ABSTRACT
Background: Horizontal condylar guidance (HCG) is registered by protrusive interocclusal records but in nonarcon articulators, these records can affect the accuracy. The present study aimed to evaluate the effect of a novel rotation coordinating device (RCD) on condylar guidance setting with protrusive interocclusal records. Materials and Methods: The study was designed as a comparative in-vitro investigation. Stone maxillary and mandibular casts were mounted on a fully adjustable instrument as the patient. Duplicate casts were mounted on an arcon and a nonarcon articulator with corresponding face bow records and in maximum intercuspation relation. Five different condylar guidance inclinations for both sides (20°, 30°, 40°, 50°, and 60°) were set on the fully adjustable instrument and 16 protrusive interocclusal records were established at each setting. HCG was set for arcon, nonarcon articulators, and nonarcon articulators with RCD. Data were analyzed using one-sample t-test to compare with actual HCG and one-way analysis of variance (α =0.05). Results: Mean HCG for studied articulators was 35.40 for arcon, 30.31 for nonarcon without RCD, and 35.61 for nonarcon with RCD which were significantly different from actual HCG (P < 0.05). HCG of the nonarcon with RCD showed no significant difference with arcon articulator (P = 0.71) while both were significantly different from nonarcon without RCD (P < 0.001). Conclusion: "The RCD" compensates the condylar guidance inclination difference between arcon and nonarcon articulators. The device precisely transfers the hinge movement of the upper member of the articulator to the condylar track.
ABSTRACT
BACKGROUND: Setting of condylar inclination is inaccurate in nonarcon articulators because of alteration of the angle between the upper member and condylar track. This article presents a device which can be attached to a nonarcon articulator to rectify errors related to alterations of maxillary occlusal plane-horizontal condylar guidance relation in nonarcon articulators. MATERIALS AND METHODS: The device provides tight connection of condylar axis to condylar track by mechanical interdigitation of fragments which are placed on condylar axis and condylar track. Condylar track rotates coordinated with condylar axis. Fragments consist of medial fragments placed on medial surface of articular fossa analogs, lateral fragments placed on lateral surface of articular fossa analogs, and condylar axis fragments placed on condylar axis. The device can be used during condylar inclination adjustment by interocclusal records, changing vertical dimension of occlusion, and occlusal adjustment of restorations. Initial evaluation of the device was performed during an opening hinge movement in a single experiment. The angle between condylar track and the upper member of the articulator was determined by calculation before and after applying hinge movement and with and without the device. RESULTS: When the device was not used, the postexperimental condylar inclination was 7.31° higher than preexperimental value. Using the device, discrepancy reached 2.17°. CONCLUSION: Using this device may lead to more accurate condylar inclination adjustment which is followed by more accurate prosthetic teeth.
