Evaluation of Tooth Size and Dental Arch Ratio in Bengali Population Sample
Orthodontic Journal of Nepal
IntroductIon Facial esthetics is dependent intimately on architectural relationship of facial skeleton so as to serve the base for structural balance. The proportional relationship of tooth material of the upper arch to the lower arch is the prerequisite to achieve functional occlusion and healthy maintenance of the system. The presence of inter-arch tooth size discrepancy leads to mal-relationship between the arches with decreased functional efficiency and disfigurement in esthetic harmony.
... sthetic harmony. Tooth size exhibits a range of variation among individuals and in populations. Accumulated evidence indicate that tooth size reflects a complex interaction between genetic and environmental factors. 1 A proportionate relationship between mesio-distal widths of maxillary dentition to that of the mandibular dentition favours an optimal post-treatment occlusion. 2 As with other human attributes, there is a variation in tooth size between male and female teeth. 3 Whereas the upper lateral incisors and lower incisors are the most homogenous. 4 Although significant differences in tooth size exist between male and female, there is no evidence of difference in upper to lower anterior tooth size proportions. 5,6 Identification of a suitable arch form and dimension is a key aspect of achieving stable, functional, and esthetic arch form in orthodontic diagnosis and treatment. 7 Furthermore, failure to customize the arch form creates the probability of relapse leading to poor prognosis. It is important to select the shape that closely matches patient's pretreatment arch form, conforming to ethnicity and malocclusion type. 8 A relative harmony in the mesio-distal dimension of the maxillary and mandibular teeth is a major factor in coordinating posterior inter-digitations, overbite and overjet in centric occlusion. 9 Bolton 10 in 1958 studied 55 Caucasian subjects with excellent occlusion using mesio-distal crown width of 12 teeth (from first permanent molar on one side to other side). Bolton obtained an overall ratio of 91.36±1.91 %. Similarly using six anterior teeth (permanent canine on one side to other side), obtained an anterior ratio of 77.26±1.65 %. This analysis is commonly used as a valuable diagnostic aid in orthodontics. These ratios gave a definite percentage of ABStrAct Introduction: In order to maintain the proper relationship between upper and lower arch, Bolton proposed anterior ratio and overall ratio. objective: To evaluate and compare the tooth size and arch size discrepancies between normal cases and Class I crowded cases of the Bengali population. To determine Bolton's overall ratio and anterior ratio in the normal sample , and to identify the possible variation in tooth-arch size ratio in subjects in Bengali population. Materials & Method: A total of 60 maxillary and mandibular pretreatment dental study casts were taken and divided into control group and study group. The descriptive statistics in respect of Bolton's anterior ratio and overall ratio were calculated. The t-test was done for the statistical difference between the two mean values. result: Bolton's ratios in Bengali population sample values were found to be similar to the original data of Caucasian population. Females showed a tendency of smaller teeth than the males. conclusion: Bolton's ratios could be consistent to use in the orthodontic diagnosis of Bengali population. It supports the concept that females showed smaller teeth than the males. Key words: Bolton anterior ratio, Bolton overall ratio, inter-arch relationships Anterior Ratio t-value = 0.70 p-Value = 0.494; Overall Ratio t-value = 1.16 p-Value = 0.263 table 2: comparison of Bolton's caucasian ratios with the Bengali sample range Mean Value Standard deviation Standard error of Mean Coefficient Variation caucasian Bengali caucasian Bengali caucasian Bengali caucasian Bengali caucasian Bengali Anterior ratio 74.5 -80.4 73.80 -83.22 77.26 78.59 1.65 2.78 0.22 0.62 2.14 3.54 overall ratio 87.5 -94.8 88.20 -95.60 91.36 92.29 1.91 2.20 0.26 0.49 2.09 2.39 Anterior Ratio t-value = 2.11 p-value = 0.046 DF = 24, Overall Ratio t-value = 1.80 p-value = 0.082 DF = 30