Micro-Raman Spectroscopy Reveals Compositional Alterations in Molar Incisor Hypomineralization and Enamel Adjacent to Demarcated Opacities

Molar incisor hypomineralization (MIH) is a developmental condition that impairs enamel mineralization in the first permanent molars and often the permanent incisors. Clinically, MIH presents as demarcated opacities, ranging from white–yellow discolorations in mild cases to yellow–brown discolorations with enamel breakdown in severe cases. The longevity of direct adhesive restorations depends on reliable bonding to sound enamel, and current clinical practice involves removing visibly affected enamel and bonding adhesive restorations to apparently sound tissue. Accurately identifying healthy enamel is therefore crucial. Despite increasing recognition of MIH, there remains a gap in understanding its pathogenesis and the optimal treatment strategies needed to ensure long-term restorative success. The enamel adjacent to demarcated opacities has not been thoroughly investigated, raising a critical question: does visually translucent, seemingly intact enamel next to MIH opacities truly represent unaffected tissue? This work uses micro-Raman spectroscopy to determine whether chemical and structural alterations extend beyond the margins of demarcated opacities into adjacent translucent enamel. The findings indicate that MIH involves not only the visibly opaque enamel but also the adjacent translucent enamel, which shows increased fluorescence, lower mineral crystallinity, and elevated acid phosphate and carbonate content. These substitutions are consistent with a more soluble and porous apatite phase that is less chemically durable in the physiological environment. The adjacent translucent region consistently occupies an intermediate position between healthy controls and opacities, supporting its classification as affected tissue, and highlighting implications for adhesive strategies, margin placement, and preventive management of MIH-affected teeth.