ABSTRACT
BACKGROUND AND AIMS: Data are limited about the effect of ceramic primers on the bond of zirconia to restorative resin composite. The aim of this study was to assess the effect of different surface treatments and two ceramic primers on shear bond strength (SBS) of zirconia to restorative resin composite. MATERIALS AND METHODS: 100 samples of zirconium ceramic blocks were randomly divided into 5 groups (n = 20) and received the following surface treatments: a)Control groupb)AL2O3 abrasionc)Nd:YAG laserd)Er:YAG lasere)Bur preparation.Next, each group was divided into two subgroups of 20. In ten out of 20 specimens in each group, monobond plus and Tetric ceram composite resin were applied on the surface. ZPrime Plus and Elite composite were applied on the surfaces of the remaining 10 specimens in each group. Samples were then subjected to shear bond strength test in a universal testing machine until fracture. The mean SBS were calculated and statistically analyzed by two-way ANOVA and T-Test. P < 0.05 was considered statistically significant. RESULTS: In ZPrime plus subgroups, diamond bur yielded the highest bond strength. Laser groups showed no significant difference with the control group. In monobond plus subgroups, SBS of air abrasion and diamond bur subgroups was highest and Nd:YAG laser showed the lowest SBS. The lowest bond strength belonged to the Nd:YAG laser subgroup of monobond plus group. CONCLUSIONS: Type of surface preparation significantly affected the bond strength.
ABSTRACT
OBJECTIVES: Chipping is one of the concerns related to zirconia crowns. The reasons of chipping have not been completely understood. This in-vitro study aimed to assess the effect of coping design on the fracture resistance of all-ceramic single crowns with zirconia frameworks. MATERIALS AND METHODS: Two types of zirconia copings were designed (n=12): (1) a standard coping (SC) with a 0.5mm uniform thickness and (2) a modified coping (MC) consisted of a lingual margin of 1mm thickness and 2mm height connected to a proximal strut of 4mm height and a 0.3mm-wide facial collar. After veneer porcelain firing, the crowns were cemented to metal dies. Afterwards, a static vertical load was applied until failure. The modes of failure were determined. Data were calculated and statistically analyzed by independent samples T-test. P<0.05 was considered statistically significant. RESULTS: The mean and standard deviation (SD) of the final fracture resistance equaled to 3519.42±1154.96 N and 3570.01±1224.33 N in SC and MC groups, respectively; the difference was not statistically significant (P=0.9). Also, the mean and SD of the initial fracture resistance equaled to 3345.34±1190.93 N and 3471.52±1228.93 N in SC and MC groups, respectively (P=0.8). Most of the specimens in both groups showed the mixed failure mode. CONCLUSIONS: Based on the results, the modified core design may not significantly improve the fracture resistance.
ABSTRACT
OBJECTIVE: The aim of this study was to assess the surface of yttrium-stabilized tetragonal zirconia (Y-TZP) after surface treatment with lasers and airborne-particle abrasion. MATERIALS AND METHODS: First, 77 samples of presintered zirconia blocks measuring 10 × 10 × 2 mm were made, sintered and polished. Then, they were randomly divided into 11 groups (n=7) and received surface treatments namely, Er:YAG laser irradiation with output power of 1.5, 2 and 2.5 W, Nd:YAG laser with output power of 1.5, 2 and 2.5 W, CO2 laser with output power of 3, 4 and 5 W, AL2O3 airborne-particle abrasion (50µ) and no treatment (controls). Following treatment, the parameters of surface roughness such as Ra, Rku and Rsk were evaluated using a digital profilometer and surface examination was done by SEM. RESULTS: According to ANOVA and Tukey's test, the mean surface roughness (Ra) after Nd:YAG laser irradiation at 2 and 2.5 W was significantly higher than other groups. Roughness increased with increasing output power of Nd:YAG and CO2 lasers. Treated surfaces by Er:YAG laser and air abrasion showed similar surface roughness. SEM micrographs showed small microcracks in specimens irradiated with Nd:YAG and CO2 lasers. CONCLUSION: Nd:YAG laser created a rough surface on the zirconia ceramic with many microcracks; therefore, its use is not recommended. Air abrasion method can be used with Er:YAG laser irradiation for the treatment of zirconia ceramic.
