Properties of a color-changeable chewing gum used to evaluate masticatory performance

PurposeTo clarify the basic properties of a color-changeable chewing gum to determine its applicability to evaluations of masticatory performance under different types of dental status.MethodsTen participants with natural dentition aged 26–30 years chewed gum that changes color during several chewing strokes over five repetitions. Changes in color were assessed using a colorimeter, and then L*, a*, and b* values in the CIELAB color system were quantified. Relationships between chewing progression and color changes were assessed using regression analysis and the reliability of color changes was assessed using intraclass correlation coefficients. We then measured 42 dentate participants (age, 22–31 years) and 47 complete denture wearers (age, 44–90 years) to determine the detectability of masticatory performance under two types of dental status.ResultsRegression between the number of chewing strokes and the difference between two colors was non-linear. The intraclass correlation coefficients were highest between 60 and 160 chewing strokes. Dentate and edentulous groups significantly differed (Wilcoxon rank sum test) and values were widely distributed within each group.ConclusionsThe color of the chewing gum changed over a wide range, which was sufficient to evaluate the masticatory performance of individuals with natural dentition and those with complete dentures. Changes in the color values of the gum reliably reflected masticatory performance. These findings indicate that the color-changeable chewing gum will be useful for evaluating masticatory performance under any dental status.     

Electromyographic activity of superficial masseter and anterior temporal muscles during unilateral mastication of artificial test foods with different textures in healthy subjects

Objectives

This study aimed to examine the electromyographic activity of superficial masseter and anterior temporal muscles during chewing gum and gummy jelly mastication in healthy subjects to reveal the difference of neuromuscular control of jaw-closing muscles, according to the food texture.

Materials and methods

Electromyographic activity was recorded in 30 adults with Angle Class I occlusion and unimpaired function from the bilateral superficial masseter and anterior temporal muscles during unilateral mastication of two test foods: standardized gummy jelly and color-changeable chewing gum. Differences in normalized electromyographic activity and asymmetry index values between gummy jelly and chewing gum mastication were analyzed during the early, middle, and late phases of mandibular closure. Furthermore, changes among the three closing phases were compared for each test food.

Results

High electromyographic activity of both muscles tended to occur bilaterally during the middle and late closing phases during gummy jelly mastication, but increased muscle activity in the late closing phase was not observed during chewing gum mastication. The asymmetry index of the superficial masseter muscle increased significantly from early to late closure, regardless of the food texture, but it tended to decrease for the anterior temporal muscle during gummy jelly mastication.

Conclusion

The different aspects of the chewing process between the comminution and mixing test measures are necessary to elicit the different human neuromuscular strategies of chewing for different test foods.

Clinical relevance

These characteristic EMG activities of the superficial masseter and anterior temporalis muscles may be used as supporting diagnostic information during patient assessments and a reference during evaluation of masticatory system disharmony or dysfunction.

     

Validity and reliability of a Self-Implementable method to evaluate masticatory performance: Use of color-changeable chewing gum and a color scale

PurposeThe objective of this study was to confirm the validity of a Self-Implementable method to evaluate masticatory performance using a newly developed color scale and color-changeable chewing gum.MethodsWe developed a dedicated color scale that enables anyone to easily check the color of the chewing gum instead of using specialist equipment. To examine the reliability of evaluating the masticatory performance by the subjects themselves, three groups of six subjects were recruited: a group of dentists, a group of adults and a group of elderly adults were asked to check the colors of the chewed samples using the color scale. The correlation between the use of the color scale and the use of a colorimeter to determine the color of the chewing gum was studied to confirm the validity of the color scale. To assess the reliability, intraclass correlation coefficients (ICCs) were determined.ResultsA strong correlation was found between the a* value measured by the colorimeter and the mean scores from the color scale. The ICCs for intra-examiner and inter-examiner consistency were more than 0.88 for all three groups.ConclusionsThis research confirmed the validity and reliability of colorimetric analysis of color-changeable chewing gum using a color scale as a Self-Implementable method of evaluating masticatory performance.     

Comparison of dynamic electromyographic analysis of masticatory capsules with materials of different textures

The aim of this study was to compare the mastication electromyographic indexes of capsules used for the masticatory efficiency evaluation “ME-mastig” and of materials of different textures (gum, raisins, and peanuts).

Methods: Thirty young, healthy, adult subjects, with an average age of 23.46?years old, with no symptoms of temporomandibular dysfunction (TMD), confirmed by the clinical exam, RDC/TMD, and the static test of electromyography (EMG) were chosen. Afterward, dynamic tests were performed (bilateral mastication of the compounds) to determine number of chewing cycles (CYCLES); masticatory frequency (FREQ); SMI (symmetrical masticatory index – corresponding to the value of neuromuscular coordination during mastication); and IMPACT (corresponding to impact – total electromyographic activity performed by the system during chewing).

Results: Cycle and frequency were similar. Regarding SMI and IMPACT, the raisin, the capsule, and the peanut were similar between each other, and different from the gum.

Conclusions: Masticatory capsules and the natural foods with different textures had similar results regarding EMG indexes.     

Is the side with the best masticatory performance selected for chewing?

ObjectiveThis study assessed the degree of relationship between masticatory laterality and lateral asymmetry of masticatory performance using silicon pieces enclosed in a latex bag.DesignForty-two young adults with natural dentition participated in this cross-sectional, observational study. They performed four different masticatory assays, each consisting of five trials of chewing three pieces of silicon for 20 cycles. In one assay, they were asked to masticate unbagged silicon free-style, whilst in the three other assays they were asked to masticate bagged silicon free-style, unilaterally on the right-hand side and unilaterally on the left-hand side. The preferred chewing side was determined by calculating the asymmetry index for both the free-style assays. Masticatory performance was determined by sieving the silicon particles and the cycle duration was also recorded. Data were analysed using independent samples or paired t-test and linear regression.ResultsMasticatory function using the bagged silicon was similar to that using the unbagged silicon. A significant and positive relationship was observed between the preferred chewing side expressed as the asymmetry index and the side with better masticatory performance. Alternate unilateral chewers demonstrated better masticatory performance than unilateral chewers. However, when free-style and unilateral chewing were compared for each subject, unilateral chewing was found to be as efficient as – or even more efficient than – free-style chewing.ConclusionsThere is a positive association between the preferred chewing side and the more efficient side. Alternate unilateral mastication per se does not promote better masticatory performance than consistently unilateral mastication.     

Reliability of a two‐colour chewing gum test to assess masticatory performance in complete denture wearers

The aim of this study was to test the reliability of a method to measure the masticatory performance of complete denture wearers employing a colour‐mixing ability test and assessment by visual and electronic colourimetric analysis. A sample of 75 subjects was selected from patients who received new conventional complete dentures. Masticatory tests were performed using a two‐colour chewing gum that was masticated for 5, 10, 20, 30 and 50 chewing cycles, performed in a random order. The mixing level of the two colours of the chewed gum was assessed visually by two independent raters based on a 5‐point ordinal scale. The specimens were flattened into a 1‐mm‐width wafer, scanned and saved as a two‐sided digital image. Each pair of images was submitted to an electronic colourimetric analysis to assess the level of colour mixture, measured by the circular variance of hue (VOH ). Overall inter‐ and intra‐rater agreements in visual analysis were 64% and 68%, respectively (almost 99% of scores ranged within ±1 point), whilst overall weighted kappa was >0.80. A proportional increase in the level of mixture occurred with increased number of chewing cycles (P  < .001). Similarly, VOH and the visual analysis were highly correlated (r = ?.89; P  < .001). Bland‐Altman plots revealed excellent agreement and extremely low systematic error between duplicated VOH measures. It was concluded that the two‐colour chewing gum test is a reliable method to assess the masticatory performance in complete denture wearers using both visual and electronic colourimetric analyses.     

Chewing Performance Calculator: An interactive clinical method for quantifying masticatory performance

Statement of problemThere is a need to quantitatively differentiate between impaired and normal mastication by using straightforward and reliable methods because currently available methods are expensive, complex, and time-consuming.PurposeThe purpose of this clinical study was to assess the reliability, validity, and clinical utility of a new Web-based software program designed to calculate masticatory performance, the Chewing Performance Calculator (CPC) measuring masticatory performance (MP), by analyzing the area of mixed bicolored chewing gum.Material and methodsOne hundred and ten participants were consecutively recruited from the School of Dentistry of the University of Salamanca. MP was determined by using 2-colored chewing gum that was masticated for a total of 20 strokes. The masticated gum was then flattened between 2 transparent glass tiles, generating a 1-mm-thick specimen that was scanned to calculate the percentage of area where the 2 colors were mixed. The area was calculated by using a photo-editing software program as described by Schimmel et al (standard method). In addition, all the images were analyzed by using the CPC Web application, which took as input the image of the masticated bolus enclosed in a custom plastic platen that allowed 3 parts of the image to be selected interactively: the platen, the bolus background, and the mixed color fraction of the bolus. The application then computed MP as a percentage. Additionally, an oral examination was carried out to record the number of occlusal units. These data were used to assess the validity of CPC by using the Pearson correlation coefficient. Construct validity was assessed by using ANOVA by comparing the MP scores obtained for masticated gums, classified upon inspection as being poorly, moderately, or highly mixed. The time spent evaluating the specimens with GSM and CPC methods was also recorded and used to indicate the usefulness of the procedure.ResultsThe MP was found to range between 5.2% and 100% (95% CI: 80.8–88.8) with the GSM and between 9.2% and 96.4% (95% CI: 60.0–67.6) with the CPC. The time needed to calculate MP by using the GSM was significantly higher (235.2 versus 260.5 seconds) than that with the CPC (42.3 to 48.6 seconds). Both methods were significantly intercorrelated (r=0.65; P<.001) and correlated with the number of occlusal units (r=0.54 for CPC and r=0.40 for GSM). The correlation coefficient of MP calculated by using CPC (r=0.54; P<.001) was greater than that calculated by using GSM (r=0.40; P<.001). Moreover, both methods showed adequate construct validity because the values calculated for MP significantly increased as the mixing of the masticated gums also increased, subjectively classified as poor, moderate, and high.ConclusionsThe CPC software program allowed MP to be determined in a valid and easy-to-use manner by using 2-colored chewing gum.     

Comparative cross-sectional study of masticatory performance and mastication predominance for patients with missing posterior teeth

PurposeMissing posterior teeth can decrease masticatory function and cause horizontal mastication deviation, i.e., mastication predominance. Mastication predominance may lead to abnormal tooth attrition and temporomandibular disorders. This study evaluated masticatory performance and mastication predominance in patients with missing posterior teeth to investigate effects of missing posterior teeth on masticatory performance and mastication predominance.MethodsThirty volunteers with normal dentition (control group), 30 patients with unilateral missing posterior teeth (unilateral group), and 23 patients with bilateral missing posterior teeth (bilateral group) participated. Gummy jellies were used to evaluate participants’ masticatory performance, and electromyography was used to assess the degree of mastication predominance. Chewing gums, gummy jellies, and peanuts were used as foods of various hardnesses for evaluating mastication predominance.ResultsCompared with the control group, masticatory performance did not differ in the unilateral group but was significantly decreased in the bilateral group. With chewing gum and gummy jellies, the degree of mastication predominance was significantly increased in both unilateral and bilateral groups than the control group. With peanuts, the degree of mastication predominance was significantly increased in the unilateral group than the control group.ConclusionsAlthough masticatory performance was not decreased in the unilateral group, the degree of mastication predominance was increased. Decreased masticatory performance was observed in the bilateral group, and for foods with normal hardness and soft foods, the degree of mastication predominance was increased. These results suggested that mastication predominance should be considered in the recovery of masticatory performance in patients with missing posterior teeth.     

The effect of bolus size on the chewing cycle in humans

No general agreement exists regarding the effect that bolus size has on masticatory movement, probably because both the size and texture of food change during mastication. In this experiment, in order to clarify the effect of bolus size on masticatory movement, a food that does not change in size and texture – chewing gum – was chosen, and the relationship between bolus size and the chewing cycle was analyzed. Ten healthy subjects in their twenties were asked to chew pieces of softened chewing gum of four different sizes. For ten cycles, beginning with the fifth cycle of mastication, gape and masticatory width were calculated for the spatial parameter of the chewing cycle, and cycle time was calculated as the temporal parameter. The relationship between these parameters and the bolus size was investigated. As the bolus size increased, the spatial and temporal parameters increased. In addition, there was a positive correlation between the bolus size and each parameter. The influence of the bolus size was as follows: gape, r = 0.91; masticatory width, r = 0.79; and cycle time, r = 0.74 (all, P < 0.001). From these results it was concluded that the shape of the chewing cycle was altered by the size of the food bolus, and that the changes in sensory input from the peripheries greatly affected the masticatory movement. Received: October 10, 2000 / Accepted: July 16, 2001     

Two‐colour chewing gum mixing ability test for evaluating masticatory performance in children with mixed dentition: validity and reliability study

The unappealing taste of the chewing material and the time‐consuming repetitive task in masticatory performance tests using artificial foodstuff may discourage children from performing natural chewing movements. Therefore, the aim was to determine the validity and reliability of a two‐colour chewing gum mixing ability test for masticatory performance (MP) assessment in mixed dentition children. Masticatory performance was tested in two groups: systemically healthy fully dentate young adults and children in mixed dentition. Median particle size was assessed using a comminution test, and a two‐colour chewing gum mixing ability test was applied for MP analysis. Validity was tested with Pearson correlation, and reliability was tested with intra‐class correlation coefficient, Pearson correlation and Bland–Altman plots. Both comminution and two‐colour chewing gum mixing ability tests revealed statistically significant MP differences between children (n = 25) and adults (n = 27, both P < 0·01). Pearson correlation between comminution and two‐colour chewing gum mixing ability tests was positive and significant (r = 0·418, P = 0·002). Correlations for interobserver reliability and test–retest values were significant (r = 0·990, P = 0·0001 and r = 0·995, P = 0·0001). Although both methods could discriminate MP differences, the comminution test detected these differences generally in a wider range compared to two‐colour chewing gum mixing ability test. However, considering the high reliability of the results, the two‐colour chewing gum mixing ability test can be used to assess masticatory performance in children, especially at non‐clinical settings.     

Novel software for quantitative evaluation and graphical representation of masticatory efficiency

Blending of chewing gums of different colours is used in the clinical setting, as a simple and reliable means for the assessment of chewing efficiency. However, the available software is difficult to use in an everyday clinical setting, and there is no possibility of automated classification of the patient's chewing ability in a graph, to facilitate visualisation of the results and to evaluate potential chewing difficulties. The aims of this study were to test the validity of ViewGum – a novel image analysis software for the evaluation of boli derived from a two‐colour mixing ability test – and to establish a baseline graph for the representation of the masticatory efficiency in a healthy population. Image analysis demonstrated significant hue variation decrease as the number of chewing cycles increased, indicating a higher degree of colour mixture. Standard deviation of hue (SDHue) was significantly different between all chewing cycles. Regression of the log‐transformed values of the medians of SDHue on the number of chewing cycles showed a high statistically significant correlation (r² = 0·94, P < 0·01). ViewGum eliminates drawbacks of previous two‐colour chewing gum test methods by the simplicity of its application. The newly developed ViewGum software provides speed, ease of use and immediate extraction of clinically useful conclusions to the already established method of chewing efficiency evaluation and is a valid adjunct for the evaluation of masticatory efficiency with two‐colour chewing gum.     

Influence of voluntary control of masticatory side and rhythm on cerebral hemodynamics

The aim of this study was to investigate the influence on cerebral hemodynamics of voluntary control of masticatory side and rhythm during gum chewing. Blood flow velocity in the middle cerebral artery was measured using transcranial Doppler ultrasonography to evaluate cerebral circulation in healthy volunteers. Heart rate and masseter muscle activity were recorded simultaneously. Volunteers performed three tasks: (1) free gum chewing, (2) gum chewing in which mastication was limited to the right side, and (3) gum chewing in which mastication was limited to the right side and rhythm was set at 1.0 Hz. Changes in cerebral circulation during pre-task, on-task, and post-task periods were analyzed using random effects model, and differences in cerebral circulation and muscle activity between tasks were analyzed using the Friedman test. In all tasks, on-task cerebral circulation was greater than pre-task. Muscle activity and masticatory rhythm varied between tasks, whereas the rate of increase in cerebral circulation did not differ significantly among tasks. These results suggest that cerebral circulation is activated during gum chewing, irrespective of voluntary control of masticatory side and rhythm.     

Distance of the contact glide in the closing masticatory stroke during mastication of three types of food

Summary  This study was designed to characterize the distance of the contact glide in the closing masticatory stroke in healthy adult subjects, during chewing of three types of food (crustless bread, chewing gum and peanuts). Mandibular movements (masticatory movements and laterality movements with dental contact) were registered using a gnathograph (MK-6I Diagnostic System) on the right and left side during unilateral chewing of the three food types. Length of dental contact was measured in masticatory cycle, which is defined as where the terminal part of the chewing cycles could be superimposed on the pathways taken by the mandible during lateral excursions with occlusal contacts. The length of dental contact during mastication of chewing gum is 1·46 ± 1 mm, during chewing of soft bread is 1·38 ± 0·7 mm and during chewing of peanuts is 1·45 ± 0·9 mm. There is no significant difference in the lengths of dental contact during mastication of three types of foods that enable direct tooth gliding.     

The 6‐min mastication test: a unique test to assess endurance of continuous chewing,normal values,reliability, reproducibility and usability in patients with mitochondrial disease

In patients with mitochondrial disease, fatigue and muscle problems are the most common complaints. They also experience these complaints during mastication. To measure endurance of continuous mastication in patients with mitochondrial diseases, the 6‐min mastication test (6MMT) was developed. This study included the collection of normal data for the 6MMT in a healthy population (children and adults). During 6 min of continuous mastication on a chew tube chewing cycles per minute, total amount of chewing cycles and the difference between minute 1 (M₁) and minute 6 (M₂) were collected in 271 healthy participants (5–80 years old). These results were compared with those of nine paediatric and 25 adult patients with a mitochondrial disease. Visual analogue scale (VAS) scores were collected directly after the test and after 5 min. A qualitative rating was made on masticatory movements. The reproducibility of the 6MMT in the healthy population with an interval of approximately 2 weeks was good. The inter‐rater reliability for the observations was excellent. The patient group demonstrated lower total amount of chewing cycles or had greater differences between M₁ and M₆. The 6MMT is a reliable and objective test to assess endurance of continuous chewing. It demonstrates the ability of healthy children and adults to chew during 6 min with a highly stable frequency of mastication movements. The test may give an explanation for the masticatory problems in patient groups, who are complaining of pain and fatigue during mastication.     

A two-colored chewing gum test for assessing masticatory performance: a preliminary study

This study was conducted to compare subjective and objective assessment methods of a two-colored chewing gum test and to find out whether these methods are capable of discriminating masticatory performances between sexes. 31 adults, 16 males and 15 females participated in this study. Each subject chewed five samples of two-colored chewing gum sticks for 5, 10, 20, 30 and 50 chewing strokes, respectively. The subjective color-mixing and shape indices for the gum bolus (SCMI-B, SSI-B) and the subjective color-mixing index and objective color-mixing ratio for the gum wafer (SCMI-W, OCMR-W) were evaluated by two independent examiners and, on a different day, re-evaluated by one of the examiners. The SCMI-B and SCMI-W assessments had inter- and intra-examiner reliable agreement at 20 or more chewing strokes. The OCMR-W measurement demonstrated high accuracy and low reproducibility between and within the examiners. There were significant gender differences in the distribution of SCMI-W scores (P = 0.044) and in the mean OCMI-W (P = 0.007). The SCMI-B and SCMI-W assessments and the OCMR-W measurement were reliable and valid at the 20 and 30 chewing strokes in this two-colored chewing gum test. The subjective color-mixing index (SCMI-W) and objective color-mixing ratio (OCMR-W) for the chewing gum wafer are capable of discriminating masticatory performance between sexes in this two-colored chewing gum test and that the OCMR-W measurement is discriminating better than the SCMI-W assessment.     

Influence of posterior dental arch length on brain activity during chewing in patients with mandibular distal extension removable partial dentures

It is well known that shortened dental arch decreases masticatory function. However, its potential to change brain activity during mastication is unknown. The present study investigates the effect of a shortened posterior dental arch with mandibular removable partial dentures (RPDs) on brain activity during gum chewing. Eleven subjects with missing mandibular molars (mean age, 66·1 years) on both sides received experimental RPDs with interchangeable artificial molars in a crossover trial design. Brain activity during gum chewing with RPDs containing (full dental arch) and lacking artificial molars (shortened dental arch) was measured using functional magnetic resonance imaging. Additionally, masticatory function was evaluated for each dental arch type. Food comminuting and mixing ability and the perceived chewing ability were significantly lower in subjects with a shortened dental arch than those with a full dental arch (P < 0·05). Brain activation during gum chewing with the full dental arch occurred in the middle frontal gyrus, primary sensorimotor cortex extending to the pre‐central gyrus, supplementary motor area, putamen, insula and cerebellum. However, middle frontal gyrus activation was not observed during gum chewing with the shortened dental arch. These results suggest that shortened dental arch affects human brain activity in the middle frontal gyrus during gum chewing, and the decreased middle frontal gyrus activation may be associated with decreased masticatory function.     

The effect of mouth breathing on chewing efficiency

Objective:To examine the effect of mouth breathing on chewing efficiency by evaluating masticatory variables.Materials and Methods:Ten adult nasal breathers with normal occlusion and no temporomandibular dysfunction were selected. Subjects were instructed to bite the chewing gum on the habitual side. While breathing through the mouth and nose, the glucide elution from the chewing gum, number of chewing strokes, duration of chewing, and electromyography (EMG) activity of the masseter muscle were evaluated as variables of masticatory efficiency.Results:The durations required for the chewing of 30, 60, 90, 120, 180, and 250 strokes were significantly (P < .05) longer while breathing through the mouth. There was no significant difference in the glucide elution rate (%) for each chewing stroke between nose and mouth breathings. The glucide elution rates for 1- and 3-minute chewing were significantly (P < .05) lower while breathing through the mouth. However, there was no significant difference in the glucide elution rate for 5-minute chewing between nose and mouth breathings. While chewing for 1, 3, and 5 minutes, the chewing stroke and EMG activity of the masseter muscle were significantly (P < .05) lower during mouth breathing.Conclusions:It takes a longer amount of time to complete chewing to obtain higher masticatory efficiency when breathing through the mouth. Therefore, mouth breathing will decrease the masticatory efficiency if the duration of chewing is restricted in everyday life.     

Two‐colour chewing gum mixing ability: digitalisation and spatial heterogeneity analysis

Many techniques are available to assess masticatory performance, but not all are appropriate for every population. A proxy suitable for elderly persons suffering from dementia was lacking, and a two‐colour chewing gum mixing ability test was investigated for this purpose. A fully automated digital analysis algorithm was applied to a mixing ability test using two‐coloured gum samples in a stepwise increased number of chewing cycles protocol (Experiment 1: n = 14; seven men, 19–63 years), a test–retest assessment (Experiment 2: n = 10; four men, 20–49 years) and compared to an established wax cubes mixing ability test (Experiment 3: n = 13; 0 men, 21–31 years). Data were analysed with repeated measures anova (Experiment 1), the calculation of the intraclass correlation coefficient (ICC; Experiment 2) and Spearman's rho correlation coefficient (Experiment 3). The method was sensitive to increasing numbers of chewing cycles (F_5,65 = 57·270, P = 0·000) and reliable in the test–retest (ICC value of 0·714, P = 0·004). There was no significant correlation between the two‐coloured gum test and the wax cubes test. The two‐coloured gum mixing ability test was able to adequately assess masticatory function and is recommended for use in a population of elderly persons with dementia.     

A two-colour chewing gum test for masticatory efficiency: development of different assessment methods

OBJECTIVE: The aim of this study was to investigate different assessment methods of a two-colour chewing gum test for masticatory efficiency to determine its validity for research and clinical purposes. MATERIALS AND METHODS: Twenty adult volunteers, eleven women and nine men (mean age of 27.5 years), participated in this study. All participants perceived their masticatory efficiency as normal. The task was to chew five samples of a two-colour chewing gum for 5, 10, 20, 30 and 50 cycles respectively. Maximum bite force was measured. All samples were assessed twice by two independent operators both, as 'bolus' and after flattening to 1 mm thick 'wafers'. The latter were scanned and the unmixed pixels counted using Adobe Photoshop Elements to calculate the ratio of unmixed colour to the total surface. RESULTS: Digital image processing confirmed a significant correlation between colour mixing and chewing duration (P < 0.001). Subjective assessment proved less accurate with fair to substantial intra-examiner agreement for 'bolus' (0.20 < kappa < 0.63) and substantial to almost perfect agreement for 'wafer' (0.60 < kappa < 0.88). Inter-examiner agreement was consistently moderate or substantial only for specimen chewed 20 cycles or longer. No significant correlation was found between the colour mixture and the maximum bite force. CONCLUSION: Digital image processing of the two-colour chewing gum test specimen provides reliable quantitative data for chewing efficiency. Visual assessments were less reliable but might still be useful in screening for chewing deficiencies in a clinical setting. In this context, the test should be performed with a flattened specimen chewed, probably for 20 cycles.     

Selection of food and chewing side for evaluating masticatory path stability

In order to find the most suitable food and chewing side for evaluating the stability of masticatory movement, three types of food with varying textures, as well as both free chewing and unilateral chewing, were utilized in analyzing the masticatory path during mastication. A piece of chewing gum, one peanut, and a slice of crispy bread were used as test foods. For 20 healthy subjects, movement of the incisal point while masticating a test food for 10s on the free side and the habitual side was recorded. Indicators representing movement path stability were calculated and compared among the foods and between the chewing sides. Masticatory movement was most stable when masticating chewing gum, and less stable for the peanut, and most unstable for the crispy bread. There was a statistically significant difference between each pair of foods for almost all of the indicators. The indicators for peanut were approximately 1.5 times larger than those for masticating chewing gum and the indicators for crispy bread were double those for the chewing gum. When comparing free chewing with unilateral chewing, the masticatory movement of unilateral chewing was significantly more stable than that of free chewing for all test foods. From these results it was suggested that, for evaluating masticatory movement path stability, the most suitable type of food was softened chewing gum and the most suitable chewing method was unilateral chewing on the habitual chewing side.