Effects of abutment size and luting cement type on the uniaxial retention force of implant-supported crowns

Statement of problem. The assumption that increasing the diameter of the abutment/crown components will provide greater resistance to crown loosening forces than standard-sized components has not been reported either with clinical trials or in the laboratory. Purpose. This study attempted to determine what effect abutment dimension and type of luting agent have on the retention of the prosthetic crown. Methods and material. Test specimens consisted of standard, wide, and "experimental" CeraOne titanium abutments and matching CeraOne gold cylinders cemented with a zinc phosphate permanent or a zinc oxide eugenol provisional cement. The mean uniaxial force (Newtons) and the load (MPa) required to dislodge the cylinder from the abutment was determined. Statistical analysis of the sample data was performed using a 2-way analysis of variance test (alpha = .05). Results. Mean uniaxial resistance force (Newtons) was significantly greater for zinc phosphate cement than for zinc oxide cement (P < .001). Abutment size was a significant factor when permanent luting cement is used (P < .001). Retention strength per unit area (MPa) of the wide abutments was lower than the standard size and "experimental" abutments. Conclusion. Permanent luting cement produced uniaxial retention forces approximately 3 times greater than provisional cement. The increase in surface area provided by a wide abutment did not result in an improvement in retention strength over the standard abutment.