[Morphological study on occlusal grove of mandibular molar of Chinese adults]

During human evolution,the morphology of mandibular molar occlusal grooves have changed from the pattern "Y" to pattern "+".Six types of occlusal grooves were classified as:Y5,Y4,+5,+5,X5 and X4. Using computer analysis,we get the result.(1)The rate of "Y5" in first mandibular molar is the highest,the rate of "X4" is the lowest.(2)The rate of "+4" in second mandibular molar is the highest,while the rate of "Y5" is the lowest. (3)The rates of each type groove between male and remale have no significant difference.Our conclusion coincides in the evolution of human mandibular molar,that is helpful to direct the clinic and anthropology study.