A new method for evaluating the threshold of periodontal ligament mechanoreceptor by slow speed mechanical stimulation.

Objectives: This study aimed to establish a reliable method for detecting the threshold for perception of force applied to tooth and to report the basic properties of force threshold in the normal dentition subjects.
Background: The perception of mechanical stimulation exerted to tooth is formed by input from periodontal ligament mechanoreceptors and intradental mechanoreceptors. Periodontal ligament mechanoreceptors respond to a wide range speed of stimulus, whereas intradental mechanoreceptors are activated only by a rapid stimulation. Reliable properties of perception have not been reported because of the difficulties to regulate velocity and degree of the stimulus.
Methods: Eighteen healthy subjects were observed in this study (mean age: 27.2 +/- 5.7 years). A loading device to generate slow speed loading was fabricated and measured as follows: (i) the fluctuation of the force threshold within a day, (ii) day-to-day fluctuation, (iii) changes in the force threshold by a transient mechanical loading.
Results: In the normal dentition, it was observed that the fluctuation within a day and day to day of the pressure sense showed no significant differences; however, a transient mechanical loading caused the sensitivity of the periodontal ligament to decrease significantly.
Conclusions: The device examining the force threshold resulted from periodontal ligament mechanoreceptors was useful in evaluating the sensitivity of the periodontal ligament.