Predictors of Clinical Success in Resin Infiltration for MIH Opacities

<b>Background/Objectives</b>: Enamel defects in molar-incisor hypomineralization (MIH) have a multifactorial etiology involving environmental, systemic, and genetic factors. These alterations represent an aesthetic and emotional challenge, especially in anterior teeth. Resin infiltration has emerged as a minimally invasive treatment for MIH opacities, though outcome predictability remains limited. This study aims to analyze the baseline characteristics of MIH enamel defects and identify specific patterns that may predict clinical outcomes. <b>Methods</b>: This was a single-arm, prospective, observational clinical study with a six-month follow-up, with a total of 101 MIH-affected teeth treated with Icon^® resin infiltration. Opacities were analyzed using CIELAB color parameters (Lab*), including luminance, lesion extent, affected tooth type, opacity location, and patient age. Treatment success was assessed using simple linear regression models with generalized estimating equations, which were based on different covariates. Clinical success was defined as the combined achievement of a significant reduction in ΔE, a decrease in L* indicating reduced opacity brightness, and a reduction in the relative surface area of the lesion at six months. <b>Results</b>: White opacities showed greater reduction after infiltration than yellow and brown ones (<i>p</i> < 0.029). Larger lesions exhibited greater improvement (<i>p</i> < 0.007). Canines and lateral incisors achieved better masking (<i>p</i> < 0.001), and incisal opacities had superior outcomes (<i>p</i> < 0.019). Additionally, younger patients experienced a greater reduction (<i>p</i> < 0.026). <b>Conclusions</b>: Resin infiltration enhances the esthetics of anterior teeth with MIH in pediatric patients. While no single predictive pattern was identified, white opacities achieved greater luminance reduction and better integration with sound enamel. Factors such as age, tooth type, opacity location, lesion extent, and color significantly influence treatment effectiveness and esthetic perception.