Cementum thickness in multirooted human molars: a histometric study by light microscopy.

Cementum distribution was studied on transversely sectioned roots of 33 three-rooted maxillary and 33 two-rooted mandibular permanent molars. The roots were sectioned at a level midway between furcation and apical region. Cementum thickness was measured at the midpoint of each of the four root surfaces and at a site exhibiting maximal cementum thickness. A reflected light microscope was used. Midpoint cementum thickness ranged between 5 and 800 microm in maxillary molars and between 5 and 700 microm in mandibular molars. Maximal cementum thickness ranged between 25 and 1140 microm in maxillary molars and between 20 and 700 microm in mandibular molars. The results indicate that cementum tends to accumulate along interradicular surfaces of multirooted molars. In addition, a tendency was noted for more cementum to occur orally than vestibularly in roots of mandibular molars as well as in buccal roots of maxillary molars. Furthermore, this study indicates that cementum accumulates in root concavities (developmental depressions), although the exact mechanism still awaits a clear explanation. Previous studies have suggested that tensile forces stimulate cementum apposition. It may be assumed, however, that masticatory function and continuing eruption of the teeth exert no discernible effect on cementum thickness in the examined region of the root. In conclusion, the observed cementum distribution could be attributed to at least two factors: one is buccal drift and the second may be the effect of root concavities. From a clinical viewpoint, the established pattern of cementum distribution in multirooted molars should be considered in endodontic and periodontal treatment.