[Fatigue and fracture resistance of the flared roots restored with computer aided design and computer aided manufacturing glass fiber posts].

OBJECTIVE

To evaluate the fatigue and fracture resistance of the flared roots restored with computer aided design (CAD) and computer aided manufacturing (CAM) glass fiber posts.

METHODS

In the study, 32 maxillary central incisors with roots longer than 13 mm were selected and their canals were flared, and the roots were allocated into 4 groups (n=8) by a random number chart: CAD/CAM glass fiber posts, prefabricated quartz fiber posts, cast gold alloy posts, and CAD/CAM zirconia posts. The posts were luted to the roots by resin cement and fabricate zirconia crown for every specimen. An addition-type silicone impression material was used to simulate the periodontal ligament. All the specimens were submitted to 1.2×10(6) cycles loaded with a 49 N force, at 45 degree to the long axis of the teeth simultaneously with 3 000 thermal cycles (5 °C-50 °C-5 °C). After that, the specimens were subjected to a load at a crosshead speed of 1 mm/min in a servo-hydraulic testing machine applied at 45 degree to the long axis of the tooth until fracture. The data were subjected to ANOVA test and the patterns of the failure were examined.

RESULTS

After the cycling loading, 4 crowns from prefabricated quartz fiber posts groups were deboned, and no other failure was found after the cycling loading; the fracture strengths of CAD/CAM glass fiber posts group [(441.5± 103.2) N] and cast gold alloy posts group [(462.9±170.0) N] were higher (F=4.613, P<0.05) than those of CAD/CAM zirconia posts group [(284.1±99.0) N] and prefabricated quartz fiber posts group [(315.4±112.3) N]; the entire specimens presented unfavorable failures.

CONCLUSION

Although further in vitro and in vivo studies are necessary, the results of this study show that the use of CAD/CAM glass fiber posts and cast gold alloy posts may achieve better outcomes in flared roots than that of CAD/CAM zirconia posts and prefabricated quartz fiber posts.