| As a very important dental material, metals are widely used in completeand removable partial dentures. Owing to the complicated microbial andacid-base circumstances in oral cavity, the surfaces of dental metal materialsmay suffer corrosion, discoloration and bacterial adhesion. These phenomenamay not only affect the appearance and useful life of dentures but also lead tosome denture-induced adverse effects and complications which will severelythreaten the health of human body. Therefore, it is very significant to find aneffective method of surface treatment to improve the surface properties of dentalmetal materials. In this study, nanometer amorphous diamond films researchedand developed by Xi’an Jiaotong University were applied to the surfacetreatment of dental Co-Cr alloys and pure Ti. The aims of this study were to finda new method to improve the surface properties of dental metal materials andprovide the theoretical and experimental bases for the clinical applications ofnanometer amorphous diamond films. In this study, a filtered cathodic vacuum arc (FCVA) system was used toprepare nanometer amorphous diamond films on dental Co-Cr alloys and pureTi. Then, scanning electronic microscopy (SEM), Atomic force microscopy(AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) wereused to analyze some characteristics of the coatings including the surfacemorphology, microstructure, elemental composition and the chemical bindingstates, and simultaneously the effects of substrate bias voltage on sp3fraction ofthe coatings were investigated. The biocompatibility of the deposited nanometeramorphous diamond films was investigated through in vitro cytotoxicity test andoral mucous membrane irritation test. Using the method of scratch test, thecritical loads of the films deposited at different substrate bias voltages and underthe conditions of Ti and TiN interlayer pretreatment were measured to researchthe effects of substrate bias voltages and interlayer pretreatment on adhesionstrength of nanometer amorphous diamond films. A portable surface roughnesstester and a drop shape analysis system were used to measure respectively theroughness and static contact angle of the coated and uncoated surfaces of Co-Cralloys and pure Ti, and the surface free energy was calculated then. Bycomparing the adhesion of Streptococcus mutans, Actinomyces viscosus andCandida albicans to the coated surfaces with that to the uncoated ones, weinvestigated the effects of nanometer amorphous diamond films deposited ondental Co-Cr alloys and pure Ti on bacterial adhesion. The main results of thisstudy were listed as the following.1. The films deposited on the surfaces of dental Co-Cr alloys and pure Tiby the FCVA system had a nano-sized thickness and were composed of sp2andsp3bonded carbon atoms. Over70%of the carbon atoms in the films are sp3bonded. These results indicated that the deposited films came up to thequalitative standards of nanometer amorphous diamond films. With theincreased substrate bias voltages, the changes of sp3fraction in the films deposited on Co-Cr alloys and pure Ti presented a first increasing and thendecreasing tendency. The maximum sp3fraction in the films deposited on Co-Cralloys and pure Ti was obtained respectively at200v and250v.2. The cell relative growth rate of nanometer amorphous diamond filmswas over90%and their graduations of cytotoxicity were0or1, which means nocytotoxicity. In addition, their mucosal stimulation index was0, which means nostimulation. Therefore, nanometer amorphous diamond films had verysatisfactory biocompatibility.3. With the increased substrate bias voltages, the changes of adhesionstrength of nanometer amorphous diamond films to Co-Cr alloys and pure Tipresented a first increasing and then decreasing tendency. The optimal adhesionstrength of the films to Co-Cr alloys and pure Ti was obtained respectively at200v and250v. Ti and TiN interlayer pretreatment could significantly increasethe adhesion strength of nanometer amorphous diamond films to Co-Cr alloysand pure Ti. The optimal interlayer pretreatment on the substrate of Co-Cr alloysand pure Ti was Ti and TiN interlayer respectively.4. After the surface treatment of nanometer amorphous diamond films, thesurface roughness of Co-Cr alloys and pure Ti significantly decreased. Inaddition, the films could significantly increase the surface free energy of Co-Cralloys but had no significant effects on that of pure Ti. Most importantly, afterthe coating surface treatment, the adhesion of Streptococcus mutans,Actinomyces viscosus and Candida albicans to Co-Cr alloys and pure Ti wassignificantly decreased. This result showed that nanometer amorphous diamondfilm surface treatment on dental Co-Cr alloys and pure Ti could significantlyreduce the bacterial adhesion. |
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