ABSTRACT
Introduction: Some studies have shown that laser irradiation on unpolymerized adhesives can improve composite-dentin adhesion. The aim of the present study was to evaluate the effect of the diode laser (810 nm) on the microleakage of multi-mode adhesive systems at enamel and dentin margins of composite restorations. Methods: Classic class V boxes were prepared on 48 sound premolar teeth and randomly divided into 6 groups (n=16). In the control groups, Scotchbond Universal (SBC), G-Premio (GBC), and Ambar U (AMC) were used by a self-etch mode. In the test groups (SBL, GBL, ABL), the 810 nm diode laser was irradiated (1 W) for 10 seconds before the polymerization of the adhesive. The boxes were restored by the resin composite. After finishing and polishing, the samples were thermocycled (5°C to 55°C) for 1000 cycles and then immersed in 0.1% methylene blue dye (48 hours). Dye penetration through the gingival and occlusal margins was measured by Stereomicroscope. The data were analyzed at the 5% significance level using Kruskal-Wallis and Mann-Whitney U tests. Results: Significant differences were found between the control and test groups (P < 0.05). The occlusal margins of the SBL and GBL groups and the cervical margin of the SBL group exhibited the lowest microleakage (P < 0.05). The AM control group showed maximum microleakage at cervical and occlusal margins. Conclusion: The irradiation of the 810 nm diode laser on the unpolymerized universal adhesive systems in a self-etch mode caused a significant reduction in enamel and dentin marginal microleakage of composite restorations.
ABSTRACT
BACKGROUND: One of the major limitations of zirconia ceramic is the difficulty to adhere to dental. Said adhesion improves the marginal sealing of the restoration, minimizing microleakage. According to the limitation of zirconia ceramic bonding, zirconia primer enhances bond strengths to Zirconia, Alumina and Metal substrates. Purpose: the aim of the current study was to determine effect of Z-primer on the shear bond strength of zirconia ceramic to dentin. MATERIAL AND METHODS: 28 newly extracted intact premolars and divided into 4 groups (n=7). In group 1, resin-based (Duo-link; Bisco, Schaumburg, IL) cement was used without applying Z-primer. In group 2, resin-based (Duo-link; Bisco, Schaumburg, IL) cement was used with applying Z-primer. In group 3, resin-based cement (Panavia F2; Kurary, Japan) was used without Z-primer. In group 4, resin- based cement (Panavia F2) with Z-primer was used. Zirconia ceramic blocks (4×4×2mm) without sandblasting were applied onto the surface of dentin then cured from 3 dimensions for 20S. Shear bond strength test was carried out after 24h. Stereo microscope was used to evaluate the zirconia ceramic and dentin topography and failure mode. RESULTS: According to the data, significant difference detected on after application of the Z-primer compared to the other groups (p<0.001). No significant difference detected between 2 types of resin cements (p>0.05). However, the highest SBS observed in second group (Duo-link(+)Zprimer) while lowest detected in first group (Duo-link(-)Zprimer). CONCLUSIONS: These results suggested application of the Z-primer increased shear bond strength between zirconia ceramic and dentin. Key words:Flexural strength, monolithic zirconia, sintering temperature, sintered-holding time.