Applicability of Pont's index in orthodontics

To investigate the applicability of Pont's index in estimating the maxillary arch width depending on the sum of mesiodistal dimensions of maxillary incisors.

Cross-sectional, comparative study.

Dental Clinics, The Aga Khan University Hospital, Karachi, from January 2006 to December 2008.

A total of 150 subjects were included. All measurements were taken on maxillary study casts by a digital caliper. The premolar arch width was taken from the first premolar of the left side to the right side at the distal end of its occlusal groove. The molar arch width was taken from the maxillary left permanent molar to the same of the right at its mesial pit on the occlusal surface. The combined width of the maxillary incisors was taken at their greatest mesiodistal widths. The predicted arch widths were estimated with the Pont's formula: Premolar width (P) = Sum of Incisor widths/80 x 100 Molar width (M) = Sum of Incisor widths/64 x 100 Incisor diameters and arch widths were described in terms of mean values, standard deviations, and coefficients of variation. Correlation coefficients were computed between observed arch widths and those predicted according to Pont's M and P indices.

The mean age was 15.8 ± 1.6 years. Low correlations existed between observed and Pont's predicted arch widths in both premolar (r = 0.364) and molar (r = 0.238) regions. Twenty two percent of interpremolar arch widths and 18% of intermolar arch widths showed differences between -1 mm to 1 mm.

Low correlations were found between observed and Pont's predicted arch widths. Pont's index is unlikely to be clinically useful as a true predictor of arch width.