A histologic study of the width and nature of inter-radicular spaces in human adult pre-molars and molars.

Serial sections of jaw segments from a human post mortem population of 29 individuals providing 116 posterior interproximal sites were examined at the light microscopic level. Minimum inter-root distances at the locale of closest proximity ranged from more than 4 mm to less than 0.1 mm. They were located in the coronal third of pre-molars and mandibular first and second molars and the middle third of maxillary first molars and second molar interproximal spaces. Cancellous bone flanked by lamina dura was found between 89.6% of the teeth examined and was observed where inter-root distances exceeded 0.5 mm. At sites of less than 0.5 mm, cancellous bone was not observed, and, instead, adjacent laminae durae appeared fused (7.7%). Bone was not observed between root surfaces which were less than 0.3 mm apart, but in these instances the roots were connected by a periodontal ligament.