Relationship between the interproximal distance of roots and the prevalence of intrabony pockets

The interproximal distance between adjacent root surfaces and the presence of intrabony pockets (IBP) facing these surfaces, was measured and recorded during 114 gingival flap procedures in 81 patients. Measurements were carried out in 344 interproximal areas and 117 IBP were detected at these sites. The correlation between the interproximal distance and the presence of IBP was positive and statistically significant (r = 0.81; P less than 0.001). The frequency of IBP increased with increasing interdental distance (slope (s) = 5.723). When interdental distances between 2.1 and 4.5 mm were analyzed, the correlation and slope were high (r = 0.96; P less than 0.01; s = 19.87). No significant correlation (r = 0.36; P greater than 0.4) existed when interproximal distances greater than 4.6 mm were analyzed separately. Intrabony pockets were frequently associated with interproximal distances greater than 2.6 mm (20-57.1%). They were less common (5-20%) when the interproximal distances were less than 2.6 mm. Two IBP in the same interdental areas were present only when these areas were greater than 3.1 mm. Based upon the present data, it seems that the frequency of IBP increased as the distance between adjacent teeth increased. However, when this distance was 4.6 mm or more, no further increase in the percentage frequency of IBP was noted.