Treatment for dental erosion: a systematic review of in vitro studies

Introduction

Dental erosion is defined as the chemical loss of dental mineralized tissue caused by exposure to nonbacterial acids (Schlueter et al., 2020). This is a multifactorial condition whose etiology and pathogenesis are related to chemical, biological, and behavioral factors (Kanzow et al., 2016). These factors, acting individually or interacting with each other, play a role in the prevention or progression control of dental erosion (Lussi, 2006).

The early diagnosis of erosive lesions is still challenging for most professionals and is usually identified as the rapid progress of tooth wear where there is already dentin hypersensitivity and the absence of lesion staining (Donovan et al., 2021). Also, other cases of erosive wear occur in the process of slow progression, which does not generate symptoms due to the response mechanism of the dentin-pulp complex that promotes the obliteration of dentinal tubules (Bartlett, 2016).

In this context, direct exposure to acids in the oral cavity promotes the demineralization of hydroxyapatite due to the undersaturation of minerals concerning the surrounding microenvironment (Shellis, Featherstone & Lussi, 2014). Therefore, saliva plays an essential role in the bioavailability of calcium and phosphate ions for the remineralization process. However, the frequent action of acids can overcome the protective effect of saliva, causing mineral dissolution that results in erosive wear (Fernando et al., 2019). To reverse this process, it is necessary to use topical remineralizing agents that contain calcium, phosphate, and mainly fluoride ions (Shen et al., 2018).

The use of fluoride in the form of mouthwash or brushing with toothpaste promotes structural remineralization, forming a mineral layer on the tooth surface and reducing subsequent demineralization, thus helping in the treatment and prevention of dental erosion (Creeth et al., 2015). Although fluoride products are often used, most fluoridated formulations alone have limited preventive effects against tooth erosion as their action on the mineralization process is limited to the surface and the near-surface layers of enamel and is restricted to the demineralized enamel layer (Lussi & Carvalho, 2015).

Numerous vehicles, such as toothpaste, rinse solutions, gels, and varnishes, are currently available as strategies for using fluorides. These products contain different types of active ingredients with distinct anti-erosive properties, and some of them have been demonstrated to be effective preventive therapies against tooth erosion (Buzalaf, Magalhães & Wiegand, 2014; Lussi et al., 2019).

The most appropriate way to access the protective effects of these products would be in vivo studies, with randomized clinical trials considered the gold standard. However, this kind of study has some limitations, such as the low accuracy of available methods for measurement of chemical tooth tissue loss, the need for prolonged studies to assess the rate of progression and the variation of this rate, the lack of control over the exposure to wear, the need for participation of large groups, to minimize contact with other erosive agents, and for several years of follow-up (West, Davies & Amaechi, 2011). Proper clinical methods must be developed and validated to assess dental erosion variables in vivo. Numerous in vitro model studies have been designed to simulate everyday intra-oral conditions as closely as possible (Wiegand & Attin, 2011). Thus, this systematic review was carried out to gather scientific evidence demonstrating the anti-erosion treatments that presented the best results in the remineralization of the tooth structure.

Materials & Methods

Results

Characteristics of the studies

A total of 522 records were identified from the database search, and 305 duplicates were found and removed. The remaining 217 were evaluated by title and abstract according to the eligibility criteria, and as a result, 204 studies were excluded at this stage.

The remaining studies (n = 13) were assessed by full-text reading: three used bovine teeth (Comar et al., 2015; Machado et al., 2019; Scandiffio et al., 2018), and one evaluated dentine (João Souza et al., 2020). Two studies did not realize the intervention group (Austin et al., 2014; Passos, Rodrigues & Santiago, 2018), and three evaluated primary teeth (Elwardani, Harhash & Zaky, 2019; Maden et al., 2017; Rallan et al., 2013), conflicting with the previously established eligibility criteria. Finally, four studies were selected in this systematic review according to the eligibility criteria (Bradna et al., 2015; João Souza et al., 2017; Panich & Poolthong, 2009; Ranjitkar et al., 2009) (Fig. 1).

The four included studies were in vitro studies. One was conducted in the Czech Republic (Bradna et al., 2015), one in Brazil (João Souza et al., 2017), one in Thailand (Panich & Poolthong, 2009), and one in the United Kingdom (Ranjitkar et al., 2009). These studies evaluated the surface of eroded tooth enamel and analyzed the effect of different remineralizing treatments.

Discussion

Our systematic review aimed to investigate effective treatments for dental erosion. Although fluoride products showed no significant reduction in enamel surface loss in the studies, there was a remineralizing effect on dental enamel after using CPP-ACP. However, the number and limitations of the included studies must be considered.

Based on the present findings, it was possible to verify that all test products (toothpaste and tooth mousses) had different effects on enamel surface loss. Comparing these products can be difficult, as many intrinsic factors can influence their protective potential, the type of experimental model, and different ways of presenting the products used. The absence of a negative control group with exposure only to water can interfere with the mean difference between groups in erosion/abrasion models. However, when evaluated individually, it is possible to demonstrate that the performance of each product depends on several factors, such as the presence or absence of fluoride; the mode of action of fluoride; the mode of action of other protective agents, such as polyvalent metal ions, amino acids, peptides, proteins and polymers, and CCP-ACP (Lussi & Carvalho, 2015).

The influence of fluoride on dental erosion depends on many factors, such as higher concentration, frequency of application, and vehicle. In these cases, the efficacy of fluoride products is attributed to the formation of precipitates on the tooth surface, which acts as a protective barrier against acid impacts (Schlueter et al., 2020). Although the studies in this review did not show a significant remineralizing effect of fluoride on tooth enamel, other recent studies in the literature have shown that the application of fluoride products after acid challenge to enamel reduced enamel loss (Zanatta et al., 2020; Ionta, dos Santos & Mesquita, 2019). The studies by Bradna et al. (2015) and João Souza et al. (2017) showed no protective effect against dental erosion, although lower enamel surface loss was observed in teeth treated with fluoride dentifrices and/or rinses. These results are limited due to the action of other factors such as calcium and phosphate ion concentration, chemical characteristics of the compounds, and different application protocols.

In addition to these therapeutic approaches, the remineralizing properties of milk protein-based complexes have been investigated, which are used in the form of peptides, among which is the amorphous casein-calcium phosphopeptide complex (CPP-ACP) (Ekambaram, Said & Yiu, 2017). There is evidence that CPP-ACP provides high concentrations of calcium and phosphate ions that, when associated with fluoride, potentiate the remineralizing effect on tooth enamel (Gokkaya et al., 2020; Alexandria et al., 2020; Bejoy et al., 2020). The casein present in the complex stabilizes phosphate and calcium ions and facilitates the formation of mineral deposits on the surface of erosive lesions (Reema, Lahiri & Roy, 2014). Therefore, CPP-ACP effectively prevents erosive lesions when applied before the acid challenge by reducing the percentage of loss of surface microhardness of human enamel (Yu et al., 2018; Bejoy et al., 2020).

Although in vitro studies are very relevant, it should be noted that, no matter how much the methodology used in these studies tries to reproduce in greater detail what happens in the oral cavity, it will never be identical. For example, in dental erosion studies, it is impossible to reproduce the acquired pellicle, which is an essential factor in protecting the tooth surface against erosion. In addition, the studies used in the present systematic review show high heterogeneity in the methodologies used, such as substrate, stages of dental erosion, evaluation times, and erosive protocols, among others. Considering all these factors, the results found in our study need to be evaluated with caution. Moreover, we suggest future well-designed studies with better standardization of the methods, allowing comparison among them and increasing the quality of scientific evidence.

Conclusions

Despite some methodological limitations in in vitro studies, including those discussed in this systematic review, the results provided imply that CPP-ACP therapies can be beneficial for dental erosion. However, these results should be evaluated with caution, and further studies are needed to establish the best treatment for dental erosion with high certainty of evidence.

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