Erosive Tooth Wear (ETW) represents a prevalent worldwide condition that affects the permanent teeth based on a largely estimation between 20 % and 45 % [1]. It is characterized, at the first stage, by irreversible mineral loss of dental structure due to non-bacterial acid exposure that determines a soft outer surface [2]. Following, the removal of the tissue is provoked by mechanical actions on the oral cavity. Extrinsic acid sources come mostly from dietary acids such as citric acid from orange juice [2], while intrinsic acid comesfrom digestive system, mainly hydrochloric acid [1,2]. Patients with eating disorders and those undergoing bariatric surgery are clinically relevant groups in this context [[1], [2], [3], [4]].

Products that can control this discomfort and painful situations while interacting with dentin [5,6] must be associated with the management of etiological factor from ETW to be promising. The available products are based on different technologies including the varnishes, targeting for long-lasting results. Duraphat, a 5 % sodium fluoride varnish, is widely used to inhibit demineralization and promote remineralization of dental tissues [[7], [8], [9]]. Furthermore, it can be used as desensitizing agent [10]. Its long-lasting fluoride release forms calcium–fluoride salts and fluorapatite, occluding dentinal tubules and reducing hypersensitivity [7,8,10].

In another category, Gluma Desensitizer, a glutaraldehyde-based resin desensitizer presents HEMA in its composition [11,12]. Gluma's action mechanism occurs through a reaction between glutaraldehyde and albumin present in dentin fluid, leading to protein coagulation. This coagulated protein polymerizes with HEMA and increases the fluid's viscosity, which reduces sensitivity by limiting fluid movement [13,14]. Besides the obliteration by deposition of salts and globulin coagulation, this resin-based material can serve as a mechanical barrier.

Also conciliating bioactive ingredients with resin monomers, PRG Barrier Coat is a light-cured resin varnish based on S-PRG particles (Surface Pre-Reacted Glass-ionomer particles) that release multiple bioactive ions such as F-, for fluorapatite formation, Sr2+ that improves acid resistance and forms strontium apatite, Al3+, for dentinal tubule occlusion and SiO32-, which reinforces the dental structure [15]. Furthermore, it has the potential to inhibit/limit demineralization [16], assist in remineralization, and act to control dentin hypersensitivity [14,17]. As Gluma, the resin component also enhances its use as a mechanical protection.

Overall, these agents are composed by ingredients with promissory effects to control the changes due to ETW [7,8,10,18,19] and their efficacy depends on intimate interaction with dentin surfaces. Once these varnishes act on dental surface, the assessment of surface microhardness and wettability can aid to check the ability of these materials to integrate with the dental tissues and determine the role on these outer layers directly exposed rather deeper surface.

Therefore, the aim of this study was to evaluate the performance of different resin-based varnishes on dentin challenged with simulated erosive protocols in distinct moments through surface microhardness (SM) and wettability (W) assessments. The null hypotheses tested were as follows: 1) there is no difference on dentin through surface microhardness and wettability assessments under the different conditions (sound, extrinsic eroded, and intrinsic eroded); 2) there is no difference on dentin through surface microhardness and wettability assessments treated with different materials (Duraphat, Gluma Desensitizer, PRG Barrier Coat); 3) there is no difference on dentin through surface microhardness and wettability assessments regarding the measurement time (initial, after product application and final).