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Occlusal form is frequently modified in clinical practice and yet we do not have detailed knowledge of the possible effects of these changes on condylar movement. The aim of this study was to quantify the effects of an alteration in the occlusion on condylar movement during a lateral excursive jaw movement. Posterior tooth guidances (i.e. metal overlays) were attached to both maxillary first molars. The movement of arbitrary condylar points on the non-working side was recorded in seven subjects during lateral excursion under natural tooth guidance (control) and was compared with that after placement of the overlays (guidance). The guidance resulted in statistically significant changes to the displacement of the arbitrary condylar points on the non-working side. For example, at a standardized (3 mm) displacement along the mid-incisor point trajectory during the lateral excursion for both control and guidance in all subjects, the corresponding displacements of the condylar points were statistically significantly decreased under the guidance situation in comparison with the control situation. These data suggest that, for the same magnitude of mandibular displacement during lateral excursion, the introduction of a posterior tooth guidance limits condylar displacement on the non-working side.