Occlusal Assessment of Zirconia Crowns Designed with the Digital Articulator and Traditional Methods.

PURPOSE: To evaluate and compare the occlusal fit of zirconia crowns designed using a digital articulator method and the traditional method in a self-controlled clinical trial. MATERIALS AND METHODS: Two zirconia crowns each were prepared for 12 patients with a single posterior tooth defect using two different methods: a digital articulator method and the traditional method. In the traditional method, casts were scanned using a model scanner, and the relative positions of the maxillary and mandibular arches were determined by the intercuspal occlusion of the casts. In the digital articulator method, casts were mounted on a mechanical articulator and scanned, and the relative positions were determined by their respective positions in the articulator. Additional dynamic occlusal adjustments of the digital articulator crowns were performed. Both groups of zirconia crowns were milled in a five-axis milling machine. The time required for occlusal adjustments, the occlusal contacts, the occlusal contact distributions, the number of occlusal contacts, the relative occlusal forces, and patient satisfaction (visual analog scale score) were evaluated. Wilcoxon test, McNemar test, and paired t test were used to compare the parameters between the two methods. RESULTS: The occlusal adjustment times for the digital articulator and traditional method crowns were 327 ± 226 seconds and 395 ± 338 seconds, respectively (P > .05). There were no significant differences in occlusal contacts, occlusal contact distributions, number of occlusal contacts, relative occlusal forces, or VAS scores between the two methods (P > .05). CONCLUSION: A digital articulator method for single-crown restoration was applied successfully. Crowns fabricated using a digital articulator or the traditional method can achieve acceptable occlusal fit for single-crown restorations.

Assessment of somatosensory changes in Chinese temporomandibular disorders arthralgia patients by quantitative sensory testing.

BACKGROUND: Somatosensory changes in Chinese temporomandibular disorders (TMD) arthralgia patients have not been fully studied by the latest technologies. OBJECTIVE: This study aims at assessing somatosensory changes in Chinese TMD arthralgia patients quantitatively. METHODS: Standardised quantitative sensory testing (QST) was performed on the pain sites and contralateral sites of 40 patients diagnosed with TMD arthralgia according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) before and after medication; similar measures were taken in 40 age- and gender-matched healthy controls. Differences within and between groups were assessed through Z-scores, two-way ANOVA and loss/gain coding system. RESULTS: The pain sites of patients presented increased sensitivity to thermal stimuli and mechanical pain stimuli together with decreased sensitivity to mechanical tactile stimuli before medication (P < .001). Before treatment, 100% of patients had somatosensory abnormalities at the pain sites; the most frequent abnormalities were somatosensory gain to cold nociceptive, pinprick and pressure stimuli, and the most frequent loss/gain score was L0G3 (no somatosensory loss with a gain of thermal and mechanical somatosensory function; 70.0%). After treatment, although the clinical symptoms and signs of 40 patients disappeared, 80.0% of the patients' pain sites still showed multiple phenotype abnormalities. The most frequent loss/gain score was L0G2 (no somatosensory loss with a gain of mechanical somatosensory function; 35.0%). CONCLUSIONS: Multiple phenotypes of facial somatosensory abnormalities were detected in Chinese TMD arthralgia patients before and after treatment, despite the disappearance of clinical signs and symptoms. Individual variations indicate a possible need for subgroup classification, individualised management and mechanism-based treatment.

Assessment of CAD-CAM zirconia crowns designed with 2 different methods: A self-controlled clinical trial.

STATEMENT OF PROBLEM: In computer-aided design and computer-aided manufacturing (CAD-CAM) dentistry, the correlation method is an efficient way to design complete crowns. However, the occlusal relationship and patient satisfaction with prostheses fabricated using this method remain unclear. PURPOSE: The purpose of this clinical trial was to compare the occlusion of monolithic zirconia crowns designed using the correlation and library methods. MATERIAL AND METHODS: Twenty-three teeth of 21 participants received 2 monolithic zirconia crowns designed by using the correlation or the library method. Defective teeth were scanned using an intraoral scanner to obtain references and working casts from before and after the preparation. Before cementation, the occlusal relationship of both crowns and patient satisfaction were evaluated, and the occlusal adjustment time was recorded. RESULTS: The correlation method resulted in less lateral occlusal interference of the crowns than the library method (P<.01). The occlusal adjustment times of the correlation and library conditions were 455.8 ±357.1 seconds and 575.3 ±488.0 seconds, respectively (P>.05). Relative occlusal force was significantly higher in the correlation than in the library condition and was related to before preparation relative occlusal force (r=0.706, P<.01). The visual analog score before occlusal adjustment was higher in the correlation than in the library condition (P<.05). The occlusal contacts, occlusal contact distributions, and number of occlusal contacts did not differ between conditions (P>.05). CONCLUSIONS: Better eccentric occlusion and reduced lateral occlusal interference were obtained when the correlation method was used to design crowns. The correlation method yielded higher relative occlusal force, which helped to restore the original occlusal force.