Corrosion Behavior Of Intraoral Fluoride Controlled-release Device To Chromium-cobalt Castings

Objective: The intraoral fluoride controlled-release device(IFRD) is a small fluoride controlled-release delivery system designed to prevent dental caries. The purpose of this study was to investigate the corrosion behavior of IFRD to chromium-cobalt castings and the safety use in removable partial dentures.Methods: Some pieces of IFRD were made by using HEM A, MMA, NaF and tubanone and 24 chromium-cobalt casting samples were cast. The samples were polished and divided into four groups randomly, then they were immersed into 20ml artificial saliva. Except for in group A, two pieces of IFRD were placed in the other three groups simultaneously. Changed artificial saliva every 24 hours, and they were sealed up at 37°C constant temperature. After 5 days and lOdays respectively, the samples in group B and C were taken out. 25 days later, the same to the samples in group A and D. All of samples that removed from artificial saliva were ultrasonically cleaned in distilled water for 20 minutes and dried, then maintained at the room temperature.Their surface roughness values were measured by interferencemicroscope,and examined by SEM.Results : The surface roughness values of group A,B,C,D were (0.171+0.012)urn, (0. 176±0.013) μm, (0. 187 ±0.020) μm, (0.297 + 0.017) μm respectively. There was no significant difference between group A, B and C. The surface roughness values in group D were significantly bigger than that in group A , B and C. The SEM examination on the rough surface of chromium-cobalt specimens showed that samples of group A, B, C had almost the same surface characteristic, smooth and clear. But samples of group D had small holes, and local corrosion appearance.Conclusions : IFRD was corrosive to chromium-cobalt castings. The longer the time ,the stronger the corrosion.