Bonding Strength of Lithium Disilicate Adhesive Crowns with Different Occluso-Cervical Preparation Heights and Cement Types

The aim of this study was to evaluate if adhesion technology with CAD/CAM can compensate for the reduction of occluso cervical preparation heights using different types of dental cement. The de-bonding failure types were then assessed. Here, 72 caries-free extracted human premolar teeth were prepared to have a remaining occlusal height of two, three, and four mm. IPS e.max lithium disilicate CAD/CAM crowns were cemented with adhesive resin cement Panavia SA, self-adhesive resin cement, RelyX Unicem Aplicap, and zinc phosphate cement. The cementation techniques were based on the manufacturer’s instructions. After thermocycling, all samples were tested for tensile bond strength via an Instron machine. One-way analysis of variance (ANOVA) with post hoc testing (P < 0.05) was performed. The means TBS for the two, three, and four-mm OCHP groups were 2.72±0.69, 3.06±0.82, and 3.25±0.79.0 MPa; ARC, SARC, and ZPC were 3.41±0.51, 3.45±0.41, 2.08±0.35 MPa, respectively with significant differences in both. The mixed cement had failures in the resin cement groups. Failure was predominantly cohesive in the zinc phosphate group. Resin cement had the highest SBS values versus ZPC values when both bonded to lithium disilicate crowns with different occlusal heights. The failure of the adhesive to the crown and/or to the tooth were the highest for the four types of resin cement. Around 25% were cohesive failures with resin cement, but this was predominately adhesive in crowns in zinc phosphate regardless of the preparation heights.

Comparison between Hydrofluoric Acid and Single-Component Primer as Conditioners on Resin Cement Adhesion to Lithium Silicate and Lithium Disilicate Glass Ceramics

This study aimed at evaluating the effects of different surface conditionings on the microshear bond strength (µSBS) of a self-adhesive resin cement to VITA Suprinity (ZLS) and IPS e.max CAD (LD). Three surface conditioning protocols were performed on ZLS and LD before luting with a self-adhesive resin cement (RelyX Unicem 2, RXU): hydrofluoric acid (HF), HF + silane (HF + S), or Monobond Etch & Prime (EP). In each group, 15 cylindrical buildups of RXU were prepared on five milled bars and submitted to a µSBS test. Data were statistically analyzed with two-way ANOVA and Tukey’s post hoc test (p < 0.05). Failure modes were recorded and classified as adhesive, mixed, cohesive in resin, or ceramic, and statistically analyzed with Fisher’s exact test (p = 0.05). One additional bar per group was used for the morphological characterization of the conditioned surface by means of SEM. The material per se did not significantly influence adhesion (p = 0.744). Conditioning protocol was a significant factor: EP yielded significantly higher μSBS than HF (p = 0.005), while no significant differences emerged between EP and HF + S (p = 0.107), or HF + S and HF (p = 0.387). The material-conditioning protocol interaction was not statistically significant (p = 0.109). Significant intergroup differences were found in distribution of failure modes: mixed failures were predominant in the ZLS/EP group, while the other groups showed a prevalence of adhesive failures. The self-etching primer showed promising results in terms of immediate bond strength of a self-adhesive resin cement to lithium-silica-based glass ceramics, suggesting its alternative use to hydrofluoric acid and silane conditioning protocols.

Influence of cement type on the fracture resistance of resin nanoceramic crowns over knife-edge margins: A pilot study

Objective: To evaluate the influence of the type of cement on the fracture resistance of full-contour resin nanoceramic crowns cemented over preparations with knife-edge margins. Methods: A right lower premolar typodont model was prepared with a 1.5-mm axial reduction, a 2.0-mm occlusal reduction, and a knife-edge vertical margin. An anatomical crown was designed from the digital scanning of the preparation using CAD/CAM software. Then, 20 crowns were milled from resin nanoceramic CAD/CAM blocks (Cerasmart270™) as well as a replica of the dental preparation in a cobalt-chrome alloy. The 20 crowns were randomly divided into two groups. Group 1 crowns were cemented with self-adhesive resin cement (G-CEM LinkAce™) and group 2 crowns with resin-modified glass ionomer cement (FujiCEM™ 2). Subsequently, they were subjected to a loading test on an Instron universal testing machine until fracture occurred. The data were statistically analyzed using the parametric Student’s t-test (α=0.05). Results: The type of cement was shown to have a statistically significant effect on the crowns’ fracture resistance (p <0.001). Group 1 presented a mean of 1284.3±340.19 Newtons, much higher than the mean recorded in group 2, of 417.9±106.35 Newtons, with an increase of 207.3% in the fracture resistance after self-adhesive luting. Conclusions: Resin nanoceramic crowns cemented with self-adhesive resin cement showed considerably higher fracture resistance than those cemented with resin-modified glass ionomer cement.

Effect of Glass Fiber Post Surface Treatment on Bond Strength of a Self-Adhesive Resin Cement: An “In Vitro” Study

Objective. This study evaluated the influence of different mechanical and chemical surface treatments alone and combined with silane on the bond strength (BS) of glass fiber posts (GFPs) using self-adhesive resin cement. Methods. Eighty-four single-rooted bovine teeth (six groups, n = 14) were submitted to BS analysis after GFP cementation. The treatments applied in the studied groups were no surface treatment (control), silane (S), 24% hydrogen peroxide (PER), 24% hydrogen peroxide and silane (PER + SIL), blasting with 50 μm aluminum oxide particles (BLAST), and blasting with 50 μm aluminum oxide particles and silane (BLAST + SIL). Results. BS differed significantly among groups ( p < 0.001). It was higher in the SIL (10.5 ± 3.5 MPa), BLAST + SIL (11.5 ± 3.2 MPa), and PER + SIL (11.6 ± 4.6 MPa) groups than in the control (6.5 ± 2.9 MPa), BLAST (8.6 ± 4.0 MPa), and PER (7.1 ± 2.8 MPa) groups, with no significant difference among groups receiving silanization. Cement post adhesive failure was more common in the SIL, BLAST, and PER + SIL groups, and cement-dentin adhesive failure was more common in the control, BLAST + SIL, and PER groups. Conclusion. These results show that silane application alone increases BS.