Investigation of surface treatments undertaken prior to resin composite repair in clinical practice

Abstract

In dentistry the repair of a failed resin composite (RC) restoration is a recognized alternative to its replacement as it is less invasive and destructive to tooth-structure. There is minimal evidence available in support of a definitive repair protocol, limitation in understanding the mechanisms behind effectiveness of repair protocols and as such there is no clear guidance for clinical practice. Therefore a questionnaire-based study was undertaken to explore how dentists manage fractured RC restorations in primary care dental practice in the UK. This information, along with the relevant literature surrounding the repair protocols was investigated. This then, informed the design of in vitro investigations to better understand potential repair protocols for RC as described by the outcome measures of shear bond strength (SBS), roughness, surface morphology and water sorption. The questionnaire-based study suggested that 70% of dentists would repair RC restorations and they used a varied combination of pretreatments in the process of making a repair. The most prevalent repair methods were surface modification by the use of a bur, application of phosphoric acid or a bonding agent. The in vitro investigations undertaken as part of the study demonstrated differences in SBS level between repair protocols. The application of a bur followed by acid etch and a bonding agent led to the highest SBS. Differences in roughness and surface morphology appeared to affect SBS level. In contrast, water sorption and aging showed minimal impact on SBS level. Conclusion: Dentists are currently repairing fractured RCs using different protocols. The in vitro investigations revealed surface treatments have different contribution to the SBS level and these differences in SBS may be explained by the accompanied change in roughness and surface morphology of RCs. The highest SBS level was achieved by the sequential use of bur, phosphoric acid and bonding agent.