Evaluation of Machining Accuracy and Consistency of Selected Implants, Standard Abutments, and Laboratory Analogs Paul P. Binon DDS MSD Private Practice of Prosthadimtics Rose ville California; Research Scientist Department of Restorative Derttistry School of Dentistry University of California San Francisco San Francisco California Thirteen implants having external hexagonal extensions were evaluated for machining accur acy and consi stenc y, A composite sco re was derived to evaluate overall manufacturing accuracy and consistency of the implants evaluated in this study. A technique to determine the rotational freedom hetween implant and abutment is descrihed, and the coronal hexagonal mati ngs of sel ect ed implants and abutments is evaluated and rep orted. Cro sso ver use and comb inations of products from different manufacturers was also evaluated fur rotational freedom. Two nonexternal he>:agonal extension implant configurations were measured for rotational movement as contrasting and comparative values, nt I Prostbodont 1995;8:162 178. T he introduction and popularity of the Brânemark implant (Nobelpharma AB, Göteborg, Sweden) rapidly stimulated the commer- cial availability of 25 variations oí implants having external hexagonai extensions,' With expanded implant use for single tooth and partially edentu- lous applications, the primary purpose of the hexagonal coronal extension has changed from a rotational torque transferring mechanism used dur- ing the surgical placement of the implant into a prosthesis indexing and antirotational mechanism,- The machined hexagonal extension on the coronal aspect of the implant and its matching abutment counterpart comprise the primary docking device between the implant and the abutment. The impres- sion coping transfers the exact oral relationship of the implant to the working cast by using the hexagonal extension as an orientation mechanism.' The hexag- onal configuration is also intended to prevent rota- tion of the abutment on the implant mating surface and to provide a more stable screw joint assembl y, '' ^ Clinical requirements often result in the crossover use of products from different manufacturers. Considerable variation has been reported in the accuracy, consistency, and fidelity of some implant components,' The amount of freedom between lhe Reprint requests: Dr Paul P Binon 1158 Cirby W ay Roseville California 95661. implant hexagonal extension and its abutment coun- terpart has also been implicated as a factor in screw joint instability.' The purpose of this study was to evaluate the machining accuracy and consistency of thirteen implants having external hexagonal exten- sions and to determine the rotational freedom between the patrix implant hexagonal extension and the matrix hexagonal abutment counterpart. Materials and Methods Evaluation of accuracy and consistency of machining is based on direct measurements obtained at selected locations, A minimum of five randomly selected implants were measured with a digital micrometer (Model 293, Mitutoyo, Tokyo, japan) and a micrometer microscope (Gertner Scientific Institute, Chicago, IL), capable of one micrometer accuracy, A larger sample size was reported whenever additional components were available for measurement. Operator error was evaluated by measuring five replications at the same location for 11 different samples. Sample variance for the replications ranged from 0 to 6,4 X 10 ' (average variance for all 11 samples was 3,71 X 10') and the standard deviation ranged from 0 to ,00075, indicating minimal operator error. Measurements were made at the following locations: coronal (head) diameter, body diameter across the threads (width), height and width of the Th e Imernational lournal of Proslhodontri 162
