Abstract
Pain was induced in the upper trapezius muscle by an injection of hypertonic saline. The intensity of pain and limited mouth opening were studied.
The subjects were 8 males between 26 and 34 years old who had complete dentition and no dysfunction of their neck, shoulder, or mandibles. A bolus of 0.5 ml hypertonic (6%, EX) and isotonic saline (0.9%, CT) was injected at the superior border of the upper trapezius muscle using a 25 G needle in a single blind, randomized crossover study. Pain intensity caused by the injection was evaluated by 100 mm visual analog scale (VAS), and the maximum mouth opening was measured using slide calipers to measure right inter-incisal distance every 30 seconds from immediately after injection to 600 seconds post-injection.
The VAS of the EX score was significantly higher than that of CT, from immediately after injection to 270 seconds (p<0.01), and the highest score was recorded at 30 seconds after injection (64.1±16.8 mm). The maximum mouth opening at baseline was approximately 54 mm in both series, and was significantly reduced in EX compared with CT from immediately after injection to 60 seconds after (p<0.05), and the lowest value in EX was 47.4±4.8 mm.
On the basis of these findings, we considered that the cause of limited mouth opening might originate in the shoulder and neck area. The result also confirmed the importance of examining of the shoulder and neck of TMD patients.
