In attempt to raise intra-oral pH, different products have been tested, including antacid tablets, gum arabic lozenges, mineral water, milk and tap water, all used for 2 min immediately after the erosive challenge [55]. All of these products were found to increase intra-oral pH when compared to the negative control (where no treatment was performed); however, the antacid tablet caused the greatest and most rapid increase in intra-oral pH. The use of different antacid suspensions and a bicarbonate solution after erosive challenge with hydrochloric acid also significantly reduced enamel surface loss [56, 57]. Thus, it is advisable to instruct the patients to rinse their mouth with water or, more effectively, to use antacid products immediately after vomiting or reflux episodes.

Aiming to protect tooth surfaces against acidic challenges, the application of fluoride and polyvalent metal fluoride compounds has been suggested. However, studies have shown that the type of fluoride compound seems to be relevant. Improved enamel protection was observed with dentifrices containing titanium tetrafluoride (TiF₄) and stannous fluoride (SnF₂) when compared to NaF [21, 58–66]. Regardless of the fluoride concentration (1,100 ppm F, 1,450 ppm F or 5,000 ppm F), NaF dentifrices did not show ability to protect the enamel against simulated erosive challenges [65, 67]. The improved protection by SnF₂ and TiF₄ was attributed to the stannous’ and titanium’s ability to interact with the tooth surfaces forming an acid-resistant film of insoluble compounds, thus increasing the tooth tissue resistance [59, 68–70]. These compounds also demonstrated precipitation of CaF₂-like deposits (CaF₂-globules) that behave as a physical barrier inhibiting the contact of the acid with enamel as well as acts as a fluoride reservoir [71, 72]. The formation of CaF₂ reservoir is known to be increased under acidic conditions compared to neutral conditions [73] and is highly dependent on the concentration of fluoride and frequency of application as well [74]. Therefore, for patients susceptible to erosion, additional measures to the daily use of conventional fluoridated toothpastes should be implemented, with best evidence for acidic formulations containing polyvalent metal fluorides.

For dentin, fluoride/stannous-containing dentifrices (1,100–1,400 ppm F) were able to significantly reduce dentin wear, whereas an amine fluoride (AmF) dentifrice (1,400 ppm F) was not [75]. Recently, Comar et al. [76] compared the effect of dentifrices containing TiF₄, NaF, and SnF₂ on tooth erosion-abrasion and the results showed a significant reduction in enamel and dentin wear (64–70 %) for TiF₄ and SnF₂ compared to placebo in vitro.

The efficacy of a NaF dentifrice in erosion prevention seems not to increase along with the fluoride concentration and the reduction of wear seems to be less than 30 % for this fluoride vehicle compared to placebo/control [77, 21]. An in situ study showed that 5,000 ppm F and 1,100 ppm F dentifrices reduced erosive and erosive-abrasive dentin wear by approximately 27.5 % compared to the placebo dentifrice, but their efficacies were not significantly different [78]. Also for enamel wear, no significant differences were found between 1,100 and 5,000 ppm F dentifrices [79]. On the other hand, Ren et al. [80] demonstrated an increase in the protection against enamel erosion (around 55 %), when a dentifrice containing 5,000 ppm (NaF) was compared to a dentifrice containing 1,450 ppm F (NaF) in situ.

On the other hand, low-fluoride dentifrices supplemented with trimetaphosphate (3 %TMP and 500 ppm F) showed inhibition of tooth wear, and, under in vitro conditions, were able to significantly reduce enamel erosion and erosion/abrasion when compared to a 1,100 ppm F dentifrice, not differing from a 5,000 ppm F dentifrice [81].

Casein phosphopeptide amorphous calcium phosphate (CPP-ACP) incorporated into patient self-applied pastes and cream (GC corporation) has been demonstrated in series of studies to promote the remineralization of enamel and dentin [44, 82–90]. These are commercially available as Tooth Mousse (Asia/Australia) and MI paste (USA) and the fluoride-containing CPP-ACFP (with 900 ppm fluoride) as Tooth Mousse-plus and MI paste-plus. In Recaldent, the calcium and phosphate ions in a soluble amorphous calcium phosphate is stabilized by the protein CPP into nanocomplexes, thus preventing precipitation during storage within the dispensing tube [91]. Following intraoral application, these nanocomplexes bind onto the tooth surfaces and dental pellicle to create a state of supersaturation of calcium and phosphate ions in the oral cavity. When the oral pH drops during an acidic challenge, the calcium is released from the CPP to provide high level of bioavailable calcium and phosphate ions to facilitate remineralization and inhibit demineralization [89]. CPP-ACP products that include fluoride would be the preferred option for erosion. Follow the manufacturer’s direction for application. However, there is a need of further studies to compare their erosive protective effect with other products such as polyvalent metal fluorides.

This technology is tailored to enhance remineralization by providing a method where calcium, phosphate and fluoride ions are made bioavailable in the oral environment at the same time. In this technology, by milling tricalcium phosphate (TCP) with organic materials (functionalization), the calcium oxides in TCP become ‘protected’ by the organic materials, thus allowing the calcium and phosphate ions of the TCP to co-exist with fluoride ions in an aqueous dentifrice base (toothpaste) without premature TCP-fluoride interactions [92]. Once applied in the presence of saliva, calcium compound is activated by saliva that degrades the protective coating, releasing calcium at the tooth surface, resulting in high fluoride and calcium bioavailability on the lesion surface and subsequent diffusion into the lesion to promote remineralization [93, 94]. Products containing functionalized tricalcium phosphate technology are commercially available from 3 M-ESPE Inc., as self-applied toothpastes, Clinpro™ 5000 with 5,000 ppm fluoride (USA) and Clinpro tooth crème with 850–950 ppm fluoride (Asia/Australia). Follow the manufacturer’s direction for application. However, there is a need of further studies to compare their erosive protective effect with other products such as polyvalent metal fluorides.

Novamin technology is incorporated in numerous products tailored chiefly to relieve dentin hypersensitivity. It is a bio-active glass (calcium sodium phosphosilicate) that binds to the tooth surfaces, and when in contact with body fluid, such as saliva, releases calcium and phosphate ions, enabling the remineralization of tooth tissue, typically forming hydroxycarbonate apatite [95]. The existing Bioactive glass (Novamin™) used in commercial toothpastes such as Sensodyne Repair & Protect and Sensodyne Complete Protection (GlaxoSmithKline, UK) does not contain fluoride, rather sodium monofluorophosphate is added paving way for possible premature formation of CaF₂ [96]. Recent innovation incorporated fluoride, strontium, potassium and zinc within the glass itself, thus enabling the delivery of Ca²⁺, PO₄ ³⁻ and F⁻ ions simultaneously in the appropriate amounts to form fluoroapatite that is more chemically stable against acid attack [97]. The fluoride-containing bioactive glass (F-BG), available in Europe, is engineered to release fluoride over a 12-h period within the oral environment. However, there is a need of further studies to compare their erosive protective effect with other products such as polyvalent metal fluorides.

Recently, some dentifrices containing polymers have been investigated due to their potential to form a protective layer on the tooth surface, strengthening the pellicle [77]. As active ingredients in toothpaste, organic polymers such as casein, ovalbumin, pectin, alginate and arabic gum, and inorganic polymers such as pyrophosphate, tripolyphosphate and polyphosphate have been studied [64]. Some of them are common dentifrice ingredients, such as carboxymethylcellulose, hydroxyethylcellulose and polyethylene glycol.

Chitosan is a cationic polysaccharide obtained by the deacetylation of chitin and has been used as active ingredient in fluoride-free dentifrice to inhibit erosion and erosion/abrasion [63]. Incorporation of chitosan into dentifrices containing fluoride and tin or Sn significantly increased the anti-erosive/anti-abrasive effect of the dentifrice for both enamel and dentin [64, 98]. Chitosan might be capable of adsorbing to solid structures with negative zeta potentials such as enamel [99], and this adsorbed layer is strikingly persistent under pH cycling conditions and under physical impacts [64]. Furthermore, chitosan seems to be able to enhance the efficacy of the Sn^+2containing dentifrice, acting as an anti-erosive/anti-abrasive agent. Immersion in each Sn⁺²-containing suspension significantly reduced tissue loss. However, after immersion in suspension + brushing, only the treatments with GelKam (3,000 ppm Sn⁺², 1,000 ppm F⁻) and with F/Sn/chitosan (1,400 ppm F, 3,500 ppm Sn and 0.5 % chitosan) significantly reduced loss compared to placebo and F/Sn dentifrices [100].

Table 8.2 summarizes the results of some studies about the effect of dentifrices in the control of tooth wear.

Mouthrinses have the advantage of simplicity of use and can be formulated to possess a refreshing flavour so as to be used to enhance salivary remineralization after acidic challenges in patients. Fluoride compounds such as polyvalent metal fluorides that might have higher efficacy at lower concentrations to allow daily application have been the focus of new formulations. Wiegand et al. [101] observed that acidic solutions of AmF and SnF₂ with the same fluoride concentration (10,000 ppm F) were similarly more effective than a NaF solution against enamel erosion. Yu et al. [102] reported that a single application of a NaF/SnCl₂ solution (500 ppm F and 800 ppm Sn) reduced enamel and dentin erosion up to 6 and 3.5 min, respectively, of constant acid flow, as analysed by calcium released into the acid. In this study, solution of NaF (500 ppm F) alone did not have a significant impact on the progression of enamel and dentin erosion [102]. While titanium tetrafluoride (TiF₄) solution (approximately 9,000 ppm F) at pH 1.2 was able to significantly reduce erosive mineral loss [103] in enamel, dentin erosion was reduced by NaF and TiF₄ solutions of similar fluoride concentration (approximately 9,000 ppm F) and pH 1.2 with no difference between them [104]. TiF₄ has been shown to provide a more acid-resistant layer when compared to SnF₂ solution [58, 60]. This protective layer is related not only to an increased fluoride uptake but also to the formation of new compounds (hydrated hydrogen titanium phosphate and titanium dioxide) [21]. However, the low pH of TiF₄ products does not allow their use as patient-applied, due to the possible cytotoxic effect on fibroblasts [105]. Therefore, this formulation should be improved to allow self-application.

The anti-erosion efficacy of low concentrated TiF₄ mouthrinse was evaluated in a two phase study [106]. In the first phase, a commercially available anti-erosion mouthrinse, Erosion Protection® (SnCl₂/NaF/AmF), applied twice daily for 1 min on each occasion was compared with low concentrated TiF₄ solutions (500 ppm F⁻, pH 2.5) using an in vitro model. In the second phase, combinations of TiF₄ and NaF (pH 4.5) with higher native pH values was compared with TiF₄ (pH 2.5) alone. In both studies, the best anti-erosive effect was still obtained with TiF₄ (pH 2.5) solution (99 % reduction of enamel wear), followed by Erosion Protection® (78 % reduction) and then a specific combination of NaF and TiF₄ solution (41 % reduction). Although combination of NaF + TiF₄ increased the pH, its effect against enamel erosion was reduced compared to TiF₄ alone, as expected, probably due to the reduction of titanium precipitation on enamel [106].

Promising results were obtained with tin-containing fluoride solutions, able to deposit metal compounds [Ca(SnF₃)₂, SnOHPO₄, Sn₃F₃PO₄], which has been shown to have higher acid resistance than particles of CaF₂ in situ [107–110]. Combination of AmF/NaF/SnCl₂ (2,800 ppm Sn⁺², 500 ppm F⁻ solution) was shown to provide 80 % of erosive wear inhibition in vitro. A non-significant difference found among different Sn⁺² concentrations, ranging from 800 to 2,800 ppm, may mean that a low concentration of tin can be used without loss of efficacy of tin fluoride solution [107]. Concentration of tin in a mouthrinse is of high clinical importance since a higher concentration induces a dull feeling on tooth surface, astringent sensation and tooth discoloration [21]. A fluoride mouthrinse (Erosion Protection®; GABA Int. AG, Switzerland) with low tin concentration (800 ppm Sn⁺² as SnCl₂, 500 ppm F⁻ as AmF and NaF) is commercially available in Europe and has been shown to reduce substance loss by 67 % in enamel and 47 % in dentin, being significantly more effective than NaF, when applied once daily for 30 s under severe erosive conditions [111] in situ. Interestingly, the anti-erosion effect of SnCl₂/AmF/NaF mouthrinse can remain stable on dentin, regardless of the presence or absence of the demineralized organic matrix (DOM), while the effect of NaF mouthrinse is lost when DOM is removed, showing promissing effect of the former from the clinical point of view [111].

The erosive process in dentin is different from the one occurring in enamel due to the presence of the DOM that makes ionic diffusion more difficult, thus slowing down the progression of erosion. The DOM is composed mainly of type-I collagen that is susceptible to degradation by proteases, thus allowing the progression of erosion [112]. Based on this, mouthrinses containing protease inhibitors, such as chlorhexidine and green tea extract [113], or even rinses with green tea [114] have been shown to reduce dentin loss (around 30–40 %) in situ when compared with control. The effect of the protease inhibitors was similar to fluoride. Thus mouthrinses containing SnCl₂/NaF/AmF, TiF₄/NaF, or protease inhibitors might have potential to benefit patients that are frequently exposed to erosive challenges.

Table 8.3