Oral motor disorders are very common in patients with CP, and oral motor treatment is therefore essential. The results of this study indicate that OMFT is an effective method to enhance oral motor skills in patients with CP. The total OMAS score gradually increased from baseline (6.00 ± 2.59) and 8 weeks (8.71 ± 3.40) to 16 weeks (10.38 ± 4.56). Every item, including mouth closure, lip closure on the utensil, lip closure during deglutition, control of the food during swallowing, mastication, straw suction, and control of liquids during deglutition, was significantly different between the treatment periods. OMFT is thus a comprehensive oral motor therapy that includes various aspects such as postural control of the head and neck, nasal breathing, sensory adaptation and advance preparation, direct manual stroking on oral structures, and the process of real food.
In a study by Baghbadorani et al. (2014), 12 patients with CP participated in 8 weeks (24 sessions total) of oral motor therapy. All OMAS items improved; however, in post hoc analysis, only four items, including mouth closure, control of the food during swallowing, control of liquids during deglutition, and mastication, significantly changed between baseline and post-treatment assessment. Only four items, including control of food during swallowing, control of liquids during deglutition and mastication, and total score, were significantly increased between the baseline and midterm assessment. In Gisel’s study (1994), spoon-feeding, biting, and chewing improved by 20 weeks but not by 10 weeks in the sensorimotor treatment group. This result may be attributed to the fact that the sensorimotor treatment group and chewing group were divided separately, and sensorimotor treatment was administered to specific oral structures. The authors of previous studies have stated that postural control and sensory and cognitive approaches should be considered together. Furthermore, qualified changes in oral motor skills were observed in the sensorimotor treatment group compared to the the chewing-only group. These findings suggest that comprehensive oral motor therapy may be more effective.
Based on the average difference from baseline and 16 weeks of OMFT, the treatment effect on mouth closure was the highest and mastication was the lowest. The highest item was mouth closure (1.33), which is in agreement with a previous study[15], while the lowest item was straw suction (0.32). Herein, mastication and straw suction were the two items with the lowest effect; both are high-level oral activities that require complex oral motor coordination, such as breathing control, oral motor control, swallowing timing, attention, and learning. Mastication involves a systematic sensorimotor combination of transfer of bolus to the molar side by the tongue, placing bolus between the tongue and cheek, safe and repetitive chewing and grinding, and moving the bolus to the back of the mouth[8, 12]. Straw drinking requires lip sealing around the straw with an outer bite, and the continuous sucking of liquid[17]. In Gisel’s study (1994), no improvement in straw drinking was observed, and the treatment effect result of this study (0,61) was two times higher than that reported in a previous study (0.32)[15], indicating that OMFT is more effective than classical oral motor treatment in straw sucking and drinking.
Participants in the former study were predominantly school-aged, with moderate dysphagia or problems in following directions[10, 15, 17]. In this study, the effect of OMFT on oral motor function was verified in children over 6 years of age (33.3%). Participants in this study may not have had any prior experience with systematic oral motor treatment, such as OMFT. Therefore, children beyond the critical age could be expected to significantly improve when providing opportunities for oral motor therapy. The effect of OMFT was found in children with audible, visible perceptive limitation, and difficulty in following directions owing to severe motor disorders.
In our study, we found that both 8 weeks and 16 weeks of OMFT were effective, although the longer treatment was more effective. This result is similar to the finding that 20 weeks is more effective than 10 weeks of OMFT in Gisel’s study (1994), while 8 weeks was more effective than 4 weeks in the study by Baghbadorani et al. (2014). Although all studies indicate that a longer treatment is beneficial, each period in the three studies was different. Therefore, additional research should be performed to accurately identify the most effective period. According to this study, at least 8 sessions of 8 weeks might be needed to enhance oral motor function, and the effective periods may depend on the development and function of children.
This study has certain limitations. First, our sample size was small (only 21). Furthermore, we did not enroll a control group; therefore, a comparison between OMFT and classical oral motor treatment and other oral treatment methods was not possible. Premature, brain lesion disease, and head and neck cancer subjects have a high ratio; hence, studies should be performed in cases of various ages.
This study indicates that OMFT is an effective oral motor therapy protocol to improve oral motor function. Our results suggest that OMFT for at least 8 weeks is needed to improve the oral motor function of patients with CP, while 16 weeks of treatment is more effective. OMFT is effective for older children and patients who have limitations in perception and difficulties in following directions.