Vanessa Cavalli

Characterization of water sorption, solubility and filler particles of light-cured composite resins

The goals of this study were to measure the water sorption (WS) and solubility (SO) of 3 composite resins containing different filler contents. Additionally, the size, shape, type and other characteristics of fillers were analyzed by scanning electron microscopy (SEM). Three composites, classified according to filler size, were selected: Filtek Supreme nanofill (3M/ESPE), Esthet-X minifill (Dentsply/Caulk) and Renamel microfill (Cosmedent Inc.). Ten disk-shaped specimens of each resin composite were made and stored in desiccators until constant mass was achieved. Specimens were then stored in water for 7 days, and the mass of each specimen was measured. The specimens were dried again and dried specimen mass determined. The WS and SO were calculated from these measurements. Data analyzed by one-way ANOVA and Tukeys post-hoc test (alpha=0.05). Composite filler particles were observed under SEM after removal of resin matrix by organic solvents. WS values were not significantly different among the resins; however, SO values were lower for Filtek Supreme. The materials presented differences in filler contents (e.g. particle size and shape). The composite resins had similar WS, while the SO was lower for the nanofill than for mini and microfill resins. The filler characteristics varied and were different among the materials.

Enamel susceptibility to red wine staining after 35% hydrogen peroxide bleaching

Concern has been expressed regarding the staining of enamel surface by different beverages after bleaching. This study investigated the influence of 35% hydrogen peroxide bleaching agents on enamel surface stained with wine after whitening treatments. Flat and polished bovine enamel surfaces were submitted to two commercially available 35% hydrogen peroxide bleaching agents or kept in 100% humidity, as a control group (n = 10). Specimens of all groups were immersed in red wine for 48 h at 37°C, immediately, 24 h or 1 week after treatments. All specimens were ground into powder and prepared for the spectrophotometric analysis. Data were subjected to two-way analysis of variance and Fishers PLSD test at 5% significance level. The amount of wine pigments uptake by enamel submitted to bleaching treatments was statistically higher than that of control group, independently of the evaluation time. Results suggested that wine staining susceptibility was increased by bleaching treatments.

Effects of Combined Use of Light Irradiation and 35% Hydrogen Peroxide for Dental Bleaching on Human Enamel Mineral Content

OBJECTIVE The objective of this study was to evaluate the effects of the combined use of light irradiation (LIR, halogen light, or LED/diode laser) and 35% hydrogen peroxide (35%HP) on human enamel mineral content. BACKGROUND DATA The use of high-intensity light has been indicated for acceleration of the rate of chemical bleaching; however, it is not known whether LIR can promote additional effects on enamel surfaces during the bleaching. MATERIALS AND METHODS One hundred enamel samples were obtained from third molars and randomly divided into 10 groups (n = 10). The control group (CG) remained untreated. Three whitening products were used: Whiteness HP Maxx, Pola Office, and Opalescence Xtra. Bleaching consisted of one session, and the products were applied three times to each specimen for 10 min each. The products were subjected, or not, to LIR during treatment with halogen light or LED/diode laser. The mineral concentration of enamel was determined before and after treatments using an FT-Raman spectroscope (FT-RS), and the amount of calcium lost from the bleached enamel surfaces was quantified with an atomic absorption spectrometer (AAS). RESULTS FT-RS results showed a decreased mineral content after all treatments, with the exception of Pola Office when irradiated with LED/diode laser and the CG. The losses of calcium detected for Pola Office and Opalescence Xtra were similar for the three situations (without or with light irradiations), whereas for Whiteness HP Maxx the lowest calcium loss was detected without LIR. CONCLUSION Most of the bleaching treatments investigated, in combination with LIR or not, can reduce the mineral content of enamel surface. LIR increased the calcium loss for Whiteness HP Maxx; no effects were observed for Pola Office and Opalescence Xtra.

Effects of the Addition of Fluoride and Calcium to Low-Concentrated Carbamide Peroxide Agents on the Enamel Surface and Subsurface

OBJECTIVE The present study aimed to determine if the addition of fluoride (F) and calcium (Ca) to home-applied 10% carbamide peroxide (CP) bleaching agents reduces mineral loss on the enamel surface and subsurface. BACKGROUND Home-applied 10% carbamide peroxide effectively whitens teeth. However, bleaching possibly promotes adverse side effects such as tooth hypersensitivity and morphological and chemical alterations, such reductions in calcium and fluoride, that affect the enamel surface. METHODS Sixty human enamel slabs were selected based on evaluation of their surface microhardness (n = 10) and submitted to the application of either a placebo agent, Whiteness™, Opalescence™, Pola Night,™ or one of two experimental carbamide peroxide gels: the first with 0.2% fluoride added and the second with 0.2% calcium added. The gel was applied for 6 h/day for 14 days. Samples were submitted to FT-Raman spectroscopy to evaluate surface mineral content before and after treatment. Additionally, cross-sectional microhardness and polarized light microscopy were carried out, to determine enamel subsurface inorganic loss and lesion depth. RESULTS A significant decrease in mineral content was observed after carbamide peroxide treatment, which resulted in increased lesion depth (p < 0.05). Cross-sectional microhardness assessment and polarized light microscopy demonstrated that all groups (except the placebo) exhibited enamel subsurface mineral loss; however, the inorganic deficit could be effectively controlled by the addition of F and Ca to the experimental bleaching agents. CONCLUSIONS The addition of F and Ca to home-applied bleaching agents may reduce enamel mineral loss.

Effect of 10% carbamide peroxide bleaching on sound and artificial enamel carious lesions

This study evaluated the effect of 10% carbamide peroxide (CP) bleaching on Knoop surface microhardness (KHN) and morphology of sound enamel and enamel with early artificial caries lesions (CL) after pH-cycling model (pHcm). Human dental enamel blocks were randomly divided into 6 groups (n=10): 1 - sound enamel bleached (S) with CP (Rembrandt/Den-Mat); 2 - S and submitted to pHcm; 3 - CL bleached with CP; 4 - CL stored in artificial saliva and submitted to pHcm; 5 - CL treated with placebo gel and submitted to pHcm; 6 - CL bleached with CP and submitted to pHcm. Enamel blocks with known initial KHN values were demineralized (groups 3 to 6) and submitted to 12 day pHcm (groups 2, 4, 5 and 6). After demineralization and treatments, KHN was determined and the specimens were examined using scanning electron microscopy (SEM). Data were analyzed statistically by ANOVA and Tukeys test at 5% significance level. The results showed that among CL groups (3 to 6) only the group 3 presented remineralization after treatments. S groups (1 and 2) showed higher KHN and presented less formation of porosities on enamel surface than CL groups after treatments. In conclusion, bleaching procedures on enamel with CL did not exacerbate the demineralization, but should be indicated with caution.

Influence of the photoinitiator system and light photoactivation units on the degree of conversion of dental composites

The aim of this study was to observe the influence of two light polymerization units (LED or halogen light) on the degree of conversion (DC) of three dental composites with lighter shades and a different photoinitiator system. The top (T) and bottom (B) surfaces of 60 discs of composite resin (Filtek™ Supreme, Filtek™ Z250, Tetric™ Ceram Bleach) cured either by LED or by halogen lamp (HL) were studied using an FT-Raman spectrometer. The degree of conversion (DC) was evaluated by following the changes in the intensity of the methacrylate C=C stretching mode at 1640 cm⁻¹. The calculated DC ranged from 54.2% (B) to 73.4% (T) and from 60.2% (B) to 76.6% (T) for the LED and HL, respectively. LED and halogen devices were able to produce an adequate DC for all the resins tested.

FT-Raman and energy dispersive X-ray fluorescence spectrometric analyses of enamel submitted to 38% hydrogen peroxide bleaching, an acidic beverage, and simulated brushing.

OBJECTIVE This study aimed to investigate the effects on enamel surface treated with hydrogen peroxide bleaching and acidic soft drink immersion and/or brushing with whitening dentifrices. MATERIALS AND METHODS Fifty-six standardized enamel slabs obtained from labial surfaces of bovine incisors were used. Enamel slabs were ground flat, polished, and randomly assigned to one of seven treatment groups: (1) control, in which no treatment was performed, (2) soft drink immersion, (3) 38% hydrogen peroxide bleaching, (4) simulated toothbrushing with whitening dentifrice, (5) soft drink immersion and bleaching, (6) soft drink immersion, bleaching, and toothbrushing, and (7) bleaching and toothbrushing. The mineral concentration of enamel surfaces was determined before and after treatments by means of Fourier transform (FT)-Raman spectroscopy and energy dispersive x-ray fluorescence spectrometry (EDXRF). Data were statistically analyzed by ANOVA and Tukey test (p < 0.05). RESULTS Raman spectroscopy results indicated that enamel mineral content decreased after all treatments except in group 1, whereas EDXRF results exhibited mineral decrease in groups 3, 4, 5, and 7. CONCLUSION Bleaching alone or in combination with soft drink immersion and brushing decreases enamel mineral content.

Influence of saliva contamination on the shear bond strength of orthodontic brackets bonded with self-etching adhesive systems

INTRODUCTION Our objective was to evaluate the influence of saliva contamination on the shear bond strength of orthodontic brackets bonded with self-etching primers. METHODS One hundred thirty-five bovine incisors were randomly divided into 3 groups, and exposed enamel surfaces were bonded with Transbond Plus Self Etching Primer (TB) (3M Unitek, Monrovia, Calif), Adhese Single Bottle (AD) (Ivoclar, Vivadent, Schaan, Liechtenstein), and Self Etch Bond (SE) (Vigodent, Rio de Janeiro, Brazil). Each group was subdivided into 3 treatments (n = 15): saliva contamination (S), saliva contamination and deionized water rinsing (SW), and no salivary contamination (C). Resin composite (Z-100, 3M/ESPE, Salt Lake City, Utah) was applied to all samples to bond the orthodontic brackets. Shear bond strength testing was carried out in a universal testing machine operating at 1.0 mm per minute. RESULTS The results were statistically analyzed with 2-way analysis of variance (ANOVA) and Tukey tests (P <0.05). Saliva contamination caused a significant decrease of enamel strength in the groups bonded with TB and SE compared with the SW and C groups. Enamel bond strengths of the C and SW groups were higher than those of the TB group, followed by the AD and SE groups. Enamel bond strength after S was higher than AD, followed by TB and SE. CONCLUSIONS The shear bond strengths of orthodontic brackets to enamel and the performance of the adhesive systems were influenced by contamination with saliva.

Enamel and dentin bond strength, interfacial ultramorphology and fluoride ion release of self-etching adhesives during a pH-cycling regime.

PURPOSE This study evaluated the effects of pH cycling on fluoride release and bond strength of two self-etching adhesive systems to both enamel and dentin. The ultramorphology of the interfaces produced by the adhesive systems were also analyzed. MATERIALS AND METHODS The buccal surfaces of bovine incisors were flattened to expose enamel and dentin, which were bonded with either Clearfil Protect Bond (CPB) or One-Up Bond F Plus (OBP). The bonded samples were prepared for microtensile bond strength (μTBS) testing, fluoride ion release, and transmission electron microscopy. pH cycling comprised demineralization (8 h/day) and remineralization (16 h/day) cycles for 8 days. The μTBS data were analyzed by two-way ANOVA, while fluoride release was analyzed using the Friedman and Wilcoxon tests. RESULTS The adhesives presented similar bond strengths to enamel. However, the dentin bond strength of CPB was higher than that of OBP. pH cycling did not influence enamel or dentin μTBS. The amount of fluoride released from the bonded enamel and dentin was low and varied among the groups. The morphological evaluation showed that the thickness of the dentin hybrid layers was similar for both adhesives. CONCLUSION The pH-cycling regime did not affect enamel or dentin bond strengths. In enamel, both the self-etching adhesives tested presented similar bond strengths, but in dentin, Clearfil Protect Bond showed higher dentin bonding than One-Up Bond F Plus.

Influence of fluoride-containing adhesives and bleaching agents on enamel bond strength

This study evaluated the influence of fluoride-containing carbamide peroxide (CP) bleaching agents and adhesive systems on bonded enamel interfaces that are part of the dynamic pH cycling and thermal cycling models. The buccal surfaces of 60 bovine incisors were restored with a composite resin and bonded with three- and two-step, etch-and-rinse, fluoride-containing adhesives, Optibond FL (FL) and Optibond Solo Plus (SP), respectively. Restored teeth were subjected to thermal cycling to age the interface. Both SP and FL adhesive-restored teeth were bleached (n = 10) with 10% CP (CP) and 10% CP + fluoride (CPF) or were left unbleached (control). Bleaching was performed for 14 days simultaneously with pH cycling, which comprised of 14 h of remineralization, 2 h of demineralization and 8 h of bleaching. The control groups (FL and SP) were stored in remineralizing solution during their bleaching periods and were also subjected to carious lesion formation. Parallelepiped-shaped samples were obtained from the bonded interface for microtensile bond strength (μTBS) testing. The enamel μTBS of the FL and SP groups (control, not bleached) were higher (p < 0.05) than those of the bleached interfaces (FL > FL + CPF = FL + CP and SP > SP + CPF = SP + CP). The groups subjected to treatment with the fluoride-containing bleaching agents exhibited similar μTBS compared to regular bleaching agents. Bleaching agents, regardless of whether they contained fluoride, decreased enamel bond strength.