Effect of Surface Coating on Bond Strength between Etched Feldspar Ceramic and Resin-Based Luting Agents

Interfacial fracture toughness of different surface treatments on zirconia-reinforced lithium silicate glass-ceramics

This study investigated the influence of different surface treatments on unfiring or firing zirconia-reinforced lithium silicate (ZLS) glass-ceramics. Celtra Duo and IPS e.max CAD blocks were cut and process following manufacturer protocols. The specimen surface was treated with seven different protocols. Two ceramic blocks with the same surface treatment were bonded with luting agent and prepared for mini-interfacial fracture toughness tests (mini-iFT). The specimens were tested after 1-week storage. The data was statistically analyzed using two-way ANOVA and Dunnett's T3 comparison (α=0.05). The highest mini-iFT of both Celtra Duo unfired and fired was shown in the HF+S group, which was not significantly different from HF+S+UA. For IPS e.max CAD, the mini-iFT was higher in the groups treated with hydrofluoric acid. Additional adhesive after silane application did not significantly improve bonding effectiveness. Therefore, surface treatment with hydrofluoric acid and silane is recommended for both unfiring and firing ZLS glass ceramics.

Effect of Resin Cement at Different Thicknesses on the Fatigue Shear Bond Strength to Leucite Ceramic

OBJECTIVES

 This in vitro study was performed to evaluate fatigue survival by shear test in the union of leucite-reinforced feldspathic ceramic using different cement thicknesses.

MATERIALS AND METHODS

 Leucite-reinforced glass ceramics blocks were sectioned in 2-mm thick slices where resin cylinders were cemented. The samples were distributed in two experimental groups (n = 20) according to the cement thickness (60 and 300 μm). The specimens of each group were submitted to the stepwise fatigue test in the mechanical cycling machine under shear stress state, with a frequency of 2 Hz, a step-size of 0.16 bar, starting with a load of 31 N (1.0 bar) and a lifetime of 20,000 cycles at each load step.

RESULTS

 The samples were analyzed in a stereomicroscope and scanning electron microscopy to determine the failure type. There is no significant difference between the mean values of shear bond strength according to both groups. Log-rank (p = 0.925) and Wilcoxon (p = 0.520) tests revealed a similar survival probability in both cement layer thicknesses according to the confidence interval (95%). The fracture analysis showed that the mixed failure was the most common failure type in the 300-μm thickness group (80%), while adhesive failure was predominant in the 60-μm thickness group (67%). The different cement thicknesses did not influence the leucite ceramic bonding in fatigue shear testing; however, the thicker cement layer increased the predominance of the ceramic material failure.

CONCLUSION

 The resin cement thicknesses bonded to leucite ceramic did not influence the long-term interfacial shear bond strength, although thicker cement layer increased the ceramic material cohesive failure. Regardless the cement layer thickness, the shear bond strength lifetime decreases under fatigue.

Do different protocols affect the success rate or bond strength of glass-ceramics repaired with composite resin? A systematic review and meta-analysis

STATEMENT OF PROBLEM

Intraoral repair techniques prevent unnecessary replacement of ceramic restorations, thereby increasing the survival rate. However, adhesion between ceramics and the composite resin is challenging and how different protocols influence adhesion is unclear.

PURPOSE

The purpose of this systematic review and meta-analysis was to analyze the influence of different protocols on repairing glass-ceramic surfaces with composite resins.

MATERIAL AND METHODS

PubMed, Scopus, ISI Web of Science, and Embase electronic databases were searched to select studies comparing bond strength values or survival rates of glass-ceramic repaired with composite resins using different surface treatment protocols. No publication year or language restriction was applied. Data sets were extracted from all included studies, and the mean differences calculated. A 95% confidence interval was calculated by using the random effect model (Rev Man 5.4).

RESULTS

The search identified 5037 studies, and 165 were assessed for eligibility. Finally, 123 in vitro studies were included in the systematic review and 48 in the meta-analysis. Considering different glass-ceramics, bond strength tests, and aged or not aged specimens, 37 meta-analyses found the effect of repair protocols: only adhesive, silane plus adhesive alone or preceded by hydrofluoric (HF) acid, airborne-particle abrasion (APA) with Al2O3 particles, silica-coated APA (SCAPA), diamond rotary instrument (DRI), and laser irradiation (LI).

CONCLUSIONS

For feldspathic porcelain, HF acid, APA, SCAPA, or DRI improved the repair micromechanical retention; applying silane is essential to HF-conditioned surfaces but the use of adhesive is optional when silane is applied. Results for leucite and lithium disilicate were inconclusive in terms of suggesting a treatment other than HF acid plus silane and adhesive applications.

Do preheated composite resin or adhesive resin layer strengthen the feldspar ceramic?

STATEMENT OF PROBLEM

Preheated composite resin and adhesive coating have been recommended as luting agents for ceramic veneers; however, information about the mechanical behavior of feldspathic porcelain veneers after using these methods is still limited.

PURPOSE

The purpose of this in vitro study was to evaluate the influence of the use of preheated composite resin or an adhesive resin layer on the strengthening of a feldspathic porcelain.

MATERIAL AND METHODS

Feldspathic porcelain disks were fabricated (N=210), etched (10% hydrofluoric acid for 90 seconds), and bonded according to resin-based luting agents (30 per group) for the biaxial flexural strength tests: photopolymerized resin cement, flowable composite resin, preheated composite resin, with or without previous adhesive coating. Characteristic strength and Weibull modulus were calculated. The viscosity of the luting agents was measured by using isothermal analyses. Finite element analysis simulated the flexural test. Fractographic and bonded interfaces were observed.

RESULTS

The use of preheated composite resin led to the lowest stress levels in the feldspathic porcelain veneers. However, it did not increase the ceramic strengthening compared with other luting agents, as higher values were observed with flowable composite resin (P<.05). The use of an adhesive resin layer had no significant effect on ceramic strengthening when associated with preheated composite resin or resin cement (P>.05). Preheated composite resin presented the highest viscosity and led to incomplete filling of the porcelain surface irregularities. Failures originated on the ceramic surface subjected to tensile stress and were typically associated with pores at the ceramic-luting agent interface.

CONCLUSIONS

The use of preheated composite resin or an adhesive resin layer did not have a positive effect on strengthening feldspathic porcelain.