The effect of post material on the characteristic strength of fatigued endodontically treated teeth Jefferson Ricardo Pereira, DDS, MSc, PhD,a Accácio Lins do Valle, DDS, PhD,b Fabio Kenji Shiratori, DDS, MSc,c Janaina Salomon Ghizoni, DDS, MSc, PhD,d and Estevam Augusto Bonfante, DDS, MSc, PhDe Dental School, University of Southern Santa Catarina, Tubarão, Brazil; Bauru Dental School, University of São Paulo, São Paulo, Brazil Statement of problem. The biomechanical properties of post systems may become more important as the amount of remaining tooth structure decreases, thus different materials may influence the characteristic strength of fatigued endodontically treated teeth. Purpose. The purpose of this study was to assess the characteristic strength and probability of survival of endodontically treated teeth restored with different intraradicular post systems. Material and methods. Forty human maxillary canines with similar root lengths were randomly divided into 4 groups (n¼10): cast post and core, stainless-steel prefabricated post, carbon-fiber post, and glass-fiber post. Cores and metallic crowns were fabricated for all specimens. Restored teeth were exposed to mechanical fatigue (250 000 cycles) in a controlled chewing simulator. Each intact specimen was mounted in a special device and aligned at a 45-degree angle to the long axis of the tooth. A universal testing machine was used to apply a static load at a crosshead speed of 0.5 mm/min until specimen failure. The maximum value was recorded in newtons (N). Probability Weibull curves (2-sided 90% confidence bounds) were calculated for each group, and a probability of survival as a function of load at failure was plotted for the groups. Results. A significantly higher characteristic strength was observed for groups carbon-fiber post (755.82 N) and cast post and core (750.6 N) (P.10), and 461.3 N for the GF and 524.8 N for the SS group (P>.10). The contour plot (Fig. 2) showed that groups CF and CP presented a significantly higher characteristic strength than GF and SS, as shown by the nonoverlap between contours. The probability of survival as a function of load plotted in Fig. 3 confirmed the trend of the pair of groups GF and SS to show a significantly lower probability of survival with load increase compared with groups CF and CP. The results of the

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Table I. Resistance to failure values of test specimens, means (SDs) of test groups and Tukey comparisons

Group

Resistance to Failure Values (N), mean (SD)*

CP

712.7 101.1a

SS

498.0 66.4a

CF

457.2 109.4a

GF

436.0 59.5b

SD, standard deviation; CP, cast post and core; SS, stainless steel; CF, carbon fiber; GF, glass fiber. *Groups with the same superscripted letters are not significantly different at P