Effect of Reinforcement by Nano-Zirconia on the Supporting Structures and Fracture Resistance of Lower Overdenture Implant Supported Denture Base

Abstract

Twenty completely edentulous patients shared in this study. They were cautiously selected to avoid factors that may adversely affect the results of the study. Conventional complete dentures were constructed following standardized clinical and laboratory prosthodontic procedures and the dentures were delivered to the patients. According to the material of construction of the planned lower implant retained overdentures, patients were equally and randomly divided into two groups. Group I, patients received upper conventional acrylic resin complete dentures and lower mini implants retained overdentures. While Group II patients received upper conventional acrylic resin complete dentures and lower mini implant retained overdentures reinforced with 5% by weight nano zirconium oxide powder. Four mini dental implants were inserted for each patient following the flapless technique in the intraforaminal region of the mandible by the aid of a surgical guide. Lower complete dentures were modified after mini implants placement to incorporate implant metal housings in order to properly seat over the osseointegrated mini implants. Digital panoramic radiographs were made for all patients to ensure mini implant osseointegration and to assess marginal bone height before implant loading. Patients were followed up six and twelve months after loading, digital panoramic radiographs were made to follow up changes in marginal bone height level during the study period. Data for bone loss were collected, and statistically analyzed. Mandibular overdentures were collected from all patients one year after delivery. New duplicate dentures were delivered to patients to compensate for the collected research dentures. The collected overdentures were tested for fracture resistance. Load was applied by the Universal Testing Machine till denture fracture occurred. These loads were recorded and tabulated for statistical analysis. The results obtained from this study revealed insignificant difference in peri-implant bone height loss of mini implants retaining nano zirconium oxide reinforced acrylic overdenture bases, compared to unreinforced acrylic mini implant retained overdenture bases. The results also revealed statistically significant increase in fracture resistance of nano zirconium oxide reinforced acrylic overdenture bases compared to unreinforced acrylic overdenture bases. However, more studies are recommended to assess different biological effects on the supporting tissues.