Methodology and criteria in the evaluation of dental implants

A Review on Biomaterials for Orthopaedic Surgery and Traumatology: From Past to Present

The principal features essential for the success of an orthopaedic implant are its shape, dimensional accuracy, and adequate mechanical properties. Unlike other manufactured products, chemical stability and toxicity are of increased importance due to the need for biocompatibility over an implants life which could span several years. Thus, the combination of mechanical and biological properties determines the clinical usefulness of biomaterials in orthopaedic and musculoskeletal trauma surgery. Materials commonly used for these applications include stainless steel, cobalt-chromium and titanium alloys, ceramics, polyethylene, and poly(methyl methacrylate) (PMMA) bone cement. This study reviews the properties of commonly used materials and the advantages and disadvantages of each, with special emphasis on the sensitivity, toxicity, irritancy, and possible mutagenic and teratogenic capabilities. In addition, the production and final finishing processes of implants are discussed. Finally, potential directions for future implant development are discussed, with an emphasis on developing advanced personalised implants, according to a patient’s stature and physical requirements.

A biocompatible model for evaluation of the responses of rat periapical tissue to a new zinc oxide-eugenol sealer

We aimed to establish an experimental animal model to evaluate materials for endodontic therapy. We focused on the biocompatibility of new paste-type zinc oxide-eugenol (ZOE) sealer. The results of this sealer were compared with those of conventional powder/liquid ZOE and eugenol-free sealers. The molars of Wistar rats were extracted and repositioned in the original socket after application of the sealers on the root apices. Mild inflammation occurred in the periapical tissue of the replanted teeth with both ZOE sealers on day 7, whereas the eugenol-free sealer induced severe inflammation. On day 14, the lesions induced by all types of sealers were healed and replaced predominantly by fibrous connective tissue. Thus, all endodontic materials showed high biocompatibility, although the extent of inflammatory reactions during the early stages varied depending on the types of materials. We demonstrated that our animal model was useful for the assessment of the biocompatibility of endodontic materials.

A radiographic, histological, and histometric study of endodontic materials

Silicone tubes filled with CRCS, a calcium hydroxide-based cement, were implanted at two different localizations in the right tibias of white male Wistar rats. A similar number of solid silicone rods were implanted in the left tibias of the same animals and were used as inert controls. Fifteen days after implantation the bone tissue reactions to these materials were evaluated by means of radiographic, histological, and histometric methods. The radiographic and histometric analysis of the tissues around the deep end of the implants showed that the amount of reactional bone formation in contact with CRCS was significantly lower than that observed in contact with the controls (p less than 0.01). Also, the cell counts obtained from the tissues in contact with CRCS were significantly less than those obtained from the controls (p less than 0.01). This methodology appears to be a refined procedure for analyzing the possible toxic effects of endodontic materials in bone tissues. However, we feel that more extensive experiments will be necessary before predicting the long-term results which could be obtained from this experimental model.

Methodological assessments of subcutaneous implantation techniques

Results from 197 subcutaneous implants on rats and 40 on mice of three different dental biomaterials were studied with emphasis on methodological evaluations. The types of implants employed allowed a differentiation between the materials based on the tissue reactions induced, but the degree of response recorded depended on the technique and the animal employed. The main problems encountered were the effect of operative trauma in short-term experiments, loss of material/tissue interface, dislodgement of tearing of sections if the materials remained in situ, folding and distortion of tissue, and difficulties in orientation of specimens for sectioning. The tube implant supplied with a window and sectioned perpendicularly on the long axis of the tube gave the least methodological problems. This "window technique" is therefore recommended as the method of choice for subcutaneous implantations. Cell density evaluations allowed quantitative determinations of the cellular response.