Effects of cement-curing mode and light-curing unit on the bond durability of ceramic cemented to dentin

Light Transmission of Various Aesthetic Posts at Different Depths and Its Effect on Push-Out Bond Strength, Microhardness of Luting Cement

Background and Objectives: One requirement for the cemented post is the light transmittance on its entire length up to the deepest portion of a root canal to ensure the complete polymerization of resin cement. This study aimed to determine the light transmission ability in different aesthetic posts at different depths and its effect on the push-out bond strength and microhardness of luting cement at the corresponding interface. Materials and Methods: Twenty endodontic posts from glass fiber posts (GFP), zirconia ceramic posts (ZCP), and highly translucent zirconium oxide posts (HTZP) were sequentially sectioned into 12.8 and 4 mm lengths after recording the light intensity using a dental radiometer. Sixty single rooted premolar teeth root canals were treated and implanted vertically in a resin block. The post space was prepared and cemented with GFP, ZCP, and HTZP posts with twenty samples each. The root portion of teeth samples were sectioned into cervical, middle, and apical portion. A universal testing machine was utilized for the push-out bond strength test for the first ten samples from each group. The remaining ten samples from each group were used for the microhardness test using a micro-indenter instrument. The data were statistically analyzed using one-way Analysis of variance and Tukey HSD tests at p < 0.05. Results: The GFP endodontic postpresented with significant highest light translucency compared to HTZP, which was significantly higher than ZCP. GFP posts showed significantly higher bond strength per unit area compared to ZCP at analogous cross sections. The hardness of luting cement was also significantly higher amongst all tested endodontic posts. Conclusions: GFP high light translucency enhanced the curing of the luting resin cement that resulted in harder cement and a stronger bond supported by hardness and push-out tests. These findings suggest that GFP is preferred to be used with light-cured luting cements for restoration of endodontically treated teeth.

Ceramic Inlays: Effect of Mechanical Cycling and Ceramic Type on Restoration-dentin Bond Strength

This study aimed to evaluate the bond strength between dentin and five different ceramic inlays in permanent maxillary premolars, with and without mechanical cycling. One hundred permanent maxillary premolars were prepared and divided into 10 groups (n=10) according to the ceramic system (IPS e.Max Press; IPS e.Max CAD; Vita PM9; Vita Mark II; and Vita VM7) and the mechanical cycling factor (with and without [100 N, 2 Hz, 1.2×106 cycles]). The inlays were adhesively cemented, and all of the specimens were cut into microbars (1×1 mm, nontrimming method), which were tested under microtensile loading. The failure mode was classified and contact angle, roughness, and microtopographic analyses were performed on each ceramic surface. The mechanical cycling had a significant effect (p=0.0087) on the bond strength between dentin and IPS e.max Press. The Vita Mark II group had the highest bond strength values under both conditions, with mechanical cycling (9.7±1.8 MPa) and without (8.2±1.9 MPa), while IPS e.Max CAD had the lowest values (2.6±1.6 and 2.2±1.4, respectively). The adhesive failure mode at the ceramic/cement interface was the most frequent. Vita Mark II showed the highest value of average roughness. IPS e.max Press and Vita Mark II ceramics presented the lowest contact angles. In conclusion, the composition and manufacturing process of ceramics seem to have an influence on the ceramic surface and resin cement bond strength. Mechanical cycling did not cause significant degradation on the dentin and ceramic bond strength under the configuration used.