Cephalometric comparisons of dentofacial parameters between Egyptian and North American adolescents

Samir E. Bishara, BDS, DDS, D. Ortho., MS,* Essam M. Abdalla, BChD, MS, PhD,** and Brad J. Hoppens, DDS, MS*** Iowa City, Iowa, Alexandria, Egypt, and Ogallala, Neb.

The purpose of this study was to develop cephalometric standards for the Egyptian adolescent boys and girls and to compare them to a matched Iowa adolescent sample. The Egyptian sample consisted of 39 boys and 51 girls with a mean age of 12.5 years. The Iowa sample consisted of 33 boys and 22 girls with a mean age of 13.0 years. Basic descriptive statistics were calculated for 35 cephalometric dentofacial parameters. The general linear models procedure, analysis of variance, was used for the comparisons between the groups. F values were calculated for the overall group comparisons, and the statistical significance was predetermined at the 0.05 level of confidence. Comparisons between the boys and girls in both populations indicated that the boys were larger in the linear dimensions of the cranial base and face heights than the girls. Comparisons between the Egyptians and the Iowans indicated that Egyptian boys have a tendency toward bimaxillary dental protrusion and a decreased overbite as compared with Iowa boys. Egyptian girls have a relatively more convex profile and a tendency toward mandibular dental protrusion. When the overall findings are evaluated, it could be concluded that, in general, there is a great similarity in the overall facial morphology between the Egyptian and Iowa populations. (AM J ORTHOD DENTOFAO ORTHOP 1 990;97:413-21 .)

T h e improvement in facial esthetics and functional occlusion are two desirable objectives of orthodontic treatment. Cephalometric norms have been used to determine the location and the severity of any existing dentofacial discrepancies and subsequently to evaluate the changes that accompany orthodontic treatment.

Differences in the dentofacial relationships of var- ious ethnic groups have been observed by many in- vestigators, and as a result, a number of standards have been developed for various racial and ethnic groups.'l" Comparisons between the various ethnic groups have led to the following general conclusions: (1) Mexicans exhibit more dental and skeletal protru- sion than white Americans 6'14'27 and the North Mexican girls have a relatively more protrusive mandible than the girls from Iowa. J4 (2) Compared with white Amer- icans, Iranians show a fiat skeletal profile with an in- creased lip convexity because of the dental protru-

*Professor, Department of Orthodontics, College of Dentistry, University of Iowa. **Assistant Professor, Department of Orthodontics, Faculty of Dentistry, Al- exandria University. ***In Private practice of orthodontics. 8/1112933

tl-4, 7-10, 12-14, 16, 17, 19, 22-24, 26

sion. 7'~6 (3) Japanese have a more protrusive dentition, an increased lower facial height, and a steeper man- dibular plane than white Americans. n.~7 (4) Compared with white Americans, black South Africans have a more protrusive maxilla, an increased ANB angle, and a greater labial inclination of the mandibular incisors. South African blacks have less protrusive upper incisors than American blacks.'9 (5) American blacks have a more protrusive maxilla and a greater bimaxillary pro- trusion than American whites.3a 3 (6) White children from the southern United States have more prominent incisors than white children from the northern United States. 2s (7) The skeletal pattern of Egyptian Nubians is similar to that of American whites except that the apical bases seem to be situated farther forward in the face. 2z (8) Egyptian adults when compared to American white adults have a greater bimaxillary protrusion, a more acute interincisal angle, a smaller gonial angle, and a smaller z angle. ~'~2

From this review, it can be concluded that differ- ences in the dentofacial relationships are present be- tween various ethnic and racial groups. Therefore it is important to develop standards for various populations. Of the cephalometric studies conducted on the Egyptian population, none provided norms for Egyptian adoles- cents. Since a large number of persons who seek ortho- dontic treatment fall within that age group, a study to

413

41 4 Bishara, Abdalla, and tIoppens Am. J. Orthod. Dentofac. Orthop. May 1990

PR

Fig, 1. Landmarks used,

develop standards for Egyptian adolescents is therefore indicated.

It is the purpose of this study to develop cephalo- metric standards for normal Egyptian boys and girls between 12 and 14 years of age. The Egyptian groups will be compared to a matched North American sample from Iowa.

MATERIALS AND METHODS The Egyptian sample

Of 500 Egyptian schoolchildren examined clinically in Alexandria, only 90 (39 boys and 51 girls) had a Class I molar and canine relationship, little or no incisor crowding, no apparent dental or skeletal discrepancies, and no history Of orthodontic treatment.

The question of whether the present sample col- lected in Alexandria Cotild be considered as a repre- sentative group of the total population has been con- sidered by Fahmy, 12 who concluded that the Egyptian population is comparatively homogenous. Harris 15 fur- ther stated: "In a relatively homogenous society, pop- ulation norms derived with suitable sampling tech- niques could provide a template against which the pa- tient's own growth record could be projected."

The Iowa sample

Lateral cephalograms of 33 boys and 22 girls were obtained from the Facial Growth Study data at the Uni- versity of Iowa. All the participants were white, and 97% were of northern European ancestory. All tbe sub- jects had acceptable occlusions with the dentitions ap- pearing to be well oriented with respect to the face.

Table I. Age distribution of Egyptian and Iowa subjects

I Sample Size E SD Range

Egyptian boys 39 i2.5 0.6 12.0-14.0 Egyptian girls 51 12.5 0.6 12.0-14.0 Iowa boys 33 13.0 0.9 12.0-14.0 Iowa girls 22 13.0 0.8 12.0-14.0

= M e a n .

SD = Standard deviation.

The ages for the male and female subjects in both populations are presented in Table I.

Landmarks used

The following landmarks were identified on each cephalogram (Fig. 1): Sella turcica (S), nasion (N), anteriormost point on the occipital condyle (O), point A (A), point B (B), pogonion (Pog), gnathion (Gn), gonion (Go), articulate (Ar), articulate pr ime (Ar'), which is the point of intersection of a perpendicular from Ar on S-Go, menton (Me), anterior nasal spine (Ans), anterior nasal spine prime (Ans'), which is ttie point of intersection of a perpendicular from Ans on N-Me, orbitale (Or), potion (Po), incision inferius (II), incision superius (IS), pronasale (Pr), labrale superius (LS), labrale inferius (LI), and soft-tissue chin (Pog'). The definitions for these landmarks Correspond to those given by Bishara 5 and Riolo et al. 21

Reliability of landmark localization and measurements

Each landmark was pricked by one investigator on the original cephalogram and checked by another in- Vestigator. The midpoint between all bilateral land- marks was used where appropriate. Each investigator measured each parameter twice. Allowable intrainves- tigator and interinvestigator differences were predeter- mined at 0.25 ° and 0.2 ram.

Cephalometric measurements

From the various landmarks described, the follow- ing angular and linear parameters were measured or calculated~,8,~sao,2J.23,24,26,28: Skeletal angular relationships

Maxilla = SNA Mandible = SNB, SNPog, FH:NPog, FH:SGn Maxilla-mandible = ANB, NAPog Anterior to posterior face = MP:SN, MP:FH Cranial base angle = NSO Saddle angle = NSAr

Volume 97 Cephalometric comparisons o f dentofacial parameters 41 fi Number 5

Table II. Descriptive statistics and results of comparisons between Egyptian and Iowa boys

Measurements

Egyptians

2 SD

lowans

7 SD

Cranial base NSAr (°) 124.5 6.0 124.3 NSO (°) 128.1 7.1. 129.5 N-O (mrn) 98.3 4.8 100.3 S-O (ram) 42.8 3.7 41,7 S-N (ram) 66.2 2.3 68,6 Skeletal angular SNA (°) 82.7 3.6 82.3 SNB (°) 79.5 3.5 79.2 ANB (°) 3.2 1.7 3. I NAPog (°) 7.4 4.0 5.4 SN Peg (°) 79.8 3.5 80.0 FH: NPog (°) 84.7 4.6 83.0 MP:SN (°) 32.9 4.4 31.2 MP: FH (°) 28.4 5.1 27.9 NSGn (°) 66.9 3.5 66.6 FH:SGn (°) 62.4 4.7 63.2 Skeletal linear Wits (mm) -0.1 2.8 -0 .8 N-Ans' (mm) 49.0 3.1 49.0 N-Me (mm) 109.4 5.2 110.9 N:Ans ' /N:Me (%) 44.9 2.6 44.2 Ar' :Go (mm) 45.3 4.0 48.0 S :Go (ram) 74.5 4.2 77.2 Ar' :Go/S :Go (%) 60.8 4.5 62.1 S :Go/N:Me (%) 68.2 3.3 69.8 Dental angular _I:T (°) 124.1 8.4 130.0 I :SN (°) 105.9 6.0 103.0 I :FH (°) 54.3 6.2 56.6 ] ' :MP (°) 98.2 5.8 95.5 Dental linear _l :APog (ram) 6.4 2.2 5.0 1 :NB (ram) 5.4 1.9 4.3 Pog:NB (mm) l, 1 1.7 1.2 OJ (mm) 2.6 1.2 2.7 OB (mm) 2.6 1.1 3.3 Soft tissue profile Holdaway STA (°) 11.2 4.7 11.5 Upper lip :Ricketts line (mm) 2.7 3.0 1.9 Lower lip : Ricketts line (ram) 1.1 3.1 1.2

Significance

5.3 NS 4.6 NS 3.9 NS 2,3 NS 5.2 S

3.4 NS 2.8 NS 1.6 NS 4.3 NS 3.1 NS . 4,2 NS 4.4 NS 4.6 NS 2,7 NS 3.9 NS

1.7 NS 2,9 NS 5.7 NS 1,7 NS 4.9 S 5,4 S 3,6 NS 4.1 NS

8.8 S 6,0 NS 6.7 NS 6.4 NS

1.9 S 1.6 S 1,6 NS 1.2 NS 1.1 S

3.9 NS 2,0 NS 2.2 NS

= Mean, SD = Standard deviation. S = Significant at <:0.05 level of confidence. NS = Not significant,

Skeletal linear relationships Wits appraisal: Defines the anteroposterior relation-

ship of point A and point B projected to the oc- clusal plane.

Anterior face heights: N-Ans', N-Me, and N-Ans'/N-Me%.

Posterior face heights: Ar'-Go, S-Go, and Ar'-Go/S-Go%.

Ratio of posterior to anterior face heights = S-Go/N-Me%.

Cranial base lengths: N-O, S-O, and S-N. Dental angular relationship

i:]-, I_:SN, I:MP, and ]':FH. Dental linear relationships

Overjet and overbite. 1: A-Peg and ]": NB and Peg: NB. Although Peg: NB

416 Bishara, Abdalta, and Hoppens Am. J. Orthoa. Dentofac. Orthop. May 1990

is not a dental_parameter, it has been traditionally included with 1 :NB.

Soft tissue profile Holdaway soft tissue angle: LS : Pog' : N-B. Upper lip to Ricketts line: LS : Pr-Pog'. Measured as

the distance of the perpendicular from the most prominent point on the upper lip to the Ricketts esthetic line.

Lower lip to Ricketts line: LI: Pr-Pog'.

Correction for magnification

Linear measurements derived from both sets of cephalograms were corrected for magnification with the appropriate magnification factor for each cephal0metric machine.

Statistical analysis

Descriptive statistics, including the mean, standard deviation, standard error of the mean, and minimum and maximum values, were computed for each variable. The analysis of variance, general linear models (GLM) procedure, was performed to determine whether or not differences existed between the four groups--Egyptian boys, Egyptian girls, Iowa boys, and Iowa girls.

F values were calculated from the GLM procedure, and if significant at F --< 0.05, the Duncan multiple range test was performed. The Duncan test is a multiple comparison test used to compare each mean with every other mean and is used to further pinpoint group dif- ferences found in the GLM analysis.

RESULTS

The descriptive statistics on 35 cephalometric vari- ables for both the Egyptian and the Iowa boys and girls are presented in Tables II and III.

Sex differences within each population

Comparisons between the Iowa boys and girls in- dicated that the boys are significantly greater in three linear cranial base parameters, S-N, S-O, N-O, and three linear facial parameters, N-Ans', Ar'-Go, and S-Go, than the girls.

Comparisons between the Egyptian boys and girls indicated that the Egyptian boys are also significantly greater than the girls in two linear cranial base param- eters, S-N and N-O, while the Egyptian girls were sig- nificantly greater than the boys in one skeletal angular parameter, namely, NSGn.

Comparisons between Egyptian and Iowa boys (Table II)

The results of the analysis of variance indicated the presence of the following significant differences be- tween the Egyptian and Iowa boys;

Cranial base parameters: The anterior cranial base length (S-N) was significantly greater in Iowa boys than in Egyptian boys.

Skeletal angular parameters." None of these param- eters were significantly different between Egyptian and Iowa boys.

Skeletal linear parameters." The total (S-Go) and posterior (Ar'-Go) face heights were significantly greater in Iowa boys than in Egyptian boys.

Dental angular and linear parameters: The inter- incisal angle was significantly smaller in Egyptian boys than in Iowa boys. On the other hand, !:A-Pog and I :NB were significantly greater in Egyptian boys. The overbite was significantly greater in Iowa boys than in Egyptian boys.

Soft tissue parameters: None of these parameters were significantly different between Egyptian and Iowa boys.

Comparisons between Egyptian and Iowa girls (Table III)

Cranial base parameters: Egyptian girls had sig- nificantly greater posterior (S-O) and total (N-O) cranial base lengths than Iowa girls,

Skeletal angular parameters." The angle of convex- ity was significantly greater in Egyptian girls than in Iowa girls, indicating a greater skeletal facial convexity in Egyptian girls.

Skeletal linear parameters." The Wits appraisal and the upper anterior face height (N-Ans') were also significantly greater in Egyptian girls than in Iowa girls.

Dental angular parameters: The mandibular inci- sors were more labially inclined in Egyptian girls as indicated by a greater ]-:MP angle and a lesser ]-:FH angle as compared with Iowa girls.

Soft tissue and dental linear parameters." None of these parameters were significantly different between the Egyptian and the Iowa girls.

DISCUSSION

Variation between and within different populations has been previously reported.* It has been suggested that factors such as sex, age, and racial origin, as well as face type, contribute to this variation. Superimposed on these factors are those characteristics that are unique for each individual. Because of such inherent variation, standards developed for any population should be used only as a reference line and not as absolute values to which all the individuals in that population should con- form to be considered "normal."

"1-4, 7-10, 12-14, 16, 17, 22-24, 26

Volume 97 Number 5 Cephalometric comparisons of dentofacial Parameters

Table IIh Descriptive statistics and results of comparisons between Egyptian and Iowa girls

Measurements Egyptians SD [ ' Yc lowansl

SD

417

Significance

Cranial base NSAr (°) 126.0 5,6 122.9 5.1 NS NSO (°) 129,1 5.7 128.0 3.5 NS N-O (mm) 96.5 6.3 93.7 3.0 S S-O (mm) 41.1 2.7 39.0 2.3 S S-N (rnm) 63.8 2.8 64.6 2.3 NS Skeletal angular SNA (°) 81,8 3.6 82.2 2,9 NS SNB (°) 78.2 3.6 79.4 3.'1 NS ANB (°) 3.6 1.7 2.7 1.8 NS NAPog (°) 7.8 4.5 4,8 4.7 S SN: Pog (*) 78.7 3.6 80.0 3.2 NS FH: NPog (°) 84.0 4.7 85.0 3.2 NS MP:SN (°) 33,1 4.9 32.8 4.8 NS MP:FH (°) 27.8 5.4 27.8 5,1 NS NSGn (°) 68.7 3,2 66.5 3.4 NS FH:SGn (°) 63.8 4.3 61.8 3.5 NS Skeletal linear Wits (mm) 0.7 2.0 -0 .8 2.1 S N-Ans' (ram) 49.1 2.7 46.7 1.8 S N-Me (mm) 107.4 4.6 105.8 5.3 NS N: Ans ' /N:Me (%) 45.7 2.2 44.2 2.0 S Ar' :Go (ram) 45.3 4.0 45,O 3.5 NS S :Go (mm) 73.7 4.4 72.5 2.8 NS Ar' :Go/S :Go (%) 61.5 4.0 62.0 3.5 NS S :Go/N:Me (%) 68.7 3.9 68.6 3.4 NS Dental angular I :T(°) 127.0 8.0 128.2 8.5 NS I :SN (°) 103.1 8.0 104,2 6.4 NS T:FH (°) 55.2 5.0 58.5 7,2 S T:MP (°) 97.5 6.3 93.5 6.3 S Dental linear 1: APog (mm) 5.6 1.7 5.6 2,0 NS I :NB (ram) 5.0 1,6 4.3 1.7 NS Pog:NB (mm) 0.7 1.4 1.3 1.4 NS OJ 2,7 0.9 2.8 1,0 NS OB 2.8 0.2 2.9 1.0 NS Soft tissue profile Holdaway STA (°) 10.6 4.2 10.7 4.8 NS Upper lip:Ricketts line (ram) 2.9 2.7 2.9 2.2 NS Lower lip:Ricketts line (mrn) 1.1 2.4 1.3 2.3 NS

= Mean. SD = Standard deviation, S = Significant at <--0.05 level of confidence. NS = Not significant.

Sex differences within populations

Considering the large number of parameters com- pared in this study, few differences were found between boys and gifts. Egyptian boys had greater cranial base dimensions than Egyptian gifts while the girls had greater NSGn angles than the boys, indicating a ten- dency toward more retrusive mandibles. When com- pared with Iowa girls, Iowa boys also had greater cra-

nial base lengths as well as longer anterior and posterior face heights.

It should be emphasized that most of the observed differences between boys and gifts in either population were in linear dimensions. This is to be expected since males are, in general, larger than females.~4 Superim- positions of facial polygons for the boys and girls in each population are presented in Figs. 2 and 3.

418 Bishara, Abdalla, and Hoppens Am. J. Orthod. Dentofac. Orthop. May 1990

O

Egypt ian Males . . . . . . . . . . Egypt ian Females

S N

t I !

Go/,

\

I

/ 1

!

/ /

;1

I

I I

I

" Me

Fig. 2. Superimposition of facial polygons for Egyptian boys and girls,

Egyptian Males . . . . . . . . . . . Iowa Males S

, ~ . . . . . . . . N

0

"-4 Me

Fig. 3. Superimposition of facial polygons for Iowa boys and girls.

Iowa Males . . . . . . . . . . Iowa Females

S m N

O

I

i

Fig. 4. Superimposition of facial polygons for EgYptian and Iowa boys,

Egyptian Females . . . . . . . . . . . . Iowa Females

S

\ ./

~ ivle

Fig. 5. Superimposition of facial polygons for Egyptian and Iowa girls.

Votume 97 C ephalometric comparisons of dentofacial parameters 419 Number 5

NAME,

MEASUREMENTS

Skeletal Angular

SNA*

SNB °

ANB*

NAPog °

SNPog °

FH:NPog °

°MP;SN o

MP:FH °

NSGn °

FH:SGn °

Skeletal Linear

Wits mm

N-Ans' rnm

N-Me mm

N:Ans'/N:Me %

Ar'-Go mm

S:Go mm

Ar':Go/S:Go %

S:Go/N:Me %

Dental Angular

/:TO _1 :SN*

T:FH*

T:MP °

Dental Linear

±:APog mm

T:NB rnm

Pog:NB mm

Soft Tissue Profile

Holdaway STA °

E-Plane:LS mm

E-Plane:LI mm

Remarks;

NUMBER BIRTH DATE SEX

MIN. I AVG. IMA×. I S.D. I I I 1 I

75 83 92 3.6

71 80 87 3.5

-1 3 6 1,7

O 7 17 4.0

72 80 88 3.5

76 86 94 4.6

25 33 42 4.4

16 28 40 5,1

60 67 74 3.4

54 62 71 4.7

-6 0 5 2.8

44 49 56 3.1

101 109 121 5.1

39 45 50 2.8

37 45 55 4.0

67 75 88 4,2

48 61 70 4.5

62 68 75 3,3

106 124 144 8.4

91 .106 124 6.0

33 54 67 6.2

88 98 113 5.8

2 6 10 2,1

1 6 9 1.9

-4 1 4 1,7

21 , , I 2ol ',1

-5 1 6 3.1

I [ 1 1

t E I Values were obtained from cephalogrsms of 39 normal Egyptian Males with a mean age of 12,5 years (12-14

years) which participated In the Iowa-Alexandria Research Study,

Fig. 6. Cephalometric standards for Egyptian adolescent boys,

Differences between populations

The present findings indicate that there are signif- icant differences in a number of cephalometric param- eters between the Egyptian and Iowa ado/escent groups. In general, Egyptian boys have a tendency toward a bimaxillary dental protrusion as compared with Iowa boys. On the other hand, Iowa boys have a greater posterior face height than Egyptian boys.

Egyptian girls have a more convex skeletal pro- file than Iowa gifts. In addition, Egyptian girls have a tendency toward greater mandibular dental protrusion.

Superimpositions of facial polygons for the Egyp- tian and Iowa boys and girls are presented in Figs. 4 and 5.

Other cephalometric studies comparing Egyptian

420 Bishara, AbdalIa, and Hoppens Am, J. Orthod. Dentofac. Orthop. May 1990

NAME

MEASUREMENTS

Skeletal Angular

SNA °

SNB °

ANB °

NAPog; SNPog °

FH:NPog °

MP;SN °

MP:FH °

NSGn °

FH:SGn °

Skeletal Linear

Wits mm

N-Ans' mm

N-Me mm

N:Ans'/N:Me %

Ar'-Go mm

S:Go mm

Ar':Go/S:Go %

S:Go/N:Me %

Dental Angular

_~:T ° / :SN*

T:FH*

T:MP*

Dental Linear

I :APog mm

T:NB ram

Pog:NB rnm

Soft Tlsaue Profile

Holdaway STA °

E-Plane:LS mm

E-Plane:LI mm

Remarks:

NUMBER

MIN. [ AVG. [ MAX. [ S.D.

73 82 91 3.6

71 78 85 3.6

0 4 8 1.7

0 8 18 4.5

72 79 86 3.6

75 84 93 4,0 ,,r

23 33 46 5,0

19 28 45 5,0

61 89 77 3,2

55 64 74 4.3

-4 1 5 2.0

43 49 56 2.7

95 107 119 4,6 ,, i

40 46 51 2.1

37 45 57 4.0

64 74 86 4,4

54 61 74 4.0

59 69 77 4.0

112 127 143 8.0

83 103 118 8,0

41 55 68 5.0

83 97 113 6.3

2 6 9 2,0

2 5 g 2.0

-3 1 4 1.4

3 I " I 2, [ ,2

'4 1 6 2.4

BIRTH DATE

I 1 I J

't ....

Ii I I I

SEX _ _

I

Values were obtained from cephelogrems of 51 normal Egyptian Females with a mean age of 12,5years (12-14 years) which participated in the iowa-Alexandria Research Study,

Fig. 7, Cephalometric standards for Egyptian adolescent girls.

and American adults found similar tendencies toward bimaxillary dental protrusion in the Egyptian popula- tion. ~,9,]0,~2 Because of the presence of these differences, cephalometric standards have been developed for the Egyptian adolescent population and are presented in Figs. 6 and 7. (Forms may be obtained from Drs. Bishara and Abdalla.)

CONCLUSIONS

Cephalometric standards for adolescent Egyptian boys and girls have been presented. Because most persons seeking orthodontic treatment are in this age range, these standards should be of value in the di- agnosis of dentofacial malrelationships in Egyptian adolescents.

Volt,me 97 Cephalometric comparisons of dentofacial parameters 42"1 Number 5

In general , there are great s imi lar i t ies in the overal l

d e n t o f a c i a l m o r p h o l o g y o f the E g y p t i a n and Iowa boys

a n d girls, wi th a t e n d e n c y t o w a r d denta l p ro t rus ion in

the Egyp t i an g roups .

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Reprint requests to: Dr. Samir E. Bishara Department of Orthodontics College of Dentistry University of Iowa Iowa City, IA 52242