What is your goal?

The way we swallow is believed to be modified by oral capacity and oral sensation. When we masticate and chew food into a bolus (Figure 1), food is moved to the throat by the tongue (Figure 2), and upon reaching the throat, the swallowing reflex occurs (Figure 3). While this reflex differs to some extent depending on the type of food, it has come to be believed that this has nothing to do with the state of the mouth. Through our experience with the swallowing ability of patients worsening or improving simply because the size of a created denture was too long or short, we came to believe that the way we swallow may be altered by making slight changes in oral capacity or oral sensation.

Many elderly people end up wearing dentures. Oral capacity and oral sensation changes when wearing dentures (Images 1 and 2). Regarding modern dentures, emphasis is placed on whether or not they allow good mastication; unfortunately, whether dentures allow good swallowing as well as mastication has not been verified as of yet.

We believe that once we figure out that oral capacity and oral sensation alter the way we swallow, an appropriately shaped denture which not only allows good mastication but also swallowing without aspiration (accidentally swallowing food into the trachea instead of the esophagus) will be determined, making daily mealtimes more enjoyable for many elderly people wearing dentures.

Figure 1

Figure 2

Figure 3

 

Image 1

Image 2

 

What types of devices do you use and what kind of experiments do you conduct?

In order to observe the way we swallow, swallowing contrast exams are carried out. With this exam, patients are asked to swallow food with a contrast medium, while images during swallowing are taken by a fluoroscope and recorded by a video device (Image 3). Based on these video images, the time for food to reach the throat from the mouth, the time to reach the esophagus from the throat, and the dimensions of the bolus of food flowing into the esophagus upon swallowing once, are measured using software for measuring time and dimension (Image 4).

In previous studies, it has been revealed that the timing of the initiation of the swallowing reflex is accelerated or delayed, depending on the patient, when the oral capacity is increased or one side of the tongue is paralyzed. This indicates that patients may time their swallowing differently from their original swallowing reflex according to the length of the created denture. It also indicates that the timing of the swallowing reflex may also differ in patients who do not have oral sensation on one side due to reasons such as stroke. This may easily lead to aspiration and is extremely dangerous.

Image 3. Swallowing contrast exam

Image 4. Swallowing contrast image   Image 5. Oral capacity was increased by increasing the height of occlusion

 

 

What is your next goal?

It has been revealed that recovering the correct oral capacity for each patient is essential in maintaining individual swallowing reflex, in addition to the fact that oral sensation is also associated with maintaining the swallowing reflex. In the future, our goal is to determine the type of sensory information the mouth gathers that changes the swallowing reflex.

 

References

(1) "Rehabilitation on Eating and Swallowing, 2nd edition." Ishiyaku Publishers Inc., Tokyo (2009)