The effect of different implant-abutment connection on screw joint stability.

Abstract

Abstract Dental implants with an internal connection have been designed in order to establish a better stress distribution when lateral external forces act on the prosthesis and minimize the forces transmitted to the fastening screw. In the present study, ten externally and ten internally hexed implants were tested with a compressive force applied with an Instron Universal machine. Four cycles of loading-unloading were applied to each specimen, in order to achieve displacements of 0.5, 1, 2 and 2.5 mm. The mean loads for the first cycle were 256.70 N for the external connection and 256 N for the internal connection implants. The independent t test did not reveal any significant differences among the two tested groups (P=.780). For the second cycle, the mean loads needed for a displacement of 1mm were 818.19 N and 780.20 N, for the external connection and the internal connection implants respectively. The independent t test revealed significant differences among the two tested groups (P<.001). In the third cycle, the mean load values for a 2mm displacement were 1394.10 N and 1225.00 N. The independent t test revealed significant differences among the two tested groups (P<.001). The mean loads for the fourth cycle were 1488.00 N for the external connection and 1029.00 N for the internal connection implants. These loads were required for a displacement of 2.5mm. The independent t test revealed significant differences among the two tested groups (P<.001). The results of this in vitro study suggest that the internal connection design of the examined implant system could not prevent screw loosening during overloading. No implant or prosthesis failure was noticed in either group.