Clinical evaluation of three occlusal registration methods for guided closure contacts.

This clinical study compared two occlusal registration methods (Occlusal Indicator Wax and Accufilm) with the T-Scan system for the identification of guided closure contacts. The patients were divided into two groups according to the centric relation-maximum intercuspation (CR-MIP) discrepancy and comparisons of guided closure contacts were performed with the paired methods. Wax and Accufilm materials were significantly different in their agreement on guided closure contacts. The T-Scan system demonstrated less of a disparity with both methods but more closely resembled the Occlusal Indicator Wax material. The CR-MIP slide also significantly affected the agreement between methods during identification of guided closure contacts.

Occlusal contact variation with changes in head position.

Ten healthy young adults were examined for changes in occlusal contacts related to three head positions: supine, sitting, and head forward. The contacts were analyzed using T-Scan special research software, which measured the time moments of the first five occlusal contacts. Time moment is a descriptive term calculated from a formula that considers both spatial (where contacts are) and temporal (when contact occurs) aspects of tooth contact and provides a quantitative basis for comparing the dynamics of tooth contact. Paired head positions were analyzed for differences using Student's t test, and it appears that in healthy young adults, initial tooth contacts are substantially influenced by posture.

Laboratory comparison of three occlusal registration methods for identification of induced interceptive contacts.

This study compared the performance of a new computerized occlusal analysis (T-Scan) system with that of Accufilm and Shimstock foil for the registration of tooth contacts on a laboratory model. Induced interceptive contacts were created on epoxy models in a mechanical closing device and the occlusal contacts were recorded for each registration method. The traditional methods were similar to the computerized analysis but the T-Scan system provided additional differential diagnostic information in force and time modes for an improved occlusal analysis.

Distribution of occlusal contacts in maximum intercuspation.

This study describes the use of the T-Scan system to record and analyze tooth contact data by calculating time moment statistics in the sagittal and transverse axes of the occlusal plane and reports the results of this method to analyze the occlusion of 93 normal subjects. Results confirm the findings of previous investigators and indicate that in a normal dentition there is a tendency for bilateral equality of the tooth contacts about the sagittal axis and that the center of effort for tooth contacts anteroposteriorly is located in the region of the first molar and is symmetrical bilaterally. Because of the rapid and accurate ability of the T-Scan system to identify the distribution of the tooth contacts, it shows great promise as a clinical diagnostic screening device for occlusion.

The effect of immediate dentures on maxillomandibular relations.

Immediate mandibular and maxillary dentures were made for six patients to determine the relative changes in the vertical dimension of occlusion and rest position over a 3-month test period. The dentures were mounted on the articular in centric occlusion (habitual). Pilkington-Turner anatomic teeth were used on the maxillary denture, which was set against a flat, noninterfering acrylic resin occlusion rim instead of mandibular posterior teeth. Positional cephalometric measurements in centric occlusion and rest position were made before extraction and at 1-week, 1-month, 2-month, and 3-month intervals. The dentures were relined after 2 months. The results were as follows: 1. In the centric occlusion position the mandible moved forward after 1 week and remained forward for the 3-month test period. 2. The rest position showed no significant change in the anteroposterior position of the mandible with time. 3. The vertical dimension of occlusion and rest showed a gradual decrease over the entire test period. 4. The reline procedure did not affect the trend of the dimensional changes. 5. A noninterfering occlusal scheme is advantageous for immediate dentures.

Tissue damage from electrosurgical power output variations in hamster tongues.

An investigation was designed to determine the differences in the amount of tissue damage produced by variations in the amount of cutting power delivered to the hamster tongue with electrosurgery. By dividing the power of an electrosurgical instrument into 5 W intervals, from the lowest setting which would produce a cut up to the 50 W setting, histometric comparisons were made in the hamster tongue. Histologic analysis showed the following: 1. The 30 W power interval produced less tissue damage than any other power interval. 2. The 25 and 35 W intervals produced significantly greater damage than the intervals from 40 thorugh 50 W. 3. Histologically the experimental defect showed an area of coagulation necrosis approximately 50 mu wide along the margin of the incision. Tissue damage decreased laterally and inferiorly from the surface of the defect except at the 30 W setting, where the damage in the epithelium and the damage in the connective tissue were essentially equal. 4. There is some validity to the sparking-dragging test for setting the power interval of an electrosurgical instrument. 5. Higher power values which produce excessive sparking should be avoided by the clinician during electrosurgery due to the imprecise nature of the clinical incision.

Histologic evaluation of electrosurgery with varying frequency and waveform.

This investigation was designed to determine the differences in tissue alteration produced by electrosurgical machines with different carrier frequencies and waveforms. Histologic analysis showed that: 1. The machine with full-wave rectification and the lowest frequency of operation (machine I, 1.7 MHz) produced significantly greater tissue alteration in the superficial tissue layers than the full-wave rectification machines with higher frequencies of operation. 2. The continuous-output waveform produced significantly less tissue alteration in the superficial tissue layers than the modulated type at the same frequency of operation. 3. Histologically, the experimental defect showed a band of coagulation necrosis approximately 50 mu wide along the margin of the incision. Tissue destruction decreased laterally and inferiorly from the surface of the defect. 4. The experimental defect was similar in shape to the physical form of the cutting electrode.