The aim of this study was to evaluate the resistance to fracture of endodontically treated teeth with flared canals restored with different post and core restorations under static and cyclic fatigue loadings. Sixty human maxillary central incisors were used. Two main groups (non-ferrule and 1-mm ferrule) were divided into three types of restoration: custom cast post-and-core (MPC), resin composite post-and-core (RCP), and resin composite core in combination with prefabricated carbon fiber post (FRC). Half of each group was subjected to a static loading test, and the other to a cyclic fatigue test. FRC exhibited a significantly higher number of load cycles than the other groups, and MPC showed the highest failure load among the tested groups. However, all FRC and MPC specimens demonstrated unfavorable root fractures. The results of this study suggested that RCP prepared with 1-mm ferrule was the most desirable restoration for structurally compromised roots, as relatively strong resistance to cyclic fatigue and fracture was revealed--given that all RCP specimens demonstrated favorable root fracture.
PURPOSE To determine effects of light curing of self-etching adhesives under ambient air or nitrogen on inhibition depths, enamel and dentin bond strengths, and marginal adaptation in dentin cavities. MATERIALS AND METHODS The adhesives investigated were: AQ Bond (AQB, Sun Medical; Kyoto, Japan), iBond (IBO, Heraeus Kulzer; Hanau, Germany), One-Up Bond F II (OUB, Tokuyama; Tokyo, Japan), and Prompt L-Pop (PLP, 3M/ESPE; Seefeld, Germany). Inhibition layer thickness (ILT) was microscopically measured on 3 disk-shaped specimens each. Shear bond strengths (SBS) on enamel and dentin (n = 8) were determined after 10 min and 24 h water storage of bonded composite specimens (Venus, Heraeus Kulzer). The marginal adaptation of bonded Venus restorations in cylindrical dentin cavities was microscopically evaluated after 10 min of specimen storage (n = 8) in water. The data were statistically analyzed using parametric and nonparametric ANOVA and post-hoc tests at p 0.05). On dentin, SBSs were higher after curing under N2 (p < 0.05). Irrespective of the curing atmosphere, marginal adaptation was good for AQB and IBO and poor for PLP; OUB revealed significantly smaller gaps under N2 than under air curing. CONCLUSION Oxygen inhibition of the four self-etching adhesives investigated had no or only moderate effects on bonding efficacy to enamel and dentin.
The aim of this study was to investigate the influence of post-core methods and the remaining radicular tooth structure on the fracture resistance of pulpless teeth. Two types of remaining radicular tooth structure were tested: one group had sufficient radicular tooth structure, and the second had thinwalled-flared canals. The prepared post holes were restored with one of five different post-core methods: the metal post and cores cemented with zinc-phosphate cement; the metal post and cores cemented with Super-Bond C & B; C-POST and composite resin core; AD POST II and composite resin core, and composite resin only. Each group was tested until the root fractured with a slowly increasing force at 90 degrees to the long axis.The results were as follows:1. The use of a metal post and cores resulted in higher fracture resistance than those recorded for teeth restored with composite resin.2. Fracture resistance of teeth restored with a metal post and cores decreased with decreasing radicular tooth structure; nevertheless, there was no significant difference.3. A composite resin post and cores could be used for the restoration of thin-walled-flared canals.4. Fractures were detected at the core-dentin interface in all specimens; therefore, core-dentin interfaces must be strengthened.
OBJECTIVE To investigate the resistance to cyclic fatigue of maxillary incisors with flared canals restored with different post-and-core materials. METHODS Thirty human maxillary central incisors were assigned randomly to two main groups (non-ferrule and 1-mm ferrule) of 15. Each main group was then divided into 3 groups of 5 specimens and restored with custom cast post-and-core (MPC), resin composite post-and-core (RCP), and resin composite core combined with prefabricated carbon fiber post (FRC), respectively. Every group was subjected to a cyclic fatigue test, and recorded the numbers of load cycles that occurred tooth fracture. All data were analyzed with two-way ANOVA and the Tukey HSD test at alpha = 0.05. RESULTS FRC revealed significantly higher fatigue strength than the other groups (P < 0.05). Preparing a dentin ferrule increased significantly fatigue resistance (P < 0.05). The favorable (retrieval) fracture pattern of the tested specimens was discovered only in RCP. CONCLUSIONS Using FRC may get a long fatigue life in restoring pulpless teeth with flared canals. Dentin ferrule preparation is necessary to enhance resistance of the restorations to cyclic fatigue.
