Changes in Sensory Thresholds of the Pulp and Periodontal Ligaments after Standardized Tooth Clenching

Objective: It is not clear how the magnitude and duration of occlusal force affects pulpal and periodontal sensations. We investigated the effects of various tooth clenching loads, in which the product of the occlusal force and duration was kept constant, on pulpal and periodontal sensations. Materials and methods: Ten men and 10 women associated with Tokyo Medical and Dental University (age ≥ 20 years) participated in this study. Changes in pulpal sensation and periodontal sensation at the left or right mandibular first premolar were compared before and after 3 experimental clenching tasks. The total loading amount, determined as “occlusal force × duration”, was kept constant across tasks. For pulpal sensation, the electrical stimulation threshold (EDT) was measured using an electric pulp tester that caused pulpal discomfort. For periodontal sensation, the interocclusal tactile threshold (ITT) was measured using the foil test. Results: There was no significant difference with respect to the change rates of EDT and ITT relative to baseline between tasks. However, change rates varied across individuals. Both EDT and ITT could be divided into 3 types: increase type, decrease type ,and no-change type. For EDT, the smaller the bite force was, the more the proportion of the decrease type tended to increase. For ITT, the increase type was predominant in each task. However, there was no statistically significant difference between tasks in both EDT and ITT. Conclusion: Although we observed no statistically significant differences, transient changes in pulpal as well as periodontal sensation were found. Even if the product of occlusal force and duration (total loading) remained constant, transient changes in pulpal and periodontal sensations might differ. In particular, the pulp may become hypersensitive, while periodontal sensation may become hyposensitive.