Effect of salivary stimulation on erosion of human and bovine enamel subjected or not to subsequent abrasion: An in situ/ex vivo study

This in situ/ex vivo study evaluated whether saliva stimulated by chewing gum could prevent or reduce the wear and the percent change in microhardness (%SMH) of bovine and human enamel submitted to erosion followed by brushing abrasion immediately or after 1 h. During 2 experimental 7-day crossover phases, 9 previously selected volunteers wore intraoral palatal devices, with 12 enamel specimens (6 human and 6 bovine). In the first phase, the volunteers immersed the device for 5 min in 150 ml of cola drink, 4 times per day (at 8, 12, 16 and 20 h). Immediately after the immersions, no treatment was performed in 4 specimens, 4 other specimens were immediately brushed (0 min) using a fluoride dentifrice, and the device was replaced into the mouth. After 60 min, the remaining 4 specimens were brushed. In the second phase, the procedures were repeated, but after the immersions, the volunteers stimulated the salivary flow rate by chewing a sugar-free gum for 30 min. Changes in wear and %SMH were measured. ANOVA and Tukey's test showed statistical differences (p < 0.05) for the following comparisons. The chewing gum promoted less wear and %SMH. A decreasing %SMH and an increasing enamel wear were observed in the following conditions: erosion only, 60 min and 0 min. The human enamel presented greater %SMH and less wear compared to bovine enamel. The data suggest that the salivary stimulation after an erosive or erosive/abrasive attack can reduce the dental wear and the %SMH.

Effect of a 4% titanium tetrafluoride (TiF4) varnish on demineralisation and remineralisation of bovine enamel in vitro

Objectives: This in vitro study assessed the effect of a 4% TiF4 varnish on demineralisation and remineralisation of sound enamel and artificial carious enamel lesions, respectively.Methods: Bovine sound and carious enamel (n = 110) were randomly allocated to each type of varnish: Duraphat (R))-D (NaF, 2.26%F, pH 4.5, Colgate-Brazil, n = 30), Duofluorid (R)-F (NaF, 2.71%F, pH 8.0, FGM-Brazil, n = 30), TiF4-T (2.45%F, pH 1.0, FGM-Brazil, n = 30) and no-fluoride-P (FGM-Brazil, pH 5.0, n = 20). For the formation of artificial enamel caries, half of the blocks were immersed in 32 mL buffer acetate solution (16 h), whereas the other half was maintained sound. The varnishes were applied onto the enamel surfaces. Thus, the samples were subjected to pH cycles (37 degrees C) for 7 days. The response variables tested were surface and cross-sectional hardness. Data were tested using Kruskal-Wallis test (p < 0.05).Results: All F varnishes significantly reduced demineralisation and increased remineralisation in comparison to placebo. The TiF4 did not significantly reduce the surface enamel softening when compared with the other F varnishes, but it decreased the loss of subsurface hardness to the same extent. In enamel blocks with previous artificial carious lesions, the TiF4 significantly improved the rehardening compared to the other varnishes up to 30 mu m depth.Conclusions: The TiF4 varnish was able to decrease the demineralisation and increase the remineralisation of previously sound and carious enamel, respectively. It was equally effective compared to NaF varnishes on reducing the demineralisation at subsurface, but it was more effective on improving the remineralisation at surface and subsurface. (c) 2007 Elsevier Ltd. All rights reserved.

The influence of daily application of fluoride products on subsurface bovine enamel lesions stored in saliva substitutes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Disinfection of Bovine Enamel by Microwave Irradiation: Effect on the Surface Microhardness and Demineralization/Remineralization Processes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Fluoride dose response in pH-cycling models using bovine enamel

The aim of this study was to establish methodologies for verification of the fluoride solution dose-response relationship using bovine enamel and pH-cycling models. Six models of the cariogenic challenge were performed, varying the time of demineralization and pH, time of remineralization, composition of de- and remineralization solutions, frequency and time of application of treatment solutions and pH-cycling duration. For the evaluation of the fluoride effect on caries dynamics, two proposed models provided for improvement in standardization of methods leading to a higher level of precision, demonstrating a dose response between treatments with regard to surface microhardness and Delta Z. For the evaluation of the fluoride effect on enamel remineralization, the addition of fluoride to the de- and remineralization solutions and the reduction of frequency and time of application of fluoride solutions led to a more suitable pH-cycling model. Copyright (C) 2005 S. Karger AG, Basel.

Effect of iron on bovine enamel and on the composition of the dental biofilm formed in situ

Objectives: This study investigated in situ the effect of iron (Fe) on the reduction of demineralization of bovine enamel, as well as on the composition of dental biofilm.Design and methods: Twelve volunteers were included in this blind crossover study, which was conducted in two stages of 14 days each. For each stage, the volunteers received palatal appliances containing four blocks of bovine enamel (4 mm x 4 mm x 2.5 mm). Six volunteers dripped a solution of 15 mmol L-1 ferrous sulphate onto the fragments and the remaining six dripped deionized water (eight times per day). After five minutes, a fresh 20% (w/v) sucrose solution was dripped onto all enamel blocks. During the experimental period the volunteers brushed their teeth with non-fluoridated dentifrice. After each stage, the percentage of surface microhardness change (%SMHC) and area of mineral toss (Delta Z) were determined on enamel and the dental biofilm formed on the blocks was collected and analysed for F, P, Ca, Fe and alkali-soluble carbohydrates. The concentrations of F, Ca and Fe in enamel were also analysed after acid biopsies.Results: There was a statistically significant increase in the P and Fe concentrations in the biofilms treated with ferrous sulphate (p < 0.05), which was not observed for F, Ca and alkali-soluble carbohydrates. The group treated with ferrous sulphate had significantly lower %SMHC and Delta Z when compared to control (p < 0.05).Conclusions: These results showed that ferrous sulphate reduced the demineralization of enamel blocks and altered the ionic composition of the dental biofilm formed in situ. (c) 2005 Elsevier Ltd. All rights reserved.

In vitro evaluation of the microhardness of bovine enamel exposed to acid solutions after bleaching

Acid erosion is a superficial loss of enamel caused by chemical processes that do not involve bacteria. Intrinsic and extrinsic factors, such as the presence of acid substances in the oral cavity, may cause a pH reduction, thus potentially increasing acid erosion. The aim of this study was to evaluate the microhardness of bleached and unbleached bovine enamel after immersion in a soda beverage, artificial powder juice and hydrochloric acid. The results obtained for the variables of exposure time, acid solution and substrate condition (bleached or unbleached enamel) were statistically analyzed by the ANOVA and Tukey tests. It was concluded that a decrease in microhardness renders dental structures more susceptible to erosion and mineral loss, and that teeth left unbleached show higher values of microhardness compared to bleached teeth.

Scanning electron microscopic study of the in situ effect of salivary stimulation on erosion and abrasion in human and bovine enamel

This in situ study investigated, using scanning electron microscopy, the effect of stimulated saliva on the enamel surface of bovine and human substrates submitted to erosion followed by brushing abrasion immediately or after one hour. During 2 experimental 7-day crossover phases, 9 previously selected volunteers wore intraoral palatal devices, with 12 enamel specimens (6 human and 6 bovine). In the first phase, the volunteers immersed the device for 5 minutes in 150 ml of a cola drink, 4 times a day (8h00, 12h00, 16h00 and 20h00). Immediately after the immersions, no treatment was performed in 4 specimens (ERO), 4 other specimens were immediately brushed (0 min) using a fluoride dentifrice and the device was replaced into the mouth. After 60 min, the other 4 specimens were brushed. In the second phase, the procedures were repeated but, after the immersions, the volunteers stimulated the salivary flow rate by chewing a sugar-free gum for 30 min. Enamel superficial alterations of all specimens were then evaluated using a scanning electron microscope. Enamel prism core dissolution was seen on the surfaces submitted to erosion, while on those submitted to erosion and to abrasion (both at 0 and 60 min) a more homogeneous enamel surface was observed, probably due to the removal of the altered superficial prism layer. For all the other variables - enamel substrate and salivary stimulation the microscopic pattern of the enamel specimens was similar.

Optical characterization of one dental composite resin using bovine enamel as reinforcing filler

The use of composite resins for restorative procedure in anterior and posterior cavities is highly common in Dentistry due to its mechanical and aesthetic properties that are compatible with the remaining dental structure. Thus, the aim of this study was to evaluate the optical characterization of one dental composite resin using bovine enamel as reinforcing filler. The same organic matrix of the commercially available resins was used for this experimental resin. The reinforcing filler was obtained after the gridding of bovine enamel fragments and a superficial treatment was performed to allow the adhesion of the filler particles with the organic matrix. Different optical images as fluorescence and reflectance were performed to compare the experimental composite with the human teeth. The present experimental resin shows similar optical properties compared with human teeth. © 2012 SPIE.

Supplementation of soft drinks with metallic ions reduces dissolution of bovine enamel

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

In vitro effect of calcium-containing prescription-strength fluoride toothpastes on bovine enamel erosion under hyposalivation-simulating conditions

Purpose: To evaluate the ability of calcium-containing prescription-strength fluoride (F) toothpastes in preventing enamel erosion under low salivary flow simulating conditions. Methods: Enamel and dentin bovine specimens were assigned to the following groups: A - placebo; B - 1,100 ppm F/NaF (Aquafresh Advanced); C - 5,000 ppm F/NaF (Prevident 5000 Booster); D - 5000 ppm F/NaF+calcium sodium phosphosilicate (Topex Renew); and E - 5,000 ppm F/NaF+tri-calcium phosphate (Clinpro 5000). Specimens were positioned in custom-made devices, creating a sealed chamber on the surface, connected to peristaltic pumps. Citric acid was injected into the chamber for 2 minutes, followed by artificial saliva (0.05 ml/minute), for 60 minutes, 4x/day, for 3 days. Aquafresh was also tested under normal salivary flow (0.5 ml/minute), as reference (Group F). Specimens were exposed to the toothpastes for 2 minutes, 2x/day. After cycling, surface loss (SL) and concentration of loosely- and firmly-bound F were determined. Data were analyzed by ANOVA. Results: Group A (placebo) presented highest surface loss (SL), while Group F had the lowest, for both substrates. For enamel, none of the dentifrices differed from Group B or among each other. For dentin, none of the dentifrices differed from Group B, but Group E showed greater protection than Group C. Group E presented the highest F concentrations for both substrates, only matched by Group D for firmly-bound fluoride on enamel. All fluoridated dentifrices tested reduced SL, with no additional benefit from higher F concentrations. Some formulations, especially Clinpro 5000, increased F availability on the dental substrates, but no further erosion protection was observed.

Effect of incorporation of remineralizing agents into bleaching gels on the microhardness of bovine enamel in situ

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Calcium glycerophosphate supplemented to soft drinks reduces bovine enamel erosion

Objective: This in vitro study evaluated the effect of calcium glycerophosphate (CaGP) supplemented to soft drinks on bovine enamel erosion. Material and methods: Four pH-cycles were performed, alternating demineralization by the beverage and remineralization in artificial saliva. Results: Mean wear (+/- SD, mu m) was 7.91 +/- 1.13, 7.39 +/- 1.01, 7.50 +/- 0.91 and 5.21 +/- 1.08 for Coca-Cola (TM) without CaGP or containing CaGP at 0.1, 1.0 or 2.0 mM, respectively, while no wear was detected for CaGP at 5.0 and 10.0 mM. Corresponding figures for Sprite Zero (TM) without CaGP or containing CaGP at 0.1, 1.0, 2.0, 5.0 or 10.0 mM were 8.04 +/- 1.30, 7.84 +/- 0.71, 7.47 +/- 0.80, 4.96 +/- 0.81, 3.99 +/- 0.10 and 1.87 +/- 0.12, respectively. Conclusion: Supplementation of both beverages with CaGP seems to be an alternative to reduce their erosive potential.

Impact of experimental Nano-HAP pastes on bovine enamel and dentin submitted to a pH cycling model

This in vitro study evaluated the preventive potential of experimental pastes containing 10% and 20% hydroxyapatite nanoparticles (Nano-HAP), with or without fluoride, on dental demineralization. Bovine enamel (n=15) and root dentin (n=15) specimens were divided into 9 groups according to their surface hardness: control (without treatment), 20 Nanop paste (20% HAP), 20 Nanop paste plus (20% HAP + 0.2% NaF), 10 Nanop paste (10% HAP), 10 Nanop paste plus (10% HAP + 0.2% NaF), placebo paste (without fluoride and HAP), fluoride paste (0.2% NaF), MI paste (CPP-ACP, casein phosphopeptide-amorphous calcium phosphate), and MI paste plus (CPP-ACP + 0.2% NaF). Both MI pastes were included as commercial control products containing calcium phosphate. The specimens were treated with the pastes twice a day (1 min), before and after demineralization. The specimens were subjected to a pH-cycling model (demineralization–6-8 h/ remineralization-16-18 h a day) for 7 days. The dental subsurface demineralization was analyzed using cross-sectional hardness (kgf/mm 2 , depth 10-220 µm). Data were tested using repeated-measures two-way ANOVA and Bonferroni's test (p<0.05). The only treatment able to reduce the loss of enamel and dentin subsurface hardness was fluoride paste (0.2% NaF), which differed significantly from the control at 30- and 50-µm depth (p<0.0001). The other treatments were not different from each other or compared with the control. The experimental Nanop pastes, regardless of the addition of fluoride, were unable to reduce dental demineralization in vitro.