The present work aims at studying the effect of gamma radiation on the hard dental tissues. Eighty adult male albino rats with weights of about 250 g were used. The rats were irradiated at 0.2, 0.5, 1.0, 2.0, 4.0 and 6.0 Gy whole-body gamma doses. The effects on hard dental tissue samples were investigated after 48 h in histological and ground sections using light microscopy. Areas of acid phosphatase activity were detected using tartrate-resistant acid phosphatase (TRAP) stains. Observation of histological sections revealed disturbance in predentin thickness and odontoblastic layer as the irradiation dose increased. In cementum, widened cementocytes lacunae were occasionally detected even with low irradiated doses. On the other hand, relatively homogenous enamel was detected with darkened areas in enamel surface at doses over than 0.5 Gy. TRAP-positive cells were detected on the surface of the dentin of irradiated groups as well as cementum surface. Minimal detectable changes were observed in ground sections.

In the present study, 40 adult male albino rats were used to study the effect of gamma radiation on the hard dental tissues (enamel surface, dentinal tubules and the cementum surface). The rats were irradiated at 0.2, 0.5, 1.0, 2.0, 4.0 and 6.0 Gy gamma doses. The effects of irradiated hard dental tissues samples were investigated using a scanning electron microscope. For doses up to 0.5 Gy, there was no evidence of the existence of cracks on the enamel surface. With 1 Gy irradiation dose, cracks were clearly observed with localized erosive areas. At 2 Gy irradiation dose, the enamel showed morphological alterations as disturbed prismatic and interprismatic areas. An increase in dentinal tubules diameter and a contemporary inter-tubular dentine volume decrease were observed with higher irradiation dose. Concerning cementum, low doses, <0.5 Gy, showed surface irregularities and with increase in the irradiation dose to ≥1 Gy, noticeable surface irregularities and erosive areas with decrease in Sharpey's fiber sites were observed. These observations could shed light on the hazardous effects of irradiation fields to the functioning of the human teeth.

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Background: Enamel is regularly subjected to demineralization and remineralization under different oral circumstances. Any interruption in the balance between demineralization and remineralization can initiate the formation of incipient caries lesions. However, in the early stage of formation these lesions can be remineralizedusing various preventive measures. Topical fluorides have shown positive results in the prevention of caries in several studies. The aim of this study was to determine the effects of combination between diode laser and topical fluoride application on the surface microhardness of the demineralized enamel. Materials and Methods: Four caries-free human premolars were examined under the stereomicroscope to exclude teeth with surface enamel defects. Buccal enamel surface microhardness (SMH) for all samples was measured by Micro Vickers Hardness Tester (MVHT). The samples were demineralized by 15% Hydrochloric acid (HCl) with PH average 4.5, then the SMH was measured. The demineralized teeth were subjected to fluoride toothpaste after diode laser application. Third evaluation for enamel SMH was performed after remineralization. Results: Enamel SMH of the control group has shown the highest values followed by the remineralization group while the least values were measured in the demineralization group. Conclusions: The results obtained in the study lead to the conclusion that application of fluoride toothpaste after diode laser could enhance the remineralization potential of the demineralized enamel.

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