Statement of problem: A dowel is essential to retain the core in case of severe tooth destruction. However, the\r\nplacement of a dowel and core may actually weaken teeth and affect their failure pattern depending on their material\r\nproperties and stress transfer.\r\nPurpose: The present study compared the fracture resistance and failure pattern of endodontically treated\r\npremolars with different amounts of tooth destruction restored with dowels of different materials: a heat pressable\r\n \r\n\r\n\Z\r\n\r\nMaterials and methods: Ninety single rooted premolars of similar dimensions were selected and divided at\r\nrandom into 9 groups (n=10) Group 1: Sound teeth (Control group), Group 2: Reduced sound teeth with 60 taper and\r\n!\"\r\n# $%\Z&\Z\Z''*#*+\Z\Z\Z\Z\r\nminimal endodontic access. Groups 4, 5 and 6 restored using a pressable ceramic dowel and core while groups 7, 8\r\n%\Z\Z\r\n-\Z\Z\Z\r\nfracture for each group was examined. The recorded values were tabulated and statistically analyzed.\r\nResults: Group 5 (tapered ceramic) showed the highest fracture mean values followed by group 6 (parallel\r\nceramic). Group 4 (parallel tapered ceramic) showed statistically similar values to group 1 (sound teeth).Group 2\r\n(Reduced sound teeth) registered 20% reduction in fracture resistance when compared to group 1 (sound teeth).\r\n# \Z\Z\Z\Z&'' to group 2. Fiber groups 7, 8 and 9 displayed\r\n\Z\Z\Z&\Z\Z''3;<\Z\Z>\r\n\r\nConclusions: Reduction of sound teeth resulted in 20% decrease in their fracture resistance. Endodontically\r\ntreated premolars with minimal access, restored with composite, maintained the same values as sound reduced\r\nteeth. Pressed ceramic bonded dowel and cores with three dowel designs displayed higher resistance means than\r\nsound reduced teeth; however, most failures were unfavorable. Fiber dowels and composite core groups registered\r\napproximately 70% of the values of sound reduced teeth but all failure patterns were favorable.
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