PREDICTION OF DENTAL ARCH DEVELOPMENT - AN ASSESSMENT OF PONTS INDEX IN 3 HUMAN-POPULATIONS

Pont's Index was established by Pont in 1909 to predict maxillary dental arch width from the sum of the mesiodistal diameters of the four maxillary incisors, The usefulness of Pont's Index is controversial and, as there has been a recent resurgence of interest in its clinical use for establishing dental arch development objectives particularly by nonspecialists, reassessment of the Index in different human populations was considered worthwhile. This study aimed to evaluate Pont's Index in untreated, noncrowded samples of Australian Aborigines (n = 80), Indonesians (N = 60), and white subjects (N = 60). Measurements were obtained directly from plaster casts; they included mesiodistal crown diameters of the four maxillary incisors, as well as intercanine, interpremolar and intermolar maxillary arch widths as specified by Pont. A series of double determinations confirmed the reliability of the method. Considerable individual variability was noted in each population with regard to the difference between observed values and Pont's estimates, ranging from -5.9 mm to +6.2 mm (interpremolar width) and -6.1 mm to +12.7 mm (intermolar width). No person displayed the ideal arch dimensions predicted by the Index, but values were within +/-1.0 mm for 17.5% of the Indonesian sample, 20.6% of the Aboriginal sample, and 30.8% of the white sample. Dental arch width was generally underestimated by the Index in Indonesians who tended to display relatively small tooth size and large arch width. A more even distribution of estimates was noted in Australian Aborigines and white subjects, with the Aborigines showing large tooth size and broad dental arches, and the white subjects displaying smaller tooth size and narrow arches, Correlation coefficients computed between observed and expected values were low in all three populations studied (range r = 0.01 to r = 0.56). Although the concept of a simple index with predictive ability is very appealing to some clinicians, the results of this study have highlighted the marked variation in values of Pont's Index for persons with apparently good occlusions, representing three different human populations. Tooth size variation was poorly correlated with arch width variation, with persons often being over or under Pont's estimation due to variation in tooth dimension, particularly in the size of the maxillary lateral incisor. It is concluded that Pont's Index is unlikely to be a useful clinical predictor of dental arch width and the index should not be used as a guide to dental arch development in contemporary populations.