Lívia Picchi Comar

Comparison of Cross-Sectional Hardness and Transverse Microradiography of Artificial Carious Enamel Lesions Induced by Different Demineralising Solutions and Gels

The aims of this study were: (1) to correlate surface (SH) and cross-sectional hardness (CSH) with microradiographic parameters of artificial enamel lesions; (2) to compare lesions prepared by different protocols. Fifty bovine enamel specimens were allocated by stratified randomisation according to their initial SH values to five groups and lesions produced by different methods: MC gel (methylcellulose gel/lactic acid, pH 4.6, 14 days); PA gel (polyacrylic acid/lactic acid/hydroxyapatite, pH 4.8, 16 h); MHDP (undersaturated lactate buffer/methyl diphosphonate, pH 5.0, 6 days); buffer (undersaturated acetate buffer/fluoride, pH 5.0, 16 h), and pH cycling (7 days). SH of the lesions (SH1) was measured. The specimens were longitudinally sectioned and transverse microradiography (TMR) and CSH measured at 10- to 220-μm depth from the surface. Overall, there was a medium correlation but non-linear and variable relationship between mineral content and √CSH. √SH1 was weakly to moderately correlated with surface layer properties, weakly correlated with lesion depth but uncorrelated with integrated mineral loss. MHDP lesions showed the highest subsurface mineral loss, followed by pH cycling, buffer, PA gel and MC gel lesions. The conclusions were: (1) CSH, as an alternative to TMR, does not estimate mineral content very accurately, but gives information about mechanical properties of lesions; (2) SH should not be used to analyse lesions; (3) artificial caries lesions produced by the protocols differ, especially considering the method of analysis.

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-D (NaF, 2.26%F, pH 4.5, Colgate-Brazil, n=30), Duofluorid-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 microm 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.

In situ effect of sodium fluoride or titanium tetrafluoride varnish and solution on carious demineralization of enamel.

This study evaluated the effect of titanium tetrafluoride (TiF(4)) formulations on enamel carious demineralization in situ. Thirteen subjects took part in this cross-over, split-mouth, double-blind study performed in three phases of 14 d each. In each subject, two sound and two predemineralized specimens of bovine enamel were worn intra-orally and plaque accumulation was allowed. One sound and one predemineralized specimen in each subject was treated once with sodium fluoride (NaF) varnish or solution (Treatment A); TiF(4) varnish or solution (Treatment B); or placebo varnish or no treatment (Treatment C). The initially sound enamel specimens were exposed to severe cariogenic challenge (20% sucrose, eight times daily for 5 min each time), whereas the predemineralized specimens were not. Eleven subjects were able to finish all experimental phases. The enamel alterations were quantified by surface hardness and transversal microradiography. Demineralization of previously sound enamel was reduced by all test formulations except for the NaF solution, while both TiF(4) formulations were as effective as NaF varnish. For the predemineralized specimens, enamel surface hardness was increased only by TiF(4) formulations, while subsurface mineral remineralization could not be seen in any group. Within the experimental protocol, TiF(4) was able to decrease enamel demineralization to a similar degree as NaF varnish under severe cariogenic challenges, while only TiF(4) formulations remineralized the enamel surface.

The erosion and abrasion‐inhibiting effect of TiF4 and NaF varnishes and solutions on enamel in vitro

OBJECTIVE. Previous in vitro study has shown that TiF(4) varnish might reduce enamel erosion. No data regarding the effect of this experimental varnish on enamel erosion plus abrasion, however, are available so far. Thus, this in vitro study aimed to analyse the effect of TiF(4) compared with NaF varnishes and solutions, to protect against enamel erosion with or without abrasion. METHODS. Enamel specimens were pre-treated with experimental-TiF(4) (2.45% F), experimental-NaF (2.45% F), NaF-Duraphat (2.26% F), and placebo varnishes; NaF (2.26% F) and TiF(4) (2.45% F) solutions. Controls remained untreated. The erosive challenge was performed using a soft drink (pH 2.6) 4 × 90 s/day (ERO) and the toothbrushing abrasion (ERO+ABR) 2 × 10 s/day, for 5 days. Between the challenges, the specimens were exposed to artificial saliva. Enamel loss was measured profilometrically (μm). RESULTS. Kruskal-Wallis/Dunn tests showed that all fluoridated varnishes (TiF(4) -ERO:0.53 ± 0.20, ERO+ABR:0.65 ± 0.19/NaF-ERO:0.94 ± 0.18, ERO+ABR:1.74 ± 0.37/Duraphat-ERO:1.00 ± 0.37, ERO+ABR:1.72 ± 0.58) were able to significantly reduce enamel loss when compared with placebo varnish (ERO:3.45 ± 0.41/ERO+ABR:3.20 ± 0.66) (P < 0.0001). Placebo varnish, control (ERO:2.68 ± 0.53/ERO+ABR:3.01 ± 0.34), and fluoridated (NaF-ERO:2.84 ± 0.09/ERO+ABR:2.40 ± 0.21/TiF(4) -ERO:3.55 ± 0.59/ERO+ABR:4.10 ± 0.38) solutions did not significantly differ from each other. CONCLUSION. Based on the results, it can be concluded that the TiF(4) varnish seems to be a promising treatment to reduce enamel loss under mild erosive and abrasive conditions in vitro.

Effect of a Single Application of TiF4 and NaF Varnishes and Solutions Combined with Nd:YAG Laser Irradiation on Enamel Erosion in Vitro

OBJECTIVE This in vitro study aimed to analyze the influence of neodymium-doped yttrium aluminum garnet (Nd:YAG) laser irradiation on the efficacy of titanium tetrafluoride (TiF(4)) and sodium fluoride (NaF) varnishes and solutions to protect enamel against erosion. BACKGROUND DATA The effect of Nd:YAG laser irradiation on NaF and AmF was analyzed; however, there is no available data on the interaction between Nd:YAG laser irradiation and TiF(4). METHODS Bovine enamel specimens were pre-treated with NaF varnish, TiF(4) varnish, NaF solution, TiF(4) solution, placebo varnish, Nd:YAG (84.9 J/cm(2)), Nd:YAG prior to or through NaF varnish, Nd:YAG prior to or through TiF(4) varnish, Nd:YAG prior to or through NaF solution, Nd:YAG prior to or through TiF(4) solution, and Nd:YAG prior to or through placebo varnish. Controls remained untreated. Ten specimens in each group were then subjected to an erosive demineralization (Sprite Zero, 4 × 90 s/day) and remineralization (artificial saliva, between the erosive cycles) cycling for 5 days. Enamel loss was measured profilometrically (μm). Additionally, treated but non-eroded specimens were additionally analyzed by scanning electron microscope (SEM) (each group n = 2). The data were statistically analyzed by ANOVA and Tukeys post-hoc test (p < 0.05). RESULTS Only TiF(4) varnish (1.8 ± 0.6 μm), laser prior to TiF(4) varnish (1.7 ± 0.3 μm) and laser prior to TiF(4) solution (1.4 ± 0.3 μm) significantly reduced enamel erosion compared to the control (4.1 ± 0.6 μm). SEM pictures showed that specimens treated with TiF(4) varnish presented a surface coating. CONCLUSIONS Nd:YAG laser irradiation was not effective against enamel erosion and it did not have any influence on the efficacy of F, except for TiF(4) solution. On the other hand, TiF(4) varnish protected against enamel erosion, without the influence of laser irradiation.

TiF4 and NaF varnishes as anti-erosive agents on enamel and dentin erosion progression in vitro

Objective This study assessed the effect of fluoride varnishes on the progression of tooth erosion in vitro. Material and Methods: Forty-eight enamel and 60 root dentin samples were previously demineralized (0.1% citric acid, pH 2.5, 30 min), leading to a baseline and erosive wear of 12.9 and 11.4 µm, respectively. The samples were randomly treated (6 h) with a 4% TiF4 varnish (2.45%F-, pH 1.0), a 5.42% NaF varnish (2.45%F-, pH 5.0), a placebo varnish and no varnish (control). The samples were then subjected to erosive pH cycles (4x90 s/day in 0.1% citric acid, intercalated with artificial saliva) for 5 days. The increment of the erosive tooth wear was calculated. In the case of dentin, this final measurement was done with and without the demineralized organic matrix (DOM). Enamel and dentin data were analyzed using ANOVA/Tukey’s and Kruskal-Wallis/Dunn tests, respectively (p<0.05). Results The TiF4 (mean±s.d: 1.5±1.1 µm) and NaF (2.1±1.7 µm) varnishes significantly reduced enamel wear progression compared to the placebo varnish (3.9±1.1 µm) and control (4.5±0.9 µm). The same differences were found for dentin in the presence and absence of the DOM, respectively: TiF4 (average: 0.97/1.87 µm), NaF (1.03/2.13 µm), placebo varnish (3.53/4.47 µm) and control (3.53/4.36 µm). Conclusion The TiF4 and NaF varnishes were equally effective in reducing the progression of tooth erosion in vitro.

Different Protocols to Produce Artificial Dentine Carious Lesions in vitro and in situ: Hardness and Mineral Content Correlation

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.

In situ effect of chewing gum containing CPP–ACP on the mineral precipitation of eroded bovine enamel—A surface hardness analysis

OBJECTIVES Stimulation of salivary flow is considered a preventive strategy for dental erosion. Alternatively, products containing calcium phosphate, such as a complex of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), have also been tested against dental erosion. Therefore, this in situ study analyzed the effect of chewing gum containing CPP-ACP on the mineral precipitation of initial bovine enamel erosion lesions. METHODS Twelve healthy adult subjects wore palatal appliances with two eroded bovine enamel samples. The erosion lesions were produced by immersion in 0.1% citric acid (pH 2.5) for 7 min. During three experimental crossover in situ phases (1 day each), the subjects chewed a type of gum, 3 times for 30 min, in each phase: with CPP-ACP (trident total), without CPP-ACP (trident), and no chewing gum (control). The Knoop surface microhardness was measured at baseline, after erosion in vitro and the mineral precipitation in situ. The differences in the degree of mineral precipitation were analyzed using repeated measures (RM-) ANOVA and post hoc Tukeys test (p<0.05). RESULTS Significant differences were found among the remineralizing treatments (p<0.0001). Chewing gum (19% of microhardness recovery) improved the mineral precipitation compared to control (10%) and the addition of CPP-ACP into the gum promoted the best mineral precipitation effect (30%). CONCLUSIONS Under this protocol, CPP-ACP chewing gum improved the mineral precipitation of eroded enamel. CLINICAL SIGNIFICANCE Since the prevalence of dental erosion is steadily increasing, CPP-ACP chewing gum might be an important strategy to reduce the progression of initial erosion lesions.

Effect of experimental mouthrinses containing the combination of NaF and TiF4 on enamel erosive wear in vitro

OBJECTIVE This study analysed the anti-erosive effect of experimental solutions containing TiF4 and NaF. METHODS Bovine enamel samples (n=15) were treated with: (1) commercial solution with SnCl2/NaF (Erosion Protection(®)); (2) experimental solution with 0.0815% TiF4; (3) 0.105% NaF; (4) 0.042% NaF + 0.049% TiF4; (5) 0.063% NaF + 0.036% TiF4 or (6) control. The samples were submitted to pH cycles and daily fluoride applications for seven days. The enamel wear was measured using a contact profilometer and analysed by ANOVA (p < 0.05). RESULTS The best anti-erosive effect was found for experimental solution with 0.0815% TiF4 (99% reduction in enamel wear), followed by SnCl2/NaF (78%) and 0.049% TiF4 + 0.042% NaF solution (41%). CONCLUSIONS The experimental solution containing a specific combination of TiF4 + NaF has the ability to partially reduce enamel erosion.

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 Bonferronis 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.