No abstract

Dental implants are artificial dental roots anchoring prosthetic restorations to replace natural teeth. Dental implant systems may have different tapered conical connections. Our research focused on the mechanical examination of implant–superstructure connections. Thirty-five samples with 5 different cone angles (24°, 35°, 55°, 75°, and 90°) were tested for static and dynamic loads, carried out by a mechanical fatigue testing machine. Fixing screws were fixed with a torque of 35 Ncm before measurements. For static loading, samples were loaded with a force of 500 N in 20 s. For dynamic loading, the samples were loaded for 15,000 cycles with a force of 250 ± 150 N. In both cases, the compression resulting from load and reverse torque was examined. At the highest compression load of the static tests, a significant difference (p = 0.021) was found for each cone angle group. Following dynamic loading, significant differences (p < 0.001) for the reverse torques of the fixing screw were also shown. Static and dynamic results showed a similar trend: under the same loading conditions, changing the cone angle—which determines the relationship between the implant and the abutment—had led to significant differences in the loosening of the fixing screw. In conclusion, the greater the angle of the implant–superstructure connection, the smaller the screw loosening due to loading, which may have considerable effects on the long-term, safe operation of the dental prosthesis.

The basis of the long-term success of dental implants is the mechanical stability of the implant and the superstructure anchored in it. In order to investigate the mechanical behaviour of the conical connection in implant-abutment units, static and dynamic load tests were performed with different conical angles and various Grade 4-5 titanium implant materials. The assembled units were mounted in self-developed loading machine and in an Instron ElectroPuls E3000 fatigue machine. For static loading, the samples were loaded with a force from 0 N to 500 N in steps of 100 N. For dynamic loading, the samples were loaded for 30,000 cycles with a force of 250 ± 150 N. In case of static testing, the compression caused by the load was measured in both horizontal and vertical directions, while in the case of dynamic fatigue, only horizontal deformation was defined. In both cases, the drive-out (reverse) torque values of the fixing screws were determined after loading. No significant differences were found between the tested materials in the reverse torque after the static load, however, significant differences were shown with regards to the alterations in cone angle (p < 0.001). After dynamic loading, significant differences (p < 0.001) were also observed between the reverse torques of the fixing screw in different angles. The static and dynamic test results showed the same tendency: under the same load conditions, the conical angle value of the implant-abutment connection revealed significant differences in the loosening of the fixing screw. In summary, it is recommended to use higher conical angle connection to avoid larger deformations in lengths and diameters of the implant at the connection and essential torque reduction of the fixing screw. Our results may contribute to the understanding of the long-term success of dental implants.