Effect of Deep Margin Elevation on CAD/CAM-Fabricated Ceramic Inlays

Area of Science:

• Restorative Dentistry
• Dental Materials Science
• Biomaterials Engineering

Background:

• Computer-aided design/computer-aided manufacturing (CAD/CAM) feldspathic ceramic inlays offer aesthetic and biocompatible restorative solutions.
• Preparation margins extending beyond the cemento-enamel junction (CEJ) pose challenges to the structural integrity of ceramic restorations.
• Deep margin elevation is a technique to manage subgingival preparation margins, but its impact on ceramic inlay integrity requires evaluation.

Purpose of the Study:

• To investigate the effect of deep margin elevation on the structural and marginal integrity of CAD/CAM-fabricated ceramic inlays.
• To compare the outcomes of different margin designs, including enamel, cementum, glass ionomer (GI), and resin-modified glass ionomer (RMGI) elevations.

Main Methods:

• Forty extracted human molars were divided into four groups based on margin location and elevation technique.
• Ceramic inlays were fabricated using CAD/CAM and bonded to teeth.
• Restorations underwent extensive thermocycling and chewing simulation, followed by microscopic assessment of ceramic fracture and marginal integrity.

Main Results:

• The cementum margin group exhibited a significantly higher ceramic fracture rate (90%) compared to enamel margin (10%), GI margin (10%), and RMGI margin (0%) groups.
• Deep margin elevation, particularly with RMGI, demonstrated a protective effect against ceramic fracture for sub-CEJ preparations.
• Increased ceramic proximal box height was correlated with a higher probability of ceramic fracture.

Conclusions:

• Deep margin elevation is a beneficial technique for enhancing the structural integrity of ceramic inlays with preparation margins below the CEJ.
• Both GI and RMGI effectively elevated margins without significant differences in outcomes between them.
• The findings suggest that careful consideration of preparation depth and margin design is crucial for the longevity of ceramic restorations.