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Morphological Observation of Collagen Fibers in the Dentin Hybird Layer after Treatment with Matrix Metalloproteinases Inhibitors

Author: LiHe
Tutor: ZhangZhiMin
School: Jilin University
Course: Stomatology
Keywords: chlorhexidine tetracycline dentin bonding collagen fibers durability
CLC: R783.3
Type: Master's thesis
Year: 2013
Downloads: 35
Quote: 0
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Bonding of prosthetic materials to enamel or dentine is a really fast developingdental defect repairing technology. Direct bonding prosthetic technology and bondingmaterials have been rapidly and constantly improving. This technology has beenwidely applied in the treatment of carious lesions, endodontics and restorative clinicaloperations. At present, total-etching technique has improved tooth enamel bondingeffects, but tooth dentin bonding has certain difficulties due to dentin tissue structureown particular characteristics and complexity of oral environment. Therefore, how tostrengthen the dentin bonding and improve its durability is a problem to be solvedurgently.In recent years, domestic and foreign scholars have been actively and deeplystudying ageing process of dentin bonding interface, trying to understand the factorswhich influence the ageing of dentin bonding interface, prevent the ageing processand improve the bonding effect. The studies include; the use of collagenolyticenzymes inhibitors, biomimetic remineralization, ethanol-wet bonding technique,hydrophobic bonding agents and antibacterial bonding agents, all geared to improvethe sealing of the dentin-adhesive interface and enhance the ability to preventdegradation over time, thus prolonging the service life of bonded materials to a certaindegree.In recent years, researches on the enzyme inhibitors have become more popular.Researches show that the matrix metalloproteinases (MMPs) released by matureodontoblasts cells and dental pulp tissue, are calcified in the form of original enzymesin the dentin structure. During dentin bonding process, the application of acid-etchingagent and bonding agent activates the host sources of MMPs, which mediate hybridlayer collagen degradation on the dentin bonding interface, participating in the breakdown of the bonding strength on the dentin bonding interface, and thus affectingthe bonding durability. The use of chlorhexidine, tetracycline and other MMPsinhibitors can delay dentin hybrid layer collagen degradation on the dentin bondinginterface and slow down the ageing of dentin bonding interface.The dentin hybrid layer(DHL)is formed at the bonding interface during dentinbonding process. DHL is a deciding factor of the bonding strength. TypeⅠcollagenfibers are the main components in the dentin matrix, etching dentin surface exposes anetwork of collagen fibers which constitute a framework of the DHL. The exposureand the degradation of the collagen fibers play a key role in the strength, durabilityand stability of the dentin bonding interface. The morphological changes of thecollagen fibers after the acid etching directly affect the dentin-restoration bond.This experiment used immune colloidal gold technique in which immune goldparticles are embedded on typeⅠcollagen fibers. Field Emission Scanning ElectronMicroscopy (FEISEM) was used to observe exposed collagen fibers on the surfaceof demineralized dentin. The study investigated condition of the DHL afterapplication of the dentin adhesives and observes exposed collagen fibers at the bottomof the DHL. A qualitative and semi-quantitative analysis and visual contrast researchwas also performed. Sodium hypochlorite solution (NaOCl) was used to inducedoptimum collagen degradation in vitro experiment to simulate the aging process. Thisstudy applied two kinds of MMPs inhibitors; chlorhexidine and tetracycline,comparatively evaluated the abilities of these two kinds of MMPs inhibitors to resistthe degradation of collagen fibrils in the hybrid layer and the ability to preventinterface ageing.The research employed available and intuitive analysis and experiments to studythe effects of MMPs inhibitors on the durability, stability and ageing process of thedentin-adhesive hybrid layer interface, perfecting important information pertaining tothe evaluation of the MMPs inhibitors’ effects on the dentin bonding.The main results were as follows:1. MMPs inhibitors pretreatment make dentine collagen fibrils after demineralization exposed more thoroughly, bulky. uniform staggered,orderly arrangement, and goodMorphology of collagen fibers make more resin infiltration into the dentin to stabilityhybrid layer during dentin bonding.2. MMPs inhibitors pretreatment make the hybrid layer of immediate dentinbonding more uniform and dense, and the adhesive layer has no obviousdemarcation with the hybrid layer,make the exposed collagen fibers at the bottom ofthe hybrid layer decrease and the weak area smaller, make collagen degradation atthe bottom of the hybrid layer decrease by the factors such as oral saliva and enzymes.3. MMPs inhibitors pretreatment protect the hybrid layer from NaOCl aging,andmake hybrid layer structure uniform and stability,slow down the aging effect onthe stability of the mixed layer and improve the durability of the dentin bonding.4. MMPs inhibitors pretreatment can decrease the collagenolysis of the collagen fibersby the artificial aging of NaOCl and make the etched collagen fibers moredimensional for resin infiltration, provide a good framework for the formation of thehybrid layer and enhances the stability of dentin bonding.Above all, chlorine, tetracycline, these two kinds of MMPs inhibitors aspretreatment agents used in the etched adhesive system, make the exposed collagenfibers after etching more dimensional for the bonding agent infiltration to make thehybrid layer more compact and slow down the artificial aging process simulated byNaOCl, perfect the MMPs inhibitor in the dentin adhesive application.

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CLC: > Medicine, health > Oral Sciences > Oral orthotics > Repair correction of dental defects
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