Comparison of tooth size and arch dimensions between normal occlusion group and class I malocclusion group

Introduction: Recognizing the main coutributing factors of crowding has always been a matter of interest in orthodontics. The purpose of this investigation was to examine the extent of which tooth size or jaw dimension contribute to dental crowding. Materials and Methods: In this cross-sectional descriptive study, two groups of dental casts were selected on the basis of having or not having dental crowding. The first group consisted of 30 pairs of dental casts (15 male and 15 female) which exhibited normal occlusion(without crowding). The second group consisted of 30 pairs of dental casts (15 male and 15 female) with gross dental crowding and classI skeletal pattern. Mean values and standard deviations of the following parameters were used to compare the two groups: individual and collective mesiodistal tooth diameters, dental arch perimetres, dental arch lengths and buccal and lingual dental arch widths in canine and molar region. To compare the two groups, two tailed student-t test, with 95 confidence interval was used. Results: On the basis of our research crowded and noncrowded group had statistically significant differences in both mesiodistal tooth diameters and transverse arch dimensions. The crowded group was found to have smaller transverse maxillary dental arch dimensions but larger tooth diameters than in the normal occlusion group. Conclusion: The results of this study suggest that consideration should be given to those treatment techniques which increase dental arch transverse width and also decrease tooth material by means of extraction or stripping.