Thesis (M.Sc.)-Cairo University- Faculty of Oral and Dental Medicine

Bibliography: p. 149-168.

Implant retained overdentures have been used widely to solve the problem of complete edentulism. They provide better retention and more patient satisfaction than the conventional complete dentures. However, the attachments used in these overdentures usually suffer from wear and may cause retention problems by time. The retention of these overdentures depends mainly on the type and design of the used attachments. The aim of this in-vitro study was to compare between the wear behavior and retention of two different attachments: Ball and Novaloc. The male part of Ball attachment was made of titanium and had a titanium elliptical female housing with a golden retention insert. As for the other attachment, the male part of Novaloc was made of carbon-based coating abutment and had a female housing made of PEEK with a white retention Peek insert. One epoxy resin model was fabricated for each group. Two implant analogues were inserted in each model at the canine area bilaterally. Four overdentures were made and divided randomly into two equal groups corresponding to Ball group and Novaloc group. Picking up of the overdentures was done with the right female part of each attachment, then a hook representing the geographical center of each denture was attached to it. ROBOTA chewing simulator was used for the insertion and removal cycles of these dentures. The software analyzed the wear of each cap regarding area, diameter, and perimeter. Then their surface was evaluated microscopically by digital microscope. This analysis was done at different intervals: baseline, 500 cycles, 1000 cycles, 1500 cycles and 2000 cycles to simulate a follow up of 1 year. Retention was also measured by universal testing machine at the same intervals mentioned before. The results showed that both groups suffered from wear by time and there was a statistically significant decrease in retention. The initial and final retention of Ball was higher than that of Novaloc. This may be attributed to the material of each of them, as the metal-to-metal friction between the male titanium part and the golden insert of the ball attachment showed better retention results than the metal-to-polymer friction between the male part of Novaloc and its PEEK cap and insert