(PR147) The Effects of Rubber Dam Clamps on Zirconia Crown Restorations

Objective: Rubber dam isolation is a standard of care in endodontics, but it is unknown if rubber dam clamps (RDCs) damage zirconia crowns. This study aimed to evaluate damage caused by rubber dam clamps placed on zirconia crowns. It was hypothesized that if RDCs are applied to zirconia crowns no detectable damage would be caused.

Methods: A typodont maxillary incisor, mandibular premolar and molar were each prepared for zirconia crowns. The teeth were scanned to create digital impressions. Ten identical crowns and dies for each tooth were designed using CAD/CAM. The incisor, premolar and molar crowns were milled from 5Y (esthetic), 4Y, and 3Y zirconia, respectively. The crowns were cemented to their corresponding dies, scrubbed with methylene blue dye and inspected for damage under a dental operating microscope. RDCs were placed on each crown for one hour, then removed. Crowns were scrubbed with methylene blue dye and inspected for damage again. Damage was documented with Image J software using a standardized scale.

Results: Preliminary results suggest RDCs are capable of fracturing anterior esthetic zirconia restorations, can cause minor damage to 4Y posterior zirconia, but do not damage 3Y zirconia. Final statistical analysis is pending.

Conclusion: Rubber dam clamps can compromise the integrity of zirconia restorations, especially on anterior esthetic crown restorations. Findings suggest that an alternate tooth should be clamped when endodontic treatment is being performed through zirconia.