Evaluating the microleakage between dentin and composite materials.

BACKGROUND: For successful restoration, it is necessary to minimize the microleakage between dentin and the composite material. OBJECTIVES: The purpose of this study was to evaluate the microleakage of 2 different resin cements (self-adhesive and conventional) on dentin treated with acid, sodium hypochlorite (NaOCl), the acid-NaOCl mixture, the erbium-doped yttrium aluminum garnet (Er:YAG) laser, and their combination. MATERIAL AND METHODS: Seventy dentin specimens were divided into 7 groups (n = 10) according to the surface treatment. Then, the specimens were divided into 2 subgroups (n = 35) according to the resin cement used during cementation with prepared composite resin blocks 5 mm × 11 mm × 3 mm: self-adhesive resin cement or conventional resin cement. Microleakage was scored and recorded at the occlusal and gingival levels, along the resin-dentin interfaces. The data was analyzed with the use of univariate analysis of variance (two-way ANOVA) and the Kruskal-Wallis test for both resin subgroups. RESULTS: The obtained results revealed that self-adhesive resin cement and conventional resin cement showed similar microleakage. Etching with sodium hypochlorite, the Er:YAG laser, the acid-NaOCl mixture, and their combination resulted in microleakage comparable to that achieved in acid etching, which is the conventional method of surface treatment. CONCLUSIONS: Microleakage exhibited by self-adhesive resin cement was similar as in the case of conventional resin cement.

The effect of metal primer application and Nd:YAG laser irradiation on the shear-bond strength between polymethyl methacrylate and cobalt-chromium alloy.

OBJECTIVE: The purpose of this study was to compare the shear-bond strengths (SBSs) of an acrylic resin and a cobalt-chromium (Co-Cr) alloy after applying a metal primer, Nd:YAG laser irradiation, or both to the sandblasted surface of the Co-Cr alloy. BACKGROUND DATA: The serviceability of a removable partial denture (RPD) is dependent on the bond strength at the resin-alloy interface. No previously published studies exist on the use of Nd:YAG lasers for preparing the surface of a Co-Cr alloy in an RPD to obtain a high-strength bond between PMMA and the alloy. METHODS: One-hundred twenty Co-Cr alloy specimens were sandblasted and randomly assigned to four equal groups: Group I, sandblasting; Group II, sandblasting + metal primer; Group III, sandblasting + Nd:YAG laser; and Group IV, sandblasting + Nd:YAG laser + metal primer. To establish the most appropriate fluence for modifying the surface of the sandblasted cast specimens, we conducted a preliminary study. Nd:YAG laser irradiation at a fluence of 46.9 J/cm(2) was selected. After the various surface treatments, each alloy specimen was embedded in PMMA to determine the SBS between PMMA and the alloy. RESULTS: Group II and III specimens exhibited higher SBSs than did those of the Group I specimens (p < 0.05), and Group IV specimens showed higher SBSs than did those of the Group II and III specimens (p < 0.05). A significant difference existed in failure types among groups (p < 0.05). Failure type was predominantly adhesive for groups I and III, but predominantly mixed for groups II and IV. CONCLUSIONS: Nd:YAG laser irradiation at a fluence of 46.9 J/cm(2) roughens the sandblasted surface of a Co-Cr alloy and increases the strength of the bond between PMMA and the alloy. This bond strength can be increased further by applying a metal primer to the laser-irradiated surface.

Microtensile bond strength of resin cement to a feldspathic ceramic.

OBJECTIVE: The purpose of this study was to evaluate the microtensile bond strength of resin cement to a feldspathic ceramic after treating the surface with (a) hydrofluoric (HF) acid, (b) air abrasion, (c) Er:YAG laser irradiation, (d) Nd:YAG laser irradiation, and (e) HF acid etching after either air abrasion or laser irradiation. BACKGROUND DATA: It is unknown whether the laser application or its combination with another treatment method can be used as a tool to roughen the surface of a feldspathic ceramic in order to increase the bond strength between the resin cement and ceramic surface. MATERIALS AND METHODS: Forty feldspathic ceramic blocks (Ceramco(TM)) were prepared and divided into eight equal groups (n = 5) according to the following surface treatments: no treatment; etching with 9.5% HF acid; air abrasion with 50 µm Al(2)O(3); Er:YAG laser irradiation; Nd:YAG laser irradiation; air abrasion plus acid etching; Er:YAG laser plus acid etching; and Nd:YAG laser plus acid etching. After surface treatment, a silane-coupling agent and resin cement (Panavia F(TM)) were applied to each block. After storing for 24 h at 37°C and thermocycling between 5°C and 55°C for 1000 cycles, the microtensile bond strength of each specimen was measured. RESULTS: The highest bond strength was obtained from HF acid etching. HF acid etching after each laser irradiation significantly increased the bond strength (p < 0.05). However, HF acid etching after air abrasion decreased bond strength when compared to air abrasion alone. CONCLUSIONS: HF acid etching is the most effective surface treatment method for a feldspathic ceramic. However, laser irradiation with either the Er:YAG or Nd:YAG laser is not an adequate method for improving the bond strength of Panavia F. The laser application should be combined with HF acid etching.

Bond strength of resin cement to yttrium-stabilized tetragonal zirconia ceramic treated with air abrasion, silica coating, and laser irradiation.

OBJECTIVE: The purpose of this study was to evaluate the shear bond strength of a resin cement to yttrium-stabilized tetragonal zirconia (Y-TZP) surfaces treated with air abrasion, silica coating, or CO(2), Er:YAG, or Nd:YAG laser irradiation, or irradiated by each laser after air abrasion. BACKGROUND DATA: Optimized methods are needed to improve the adhesive bonding between resin cement and Y-TZP ceramic. METHODS: Twelve specimens were irradiated with each laser at different parameters and examined by scanning electron microscopy to determine which parameters to use in this study. One hundred forty-one Y-TZP discs were assigned to nine groups: C, no treatment; AA, air abrasion; CJ, silica coating; ER, Er:YAG laser; ND, Nd:YAG laser; CO, CO(2) laser; AA+ER, air abrasion + Er:YAG laser; AA+ND, air abrasion + Nd:YAG laser; AA+CO, air abrasion + CO(2) laser. The composite cylinders were fabricated. After the surface treatments, the specimens were silanized and composite cylinders were cemented with the resin cement. The shear bond strength test was performed after specimens were stored in water for 24 h and after thermocycling for 500 cycles. RESULTS: The highest bond strength was obtained in the AA group and was similar to that of the CJ group. In C, ER, CO, ND, AA+ND, and AA+CO groups, the shear bond strengths were similar to each other according to the Duncan test results. The lowest bond value was obtained in the AA+ER group. CONCLUSION: Although air abrasion and silica coating were the most effective surface treatment methods, CO(2) and Er:YAG laser irradiation alone or Nd:YAG laser irradiation after air abrasion may be used as an alternative treatment method to increase the bond strength between resin cement and Y-TZP material.

Shear bond strength of repair composite resin to an acid-etched and a laser-irradiated feldspathic ceramic surface.

OBJECTIVE: The purpose of this study was to evaluate the shear bond strength of a repair composite resin to a feldspathic ceramic surface that had been either etched with 9.5% hydrofluoric acid (HFA), irradiated by an Er:YAG or Nd:YAG laser, or etched with 9.5% HFA after being irradiated by each laser type. BACKGROUND DATA: New findings have shown that combined laser irradiation and acid etching of a ceramic surface can be used to roughen ceramic surfaces. METHODS: Seventy-eight feldspathic ceramic discs were assigned to six surface treatment groups (n = 13): C, no treatment; HFA, 9.5% HFA etching; ER, Er:YAG laser irradiation; ND, Nd:YAG laser irradiation; ER + HFA, Er:YAG laser irradiation followed by HFA etching; ND + HFA, Nd:YAG laser irradiation followed by HFA etching. The surface of one disc from each treatment group was examined under a scanning electron microscope. After the surface treatments and silanization, a repair composite resin was applied to each disc using a commercial ceramic repair kit. Shear bond strength testing was then done after storing the specimens in distilled water for 24 h at 37 degrees C and thermocycling. Each ruptured specimen was examined under a stereoscopic light microscope. RESULTS: The highest shear bond strength was found after HFA etching, and the lowest was found after Er:YAG laser irradiation. HFA etching also caused the most pronounced changes of all the surface treatments. When HFA was applied after either laser irradiation, the fissures and cracks were larger than those seen on the only laser-irradiated surfaces. CONCLUSIONS: HFA etching is the most effective surface treatment for increasing the shear bond strength between a repair composite resin and a feldspathic ceramic surface. The shear bond strength after laser irradiation can be increased by HFA etching, but the strength of the bond is still smaller than that after HFA etching alone.