Defect-orientated onlay with cavity design optimization and cervical margin relocation: a case report

For restoring extensive cavities in severely damaged or decayed posterior teeth, especially those with thin walls, indirect restorations are recommended rather than direct fillings. Regarding indirect restorations for inlays and onlays, composite resin-based CAD/CAM materials are considered to have several advantages over ceramics such as easy manufacturing, lower cost, and simpler repairability. A case is presented in this article in which the treatment plan and protocol combine multiple evidence-based clinical techniques such as immediate dentin sealing (IDS), cavity design optimization (CDO), and cervical margin relocation (CMR). For CDO and CMR, two different types of flowable composite resins with different viscosities were used. Restoring such extensively damaged teeth using a defect-oriented adhesive technique is considered a challenge both in terms of the preservation of healthy tooth structure and the proper isolation for adhesive luting. The IDS technique was used to enhance the bonding to the remaining dentin, while CDO was performed to avoid unnecessary removal of vital tooth structure, for example, undercuts. The deep subgingival margins were elevated using the CMR technique to facilitate the impression taking and a contamination-free luting of the final restoration. Combining the aforementioned techniques enabled a defect-oriented, minimally invasive restoration of a severely decayed tooth. The aim of this article is to present those techniques in a simplified way through a clinical case as a step-by-step guide for the practitioner. Keywords: onlay, minimally invasive, immediate dentin sealing, cavity design optimization, cervical margin relocation, flowable composite, CAD/CAM, composite blocks