1. Introduction
Recently, it has been suggested that oral microorganisms are associated with systemic disease and that dentures represent a reservoir for these microorganisms [1–4]. Denture plaque is associated not only with oral disease, such as denture stomatitis, periodontitis, and caries, but also systemic disease, including aspiration pneumonia, gastrointestinal infection, and pleural infection. Therefore, effective denture plaque control is necessary to prevent these diseases, especially in an aging society [1–4].
There are three methods of denture cleaning: mechanical, chemical, and thermal. The mechanical method uses brushes and ultrasonic devices, the chemical method involves soaking the denture in cleansers, and the thermal method involves the use of microwave ovens [1,3,4]. A systematic review by de Souza et al. [3] reported that denture cleansers and brushing are more effective than placebo at reducing plaque coverage and microbial counts of anaerobes and aerobes on the complete denture base. However, these findings are not generalizable due to the wide range of different interventions and outcome variables.
An in vitro study by Paranhos et al. [5] demonstrated that a combination of mechanical and chemical methods was more effective at reducing microbial biofilms on acrylic resin specimens than the chemical method alone. An in vivo study by Dills et al. [6] showed that mechanical and chemical methods were more effective than no treatment for reducing plaque microorganisms, and a combination of mechanical and chemical methods was more effective than mechanical and chemical methods alone. It appears that mechanical or chemical methods alone may be insufficient for adequate denture cleaning, but a combination of the two is more effective [1–10].
There is limited information available regarding the evaluation of mechanical and chemical methods, and comparisons between the two, due to lack of standardized methods for examining the efficacy of denture cleaning methods [1,3,4]. Moreover, little is known about the effect of different methods on patient satisfaction and preferences, costs, adverse effects, and mucosa under the denture base [3,4]. Although dentists tend to objectively evaluate denture cleanliness, elderly patients often show little interest in the matter.
Recently, the adenosine triphosphate (ATP) bioluminescence method has increased in popularity for evaluating environmental cleanliness [11]. ATP is a basic source of energy for all living organisms. The ATP bioluminescence method measures the amount of ATP as an indication of contaminant level. It is used not only to evaluate public hygiene and cleanliness in hospitals, but also to assess oral hygiene, caries risk, and root canal bacteria [11–16]. Therefore, the ATP bioluminescence method can be applied in various situations as a simple and rapid inspection method; however, little is known about the appropriateness of this method for evaluating denture cleanliness.
In the present study, we initially evaluated the reliability and validity of ATP bioluminescence as an inspection method for denture cleanliness. We then evaluated the effectiveness of the mechanical denture cleaning method versus a combination of mechanical and chemical methods in terms of denture cleanliness, patient satisfaction, and oral health-related quality of life (OHRQoL). To the best of our knowledge, no previous study has investigated the effects of different denture cleaning methods on patient satisfaction [3]. The null hypothesis of this study was that there are no differences in denture cleanliness, patient satisfaction, and OHRQoL between the mechanical method, and a combination of mechanical and chemical methods.
2. Materials and methods
2.1. Pilot study
The reliability and validity of ATP bioluminescence as an inspection method of denture cleanliness was evaluated. To evaluate reliability, the upper complete dentures of five patients were assessed three times using the ATP bioluminescence method, and the interclass correlation coefficient was calculated. To evaluate validity, the upper complete denture of 12 patients was assessed using the ATP bioluminescence method, stained photograph method, and a simple quantification of C. albicans at initial patient hospital visit and after denture cleaning by dentists. The Spearman’s rank-correlation coefficient between the ATP biolumi-nescence method and stained photograph method, and between the ATP bioluminescence method and simple quantification of C. albicans, was calculated.
The score of the correlation coefficients was judged in accordance with the guideline. This guideline expressed 0.0–
0.20 as slight, 0.21–0.40 as fair, 0.41–0.60 as moderate, 0.61–0.80 as substantial, and 0.81–1.00 as almost perfect [17].
The intraclass correlation coefficient of the ATP biolumines-cence method was 0.93, which indicates high reliability. The Spearman’s rank-correlation coefficients between the ATP biolu-minescence method and stained photograph method, and between the ATP bioluminescence method and simple quantification of C. albicans, were 0.63 (p = 0.001) and 0.52 (p = 0.001), respectively; this indicates acceptable validity.
2.2. Participants
A total of 33 edentulous individuals were assessedfor eligibility in this study. The participants comprised patients who visited the Tokyo Medical and Dental University Hospital Faculty of Dentistry (Tokyo, Japan) for new fabrication, adjustment, or recall of complete dentures during 2016. All participants provided written informed consent and received an explanation of the study. Exclusion criteria included the following: serious systemic illness; difficulty with responding to the questionnaire; use of metallic base dentures; constant use of denture stabilizers; and use of dental tissue conditioner with dentures.
The sample size was based on information from a previous report. The primary outcome was measured according to the stained photograph method. This study reported that the mean and SD of the mechanical method are 39.53 and 22.56, respectively, and the mean and SD of the combination method are 18.40 and
16.11, respectively [10]. We calculated the sample size with a power of 80 % at a 5 % level of significance (two-tailed test), assuming a 20 % dropout rate. The total sample size for the two groups was calculated to be 30 participants.
2.3. Study design
This study was a controlled, before-and-after trial involving two parallel groups. Thirty participants were randomly allocated to one of two groups (n = 15 each): mechanical method or combination method. Baseline data of the participants were examined and dentists were assigned to clean each denture by brushing for 1 min using a denture brush (Erac Gishi brush, Lion, Tokyo, Japan) and denture cleansers (Polident Fresh Cleanse, GlaxoSmithKline, Tokyo, Japan), followed by cleaning the dentures using ultrasonic vibration (SPEED SONIC 1510, Mortia, Tokyo, Japan) in a specific ultrasonic vibration denture cleanser (Denture Cleaner, GC, Tokyo, Japan), and then brushing them again in the same manner.
The specific method of denture cleaning was then explained to each group of study participants. Participants in the mechanical method group were instructed to brush their dentures after each meal for 2 min using tap water and a denture brush, and soak the dentures in saline solution (isotonic sodium chloride solution, Chemix Inc., Yokohama, Japan) while they slept. Individuals in the combination method group were instructed to brush the dentures the same way, but to soak them in denture cleansers (Polident, GlaxoSmithKline) while they slept. Both groups were required to clean the dentures accordingly for 3 weeks. The study protocol was approved by the Tokyo Medical and Dental University (Ethics Committee of the Faculty of Dentistry, Tokyo Medical and Dental University, No. 1276).
2.4. Outcomes
For the objective evaluation of denture cleanliness, the ATP bioluminescence method, stained photograph method, and simple quantification of C. albicans in the upper complete denture and oral mucosa were performed. General participant satisfaction, ease of cleaning, comfort, and esthetics were measured using a 100 mm visual analog scale (VAS). OHRQoL was measured using the Japanese version of the Oral Health Impact Profile for edentulous patients (OHIP-EDENT-J). These parameters were examined immediately before the intervention and three weeks after the intervention.
2.4.1. ATP bioluminescence method
The ATP bioluminescence method is based on a chemical reaction catalyzed by luciferase. The amount of light generated by this reaction, which is proportional to the amount of ATP present, is expressed as relative light units (RLU) [11–16]. The upper complete denture was first rinsed under running water for 10 s. The specific pen (LuciPac Pen, Kikkomanbiochemifa, Tokyo, Japan) was then moistened, and the internal surfaces of the upper complete denture were swabbed using the pen for 30 s. Finally, the pen was set in an ATP bioluminescence meter (Lumitester PD-30, Kikko-manbiochemifa) for 10 s, after which the RLU value was calculated.
2.4.2. Stained photograph method
The internal surface denture plaque was initially stained in
upper complete dentures using a plaque staining solution (Prospec, GC). The surfaces were then photographed using a digital camera (D70, Nikon, Tokyo, Japan) with standard film-object distance and exposure time. The camera was fixed on a stand (CSC-10, LPL, Tokyo, Japan) and camera platform (PHD-51, Velbon, Tokyo, Japan). Photographs were imported to a computer. Total surface area and stained area were measured using image-processing software (ImageJ). The percentage of stained area was calculated using the total surface area of the internal denture base [10,18].
2.4.3. Simple quantification of C. albicans
The upper complete denture and oral mucosa were examined
for C. albicans using a specific swab (Stomastat, Dentsplay, Tokyo, Japan) [19–21]. Following attachment, the swab was soaked in culture solution and placed in an incubator at 37 C for 24 h after 20 s of swabbing. C. albicans was quantified according to three stages; < 100 colony-forming units (CFU)/mL ( stage); approximately 7000 CFU/mL ( stage); and > 70,000 CFU/mL (+stage).
Each stage was assigned a score as follows: stage = 1; stage = 2; and +stage = 3.
2.4.4. Participant satisfaction and OHRQoL
General participant satisfaction, ease of cleaning, comfort, and
esthetics were evaluated using the 100 mm VAS for subjective satisfaction [22,23]. OHRQoL was evaluated using the OHIP-EDENT-J. The OHIP-EDENT-J is scored between 0 and 76, and the higher the score, the lower the OHRQoL [24].
2.5. Randomization process
Block randomization was conducted for participant grouping. The randomization scheme was generated using an online protocol (www.randomization.com) [25]. Participants were randomized into 3 blocks.
2.6. Statistical analysis
Data regarding the ATP bioluminescence method, stained photograph method, simple quantification of C. albicans, each category of the 100 mm VAS, and the OHIP-EDENT-J OHRQoL, were found to be non-normally distributed. The Mann–Whitney U test was used to compare results from the ATP bioluminescence method, stained photograph method, simple quantification of C. albicans, each category of the 100 mm VAS, and OHIP-EDENT-J OHRQoL between the two groups, at baseline and after intervention. Statistical analyses were performed using statistical analysis software (SPSS version 22, IBM, Armonk, NY, USA). The significance level was set at 0.05.
3. Results
3.1. Participants
A flow disgram for the study is presented in Fig. 1. A total of 33 edentulous individuals were assessed for eligibility in this study. One individual declined to participate. One participant in each group was lost to follow-up. Therefore, a total of 30 participants (19 men,11 women; mean [ standard deviation] age, 79.4 6.9 years; range, 64–92 years) were analyzed in this study.
3.2. Baseline characteristics
The baseline characteristics of the participants are summarized in Table 1 and Table 2. There were no significant differences in any characteristic between the groups.
3.3. Between-group comparison after intervention
Between-group comparisons are summarized in Table 3. No significant differences were found for C. albicans abundance in the oral mucosa, general participant satisfaction, ease of cleaning, comfort and
esthetics, or OHIP-EDENT-J.
4. Discussion
This study evaluated the effectiveness of a mechanical denture cleaning method versus a combination of mechanical and chemical methods on denture cleanliness, patient satisfaction, and OHRQoL. Current understanding of the effects of different denture cleaning methods on patient satisfaction and OHRQoL is limited [3,4]. Patients themselves necessarily perform denture cleaning. To maintain adequate denture cleaning habits, however, the cleaning method should improve not only objective denture cleanliness, but also patient satisfaction and OHRQoL, which in turn would enhance the motivation to clean dentures properly and thoroughly. To the best of our knowledge, this was the first study to assess the effect of denture cleaning on patient satisfaction and OHRQoL.
Although there are numerous denture cleanliness inspection methods, no previous study appears to have evaluated the ATP bioluminescence method [1,3,4]. An in vivo study by Chan et al. [7] attempted to homogenize denture condition before interventions by refraining from denture cleaning for 48 h. The in vivo study by Cruz et al. [10] homogenized denture condition before interventions by brushing with a denture brush and liquid soap. There is a large variability in denture contamination due to differences in baseline usage conditions. Therefore, we should attempt to homogenize denture contamination before intervention to increase the accuracy of comparisons. Previous studies have used two methods of homogenizing denture contamination: denture contamination and denture cleaning. We selected the latter method for the present study due to the measurement limitations of the ATP bioluminescence method. If the levels of contaminants on the denture are excessive, the RLU often exceeds the measurement limitation, resulting in an inaccurate measurement value, making changes between before and after intervention undetectable. Therefore, we believe that the denture cleaning method leads to the most accurate intervention comparisons.
The ATP bioluminescence method is a simple and rapid inspection method, mainly used to evaluate public hygiene and cleanliness in hospitals. However, little is known about its suitability for evaluating denture cleanliness [11–16]. Therefore, we evaluated the reliability and validity of the ATP biolumines-cence method as an inspection method of denture cleanliness in a pilot study. The results showed that the reliability and validity of the ATP bioluminescence method are high, indicating that it is a useful inspection method for denture cleanliness. Alternative methods require specific equipment and are more time consuming. The stained photograph method requires a camera, stand, computer, and image processing time. The simple quantification of
C. albicans requires an incubator and 24 h of culture. In contrast, the ATP bioluminescence method is easy and only takes approximately it
requires only one hospital visit; therefore, it can reduce time and costs compared with other methods. Furthermore, the ATP bioluminescence meter and pen are small and easy to carry. Therefore, this method can be used to evaluate denture hygiene not only in a large hospital or research laboratory, but also in clinics, care facilities, and at home. It is expected that the ATP bioluminescence method will become useful for the evaluation of denture cleanliness and for instructing patients on denture cleaning. For these reasons, we believe that the ATP biolumines-cence method is feasible and can be standardized.
There were no significant differences in participant baseline characteristics due to block randomization. The results of this study showed that, based on ATP bioluminescence, staining, and C. albicans abundance in the upper complete dentures, the combination method was significantly more effective at denture cleaning than the mechanical method alone. These findings are in agreement with previous studies [1–5,7–10]. However, there was no significant difference in C. albicans in the oral mucosa between the methods. This indicates that the combination method can effectively remove more C. albicans from dentures, but not from the oral mucosa.
In the present study, the effects of different denture cleaning methods on patient satisfaction and OHRQoL did not become evident. There were also no significant differences in general participant satisfaction, ease of cleaning, comfort, esthetics, and OHRQoL between methods. A previous study reported that OHIP-EDENT-J score decreased by 10 compared with before and after fabrication of upper and lower complete dentures [24]. There are no previous studies investigating OHIP-EDENT-J of denture cleaning method. Therefore, we used this score as an alternative for clinically significant changes in OHIP-EDENT-J. In this study, OHIP-EDENT-J score of the mechanical method decreased by 1 and OHIP-EDENT-J score of the combination method decreased by 5 compared with before and after intervention. Therefore, this would suggest there were no clinically significant changes from the intervention. However, even if denture cleaning improves denture hygiene, it does not necessarily increase participant satisfaction or OHRQoL. This may have been because some of the participants were elderly individuals, who may have devoted little attention to denture cleanliness. Alternatively, it may be due to differences in denture cleanliness standards between the dentists and participants [26]. Nevertheless, there could have been a significant amount of contaminants on the dentures, regardless of whether the patients reported general satisfaction or high OHRQoL scores; therefore, we may not simply accept patient impressions about cleanliness. We may choose to make patients aware of how much contaminant is present on their dentures by showing them stained dentures and ATP bioluminescence scores, and explaining how harmful denture contaminants can be, causing not only oral disease(s), such as denture stomatitis, periodontitis, and caries, but also systemic diseases, including aspiration pneumonia, gastrointestinal infection, and pleural infection. We must educate patients about denture care, and patients should be encouraged to be more concerned with denture cleanliness and maintenance.
This study had several limitations. The intervention period was 3 weeks, which may have been too short to observe changes in C. albicans that had already colonized the oral mucosa, patient satisfaction, and OHRQoL based on daily habits. Therefore, further studies with longer-term intervention are required. In this study, the primary outcome was measured using the stained photograph method, and the sample size was calculated. Our sample size, however, may have been too small to detect significant differences in general participant satisfaction, ease of cleaning, comfort, esthetics, and OHRQoL. The participants included only patients who visited the hospital; therefore, they may tend to report high general satisfaction, ease of cleaning, comfort, esthetics, and OHRQoL. More participants from a wider sphere (e.g., care facilities and homes) are needed in future studies. Especially with regard to general participant satisfaction, ease of cleaning, comfort, and esthetics, the average baseline scores (70.5, 82.9, 72.7, and 79.5) were all high; therefore, a ceiling effect may have been present, which would have made the emergence of significant differences difficult to detect.
In addition, we did not analyze the effect of denture characteristics, such as duration of use and repair marks, on the effectiveness of the denture cleaning methods because the number of participants was relatively small. Considering that denture characteristics can vary widely, future studies should enroll a larger number of participants. This study allocated participants to one of only two cleaning groups; however, there are several other denture cleaning methods, including the chemical method alone and an ultrasonic device method. A greater variety of methods should, therefore, be evaluated and compared in future studies.
5. Conclusion
A combination of mechanical and chemical denture cleaning methods is more effective at improving objective denture cleanliness than the mechanical method alone. Although a combination of mechanical and chemical methods reduces the abundance of C. albicans on dentures to a greater extent than the mechanical method alone, it does not achieve the same effect in the oral mucosa. Furthermore, even if denture cleaning improves denture hygiene, it may not increase patient satisfaction and OHRQoL.
Conflicts of interest
There are no conflicts of interest to declare.
SOURCE: Journal of Prosthodontic Research, Feb 2018
