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Anti-Erosion

Dental erosion is prevalent in children and adults globally, with some researchers finding it present in approximately half of adolescents (Al-Dlaigan et al. 2001; McGuire et al. 2009). Estimated prevalence in some locations can be found in Figure 6.

Estimated prevalence of dental erosion among youth

Figure 6. Estimated prevalence of dental erosion among youth

(Nayak et al. 2010; Hou et al. 2009; Wiegand et al. 2006; Deery et al. 2000; Kazoullis et al. 2007; Wang et al. 2010; Manaf et al. 2012; Mantonanaki et al. 2013; Nahás et al. 2011)

Dental erosion occurs primarily due to the excessive presence of non-bacterial extrinsic acids (especially dietary acids such as acidic drinks), as well as intrinsic gastric acid associated with gastroesophageal reflux disease (GERD) and bulimia (Moazzez et al. 2004; Bouqot & Seime 1997). Dental erosion involves the demineralization and softening of the tooth surface, which once softened, is highly susceptible to abrasion and attrition (Figure 7). A diagnosis of erosion can be made based on the pattern of surface loss of enamel and/or dentin (Figures 8a,b)

Figure 7. Demineralization associated with dental erosion

Demineralization associated with dental erosion
Generalized erosion
Severe palatal erosion and loss of Courtesy of Prof. Ian Meyers tooth structure

Figure 8a. Generalized erosion
Courtesy of Prof. Ian Meyers

Figure 8b. Severe palatal erosion and loss of tooth structure.
Courtesy of Prof. Ian Meyers

Unlike dental caries where demineralization is initially mainly subsurface and is also reversible in its early stages, dental erosion involves repeated demineralization of the surface with subsequent surface loss and this process is irreversible (Figures 9a, b).

Dental caries process

Figure 9a. Dental caries process

Reversible
Enamel crystals are weakened, but remain structurally intact. The early caries process is reversible

Dental erosion process

Figure 9b. Dental erosion process

Irreversible
Enamel crystals are damaged structurally from the surface down into the tooth. The erosive process is irreversible

Mechanism of action for anti-erosion effect of stabilized stannous fluoride

The deposition of stannous ions at the tooth surface helps protect it against dental erosion (Faller & Eversole 2014):

  • Deposition of stannous fluorophosphate or stannous oxide layers onto enamel surfaces has been reported after stannous fluoride treatment
  • Deposition occurs primarily as a result of the attachment of the stannous ion to free phosphate sites on the surface of enamel
  • Stannous forms a protective layer on the surface that is highly resistant to acids

A recent in vitro study compared the ability of various fluoride toothpastes to form a protective barrier layer (Faller & Eversole 2014). The toothpastes evaluated included 1,100 ppm stannous fluoride, 1,100 ppm sodium fluoride, 1,000 ppm sodium monofluorophosphate and 1,400 ppm amine fluoride. The study involved exposing etched samples to toothpaste-saliva slurries, rinsing them, and then exposing them to 2% alizarin Red-S. Dye deposition was assessed using a 5-point scale, with 0 being no dye deposition and 4 being complete dye coverage. A low score indicates a barrier layer is present, preventing the deposition of dye. The stannous fluoride toothpaste had the lowest score, 0.25. At the other extreme, amine fluoride resulted in a score of 3.7 (Figure 10). This in vitro test confirmed the ability of stannous to form a protective barrier layer, and demonstrated that stannous fluoride is a preferred fluoride for delivering an enamel protection benefit via a barrier mechanism to erosive acids.

Figure 10. Degree of dye deposition on enamel samples following exposure to toothpaste slurry followed by dye

* Average deposition of stain (based on the 5-point scale)

Degree of dye deposition on enamel samples following exposure to toothpaste slurry followed by dye

Other in vitro tests have also demonstrated the superior protective effect of stannous fluoride-treated enamel slabs in comparison to sodium fluoride-treated enamel slabs during an erosive challenge (Figure 11; Faller 2012). Exposure to dietary acid in an erosion cycling model resulted in surface demineralization and surface loss for the slabs treated with sodium fluoride toothpaste slurry while minimal demineralization or surface loss occurred with the slabs treated with stannous fluoride toothpaste slurry.

Stannous fluoride vs. sodium fluoride in in vitro treated enamel slabs

Figure 11. Stannous fluoride vs. sodium fluoride in in vitro treated enamel slabs

Stannous fluoride protects against erosion

Erosion Research Summaries

The following study summaries represent a sample of research demonstrating the benefits of stabilized stannous fluoride dentifrice for protection against acid erosion.

In addition, an independent consensus statement by the European Federation of Conservative Dentistry found “oral hygiene products, such as toothpastes or mouth rinses, containing stannous fluoride or stannous chloride have the potential to slow the progression of erosive tooth wear.” The authors found data are limited for other products. (Carvalho et al. 2015)

The Protective Effects of Toothpaste Against Erosion By Orange Juice: Studies in Situ and in Vitro

Reference: Hooper SM, Newcombe RG, Faller R, Eversole S, Addy M, West NX. J Dent. 2007 Jun;35(6):476-81. Epub 2007 Feb 27

CONCLUSION

The results of this study provide further support for tooth brushing before meals. Results further suggest the stannous fluoride dentifrice could be used to provide significant erosion protection in susceptible patients versus that provided by conventional fluoride products.

OBJECTIVE

Consumption of soft drinks, fruit juices and sport drinks has increased dramatically in the UK, the US, and elsewhere. Previous studies have demonstrated the erosive nature of these acidic soft drinks. The objective of this study was to determine the protective effects of experimental stannous fluoride-based toothpaste, containing sodium hexametaphosphate, against an erosive challenge (orange juice) on tooth enamel.

MATERIALS AND METHODS

  • This research included a 15-day challenge in vitro study and a 15-day in situ single blind, 3-way, crossover clinical trial.
  • The following formulations were tested:
    1. experimental stannous fluoride dentifrice with sodium hexametaphosphate for cosmetic benefits (P&G);
    2. a benchmark sodium fluoride dentifrice (Crest® Cavity Protection, P&G);
      and
    3. negative control, water.

  • Flat, polished human enamel samples with a surface profile of +/-0.1μm, were exposed to the three regimens.
  • The orange juice used as erosion challenge had a pH 3.8.
  • 15 volunteers wore an intra-oral appliance with 2 specimens of enamel embedded in the mid-palatal region from 9:00 to 17:00 (removed for 1 hour at lunchtime). Whilst appliances were in place, no food or drink other than water and the designated orange juice were consumed. Volunteers were asked to rinse with a toothpaste slurry or water at 9:00 and 13:00 followed by consumption of 250 ml orange juice 1 and 3 h later.
  • Subjects were treated with one study formulation for 5 days followed by two nontreatment days.
  • A profilometer was used to measure depths of the resulting eroded areas at days 5, 10 and 15.

RESULTS

There was significantly more erosive damage on the specimens exposed to the benchmark toothpaste (NaF) and negative control (water) compared to the test stannous fluoride toothpaste in both the in situ (Figure 1) and in vitro (Figure 2) studies.

Figure 1. In Situ Loss of Material*

In Situ Loss of Material

Figure 2. In Vitro Loss of Material*

In Vitro Loss of Material

* mean value based on duplicate determinations of two enamel specimens

Enamel Protection vs. Abrasivity - A Study of Relevance

Reference: Faller RV, Eversole SL, Tzeghai G. J Dent Res. 2009;88 (Spec Iss A): Abstract 3368.

CONCLUSION

  • These results indicate
    1. the primary driver for enamel protection benefits is more likely the particular F salt, rather than RDA of the formulation. and
    2. this model is reproducible.
  • Under the conditions of these studies, SnF2 provided superior protection against acid mediated enamel tooth surface loss.

OBJECTIVE

Dentifrices with RDA< 250 are considered safe for daily use. Some researchers believe products with low RDA may be less aggressive on erosively softened enamel. Others believe that once softened, erosively challenged enamel will be removed by any friction, even by the tongue. This research was conducted to determine the primary driver of enamel protection benefits: is abrasivity or fluoride (F) salt the more important factor?

MATERIALS AND METHODS

  • Cores of extracted, human enamel were cleaned, ground and polished to provide a virgin enamel surface, soaked in human saliva (pellicle formation), and treated in a 1:3 (product:saliva) slurry of toothpaste representing a range of actives/RDA values [SnF2(RDA~150), NaF#1(RDA~100), NaF#2(RDA~50)].
  • Specimens were subjected to dynamic pH cycling conditions including exposure to multiple 1% citric acid challenges over a 5-day period.
  • Treatment slurries and saliva baths were constantly stirred to ensure a steady flow,representing repetitive challenges to the enamel by a combination of common dietary acid and abrasive elements.
  • The study was run in duplicate to test model reproducibility. Results were averaged.

RESULTS

  • The product with RDA~150 provided significant (P=0.05, ANOVA) protection against damage (8.0μm of surface loss), with lower RDA products (RDA~50 or 100) showing no significant differences between them in their ability to protect enamel against damage (27.3 and 25.4μm of surface loss, respectively). See Table and Figure.
  • It is important to note the active F species in the RDA~150 formulation was SnF2. SnF2 provides significant protection against erosive acid damage by forming a protective barrier layer on the enamel surface, protecting against external challenges.
  • The model is reproducible.

Table. Results

RDA Results

Figure Average % Reduction in Total Mineral Loss*

Average Percentage Reduction in Total Mineral Loss

* (vs. NaF product)

A Randomized Clinical Trial to Measure the Erosion Protection Benefits of a Stannous Fluoride Dentifrice versus a Triclosan/Copolymer Dentifrice

Reference: N. West, T. He, Hellin N, et al. J Dent Res 2017;96 (Spec Iss A): Abstract 0610

KEY CLINICAL FINDINGS

Crest® PRO-HEALTH™ Advanced dentifrice (SnF2) demonstrated significantly greater protection against dental erosion relative to the Colgate Total (triclosan/copolymer) dentifrice in a 10-day in situ clinical study. At Day 10, the SnF2 dentifrice demonstrated 93.5% lower enamel loss than the triclosan/copolymer dentifrice with median loss of 0.097 μm and 1.495 μm, respectively, which wasstatistically significant (P<0.0001). See Figure. Both products were well tolerated.

Figure. Treatment comparison at Day 10: Median Change in Enamel (μm)

Treatment comparison at Day 10: Median Change in Enamel (μm)

* Treatment difference at Day 10 was statistically significant. P<0.0001 N=34.

OBJECTIVE

To compare the enamel protection efficacy (loss of tooth enamel due to erosion as measured by surfometry) of a marketed stannous fluoride dentifrice and a marketed triclosan/copolymer sodium fluoride dentifrice in a 10-day in situ erosion model.

STUDY DESIGN

  • A single center, double-blind, randomized, 2-treatment, and 4-period crossover clinical study was conducted involving healthy adults.
  • Subjects presented for 4 study periods and were randomized to treatment sequences, receiving one of the two marketed dentifrice products each period:
  1. Crest® PRO-HEALTH Advanced — 0.454% Stannous fluoride (1100 ppm fluoride), The Procter & Gamble Company, Cincinnati, OH.
  2. Colgate® Total® Clean Mint — 0.24% Sodium fluoride with 0.3% Triclosan/ copolymer, Colgate-Palmolive Co., New York, NY.
  • Each study period was comprised of 10 treatment days. On each treatment day, subjects brushed their teeth at home in their usual manner, using a non-treatment toothpaste (Crest® Decay Protection, 1450 ppm F as sodium fluoride, Procter & Gamble) and a manual toothbrush (Oral-B® 35, Procter & Gamble) supplied at the screening visit.
  • Subjects then attended the clinical trials unit where they collected their upper palatal intra-oral appliance fitted with two enamel samples and placed it in their mouth. Subjects wore the appliance for approximately 6 hours total over the course of each study day. While wearing the appliance, subjects swished twice a day with their assigned treatment toothpaste slurry at the clinical site for 60 seconds.
  • The erosive challenge occurred with the appliance in the mouth. The subjects were required to sip 25mL of orange juice over a timed minute, swishing it around their mouth, then spitting out. This was repeated 10 times so that a total of 250mL of orange juice was exposed to the enamel samples over a 10 minute period. The erosive challenge occurred a total of four times on each treatment day.
  • On Day 10, the enamel samples were measured for tissue loss using a calibrated contact surface profilometer. Measurements were taken at baseline, prior to the start of the study, and at the end of treatment Day 10. Fresh enamel samples were placed in the intra-oral appliance at the beginning of each study period.

A Randomized Clinical Trial to Measure the Erosion Protection Benefits of a Stabilized Stannous Fluoride Dentifrice versus a Control Dentifrice

Reference: XY Zhao1, T He2, Y He2, C Cheng2, HJ Chen2.

1Fourth Military Medical University, Xi’an, PR China; 2Procter & Gamble.

KEY CLINICAL RESULTS

The experimental stabilized stannous fluoride (SnF2) dentifrice provided 26.9% greater erosion protection relative to the control dentifrice at Day 10 (P<0.03).

Figure 1. Enamel loss at Day 10

Enamel loss at Day 10

*Lussi A. Int Dent J 2014; 64 (Suppl 1): 2-3.

OBJECTIVE

To compare the enamel protection efficacy of a stabilized stannous fluoride dentifrice and a marketed control dentifrice in a 10-day in situ erosion model.

STUDY DESIGN

  • A single center, double-blind, randomized, 2-treatment, and 3-period crossover clinical study was conducted involving healthy adults.
  • Subjects presented for 3 study periods and were randomized to treatment sequences, receiving one of the two marketed dentifrice products each period:
  1. Experimental 0.454% stabilized SnF2 dentifrice (Crest® PRO-HEALTH Clean Mint [Smooth Formula], Procter & Gamble)
  2. Sodium fluoride dentifrice with potassium nitrate marketed for protection from the effects of acid erosion (Sensodyne® Pronamel®, GlaxoSmithKline)
  • Each study period was comprised of 10 treatment days. On each treatment day, subjects brushed their teeth at home in their usual manner, using a non-treatment toothpaste and a regular, soft manual toothbrush supplied at the screening visit.
  • Subjects then attended the clinical trials unit where they collected their lower palatal intraoral appliance fitted with 8 enamel samples and placed it in their mouth. Subjects wore the appliance for approximately 6 hours total over the course of each study day. While wearing the appliance, subjects brushed their lingual teeth for 30 seconds, and swished with their assigned treatment toothpaste slurry for 90 seconds twice a day under the supervision of clinic staff.
  • The erosive challenge occurred with the appliance in the mouth. The subjects were required to sip 25mL of orange juice over a timed minute, swishing it around their mouth, then spitting out. This was repeated 10 times so that a total of 250mL of orange juice was exposed to the enamel samples over a 10 minute period. The erosive challenge occurred a total of four times on each treatment day.
  • On Day 10, the enamel samples were measured for tissue loss using a calibrated contact surface profilometer. Measurements were taken at baseline, prior to the start of the study, and at the end of treatment Day 10. Fresh enamel samples were placed in the intra-oral appliance at the beginning of each treatment period.
  • Statistical analyses utilized a general linear mixed model with period and treatment as fixed effects and subject as a random effect.

CLINICAL COMMENT

Stabilized SnF2 dentifrice has been shown to provide significantly greater protection from acid erosion compared to other types of fluoride dentifrice.* In this trial, a novel stabilized stannous fluoride dentifrice showed a significant anti-erosion benefit over a sodium fluoride/potassium nitrate dentifrice which is marketed for protecting enamel against acid erosion. Dental professionals should consider recommending this SnF2 dentifrice for its high level of protection against acid erosion as well as its benefits for reduction of gingivitis and plaque.

*Lussi A. Int Dent J 2014; 64 (Suppl 1): 2-3.

CLINICAL SIGNIFICANCE: EROSION

Stannous Fluoride Clinical Significance
  • The prevalence of dental erosion is increasing due to changes in the modern diet, which includes more acidic beverages.
  • Dental erosion is irreversible and therefore must be prevented.
  • The protective coating deposited on the tooth surface through the use of stabilized stannous fluoride dentifrice offers exceptional protection against erosion, making this dentifrice a suitable option for the prevention of erosion.
  • Relative to other fluorides, stannous fluoride provides greater protection against enamel erosion.
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