Effect of NaF, SnF(2), and TiF(4) Toothpastes on Bovine Enamel and Dentin Erosion-Abrasion In Vitro

Spatially resolved composition of bovine dental enamel in permanent incisors

OBJECTIVE

To quantify component volumes (mineral, organic, total water, firmly and loosely bound water volumes, and permeability) at histological points in bovine enamel and investigate their association with bovine enamel's optical behavior and fracture toughness (FT).

DESIGN

In vitro, cross-sectional, and experimental study. Longitudinal ground sections of ten permanent bovine incisors were analyzed using microradiography, polarizing microscopy, microhardness tester, and confocal laser fluorescence microscopy (CLFM). Continuous data were analyzed using regression and correlation tests.

RESULTS

Bovine enamel exhibited gradients in both composition and FT from the surface inward, with the inner third showing positive birefringence in water immersion and opaque areas under immersion in air (explained by composition gradients), along with intermediate FT. Bovine enamel presented mineral volume of 79.6 % ( ± 2.7 %), water volume of 11.4 % ( ± 20.4 %), organic volume of 9.1 % ( ± 2.4 %), and permeability of 6.5 % ( ± 0.5 %). Water loss upon air drying was 1/5th of that in human enamel, representing a novel finding in enamel biology. The organic gradient was confirmed by CLFM. The ratio of firmly bound water to organic content was negatively associated with fracture toughness across the enamel layer.

CONCLUSION

bovine enamel differs from human enamel in terms of composition, birefringence, and permeability, requiring caution when interpreting results from studies using it to test dental products intended for humans. The composition of bovine enamel fully explained its optical behavior and partially explained its FT gradient.

Effects of different toothpastes against erosive tooth wear of enamel and dentine in vitro

BACKGROUND

The increase in the prevalence of erosion lesions worldwide has led researchers to develop effective toothpastes with different ingredients to prevent erosion that can protect the tooth surface against acid attacks. There remains a lack of consensus in the literature regarding which toothpaste formulation exhibits the most effective preventive action against erosive tooth wear, highlighting the necessity for further investigation in this field. This study aimed to evaluate the preventive effect of brushing with toothpastes with different ingredients on enamel and dentine erosion.

METHODS

The crowns and roots of ninety recently extracted bovine incisors were seperated and ground flat to obtain enamel and dentine surfaces. The obtained specimens were then divided into six groups: Curaprox Enzycal Zero Flouride (fluoride-free), Colgate Total 12 (1450 ppm NaF), Splat Biocalcium (fluoride-free and Nano-HAP), Colgate ProRelief (1450 ppm NaF and arginine), Sensodyne Repair and Protection (1450 ppm NaF and novamin), Opalescence Whitening (1100 ppm NaF). The specimens were immersed in a demineralizing solution for 2 min and in an artificial saliva for 60 min 4 times a day for 5 days. Brushing was performed with the aid of a charged toothbrush immediately after the first and last erosive attacks. Initial and final surface roughness (at the end of fifth day) were measured using a 3D profilometer. The Wilcoxon test was used to compare initial and final roughness values (p < 0.05).

RESULTS

Opalescence Whitening and Curaprox Enzycal Zero Fluoride significantly increased both enamel and dentine surface roughness compared to baseline, demonstrating rougher surfaces than all other groups except Colgate ProRelief (p < 0.001). Sensodyne Repair and Protection and Colgate Total 12 resulted in the smoothest enamel and dentine surfaces, respectively. The increase in surface roughness was significantly higher for enamel samples compared to dentine samples in the Opalescence Whitening group (p < 0.001).

CONCLUSIONS

Whitening toothpastes may exacerbate dental erosion by increasing surface roughness. The protective properties of fluoride-free toothpastes vary depending on their active ingredient.

Influence of using different toothpaste during bleaching with violet LED light (405 nm) on the colour and roughness of dental enamel: an in vitro study

This in vitro study aimed to investigate potential changes in the color and roughness of dental enamel resulting from the use of different toothpaste formulations during bleaching with violet LED light (405 nm). Sixty specimens of bovine incisors, each measuring 6 × 6 × 3 mm, were segregated into six distinct experimental groups based on their respective treatments (n = 10): C + VL: Brushing with Colgate® Total 12 + bleaching with violet LED; LB + VL: Brushing with Colgate® Luminous White Brilliant + bleaching with violet LED; LI + VL: Brushing with Colgate® Luminous White Instant + violet LED bleaching; C: Brushing with Colgate® Total 12; LB: Brushing with Colgate® Luminous White Brilliant; LI: Brushing with Colgate® Luminous White Instant. The examined variables included alterations in color (∆L*, ∆a*, ∆b*, ∆Eab, and ∆E00), surface roughness (Ra), and scanning electron microscopy observations. No statistically significant distinctions emerged in total color variations (∆E00 and ∆E) among the groups under scrutiny. Notably, the groups that employed Colgate® Luminous White Instant displayed elevated roughness values, irrespective of their association with violet LED, as corroborated by scanning electron microscopy examinations. It can be concluded that whitening toothpastes associated to violet LED do not influence the color change of dental enamel in fifteen days of treatment. Toothpastes with a higher number of abrasive particles showed greater changes in enamel roughness, regardless of the use of violet LED.

Toothpaste containing TiF4 and chitosan against erosive tooth wear in situ

OBJECTIVE

This study compared the protective effect of an experimental TiF4/Chitosan toothpaste with a commercial toothpaste on the prevention of erosive tooth wear (ETW) in situ.

METHODS

Fifteen subjects took part in this crossover and double-blind study, in which they wore a palatal appliance containing 4 bovine enamel and 4 dentin in 3 phases (5 days each). Half of the samples were subjected to erosive challenges (90 s in 0.1 % citric acid, pH 2.5, 4 times/day), and the other half to erosive plus abrasive challenges (15 s plus 45 s of contact, 2 times/day). The phases corresponded to the application of the different toothpastes: 1) TiF4 (1400 ppm F-) plus Chitosan, 2) Elmex®, Erosion Protection (1400 ppm F-, Chitosan), and 3) Placebo (negative control). Tooth wear was measured using contact profilometry (μm) and submitted to two-way RM ANOVA/Tukey test (p < 0.05).

RESULTS

No significant differences were detected between the experimental and commercial toothpastes, regardless of the challenge on both tissues. Both significantly reduce ETW compared to negative control (p < 0.0006). Tooth wear was increased by brushing only on eroded enamel (p < 0.01), but not on dentin (p = 0.6085). TiF4/Chitosan [erosion 2.98 ± 1.12 μm vs. erosion and abrasion 3.12 ± 1.33 μm] and Elmex® toothpastes [erosion 2.35 ± 0.93 μm vs. erosion and abrasion 2.98 ± 1.0 μm] minimized the impact of brushing compared to placebo on enamel [erosion 4.62 ± 1.48 μm vs. erosion and abrasion 5.15 ± 1.50 μm].

CONCLUSIONS

TiF4 plus chitosan toothpastes showed to be effective in minimizing the ETW as the commercial toothpaste is in situ.

CLINICAL RELEVANCE

The experimental toothpaste has similar effect against ETW compared to the commercial toothpaste. Considering the increased ETW prevalence worldwide, this result supports clinical trials and a possible application of this experimental anti-erosive toothpaste in the future.

Effect of the β-tricalcium phosphate particle on dental enamel associated with 10% carbamide peroxide bleaching

Background

Since bleaching gels can cause adverse effects on tooth enamel, it is important to evaluate new remineralizing agents on the market and their effects.

Material and Methods

Seventy-five bovine enamel/dentin blocks (4x4x3mm) were randomly divided into six groups (n=10): Negative Control (NC) with no bleaching treatment or brushing; 10 CP (Carbamide Peroxide) (no brushing - Whiteness Perfect FGM); CT12 + 10 CP (Colgate Total® 12); ES + 10 CP (Elmex® Sensitive); BPC + 10 CP (Bianco® ProClinical); CMP + 10 CP (Colgate® Máxima Proteção Anticáries). The color was evaluated by reflectance spectrophotometry (∆E*ab, ∆E00, and ∆WID) at times T1 (baseline), T2 (24 hours after brushing), and T3 (24 hours after bleaching). Knoop microhardness (KHN) analysis were performed at T3. The enamel surface was qualitatively analyzed by Scanning Electron Microscopy (SEM). The data were analyzed using generalized linear models through descriptive and exploratory analyses, and a significance level of 5% was considered.

Results

Significant differences were observed when the bleached groups were compared to the NC group for ∆E*ab, ∆E00, and ∆WID at time T3 (p= <0.0001). However, the bleached groups presented no significant differences regarding studied times (p> 0.05). KHN did not differ significantly among the six groups (p=0.7585).

Conclusions

Toothpastes with tricalcium phosphate (β-TCP) do not intervene with the efficacy of bleaching treatment with 10% carbamide peroxide. Although a slight mineral deposition on enamel surface can be observed on SEM images, KHN was not significantly altered, and the polishing of the samples were maintained. Key words:Dental Bleaching, Carbamide Peroxide, Hydrogen Peroxide, Dental Enamel, Tricalcium Phosphate.

Impact of combined at-home bleaching and whitening toothpaste use on the surface and color of a composite resin

Objective

This in vitro study aimed to evaluate the effects of different whitening toothpastes on a composite resin during at-home bleaching with 10% carbamide peroxide.

Materials and Methods

Sixty samples (7 mm × 2 mm) were used for color and roughness analyses, while another 60 samples (3 mm × 2 mm) were utilized to assess microhardness. The factors analyzed included toothpaste, for which 5 options with varying active agents were tested (distilled water; conventional toothpaste; whitening toothpaste with abrasive agents; whitening toothpaste with abrasive and chemical agents; and whitening toothpaste with abrasive, chemical, and bleaching agents). Brushing and application of whitening gel were performed for 14 days. Surface microhardness (SMH), surface roughness (Ra), and color (∆L*, ∆a*, ∆b, ∆E*ab, and ∆E00) were analyzed. The Ra and SMH data were analyzed using mixed generalized linear models for repeated measures, while the color results were assessed using the Kruskal-Wallis and Dunn tests.

Results

Between the initial and final time points, all groups demonstrated significant increases in Ra and reductions in SMH. No significant differences were found between groups for SMH at the final time point, at which all groups differed from the distilled water group. Conventional toothpaste exhibited the lowest Ra, while whitening toothpaste with abrasive agent had the highest value. No significant differences were observed in ∆L*, ∆a*, and ∆b.

Conclusions

While toothpaste composition did not affect the color stability and microhardness of resin composite, combining toothbrushing with whitening toothpaste and at-home bleaching enhanced the change in Ra.

The protective effect of the experimental TiF4 and chitosan toothpaste on erosive tooth wear in vitro

This study evaluated the protective effect of TiF₄ and chitosan toothpaste on erosive tooth wear (ETW) in vitro. Enamel and dentin samples were randomly assigned to toothpastes (n = 12): (G1) TiF₄ (1400 ppm F⁻), (G2) 0.5% chitosan (75% deacetylation, 500 mPas), (G3) TiF₄ (1400 ppm F⁻) plus 0.5% chitosan (75% deacetylation, 500 mPas), (G4) Placebo, (G5) Erosion Protection (Elmex-GABA, 1400 ppm F⁻). Twelve samples were only eroded. All samples were submitted to erosive pH cycles and G1 to G5 to abrasive challenges using toothpastes’ slurries plus 45 s of treatment, for 7 days. The final profile was overlaid to the baseline one for the ETW calculation (µm). The data were subjected to Kruskal–Wallis/Dunn tests. TiF₄ toothpastes, regardless of the presence of chitosan, were able to significantly reduce ETW compared to placebo, while chitosan alone was similar to placebo for both tissues. The toothpastes containing TiF₄ were even superior to the commercial Elmex toothpaste on enamel, while they were similar on dentin; both were also significantly different from placebo for both tissues. TiF₄ and Elmex toothpastes minimized the impact of brushing on eroded surface. In conclusion, TiF₄ toothpastes, regardless the presence of chitosan, showed to be effective in minimizing ETW in vitro.

What is the effectiveness of titanium tetrafluoride to prevent or treat dental caries and tooth erosion? A systematic review

OBJECTIVES

Answer the question: What is the effectiveness of titanium tetrafluoride (TiF₄) when compared to other fluorides, placebo solution or a negative control to prevent or treat dental caries and tooth erosion?

MATERIALS AND METHODS

This review is in accordance with PRISMA guidelines. In vivo and in situ studies that used TiF₄ over enamel or dentine were included. Electronic searches were conducted on MEDLINE, Scopus, Embase, WOS, Cochrane Library, VLH, Clinical Trials and OpenGrey. Risk of bias (ROB) assessments used RoB2 and ROBINS-I for randomized and non-randomized controlled trials (RCTs and on-RCTs); Syrcle's ROB tool for animal studies; and a modified tool proposed by Hollanders for in situ studies.

RESULTS

A total of 28 studies met the eligibility criteria. From these, 6 were in humans (3 RCT and 3 Non-RCT); 4 were in animals and 18 were in situ. For in vivo studies, all RCTs have some concerns related to ROB and all of the non-RCT studies were classified as with serious risk. One animal study had a low and three a high ROB. Regarding in situ studies, seven had a low, ten had an average and only one had a high ROB. The certainty of the evidence (GRADE) ranged from moderate to very low.

CONCLUSIONS

Although most of the results suggest a positive effect of TiF4 on the prevention and treatment of caries and dental erosion, it is not possible to have definitive conclusions due to the high studies' methodological heterogeneity, and the low quality of evidence for most outcomes.

REGISTRATION

The protocol of this syste. atic review was registered in the OPEN SCIENCE FRAMEWORK database (osf.io/6dgs9) DOI:10.17605/OSF.IO/KUZA7 on 6 August 2020.

Reduction in erosive tooth wear using stannous fluoride-containing dentifrices: a meta-analysis

Dentifrices containing different active agents may be helpful to allow rehardening and to increase the resistance of the eroded surface to further acids or mechanical impacts. This study aimed to compare the effects of conventional (sodium fluoride [NaF]) and stannous fluoride (SnF2)-containing dentifrices on reducing erosive tooth wear (ETW). The PubMed/MEDLINE, Scopus, LILACS, BBO, EMBASE, TRIP electronic databases, and grey literature were searched until January 2021 to retrieve relevant in vitro and in situ studies related to research question. There were no restrictions on publication year or language. Two authors independently selected the studies, extracted the data, and assessed the risk of bias. ETW data were pooled to calculate and compare both dentifrices (overall analysis) and in vitro and in situ studies separately (subgroup analysis). Statistical analyses were performed using RevMan5.3 with a random effects model. Of 820 potentially eligible studies, 101 were selected for full-text analysis, and 8 were included in the systematic review and meta-analysis. There was a significant difference between SnF2-containing dentifrices and NaF dentifrices only for in vitro studies (p=0.04), showing a higher effect of the SnF2-containing dentifrices against the erosion/abrasion (effect size: -6.80 95%CI: -13.42; -0.19). Most in vitro and in situ studies had high and low risk of bias, respectively. In vitro literature suggests that the ETW reduction is greater when using SnF2-containing dentifrices instead NaF-containing dentifrices. However, the evidence level is insufficient for definitive conclusions. Clinical trials are necessary for a better understanding of the effect of these compounds on ETW.

Effect of different citrus sweets on the development of enamel erosion in vitro

The increased consumption of citrus sweets can contribute to the development of erosive tooth wear (ETW).

Efficacy of a Stannous-containing Dentifrice for Protecting Against Combined Erosive and Abrasive Tooth Wear In Situ

PURPOSE

The in-situ efficacy of an experimental stannous (Sn)-containing sodium fluoride (NaF) dentifrice against erosion and erosive tooth wear was compared with a conventional NaF dentifrice.

MATERIALS AND METHODS

This was a randomised, controlled, double-blind, parallel-group clinical trial. Mandibular appliances containing four enamel specimens (2 per side [L/R] of the appliance) were worn by 60 generally healthy adult subjects. Subjects were randomised to treatment based on age and gender. Treatments included a Sn-containing NaF or conventional NaF dentifrice. Conditions of erosion (dentifrice slurry treatment) and erosion/tooth wear (dentifrice slurry plus brushing) were compared. Dentifrices were used twice per day for 30 s of lingual brushing, followed by 90 s of slurry exposure. In addition, the two specimens on the left side of the mouth were brushed for 5 s each, using a power toothbrush. All specimens were exposed to four daily erosive challenges with commercial orange juice (pH 3.6). Tooth wear was measured as enamel loss using non-contact profilometry on day 10.

RESULTS

At the day 10 visit, the adjusted mean (SE) enamel loss for specimens receiving slurry (erosion) treatment was 4.7 µm (0.61) [Sn-containing NaF] and 8.73 µm (1.12) [NaF control], with results demonstrating a statistically significant benefit for the Sn-containing dentifrice (46.2% benefit; p = 0.009). For specimens exposed to erosion/tooth wear conditions, enamel loss = 6.68 µm (1.29) (Sn-containing NaF) and 10.99 µm (1.29) (NaF group), with results statistically significant (p = 0.048; 39.2% better, favouring the Sn-containing dentifrice). When data were combined, enamel loss (SE) for all specimens subjected to erosion + erosion/tooth wear was 5.61 µm (0.77) (Sn-containing NaF]) and 9.9 µm (1.3) (NaF group). The difference again was statistically significant, favouring the Sn-containing group (p = 0.022; 43.4% better).

CONCLUSIONS

The Sn-containing dentifrice demonstrated significantly better protection than did NaF under erosive and erosive/tooth wear conditions.

Chemical, structural and mechanical characterization of bovine enamel

OBJECTIVE

The purpose of this investigation was to establish microstructure, microhardness, fracture toughness, chemical composition, and crack repair of bovine enamel and to compare these features with their human counterparts.

DESIGN

Bovine enamel fragments were prepared and optical microscopy and atomic force microscopy were used to establish microstructure; Raman spectroscopy was used to estimate composition and microindentation using Vickers testing was performed to evaluate hardness.

RESULTS

A strong dependence between indentation load and microhardness values was observed, as was the case in human enamel. Similar microstructure and chemical composition between bovine and human enamel, 7.89% lower microhardness and 40% higher fracture toughness values for bovine enamel were found.

CONCLUSION

From a structural and mechanical standpoint, bovine enamel is a suitable alternative to human enamel for in vitro testing of dental products.

Do Abrasives Play a Role in Toothpaste Efficacy against Erosion/Abrasion?

Abrasives may counteract the efficacy of anti-erosion toothpastes either due to physical effects or due to interaction with active agents. This study aimed to investigate whether the amount of abrasives is a determinant for the efficacy of Sn2+-containing toothpastes with or without chitosan additive. Enamel samples were eroded (0.50 wt% citric acid, pH 2.5; 6 × 2 min/day) on a shaking desk - 30/min in experiment 1 (E1) and 35/min in experiments 2 (E2) and 3 (E3) - and immersed in toothpaste slurries (2 × 2 min). Half of the samples were additionally brushed (15 s, load 200 g) within the immersion time. The toothpastes contained 0, 5, 10, 15, and 20% silica. In E1 and E2 the active ingredients were F- (700 ppm as amine fluoride, 700 ppm as NaF) and Sn2+ (3,500 ppm as SnCl2); in E3 chitosan (0.5%) was additionally added. The placebo contained 20% silica. Tissue loss was determined profilometrically. In E1, slurries completely inhibited tissue loss; distinct surface deposits occurred. With brushing, tissue loss significantly increased up to an abrasive content of 10%, but decreased significantly with higher amounts; 20% silica revealed similar values as the abrasive-free formulation. In E2, all slurries inhibited tissue loss distinctly irrespective of the amounts of abrasives. With brushing, a similar trend as in E1 was observed but with much less efficacy. The chitosan-containing formulations in E3 were much more effective; similar results as in E1 were found. In conclusion, the amount of abrasives had no effect when toothpastes were applied as slurries, but played an important role with brushing.

Effect of toothpastes containing different NaF concentrations or a SnF2/NaF combination on root dentine erosive lesions, in vitro

BACKGROUND

Fluoride toothpastes presumably offer some protection against acid erosion. However, uncertainty exists towards fluoride's efficacy relatively to the concentration and the type of chemical compound used. This in vitro study evaluated the relative efficacy of toothpastes containing sodium fluoride in different concentrations or a stabilized stannous fluoride/sodium fluoride system on root dentine erosion.

MATERIAL AND METHODS

Bovine dentin specimens were allocated into four groups (n=10): control (no F), 1450ppm F (as NaF), 5000ppm F (as NaF) and 1450ppm F (1100ppm as stabilized SnF2 and 350ppm as NaF)/sodium hexamethaphosphate. The specimens were submitted to 6 daily cycles of erosion (0.3% v/v citric acid, pH=3.2, 20 min) and remineralization (~22h), interspersed by 2-min immersions in 1:3 w/v of dentifrice/distilled water slurries. Subsequently, they were subjected to a 24-h acid resistance test (0.3% v/v citric acid, pH=3.2) without any further treatments. Surface loss was quantified by contact profilometry. Data were analysed through one-way ANOVA and Bonferroni's tests (p≤0.05).

RESULTS

In both experiments, all fluoride groups, showed significantly less tissue loss compared to the control (p<0.001-p=0.018). During erosion cycling, no significant differences were found among the fluoride groups. During the acid resistance test, the 5000ppm F toothpaste produced significantly superior effect than both 1450ppm F products (p=0.010, (p<0.001), which performed similarly.

CONCLUSIONS

Under less aggressive erosive conditions, fluoride toothpastes did not differ in their ability to protect dentine surfaces. However, in severely erosive environment, the 5000ppm F toothpaste performed superiorly to the other tested products. Key words:Dentine, sodium fluoride, stannous fluoride, tooth erosion, toothpaste, contact profilometry.

Impact of CO2 laser and stannous fluoride on primary tooth erosion

This study evaluated in vitro the effect of input power of CO2 laser, either associated or not to stannous fluoride (SnF2) gel, for the control of intrinsic erosion in primary teeth. One hundred four enamel slabs (3 × 3 × 2 mm) from human primary molars were flattened and polished. Adhesive tapes were placed on their surface leaving a window of 3 × 1 mm. Slabs were then cycled four times in 0.01 M hydrochloric acid (pH 2, 2 min) and in artificial saliva (2 h) for creation of erosive lesions. Specimens were randomly assigned into eight groups (n = 13) according to fluoride application [absent (control) or 0.4% stannous fluoride gel (SnF2)] and input power of CO2 laser [unlased (control), 0.5, 1.0 or 1.5 W]. The CO2 laser irradiation was performed in an ultra-pulse mode (100 μs of pulse duration), 4-mm working distance, for 10 s. Specimens were then submitted to further erosive episodes for 5 days and evaluated for enamel relative permeability. Fluoride did not show any protective effect for any of the laser-treated groups or control (p = 0.185). However, a significant effect was detected for input power of CO2 laser (p = 0.037). Tukey's test showed that there was a significant statistically difference between specimens irradiated with 0.5 and 1.5 W (p = 0.028). The input power of 0.5 W showed lower permeability. Variation of input power CO2 laser can influence enamel permeability, at the power of 1.5 W which promoted greater permeability.

Artificial Saliva Formulations versus Human Saliva Pretreatment in Dental Erosion Experiments

The aim of this study was to evaluate the erosion-preventive effect of different artificial saliva formulations and human saliva in vitro compared to human saliva in situ. In the in vitro experiment, bovine enamel and dentin specimens were stored in artificial saliva (4 different formulations, each n = 20), deionized water (n = 20) or human saliva (n = 6 enamel and dentin specimens/volunteer) for 120 min. In the in situ experiment, each of the 6 enamel and dentin specimens was worn intraorally by 10 volunteers for 120 min. The specimens were then eroded (HCl, pH 2.6, 60 s). Half of the specimens were subjected to microhardness analysis (enamel) and the determination of calcium release into the acid (enamel and dentin), while the other half were again placed in the respective medium or worn intraorally, respectively, for 120 min before a second erosion was performed. Knoop microhardness of enamel and the calcium release of enamel and dentin into the acid were again determined. Statistical analysis was conducted by two-way repeated-measures ANOVA or two-way ANOVA (α = 0.05). Enamel microhardness was not significantly different between all test groups after the first and the second erosive challenge, respectively. Enamel calcium loss was significantly lower in situ compared to the in vitro experiment, where there was no significant difference between all test groups. Dentin calcium loss was significantly lower than deionized water only after the first and than all except one artificial saliva after the second erosion. Under the conditions of this experiment, the use of artificial saliva formulations and human saliva in vitro does not reflect the intraoral situation in dental erosion experiments adequately.

Effects of diode laser therapy and stannous fluoride on dentin resistance under different erosive acid attacks

OBJECTIVE

This in vitro study aimed to evaluate the effect of a low intensity diode laser (λ=808 nm; 60 J/cm2) associated with stannous fluoride on the inhibition of dentin erosion by assessing percentage of superficial hardness loss (%SHL) and calcium release into the acid solution.

MATERIALS AND METHODS

Human root dentin slabs were assigned to eight groups (n=10), according to treatments (control, stannous fluoride, diode laser therapy, and the combination of stannous fluoride and laser therapy), and acid challenge (hydrochloridric or citric acid). All slabs were subjected to a previous 2 h acquired pellicle formation; laser and fluoride treatments were performed according to the groups. Subsequently, the slabs were exposed to erosive challenge (0.01 M hydrochloridric acid or citric acid 1% for 60 sec). Additionally, calcium released into the acid solution during erosive challenge was analyzed by photometric test. Data were analyzed by ANOVA followed by Tukey's test (p<0.05).

RESULTS

Mean values (±SD) for %SHL of treated groups did not present statistically significant differences, regardless of the erosive challenge. However, in relation to released calcium concentration, groups treated with laser presented statistically significant lower calcium loss under hydrochloridric acid challenge (p<0.001). To groups under citric acid attack, only the combination of treatments (p=0.037) was able to show a protective effect on dentin.

CONCLUSIONS

Under the conditions of this study, 808 nm diode laser with or without stannous fluoride could effectively reduce dentin surface loss under both acid exposures. Only calcium concentration analysis was sensitive enough to measure the effects under the tested conditions.