Evaluation of a self-assessed screening test for masticatory ability of Taiwanese older adults
Kun-Jung Hsu1,2, Huey-Er Lee3,4, Shou-Jen Lan5, Shun-Te Huang6,7, Chun-Min Chen3,8 and Yea-Yin Yen6
1School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; 2Department of Family Dentistry, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan;3Department of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan;4Department of Prosthodontics, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan;5Department of Healthcare Administration, College of Health Science, Asia University, Taichung, Taiwan;6Department of Oral Hygiene, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; 7Department of Pedodontics, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan;8Department of Oral and Maxillofacial Surgery, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
doi: 10.1111/j.1741-2358.2012.00632.x
Evaluation of a self-assessed screening test for masticatory ability of Taiwanese older adults Objectives: The aim of this study was to evaluate a screening test based on a food intake questionnaire to discriminate the masticatory ability of Taiwanese older adults with 20 and more natural teeth and at least 8 functional tooth units (FTUs) from the masticatory ability of those with fewer than 20 natural teeth and 8 FTUs.
Materials and Methods: The subjects were 2244 patients (mean age, 60.4±10.0 years) recruited from 23 counties and cities in Taiwan. Information about their demographic data, dentition, and masticatory ability was collected. Masticatory ability was measured for 23 food groups comprising 35 common Taiwanese foods, and receiver operation characteristic curve analysis was performed.
Results: The results showed that the final questionnaire included 14 food groups and a subject choosing
’difficult to eat‘ responses for 4 and more of these food groups had the same masticatory ability as in- dividuals with fewer than 20 natural teeth and 8 FTUs.
Conclusion: In conclusion, foods that are the most difficult to eat are not necessarily good discriminatory indicators. Hence, the 14-food group questionnaire can be considered the best screening test for masticatory ability of Taiwanese older adults in terms of the presence of 20 and more natural teeth and at least 8 FTUs.
Keywords: natural tooth, functional tooth units, masticatory ability, receiver operation characteristic curve.
Accepted 4 September 2011
Introduction
Good masticatory ability is important for both physical functioning and mental health1. Studies have shown that good masticatory ability has a positive impact on food choice1, nutritional sta- tus2,3, general health4–6, high-level functional capacity7, cognitive status5 and cerebral blood volume6. Besides, Miura et al.8 found that masti- catory ability has a significant relationship with the quality of life of the Japanese elderly.
Missing teeth caused by untreated oral diseases are often blamed for impaired masticatory ability.
The factors that might affect masticatory ability in- clude tooth loss9, retained posterior root tips10, number of remaining natural teeth11,12, number of
functional units (i.e. any opposing natural or pros- thetic tooth pair)13, number of posterior functional units14,15and number of functional tooth units (i.e.
pairs of occluding posterior natural teeth (NT) or fixed prostheses where an occluding molar pair is counted as 2 units and an occluding premolar pair is counted as 1 unit)11–13,16,17
. In 1992, the World Health Organisation (WHO) proposed the treat- ment goal for oral health of maintaining a func- tional, aesthetic, natural dentition with not <20 teeth18. The purpose was to prevent missing teeth and maintain masticatory ability in the elderly.
The first step for improving masticatory function is to understand the present status of masticatory function. Two methods are used to assess masticatory function: an objective method based
on laboratory results (masticatory efficiency/per- formance/capacity) and a subjective method based on questionnaire and interview results (mastica- tory ability)19. The objective method includes assessment of the modified Mastication Perfor- mance Index20, maximal bite force21,22, mastica- tory efficiency23 or swallowing threshold24. Although the objective method can generate accurate information, it tends to require greater manpower, special equipment and time as well as the subjects’ willingness and patience. On the other hand, the subjective method appears simpler, is easy to administer and costs less; however, its credibility and accuracy are challengeable. Never- theless, Hirai25 and Miura26 indicated that a mas- ticatory ability index established by using a food intake questionnaire has higher validity and pro- vides more consistent results than precision tools.
Takata et al.27 showed that self-assessed chewing ability evaluated by using a food intake question- naire but not the number of teeth is associated with the quality of life of the Japanese elderly. Hence, the use of a food intake questionnaire is important and necessary for epidemiological studies and clinical evaluation of masticatory ability.
In the recent years, as medicine has advanced, the population of middle-aged and older individuals has increased rapidly, resulting in a growing demand for oral health care among the elderly. A similar trend has been observed in Taiwan. Ueno et al.12showed that it is important for adults aged 40–75 years to maintain 20 and more NT and at least 8 functional tooth units (FTUs) to reduce self-assessed chewing difficulty. Considering the treatment goal of 20 and more NT and at least 8 FTUs for good masticatory ability of older adults, what kind of food intake questionnaire would be best suited as a screening test? The purpose of this study was to evaluate a self-assessed screening test based on a food intake questionnaire to discriminate the masticatory abil- ity of Taiwanese older adults with 20 and more NT and at least 8 FTUs from the masticatory ability of those with fewer than 20 NT or 8 FTUs.
Subjects and methods
Subjects
Between March and December 2006, patients aged 45 years and over were recruited from Taiwanese dental clinics in accordance with the population structure of Taiwan in 2005. With the Taiwan Dental Association’s support, 319 dental clinics in 23 counties and cities of Taiwan participated in the study. Participation was voluntary. Vegetarians,
those who did not eat the listed foods and those who could not complete the questionnaire were excluded. All the subjects signed an informed consent form before data collection.
Food intake questionnaire
The subjects were questioned about basic demo- graphic data (gender, age and educational level). In Taiwan, Chinese buffet restaurants provide all kinds of daily Taiwanese foods. To gather infor- mation on daily Taiwanese foods, we visited 15 Chinese buffet restaurants in Taichung City. We recorded the types of daily food used for lunch and dinner every day for 3 months. From the result of the investigation, a list of 35 foods with different textures, including hardness, viscosity, fracturabil- ity and chewiness, was selected with the help of nine experts. Three choices were associated with each food group –’2: able to eat’, ‘1: difficult to eat’, and ‘0: unable to eat’ – where each answer was associated with a score. Then, nine experts and 15 patients aged 45 years and over ranked 35 daily Taiwanese foods according to the difficulty in chewing them. A food ranking based on the aver- age scores was devised, and foods with similar chewing difficulty were grouped, yielding 23 food groups.
A food intake questionnaire on the 23 food groups was developed to evaluate the masticatory ability of each subject. Three choices were permit- ted for each food group: ‘easy to eat’, ‘difficult to eat’ and ‘unable eat’. Then, the food intake ques- tionnaire was tested with 30 patients aged 45 years and over. The internal consistency of the ques- tionnaire was assessed by Cronbach’s alpha, and the test–retest reliability was assessed on the basis of Spearman’s rank correlation coefficient, with a week between the tests. Cronbach’s alpha of the questionnaire was 0.830 and Spearman’s rank correlation coefficient was 0.801.
Dental examination
The subjects underwent clinical dental examina- tions by trained and calibrated dentists in the par- ticipating dental clinics in accordance with the WHO format28. Each subject sat in a dental chair, and a dental operatory light, dental mouth mirror and dental probe were used for the examination, but no radiographs were taken. All the participat- ing dentists attended a workshop and were requested to practice two case records each to complete the designed research workshop before the study. They also received a dental examination
manual describing the detailed criteria for the study. Dentists with a j coefficient agreement of
<0.70 were excluded.
Teeth that were sound, decayed, filled or filled but decayed were regarded as NT. Teeth with grade III mobility, retained roots and extensive crown destruction (i.e. at least three quarters of the clin- ical crown was destructed) were excluded. Func- tional tooth units (FTUs) were defined as pairs of occluding posterior natural teeth or fixed artificial teeth, including abutment teeth, pontics and implant-supported prostheses. Fixed artificial teeth with grade III mobility were excluded. The number of FTUs for premolars was 1 and 2 units for molars.
Third molars were not included; thus, 28 NT or 12 FTUs indicate an intact dentition.
Statistical analysis
The subjects were categorised as those with 20 and more NT and at least 8 FTUs (‡20 NT + 8FTU group) and those with <20 NT or 8 FTUs (<20 NT or 8 FTU group). The goal of statistical analysis was to determine the best food intake questionnaire for discriminating the masticatory ability of these groups. Chi-square tests were conducted to deter- mine the distribution of the subjects in the
‡20 NT + 8 FTU and <20 NT or 8 FTU groups with respect to age, gender and educational level. The three choices for each food group were dichoto- mised as ‘easy to eat’ and ‘difficult to eat’, and the proportion of ‘difficult to eat’ responses to each food group was compared between the groups and ranked by the differences.
On the basis of the number of top-ranked food groups, we established 23 food intake question- naires for discriminating subjects into the
‡20 NT + 8 FTU group or <20 NT or 8 FTU group on the basis of their masticatory ability. For example, the first food intake questionnaire listed the highest ranked food group; the second food intake questionnaire listed the two food groups ranked at first and second; the third food intake questionnaire included the first three kinds of food groups and so forth. Then, receiver operating characteristic (ROC) curve analysis was used to determine the most appropriate food groups among the 23 kinds of food groups to discriminate the masticatory ability of subjects in the
‡20 NT + 8 FTU and <20 NT or 8 FTU groups and establish the threshold value of each food group, for indicating whether a subject belonged to the
<20 NT or 8 FTU group or not.
A ROC curve is a plot of the sensitivity vs.
1-specificity for assessing the ability of a screening
test to discriminate those without disease from those with disease. The x-axis and y-axis values on the ROC curve reflected false-positive (1-specific- ity) and true-positive (sensitivity) diagnoses, respectively. The different points on the curve correspond to the different threshold points used to designate the test positive. In determining the best diagnostic tool for the same disease, if there is no special consideration concerning sensitivity or specificity, a larger area under the ROC curve (AUC) represents a higher level of suitability.
Therefore, AUCs were used to determine the most appropriate food groups for the questionnaire and threshold points closest to (0,1) were used to dis- criminate between the subject groups29. A test with 0.8£ AUC < 0.9 is considered an excellent dis- criminator, and AUC ‡ 0.9 indicates outstanding discrimination, but it is rarely observed30. A p-va- lue of 0.05 was considered significant. All statistical analyses were performed by using SAS (Jump8) statistical software (SAS Institute, Inc., Cary, NC, USA).
Results
In this study, 2244 subjects (1089 men and 1155 women; mean age, 60.4 ± 10.0 years) were recruited. The mean age in the ‡20 NT + 8 FTU and <20 NT or 8 FTU groups was 57.8 ± 8.9 and 67.0 ± 9.8 years (p < 0.0001), respectively. The mean number of NT in the ‡20 NT + 8 FTU and
<20 NT or 8 FTU groups was 25.1 ± 2.7 and 10.4 ± 6.2 (p < 0.0001), respectively, and the mean number of FTUs was 9.5 ± 2.9 and 1.1 ± 1.7 (p < 0.0001), respectively. Table 1 shows the demographic data of the subject groups. The
<20 NT or 8 FTU group tended to be older and have lower educational level.
Table 2 shows the distribution and difference in the proportions of ‘difficult to eat’ responses to the 23 food groups between the subject groups. For example, with regarding to ‘sliced guava’, 72.81%
of the <20 NT or 8 FTU group chose ‘difficult to eat’, whereas only 22.72% of the ‡20 NT + 8 FTU group chose the same response.
The food intake questionnaire with the first food group (Sliced guava) showed the lowest AUC value (0.7505), while the first 14 food groups showed the largest AUC value (0.8294) (Table 3). Considering that a larger AUC represents a higher level of suitability, these 14 food groups were selected for the final food intake questionnaire. In this ques- tionnaire, the number of threshold points for the
<20 NT or 8 FTU group ranged from 0 to 14, and in determining the threshold points for this group,
1-specificity and sensitivity values closest to (0,1) were used. As shown in Table 4, the shortest dis- tance existed when the number of food groups was 4. Hence, a subject with four or more ‘difficult to eat’ responses to the 14-food group questionnaire would be categorised into the <20 NT or 8 FTU group.
Discussion
Subjective assessment of masticatory ability is easier and more effective for understanding masti- catory function as well as more suitable for epidemiological studies with a large sample size than objective assessment of masticatory perfor- mance25. To determine how dental treatment can improve masticatory function, both self-assessed masticatory ability and the patients’ feelings are crucial. The present study was conducted to eval- uate a screening test based on a food intake ques- tionnaire to discriminate the masticatory ability of Taiwanese older adults with 20 and more NT and at least 8 FTUs from the masticatory ability of those with <20 NT or 8 FTUs. By ROC curve analysis, 14 food groups were selected from among 35 common Taiwanese foods for the final food intake ques- tionnaire. A subject choosing ‘difficult to eat’ re- sponses to four and more of the 14 food groups was considered to have the same masticatory ability as individuals with fewer than 20 NT or 8 FTUs.
The 14 food groups in the final questionnaire mainly comprised hard or tough foods. Such foods serve as better discriminatory indicators than do soft foods. In a previous study, five of 30 foods were selected as key foods (e.g. dried cuttlefish, raw carrot and dried peanut) to test the subjects’ mas- ticatory ability; all the selected foods were hard or tough in terms of physical properties22. Other studies have indicated that the ability to chew hard food is highly correlated with the maximum biting ability22,31. Therefore, the results of the present study are in agreement with the findings of these studies. However, foods that are the hardest or most difficult to eat are not necessarily good dis- criminatory indicators. For example, in the present study, sugarcane was considered the hardest food in both the subject groups, but it was less discrim- inatory than easier-to-eat foods (e.g. squid, sliced guava and stir-fried peanut). In other words, foods considered easy to eat by people with good chew- ing ability but difficult to eat by those with poor chewing ability are the ideal discriminatory indi- cators.
In the study, food group including one or more kinds of food with similar chewing difficulty was used in the food intake questionnaire. This could also be seen in many studies9,10,15,32. In Leake’s study32, chewing ability was evaluated by a five- item index comprised five food intake questions.
The food intake question also included one or more Table 1. Demographic characteris- tics between20 NT + 8 FTUs group and <20 NT or 8 FTUs group (N = 2244)
20 NT + 8 FTUs group
<20 NT or 8 FTUs group
p-value
n % n %
Total 1615 72.0 629 28.0
Age (year)
45–54 696 90.5 73 9.5 <0.0001
55–64 481 76.6 147 23.4
65–74 317 56.8 241 43.2
75+ 121 41.9 168 58.1
Sex
Men 765 70.3 324 29.7 0.0779
Women 850 73.6 305 26.4
Education
Elementary school or less 625 58.9 437 41.1 <0.0001
Junior high school 237 78.0 67 22.0
Senior high school 371 82.4 79 17.6
College 382 89.3 46 10.7
20 NT + 8 FTUs group: subjects with 20 or more natural teeth and eight or more FTUs.
<20 NT or 8 FTUs group: subjects with <20 natural teeth or 8 FTUs.
p-value is calculated by chi-square test.
FTU, functional tooth unit; NT, natural teeth.
kinds of food. Moreover, in the study of Foester et al.10, the chewing index of Leak32 was adapted by including the word ‘or something very similar to that’ to each food intake question. The purpose was to decrease the likelihood of the response ‘have not tried’ of a subject and thus prevent any influence of missing data on the results.
To use time efficiently and avoid the subjects’
impatience, a questionnaire should not contain too many or complicated questions. Kim et al.22selected five key foods from 30 foods to simplify the ques- tionnaire. In the present study, the final question- naire comprised 14 food groups selected from 35 common foods in Taiwan to discriminate the masti- catory abilities of the‡20 NT + 8 FTU and <20 NT or 8 FTU groups. The food groups used as discrimina- tory indictors were chosen on the basis of ROC curve analysis. A similar practice has been used in other fields. In a Self-report Screening Test for Areca Quid Abuser study, which also used ROC curve analysis, 11 questions were selected from 52 questions in the
original self-administered questionnaire to deter- mine whether a subject was an abuser or not29.
In general, studies using food intake question- naires to evaluate subjective masticatory ability are based on comparisons of the number and variety of selected foods. Zeng et al.33 used 39 kinds of Chi- nese foods to evaluate an index of eating difficulty and selected five food groups for the final ques- tionnaire. Hirai’s25 research was based on the masticatory scores converted from 35 kinds of food to evaluate masticatory ability, where a higher score represented better masticatory ability. An advantage of food intake questionnaires is that they help to group people with different levels of mas- ticatory ability. However, such grouping fails to provide relevant information about the types and number of foods and the threshold points for a given goal (e.g. the masticatory ability of people having 20 and more NT and at least 8 FTUs). The findings of the present study could overcome the shortcomings of other food intake questionnaires.
Table 2. Proportions of answers, ‘difficulty to eat’, to questions between 20 NT + 8 FTUs group and <20 NT or 8 FTUs group
Rank food group
20 NT + 8 FTUs group (%) (n = 1089)
<20 NT or 8 FTUs group (%) (n = 1155)
Difference
(%) p-value
1 Sliced guava 22.72 72.81 50.09 <0.0001
2 Squid 22.54 71.86 49.32 <0.0001
3 Soy sauce-braised pork ears 25.82 75.04 49.22 <0.0001
4 Stir-fried peanut 16.72 62.80 46.08 <0.0001
5 Fried chicken leg or chicken fillet 16.47 62.00 45.53 <0.0001
6 Grilled calamari or soy sauce-braised chicken gizzard
36.16 80.29 44.13 <0.0001
7 Boiled sweet corn on the cob 12.32 54.85 42.53 <0.0001
8 Sugar cane (not juice) 48.98 90.46 41.48 <0.0001
9 Sliced apple or pear 8.92 48.81 39.89 <0.0001
10 Sliced cucumber or kidney bean 4.27 33.86 29.59 <0.0001
11 Boiled bamboo shoots or broccoli 3.96 32.59 28.63 <0.0001
12 Boiled white radish or carrot 1.49 28.60 27.11 <0.0001
13 Sliced orange 4.21 30.37 26.16 <0.0001
14 Sliced star fruit or bell fruit 3.53 29.25 25.72 <0.0001
15 Pickled lettuce in soy sauce or pickled cucumber in soy sauce (canned)
3.78 28.78 25.00 <0.0001
16 Sliced sweet pepper 2.72 26.39 23.67 <0.0001
17 Water spinach or cabbage 2.66 23.69 21.03 <0.0001
18 Sliced melon or tangerine 2.48 22.73 20.25 <0.0001
19 Sliced watermelon or pineapple 2.04 15.26 13.22 <0.0001
20 Steamed sweet potato or taro 0.99 13.83 12.84 <0.0001
21 Papaya or banana 1.11 11.92 10.81 <0.0001
22 Fish (steamed) 3.22 13.50 10.28 <0.0001
23 Tofu 0.43 8.11 7.68 <0.0001
p-value is calculated from two-sample t-test.
FTU, functional tooth unit; NT, natural teeth.
The number of FTUs, defined as pairs of occlud- ing posterior natural teeth or fixed prostheses (molars = 2 units, bicuspids = 1 unit), is a key determinant of masticatory ability12,17,20. In 2003, Sarita et al.34found that complete premolars and at least an occluding pair of molars are sufficient for good masticatory ability. In many studies, 20 remaining natural teeth were considered the stan- dard for a functional dentition11,12,17,35,36
. Through food intake questionnaires based on different treatment goals, one can evaluate the number of natural teeth, fixed prostheses, FTUs or their com- bination and whether a type of removal denture supported by implant or not is needed to reach the treatment goals. Accordingly, a treatment plan for prostheses can be modified.
As per data from Taiwan’s National Health Insur- ance (NHI) database, 2.75 million adults (35.9%) aged 45 years and older visited a dentist in 200637. A study of determinants of dental care utilisation showed that people with lower income levels are less likely to visit their dentist regularly38. Studies also showed that the greatest barrier to dental services among people older than 55 years is the cost of treatment39,40. A study focusing on people older than 55 years in the United States showed that people with teeth are more likely to use dental services than those without teeth40. In Taiwan, however, a single-payer NHI system has been available for years. The NHI system provides the Taiwanese with equitable access to health care, improved financial risk protection and equity in Table 3. Areas under receiver operation characteristic
curves of cumulated food item groups
Number of cumulated top rank
food groups Food group added each time Area
1 Sliced guava 0.7505
2 Squid 0.7937
3 Soy sauce-braised pork ears 0.7991
4 Stir-fried peanut 0.8086
5 Fried chicken leg or chicken fillet 0.8104 6 Grilled calamari or soy
sauce-braised chicken gizzard
0.8107 7 Boiled sweet corn on the cob 0.8127
8 Sugar cane (not juice) 0.8219
9 Sliced apple or pear 0.8253
10 Sliced cucumber or kidney bean 0.8270 11 Boiled bamboo shoots or broccoli 0.8274 12 Boiled white radish or carrot 0.8282
13 Sliced orange 0.8293
14 Sliced star fruit or bell fruit 0.8294 15 Pickled lettuce in soy sauce or
pickled cucumber in soy sauce (canned)
0.8292
16 Sliced sweet pepper 0.8292
17 Water spinach or cabbage 0.8290
18 Sliced melon or tangerine 0.8290
19 Papaya or banana 0.8287
20 Steamed sweet potato or taro 0.8288
21 Papaya or banana 0.8289
22 Fish (steamed) 0.8282
23 Tofu 0.8282
Table 4. Identifying cut-off point for the set of 14-food group test
Cut-off point for number of answer, ‘difficulty to
eat’, to food groups Probability 1-specificity Sensitivity True positive
True negative
False positive
False
negative Distance
14 0.8787 0.005 0.1192 75 1607 8 554 0.8808
13 0.8414 0.013 0.2051 129 1594 21 500 0.7950
12 0.7952 0.0198 0.2464 155 1583 32 474 0.7539
11 0.7398 0.0322 0.3211 202 1563 52 427 0.6797
10 0.6755 0.0402 0.3752 236 1550 65 393 0.6261
9 0.6038 0.0632 0.4436 279 1513 102 350 0.5600
8 0.5273 0.0929 0.5294 333 1465 150 296 0.4797
7 0.4496 0.1245 0.6153 387 1414 201 242 0.4043
6 0.3742 0.1604 0.6661 419 1356 259 210 0.3704
5 0.3045 0.2149 0.7313 460 1268 347 169 0.3441
4 0.2427 0.2601 0.7758 488 1195 420 141 0.3434
3 0.1901 0.3084 0.8156 513 1117 498 116 0.3593
2 0.1466 0.3932 0.868 546 980 635 83 0.4148
1 0.1117 0.5536 0.9237 581 721 894 48 0.5588
0 0.0843 1 1 629 0 1615 0 1
0 0.0843 1 1 629 0 1615 0 1
health care financing41. Therefore, the costs of dental services are relatively low in Taiwan.
This study has a number of limitations. Firstly, the subjects were recruited from local dental clinics and may differ from the general population. People who are less concerned about dental health or hold negative attitudes towards dental services are less likely to use these services, and this group tends to include those with poorer dental health. Therefore, studying subjects from dental clinics could lead to an overestimation of the number of remaining teeth. However, the purpose of the present study was to evaluate a screening test based on a food intake questionnaire for discriminating masticatory ability and not the prevalence of tooth loss or chewing difficulty. In addition, the single-payer NHI system in Taiwan helped to reduce the bias caused by including subjects from dental clinics as the study sample. Secondly, the types of food chosen are common in Taiwan and might not be appropriate for similar studies in other countries or areas. Sometimes, the same food might be eaten in a different way in another country or area and might be perceived differently by different people.
Taiwanese foods are influenced by the Chinese culture, but there are many differences in cuisine and the style of eating. An index of eating difficulty for older southern Chinese people comprises 10 Chinese food items, including whole apple, roast pork ribs, corn on the cob and cooked green veg- etables33. In Taiwan, however, sliced apple, boil pork ribs and boil or roast corn on the cob are the daily common foods. Sliced sweet pepper, water spinach and broccoli are all green vegetables, but they were different discriminatory indicators in the present study.
Among the subjects, 28.0% belonged to the
<20 NT or 8 FTU group and most were elderly. The mean number of NT in the <20 NT or 8 FTU group was only 10.4. In other words, the proportion of removable prosthesis use in this group was high (50.1%), especially among the elderly (59.69%).
Therefore, the design of removable dentures that can improve the masticatory ability of middle-aged and older people or improve their masticatory ability to a similar level as that of people with 20 and more NT and at least 8 FTUs is important, given the increase in the elderly population.
In conclusion, foods considered easy to eat by people with good chewing ability but difficult to eat by those with poor chewing ability are the ideal discriminatory indicators of masticatory ability.
Hence, the 14-food group questionnaire can be considered the best screening test for masticatory ability of Taiwanese adults aged 45 years and over
in terms of the presence of 20 and more NT and at least 8 FTUs. However, whether this questionnaire is suitable for other ethnicities needs further investigation.
Acknowledgements
This study was supported by a grant (DOH95- HP-1318) from the Bureau of Health Promotion, Department of Health, Taiwan.
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Correspondence to:
Yea-Yin Yen, Department of Dental Hygiene and Oral Hygiene, College of Dental Medicine, Ka- ohsiung Medical University, No.100, Tzyou 1st Rd, San Ming District, Kaohsiung 807, Taiwan.
Tel.: +886 7 3229746 Fax: +886 7 3157024
E-mail: taihen.n4545@msa.hinet.net
