Position accuracy of manually repositioned abutments in various implant-abutment interfaces

Objectives:

The present study investigated the position stability of implant-abutment connections of six commercially available implant systems. Abutments were manually de- and reassembled.

Material and Methods:

For these purposes, six implant fixtures of each implant system (Straumann ITI, Straumann Bone Level, Steri Oss, Camlog, Astra Tech, Replace Select) were fixated in a stainless steel model. A standardized test body was fixated on the abutment (abutment-test body complex=ATBC). Implant-abutment connections were released and reaffixed 20times each by three test persons with differing skills concerning implantology and the working thesis. The system-specific screwdrivers were used. Changes of position of the ATBC were determined using a precision Video check analysis system. Results were measured three-dimensional in a coordinate system.

Rotational, vertical and canting moments were evaluated and statistical analysis was performed with two factorial nonparametric analysis for repeated measurements.

Results:

The investigated implant-abutment connections showed rotational movements from 0.002° to 4.8°. Camlog implants displayed the smallest rotational freedom with values being statistically significant from all other systems tested (all P<0.001). Steri Oss, Astra Tech, Bone Level and Replace Select displayed similar rotational values (P<0.001). Vertical deviations of the ATBC ranged from 1 to 83µm, whereas ITI and Astra Tech implants showing no statistical significant difference to each other (P=0.849) displayed the highest vertical discrepancies. All other systems showed a vertical deviation of less than 15µm. Canting moments of the ATBC (0.00° - 0.31°) were not significant between the systems.

Conclusion:

Several implant-abutment connections proved to be not as precise as promoted. The three-dimensional inaccuracy of repositioned abutments, in dependence of the system used, may affect problems encountered with implant-retained restorations.