The Study Of Resistance Of Maxillary First Molar Restored By Different Forms Of Post And Core Crown

Objective: This in vitro study tested the fracture resistance of maxillary first molar restored by different post and core forms on the fracture strength and fracture patterns.The two factors were evaluated to provide experimental basis for clinical application.Method: A total of 20 recently extracted, sound human maxillary first molar of similar size were used for the study. And then they were randomly divided into 2 groups of 10 teeth each. The teeth were endodontieally treated after the crowns were cut off from the point 2 mm up the cemento-enamel junction. Group A: The teeth were restored by cast split post and core on the lingual root and the distal buccal root; Group B: The teeth were restored by cast single post and core on the lingual root. All the teeth were prepared, remaining 2 mm dentine ferrule and 0.5 mm sh oulder at the cemento-enamel junction, after all the posts and cores being cemented with ZPC. And then the metal crowns were fabricated and cemented with ZPC. Each specimen was embedded in acrylic resin 2 mm below the cemento-enamel junction and then secured in a CMT7104 universal load-testing machine to test the fracture strength. A vertical compressive load was applied at the foss on the occlusal surface until fracture, at a crosshead speed of 1 mm/min. Fracture loads and patterns were recorded.Results:1 the mean failure loads obtained from destruction test were as follows: Group A : 791.01±43.08N; Group B: 633.95±47.96N. 2 T-test analysis indicated that there was significant difference of destruction test values among the two groups (P<0.05) 3 The fracture of specimens were classified as the fracture on the apical third of the root and the orifice of the root. Group A : 8 teeth showed the fracture on the apical third of the root, 2 teeth showed the fracture on the orifice of the root; Group B: 1 teeth showed the fracture on the apical third of the root, 9 tooth showed the fracture on the orifice of the root. 4 Fisher exact test indicated that there was significant difference of destruction test values among the two groups (P<0.05)Conclusions:1 The teeth could be reinforced the fracture resistance after being restored by cast split post and core 2 The teeth restored by cast single post and core could show the fracture on the orifice of the root more than the teeth restored by cast split post and core.