Selecting the correct abutment is the greatest area of concern for the restorative dentist. A universal abutment with prefabricated coping can greatly simplify treatment protocol in implant dentistry.A hexagonally shaped abutment, with or without modification, can be used in different clinical applications. A prefabricated castable coping designed to fit the hexagonal shape of the abutment and its shouldered margin was cemented to a hexagonal abutment. Pull out tests using an Instron unit were used to evaluate the retentive strength of a cemented coping in unmodified and modified forms. The unmodified abutment with 3mm high parallel walls produced the highest retentive strength (71.17 Kgf , SD 15.277). Removal of one of the hexagonal surface maintained 80% of the retentive
strength \(60.00 Kgf, SD 14.36). Further removal of the second and third surfaces produced no more significant reduction in retentive strength, (57.01 Kgf, SD 13.82) & 55.99 Kgf , SD 12.16) respectively. Removal of the remaining three surfaces produced a cylindrical abutment, which demonstrated the weakest retentive strength (41.43 Kgf, SD 8.91).
Clinically , selective removal of three adjacent surfaces on the hexagonal abutment allows its use in multiple implant bridge construction. The maximum allowance for angulation of the implant in any direction is 15 degrees. In single implant restorations when the abutment margin is subgingival, the crown itself can be angulated to achieve the desired profile. Implication of this study suggests not only the efficacy of utilizing a universal abutment but simplified prosthetics for single and multiple implant restoration.
1. Assif D, Azoulay S, Gorfil G. The degree of zinc phosphate cement coverage of complete crown preparations and its effect on crown retention. J Prosthe Dent 1992;68:275-278.2. English CE. Externally hexed implants, abutments, and transfer devices: A comprehensive overview. Implant Dent 1992;1:273-282.This research is self supported.