Effect of engraving speeds of CO2 laser irradiation on In-Ceram Alumina roughness: a pilot study.

OBJECTIVES: The aim of the study was to determine the effect of CO2 laser on surface roughness of In-Ceram-Alumina-ceramic. MATERIALS AND METHODS: Four aluminum-oxide ceramic disc specimens were prepared of In-Ceram Alumina. Discs received CO2 laser irradiation with different engraving speeds (100, 400, 600 and 800 mm/min) as a surface treatment. The roughness of the surfaces was measured on digital elevation models reconstructed from stereoscopic images acquired by scanning-electron-microscope. Surface roughness data were analyzed with One-Way-Analysis-of-Variance at a significance level of p<0.05. RESULTS: There was no significant difference between the roughness values (p=0.82). Due to higher laser durations, partial melting signs were observed on the surfaces. Tearing, smearing and swelling occurred on melted surfaces. Swelling accompanying melting increased the surface roughness, while laser power was fixed and different laser engraving speeds were applied. CONCLUSION: Although different laser irradiation speeds did not affect the roughness of ceramic surfaces, swelling was observed which led to changes on surfaces.

Effect of repeated firings on microtensile bond strength of In-Ceram Alumina with two different veneering ceramics.

Microtensile bond strengths of In-Ceram Alumina cores veneered with two ceramics after different numbers of firing cycles were evaluated. After In-Ceram Alumina cores were fabricated, they were veneered with either Vitadur Alpha or Vita VM7. A control group of each core-veneer combination was fired twice, and a second group was fired five times to induce thermal fatigue. Obtained microbars were subjected to microtensile bond strength tests. Data were analyzed using two-way analysis of variance. Microtensile bond strength values for Vita VM7 specimens were higher than those for Vitadur Alpha (P < .001). Although the number of firing cycles revealed no change in bond strength, the veneering material proved to be an important factor.

Effect of bleaching on staining susceptibility of resin composite restorative materials.

STATEMENT OF THE PROBLEM: Effect of bleaching procedures on staining susceptibility of resin restorative materials is still questionable. PURPOSE: The aim of this study was to evaluate the staining susceptibility of restorative materials bleached with 20% carbamide peroxide home bleaching agent and subsequently immersed in coffee and tea. MATERIALS AND METHODS: Forty-two disk-shaped specimens were fabricated for each of the resin composites (Filtek Supreme XT [3M ESPE, St. Paul, MN, USA], Ceram-X Mono [Dentsply, Konstanz, Germany], and Aelite All Purpose Body [BISCO, Inc., Shaumburg, IL, USA]). The baseline color values were measured with a spectrophotometer. The specimens of each restorative material were randomly divided into two groups (N = 21). While the first group specimens were stored in distilled water (nonbleaching group-control), bleaching agent (Opalescence PF 20% [Ultradent Poducts, South Jordan, UT, USA]) was applied on the top surface of each specimen of the second group (bleaching group). After color change values were measured, the specimens were randomly divided into three subgroups (N = 7) according to the staining solutions. The color change values (DeltaE*ab) were calculated and the data were subjected to analysis of variance. Statistical significance was declared if the p value was 0.05 or less. RESULTS: There was no statistically significant difference within each restorative material's DeltaE*ab values after bleaching (p = 0.714). Also, the staining solutions did not cause a statistically significant difference between DeltaE*ab values of bleaching compared with nonbleaching groups (p = 0.146). Significant interaction was found only between restorative materials and staining solutions (p = 0.000). CONCLUSION: Bleaching of the tested resin composites did not increase their susceptibility to extrinsic staining in vitro. CLINICAL SIGNIFICANCE Bleaching did not affect staining susceptibility of the tested resin composite restorative materials. (J Esthet Restor Dent 21:407-415, 2009).

Surface roughness and bond strengths of glass-infiltrated alumina-ceramics prepared using various surface treatments.

OBJECTIVES: To compare and evaluate effects of CO(2) laser and conventional surface treatments on surface roughness and shear bond strengths of glass-infiltrated alumina-ceramics to dentin. METHODS: One hundred fifty ceramic discs of In-Ceram Spinell, In-Ceram Alumina and In-Ceram Zirconia (n=50) were prepared. Specimens which were divided into 5 groups (n=10) were untreated (control group), sandblasted, airborne particle abraded, etched with 9.6% hydrofluoric acid or irradiated with CO(2) laser. Scanning electron microscope was used at 1000x magnification for qualitative examination. Following surface roughness (Ra) determination by profilometry, discs were cemented on extracted-human-molar teeth. Cemented specimens were stored in distilled water at 37 degrees C for 1 week. Shear bond strength (MPa) test was performed using a universal testing machine at a crosshead speed of 1mm/min. Statistical comparisons were made with Wilcoxon signed ranked test, Kruskall Wallis test and Spearman's correlation coefficient. RESULTS: All surface treatments produced rougher surfaces than the untreated groups of all ceramics (P<.05). Sandblasting demonstrated a rougher surface on In-Ceram Spinell than In-Ceram Alumina and In-Ceram Zirconia (P<.05). While CO(2) laser irradiation showed significantly higher bond strength for In-Ceram Spinell (P<.05), both airborne particle abrasion and CO(2) laser irradiation showed higher bond strengths for In-Ceram Zirconia (P<.05). Airborne particle abrasion demonstrated higher bond strength for In-Ceram Alumina and In-Ceram Zirconia (P<.05). No significant relationship was determined between surface roughness (Ra) and shear bond strength values (MPa) among ceramic groups. CONCLUSIONS: Sandblasting is an effective surface treatment for roughening surfaces of In-Ceram Spinell. Although CO(2) laser irradiation does not increase surface roughness, it reveals the highest bond strength.

The implant-abutment interface of alumina and zirconia abutments.

BACKGROUND: Although ceramic and titanium abutments are widely used in clinical practice, the mechanical characterization of the implant-abutment interface for ceramic abutments has not been evaluated after the dynamic loading. PURPOSE: The purpose of this study was to assess the implant-abutment interface after the dynamic loading of titanium, alumina, and zirconia abutments. MATERIALS AND METHODS: Fifteen aluminum oxide, zirconium oxide, and titanium abutments were manufactured by the Procera System (Nobel Biocare AB, Göteborg, Sweden) and were connected to Ø 3.75 x 13-mm regular platform implants (MK III, Nobel Biocare AB) secured in a 30 degrees inclined plane. A mechanical testing machine applied compressive dynamic loading between 20 and 200 N at 1 Hz on a standard contact area of copings cemented on abutments for 47.250 cycles. The measurements of microgaps at the implant-abutment interface from the labial, palatinal, mesial, and distal surfaces of each specimen were undertaken by scanning electron microscope analyses prior to and after the experiments. The data of the microgaps before and after the dynamic loading were statistically assessed using the Wilcoxon signed rank test and the Kruskal-Wallis variance analysis (alpha = 0.05). RESULTS: Coping fracture, abutment fracture, or abutment screw loosening or fracture was not detected in any specimen during the entire test period. After the dynamic loading, the titanium abutment control group revealed an increased microgap (3.47 microm) than zirconia (1.45 microm) and alumina (1.82 microm) groups at the palatinal site (p < .05). The mean measurement values at different measurement sites of specimens within and between each abutment group were similar (p > .05). CONCLUSION: Owing to their comparable microgap values at the implant-abutment interface after the dynamic loading, ceramic abutments can withstand functional forces like conventional titanium abutments.