33 122.84 98.81 109.10 26.09
4.29 4.01 2.46 7.50 5.82 8.04 5.02
82 79 3 119 95 104 23
88 84 6 128 102 115 30
(MIA), upper incisor tip (UIT), and lower incisor tip (LIT). The definitions of the various landmarks have been reported previously.14 From these landmarks, the following skeletal and dental angles were measured: sella-nasion-A-point angle (SNA), sella-nasion-B-point angle (SNB), A-point-nasion-B-point angle (ANB), upper incisor axis to Frankfort plane angle (UI-FP), lower incisor axis to mandibular plane angle (LI-MP), interincisal angle (UI-LI), and Frankfort mandibular plane angle (FMA). Statistical analysis
The error during tracing, landmark selection, and measuring was determined by repeating the tracings of 25 randomly selected radiographs 1 month later. Dahlberg’s formula,26 公⌺d2/2n, where d is the difference in the measurement between the first and second tracings and n is the sample size, was used to calculate measurement error. The error of the measurements, 0.1° to 0.4°, for the variables was minimal. Systematic error was estimated by using a paired t test; the differences between the first and second measurements were statistically insignificant. The EPI INFO version 6 statistical software27 was used for further statistical analysis. The basic descriptive statistics, including the means, standard deviations, and maximum and minimum values were computed for
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American Journal of Orthodontics and Dentofacial Orthopedics Volume 128, Number 5
Table III.
Comparison of Igbo means with Lagos and Hausa-Fulani cephalometric norms Lagos standards† (n ⫽ 100)
Igbo standards (n ⫽ 100)
Hausa-Fulani standards‡ (n ⫽ 100)
Angle
Mean
SD
P
Mean
SD
P
Mean
SD
SNA SNB ANB UI-FP LI-MP UI-LI FMA
88.90 84.48 4.39 126.03 100.69 108.91 24.38
4.15 3.71 2.30 6.77 5.45 9.66 5.64
0.00* 0.00* NS 0.00* 0.01* NS 0.02*
85.54 81.22 4.33 122.84 98.81 109.10 26.10
4.30 4.00 2.46 7.50 5.80 8.00 5.00
0.00* NS 0.00* NS 0.03* 0.00* 0.05*
82.35 80.35 2.07 122.3 97.1 113.6 24.80
3.50 3.30 2.80 12.80 5.50 12.8 4.40
NS, Not significant. *Significant difference at P ⬍ .05. † From Durosinmi-Etti.24 ‡ From Utomi.25
each cephalometric variable. The Student t test was used to assess sex differences in the measured values and to evaluate any differences between the craniofacial dimensions of Igbo children and related Nigerian children and other norms established by other investigators. The differences in the mean values were regarded as statistically significant if P ⬍ .05. RESULTS
The cephalometric findings by sex are listed in Table I. There was no statistically significant sex difference between the measurements of boys and girls; therefore, the combined data were analyzed, and the means, standard deviations, and ranges are given in Table II as the norms for Nigerian Igbo children. These norms were further compared with Lagos and Hausa-Fulani children’s norms (Table III). There were statistically significant differences (P ⬍ .05) in most of the measured cephalometric variables between the 3 groups, with the exception of SNB and UI-FP between Igbo and Hausa-Fulani children, and ANB and UI-LI between Igbo and Lagos children, respectively. DISCUSSION
The cephalometric values obtained in this study did not show any significant statistical difference between Igbo boys and girls; this agreed with previous findings for other major ethnic groups in Nigeria.22,24,25 The numerical values determined for the dental and skeletal variables showed some statistically significant differences in cephalometric norms of Igbo children in Enugu in southeastern Nigeria when compared with children from Lagos in southwestern Nigeria, where Yoruba is the predominant ethnic group, and HausaFulani children in Kaduna in northern Nigeria. The mean SNA and SNB values show that Igbo children
also have prognathism of the maxilla and mandible relative to anterior cranial base, which was observed by Isiekwe and Sowemimo21 and Durosinmi-Etti24 in adults and children, respectively, from southern Nigeria. The mean SNA value obtained in this study for Igbo children is also similar to that of black American children (P ⬎ .05) and showed prognathism of the maxilla when compared with American whites.11,12 However, SNB was similar in both Igbo and HausaFulani children (P ⬎ .05). The anteroposterior skeletal relationship of the maxilla and the mandible to the anterior cranial base was similar for Igbo and Lagos children. However, ANB in the Igbo is 2.26° significantly higher than that of the Hausa-Fulani. Utomi25 observed that HausaFulani children have less prognathic maxillae, with their denture bases slightly more posterior in relation to the cranial base than children from southern Nigeria. The value obtained was 1.5° significantly higher than that of American whites.11 This study also showed protrusive dentoalveolar relationships with associated bimaxillary proclination in Igbo children; this has been described as a feature of the Nigerian profile.23-25 UI-LI was similar in Igbo and Lagos children, and also the inclination of UI-FP between Igbo and Hausa-Fulani children (P ⬎ .05). Alexander and Hitchcock28 reported similar findings of procumbent and protrusive maxillary and mandibular incisors in American blacks. Savage29 reported bimaxillary protrusion as a general feature of Bantu children of West Lake Province of Tanganyika. Chan30 observed bimaxillary dental protrusion in Cantonese people when compared with white standards, matched only by the American black and the Australian aborigine. Igbo children have significantly steeper FMAs than other Nigerian ethnic groups. Drummond12 and
656 Ajayi
Kapila18 also reported high values for FMA in black American children and Kenyan children of Kikuyu descent. CONCLUSIONS
The profiles of Igbo children differ from those of other ethnic and racial groups. Their basal arches are more anteriorly placed in relation to the anterior cranial base. They also have prominent bimaxillary proclination, which is consistent with the southern Nigerian population, and a tendency toward a protrusive skeletal pattern. Cephalometric standards for Igbo children will aid in diagnostic evaluation and treatment planning for Nigerian orthodontic patients of Igbo descent. Because the various published cephalometric standards represent population averages, it is important to consider each patient’s treatment goals and needs during evaluation and treatment planning. It would further be desirable to evaluate linear measurements and the soft tissue profiles of Nigerian children for use in planning orthodontic treatment and orthognathic surgery. REFERENCES 1. Margolis H. Basic facial pattern and its application in clinical orthodontics. Am J Orthod 1947;33:631-41. 2. Downs WB. Variations in facial relationships: their significance in treatment and prognosis. Am J Orthod 1948;34:812-40. 3. Tweed CW. The Frankfort-mandibular incisor angle (FMIA) in diagnosis and treatment planning and prognosis. Angle Orthod 1954;24:121-69. 4. Steiner CC. Cephalometrics for you and me. Am J Orthod 1953;39:729-55. 5. Coben SE. The integration of facial skeletal variants. Am J Orthod 1955;41:407-34. 6. Ricketts RM. Cephalometric analysis and synthesis. Angle Orthod 1960;31:141-56. 7. McNamara JA Jr. A method of cephalometric analysis. In: McNamara JA Jr, editor. Clinical alteration of the growing face. Monograph 12. Craniofacial Growth Series. Ann Arbor: Center for Human Growth and Development; University of Michigan; 1983. 8. Sassouni V. Roentgenographic cephalometric analysis of cephalofacial-dental relationships. Am J Orthod 1955;41:735-64. 9. Cotton WN, Takano WS, Wong WW. The Downs analysis applied to three other ethnic groups. Angle Orthod 1951;21:21320. 10. Altemus LA. A comparison of cephalofacial relationships. Angle Orthod 1960;30:223-40.
American Journal of Orthodontics and Dentofacial Orthopedics November 2005
11. Taylor WH, Hitchcock HP. The Alabama analysis. Am J Orthod 1966;52:245-65. 12. Drummond RA. A determination of cephalometric norms for the Negro race. Am J Orthod 1968;54:670-86. 13. Nanda R, Nanda RS. Cephalometric study of the dentofacial complex of North Indians. Angle Orthod 1969;39:22-8. 14. Riolo ML, Moyers RE, McNamara JA, Hunter SW. An atlas of craniofacial growth: cephalometric standards from the University School Growth Study. Ann Arbor: Center for Human Growth and Development; University of Michigan; 1974. 15. Richardson ER. Racial differences in dimensional traits of the human face. Angle Orthod 1980;50:301-11. 16. Bishara SE. Longitudinal cephalometric standards from 5 years of age to adulthood. Am J Orthod 1981;79:35-44. 17. Park I, Bowman D, Klapper L. A cephalometric study of Korean adults. Am J Orthod Dentofacial Orthop 1989;96:54-9. 18. Kapila S. Selected cephalometric angular norms in Kikuyu children. Angle Orthod 1989;59:139-43. 19. Miyajima K, McNamara JA, Kimura T, Murata S, Lizuka T. Craniofacial structure of Japanese and European-American adults with normal occlusios and well-balanced faces. Am J Orthod Dentofacial Orthop 1996;110:431-8. 20. Basciftci FA, Uysal T, Buyukerkmen A. Craniofacial structure of Anatolian Turkish adults with normal occlusions and wellbalanced faces. Am J Orthod Dentofacial Orthop 2004;125:36672. 21. Isiekwe MC, Sowemimo GOA. Cephalometric findings in a normal Nigerian population sample and adult Nigerians with unrepaired clefts. Cleft Palate J 1984;21:323-8. 22. Isiekwe MC. A distribution of antero-posterior skeletal jaw relationships in a Nigerian population. Afr Denl J 1987;1:23-7. 23. Isiekwe MC. A cephalometric study of incisor angulations in a Nigerian population. Br J Orthod 1989;16:177-81. 24. Durosinmi-Etti TF. Cephalometric values of school children in Lagos (ages 12-14 years) [thesis]. Lagos, Nigeria: Lagos University Teaching Hospital; 1992. 25. Utomi IL. Cephalometric values in Hausa-Fulani school children in Kaduna [theses]. Lagos, Nigeria: Lagos University Teaching Hospital; 1998. 26. DahIberg G. Statistical methods for medical and biological students. New York: Interscience Publications; 1940. 27. Dean AG, Dean JA, Coulombier D, Brendel KA, Smith DC, Burton AH, et al. Epi Info, Version 6: a word-processing, database and statistics program for public health on IBMcompatible microcomputers. Atlanta: Centers for Disease Control and Prevention; 1995. 28. Alexander TL, Hitchcock HP. Cephalometric standards for American Negro children. Am J Orthod 1978;74:298-304. 29. Savage M. A dental investigation of Bantu children. Angle Orthod 1963;33:105-9. 30. Chan GKH. A Cephalometric appraisal of the Chinese (Cantonese). Am J Orthod 1972;61:279-85.
Cephalometric norms of Nigerian children Emmanuel Olubusayo Ajayi Benin City, Nigeria Introduction: The purpose of this study was to develop cephalometric standards for Nigerian children. Methods: The average values of 7 dentoskeletal angles were determined from standardized lateral head radiographs of 100 schoolchildren (aged 11 to 13 years; mean, 12.6 years) in Enugu, a city in southeastern Nigeria. The children, born to Nigerian parents of Igbo ancestry (Igbo is 1 of the 3 major ethnic groups in Nigeria), were selected on the basis of a well-balanced face and acceptable profile, Class I occlusion with normal overjet and overbite, minor or no crowding or spacing, and no history of orthodontic treatment. Results: There were no statistically significant differences in cephalometric measurements between boys and girls; thus, the data were combined for analysis. The mean values and standard deviations obtained for the measured variables were: SNA, 85.5° (⫾ 4.3°); SNB, 81.2° (⫾ 4.0°); ANB, 4.3° (⫾ 2.5°); UI-FP, 122.8° (⫾ 7.5°); Ll-MP, 98.8° (⫾ 5.8°); Ul-LI, 109.1° (⫾ 8.0°); and FMA, 26.1° (⫾ 5.0°). Conclusions: Compared with the norms for other ethnic groups, Igbo children have a prognathic relationship of the maxilla and the mandible to the anterior cranial base with a tendency toward a protrusive skeletal pattern. The children also exhibited prominent bimaxillary proclination with procumbent and protrusive maxillary and mandibular incisors and a steep Frankfort-mandibular plane angle. The findings emphasize the need for group-specific norms for orthodontic diagnosis and treatment planning, and provide cephalometric standards for Igbo children. (Am J Orthod Dentofacial Orthop 2005;128:653-6)
R
adiographic cephalometry has been used extensively to study facial form and develop norms to aid in orthodontic diagnosis and treatment planning. It is also used to assess treatment progress and craniofacial growth, to predict growth for individual patients, and for other tasks in orthodontic research. Many cephalometric analyses have been made to establish norms for ideal facial proportions and occlusion, presenting average measurements of skeletal or dental patterns and their ranges.1-8 The cephalometric norms of different ethnic and racial groups established in various studies show that normal measurements for 1 group are not necessarily normal for another group; each racial group must be treated according to its own characteristics. A number of standards have been developed for various racial and ethnic groups.9-20 It is important to compare a patient’s cephalometric findings with the norms for his or her ethnic group for an accurate diagnostic evaluation, while considering his or her treatment goals and needs. Miyajima et al19 also noted that a patient might seek a treatment plan that is based in part on norms for his or her racial or ethnic group. Lecturer and consultant orthodontist, Orthodontic Unit, Department of Preventive Dentistry, College of Medical Sciences, University of Benin, Benin City, Nigeria. Reprint requests to: Dr Emmanuel O. Ajayi, PO Box 7272, Surulere, Lagos, Nigeria; e-mail, [email protected]. Submitted, February 2005; revised and accepted, May 2005. 0889-5406/$30.00 Copyright © 2005 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2005.07.002
Attempts to establish cephalometric norms for the Nigerian population have been made. Nigeria has the largest population of blacks in the world—about 120 million people. Isiekwe and Sowemimo21 published cephalometric values for adult Nigerians based on a study of 15 men and 5 women, aged 18 to 25 years, with ideal occlusions. Isiekwe22,23 also assessed anteroposterior skeletal jaw relationships and incisor angulations in a Nigerian sample. Nigeria has 3 major ethnic groups: Yoruba, Hausa, and Igbo. Variations in their craniofacial morphologies were evaluated by Durosinmi-Etti24 and Utomi,25 using samples of 12- to 14-year-olds in Lagos and 11- to 13-year-olds in Kaduna, respectively. These studies evaluated similar cephalometric parameters and showed variations in the cephalometric standards. The purposes of this study were (1) to establish cephalometric standards of children from the largest ethnic group of southeastern Nigeria, the Igbo, that can be used as baseline data for diagnostic purposes and planning orthodontic treatment; (2) to identify sex differences between Igbo boys and girls; and (3) to compare Igbo norms to the published standards of related Nigerian ethnic groups and other similar studies. MATERIAL AND METHODS
The material consisted of standardized lateral cephalometric radiographs of 100 volunteer Igbo children from public and private secondary schools in Enugu in 653
654 Ajayi
American Journal of Orthodontics and Dentofacial Orthopedics November 2005
Table I.
Comparison of mean and standard deviation of cephalometric measurements between Nigerian Igbo boys and girls Boys (n ⫽ 66)
Girls (n ⫽ 34)
Measurement (°)
Mean
SD
Mean
SD
P
SNA SNB ANB UI-FP LI-MP UI-LI FMA
85.63 81.30 4.35 123.08 99.21 108.10 26.14
4.30 4.14 2.50 7.68 5.53 8.36 4.74
85.35 81.07 4.28 122.38 98.03 111.03 25.99
4.33 3.81 2.42 7.22 6.36 7.10 5.58
NS NS NS NS NS NS NS
NS, Not significant. *Significant difference at P ⬍ .05. Table II.
Figure. Landmarks, planes, and angles measured in Igbo children. SNA, sella-nasion-A-point; SNB, sellanasion-B-point; ANB, A-point-nasion-B-point; UI-FP, upper incisor axis to Frankfort plane angle; LI-MP, lower incisor axis to mandibular plane angle; UI-LI, interincisal angle; FMA, Frankfort mandibular plane angle.
southeastern Nigeria. There were 66 boys and 34 girls, aged 11 to 13 years (mean, 12.6 ⫾ 0.6 years). Attempts were made to select children with balanced faces and acceptable profiles, Class I occlusions with normal overjet and overbite, minor or no crowding or spacing, and no history of orthodontic treatment, and born of Nigerian parents of Igbo ancestry from any of the 5 states of defunct Eastern Nigerian (presently southeastern Nigeria). Authorization and consent were obtained from the principals of the schools and the parents of the children. Lateral cephalograms of 100 children were taken. Each subject was positioned in the cephalostat with the head oriented to the Frankfort horizontal plane and the teeth in centric occlusion with the lips relaxed. The cephalometric radiographs were traced onto 0.003-in matte finish acetate sheets over an illuminated viewing box by using a standard technique. All radiographs were traced by the author, and angular measurement were made with a protractor and recorded to the nearest 0.5°. The following landmarks were identified on each cephalogram (Figure): sella turcica (S), nasion (N), orbitale (O), porion (P), gnathion (Gn), pogonion (Pog), gonion (Go), menton (M), anterior nasal spine (ANS), posterior nasal spine (PNS), A-point, B-point, maxillary incisor apex (MxIA), mandibular incisor apex
Cephalometric norms of Igbo children
Measurement (°)
Mean
SD
Minimum
Maximum
SNA SNB ANB UI-FP LI-MP UI-LI FMA
85.54 81.22 4.33 122.84 98.81 109.10 26.09
4.29 4.01 2.46 7.50 5.82 8.04 5.02
82 79 3 119 95 104 23
88 84 6 128 102 115 30
(MIA), upper incisor tip (UIT), and lower incisor tip (LIT). The definitions of the various landmarks have been reported previously.14 From these landmarks, the following skeletal and dental angles were measured: sella-nasion-A-point angle (SNA), sella-nasion-B-point angle (SNB), A-point-nasion-B-point angle (ANB), upper incisor axis to Frankfort plane angle (UI-FP), lower incisor axis to mandibular plane angle (LI-MP), interincisal angle (UI-LI), and Frankfort mandibular plane angle (FMA). Statistical analysis
The error during tracing, landmark selection, and measuring was determined by repeating the tracings of 25 randomly selected radiographs 1 month later. Dahlberg’s formula,26 公⌺d2/2n, where d is the difference in the measurement between the first and second tracings and n is the sample size, was used to calculate measurement error. The error of the measurements, 0.1° to 0.4°, for the variables was minimal. Systematic error was estimated by using a paired t test; the differences between the first and second measurements were statistically insignificant. The EPI INFO version 6 statistical software27 was used for further statistical analysis. The basic descriptive statistics, including the means, standard deviations, and maximum and minimum values were computed for
Ajayi 655
American Journal of Orthodontics and Dentofacial Orthopedics Volume 128, Number 5
Table III.
Comparison of Igbo means with Lagos and Hausa-Fulani cephalometric norms Lagos standards† (n ⫽ 100)
Igbo standards (n ⫽ 100)
Hausa-Fulani standards‡ (n ⫽ 100)
Angle
Mean
SD
P
Mean
SD
P
Mean
SD
SNA SNB ANB UI-FP LI-MP UI-LI FMA
88.90 84.48 4.39 126.03 100.69 108.91 24.38
4.15 3.71 2.30 6.77 5.45 9.66 5.64
0.00* 0.00* NS 0.00* 0.01* NS 0.02*
85.54 81.22 4.33 122.84 98.81 109.10 26.10
4.30 4.00 2.46 7.50 5.80 8.00 5.00
0.00* NS 0.00* NS 0.03* 0.00* 0.05*
82.35 80.35 2.07 122.3 97.1 113.6 24.80
3.50 3.30 2.80 12.80 5.50 12.8 4.40
NS, Not significant. *Significant difference at P ⬍ .05. † From Durosinmi-Etti.24 ‡ From Utomi.25
each cephalometric variable. The Student t test was used to assess sex differences in the measured values and to evaluate any differences between the craniofacial dimensions of Igbo children and related Nigerian children and other norms established by other investigators. The differences in the mean values were regarded as statistically significant if P ⬍ .05. RESULTS
The cephalometric findings by sex are listed in Table I. There was no statistically significant sex difference between the measurements of boys and girls; therefore, the combined data were analyzed, and the means, standard deviations, and ranges are given in Table II as the norms for Nigerian Igbo children. These norms were further compared with Lagos and Hausa-Fulani children’s norms (Table III). There were statistically significant differences (P ⬍ .05) in most of the measured cephalometric variables between the 3 groups, with the exception of SNB and UI-FP between Igbo and Hausa-Fulani children, and ANB and UI-LI between Igbo and Lagos children, respectively. DISCUSSION
The cephalometric values obtained in this study did not show any significant statistical difference between Igbo boys and girls; this agreed with previous findings for other major ethnic groups in Nigeria.22,24,25 The numerical values determined for the dental and skeletal variables showed some statistically significant differences in cephalometric norms of Igbo children in Enugu in southeastern Nigeria when compared with children from Lagos in southwestern Nigeria, where Yoruba is the predominant ethnic group, and HausaFulani children in Kaduna in northern Nigeria. The mean SNA and SNB values show that Igbo children
also have prognathism of the maxilla and mandible relative to anterior cranial base, which was observed by Isiekwe and Sowemimo21 and Durosinmi-Etti24 in adults and children, respectively, from southern Nigeria. The mean SNA value obtained in this study for Igbo children is also similar to that of black American children (P ⬎ .05) and showed prognathism of the maxilla when compared with American whites.11,12 However, SNB was similar in both Igbo and HausaFulani children (P ⬎ .05). The anteroposterior skeletal relationship of the maxilla and the mandible to the anterior cranial base was similar for Igbo and Lagos children. However, ANB in the Igbo is 2.26° significantly higher than that of the Hausa-Fulani. Utomi25 observed that HausaFulani children have less prognathic maxillae, with their denture bases slightly more posterior in relation to the cranial base than children from southern Nigeria. The value obtained was 1.5° significantly higher than that of American whites.11 This study also showed protrusive dentoalveolar relationships with associated bimaxillary proclination in Igbo children; this has been described as a feature of the Nigerian profile.23-25 UI-LI was similar in Igbo and Lagos children, and also the inclination of UI-FP between Igbo and Hausa-Fulani children (P ⬎ .05). Alexander and Hitchcock28 reported similar findings of procumbent and protrusive maxillary and mandibular incisors in American blacks. Savage29 reported bimaxillary protrusion as a general feature of Bantu children of West Lake Province of Tanganyika. Chan30 observed bimaxillary dental protrusion in Cantonese people when compared with white standards, matched only by the American black and the Australian aborigine. Igbo children have significantly steeper FMAs than other Nigerian ethnic groups. Drummond12 and
656 Ajayi
Kapila18 also reported high values for FMA in black American children and Kenyan children of Kikuyu descent. CONCLUSIONS
The profiles of Igbo children differ from those of other ethnic and racial groups. Their basal arches are more anteriorly placed in relation to the anterior cranial base. They also have prominent bimaxillary proclination, which is consistent with the southern Nigerian population, and a tendency toward a protrusive skeletal pattern. Cephalometric standards for Igbo children will aid in diagnostic evaluation and treatment planning for Nigerian orthodontic patients of Igbo descent. Because the various published cephalometric standards represent population averages, it is important to consider each patient’s treatment goals and needs during evaluation and treatment planning. It would further be desirable to evaluate linear measurements and the soft tissue profiles of Nigerian children for use in planning orthodontic treatment and orthognathic surgery. REFERENCES 1. Margolis H. Basic facial pattern and its application in clinical orthodontics. Am J Orthod 1947;33:631-41. 2. Downs WB. Variations in facial relationships: their significance in treatment and prognosis. Am J Orthod 1948;34:812-40. 3. Tweed CW. The Frankfort-mandibular incisor angle (FMIA) in diagnosis and treatment planning and prognosis. Angle Orthod 1954;24:121-69. 4. Steiner CC. Cephalometrics for you and me. Am J Orthod 1953;39:729-55. 5. Coben SE. The integration of facial skeletal variants. Am J Orthod 1955;41:407-34. 6. Ricketts RM. Cephalometric analysis and synthesis. Angle Orthod 1960;31:141-56. 7. McNamara JA Jr. A method of cephalometric analysis. In: McNamara JA Jr, editor. Clinical alteration of the growing face. Monograph 12. Craniofacial Growth Series. Ann Arbor: Center for Human Growth and Development; University of Michigan; 1983. 8. Sassouni V. Roentgenographic cephalometric analysis of cephalofacial-dental relationships. Am J Orthod 1955;41:735-64. 9. Cotton WN, Takano WS, Wong WW. The Downs analysis applied to three other ethnic groups. Angle Orthod 1951;21:21320. 10. Altemus LA. A comparison of cephalofacial relationships. Angle Orthod 1960;30:223-40.
American Journal of Orthodontics and Dentofacial Orthopedics November 2005
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