Deflections of an implant-supported cantilever beam subjected to vertically directed loads. In vitro measurements in three dimensions using an optoelectronic method. II Analysis of methodological errors.

Aim: The aim of this study was to evaluate the accuracy, i.e. trueness (validity) and precision (repeatability) for load-dependent deflections in three dimensions of an implant-supported cantilever beam obtained with an optoelectronic motion analysis system compared with a well-known reference method.

Materials And Methods: A cantilever beam with a length of 22 mm (roughly corresponding to the width of two premolars) was screw-connected to an implant-abutment unit stiffly anchored in a steel plate. The positional changes of beam-end were measured when the beam-end step by step was subjected to four loads, 15.5-40.1 N. This measurement procedure was repeated to comprise six consecutive measurements. The trueness of the method was estimated by comparing the data obtained for vertical deflections with those from a reference method where a hydraulic test system was used to measure the load-deflection ratios of the same beam when subjected to the four mentioned vertical loads.

Results: All applied transducer-mediated loads had accuracies (truenesses and repeatabilities below 0.05%). Also, the trueness and precision of the reference method, regarding both movements (deflections) of tested objects and magnitude of applied loads, were tested and found to be high, not exceeding 0.5%. The optoelectronic method however underestimated the smallest vertical deflections for the cantilever beam when compared with the data obtained from the reference method. The underestimation was 26.4%, 15.5% and 8.6% for loads 15.5, 26.6 and 32.6 N, respectively, while there was a slight overestimation of 1.2% for 40.1 N. The precision for the optoelectronic method was found to be for z-axis 1.8 μm, y-axis 3.8 μm and x-axis 1.9 μm.

Conclusion: It can be concluded that the trueness (validity) for the optoelectronic method is very high for deflections above 143 μm. The precision (repeatability) of the optoelectronic method was found to be very high.