Evaluation Of Fracture Resistance Of Different Post-Core Systems

A post - core system is usually used to provide retention for final crown restoration when a large portion of the clinical crown has been lost after endodontic treatment. But the longevity of restoration can be decreased because of tooth fracture, post or core fracture, dislodgement of post or any combination of these. This in vitro study compared the fracture resistance of different post -core systems cemented with various cements in order to provide guidance for clinical choice of post - core systems and luting cements.Methods1. Ninety intact extracted human maxillary central incisors or canines with similar root size were sectioned at the cementoenamel junction. After endodontic therapy of the root, post - holes were prepared to a depth of 10mm with a diameter 1. 5mm Parapost drill, which is matched to the Parapost.2. All roots were embedded with autopolymerizing resin in plastic cylinder, 20mm high and 15 mm in diameter located in center and paralleled with the cylinder. All samples were divided into 9 groups randomly and equally. Different posts were cemented respectively with different luting cements, and the cores with the same dimensions were then constructed with a dual - cured composite core material.3. The specimens were tested in a universal testing machine. The testing machine applied loads to the core on the palatal side at an angle 90 degree to thelong axis of the root with crosshead speed of 0. 5mm/min and a load - cell capacity of 1000N. Failure threshold was defined as the point at witch a specimen occur permanent plastic deformation. Also, the number of core fractures was recorded for each group.4. All data were collected and analyzed statistically by using SPSS11. 0 program software.ResultsThere were distinct differences in fracture resistance among different post -core systems. Cast post - core and Parapost with composite core demonstrated significantly higher fracture resistance than Parapost Fiber White with composite core (P <0. 05) , but there was no significant difference between cast post -core and Parapost with composite core (P >0.05).The effects of different luting cements on the fracture resistance of different post - core systems had no significant difference.The group with Parapost Fiber White had significantly fewer incidences of core fracture than the group with Parapost.Conclusion1. Different post - core systems had significant difference in fracture resistances.2. The effects of different luting cements on the fracture resistance of different post - core systems had no significant difference.3. The use of glass fiber post reduced the incidence of the core fracture.