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Purpose: To evaluate the effect of heated and room-temperature hydrofluoric (HF) acid on surface roughness parameters (Ra and Rq) and microtensile bond strength (µTBS) on feldspathic ceramic and lithium-disilicate glass-ceramics. Materials and Methods: Disk-shaped samples made from both ceramics were divided into groups according to surface treatment: feldspathic ceramic polished surface (FP), feldspathic ceramic + 60 s of 9% HF acid etching at room temperature (FC), feldspathic ceramic + 60 s of 9% HF acid etching heated to 70°C (F70), lithium-disilicate polished surface only (LP), lithium disilicate + 20 s of 9% HF acid etching at room temperature (LC), and lithium disilicate + 20 s of 9% HF acid etching heated to 70°C (L70). To evaluate Ra and Rq, non-overlapping readings were taken on the surface of each sample with a contact stylus profilometer. To measure microtensile bond strength (µTBS), samples of groups FC, F70, LC and L70 received their corresponding surface treatment, were silanized and then bonded using a dual-cure composite cement to resin composite disks. After 24 h, samples were sectioned to obtain specimens for µTBS. Representative samples from each group were examined using scanning electron microscopy (SEM) to analyze the morphology of the etched surface. The data were analyzed for statistical significance using Welch's ANOVA with the Games-Howell multiple-comparison post-hoc test. Results: For both surface roughness parameters and HF acid etching at room temperature (FC and LC) showed a significant increase (p < 0.001) in surface roughness when compared to polished surfaces (FP and LP). Furthermore, the use of heated HF acid etching significantly increased (p < 0.001) the surface roughness of the ceramic when compared to their counterpart sample of HF acid etching at room temperature. Group L70 obtained the highest µTBS of all groups (29.11 ± 8.26 MPa) and was significantly higher (p < 0.001) than that of the other experimental groups. There were no statistical differences (p > 0.05) between groups FC (19.94 ± 4.14), F70 (18.24 ± 5.29), and LC (17.87 ± 6.96). Conclusion: The use of 9% HF acid etching heated to 70°C resulted in significantly higher surface roughness and improved bond strength onto lithium-disilicate glass-ceramic compared to surface HF acid etching at room temperature. [ABSTRACT FROM AUTHOR]

Introduction: To compare 3 methods of crimping orthodontic hooks with 2 different types of force using tiebacks or elastomeric chains. Methods: 100 crimped hooks, 100 dotted hooks and 100 hooks with a V stop bending on the archwire, divided into 6 groups were put to detachment test in a universal machine SHIMADZU 5000 applying force by means of tiebacks and elastomeric chains, for the use of the machine an accessory base and arm was designed to keep the test stable and standardized. Data were analyzed using GraphPad Prims 8 for Windows. Significance was predetermined at α =0.05. The Shapiro-Wilk test was used to test the data for normality. The data were not normally distributed and therefore the Kruskal Wallis test was used to determine differences between groups, followed by Dunn's multiple comparisons test. Results: The maximum forces obtained for the detachment of an orthodontic hook was up to 2.87kg which was recorded by the group of dotted hooks and with force applied with elastomeric chain and the one with the lowest force was 0.87kg with hooks only crimped. The tie backs showed a more controlled force in all groups and the groups with a "V stop" bend also showed the most stable tests and none displacement of the hook but more eviction and break of the hooks. Conclusions: In the study it was determined that the crimping method is not sufficient for the stability of the hook so pointing it or performing a V stop bend on the wire increases its stability before the maximum force of detachment and clinically gives advantages in the dental movement although it increases the consultation or laboratory time for its realization. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effect of heated and room-temperature hydrofluoric (HF) acid on surface roughness parameters (Ra and Rq) and microtensile bond strength (μTBS) on feldspathic ceramic and lithium-disilicate glass-ceramics., Materials and Methods: Disk-shaped samples made from both ceramics were divided into groups according to surface treatment: feldspathic ceramic polished surface (FP), feldspathic ceramic + 60 s of 9% HF acid etching at room temperature (FC), feldspathic ceramic + 60 s of 9% HF acid etching heated to 70°C (F70), lithium-disilicate polished surface only (LP), lithium disilicate + 20 s of 9% HF acid etching at room temperature (LC), and lithium disilicate + 20 s of 9% HF acid etching heated to 70°C (L70). To evaluate Ra and Rq, non-overlapping readings were taken on the surface of each sample with a contact stylus profilometer. To measure microtensile bond strength (μTBS), samples of groups FC, F70, LC and L70 received their corresponding surface treatment, were silanized and then bonded using a dual-cure composite cement to resin composite disks. After 24 h, samples were sectioned to obtain specimens for μTBS. Representative samples from each group were examined using scanning electron microscopy (SEM) to analyze the morphology of the etched surface. The data were analyzed for statistical significance using Welch's ANOVA with the Games-Howell multiple-comparison post-hoc test., Results: For both surface roughness parameters and HF acid etching at room temperature (FC and LC) showed a significant increase (p < 0.001) in surface roughness when compared to polished surfaces (FP and LP). Furthermore, the use of heated HF acid etching significantly increased (p < 0.001) the surface roughness of the ceramic when compared to their counterpart sample of HF acid etching at room temperature. Group L70 obtained the highest μTBS of all groups (29.11 ± 8.26 MPa) and was significantly higher (p < 0.001) than that of the other experimental groups. There were no statistical differences (p > 0.05) between groups FC (19.94 ± 4.14), F70 (18.24 ± 5.29), and LC (17.87 ± 6.96)., Conclusion: The use of 9% HF acid etching heated to 70°C resulted in significantly higher surface roughness and improved bond strength onto lithium-disilicate glass-ceramic compared to surface HF acid etching at room temperature.

Purpose: To evaluate Streptococcus mutans biofilm formation over different restorative dental materials., Methods: Using a bioreactor over 72 hours, four commercially available ceramics were evaluated: IPS E-max Press, IPS E-max CAD, Lava Ultimate CAD-CAM, Vita Enamic and two resin composites (SR Nexco Paste and Brilliant NG). The results were evaluated using atomic force microscopy and confocal microscopy, the biofilm was stained and the arbitrary fluorescence units (AFU) quantified., Results: The results showed that IPS E-max CAD had the lowest roughness values (4.29±1.79 nm), while the highest values were observed for Vita Enamic discs ( (77.13±17.35 nm). Analysis of S. mutans biofilm formation by AFU revealed lower values for IPS E-max CAD (6.77±1.67 nm); the highest values were found for Lava Ultimate (79.99±22.23 nm). Regarding the composite groups, SR Nexco Paste showed roughness values of 15.07±2.77 nm and lower arbitrary fluorescence units of 30.92±12.01 nm than Brilliant NT. There was a correlation between the surface roughness of ceramics and composite with S. mutans biofilm formation., Clinical Significance: The adhesion of oral bacteria to restorative dental materials plays a key role in the success of dental treatment; the surface roughness influences the S. mutans biofilm formation., Competing Interests: The authors declared no conflicts of interest. This work was supported by a grant to Paulina Contreras-Guerrero as a CONACYT fellow (Grant 6118114-574819)., (Copyright©American Journal of Dentistry.)