Masticatory Side-switch and Mixing Ability.

Study Overview
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Brief Summary
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The main aim of this cross-over intervention study is to assess the effect of masticatory side-switch frequency on different aspects of masticatory function, including masticatory mixing ability and rhythm. A secondary aim is to explore the subjective perception of taste, muscular fatigue, and saliva production through a VAS. Thirty-six volunteers recruited for convenience, among students of the Degree of Dentistry of the Faculty of Medicine and Health Sciences of the University of Barcelona, will perform 6 tests, each consisting of 2 assays, chewing a two-coloured chewing gum, during 40 masticatory cycles. The tests will be randomised masticatory sequences of free-style, unilateral-right, unilateral-left, switching the chewing side at 5% G05, at 15% G15 and at 25% G25. Video recordings of these tests will be made to later assess, on slow playback, the change of the chewing side and the masticatory rhythm. The masticatory mixing ability will be determined through the scanning and posterior analysis of the red-channel in the histogram plug-in in ImageJ (R).

Detailed Description
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This this cross-over intervention study aims to assess the effect of masticatory side-switch frequency on different objective aspects of masticatory function, including masticatory mixing ability and rhythm, as well as the subjective perception of taste, muscular fatigue, and saliva production through a VAS. Each of the thirty-six volunteers recruited for convenience, among students of the Degree of Dentistry of the Faculty of Medicine and Health Sciences of the University of Barcelona, will perform 6 tests, each consisting of 2 assays, chewing a two-coloured chewing gum, during 40 masticatory cycles. One test involves freestyle mastication in which the participant will be asked to masticate the chewing gum. Two tests involve chewing the gum unilaterally (i.e., only on the right-hand side, and only on the left) varying the order of these assays. In the last three tests, the volunteer will switch chewing side in 5% (G05), 15% (G15), or 25% (G25) respectively; the sequence of the assays will be randomized. Twenty-four of these volunteers will be randomly selected to repeat these tests after a period of two weeks. The masticatory mixing ability will be determined through the mixing capacity index (MCI), obtained from through the scanning and posterior analysis of the red-channel in the histogram plug-in in ImageJ (R), and the masticatory rhythm will be assessed through the masticatory frequency as the ratio of masticatory cycle number to masticatory time. The control variables will include age and sex.

Official Title
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Effect of Side Switch Frequency on Masticatory Mixing Ability and Perception of Taste, Muscular Fatigue and Saliva Production: A Randomized Crossover Trial.

Conditions
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Chewing Problem, Mastication Disorder

Intervention / Treatment
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* Behavioral: F
* Behavioral: R
* Behavioral: L
* Behavioral: G05
* Behavioral: G15
* Behavioral: G25


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Older than 18 years old. Natural dentition (minimum 24 teeth) Exclusion Criteria: Active orthodontics treatment. Intraoral pain. Temporomandibular joint pain. Masticatory muscle pain. Large dental restorations. Dental prosthesis. Edentulous spaces.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: F-R/L-G05/G15/G25 or G25/G15/G05-L/R-F Sequence<br>First, 2 freestyle masticatory assays (F). Second, 2 only-right (R) and 2 only-left (L) masticatory assays in the following order (R-L-L-R). Third, 6 masticatory assays changing in 5% (G05), 15% (G15) or 25% (G25) in the following order (G05-G15-G25-G25-G15-G05). Or First, 6 masticatory assays changing in 5% (G05), 15% (G15) or 25% (G25) in the following order (G05-G15-G25-G25-G15-G05). Second, 2 only-left (L) and 2 only-right (R) masticatory assays in the following order (L-R-R-L). Third, 2 freestyle masticatory assays (F). | Behavioral: F<br>* The participant will be asked to chew the two-coloured chewing gum naturally.<br>Behavioral: R<br>* The participant will be asked to chew the two-coloured chewing gum on the right-side.<br>Behavioral: L<br>* The participant will be asked to chew the two-coloured chewing gum on the left-side.<br>Behavioral: G05<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 5%.<br>Behavioral: G15<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 15%.<br>Behavioral: G25<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 25%.<br>|
| Active Comparator: F-R/L-G05/G25/G15 or G15/G25/G05-F-L/R Sequence<br>First, 2 freestyle masticatory assays (F). Second, 2 only-right (R) and 2 only-left (L) masticatory assays in the following order (R-L-L-R). Third, 6 masticatory assays changing in 5% (G05), 15% (G15) or 25% (G25) in the following order (G05-G25-G15-G15-G25-G05). Or First, 6 masticatory assays changing in 5% (G05), 15% (G15) or 25% (G25) in the following order (G05-G25-G15-G15-G25-G05). Second, 2 only-left (L) and 2 only-right (R) masticatory assays in the following order (L-R-R-L). Third, 2 freestyle masticatory assays (F). | Behavioral: F<br>* The participant will be asked to chew the two-coloured chewing gum naturally.<br>Behavioral: R<br>* The participant will be asked to chew the two-coloured chewing gum on the right-side.<br>Behavioral: L<br>* The participant will be asked to chew the two-coloured chewing gum on the left-side.<br>Behavioral: G05<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 5%.<br>Behavioral: G15<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 15%.<br>Behavioral: G25<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 25%.<br>|
| Active Comparator: F-R/L-G15/G05/G25 or G25/G05/G15-F-L/R Sequence<br>First, 2 freestyle masticatory assays (F). Second, 2 only-right (R) and 2 only-left (L) masticatory assays in the following order (R-L-L-R). Third, 6 masticatory assays changing in 5% (G05), 15% (G15) or 25% (G25) in the following order (G05-G15-G25-G25-G15-G05). Or First, 6 masticatory assays changing in 5% (G05), 15% (G15) or 25% (G25) in the following order (G15-G05-G25-G25-G05-G15). Second, 2 only-left (L) and 2 only-right (R) masticatory assays in the following order (L-R-R-L). Third, 2 freestyle masticatory assays (F). | Behavioral: F<br>* The participant will be asked to chew the two-coloured chewing gum naturally.<br>Behavioral: R<br>* The participant will be asked to chew the two-coloured chewing gum on the right-side.<br>Behavioral: L<br>* The participant will be asked to chew the two-coloured chewing gum on the left-side.<br>Behavioral: G05<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 5%.<br>Behavioral: G15<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 15%.<br>Behavioral: G25<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 25%.<br>|
| Active Comparator: F-R/L-G15/G25/G05 or G05/G25/G15-F-L/R Sequence<br>First, 2 freestyle masticatory assays (F). Second, 2 only-right (R) and 2 only-left (L) masticatory assays in the following order (R-L-L-R). Third, 6 masticatory assays changing in 5% (G05), 15% (G15) or 25% (G25) in the following order (G15-G25-G05-G05-G25-G15). Or First, 6 masticatory assays changing in 5% (G05), 15% (G15) or 25% (G25) in the following order (G15-G25-G05-G05-G25-G15). Second, 2 only-left (L) and 2 only-right (R) masticatory assays in the following order (L-R-R-L). Third, 2 freestyle masticatory assays (F). | Behavioral: F<br>* The participant will be asked to chew the two-coloured chewing gum naturally.<br>Behavioral: R<br>* The participant will be asked to chew the two-coloured chewing gum on the right-side.<br>Behavioral: L<br>* The participant will be asked to chew the two-coloured chewing gum on the left-side.<br>Behavioral: G05<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 5%.<br>Behavioral: G15<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 15%.<br>Behavioral: G25<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 25%.<br>|
| Active Comparator: F-R/L-G25/G05/G15 or G15/G05/G25-F-L/R Sequence<br>First, 2 freestyle masticatory assays (F). Second, 2 only-right (R) and 2 only-left (L) masticatory assays in the following order (R-L-L-R). Third, 6 masticatory assays changing in 5% (G05), 15% (G15) or 25% (G25) in the following order (G25-G05-G15-G15-G05-G25). Or First, 6 masticatory assays changing in 5% (G05), 15% (G15) or 25% (G25) in the following order (G25-G05-G15-G15-G05-G25). Second, 2 only-left (L) and 2 only-right (R) masticatory assays in the following order (L-R-R-L). Third, 2 freestyle masticatory assays (F). | Behavioral: F<br>* The participant will be asked to chew the two-coloured chewing gum naturally.<br>Behavioral: R<br>* The participant will be asked to chew the two-coloured chewing gum on the right-side.<br>Behavioral: L<br>* The participant will be asked to chew the two-coloured chewing gum on the left-side.<br>Behavioral: G05<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 5%.<br>Behavioral: G15<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 15%.<br>Behavioral: G25<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 25%.<br>|
| Active Comparator: F-R/L-G25/G15/G05 or G05/G15/G25-F-L/R Sequence<br>First, 2 freestyle masticatory assays (F). Second, 2 only-right (R) and 2 only-left (L) masticatory assays in the following order (R-L-L-R). Third, 6 masticatory assays changing in 5% (G05), 15% (G15) or 25% (G25) in the following order (G25-G15-G05-G05-G15-G25). Or First, 6 masticatory assays changing in 5% (G05), 15% (G15) or 25% (G25) in the following order (G25-G15-G05-G05-G15-G25). Second, 2 only-left (L) and 2 only-right (R) masticatory assays in the following order (L-R-R-L). Third, 2 freestyle masticatory assays (F). | Behavioral: F<br>* The participant will be asked to chew the two-coloured chewing gum naturally.<br>Behavioral: R<br>* The participant will be asked to chew the two-coloured chewing gum on the right-side.<br>Behavioral: L<br>* The participant will be asked to chew the two-coloured chewing gum on the left-side.<br>Behavioral: G05<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 5%.<br>Behavioral: G15<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 15%.<br>Behavioral: G25<br>* The participant will be asked to chew the two-coloured chewing gum changing the side in 25%.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Masticatory mixing ability | Masticatory mixing ability will be calculated from the mixing capacity for each type of test (free, right, left and guided). Chewing gum will flattened between two rigid surfaces to a thickness of 1.5 mm. The two sides of the chewing gum will then be scanned at a resolution of 300 dpi. The images will be processed with ImageJ with the Color-Histogram plugin. Before mixing, the green and red color of the chewing gum are represented in the histogram of the red channel as two separate peaks: one in low intensity and one in high intensity, representing the green and red color of chewing gum, respectively. After mixing, the colors are mixed and so the two peaks merge into one peak. The standard deviation of the intensity distribution is taken as a measure of the mixture of the two colors in the chewing gum. The standard deviation at an early stage of mixing is relatively high, and decreases as the colors are mixed; thus, a high value of the mixing index means a high mixing capacity. | 1 hour | 
| Side-switch Index | The number of side switches during the 40 masticatory cycles for each assay will be determined using slow playback of the video recordings of the freestyle mastication test. In the case that this switch is a change of side from left to right or right to left, we will assign a value of 1. If this switch consists of a change from the right or left to central or vice versa, we will assign a value of 0.5. If there is no change of side, the value assigned to this chewing cycle will be 0. To determine the Side-switch Index, the number of side changes will be divided by the maximum number of changes possible during these 5 assays (78). | 1 hour | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Masticatory Frequency | Masticatory frequency will be assessed as the ratio of masticatory cycle number to masticatory time (in cycles per minute). | 1 hour | 
| Degree of muscular fatigue during this masticatory assay | The degree of muscular fatigue while chewed the gum was assessed by asking the question How much muscular fatigue do you think this masticatory test caused you? using a 0-10 point scale (considering 0= Not at all to 10= very much). Participants will rate the masticatory test after each assay. | 1 hour | 
| Degree of salivary secretion during this masticatory assay | The degree of salivary secretion while chewed the gum was assessed by asking the question How much saliva secretion do you think this masticatory test caused you? using a 0-10 point scale (considering 0= Not at all to 10= very much). Participants will rate the masticatory test after each assay. | 1 hour | 
| Degree of taste perception during this masticatory assay | The degree of taste perception while chewed the gum was assessed by asking the question To what degree do you think this masticatory test facilitates taste perception? using a 0-10 point scale (considering 0= Not at all to 10= very much). Participants will rate the masticatory test after each assay. | 1 hour | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Chewing side, Masticatory side-switch, Mastication, Masticatory rhythm, Masticatory performance, Masticatory mixing ability