Prevention of Artificial Caries: Effect of Bonding Agent, Resin Composite and Topical Fluoride Application

Prevention of acidic attack on tooth enamel surfaces using polishing paste containing ion-releasing filler

The purpose of this study was to investigate the ability of polishing paste containing surface pre-reacted glass-ionomer (S-PRG) filler to prevent acidic attack on tooth enamel surfaces. Resin composites were filled in the standardized cavities and finished with silicon carbide paper. These specimens were divided into three groups: the unpolished "control" group, the "PRG" group polished with S-PRG paste, and the "DDP" group polished with diamond-containing polishing paste. Following polishing, the specimens were immersed in a lactic acid buffer solution for 28 days. Optical coherence tomography (OCT) signals were measured to obtain the signal intensity and width at 1/e² at selected locations on the enamel surface adjacent to the restoration. Although signal intensity significantly increased in all groups, widths at 1/e² did not change significantly in the PRG group. For both the control and DDP groups, signal intensity and width at 1/e² increased and decreased over time, respectively.

Use of new scratch test and tensile test for evaluation of bond strength of selfadhesive flowable resin composite for repair of artificial tooth erosion

The purpose of this study was to use a new scratch test and tensile test to evaluate the bond strength between artificial erosive enamel or dentin and self-adhesive resin composites as a coating material. Coronal enamel or dentin surface was exposed to an erosive cycle (artificial saliva [AS], pH:7.0 for 6.5 h and acidic carbonated beverages for 5 min, alternated 3 times per day) for the eroded-surface or stored in AS for the remineralized-surface. Two self-adhesive flowable resin composites, Fusio and LLB-CR6 (prototype), and a conventional flowable resin composite, BEAUTIFIL FLOW with self-etching primer system, Clearfil Mega Bond, were applied to enamel or dentin surfaces; and then the bond strengths were measured. For the eroded-surface, there were no significant differences in bonding strength among all materials, as assessed by the new scratch test. Thus, these self-adhesive flowable resin composites might be useful for coating materials on acid-eroded tooth surfaces.

A New Customized Bioactive Glass Filler to Functionalize Resin Composites: Acid-Neutralizing Capability, Degree of Conversion, and Apatite Precipitation

This study introduced an experimental bioactive glass (BG) with a lower Na₂O content than conventional BG 45S5 (10.5 wt% vs. 24.5 wt%), additionally containing CaF₂ (12 wt%) and a network connectivity similar to that of BG 45S5. A series of experimental composites functionalized with 5-40 wt% of the novel BG was prepared and compared to a corresponding series of experimental composites functionalized with 5-40 wt% of BG 45S5. Commercial acidneutralizing materials (alkasite, giomer, and glass ionomer) were used as references. The capabilities of the materials to neutralize hydrochloric acid (pH = 2.6) and lactic acid (pH = 4.5) were evaluated by real-time pH measurements over 1 h. The degree of conversion and precipitation of calcium phosphate were also investigated. Data were analyzed using one-way and Welch ANOVA at an overall level of significance of 0.05. The acid-neutralizing potential of the experimental BG incorporated into resin composites was generally comparable to that of BG 45S5, and better than that of a giomer and glass ionomer. Fluorine was identified in the precipitate that developed on the composites functionalized with the experimental BG, suggesting a capability of forming fluorapatite. Unlike the 45S5 composition, the experimental BG did not impair the degree of conversion of resin composites. The novel BG filler is therefore an interesting candidate for future investigations of caries-preventive resin composites, and their potential clinical applicability for restorative, preventive, and orthodontic purposes.

Alternative model for cathepsin K activation in human dentin

OBJECTIVE

To evaluate the protease activity in dentin matrices subjected to lactic acid (LA) in comparison to polyacrylic acid (PAA) challenge model at cathepsin K (CT-K) optimum pH 5.5 to assess effectiveness of inhibitors in dentin collagen degradation.

METHODS

Dentin disks measuring 0.5mm prepared from human molars were completely demineralized in 10% H₃PO₄. Demineralized dentin disks were challenged with 0.1M LA, 1.1mM PAA, artificial saliva (AS), or deionized water (C) for 24h or 7-days. Dentin collagen properties were tested by measurement of %dry mass change, and ultimate tensile strength (UTS). Degradation of dentin type I collagen was measured by telopeptide assays measuring the sub-product release of C-terminal cross-linked telopeptides (ICTP) and C-terminal peptide (CTX) in the incubation media in relation to total protein concentration, which correlates with matrix metalloproteinases (MMPs) and CT-K activities.

RESULTS

Gravimetric analysis showed statistically significant difference between C and other groups (p<0.04) at 24h. LA specimens showed significantly higher weight loss from 24h to 7-days (p=0.02). UTS revealed statistically significant difference between AS and LA at 24h and 7-days. UTS at 24h and 7-days for C and AS had significantly higher mean values compared to LA and PAA. Telopeptide assays reported that CTX_tp results showed that LA at 24h had significantly higher mean values compared to C and AS.

SIGNIFICANCE

LA has the ability to activate endogenous CT-K in dentin as measured by the release of CTX (CT-K specific telopeptide). This LA based model has the potential application for further investigations on the activity and possible inhibitors of CT-K in human dentin.

Desenvolvimento de lesões de cárie em dentina em um modelo de biofilme simplificado in vitro: um estudo piloto

Resumo Introdução Modelos laboratoriais de biofilmes vêm sendo desenvolvidos com a finalidade de simular o ambiente bucal e o processo de formação da cárie dental. Objetivo Estabelecer e padronizar um modelo de biofilme in vitro para o desenvolvimento de lesões de cárie em dentina. Material e método Doze discos padronizados de dentina bovina foram divididos em três tempos experimentais: 4, 7 e 10 dias. As amostras de cada tempo experimental foram inoculadas com Streptococcus mutans UA 159 em meio de cultura BHI com 1% de sacarose e cultivadas em anaerobiose. As variáveis de resposta foram a perda de dureza integrada (ΔS) dos discos de dentina e dureza do substrato em diferentes profundidades. Os dados de ΔS foram analisados através de ANOVA seguido do teste Tukey, ambos com significância de 5%, e os dados de dureza de profundidade de lesão analisados descritivamente. Resultado Houve maior perda mineral aos 10 dias de crescimento microbiológico quando comparados aos 4 dias (p = 0,034), no entanto não houve diferença entre 7 e 10 dias (p = 0,853). O grupo de 4 dias mostrou perda de dureza em regiões mais superficiais (10-40µm); e o grupo de 10 dias mostrou desmineralização em áreas mais profundas, até 150 µm. Conclusão O modelo proposto mostrou-se capaz de desenvolver lesões de cárie artificiais em dentina. Em 7 dias, as lesões subsuperficiais de dentina foram adequadas para estudos de des-remineralização.

Different protocols to produce artificial dentine carious lesions in vitro and in situ: hardness and mineral content correlation

This study compared dentine demineralization induced by in vitro and in situ models, and correlated dentine surface hardness (SH), cross-sectional hardness (CSH) and mineral content by transverse microradiography (TMR). Bovine dentine specimens (n = 15/group) were demineralized in vitro with the following: MC gel (6% carboxymethylcellulose gel and 0.1 M lactic acid, pH 5.0, 14 days); buffer I (0.05 M acetic acid solution with calcium, phosphate and fluoride, pH 4.5, 7 days); buffer II (0.05 M acetic acid solution with calcium and phosphate, pH 5.0, 7 days), and TEMDP (0.05 M lactic acid with calcium, phosphate and tetraethyl methyl diphosphonate, pH 5.0, 7 days). In an in situ study, 11 volunteers wore palatal appliances containing 2 bovine dentine specimens, protected with a plastic mesh to allow biofilm development. The volunteers dripped a 20% sucrose solution on each specimen 4 times a day for 14 days. In vitro and in situ lesions were analyzed using TMR and statistically compared by ANOVA. TMR and CSH/SH were submitted to regression and correlation analysis (p < 0.05). The in situ model produced a deep lesion with a high R value, but with a thin surface layer. Regarding the in vitro models, MC gel produced only a shallow lesion, while buffers I and II as well as TEMDP induced a pronounced subsurface lesion with deep demineralization. The relationship between CSH and TMR was weak and not linear. The artificial dentine carious lesions induced by the different models differed significantly, which in turn might influence further de- and remineralization processes. Hardness analysis should not be interpreted with respect to dentine mineral loss.

Cariostatic effect of fluoride-containing restorative materials associated with fluoride gels on root dentin

Secondary caries is still the main cause of restoration replacement, especially on the root surface

Enamel remineralization by fluoride-releasing materials: proposal of a pH-cycling model

This study proposes a pH-cycling model for verifying the dose-response relationship in fluoride-releasing materials on remineralization in vitro. Sixty bovine enamel blocks were selected for the surface microhardness test (SMH1). Artificial caries lesions were induced and surface microhardness test (SMH2) was performed. Forty-eight specimens were prepared with Z 100, Fluroshield, Vitremer and Vitremer ¼ diluted - powder/liquid, and subjected to a pH-cycling model to promote remineralization. After pH-cycling, final surface microhardness (SMH3) was assessed to calculate percent recovery of surface microhardness (%SMHR). Fluoride present in enamel (μg F/mm3) and in the pH-cycling solutions (μg F) was measured. Cross-sectional microhardness was used to calculate mineral content (∆Z). There was no significant difference between Z 100 and control groups on analysis performed on - %SMHR, ∆Z, μg F and mg F/mm3 (p>0.05). Results showed a positive correlation between %SMHR and μg F/mm3 (r=0.9770; p=0.004), %SMHR and μg F (r=0.9939; p=0.0000001), ∆ and μg F/mm3 (r=0.9853; p=0.0002), ∆ and μg F (r=0.9975; p=0.0000001) and between μg F/mm3 and μg F (r=0.9819; p=0.001). The pH-cycling model proposed was able to verify in vitro dose-response relationship of fluoride-releasing materials on remineralization.