Quantification of Pain Thresholds in Orthodontic Patients Using Strain Gage Techniques

Abstract

The purpose of this study was to assess the suitability of a pain model that utilizes the application of force between teeth as the noxious stimulus. Also, the time course of pain threshold alterations in patients subjected to orthodontic treatment was explored. A simple pressure algometer utilizing strain gages was produced to apply and measure the force required to reach the pain threshold of incisor teeth (central-lateral pairs) for three consecutive days. Fifteen orthodontic patients were used (nine females, six males) with incisors in good alignment and with interproximal contact. Each patient was used for both control and experimental measurements in each arch. Baseline pain threshold measurements were taken on the first day and individual orthodontic springs placed on the experimental side. The control side was the adjacent central-lateral incisor pair on the other side of the arch where no spring was placed. Additional measurements were taken the second and third day in each quadrant. A great variability in pain response between patients was evident. Significantly lower pain threshold levels were observed a day after the initial spring activation followed by an increase in the pain threshold the second day after spring activation. In the mandibular arch, the treatment by day interaction was significant, with the experimental side pain threshold substantially lower than control on the second and third day. Pain thresholds in males were significantly higher only in the maxilla, although there was a tendency for lower pain sensitivity in males for both arches. An apparent crossover of sensitivity between arch sides was observed in this study. The present model was shown to be suitable to study pain thresholds associated with orthodontic forces, and the pressure algometer was able to quantify pain threshold with objective measurements. The model could be used clinically to screen patients with low pretreatment pain thresholds so modifications of treatment mechanics or pharmacologic means could be used to allay patient pain.