Evaluation of Four Centric Relation Location Techniques Using Ultrasonic Axiography

Objectives: The reproducibility of current centric relation location techniques and their effect upon the mandibular condyles is not known. The purpose of this study was to record three dimensional condylar points located utilizing four commonly used centric relation positioning methods and characterize the relationships to the maximum intercuspal position.

Methods: Fifteen subjects (9 male, 6 female, average age 30.6 years) exhibiting no symptoms of TMD or joint laxity, with non restored anterior teeth and an Angle class I occlusion were evaluated. The SAM ultrasonic Axioquick Recorder and software recorded and measured the differences between condylar points (X,Y,Z axes) determined by the four Centric Relation (CR) location techniques and the Maximum Intercuspation Position (MIP). A mandibular paraocclusal clutch enabled the reference MIP to be jig located, and three randomized programs sequenced each trial. The prefabricated acrylic resin Lucia jig (LJ) and the Leaf gauge (LG) were patient guided, and Bimanual Manipulation (BM) and Chin Point guidance (CP) were operator guided location techniques. Wilcoxon and Friedman's non-parametric tests evaluated the median data and the three dimensional (3D) distance from the MIP reference point was determined by the Pythagorean Theorem.

Results: The MIP jig position showed high 3D repeatability (median difference 0.07mm to 0.13mm) and the CR technique medians showed little three dimensional variation (0.18mm) from MIP, BM=0.27mm, CP=0.40mm, LJ=0.46mm, LG=0.46mm. There were statistically significant differences in the X axis between BM and CP (p=0.001), BM and LJ (p=.011), CP and LG (p=0.012), LJ and LG (p=.001) and the Z axis between LG and LJ (p=.008). The BM and LG technique exhibited the most superior and anterior location of the condylar position.

Conclusions: Though statistically significant differences existed, there is no clinically relevant difference between the condylar position located by four centric relation techniques, and all four methods are highly repeatable.