Microstructures and mechanical characteristics of primary teeth affected by regional odontodysplasia

Abstract

Regional odontodysplasia (ROD) is a rare, localized disorder of tooth hard tissues that can affect primary and permanent dentitions. However, its definitive etiology remains unclear and only a few studies have reported the detailed microstructures and mechanical characteristics of the affected teeth. Objective: This study investigates the microstructural and mechanical characteristics of primary teeth affected by ROD. Methodology: A total of two ROD-affected primary teeth from two different cases underwent clinical examinations. In addition to control samples of caries-free retained primary teeth, the affected samples were examined using micro-computed tomography (micro-CT), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and nanoindentation analysis. Results: Clinical findings revealed yellowish discoloration, rough surfaces, and root resorption on the affected teeth. Radiographs indicated hypocalcified enamel, widened pulp chambers, and delayed development of permanent teeth. Micro-CT showed affected teeth with thinner and uneven enamel, disordered dentin, and reduced mineral density. XRD analysis found reduced crystallinity. SEM and TEM analyses revealed hypoplastic and loosely packed enamel crystals, whereas dentin exhibited disorganized collagen fibrils and poorly mineralized crystals. EDS analysis showed a reduced calcium/phosphorus ratio and an increased magnesium/calcium ratio in the affected enamel. Nanoindentation tests found reduced hardness and elastic modulus in ROD-affected enamel compared with control teeth. Conclusion: ROD-affected primary teeth display significant microstructural abnormalities and compromised mechanical properties, underscoring the need for early intervention and long-term monitoring to prevent complications.