[Effect of amalgam cuspal coverage on the fracture resistance of endodontically treated teeth]

ABSTRACT

Endodontically treated teeth are prone to fracture because they loose a large amount of their structure. The treatment plan of those teeth is completed when they are rehabilitated with a strong and functional restoration. The purpose of this study was to evaluate the fracture resistance of endodontically treated teeth restored with amalgam cuspal coverage in comparison with other restorative techniques. 40 human healthy maxillary premolars were divided into 4 groups group1 [S] sound teeth, group 2[Co] endodontically treated teeth with MOD cavity restored with bonding and composite, group 3[Am-B] endodontically treated teeth with MOD cavity restored with bonding and amalgam and group 4 [Am-CC] endodontically treated teeth with MOD cavity restored with amalgam cuspal coverage. Then the restorations were stored in water and room temperature for 100 days at then thermocycled for 500 cycles between water baths at [5.5 +/- 1] and [55 +/- 1][degree]C. The fracture resistance was evaluated by Universal Testing Machine [Instron, 1195 UK] with the compressive force of about 2000 N in 0.5 mm/min. The fracture modes were evaluated in four groups by a stereomicroscope. Statistical analysis [Scheffe test] was done for all groups [P<0.05 was considered as the level of meaningfulness]. The highest fracture resistance was found in group 4 [Am-CC] [976 +/- 23.27 N] that had no significant difference with sound tooth [P>0.05]. The lowest fracture resistance was found in group 2 [Co] [384 +/- 137.4 N] that had no significant difference with group 3 [Am-B] [P>0.05]. The fracture resistance in group 4 was significantly higher than group 2 [Co] and 3 [Am-B]. The fracture mode in group 1 was cohesive within tooth and in group 2 [Co] and 3 [Am-B] was mixed cohesive and adhesive, and in group 4 was cohesive within restorative material. The highest fracture resistance was obtained in teeth that received amalgam cuspal coverage.