McNamara ’ s Cephalometric Analysis of Adult Brahmins of Kathmandu

The uniqueness of McNamara Analysis (1984) is that; it expresses jaw size as well as its position in reference to N perpendicular. This gives the facial skeletal profile picture making the analysis easily communicable. Acknowledging its simplicity this analysis system was used in analyzing craniofacial structure of different ethnic groups (Japanese,5 Turkish,6 Saudis,7 Chinese8). In addition, it also stated gender diversity beside ethnic diversity.


INTRODUCTION
Standardized radiographic technique by Broadbent and   Hofrath in 1931 1 permitted precise vertical and sagittal measuring of craniofacial structures.Since then different analysis such as Downs, 2 Steiner, 3 McNamara 4 systems evolved in different ethnic groups.Analysis (1984) is that; it expresses jaw size as well as its position in reference to N perpendicular.This gives the facial skeletal profile picture making the analysis easily communicable.

The uniqueness of McNamara
Acknowledging its simplicity this analysis system was used in analyzing craniofacial structure of different ethnic groups (Japanese, 5 Turkish, 6 Saudis, 7 Chinese 8 ).In addition, it also stated gender diversity beside ethnic diversity.
Cephalometric studies using other analysis system have been performed earlier on Nepalese Population. 9

MATERIALS AND METHOD
Ethical approval was obtained from the Institutional Review Board (IRB).Convenience sampling was performed among college students of different locations in Kathmandu, conforming to exclusion and inclusion criteria.Informed and signed consent were taken from the participants who were selected.

Radiographic Technique
Radiographs were taken in natural head position 10  behind the lead loaded door to reduce cumulative lethal effect. 11The distance from the source to the Mid Sagittal Plane was 134 cm and the distance from Mid Sagittal Plane to x-ray film was 18 cm.Linear measurements had 13% enlargement.

Cephalometric Method
The lateral cephalograms of two comparison groups were traced in random in order to prevent the researcher-bias.
Since Error in cephalometry is due to lack of reproducibility of landmarks rather than the difference in measurements; landmarks were relocated for their validity and average of the two was taken in case of differences.Intraobserver variation in identifying and locating anatomical landmarks during tracing and measurements assessed by using paired t-test showed no statistically significant intra examiner error. 12teral radiographic cephalograms were traced and measured.Table 1 presents the cephalometric Landmarks required for McNamara analysis with its description.Figure

Statistical Analysis
Descriptive statistics were derived from the quantitative data using SPSS (Statistical Package for Social Science).
Then the data were presented in tables and t-test was performed at the level of significance .05.

RESULT
The characteristic and frequency of quantitative data of eleven different variables of craniofacial structures showed normal distribution approximately in frequency distribution graphs.Statistically significant age differences between the sample groups were not observed as shown in Table 2.
Comparison of adult Brahmin males and females is expressed in Table 3. Adult Brahmin males had significantly larger Effective Mandibular Length (p≤0.001), Maxillomandibular Differential (p≤0.05) and Lower Anterior Facial Height (p≤0.01)than adult Brahmin females.

Table 1: Description of Landmarks
Anterior nasal spine (ANS) Spinous process of the maxilla forming the most anterior projection of the floor of the nasal cavity.

Pogonion (Pog)
Most prominent point on the anterior aspect of symphysis of mandible.
Anatomical Gnathion (Gn) The most anteroinferior aspect of the mandibular symphysis Menton (Me) The most inferior point on the symphysis of the mandible.

DISCUSSION
Sample selection of previous studies were based on occlusal evaluation/facial esthetic or both as in the present study. 4,5,8,15 Frfort horizontal plane is one of the Reference Plane of this study.Since machine Porion deviates from anatomic Porion by 10 mm, anatomic Porion was used in this study. 16xual dimorphism was observed in previous studies when male and female subjects within Chinese, 17 Mexican Americans, 18 and Japanese 19 were compared.Significant gender difference observed within the adult Brahmin groups of Kathmandu indicated sexual dimorphism.So further comparisons of Brahmins with other ethnic groups required separate comparison for male and female groups.
Radiographic magnification error is the possible problem encountered in this analysis system due to greater linear distances of the parameters used.Hence, for accuracy, measurements of this study were made comparable with the radiographic magnification of the reference sample (changed from 13% to 8%). 13,14 illary length in adult male Brahmins of Kathmandu (85.23 mm) were greater than female Brahmins of Kathmandu (82.57mm) but it was positioned more posteriorly in reference to Nasion perpendicular plane in male Brahmins of Kathmandu (-0.62 mm) and more anteriorly placed in female Brahmins of Kathmandu (0.90 mm).Mandibular Length was significantly greater in male Brahmins of Kathmandu subjects, however chin prominence was lesser in males as indicated by Pogonion to Nasion Perpendicular (-3.12 mm in males, -1.86 mm in females).
with right side facing the cassette.This position was fixed with the forehead clamp positioned at Nasion.Parallel position of Mid Saggital Plane of the subject with the sensor was fixed by positioning ear rods in ear holes.The central beam of the x-ray tube passed through the ear rod and Orthodontic Journal of Nepal, Vol. 6 No. 2, December 2016 external auditory meatus, perpendicular to the cassette.In this position the subject was exposed with maximum intercuspation and lips in light contact.The subject was asked to stand still during exposure until the beep sound stops.Digital Sordex Cranex Excel Ceph 71 Kvp, 6 mA was exposed for 1.2 seconds by the operator standing

1
presents their localization.Pradhan R, Rajbhandari A, Shrestha SL: McNamara's Cephalometric Analysis of Adult Brahmins of Kathmandu Magnification factor Measurements obtained were made comparable with the magnification factor of the reference sample in the following manner: Y = X* Magnification factor of McNamara sample / magnification factor of present study Y = Adjusted measurement X = Raw measurement13,14 Gonion (Go) Most posterior inferior point on ramus of the mandible.Porion (Po) Superior aspect of external auditory meatus.Orbital (Or) Lowest point on the inferior bony margin of the orbit.The point used is halfway between the right and left orbital.Pterygomandibular Fissure (PTM) Posterior superior aspect of Pterygomaxillary Fissure.Cephalometric Gnathion (cGn) Intersection of Facial Plane and Mandibular Plane.

Figure 1 :
Figure 1: Cephalometric Landmarks and Planes Largestgroups of Kathmandu's population being Newars, Brahmins and Chhetris, norms of these groups needs to be Research Article established for appropriate comparison.Hence this study aimed to establish norms for adult Brahmins of Kathmandu using McNamara analysis.

Table 4 : Comparison of cephalometric means between male Brahmins and Caucasians Variables Caucasian Brahmin Mean Difference p-Value Mean SD Mean SD
* p ≤ 0.05; ** p ≤ 0.01; *** p ≤ 0.001Comparison of adult males and female Brahmin andCaucasian were expressed in Table4 and 5. Adult