Changes in roughness of denture base and reline materials by chemical disinfection or microwave irradiation: Surface roughness of denture base and reline materials

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Measurement of Interfacial Porosity at the Acrylic Resin/Denture Tooth Interface

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Weight loss and changes in surface roughness of denture base and reline materials after simulated toothbrushing in vitro

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Surface roughness of denture base and reline materials after disinfection by immersion in chlorhexidine or microwave irradiation

Background: This study evaluated the effect of disinfection by immersion and microwave irradiation on the roughness of one denture base resin (Lucitone-L) and five relining materials, three hard (Tokuyama Rebase II-TR, New Truliner-NT, Ufigel Hard-UH) and two resilient (Trusoft-T, Sofreliner-S).Methods: Fifty specimens were made and divided into groups: CL2 specimens were brushed with 4% chlorhexidine (1 min), immersed in the same solution (10 min) and immersed in water (3 min); MW2 specimens were immersed in water and microwave irradiated (650W; 6 min); CL2 and MW2 specimens were disinfected twice; CL7 and MW7 specimens were submitted to seven cycles using chlorhexidine or microwave irradiation, respectively; W specimens were not disinfected and remained in water (37 degrees C; 7 days).Results: Results were statistically analysed (p = 0.05) and revealed that, at baseline, the highest mean value was observed for T (p < 0.001). Material NT showed increase in roughness after the first (p = 0.003), second (p = 0.001), seventh (p = 0.000) cycles of microwave disinfection and after 7 days of immersion in water (p = 0.033).Conclusions: Resilient liner S presented significant increase in roughness after the second cycle of disinfection with chlorhexidine (p = 0.003). Material T exhibited significantly decreased roughness in group W (p = 0.010), while microwaving produced severe alterations on its surface.

Effect of microwave disinfection on the surface roughness of three denture base resins after tooth brushing

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Assessing the surface roughness of a posterior resin composite: effect of surface sealing

This study assessed the in vitro influence of surface sealing on the surface roughness of a posterior resin composite before and after tooth-brushing. Thirty. specimens (13 nun diameter x 1 mm high) were fabricated from Filtek-P60 resin composite and randomly assigned to three groups (n=10): a non-sealed control and two groups sealed with one of the tested materials-a surface-penetrating sealant (Protect-it!-PI) and a one bottle adhesive system (Single Bond-SB). The samples were subjected to a surface roughness reading to determine the initial roughness, then submitted to simulated toothbrushing with 35,600 cycles for 100 minutes. Specimens were then cleaned and a post-abrasion surface roughness reading accomplished. Means (pm), recorded before (B) and after (A) toothbrushing, and standard deviations were: Control-(B): 0.032 (+/-0.005), (A): 0.054 (+/-0.005); PI-(B): 0.034 (+/-0.005), (A): 0.060 (+/-0.034); SB (B): 0.031 (+/-0.004), (A): 0.047 (+/-0.007). Data were tabulated and submitted to two-way ANOVA. No statistically significant difference was observed when the control and experimental groups were compared. However, a significant difference (p<0.05) was found between the measurements performed before and after toothbrushing. Based on these results, it may be concluded that using either a surface penetrating sealant or a one bottle adhesive system did not provide the optimization of superficial integrity. The use of a dentifrice and toothbrush resulted in significant alterations to the surface smoothness of the resin composite.

Analysis of surface roughness of glass-ionomer cements and compomer

The purpose of this study was to evaluate the surface roughness of two glass-ionomer cements (Vitremer and Chelon-Fil), and one compomer (Dyract) when submitted to different finishing/polishing procedures at different times. A hundred 80-sample discs were made of each material and randomly divided into six finishing/polishing groups: mylar strip (control); Sof-Lex discs; diamond burs; diamond burs/Sof-Lex discs; 30-fluted carbide bur; 30-fluted carbide bur/Sof-Lex discs. These procedures were carried out immediately after preparation of the samples, after 24 and 168 h. Average surface roughness (Ra) was measured with a profilometer and the values were compared using anova (P < 0.05). The smoothest surface for all materials was obtained when cured in contact with the mylar strip. All other tested products increased surface roughness of restorative materials, but Sof-lex discs lead to better results. The worst results were verified with diamond burs. The finishing/polishing procedures, when performed immediately, can improve the roughness of glass-ionomer cements but not of the compomer tested.

Interfacial surface charge and free accessibility to the PLA(2)-active site-like region are essential requirements for the activity of Lys49 PLA(2) homologues

Lys49 phospholipase A(2) homologues are highly myotoxic and cause extensive tissue damage but do not display hydrolytic activity towards natural phospholipids. The binding of heparin, heparin derivatives and polyanionic compounds such as suramin result in partial inhibition (up to 60%) of the myotoxic effects due to a change in the overall charge of the interfacial surface. In vivo experiments demonstrate that polyethylene glycol inhibits more than 90% of the myotoxic effects without exhibiting secondary toxic effects. The crystal structure of bothropstoxin-I complexed with polyethylene glycol reveals that this inhibition is due to steric hindrance of the access to the PLA(2)-active site-like region. These two inhibitory pathways indicate the roles of the overall surface charge and free accessibility to the PLA2-active site-like region in the functioning of Lys49 phospholipases A(2) homologues. Molecular dynamics simulations, small angle X-ray scattering and structural analysis indicate that the oligomeric states both in solution and in the crystalline states of Lys49 phospholipases A2 are principally mediated by hydrophobic contacts formed between the interfacial surfaces. These results provide the framework for the potential application of both clinically approved drugs for the treatment of Viperidae snakebites. (c) 2006 Elsevier Ltd. All rights reserved.

Interfacial concentrations of chloride and bromide in zwitterionic micelles with opposite dipoles: Experimental determination by chemical trapping and a theoretical description

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Topography of funneled landscapes determines the thermodynamics and kinetics of protein folding

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Surface Roughness and Bacterial Adherence to Resin Composites and Ceramics

Purpose: The aim of this study was to evaluate the surface roughness and the in vitro adherence of Streptococcus mutans to indirect aesthetic restorative materials that are uncoated with saliva.Materials and Methods: Four groups of restorative materials were evaluated according to material type: (1) microparticulate feldspathic ceramic; (2) leucite-reinforced feldspathic ceramic; (3) microhybrid resin composite and (4) microfilled resin composite. Twenty standardised samples of each material were produced. Roughness analysis (Ra, n = 10) was performed using a roughness analyser. Adhesion tests (n = 10) were carried out in 24-well plates; colony-forming units (CFU/mL) were evaluated. The mean values of roughness (mu m) and adherence (CFU/mL) for each group were subjected to an analysis of variance and a Tukey test.Results: The leucite-reinforced feldspathic ceramic was rougher and presented higher bacterial adherence than the microparticulate feldspathic ceramic. The resin composites were similar with regard to surface roughness and bacterial adherence.Conclusions: The microhybrid and microfilled resin composites were similar and the leucite-reinforced feldspathic ceramic was rougher and presented higher bacterial adherence than the microparticulate feldspathic ceramic.

Interfacial fracture of dentin adhesively bonded to quartz-fiber reinforced composite

The paper presents the results of an experimental study of interfacial failure in a multilayered structure consisting of a dentin/resin cement/quartz-fiber reinforced composite (FRC). Slices of dentin close to the pulp chamber were sandwiched by two half-circle discs made of a quartz-fiber reinforced composite, bonded with bonding agent (All-bond 2, BISCO, Schaumburg) and resin cement (Duo-link. BISCO, Schaumburg) to make Brazil-nut sandwich specimens for interfacial toughness testing. Interfacial fracture toughness (strain energy release rate, G) was measured as a function of mode mixity by changing loading angles from 0 degrees to 15 degrees. The interfacial fracture surfaces were then examined using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) to determine the failure modes when loading angles changed. A computational model was also developed to calculate the driving forces, stress intensity factors and mode mixities. Interfacial toughness increased from approximate to 1.5 to 3.2 J/m(2) when the loading angle increases from approximate to 0, 0 to 15 degrees. The hybridized dentin/cement interface appeared to be tougher than the resin cement/quartz-fiber reinforced epoxy. The Brazil-nut sandwich specimen was a suitable method to investigate the mechanical integrity of dentin/cement/FRC interfaces. (C) 2011 Elsevier B.V. All rights reserved.

Effect of multiple firing and silica deposition on the zirconia-porcelain interfacial bond strength

Objectives. To test the hypothesis that multiple firing and silica deposition on the zirconia surface influence the bond strength to porcelain.Materials and methods. Specimens were cut from yttria-stabilized zirconia blocks and sintered. Half of the specimens (group S) were silica coated (physical vapor deposition (PVD)) via reactive magnetron sputtering before porcelain veneering. The remaining specimens (group N) had no treatment before veneering. The contact angle before and after silica deposition was measured. Porcelain was applied on all specimens and submitted to two (N2 and S2) or three firing cycles (N3 and S3). The resulting porcelain-zirconia blocks were sectioned to obtain bar-shaped specimens with 1 mm(2) of cross-sectional area. Specimens were attached to a universal testing machine and tested in tension until fracture. Fractured surfaces were examined using optical microscopy. Data were statistically analyzed using two-way ANOVA, Tukey's test (alpha = 0.05) and Weibull analysis.Results. Specimens submitted to three firing cycles (N3 and S3) showed higher mean bond strength values than specimens fired twice (N2 and S2). Mean contact angle was lower for specimens with silica layer, but it had no effect on bond strength. Most fractures initiated at porcelain-zirconia interface and propagated through the porcelain.Significance. The molecular deposition of silica on the zirconia surface had no influence on bond strength to porcelain, while the number of porcelain firing cycles significantly affected the bond strength of the ceramic system, partially accepting the study hypothesis. Yet, the Weibull modulus values of S groups were significantly greater than the m values of N groups. (C) 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.