Comparative analysis of endocrown fracture resistance and marginal adaptation: CAD/CAM technology using lithium disilicate vs. zirconia-reinforced lithium silicate ceramics.

Aims: The present study aimed to compare the fracture resistance and marginal adaptation of endocrowns fabricated using lithium disilicate (LDS) and zirconia-reinforced lithium silicate 9ZLS) ceramics by the computer-aided design and computer-aided manufacturing (CAD/CAM) technology. Materials and Methods: In this in vitro experimental study, 24 extracted mandibular first molars received standard endocrown preparation and were randomly assigned to two groups (n = 12) for the fabrication of endocrowns with ZLS (Suprinity) and LDS (IPS e.max CAD) ceramics. After scanning the teeth with a CAD scanner, endocrowns were designed by inLab Software version 15 (inLab SW 15) and prepared by an imes-icore 350i milling machine. The vertical marginal gap of endocrowns was measured under a stereomicroscope at three steps before and after cementation and after thermomechanical cycles. The fracture resistance of specimens was then measured by load application at a 45° angle. Mode of failure was also determined as reparable or irreparable. Data were analyzed using Pearson's correlation test and t-test. Results: The mean fracture resistance of ZLS endocrowns was significantly higher than that of LDS endocrowns (P = 0.000). The reparability of ZLS endocrowns was zero, while that of LDS endocrowns was 83.33 %. The vertical marginal gap was significantly smaller in ZLS than in LDS endocrowns at all three time points (P < 0.05). Also, the marginal gap increased by cementation and thermomechanical cycles in both groups. Conclusion: ZLS and LDS endocrowns both showed acceptable vertical marginal adaptation. ZLS had superior marginal adaptation and higher fracture resistance.

Evaluation of One- and Two-Step Impression Techniques and Vertical Marginal Misfit in Fixed Prothesis.

Methods: 12 impressions were made of a resin maxillary model (second premolar and second molar) with two prepared abutment teeth using vinyl polysiloxane (VPS); the margin of the second premolar was 0.5 mm subgingivally; and the margin of the second molar tooth was at the level of the gingiva. Impressions were made using two techniques: one-step and two-step putty/light materials. A three-unit metal framework was fabricated on the master model using the computer-aided design/computer-aided manufacturing (CAD/CAM) technique. The vertical marginal misfit was evaluated in the buccal, lingual, and mesial and distal surfaces of the abutments on the gypsum casts using a light microscope. Data were analyzed using the independent t-test (α < 0.05). Results: The results showed significantly lower vertical marginal misfit in all six areas evaluated around the two abutments in the two-step impression technique compared with the corresponding values in the one-step technique. Conclusion: Vertical marginal misfit in the two-step technique with a preliminary putty impression was significantly lower than in the one-step putty/light-body technique.

Assessment of Marginal and Internal Adaptation in Provisional Crowns Utilizing Three Distinct Materials.

AIMS: This study aimed to assess the marginal and internal adaptation of provisional crowns fabricated from polymethyl methacrylate (PMMA) blocks by the computer-aided design/computer-aided manufacturing (CAD/CAM) system, autopolymerizing PMMA, and acrylic base composite resin. MATERIALS AND METHODS: In this in vitro experimental study, a brass die was obtained, and provisional crowns were fabricated in three groups using Teliocad PMMA blocks by the CAD/CAM system, Tempron GC auto-polymerizing PMMA, and Bisico acrylic base composite resin (n = 7 in each group). The provisional crowns were coded and randomly placed on the die. Their marginal adaptation was evaluated under a stereomicroscope at 40× magnification, while their internal adaptation was assessed by the replica technique. Data were analyzed by one-way analysis of variance (ANOVA) (α = 0.05). RESULTS: The mean marginal gap was the highest in autopolymerizing PMMA and the lowest in the CAD/CAM PMMA group (p < 0.05). The mean marginal gap in the autopolymerizing PMMA group was significantly higher than that in the resin material (p = 0.014) and CAD/CAM PMMA (p = 0.000) groups. The difference between the resin material and CAD/CAM PMMA groups was not significant (p = 0.13). The mean internal gap was the highest in autopolymerizing PMMA group and the lowest in CAD/CAM PMMA group (p < 0.05). The mean internal gap in autopolymerizing PMMA group was significantly higher than that in composite resin (p = 0.002) and CAD/CAM PMMA (p = 0.00) groups. The difference between the resin material and CAD/CAM PMMA groups was not significant (p = 0.322). CONCLUSION: Computer-aided design/Computer-aided manufacturing PMMA provisional crowns showed the highest marginal and internal adaptation followed by acrylic base resin material crowns. CLINICAL SIGNIFICANCE: Computer-aided design/computer-aided manufacturing PMMA crowns demonstrate superior marginal and internal adaptation compared with autopolymerizing PMMA and acrylic base composite resin crowns, suggesting CAD/CAM technology's potential for enhancing clinical outcomes. How to cite this article: Jalalian E, Younesi F, Golalipour S, et al. Assessment of Marginal and Internal Adaptation in Provisional Crowns Utilizing Three Distinct Materials. J Contemp Dent Pract 2023;24(11):853-858.

Fluorescence and Opalescence of Two Dental Composite Resins.

OBJECTIVE: Lifelike esthetic appearance of dental restorations is among the main goals in restorative dentistry. This study aimed to assess and compare the opalescence and fluorescence of two dental composite resins. MATERIALS AND METHODS: This in vitro experimental study evaluated the A2 shade of Filtek Z350 XT Enamel, Filtek Z350 XT Dentin, Aelite Aesthetic Enamel, and Aelite All Purpose Body composite resins. Composite discs were fabricated with 10 mm diameter and 0.5 and 1 mm thicknesses (n = 2) using a plexiglass mold and subjected to colorimetry. The color parameters were determined according to the International Commission on Illumination (CIE) L*a*b* system using a spectrophotometer. The fluorescence and opalescence were also measured and reported separately for 0.5 and 1 mm thicknesses of Z350, Aelite Body, and Enamel composite resins. To determine the opalescence, the color of samples in the reflectance mode was measured using a calibration cylinder and in the transmittance mode in presence of 100% ultraviolet (UV) light. To determine the fluorescence, the color of samples against a white background in the reflectance mode in presence or absence of 100% UV light was measured. STATISTICAL ANALYSIS: Data were analyzed using SPSS via three-way analysis of variance and independent t-test. RESULTS: The fluorescence of 0.5 mm thickness of all composites was higher than that of 1 mm thickness (p < 0.05). The fluorescence of Aelite was higher than that of Z350 (p < 0.05). The fluorescence of Aelite Enamel was higher than that of Aelite Body irrespective of their thickness, but the results were opposite for Z350 (p < 0.05). In Aelite composite, opalescence increased by an increase in thickness (p < 0.05). The opalescence of Aelite was significantly higher than that of Z350 (p < 0.05). The opalescence of 0.5 mm thickness of Aelite Enamel was higher than that of Aelite Body, while the opalescence of 1 mm thickness of Z350 Body was higher than that of Z350 Enamel (p < 0.05). CONCLUSION: Thickness, type, and brand of composite resins affected their fluorescence and opalescence.