Relationship b etween Bolton Discrepancy, Arch Form a nd Basal Arch Length i n Orthodontic Pat ients: A Cross Sectional Study in a Pakistani Sample

Abstract

Introduction: Bolton tooth size discrepancy (TSD) is the disparity among the sizes of maxillary and mandibular individual teeth. TSD can lead to problems at finishing stage of Orthodontic treatment in terms of achievement of ideal occlusion. This study helped to explore the likely relationship between various arch forms and clinically significant tooth-size discrepancy and to compare the average basal arch length with that of the patients with significant Bolton tooth-size discrepancy in Pakistani population. This knowledge would be beneficial in Orthodontic treatment planning.

Material and Methods: A retrospective cross sectional study was carried out on archive records of Margalla Institute of Health Sciences. A total of 291 records with significant Bolton Discrepancy (TSD >2%) were screened. Sample size was calculated using Raosoft© Sample Size Calculator that came out to be 166. However 256 dental casts (144 males & 112 females) met our selection criteria and thus all were included. Basal arch length (BAL) and arch forms were also determined for each case. BAL was categorized into three groups; excessive, average and decreased. Arch forms were defined as squarish, tapering and ovoid.

Results: Statistically insignificant difference was found in the gender based comparison. However, there were statistically significant differences between the mandibular average arch length and increased arch length for Bolton’s Overall Ratio (BOR) (p = 0.01). The prevalence of both (Bolton’s Anterior Ratio) BAR and BOR was significant in tapered arch form (p < 0.05)

Conclusions: Bolton TSD is more prevalent in tapered arch form. Further studies are encouraged to find any racial/ ethnic differences. Average arch length and increased arch length groups have statistically significant BOR difference.