Effect of anaerobic or/and microaerophilic atmosphere on microcosm biofilm formation and tooth demineralization

Abstract Microcosm biofilms can reproduce the complexity of a dental biofilm. However, different forms of cultivation have been used. The impact of the culture atmosphere on the development of microcosm biofilms and their potential to cause tooth demineralization has not yet been deeply studied. Objective This study analyzes the effects of three experimental cultivation models (microaerophile vs. anaerobiosis vs. experimental mixed) on the colony-forming units (CFU) of the cariogenic microorganisms and tooth demineralization. Methodology 90 bovine enamel and 90 dentin specimens were distributed into different atmospheres: 1) microaerophilia (5 days, 5% CO2); 2) anaerobiosis (5 days, jar); 3) mixed (2 days microaerophilia and 3 days anaerobiosis), which were treated with 0.12% chlorhexidine (positive control - CHX) or Phosphate-Buffered Saline (negative control - PBS) (n=15). Human saliva and McBain's saliva containing 0.2% sucrose were used for microcosm biofilm formation, for 5 days. From the second day to the end of the experiment, the specimens were treated with CHX or PBS (1x1 min/day). Colony-forming units (CFU) were counted, and tooth demineralization was analyzed using transverse microradiography (TMR). Data were subjected to two-way ANOVA and Tukey's or Sidak's test (p<0.05). Results CHX was able to reduce total microorganism's CFU compared to PBS (differences of 0.3-1.48 log10 CFU/mL), except for anaerobiosis and microaerophilia in enamel and dentin biofilm, respectively. In the case of dentin, no effect of CHX on Lactobacillus spp. was observed. CHX significantly reduced enamel demineralization compared to PBS (78% and 22% reductions for enamel and dentin, respectively). Enamel mineral loss did not differ when compared with the other atmospheres; however, the enamel lesion depth was greater under anaerobiosis. Dentin mineral loss was lower under anaerobiosis when compared with the other atmospheres. Conclusion The type of atmosphere has, in general, little influence on the cariogenic ability of the microcosm biofilm.

Characterization of white spot lesions formed on human enamel under microcosm biofilm for different experimental periods

Abstract The initial characteristics of white spot lesion (WSLs), such as the degree of integrated mineral loss (ΔZ), depth and pattern of mineral distribution, have an impact on further demineralization and remineralization. However, these lesion parameters have not been evaluated in WSLs produced from microcosm biofilms. Objective: This study characterized artificial white spot lesions produced on human enamel under microcosm biofilm for different experimental periods. Methodology: In total, 100 human enamel specimens (4x4mm) were assigned to 5 distinct groups (n=20/group) differing according to the period of biofilm formation (2, 4, 6, 8 or 10 days). Microcosm biofilm was produced on the specimens from a mixture of human and McBain saliva at the first 8h. Enamel samples were then exposed to McBain saliva containing 0.2% sucrose. WSLs formed were characterized by quantitative light-induced fluorescence (QLF) and transverse microradiography (TMR). Data were analyzed by ANOVA/Tukey or Kruskal-Wallis/Dunn tests (p<0.05). Results: A clear time-response pattern was observed for both analyses, but TMR was able to better discriminate among the lesions. Regarding QLF analysis, median (95%CI; %) changes in fluorescence ∆Z were -7.74(-7.74:-6.45)a, -8.52(-8.75:-8.00)ab, -9.17(-10.00:-8.71)bc, -9.58(-10.53:-8.99)bc and -10.01(-11.44:-9.72)c for 2, 4, 6, 8, and 10 days, respectively. For TMR, median (95%CI; vol%.µm) ∆Z were 1410(1299-1479)a, 2420(2327-2604)ab, 2775(2573-2899)bc, 3305(3192-3406)cd and 4330(3972-4465)d, whereas mean (SD; µm) lesion depth were 53.7(12.3)a, 71.4(12.0)a, 103.8(24.8)b, 130.5(27.2)bc, 167.2(39.3)c for 2, 4, 6, 8 and 10 days, respectively. Conclusion: The progression of WSLs formed on human enamel under microcosm biofilm can be characterized over 2-10 days, both by QLF and TMR analyses, although the latter provides better discrimination among the lesions.

Effect of fluoride, chlorhexidine or Nd:YAG on the progression of root dentin demineralization after removal of the demineralized organic matrix

Abstract Quantification of collagen degradation is an important parameter to evaluate dentin caries for preventive aid. Objectives: Evaluate preventive methods against root collagen degradation by the hydroxyproline assay (HYP) and microradiography technique (MRT). Methodology: Five bovine root dentin blocks were obtained and subjected to an artificial demineralization process by acetate buffer (pH 5) to induce carious lesion formation. Samples were subjected to the following therapeutic treatments: 1) 0.12% chlorhexidine for 1 min, 2) 2% fluoride for 1 min, 3) Nd:YAG Laser (400 μm diameter optical fiber, 10 Hz frequency, 60 mJ/pulse energy, 48 J/cm2 energy density, in noncontact mode for 10 s), 4) deionized water (control) for 1 min, 5) MRT control group (without treatment and removal of collagen). Samples were exposed to degradation by a collagenase enzyme for five days. The enzyme solution was collected, by colorimetry in a spectrophotometer, from the collagen matrix for the hydroxyproline release analysis. The same samples were subjected to an additional two days of demineralization to induce the progression of mineral loss. Samples were analyzed by MRT for the visualization of their degraded areas (estimation of lesion depth and mineral loss). ANOVA was applied to compare hydroxyproline release rates. MRT data were subjected to the Kruskal-Wallis test, followed by the Dunn's test. Comparisons between the initial five-day and the subsequent two-day demineralization processes were performed by repeated t-test or Wilcoxon (p<0.05) measurements. Results: The amount of HYP released from the dentin samples failed to show significant differences among the groups (p=0.09). Fluoride and chlorhexidine were able to interact with the samples, reducing the progression of dentin caries after removal of the demineralized organic matrix. CHX was the only treatment able to show significant lower lesion depth than the negative control. Conclusion: Chlorhexidine and fluoride were effective in reducing root caries progression.

Acceptability and effect of TiF4 on dental caries: a randomized controlled clinical trial

Abstract: This randomized three-armed controlled clinical trial compared the effect of titanium tetrafluoride (TiF4) and sodium fluoride (NaF) varnishes on caries control in smooth surfaces of permanent dentition and children's acceptability. Sixty children (6-8 y/o) were randomly divided into TiF4 (2.45% F-), NaF (2.26% F-) or placebo (control) groups. Varnishes were applied on permanent teeth once a week for the first 4 weeks and after the 6th and 12th months of the study. The variables were as follows: International Caries Detection and Assessment System (ICDAS) scores, quantitative fluorescence changes, visual plaque index (VPI) and degree of acceptability. Two-way RM-ANOVA, ANOVA/Tukey and χ2 tests were performed (p < 0.05). No differences were found between the treatments with respect to ICDAS scores (p = 0.32). Only TiF4 reduced the mean fluorescence loss significantly at 18 months compared to the baseline (p = 0.003). TiF4 showed a lower percentage of new caries lesions by tooth surface than the placebo, while NaF did not induce such a change (p < 0.014). Regardless of the treatment, more than 95% of the participants reported being satisfied. For all groups, the VPI decreased significantly at 3 months compared to the baseline value (p < 0.001), with no differences between the treatments (p = 0.17). TiF4 had a similar ability to control caries lesions as NaF; however, only TiF4 differed from the placebo (p = 0.004). The acceptability of TiF4 varnish was similar to that of NaF varnish.

Commercial antimicrobials mouthrinses on caries and periodontitis-related biofilm control: a review of literature / Enxaguatórios comerciais antimicrobianos sobre o controle do biofilme relacionado à cárie dentária e à doença periodontal­ uma revisão de literatura

Esta revisão tem como objetivo discutir o potencial antimicrobiano de diferentes enxaguatórios bucais em relação ao controle da cárie dentária e doença periodontal. A pesquisa foi realizada usando PubMed e as seguintes palavras-chave: "agente antimicrobiano" ou "agente antiplaca", "biofilme dental" e "cárie dentária" ou "doença periodontal" ou "gengivite". Foram selecionados os estudos publicados em inglês, de 2011 a 2015, em revistas com fator de impacto maior que 0,8. Foram encontrados no total 22 artigos, 13 relacionados à cárie dentária e 9 relacionados à doença periodontal. Entre os 13 estudos envolvendo bactérias e/ou biofilme cariogênicos, 6 foram realizados in vitro, 3 in situ e 4 in vivo. Entre os 9 estudos envolvendo doença periodontal, 2 foram in vitro e 7 in vivo. Os principais agentes ativos testados foram: CHX-Clorexidina, CPC-cloreto de cetilpiridínio e OE-óleos essenciais (com álcool ou sem álcool). A CHX foi comparada ao OE em 6 estudos, mostrando superioridade em 3 estudos, similaridade em 1 estudo e inferioridade em 2 estudos. CPC mostrou menor efeito na redução da placa em comparação à CHX e ao OE. Ainda há controvérsias sobre o efeito do álcool, mas alguns estudos têm mostrado superioridade no caso de OE e CHX com álcool sobre biofilmes cariogênicos e periodontopatogênicos, respectivamente, quando comparados à versão sem álcool; para o CPC, não foi encontrada diferença. Mais estudos clínicos são necessários para melhor compreensão sobre mecanismo de ação e as diferenças de desempenho entre os agentes antiplaca.(AU)

This review aims to discuss the antimicrobial potential of different mouthrinses in respect to the control of dental caries and periodontal disease. The survey was conducted using PubMed and the following keywords: "antimicrobial agent" or "antiplaque agent", "dental biofilm" and "dental caries" or "periodontal disease" or "gingivitis". Only studies published in English, from 2011 to 2015, in journals with impact factor greater than 0.8, were selected. We found a total of 22 papers, 13 related to dental caries and 9 related to periodontal disease. Among the 13 studies involving cariogenic bacteria and/or biofilm, 6 were conducted in vitro, 3 in situ and 4 in vivo. Among 9 studies involving periodontal disease, 2 were in vitro and 7 in vivo. The main active agents tested were: CHX-Chlorhexidine, CPC-cetylpyridinium chloride and EO-Essential oils (alcohol/or alcohol-free). CHX was compared to EO in 6 studies, showing superiority in 3 studies, similarity in 1 study and inferiority in 2 studies. CPC has shown lower effect in plaque reduction compared to CHX and EO. There is still controversy about the effect of alcohol, but some studies have shown superiority for EO and CHX with alcohol on cariogenic and periodontopathogenic biofilms, respectively, when compared to alcohol-free version; for CPC, no difference was found. More clinical studies are needed for better understanding the mechanism of action and the differences in performance among the antiplaque agents.(AU)