Purpose: To investigate the resistance of an implant crown telescopically engaged to a geometrically defined hexagonal abutment with and without cement under compressive dynamic cyclic fatigue loading.
Materials and methods: 40 crowns, 9 mm in height, were cast from prefabricated plastic copings each telescopically engaged to a 3 mm high machined hexagonal abutment. 20 crowns were retained with zinc phosphate cement and 20 crowns were retained with a screw. A vertical load of 15 kg was applied to all samples under oscillation. A Periotest was used to measure the mobility of the implant crown in Periotest values (PTV). Test endpoints were defined by; fatigue cycles ≥ 20 million; crown PTV > 10; or if samples became visibly loose or component fracture.
Results: Cement-retained crowns failed on average at 2.60 x 106 cycles ± 2.27, while screw-retained crown samples failed at 2.17 x 106 cycles ± 1.27 with no significant difference (p > 0.05). Implant and abutment screw fractures were the most prevalent mode of failure in the cement-retained group, while in the screw-retained group failures were caused by the loosening of one or both screw joints. The rate of increase in PTV was higher in the screw-retained group than in the cement-retained group.
Conclusions: Under the experimental conditions, an implant crown telescopically engaged vertically to a 3 mm tall hexagonal abutment, under compressive dynamic cyclic fatigue loading with or without cement demonstrated no differences in resistance or failure outcomes. A cement-retained implant crown with telescopic engagement to the abutment is more rigid, resulting in more implant and abutment screw fractures than loosening.
Keywords: Dynamic Cyclic Fatigue Loading; Emergence Profile; Implant Crown; Screw vs Cement Retention; Set Screw; Telescopic Engagement.