The effect of topical fluoride applications on the surface free energy of human enamel--an in vitro study

The surface free energy gamma s and its polar and dispersion components gamma Sp and gamma Sd were determined from contact angle measurements on human enamel treated with sodium fluoride, acidulated phosphate fluoride (APF), and aminfluoride solutions. Sodium fluoride solutions only slightly influenced the surface free energy component gamma Sp. The gamma Sp value of the APF-treated human enamel increased from 52 to 66 erg X cm-2. The gamma Sp value after aminfluoride treatment decreased from 52 to 19 erg X cm-2. The gamma Sd values remained about 35 erg X cm-2 for all specimens measured. It is suggested that aminfluoride-treated enamel surfaces may exhibit a reduced tendency for bacterial adhesion.     

Flowable resin used as a sealant in molars affected by dental fluorosis: a comparative study

The decline in prevalence and incidence of dental caries in developed countries over the last two decades is considered to be due mainly to the widespread use of fluoride in different forms, but simultaneously with decline in caries, an increase in dental fluorosis has been reported. The aim of this study was to compare the Conventional Sealant Technique (CST) and Enameloplasty Sealant Technique (EST) using a flowable resin as sealant in molars affected by dental fluorosis. A total of 40 extracted third molars affected by dental fluorosis were divided at random into two groups of 20 teeth each, and Tetric Flow resin was used as sealant. All teeth were studied for lateral adaptation and resin penetration by direct and indirect techniques; all samples were replicated in epoxy resin and were evaluated with Scanning Electron Microscopy (SEM). The results demonstrated that EST allowed a deeper sealant penetration and a superior sealant adaptation than CST, both in direct and indirect evaluations by SEM. The most important variables being penetration-interface and penetration depth both being statistically significant (p<0.05). The CST did not flow into the bottom of the fissures, leaving spaces that can favor the fracture of the material and initiate the process of dental caries. We conclude that a flowable ceromer is an excellent material alternative to be used as sealant and that EST is quite necessary in molars affected by dental fluorosis, the combination of both being a reliable method to be used as primary prevention approach of dental caries in endemic areas of dental fluorosis.     

Chitosan whiskers from shrimp shells incorporated into dimethacrylate-based dental resin sealant

A resin-based sealant containing chitosan whiskers was developed for use as a pit and fissure sealer. Chitosan whiskers were synthesized and then characterized using Fourier transform infrared spectrometry and transmission electron microscopy. The whiskers were next incorporated into dimethacrylate monomer at various ratios by weight and subsequently analyzed for their antimicrobial and physical properties. The dimethacrylate-based sealant containing chitosan whiskers had a greater antimicrobial activity than control sealant and they were comparable with antimicrobial commercial resin sealants. The inclusion of the whiskers did not reduce the curing depth or degree of double bond conversion and the reduction in hardness was minimal. In conclusion, a resin-based sealant containing chitosan whiskers can be considered an effective antimicrobial pit and fissure sealant.     

Effect of surface sealant and staining on the fluorescence of resin composites

STATEMENT OF PROBLEM: Natural teeth and several commercial resin composites emit a strong blue fluorescence when exposed to ultraviolet (UV) light, which makes teeth whiter and brighter in daylight. Surface sealant and staining may change the fluorescence of resin composites. PURPOSE: The purpose of this study was to determine the effect of surface sealant application and staining/stain removal on the fluorescence of resin composites. MATERIAL AND METHODS: Spectral reflectance and color of 4 resin composites (Filtek Supreme, Gradia Direct, Simile, and Vit-l-escence) were measured with/without application of a surface sealant (BisCover) at baseline and after staining/stain removal (n = 5). A UV filter was used to exclude or include the UV component of illumination. Fluorescence spectra were calculated by subtracting the spectral reflectance values of the UV component excluded condition from those of UV included condition. For staining, specimens were sequentially immersed in mucin, chlorhexidine, and a tea solution. Stain removal was performed by ultrasonic cleaning and PBS (phosphate buffered saline) immersion. Color difference (DeltaE 00) by the UV component was calculated based on CIEDE2000 color system. Delta E 00 due to staining and stain removal were also calculated. Changes in color and fluorescence by the staining and stain removal were analyzed by 2-way analysis of variance (alpha=.05). RESULTS: Sealant application decreased fluorescence of resin composites. After staining, fluorescence was not detected except for 1 composite. After stain removal, a decrease in fluorescence from the baseline was observed, and 2 composites showed significant decrease ( P <.05). CONCLUSION: Fluorescence of resin composites decreased or disappeared after surface sealant application and/or staining procedure.     

Effect of surface sealant on the color stability of composite resin restorations

This study investigated the effect of sealant application on the color stability of composite resin restorations. Cavities in bovine incisors were restored with composite resin (Opallis; FGM) and the teeth were assigned to 4 groups (n=10). A sealant (Fill Glaze; Vigodent) was applied over the restorations of 2 groups. Baseline color measurements based on the CIEL*a*b* system were carried out using a spectrophotometer. Half the number of specimens was immersed in distilled water, and half was immersed in coffee 4 h/day. Color measurements were repeated after 1 h, 24 h, 7 days and 3 months. Data for each immersion solution were separately subjected to a two-way repeated measures ANOVA and Tukey's test (α=0.05). For the group without sealant immersed in water, no significant differences were observed among the periods (p ≥ 0.138), but the color was different compared with baseline (p<0.001). For the group with sealant application, the periods baseline, 1 h and 3 months presented similar results (p ≥ 0.924). For groups immersed in coffee, when the sealant was not used, no significant differences were detected between the baseline and the periods 1 h and 24 h (p ≥ 0.499), but the color changed significantly thereafter (p ≤ 0.003). In the group with sealant, significant differences were detected for all periods compared with each other (p<0.001). In conclusion, application of sealant dramatically increased the staining of the restorations exposed to coffee.     

Influence of chemo-mechanical caries removal on the surface topography of dental composite resin and glass-ionomer materials: an in vitro study

The aim of the present study was to investigate the influence of a chemo-mechanical caries removal system, Carisolv gel, on the surface topography of dental filling materials. Thirty specimens of a composite resin (Spectrum) and a compomer (Dyract AP) and 60 specimens of a glass-ionomer (Ketac-Fil Plus) were prepared. The surface topography was investigated with an optical interferometer before and after chemical exposure for 5, 10, or 20 min. Each specimen acted as its own control. The topographical part of the glass-ionomer materials was performed in two series with different drying procedures, since this material exhibits a higher sensitivity to dehydration than the other materials. The surface topographical investigations were complemented with contact angle measurements. After Carisolv gel exposure the density of summits and the developed surface area ratio (3D/2D) were slightly smaller for the composite resin and the compomer. For the minimally dried glass-ionomer material, the results indicated a reduction of the height of the surface structures, as well as a surface area enlargement, after Carisolv gel exposure. No statistically significant changes of contact angles due to Carisolv gel exposure could be detected for any material investigated. If dental filling materials of composite resin or glass-ionomer materials are exposed to Carisolv gel, no or only minor surface topographical changes can be expected. n     

人牙髓干细胞体外诱导分化为平滑肌细胞的研究

目的探究人牙髓干细胞(dental pulp stem cells,DPSC)向人平滑肌细胞(smooth muscle cell,SMC)分化的体外诱导方法。方法体外分离SMC,获取SMC的条件培养液(conditional medium,CM)。通过比较,筛选出SMC体外诱导培养液的最佳配方和浓度。体外诱导DPSC向SMC分化,通过形态学观察以及SMC表面标记物基因和蛋白表达进行检测。结果在含有转换生长因子β-1(transforming growth factorβ-1,TGF-β1)和SMC-CM的SMC体外诱导培养液作用下14 d,DPSC分化为成熟的SMC样细胞。结论 DPSC有潜能分化为成熟的SMC样细胞,为平滑肌组织工程再生种子细胞的选择提供了一种新的、无创伤、无伦理道德问题的细胞来源。     

Integrity testing of a smooth surface resin sealant around orthodontic brackets using a new Fluorescence-aided Identification Technique (FIT)

Objective:To investigate the integrity of a fluorescing resin-based sealant placed around orthodontic brackets using the Fluorescence-aided Identification Technique (FIT).Materials and Methods:Standard brackets were bonded to the buccal surfaces of 17 extracted sound permanent premolar crowns sealed with ProSeal^®. Specimens were thermocycled (20,000 cycles, 5–55°C), and toothbrushing was simulated using an electric toothbrush and artificial aqueous toothpaste slurry. Changes in the sealed area were measured after one, two, three, and four alternating thermocycling-brushing cycles simulating 2 years of wear. Digital images were captured applying FIT (405 nm) using a digital camera–equipped stereomicroscope. ImageJ was used to measure sealant integrity and loss.Results:There was a time-dependent decrease in sealed areas by between 21% and 100% (mean 54%). The sealant lost its integrity immediately after the first cycle, and unfilled areas were observed in all samples.Conclusions:The analyzed sealant lost its integrity over time. Using the proposed FIT, sealed surfaces were easily verified and quantified.     

Assessing microleakage in resin composite restorations rebonded with a surface sealant and three low-viscosity resin systems.

OBJECTIVES: The aim of this study was to assess the ability of three low-viscosity resin systems (Unibond, Single Bond, and Fluorseal), used as rebonding agents, and a specific surface-penetrating sealant (Fortify) to prevent microleakage in Class V resin composite restorations. METHOD AND MATERIALS: Fifty Class V cavities with the occlusal margin in enamel and the cervical margin in dentin and cementum were prepared on both the buccal and lingual surfaces of sound extracted premolars and restored with a hybrid light-cured resin composite. After finishing and polishing, restorations were randomly assigned to one of five equal groups (n = 10): a control, without surface sealing, and four experimental groups in which margins were etched and rebonded. Specimens were thermocycled, immersed in a 50% silver nitrate solution, sectioned longitudinally, and analyzed for leakage at the occlusal and cervical interfaces. RESULTS: Statistical analysis showed significantly less leakage at the enamel margins for all groups. Fortify and Unibond were statistically similar and provided better marginal sealing at dentin and cementum interfaces. Fluorseal showed the poorest ability to prevent microleakage. CONCLUSION: The rebonding technique may substantially minimize microleakage at dentin and cementum margins of composite restorations, when a resin system with sufficiently low viscosity is used as a surface sealant, regardless of whether it has been specified for such a purpose.     

Material properties on enamel and fissure of surface pre-reacted glass-ionomer filler-containing dental sealant

Purpose

In pediatric dentistry, sealants have been used to prevent caries. Due to its material properties such as fluoride-releasing ability and physical strength, surface pre-reacted glass (S-PRG) filler is added primarily to resin-based dental materials for clinical use. In this study, we investigated the properties of S-PRG filler containing sealant.

Influence of coffee on reflectance and chemistry of resin composite protected by surface sealant

PURPOSE: To assess the influence of the light-curing unit type and whether or not it was worth using surface sealant protection on resin composite restorative materials stained by coffee. Another objective was to propose the monitoring of coffee staining by FT-Raman spectroscopy using carbon-hydrogen (C-H) bonds as reference to the composite matrix degradation. METHODS: Sixty cylindrical specimens of resin composite were prepared and divided into six groups: HC (control)--cured with a halogen light; LC (control) cured with a LED; HF--cured with a halogen light + Fortify Plus; LF--cured with a LED + Fortify Plus; HP--cured with a halogen light + PermaSeal; LP--cured with a LED + PermaSeal. After storage for 24 hours at 37% and 100% of relative humidity, the top surface was protected, and the other surfaces isolated. Polishing with paper discs was performed after 24 hours of curing and prior to FT-Raman spectroscopy and reflectance measurements. All specimens were submitted to coffee staining for 14 days and evaluated by both systems. Results were statistically analyzed by ANOVA and Tukey tests. RESULTS: FT-Raman spectrum only showed significant changes in groups LC and LP (P< 0.05). Reflectance demonstrated that staining was present in all specimens protected by sealants. Sealant staining was larger in the HF (P < 0.001) group.     

Cytotoxicity of polymerized resin cements on human dental pulp cells in vitro

ObjectivesThis study was designed to evaluate the cytotoxicity of several resin-based cements (Panavia F, Super-Bond C&B, Chemiace II) after polymerization on cultured human dental pulp cells.MethodsAfter polymerization, specimens from three resin-based cements were eluted with fresh Dulbecco's modified Eagle's medium (DMEM) without serum for 72 h, at 37 °C, using 0.4 g of each substance per milliliter of fresh medium. Elutes obtained during this step were passed through a 0.22-μm filter and diluted with the culture medium by a ratio of 75%, 50%, 25% (v/v). Cytotoxicity of elutes were evaluated by the relative growth rates (RGR) of pulp cells with a modified 3-(4, 5-dimethyl-thiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) assay. The RGR of pulp cells were statistic analyzed by the one-way analysis of variance among the groups.ResultsThe RGR of cells exposed to 100% concentration of elution of Panavia F, Super-Bond C&B, and Chemiace II were 74.42%, 85.54%, and 82.39%, respectively. The RGR increased along with the elution of cements diluted. There was significant difference between the Panavia F group and Super-Bond C&B group (p < 0.01), but there was no significant difference in the cytotoxicity between Chemiace II and Super-Bond C&B.ConclusionsAfter polymerization, three resin-based cements (Panavia F, Super-Bond C&B, Chemiace II) induced slight cytotoxicity. The sensitivity of cytotoxicity to human pulp cells depended on the resin-based cements and the concentration of the elution. Super-Bond C&B is the least cytotoxic agent among the three resin-based cements.     

复合树脂细胞毒性检测方法的进展

良好的生物相容性是保证复合树脂临床应用安全有效的重要标准,体外细胞毒性实验作为生物学评价筛选实验最常用的项目之一,对复合树脂临床应用具有指导意义。该文就体外细胞毒性实验方法的进展作一综述。