Fractography of clinically fractured, implant-supported dental computer-aided design and computer-aided manufacturing crowns. (17th November 2017)

• Record Type: Journal Article
• Authors: Lohbauer, Ulrich; Belli, Renan; Cune, Marco S; Schepke, Ulf
• Is Part Of: SAGE open medical case reports. Volume 5(2017)
• Publication Date: 2017-11-17
• Subjects: Dentistry -- fractography -- computer-aided design and computer-aided manufacturing composite -- adhesive failure -- crown restoration -- lava -- ultimate -- hydrolytic degradation; Clinical medicine -- Case studies -- Periodicals; 616.09
• DOI: 10.1177/2050313X17741015
• Languages: English
• ISSNs: 2050-313X

Abstract

Today, a substantial part of the dental crown production uses computer-aided design and computer-aided manufacturing (CAD/CAM) technology. A recent step in restorative dentistry is the replacement of natural tooth structure with pre-polymerized and machined resin-based methacrylic polymers. Recently, a new CAD/CAM composite was launched for the crown indication in the load-bearing area, but the clinical reality forced the manufacturer to withdraw this specific indication. In parallel, a randomized clinical trial of CAD/CAM composite crowns luted on zirconia implant abutments revealed a high incidence of failure within the first year of service. Fractured crowns of this clinical trial were retrieved and submitted to a fractographic examination. The aim of the case series presented in this article was to identify failure reasons for a new type of CAD/CAM composite crown material (Lava Ultimate; 3M Oral Care, St. Paul, Minnesota, USA) via fractographic examinations and analytical assessment of luting surfaces and water absorption behavior. As a result, the debonding of the composite crowns from the zirconia implant abutments was identified as the central reason for failure. The adhesive interface was found the weakest link. A lack of silica at the zirconia surface certainly has compromised the bonding potential of the adhesive system from the beginning. Additionally, the hydrolytic stress released from swelling of the resin-based crown (water absorption) and transfer to the luting interface further added to the interfacial stress and most probably contributed to a great extend to the debonding failure.