Coronal tooth structure in root‐treated teeth prepared for complete and partial coverage restorations

Summary  This in vivo study assessed the remaining coronal tooth structure in teeth prepared for complete and partial coverage restorations using 3D‐scanning and a Tooth Restorability Index (TRI). The cuspal coverage preparation designs selected by 10 postgraduate dentists and 10 general dental practitioners were recorded in a questionnaire. Eighteen patients had molar root treatment completed at the Eastman Dental Hospital and were prescribed a coronal‐radicular amalgam core and cast restoration. Each tooth was prepared in vivo by one operator for a cast restoration. Two clinical impressions were made to produce two dies: one of remaining coronal tooth structure before crown preparation and a second die of coronal tooth structure in vivo after crown preparation. For teeth prepared for partial coverage in vivo ( n  = 13), a third die was prepared in vitro representing remaining tooth structure after complete coverage preparation. The three dies were of tooth structure prior to core placement. All dies ( n  = 31) were scanned using a laser profilometer and the volume of remaining tooth structure calculated. Four observers scored 31 dies using the TRI. The percentage loss of coronal tooth volume following a complete instead of a partial coverage preparation varied from 3·29% to 45·23% and the mean TRI fell from 10·7 to 7·5 units. There was a strong correlation between mean TRI and scanned volume of tooth structure ( P  = 0·013). Over 50% of the dentists altered their initial choice of restoration design from complete to partial coverage. Complete coverage preparations removed more tooth structure than partial coverage.