Heating Effects of Ultrasound Applied to Extracted Molars: Is it safe to apply ultrasound to the temporomandibular joint? s

Abstract

Background and purpose This study investigated the effects of therapeutic ultrasound (TUS) on the pulpal temperature of extracted molars to determine whether it is safe to apply this modality in cases of temporomandibular joint (TMJ) dysfunction. Methods This experiment was performed in the anatomy laboratory at a Texas university, where the extracted teeth were divided into two groups: 15 teeth without fillings (group 1) and 15 with fillings (group 2). All received ultrasound under water at 1.0 W/cm2 for five minutes at 1 MHz continuous duty cycle. Temperature was measured in degrees Celsius with a thermistor, before treatment, immediately after, and at one and five minutes after treatment. Data were analysed using a repeated measures ANOVA with appropriate post hoc tests. Results An ANOVA for repeated measures showed that there was a significant interaction between the temperature of the teeth over time and the type of tooth (with or without fillings) (F(3,84) = 16.12, P < 0.001). Post hoc tests showed that there were no significant differences between the two groups before treatment, and after one and five minutes, but there was a significant difference immediately after exposure to TUS. Group 1 heated more than group 2 (2.63° versus 1.45°). Conclusions Using US applied to the teeth, temperature increased by only a few degrees. Because this is within the margin of safety for heating dental pulp, and because TUS applied to the TMJ is likely to result in even less radiant heat, TUS may be safely applied to the TMJ region without fear of overheating and damaging teeth or fillings. This study investigated the effects of therapeutic ultrasound (TUS) on the pulpal temperature of extracted molars to determine whether it is safe to apply this modality in cases of temporomandibular joint (TMJ) dysfunction. This experiment was performed in the anatomy laboratory at a Texas university, where the extracted teeth were divided into two groups: 15 teeth without fillings (group 1) and 15 with fillings (group 2). All received ultrasound under water at 1.0 W/cm2 for five minutes at 1 MHz continuous duty cycle. Temperature was measured in degrees Celsius with a thermistor, before treatment, immediately after, and at one and five minutes after treatment. Data were analysed using a repeated measures ANOVA with appropriate post hoc tests. An ANOVA for repeated measures showed that there was a significant interaction between the temperature of the teeth over time and the type of tooth (with or without fillings) (F(3,84) = 16.12, P < 0.001). Post hoc tests showed that there were no significant differences between the two groups before treatment, and after one and five minutes, but there was a significant difference immediately after exposure to TUS. Group 1 heated more than group 2 (2.63° versus 1.45°). Using US applied to the teeth, temperature increased by only a few degrees. Because this is within the margin of safety for heating dental pulp, and because TUS applied to the TMJ is likely to result in even less radiant heat, TUS may be safely applied to the TMJ region without fear of overheating and damaging teeth or fillings.