Repeatability and Reproducibility of Condylar Guidance Angle Measurement Using a Semi-adjustable Articulator

Abstract

Background: Accurate determination of sagittal condylar inclination (SCI) and Bennett angle (BA) on a semi-adjustable articulator plays a crucial role in ensuring prosthodontic stability and occlusal harmony. However, quantitative data regarding the repeatability and reproducibility of this manual adjustment protocol in Vietnam remain limited. Objective: To evaluate the repeatability and reproducibility of measuring SCI and BA angles using interocclusal records on a semi-adjustable articulator. Materials and Methods: An experimental study was conducted on 35 healthy volunteers (17 males, 18 females; aged 19–39 years) with normal physiological masticatory systems. Plaster cast models were mounted on a LabMate 500SH articulator utilizing facebow transfers and combination bite registration materials—O-bite (addition silicone) and Luxabite (bis-acryl resin). Two independent examiners measured bilateral SCI and BA angles in 3 independent repetitions, spaced 48 hours apart. Results: The mean left SCI angle (33.07° ± 11.97°) was significantly higher than the right SCI angle (26.99° ± 11.97°) with p = 0.002; bilateral Bennett angles showed no statistically significant difference (Left: 15.73° ± 7.50°; Right: 15.10° ± 7.38°; p = 0.708). Intra-examiner repeatability demonstrated high consistency with ICC > 0.988 across all angles. Inter-examiner reproducibility achieved excellent agreement with ICC > 0.982 (95% CI: 0.966–0.996). Bland-Altman analysis revealed minimal mean bias between examiners (ranging from -0.69° to 0.21°) with narrow 95% limits of agreement. Conclusion: Condylar guidance angle measurement using a semi-adjustable articulator combined with O-bite and Luxabite registration materials exhibits excellent repeatability and reproducibility. The high individual variation and asymmetry of the SCI angle underscore the clinical necessity of recording patient-specific eccentric bite registrations rather than relying on default average parameters like 30°.