Centric relation registration with intraoral central bearing on curved vs. flat plates with rim trays in edentulous...

The aim of this study was to compare jaw relation record in the completely edentulous patient using acrylic rim trays with curved or flat registration plates or using the manual guidance technique. The study included 17 patients - 11 female and 6 male, average age 70 years. Three jaw relation records were taken during one session, in the same vertical dimension, using acrylic rim trays: (1) with manual guidance (IM), (2) with self-guided recording system with acrylic rim tray and central support using a curved plate (BYC) and (3) with self-guided recording system with acrylic rim tray and central support using a flat plate (BYR). The models were mounted on a Whip Mix 2240 articulator to which a condyle position device (Orthodent) was added to register, at the level of the condyle box and incisal table, the differences among the positions recorded with the different setups (IM, BYC and BYR). The distances were measured on millimeter paper provided by the recording system manufacturer. For statistical analysis, confidence intervals (95%) were calculated for the mean differences and Student's t-test for paired data (significance level: alpha<0.05). On both the mesiodistal plane and the vertical plane at the level of each condyle box and the incisal table, there were statistically significant differences among the three systems (p<0.001). At the level of incisal table, BYC and BYR provided more retrusive records than IM [arithmetic means (standard deviations) in millimeters: 3.82 (2.10) and 4.53 (2.18), respectively). The records obtained with BYR were significantly more retrusive with BYC [arithmetic mean (standard deviation) in millimeters: 1.41 (1.00)]. We reject the null hypothesis that proposes that all three registration systems described are clinically equivalent for establishing a jaw relation record in completely edentulous patients.