Retention and wear evaluation of two different clip materials on milled polyetheretherketone bar for implant retained mandibular overdenture

Abstract Purpose To evaluate the retention and wear of two different clip materials [plastic and milled polyetheretherketone (PEEK)] on milled PEEK bar for implant retained mandibular overdenture. Materials and methods Fourteen ready-made mandibular edentulous epoxy resin models were used. Two-implant analogs were installed in the canine area. Two non-hex titanium base (Ti-base) abutment were connected to the implant analogs. The epoxy cast with Ti-base abutment was scanned by a laboratory scanner. Designing of the bar on the software was done and converted to STL file, which was transferred to the milling machine for manufacturing of the bar. The milled PEEK bar (BioHPP) was cemented to the abutment by resin cement-adhesive material. Group I was ready-made plastic clip and group II was milled PEEK (BioHPP) clip. Dentures were constructed by the conventional method and direct pickup of the clips were done. The final constructed mandibular overdentures were subjected to 150 000 cycle of bi-axial chewing simulating cycles and 1440 insertion-removal cycles which equal four times insertion and removal per day which equal 1 year follow up. The retention of the samples was measured using universal testing machine at the baseline and after 3, 6, 9, and 12 months. Wear features of the clips were also measured by topographic variation using USB digital microscope with built in camera at the same periods. Result As regard to retention test, at the baseline and after 3 months of chewing simulator. There was no significant difference between the two groups but after 6, 9, and 12 months of chewing cycles simulation there was a significant difference between two groups in favor of the milled PEEK clip. Regarding the topographic variation which indicate wear there was no significant difference between the two groups except at the baseline with high topographic variation in the PEEK clip. Conclusion Milled PEEK clip showed superior retentive properties after application of chewing simulator than the plastic clip. The plastic clip undergoing a greater loss of retention than PEEK clip. So there was statistically significant differences in retention between both clips. The PEEK clip showed a high surface roughness at the baseline than the plastic clip and then there was a nonsignificant difference between them at 3, 6, 9, and 12 months.