Abstract
Hypoplastic amelogenesis imperfecta is a widespread hereditary disease that causes the loss of enamel. The purpose of this study was to investigate the nanoscratch resistance of hypoplastic amelogenesis imperfecta for providing a reference for restorative treatment. Four unerupted third molars from a patient diagnosed with hypoplastic amelogenesis imperfecta and seven unerupted third molars from normal individuals were compared. Atomic force microscopy and energy-dispersive X-ray spectroscopy were used to observe the microstructure and composition of the teeth (enamel and dentin). The nanoscratch tests of teeth (enamel and dentin) were investigated using a nanoscratch tester, scanning electron microscopy, and a stylus profilometer. The results indicated that hypoplastic amelogenesis imperfecta teeth had different microstructures compared to normal teeth. Hypoplastic amelogenesis imperfecta demonstrated a higher composition of organic substance. Meanwhile, the friction coefficient of hypoplastic amelogenesis imperfecta was higher than that of normal teeth, and inferior frictional resistance of hypoplastic amelogenesis imperfecta teeth was observed. The main damaging mechanisms observed in hypoplastic amelogenesis imperfecta under nanoscratch were the combination of delamination, debris, and cracks in enamel with delamination, debris, and plastic deformation in dentin. Our findings suggested that new dental restorative materials should be selected to match the mechanical properties of hypoplastic amelogenesis imperfecta.
Highlights
Amelogenesis imperfecta (AI) is a multiple group of hereditary diseases that affects the enamel of teeth and reduces enamel thickness or decreases mineralization.[1,2] the exact global incidence of this disease is uncertain, it is estimated that from 1 in 2000 up to 1 in 18,000 people are affected by it.[3,4] AI may be differentiated into three main groups: hypoplastic, hypocalcified, and hypomature based on clinical presentation of defects.[5]
The surface microhardness (SMH) decreased by 10.9% and 9.8% in the enamel and dentin, respectively
Obvious crystals in uniform grain size and some randomly distributed dentin tubules can be seen in normal dentin
Summary
Amelogenesis imperfecta (AI) is a multiple group of hereditary diseases that affects the enamel of teeth and reduces enamel thickness or decreases mineralization.[1,2] the exact global incidence of this disease is uncertain, it is estimated that from 1 in 2000 up to 1 in 18,000 people are affected by it.[3,4] AI may be differentiated into three main groups: hypoplastic, hypocalcified, and hypomature based on clinical presentation of defects.[5]. The restoration materials, applied consistently with the mechanical properties and tribological characteristics of hypoplastic AI, can protect existing teeth and prolong the life of the prosthesis.[10,11] Many previous studies presented the mechanical behaviors of enamel related to enamel’s microstructures.[12,13] Significant microstructural differences have been found between hypoplastic AI and normal enamel. A mineralized structure, can support the enamel and prevent the enamel from fracture,[17] and in many cases of AI, dentin is frequently exposed to oral environment after the loss of enamel.[6] observing the microstructure and mechanical properties of dentin is essential. This study aims to observe the nanoscratch resistance of hypoplastic AI teeth (enamel and dentin) in terms of microstructure and composition by AFM, energy-dispersive X-ray spectroscopy (EDX) and nanoscratch tester
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