17 June 2020

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How to lute chairside CAD-CAM ceramics

Co-authors: A. Comba, F. Del Bianco

Lorenzo Breschi

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In recent years the use of chairside CAD/CAM ceramics restorations has rapidly increased. The choice of materials includes zirconia-reinforced lithium silicate (VS), infiltrated ceramic with polymers (VE) and nanoceramic resin (GC). Considering the great variety of cementation protocols and luting cements the bond strength of different chairside computer-aided design and computer-aided manufacturing (CAD-CAM) restorative materials to dentin with different resin cements needs to be assayed.            
The study conducted by Seda Ustun et al. tested the in vitro bond strength of different CAD/CAM ceramics materials luted with different resin cement immediately and after thermal aging.  

Materials and Methods
 The occlusal surfaces of 63 molar teeth of similar size were flattened, and rectangular specimens of 2.5 mm in thickness (n=21 per group)  were obtained from zirconia-reinforced lithium disilicate (Vita Suprinity-VS), polymer infiltrated ceramic (Vita Enamic-VE), and resin nanoceramic (GC Cerasmart-GC). The specimens were divided into three subgroups (n=7) and cemented using total etch (TE), self-etch (SE), and self-adhesive (SA) cement systems. The teeth were sectioned vertically into 2 equal parts and half of the specimens were subjected to thermal aging with 5000 cycles. The shear bond strength test of all the specimens was measured. Fractured ceramic surfaces were examined by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) analysis. The Shapiro-Wilk test, 3-way analysis of variance (ANOVA), and Fisher Least Significant Difference (LSD) tests were used to analyze the shear bond strength test data (a=.05).

Results
 From the collected data, the authors showed that the highest bond strength value was found for the group non-thermal aged VS-TE and the lowest for the group thermal aged VE-TE. Significant interaction was found between TE and SE cemented ceramics (P<.001). For specimens cemented with the SA system, significant interaction was found among ceramics with thermal aged specimens (P<.001). Thermal aging significantly decreased the mean bond strength (P<.05).  

Conclusions
 Seda Ustun et al. concluded that, based on the findings of their in vitro study:
 1. TE or SA systems might be recommended for VS ceramic restorations.
 2. Cementation of VE and GC ceramic restorations with SE systems could be recommended.
 3. The thermal aging process significantly reduced the bond strength values of all ceramic materials, regardless of the cementation systems. Total etch and self-adhesive cementation systems can be recommended for Vita Suprinity restorations. To cement GC Cerasmart and Vita Enamic restorations, self-etch cementation systems may be more advantageous.

  For additional information:  Effect of different cement systems and aging on the bond strength of chairside CAD-CAM ceramics.