The effect of post material on the characteristic strength of fatigued endodontically treated teeth.
BACKGROUND
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.


OBJECTIVE
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.


METHODS
Forty human maxillary canines with similar root lengths were randomly divided into 4 groups (n=10): 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<.05) compared with glass-fiber post (461.35 N) and stainless-steel prefabricated post (524.78 N) groups. All the roots in the cast post and core group demonstrated catastrophic fracture, whereas the remaining groups had no root fractures.


CONCLUSIONS
Prefabricated posts made of glass fiber and stainless steel showed significantly lower characteristic strength and probability of survival than cast post and core, whereas crowns with carbon-fiber posts presented a single load similar to the fracture values of cast posts.
Associate Clinical Professor and Researcher Coordinator, Department of Prosthodontics, Dental School, University of Southern Santa Catarina, Tubarão, Brazil. Electronic address: jeffripe@rocketmail.com.
Jefferson Ricardo
JR
Pereira
Associated Clinical Professor, Department of Prosthodontics, Bauru Dental School, University of São Paulo, São Paulo, Brazil.
Accácio Lins
AL
do Valle
Private practice, Itu, São Paulo, Brazil.
Fabio Kenji
FK
Shiratori
Associate Clinical Professor and Researcher Coordinator, Department of Prosthodontics, Dental School, University of Southern Santa Catarina, Tubarão, Brazil.
Janaina Salomon
JS
Ghizoni
Associate Clinical Professor, Department of Prosthodontics, Bauru Dental School, University of São Paulo, São Paulo, Brazil.
Estevam Augusto
EA
Bonfante
D017607:Aluminum Compounds / Q000737:chemistry; D001696:Biomechanical Phenomena; D002244:Carbon / Q000737:chemistry; D000077482:Carbon Fiber; D002858:Chromium Alloys / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry; D003734:Dental Casting Investment / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis / Q000295:instrumentation; D005898:Glass / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D011176:Post and Core Technique / Q000295:instrumentation*; D011897:Random Allocation; D019279:Resin Cements / Q000737:chemistry; D018915:Root Canal Preparation / Q000379:methods; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical; D016019:Survival Analysis; D014082:Tooth Fractures / Q000503:physiopathology; D014092:Tooth Root / Q000293:injuries; D019553:Tooth, Nonvital / Q000503:physiopathology* / Q000628:therapy
D017607:Aluminum Compounds; D000077482:Carbon Fiber; D002858:Chromium Alloys; D003188:Composite Resins; D003722:Dental Alloys; D003734:Dental Casting Investment; D003764:Dental Materials; C444701:Filtek Z250; C528569:Rely-X; D019279:Resin Cements; C009753:fiberglass; D013193:Stainless Steel; D002244:Carbon; D003300:Copper