DIFFERENCE IN THE MECHANISM OF BALANCING-SIDE DISCLUSION BETWEEN 1ST AND 2ND MOLARS

This study investigates the cusp angle and movement variables related to balancing-side disclusion and compares the characteristics between the Ist and 2nd molar regions. Fifty-six normal young adults were divi ded into two groups according to balancing-side contact: a disclusion group consisting of 40 subjects (80 excursions), and a non-disclusion group consisting of 16 subjects (20 excursions). Lateral excursions we re measured in six-degrees of freedom, and the inclinations of the fro ntal paths were calculated on the working-side canine, balancing-side Ist and 2nd molars and balancing-side condylar point. The cusp angle w as measured using a three-dimensional digitizer. While there were no d ifferences between disclusion and nondisclusion groups in the inclinat ion of the balancing-side condylar path, significant differences were found in the cusp angle and the inclination of the working-side canine path. In the non-disclusion group, the cusp angle of the 2nd molar wa s markedly greater than that of the Ist molar. It was concluded that t he inclination of the anterior guidance and the cusp angle of related teeth have a great effect on the occurrence of balancing-side disclusi on and that the mechanism of high frequent balancing-side contacts at the 2nd molar was characterized by its greater cusp angle compared to the Ist molar.