Effect of pretreatment of root dentin surface with cold atmospheric plasma on improving the bond strength of fiber post and resin cement: In vitro study.

INTRODUCTION: Achieving stable adhesion between fiber post and interradicular dentin is a challenging process in the restoration of endodontically treated teeth. This study was conducted to investigate the effect of surface pretreatment with cold atmospheric plasma (CAP) on improving the bond strength between them. MATERIALS AND METHODS: Forty-eight single-canal mandibular premolars were cut 1 mm above the cementoenamel junction to keep the root length of 14 mm or more. After endodontic treatment and preparation of the post space, the teeth were divided into four groups regarding the pretreatment of dentin surfaces, including normal saline, ethylenediaminetetraacetic acid (EDTA), CAP, and CAP + EDTA groups. The data were analyzed using paired and independent t-test and one-way analysis of variance and the significance level was set at p < .05. RESULTS: The bond strength was significantly higher in the coronal third than in the apical third in all the groups. Moreover, the bond strength was significantly higher in the CAP + EDTA-treated group. The bond strength increased significantly in the CAP group compared to the normal saline group. In addition, the bond strength increased significantly in the CAP or EDTA groups compared to the control group. The lowest bond strength belonged to the control group (normal saline). CONCLUSION: The surface pretreatment with CAP (alone or in combination with EDTA) played a significant role in improving the bond strength of fiber post and root canal dentin.

Effect of Nonthermal Plasma on Shear Bond Strength of Translucent Zirconia in Layering Ceramic.

Background: Today, various methods are used to increase the bond strength of zirconia in layering ceramics. This study evaluated the effects of nonthermal argon plasma on zirconia shear bond strength to layering porcelain. Materials and Method. In this experimental study, 42 square blocks of zirconia were prepared and randomly divided into three groups (n = 14) according to the applying surface treatment: (1) the control group (without any surface treatment), (2) the plasma-treated group with argon nonthermal plasma, and (3) the air abrasion group with 50 µm Al2O3 particles. All samples were layered with porcelain. One sample from each group was evaluated by electron microscopy (SEM) to examine the cross-sectional area of the zirconia-ceramic bond. The rest of the specimens were subjected to thermocycling with 5,000 baths to imitate the aging process in the mouth and then were tested for shear bond strength. The failure pattern of the samples was examined by stereomicroscope. Bond strength data were analyzed by one-way ANOVA test in three groups and Tamhane post hoc test in pairs. The significance level of p-value was considered 0.05. Results: The shear bond strength of the plasma-treated group was significantly higher than the control group (p = 0.032) but the shear bond strength between the sandblast and the plasma-treated group was not significantly different (p = 0.656). The shear bond strength between the sandblast and the control group was also not significant (p = 0.202). Regarding the mode of failure, failures were mostly adhesive and then mixed. Examination of the samples under SEM showed that the bond area is the thickest in the sandblast group and also the surface roughness is the highest in the sandblast group and the lowest in the control group. Conclusion: This study demonstrated that the use of nonthermal argon plasma treatment is an effective way to enhance the quality and quantity of shear bond strength between layering porcelain and zirconia.