Flexural Strength, Elastic Modulus and Remineralizing Abilities of Bioactive Resin-Based Dental Sealants

Objective: To assess the remineralizing abilities and compare the flexural strength and elastic modulus of different bioactive pit and fissure sealants. Materials and Methods: Human enamel samples were randomly and blindly sealed with one of the following bioactive materials: BioCoat (Bc), ACTIVA KIDS (Av) and BeautiSealant (Bu). Seal-it (Si) was used as a non-bioactive sealant beside a control blank (B) group with no sealant. The sealed samples were subjected to a pH-cycling model (7 days of demineralization–remineralization cycles). The enamel surface hardness change (SHC), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) and polarized light microscopy were used to assess the remineralizing abilities of the studied sealants. Flexural strength and elastic modulus were also assessed following the ISO 4049 protocols. One-way analysis of variance (ANOVA) was used to analyze the results. Results: Bc sealant showed the highest FS and EM (p < 0.05). The contact with Bc and Bu sealants showed significantly lower %SHL (p < 0.05) in comparison to the other. These findings were supported by the results of SEM-EDX and polarized imaging by showing higher percentages of calcium and phosphate ions with the former sealants and thinner demineralized enamel bands. Conclusion: In this study, Bc showed the highest flexural strength. Bc and Bu sealants outperformed the other studied sealants in terms of their remineralization abilities.

The effect of various fluoride products on dentine lesions during pH-cycling

This study compared the effect of topically applied fluoride products on dentine lesions in an in vitro experiment. Demineralized bovine dentine specimens were treated once with either SDF solution (35,400 ppm F), NaF varnish (22,600 ppm F), TiF4 solution (9,200 ppm F), SnF2 gel (1,000 ppm F), no treatment (control) or preserved as baseline lesions. After the application and subsequent removal of the fluoride products, the specimens were subjected to pH-cycling. Calcium loss and uptake in the de- and remineralization buffers were assessed daily. Fluoride release into the buffers was analyzed on day 1, 2, 3, 5, 8 and 13. After the pH-cycling period, mineral distribution throughout the lesion depth was analyzed using transversal microradiography (TMR). X-ray energy-dispersive spectroscopy (EDS) examined the deposition of silver, titanium and tin after application of SDF, TiF4, and SnF2, respectively. Overall, calcium loss and uptake analysis in the de- and remineralization buffers revealed that the SDF product was the most effective in inhibiting lesion progression, followed by the TiF4, NaF, and SnF2 products. Fluoride analysis disclosed a steep reduction of the amount of fluoride released into de- and remineralization buffers with time. The fluoride effects on de- and remineralization continued beyond the days that fluoride was released into the buffers. TMR analysis showed significant remineralization in the outer zone of the dentine lesions for all fluoride products, with SDF giving hyper-mineralization in this zone. In the inner zone, lesions developed in all fluoride groups, with the smallest in the SDF group. EDS showed silver and titanium deposition in depth up to 85 μm and 8 μm, respectively, while no tin deposition was observed. The silver in the dentine lesions did not contribute significantly to the density of the TMR profiles in the SDF group. In conclusion, all topical fluoride products protected the dentine lesions against lesion progression, but at different degrees. SDF showed a superior effect in protection against further demineralization and enhancement of remineralization. This was probably attributed to its fluoride concentration that was the highest among the fluoride products.

Chemical, Microstructural and Morphological Characterisation of Dentine Caries Simulation by pH-Cycling

In vitro simulation of natural caries is of great importance in dental research for the development of more effective clinical treatments. The pH-cycling (pHc) procedure consists of a dynamic caries process with alternating de-remineralisation periods. The current research aims to evaluate the effects of the pHc procedure on mineral dentine properties in comparison with sound dentine and natural residual caries. For this purpose, dentine slices from human third molars were submitted to cycling periods of 14 and 28 days. The chemical composition, morphological and microstructural properties of the dentine samples were examined by infrared and Raman spectroscopies, X-ray diffraction, and scanning electron microscopy techniques. In addition, the depth of the demineralisation front was evaluated by Masson’s trichrome (MT) staining. The results showed that the pHc procedure led to notable changes in the mineral composition and the crystalline characteristics with respect to sound dentine and some extent to natural caries. The MT results revealed that pHc 28 yields a deeper lesion than pHc 14, simulating potential progression of natural caries. The results of this study provide a better understanding of the mechanisms of demineralisation that could occur in an in vivo environment and provide a standardised substrate similar to natural residual caries.

Effect of experimental moringa and propolis toothpastes on surface microhardness of simulated hypersensitive dentin

Objective Objective was to investigate the effect of NovaMin toothpaste and two experimental toothpastes on surface microhardness of hypersensitive dentin. Methods Eighty specimens were prepared and divided randomly into eight groups (n = 10/group) according to the tested toothpastes (NovaMin, moringa and propolis toothpastes) and the acidic challenge (with or without 6% citric acid challenge). Enamel surfaces were removed, and the dentin surfaces were exposed on which the three tested toothpastes were brushed twice a day for 1 week using an electric toothbrush, then a 4-d citric acid cycling model with pH 5 was performed. The prepared specimens were stored in artificial saliva until the microhardness test was performed. Statistical analysis was done using One-way ANOVA followed by Tukey post hoc test. Results NovaMin-containing toothpaste showed an increased dentin surface microhardness following a week of twice daily brushing compared to other groups. However, NovaMin-containing toothpaste showed the highest microhardness values following pH cycling with citric acid of pH 5 compared to other tested groups. Conclusions NovaMin-containing toothpaste showed a partial recovery of dentin microhardness at pH 5 during the acidic challenge. Moreover, propolis- and moringa-containing toothpastes had an insignificant effect on dentin surface microhardness with and without citric acid challenge.

Effect of Sodium Fluoride Varnish and Potassium Iodide on Remineralization Efficacy of Silver Diamine Fluoride

The purpose of this study was to compare the effect of sodium fluoride(NaF) varnish and potassium iodide(KI) on remineralization efficacy of silver diamine fluoride(SDF) by measuring microhardness and evaluating surface morphology by scanning electron microscope(SEM). Artificial caries lesions were induced on extracted primary molars and vickers microhardness was measured. Specimens were randomly separated into 4 groups for treatment. The specimens in group I were treated with SDF, group II with NaF varnish after SDF, group III with KI after SDF and group IV with distilled water. After 8 days of pH cycling, vickers microhardness was measured and difference before and after treatment was calculated. For SEM, 2 samples were evaluated respectively after enamel polishing, lesion formation and after pH cycling. Group III showed highest increase in microhardness. Group I showed higher increase in microhardness than Group II but without statistical difference. Group IV showed lowest increase in microhardness value among 4 groups. On SEM image, group I, II and III showed smoother and less irregular surface compared to group IV. Amorphous crystal pellicles were observed in group III. In conclusion, SDF, SDF and NaF, SDF and KI groups showed smoother surface and increase in microhardness suggesting the possibility that remineralization effect might take place in oral conditions. In addition, in limited conditions of this study, applying NaF varnish after SDF did not increase the remineralization efficacy of SDF while KI significantly increased the remineralization efficacy of SDF. However, additional study considering various conditions that might affect demineralization and remineralization in clinical situations need to be conducted.

Evaluation of Wear Properties of Four Bulk-Fill Composites: Attrition, Erosion, and Abrasion

Purpose. Wear and increased surface roughness are among the reasons for failure of posterior composite restorations. Considering the widespread use of bulk-fill composites in the posterior region, information about their wear resistance is imperative. The aim of this study was to compare the wear and surface roughness of four bulk-fill composite resins with a conventional composite. Methods. Thirty composite discs ( 4 mm × 10 mm ) were fabricated from EverX Posterior (GC), X-tra fil (Voco), Filtek Bulk-Fill Posterior (3M, USA), SonicFill 2 (Kerr), and Z250 (3M) composites. The baseline weight and surface roughness of specimens were measured. For the assessment of the attrition wear, the specimens were placed in a chewing simulator (Mechatronik). pH cycling was performed to erode the composite discs. They were then placed in a tooth brushing simulator machine (Dorsa) for abrasion wear. Finally, the weight and surface roughness of the specimens were measured. Data were compared using one-way ANOVA ( alpha ≤ 0.05 ). Results. One-way ANOVA showed that the mean weight changes were significant after attrition, abrasion, and erosion ( P = 0.019 ), but changes in surface roughness were not significant ( P ≥ 0.05 ). The results of Tukey’s test showed no significant difference between the bulk-fill composites and Z250 regarding weight loss ( P ≥ 0.05 ), but the weight loss of X-tra fil was significantly greater than that of EverX ( P = 0.007 ) and Filtek Bulk-Fill ( P = 0.005 ). Conclusions. Considering the limitations of this study, it appears that the wear and surface roughness of bulk-fill composites are within the acceptable range and are not different from those of a conventional composite.

Sodium p-Toluenesulfinate Enhances the Bonding Durability of Universal Adhesives on Deproteinized Eroded Dentin

The effects of deproteinization using sodium hypochlorite (NaOCl) and the subsequent application of an antioxidant (sodium p-toluenesulfinate, STS) onto the bonding durability of universal adhesives on eroded dentin were investigated. Untreated sound dentin served as the control, whereas eroded dentin, which had been prepared by pH-cycling in 1% citric acid and a remineralization solution, was either untreated, deproteinized with a 10% NaOCl gel or deproteinized with the 10% NaOCl gel and subsequently treated with an STS-containing agent. The dentin surfaces were bonded using a universal adhesive (Clearfil Universal Bond Quick, Scotchbond Universal or G-Premio Bond), and the micro-tensile bond strength (µTBS) test was performed after 24 h or 10,000 thermal cycles. The µTBS data were statistically analyzed using a three-way ANOVA and Tukey’s HSD post hoc tests. The lowest µTBS was measured on untreated eroded dentin (p < 0.001). Deproteinization of eroded dentin resulted in µTBS similar to untreated sound dentin (p > 0.05), but the highest µTBS was obtained if deproteinization was followed by the application of STS. Thermocycling significantly decreased µTBS in all groups (p < 0.001), except for STS-treated, deproteinized, eroded dentin (p > 0.05). This indicated that deproteinization, followed by the application of STS, could enhance the bonding durability of universal adhesives on eroded dentin.

Assessment of the Effect of Acid and Base Cycling on Mechanical Properties of Various Esthetic Restorative Materials

Objective: The purpose of this study is the evaluation of the effect of pH cycling, including both acidic and alkaline environments, on the mechanical properties of tooth-colored restorative materials. Methods and Materials: 20 rectangular bar specimens of one bulk-fill restorative composite, two conventional nanohybrid restorative composites, and one restorative resin-modified glass ionomer were produced according to ISO 4049. Half of the materials were stored in an acid and base cycling defined as two-day storage in acidic (pH =4) and alkaline (pH=8) solutions. The rest of the materials were incubated in distilled water as a control group. The storage lasted for 48 days. Finally, flexural strength, elastic modulus, and microhardness of the specimens in each group determined. Data analyzed with Kruskal-Wallis, Dunn, MANOVA, Tukey HSD and T-test. Results: The pH cycling model had a significant influence on all mechanical properties of the bulk-fill restorative composite and resin-modified glass ionomer than those stored in water (P <0.05). One of the conventional nanohybrid restorative composites showed a significant reduction in elastic modulus and microhardness while the other one showed a significant reduction only in flexural strength. Conclusion: pH cycling negatively affects the mechanical properties of resin composites, and the materials’ composition is an important factor in the degradation of the resin-based materials examined.

THE EFFECTIVENESS OF COMPOMER AND GIC AGAINST PREVENTION IN ENAMEL DEMINERALIZATION

Background: Several studies showed that fluoride interferes in the dynamics involved in the development of caries and could present an antimicrobial effect or provide demineralization inhibition or dental remineralization. The development of fluoride-releasing materials can contribute to a preventive of demineralization. GIC and Compomer are restorative materials containing fluoride which can prevent demineralization. Purpose: To analyze the effectiveness of Compomer and GIC against prevention in enamel demineralization. Method: The cavities were made on 18 bovine teeth which grouped into 3 groups, each group consisting of 6 bovine teeth. After the restorative procedures, the teeth were submitted to demineralization and remineralization cycling during 14 days. The sections of the teeth were examined under scanning electron microscope after undergoing pH cycling. The data were analyzed using the Kruskal-Wallis and Tukey Test (p<0.05). Results: GIC group showed the lowest lesion depth of demineralization (10.9883 ± 0.74333) followed by Compomer group (25.4183 ± 3.44268) and Control group (88.9783 ± 3.02495). Conclusion: GIC restorative materials have a better enamel demineralization prevention effect than Compomer. Keywords: compomer, demineralization, fluoride, GIC, remineralization