EFFECT OF NANO HYDROXYAPATITE ON NORMAL AND GAMMA IRRADIATED HUMAN ENAMEL SURFACE AFTER ORTHODONTIC TREATMENT (SEM STUDY)

Objectives: To evaluate the effect of Nano-Hydroxyapatite gel on the remineralization of normal and gamma irradiated human enamel surface before orthodontic bracket bonding and after brackets debonding, using scanning electron microscope. Methods: A total number of sixty extracted sound human premolars teeth were collected. The sample was divided into two equal groups according to exposure to radiation: Group 1: Irradiated Enamel, Group 2: Non-Irradiated Enamel. Each group was further divided into three subgroups; subgroup i, application of Nano-hydroxyapatite before bonding of orthodontic brackets, subgroup ii, application of Nano-hydroxyapatite after debonding of orthodontic brackets and subgroup iii: no application (control group). Results: SEM of normal enamel surface revealed masking of the prismatic structure by a layer of partially adsorbed Nanohydroxyapatite crystals. Hydroxyapatite crystals microclusters of variables sizes adhered to the enamel surface. Irradiated enamel revealed a spattered deposit showing focal micro pits denoting the adherence of nanocrystals to the pores created by radiation. Nano-hydroxyapatite application after orthodontic bracket debonding of normal Enamel showed areas with maintained prismatic structure alternating with areas showing damaged enamel micro-surface. Higher magnifications revealed confluence of the prismatic and inter-prismatic structures and surface irregularities. Conclusions: Nano-hydroxyapatite helped maintenance of the prismatic structure after orthodontic brackets debonding. Partially repaired enamel surface and microstructural alterations were observed in irradiated Nano-hydroxyapatite treated teeth. Application of Nano-hydroxyapatite before bonding of orthodontic brackets helps preservation of enamel structure.