MEASURING FIT AT THE IMPLANT PROSTHODONTIC INTERFACE

Four centers in the United States and Sweden have been working for 2 y ears to develop systems and methods for measuring fit at the prosthodo ntic interface, Two systems are based on stylus contact techniques, on e system uses a laser as its reader source, and one system is photogra mmetric. All the systems are capable of providing data as three-dimens ional x, y, and z axes coordinate values that can be transformed into linear and angular data that characterize the bearing surfaces of abut ments or abutment replicas and their mating components in the prosthes is framework, The centroid, a single point computed from the collected data, was the measurement unit, derived for these bearing surfaces, t hat was used to compare the systems, All four methods can most likely detect misfits that are relevant in the clinical setting; however, onl y one system can be used intraorally, When any measurement system is a ssessed, the data should always be examined for repeatability to estab lish the reliability of the system, This investigation made comparison s among the measurement methods used at the four centers, It was appar ent from this study that comparisons of data from measurement systems should be rounded to the nearest 10 mu m, The SDs determined in the co mparisons were larger than 5 mu m and therefore misfits should be calc ulated in terms smaller than 10 mu m, This final point is important to the clinician who relies on research reports about precision of fit w hen selecting treatment approaches in caring for the implant prosthodo ntic needs of their patients.