Tooth Size and Arch Widths in Crowded Class I Malocclusion

Objective: To examine the extent to which maxillary arch width and tooth size contributes to dental crowding. Methods: A cross-sectional study was conducted for six months after approval of synopsis  by  ERC  of KMDC with 96 patients at department of orthodontics, Karachi Medical and Dental College, Karachi, Paki- stan. Patients with age 13-21 years with maligned teeth, over-crowding, presence of all fully erupted per- manent teeth and all angle classes were included, whereas patients with history of orthodontic treatment, presence of fractured restorations/crowns with tooth anomalies such as number, size, form and position as confirmed on clinical examination and craniofacial anomalies/syndromes were excluded. Maxillary crowding was calculated as the millimetre difference between arch perimeter and the sum of tooth widths of both second premolars. Arch perimeter was measured from the mesial aspect of the permanent first    molar to its antimere with a brass wire. Intermolar arch width was calculated as distance from the central  fossa of permanent maxillary first molar to its antimere. Data was analysed using SPSS 23.0. Prior to  analysis assumptions were tested; an independent sample t-test was used to compare differences  in  crowded maxillary arch widths and spearman correlation was used to determine relationship between variables. Results: Significant differences were obtained in anterior (t(63) = -2.547, p=0.047) and posterior tooth size (t(63)= -2.218,  p=0.030) in patients with mild, moderate and severe maxillary crowded arches and an in-verse weak correlation was obtained against maxillary crowding and maxillary arch widths (r=-0.054) and maxillary crowding and anterior tooth (r= -0.201) and posterior tooth size (r= -0.353). Conclusion: An inverse significant relation was found between crowding and tooth sizes & significantly different tooth sizes were observed in patients with mild, moderate and severe maxillary crowding.