Molar access: shape and outline according to orifice locations

This study was designed to relate, in molars, the access outline on the occlusal surface to the canal orifices. The occlusal surfaces of maxillary and mandibular molars were photographed and prints made. The crowns were then sectioned at the level of the pulpal floor to expose the canal orifices. Transparent photographs of the orifices were taken and projected on the occlusal photograph; the orifice locations were marked directly on the print. Orifice location demonstrated a fairly regular pattern relative to the occlusal surface in all four molar groups. The resulting outline scribed from the orifices tended to be centered mesiodistally on the crown of each group and did not extend to the marginal ridges. The results indicate that classic access drawings are too far mesial.