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

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1 Available online at Journal of Prosthodontic Research 54 (2010) Original article Validity and reliability of a Self-Implementable method to evaluate masticatory performance: Use of color-changeable chewing gum and a color scale Miho Kamiyama DDS, PhD*, Manabu Kanazawa, Yukiko Fujinami, Shunsuke Minakuchi Complete Denture Prosthodontics, Department of Masticatory Function Rehabilitation, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo , Japan Received 15 May 2009; received in revised form 15 July 2009; accepted 17 August Abstract Purpose: The 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. Methods: We 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. Results: A 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. Conclusions: This 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. # 2009 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved. Keywords: Masticatory performance; Color-changeable chewing gum; Color scale; Inter-examiner consistency; Intra-examiner consistency 1. Introduction People are now increasingly aware of the importance of mastication [1,2]. It is a concern when instructing school children to chew well and when developing meal plans for elderly people who require nursing care. Therefore, a simple and easy method to evaluate masticatory performance is desired, not only for use at specialized institutions such as university hospitals or laboratories, but also at local health centers, nursing-care facilities or at home. Previous methods for evaluating masticatory performance have been broadly divided into either subjective methods or objective methods. The former are implemented through various questionnaires, while the latter indicate the condition of the chewed mastication material with a numerical value. The * Corresponding author. Tel.: ; fax: address: m.nakamura.ore@tmd.ac.jp (M. Kamiyama). subjective methods do not require special devices and can be implemented simply and easily in clinical situations. Although various questionnaires provide comprehensive evaluation of masticatory performance, in some cases, the patients subjective judgments are dependent on factors such as the patients like or dislike of a food type. Previous studies reported only a weak correlation between chewing tests and the patients own evaluations [3,4]. The objective methods have achieved progressive development. Those reported in recent years include measuring the degree of glucose by gummy jelly [5] or measuring changes of a chewed wax cube [6 8]. Such tests have become much simpler and easier compared with the classic sieve test [9]. However, it is still difficult to conduct a wide-ranging survey at home or at dental offices, because these methods still require expensive and bulky equipment. Consequently, we developed a new color-changeable chewing gum [10 13]. By using this chewing gum and a handheld colorimeter, it is possible to evaluate the masticatory performance of fully dentate people at any location [12] /$ see front matter # 2009 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved. doi: /j.jpor

M. Kamiyama et al. / Journal of Prosthodontic Research 54 (2010) 24 28 25 However, problems still remain because this method requires special devices.

Methods based on color scales are applied in other medical settings because of their simple and convenient objective evaluation procedures [14,15].

2 M. Kamiyama et al. / Journal of Prosthodontic Research 54 (2010) However, problems still remain because this method requires special devices. Therefore, we have developed a dedicated color scale that enables everyone to easily and visually check the color of the chewing gum. Methods based on color scales are applied in other medical settings because of their simple and convenient objective evaluation procedures [14,15]. They are used not only in laboratories and specialized institutions, but also in a wider range of fields because such scales require only a few minutes by the user to reach an objective evaluation. Colorimetric methods using color scales are inexpensive and simple to use. Furthermore, this method offers the advantage that the subjects can evaluate their own masticatory performance at any location. The aim of this study was to confirm the validity of an evaluation method of masticatory performance with colorchangeable chewing gum using a color scale compared with the conventional method using a colorimeter. We also assessed the Self-Implementability of this new method by having the three groups of subjects, consisting of dentists, adult and elderly adults, perform the test by themselves. This study was performed with the approval of the Ethical Committee of Tokyo Medical and Dental University, and informed consent was obtained from all subjects prior to the experiment. 2. Materials and methods 2.1. Color-changeable chewing gum By adding flexible glycerine fatty acid ester and microcrystalline wax to the gum base, the properties of the chewing gum (Masticatory Performance Evaluating Gum XYLITOL 1 [70 mm 20 mm 1 mm, 3.0 g]; Lotte Co., Ltd., Saitama, Japan) (Fig. 1) can be adjusted to not adhere to denture materials to allow easy chewing, even by complete denture wearers who have reduced occlusal force. Furthermore, the gum base contains red, yellow, and blue dyes, citric acid, and xylitol. The ph inside the chewing gum is kept low by the citric acid and the red color uses a synthetic colorant that does not leach out from the chewing gum under the acid condition. Before mastication, the chewing gum has a yellowish-green color because of the presence of yellow and blue pigments. When the chewing gum is mixed with saliva as mastication proceeds, the ph inside the chewing gum increases because of the excretion of the citric acid into the saliva and, at the same time, elution of the yellow and blue pigments changes the color of the chewing gum from yellowish-green to red Developing the color scale Five fully dentate dentists from Complete Denture Prosthodontics, Tokyo Medical and Dental University were instructed to chew the Masticatory Performance Evaluating gum for 20, 40, 60, 80, 100, 120, 140, 160, 180 and 200 strokes. We examined the changes of the collected chewing gums and picked out five intermediate colors. On the computer, using image retouching software (Photoshop CS3 Adobe systems Fig. 1. Color-changeable chewing gum (Masticatory Performance Evaluating Gum XYLITOL 1 ; Lotte Co., Ltd. Saitama, Japan). Fig. 2. The dedicated color scale. A five color chart with a 100-mm long visual analog scale. Inc. 1, San Jose, CA, USA), we created the five colors to be as similar as possible to those picked based on the visual observations by the authors and hence created the five color chart. The color scale was then linked to a 100-mm long visual analog scale (VAS) (Fig. 2) Preparing the colorimetric samples Six fully dentate dentists from Complete Denture Prosthodontics, Tokyo Medical and Dental University were instructed to chew the chewing gum well, without given instructions with regard to chewing side. The subjects chewed the chewing gum at a frequency of 1 stroke per second until they reached the instructed number of strokes (40, 80, 120, 160 and 200 times). The subjects were asked to rest for a sufficient time. Between each trial, to apply the blind method, we conducted simple randomization using the table of random digits generated by the third party. The chewed gum was collected immediately after chewing and compressed to a thickness of 1.5 mm in a polyethylene film between two glass plates. A total of 30 samples of chewing gum (Fig. 3) were prepared. The samples were numbered randomly Evaluation method Three groups of six subjects (total: 18 examiners) without visual impairments such as color blindness were recruited. The dentist group comprised dentists from Complete Denture Prosthodontics, Tokyo Medical and Dental University (mean age, 29.8 years; range years). The adult group comprised undergraduate students from Tokyo Medical and Dental University (mean age: 22.8 years; range years). The elderly adult group comprised patients aged 70 years or over who sought treatment at the Prosthodontics, University Hospital of Dentistry, Tokyo Medical and Dental University (average age: 74.5 years; range years). The elderly adults completed the Hasegawa Dementia Scale-Revised [16] to verify that they had no suspected dementia.

26 M. Kamiyama et al. / Journal of Prosthodontic Research 54 (2010) 24 28 Fig. 3. Samples, chewed gum was compressed to a thickness of 1.5 mm in a polyethylene film between two glass plates.

They were asked to indicate the place that you think is the closest to the sample and were instructed to mark the VAS while viewing the sample.

3 26 M. Kamiyama et al. / Journal of Prosthodontic Research 54 (2010) Fig. 3. Samples, chewed gum was compressed to a thickness of 1.5 mm in a polyethylene film between two glass plates. The examiners assessed the colors of 30 samples of chewing gum using the color scale. They were asked to indicate the place that you think is the closest to the sample and were instructed to mark the VAS while viewing the sample. Each result was converted to a numerical value determined by measuring in millimeters from the left-hand end of the 100-mm long VAS line to the point that the examiner marked; the measured value was defined as the color score. For respective samples, a colorimeter (CR-13; KonicaMinolta, Tokyo, Japan) measured the a* value (CIE-L*a*b* color system) through the polyethylene film (Fig. 4). The color readings were performed at five points on a single side: at the center of the compressed gum, and approximately 3 mm above, below and to the right and to the left of the center. A mean value of the five points was then determined. To confirm the validity, the relationship between the a* value and the color score was determined. The 30 samples of chewing gum chewed by the subjects were numbered one through 30. The order of examining the 30 samples was decided by applying simple randomization using the table of random digits. The randomized 30 samples were grouped as a single cycle. Six examiners of the same group examined the cycle three times. The cycle was randomized differently for each trial. The authors calculated the color score for each value on the VAS marked by the examiners. The same trials were conducted by all three groups. The process from the beginning of chewing to prepare the reference samples through the end of all examinations by the 18 examiners of the three groups was set to be completed within 12 h Statistical analysis For validity, we calculated the mean value of the color scores measured by all of the examiners. Pearson s correlation coefficients were calculated to determine the correlation Fig. 4. Assessment of the compressed gum using a colorimeter (CR-13; Konica-Minolta, Tokyo, Japan). The color of the compressed gum was assessed at five points and a mean value of the five points was determined. between the a* value measured by the colorimeter and the average color score values. Reliability was assessed using intraclass correlation coefficients (ICCs) for intra-examiner and inter-examiner consistency. Intra-examiner consistency: for each examiner, the ICC was computed based on the results from the three repetitions of the test. Inter-examiner consistency: for each group, ICC was computed based on results of the test performed by each of the six examiners within that group. The level of significance was set at 0.05 and we used statistical analysis software (SPSS Base 16.0 for Windows, SPSS Japan Inc., Tokyo, Japan). 3. Results The a* value of the samples ranged from 1 to The a* value tended to increase with increasing number of chewing strokes. Fig. 5 shows the correlation between the a* value and the mean color score according to the number of chewing strokes. A strong correlation was found between the mean color score and the a* value (Pearson s correlation coefficient, 0.979). Table 1 shows the ICCs. The mean ICCs for intra-examiner consistency were 0.94 for the dentist group, 0.89 for the adult group and 0.88 for the elderly adult group. The ICCs for interexaminer consistency were 0.91 for the dentist group, 0.89 for the adult group, 0.89 for the elderly adult group and 0.86 for all examiners combined.

4 M. Kamiyama et al. / Journal of Prosthodontic Research 54 (2010) Table 1 Intraclass correlation coefficients for each group of examiners. Group Dentists Adults Elderly adults Inter-examiner consistency Intra-examiner consistency, average (individual values) 0.94 (0.91, 0.92, 0.93, 0.95, 0.97, 0.97) 0.89 (0.8, 0.85, 0.9, 0.91, 0.93, 0.96) 0.88 (0.81, 0.86, 0.87, 0.89, 0.91, 0.94) Fig. 5. Correlation between a* values and color scores, each marker indicates the number of chewing strokes of the respective samples. We calculated the mean color score for all examiners. The Pearson s correlation coefficient between the a* value measured by the colorimeter and the average value of the color scores was Discussion Masticatory performance is defined as a measure of the comminution of food attainable under standardized testing conditions [17] and indicates the comprehensive ability required for mastication. Because the method using colorchangeable chewing gum demonstrates masticatory performance more focused on mixing ability, it does not necessarily correspond to the comminuting ability determined by the sieve test. However, a previous study [8] showed a significant correlation between the mixing ability and the comminuting ability. Furthermore, several studies have validated newly developed methods by showing positive correlations with the sieve test [5,7,12]. These findings also confirm that the sieve test provides the most adequate comparative method for validation of novel methods. Accordingly, we have discussed the relationship with the sieve test in this study. In our study, a positive correlation was confirmed between the a* values measured by a colorimeter and the color scores obtained using the color scale. A previous study showed a significant correlation between the a* values and the masticatory efficiency assayed by the sieve test and that it would be possible to evaluate the masticatory performance of fully dentate subjects using the a* value [12]. Therefore, the color scores correlate with masticatory efficiency, and we estimated the validity of a method of evaluating masticatory performance using a color scale. ICCs for inter-examiner consistency and intra-examiner consistency were calculated to confirm the reliability of measuring masticatory performance using a color scale. The former assessed the consistency of the results obtained from different examiners comparing the same sample, while the latter assessed the consistency of the results obtained from the same examiner comparing colors of the same samples in different periods of time. As a result, the ICCs for interexaminer and intra-examiner consistency ranged from 0.86 to 0.94, which were sufficiently high to establish the reliabilities for all three groups, suggesting Self-Implementability of the method that not only dentists but also the general public, including elderly adults with clear understanding of the testing procedure, would be able to evaluate the color of the chewed gum by themselves. In a previous experiment to assess the reliability of measuring masticatory performance using a wax cube, a test retest approach, with the retest performed 1 week after the first test, was performed in addition to the two reliability tests [7]. However, the a* value of the chewed gum started to change at around 12 h after mastication. Therefore, in this study, the test retest procedure was not conducted. Here, we examined the reliability of the color scale by including three distinct groups of examiners (dentists, adults and elderly adults). Masticatory performance is generally assessed by specialists, rather than by the subjects themselves. However, in this study, we investigated a simple evaluation method that enables subjects to self-evaluate their performance. Therefore, to assess the reliability of examiners, we included a group of adults and a group of elderly adults, who could actually be subjects, in addition to a group of dentists. We hope that, in the future, this method can enable anyone, anywhere, to simply evaluate their own masticatory performance. Therefore, this Self-Implementable method serves as a basis for a large-scale masticatory performance survey with a large number of subjects, which was previously considered impractical. To that end, the oral conditions, mastication patterns and the patients individual data and the associations between these factors and color changes of the gum can be investigated in detail. 5. Conclusion This study confirmed the validity and reliability of this Self- Implementable method of evaluating masticatory performance with color-changeable chewing gum using a color scale. References [1] Soini H, Muurinen S, Routasalo P, Sandelin E, Savikko N, Suominen M, et al. Oral and nutritional status is the MNA a useful tool for dental clinics. J Nutr Health Aging 2006;10:495 9.

5 28 M. Kamiyama et al. / Journal of Prosthodontic Research 54 (2010) [2] Gavião MB, Raymundo VG, Rentes AM. Masticatory performance and bite force in children with primary dentition. Braz Oral Res 2007;21: [3] Slagter AP, Olthoff LW, Bosman F, Steen WH. Masticatory ability, denture quality, and oral conditions in edentulous subjects. J Prosthet Dent 1992;68: [4] Van der Bilt A, Olthoff LW, Bosman F, Oosterhaven SP. Chewing performance before and after rehabilitation of post-canine teeth in man. J Dent Res 1994;73: [5] Kobayashi Y, Shiga H, Arakawa I, Yokoyama M. The effectiveness of measuring glucose extraction for estimating masticatory performance. Prosthodont Res Pract 2006;5: [6] Sato H, Fueki K, Sueda S, Sato S, Shiozaki T, Kato M, et al. A new and simple method for evaluating masticatory function using newly developed artificial test food. J Oral Rehabil 2003;30: [7] Sato S, Fueki K, Sato H, Sueda S, Shiozaki T, Kato M, et al. Validity and reliability of a newly developed method for evaluating masticatory function using discriminant analysis. J Oral Rehabil 2003;30: [8] Sugiura T, Fueki K, Igarashi Y. Comparisons between a mixing ability test and masticatory performance tests using a brittle or an elastic test food. J Oral Rehabil 2009;36: [9] Manly RS, Braley LC. Masticatory performance and efficiency. J Dent Res 1950;29: [10] Hayakawa I, Watanabe I, Hirano S, Nagao M, Seki T. A simple method for evaluating masticatory performance using a color-changeable chewing gum. Int J Prosthodont 1998;11: [11] Hirano S, Takahashi Y, Watanabe I, Wu C, Hayakawa I. Application of color-changeable chewing gum for measuring masticatory performance of complete denture wearers. J Jpn Prosthodont Soc 2001;45: [12] Hirano K, Takahashi Y, Hirano S, Hayakawa I, Seki T. A study on measurement of masticatory ability using a color-changeable chewing gum with a new color reaction. J Jan Prosthodontics 2002;46: [13] Ishikawa Y, Watanabe I, Hayakawa I, Minakuchi S, Uchida T. Evaluation of masticatory performance of complete denture wearers using colorchangeable chewing gum and other evaluating methods. J Med Dent Sci 2007;54: [14] Abrahams M, Ram D, Das S, Britt RP. Use of the WHO hemoglobin color scale in family welfare clinics in India. Southeast Asian J Trop Med Public Health 2005;36: [15] Konishi N, Kawada A, Morimoto Y, Watake A, Matsuda H, Oiso N, et al. New approach to the evaluation of skin color of pigmentary lesions using Skin Tone Color Scale. J Dermatol 2007;34: [16] Hasegawa K. The clinical issues of age-related dementia. Tohoku J Exp Med 1990;161: [17] The Glossary of Prosthodontic Terms. J Prosthet Dent 2005;94:10 92.

Original Article. Reliability and validity of a quantitative color scale to evaluate masticatory performance using color-changeable chewing gum

Original Article. Reliability and validity of a quantitative color scale to evaluate masticatory performance using color-changeable chewing gum J Med Dent Sci 2014; 61: 1-6 Original Article Reliability and validity of a quantitative color scale to evaluate masticatory performance using color-changeable chewing gum Yohei Hama 1), Manabu Kanazawa