Purpose This study is to investigate the effect of milling custom fit anatomical post and cores from fiber reinforced composite and high‐density polymer blocks using CAD/CAM technology on the bond strength to root canal dentin compared with prefabricated fiber posts, and to evaluate the influence of thermal cycling on the push out bond strength of the tested materials. Materials and Methods Eighty extracted single‐rooted premolars, endodontically treated and prepared to receive the posts, were randomly divided into four groups (n = 20): BLC: Custom‐milled fiber‐reinforced composite posts and cores (Trilor, Bioloren), AMC: Custom‐milled high‐density polymer posts and cores (Ambarino, Creamed), BLP: Prefabricated fiber‐reinforced composite posts and composite core buildups (Bioloren; Filtek Bulk Fill Posterior, 3M). The posts used have the same matrix and fiber composition as BLC, RXP: Prefabricated posts and composite core buildups (RelyX fiber post, 3M; Filtek Bulk Fill Posterior); used as a control group. All of the posts were cemented using a self‐adhesive resin cement (RelyX U200, 3M). Half of the sample was randomly assigned to thermal cycling in distilled water for 6,000 cycles to simulate aging, while the other half was tested for bond strength without thermal cycling. A push‐out test was conducted using a universal testing machine until failure. Bond strength values were calculated in megapascals (MPa). The mode of failure was observed using a stereo microscope. Results were analyzed by two‐way ANOVA followed by a Bonferroni post hoc test for comparison. The level of significance was set at p < 0.05. Results Push‐out bond strength was significantly higher (p <0.001) in the CAD/CAM post groups than in the groups with prefabricated posts regardless of the post material, while aging of the teeth did not significantly affect the push‐out strength (p = 0.536). Failures were adhesive between cement and dentin for all groups except for AMC, where adhesive failure between the cement and the post was also observed. Conclusion The CAD/CAM manufacturing technique was proved to ameliorate the retention of the post and cores in the root canal. Thermal cycling did not affect the bond strength of the tested groups.

Within the limitations of this study there was no difference for the same inlay/onlay cavity design between vital and nonvital teeth. In nonvital teeth, it seems that filling the pulp chamber with a ceramic core material is not important. Long-term observation periods are needed to reinforce the clinical behavior outcome.

When fabricating indirect post and core, internal coronal walls are tapered to remove undercuts and allow a better adaptation. To evaluate the fracture strength of anterior tooth reconstructed with post and core and crowned, with two different taper of internal coronal walls, 6° and 30° to the long axis, two groups of 30 clear plastic analogues simulating endodontically treated maxillary central incisors were prepared. The analogues crowned were subjected to a compressive load with a 1-kN cell at a crosshead speed of 0.05 mm/min at 130° to the long axis until fracture occurred. Data were analyzed by Lillifors and Mann–Whitney tests. Mean failure loads for the groups were as follows: group I 1038.69 N (standard deviation ±243.52 N) and group II 1231.86 N (standard deviation ±368.76 N). Statistical tests showed significant difference between groups (p = 0.0010 < 0.01). Increasing the taper of internal coronal walls appears to enhance the fracture resistance of anterior maxillary teeth post and core reconstructed.

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Aim:The study aimed to assess the effect of friction and adhesion on the pushout bond strength of CAD/CAM fiber-reinforced composite (FRC) post and cores in comparison to prefabricated fiber posts. Materials and methods: Thirty extracted single-rooted premolars were divided into three groups (N = 10): CP: CAD/CAM FRC posts (Trilor, Bioloren) cemented with self-adhesive resin cement (Rely X U200, 3M) as control group. CPL: CAD/CAM FRC composite posts cemented with the same self-adhesive resin cement after lubricating the root canal with petroleum jelly (Vaseline, Unilever) to prevent adhesion. RXP: prefabricated posts cemented with self-adhesive resin cement. Specimens were subjected to thermal cycling and then to pushout tests. The mode of failure was observed using a stereomicroscope. Results were analyzed by two-way ANOVA followed by a Tukey's post hoc test for comparison, p = 0.05. Results: Push-out bond strength was significantly lower in the RXP group (8.54 ± 3.35 MPa) in comparison to CP (12.10 ± 1.38 MPa), while no significant differences were concluded between the other groups. Failure was mostly adhesive for CPL and RXP and adhesive and mixed for CP. Conclusion: Custom made CAD/CAM posts have a positive effect on the retention of FRC posts to root canal walls while adhesion between self-adhesive cement and root dentin did not influence significantly the pushout bond strength of CAD/CAM posts to root canal. Clinical significance: The friction of well-adapted CAD/CAM fiber post and cores plays a predominant role in the success of post restorations of endodontically treated teeth.