Analysis of the potential for dental wear of acidic diet : Literature review

Objective: The aim of this study was to perform an acid wear properties review (pH, entitlement and buffering effect) of diets that can influence dental and restorative aging. Methodology: Manuscripts from the Pubmed database were collected. The search terms were: “Dental erosion”, “Erosion”, “Food habits”, “acidity”, “tooth enamel solubility”, “carbonated drinks”, “hydroxyapatite” and “alcoholic beverage consumption” between the years of 1995 and 2020. Result: 755 manuscripts were initially obtained, but after analyzing the inclusion and exclusion criteria, 15 manuscripts were selected at the end. After analyzing the 15 manuscripts included in the literature review, the results of the study showed that most of the diets evaluated had a pH lower than 5.5, except for coffee and mineral water. The soft drinks and Kombucha had lower pH values and therefore more corrosive potential. Conclusion: Based on the results of this study, it may be concluded that most of the diets evaluated present a corrosive potential for dental structure and restorative materials.

Frequent and prolonged contact of teeth or restorative materials with acidic foods promote erosion or biocorrosion. This is a complex process that happens in a chemical reaction and the potential of acids aggression for the teeth depends on some chemical properties of these food (Shellis, Featherstone, & Lussi, 2014). Properties as the analysis of Development, v. 9, n. 11, e44191110004, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i11.10004 4 pH shows the amount of H + released during the chemical reaction (Grippo, Simring, & Coleman, 2012). Also, another characteristic that helps to understand the potential of aggression is pKa because it is related to the ability that some substance to release the H + ions by measuring the pH when 50% of substance is dissociated (Shellis et al., 2014). Moreover, it is important to understand titration to determine the time that acids take to be buffered when it reacts with titrating substances (Grippo et al., 2012).
All those properties are related to the surface degradation caused by biocorrosion and it can be the reason for appearance of non-carious cervical lesions (NCCL), dentin hypersensitivity (DH) and tooth wear. However, they are not caused by isolated factors (Teixeira, Zeola, Machado, Gomes, Souza, Mendes & Soares et al., 2018). There are factors such as stress and friction that have a complex interaction between them causing these lesions. During the diagnosis is important to consider all modifying and etiologic factors to initiate the treatment and determinate the correct diagnosis (Grippo et al., 2012). Some factors act more intensely according to different lifestyle and some of them affect more than others (Peumans, Politano, & Van Meerbeek, 2020).
Biocorrosion is one of the most intense potential to development of DH and NCCL and it has a mechanism of degradation that involves chemical reactions between acid contained on food sources and mineral tissues (Shellis et al., 2014). Thus, the ions H + are liberated from these foods when they are on an aqueous solution and they react with hydroxyapatite molecules contained on enamel and dentin. The H + ions react mainly with OHand PO4 3-. Thereby, it breaks down the hydroxyapatite molecule, consequently the mineral crystals and degraded it (Shellis et al., 2014).
Resin-based composites (RBC) are also affected by acid foods and beverage. The surface degradation of restorations cause discoloration, increase surface roughness and decrease surface microhardness (Silva, Sales, Pucci, Borges, & Torres, 2017;Tanthanuch, Kukiattrakoon, Eiam, Pokawattana, Pamanee, Thongkamkaew & Kochatung, 2018). The reason why all these changes happen is that the acidity increases in dissolving and soften the polymer matrix. Thus, filler particles are dislodged resulting a decrease in the load resistance and worsen physical and mechanical properties of RBC (Santos, Clarke, Braden, Guitian, & Davy, 2002). Therefore, the aim of this study is to understand and evaluate the impact of pH and the titration of acidic foods for the appearance of non-carious lesions and degradation of tooth surface and restorative materials. Development, v. 9, n. 11, e44191110004, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i11.10004 5 The objective of this study was to perform a biocorrosion properties review (Potential of Hydrogen-pH, Titratable acid and buffer effect) of various foods that can influence dental and restorative aging.

Methodology
This is an integrative review carried out through the following steps: establishing the research question, searching the literature, extracting and organizing information, evaluating the included studies, interpreting the results and presenting the review (Souza, Silva & Carvalho, 2010). The review was conducted to answer the following research question: What are the biocorrosive potential of foods present in the population's diet? The search for the manuscripts was carried out in June 2020 in the PubMed / MEDLINE database consulted in the Health Science Descriptors (DeCS): "tooth erosion", "erosion", "feeding behavior", "acidity", "Dental Enamel Solubility", "Carbonated Beverages", "Hydroxyapatites", "alcoholic beverages"; "dentistry", "tooth" and "dental wear".
The Inclusion criteria were: English manuscripts that performed experimental design in laboratory (in vitro) and observational studies that included information about dental biocorrosion/erosion and acidic diet. The exclusion criterion was: manuscripts that did not analyze the effects of the dental wear and acidic diet components. Initially, the individual search for descriptors was carried out, and then crossings were carried out in pairs or trios, interconnected by the Boolean operator and. After this stage, the titles and abstracts of the selected studies were thoroughly read.
The buffering capacity at the pH value of the product. Source: Authors.

Grape
Not specified Lussi et al., 2004;Lussi et al., 2012) 3. The buffering capacity at the pH value of the product. Source: Authors.

Mean of Kombucha tea
The buffering capacity at the pH value of the product. Source: Authors.

Discussion
The extrinsic factor that can influence dental corrosion include the consumption of acidity foods and beverages (MA et al., 2016;Nogueira et al., 2000;Zanatta, Esper, Valera, Melo, & Bresciani, 2016). This biocorrosion can be related to pH of those foods and beverages since the critical pH for enamel dissolution is 5.5. Below this value the degree of minerals saturation contain in the saliva is not enough to control mineral loss (Lussi, Jaeggi, & Zero, 2004;Lussi, Megert, Shellis, & Wang, 2012;Seow & Thong, 2005). A healthy tooth surface is composed mainly of hydroxyapatite which are calcium phosphate crystals. When this element is immersed in a solution which has a low pH the hydroxyapatite ions dissolve and then re-associate with ions H + from the medium. This exchange occurs in a state of equilibrium between the substances (Shellis et al., 2014). However, this ions loss collaborates to demineralization of tooth and consequently favor biocorrosion (Lussi et al., 2004;Lussi et al., 2012;Seow & Thong, 2005). Another factor that influence on teeth acid wear is the degree of dissociation of acid. This happens due to the existence of variation between Development, v. 9, n. 11, e44191110004, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i11.10004 16 solutions and the fact that it is not all acid that dissociates completely. The pkA constant indicates this degree of dissociation of acid and this is another important value to be considered (Lussi et al., 2004;Shellis et al., 2014). Therefore, the amount of H+ ions present in the solution leads to a lower or moderate pH and consequently influences the corrosive potential. Not only the pH but other factors that are still to be discussed contribute to this potential (Cochrane et al., 2012). This behavior can explain the reasons to beverages such as citric juices, soft drinks kombucha, guarana soft drinks, tonics, flavored sparkling water and some teas are potentially harmful as it is seen on tables.
Other properties that are related to the corrosive potential of foods and beverages are buffering capacity and titratable acidity (Lussi et al., 2012;Zero, 1996). Buffering is the ability of a product not to vary or to vary its pH not too much in a given situation (Shellis et al., 2014). The better the buffering capacity of a solution, the longer it will take for the pH to be neutralized by saliva. Thus, the dissolution of the minerals surface in the tooth will take longer to crease, increasing the biocorrosive potential (Barbour, Parker, Allen, & Jandt, 2003;Lussi, Jaeggi, & Jaeggi-Scharer, 1995;Lussi et al., 2012;Zero, 1996). The buffering capacity can change according to the acid and pH of the solution. However, it is important to consider that factors such as volume and contact time to tooth surface with the solution directly influence the buffering effect (Larsen & Nyvad, 1999;Shellis, Barbour, Jones, & Addy, 2010;Shellis et al., 2014).
In addition, titratable acidity is an important property to be analyzed. It is related with the concentration of undissociated acids in the solution and this factor plays an important role on dental corrosion (Larsen & Nyvad, 1999). Titratable is measured by the H+ concentration between an initial pH and a determinate final pH value and generally is calculated in pH 5.5 and 7.0 (Larsen & Nyvad, 1999;Lussi et al., 2012;Shellis et al., 2014). These undissociated acids pin and diffuse more easily on the enamel surface and the release of these ions keep the pH low and the dissolution of minerals continues to occur (Barbour et al., 2003;Lussi & Carvalho, 2015). Resuming, titratable acidity is a good indicator to study the corrosive potential of acidic food and beverages once it shows the amount of H + ions that are available to interact with the tooth surface (Brown, Smith, Shaw, Parry, & Smith, 2007;Jensdottir, Bardow, & Holbrook, 2005).
As it can be seen on tables, some beverages and foods have higher titratable acidity and buffering capacity than others. Fruit juices, tonic drinks, vinegar, orange, yogurt, energy drinks and champagne have shown higher values of these properties and consequentially have an aggressive corrosion potential.
The consumption of acid foods and beverages do not only degraded tooth surface but also composite resin restorations (Jaeggi, Gruninger, & Lussi, 2006;Peutzfeldt, Jaeggi, & Lussi, 2014;Wu & McKinney, 1982). Composite materials are constituted by organic matrix, inorganic particles, a coupling agent and an initiator system (Soares, Peres, Wobido & Machado, 2019). Applying a correct technique, all those factors contribute to adequate properties of the material. However, an acid diet could create a critical pH environment which can degrade composite resin. This mechanism occurs due to the deranged of the composite polymers by broking its chemical bonds between molecules. This result generated an alteration on physical and mechanical properties, such as hardness, surface roughness and color variation (Münchow, Machado, Ramos & Rodrigues-Junior, 2014).
The increased surface roughness creates an environment to accumulation of biofilm, making it more susceptible to secondary caries and periodontal diseases (Garcia-Godoy, Garcia-Godoy, & Garcia-Godoy, 2003). The absorption of pigments is also increased by the modifications of restorations surfaces caused by an acid diet. The pigments contained on food and beverages are more easily absorbed on composite resin surface. Thus, eating habits and food diet have a direct correlation to composite resin restoration longevity (Bagheri, Burrow, & Tyas, 2005).
Moreover, beverages that contain alcohol in its composition could produce corrosive damage to composite restorations even if the pH is neutral or close to it (MA et al., 2016).
The reason why this damage happen is that the alcohol diffuses into the polymer matrix of the composite material causing hydrolysis. In this process are created gaps between the linear chains of the polymers and the chemical bond present between filler particles and the resin matrix loss straight (Santos et al., 2002). Due to filler particles are dislodge from the outer surface of the material, there is a reduction of hardness and increase of roughness surface (Ablal et al., 2009;MA et al., 2016). The polymer matrix suffers a plasticizer effect and consequently its degradation (Ablal et al., 2009).
It is important to remain that the corrosive potential of foods and beverages is also influenced by the factors association that help to remove hard tooth tissue. The oral cavity is in a constant change and friction, mechanical efforts and tension also corroborates and intensify the damage caused by acid foods and beverages. The tooth tissue affect by a critical pH is more easily removed by friction factors and it intensifies tissue loss Shitsuka, Palma, Pedron, Polotow, Barros, Leite & Corrêa, 2020).
Since most people daily routine is surrounded by an acid diet it is important to give orientations to patients about how to decrease damage to teeth. Intensifying the salivary flux by chewing sugar-free candies and gums could benefit soft and hard tissues for being able to increase saliva amount able to achieve its buffering effect (Dawes, 2008). It is also recommended to rinse the mouth carefully before brush the teeth when the cavity was exposed to acid food and beverages. Furthermore, a collaboration between dentists and nutritionists could bring good results. Explaining to these professionals about the patients' oral disease, nutritionists can adapt routine diet switching acid foods to the one's with higher pH. When it is not possible to change beverages belong to the diet, drink it with a straw could decrease its contact to teeth surface (Amaechi & Higham, 2005;Carvalho et al., 2016;Zero, 1996). By following some of these recommendations, corrosion can be controlled and prevented on population (Maltarollo, Pedron, Medeiros & Shitsuka, 2020).

Conclusion
The results of this study revealed the importance of knowledge about biocorrosive potential of the food consumed in routine and the influence on oral health. It is concluded that most of the foods analyzed in this study had a pH below the critical to generate changes in the tooth structure and composite resins. It is noteworthy that more studies are needed about biocorrosive potential in the tooth and composite resins degradation and related to contemporary lifestyle diet.