Measuring Tooth Hypersensitivity

Many of the same stimuli that cause hypersensitivity in the oral cavity are utilized to elicit tooth hypersensitivity in the experimental setting: tactile, thermal, osmotic, and electrical. Passing a sharp dental explorer over the sensitive area of a tooth and asking the client to grade the pain response on a numeric severity scale, such as 0-3, is the simplest tactile method used in research. Lack of standardization of pressure and location of the explorer on the tooth affects research findings. For these reasons, more sophisticated tactile stimulation methods have been developed to control for these factors.10-12 Similar technology has been developed for standardizing standardizing thermal, osmotic, and electrical testing.13-16

Further standardization difficulties arise when attempts are made to quantify a subject’s assessment of a change in pain sensation. Pain is a subjective phenomenon which defies objective measurement. Most clinical trials have employed either the Verbal Rating Scale (VRS) or the Visual Analog Scale (VAS). A VRS may have three to five descriptors that allow a person to verbally grade the degree of discomfort. The VAS approach provides a line, usually 10 cm in length, that represents a continuum from no pain to severe pain. Subjects place a mark at the location that best indicates their level of discomfort. The VAS has generally been found to be more reproducible, and therefore, more appropriate for hypersensitivity measurement than the VRS.15 However, both approaches rely on an individual’s subjective assessment of change in the intensity of pain. Examples of a VAS and VRS are shown in Table I.