Craniofacial morphometric evaluation of Bangladeshi adults by lateral cephalometry with Tweed-Merrifield analysis ”

a. Assistant Professor & Head,Department of Orthodontics & Dentofacial Orthopedics, Update Dental College & Hospital, Dhaka. b. Medical Officer, Department of Orthodontics, Faculty of Dentistry, Bangabandhu Sheikh Mujib Medical University, Dhaka. c. Assistant Professor, Department of Oral & Maxillofacial Surgery, MARKS Dental College & Hospital, Dhaka d. Lecturer, Department of Orthodontics & Dentofacial Orthopedics, Update Dental College & Hospital, Dhaka.


Introductions:
Ethnical and racial variations of craniofacial morphometry among different population have been reported by many researchers 1 .From an orthodontist point of view management of dento-alveolar and craniofacial structurealways aimed to attain a specific norm for a specific populations 2 .After evaluation of lateral cephometric radiograph with proper radiation exposure and standard technique, the use of cephalometric studies was introduced in classical anthropometry and its today being constantly used in the evaluation of craniofacial variations 1 .The main goals of cephalometric analysis are to evaluate the dentofacial and skeletal relationship, of the five major functional components of the face: the cranium and the cranial base, the skeletal maxilla, the skeletal mandible, the maxillary dentition and the alveolar process, and the mandibular dentition and alveolar process 3 .The important goals of orthodontic treatment are the maintenance of facial balance and harmony as well as ideal occlusion.If facial balance does not exist it should be overriding priority of orthodontic treatment 4 .Angle's philosophy 5 of retaining all thirty two permanent teeth does not fullfill balance the facial balance and harmony in post treatment cases.On the other hand tweed by using cephalometric radiograph introduced a new norm to achieve facial aesthetics 6 .His standard leads orthodontics into the extraction of first premolar to achieve post treatment stability better facial aesthetics and harmony.However, the measurement proposed for these analyses were achieved based on a white American sample and may not be applicable as references for diagnosis and treatment planning of other ethnic group.It is unscientific to use cephalometric norm of a specific racial group for another different group o populations.It is important to have data concerning relevant human group for purposes of clinical diagnosis and planning of treatment.These data may also be useful in forensic dentistry.The ethnic differences in facial profile and skeletal features should be considered during treatment, especially in orthodontics, maxillofacial surgery and prosthodontics where arch shape can be modified appreciably 4 .
Therefore the aim of this study was to evaluate the morphometric norm for Bangladeshi populations with study population and comparing the value with those of previous study on other Bangladeshi populations.To evaluate the gender discrepancy of the norm and compare that with rest other previous study on Bangladeshi populations.There is patchy & paucity of such standard for Bangladeshi orthodontic populations.So far there is only one research 7 has been reported with lateral cephalometric radiograph by tweed's analysis on Bangladeshi population, which was constitute of mostly undergraduate dental school students.Therefore our study was aimed to perform in a larger number of populations with orthodontic complain, so that the norm for Bangladeshi orthodontic populations could be revealed, and compare our study result with that of previous study so that a mean norm could me calculated for future references.

Materials and Methods:
A cross sectional observational type of study were performed where the study populations included 112 lateral cephalogram of Bangladeshi collected from the patients' record of orthodontics department, faculty of dentistry, BSM Medical University and another two private orthodontic office of Dhaka, Bangladesh.The 112 radiographs (56 male and 56 female) were selected on the basis of having a harmonious face with a convex facial profile (from their photographic record), Angles 5 class I molar relationship with presence of all permanent teeth up to second molar (from their dental cast record), and without history of any type of previous orthodontic treatment (fixed/ removable/ functional).Their ages range from 16 years to 26 years with mean age of 19(±2.13)years of age.Those entire lateral cephalometric radiographs were taken from a specific non-government diagnostic center of Dhaka, with a single operator with specific radiographic machine Broadbent Bolton cephalometer (Siemens, Erlanger, Germany).The radiograph operator was instructed to record the lateral cephalometric radiograph when the each subject position in the cephalostat with the head oriented to the Frankfort horizontal plane and the teeth in centric occlusion with lip relaxed.All those recored radiograph were traced manually and analysis by a single investigator to avoid the investigator error.Tracing were done on a systemic manner with manually on A4 size tracing paper and 2B hard pencil with well illumination viewer.The image lines were traced without stopping or lifting the pencil, eraser were avoided as much as possible.Bilateral structures were first traced independently.An average was then drawn by dotted line with visual approximation (Figure 1).Then the interpretation were measured and evaluated by SPSS 17 (Chicago, USA) for statistical analysis.

Results:
The significance level for this study was set at p <0.05 and highly significant at p <0.001.The descriptive statistics were done for all lateral cephalometric radiographs to evaluate angular measurements for the entire sample (112 subjects) from both genders of Bangladeshi population (Tables 1).For each variable, mean and standard of deviation (SD) were obtained.
The p-values for all the comparisons were statistically not significant among gender.

Table 1 : Comparative statistics of Bangladeshi Adults with Tweed Analysis with that of Caucasian, Nepalese and previous study on Bangladeshi population by Alam MK et all.
Graphical Comparison of tweed's angle among present populations, with that of Caucasians 6 , Nepalese 8 , and Alam MK et all's 7 study.