## 4 Discussion
Herein, bovine teeth were chosen due to the difficulty in obtaining human teeth in a sufficient quantity and with adequate quality, knowing that there is evidence that bovine teeth can be used instead of human ones without compromising the results of microshear and tensile bond strength, enamel, dentin studies, or microhardness [30]. Additionally, the relatively small and irregular surface area of human teeth can be a limiting factor for certain tests that require flat surfaces of consistent thickness, such as those used in this study. On the other hand, it is believed that the presence of theobromine, in association with calcium and phosphate ions, promotes the enlargement of hydroxyapatite crystals, thereby contributing to the increase in enamel microhardness and resistance to mineral dissolution during acid challenge [19]. Oxygen and nitrogen atoms in the theobromine molecule, due to their high electronegativity, attract calcium and phosphate ions, which have lower electronegativity, leading to the formation of theobromine apatite crystals [19; 31]. Theobromine molecules, being smaller than the micropores created by enamel acid dissolution, are able to traverse these pores and infiltrate the hydroxyapatite crystal structure [31]. This was not observed in the current study, which may suggest that the molecules may have been trapped within the varnish, preventing them from crossing. A potential limitation of the current study is the uncertain bioavailability of the bioactive compounds _tt_-farnesol, quercetin, and theobromine in the experimental varnishes. Although the formulations were based on existing evidence of the compounds' potential effects, the varnish excipients may have influenced the release and activity of these compounds. This could have affected their solubility and interaction with enamel, potentially impacting the efficacy observed in this study. Future studies should investigate how varnish formulations influence the bioavailability of these compounds to optimize their therapeutic potential. Emerging evidence also indicates oral protective properties in quercetin. Quercetin, a polyphenol-based phytoestrogen, is found in a wide range of vegetables, fruits, seeds, grains, tea, and wine [32]. Its topical application might be beneficial due to its antioxidant, anti-inflammatory, and antibacterial properties [33]. [PERSON] et al. (2016) [17] investigated quercetin's effectiveness as a remineralization agent for root caries, finding that it could inhibit demineralization and promote remineralization in root caries lesions. This effect may be attributed to quercetin's ability to form complexes with calcium ions, due to the presence of a hydroxyl group in its molecular structure [17]. This study, however, could not confirm the action of quercetin in enamel demineralization, as its analyses were conducted on root lesions. Nonetheless, based on this, we can conduct studies aiming to analyze its potential in enamel demineralization, either alone or in combination with other natural compounds. Regarding _tt_-farnesol, it is a natural sesquiterpene. [PERSON] et al. (2019) observed that the incorporation of _tt_-farnesol into a glass ionomer cement improved the antibacterial activity against _S. mutans_[34]. This aligns with the findings of [PERSON] et al. (2011) [35], who showed that _tt_-farnesol enhances the proton permeability of the _S. mutans_ cell membrane, leading to cytoplasmic acidification and increased acid sensitivity. Additionally, _tt_-farnesol affects the synthesis of extracellular polymeric substances (EPSs) in _S. mutans_ biofilms, particularly insoluble glucans, without directly inhibiting the enzymatic activity of glucosyltransferase (Gfts) [35]. Given that caries is a condition dependent on biofilm formation, the compound was chosen in an attempt to associate the antimicrobial properties that it has been found to possess with the remineralizing properties found in quercetin and theobromine. Future studies should be evaluated to analyze its antimicrobial action.