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Table of Contents
ORIGINAL ARTICLE
Year : 2019  |  Volume : 3  |  Issue : 3  |  Page : 75-80

Effects of brushing and immersion in denture cleanser on the surface roughness of polymethyl methacrylate


1 Department of Dental Material, Faculty of Dentistry, Trisakti University, Jakarta, Indonesia
2 Department of Dental Material, Faculty of Dentistry, Maranatha University, Bandung, Indonesia

Date of Submission28-Jun-2019
Date of Decision13-Aug-2019
Date of Acceptance01-Sep-2019
Date of Web Publication14-Oct-2019

Correspondence Address:
Dr. Octarina
Department of Dental Material, Faculty of Dentistry, Trisakti University, Jakarta 11440
Indonesia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/SDJ.SDJ_19_19

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  Abstract 


Background: The proper method for cleaning dentures is important to prevent an increase in the surface roughness average (Ra). An average roughness value above 0.2 μm can increase bacterial colonization. Objective: The aim of this study was to investigate the effects of brushing and immersion in denture cleanser on the surface roughness of polymethyl methacrylate (PMMA) materials. Methods: Fifty PMMA samples (18 mm × 10 mm × 2 mm) were randomly divided into five groups (n = 10 each): immersion in distilled water (Group A), brushing without toothpaste (Group B), brushing with toothpaste (Group C), immersion in denture cleanser and brushing without toothpaste (Group D), and immersion in denture cleanser and brushing with toothpaste (Group E). The surface roughness was measured using a surface roughness tester before and after the treatment. The results were obtained by calculating the difference between the initial and final surface roughness values. The data were analyzed using Welch's one-way analysis of variance and the Games–Howell post hoc test. Results: The mean Ra values were 0.033 ± 0.024 μm for Group A, 0.057 ± 0.018 μm for Group B, 1.551 ± 1.234 μm for Group C, 0.102 ± 0.026 μm for Group D, and 1.695 ± 1.158 μm for Group E. There were statistically significant differences among the groups, with the exception of Groups A and B and Groups C and E. Conclusion: Brushing without toothpaste had the least effect on increasing the surface roughness, whereas brushing with toothpaste and immersion in denture cleanser greatly increased the surface roughness.

Keywords: Brushing, denture cleanser, polymethyl methacrylate, surface roughness


How to cite this article:
Kurniawan AV, Octarina, Dwifulqi H. Effects of brushing and immersion in denture cleanser on the surface roughness of polymethyl methacrylate. Sci Dent J 2019;3:75-80

How to cite this URL:
Kurniawan AV, Octarina, Dwifulqi H. Effects of brushing and immersion in denture cleanser on the surface roughness of polymethyl methacrylate. Sci Dent J [serial online] 2019 [cited 2019 Dec 6];3:75-80. Available from: http://www.scidentj.com/text.asp?2019/3/3/75/269000




  Background Top


The most common material used as a denture base is polymethyl methacrylate (PMMA). PMMA heat-cured acrylic resin has been widely used in dentistry due to its advantageous properties, such as its low cost, excellent esthetic properties, ease of manipulation and repair, and good biocompatibility in the oral cavity.[1] The use of dentures must be followed by regular denture cleaning, which will improve the longevity of the dentures and the patient's oral health.[2],[3] Denture cleaning is also essential for the prevention of halitosis, caries development in the abutment teeth, biofilm formation, and calculus accumulation on the dentures, which causes periodontal disease.[4]

The denture cleaning procedure can be performed mechanically, chemically, or with a combination of both methods. The mechanical procedure can be done by brushing the dentures. One popular method for cleaning the dentures is to use a toothbrush, water, and toothpaste, which is simple, inexpensive, and effective for removing organic deposits.[5],[6] The standard recommendation for brushing dentures consists of using a soft-bristle brush with water or soap.[7] A soft-bristle toothbrush must be used because the stiffness of the toothbrush can affect the dentures' surface roughness.[5] Brushing will reduce biofilm formation and eliminate debris on the denture surface.[8] The chemical procedure can be performed by immersing the dentures in denture cleanser solution, which will prevent microbial colonization, while also effectively removing stains and biofilm on the irregular denture surface.[2],[8] This method can be chosen as an alternative because of its simple technique and the solution's ability to access all areas of the denture, including the parts that are mechanically inaccessible.[9]

Appropriate denture cleaning by following the instructions and the compatibility with the dentures' base material is important. An improper cleaning method can cause several detrimental effects, such as increasing the surface roughness of the denture base. The alteration of the surface roughness can enhance microbial retention on the denture surface.[3],[10] The maximum surface roughness value of a denture base against bacterial adhesion is 0.2 μm.[7] A material's surface roughness can be measured using a surface roughness tester. An object's surface is measured in micrometers, and the device will show the results of various parameters, one of which is the roughness average (Ra).[11] The Ra is the most common parameter used for describing the surface roughness because it represents a good overall description of the height variations.[12],[13] The aim of this research was to investigate the effects of brushing and immersion in denture cleanser on the surface roughness of PMMA.


  Methods Top


The materials used in this research are presented in [Table 1]. The samples consisted of fifty PMMA plates (18 mm × 10 mm × 2 mm), which were made from heat-cured acrylic resin (SR Triplex Hot; Ivoclar Vivadent, Schaan, Liechtenstein). The samples were made by mixing the powder and liquid in accordance with the manufacturer's instructions. They were stirred together until the mass was homogenous; then, the resin was packed into molds and cured. The curing process consisted of boiling the molds for 45 min. The molds were cooled until they reached room temperature; then, all of the samples were removed and finished with 320, 400, and 600 grit sandpaper. The samples were also polished so that they had the same surface roughness. The samples were first polished with pumice, followed by chalk powder (CaCO3). Each polishing material was mixed with water to produce a paste. Each paste was rubbed over the sample surfaces and they were abraded with a felt cone and rag wheel on a lathe machine. Then, the samples were rinsed with tap water to remove any residual abrasive particles.
Table 1: Materials used in this study

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The surface roughness measurements were taken at the middle of each sample using a surface roughness tester (Taylor Hobson Surtronic S-100 Handheld Series; Ametek Inc., Berwyn, PA, USA) before and after the treatment. The measurements were taken three times to obtain the initial and final surface roughness value means. The samples were fixed on a flat surface, and the surface roughness tester was calibrated at a speed of 1 mm/s, transverse length of 4 mm, interval (cut off length) of 0.8 mm, and range of 100 μm.

Fifty samples were randomly divided into five groups, and each group consisted of ten samples: immersion in distilled water (Group A), brushing without toothpaste (Group B), brushing with toothpaste (Group C), immersion in denture cleanser and brushing without toothpaste (Group D), and immersion in denture cleanser and brushing with toothpaste (Group E).

The samples from Group A were immersed in 200 ml of distilled water at room temperature. The samples from Groups B and D were brushed with 1 ml of distilled water, whereas the samples from Groups C and E were brushed with a homogeneous substance consisting of toothpaste and distilled water at a ratio of 1:1. For Groups B, C, D, and E, the samples were brushed using electric toothbrushes (Oral B Precision Clean; Braun GmbH, Kronberg, Germany) that were fixated using universal table vises, and the load applied to each brush head was 200 g. The brushing procedure was performed for 20 s, and it was repeated 365 times. Between each brushing procedure, the samples were rinsed in running distilled water. For Groups D and E, the samples were immersed in a denture cleanser solution that was prepared by adding one denture cleanser tablet (Polident; GlaxoSmithKline, Durham, NC, USA) to 200 ml of distilled water at room temperature. This procedure was performed for 5 min, and it was repeated 52 times. These treatments were meant to equal 1 year of denture cleaning by brushing every day and immersing the dentures once a week.

Statistical analysis

The results were obtained by calculating the differences between the initial and final surface roughness. The data were analyzed using Welch's one-way analysis of variance (ANOVA) and the Games–Howell post hoc test (IBM SPSS Statistics for Windows, version 23.0; IBM Corp., Armonk, NY, USA) to determine any statistically significant differences among the five groups. P <0.05 was considered statistically significant.


  Results Top


The mean surface roughness values before and after the treatments and the differences in the surface roughness values are presented in [Table 2]. Group B (brushed without toothpaste) showed the least change in the surface roughness when compared to the other groups. The groups in which the samples were brushed with toothpaste, whether they were immersed in denture cleanser or not (Groups E and C), had the highest surface roughness values. Both the groups showed values above the threshold of 0.2 μm.
Table 2: Mean surface roughness values (Ra, μm) and standard deviations

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The statistical analysis of the differences in the surface roughness using Welch's one-way ANOVA and the Games–Howell post hoc test is presented in [Table 3]. It shows that there were significant differences among all of the groups (P< 0.05), with the exception of Groups A and B, with P = 0.112, and Groups C and E, with P = 0.999.
Table 3: Statistical analysis of the differences in the surface roughness means among the five groups using Welch's one-way analysis of variance and the Games-Howell post hoc test

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  Discussion Top


The results of this research showed that cleaning the dentures by brushing without toothpaste had the least effect on the surface roughness. Brushing without toothpaste and immersion in the denture cleanser increased the surface roughness significantly [Table 3], yet the final surface roughness was still below the threshold for microbial adhesion of 0.2 μm. Brushing with toothpaste, whether immersed in the denture cleanser or not (Groups E and C), greatly increased the surface roughness values above the threshold of 0.2 μm.

The Group B data shown in [Table 2] suggest that the results of brushing using a toothbrush with water were clearly different from the other groups. Group B had the lowest increase in the surface roughness when compared to Groups C, D, and E. In addition, Group B had a higher average roughness value than that of the control group, as shown in [Table 3]; however, this difference was not statistically significant (P > 0.05), which is similar to the results of several other studies.[7],[14],[15] It was shown that brushing using a toothbrush with distilled water did not significantly increase the surface roughness, which can be explained by the absence of abrasive particles or chemical reactions affecting the PMMA.[7]

In Group D, in which the samples were brushed without toothpaste and immersed in denture cleanser, the surface roughness of the PMMA showed a statistically significant increase, even though the resulting increase in the roughness was below the roughness threshold of <0.2 μm. In [Table 2], it can be seen that the average value of the surface roughness difference for group D was higher than that for group B because of the immersion effect of the denture cleanser. Increased roughness due to the toothbrush is highly influenced by the technique, frequency, and pressure used when brushing.[16] However, these factors were standardized for each group, so it can be seen that the denture cleanser can increase the surface roughness. Peracini et al. reported that immersion in denture cleansers in the alkaline peroxide or alkaline percarbonate group significantly increased the surface roughness, but it remained below the 0.2 μm threshold so as not to increase the microorganism retention.[8] The roughness increases due to the effects of the effervescent tablets, which release oxygen bubbles when put in water during mechanical cleaning.[8],[17] King and Morgan stated that, in addition to the effects of the oxygen release, the presence of citric acid in the denture cleaner can react with the oxidizing agents and create stronger reactions that can increase the surface roughness of the material.[18]

Group E, in which the treatment consisted of both brushing with toothpaste and immersion in denture cleanser, had the highest difference in the surface roughness followed by Group C, which was only brushed with toothpaste. The average roughness values before and after the treatment are shown in [Table 2], which shows the equivalent values as if the sample had been cleaned daily for 1 year. The roughness values in the two groups passed the 0.2 μm roughness threshold, suggesting that these treatments could increase microorganism retention as well as decrease the glossy appearance of the dentures' base surface.[16] The results of both groups were statistically significant (P< 0.05). Both the sample surfaces in Groups C and E grew rougher due to brushing with toothpaste, which is shown in [Figure 1] and [Figure 2]. The graphs show the two-dimensional changes in the surface profiles before and after the treatment. Both of these post-treatment graphs showed higher peaks and deeper valleys than the pretreatment values, as well as when compared to the graphs for Group A [Figure 3], Group B [Figure 4], and Group D [Figure 5]. This reflects the findings when comparing the Rp, Rv, and Rt values from the samples in Groups C and E, which were a lot higher than the values in the other groups. Rp is the maximum height of the profile above the mean line within the sampling length, and Rv is the maximum depth of the profile below the mean line within the sampling length. Rt is the maximum peak to valley height of the profile. These results are also consistent with the research conducted by Verran et al., who stated that toothpaste produces deeper strokes on the surface of PMMA when compared to a control group; however, this also strongly depends on the abrasive contents of the toothpaste. These conditions can be seen on the microscopic photographs as well as the surface profiles of the resins.[19] The results are also supported by the study by Pisani et al., who concluded that the increase in the surface roughness above the 0.2 μm threshold could be traced back to the abrasive property of sodium bicarbonate.[5] The toothpaste used in this study also contained sodium bicarbonate, along with other abrasive materials, such as calcium carbonate, silicone dioxide, and inorganic phosphate, which can abrade the surface of acrylic resin when it is brushed.[6],[14],[20],[21]
Figure 1: Graph and surface roughness values of a sample from Group C before treatment (a) and after treatment (b). Ra: Mathematical average of the measured profile height and depth from the mean line, Rt: Maximum peak to valley height of the profile in the assessment length, Rv: Maximum depth of the profile below the mean line within the sampling length, Rp: Maximum height of the profile above the mean line within the sampling length

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Figure 2: Graph and surface roughness values of a sample from Group E before treatment (a) and after treatment (b). Ra: Mathematical average of the measured profile height and depth from the mean line, Rt: Maximum peak to valley height of the profile in the assessment length, Rv: Maximum depth of the profile below the mean line within the sampling length, Rp: Maximum height of the profile above the mean line within the sampling length

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Figure 3: Graph and surface roughness values of a sample from Group A (control) before treatment (a) and after treatment (b). Ra: Mathematical average of the measured profile height and depth from the mean line, Rt: Maximum peak to valley height of the profile in the assessment length, Rv: Maximum depth of the profile below the mean line within the sampling length, Rp: Maximum height of the profile above the mean line within the sampling length

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Figure 4: Graph and surface roughness values of a sample from Group B before treatment (a) and after treatment (b). Ra: Mathematical average of the measured profile height and depth from the mean line, Rt: Maximum peak to valley height of the profile in the assessment length, Rv: Maximum depth of the profile below the mean line within the sampling length, Rp: Maximum height of the profile above the mean line within the sampling length

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Figure 5: Graph and surface roughness values of a sample from Group D before treatment (a) and after treatment (b). Ra: Mathematical average of the measured profile height and depth from the mean line, Rt: Maximum peak to valley height of the profile in the assessment length, Rv: Maximum depth of the profile below the mean line within the sampling length, Rp: Maximum height of the profile above the mean line within the sampling length

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In this study, we determined the differences in the surface roughness of PMMA equivalent to a usage for one year, while dentures are generally used for more than five years.[22] Additional research should be done to effectively observe the long-term effects of denture cleaning, as well as the effects of other cleaning methods, such as the use of soap or mouthwash, and their impacts on the surface roughness of PMMA.


  Conclusion Top


Brushing without toothpaste had the least effect on increasing the surface roughness when compared to the other methods. Brushing with toothpaste and immersion in denture cleanser greatly increased the surface roughness of the PMMA.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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