Effect of Abutment Surface Roughness on Retention After Fatigue Simulation

Objectives: The purpose of this study was to compare the retention after fatigue simulation of a cast metal coping on a prefabricated implant abutment treated with air-abrading particles and cemented with two provisional luting agents.

Methods: 12 Straumann prefabricated cementable abutments were connected to implant analogs and mounted in acrylic resin blocks. 12 crowns with occlusal retention loops were cast with high-noble alloy using plastic implant copings. Crowns were randomly assigned to 2 groups with 6 implant assemblies in each group. Group SA acted as the control and abutments were not air abraded. Group AO abutments were air abraded with 50 micron aluminum oxide. Three assemblies in each group were cemented with ImProv resin cement, and three with Premier Implant cement. All samples were thermal cycled between 4^oC and 55^oC for 6,000 cycles and cyclic loaded (MTS) under 50N force 90^o vertically with 2Hz for 50,000 cycles. Crown retention was tested using an Instron at crosshead speed of 0.5mm/min at 5,000N load. Retention was measured in Newtons at crown/abutment separation. Cement residue on crowns and abutments were cleaned and the cementation, fatigue and retention procedures were repeated for a second trial. Data were analyzed using qualitative statistics.

Results: First trial mean retention forces for SAimprov (103.83N ±4.91), SApremier (15.27N ±.55), AOimprov (916.60N ±86.43), AOpremier (460.37N ±25.06).   Second trial mean forces for SAimprov (143.13N ±25.04), SApremier (34.13N ±7.16), AOimprov (978.63N ±53.29), AOpremier (656.97N ±171.30).

Conclusions: ImProv cement showed higher retention values than Premier Implant cement in both groups.  Air-abrasion of abutments had a positive effect on retention in both groups. Re-cementation may result in greater retention if proper cleaning procedures are observed.