Efeito de materiais restauradores fluoretados no desenvolvimento de carie secundaria em dentina redicular

Orientadores: Monica Campos Serra, Jaime Aparecido CuryTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: Materiais restauradores fluoretados têm demonstrado capacidade de inibir a progressão da cárie secundária em dentina radicular in vitro. Entretanto, este potencial cariostático ainda necessita ser avaliado em determinados materiais restauradores e testado quanto à sua extensão a partir da margem da restauração e à sua efetividade in vivo. Este trabalho, apresentado na forma de 4 artigos, teve por objetivos (1) avaliar o efeito cariostático in vitro de sistemas adesivos contendo fluoretos (SAF) em dentina radicular, (2) determinar a extensão do efeito cariostático in vitro de restaurações realizadas com cimento de ionômero de vidro (CIV), ionômero de vidro modificado por resina (IVMR), resina composta modificada por poliácidos (RCMP) e resina composta fluoretada (RCF) em dentina radicular, (3) desenvolver um modelo in situ para o estudo da cárie radicular e (4) testar se o CIV é importante na inibição do desenvolvimento de cárie secundária radicular in situ quando um dentifrício fluoretado é constantemente utilizado. Os SAFs não demonstraram efeito cariostático. O CIV e o IVMR demonstraram efeito cariostático em dentina radicular até 0,3 e 0,15 mm da margem das restaurações, respectivamente, contrastando com a ausência de efeitos da RCMP e a RCF. O modelo in situ proposto demonstrou ser adequado para o estudo da progressão e inibição da cárie radicular. Nenhum efeito cariostático adicional pôde ser atribuído ao CIV ao se utilizar dentifrício fluoretado no modelo de cárie radicular in situ. Conclui-se que o efeito cariostático, assim como sua extensão em dentina radicular, é dependente do material restaurador e apresenta relevância questionável em condições in situ, ao se utilizar dentifrício fluoretado freqüentementeAbstract: In vitro studies have shown that fluoride containing restorative materials can inhibit root dentin secondary caries. However, questions still arise on the potential of some restorative materials, on the extension of the cariostatic effect from the restoration margins and on the in vivo ability of such materials to prevent secondary root caries. This thesis, comprised by 4 manuscripts, was designed (1) to test the cariostatic effect of fluoride containing adhesive systems (FAS) in vitro, (2) to determine the extension of the cariostatic effect of a glass-ionomer cement (GIC), a resin-modified glass-ionomer (RMGI), a polyacid-modified composite resin (PMCR) and a fluoridated composite resin (FCR) on root dentin in vitro, (3) to develop an in situ model for the study of root caries and (4) to assess whether the GIC is important or not to prevent secondary root caries in situ when fluoride dentifrice is frequently used. The FASs tested showed no evident cariostatic effect. The GIC and the RMGI showed cariostatic effect up to 0.3 and 0.15 mm from the margin of the restoration, respectively, contrasting to the lack of effect of PMCR and FCR. The in situ model tested was proven to be adequate to the study of either root caries progression or root caries inhibition. No additional cariostatic effect could be attributed to the GIC when fluoride dentifrice was used in situ. It could be concluded that the cariostatic potential as well as the extension of this effect on root dentin is dependent of the fluoride containing restorative material and may not be relevant in in situ conditions when fluoride dentifrice is frequently used.DoutoradoDentísticaDoutor em Clínica Odontológic

Power-law versus exponential distributions of animal group sizes

There has been some confusion concerning the animal group-size: an exponential distribution was deduced by maximizing the entropy; lognormal distributions were practically used; a power-law decay with exponent {3/2} was proposed in physical analogy to aerosol condensation. Here I show that the animal group-size distribution follows a power-law decay with exponent 1, and is truncated at a cut-off size which is the expected size of the groups an arbitrary individual engages in. An elementary model of animal aggregation based on binary splitting and coalescing on contingent encounter is presented. The model predicted size distribution holds for various data from pelagic fishes and mammalian herbivores in the wild.Comment: 19 pages,9 figures, to appear in J. Theor. Bio

Strontium and Caries: A Long and Complicated Relationship

Investigations into the role of strontium (Sr) in caries prevention have attracted great interest in the research community in the past, with their peak in the 1970–80s. To this date, no clear indication of the relative importance of Sr in caries prevention has been provided. A vast number of animal caries, epidemiological and mechanistic studies have been conducted. Although there is much discrepancy, the majority of studies suggest that Sr exhibits some cariostatic properties, predominantly in the presence of fluoride. An optimum Sr concentration of 5–10 ppm in drinking water has been proposed as a direct result of several epidemiological caries studies. Despite these results, no direct link can be established between Sr and caries prevention as, to date, no relevant, randomized controlled trials have been reported. The extrapolation of potential cariostatic properties of Sr from epidemiological studies is difficult due to the co-presence of several other trace elements in the water of the study areas, with many of these elements being attributed cariostatic properties in their own right. Furthermore, the role of caries risk factors was not taken into consideration. There is a clear need for further research, especially on the mineral phases in the dental hard tissues, plaque and plaque fluid associated with Sr as these may give rise to a better understanding of this subject matter. Based on the current data, the cariostatic properties of Sr, or at least those proposed by some authors, cannot be supported

Fluoride dose-response of human and bovine enamel caries lesions under remineralizing conditions

Purpose: To investigate the relative fluoride dose-response of human and bovine enamel caries lesions under remineralizing conditions and utilizing an established pH cycling model. Methods: Early caries-like lesions were formed in human and bovine enamel, characterized using Vickers surface microhardness (VHN) and assigned to five dentifrice treatment groups: 0/250/1100 ppm fluoride as sodium fluoride (F as NaF) formulation 1; 1100 ppm F as NaF formulation 2; 1000 ppm F as monofluorophosphate (MFP) formulation 3. The daily pH cycling regimen comprised: 4xl-minute dentifrice slurry treatments; lx4-hour acid challenge and intermittent remineralization in a l:l-mixture of pooled human/ artificial saliva. After 20 days, VHN of specimens were measured again and changes from lesion baseline calculated (REM). Subsequently, enamel fluoride uptake (EFU) was determined using the microdrill technique and specimens were demineralized again to determine their acid resistance (DEM). Data were analyzed using two-way ANOVA (factors: enamel, dentifrice). Results: Both enamel type and dentifrice as well as their interaction affected REM and DEM. EFU was only affected by dentifrice. Human and bovine enamel showed a good fluoride dose-response for REM and correlated well. However, bovine enamel showed more remineralization than human enamel. There were good correlations between dentifrice-F concentration vs. REM and EFU, and between REM vs. EFU, regardless of enamel type

Effectiveness and Mechanisms of Action of Whitening Dentifrices on Enamel Extrinsic Stains

poster abstractWhitening dentifrices utilize different approaches for stain removal and/or prevention, including the use of abrasive, oxidizing and chemical cleaning agents. The objectives of this in vitro study were: 1. to compare the whitening effect of commercial whitening and non-whitening dentifrices; 2. to verify the mechanism of action of whitening dentifrices by contrasting two experimental models: chemical (toothpaste exposure only) and chemo-mechanical (toothpaste exposure with tooth brushing abrasion). Two hundred fifty six bovine enamel specimens (10x10mm) were prepared and partially stained. They were assigned to 8 groups: 6 whitening dentifrices, 1 non-whitening reference dentifrice and deionized water (control); and further divided in 2 subgroups (n=16) according to the experimental models: chemical or chemo-mechanical. Specimens were daily exposed to dentifrice slurries 2x/day for 1min and brushed or not, according to each model. In between dentifrice treatments, specimens were exposed to the staining solution for 5h. This protocol was repeated for 5 consecutive days and enamel color changes (Delta E) were measured by spectrophotometry, after each day. The abrasivity of the toothpastes was determined using standard test (ISO 11609). Significantly higher Delta E values (whitening effect) were observed for all groups (p0.05). Whitening dentifrices can be effective preventing/removing enamel surface staining, when associated to tooth brushing abrasion. This seemed to be modulated mainly by the abrasive level of the tested toothpastes, with no action attributed to the chemical agents

Efficacy of stannous, fluoride and their their combination in dentin erosion prevention in vitro

The aim of this study was to compare the protective effects of solutions containing stannous (Sn), fluoride (F) and their combination in the prevention of dentin erosion. Forty bovine root dentin specimens (4’4’2 mm3) were prepared and randomly assigned to 4 groups (n = 10): SnCl2 (800 ppm/6.7 mM Sn), NaF (250 ppm/13 mM F), NaF/SnCl2 (800 ppm/6.7 mM Sn; 250 ppm/13 mM F), and deionized water (DIW) as a negative control. An acquired pellicle was formed on dentin samples by incubation in clarified, pooled, stimulated human saliva for 24 hours. The specimens were subjected to 5 daily cycles, each consisting of 5 of min demineralization (0.3%/15.6 mM citric acid, pH 2.6, 6’/day) and 60 min of re-mineralization in clarified human saliva. Thirty minutes after the 1st, 3rd and 5th demineralization episodes of each day, the specimens were treated with one of the test solutions for 2 min. Surface loss was measured via optical profilometry. Mixed-model ANOVA followed by Tukey’s test were used for the statistical analysis. Sn, F, and their combination significantly reduced the dentin surface loss by 23%, 36%, and 60% compared with DIW, respectively. All groups were significantly different (p < 0.05). The combination of Sn and F significantly reduced the amount of dentin surface loss compared with all other groups. The F group also significantly reduced surface loss compared with Sn and DIW, followed by the Sn group, which showed significantly greater protection compared with the DIW control. The daily use of a combined fluoride and stannous solution is promising for preventing dentin erosion

In situ anticaries efficacy of dentifrices with different formulations – A pooled analysis of results from three randomized clinical trials

Objectives Data generated from three similar in situ caries crossover studies presented the opportunity to conduct a pooled analysis to investigate how dentifrice formulations with different fluoride salts and combinations at concentrations of 1400–1450 ppm F, different abrasive systems and in some cases, carbomer (Carb), affect enamel caries lesion remineralization and fluoridation. Methods Subjects continuously wore modified partial dentures holding two gauze-covered partially-demineralized human enamel specimens for 14 days and brushed 2×/day with their assigned dentifrice: Study 1: sodium fluoride (NaF)/Carb/silica, NaF/silica, NaF + monofluorophosphate (MFP)/chalk; Study 2: NaF/Carb/silica, NaF + MFP/dical, amine fluoride (AmF)/silica; Study 3: NaF/Carb/silica, NaF + stannous fluoride (SnF2)/silica/hexametaphosphate (HMP). All studies included Placebo (0 ppm F) and/or dose-response controls (675 ppm F as NaF [675F-NaF]) ±Carb. Specimens were evaluated for percentage surface microhardness recovery (SMHR) and enamel fluoride uptake (EFU). Results All 1400–1450 ppm F dentifrices except NaF + SnF2/silica/HMP provided significantly greater lesion remineralization than Placebo (p < 0.0001): differences in SMHR ranged from 17.46% (NaF + MFP/dical) to 26.66% (AmF/silica). For EFU (back-transformed log EFU), all 1400–1450 ppm F dentifrices gave significant fluoride uptake compared to Placebo (p < 0.0001): increases in EFU ranged from 4.95 μg F/cm2 (NaF + SnF2/silica/HMP) to 16.32 μg F/cm2 (NaF/carb/silica). Dentifrices containing NaF or AmF as sole fluoride source provided the greatest remineralization and fluoridation; Carb addition did not alter fluoride efficacy; some excipients appeared to interfere with the cariostatic action of fluoride. Treatments were generally well-tolerated with ≤4 treatment-related adverse events per study. Conclusion Commercially available fluoride dentifrices varied greatly in their ability to remineralize and fluoridate early caries lesions. Clinical significance Fluoride dentifrices are the most impactful anticaries modality worldwide. While clinical caries trials have not consistently shown the superiority of one formulation over another, these findings using a sensitive in situ caries model indicated that dentifrices containing NaF or AmF as the sole fluoride source provided the greatest remineralization and fluoridation benefits

Comparison Between Radiotracer and Surface Profile Methods for the Determination of Dentifrice

poster abstractIntroduction: ISO11609 states that a surface profile (Sp) method can be used to determine dentifrice abrasivity in relation to dentin (RDA) as an alternative to the traditional radiotracer method (Rt). A comparison between both methods was performed in this study. Methods: Specimens from human root dentin were prepared for each method and randomly assigned to 8 dentifrice/abrasive groups (n=8), which represented a wide abrasivity range. Aqueous dentifrice slurries or abrasive suspensions in a solution containing 0.5% carboxymethylcellulose and 10% glycerin were used to brush specimens in a custom-made V-8 cross-brushing machine. Two independent studies (Sp, Rt) were carried out. For Rt, the specimen preparation, study design, analysis and calculation of the abrasive level (RDA) followed the ISO11609/Annex A guidelines. Similarly for Sp, the ISO11609/Annex B recommendations were followed, except by the number of brushing strokes, which was pre-determined to be 2000 strokes (instead of 10000) in a preliminary test. Data were analyzed using ANOVA and Tukey tests, with significance level set at 5%. The correlation between methods was also investigated. Results: Overall, higher variation and RDA values were observed for the Sp method compared to Rt. While good correlation was found between methods (R2=0.841), group ranking was dissimilar and better statistical differentiation among groups was observed in Rt. Conclusions: The Rt method showed to be a more standardized and robust method compared to Sp for the determination of RDA values of dentifrices/abrasives. Sp needs to be further developed before being considered as an equivalent test method for RDA. The determination of the abrasive levels of toothpastes using standard testing methods is important to guide oral care professionals and patients on the prevention of toothbrushing abrasive wear

Interaction between toothpaste abrasivity and toothbrush filament stiffness on the development of erosiveabrasive lesions in vitro

Objectives To investigate the loss of enamel and dentin surface caused by the interaction between abrasives in toothpaste and toothbrush filament stiffness. Methods The study followed a 2 (high-level or low-level abrasive; silica) × 3 (filament stiffness; soft, medium or hard) × 2 (cycling time; 3 or 5 days) factorial design. Polished bovine enamel and dentin specimens (n = 8 each per group) were subjected to 5 days of erosion/abrasion cycling: erosion (5 minutes, four times daily, 0.3% citric acid, pH 3.75); abrasion (15 seconds, twice daily, 45 strokes each, 150 g load, automated brushing machine); and fluoride treatment [15 seconds with abrasion and 45 seconds without abrasion; 275 p.p.m. fluoride (F−) as sodium fluoride (NaF) in abrasive slurry]. Enamel and dentin specimens were exposed to artificial saliva between erosion and abrasion/F− treatment (1 hour) and at all other times (overnight). Non-contact profilometry was used to determine surface loss (SL) after 3 and 5 days of cycling. Data were analysed using three-way analysis of variance (ANOVA) (factors: abrasive/filament stiffness/time), with separate analyses conducted for enamel and dentin. Results For enamel, only ‘cycling time’ was found to affect SL, with 5 days of cycling resulting in a greater SL than 3 days of cycling. Overall, there was little SL for enamel (range: 0.76–1.85 μm). For dentin (SL range: 1.87–5.91 μm), significantly higher SL was found for 5 days of cycling versus 3 days of cycling, with particularly large differences for hard stiffness/high-level abrasive and medium stiffness/low-level abrasive. For high-level abrasive, after 5 days of cycling hard stiffness resulted in significantly higher SL than did medium stiffness, with no other significant differences according to stiffness. Overall, high-level abrasive resulted in significantly higher SL than did low-level abrasive, with strong effects for all combinations, except medium stiffness after 5 days. Conclusion The interplay between abrasivity and filament stiffness appears to be more relevant for dentin than for enamel

Artificial biofilm thickness and salivary flow effects on fluoride efficacy – A model development study

This laboratory model development study investigated the interaction between artificial biofilm thickness and salivary flow rate on fluoride-mediated prevention of enamel caries lesion formation. This 5-day pH cycling study on sound bovine enamel specimens utilized a continuous flow model and followed a 4 (agarose biofilm thickness-‘no biofilm’/1/2/3mm)×2 (remineralizing solution flow rate-0.05/0.5ml/min)×2 (fluoride-0/383ppm as sodium fluoride) factorial design. Vickers surface microhardness change was the outcome measure. Data were analyzed with three-way ANOVA. The three-way interaction gel thickness×flow rate×fluoride concentration was significant (p=0.0006). 383ppm fluoride caused less softening than 0ppm regardless of gel thickness or flow rate. 0.5ml/min flow rate caused less softening than 0.05ml/min for ‘no biofilm’ and 1mm biofilm thickness regardless of fluoride concentration, for 2 and 3mm with 0ppm F but not for 383ppm F. For 0.05ml/min, softening was reduced as gel thickness increased from ‘no biofilm’-1-2mm, but not from 2-3mm. For 0.5ml/min, ‘no biofilm’ caused more softening than 1, 2, and 3mm, but 1, 2, and 3mm were not different from each other for both 0 and 383ppm F. The present findings suggest that the efficacy of fluoride in preventing enamel demineralization is affected by both biofilm thickness and salivary flow rate, with both thicker biofilms and higher flow rate resulting in less demineralization