Accuracy of Marginal and Internal Adaptation of Advanced Lithium Disilicate Crowns Using Different Margin Designs (In...

Area of Science:

• Dental Materials Science
• Prosthodontics
• CAD/CAM Dentistry

Background:

• Advanced lithium disilicate glass ceramics provide excellent esthetics for dental restorations.
• Conservative vertical preparations (vertipreps) lack extensive scientific evidence regarding esthetic outcomes compared to traditional shoulder or chamfer designs.

Purpose of the Study:

• To evaluate the marginal adaptation and internal fit of advanced lithium disilicate (CEREC Tessera) crowns fabricated using CAD/CAM technology.
• To compare the fit of crowns fabricated with three distinct margin designs: chamfer, rounded shoulder, and vertiprep.

Main Methods:

• Three mandibular molar typodont teeth were prepared with chamfer (0.5 mm), rounded shoulder (1 mm), and vertiprep (0.2 mm) margin designs.
• CAD/CAM milling was used to fabricate advanced lithium disilicate crowns (n=8 per group).
• Marginal adaptation was assessed using stereomicroscopy, and internal fit was evaluated after sectioning the crowns.

Main Results:

• Significant differences were found in both marginal adaptation (p < 0.001) and internal fit (p < 0.001) among the margin designs.
• The vertiprep group exhibited the smallest internal gap (70.09 µm), indicating superior internal fit.
• Marginal adaptation was greatest in the rounded shoulder group (125.45 µm), followed by chamfer (107.31 µm) and vertiprep (101.79 µm).

Conclusions:

• The vertiprep margin design demonstrated the best internal fit for advanced lithium disilicate CAD/CAM crowns.
• While vertiprep showed the least marginal gap, its adaptation was not significantly different from the chamfer design.
• These findings suggest vertiprep is a viable conservative margin design for achieving optimal internal fit in lithium disilicate restorations.