Fernanda Miori Pascon

Effect of sodium hypochlorite on dentine mechanical properties. A review.

OBJECTIVES The aim of this study was to carry out a review on the effect of sodium hypochlorite (NaOCl) on the mechanical properties of root dentine. DATA/SOURCES The authors searched the Cochrane Library, Embase, PubMed and the Web of Science for papers published from 1984 to 2008. The main search terms used were: dentine, root canal dentine, sodium hypochlorite, mechanical analysis, elastic modulus, hardness, roughness, flexural strength, compressive strength. STUDY SELECTION The inclusion criteria were studies that evaluated the effect of NaOCl solution, used as an irrigant in endodontics, on the mechanical properties of root dentine. Those studies that were considered to be unrelated to the question addressed, that had investigated NaOCl as a deproteinizing agent, had not evaluated the effect of NaOCl on the mechanical properties of dentine, and that indirectly verified the effect of NaOCl on endodontically treated teeth were excluded. The selected papers were assigned to a score (A-C), according to predetermined criteria. A total of 16 papers were selected, and nine papers were included in the critical appraisal. Five papers were classified as grade A, 4 as grade B, and no paper was classified as grade C. CONCLUSIONS Based on this review, the authors suggest that there is strong evidence showing that sodium hypochlorite adversely alters the mechanical properties of root dentine, when used as an endodontic irrigant.

Inhibition of mineral loss at the enamel/sealant interface of fissures sealed with fluoride- and non-fluoride containing dental materials in vitro

Objective. In this in vitro study we evaluated the enamel mineral loss effect of fluoride-containing and non-fluoride-containing materials at different distances from the sealant margin, and verified the fluoride-releasing capability of these materials. Material and methods. Extracted molars were randomly assigned into nine groups (n=12): Concise (C), FluroShield (F), Helioseal Clear Chroma (H), Vitremer (V), Fuji II-LC (FII), Ketac Molar (KM), Fuji IX (FIX), Single Bond (SB), and Clearfil Protect Bond (CF). All groups were subjected to thermo and pH cycling. Enamel mineral loss was evaluated by cross-section micro-hardness analysis at distances: −100 µm, 0 µm, 100 µm, 200 µm. The mineral loss data were analyzed using a multi-factor ANOVA with split-plot design, and fluoride-released data were submitted to ANOVA and Tukey tests. Results. FIX demonstrated a lower mineral loss than C, F, and H, but did not differ from the SB, CF, V, FII, and KM groups, which also demonstrated no difference among them. C, F, H, and V presented the highest mineral loss, with no difference among them. V did not differ from the other groups (p>0.05). Regarding the different distances from the sealant margin, −100 µm presented the lowest mineral loss. FIX showed the highest fluoride release on the 7th and 14th days of evaluation, while CF showed high fluoride release only on the 7th day. Conclusion. Resin sealant did not prevent enamel mineral loss, contrary to glass-ionomer cement, which showed the highest capacity for fluoride release. It is not exclusively the presence of fluoride in a materials composition that indicates its capability to interfere with the development of enamel caries-like lesions.OBJECTIVE In this in vitro study we evaluated the enamel mineral loss effect of fluoride-containing and non-fluoride-containing materials at different distances from the sealant margin, and verified the fluoride-releasing capability of these materials. MATERIAL AND METHODS Extracted molars were randomly assigned into nine groups (n = 12): Concise (C), FluroShield (F), Helioseal Clear Chroma (H), Vitremer (V), Fuji II-LC (FII), Ketac Molar (KM), Fuji IX (FIX), Single Bond (SB), and Clearfil Protect Bond (CF). All groups were subjected to thermo and pH cycling. Enamel mineral loss was evaluated by cross-section micro-hardness analysis at distances: -100 microm, 0 microm, 100 microm, 200 microm. The mineral loss data were analyzed using a multi-factor ANOVA with split-plot design, and fluoride-released data were submitted to ANOVA and Tukey tests. RESULTS FIX demonstrated a lower mineral loss than C, F, and H, but did not differ from the SB, CF, V, FII, and KM groups, which also demonstrated no difference among them. C, F, H, and V presented the highest mineral loss, with no difference among them. V did not differ from the other groups (p > 0.05). Regarding the different distances from the sealant margin, -100 microm presented the lowest mineral loss. FIX showed the highest fluoride release on the 7th and 14th days of evaluation, while CF showed high fluoride release only on the 7th day. CONCLUSION Resin sealant did not prevent enamel mineral loss, contrary to glass-ionomer cement, which showed the highest capacity for fluoride release. It is not exclusively the presence of fluoride in a materials composition that indicates its capability to interfere with the development of enamel caries-like lesions.

Morphological and chemical changes in dentin after using endodontic agents: Fourier transform Raman spectroscopy, energy-dispersive x-ray fluorescence spectrometry, and scanning electron microscopy study

We examine the morphological and chemical changes in the pulp chamber dentin after using endodontic agents by scanning electron microscopy (SEM), Fourier transform Raman spectroscopy (FT-Raman), and micro energy-dispersive x-ray fluorescence spectrometry (μEDXRF). Thirty teeth were sectioned exposing the pulp chamber and divided by six groups (n=5): NT-no treatment; CHX-2% chlorhexidine; CHXE-2% chlorhexidine+17% EDTA; E-17% EDTA; SH5-5.25% NaOCl; SH5E-5.25% NaOCl+17% EDTA. The inorganic and organic content was analyzed by FT-Raman. μEDXRF examined calcium (Ca) and phosphorus (P) content as well as Ca/P ratio. Impressions of specimens were evaluated by SEM. Data were submitted to Kruskal-Wallis and Dunn tests (p<0.05). Differences were observed among groups for the 960 cm(-1) peak. Ca and P content differences were significant (SH5>NT=SH5E>CHX>E>CHXE). CHXE and E presented the highest Ca/P ratio values compared to the other groups (p<0.05). The SEM images in the EDTA-treated groups had the highest number of open tubules. Erosion in the tubules was observed in CHX and SH5E groups. Endodontic agents change the inorganic and organic content of pulp chamber dentin. NaOCl used alone, or in association with EDTA, was the most effective agent considering chemical and morphological approaches.

NaOCl effects on primary and permanent pulp chamber dentin

OBJECTIVES The dentin quality of primary and permanent pulp chamber was inspected by Fourier-transformed Raman spectroscopy (FT-Raman) and scanning electron microscopy (SEM). Fragments of pulp chamber dentin were obtained from 20 human molar crowns (primary and permanent). METHODS The fragments were assigned to 8 groups (n=5)-Primary teeth: G1, pulp chamber dentin; G2, pulp chamber dentin irrigated with NaOCl 1% (30 min); G3, pulp chamber dentin irrigated with NaOCl 1% (30 min) and etched by 35% phosphoric acid; G4, pulp chamber dentin etched by 35% phosphoric acid. Permanent teeth: G5, pulp chamber dentin; G6, pulp chamber dentin irrigated with NaOCl 1% (30 min); G7, pulp chamber dentin irrigated with NaOCl 1% (30 min) and etched by 35% phosphoric acid; G8, pulp chamber dentin etched by 35% phosphoric acid. The spectra were subjected to the Cluster analysis. The SEM images were scored. RESULTS Inorganic content: There was a difference between primary and permanent dentin. The groups treated with NaOCl were statistically similar between them, but differed from the groups not treated. Organic content: There was no difference between primary and permanent dentin. The groups became similar after NaOCl and phosphoric acid treatments. The microscopic images showed the presence of calcospherites on permanent dentin and their absence on primary dentin. CONCLUSIONS The NaOCl changed the inorganic content in both dentitions; regardless of the following phosphoric acid etching. However, the chemical changes caused by NaOCl were not detected by SEM when it was followed by etching.

Influence of environmental conditions on properties of ionomeric and resin sealant materials

Objectives: The aim of this study was to determine the effect of environmental conditions on the degradation of ionomeric and resin sealant materials. Material and Methods: FluroShield, Vitremer, and Ketac Molar disc-shaped specimens (n=18/material) were prepared, polished, subjected to initial hardness and roughness readings. Six discs of each material were randomly assigned to one of three different storage solutions: 0.3% citric acid (CA), demineralization solution (DE), and remineralization solution (RE). The specimens were individually immersed in 3 mL of the test solutions, which were daily changed. After 15 days of storage, new surface roughness and hardness readings were done. Fluoride release in the solutions was measured within 15 days. Data were analyzed by ANOVA and Tukeys and Contrast tests (α=0.05). Results: The storage in CA increased the roughness of Vitremer and Ketac Molar. A significant reduction in hardness was observed for all materials after storage in all solutions. For all materials, the greatest amounts of fluoride release occurred during the 1st day. FluroShield presented the same patterns of fluoride release in all solutions. Ketac Molar and Vitremer released the highest amounts of fluoride in the CA solution. Conclusions: Ionomeric materials are more susceptible to degradation than resin-based materials under acidic conditions. Acidic conditions lead to a higher fluoride release from ionomeric materials.

Inhibition of enamel mineral loss by fissure sealant: An in situ study

OBJECTIVES This study evaluated the effect of fluoride and non-fluoride sealants on hardness decrease (HD) and marginal adaptation (MA) on enamel substrates after cariogenic challenge. METHODS Occlusal enamel blocks, from human third molars, were randomly divided into six groups (n=12), according to occlusal fissures condition (S - sound; C - caries-like lesion; CF - caries-like lesion+topical fluoride) and sealants (F - FluroShield; H - Helioseal Clear Chroma). Lesion depths were 79.3±33.9 and 61.3±23.9 for C and CF groups, respectively. Sealants were placed on occlusal surface and stored at 100% humidity (37°C; 24h/d). HD was measured by cross-sectional microhardness analysis at the sealant margin distances: -1 (under sealant), 0 (sealant margin), 1, 2 (outer sealant). Sealant MA was observed by polarized light microscopy and scored according to: 0 - failure (no sealant MA or total sealant loss); 1 - success (sealant MA present). MA and HD were analysed by ANOVA-R and mixed model analysis, respectively. RESULTS For HD (ΔS), F values (6900.5±3686.6) were significantly lower than H values (8534.6±5375.3) regardless of enamel substrates and sealant margin distances. Significant differences were observed among sealant margin distances: -1 (5934.0±3282.6)<0 (8701.5±6175.7)=1 (8473.2±4299.4)=2 (7761.5±4035.1), regardless of sealant and substrate. MA was similar for all groups (p≥0.05). CONCLUSION MA was not affected by sealant type or substrate condition, whereas enamel HD was favourably impacted by fluoride in the sealant. In addition, sealants were more effective as a physical barrier than as its chemical potency in reducing enamel HD. CLINICAL SIGNIFICANCE Sealing with a fluoride material is a recommended procedure to prevent caries of occlusal permanent molars in high-caries-risk patients, even though those exhibiting white spot lesions, since the enamel hardness decrease when fluoride sealant was used in vitro.

Effect of gamma irradiation on fluoride release and antibacterial activity of resin dental materials

This study evaluated the effect of gamma irradiation on fluoride release and antibacterial activity of FluroShield (FS) and Clearfil Protect Bond (CPB). Four groups were formed: G1-FS + gamma; G2-FS without gamma; G3-CPB + gamma; G4-CPB without gamma. For fluoride release analysis, 12 disks of each material were prepared and covered with nail polish, except for one side (50.4 mm(2) area). G1 and G3 were sterilized with a 14.5 KGy dose at 27 degrees C for 24 h, while G2 and G4 (controls) were not sterilized and were maintained under the same time and temperature conditions. Fluoride release measurements were made in duplicate (n=6) by an ion specific electrode. The antibacterial activity of the CPB and FS against Streptococcus mutans after gamma sterilization was evaluated by the agar-disc diffusion method. The diameter of the zones of microbial growth inhibition was recorded after 48 h. Data were analyzed statistically by ANOVA and Tukeys test (alpha=5%). Gamma sterilization decreased the fluoride release of FS by approximately 50%, while CPB was not affected. There was no statistically significant difference (p>0.05) in the antibacterial effect of CPB between gamma and non-gamma sterilization groups. FS presented no antibacterial activity. Gamma irradiation decreased the fluoride release of FS, but did not affect the antibacterial activity of the studied materials.

Molecular and Structural Evaluation of Dentin Caries-Like Lesions Produced by Different Artificial Models

This study evaluated structural and molecular issues of dentin caries-like lesions produced by different artificial models (ACL) compared with natural caries lesions (NCL). One hundred twenty-four sound occlusal dentin blocks and 47 carious blocks were obtained and surface hardness was analyzed (SH1). They were assigned to groups according to ACL: GB: Biological; GC: Chemical; GIS: In situ; GNC: natural caries (control). Blocks from groups 1, 2 and 3 were submitted to caries lesion induction. NCL and ACL blocks were submitted to surface hardness (SH 2), FT-Raman and µEDXRF analysis. All blocks were longitudinally sectioned and one of the halves was submitted to cross-sectional hardness (CSH) and the other to SEM analysis. SH1 and SH2 data were submitted to t test (unpaired and paired, respectively), CSH and SEM data to two-way and one-way ANOVA respectively, and Tukey and t tests, respectively (p<0.05). Data from FT-Raman/µEDXRF were submitted to one-way ANOVA and Dunnett multiple-comparisons test (a=0.05). GB and GNC showed lowest SH2 values that were significantly different from GC and GIS. Regarding CSH, GB and GNC showed no significant difference between them. SEM showed similar caries lesion depth for GB and GNC, being significantly higher than for GC and GIS. µEDXRF showed similar values of calcium and phosphate for GB and GNC; GNC values were significantly different from GIS. No significant difference was found among the groups concerning phosphate, carbonate and CH bonds values. For collagen type I, GC values were significantly different compared to other groups. It may be concluded that caries-like lesions produced by GB were the closest model to NCL.

Evaluation of sorption/solubility, softening, flexural strength and elastic modulus of experimental resin blends with chlorhexidine

OBJECTIVES To evaluate physical-chemical properties of experimental diacetate chlorhexidine (CHX)-added resin blends. METHODS Blends were formulated: G1)TEGDMA; G2)TEGDMA/0.1%CHX; G3)TEGDMA/0.2%CHX; G4)TEGDMA/UDMA; G5)TEGDMA/UDMA/0.1%CHX; G6)TEGDMA/UDMA/0.2%CHX; G7)TEGDMA/BisEMA, G8)TEGDMA/BisEMA/0.1%CHX; G9)TEGDMA/BisEMA/0.2%CHX. Icon(®) was the control group. For sorption/solubility (SS), cylindrical specimens (n=5) were prepared and their weight obtained. The specimens were immersed in deionized water for 7days at 37°C and their weight was verified again. SS were calculated using accepted formulas. For softening, cylindrical specimens (n=10) were prepared and initial Knoop hardness number (KHN) obtained. The specimens were immersed in absolute ethanol for 24h at 37°C and final KHN accomplished. Softening values were calculated by KHN reduction percentage. For elastic modulus (EM) and flexural strength (FS) bar specimens were prepared (n=10) and values obtained with a universal device (three point, 5mm distance, 0.5mm/min, load of 50N). The data was analyzed using one-way ANOVA and Tukey test (α=5%). RESULTS TEGDMA/BisEMA blends and Icon(®) showed the lowest sorption from blends (p>0.05), and Icon(®) was the most soluble material (p<0.01). TEGDMA/UDMA/0.1%CHX showed the highest softening, similar to Icon(®) (p>0.05). For EM, all blends were different than Icon(®) (p<0.01). For FS, TEGDMA blends were similar to Icon(®), showing the lowest averages (p>0.05). CONCLUSIONS Monomers chemical characteristics influenced the physical-chemical properties of experimental blends more than CHX. Between the blends tested, UDMA blends presented satisfactory results for assays evaluated. CLINICAL SIGNIFICANCE Infiltrants CHX-added could arrest and reinforce initial caries lesions, and the antimicrobial effect could prevent new lesions in sound enamel adjacent to the infiltrated area.

In-Depth Polymerization of a Self-Adhesive Dual-Cured Resin Cement

The aim of this study was to assess Knoop hardness at different depths of a dual-cured self-adhesive resin cement through different thicknesses of Empress Esthetic® ceramic.Flattened bovine dentin was embedded in resin. The cement was inserted into a rubber mold (0.8 x 5 mm) that was placed between two polyvinyl chloride plastic films and placed over the flat dentin and light cured by Elipar Trilight-QTH (800 mW/cm2) or Ultra-Lumelight-emitting diode (LED 5; 1585 mW/cm2) over ceramic disks 1.4 or 2 mm thick. The specimens(n=6) were stored for 24 hours before Knoop hardness (KHN) was measured. The data were submitted to analysis of variance in a factorial split-plot design and Tukeys test (a=0.05).There was significant interaction among the study factors. In the groups cured by the QTHunit, an increase in ceramic thickness resulted in reduced cement hardness values at all depths, with the highest values always being found in the center (1.4 mm, 58.1; 2 mm, 50.1)and the lowest values at the bottom (1.4 mm,23.8; 2 mm, 20.2). When using the LED unit, the hardness values diminished with increased ceramic thickness only on the top (1.4 mm,51.5; 2 mm, 42.3). In the group with the 1.4-mm-thick disk, the LED curing unit resulted in similar values on the top (51.5) and center(51.9) and lower values on the bottom (24.2).However, when the cement was light cured through the 2-mm disk, the highest hardness value was obtained in the center (51.8), followed by the top (42.3) and bottom (19.9),results similar to those obtained with the QTH curing unit (center > top > bottom). The hardness values of the studied cement at different depths were dependent on the ceramic thickness but not on the light curing units used.