## 1 Introduction  
Dental enamel is a highly mineralized acellular connective tissue formed by specialized cells known as ameloblasts. It is composed largely of hydroxyapatite (98%), with some organic components and water (2%) [1]. Developmental defects in enamel may be due to genetic mutations [2], environmental alterations, infection, medication, radiation, or trauma [3, 4]. When the composition of dental enamel undergoes a reduction in hydroxyapatite, an increase in organic components that cause dental discoloration appear, which are commonly known as 'white spots' [5]. These are characterized by an intact exterior surface and a deeper demineralized area [6]. The spots are perceived by the human eye as opaque white-colored lesions due to refraction of the light that falls on the demineralized areas that have a refractive index (RI) lower than that of healthy enamel (RI = 1.62-1.65), similar to air or water (RI = 1.00-1.33) [7]. Emanuel defects occur as a result of damage occurring either before or after an eruption in the affected tooth [8, 9]. Pre-eruptive lesions are considered to derive from dental fluorosis, dental treatments, or from cases of molar incisor hypomineralization (MIH) [5, 10, 11]. Post-eruptive lesions, also known as white spot lesions (WSLs), are white spots that appear after orthodontic treatment. The prevalence of these spots is 24%, or anywhere between 50% and 97% following treatment with orthodontic multibrackets and multibands, which mainly affect the gingival third of the vestibular faces of the maxillary incisors [12; 13; 14; 15]. Various techniques have been established to improve the esthetics of these enamel surface lesions [16]. In recent years, tooth whitening has become a widely used technique as it is safe, economically feasible, and minimally invasive. It eliminates internal and external discolorations from teeth and camouflages white spots on the surface by increasing the general luminosity of the affected tooth [17; 18]. Another option is remineralization with fluoride or casein phosphopeptide, which can also produce good results when restoring the surface layers of caries lesions. However, clinical trials have not reported any cosmetic improvements, since the white spots tend to persist long term [19; 20]. It is also considered to be a rather unpredictable treatment that requires prompt application and patient collaboration [21; 22; 23; 24]. Lastly, microabrasion with 6.6% hydrochloric acid (HCl)-based products is an effective treatment for white spots that involves the removal of the affected adamantine tissue [16; 25; 26; 27; 28; 29; 30; 31; 32]. Erosion using 15% HCl-based products and subsequent infiltration of the intercrystalline spaces with low viscosity resin without milling the affected surface is a minimally invasive treatment that camouflages white spots, since the infiltration resin has a similar refractive index (I.R: 1.52) to hydroxyapatite. The refraction of light falling on the resin makes the human eye perceive the tooth color as unaltered in white spot areas [33; 34; 35; 36; 37]. As the HCl-based products used in this technique work through the erosion of the enamel, the site of application to the tooth's vestibular surface should be considered carefully in relation to the product's erosive capacity. In this context, [PERSON] et al. [38] found that in the crown's middle third, within an interval of 3-5 mm from the cemento-enamel junction, the enamel has a thickness of 0.54-0.75 mm to the dentin. According to the manufacturer's instructions, the etching time for 15% HCl is two minutes. If the white spots persist, etching can be repeated twice more, making a total etching time of six minutes; however, repeated etching on the enamel surface will cause a greater breakdown of enamel prisms. For this reason, it is important to quantify the capacity for eliminating the products used and ensure that they do not reach the dentin-enamel interface in order to avoid problems derived from HCl infiltration into the dentin tubules.