Objectives: Screw stretch (elongation) has been reported in the engineering literature as a factor in measuring tensile loading within a screw. The “time of flight” for an ultrasonic sound wave to travel the length of a screw is a function of screw length. The objective of this study was to use a miniature ultrasonic transducer to measure TOF delay caused by screw stretch as a result of the application of tensile stress to the screw.

Methods: An experimental Testing System was designed for this study that would deliver tensile loads to an abutment screw. An ultrasonic transducer was positioned in the head of the abutment screw to transmit and received sound “time of flight” data. TOF data was collected at Zero N and following the application of incremental tensile loads (Zero N to 400 N) to the screw. The correlation of the TOF delay (y) data versus the applied loads (x) was analyzed.

Results: Simple Regression Analysis demonstrated a linear relationship (y = 0.0224x – 0.2128) between TOF data and incremental tensile loads applied to the abutment screw with a high correlation (R2 = 0.9997).

Conclusion: The results of this study supported the use of an ultrasonic transducer to collect TOF data as a measurement of applied tensile loads in an abutment screw. (Supported by NIDR SBIR Grant # 1R43DE13454-01)

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