الفهرس 
INTRODUCTION AND REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
In the recent years, the average of cancer had increased for childhood especially head and neck cancer. Usually the treatment of cancer is using chemotherapy or combination of chemotherapy and radiotherapy. Using ionizing radiation in cancer treatment is useful but it causes damage in normal tissues located in the field of radiation. Even with the most optimal radiotherapeutic schedule, unwanted radiation-induced changes will occur in oral tissues. Growth retardation of the facial skeleton in children after irradiation affects mainly the skin, jaws, teeth and tissue oral tissue.
The aim of the present study was to evaluate the possible direct effects of different doses of gamma radiation on the dental tissue responsible for eruption. The study included numerical measurements of eruption rate, histological investigation using light microscope and spectral analysis using FTIR spectrometer. 105 Albino rats were used in this study. The rats were classified into 7 groups according to the following:
C1: Control group was kept away from the building of radiation facility.
C1: Control group was moved with the irradiated groups but kept outside the irradiation cell.
R1: irradiated with 0.5 Gy.
R2: irradiated with 1.0 Gy.
R3: irradiated with 2.0 Gy.
R4: irradiated with 4.0 Gy.
R5: irradiated with 6.0 Gy.
A reference point on the lower incisors of each rat was made by a diamond stone with a low speed motor under copious cooling. The eruption rate was measured every 3 days during the experiment period (15 days) so that there were five measures (3, 6, 9, 12 and 15 days). For histological examination and spectral analysis, three rats were scarified from each group after the eruption rate measurement.
The rats were killed by cervical dislocation and the lower mandible were dissected into two halves. One half of each mandible was identified and prepared for histological examination to apical region, ameloblasts, odontoblasts and periodontal ligament by decalcifying and staining it with Hematoxylin and Eosin (H & E), while the other half was prepared for FTIR analysis.
The numerical data were collected and analyzed for eruption rate showed that in control groups that the eruption rate was almost constant throughout the experiment period. By analyzing the mean of the eruption length in the studied periods (6, 9, 12 and 15 days) it was found that the eruption lengths were two, three, four and five times of the eruption length after 3 days, respectively, indicating a regularity of the rate of eruption and gamma radiation decreases the rate of eruption at doses of 4 Gy and more.
The histological examination showed that the apical cells distorted in the samples taken from animal irradiated with 4.0 Gy and atrophied in the samples taken from the animals irradiated with 6.0 Gy the ameloblasts most sensitive cells to radiation. The distortion appears in the ameloblasts in the sample taken from animals irradiated with 2.0 Gy and the distortion increase with increasing exposure. The periodontal ligament was affected in the samples collected from animals irradiated with 2.0 Gy and the intermediate plexus was not obvious. The periodontal ligament detached from the alveolar bone in the samples taken from animals irradiated with 4.0 and 6.0 Gy. The deleterious effects of radiation on the periodontal ligament encounter a delay in eruption. The odontoblasts appear distorted and separated from predentin in the samples taken from animals irradiated with 4.0 and 6.0 Gy.
FTIR spectroscopy could significantly differentiate between the used specimens indicating significant changes for symmetric and anti-symmetric phosphate vibrations, indicating a shift toward the higher content of DNA, the presence of H-bonds as an indication of the polypeptide chains assuming regular secondary structures of proteins and the CH group stretching, indicating vibrations of the CH2 and CH3 groups in acyl chains of lipids. This may throw light on the slowing of the eruption rate due to gamma irradiation and confirms the results obtained in case of the eruption rate measurement and histological analysis.
According to the obtained results, the teeth forming cells were affected by 2.0 Gy and the periodontal ligament were affected by 2.0 Gy. So the teeth must not expose to ionizing radiation reach to 2.0 Gy especially in the periods of eruption.