Research On Characteristics Of Fretting Wear Of Two Kinds Of Dental Alloys

With the development of medical technology and material science, the scope of the application of dental alloy becomes wider and wider. Most of the precision attachments were made of the dental alloy, so it is inevitably occur of the dental alloy' fretting damage when these attachments work in oral. The harmfulness of fretting damage becomes more and more important. While up to now, main of the research on fretting has been focused on the industry area, few publications on the fretting damage in oral environment are found in the literatures and the systematic studies on the mechanism of fretting damage are even more limited. Therefore, referred to the real conditions in oral, the fretting damage behavior of typical dental alloys in kinds of artificial saliva and air mediums has been investigated in this thesis, and the damage mechanism of the two dental alloys has been analyzed. The studies will not only show its significant importance in medicine, but also exhibit an important academic value.The fretting wear experiments were performed by a hydraulic fretting test rig equipped with liquid container. The systematic studies have been conducted on the fretting wear behavior of two typical dental alloys (System 18 and VBV) in two different mediums (air and artificial saliva). The imposed loads were 50N and 100N, the frequency was 2Hz, the number of cycles varied from 1 to 5×10~4. Combined with the analysis on the frictional dynamic behavior, the fretting worn scars have been carefully characterized through optical microscope, scanning electrical microscope (SEM), and energy dispersive X-ray spectrum (EDX).The obtained conclusions are listed as following:1. Fretting friction-displacement curves have relations with the feature of the dental alloys, It is easier to occur the partial slip regime for System18 dental alloy, VBV dental alloy has a wider gross slip regime;2. Artificial saliva medium and imposed load could transform the partial slip regime of two dental alloys: artificial saliva could make the partial slip regime transform to small displacement amplitude; while high load could make the partial slip regime transform to large displacement amplitude. Fretting wear has relations with the medium and the imposed load: Artificial saliva medium reduced the fretting damage for System 18 dental alloy; while for VBV alloy, the corrosion effect play an important role under a high load. The wear was more severe under high load than that of the low vertical load, the fretting damage was mainly at the contact edge, and the contact center has a slight damage;3. The fretting wear damage mechanism of the two dental alloys is similar; the main fretting wear damage mechanism of two dental alloys was the joint of abrasion and delamination.