Effect of ionizing radiation and cariogenic biofilm challenge on root-dentin caries.

OBJECTIVES: To evaluate the effect of ionizing radiation and cariogenic biofilm challenge using two continuous flow models, normal and reduced salivary flow, on the development of initial root-dentin caries lesions. MATERIALS AND METHODS: Microcosm biofilms were grown under two salivary flow rates (0.06 and 0.03 mL min-1) and exposed to 5% sucrose (3 × daily, 0.25 mL min-1, 6 min) dripped over non-irradiated and irradiated root-dentin blocks for up to 7 days. The vibration modes of root dentin, matrix/mineral (M/M), and carbonate/mineral (C/M) ratios were evaluated by FTIR. The mineral density was assessed by micro-CT. RESULTS: With normal salivary flow, FTIR revealed an increase in the organic matrix (amide III) and a decrease in the mineral phase (ν4, ν2 PO43-, AII + ν2 CO32-, C/M) in caries lesions. Irradiated dentin exhibited a reduction in the mineral phase (ν1, ν3 PO43-, ν2 CO32-, C/M). Differences in mineral densities were not significant. With reduced salivary flow, FTIR also revealed increased organic matrix (amide III) for irradiated caries lesions and decrease in mineral phase (v4, v2 PO43-, v2 CO32-, and C/M) in caries lesions. ν1, ν3 PO43- precipitated on the surface of irradiated dentin and a lower mineral density was observed. CONCLUSIONS: Initial caries lesions differed between non-irradiated and irradiated dentin and between normal and reduced salivary flow rates. Significant mineral loss with exposure of the organic matrix and low mineral density were observed for irradiated dentin with a reduced salivary flow rate. CLINICAL RELEVANCE: Ionizing radiation associated with a reduced salivary flow rate enhanced the progression of root-dentin caries.

Influence of biofilm removal from the tooth-restoration interface on the progression of secondary caries lesions: a preliminary in vitro model study.

This study investigated the effects of biofilm removal from the tooth-restoration surface on secondary caries lesion progression. Biofilms were grown for up to 28 days on resin-restored enamel-dentin disks with an interfacial gap with DMM or DMM + 1% sucrose under five different protocols of Visible Biofilm Removal (V-BR; n = 7): (1) without V-BR, (2) with partial V-BR, (3) with total V-BR, (4) with total V-BR and saliva reinoculation, and (5) without V-BR under 9 h of cariogenic challenge. V-BR was performed at 7, 14 and 21 days. ΔS and CFU counts served as outcome variables. Linear regression models showed that ΔS values were higher for outer lesions than wall lesions, and outer lesion progression generally increased over time (p < 0.01). All protocols tested, except total V-BR, increased the lactobacilli count (p < 0.005). V-BR did not influence the progression of caries lesions on the cavity wall in this biofilm model.

Factors affecting the color stability and staining of esthetic restorations.

This study aimed to assess the color stability of two composite resins, unprotected or protected with a hydrosoluble gel (oxygen inhibitor) during final polymerization, when subjected to different staining solutions and daily tooth brushing simulation. Nanohybrid composite (IPS Empress Direct) or nanofilled composite (Filtek Z350) were used to produce round samples that were either unprotected or protected with a hydrosoluble gel before the final cycle of polymerization. For 5 days, the samples were immersed for 1 h/day in four different staining solutions: distilled water (control), coffee, soft drink, and red wine. Once a day, the samples were also subjected to mechanical brushing with soft-bristled brushes for 30 min. The combination of experimental conditions produced 16 groups (n = 10). Color changes (ΔE) were evaluated at baseline and after mechanical brushing cycles for 1, 3, and 5 days. Data were analyzed by linear regression models. Protection with hydrosoluble gel was able to significantly reduce the color change only on the first day (p = 0.001). The type of composite resin did not significantly affect the color change over the days. Wine affected composite resin color change only on the first day (p = 0.002). Over time, color stability of composite resins did not improve with the protection of a hydrosoluble gel before the final polymerization.

Addition of ammonium-based methacrylates to an experimental dental adhesive for bonding metal brackets: Carious lesion development and bond strength after cariogenic challenge.

INTRODUCTION: In this study, we evaluated the caries inhibition and shear bond strength achieved with the addition of the antibacterial monomer [2-(Methacryloyloxy)ethyl] trimethylammonium chloride (MADQUAT) to an adhesive used to bond orthodontic brackets. METHODS: Experimental adhesives were formulated with addition of 0% (control), 5%, or 10% MADQUAT followed by measurement of the degree of conversion. These adhesives were used to lute brackets to the enamel of premolars (n = 30). Biofilm from a microcosm model was cultivated in half of the specimens under cariogenic challenge for 5 days. The brackets were subjected to a shear bond strength test followed by measurement of the internal hardness of the enamel around the brackets to calculate the integrated mineral loss. RESULTS: The addition of MADQUAT slightly increased the degree of conversion. Adhesive containing 10% MADQUAT significantly reduced the integrated mineral loss around the bracket but also resulted in the lowest values of bond strength. No effects on bond strength and integrated mineral loss were observed with the addition of 5% MADQUAT to the adhesive. The cariogenic challenge did not affect the bond strength and the failure mode. CONCLUSIONS: MADQUAT was effective to reduce the integrated mineral loss only when added to the adhesive at a concentration of 10% despite the reduction of bond strength.

Influence of caries activity and number of saliva donors: mineral and microbiological responses in a microcosm biofilm model.

OBJECTIVE: this study evaluated the mineral and microbiological response of biofilms originating from different types of saliva inoculum with distinct levels of caries activity. METHODOLOGY: the biofilms grown over enamel specimens originated from saliva collected from a single donor or five donors with two distinct levels of caries activity (caries-active and caries-free) or from pooling saliva from ten donors (five caries-active and five caries-free). The percentage surface hardness change (%SHC) and microbiological counts served as outcome variables. RESULTS: the caries activity of donors did not affect the %SHC values. Inoculum from five donors compared to a single donor showed higher %SHC values (p=0.019). Higher lactobacilli counts were observed when saliva from caries-active donors was used as the inoculum (p=0.017). Pooled saliva from both caries activity levels showed higher mutans streptococci counts (p<0.017). CONCLUSION: Overall, pooled saliva increased the mineral response of the derived biofilms, but all the inoculum conditions formed cariogenic biofilms and caries lesions independently of caries activity.

Antiseptics and microcosm biofilm formation on titanium surfaces.

Oral rehabilitation with osseointegrated implants is a way to restore esthetics and masticatory function in edentulous patients, but bacterial colonization around the implants may lead to mucositis or peri-implantitis and consequent implant loss. Peri-implantitis is the main complication of oral rehabilitation with dental implants and, therefore, it is necessary to take into account the potential effects of antiseptics such as chlorhexidine (CHX), chloramine T (CHT), triclosan (TRI), and essential oils (EO) on bacterial adhesion and on biofilm formation. To assess the action of these substances, we used the microcosm technique, in which the oral environment and periodontal conditions are simulated in vitro on titanium discs with different surface treatments (smooth surface - SS, acid-etched smooth surface - AESS, sand-blasted surface - SBS, and sand-blasted and acid-etched surface - SBAES). Roughness measurements yielded the following results: SS: 0.47 µm, AESS: 0.43 µm, SB: 0.79 µm, and SBAES: 0.72 µm. There was statistical difference only between SBS and AESS. There was no statistical difference among antiseptic treatments. However, EO and CHT showed lower bacterial counts compared with the saline solution treatment (control group). Thus, the current gold standard (CHX) did not outperform CHT and EO, which were efficient in reducing the biofilm biomass compared with saline solution.

Influence of caries activity and number of saliva donors: mineral and microbiological responses in a microcosm biofilm model

Abstract Objective this study evaluated the mineral and microbiological response of biofilms originating from different types of saliva inoculum with distinct levels of caries activity. Methodology the biofilms grown over enamel specimens originated from saliva collected from a single donor or five donors with two distinct levels of caries activity (caries-active and caries-free) or from pooling saliva from ten donors (five caries-active and five caries-free). The percentage surface hardness change (%SHC) and microbiological counts served as outcome variables. Results the caries activity of donors did not affect the %SHC values. Inoculum from five donors compared to a single donor showed higher %SHC values (p=0.019). Higher lactobacilli counts were observed when saliva from caries-active donors was used as the inoculum (p=0.017). Pooled saliva from both caries activity levels showed higher mutans streptococci counts (p<0.017). Conclusion Overall, pooled saliva increased the mineral response of the derived biofilms, but all the inoculum conditions formed cariogenic biofilms and caries lesions independently of caries activity.

New Post-COVID-19 Biosafety Protocols in Pediatric Dentistry

Abstract The most recent Severe Acute Respiratory Syndrome - COVID-19 - caused by coronavirus infection (SARS-CoV-2) has high-virulence transmission and direct human contagiousness by proximity. Thus, the considerable occupational risk in pediatric dentistry is evident, given the nature and form of procedures performed in an outpatient setting. Thus, the aim of this paper was to identify and contextualize technical and scientific information available to date aimed at preventing and minimizing risks for patients, caregivers and professionals. The results indicate that protective measures are being developed considering procedures according to risks and benefits, and five points stand out: 1. Regulation of resumption of elective procedures, screening and scheduling patients; 2. Restructuring clinical environment and infection control; 3. Improvement of personal protective equipment and biosafety recommendations; 4. Maximization of the use of non-invasive techniques, use of high-powered dental suction, and absolute isolation of the operative field; and 5. Minimization of the use of air-water syringe, dental spittoon and high-speed handpiece. The measures to be taken require reflection for the restart of a "new clinical practice", especially aiming at behavioral and structural changes regarding operational biosafety.

Desenvolvimento de lesões de cárie em dentina em um modelo de biofilme simplificado in vitro: um estudo piloto / Development of dentin caries lesions in an in vitro simplified biofilm model: a pilot study

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.

Introduction: Oral laboratory biofilm models have been developed to reproduce the oral environment and the process of caries lesion formation in vitro. Objective: To establish and standardize an in vitro biofilm model for the development of caries lesions in dentin. Material and method: Twelve standardized bovine dentin discs were assigned into three experimental times: 4, 7, and 10 days. Samples of each experimental period were inoculated with Streptococcus mutans UA 159 in a BHI culture medium with 1% sucrose, and cultured under anaerobic conditions. The integrated hardness loss (ΔS) of dentin discs and the hardness of the substrate at different depths were considered as response variables. The ΔS data were analysed by ANOVA followed by Tukey's test, both with significance level of 5%, and the data of hardness at different depths were analysed descriptively. Result: There was a higher hardness loss after 10 days of microbial growth when compared to 4 days (p = 0.034), however, there was no difference between 7 and 10 days (p = 0.853). The 4-day group showed loss of hardness of the surface layers (10-40μm) and the 10-day group showed demineralization in the deeper area around 150µm. Conclusion: The proposed model was able to develop artificial caries lesions in dentin. In 7 days, the dentin sub superficial lesions were suitable to des-remineralisation studies.

Antiseptics and microcosm biofilm formation on titanium surfaces

Abstract Oral rehabilitation with osseointegrated implants is a way to restore esthetics and masticatory function in edentulous patients, but bacterial colonization around the implants may lead to mucositis or peri-implantitis and consequent implant loss. Peri-implantitis is the main complication of oral rehabilitation with dental implants and, therefore, it is necessary to take into account the potential effects of antiseptics such as chlorhexidine (CHX), chloramine T (CHT), triclosan (TRI), and essential oils (EO) on bacterial adhesion and on biofilm formation. To assess the action of these substances, we used the microcosm technique, in which the oral environment and periodontal conditions are simulated in vitro on titanium discs with different surface treatments (smooth surface - SS, acid-etched smooth surface - AESS, sand-blasted surface - SBS, and sand-blasted and acid-etched surface - SBAES). Roughness measurements yielded the following results: SS: 0.47 µm, AESS: 0.43 µm, SB: 0.79 µm, and SBAES: 0.72 µm. There was statistical difference only between SBS and AESS. There was no statistical difference among antiseptic treatments. However, EO and CHT showed lower bacterial counts compared with the saline solution treatment (control group). Thus, the current gold standard (CHX) did not outperform CHT and EO, which were efficient in reducing the biofilm biomass compared with saline solution.