New method for determining surface roughness of tongue

Comparison of Tongue Characteristics Classified According to Ultrasonographic Features Using a K-Means Clustering Algorithm

The precise correlations among tongue function and characteristics remain unknown, and no previous studies have attempted machine learning-based classification of tongue ultrasonography findings. This cross-sectional observational study aimed to investigate relationships among tongue characteristics and function by classifying ultrasound images of the tongue using a K-means clustering algorithm. During 2017–2018, 236 healthy older participants (mean age 70.8 ± 5.4 years) were enrolled. The optimal number of clusters determined by the elbow method was 3. After analysis of tongue thickness and echo intensity plots, tongues were classified into three groups. One-way ANOVA was used to compare tongue function, tongue pressure, and oral diadochokinesis for /ta/ and /ka/ in each group. There were significant differences in all tongue functions among the three groups. The worst function was observed in patients with the lowest values for tongue thickness and echo intensity (tongue pressure [P = 0.023], /ta/ [P = 0.007], and /ka/ [P = 0.038]). Our results indicate that ultrasonographic classification of tongue characteristics using K-means clustering may aid clinicians in selecting the appropriate treatment strategy. Indeed, ultrasonography is advantageous in that it provides real-time imaging that is non-invasive, which can improve patient follow-up both in the clinic and at home.

In situ oral lubrication and smoothness sensory perception influenced by tongue surface roughness

BACKGROUND

The human tongue is important in the oral processing of food and in sensory perception. Tongue topography could influence delicate differences in sensory perception. It is hypothesized that tongue surface roughness could alter oral lubrication status and affect perception of smoothness. Fifteen participants with varying levels of tongue surface roughness were recruited and tested. Participants' in situ oral lubrication status without and after consumption of fluid food (milk with varying fat content and maltodextrin solutions with different shear viscosities) was measured. Participants' smoothness sensory scores were also recorded.

RESULTS

The in situ friction coefficient (0.299-1.505) was significantly positively correlated with tongue-surface roughness (54.6-140.0 μm) in all types of test fluid samples across participants. Oral lubrication was significantly decreased when participants consumed the test fluid samples compared with no liquid food consumption, for all test fluid sample types (P < 0.05). No significant differences in in situ friction coefficient were found after participants consumed different test fluid samples, and this was mainly attributed to the limited quantities of fluid residuals in the oral cavity after expectoration. Participants whose tongue surface roughness differed did not exhibit significant differences in smoothness perception with different test fluid samples.

CONCLUSION

Tongue surface roughness has a strong impact on in situ oral lubrication, and fluid food intake reduces in situ oral lubrication significantly. Saliva film and tongue surface roughness might play greater roles in oral lubrication and smoothness sensory perception if fluid is expectorated after consumption. The association between oral physiology and texture perception still needs further elucidation. © 2021 Society of Chemical Industry.

Texture contrast: Ultrasonic characterization of stacked gels' deformation during compression on a biomimicking tongue

When undergoing compression during oral processing, stacked gels display different mechanical properties that shape perceptions of texture contrasts (Santagiuliana et al., 2018). However, to date, characterizing the mechanical responses of individual gel layers has been impossible. In this study, an ultrasound (US) technique was developed, that allowed such deformation dynamics to be visualized in real time. Stacked gels were created using layers (height: 5 mm) of brittle agar and elastic gelatin in different combinations. In a series of experimental tests, different stacked gel combinations were placed on a rough, deformable artificial tongue model (ATM) made of polyvinyl alcohol; a texture analyzer was used to apply uniaxial force, and deformation was monitored by an US transducer (5 MHz) located under the ATM.

From the obtained results, it was observed that the deformation of ATM surface during compression was in accordance with the force recorded by the texture analyzer, suggesting a collaborative response of different layers under compression. Moreover, US imaging revealed that differences in Young's modulus values between layers led to heterogeneous strain distributions, which were more pronounced for the agar layers. Biopolymer elasticity was also a key factor. Regardless of combination type, the gelatin layers never fractured; such was not the case for the agar layers, especially those with lower Young's modulus values. The results of this US study have thus paved the way for a better understanding of the mechanical deformation that occurs in heterogeneous foods, a phenomenon that has been difficult to examine because of the limitations of conventional techniques.

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Agar and gelatin bilayer gels were compressed on deformable artificial tongue models.

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Compressions and relaxations were monitored with a non-invasive ultrasound method.

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Deformations in artificial tongue and food layers were assessed with signal processing.

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The method shows potential for understanding texture contrast perception.

Using ultrasound to characterize the tongue-food interface: An in vitro study examining the impact of surface roughness and lubrication

We measured the apparent reflection coefficient of a 1-MHz ultrasound compressional wave at the interface between rough and lubricated tongue mimicking surfaces and various food gels, composed of agar or gelatin. For the smoothest mimicking surface, when a lubricating layer was present, the apparent reflection coefficient was fairly similar for the different food gels (33.6% on average). The apparent reflection coefficient was significantly larger in the following situations: (i) tongue asperities were high and dense; (ii) lubrication levels were low; and (iii) gels were less rigid (range for the different gels-45.9-84.3%). The apparent reflection coefficient conveys the ability of food gels to mold themselves to surface asperities or to form a coupling film of liquid at the interface. This study demonstrates that ultrasound methods can and should be used to explore the physical phenomena that underlie the texture perceptions resulting from tongue-palate interactions.

A new technique for tongue brushing and halitosis reduction: the X technique

The tongue is one of the primary sources of halitosis. The manual or mechanical removal of biofilm is known to decrease oral malodor.