Efficacy of soft palatal augmentation prosthesis for oral functional rehabilitation in patients with dysarthria and dysphagia: a protocol for a randomised controlled trial.

INTRODUCTION: Palatal augmentation prosthesis (PAP) is used in patients with articulation and swallowing disorders caused by postoperative loss of tongue tissue due to tongue cancer, cerebrovascular disease sequelae and age-related hypofunction. We have previously reported a newly designed soft PAP fabricated using an thermoplastic material that is particularly appropriate for early intervention. However, the effect of soft PAP on oral function improvement remains to be elucidated. The aim of this study is to investigate whether soft PAP can improve dysarthria and dysphagia occurring as cerebrovascular disease sequelae. METHODS AND ANALYSIS: This prospective, randomised, controlled trial will compare the immediate and training effects of rehabilitation using soft PAP with those of rehabilitation without using it. Primary outcomes are the single-word intelligibility test score and pharyngeal transit time (PTT). Secondary outcomes are tongue function (evaluated based on maximum tongue pressure, repetitions of tongue pressure and endurance of tongue pressure), articulation function (evaluated based on speech intelligibility, oral diadochokinesis, Voice-Related Quality of Life (V-RQOL)) and swallowing function (evaluated using Eating Assessment Tool-10). The study results will help determine the efficacy of Soft PAP in improving functional outcomes of word intelligibility and PTT. We hypothesised that early rehabilitation using Soft PAP would more effectively improve articulation and swallowing function compared with conventional rehabilitation without using soft PAP. ETHICS AND DISSEMINATION: Ethical approval was obtained from the Okayama University Certified Review Board. The study findings will be published in an open access, peer-reviewed journal and presented at relevant conferences and research meetings. TRIAL REGISTRATION NUMBER: jRCTs062200054.

Effect of masseter muscle activity during wakefulness and sleep on tooth wear.

PURPOSE: To investigate the effect of masseter muscle activity during wakefulness and sleep on tooth wear. METHODS: Sixteen participants with no or mild tooth wear (NMTW group) and sixteen participants with moderate-to-severe tooth wear (MSTW group) were enrolled. The severity of tooth wear was evaluated using the occlusal and incisal indices of the tooth wear index. Surface electromyography was performed to record the electrical activity of the left masseter muscle during wakefulness and sleep. Electromyographic activity was detected using an electromyographic threshold of 5% and 20% of maximal voluntary clenching (MVC). The total duration of electromyographic activity and bruxism episodes were calculated. RESULTS: The mean ages of the NMTW and MSTW groups were 71.75 ± 7.61 years and 71.69 ± 7.49 years, respectively. The mean cumulative duration of electromyographic activity during wakefulness using a threshold of >5% MVC was 6.44 ± 4.52 min/h and 13.62 ± 10.08 min/h for the NMTW and MSTW groups, respectively (p=0.048). The mean total durations of electromyographic activity during wakefulness and sleep using a threshold of >20% MVC were 1.08 ± 1.70 min/h and 1.05 ± 3.02 min/h, respectively, in the NMTW group and 4.78 ± 6.37 min/h and 1.61 ± 1.79 min/h, respectively, in the MSTW group (p=0.048 and p=0.003, respectively). CONCLUSION: These results suggest that masseter electromyographic activity during wakefulness and sleep may be related to the severity of tooth wear.

Coordination of surface electromyography activity in the posterior tongue region during mastication of differently textured foods.

BACKGROUND: Masticatory movement occurs complicatedly and bilaterally. Although the tongue plays an important role in mastication, bilateral tongue function during mastication has not been clarified yet. OBJECTIVE: To investigate the effect of food properties on posterior tongue activity and coordination of muscles bilaterally by electromyography (EMG). METHODS: Twenty healthy adults (10 males and 10 females; mean age 28 years; range: 22-33 years) participated in this study. Three test foods, gummy jelly (hard food), sponge cake (soft food requiring crushing), and mashed potatoes (soft food not requiring crushing), were used. Bilateral masseter N-EMG (surface electromyography for measuring the muscle activity of posterior tongue) and submental EMG were carried out while the participants chewed three test foods. The participants were instructed to masticate three test foods only on the right side and only on the left side unilaterally. RESULTS: In the case of gummy jelly, N-EMG activity on the mastication side was significantly larger than that on the non-mastication side (P < .01). Regarding temporal relationship between the masseter and N-EMG activity, in the case of gummy jelly, the percentage of cases where the N-EMG peak was observed during masseter muscle EMG bursts was significantly higher than those for sponge cake and mashed potatoes (P < .01). CONCLUSION: N-EMG activity on the mastication side was significantly larger than that on the non-mastication side in the mastication of hard foods. Tongue showed activity pattern changes and coordinated with the masseter muscle depending on food texture.

Effect of food properties and chewing condition on the electromyographic activity of the posterior tongue.

BACKGROUND: Retraction of the posterior tongue facilitates bolus formation, food transfer and Stage II transport in chewing and swallowing. Surface electromyography of the neck region (N-EMG) enabled the evaluation of muscle function at the posterior tongue. Although previous studies showed that food hardness increased masticatory muscles EMG activity and volitional chewing altered swallowing, the effect of food properties and chewing condition on N-EMG activity has not yet been elucidated. OBJECTIVE: To investigate the effect of food properties and chewing conditions on N-EMG. METHODS: Twelve healthy adults (six men and six women, mean age 28.1 ± 2.7) participated in this study. Three test foods were used: a cookie (solid food), crushed cookies adjusted using agar and water (semisolid food) and crushed cookies adjusted using thickening agent and water (soft food). Masseter and submental muscle EMG and N-EMG activity were recorded while chewing the three test foods. Participants were instructed to masticate the three test foods in three chewing conditions: (a) chewing freely, (b) chewing test foods with the same number of chewing cycles as when chewing solid food and (c) chewing with a maximum effort. RESULTS: Total N-EMG activity when chewing solid food was higher than that in the other two test foods regardless of the chewing condition. In soft food and semisolid food, the total N-EMG activity was increased by increasing the number of chewing cycles. CONCLUSION: The total N-EMG activity was increased while chewing hard food, which indicates the positive effect of chewing hard food on rehabilitation at the posterior tongue.