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Accuracy of Marginal and Internal Adaptation of Advanced Lithium Disilicate Crowns Using Different Margin Designs (In
Hossam A Mohamed1, Amir Azer1, Rewaa G AboElHassan1
1Department of Conservative Dentistry, Fixed Prosthodontics, Faculty of Dentistry, Alexandria University, Alexandria, Egypt, alexu.edu.eg.
Background:
Advanced lithium disilicate glass ceramics offer excellent esthetics, but conservative crown preparations are not always the preferred choice. Various margin designs are available; however, more conservative vertical preparations (vertipreps) have less scientific evidence supporting their esthetic outcomes compared to shoulder or chamfer designs.
Aim Of The Study:
To assess the marginal adaptation and internal fit of crowns fabricated from advanced lithium disilicate (CEREC Tessera) using computer-aided design and manufacturing (CAD/CAM) with three distinct margin designs.
Materials And Methods:
Three mandibular molar typodont teeth were prepared with three finish line designs: chamfer 0.5 mm (C), rounded shoulder 1 mm (RS), and vertiprep 0.2 mm (V) using a modified dental surveyor for standardization. Silicone replicas were used to create epoxy resin dies. Twenty-four crowns were produced on the replicated resin dies, with eight crowns for each finish line design (n = 8). Preparations were scanned using an intraoral scanner (Carestream Dental LLC, 3625 Cumberland Blvd., Ste. 700, Atlanta, GA 30339), and advanced lithium disilicate (Tessera) crowns were milled via CAD/CAM. Crowns were cemented onto their respective dies, and marginal adaptation was measured using a stereomicroscope; then, crowns were sectioned using a microtome to evaluate internal fit.
Results:
One-way ANOVA showed a significant difference in the marginal adaptation among groups (p < 0.001). Group RS had the largest gap (125.45 ± 12.11 µm), followed by Group C (107.31 ± 9.25 µm) and Group V (101.79 ± 9.01 µm). Internal fit also differed significantly (p < 0.001), with Group V having the smallest gap (70.09 ± 8.45 µm), followed by Group RS (87.85 ± 6.82 µm) and Group C (94.45 ± 9.21 µm).
Conclusion:
The vertiprep showed the least marginal adaptation and best internal fit compared to shoulder and chamfer designs, with no significant difference in marginal gap between vertiprep and chamfer.
