The effect of increasing sodium fluoride concentrations on erosion and attrition of enamel and dentine in vitro

Objectives

To investigate the effect of an aqueous sodium fluoride solution of increasing concentration on erosion and attrition of enamel and dentine in vitro.

Methods

Enamel and dentine sections from caries-free human third molars were polished flat and taped (exposing a 3 mm × 3 mm area) before being randomly allocated to 1 of 5 groups per substrate (n = 10/gp): G1 (distilled water control); G2 (225 ppm NaF); G3 (1450 ppm NaF); G4 (5000 ppm NaF); G5 (19,000 ppm NaF). All specimens were subjected to 5, 10 and 15 cycles of experimental wear [1 cycle = artificial saliva (2 h, pH 7.0) + erosion (0.3% citric acid, pH 3.2, 5 min) + fluoride/control (5 min) + attrition (60 linear strokes in artificial saliva from enamel antagonists loaded to 300 g)]. Following tape removal, step height (SH) in μm was measured using optical profilometry.

Results

When the number of cycles increased the amount of tooth surface loss increased significantly in enamel and dentine after attrition and erosion and for dentine after attrition. Attrition and erosion resulted in greater surface loss than attrition alone after 15 cycles of experimental wear of enamel. 5000 ppm and 19,000 ppm sodium fluoride solutions had a protective effect on erosive and attritional enamel tooth wear in vitro, however no other groups showed significant differences.

Conclusions

The more intensive the fluoride regime the more protection was afforded to enamel from attrition and erosion. However, in this study no such protective effect was demonstrated for dentine.     

Effect of a pulsed CO2 laser and fluoride on the prevention of enamel and dentine erosion

Objective

The hypotheses of this study was that pulsed CO₂ laser (λ = 10.6 μm) treatment in combination (or not) with previous fluoride gel application could increase the resistance of enamel and dentine to erosion, throughout successive erosive challenges.

Design

Thirty-two bovine specimens of enamel and of root dentine were flattened, polished and randomly assigned to the following treatments (n = 8): fluoride (F), laser (L), fluoride + laser (FL) or no treatment as negative control (C). The treated specimens were submitted to demineralization (0.3% citric acid, pH 2.45, for 5 min) and remineralization (artificial saliva, for 60 min) cycles, three times a day, for 3 days. Dental surface loss as well as the concentration of calcium, phosphorus and fluoride in the demineralizing solutions were determined after each cycling day. Enamel and dentine were analysed separately using repeated measures ANOVA for ranks (α = 0.05).

Results

The association between fluoride and laser (FL) resulted in the lowest enamel and dentine surface loss values throughout the cycles, differing significantly from the control group. No clear benefit of FL over the F or L treatments was observed. There was a non-significant trend (p > 0.05) for FL to release less calcium, phosphorus and fluoride into the demineralizing solutions when compared to the other groups.

Conclusions

Pulsed CO₂ laser (λ = 10.6 μm) alone was not able to prevent enamel or dentine surface losses due to erosion. Laser treatment in combination with fluoride showed some protection, but the effect does not appear to be synergistic.     

Inhibition of tooth erosion by milk containing different fluoride concentrations: An in vitro study

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 ppm F; (2) 2.5 ppm F; (3) 5 ppm F; (4) 10 ppm F (all after erosion); (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 (4× 90 s in soft drink) and treatments for 5 days. 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 (μm), 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.     

Preventive effects of dentifrice containing 5000ppm fluoride against dental erosion in situ

Objective

To evaluate the effectiveness of a dentifrice with 5000 ppm fluoride in preventing dental erosion by orange juice in situ in comparison to a control dentifrice with 1450 ppm fluoride.

Methods

This was a double-blind and randomized clinical study with a cross-over design. Sixteen subjects wore an intra-oral appliance containing two enamel disks with an exposed surface of approximately 2 mm × 5 mm. Enamel disks in the study group were treated with a dentifrice with 5000 ppm fluoride and in the control group with 1450 ppm fluoride. The subjects rinsed with slurries of study dentifrices for one minute before immersing the enamel disks in 250 ml orange Juice four times in an 8-h period daily. The treatment procedure was repeated for three 5-day phases for each dentifrice. Enamel erosion was measured after each 5-day treatment phase using a focus-variation 3D scanning microscopy. Medians and inter-quartile ranges (IQR) of mean erosion depth were compared between the groups.

Results

The mean erosion depths of enamel varied greatly amongst the subjects. Enamel treated with 5000 ppm fluoride had less erosion (median 5.7 μm, IQR 4.5 μm) as compared to the control (median 12.6 μm, IQR 12.3 μm) after 15 days of fluoride treatment and erosive challenge cycles (p < 0.05).

Conclusions

Enamel treated with 5000 ppm fluoride had significantly improved resistance to erosion by orange juice. Periodic application of 5000 ppm fluoride may be beneficial in individuals at risk of acidic erosion associated with soft drink consumptions.     

Randomised in situ trial on the effect of milk and CPP-ACP on dental erosion

Objectives

This randomised in situ study aimed to analyse the effect of milk (with or without 5 ppm F) and CPP-ACP pastes (with or without 900 ppm F) on dental erosion.

Methods

The study was a seven phase (5 days each) crossover design involving 15 participants wearing intraoral appliances with enamel and dentine specimens. Specimens were extraorally eroded (erosive soft drink, 6 × 90 s/day) and brushed (2 × 30 s/day, 2 N) using a non-fluoridated toothpaste (negative control). The test products were milk, milk + 5 ppm F (twice daily, each 100 ml/2 min), CPP-ACP paste, CPP-ACP paste + 900 ppm F (3 min/day) or a SnCl₂/AmF/NaF mouthrinse (positive control, 30 s/day), which were applied immediately after erosion with the appliances in the oral cavity. In an additional group, a fluoridated toothpaste was used without any additional test product. Tissue loss was determined profilometrically after 5 days and statistically analysed by linear mixed models methodologies (p < 0.05).

Results

Compared with the negative control (non-fluoridated toothpaste only, enamel: 2.2 ± 1.3 μm; dentine: 3.8 ± 2.2 μm), enamel and dentine loss was significantly reduced by the use of fluoridated toothpaste (enamel: 1.1 ± 1.0 μm; dentine: 2.4 ± 1.7 μm) and the SnCl₂/AmF/NaF mouthrinse (1.5 ± 1.5 μm; dentine: 1.8 ± 1.9 μm).

Conclusions

Milk and CPP-ACP were not effective in reducing enamel and dentine loss significantly, independently of the presence of fluoride.

Clinical significance

Enamel and dentine erosion were significantly reduced by the use of a fluoridated toothpaste or a SnCl₂/AmF/NaF mouthrinse, but not by milk or CPP-ACP under the conditions of the present study.

Clinical trials registration

NCT01566357.     

In vitro evaluation of the erosive potential of orange juice modified by food additives in enamel and dentine

Objectives

To evaluate the erosive potential of orange juice modified by food additives in enamel and dentine.

Methods

Calcium lactate pentahydrate (CLP), xanthan gum (XG), sodium linear polyphosphate (LPP), sodium pyrophosphate tetrabasic (PP), sodium tripolyphosphate (STP) and some of their combinations were added to an orange juice. Pure orange juice and a calcium-modified juice were used as negative (C−) and positive (C+) controls, respectively. In phase 1, 15 modified orange juices were tested for erosive potential using pH-stat analysis. In phase 2, the additives alone and the combination with good results in phase 1 and in previous studies (CLP + LPP) were tested in an erosion-remineralization cycling model. In phase 3, the erosion and remineralization episodes were studied independently. Enamel was analysed by surface microhardness (SMH) and profilometry, whilst dentine by profilometry.

Results

In phase 1, reduction of the erosive potential was observed for all additives and their combinations, except XG alone. In phase 2, no detectable enamel loss was observed when CLP, LPP and CLP + LPP were added to the juice. XG, STP and PP had enamel loss similar to C− (p > 0.05). Amongst additives, the combination CLP + LPP showed the highest SMH values followed by CLP (p < 0.05). All the other groups presented SMH values similar to C− (p > 0.05). For dentine, only CLP + LPP lead to surface loss values lower than C− (p < 0.05). In phase 3, CLP, LPP and CLP + LPP seemed to protect against erosion; whilst none of the tested compounds seemed to interfere with the remineralization process.

Conclusions

CLP and LPP reduced erosion on enamel and this effect was enhanced by their combination. For dentine, only the combination CLP + LPP reduced erosion.     

Enamel and dentine remineralization by nano-hydroxyapatite toothpastes

Objectives

This in vitro study evaluated the effects of nano-hydroxyapatite (n-HAp) toothpastes on remineralization of bovine enamel and dentine subsurface lesions.

Methods

Specimens were demineralized, randomly divided into five groups, and exposed to an aqueous remineralizing solution for two and five weeks (37 °C). Brushing procedures were performed with the respective toothpaste/storage solution slurry twice daily (2 × 5 s; total contact time of the slurries 2 × 120 s/d): storage in remineralizing solution only (0); additional brushing with B (20 wt% zinc carbonate nano-hydroxyapatite, ZnCO₃/n-HAp); BS (24 wt% ZnCO₃/n-HAp); E (0.14 wt% amine fluoride); or A (7 wt% pure n-HAp). Differences in mineral loss (ΔΔZ) before and after storage/treatment were microradiographically evaluated.

Results

Dentine groups 0, B, BS, and A showed significantly higher ΔΔZ values compared to E (p < 0.05; ANOVA). Enamel ΔΔZ values of group A were significantly higher compared to group E (p < 0.05), whilst no significant differences of these groups could be observed compared to 0, B, and BS (p > 0.05).

Conclusions

With the in vitro conditions chosen, toothpastes containing n-HAp revealed higher remineralizing effects compared to amine fluoride toothpastes with bovine dentine, and comparable trends were obtained for enamel.     

Application of cerium chloride to improve the acid resistance of dentine

Objective

To investigate the effect of cerium chloride, cerium chloride/fluoride and fluoride application on calcium release during erosion of treated dentine.

Methods

Forty dentine samples were prepared from human premolars and randomly assigned to four groups (1-4). Samples were treated twice a day for 5 days, 30 s each, with the following solutions: group 1 placebo, group 2 fluoride (Elmex fluid), group 3 cerium chloride and group 4 combined fluoride and cerium chloride. For the determination of acid resistance, the samples were consecutively eroded six times for 5 min with lactic acid (pH 3.0) and the calcium release in the acid was determined. Furthermore, six additional samples per group were prepared and used for EDS analysis. SEM pictures of these samples of each group were also captured.

Results

Samples of group 1 presented the highest calcium release when compared with the samples of groups 2-4. The highest acid resistance was observed for group 2. Calcium release in group 3 was similar to that of group 4 for the first two erosive attacks, after which calcium release in group 4 was lower than that of group 3. Generally, the SEM pictures showed a surface coating for groups 2-4. No deposits were observed in group 1.

Conclusion

Although fluoride showed the best protective effect, cerium chloride was also able to reduce the acid susceptibility of dentine significantly, which merits further investigation.     

Prevention of dentine erosion by brushing with anti-erosive toothpastes

Objective

This in vitro study aimed to investigate the preventive effect of brushing with anti-erosive toothpastes compared to a conventional fluoride toothpaste on dentine erosion.

Materials and methods

Bovine dentine specimens (n = 12 per subgroup) were eroded in an artificial mouth (6 days, 6 × 30 s/day) using either citric acid (pH:2.5) or a hydrochloric acid/pepsin solution (pH:1.6), simulating extrinsic or intrinsic erosive conditions, respectively. In between, the specimens were rinsed with artificial saliva. Twice daily, the specimens were brushed for 15 s in an automatic brushing machine at 2.5 N with a conventional fluoride toothpaste slurry (elmex, AmF) or toothpaste slurries with anti-erosive formulations: Apacare (NaF/1% nHAP), Biorepair (ZnCO₃-HAP), Chitodent (Chitosan), elmex Erosionsschutz (NaF/AmF/SnCl₂/Chitosan), mirasensitive hap (NaF/30% HAP), Sensodyne Proschmelz (NaF/KNO₃). Unbrushed specimens served as control. Dentine loss was measured profilometrically and statistically analysed using two-way and one-way ANOVA followed by Scheffe‘s post hoc tests. RDA-values of all toothpastes were determined, and linear mixed models were applied to analyse the influence of toothpaste abrasivity on dentine wear (p < 0.05).

Results

Dentine erosion of unbrushed specimens amounted to 5.1 ± 1.0 μm (extrinsic conditions) and 12.9 ± 1.4 μm (intrinsic conditions). All toothpastes significantly reduced dentine erosion by 24–67% (extrinsic conditions) and 21–40% (intrinsic conditions). Biorepair was least effective, while all other toothpastes were not significantly different from each other. Linear mixed models did not show a significant effect of the RDA-value of the respective toothpaste on dentine loss.

Conclusion

Toothpastes with anti-erosive formulations reduced dentine erosion, especially under simulated extrinsic erosive conditions, but were not superior to a conventional fluoride toothpaste.     

The effect of casein phosphopeptide–amorphous calcium phosphate on erosive enamel and dentine wear by toothbrush abrasion

Objective

In addition to its role as a remineralizing agent in preventing dental caries, calcium product (CPP–ACP) delivered as a mousse (Tooth Mousse^®, TM) can reduce erosion of enamel and dentine. The aim of this study was to determine whether CPP–ACP could also reduce erosive tooth wear involving toothbrush abrasion.

Methods

Flat, polished enamel and dentine specimens (n = 72) were subjected to 10 wear regimes, with each regime involving erosion in 0.3% citric acid (pH 3.2) for 10 min followed by toothbrush abrasion in a slurry of fluoride-free toothpaste and artificial saliva (1:3 ratio by weight) under a load of 2N for 200 cycles. The specimens were immersed in artificial saliva for 2 h between wear regimes. In the experimental group 1, TM (containing CPP–ACP) was applied at the beginning of each wear episode for 5 min whereas TM− (without CPP–ACP) was applied in the experimental group 2. No mousse was applied in the control group.

Results

TM significantly reduced enamel wear (mean ± S.E., 1.26 ± 0.33 μm in the experimental group 1 vs 3.48 ± 0.43 μm in the control group) and dentine wear (2.16 ± 0.89 μm in the experimental group 1 vs 10.29 ± 1.64 μm in the control group), and dentine wear was significantly less in the experimental group 1 than in the experimental group 2 (5.75 ± 0.98 μm).

Conclusion

The finding that TM reduced erosive tooth wear involving toothbrush abrasion, probably by remineralizing and lubricating eroded tooth surfaces, may have implications in the management of tooth wear.     

Influence of the digestive enzymes trypsin and pepsin in vitro on the progression of erosion in dentine

Objectives

In patients with eating disorders, gastric and pancreatic enzymes could possibly reach the oral cavity during vomiting and could perhaps degrade the organic matrix of eroded dentine. This in vitro study sought to investigate whether pepsin, trypsin or the combination of both, have an influence on erosive mineral loss in dentine and whether they are able to degrade the organic matrix.

Methods

Sixty-four human dentine specimens were prepared and randomly divided into four groups. Specimens were cyclically de- and remineralised for six days. Demineralisation was performed with an HCl-solution (6× 5 min daily, pH 1.6) in groups 1 and 3; in groups 2 and 4 the demineralisation solution additionally contained pepsin (750 μg/ml). After demineralisation, specimens of groups 3 and 4 were treated with a trypsin solution (6× 10 min daily, 2000 BAEE/ml). After each day, mineral content (μm) was determined microradiographically, and the matrix degradation was determined by hydroxyproline analysis.

Results

After six days, treatment with pepsin (group 2) or trypsin (group 3) had no significant influence on mineral loss. The combined impact of pepsin and trypsin led to significantly higher mineral loss (group 4: 202.5 ± 37.4) compared to all other groups (group 1: 139.1 ± 29.5, p ≤ 0.001; group 2: 108.8 ± 34.7, p ≤ 0.001; group 3: 157.8 ± 37.2, p ≤ 0.05). Hydroxyproline was found in all pepsin-solutions but in no trypsin- or HCl-solutions.

Conclusion

The combined impact of pepsin and trypsin intensified dentine erosion progression in vitro. This could be one reason for the fast proceeding of dental erosion in patients with chronic vomiting.     

Shear bond strength of porcelain laminate veneers to enamel,dentine and enamel–dentine complex bonded with different adhesive luting systems

Objectives

The aim of this study was to evaluate the shear bond strength of porcelain laminate veneers to 3 different surfaces by means of enamel, dentine, and enamel–dentine complex.

Methods

One hundred thirty-five extracted human maxillary central teeth were used, and the teeth were randomly divided into 9 groups (n = 15). The teeth were prepared with 3 different levels for bonding surfaces of enamel (E), dentine (D), and enamel–dentine complex (E–D). Porcelain discs (IPS e.max Press, Ivoclar Vivadent) of 2 mm in thickness and 4 mm in diameter were luted to the tooth surfaces by using 2 light-curing (RelyX Veneer [RV], 3M ESPE; Variolink Veneer [VV], Ivoclar Vivadent) and a dual-curing (Variolink II [V2], Ivoclar Vivadent) adhesive systems according to the manufacturers’ instructions. Shear bond strength test was performed in a universal testing machine at 0.5 mm/min until bonding failure. Failure modes were determined under a stereomicroscope, and fracture surfaces were evaluated with a scanning electron microscope. The data were statistically analysed (SPSS 17.0) (p = 0.05).

Results

Group RV-D exhibited the lowest bond strength value (5.42 ± 6.6 MPa). There was statistically no difference among RV-D, V2-D (13.78 ± 8.8 MPa) and VV-D (13.84 ± 6.2 MPa) groups (p > 0.05). Group VV-E exhibited the highest bond strength value (24.76 ± 8.8 MPa).

Conclusions

The type of tooth structure affected the shear bond strength of the porcelain laminate veneers to the 3 different types of tooth structures (enamel, dentine, and enamel–dentine complex).

Clinical significance

When dentine exposure is necessary during preparation, enough sound enamel must be protected as much as possible to maintain a good bonding; to obtain maximum bond strength, preparation margins should be on sound enamel.     

Effect of TiF4, ZrF4, HfF4 and AmF on erosion and erosion/abrasion of enamel and dentin in situ

Objective

This in situ study aimed to analyse the impact of different tetrafluorides (TiF₄, ZrF₄ and HfF₄) and AmF on erosion and erosion plus abrasion of enamel and dentin.

Design

Ten volunteers took part in this crossover and double-blind study performed in 8 phases of each 3 days. In each phase, 2 bovine enamel and 2 dentin specimens were fixed in intraoral appliances. One enamel and one dentin sample were pretreated once with TiF₄, ZrF₄, HfF₄ or AmF (all 0.5 M F) for 60 s, while the other samples remained unfluoridated and served as control. Then, all samples were subjected to either erosion only (4 times/day, 90 s) or to erosion and abrasion (2 times/day, 30 s/sample). Toothbrushing abrasion was performed 90 min after the first and last erosion with an electrical toothbrush and fluoridated toothpaste at 1.2 N. After 3 days, enamel and dentin loss was assessed by profilometry (μm) and analysed by repeated measures ANOVA and paired t-test (p < 0.05).

Results

All fluoride solutions reduced enamel and dentin loss significantly compared to the controls. Generally, eroded samples showed less wear than eroded and abraded samples. The protective potential of the fluorides was not significantly different and was only slightly, but mostly not significantly, decreased by abrasion. The protective effect of the fluoride solutions was similar in enamel and dentin.

Conclusion

Tetrafluorides and AmF are able to reduce erosion and erosion plus abrasion in situ and are almost equally effective.     

Assessing fluoride treatment and resistance of dental enamel to soft drink erosion in vitro: Applications of focus variation 3D scanning microscopy and stylus profilometry

Objectives

This study assesses the application of the focus variation 3D microscopy for the evaluation of dental erosion and fluoride treatment for prevention of enamel erosion in vitro.

Methods

Human dental enamel disks were treated with Prevident 5000^® (PV, n = 15) for 1 week and compared with a reference group (PN, n = 15) after orange juice erosion in vitro. A focus variation 3D scanning microscope (IFM) and a stylus type profilometer (SSP) were used to evaluate the erosion depths on enamel. 3D topographic images were taken with vertical resolutions of 0.1 and 0.02 μm. Scratch marks depths from SSP were measured on IFM images. Measurements were compared between the SSP and IFM and between the two study groups.

Results

The SSP and IFM measurements of eroded enamel surfaces showed similar trends between the two methods and between the two study groups. The SSP and the IFM measurements were statistically significantly different but correlated with each other. PV group showed consistently lower erosion depth than PN in all profile measures using both SSP and IFM. The stylus tip created scratch marks that were significantly different in depths between the eroded and the reference surfaces in both groups.

Conclusions

The focus variation 3D microscopy is a powerful tool in evaluating surface topography associated with enamel erosion and in assessing the treatment effects of anti-erosive therapies. Topical treatment with Prevident 5000^® significantly increased enamel resistance to erosion by orange juice and should be considered as a treatment choice in patients susceptible to acidic dental erosion.     

Effect of open-sandwich vs. adhesive restorative techniques on enamel and dentine demineralization: An in situ study

Objectives

To assess in situ the effect of different restorative techniques used with fluoride-releasing materials on enamel and dentine demineralization in the presence of a cariogenic challenge.

Methods

Thirty human molars were prepared for 60 Class V cavities, with enamel and dentine margins. The teeth were divided into four groups (n = 15): L1 – open sandwich technique with a conventional glass ionomer cement (GIC), L2 – open sandwich technique with a resin-modified GIC, A1 – total-etch bonding with a fluoride-containing adhesive, A2 – total-etch bonding with a nonfluoride-containing adhesive. All the cavities were restored with a nanofilled composite. Fifteen volunteers used appliances containing one specimen from each group. The cariogenic challenge was carried out with a 20% sucrose solution 8×/day for 7 days. The specimens were sectioned for microhardness test and EDS analysis at different depths below the enamel and dentine margins (25, 50 and 100 μm) and distances from the tooth-restoration interfaces (25 and 75 μm). The data were analyzed by ANOVA and Games–Howell test (α = 5%).

Results

Both GICs produced higher hardness in enamel at all depth-and-distance combinations, but only L1 produced higher hardness in dentine (p < 0.05). L2 and A1 exhibited similar dentine hardness at 25 μm distance for all depths (p > 0.05). L1 demonstrated significantly higher amounts of calcium in dentine than the other groups, but had similar amounts in enamel to L2 and A1.

Conclusions

The open sandwich technique using conventional GIC proved more effective in reducing enamel and dentine demineralization at depths of up to 100 μm under a cariogenic challenge.

Clinical significance

Conventional GICs should be considered the materials of choice for lining of cavities not having all margins in enamel, particularly using the open sandwich technique.     

Effects of CPP-ACP with sodium fluoride on inhibition of bovine enamel demineralization: a quantitative assessment using micro-computed tomography

Objectives

The present study evaluated the effects of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and CPP-ACP with 900 ppm fluoride (CPP-ACPF) pastes on inhibition of enamel demineralization over time, using polychromatic micro-computed tomography (micro-CT).

Methods

Enamel blocks were prepared from bovine teeth. The specimens were each treated by one of the following agents, 30 min daily for 7 days: deionized water (negative control); CPP-ACP paste; CPP-ACPF paste; and NaF solutions (positive controls) (90, 900, and 9000 ppm F). After treatment, the specimens were immersed in a demineralizing solution (pH 4.5) for 24, 72, and 120 h. Mean mineral loss (ML) and lesion depth (LD) after each period were determined from mineral density profiles obtained using micro-CT.

Results

ML values in all the treatment groups were significantly smaller than those in the control group after 72 and 120 h of demineralization (p < 0.05, two-way ANOVA and t-test with Bonferroni correction). ML values in CPP-ACPF and NaF solution groups were significantly smaller compared to CPP-ACP group after 72 h (p < 0.05). LD values in the CPP-ACPF and all the NaF solutions groups were significantly smaller compared to the control group after 120 h (p < 0.05). The 9000 ppm F group showed the lowest nominal ML and LD values.

Conclusions

The application of CPP-ACP or CPP-ACPF pastes to sound enamel surfaces resulted in inhibition of enamel demineralization, and a better effect was noted for the latter paste. Quantitative assessment using polychromatic micro-CT demonstrated to be useful for detecting mineral density changes.     

Combined effect of a fluoride-, stannous- and chitosan-containing toothpaste and stannous-containing rinse on the prevention of initial enamel erosion–abrasion

Objectives

The aim of this study was to assess the preventive effect of a fluoride-, stannous- and chitosan-containing (F/Sn/chitosan-) toothpaste (TP) on initial enamel erosion and abrasion.

Methods

In total, 150 human premolar enamel specimens were ground, polished and divided into 5 toothpaste/rinse groups (n = 30): (G1) placebo-TP/tap water, (G2) sodium fluoride (NaF-) TP/tap water, (G3) F/Sn/chitosan-TP/tap water, (G4) F/Sn/chitosan-TP/Sn-rinse, (G5) NaF-TP/NaF-rinse. The 8-day erosion–abrasion cyclic treatment (one cycle/day) consisted of incubating the samples in artificial saliva (30 min), then submitting the samples to toothbrush abrasion (2 min incubation in toothpaste slurry; brushing with 20 toothbrush strokes) and rinsing (2 min; 10 ml) with the respective solution: tap water (G1–G3), Sn-rinse (G4) or NaF-rinse (G5). Afterwards, the samples were submitted to erosion (2 min; 30 ml 1% citric acid, pH = 3.6). Surface microhardness (SMH) was measured initially and after every abrasion and erosion treatment. Enamel substance loss was calculated after each abrasion. Non-parametric ANOVA followed by Wilcoxon rank tests were used for analysis.

Results

G1 presented the greatest SMH decrease, while G4 presented the least SMH decrease (p < 0.001). G3 had a similar SMH decrease to G2 and G5. Substance loss was significantly lower in G4 than all other groups (p < 0.05), closely followed by G3. Both G2 and G5 showed similar calculated enamel substance loss to G1.

Conclusion

The treatment with F/Sn/chitosan-TP and tap water provided a similar SMH decrease to both NaF-TP groups, but significantly lower substance loss. F/Sn/Chitosan-TP and Sn-rinse showed a better preventive effect, which promoted less SMH decrease and reduced substance loss.

Clinical significance

The toothpaste containing fluoride, stannous and chitosan shows promising results in reducing substance loss from erosion and abrasion. The combination of this toothpaste with the stannous-containing rinse showed even better prevention against erosion–abrasion.     

A qualitative and quantitative investigation into the effect of fluoride formulations on enamel erosion and erosion-abrasion in vitro

Objectives

To investigate the effect of a single application of highly concentrated SnF₂ and NaF solutions and a NaF/CaF₂ varnish on human enamel subjected to hydrochloric acid erosion and tooth brush abrasion.

Methods

Forty enamel samples were prepared from human third molars and NaF (9500 ppm, pH 8.0), SnF₂ (9500 ppm, pH 2.6) solutions; Bifluorid10^® varnish (42,500 ppm, NaF 5%, CaF₂ 5%) and deionized water (control) was applied to the enamel. Following this three, six and nine cycles of erosion [1 cycle = erosion (0.01 M HCl, pH 2.2, 2 min) + artificial saliva (1 h, pH 7.0)] and erosion-abrasion [1 cycle = erosion (0.01 M HCl, pH 2.2, 2 min) + artificial saliva (1 h, pH 7.0) + abrasion (120 linear strokes in artificial saliva from Tepe medium soft brushes 200 g loading)] were carried out. The fluoride treated enamel was analysed using Knoop microhardness, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS).

Results

For erosion alone, there was significantly less microhardness reduction in the Bifluorid10^® group after three and six cycles of erosion (P < 0.05), however no other groups showed statistically different hardness (P > 0.05). The EDS analysis showed that only the Bifluorid10^® group had any detectable fluorine following erosion and erosion-abrasion (0.1 wt.% and 0.2 wt.% fluorine respectively). The surface fluorine was found to have been removed after erosion and erosion-abrasion for all other surface treatments. Although precipitates were observed after application of the surface treatments, following erosion-abrasion, no visible surface effects from any fluoride preparation remained.

Conclusions

Enamel surface precipitates from application NaF, SnF₂ solutions appear to not be able to provide protection against gastric erosion and tooth brush abrasion. The NaF/CaF₂ varnish provided limited protection against erosion but the role for such varnishes in gastric erosion and tooth brush abrasion remains uncertain.     

Prevention of toothbrushing abrasion of acid-softened enamel by CO(2) laser irradiation

Objective

The aim of the present study was to evaluate the effect of CO₂ laser irradiation (10.6 μm) at 0.3 J/cm² (0.5 μs; 226 Hz) on the resistance of softened enamel to toothbrushing abrasion, in vitro.

Methods

Sixty human enamel samples were obtained, polished with silicon carbide papers and randomly divided into five groups (n = 12), receiving 5 different surface treatments: laser irradiation (L), fluoride (AmF/NaF gel) application (F), laser prior to fluoride (LF), fluoride prior to laser (FL), non-treated control (C). After surface treatment they were submitted to a 25-day erosive-abrasive cycle in 100 ml sprite light (90 s) and brushed twice daily with an electric toothbrush. Between the demineralization periods samples were immersed in supersaturated mineral solution. At the end of the experiments enamel surface loss was determined using a contact profilometer and morphological analysis was performed using scanning electron microscopy (SEM). For SEM analysis of demineralization pattern, cross-sectional cuts of cycled samples were prepared. The data were statistically analysed by one-way ANOVA model with subsequent pairwise comparison of treatments.

Results

Abrasive surface loss was significantly lower in all laser groups compared to both control and fluoride groups (p < 0.0001 in all cases). Amongst the laser groups no significant difference was observed. Softened enamel layer underneath lesions was less pronounced in laser-irradiated samples.

Conclusion

Irradiation of dental enamel with a CO₂ laser at 0.3 J/cm² (5 μs, 226 Hz) either alone or in combination with amine fluoride gel significantly decreases toothbrushing abrasion of softened-enamel, in vitro.     

Effect of sodium,amine and stannous fluoride at the same concentration and different pH on in vitro erosion

Objective

This study aimed to compare the effects 0.5% and 1% sodium, amine and stannous fluoride at different pH on enamel erosion in vitro.

Methods

Bovine enamel samples were submitted to a cyclic de- and remineralisation for 3 days. Each day, the samples were exposed for 120 min to pooled human saliva and subsequently treated with one of the fluoride solutions for 3 min: amine fluoride (AmF, 0.5% and 1% F⁻), sodium fluoride (NaF, 0.5% and 1% F⁻), each at pH 3.9 and 7.0, and stannous fluoride (SnF₂, 0.5% and 1% F⁻), at pH: 3.9. Additionally, two groups were treated with fluoride-free placebo solutions (pH: 3.9 and 7.0) and one group served as control (no fluoridation). Ten specimens each group were inserted in a so-called artificial mouth and eroded six times daily with hydrochloric acid (pH 2.6) for 90 s each intermitted by exposure to artificial saliva (1 h). After 3 days, enamel loss was analyzed profilometrically and evaluated statistically by ANOVA.

Results

Only the acidic 0.5% and 1% SnF₂ and 1% AmF solutions were able to reduce erosive enamel loss significantly, while all other solutions and placebos did not differ significantly from the control. Between the acidic SnF₂ and the 1% AmF solutions no significant differences could be detected.

Conclusion

At the same concentrations, acidic SnF₂ and AmF may be more effective than NaF to protect enamel against erosion.