Enamel Softening Can Be Reduced by Rinsing with a Fluoride Mouthwash Before Dental Erosion but Not with a Calcium Solution

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.

Morphological and Elemental Evaluation of Investigative Mouthwashes to Repair Acid-Eroded Tooth Surface

Purpose

Erosive tooth wear (ETW) is characterized by subsurface demineralization and tooth substance loss with crater formation. Remineralization of subsurface demineralization has previously been demonstrated; however, repair of the eroded surface is still under investigation. This study investigated the effectiveness of mouthwashes containing hydrolyzed wheat protein (HWP) in repairing ETW through promotion of organized crystal growth.

Methods

Enamel Erosion was created on 210 enamel blocks by 10-minute demineralization in 1% Citric Acid (pH 3.5). Then, blocks were randomly assigned to seven groups (30/group); (A) 0.2% HWP, B) 1% HWP, (C) 2% HWP, (D) 1% HWP + 0.05% NaF, (E) Listerine™ mouthwash, (F) 0.02% NaF Crest™ Pro-health mouthwash and (G) artificial saliva (AS) only. Groups were subjected to daily pH-cycling consisting of one 5-minute erosive challenge with citric acid, three 1-minute mouthwash treatment periods, and then storage in AS for the rest of the time for 28 days. Treatment effects were assessed using SEM-EDX. Statistical analysis was by ANOVA and Tukey's multiple comparison.

Results

In groups exposed to HWP-containing mouthwashes, there was growth of fiber-like crystals that increased in packing density in a dose-dependent manner (0.2%, 1%, 2%) on the eroded enamel surfaces, with increased calcium and phosphate contents on the treated surfaces. The non-HWP-containing groups had the eroded surfaces covered by structureless deposit layer firmly attached to the surface.

Conclusion

Treating eroded enamel surface with HWP-containing mouthwash resulted in repair of the damaged tissue by formation of a protective layer of crystal deposits within and on the eroded enamel tissue.

Improved Enamel Acid Resistance by Highly Concentrated Acidulated Phosphate Sodium Monofluorophosphate Solution

Sodium monofluorophosphate (MFP) is a component of fluoride-containing dentifrices and is more biosafe than the conventional sodium fluoride (NaF). MFP can respond not only on the tooth surface layer but also deep into the enamel. We aim to confirm that high concentrations of acid phosphate MFP (AP-MFP, 9000 ppmF), used in professional care, could lead to a highly biosafe fluoride application method that acts through the deep enamel layers. Sample groups were respectively treated in vitro with NaF, acidulated phosphate fluoride (APF), MFP, and AP-MFP, and the samples were compared against an untreated group. Characterizations after fluoride application confirmed that MFP and AP-MFP treatments improved the acid resistance of enamel compared to that of conventional methods. Furthermore, the acid resistance of highly concentrated MFPs improved by using phosphoric acid. Although the acid resistance from the AP-MFP method is not as good as that using APF, AP-MFP can act both on the surface layer and deep into the enamel. Moreover, AP-MFP retains fluoride ions as much as APF does on the tooth surface. The proposed fluoride application method using AP-MFP introduces a dental treatment for acid resistance that is highly biosafe and penetrates deep layers of the enamel.