Molar-incisor hypomineralization (MIH) is a qualitative defect of dental enamel, in which low mineral content and high protein content compromise the effectiveness of remineralizing treatments. Various agents have been used to remove proteins from hypomineralized enamel, such as sodium hypochlorite (NaOCl). Sodium hypochlorite is an antimicrobial irrigant capable of dissolving tissues. The amorphous calcium fluoride casein phosphate phosphopeptide (CPP-ACPF) is used as a remineralizing agent for MIH lesions, it is capable of stabilizing calcium, phosphate, and fluoride ions on the tooth surface, maintaining them in an amorphous form. Therefore, the objective of this study is to evaluate the clinical performance of CPP-ACPF dental mousse on deproteinized hypomineralized enamel.

MIH is characterized by a marked opacity, asymmetrically involving the first permanent molars and incisors. In more severe cases of MIH, in addition to the retention of matrix proteins that should have been removed during the enamel maturation process, its more porous structure allows the penetration of proteins present in saliva, which bind to the poorly developed hydroxyapatite crystals. The high protein content of enamel with MIH also promotes the growth of proteolytic bacteria, posing a challenge for the adhesion of restorative materials and treatments for hypersensitivity. Some products containing CPP-ACPF have been used in children with MIH, it can stabilize calcium, phosphate, and fluoride ions on the tooth surface. Given that MIH lesions have a high protein content that may prevent the mineralizing agent from reaching the underdeveloped enamel prisms, it is expected that treatment with CPP-ACPF will be more effective following prior deproteinization of the affected enamel. A double-blind, split-mouth, randomized clinical trial will be conducted. The teeth included in the study will be permanent upper or lower molars with MIH in children aged 7 to 9 years. Two properly calibrated examiners will select the participants, and the diagnosis of MIH lesions will be based on the criteria of the European Association of Paediatric Dentistry (EAPD). The inclusion criteria will be: one permanent molar without MIH; at least two permanent molars with mild MIH lesions (demarcated opacities without structural loss), with or without sensitivity, of a cream-white or yellowish color, and 2 mm in diameter; and without visible bacterial biofilm. The selected teeth from each participant will be divided into 3 groups: Control Group (molars without hypomineralization); CPP-ACPF Group (hypomineralized molars treated with CPP-ACPF); and NaOCl/CPP-ACPF Group (hypomineralized molars deproteinized with 5.25% NaOCl, with application time based on laboratory study findings, and treated with CPP-ACPF). The randomization of treatments for hypomineralized teeth will be performed at the time of treatment. The following data collection tools will be used: a questionnaire to collect demographic and socioeconomic information, as well as information on etiological factors for MIH; clinical examination to assess the following aspects of the lesions: location (occlusal or middle third), lesion area (in mm²), color (cream-white or yellowish), visual appearance (shiny or opaque), sensitivity, and lightness of the lesion color (L). The tooth's L will be measured three times to obtain the average of the values. The data will be analyzed descriptively and inferentially. Clinical analyses will include intragroup comparisons (between follow-up times) and intergroup comparisons (between group outcomes), at a 5% significance level.

Inclusion Criteria:

• Children with at least one permanent molar without MIH.
• At least two permanent molars with mild MIH lesions (demarcated opacities without structural loss)
• Lesions may be with or without sensitivity
• Lesions cream-white or yellowish in color
• Lesions ≥ 2 mm in diameter
• Lesions may be on the same or different dental arches

Exclusion Criteria:

• Visible bacterial biofilm
• Enamel malformations associated with syndromes
• Amelogenesis imperfecta
• Fluorosis
• Allergy to milk proteins (casein)