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Introduction:With the fast development of nanotechnology and its wide application within the biomedical field, the toxic effect of nanomaterials has attracted numerous attention. Consequently, a crucial subfield termed nan-toxicology has emerged, which is mostly defined because the study of the interactions between nanomaterials and biological systems with a stress on identifying the link between the physicochemical parameters and therefore the occurrence of toxic effects. Aim: The aim was to study the possible toxic effect of intraperitoneal administration of gold nanoparticles on the periodontal ligament of albino rats and moreover the possibility of onemonth recovery period through hematoxylin and eosin stained sections for histological evaluation and transmission electron microscope for ultrastructural evaluation. Material and Methods: Forty-six male albino rats were employed in this investigation. They were divided into the subsequent groups: Group (1) (16 rats) served as controls, they received daily intraperitoneal injection of the solvent (deionized water 0.5 ml) for 21 days. Group (2) (15 rats) received 10mg/kg weight of AuNP solution intraperitoneally daily for 21 days. Group (3) (15 rats) were treated the identical way as Group 2 for 21 days and so left for one-month as a recovery period. The experiment lasted for 21 days for group 2 then the rats were euthanized by cervical dislocation. While the rats of group 3 were euthanized by cervical dislocation after 1 month of treatment stoppage with gold nanoparticles for recovery period; their lower jaws of each rat were dissected out, separated into two halves, the right halves were used for structural examination while the left halves were used for ultrastructural examination. Results: Examination of the PDL obtained from the group II animals showed marked dissociation and degeneration of collagen fiber bundles. The examined fibers of the rats which were allowed a recovery period showed improvement within the condition of structure and ultrasturctural features of the fibers and cells of PDL. Conclusion: Our data suggest that AuNPs exert detrimental effects on cell structure and ultrastructure consequently cell function that would reverse following AuNPs removal.