Electron Microscope comparison of carvosurface margins prepared by different methods

Uneven occlusal carvosurface margins (CSM) could result in inferior marginal adaptation of the restoration, with detrimental consequences such as marginal leakage and recurrent caries. OBJECTIVE: The objective of this investigation was to assess the effect of six different cavity preparation techniques on the quality of carvosurface margins. METHODS: Eighteen sound, extracted, human molars were divided into six groups of three teeth each. Occlusal cavities were prepared to a depth of 0,5mm in dentine. Outline forms were all prepared to the same pattern. The 6 instruments/devices used to prepare the cavities were: Carbide fissure bur, Coarse diamond fissure bur, Medium diamond fissure bur, Fine diamond fissure bur, Water laser and Water cut sandblaster Aquacut. Specimens were sectioned below the anatomical crown and stored in distilled water for 10 days. Samples were subsequently evaluated in a Scanning Electron Microscope utilizing 3 independent evaluators. A five- point scoring system was used to evaluate the margins i.e. 1 = Acceptable (even/ uninterrupted CSM), 2 = Acceptable (few CSM interruptions), 3 = Acceptable (more CSM interruptions), 4 = Not acceptable (more than half of CSM damaged), and 5 = Totally not acceptable (No CSM is visible, total destruction). RESULTS: The carbide burs, fine diamond and Aquacut produced an acceptable CSM, however the Aquacut left a crust at the CSM. Coarse diamonds were not acceptable (dislodgement of enamel pieces) with medium diamonds CSM damage was less visible, but there was enamel smearing. The laser caused ablation at the CSM. No normal enamel prisms were visible. CONCLUSION: Different cavity preparation regimens produced different results. The laser was the most damaging.