Abstract
The purpose of this study was to investigate the effect of non-thermal atmospheric pressure plasma (NTP) treatment on the sandblasting of mechanical method and zirconia primer of chemical method used to increase the bond strength between zirconia and resin cement. In this study, Y-TZP was divided into 4 groups according to the surface treatment methods as follows: Zirconia primer (Pr), NTP + Zirconia primer (NTP + Pr), Sandblasting + Zirconia primer (Sb + Pr), Sandblasting + NTP + Zirconia primer (Sb + NTP + Pr). Then, two types of resin cement (G-CEM LinkAce and Rely X-U200) were used to measure the shear bond strength (SBS) and they were divided into non-thermal cycling group and thermal cycling group for aging effect. Statistical analyses were performed using the Kruskal-Wallis test and Mann-Whitney U test. The result of the surface energy (SE), there was no significant difference among the groups (p > 0.05). As a result of the SBS test, the Sb + Pr group had a significantly higher SBS value than the other groups regardless of the resin cement type (p < 0.05), and the decrease rate after thermal cycling treatment was the lowest. On the other hand, the NTP + Pr group showed significantly lower SBS values than the other groups except for the case of using Rely X-U200 (p < 0.05), and the reduction rate after thermal cycling was the highest. The Sb + NTP + Pr group did not differ significantly from the Pr group (p > 0.05). Within the limitations of two successive studies, treatment with NTP after sandblasting used for mechanical bond strength showed a positive effect on initial SBS. However, when NTP was treated before the zirconia primer used for the chemical bond strength, it showed a negative effect on SBS compared to other treatment methods, which was noticeable after the thermal cycling treatment.
Highlights
As the CAD-CAM system was developed and patients’ interest in aesthetics was being increased, Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) was being commonly used in ceramic core material because its favorable physical and esthetic properties [1,2,3]
When non-thermal atmospheric pressure plasma (NTP) was treated before the zirconia primer used for the chemical bond strength, it showed a negative effect on Shear Bond Strength (SBS) compared to other treatment methods, which was noticeable after the thermal cycling treatment
For Rely X-U200 cement, SBS was reduced by 17.63% (Pr), 67.19% (NTP + Pr), 13.53% (Sb + Pr), 27.15% (Sb + NTP + Pr)
Summary
As the CAD-CAM system was developed and patients’ interest in aesthetics was being increased, Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) was being commonly used in ceramic core material because its favorable physical and esthetic properties [1,2,3]. The feldspathic ceramic restorations, which was commonly used before Y-TZP was developed, obtained mechanical retention using hydrofluoric acid etching and chemically altered the surface using primer containing silane coupling agent to increase bond strength with a resin cement [4,5]. These methods were not Materials 2020, 13, 3934; doi:10.3390/ma13183934 www.mdpi.com/journal/materials. No consensus yet exists for what is the effective bonding method to Y-TZP prosthesis [22,23,24]
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