An evaluation of the adequacy of PONT's index

Kim, Seong Hun; Lee, Ki Soo

Abstract

Dental arch expansion in one of the method used to solve the dental crowding problem by non-extraction. Many formulae using tooth size have been suggested to predict ideal inter-premolar and inter-molar width. The purpose of this study was to evaluate the adequacy of some of some upper dental arch width prediction methods, namely Pont's method, Schmuth's method and Cha's method. The sample consisted of the casts of 119 Korean young adults who had no muscular abnormality, no skeletal discrepancy, and Angle's Class I molar relationships. Measurements were obtained directly form plaster casts; they included mesiodistal crown diameters of the four maxillary incisors, as well as maxillary inter-first-premolar and inter-first-molar arch widths as specified by Pont. The correlation coefficients between the sum of incisors(SI) and upper dental arch width were calculated. The differences between predicted width and actual width wee classified as overestimated, properestimated, and underestimated. The data obtained from each group were analyzed for statistical differences. The results were as follows : 1. Upper dental arch width indices were calculated from SI in normal occlusion (81.96 : premolar index, 62.55 : molar index). 2. Low correlations between SI and arch width were noted in normal occlusion (0.50 in the inter-premolar width, 0.39 in the inter-molar width). 3. Pont's formula and Schmuth's formula tended to overestimate the inter-premolar. A more even distribution of estimates was noted in Cha's formula. 4. Cases within 1mm range of observed inter-premolar width were 45% in the Pont's formula, and 39% in the Schmuth's formula. 5. All formulae had a tendency to underestimate the inter-molar width, but Cha's formula had better predictability than others. 6. Cases within 1mm range of observed inter-molar width were 40% in the Cha's formula, 29% in the Pont's formula, and 13% of Schmuth's formula. The data presented in this study dose not support the clinical usefulness of ideal arch width prediction methods using the mesiodistal width of maxillary incisors.