Topographical characteristics of root trunk length related to guided tissue regeneration.

Thirty-seven molars with 94 furcations were selected for a topographical study of root trunks to clarify the possible factors which may affect the clinical application of guided tissue regeneration technique. A pre-determined plane was marked on the root trunk of each tooth 1 or 2 mm below the cemento-enamel junction (CEJ). The plane followed the presumed position of the occlusal border of the Teflon membrane. Cross sectioning of the root was then performed following the plane, and the width of the gap between the membrane and root surface was measured with the aid of a stereomicroscope. The results revealed, within the limited samples of this study, 94% of the furcations possessed variant depth of developmental concavities on the root trunks. These superficial irregularities at the entrances of furcations may prevent complete adaptation of the coronal microstructure of the Teflon membrane along their root surfaces. The width of the gaps between root surfaces and membranes ranged from 0.000 mm to 2.250 mm for all tooth samples. The study implied that the subgingival application of guided tissue membranes 1 to 2 mm below CEJ cannot ensure complete adaptation of furcation defects with their coronal microstructures in the majority of molars.