Tamires Timm Maske

Influence of the Inoculum Source on the Cariogenicity of in vitro Microcosm Biofilms.

This study investigated the cariogenic potential of biofilms originating from different types of inoculum (saliva and dental plaque) from caries-active and caries-free individuals. Ten volunteers were selected from each caries condition for the paired collection of saliva and dental plaque. Microcosm biofilms were grown in triplicate from each inoculum on enamel specimens in 24-well plates under cariogenic challenge. After 10 days, the biofilms were collected for analysis of outcome variables: percentage of surface hardness change (%SHC) and microbiological composition of biofilms. Statistical analysis was performed using the t test, the linear multivariate analysis model and Pearsons correlation coefficients (α = 0.05). A comparative analysis between microbiological baseline data showed higher counts of mutans streptococci in plaque samples within caries-active individuals; a comparative analysis of colony-forming unit (CFU) counts between individuals with different caries status showed higher counts of acid-tolerant microorganisms and mutans streptococci in dental plaque and of acid-tolerant microorganisms in saliva. After 10 days of biofilm growth, the CFU values for total microorganisms, lactobacilli, mutans streptococci and acid-tolerant bacteria, as well as for SHC, were not statistically significant, considering the type of inoculum and caries condition (p > 0.05). A positive correlation was found for %SHC and CFU counts of acid-tolerant bacteria (r = 0.406) and lactobacilli (r = 0.379). Under the limits of this study, the cariogenic potential of biofilms, formed under identical conditions in vitro, is similar, regardless of baseline differences between the source and type of inoculum.

An in vitro dynamic microcosm biofilm model for caries lesion development and antimicrobial dose-response studies

Abstract Some dynamic biofilm models for dental caries development are limited as they require multiple experiments and do not allow independent biofilm growth units, making them expensive and time-consuming. This study aimed to develop and test an in vitro dynamic microcosm biofilm model for caries lesion development and for dose-response to chlorhexidine. Microcosm biofilms were grown under two different protocols from saliva on bovine enamel discs for up to 21 days. The study outcomes were as follows: the percentage of enamel surface hardness change, integrated hardness loss, and the CFU counts from the biofilms formed. The measured outcomes, mineral loss and CFU counts showed dose-response effects as a result of the treatment with chlorhexidine. Overall, the findings suggest that biofilm growth for seven days with 0.06 ml min−1 salivary flow under exposure to 5% sucrose (3 × daily, 0.25 ml min−1, 6 min) was suitable as a pre-clinical model for enamel demineralization and antimicrobial studies.

Correlation between the cariogenic response in biofilms generated from saliva of mother/child pairs.

This study aimed to correlate the cariogenic responsiveness of biofilms generated from the saliva of mothers and children. The mother–child pairs were classified according to the children’s caries levels: caries-free, early childhood caries (ECC) or severe ECC. Microcosm biofilms were grown on enamel discs for 10 days. Factors under evaluation were caries experience levels, inoculum source (mothers and children) and growth conditions including cariogenic challenge (growth medium provided with and without sucrose) and no cariogenic challenge (growth medium sucrose-free). Statistical analysis was performed with ANOVA and Tukey’s test, and the Spearman correlation test. Regular sucrose exposure resulted in a higher surface hardness change (%SHC). The correlation between biofilms formed from saliva of mother–child pairs was significant regarding pH, total aciduric microorganisms and lactobacilli counts under cariogenic challenge. Biofilm growth originating from mother–child pairs under regular sucrose exposure promoted the same cariogenic response independently of caries experience and the microbiological profile of the donors.

Failed bonded interfaces submitted to microcosm biofilm caries development

OBJECTIVES This study aimed to evaluate the dentin wall carious lesion development of different composite-dentin interfaces in the presence of two adhesive bonding materials in the gaps, using a microcosm biofilm model. METHODS Dentin samples were prepared (10.4mm(2)) and restored with a composite resin using two adhesive systems (etch-and-rinse and self-etch techniques). Different conditions with respect to composite-dentin interfaces were produced with a 200μm gap: failed bonded without ageing or after mechanical ageing, or non-bonded with or without the presence of adhesive material on the dentin wall. For cariogenic challenge, specimens were subjected to a biofilm microcosm model for 14days to create caries-like wall lesions. Before and after caries development, transverse wavelength-independent microradiography images were taken, and lesion depth and mineral loss were measured. Data were analysed with linear regression models (p<0.05). RESULTS The composite-dentin interface conditions significant influenced the caries development: lesion development was reduced by the presence of the adhesive material on dentin wall, while lesion development was increased by the mechanical ageing (p=0.019). There was no difference between the adhesive materials (p values>0.05). CONCLUSION Different composite-dentin interfaces influence wall lesion development in gaps, with the interfaces submitted to ageing showing less carious protection than those interfaces with the presence of adhesive covering the dentin. CLINICAL SIGNIFICANCE The presence of adhesive bonding material in the gaps plays a role on the wall caries lesion development.

Bonding of Adhesive Luting Agents to Caries-affected Dentin Induced by a Microcosm Biofilm Model.

OBJECTIVES To evaluate the bond strength of adhesive luting agents applied to caries-affected dentin (CAD). METHODS Thirty-six noncarious human third molars were abraded to expose an occlusal dentin surface. Caries lesions were induced in half of the samples using a microcosm biofilm model. Biofilm was cultivated under an anaerobic atmosphere for 14 days in a medium enriched with mucin. The same medium containing 1% sucrose was alternated for 4 hours per day. Cylinders of resin cement (RelyX ARC, RelyX U200, or BisCem) were built up over the dentin substrate and submitted to shear bond load. The samples were then longitudinally sectioned. The hardness and elastic modulus of dentin were measured at different depths from the occlusal surface. A three-dimensional finite element simulation was performed to analyze the residual stress distribution during the shear bond strength test. Bond strength data were analyzed by two-way analysis of variance (ANOVA) and hardness and elastic modulus by split-plot ANOVA. Multiple comparisons were performed with the SNK test (α=0.05). RESULTS For all cements, the highest bond strengths were observed in sound dentin. Relyx ARC bond strength was similar to that of RelyX U200 for both substrates; BisCem had the lowest values. CAD had lower hardness (above a depth of 100 μm) and elastic modulus (above a depth of 150 μm) values than sound dentin. Stress distribution during the bond strength test was similar under all experimental conditions. CONCLUSION Impairment of the mechanical properties of dentin promoted by carious lesions reduced the bond strength of adhesive luting agents.

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.

Minimal Gap Size and Dentin Wall Lesion Development Next to Resin Composite in a Microcosm Biofilm Model

This in vitro study investigated the development of dentin wall lesions next to resin composite containing very small gap sizes using an in vitro biofilm model, and evaluated whether a relevant threshold for the gap size could be established. Microcosm biofilms were grown for 14 days within small interfacial gaps between dentin-resin composite discs under intermittent cariogenic challenge. The factor under study was gap size: samples were either restored with composite resin without adhesive procedure (no intentional gap; no bonding [NB] group) or with intentional gaps of 30, 60, or 90 µm, or with complete adhesive procedure (no gap; bonding [B] group). Secondary caries wall lesion progression was measured in lesion depth (LD) and mineral loss (ML) using transversal wavelength independent microradiography at 3 locations: outer surface lesion and wall lesions at 200 and 500 µm distance from gap entrance. Results from linear regression analysis showed that the presence of an intentional gap (30, 60, and 90 µm) affected the secondary caries progression at 200 µm from the gap entrance (p ≤ 0.013). The NB group did not show significant wall lesion development (ML and LD, p ≥ 0.529). At 500 µm distance almost no wall caries development was observed. In conclusion, dentin wall lesions developed in minimal gap sizes, and the threshold for secondary wall lesion development was a gap of around 30 µm in this microcosm biofilm model.

New adhesive system based in metals cross-linking methacrylate

This study evaluated the anti-antibiofilm potential of silver methacrylate (Ag) or di-n-butyldimethacrylatetin (Sn) in experimental adhesive systems. Ag and Sn methacrylates were incorporated at 0.5mol%, 1mol% and 2mol% in an adhesive resin. The anti-antibiofilm potential, degree of conversion (DC), microtensile bond strength (μTBS), water sorption/solubility (WSR/SL), bonded interfaces pattern (SEM), cytotoxicity and leaching of Ag and Sn ions were evaluated. Data were statistically analyzed considering α = 0.05. Only Ag at 2% affected DC and μTBS. Ag at 1% and 2% and Sn at 1% and 2% showed anti-biofilm potential against Mutans streptococci. Ag at 1% and 2% and Sn at 2% showed a statistically significant difference to the control in WSR/SL (p < 0.05). The additions of metal methacrylate did not affect cell viability, being the adhesive resins statistically similar to controls. Leached metals of Ag were more than 100x higher than for Sn. Between the concentration tested, Ag and Sn methacrylate at 1% presented an anti-biofilm effect without altering the mechanical properties evaluated.

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. HighlightsBrackets were fixed using adhesives with 0%, 5%, or 10% antibacterial monomer.Bond strength and mineral loss were analyzed after cariogenic challenge.Adding 10% antibacterial monomer to the adhesive reduced the mineral loss.Lowest bond strength was observed for adhesive with the 10% antibacterial monomer.

The effect of non-restorative treatments on the progression of artificial dentine caries lesions underneath enamel

Purpose: To develop an experimental model for hidden caries lesions and to evaluate the effect of 0.12% chlorhexidine (CHX) and 1.23% acidulated phosphate fluoride (APF) on biofilm formation and on the dentine demineralization. Methods: Dentine discs with artificial lesions were divided into four subgroups (500-100-0µm gaps or sound enamel). Enamel discs were adapted over the dentine samples and fixed in acetate matrices. Microcosm biofilms were formed on the specimens for 10 days (cariogenic condition). Specimens from subgroups (n = 9) were individually treated for 1 min by daily immersion in CHX or saline, or weekly in APF suspension. Biofilms were quantified [total microorganism (TM) and mutans streptococci (MS)]. Mineral profiles were assessed by Transverse Microradiography. Data were analyzed by ANOVA, Holm-sidak and paired t-test (p<0.05). Results: CHX decreased MT counts and increased MS counts compared to other treatments in gaps presence or absence (p<0.05). For the control, 500 µm gap caused higher TM counts (p = 0.024). No significant differences (treatment groups X subgroups) were found for the mineral profiles. Conclusion: 500 µm gap does not generate higher microbial colonization and CHX does not inhibit MS colonization of surfaces. APF and CHX showed positive trend for lesions remineralization.