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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., (Copyright © 2012 S. Karger AG, Basel.)

This proof-of-concept study assessed whether the reduction of the degradation of the demineralized organic matrix (DOM) by pre-treatment with protease inhibitors (PI) is effective against dentin matrix loss. Bovine dentin slices were demineralized with 0.87 M citric acid, pH 2.3, for 36 hrs. In sequence, specimens were treated or not (UT, untreated) for 1 min with gels containing epigallocatechin 3-gallate (EGCG, 400 µM), chlorhexidine (CHX, 0.012%), FeSO(4) (1 mM), NaF (1.23%), or no active compound (P, placebo). Specimens were then stored in artificial saliva (5 days, 37°C) with the addition of collagenase (Clostridium histolyticum, 100 U/mL). We analyzed collagen degradation by assaying hydroxyproline (HYP) in the incubation solutions (n = 5) and evaluated the dentin matrix loss by profilometry (n = 12). Data were analyzed by ANOVA and Tukey's test (p < 0.05). Treatment with gels containing EGCG, CHX, or FeSO(4) led to significantly lower HYP concentrations in solution and dentin matrix loss when compared with the other treatments. These results strongly suggest that the preventive effects of the PI tested against dentin erosion are due to their ability to reduce the degradation of the DOM.

This review discusses the role of matrix metalloproteinases (MMPs) in the development of dentin erosion and the protective effects of MMP inhibitors, based on recent evidence from in vitro and in situ studies. MMPs are present in both dentin and saliva and play an important role in dentin erosion progression. Enzymatic removal of the organic matrix by MMPs increases the demineralization process, since the demineralized organic matrix has been shown to hamper ionic diffusion after an acidic challenge. Recent evidence from in vitro and in situ studies has shown a protective role of MMP inhibitors against dentin erosion and erosion plus abrasion. The inhibitors tested were green tea and its active epigallocatechin-gallate (EGCG), ferrous sulfate, and chlorhexidine. They have been tested in dentifrices, solutions, and gels. The latter led to a more pronounced protective effect against dentin erosion and erosion plus abrasion. The protection was long-lasting and could be observed after up to 10 days of severe erosive and erosive-plus-abrasive challenges in situ. Thus, the use of MMP inhibitors has emerged as an important preventive tool against dentin erosion. Clinical studies should be conducted to confirm the results obtained and to give support to the establishment of clinical protocols of use.

Background: Matrix metalloproteinase (MMP) inhibitors reduce dentine erosion. This in vitro study evaluated the effect of the supplementation of soft drinks with green tea extract, a natural inhibitor of MMPs, on their erosive potential against dentine., Methods: For each drink tested (Coca-Cola, Kuat guarana, Sprite and light Coca-Cola), 40 dentine specimens were divided into two subgroups differing with respect to supplementation with green tea extract at 1.2% (OM24, 100%Camellia sinensis leaf extract, containing 30 ± 3% of catechin; Omnimedica, Switzerland) or not (control). Specimens were subjected to four pH cycles, alternating de- and remineralization in one day. For each cycle, samples were immersed in pure or supplemented drink (10 minutes, 30 mL per block) and in artificial saliva (60 minutes, 30 mL per block) at 37 °C, under agitation. Dentine alterations were determined by profilometry (μm). Data were analysed by two-way ANOVA and Bonferroni's test (p < 0.05)., Results: A significant difference was observed among the drinks tested with Sprite leading to the highest surface loss and light Coca-Cola to the lowest. Supplementation with green tea extract reduced the surface loss by 15% to 40% but the difference was significant for Coca-Cola only., Conclusions: Supplementation of soft drinks with green tea extract might be a viable alternative to reduce their erosive potential against dentine., (© 2011 Australian Dental Association.)

Metalloproteinases (MMPs) have been implicated with metabolism of collagen in physiological and pathological processes in human dentine. As bovine teeth have been used as a substitute for human teeth in laboratory analysis, this study evaluated the activity of MMP-2 and -9 in bovine versus human dentine. Bovine and human dentine fragments, from crowns and roots, were powderized. Protein extraction was performed by two protocols: a neutral extraction with guanidine-HCl/EDTA (pH 7.4) and an acidic extraction with citric acid (pH 2.3). Gelatinolytic activities of extracts were revealed by zymography. MMP-2 and -9 were detected in crown and root dentine from bovine and human teeth. Total activities of MMP-2 were 11.4 ± 2.2, 14.6 ± 2.0, 9.7 ± 1.2 and 12.4 ± 0.9 ng/ml for bovine root, human root, bovine crown and human crown dentine, respectively. Corresponding activities for MMP-9 were 14.9 ± 2.0, 15.3 ± 1.3, 15.4 ± 1.3 and 15.5 ± 1.3 ng/ml, respectively. Bovine dentine was found to be a reliable substrate for studies involving the activity of MMP-2 and -9., (Copyright © 2011 S. Karger AG, Basel.)

Objectives: This in situ/ex vivo study evaluated whether a rinse with an iron solution could reduce wear and the percentage of microhardness change of human enamel and dentine submitted to erosion followed by brushing after 1 or 30min., Design: During 2 experimental 5-day crossover phases (wash-out period of 10 days), 10 volunteers wore intraoral palatal devices, with 12 specimens (6 of enamel and 6 of dentine) arranged in 3 horizontal rows (4 specimens each). In one phase, the volunteers immersed the device for 5min in 150mL of cola drink, 4 times a day. Immediately after immersion, no treatment was performed in one row. The other row was brushed after 1min using a fluoride dentifrice and the device was replaced into mouth. After 30min, the remaining row was brushed. In the other phase, the procedures were repeated, but after immersion the volunteers rinsed for 1min with 10mL of a 10mM ferrous sulphate solution. Changes in surface microhardness (%SMH) and wear (profilometry) of enamel and dentine were measured. Data were tested using ANOVA and Tukey's tests (p<0.05)., Results: The enamel presented more wear than dentine, under all experimental conditions. The iron solution caused a significant reduction on the %SMH in enamel, and a significant reduction on the wear in dentine, regardless the other conditions., Conclusions: Rinsing with an iron solution after an erosive attack, followed or not by an abrasive episode, may be a viable alternative to reduce the loss of dental structure.

It is known that some metal salts can inhibit matrix metalloproteinase (MMP) activity, but the effect of iron has not been tested yet. On the other hand, it has recently been suggested that MMP inhibition might influence dentine erosion. Based on this, the aims of this study were: (1) to test in vitro the effect of FeSO4 on MMP-2 and -9 activity, and (2) to evaluate in situ the effect of FeSO4 gel on dentine erosion. MMP-2 and -9 activities were analysed zymographically in buffers containing FeSO4 in concentrations ranging between 0.05 and 1.5 mmol/l or not. Volunteers (n = 10) wore devices containing bovine dentine blocks (n = 60) previously treated with the following gel treatments: FeSO4 (1 mmol/l FeSO4), F (NaF 1.23%; positive control) and placebo (negative control). The gels were applied once and removed after 1 min. Erosion was performed extraorally with Coca-Cola 4 times per day for 5 min over 5 days. Dentine wear was evaluated by profilometry. The data were analysed by Kruskal-Wallis and Dunn’s tests (p < 0.05). FeSO4 inhibited both MMP-2 (IC50 = 0.75 mmol/l) and MMP-9 (IC50 = 0.50 mmol/l) activities. In the in situexperiment, the mean wear (± SD) found for the F gel (0.79 ± 0.08 μm) was significantly reduced in more than 50% when compared to the placebo gel (1.77 ± 0.33 μm), but the FeSO4 gel completely inhibited the wear (0.05 ± 0.02 μm). Since FeSO4 was able to inhibit MMP in vitro, it is possible that the prevention of dentine wear by the FeSO4 gel in situ might be due to MMP inhibition, which should be investigated in further studies. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Matrix metalloproteinase (MMP) inhibition has been shown to reduce dentin caries progression, but its role in dental erosion has not yet been assessed. This study tested the hypothesis that gels containing MMP inhibitors (epigallocatechin gallate-EGCG and chlorhexidine) can prevent dental erosion. Volunteers (n = 10) wore palatal devices containing bovine dentin blocks (n = 10/group) treated for 1 min with EGCG at 10 (EGCG10) or 400 µM (EGCG400), chlorhexidine at 0.012%, F at 1.23% (NaF), and no vehicle (placebo). Erosion was performed with Coca-Cola® (5 min) 4X/day during 5 days. The wear, assessed by profilometry (mean ± SD, µm), was significantly reduced by the gels containing MMP inhibitors (0.05 ± 0.02a, 0.04 ± 0.02a, and 0.05 ± 0.02a for EGCG10, EGCG400, and chlorhexidine, respectively) when compared with NaF (0.79 ± 0.35b) and placebo gels (1.77 ± 0.35b) (Friedman and Dunn's tests, p < 0.01). The use of gels delivering MMP inhibitors was shown to prevent erosion and opens a new perspective for protection against dental erosion. [ABSTRACT FROM AUTHOR]

This in situ/ex vivo study assessed the effect of different concentrations of fluoride in dentifrices on dentin subjected to erosion or to erosion plus abrasion. Ten volunteers took part in this crossover and double-blind study performed in 3 phases (7 days). They wore acrylic palatal appliances containing 4 bovine dentin blocks divided in two rows: erosion and erosion plus abrasion. The blocks were subjected to erosion by immersion ex vivo in a cola drink (60 s, pH 2.6) 4 times daily. During this step, the volunteers brushed their teeth with one of three dentifrices D (5,000 ppm F, NaF, silica); C (1,100 ppm F, NaF, silica) and placebo (22 ppm F, silica). Then, the respective dentifrice slurry (1:3) was dripped on dentin surfaces. While no further treatment was performed in one row, the other row was brushed using an electric toothbrush for 30 s ex vivo. The appliances were replaced in the mouth and the volunteers rinsed with water. Dentin loss was determined by profilometry and analyzed by 2-way ANOVA/Bonferroni test (a = 0.05). Dentin loss after erosive-abrasive wear was significantly greater than after erosion alone. Wear was significantly higher for the placebo than for the D and C dentifrices, which were not significantly different from each other. It can be concluded that the presence of fluoride concentrations around 1,100 ppm in dentifrices is important to reduce dentin wear by erosion and erosion + abrasion, but the protective effect does not increase with fluoride concentration. Copyright © 2008 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

The bonding of resin-modified glass ionomer cements to dentin remains a challenge in clinical routine. In an attempt to improve this property, different materials and techniques have been proposed. This study investigated the shear bond strength of resin-modified glass ionomer cements (Vitremer, 3M/ESPE and Fuji II LC Improved, GC) to human dentin using two one-bottle adhesive systems (Prime & Bond 2·1, Dentsply and Single Bond, 3M/ESPE). The restored specimens were stored in deionized water for 24 h at 37 ± 1 °C, and then the bonded surfaces were tested in shear strength using a Universal testing machine at a crosshead speed of 0·5 mm min−1. Bond strength means were recorded and failure modes were assessed with a stereomicroscope at 40× magnification. Data were submitted to two-wayanova and multiple comparisons were performed using a Tukey statistical test ( P < 0·05). Fuji II LC Improved yielded higher bond strength ( P < 0·05) than Vitremer in all experimental conditions. No statistically significant differences ( P > 0·05) were observed among the proposed dentin surface treatments, although a slight decrease in bond strength was observed when phosphoric acid was used alone. Bond strengths of the resin-modified glass ionomer cements to dentin seemed to be more material-dependent than surface treatment-dependent. It may be concluded that the one-bottle adhesive systems tested in this study did not improve the bond strength of the resin-modified glass ionomer cements to dentin. [ABSTRACT FROM AUTHOR]

Objectives: This in vitro study assessed the effect of milk containing different fluoride concentrations on tooth erosion. Methods: Bovine enamel and root dentine specimens were treated with: (1) bovine whole milk with 0 ppmF; (2) 2.5 ppm F; (3)5 ppmF;(4) 10 ppmF (all aftererosion); (5)whole milk with 0 ppm F (before erosion); (6) NaF (0.05% F, positive control, after erosion) or (7) 0.9% NaCl (negative control, after erosion). The specimens were submitted to pH cycles (490 s in soft drink) and treatmentsfor5days. The specimens were immersed in the treatment solutions for 1 min(only at the first cycle each day) with further exposition to 1:1 milk:saliva slurry for 10 min. The tooth loss was measured using a contact profilometer and statistically analysed ( p < 0.05). Results: Rinsing with milk before erosive challenge significantly reduced tooth loss compared to negative control (67% and 24% reduction in dentine and enamel loss, respectively) and to milk after erosive challenge, only for dentine. The addition of fluoride to milk also reduced tooth loss compared to negative control, but with no significant differences among fluoride concentrations for enamel and dentine (mm), respectively: 0 ppm (3.63 ± 0.04 and 2.51 ± 0.53), 2.5 ppm F (2.86 ± 0.42 and 1.96 ± 0.47), 5 ppm F (2.81 ± 0.27 and 1.77 ± 0.44), 10 ppm F (2.03 ± 0.49 and 1.68 ± 0.59). There was a negative and significant correlation between [F] and the tooth loss. Conclusions: Daily rinse with milk containing F is able to reduce both enamel and dentine erosion in vitro. Clinical significance: Since the prevalence of dental erosion is steadily increasing, rinse with milk or its derivate might be an important strategy to reduce the progression of tooth erosion. [ABSTRACT FROM AUTHOR]

Objective: This study investigated the prevalence of dental wear in 12-year-old adolescents using a modification of the tooth wear index (TWI). The modifications were proposed in order to fit with the World Health Organization standard, thus allowing application of the index in broad epidemiological surveys. Study design: An epidemiological cross-sectional survey was performed by trained, calibrated examiners, using a modified version of the TWI. Methods: Urban elementary schools were chosen because they provide a fair representation of the city's population in terms of socio-economic status. The sample included 295 adolescents, selected randomly and systematically. Dental wear was assessed by calibrated examiners (kappa > 0.85), using a modified version of the TWI. This modified version includes a code for teeth restored due to wear, and another code for teeth that cannot be assessed. In addition, it does not differentiate the depth of dentine involvement. Proportions and confidence intervals were used to describe the prevalence of dental wear. Mann-Whitney test was used to detect differences in the degree of dental wear between males and females. The level of statistical significance was set at 5%. Results: In total, 24,780 dental surfaces were evaluated. Among these surfaces, 73.10% did not present dental wear, 24.10% had incipient lesions, 2.46% had moderate lesions and 0.34% had been restored. No severe lesions were detected. Tooth wear was mainly seen on the occlusal/incisal surfaces (26.55%), involving enamel or enamel-dentine, but not the secondary dentine or pulp. The prevalence of dental wear was 26.90%. Considering the different teeth, wear was present in 53.22% of incisors, 50.51% of canines, 10.17% of premolars and 10.85% of molars. The prevalence of the different degrees of dental wear was similar in males and females (P > 0.05). Conclusion: The modified TWI seems to be an effective tool for use in broad epidemiological surveys, due to easier calibration and high reproducibility rates. [ABSTRACT FROM AUTHOR]