OXIS Classification of Interproximal Contacts of Primary Molars and Its Prevalence in Three- to Four-Year-Olds

The purpose of this study was to investigate the prevalence of different interproximal contact areas of primary molars, as described in the OXIS classification, in a group of three- to four-year-old caries-free children. This cross-sectional study was carried out with a representative sample of 4,476 contact areas of 1,119 caries-free school children. A single calibrated examiner performed a type III examination to assess the type of contact area between primary molars, as seen from the occlusal view. The contacts were scored as O (open contact), X (point contact), I (straight contact), and S (curved contact) using OXIS classification. The prevalence of the types was expressed in the form of numbers and percentages. The findings were subjected to chi-square and McNemar's tests. The most common contact type was I (75.5 percent), followed by S (15.3 percent), O (5.8 percent), and X (3.3 percent). Significant differences were obtained (P<0.001) when the inter- arch comparison was performed for all except the X type of contact. Further, 401 (35.8 percent) children had more than one type of contact in dif- ferent quadrants. The present study highlights the existence of four different types of interproximal contact areas, O, X, I, and S, in caries-free three- to four-year-olds.