RESUMO
Objectives: The aim of the present investigation was to study the effects of NaOCl and glutaraldehyde pretreatment on surface topography of denting and microtensile bond of resin-based composite to dentin
Materials and methods: For SEM examination, a three-millimeter thick dentin discs from the middle third of the crowns of 30 human first molar teeth were obtained. The samples were divided into three group [n=10], relative to the pretreatment utilized i.e., washing only, 2.5% NaOCl or 2% glutaraldehyde. Each group was further subdivided into two subgroups [n=5], relative to the washing used i.e., water or ethanol. Pretreated dentin surfaces were subjected to SEM examination. For microtensile bond strength test, the occlusal surfaces of 30 human first molar teeth were ground flat to the middle third of the crowns. The samples were divided according to the grouping system mentioned before and then bonded with the ethanol based Excite adhesive and restored with the Tetric-ceram hybrid dental composite cores. All samples were sectioned to 1mm[2] sticks and subjected to microtensile bon strength test
Results: SEM results revealed, regardless the washing material used, 2% glutaraldehyde pretreatment of dentin had minimal effects on smear layer removal but it resulted in raising of the collagen fibers at orifices of the dentinal tubules. 2.5% NaOCl pretreatment resulted in complete removal of the smear layer, blugs and collagen fibers at the dentinal tubule orifices. Statistical analysis of the microtensile bond strength values revealed that both pretreatment materials improved the bond strength to dentin, with significant values when water washing was used. Ethanol washing showed significant improvement in the bond strength among all the tested groups
Conclusions: Under the conditions of the present investigation the following conclusions were evident: Washing of cavities with ethanol before acid-etching, although does not affect the dentin surface topography, will enhance sealing and bonding of ethanol based adhesive systems to tooth structures. Pretreatment of dentin with 2% glutaraldehyde, is a promising approach for cavity disinfection, improvement of sealability of restorations and dentin desensitization. Pretreatment of dentin with 2% glutaraldehyde followed by washing with ethanol will enhance excellent sealing. Regarding to its effects on the surface topography of dentin and surface tension of fluids, 2.5% NaOCl application may be considered a new approach to dentin conditioning. In deep cavities, the surface topographic changes found with 2.5% NaOcl pretreatment, although improve bonding to dentin, when followed by acid-etching may invite chemicals used in adhesion steps and restoration to the dental pulp
RESUMO
Nitric oxide [NO] produced by NO synthase [N O S] is considered a factor for vascular and immune system control, and it is increased according to mechanical stimuli. This study was aimed to examine the expression of Nitric oxide synthase in the periodontal ligament and alveolar bone surrounding the nonfunctional and hyperfunctional teeth. Twenty five rabbits used in this study were classified as five rabbits for teeth in normal occlusion, ten rabbits with nonfunctional right lower first molar by grinding the opposing teeth and ten rabbits with right lower first molar in trauma from occlusion by bonding 0.5 mm3 of light - cured composite. After two weeks all animals were sacrificed, the specimens were taken and prepared for immunohistochemical staining of N O S. the quantitative evaluations of the immune reactions were performed by digital image analysis. The result of this study had revealed that the N O S more detectable in the blood vessels, periodontal ligament and bone cells surrounding teeth subjected to trauma from occlusion followed by teeth in normal occlusion but less detectable surrounding nonfunctional teeth. So we conclude that Nitrous Oxide mediator which synthesized from L-arginine in process catalyzed by nitric oxide synthase may play an important regulatory role blood vessels expansion and as mediator of mechanical stress maintaining the integrity of periodontal tissue under physiological conditions