Marginal and internal fit of CAD-CAM composite resin and ceramic crowns before and after internal adjustment.

STATEMENT OF PROBLEM: With the development of computer-aided design and computer-aided manufacturing (CAD-CAM) technology, dentists may determine internal spacing by using the CAD-CAM software program and make internal adjustments during the clinical evaluation appointment. How these factors affect marginal adaptation is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the marginal and internal adaptation of CAD-CAM ceramic and composite resin crowns with different internal spacings before and after internal adjustment by using microcomputed tomography. MATERIAL AND METHODS: Eight third molars were prepared for a complete crown, and 32 crowns were milled at chairside from composite resin and ceramic materials with different internal spacing (30 µm and 80 µm). After an initial microcomputed tomography scan, the same crowns were adjusted and scanned again. Axial space, occlusal space (OS), marginal discrepancy, and absolute marginal discrepancy were evaluated in both analyses. The need for internal adjustment was determined by an experienced clinician by using a silicone film. The number of internal adjustments was also recorded. The data were analyzed by using a 3-way ANOVA (material, internal spacing, and internal adjustment) and the Bonferroni correction (α=.05). RESULTS: For axial space, only the material factor was significantly different (P<.001), with the ceramic having the lowest value. For OS, both internal spacing and adjustments presented a statistical difference among groups with the lowest OS values obtained for 80-µm spacing after adjustment. For marginal discrepancy and absolute marginal discrepancy, the adjustment factor also had a significant effect, and the adjustment resulted in smaller measures for both variables. The 30-µm spacing required more adjustments than the 80-µm spacing (P<.05). CONCLUSIONS: Both the internal adaptation and marginal adaptation were influenced by the internal adjustment, resulting in improved values for both. Although no differences were observed between the 30-µm and 80-µm spacings after internal adjustment for marginal adaptation, the 30-µm spacing required twice as many adjustments, resulting in longer clinical sessions.

Marginal and internal fit of CAD-CAM-fabricated composite resin and ceramic crowns scanned by 2 intraoral cameras.

STATEMENT OF PROBLEM: The precision of fit of chairside computer-aided design and computer-aided manufacturing (CAD-CAM) complete crowns is affected by digital impression and restorative material. PURPOSE: The purpose of this in vitro study was to evaluate by microcomputed tomography (µCT) the marginal and internal adaptation of composite resin and ceramic complete crowns fabricated with 2 different intraoral cameras and 2 restorative materials. MATERIAL AND METHODS: Ten extracted human third molars received crown preparations. For each prepared molar, 2 digital impressions were made with different intraoral cameras of the CEREC system, Bluecam and Omnicam. Four groups were formed: LB (Lava Ultimate+Bluecam), EB (Emax+Bluecam), LO (Lava Ultimate+Omnicam), and EO (Emax+Omnicam). Before measuring the precision of fit, all crowns were stabilized with a silicone material. Each unit (crown + prepared tooth) was imaged with µCT, and marginal and internal discrepancies were analyzed. For the 2D analysis, 120 measurements were made of each crown for marginal adaptation, 20 for marginal discrepancy (MD), and 20 for absolute marginal discrepancy (AMD); and for internal adaptation, 40 for axial space (AS) and 40 for occlusal space (OS). After reconstructing the 3D images, the average internal space (AIS) was calculated by dividing the total volume of the internal space by the contact surface. Data were analyzed with 2-way ANOVA and quantile regression. RESULTS: Regarding marginal adaptation, no significant differences were observed among groups. For internal adaptation measured in the 2D evaluation, a significant difference was observed between LO and EO for the AS variable (Mann-Whitney test; P<.008). In assessment of AIS by the 3D reconstruction, LB presented significantly lower values than the other groups (Tukey post hoc test; P<.05). Bluecam presented lower values of AIS than Omnicam, and composite resin crowns showed less discrepancy than did ceramic crowns. CONCLUSIONS: The marginal adaptations assessed in all groups showed values within the clinically accepted range. Moreover, the composite resin blocks associated with the Bluecam intraoral camera demonstrated the best results for AIS compared with those of the other groups.