Efficacy of the stannous ion and a biopolymer in toothpastes on enamel erosion/abrasion

Experimental toothpastes containing β-TCP nanoparticles functionalized with fluoride and tin to prevent Erosive Tooth Wear

OBJECTIVES

The present study aimed to synthesize toothpastes containing Beta- TriCalcium Phosphate (β-TCP) nanoparticles, functionalized with fluoride and tin, and test their ability to reduce erosive tooth wear (ETW).

METHODS

Toothpastes were synthesized with the following active ingredients: 1100 ppm of fluoride (as sodium fluoride, F-), 3500 ppm of tin (as stannous chloride, Sn2+), and 800 ppm of β-TCP (Sizes a - 20 nm; and b - 100 nm). Enamel specimens were randomly assigned into the following groups (n = 10): 1. Commercial toothpaste; 2. Placebo; 3 F-; 4. F- + β-TCPa; 5. F- + β-TCPb; 6. F- + Sn2+; 7. F- + Sn2+ + β-TCPa and 8. F- + Sn2+ + β-TCPb. Specimens were subjected to erosion-abrasion cycling. Surface loss (in µm) was measured by optical profilometry. Toothpastes pH and available F- were also assessed.

RESULTS

Brushing with placebo toothpaste resulted in higher surface loss than brushing with F- (p = 0.005) and F- + β-TCPb (p = 0.007); however, there was no difference between F- and F- + β-TCPb (p = 1.00). Commercial toothpaste showed no difference from Placebo (p = 0.279). The groups F-, F- + β-TCPa, F- + β-TCPb, F- + Sn2+, F- + Sn2+ + β-TCPa and F- + Sn2+ + β-TCPb were not different from the commercial toothpaste (p > 0.05). Overall, the addition of β-TCP reduced the amount of available fluoride in the experimental toothpastes. The pH of toothpastes ranged from 4.97 to 6.49.

CONCLUSIONS

Although toothpaste containing β-TCP nanoparticles protected enamel against dental erosion-abrasion, this effect was not superior to the standard fluoride toothpaste (commercial). In addition, the functionalization of β-TCP nanoparticles with fluoride and tin did not enhance their protective effect.

CLINICAL SIGNIFICANCE

Although β-TCP nanoparticles have some potential to control Erosive Tooth Wear, their incorporation into an experimental toothpaste appears to have a protective effect that is similar to a commercial fluoride toothpaste.

Effect of combining aminomethacrylate and fluoride against erosive and abrasive challenges on enamel and dentin

This study evaluated the effect of solutions containing aminomethacrylate copolymer (AA) and sodium fluoride (F; 225 ppm F-) or fluoride plus stannous chloride (FSn; 225 ppm F-, 800 ppm Sn2+) against enamel and dentin erosion/abrasion. Solutions F, FSn, AA, F+AA, FSn+AA, and deionized water as negative control were tested. Bovine enamel and dentin specimens (n = 13/solution/substrate) underwent a set of erosion-abrasion cycles (0.3% citric acid [5 min, 4×/day], human saliva [1 h, 4×/day], brushing [15 s, 2×/day], and treatments [2 min, 2×/day]) for each of five days. Initial enamel erosion was evaluated using Knoop microhardness after the first and second acid challenge on day 1, and surface loss with profilometry after day 5. KOH-soluble fluoride was assessed. Data were analyzed with ANOVA/Tukey tests. The combination of fluoride and AA resulted in higher protection against enamel erosion, whereas this was not the case for the combination of AA and FSn. All treatments protected against enamel and dentin loss. The lowest surface loss values were observed with F+AA and FSn+AA. The polymer did not significantly influence the KOH-soluble fluoride formation on enamel/dentin specimens. The aminomethacrylate copolymer effectively enhanced the efficacy of sodium fluoride against initial erosion and improved the control of enamel and dentin wear of F and FSn solutions.

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.

Characteristics of tin-containing fluoride toothpastes related to erosive tooth wear protection

OBJECTIVES

To assess the effect of different tin-containing toothpastes on the control of erosive tooth wear in enamel and dentin.

METHODS

Enamel and dentin slabs were randomly distributed into 7 experimental groups (n = 10/substrate): C-: negative control (Artificial saliva); AmF (regular fluoridated toothpaste without tin); Sn-1 (SnF2/NaF); Sn-2 (SnF2/NaF/SnCl2); Sn-3 (SnCl2/NaF); Sn-4 (SnF2/SnCl2); Sn-5 (SnCl2/AmF/NaF/chitosan). Specimens were submitted to 5-day erosion-abrasion cycling. Surface loss (SL) was determined with an optical profilometer. Tin deposition on the tooth surfaces and some characteristics of the toothpastes (pH, potentially available F-, %weight of solid particles, and RDA) were also assessed. Data were statistically analyzed (α = 0.05).

RESULTS

For enamel, the Sn-2 presented the lowest SL, not differing significantly from AmF, C+, and Sn-3. The SL of these groups was significantly lower than the C-, except for Sn-3. Sn-1 and Sn-4 were also not significantly different from C-. For dentin, C- significantly showed the highest SL values, whilst, Sn-1 presented the lowest SL, not differing significantly from AmF, Sn-2, C+, and Sn-3. There was a significant positive association between enamel SL and the pH and tin deposition. Dentin SL was significantly negatively associated with the %weight of solid particles and RDA.

CONCLUSIONS

Most of the tin-toothpastes were able to exhibit some protection against ETW. In this process, the toothpastes characteristics play a role, as lower enamel SL was significantly associated with lower pH values and tin deposition; and lower dentin SL was associated with higher %weight of solid particles and RDA of the toothpastes.

CLINICAL SIGNIFICANCE

Tin-containing toothpastes can be used for erosive tooth wear protection, but our study showed that their effect depends on the pH, amount of tin deposition, % weight of solid particles and RDA of the toohpastes.

Combined use of stannous fluoride-containing mouth rinse and toothpaste prevents enamel erosion in vitro

OBJECTIVE

To compare the protective effect of commercial stannous-containing mouth rinses on enamel erosion in a simulated 5-day in vitro cycling model.

MATERIALS AND METHODS

81 human enamel specimens were embedded in resin blocks and divided into nine groups as follows; group 1: stannous fluoride (1000SnF2) toothpaste; groups 2,3, and 4 were the same as group 1 plus Elmex®, PerioMed™, and Meridol®, respectively, group 5: stannous fluoride (1450SnF2) toothpaste, groups 6, 7, and 8 were the same as group 5 plus Elmex®, PerioMed™, and Meridol®, respectively, group 9: negative control. An erosive challenge was induced with a 1 min hydrochloric acid (0.01 M, pH 2.2) treatment 3 times per day. Each cycle included immersing in the toothpaste slurry twice for two minutes and a one-minute rinse. The enamel slabs were immersed in artificial saliva between each erosive cycle and incubated overnight at 37 °C. Surface hardness loss and enamel loss were determined by Knoop surface hardness and non-contact profilometry, respectively. Finally, enamel surfaces were analyzed by scanning electron microscopy and X-ray energy dispersive spectroscopy (SEM/EDS).

RESULTS

All three mouth rinses had similar protective effects against erosion when using adjunct with 1000 SnF2 toothpaste (p > 0.05). With 1450 SnF2 toothpaste, Elmex® presented significantly lower surface hardness loss than Meridol® (p < 0.05). The combined use of Elmex® or PerioMed™ with toothpaste provided significantly better erosion protection than toothpaste alone, either 1000 or 1450 SnF2. In addition, 1000SnF2 toothpaste adjunct with mouth rinse is comparable to 1450 SnF2 toothpaste alone in preventing enamel erosion.

CONCLUSION

All three mouth rinses reduced enamel erosion. The additional use of a high concentration stannous containing mouth rinse with 1450 SnF2 toothpaste increases the protective effect against enamel erosion in vitro.

CLINICAL SIGNIFICANCE

To date, no standard protocol for preventing dental erosion is available. There are three stannous-containing mouth rinses on the market; however, no study compared their efficacy or indicated whether using adjuncts with anti-erosion toothpaste provides additional benefits. This study found that adding stannous mouth rinse to twice-daily toothpaste increases erosion protection.

Different vehicles containing CaneCPI-5 reduce erosive dentin wear in situ

OBJECTIVE

This study evaluated the protective capacity of a sugarcane-derived cystatin (CaneCPI-5) in different vehicles (1-solution and 2-chitosan gel) against erosive dentin wear in situ.

METHODS

In part-1, 15 volunteers participated in a crossover protocol (solutions): Water; Elmex™ and CaneCPI-5. The volunteers wore an appliance with 4 dentin samples for 5 days. These samples were treated with a drop of the solutions for 1 min (4X/d), then the acquired pellicle (AP) was formed and the samples were subjected to erosive challenges (EROSION: citric acid, for 90 s, 4X/day). 2X/day, half of the samples were also abraded for 15 s (ABRASION). In part-2, 16 volunteers participated in a crossover protocol (gel): No gel, Chitosan gel, Chitosan gel + NaF and Chitosan gel + CaneCPI-5. The volunteers also wore an appliance. The samples were treated once/day with the gel or not for 4 min, then the AP was formed and the samples were subjected to erosive and abrasive challenges, as reported in part-1. Dentin wear was measured by profilometry. Data were analyzed by two-way RM-ANOVA and Sidak's tests (p < 0.05).

RESULTS

Part-1: Elmex™ and CaneCPI-5 significantly reduced dentin loss in comparison with Water for the EROSION/ABRASION conditions (p < 0.05). Part-2, all the treated groups significantly reduced the dentin loss in comparison to the No gel. The greatest reduction was found for the gel + CaneCPI-5 group for the EROSION/ABRASION (p < 0.05).

CONCLUSION

The solution and chitosan gel containing CaneCPI-5 protected against erosive dentin wear in situ.

CLINICAL RELEVANCE

These different vehicles are probably sufficient for protecting people with high risk of developing erosive dentin wear.

Role of Chitosan Hydrogels in Clinical Dentistry

Biopolymers are organic polymers that can be treated into intricate designs with porous characteristics that mimic essential biologic components. Due to their superior biosafety, biodegradability, biocompatibility, etc., they have been utilized immensely in biomedical engineering, regeneration, and drug delivery. To obtain the greatest number of results, a literature search was undertaken in scientific search engines utilizing keywords. Chitosan is used in a variety of medical sectors, with the goal of emphasizing its applications and benefits in the clinical dental industry. Chitosan can be dissolved in liquid form and combined with other substances to create a variety of products, including fibers, hydrogels, membranes, microspheres, resins, sponges, pastes, tablets, and micro granules. Chitosan has been studied in a variety of dental applications. Chitosan is used in the prevention of caries and wear, in pulpotomy to accelerate osteogenesis in guided tissue regeneration due to its hemostatic property, and primarily to benefit from its antimicrobial activity by adding it to materials, such as glass ionomer cement, calcium hydroxide, and adhesive systems. With its antibacterial activity and biocompatibility, chitosan is leading the pack as a promising ingredient in the production of dental materials. The current review provides an update on the background, fundamentals, and wide range of uses of chitosan and its gels in dental science.

Film-Forming Polymers for Tooth Erosion Prevention

Different agents have been proposed to prevent the progression of acid induced dental substance losses, which are called erosive tooth wear (ETW), such as fluorides, calcium, and phosphate-based products; however, there is a need for a further increase in efficacy. Recently, the ability of polymers to interact with the tooth surface, forming acid resistant films, has come into the focus of research; nevertheless, there is still the need for a better understanding of their mode of action. Thus, this article provides an overview of the chemical structure of polymers, their mode of action, as well as the effect of their incorporation into oral care products, acid beverages, and antacid formulations, targeting the prevention of ETW. Recent evidence indicates that this may be a promising approach, however, additional studies are needed to confirm their efficacy under more relevant clinical conditions that consider salivary parameters such as flow rate, composition, and clearance. The standardization of methodological procedures such as acid challenge, treatment duration, and combination with fluorides is necessary to allow further comparisons between studies. In conclusion, film-forming polymers may be a promising cost-effective approach to prevent and control erosive demineralization of the dental hard tissue.

Preventive effect of chitosan gel containing CaneCPI-5 against enamel erosive wear in situ

OBJECTIVE

This study evaluated the preventive effect of a chitosan gel containing CaneCPI-5 against enamel erosion and erosion + abrasion in situ.

METHODS

Sixteen volunteers participated in a crossover, double-blind protocol, comprising 4 phases: (1) no treatment (Nt); (2) chitosan gel (Cg); (3) chitosan gel + 12,300 ppm NaF (Cg + NaF); and (4) chitosan gel + 0.1 mg/mL CaneCPI-5 (Cg + Cane). Volunteers wore an appliance containing 4 specimens. Once/day, they applied the gel (except for Nt) (4 min/specimen). Erosive challenges were performed extra-orally (0.1% citric acid, 90 s, 4 × /day; ERO). Specimens were also abraded (toothbrush, 15 s/specimen, 2 × /day; ERO + ABR). Enamel wear was assessed by profilometry and relative surface reflection intensity (%SRI). Two-way RM-ANOVA/Sidak's tests and Spearman's correlation were used (p < 0.05).

RESULTS

For profilometry, ERO + ABR promoted significantly greater wear when compared with ERO. There was a significant difference among all treatments. The lowest enamel loss occurred for Cg + Cane, followed by Cg + NaF, Cg, and Nt (p < 0.05). The %SRI was significantly lower for ERO + ABR when compared to ERO, only for the Nt group. The greatest %SRI was found for the Cg + NaF and Cg + Cane groups, which did not differ significantly, regardless of the conditions. The lowest %SRI was found for the Nt and Cg groups, which did not differ from each other, regardless of the conditions. The Nt group did not differ significantly from the Cg + NaF (ERO). There was a significant correlation between both analyses.

CONCLUSION

The incorporation of CaneCPI-5 in the chitosan gel prevented erosive wear in situ.

CLINICAL RELEVANCE

These results open a new perspective for the use of CaneCPI-5 in other application vehicles, such as chitosan gel.

Effect of air-abrasion pretreatment with three bioactive materials on enamel susceptibility to erosion by artificial gastric juice

OBJECTIVE

The purpose of the study was to investigate the protective effect of three in-office preventive treatments with bioactive materials against enamel erosion induced by artificial gastric juice similar to that found in gastroesophageal reflux disease (GERD) patients. The treatments included air-abrasion of enamel with a fluoride-containing bioactive glass (BioMinF®), Bioglass 45S5 (ProSylc) and nano-hydroxyapatite (MI Pearls) to test enamel susceptibility following an erosive challenge.

METHODS

Enamel surface loss was evaluated using confocal microscopy, while changes in enamel surface roughness and morphology were also investigated after the treatments. SEM and EDS were used to observe formation of apatite crystals on enamel and to detect alterations in mineral composition. In Group 1 (negative control) the specimens did not receive any treatment; Group 2 specimens (positive control) treated with 0.4 % SnF₂, while in Groups 3-5 enamel was air-abraded with BioMinF®, ProSylc and MI Pearls, respectively.

RESULTS

All the experimental groups reduced significantly enamel surface loss compared to the negative control group (p < 0.05), except for the MI Pearls treatment (p > 0.05). The most protective behavior against erosion presented the treatment with SnF₂. BioMinF induced the larger amount of apatite crystals on the enamel surface, followed by ProSylc.

SIGNIFICANCE

BioMinF and ProSylc treatments may be beneficial against dental erosion induced by gastric juice in GERD patients, while MI Pearls treatment may not suitable for this indication. Both materials promote formation of apatite crystals on enamel in acidic conditions protecting the surface from the erosion. The tested treatments may be useful in GERD patients who cannot comply with at-home therapies with SnF₂.

In vitro evaluation of the effects of different particle types in toothpastes on the efficacy against enamel erosion and wear

The effects of the particle fraction in toothpastes in the context of erosion and erosive tooth wear has not been fully elucidated. Thus, aim of this study was to investigate experimental toothpastes, each with one specific particle type. Toothpastes with seven different types of silica or alumina were prepared as slurry either with or without active ingredients (NaF or F/Sn). Human enamel samples were exposed to a cyclic erosion/abrasion model, and were either treated with the respective slurries only or additionally brushed in a brushing machine. Tissue loss was profilometrically monitored. After treatment with slurries without active ingredients or with NaF, tissue loss increased significantly within groups over time (p < 0.001 each). At the end of the trial, there were minor differences between groups (not exceeding 10-20%; p > 0.05 for most comparisons). After treatment with the F/Sn slurries, tissue loss stagnated completely over time, with the exception of one silica type and alumina, but both still reduced tissue loss by 40-50% (compared to control p < 0.001 each). Relative to the type of the active ingredient, the particle type seems to be a secondary factor for the efficacy of toothpastes on erosion and erosive tooth wear in enamel.

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.

Analysis of clinical trials on biomaterial and therapeutic applications of chitosan: A review

Chitosan is a modified natural carbohydrate polymer derived from chitin that occurs in many natural sources. It has a diverse range of applications in medical and pharmaceutical sciences. Its primary and permitted use is biomaterial in medical devices. Chitosan and its derivatives also find utility in pharmaceuticals as an excipient, drug carrier, or therapeutic agent. The USFDA has approved chitosan usage as a biomaterial but not for pharmaceutical use, primarily because of the concerns over its source, purity, and immunogenicity. A large number of clinical studies are underway on chitosan-based materials/ products because of their diverse applications. Herein, we analyze clinical studies to understand their clinical usage portfolio. Our analysis shows that >100 clinical studies are underway to investigate the safety/efficacy of chitosan or its biomaterials/ nanoparticles, comprising ~95% interventional and ~ 5% observational studies. The regulatory considerations that limit the use of chitosan in pharmaceuticals are also deliberated. TEASER: Clinical Trials of Chitosan.

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.

The Application of Chitosan Nanostructures in Stomatology

Chitosan (CS) is a natural polymer with a positive charge, a deacetylated derivative of chitin. Chitosan nanostructures (nano-CS) have received increasing interest due to their potential applications and remarkable properties. They offer advantages in stomatology due to their excellent biocompatibility, their antibacterial properties, and their biodegradability. Nano-CSs can be applied as drug carriers for soft tissue diseases, bone tissue engineering and dental hard tissue remineralization; furthermore, they have been used in endodontics due to their antibacterial properties; and, finally, nano-CS can improve the adhesion and mechanical properties of dental-restorative materials due to their physical blend and chemical combinations. In this review, recent developments in the application of nano-CS for stomatology are summarized, with an emphasis on nano-CS’s performance characteristics in different application fields. Moreover, the challenges posed by and the future trends in its application are assessed.

Impact of mucin on the anti-erosive/anti-abrasive efficacy of chitosan and/or F/Sn in enamel in vitro

The application of stannous ions in combination with fluoride (F/Sn) is one of the central strategies in reducing erosive tooth wear. F/Sn efficacy can be enhanced by adding chitosan, a positively charged biopolymer. For patients with low saliva flow, this efficacy, however, is not sufficient, making further improvement desirable. This could be achieved by combining chitosan with other molecules like mucin, which together might form multilayers. This in-vitro study aimed to investigate the effect of chitosan, mucin, F/Sn and combinations thereof on enamel erosion and erosion-abrasion. Human enamel samples (n = 448, 28 groups) were cyclically eroded or eroded-abraded (10 days; 6 × 2 min erosion and 2 × 15 s/200 g abrasion per day). Samples were treated 2 × 2 min/day with solutions containing either, chitosan (50 or 500 mPas), porcine gastric mucin, F/Sn or combinations thereof after abrasive challenge. Tissue loss was measured profilometrically, interaction between hard tissue and active agents was assessed with energy dispersive spectroscopy and scanning electron microscopy. Chitosan and F/Sn showed the expected effect in reducing tissue loss under erosive and under erosive-abrasive conditions. Neither mucin alone nor the combinations with mucin showed any additional beneficial effect.

Protective effect of anti-erosive solutions enhanced by an aminomethacrylate copolymer

OBJECTIVE

To investigate if an aminomethacrylate copolymer (AMC) could potentiate the anti-erosive effect of solutions containing sodium fluoride -F (225 ppm F^-) and sodium fluoride associated to stannous chloride -FS (800 ppm Sn²⁺).

METHODS

The experimental solutions (F, FS, AMC, AMC + F, AMC + FS, and deionized water-DW as negative control) were tested in the presence of acquired pellicle. Polished bovine enamel specimens (n = 13/group) were submitted to an erosion-rehardening cycle (2 h immersion in human saliva, 5 min in 0.3 % citric acid, 1 h in human saliva, 4×/day, 5 days). Treatment with the solutions was performed for 2 min, 2×/day. The rehardening (%Re) and protective (%Prot) potential of the solutions were assessed in the beginning of the experiment, and the surface loss (SL) by contact profilometry after 5 days. Additional bovine specimens (n = 5/group) were prepared to evaluate the contact angle on the treated enamel surface. The zeta potential of the dispersed hydroxyapatite (HA) crystals after the treatment with the solutions was also measured (n = 3/group). Data were statistically analyzed (α = 0.05).

RESULTS

The association with AMC improved the %Re and the %Prot for W and F, but not for FS. The results of SL were: AMC + F = AMC + FS < AMC < FS < F < DW. The presence of AMC significantly reduced the contact angle on enamel surfaces. The HA presented a strong negative surface charge after the treatment with DW, F and FS, whereas after the treatment with the solutions containing AMC it became positive.

CONCLUSION

AMC has potential to enhance the anti-erosive effect of fluoride solutions.

CLINICAL SIGNIFICANCE

The aminomethacrylate copolymer (AMC) may be a promising agent to be added to oral care products for the prevention of erosive tooth wear.

Effect of chitosan solutions with or without fluoride on the protection against dentin erosion in vitro

The aim of this study was to assess the protective effect of experimental solutions containing chitosan at different viscosities with or without fluoride (TiF₄ /NaF) on dentin loss in vitro. Bovine dentin samples (n = 15) were prepared and allocated to one of the following treatments: (i) 0.5% chitosan (500 mPas); (ii) 0.5% chitosan (2,000 mPas); (iii) 0.042% NaF and 0.049% TiF₄ ; (iv) as (iii) with addition of 0.5% chitosan (500 mPas); (v) as (iii) with addition of 0.5% chitosan (2,000 mPas); (vi) commercial solution with SnCl₂ /AmF/NaF (positive control); or (vii) deionized water (negative control). The samples were submitted to pH cycling for 7 d (0.1% citric acid, 4 × 90 s d^-1 ). The treatment was applied once a day for 30 s. The dentin loss was quantified using a contact profilometer. Three samples per group were evaluated using scanning electron microscopy. The dentin loss (μm) was submitted to anova and Tukey's test for differences between treatments. Among the treatments tested, only chitosan 500 mPas was able to statistically significantly reduce the dentin loss compared to the negative control, being similar to the positive control. TiF₄ /NaF, whether with or without chitosan, had no protective effect. Chitosan 500 mPas and SnCl₂ /AmF/NaF solutions have comparable protective effect against dentin erosion in vitro.

Enhancing the Anti-Erosive Properties of Fluoride and Stannous with the Polymer Carbopol

This in vitro study investigated whether Carbopol 980 polymer could potentiate the anti-erosive effect of solutions containing sodium fluoride (F) and sodium fluoride associated with stannous chloride (FS). The dissolution of hydroxyapatite treated with the experimental solutions (F [500 ppm F-], F + Carbopol [0.1%], FS [500 ppm F- + 800 ppm Sn2+], FS + Carbopol) was evaluated. Deionized water was the negative control, and a commercial mouth rinse (AmF/NaF/SnCl2; 500 ppm F + 800 ppm Sn2+; Elmex® Erosion Protection) was the positive control. The solutions were also evaluated in an erosion-rehardening protocol, with two treatments per day, using bovine enamel specimens (n = 15) and human saliva. The acid challenge was performed using 0.3% citric acid (pH 2.6) for 2 min. Microhardness was measured at different times: baseline, after the first erosive challenge, after treatment, and after the second erosive challenge. Based on microhardness values, the demineralization, rehardening, and protective potentials were calculated. The alkali-soluble fluoride on enamel surfaces was also measured. Data were analyzed using ANOVA and Tukey tests (α = 0.05). Groups treated with FS + Carbopol showed the lowest hydroxyapatite dissolution and the highest rehardening and protective potentials. The measurement of alkali-soluble fluoride on enamel surfaces was also higher in the FS + Carbopol group. Carbopol was able to significantly increase the protective effect of the fluoridated solutions in addition to optimizing the adsorption of fluoride on the enamel surface.

In situ efficacy of an experimental toothpaste on enamel rehardening and prevention of demineralisation: a randomised, controlled trial

Background

A novel sodium fluoride toothpaste containing lactate ion and polyvinylmethylether-maleic anhydride has been developed to promote enamel remineralisation and resistance to demineralisation. In this in situ study, we compared this toothpaste (‘Test’) with a stannous fluoride-zinc citrate (SnF₂-Zn) toothpaste (‘Reference’) (both 1100–1150 ppm fluoride) and a fluoride-free toothpaste (‘Placebo’) using an enamel dental erosion-rehardening model.

Methods

In each phase of this randomised, investigator-blind, crossover study, participants wore palatal appliances holding bovine enamel specimens with erosive lesions. They brushed their natural teeth with either the Test, Reference or Placebo toothpastes, then swished the resultant slurry. Specimens were removed at 2 h and 4 h post-brushing and exposed to an in vitro acid challenge. Surface microhardness was measured at each stage; enamel fluoride uptake was measured after in situ rehardening. Surface microhardness recovery, relative erosion resistance, enamel fluoride uptake and acid resistance ratio were calculated at both timepoints.

Results

Sixty two randomised participants completed the study. Test toothpaste treatment yielded significantly greater surface microhardness recovery, relative erosion resistance and enamel fluoride uptake values than either Reference or Placebo toothpastes after 2 and 4 h. The acid resistance ratio value for Test toothpaste was significantly greater than either of the other treatments after 2 h; after 4 h, it was significantly greater versus Placebo only. No treatment-related adverse events were reported.

Conclusions

In this in situ model, the novel-formulation sodium fluoride toothpaste enhanced enamel rehardening and overall protection against demineralisation compared with a fluoride-free toothpaste and a marketed SnF₂-Zn toothpaste.

Trial registration

ClinicalTrials.gov; NCT03296072; registered September 28, 2017.

In Vitro Comparison of Fluoride, Magnesium, and Calcium Phosphate Materials on Prevention of White Spot Lesions around Orthodontic Brackets

One common negative side effect of orthodontic treatment with fixed appliances is the development of white spot lesions (WSLs) around brackets. This study is aimed at comparing the efficacy of various oral hygiene practices in preventing enamel demineralization around orthodontic brackets under similar in vitro conditions. The study included 90 extracted bovine incisors, which were randomized into six groups: fluoride toothpaste (FT), nonfluoride toothpaste (NFT), fluoride varnish plus fluoride toothpaste (FV+FT), CPP-ACP varnish plus fluoride toothpaste (CPP-ACP+FT), medical minerals gel plus nonfluoride toothpaste (MMG+NFT), and no intervention (control). All groups were subjected to demineralization and remineralization cycles. Visual appraisals were used to evaluate the changes in the enamel surface appearance at the beginning and end of the experiment. The changes in the demineralization degree were evaluated by measuring the Ca⁺² concentration in the demineralization solution at different time points. The majority of teeth in the CPP-ACP+FT group exhibited no shift in appearance, whereas in the other groups, a slight change in enamel translucency was observed. At all the time points, the Ca⁺² concentration in the demineralization solution in the CPP-ACP+FT group was the least among all other groups. At day 5, MMG+NFT's preventive efficacy was significantly higher than FV+FT's, but at days 10, 15, and 19, their efficacy was similar. However, at all the time points, MMG+NFT's efficacy was significantly higher than that of control, whereas FV+FT's efficacy was decreased at days 10, 15, and 19 and was close to the efficacy of control. To fight WSLs, early diagnosis was of great importance and examination of the tooth surface after air-drying for 5 s was recommended.

Using fluoride mouthrinses before or after toothbrushing: effect on erosive tooth wear

OBJECTIVES

1. To evaluate the use of fluoridated mouthrinses before or after toothbrushing on erosive tooth wear. 2. To compare the anti-erosive effect of the combination toothpaste and mouthrinse containing fluoride, with or without stannous chloride.

DESIGN

Enamel and dentin specimens were randomly distributed into groups (n = 10 of each substrate/group): B-brushing, B + R-brushing + rinsing, and R + B-rinsing + brushing. The treatments were performed using a fluoride toothpaste (B_F: 1400 ppm fluoride, as amino fluoride-AmF) combined or not with a fluoride mouthrinse (R_F: 250 ppm fluoride, as AmF and sodium fluoride-NaF) or fluoride and stannous toothpaste (B_F+Sn: 1400 ppm fluoride, as AmF and NaF, 3500 ppm stannous, as stannous chloride-SnCl₂ and 0.5% chitosan) combined or not with fluoride and stannous mouthrinse (R_F+Sn: 500 ppm fluoride, as AmF and NaF, 800 ppm stannous, as SnCl₂). As control, brushing was performed with artificial saliva (B_C). Specimens were submitted to a 5-day erosive-abrasive cycling model. Treatments were performed twice daily. Surface loss (SL) was determined by optical profilometry. Data were analyzed by ANOVA and Games-Howell tests (α = 0.05).

RESULTS

For enamel, R_F+B_F and R_F+Sn+B_F+Sn presented significantly lower SL than the control, with R_F+B_F being significantly lower than R_F+Sn+B_F+Sn. For dentin, B_C had the lowest SL, not differing from B_F+Sn+R_F+Sn, R_F+Sn+B_F+Sn and B_F. Groups R_F+B_F and B_F+R_F showed highest SL, not differing from B_F+Sn and B_F+Sn.

CONCLUSIONS

For enamel, the use of a mouthrinse before brushing was able to reduce erosive wear for both fluoride and stannous products. For dentin, the use of stannous-containing products, irrespective of the order of application, presented superior effects.

Effect of air-abrasion pre-treatment with bioactive glass 45S5 on enamel surface loss after erosion/abrasion challenge

OBJECTIVES

The aim of this in vitro study was to evaluate the effect of air-abrasion surface pre-treatment with bioactive glass (BAG) 45S5 on enamel surface loss after erosion/abrasion challenge.

METHODS

Twenty-four sound bovine incisors were used for this study. Four experimental groups (n=12) were assigned as follows: Group 1 was the negative control group, Group 2 specimens were treated with a SnF₂ gel (positive control group), Group 3 specimens were air-abraded with BAG 45S5 (ProSylc) and Group 4 received both treatments. The specimens were submitted to erosion/abrasion challenge using a common soft drink. Enamel surface loss was evaluated using an optical profilometer. Additionally, surface roughness (VSI method) and surface microhardness (Vickers method) changes were evaluated, as well as SEM and EDS analyses were performed on enamel surface. The data were statistically analyzed using one-way ANOVA and Tukey's post-hoc test at a level of significance a=0.05.

RESULTS

Surface pre-treatment with BAG 45S5 reduced surface loss in comparison with negative control group (p<0.001), which exhibited the highest surface loss of the experimental groups (p<0.05). The positive control group (SnF₂ treatment) and Group 4 specimens, which received both air-abrasion pre-treatment and SnF₂ treatment, presented the lowest surface loss (p<0.05), but did not show significant differences to each other (p=0.65).

SIGNIFICANCE

Air-abrasion pre-treatment with BAG 45S5 may be beneficial as an in-office preventive method for the limitation of enamel erosive wear induced by excessive consumption of soft drinks. The clinical significance of the results regarding this preventive method should be confirmed by clinical studies.

Clinical effect of stannous fluoride and amine fluoride containing oral hygiene products: A 4-year randomized controlled pilot study

This 4-year randomized controlled trial (RCT) aimed at investigating whether routine home use of both a SnCl₂/AmF/NaF-containing mouth rinse and toothpaste has a preventive effect on oral health. Fifty-four test subjects were examined in biannual intervals. The primary endpoint “dental erosion” was determined by the Basic Erosive Wear Examination (BEWE). The secondary endpoints were “saliva pH”, “dentin hypersensitivity” generated by Visual Analogue Scale (VAS), and “discoloration” measured by the Lobene Stain Index (LSI). A mixed model for repeated measures (MMRM) was used to analyze the primary endpoint “dental erosion”. Primary analysis showed a significant intervention effect of the SnCl₂/AmF/NaF-containing test product (p₁ = 0.0242). This result was confirmed by two additional MMRM-based sensitivity analyses. Comparison of all models showed “dental erosion” values of the intervention group  below values of the control group. Discoloration of the teeth was significantly higher in the intervention than in the control group at all time points. Saliva pH and dentin hypersensitivity were not significantly different between groups over four years. In summary, this RCT is the first to indicate a possible preventive effect of SnCl₂/AmF/NaF-containing oral hygiene products on dental erosion over a follow-up period of four years.

Is the dentifrice containing calcium silicate, sodium phosphate, and fluoride able to protect enamel against chemical mechanical wear? An in situ/ex vivo study

OBJECTIVES

The aim of this study was to investigate the effect of a dentifrice that contains calcium silicate, sodium phosphate, and fluoride on erosive-abrasive enamel wear.

MATERIAL AND METHODS

This randomized, single-blind in situ/ex vivo study was conducted with four crossover phases of 5 days (one group tested per phase). Bovine enamel blocks (n = 256) were allocated to 16 volunteers and 8 groups. The groups under study were test dentifrice, with calcium silicate, sodium phosphate, and 1450 ppm sodium monofluorophosphate; tin dentifrice, with 3500 ppm stannous chloride, 700 ppm amine fluoride, and 700 ppm sodium fluoride; conventional dentifrice, with 1450 ppm sodium monofluorophosphate; and control (deionized water). Half of the enamel blocks were subjected to erosion and the other half to erosion plus abrasion. The daily extraoral protocol consisted in four citric acid exposures (2 min) and two applications of dentifrice slurry on all blocks for 30 s; after, half of the blocks were brushed for 15 s. The response variable was enamel loss. Data were analyzed by two-way ANOVA and Fisher's test (p < 0.05).

RESULTS

For erosion, the test dentifrice promoted less enamel loss than water (4.7 ± 3.1 and 5.8 ± 2.5 μm, respectively, p < 0.05), and did not differ from tin (4.8 ± 2.5 μm) and conventional (4.8 ± 1.4 μm) dentifrices (p > 0.05). However, the test dentifrice (7.7 ± 3.8 μm) promoted higher wear after erosive plus abrasive procedures than tin (5.4 ± 1.5 μm) and conventional (6.2 ± 1.7 μm, p < 0.05) dentifrices, and did not differ from water (6.9 ± 2.0 μm).

CONCLUSIONS

The investigated dentifrice reduced enamel loss against acid challenge but had no effect against acid and brushing challenge.

CLINICAL RELEVANCE

Little is known regarding the preventive effect of dentifrices indicated for dental erosion. The tested anti-erosive dentifrice was unable to protect enamel when erosion was associated to toothbrushing abrasion.

Clinical management and prevention of dental caries in athletes: A four-year randomized controlled clinical trial

The aims of this four-year randomized controlled clinical trial were to gain insights into management and prevention of dental caries and the effect of stannous fluoride products in athletes. Fifty-four participants were randomized into test and control groups. The test group used special stannous fluoride products. The primary endpoint dental caries was assessed by the ICDAS-II-System and analyzed both by a linear mixed model for repeated measures and a generalized linear mixed model. During the observation period an increase in caries-free surfaces from 64.91 ± 6.42 at baseline to 73.22 ± 4.43 was observed. In surfaces with caries superficialis and caries media, a decrease from 13.94 ± 5.70 and 2.96 ± 2.55 surfaces at baseline to 7.89 ± 3.18 and 0.46 ± 0.78 after 2.5 years was noted, respectively. The analysis showed no effect of stannous fluoride products, but a significant difference for the time of examination (p < 0.0001). In addition, it could be shown that at any time of examination, the odds of developing caries media on a new surface was significantly lower than at baseline (up to 25-times). Due to biannual dental examinations, professional tooth cleaning and restorative treatment the number of caries-free surfaces increased and the odds of a new surface to be afflicted with caries media decreased 25-fold.

Do fluoride toothpastes have similar preventive effect in permanent and primary teeth against erosive tooth wear?

BACKGROUND

Little is known about fluoride toothpastes effect on primary teeth submitted to erosive tooth wear.

OBJECTIVES

To evaluate the preventive effect of different toothpastes on surface loss (SL) after severe erosion/abrasion model and to compare this effect between permanent (PT) and primary teeth (pt).

DESIGN

Enamel samples were randomly divided according toothpastes groups (n = 17). G1: placebo; G2: NaF; G3: AmF-NaF-SnCl2 anti-erosion; G4: SnF2 ; and G5: NaF anti-erosion for children. Samples were incubated in artificial saliva (1 hour), submitted to erosive challenge (3 minutes; 1% citric acid; pH3.6; at 25°C) and to toothbrush abrasion (2 minutes slurry immersion; 50 strokes; 200 g) during 30 cycles. Surface loss (μm; mean ± SD) was quantified by contactless profilometry. The effects of the two covariables "tooth" and "toothpaste" were analysed by non-parametric ANOVA, variables with significant effects were tested by Wilcoxon tests.

RESULTS

pt showed significantly higher surface loss than PT in all groups (P < 0.001). The mean values of SL of each group were: G1 PT 18.18(±3.98), pt 25.65(±9.21); G2 PT 14.76(±2.82), pt 18.11(±3.92); G3 PT 12.62(±5.29), pt 15.61(±6.70); G4 PT 17.12(±2.24), pt 23.41(±7.9); G5 PT 13.24(±1.29), pt 18.28(±8.96).

CONCLUSIONS

In permanent teeth, G3 showed the best preventive effect. In primary teeth, G1, G3, and G5 showed similar effect.

Evaluation of a clinical preventive treatment using Er,Cr:YSGG (2780 nm) laser on the susceptibility of enamel to erosive challenge

The purpose of this in vitro study was to evaluate the effect of a clinical preventive treatment using Er,Cr:YSGG laser irradiation on bovine enamel susceptibility after erosive challenge. Twelve sound bovine incisors were used and twenty-four enamel specimens were prepared in total. Two experimental groups (n = 12) were assigned as follows: Group 1 was the control group and in Group 2, the enamel specimens were irradiated with an Er,Cr:YSGG (2780 nm) laser system for 20 s, with average output power of 0.25 W, pulse repetition rate at 20 Hz without water or air flow and the pulse duration was fixed at 140 μsec. The tip diameter was 600 μm, the tip to tissue distance was 1 mm, the speed of handpiece movement was 2 mm/s, the power density was 88.34 W/cm², and the fluence was 31.25 J/cm². The specimens were submitted to erosive challenge using a common soft drink. Surface microhardness changes, surface roughness changes, and surface loss were evaluated after erosive challenge. The data were statistically analyzed using one-way ANOVA and Tukey's post-hoc test at a level of significance a = 0.05. Er,Cr:YSGG laser-treated enamel exhibited significantly less decrease in surface microhardness and significant less surface loss compared to control enamel after the erosive challenge (p < 0.05). The experimental groups did not show significant differences in surface roughness increase after the erosive challenge (p > 0.05). Er,Cr:YSGG laser treatment may be promising for the limitation of enamel erosive tooth wear induced by excessive consumption of soft drinks. Clinical studies are needed to clarify whether this protective effect is clinically significant.

Anti-Erosive Effect of Solutions Containing Sodium Fluoride, Stannous Chloride, and Selected Film-Forming Polymers

The aim of this study was to evaluate the anti-erosive effect of solutions containing sodium fluoride (F: 225 ppm F–), stannous chloride (Sn: 800 ppm Sn2+), and some film-forming polymers (Gantrez: Poly [methylvinylether-alt-maleic anhydride]; PGA: propylene glycol alginate; Plasdone: poly[vinylpyrrolidone]; and CMC: carboxymethylcellulose). Solutions were tested in an erosion-remineralization cycling model, using enamel and dentin specimens (n = 10, for each substrate). Distilled water was the negative control. Cycling consisted of 120 min immersion in human saliva, 5 min in 0.3% citric acid solution, and 120 min of exposure to human saliva, 4×/day, for 5 days. Treatment with solutions (pH = 4.5) was carried out 2×/day, for 2 min. Surface loss (SL) was evaluated with optical profilometry. Zeta potential of hydroxyapatite crystals was determined after treatment with the solutions. Data were statistically analyzed (α = 0.05). For enamel, all polymers showed significantly lower SL (in µm) than the control (11.09 ± 0.94), except PGA (10.15 ± 1.25). PGA significantly improved the protective effect of F (4.24 ± 0.97 vs. 5.64 ± 1.60, respectively). None of the polymers increased the protection of F+Sn (5.13 ± 0.78). For dentin, only Gantrez (11.40 ± 0.97) significantly reduced SL when compared with the negative control (12.76 ± 0.75). No polymer was able to enhance the effect of F (6.28 ± 1.90) or F+Sn (7.21 ± 1.13). All fluoridated solutions demonstrated significantly lower SL values than the control for both substrates. Treatment of hydroxyapatite nanoparticles with all solutions resulted in more negative zeta potentials than those of the control, except Plasdone, PGA, and F+Sn+PGA, the latter two presenting the opposite effect. In conclusion, Gantrez, Plasdone, and CMC exhibited an anti-erosive effect on enamel. PGA increased the protection of F. For dentin, only Gantrez reduced erosion.

Effect of Phosphorylated Chitosan on Dentin Erosion: An in vitro Study

The aim of this study was to evaluate the antierosive effect of phosphorylated chitosan in dentin. Bovine dentin specimens were randomly distributed into the following groups: (1) no treatment (NoTx/negative control), (2) phosphate-buffered saline solution (PBS), (3) AmF/NaF/SnCl2 (positive control), (4) 0.5% chitosan solution (Chi), (5) 0.5% neutral phosphorylated (NP)-Chi, and (6) 0.5% alkaline phosphorylated (AP)-Chi. The specimens were submitted to de-remineralization treatment cycles for 5 days: 0.5% citric acid (2 min), remineralizing solution (30 min), and surface treatment according to assigned groups (2 min, 6×/day). The loss of dentin surface was measured by profilometry. Hardness and modulus of elasticity were measured using a nanoindenter equipped with a Berkovich diamond tip. The dentin surface was analyzed by scanning electron microscopy (SEM). The largest loss of dentin was observed in the No Tx and PBS groups (approx. 25 µm). The group treated with AmF/NaF/SnCl2 showed less loss of dentin (67% reduction vs. NoTx and PBS), followed by the groups treated with NP-Chi and AP-Chi (33% reduction), and Chi (18% reduction). Nanohardness and modulus of elasticity were similar in the NoTx and PBS groups, with a small increase in stiffness in all other groups. SEM revealed that the experimental solution of AP-Chi had a favorable effect on maintaining the integrity of collagen fibrils. AmF/NaF/SnCl2 showed a preserved mineralized collagen surface. Further studies are warranted to explore this nontoxic phosphorylated chitosan polymer as an effective agent in the prevention and treatment of dental erosion.

A novel turn-on fluorescent probe for the multi-channel detection of Zn2+ and Bi3+ with different action mechanisms

A novel multifunctional sensor, RSPT, was identified and developed for multichannel turn-on fluorescent responses to Zn²⁺ and Bi³⁺ in practice.

Susceptibility of bovine dental enamel with initial erosion lesion to new erosive challenges

This in vitro study evaluated the impact of initial erosion on the susceptibility of enamel to further erosive challenge. Thirty bovine enamel blocks were selected by surface hardness and randomized into two groups (n = 15): GC- group composed by enamel blocks without erosion lesion and GT- group composed by enamel blocks with initial erosion lesion. The baseline profile of each block was determined using the profilometer. The initial erosion was produced by immersing the blocks into HCl 0.01 M, pH 2.3 for 30 seconds, under stirring. The erosive cycling consisted of blocks immersion in hydrochloric acid (0.01 M, pH 2.3) for 2 minutes, followed by immersion in artificial saliva for 120 minutes. This procedure was repeated 4 times a day for 5 days, and the blocks were kept in artificial saliva overnight. After erosive cycling, final profile measurement was performed. Profilometry measured the enamel loss by the superposition of initial and final profiles. Data were analyzed by t-test (p<0.05). The result showed no statistically significant difference between groups (GS = 14.60±2.86 and GE = .14.69±2.21 μm). The presence of initial erosion on bovine dental enamel does not enhance its susceptibility to new erosive challenges.

A New Laser-Processing Strategy for Improving Enamel Erosion Resistance

In the present study, a new automatic laser-processing strategy allowing standardized irradiation of natural tooth areas was investigated. The objective was to find a combination of laser parameters that could cause over a 600°C temperature increase at the enamel surface while not damaging enamel, avoiding temperature change above 5.5°C in the pulp and increasing enamel erosion resistance. Seventy-seven bovine enamel samples were randomly divided into 6 laser groups and 1 negative control (C/no treatment/ n = 11). A scanning strategy (7 × 3 mm) was used for the CO₂ laser treatment (λ = 10.6 µm, 0.1-18 J/cm²) with different pulse durations-namely, 20 µs (G20), 30 µs (G30), 55 µs (G55), and 490 µs (G490), as well as 2 modified pulse distances (G33d, G40d). Measurements of temperature change were performed at the surface (thermal camera/50 Hz), at the underside (thermocouples), and at the pulp chamber using a thermobath and human molars ( n = 10). In addition, histology and X-ray diffraction (XRD/ n = 10) were performed. Erosion was tested using an erosive cycling over 6 d, including immersion in citric acid (2 min/0.05 M/pH = 2.3) 6 times daily. Surface loss was measured using a profilometer and statistical analysis with a 2-way repeated-measures analysis of variance (α = 0.05). Only G20 fulfilled the temperature requirements at the surface (619 ± 21.8°C), at the underside (5.3 ± 1.4°C), and at the pulp (2.0 ± 1.0°C), and it caused no mineral phase change and significant reduction of enamel surface loss (-13.2 ± 4.0 µm) compared to C (-37.0 ± 10.1 µm, P < 0.05). A laser-scanning strategy (20 µs/2 kHz/1.25 J/cm², 3.4 mm/s) has been established that fulfilled the criteria for biological safety and significantly increased enamel erosion resistance (64%) in vitro.

Chitosan Biomaterials for Current and Potential Dental Applications

Chitosan (CHS) is a very versatile natural biomaterial that has been explored for a range of bio-dental applications. CHS has numerous favourable properties such as biocompatibility, hydrophilicity, biodegradability, and a broad antibacterial spectrum (covering gram-negative and gram-positive bacteria as well as fungi). In addition, the molecular structure boasts reactive functional groups that provide numerous reaction sites and opportunities for forging electrochemical relationships at the cellular and molecular levels. The unique properties of CHS have attracted materials scientists around the globe to explore it for bio-dental applications. This review aims to highlight and discuss the hype around the development of novel chitosan biomaterials. Utilizing chitosan as a critical additive for the modification and improvement of existing dental materials has also been discussed.

In situ evaluation of fluoride-, stannous- and polyphosphate-containing solutions against enamel erosion

OBJECTIVE

To evaluate the anti-erosive effect of solutions containing sodium fluoride (F: 225ppm of fluoride), sodium fluoride+stannous chloride (F+Sn: 225ppm of fluoride+800ppm of stannous), sodium fluoride+stannous chloride+sodium linear polyphosphate (F+Sn+LPP: 225ppm of fluoride+800ppm of stannous+2% of sodium linear polyphosphate), and deionized water (C: control), using a four-phase, single-blind, crossover in situ clinical trial.

METHODS

In each phase, 12 volunteers wore appliances containing 4 enamel specimens, which were submitted to a 5-day erosion-remineralization phase that consisted of 2h of salivary pellicle formation with the appliance in situ, followed by 2min extra-oral immersion in 1% citric acid (pH 2.4), 6x/day, with 90min of exposure to saliva in situ between the challenges. Treatment with the test solutions was performed extra-orally for 2 min, 2x/day. At the end of the experiment, surface loss (SL, in μm) was evaluated by optical profilometry. Data were analyzed using ANOVA and Tukey tests (α=0.05). The surface of additional specimens was evaluated by x-ray diffraction after treatments (n=3).

RESULTS

C (mean SL±standard-deviation: 5.97±1.70) and F (5.36±1.59) showed the highest SL, with no significant difference between them (p>0.05). F+Sn (2.68±1.62) and F+Sn+LPP (2.10±0.95) did not differ from each other (p>0.05), but presented lower SL than the other groups (P<0.05). Apatite and stannous deposits on specimen surfaces were identified in the x-ray analysis for F+Sn and F+Sn+LPP.

CONCLUSIONS

Sodium fluoride solution exhibited no significant anti-erosive effect. The combination between sodium fluoride and stannous chloride reduced enamel erosion, irrespective of the presence of linear sodium polyphosphate.

CLINICAL SIGNIFICANCE

Under highly erosive conditions, sodium fluoride rinse may not be a suitable alternative to prevent enamel erosion. A rinse containing sodium fluoride and stannous chloride was shown to be a better treatment option, which was not further improved by addition of the sodium linear polyphosphate.