A Comparative Study on Micro Hardness and Structural Changes of Dentin Floor Cavity Prepared by Er: YAG Laser Irradiation and Mechanical Bur.
BACKGROUND
Laser irradiation makes structural and chemical changes on the dental hard tissues. These changes alter the level of solubility and permeability of dentin.


OBJECTIVE
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.


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 (α≤o.o5).


RESULTS
The means and the standard deviation of the microhardness were 69.77±25.62 and 51.33±9.31 Kg/mm(2) 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).


CONCLUSIONS
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.
Dental Materials Research Center, Dept. of Operative Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
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Arbabzadeh
Dental Student, Faculty of Dentistry, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
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Birang
Torabinejad Dental Research Center, Dept. of Operative Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
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Nazem
Dentist, School of Dentistry, Isfahan University of Medical Science, Isfahan, Iran.
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Abbasian
Dental Student Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
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Koosha
Dental Implant Research Center, Dept. of Periodontics, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
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Birang
Bur; Er: YAG laser; Microhardness; Vickers Hardness Test