ABSTRACT
Statement of Problem: Laser irradiation makes structural and chemical changes on the dental hard tissues. These changes alter the level of solubility and permeability of dentin
Purpose: The aim of this study was to compare the microhardness and the structural changes in the dentin cavity floor prepared with Er: YAG laser and bur
Material and Methods: In this experimental study, fifteen intact human molars were selected. Two square cavities were prepared on the buccal and lingual surfaces of each tooth. One side was randomly prepared by Er:YAG laser and the other side by bur
The specimens were divided into two halves. Consequently, there were 30 samples in every group. One half was assigned for the Vickers's hardness test and the other one, for determination of Ca and P percentage and atomic elements analysis. The data were analyzed by Paired T-tests through SPSS16 [ alpha
Results: The means and the standard deviation of the microhardness were 69.77+/-25.62 and 51.33+/-9.31 Kg/mm2 in the laser and bur groups, respectively. Statistical analysis showed significant differences between the two groups [p=0.017]. Weight percentage of calcium in the laser cavity [65.5] was less than the bur cavities [68.21] and the difference was significant [p= 0.037]
Conclusion: The hardness of dentin in laser group was higher than the bur group because of the higher mineral content of the dentin. The hardness and the mineral content of dentin are important factors in the bonding effectiveness of the dental materials so with laser cavity preparation, good mineral substrate are available for a better bonding
ABSTRACT
Obestatin is a gastrointestinal-peptide hormone which influences glucose and lipid metabolism, body weight and energy homeostasis. Very little is known about the association between gut peptides and thyroid diseases. The aim of the present study was to investigate the association between serum concentrations of obestatin and thyroid function in subclinical hypothyroid and hyperthyroid subjects. This study was performed on 35 hypothyroid, 35 hyperthyroid and 35 euthyroid subjects [controls] who referred to the Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences. In all participants, serum levels of obestatin, TSH, FT3, FT4, insulin, glucose as well as BMI were assessed. Serum obestatin, FT3, FT4 and TSH were measured by ELISA, Electrochemiluminescence immunoassay [ECLIA] and Immunoradiometric assay [IRMA], respectively. Data were analyzed by T-test, One-Way ANOVA and Pearson correlation using SPSS 16. Serum concentrations of obestatin in both hypothyroidism and hyperthyroidism [0.04 +/- 0.01 and 0.05 +/- 0.02 ng/ml respectively] were significantly lower than in the control group [0.09 +/- 0.01 ng/ml], [P-value<0.001]. No significant correlations were observed between serum levels of obestatin and FT3, FT4, and TSH. Our results indicated obestatin concentrations were significantly associated with thyroid function