The Research Of Influence Produced By Beryllium Ions From Dental Restoration Material-Nickel-Chromium Alloys On Subgingival Microbes

Metal material or material containing metal is usually used in restoration when the tooth is damaged or lost.Non-noble metal material has been widely used in dental clinical restoration, for its favorable mechanical properties and low cost. As the crown or fixed bridge retainer,the restoration margin is always sited in subgingiva. But in clinic, hyperplasia and swelling of the gingiva around the cervical part of the prosthesis are usually occurred. Accompanying with it, gingival fluid increases and gingival indexes elevate. Although a lot of scholars have brought forward different kinds of possible mechanisms to explain these phenomena, there is still no convincing proof provided. Nickel-chromium alloy is one kind of non-noble metal material,which is widely used in crowns and bridges restoration .Beryllium( < 2%) is added to some nickel-chromium alloys,for the purpose of that: reducing melting point for easily casting;enhancing the bond to composite resin;promoting non-noble crystal more finer.In oral warm and moisture circumstance,alloy is easily to be eroded to release metal ions.The anti-corrosive ability of nickel-chromium alloy with beryllium is significantly weaker than that without it. Beryllium is mainly limited in the surface layer of the alloy cast and composes 30% of that. As a result, beryllium(II) ion is one of the main releasing elements. The former researches about restoration material mainly focuse on influence of mechanical and physical properties on biotoxicity to tissue and organ in oral,but reaserch about influence of ions released from dental alloy on periodontal microorganism is few. This research aims to examine the influences produced by Beryllium (II) ions on the growth and metabolisms of Streptococcus oralis (S.oralis) and Porphyromonas gingivalis (P. gingivalis). And futher analysis of the molecular mechanisms of these changes in order to illuminate the reasons for post-prosthodontic damage in periodontal tissues is needed.