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Int Chin J Dent 2010; 10: 51-56.

A questionnaire survey of dental students in Japan, China, andIndonesia about denture cleansers
Guang Hong, DDS, PhD,a Ying-Ai Li, DDS, PhD,b Yun-Min Lian, DDS,c Shinsuke
Sadamori, DDS, PhD,b Taizo Hamada, DDS, PhD,a and Hiroshi Murata, DDS, PhDda

Department of Oral Health Care Promotion, Graduate School of Dentistry, Tohoku University, Sendai,b
Japan, Department of Prosthetic Dentistry, Graduate School of Biomedical Sciences, Hiroshimac
University, Hiroshima, Japan, Department of Prosthetic Dentistry, The Second Hospital of HebeidMedical University, Shijiazhuang, P. R. China, and Department of Prosthetic Dentistry, Graduate
School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
Purpose: It is not definite about how much knowledge, experience, and opinion the dental students have about
denture cleansers. The purpose of this study was to investigate the interest and knowledge about denturecleansers of dental student in Japan, China, and Indonesia.
Materials and Methods: Forty-seven dental students from Japan (Hiroshima University), 38 dental students
from China (Hebei Medical University and Wuhan University), and 29 dental students from Indonesia(Airlangga University) were surveyed in this study.
Results: The response rate was 92.1%. Significant differences were found among the three countries for allquestions. For the question “Have you heard of denture cleanser?”, 100% of Japanese students answered “Yes”,
whereas 40.5% of Chinese students and 13.8% of Indonesian students answered “No”. Japanese students
recognized denture cleansers in TV commercials more often than Chinese and Indonesian students (Q8). For thequestion “Do you think the use of denture cleanser is more effective than a clinical intervention?”, about 75% of
the subjects in Japan answered “Yes”; however, over 55% of subjects in China and Indonesia answered “No”.
Conclusion: The results suggest that there are differences in the awareness and knowledge about denturecleansers among the three countries of Japan, China and Indonesia. Chinese dental students had the least
knowledge about denture cleansers compared with the other two countries. (Int Chin J Dent 2010; 10: 51-56.)
Key Words: China, dental student, denture cleanser, Indonesia, Japan, questionnaire

Introduction
Commercial denture cleansers may be classified into the following groups: neutral peroxides with enzymes,
enzymes, acids, hypochlorites, peroxides, crude drugs, and mouth rinses for dentures.1 Denture cleansers havebeen widely used in prosthodontics to prevent colonization of Candida albicans and related Candida species andformation of denture plaque.2-5 They have been shown to significantly reduce the number of microorganisms on
dentures in a hospitalized geriatric population.6 However, denture cleansers can cause significant deteriorationof the physical and mechanical properties of denture base materials if not correctly used.7-12 Murdoch-Kinch etal.13 reported that oral mucosal injury can be caused by denture cleansers.
Denture wearers would benefit greatly from a dental professional’s guidance about the use of denturecleansers. However, the awareness and knowledge of Japanese, Chinese, and Indonesian dental students about
denture cleansers remain unclear. A recently published study reported that there were many differences in theunderstanding and experience of denture cleansers in the clinic among Japanese, Chinese, and Indonesian
dentists.14 Japanese dentists were the most informed about denture cleansers.
Because dental students have incomplete knowledge about dental services, it was thought that TV
commercials about denture cleansers may have an effect on the students’ awareness and knowledge. The
purpose of this study was to clarify Japanese, Chinese, and Indonesian dental students’ recognition of denturecleansers and to investigate any differences in their understanding of denture cleansers based on their nationality.

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Materials and Methods
In this study, 114 dental students were asked to complete and return a structured questionnaire (Table 1). The
subjects were selected at random from fourth-year undergraduate dental students in Japan (Hiroshima University,
Hiroshima), fourth-year undergraduate dental students in China (Hebei Medical University, Shijiazhuang;
Wuhan University, Wuhan) and fifth-year undergraduate dental students in Indonesia (Airlangga University,
Surabaya). They included 47 Japanese dental students (men, 26; women, 21; mean age: 23.6 years); 38 Chinese
dental students (men, 22; women, 16; mean age: 22.8 years) and 29 Indonesian dental students (men, 3; women,
26; mean age: 23.1 years). The questionnaire was distributed and collected in Japan, China and Indonesia from2006 to 2007 after the aim of the survey was explained to the subjects and their consent was obtained.
Table 1.

Questionnaire items and percentage distributions of answers by dental students
Item descriptions

Q 1. Have you heard of denture cleansers?

Q 2. Do you know what the function of a denture cleanser is?

Q 3. Do you know of any disadvantages of denture cleansers?

Q 4. How many imported brands of denture cleanser do you know?

Q 5. How many domestic brands of denture cleanser do you know?

Q 6. Have you ever been taught about denture cleansers?

Q 7. Have you ever seen denture cleansers in books or lecture meetings?

Q 8. Have you ever seen any TV commercials about denture cleansers?

Q 9. Do you know any alternatives to denture cleansers?

Q10. Have you ever seen denture cleansers in the clinic?

Q11. Do you think the use of denture cleanser is more effective than a clinicalintervention?

JPS
CNS
INS
JPS
CNS
INS
JPS
CNS
INS
JPS
CNS
INS
JPS
CNS
INS
JPS
CNS
INS
JPS
CNS
INS
JPS
CNS
INS
JPS
CNS
INS
JPS
CNS
INS
JPS
CNS
INS

Category score
2
1
0
15
32
0
0
22
15
0
25
4
19
28
0
2
20
14
1
27
1
3
24
20
0
7
29
0
19
10
0
5
42
0
6
28
3
1
26
7
28
12
2
6
26
0
1
28
7
24
16
0
10
24
0
20
9
8
25
14
0
9
27
0
18
10
24
21
2
0
4
32
3
5
21
2
7
38
0
8
28
1
14
14
5
16
26
1
10
25
0
7
22
26
9
12
0
18
14
4
13
12

A

χ2 test
**

A

**

A

**

B

**

B

**

C

**

C

**

C

*

A

**

C

**

A

**

A 2: Yes, very much, 1: Yes, but only a little, 0: No B 2: Three or more, 1: Less than three, 0: None C 2: Yes, often, 1: Yes,
occasionally, 0: No *: p<0.01 **: p<0.001 NS: Not significant

The questionnaire was written in Japanese and then translated into Chinese and Indonesian. After discussion
with the staff in Japan, China, and Indonesia, it was decided to retain the same estimation criteria. The
questionnaire consists of 11 questions (five questions about knowledge and comprehension; four questions about
education; two questions about clinical practice). Each question had three response options; “No” or “None”(score 0), “Yes, but only a little”, “Yes, occasionally” or “Less than three” (score 1), and “Yes, very much”,

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Int Chin J Dent 2010; 10: 51-56.

“Yes, often” or “Three or more” (score 2).
Chi-square tests were used to examine the differences in the responses for each item on the questionnaire
among the three countries. Forward stepwise logistic regression analyses were then carried out on the dependent
variable (between Japan and China; between Japan and Indonesia; and between China and Indonesia). The Waldstatistic was used to test the null hypothesis that the regression coefficients were zero. The Negelkerke R2statistic was used to discriminate how well the model was able to distinguish between the awareness andknowledge of dental students in the three countries. All analyses were computed with SPSS for Windows
operating system (SPSS 16, SPSS Japan Inc., Tokyo, Japan).

Results
The response rate was 92.1%: Japanese students, 100%; Chinese students, 78.9%; and Indonesian students
96.6%.

Questionnaire items and percentage distribution of responses are shown in Table 1.

Significant

differences between the three countries were found for all questions. Compared with Chinese and Indonesianstudents, more Japanese students not only knew about denture cleansers, but also had a clear understanding of its
purpose and directions for its use (Q1 and Q2). For the question “Do you know of any disadvantages of denturecleansers?”, 42.6% of Japanese students; 80.6% of Chinese students and 34.5% of Indonesian students answered“No”.

For the question “How many imported brands of denture cleanser do you know?”, over 80% of

respondents answered “None”. For the question “How many domestic brands of denture cleanser do you
know?”, 74.5% of Japanese students answered “Less than three”, whereas 76.5% of Chinese students and 96.6%
of Indonesian students answered “None”. For Q6 and Q7, over 70% of Chinese students answered “No”.
Japanese students recognized denture cleansers in TV commercials more often than Chinese and Indonesianstudents (Q8). There was a significant difference in the knowledge of the therapeutic effects of denture cleanser
among students in three countries (Q11).
Table 2.

Results of binary logistic regression analysis using Wald methods between Japan and China

Item No.
Forward stepwise (Wald)
Q 8: TV commercials of DC*
Q11: Effectiveness of DC*

B

S.E.

Wald chi-square

FreedomP

Exp (B)

5.98
2.51

1.52
1.25

15.45
4.01

1
1

0.000
0.045

393.0512.28* denture cleanser, For the forward stepwise method, variables were entered in step 1 to 2: Q8, Q11 in that order.

Table 2 shows the estimated coefficients and related statistics from the logistic regression model that predicts
group membership (between Japan and China). The model contained two variables using a forward stepwise
method (P<0.05): Q8 (TV commercials of DC) and Q11 (Effectiveness of DC).
Table 3.

Results of binary logistic regression analysis using Wald methods between Japan and Indonesia

Item No.
Forward stepwise (Wald)
Q 5: Domestic brands of DC*
Q 8: TV commercials of DC*
Q 9: Alternatives to DC*

B

S.E.

Wald chi-square

FreedomP

Exp (B)

-3.89
-2.06
2.51

1.32
0.73
1.07

8.65
7.92
5.56

1
1
1

0.003
0.005
0.018

0.21
0.13
12.36

* denture cleanser, For the forward stepwise method, variables were entered in step 1 to 4: Q5, Q8, Q9 in that order.

Table 3 shows the estimated coefficients and related statistics from the logistic regression model that predicts
group membership (between Japan and Indonesia).

The model contained three variables using a forward

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Int Chin J Dent 2010; 10: 51-56.

stepwise method (P<0.1): Q5 (Domestic brands of DC), Q8 (TV commercials of DC) and Q9 (Alternatives toDC). Table 4 shows the estimated coefficients and related statistics from the logistic regression model thatpredicts group membership (between China and Indonesia). The model contained three variables using a
backward stepwise method (P<0.1): Q3 (Disadvantages of DC), Q5 (Domestic brands of DC) and Q7 (Seen DC
in books or lecture meetings).
Table 4.

Results of binary logistic regression analysis using Wald methods between China and Indonesia

Item No.
Forward stepwise (Wald)
Q 3: Disadvantages of DC*
Q 5: Domestic brands of DC*
Q 7: Seen DC* in books or lecture meetings

B

S.E.

Wald chi-square

FreedomP

Exp (B)

3.28
-4.31
2

1.15
1.66
0.88

8.14
6.75
5.23

1
1
1

0.004
0.009
0.022

26.69
0.01
7.42

* denture cleanser, For the forward stepwise method, variables were entered in step 1 to 4: Q3, Q5, Q7 in that order.

Table 5 shows that 46 Japanese students (97.9%) and 28 Chinese students (93.3%) were correctly predictedusing the method outlined above. The Nagelkerke R2 statistic was 0.877; that is, 87.7% of the variation in theoutcome variable was explained by the logistic regression model. Table 6 shows that 44 Japanese students(93.6%) and 23 Indonesian students (82.1%) were correctly predicted. The Nagelkerke R2 statistic was 0.777;
that is, 77.4% of the variation in the outcome variable was explained by the logistic regression model. Table 7
shows that 27 Chinese students (90.0%) and 25 Indonesian students (89.3%) were correctly predicted. The
Nagelkerke R2 statistic was 0.650; that is, 65.0% of the variation in the outcome variable was explained by thelogistic regression model.
Tables 5-7.
Observed and predicted group membership using Wald methods between two countries
Table 5.
Table 6.
Table 7.
Predicted country
Predicted country
Predicted country
Group Japan China
Group
Japan Indonesia
Group
China Indonesia
Forward stepwise (Wald)
Forward stepwise (Wald)
Forward stepwise (Wald)
Japan
46
1
97.9
Japan
44
3
93.6
China
27
3
China
2
28
93.3
Indonesia
523
82.1
Indonesia
3
25
Total
96.1
Total
89.3
Total
2

90.0
89.3
89.7

The cut value is 0.50. Negalkerke R =0.877 (Table 5), 0.777 (Table 6), and 0.650 (Table 7) (forward stepwise).
* Responses of eight Chinese students and one Indonesian student were deleted because they did not give complete answers in
the questionnaire.

Discussion
In the clinic, patients would benefit greatly from a dentist’s guidance in the use of denture cleansers. This
study was designed to survey the knowledge, understanding and level of education about denture cleansers
among Japanese, Chinese, and Indonesian dental students.
More than 59% of Chinese students and more than 86% of Indonesian students said that they had heard only alittle about denture cleansers and that they knew only a little of their function, and over 80% of dentists in China
answered that they did not know of any disadvantages of denture cleansers. It is important for dentists to be
familiar with the disadvantages of denture cleansers; in particular, the risk of oral mucosal injury caused byinappropriate use of denture cleansers.13 In China, professional education about denture cleansers is a morepressing need than in the other two countries. Over 76% of the students in China and more than 96% of theIndonesian students did not know of any domestic brands of denture cleanser. In China and Indonesia, domestic
manufacturer of denture cleansers is almost non-existent, and they are reliant on imports; this may be why many
dental students in China and Indonesia did not know of any domestic brands. In addition, the difference in the54

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Int Chin J Dent 2010; 10: 51-56.

economic strength among the countries may have affected the students’ answers. Furthermore, the answers to
the questions regarding imported and domestic denture cleanser products may have been related to differences in
the production of denture cleansers among the three countries.
Over 70% of students in China responded that they had never been taught about denture cleansers, and had
never seen denture cleansers in books or lecture meetings. However, only approximately 30% of Japanese
students and Indonesian students answered "No" to these questions. In Indonesia, specialty books containing
information about denture cleansers that were translated from Japanese into Indonesian were being used as
textbooks. This may be why the Chinese students’ responses were so low to these questions, as they had mostly
never been taught about denture cleansers, and had never seen denture cleansers in books or lecture meetings.
Over 70% of students in China and Indonesia responded that they had never seen denture cleansers on
television. This could be due to the fact that mass media is more developed in Japan than in China and Indonesia.
This suggests that Japanese students not only receive education about denture cleansers in dental school, but arealso exposed to information about denture cleansers through TV commercials. Students should be taught
evidence-based facts about denture cleansers in dental school by specialist prosthodontists. We also suggest that
it is particularly important to teach students about the advantages and disadvantages of denture cleansers as partof their professional education.
Over 69% of Chinese students and over 75% of Indonesian students stated that they had never seen denturecleansers in the clinic. There are various environmental differences among the three countries, such as theeducation system and the clinical system, which could affect awareness about denture cleansers.
The results of our study suggest that using only two out of the 11 questions (Q8: TV commercials of DC, andQ11: Effectiveness of DC) allowed the nationality of the dental students in Japan and China to be almost
correctly predicted (96.1%) by the model. Using only three items (Q5: Domestic brands of DC, Q8: TV
commercials of DC, and Q9: Alternatives of DC), the nationality of dental students in Japan and Indonesia wasalmost correctly predicted (89.3%). Finally, using only three items (Q3: Disadvantages of DC, Q5: Domestic
brands of DC, and Q7: Seen DC in books or lecture meetings), the nationality of dental students in China andIndonesia was almost correctly predicted (89.7%). However, some limitations can be identified in this study: theindirect translation of the questionnaire from Japanese to Chinese and Indonesian; and the small sample sizes. It
is unknown whether the results can be generalized to other samples; therefore, it is necessary to conduct future
research in more diverse samples.
Acknowledgment
This research was supported in part by a Grant-in-Aid (No. 21791899) for Scientific Research from the Ministry of Education, Culture,
Sports, Science and Technology, Japan.

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Correspondence to:
Dr. Guang Hong
Department of Oral Health Care Promotion, Graduate School of Dentistry, Tohoku University
4-1, Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan
Fax: +81-22-717-8345 E-mail: hong@m.tohoku.ac.jp
Accepted November 30, 2010.

Copyright ©2010 by the International Chinese Journal of Dentistry.

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