Centric slide in different Angle classes of occlusion.

Most of the literature states that slide from centric relation occlusion (OCR) to intercuspal position (ICP) occur at approximately 90% of people, and on average is 1 mm long. The purpose of this study was to test the possible differences in OCR-ICP slide between different Angle classes of occlusion. Study included 98 participants (58 class I, 10 class II/1, 14 class II/2, 16 class III). Each participant gave written informed consent, which was approved by the Ethical Committee of the School of Dentistry, University of Zagreb. Recordings were obtained by the electronic ultrasound measuring device (Arcus Digma II, Kavo, Germany), using module "EPA-Electronic Position Analysis". Reference position was ICP, while OCR was achieved with training participants to move mandible posteriorly (no guidance). Data were transferred to the computer, and processed and analyzed with device's software. For every participant, distance between ICP and OCR was measured (x-anteroposterior, y-vertical, z-transversal values). Analysis of variance, followed by Newman-Keuls test was applied. Analysis of variance showed significant differences in vertical values of OCR-ICP slide (p=0.045). Newman-Keuls test for vertical distances between tested groups showed significant difference between II/2 and II/1 (p=0.049), and between II/2 and I (p=0.043). Out of 98 participants, none showed coincidence of OCR and ICP position. Unlike other studies, Angle class II/2 showed smaller movements in vertical direction, in comparison with Angle class I and II/1. Since function and morphology of the TMJ are closely related, it is possible that smaller OCR-ICP slide in vertical direction, as expression of anatomy/function, happens at Angle class II/2. This could be explained by „locked occlusion“, and posterior condylar position in Angle class II/2 advocated by some authors. In concordance with novel studies, coincidence of OCR and ICP position is less than 10 %. [ABSTRACT FROM AUTHOR]