In vitro evaluation of surface roughness of titanium abutments after air polishing with different abrasive powders.

OBJECTIVES: The purpose of this study was to evaluate the effects of air polishing with sodium bicarbonate and erythritol powders on surface roughness and morphological changes in titanium abutments. METHODS: A total of 45 grade V titanium discs were divided in three groups: Group A (Control) air polished with air/water; Group B, air polished with sodium bicarbonate powder; and Group C, air polished with erythritol powder. After air polishing, the samples' roughness (Sa) in micrometres were analysed with an optical profilometer. The samples' surface morphology study was conducted via scanning electronic microscope (SEM). Data were described using mean and standard deviation of roughness values (Sa). Inferential analysis was performed using the ANOVA multiple comparison test followed by Tukey's post hoc test. Both tests used a 5% level of significance. RESULTS: After air polishing, average roughness of group A, B and C were 0.036, 0.046 and 0.037 µm, respectively, with statistically significant differences between groups A and B (p < 0.05). No statistically significant differences were found between group A and group C, as well as between group B and C (p > 0.05). As for the morphology analysis, damages to the titanium surface were only observed in group B. CONCLUSIONS: The study indicates that air polishing with erythritol powder maintains titanium abutment integrity better than sodium bicarbonate, which increased surface roughness and caused damage. Erythritol is preferable for minimizing surface alterations and maintaining morphological stability.

Influence of solvents and composition of etch-and-rinse and self-etch adhesive systems on the nanoleakage within the hybrid layer.

AIM: The goal of this study was to evaluate nanoleakage within the hybrid layer yielded by etch-and-rinse and self-etch adhesive systems, with different solvents and compositions. MATERIALS AND METHODS: Four adhesives were applied onto 20 human dentin disks: group A: Adper Scotchbond 1XT(™) (3M ESPE), group B: One Coat Bond(®) (Coltène Whaledent), group C: AdheSE(®) (Ivoclar Vivadent) and group D: Xeno-V(®) (Dentsply). The samples were immersed in aqueous ammoniacal silver nitrate for 24 hour, prepared and observed under field-emission scanning electron microscopy with backscattered electrons. Microphotographs were scanned and data were processed. The mean value and standard deviation were calculated. Kruskal- Wallis and Mann-Whitney tests were used (p < 0.05). RESULTS: All the adhesives showed nanoleakage within the hybrid layer: Adper Scotchbond 1XT(™) (218.5 µm ± 52.6 µm), One Coat Bond(®) (139.6 µm ± 79.0 µm), AdheSE(®) (92.7 µm ± 64.8 µm) and Xeno-V(®) (251.0 µm ± 85.2 µm). AdheSE(®) yielded less nanoleakage than Adper Scotchbond-1XT(™) (p = 0.003) and than Xeno-V(®) (p = 0.007). No other statistically significant differences were detected. CONCLUSION: Two-step self-etch adhesive system (AdheSE(®)) might contribute for lower nanoleakage deposition and thus better performance in dentin adhesion. CLINICAL SIGNIFICANCE: The two-step self-etch adhesive system showed the lowest nanoleakage deposition compared with the other adhesive systems evaluated, which seems to indicate a better behavior when a restoration is performed in dentin and possibly can lead to a durable adhesion along time.

Effect of ozone gas on the shear bond strength to enamel.

UNLABELLED: Ozone is an important disinfecting agent, however its influence on enamel adhesion has not yet been clarified. OBJECTIVE: Evaluate the influence of ozone pretreatment on the shear strength of an etch-and-rinse and a self-etch system to enamel and analyze the respective failure modes. MATERIAL AND METHODS: Sixty sound bovine incisors were used. Specimens were randomly assigned to four experimental groups (n=15): Group G1 (Excite® with ozone) and group G3 (AdheSE® with ozone) were prepared with ozone gas from the HealOzone unit (Kavo®) for 20 s prior to adhesion, and groups G2 (Excite®) and G4 (AdheSE®) were used as control. Teeth were bisected and polished to simulate a smear layer just before the application of the adhesive systems. The adhesives were applied according to the manufacturer's instructions to a standardized 3 mm diameter surface, and a composite (Synergy D6, Coltene Whaledent) cylinder with 2 mm increments was build. Specimens were stored in 100% humidity for 24 h at 37°C and then subjected to a thermal cycling regimen of 500 cycles. Shear bond tests were performed with a Watanabe device in a universal testing machine at 5 mm/min. The failure mode was analyzed under scanning electron microscope. Means and standard deviation of shear bond strength (SBS) were calculated and difference between the groups was analyzed using ANOVA, Kolmogorov-Smirnov, Levene and Bonferroni. Chi-squared statistical tests were used to evaluate the failure modes. RESULTS: Mean bond strength values and failure modes were as follows: G1--26.85±6.18 MPa (33.3% of adhesive cohesive failure); G2--27.95±5.58 MPa (53.8% of adhesive failures between enamel and adhesive); G3--15.0±3.84 MPa (77.8% of adhesive failures between enamel and adhesive) and G4--13.1±3.68 MPa (36.4% of adhesive failures between enamel and adhesive). CONCLUSIONS: Shear bond strength values of both adhesives tested on enamel were not influenced by the previous application of ozone gas.

Biodegradation of acrylic based resins: A review.

OBJECTIVES: The development of different types of materials with application in dentistry is an area of intense growth and research, due to its importance in oral health. Among the different materials there are the acrylic based resins that have been extensively used either in restorations or in dentures. The objective of this manuscript was to review the acrylic based resins biodegradation phenomena. Specific attention was given to the causes and consequences of materials degradation under the oral environment. DATA AND SOURCES: Information from scientific full papers, reviews or abstracts published from 1963 to date were included in the review. Published material was searched in dental literature using general and specialist databases, like the PubMED database. STUDY SELECTION: Published studies regarding the description of biodegradation mechanisms, in vitro and in vivo release experiments and cell based studies conducted on acrylic based resins or their components were evaluated. Studies related to the effect of biodegradation on the physical and mechanical properties of the materials were also analyzed. CONCLUSIONS: Different factors such as saliva characteristics, chewing or thermal and chemical dietary changes may be responsible for the biodegradation of acrylic based resins. Release of potential toxic compounds from the material and change on their physical and mechanical properties are the major consequences of biodegradation. Increasing concern arises from potential toxic effects of biodegradation products under clinical application thus justifying an intensive research in this area.