Variability of arch forms in various vertical facial patterns

Objective: To compare arch forms in various vertical facial patterns and to make arch form guides based on posterior intermolar widths. Study Design: Cross-sectional comparative study. Place and Duration of Study: The Aga Khan University Hospital, Karachi, from June 2007 to May 2008. Methodology: Subjects with age range of 13-30 years were selected having full complement of teeth (upto second permanent molars) with absence of severe crowding (less than 7 mm). Exclusion criteria were presence of dental anomalies, previous dentoalveolar surgery, trauma or orthodontic treatment and craniofacial syndromes. One hundred subjects including 40 normodivergent, 30 hypodivergent and 30 hyperdivergent cases were selected. Occlusograms were made and various arch dimensions were measured. Arch forms were calculated according to ratios of three sagittal to three transverse dimensions. Results: The mean age of the sample was 21 years and 5 months. Differences in arch dimension were found only in maxillary total arch length (p=0.03) and mandibular posterior intermolar width (p=0.04). Wide lower arches were predominant in all face types. Wide upper arches were predominant in only hypo- and hyperdivergent subjects. Conclusion: Wide lower arches were predominant in all face types whereas wide upper arches were predominant in both hypo- and hyperdivergent subjects. A non-linear relationship was found between arch length and arch width; so arch form guides could not be made for specific face types.