| Along with the population aging, the complete denture wearers will increase. Poor retention and stability is a commonly clinical problem for those patients with poor denture bearing tissues. Implant restoration is a good choice, however many patients can not accept it because of its high cost, complicated operation, or other reasons. It is common to use denture adhesives (DA) to enhance complete denture retention and stability abroad. But the the domestic research and application of DA lags and there is no good DA product made by China.The active ingredients of modern commercially available DA commonly contain carboxymethylcellulose (CMC) and polymethyl vinyl ether-maleic anhydride (PVM-MA). CMC quickly dissolves due to its high level of solubility and provide a strong initial hold. However, there are still the problems of insufficient bonding strength and duration of action. To improve the performance of it, manufacturers introduced the products that contain PVM-MA zinc salts. However, some recent reports suggested that the chronic excessive use of zinc-containing adhesives might result in hypocupraemia and serious neurological disease.Low-substituted hydroxypropyl cellulose (L-HPC) is a low-substituted hydroxyp-yl ether of cellulose which is insoluble in water but it swells and becomes sticky in water. The aim of this study was to develop a new denture adhesive containing three synthetic polymers with different degrees of solubility in water, i.e, CMC, PVM-MA and L-HPC.This research includes the following three parts.1. Development and performance tests of denture adhesive.Three synthetic polymers with different degrees of solubility in water were selected as the active ingredients of experimental DA, i.e, CMC, PVM-MA and L-HPC. The formulas were screened by using an orthogonal experimental design to obtain a new DA with the optimum physical and chemical properties. The bonding strength, flowability, pH value, pH stability and cleaning performance of new denture adhesive were evaluated according to ISO-10873-2010standard and compared with that of one commercial denture adhesive (Protefix cream, Germany). The results showed that the DA containing L-HPC developed by this study has better adhesive performance than the Protefix. The pH test showed that it was nearly neutral and has pH stability. In addition, it is easy to clean.2. Biological evaluation of the developed denture adhesive.The biological safety of the developed denture adhesive was evaluated according to ISO10993, GB/T16886and YY/T standards. The following tests were included:in vitro cytotoxicity test, short-term systemic toxicity test, oral mucous membrane irritation test and skin sensitization test. The results exhibited that the tested denture adhesive has no cytotoxic effects on the primary human oral fibroblasts and L929cells, whereas has slight cytotoxicity to the primary human oral keratinocytes. The denture adhesives tested has no short-term systemic toxicity, oral mucous irritation and sensitization. It meets the requirements of the relevant standards of biological materials.3. Preliminary clinical evaluation of the developed denture adhesive.On the basis of the pre-trial, the newly developed DA was applied to ten complete denture wearers and the questionnaires were filled out. The results showed that most of the patients think the adhesive cream can improve the denture retention, stability and masticatory ability and the duration of action can last about12～16h. Additionally, it could effectively eliminate or diminish the food impaction. Finally, it was easy to remove from the dentures and oral mucosa.In conclusion, the developed DA exhibited good physical and chemical properties and biological compatibility. The good clinical effectiveness was also showed in the preliminary clinical study. However, the long-term safety and clinical effectiveness of it need to be further verified. |
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