Mixing Ability Index Research Articles

Changes in masticatory function after injection of botulinum toxin type A to masticatory muscles

This study examined changes in masticatory function after botulinum toxin type A (BTX-A) injection using objective and subjective tests during 12weeks. Also, we compared differences in masticatory function between group in which only masseter muscle (M group) was injected and group in which masseter and temporal muscle (M-T group) were injected. Forty subjects were assigned into two groups; M group (n=20) and the M-T group (n=20). The Meditoxin(®) was used as BTX-A injection. The mixing ability index (MAI) was used as the objective indicator, and visual analogue scale (VAS) and food intake ability (FIA) index were used as subjective indicators. Overall, the masticatory function drastically declined after 4weeks and gradually recovered with time. Compared with the pre-injection state, the masticatory function decreased by 89·2% (MAI), 12·2% (FIA) and 32·2% (VAS) 4weeks after the injection (P<0·05). When the results between M group and M-T group were compared, scores of VAS and FIA were significantly different 4weeks after the injection (P<0·05), but the MAI score showed no significant difference between two groups. In conclusion, this study showed that masticatory function was significantly decreased after BTX-A injection into the masticatory muscle after 4 and 8weeks from injection. However, masticatory efficiency measured using MAI could completely recover after 12weeks. Furthermore, after 8weeks from the injection, the masticatory function measured after injection into only the masseter muscle was similar to that measured after injection into both masseter and temporal muscle.

보툴리눔 A형 독소가 저작효율에 미치는 영향

This study was aimed to evaluate the masticatory efficiency after botulinum toxin type A (BTX-A) injection during 12 weeks using objective and subjective test. Also, we compared the difference of masticatory efficiency between group that injected into the masseter muscle only (M-group) and group that injected into the masseter and temporalis muscle (M-T group). The mixing ability index (MAI) was used as the objective indicator, and visual analogue scale (VAS) and food intake ability (FIA) index were used as the subjective indicators. It was concluded that masticatory efficiency was significantly lowered after a BTX-A injection into the masticatory muscle, but it gradually recovered in a predictable pattern by the 12 weeks. The disturbance of subjective masticatory efficiency was lasted longer than objective masticatory efficiency. The masticatory efficiency was lower in M-T group than M group. It was statistically significant in the VAS and FIA at 4 weeks, but the MAI showed no significancy. After 4weeks, there was rapid recovery of muscle function in M-T group, and the difference between two groups was not significant. It could be concluded that there will be no serious disturbance of mastication compared to injection is done only into the masseter muscle, even if injection is done into the masseter and temporalis muscle in dose of this study. According to the food properties, it was confirmed that people feel more discomfort on taking hard and tough foods after BTX-A injection and not only hard foods, but also intake of soft and runny foods were influenced by botulinum toxin injection.

Effects of delayed‐onset muscle soreness on masticatory function

The aim was to clarify the effects of experimentally provoked delayed-onset muscle soreness (DOMS) in the jaw-closing muscles on subjective and objective measures of masticatory function. Twenty-one dentate female subjects, without pain-related signs and symptoms of temporomandibular disorders, participated. Delayed-onset muscle soreness was provoked with eccentric and concentric contractions of the jaw-closing muscles using a custom-made apparatus. At baseline, and 24 h and 1 wk after the exercises, data were gathered on the subjective measures of muscle fatigue, muscle pain, and masticatory chewing ability using visual analogue scale (VAS) scores, on the maximum voluntary bite force (MVBF), and on the food Mixing Ability Index (MAI). After 24 h, muscle fatigue and muscle pain had increased and the MAI had decreased. All had returned to baseline levels after 1 wk. There were no significant changes found in the chewing ability VAS scores and in the MVBF over time. After correction for its baseline value, the MAI after 24 h was found to be significantly related to the muscle pain after 24 h. In conclusion, DOMS in the jaw-closing muscles can cause a decrease in the objectively scored chewing ability, while the subjectively scored chewing ability remained the same.

Association between occlusal curvature and food comminution and mixing in human young adults with permanent dentitions

ObjectiveOcclusal curvatures in human adult dentition such as the curve of Spee, curve of Wilson and Monsons's sphere provide clinical guidance for prosthetic rehabilitation and orthodontic treatment. However, association between occlusal curvature and masticatory function is not known. The aim of this study was to investigate the association between occlusal curvature and food comminuting and food mixing ability in human young adults with permanent dentitions. DesignFifty young adults with complete dentitions (mean age, 25.0 years) participated in the study. Occlusal curvature was determined by a three-dimensional analysis of the mandibular arch according to the Broadrick flag method. Food comminuting ability was assessed using a masticatory performance test with peanuts as test food and it was scored as median particle size. Food mixing ability was assessed using a mixing ability test with a two-coloured wax cube and it was scored as mixing ability index. ResultsA linear regression analysis identified the sphere radius of occlusal curvature as significant predictor for both median particle size and mixing ability index after controlling for maximum bite force (P<0.001). These results indicated that subjects with a flatter curvature (larger sphere) in the mandibular arch showed better food comminuting and mixing ability. Coefficient of determination (R2) of occlusal curvature related to median particle size and mixing ability index was comparable to that of maximum bite force. ConclusionOcclusal curvature seems to be associated with food comminuting and mixing ability in human young adults with permanent dentitions.

A structural equation model to investigate the impact of missing occlusal units on objective masticatory function in patients with shortened dental arches

The aim of this study was to investigate the impact of missing occlusal units (MOUs) on objective masticatory function with respect to food comminuting and mixing ability. Sixty partially dentate patients (mean age, 64·1 years) with shortened dental arches participated in the study. Food comminuting ability was assessed using a masticatory performance test with peanuts as a test food. Food mixing ability was assessed using a mixing ability test with a two-coloured wax cube. Maximum bite force (MBF) was measured using a pressure-sensitive film as a mediator for food comminuting and mixing ability. A structural equation model was constructed based on a hypothesis that MOUs would be associated with reduced MBF and impairment of food comminuting and mixing ability. Structural equation modelling analysis found significant direct effects of MOU on median particle size and mixing ability index (MAI) (P < 0·001). In addition, MOU had significant indirect effects on median particle size and MAI with MBF as a mediator (P < 0·05). These results suggest that decrease in occlusal platform area and reduced MBF because of MOUs are associated with the impairment of food comminution and mixing in patients with shortened dental arches.

Objective and subjective assessment of masticatory function for patients with temporomandibular disorder in Korea

This study examined the differences in the masticatory function of patients with temporomandibular disorder (TMD) in Korea. The experimental groups were as follows: 23 patients with painful arthralgia classified as pain group according to the research diagnostic criteria for temporomandibular disorder (RDC/TMC) and 28 patients with pain-free disc displacement and reduction classified as clicking group. The subjects were obtained from those who had visited Yonsei University Dental Hospital from 2007 to 2008. Twenty dental students without TMD symptoms were enroled as the normal control group. The Mixing Ability Index (MAI) was used as the objective index, and the Food Intake Ability (FIA) Index, Visual Analogue Scale (VAS) and oral health impact profile (OHIP) were used as the subjective indices. The MAI, FIA and VAS were significantly lower in the pain group than in the normal and clicking groups (P<0·05). The pain group showed a MAI, FIA and VAS of 16%, 81% and 67%, respectively, compared to that of the normal group. However, there were no significant differences in the MAI, FIA and VAS between the clicking and normal groups. The pain and clicking groups showed a 1·7 and 1·4 times higher OHIP value than the normal group (P<0·05). The MAI and subjective indices, such as the FIA (r=0·40) and VAS (r=0·48), showed a moderate correlation (P<0·01). In conclusion, pain is the main factor for the reduced masticatory function in patients with TMD in Korea, and the joint sound, not the masticatory function, affects the declining OHIP.

Subjective food intake ability in relation to the Mixing Ability Index in Korean adults

This study examined the association between the subjective food intake ability (FIA) using a questionnaire with 30 types of foods and the objective Mixing Ability Index (MAI) using a two-coloured wax cube. A total of 147 subjects (32 males, 115 females, mean age: 54.9 +/- 20.7) were enrolled in this study. The FIA for 30 food types and the key food intake ability (KFIA) for five key food types were obtained using a self-assessed questionnaire to evaluate the subjective chewing ability. The objective chewing ability was evaluated by asking the subjects to chew a wax cube for 10 strokes. The MAI was calculated by image analysis of the chewed wax cube. The Pearson's correlation between the subjective FIA and objective MAI was analysed according to age and number of post-canine teeth lost. The FIA for the 30 foods and five key food types showed a moderate correlation with the MAI (r = 0.51, 0.55, respectively, P < 0.01). The KFIA of the denture wearing group (r = 0.44, P < 0.01) and over 60-year-old group (r = 0.49, P < 0.01) showed a significantly higher correlation with the MAI than the other groups. In conclusion, there was a moderate correlation between the subjective FIA and objective MAI in Korean adults.

Investigation of predictors affecting food mixing ability in mandibulectomy and/or glossectomy patients

Several previous reports have described factors that affect masticatory function. However, there are no known predictors that affect the food mixing ability of the masticatory function, and it has been impossible to predict masticatory function in mandibulectomy and/or glossectomy patients. The purpose of the present study was to develop a numerical formula that could predict the food mixing ability of the masticatory function among mandibulectomy and/or glossectomy patients. The null hypothesis of the study was that five predictors, namely mandibulectomy, mandibular continuity, number of residual mandibular teeth, occlusal units and tongue movement score, were unable to account for the mixing ability index (MAI) in mandibulectomy and/or glossectomy patients. The subjects were 20 patients who had undergone mandibulectomy and/or glossectomy. The above-described five predictors were assessed. Tongue movement was evaluated with a tongue movement test and the MAI was evaluated with a mixing ability test. Multiple regression analysis was used to examine whether the five predictors affected the MAI after prosthetic treatment. A regression equation was determined for the five predictors (R(2)=0.83; adjusted R(2)=0.77; p<0.001). The obtained regression equation could successfully account for the MAI in mandibulectomy and/or glossectomy patients.

Comparisons between a mixing ability test and masticatory performance tests using a brittle or an elastic test food

A variety of chewing tests and test items have been utilized to evaluate masticatory function. The purpose of this study was to compare a mixing ability test with masticatory performance tests using peanuts or gummy jelly as test foods. Thirty-two completely dentate subjects (Dentate group, mean age: 25.1 years) and 40 removable partial denture wearers (RPD group, mean age: 65.5 years) participated in this study. The subjects were asked to chew a two-coloured paraffin wax cube as a test item for 10 strokes. Mixing Ability Index (MAI) was determined from the colour mixture and shape of the chewed cube. Subjects were asked to chew 3 g portions of peanuts and a piece of gummy jelly for 20 strokes, respectively. Median particle size of chewed peanuts was determined using a multiple-sieving method. Concentration of dissolved glucose from the surface of the chewed gummy jelly was measured using a blood glucose meter. Pearson's correlation coefficient was used to test the relationships between the MAI, median particle size and the concentration of dissolved glucose. Mixing Ability Index was significantly related to median particle size (Dentate group: r = -0.56, P < 0.001, RPD group: r = -0.70, P < 0.001), but not significantly related to glucose concentration (Dentate group: r = 0.12, RPD group: r = 0.21, P > 0.05). It seems that ability of mixing the bolus is more strongly related to the ability of comminuting brittle food than elastic food.

Comparison of food mixing ability among mandibulectomy patients

Many papers have been published on surgical mandibulectomy and reconstruction. However, only a few reports refer to masticatory function after prosthodontic treatment in mandibulectomy patients. The aim of this study was to investigate the masticatory function of mandibulectomy patients. Twenty-three subjects (10 males and 13 females, with an average age of 63 years) participated in this study: 11 subjects who had undergone unilateral marginal mandibulectomy, six subjects with unilateral segmental mandibulectomy with reconstruction and six subjects with hemimandibulectomy without reconstruction. Mixing Ability Index (MAI) was used to measure masticatory function on the non-defect side and on the defect side with a prosthesis installed. Comparisons were carried out among the marginal, segmental and hemimandibular groups and between the non-defect side and the defect side. Consequently, our study indicates these results. On the non-defect side, a significant difference was found between the marginal and the segmental groups, and between the marginal and the hemimandibular groups. In the marginal and the segmental groups, a significant difference was found between the non-defect and the defect sides. In conclusion, our study suggests that MAI is an adequate tool to study the masticatory function in mandibulectomy patients, the masticatory function of the mandibulectomy patients is more impaired than that of the ordinary removable partial denture patients, and that surgical intervention affects the masticatory function on not only the defect side but also the non-defect side in mandibulectomy patients.

Association between food mixing ability and electromyographic activity of jaw‐closing muscles during chewing of a wax cube

The purpose of this study was to clarify association between food mixing ability and activity of jaw-closing muscles during chewing of a wax cube. Twenty subjects with complete dentitions (mean age 24.1 years) were directed to chew a two-coloured paraffin wax cube for 10 strokes on preferred chewing side. Surface electromyograms (EMG) were recorded from the right and left masseter and anterior temporalis muscles during chewing of the wax cube. Maximum voltage, duration and muscle work for burst of each chewing cycle were measured on integrated EMG in each muscle. Food mixing ability was estimated as mixing ability index determined from the colour mixture and shape of the chewed wax cube. Some EMG parameters of all muscles except for masseter muscle on non-chewing side showed significant positive correlations with the mixing ability index (r = 0.45-0.56, P < 0.05). However, most of the EMG parameters correlated with one another. As a result, only muscle work of masseter muscle on the chewing side was identified as a significant predictor accounting for 28% interindividual variation in the mixing ability index (P < 0.01). These results suggest that activity of jaw-closing muscles during chewing the wax cube seems to be weakly related to food mixing ability.

Association between food mixing ability and mandibular movements during chewing of a wax cube

The purpose of this study was to clarify whether masticatory movements during chewing of a wax cube associate with food mixing ability. Twenty-six dentate subjects (mean age 25.3 years) were directed to chew a two-coloured paraffin wax cube for 10 strokes on preferred chewing side. Mixing Ability Index (MAI) was determined from the colour mixture and shape of the chewed wax cube. MAI was employed as an estimate of food mixing ability. Mandibular movements during chewing of the wax cube were recorded using a six-degrees-of freedom jaw movements recording system, and motion of a lower incisal point of the mandible was computed. Twelve parameters of masticatory movements in relation to mandibular excursion, angle, velocity, cycle duration, duration of each phase were measured for each masticatory cycle. In addition, unilateral maximum biting was performed, and the maximum force during biting was measured using a force-transducer. A multiple regression analysis identified vertical amplitude, closing duration, closing angle and maximum bite force as significant predictors accounting for 63% of inter-subject variation (adjusted R(2)) in the MAI (P < 0.05). Only some parameters of masticatory movements seem to have an influence on the MAI in dentate subjects.

Influence of food platform width of mandibular removable partial denture on food mixing ability

The aim of this study was to clarify the influence of food platform width on food mixing ability in patients with mandibular removable partial dentures (RPDs). Twelve subjects (six males and six females, mean age 56.8 years) with intact dentition except for unilaterally missing mandibular first and second molars participated in the study. The food platforms of their RPDs were made of light polymerized composite and three platform conditions were evaluated. A food platform (Control condition) had 7 mm width with a central focus on the top of the residual ridge. Narrowed platforms (5 mm) were created by trimming a lingual portion (Buccally oriented occlusion, Buccal condition) or a buccal portion (Lingually oriented occlusion, Lingual condition) from the control. Subjects chewed a standardized wax cube which provided an estimate of food mixing ability [Mixing Ability Index (MAI)] for each of the three platforms. A significant effect (P < 0.001) on the MAI was found for food platform type (repeated measures one-way analysis of variance). Tukey multiple comparisons found significant differences of MAI between Control condition (1.05 +/- 0.26) and Buccal condition (0.86 +/- 0.23) (P = 0.032), and between Control and Lingual condition (0.54 +/- 0.37) (P < 0.001). Furthermore, MAI with Lingual condition was significantly smaller than that with Buccal condition (P < 0.001). These results suggest that reduction in the width of the food platform may impair masticatory function and the buccal portion of mandibular food platform of RPD is more critical for food mixing than the lingual portion of the platform.

Factors Associated with Masticatory Performance in Unilateral Distal Extension Removable Partial Denture Patients

Masticatory performance of denture patients is an outcome of the intricate inter-relationship between patient characteristics and denture construction. This study aimed to identify both patient- and denture-related factors associated with masticatory performance in unilateral distal extension removable partial denture patients (RPDs). Seventy-two patients (25 male and 47 female, mean age 63.4 +/- 6.7 years) with unilateral distal extension RPDs were included in the study. The Mixing Ability Index (MAI) obtained from a chewing test using standard two-colored wax cubes, determined masticatory performance. The effect of each evaluated factor on masticatory performance was first determined by an independent t-test or one-way analysis of variance. The statistically significant factors were entered in a model of multivariate linear regression analysis to estimate the independent effect on MAI. The MAI ranged from -3.06 to 0.80 (Mean -0.71 +/- 0.86). Univariate analyses identified male gender, high maximum bite force, more functional tooth units, and natural dentition opposing RPDs as patient factors increasing the MAI. Multivariate analysis (adjusted R(2)= 0.346) revealed that gender (p < 0.001), maximum bite force (p= 0.02), and number of functional tooth units (p= 0.03) were independent predictors for masticatory performance. None of the denture-related factors had a significant influence on MAI. Gender, maximum bite force, and number of functional tooth units were the main factors influencing masticatory performance of unilateral distal extension RPD patients.

Detection of improvement in the masticatory function from old to new removable partial dentures using mixing ability test

The aim of this study was to determine the sensitivity of the Mixing Ability Test to detect improvement of masticatory function in subjects on transition from old to new removable partial dentures. Thirty-two subjects (seven males, 25 females, mean age 65.0 years) with distal extension partially edentulous area in mandible and/or maxilla participated in the study. The following reasons were presented for replacing the old removable partial dentures with new ones: fracture and/or poor fitness of retainers, extraction of abutment teeth, poor fitness of denture base, severe wear of artificial teeth and request for metal base dentures. Masticatory function with old and new removable partial dentures after an adaptation period (mean 27.4 weeks) was evaluated by the Mixing Ability Test. Subjects were asked to masticate five two-coloured wax cubes with each removable partial denture. Mixing Ability Index was obtained from the colour mixture and shape of the masticated cubes. Wilcoxon signed-rank test was used to test the difference of Mixing Ability Indexes between old and new removable partial dentures. The mixing ability indexes with new removable partial dentures (mean+/- s.d.: 0.70+/- 0.68) was significantly higher (P<0.001) than those with old removable partial dentures (-0.11+/-1.13). The results suggest that the Mixing Ability Test was capable of detecting improvement in masticatory function with new removable partial dentures.

Influence of length of food platform on masticatory performance in patients missing unilateral mandibular molars with distal extension removable partial dentures.

Reduction of the size of food platform of a distal extension removable partial denture has been recommended to decrease functional load on the abutment teeth and residual ridges. The purpose of this study was to investigate the influence of shortening food platform on masticatory performance. Eight subjects unilaterally missing mandibular molars participated in the study. A unilateral design was used for the denture framework. The length of the food platform was changed as follows. Initially, (A) was adjusted so that the distal end of the platform was in accordance with the distal end of maxillary second molar. Next, the platform was shortened successively to 15 mm (B) and 10 mm (C). Subjects were asked to masticate 2-colored wax cubes to evaluate masticatory performance. Mixing Ability Index was calculated from the color mixture and the form of masticated cubes. Repeated measures one-way ANOVA indicated significant difference of Mixing Ability Index among platforms (P < 0.0001). The Dunnett's test indicated no significant difference between A (1.27 +/- 0.29) and B (1.36 +/- 0.29), and a significant difference between A and C (0.89 +/- 0.30), (P < 0.001). Masticatory performance decreased significantly when the length of food platform was shortened to 10 mm.

A new and simple method for evaluating masticatory function using newly developed artificial test food.

The aim of this study was to develop an objective evaluation system for the masticatory function. This system used paraffin wax cubes as a test food, which had six red- and green-coloured layers so that each of the six surfaces showed a pseudo-checkered pattern. A total of 100 paraffin cubes were chewed by 37 subjects and the images of these samples were captured and analysed using a digital image analyzer. With regard to the colour and the shape of each sample, five parameters were obtained. Furthermore, an independent examiner graded the degree of colour mixing in the chewed samples into three groups (poor, medium and good) by visual inspection. A discriminant analysis was performed using the five variables as predictors of two groups (good and poor). Mixing Ability Index (MAI) was calculated from the discriminant function and using this index, 97% of the samples from these two groups were classified correctly. This system needed only a few minutes to complete and is easy to use. Therefore, it has high potentials for clinical use.