International Medical Journal Vol. 20, No. 3, pp. 345 - 348 , June 2013

ORAL SURGERY

Cephalometric for Orthognathic Surgery (COGS) forBangladeshi Population

Mohammad Khursheed Alam1), Rehana Basri2), Kathiravan Purmal2),

Shaifulizan Ab Rahman3), Ramizu Shaari3),

Mohammad Emadul Haq4)

ABSTRACT

Objectives: To establish hard tissue cephalometric norms for orthognathic surgery (COGS) for Bangladeshi adults and tocompare their mean differences with the established values of Caucasian COGS norms.

Materials and Methods: The study sample consisted of 100 standardized lateral cephalometric radiographs of Bangladeshiadult including 50 males and 50 females with an average age of 20 years were studied. The criteria of selection were Class I nor-mal occlusion, no skeletal abnormality or deformity, and no previous orthodontic treatment. All cephalometric landmarks werelocated and determined and subsequently all measurements were done according to COGS analysis.

Results: Of the 23 measurements, 15 were highly significantly different between the sexes whereas 2 were insignificant.Mean established values according to COGS analysis were also presented to show the differences with the Bangladeshi adults.Bangladeshi males and females had significant differences in most of the cephalometric measurements; males had larger mea-surements than females in almost all variables.

Conclusion: This study may be valuable in providing specific COGS in diagnosis and treatment planning for orthognathicsurgery for Bangladeshi adults.

KEY WORDS

lateral cephalometric radiographs, COGS norms, Bangladeshi adult

Received on July 6, 2012 and accepted on October 17, 20121) Orthodontic Unit, School of Dental Sciences, Health Campus, Universiti Sains Malaysia2) School of Dental Sciences, Health Campus, Universiti Sains Malaysia 3) Oral Surgery, School of Dental Sciences, Health Campus, Universiti Sains Malaysia4) City Dental CollegeCorrespondence to: Mohammad Khursheed Alam(e-mail: dralam@gmail.com)

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INTRODUCTION

Careful diagnosis of facial, skeletal and dental problems is thekey point for the successful treatment of the orthognathic surgery.For this reason a specialized cephalometric appraisal system calledcephalometric for orthognathic surgery analysis (COGS) concerningthe hard tissue of the face had been developed by Burstone and col-leagues (Burstone et al., 1978). The COGS analysis of the hard tissuedepicts the horizontal and vertical positions of facial bones by the useof steady harmonize system; the sizes of bones are represented bydirect linear measurements and the shape by angular measurements.

In our previous study we have established cephalometric stan-dards of Malaysian Indian (Kathiravan et al., 2012), MalaysianChinese (Kathiravan et al., 2012), Bangladeshi populations usingDown's analysis (Alam et al., 2012), Steiner analysis (Alam et al.,2012), Bjork-Jarabaks' analysis (Alam et al., 2012), Holdway's analy-sis (Alam et al., 2012), McNamara analysis (Alam et al., 2012),Harvold's analysis (Alam et al., 2012), Tweed's and Wit's analysis(Alam et al., 2012) and we also established cephalometric lip mor-phology in a Bangladeshi population (Alam et al., 2012). So far nostudy has been done on Bangladeshi adult population using COGSanalysis which is indispensible for the diagnosis and treatment plan-ning for orthognathic surgery. In the treatment planning for orthog-nathic surgery, COGS analysis has been extensively used for research(Conner and Moshiri, 1985; Wylie et al., 1987; Flynn et al., 1989;Rafael et al., 1998). Some studies found craniofacial features distinctin certain ethnic groups as compared to those of other populations.

Due to this ethnic variation it is unscientific to use or apply cephalo-metric norms specific for one racial group on a different population.

In Caucasian COGS study (Burstone et al., 1978), Sella-Nasinplane was used as a reference plane. The same procedure was fol-lowed in the current study. COGS analysis (Burstone et al., 1978) isspecially considered for patients who necessitate orthognathicsurgery and was developed by identifying different landmarks andmeasurements that can be altered by general surgical procedures.Because measurements are primarily linear, they may be eagerlyapplied to prediction overlays and study cast mountings and mayserve as a basis for the assessment of post-treatment stability. Thepurpose of this study was to investigate the hard tissue cephalometricnorms for orthognathic surgery (COGS) for Bangladeshi adults andto compare between Bangladeshi adult male and female. This investi-gation also aimed to compare the mean difference with the estab-lished Caucasian COGS (Burstone et al., 1978) standards.

SUBJECTS AND METHODS

The study sample consisted of 100 standardized lateral cephalo-metric radiographs of Bangladeshi adults including 50 males and 50females with an average age of 20 years were studied. The subjectswere selected on the basis of inclusion criteria from the students anddental patients of Dental Institutes under Dhaka University.

The inclusion criteria of the subjects consisted of

C 2013 Japan International Cultural Exchange Foundation& Japan Health Sciences University

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1. normal occlusion 2. no previous orthodontic treatment 3. no skeletal abnormality or deformity 4. no craniofacial abnormality5. no incisor crowding 6. both parents and grandparents being Bangladeshis without any

interracial marriage.

The study period was from April 2008 to April 2011. The analy-ses employed according to the Caucasian COGS (Burstone et al.,1978) standards are shown in Figure 1. All radiographs and tracingswere done by a single investigator. Tracing was done in a standardmanner.

Control of Error: Twenty randomly selected lateral cephalomet-ric radiographs were retraced and re measured to calculate the errorin the method. The reliability of the method was analyzed by theDalhberg's formula: ME = S(x1-x2)2/2n, where x1 is the first mea-surement, x2 the second measurement and n the number of repeatedrecords (Houston WJB, 1983). This formula determines the differ-ence between 2 measurements taken at least one month apart.

Statistical Analysis: After collection, the data was verified andanalyzed statistically using SPSS 19 (Chicago, USA) program. Anindependent t-test was employed to test for gender differences and tofind out whether there was signif icant difference betweenBangladeshi males and females at 5% level (P < 0.05).

RESULTS

Descriptive statistics and the independent t-test results of theBangladeshi adult males and females were summarized in Table 1and 2. Of the 23 measurements, 15 were highly significant different

between the sexes whereas 2 were insignificant. Mean establishedvalues according to COGS analysis (Burstone et al., 1978) were alsopresented to compare the difference with the present study (Table 1).Bangladeshi males and females had significant differences in most ofthe cephalometric measurements; males had larger measurementsthan females. Bangladeshi males had an increase in the posterior cra-nial base length, the mandible, maxilla and chin significantly protrud-ed and larger in length, increase in mandibular plane angle, largermaxillary length, and almost similar proclination of lower incisorsthan Bangladeshi female (Table 1 and 2). Mean differences werefound between cephalometric mean values of Bangladeshi male,female and with the male and female Caucasian COGS analysis val-ues (Table 1 and 2).

To test the level of error involved in the present study, lateralcephalometric radiographs from each group were randomly selectedand measurements were repeated one month apart. The reproducibili-ty of the measurements was assessed by comparing the data taken atone month difference. Dahlberg's formula was used to determine themethod-error, which did not exceed 0.49 mm for the linear variables,0.93 degree for the angular variables (Houston WJB, 1983).

DISCUSSION

This investigation determines the hard tissue cephalometricnorms for orthognathic surgery (COGS analysis) for Bangladeshiadults and compares the disparity between Bangladeshi adult maleand female. This investigation also determines to compare the meandifference with the established Caucasian COGS (Burstone et al.,1978) standards. In this study the samples were from students anddental patients with the age group between 18 to 24 years. The sam-ple size in this study was 100 (50 male and 50 female) and compara-tively much higher than the number of subjects in the previous stud-ies (Burstone et al., 1978). Subjects with normal occlusion, no previ-ous orthodontic treatment, full dentition from second molar to secondmolar, no skeletal abnormality, no facial abnormality and no incisorcrowding were included in the study.

Racial skeletal and dental distinctiveness of the face take part in asignificant role in orthodontic and orthognathic treatment planning.Therefore, the mean values for measurements of one racial groupcould not be considered normal for others. Numerous studies (Connerand Moshiri, 1985; Wylie et al., 1987; Shalhoub et al., 1987; Flynnet al., 1989; Bishara et al., 1990; Rafael et al., 1998; Hamdan andRock, 2001; Hassan, 2006; Kathiravan et al., 2012; Alam et al.,2012) have shown the differences between racial groups were evi-dent. The mean difference values for Bangladeshi males and femaleswere different in almost all of the measurable parameters when com-pared to COGS analysis values (Burstone et al., 1978). These find-ings were in accordance with Flynn et al. (1989) and Rafael et al.(1998). Cephalometric studies which reported the existence of ethnicdifferences when Japanese and African Americans were comparedwith Causcasian COGS analysis (Burstone et al., 1978).

It had been observed that Bangladeshi males and females had sig-nificant differences in most of the cephalometric measurements;males had larger measurements than females. Bangladeshi males hadan increase in the posterior cranial base length, the mandible, maxillaand chin significantly protruded and larger in length, increase inmandibular plane angle, larger maxillary length, and almost similarproclination of lower incisors than Bangladeshi female.

In the present study Mean differences were found betweencephalometric mean values of Bangladeshi male, female and with themale and female Caucasian COGS analysis values (Burstone et al.,1978). These skeletal measurements can be interpreted asBangladeshi males are having prognathic facial pattern. This may beexplained by the anterior position of mandible and maxilla, promi-nent chin, and backward rotation of the mandible. The present find-ings were in agreement with Nanda and Nanda (1969), Al-Jasser(2000, 2005), and Hassan (2006) who reported almost similar find-ings that Saudis have a tendency toward bimaxillary protrusionalthough different samples and analyses were used. The results of thestudy conducted by Valiathan (1974) supports the convexity ofIndian facial profile and procumbency of the teeth. WhereasKharbanda et al. (1989) study on Aryo-Dravidians, a major ethnicgroup occupying Punjab and Kashmiri's facial norms were not differ-ent from Chinese and Iranians.

The cephalometric norm plays a vital role in the diagnosis oforthognathic surgical case. Even though there are plenty of surgical

Alam M. K. et al.

Figure 1. Cranial base length and vertical skeletal, dental andmaxilla/mandibular measurements:1: posterior cranial base (AR-PTM), 2: anterior cranial base (PTM-N), 3:upper anterior facial height (N-ANS), 4: lower anterior facial height (ANS-GN), 5: upper posterior facial height (PNS-N), 6: mandibular plane angle(MP-HP), 7: upper anterior dental height (U1-NF), 8: lower anterior dentalheight (L1-MP), 9: upper posterior dental height (UM-NF), 10: lower poste-rior dental height (LM-MP), 11: maxillary length (PNS-ANS), 12: chindepth (B-PG), 13: gonial angle (AR-GO-GN).

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cephalometric norms, they are mostly established on the Caucasianpopulation, which might lead wrong diagnosis in case of populationother than Caucasian. In view of the findings of this study, it is evi-dent that there are some fundamental variations in the COGS analysisof Bangladeshi adults. These differences should be kept in mind tofacilitate better diagnosis and treatment of the Bangladeshi adultorthodontic and orthognathic patients.

CONCLUSION

This study has established COGS for the Bangladeshi adults.COGS analysis in Bangladeshi population showed sexual dimor-phism in vertical skeletal, dental and maxilla/mandibular measure-ments and varied from the established COGS norms of Burstone et

Cephalometric for Orthognathic Surgery (COGS) for Bangladeshi Population

Table 1. COGS value of Bangladeshi population and Caucasian established values

Variables Present study Caucasian

Sex N Mean Total Mean SD N Mean SD

Cranial base

Posterior cranial base (AR-PTM) M 50 70.51 69.89 1.06 14 37.1 2.8

F 50 69.27 16 32.8 1.9

Anterior cranial base (PTM-N) M 50 33.62 33.14 2.21 14 52.8 4.1

F 50 32.65 16 50.9 3

Horizontal skeletal relation

Facial convexity (N-A-PG) M 50 2.68 2.38 1.30 14 3.9 6.4

F 50 2.08 16 2.6 5.1

Maxillary protrusion [N-A(HP)] M 50 2.51 1.21 1.33 14 0 3.7

F 50 -0.09 16 -2 3.7

Mandibular protrusion [N-B(HP)] M 50 -3.83 -4.65 1.15 14 -5.3 6.7

F 50 -5.47 16 -6.9 4.3

Chin protrusion (N-PG) M 50 -2.43 -3.75 1.18 14 -4.3 8.5

F 50 -5.07 16 -6.5 5.1

Vertical skeletal and dental

Upper anterior face height (N-ANS) M 50 57.96 55.74 2.14 14 54.7 3.2

F 50 53.51 16 50 2.4

Lower anterior face height (ANS-GN) M 50 72.46 68.64 2.30 14 68.6 3.8

F 50 64.81 16 61.3 3.3

Upper posterior face height (PNS-N) M 50 57.76 55.94 2.30 14 53.9 1.7

F 50 54.11 16 50.6 2.2

Mandibular plane angle (MP-HP) M 50 24.80 24.24 2.18 14 23 5.9

F 50 23.68 16 24.2 5

Upper anterior dental height (UI-NF) M 50 34.36 32.69 2.30 14 30.5 2.1

F 50 31.01 16 27.5 1.7

Upper posterior dental height (U6-NF) M 50 30.06 28.29 2.30 14 26.2 2

F 50 26.51 16 23 1.3

Lower posterior dental height (L6-MP) M 50 39.66 37.64 2.30 14 35.8 2.6

F 50 35.61 16 32.1 1.9

Lower anterior dental height (L1-MP) M 50 48.86 46.59 2.30 14 45 2.1

F 50 44.31 16 40.8 1.8

Maxilla and mandible

Maxillary length (PNS-ANS) M 50 61.56 58.84 2.30 14 57.7 2.5

F 50 56.11 16 52.6 3.5

Mandibular ramus length M 50 45.98 45.35 2.08 14 52 4.2

F 50 44.72 16 46.8 2.5

Mandibular body length M 50 71.76 70.83 0.90 14 83.7 4.6

F 50 69.89 16 74.3 5.8

Chin depth (B-PG) M 50 12.76 11.74 2.30 14 8.9 1.7

F 50 10.71 16 7.2 1.9

Gonial angle (AR-GO-GN) M 50 125.94 124.62 2.90 14 119.1 6.5

F 50 123.29 16 122 6.9

Dental relationships

Occlusal plane (OP-HP) M 50 10.06 10.34 2.30 14 6.2 5.1

F 50 10.61 16 7.1 2.5

Upper incisors inclination (UI-NF) M 50 114.86 115.44 2.30 14 111 4.7

F 50 116.01 16 112.5 5.3

Lower incisors inclination (L1/GO-ME) M 50 92.24 91.69 3.46 14 95.9 5.2

F 50 91.13 16 95.9 5.7

Wits analysis [A-B(OP)] M 50 0.34 0.32 3.16 14 -1.1 2

F 50 0.31 16 -0.4 2.5

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al,. 1978. This study may be valuable in providing specific COGS indiagnosis and treatment planning for orthognathic surgery forBangladeshi adults.

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Table 2. Statistical comparison of COGS analysis between Bangladeshi males and females

Mean SE 95% Confidence p value

Variables difference difference interval

Lower Upper

Cranial base

Posterior cranial base (AR-PTM) 1.240 0.212 0.819 1.661 0.000 **

Anterior cranial base (PTM-N) 0.970 0.442 0.092 1.848 0.031 *

Horizontal skeletal relation

Facial convexity (N-A-PG) 0.600 0.260 0.084 1.116 0.023 *

Maxillary protrusion [N-A(HP)] 2.600 0.268 2.069 3.131 0.000 ***

Mandibular protrusion [N-B(HP)] 1.640 0.232 1.180 2.101 0.000 ***

Chin protrusion (N-PG) 2.640 0.238 2.167 3.113 0.000 ***

Vertical skeletal and dental

Upper anterior face height (N-ANS) 4.450 0.428 3.601 5.299 0.000 ***

Lower anterior face height (ANS-GN) 7.650 0.461 6.735 8.565 0.000 ***

Upper posterior face height (PNS-N) 3.650 0.461 2.735 4.565 0.000 ***

Mandibular plane angle (MP-HP) 1.120 0.435 0.256 1.984 0.012 *

Upper anterior dental height (UI-NF) 3.350 0.461 2.435 4.265 0.000 ***

Upper posterior dental height (U6-NF) 3.550 0.461 2.635 4.465 0.000 ***

Lower posterior dental height (L6-MP) 4.050 0.461 3.135 4.965 0.000 ***

Lower anterior dental height (L1-MP) 4.550 0.461 3.635 5.465 0.000 ***

Maxilla and mandible

Maxillary length (PNS-ANS) 5.450 0.461 4.535 6.365 0.000 ***

Mandibular ramus length 1.260 0.416 0.435 2.085 0.003 **

Mandibular body length 1.870 0.179 1.514 2.226 0.000 ***

Chin depth (B-PG) 2.050 0.461 1.135 2.965 0.000 ***

Gonial angle (AR-GO-GN) 2.650 0.579 1.501 3.799 0.000 ***

Dental relationships

Occlusal plane (OP-HP) -0.550 0.461 -1.465 0.365 0.236

Upper incisors inclination (UI-NF) -1.150 0.461 -2.065 -0.235 0.014 *

Lower incisors inclination (L1/GO-ME) 1.110 0.691 -0.262 2.482 0.111

Wits analysis [A-B(OP)] 0.030 0.060 -0.090 0.150 0.621 ***