ORIGINAL RESEARCH


https://doi.org/10.5005/jp-journals-10019-1419
International Journal of Prosthodontics and Restorative Dentistry
Volume 13 | Issue 3 | Year 2023

Comparative Evaluation of Surface Roughness and Adhesion of Candida albicans on Conventional Heat-cured, Injection-molded Thermoplastic Resin and CAD-CAM Denture Base Resin as Affected by Denture Cleanser: An In Vitro Study


Neha Chaudhary1, Bhupender Yadav2, Sumit Phukela3, Abhishek Nagpal4, Omkar Shetty5, Manisha Khandait6

1–5Department of Prosthodontics, Crown & Bridge and Implantology, Faculty of Dental Sciences, Shree Guru Gobind Singh Tricentenary University, Gurugram, Haryana, India

6Department of Microbiology, Faculty of Dental Sciences, Shree Guru Gobind Singh Tricentenary University, Gurugram, Haryana, India

Corresponding Author: Bhupender Yadav, Department of Prosthodontics, Crown & Bridge and Implantology, Faculty of Dental Sciences, Shree Guru Gobind Singh Tricentenary University, Gurugram, Haryana, India, Phone: +91 8743019484, e-mail: drbhupinderyadav@gmail.com

Received on: 01 April 2023; Accepted on: 19 August 2023; Published on: 29 September 2023

ABSTRACT

Purpose: The purpose of this in vitro study was to evaluate and compare the surface roughness (Ra) and adhesion of Candida albicans (C. albicans) on conventional heat-cured, injection-molded thermoplastic resin and computer-aided design/computer-aided manufacturing (CAD-CAM) denture base resin as affected by denture cleanser solution at baseline, 15, 30, and 45 days.

Materials and methods: A rectangular-shaped metal die was fabricated to make heat-cure (n = 80) and injection-molded thermoplastic denture base resin (n = 80) disks of uniform dimensions, whereas CAD-CAM disks (n = 80) were made by scanning the wax disk and milling of polymethylmethacrylate (PMMA) block. All the 240 specimens were immersed in the two different solutions, that is, artificial saliva solution (n = 120) as the control group and denture cleansing solution (n = 120) as a test group for a period of 0, 15, 30, and 45 days for 8 hours, respectively followed by Candida colonization. The Ra was evaluated by surface profilometer SJ-201, followed by the measurement of Candida colonization. The statistical analysis was done using repeated measures analysis of variance (ANOVA) test, one-way ANOVA, and independent t-test.

Results: The Ra of heat-cured cured samples were 0.87 ± 0.01, 0.85 ± 0.02, 0.84 ± 0.02, and 0.83 ± 0.02 μm; injection-molded thermoplastic resin samples were 1.03 ± 0.01, 1.03 ± 0.04, 1.02 ± 0.03, and 1.00 ± 0.05 μm; and of CAD-CAM resin samples were 0.42 ± 0.01, 0.41 ± 0.02, 0.40 ± 0.03, and 0.40 ± 0.03 μm, respectively, when immersed in artificial saliva at baseline and intervals of 15, 30, and 45 days. The Ra of heat-cured samples were 1.12 ± 0.011, 1.21 ± 0.008, 1.25 ± 0.011, and 1.56 ± 0.008 μm; injection-molded thermoplastic resin samples were 1.31 ± 0.010, 1.45 ± 0.008, 1.76 ± 0.010, and 2.26 ± 0.014 μm; and of CAD-CAM resin samples were 0.86 ± 0.016, 1.07 ± 0.008, 1.12 ± 0.008, and 1.18 ± 0.015 μm, respectively, when immersed in denture cleansing solution at baseline, 15, 30, and 45 days. A similar trend was visible in the adherence of Candida to the denture base resins; the least adherence was seen in CAD-CAM resin, followed by heat-cured resin and injection-molded thermoplastic denture base resins.

Conclusion: Within the limitations of the study, it was concluded that CAD-CAM denture base resins may be the preferred choice over conventional heat-cured or thermoplastic denture base resins for the fabrication of removable dental prosthesis to minimize Candida adherence and thus preventing opportunistic fungal infections in geriatric individuals.

How to cite this article: Chaudhary N, Yadav B, Phukela S, et al. Comparative Evaluation of Surface Roughness and Adhesion of Candida albicans on Conventional Heat-cured, Injection-molded Thermoplastic Resin and CAD-CAM Denture Base Resin as Affected by Denture Cleanser: An In Vitro Study. Int J Prosthodont Restor Dent 2023;13(3):145–153.

Source of support: Nil

Conflict of interest: None

Keywords: Candida albicans, Computer-aided design/computer-aided manufacturing resin, Denture base, Denture cleanser, Surface roughness

INTRODUCTION

The dynamics of today’s population are changing. With an increasingly old age population, medical care today has to be planned accordingly. Edentulousness is the most common problem haunting today’s population as a result of the increasing percentage of higher age groups.1

Microbial organization and formation of biofilms on polymethylmethacrylate (PMMA)—based prosthesis within the oral cavity cause denture stomatitis. While existing literature highlights the contribution of various specific pathogens to dental plaque formation, empirical in vivo investigations, have consistently identified Candida albicans (C. albicans) as the predominant opportunistic organism associated with denture stomatitis.2-4 Multiple epidemiological investigations have demonstrated that the prevalence of denture-associated stomatitis ranges from 10 to 75% across various study populations, with higher rates observed among elderly and institutionalized individuals attributed to inadequate oral hygiene practices and extended prosthesis usage periods.5-7

The attachment of dental plaque has been impacted by the surface-free energy surface roughness (Ra). Ra is decided by the presence of consistency and alternative irregularities on the dental appliance and will provide a favorable place to retain microbic dental plaque and stain.8 Because of the surface characteristics of the acrylic prosthesis, C. albicans is more abundant on the surfaces of the prosthesis bases compared to the mucous membrane that holds the prosthesis.9

Denture cleansers are made from a variety of components, the most prevalent of which are cleansers containing sodium hypochlorite and alkaline peroxides.10 Peroxide cleansers are said to be effective against newly developed plaque and stains; however, they may require prolonged immersion of the prosthesis. Alkaline hypochlorite has the added benefit of being effective against both bacterial and fungal growth, as well as removing stains and other organic debris.11 There are reviews12,13 that denture cleansers adversely affect the physical properties of polyamide and PMMA denture base materials, and findings recommend that modifications in physical properties are influenced by the polymerization type in addition to the sort of denture base used.

Prior research efforts have primarily concentrated on the detrimental impact of biofilm on dental restorations, along with the reaction of denture cleanser solution on conventional resin and thermoplastic resins.14,15 Nonetheless, the impact of denture cleansers on computer-aided design/computer-aided manufacturing (CAD-CAM) denture base resins remains a topic that has not received substantial research attention.

Also, how the Ra produced on the resin surface due to the action of regular usage of denture cleansing solution affects the colonization of C. albicans is a slightly less explored area. So, the purpose of this research was to evaluate and compare the Ra and adhesion of C. albicans on heat-cured, injection-molded thermoplastic and CAD-CAM resin as affected by denture cleanser solution. The null hypothesis was that there would be no discernible difference in Ra due to denture cleanser utilization and the adherence of Candida among the three types of denture base resin.

MATERIALS AND METHODS

The current research was carried out at the Department of Prosthodontics, Faculty of Dental Sciences, Shree Guru Gobind Singh Tricentenary University in Gurugram. Additionally, it involved collaboration with Narang Metallurgical and Spectro Services located in Jhandewalan Extension, New Delhi. The study received ethical clearance from the institutional ethics committee, with the reference number (SGTU/FDS/MDS/24/1/547). A total of 240 uniform-sized denture-based resin disks were fabricated. These disks were made using heat-cured, injection-molded thermoplastic material and CAD-CAM resin.

Fabrication of Metal Die

A metal die with a rectangular shape was manufactured to produce denture-based resin disks that maintained uniform measurements (2 cm x 2 mm). The inside diameter was set at 2 cm, while the height of the stainless-steel insert was 2 mm shorter than the ring’s height in accordance with the specimen standards outlined by the International Organization for Standardization (Fig. 1).16

Fig. 1: Metal die for fabrication of 2 cm x 2 mm specimens

Fabrication of Resin Samples

A thin coating of petroleum jelly was applied to the metal mold’s surface. Subsequently, molten modeling wax (Pyrax, Mumbai, India) was poured into the metal mold’s aperture. The upper component, after coating with petroleum jelly, was promptly positioned onto the metal mold. Once the wax had fully hardened, the resulting wax sample was retrieved from the mold. A total of 160 wax samples were made using the same method. These wax specimens were subsequently processed into two types of samples—heat-cured acrylic resin samples (n = 80) and flexible resin samples (n = 80) (Fig. 2).

Fig. 2: Sample disks of conventional heat-cured, flexible, and CAD-CAM resin

The wax samples were invested in the flask according to the manufacturer’s recommendations for water–powder ratio, mixing time, and setting time. Flasks were kept for dewaxing in boiling water for 5 minutes, 1 hour after investing. Except for the mold cavity, every surface of the stone was coated with a thin layer of alginate separating media. The heat-cured denture-based resin (Travelon heat-cure, Dentsply, Mumbai, India), polymer, and monomer were combined in a 3:1 volume ratio and mixed within a porcelain jar. Upon reaching a dough-like consistency, the mixture was carefully packed into the mold. The flasks containing the mixture were then secured, and a force of 20 kN was applied for a duration of 30 minutes to ensure proper closure. To prepare for curing, the flasks were immersed in water in an acrylizer at room temperature for 7 hours. Following this, the curing process involved subjecting the flasks to temperatures of 700°C for 7 hours, followed by 100°C for an additional 30 minutes. These temperature levels were selected to achieve comprehensive polymerization. The resulting cured samples underwent finishing and polishing procedures, resulting in the creation of 80 test specimens.17

The preparation of thermoplastic resin samples utilized the injection molding technique, requiring a custom-designed flask. This flask was composed of two nearly identical components. Within one section of the flask, wax models were positioned, and dental stone was employed as the investing material, effectively filling that portion. Wax sprues were added to create an inlet for the resin mixture. The other section of the flask was then brought into proximity and also filled with dental stones. Once the stone had solidified, the process of dewaxing was executed, followed by cleansing the flask with a mild detergent solution to eliminate any residual wax.

The thermoplastic resin used was the Lucitone flexible resin system (Dentsply Sirona Inc, Mumbai, India) in cartridge format. The flask was assembled, and both the flask and the cartridge containing molten nylon were introduced into the injection unit. Sustaining a constant pressure of five bars, the injection molding was sustained for 1 minute before the assembly was withdrawn and disengaged. Prior to the process of deflasking, the flask was allowed to cool for a period of 5 minutes.17 The samples were retrieved and subjected to finishing and polishing processes. This methodology was consistently applied to prepare a total of 80 test specimens.

Preparation of CAD-CAM Denture-based Resin Samples

A total of 80 disks, each measuring 10 × 2 mm, were meticulously designed utilizing Exocad software (Exocad GmbH, Darmstadt, Germany). The designed stereolithography file was subsequently transmitted to an integrated milling machine (PM3, Ivoclar Vivadent, Schaan, Liechtenstein), which facilitated the creation of these 80 disks from a PMMA block (Ruthinium disk; Dental Manufacturing S.p.A., Beijing, China). Subtle modifications were applied by detaching the samples from their supporting struts. To refine the surface, waterproof paper was employed, followed by polishing of samples using pumice. Upon completion of the polishing process, the disks underwent cleansing with water and soap, a procedure carried out using a standard toothbrush. This was followed by a treatment involving a steam jet for thorough cleaning and preparation.12

Grouping of Samples

The collected samples were categorized into two groups, outlined as follows:

  • Group 1 (control group; n = 120) divided into three subgroups—heat-cured acrylic resin (1A; n = 40), injection-molded thermoplastic resin (1B; n = 40), and CAD-CAM denture-based resin (1C; n = 40) with samples immersed in artificial saliva (Wet Mouth, ICPA, Mumbai, India). Groups 1A, 1B, and 1C were further subdivided into groups 1Ai, 1Aii, 1Aiii, 1Aiv, group 1Bi, 1Bii, 1Biii, 1Biv, and group 1Ci, 1Cii, 1Ciii, 1Civ based on the duration of immersion, that is, 0, 15, 30, and 45 days, respectively.

  • Group 2 (test group; n = 120) was divided into three subgroups—heat-cured acrylic resin (2A; n = 40), injection molded thermoplastic resin (2B; n = 40), and CAD-CAM denture-based resin (2C; n = 40) with samples immersed in the freshly prepared denture cleanser solution (Clinsodent, ICPA, Mumbai, India). The denture cleanser solution was prepared by dissolving Clinsodent denture cleansing tablet into warm water covering the samples (Fig. 3). Group 2A, 2B, 2C were further subdivided into groups 2Ai, 2Aii, 2Aiii, 2Aiv, 2Bi, 2Bii, 2Biii, 2Biv, and 2Ci, 2Cii, 2Ciii, 2Civ, based on duration of immersion, that is, 0, 15, 30, and 45 days, respectively.

Fig. 3: Immersion of disks in a denture cleanser solution

Evaluation of Ra

The specimens underwent a finishing process, advancing through progressively finer grits involving 150, 360, and 500-grit abrasive papers (Silicon carbide abrasive paper, UGR, China), followed by polishing using slurry pumice. To facilitate orientation and measurement, a minor indentation was created on one side of each heat-cured resin, injection-molded thermoplastic resin, and CAD-CAM denture base material disk. This indentation was achieved using a round bur. The purpose of this depression was to serve as a marker indicating the specific side from which Ra is to be measured. Each individual sample disk was carefully placed within a Petri dish, and a numbering system was implemented to ensure precise sample identification.17

At the baseline, initial Ra measurements (μm) of all the samples were made by using a profilometer (SJ-201; Mitutoyo Surftest Kawasaki, Kanagawa, Japan) after being placed in distilled water for 24 hours, followed by Candida inoculation (Fig. 4) and colony count. The samples of the group (1Aii, 1Bii, 1Cii) were immersed in artificial saliva, and samples of the group (2Aii, 2Bii, 2Cii) were immersed in denture cleanser solution for 15 days for 8 hours daily and assessed for Ra, followed by Candida inoculation. The same methodology was followed for samples that were tested after 30 and 45 days of immersion in artificial saliva and denture cleanser solution, followed by Candida inoculation. The alterations in Ra and the colony count of Candida were assessed before and after exposure to artificial saliva and denture cleanser solutions for durations of 15, 30, and 45 days. Subsequently, these changes were compared for analysis (Fig. 5).

Figs 4A to C: Candida colonies seen under a microscope (A) heat-cured denture base resin; (B) flexible denture base resin; (C) CAD-CAM denture base resin

Fig. 5: Profilometer used for measuring surface roughness

To assess the surface characteristics, a profilometer was employed both prior to and following the immersion procedures. A diamond stylus featuring a tip radius of 5 μm was systematically traversed across the surface, maintaining a consistent load of 0.75 μN. The measurement encompassed a range of 350 μm and was executed at a speed of 0.5 mm/second. This process aimed to determine the roughness profile value, measured in micrometers.16

All samples underwent three tracing cycles at three distinct points. This resulted in a total of nine readings per sample. The mean Ra measurement, derived from the average of these nine readings, was regarded as the representative value for each specimen. In order to quantify changes, the initial Ra values were subtracted from those observed postimmersion. These resulting Ra values were then tabulated, allowing for the computation of descriptive statistics. In order to establish a surface characterization, a single representative specimen was selected from each group. These specimens were chosen based on their Ra values closely aligning with the group’s mean values. The method’s primary advantage lies in its straightforward execution, accuracy, and ease with which mean Ra values for the acrylic specimens can be determined.

Culture of C. albicans and Inoculation on the Samples

Candida isolates were cultivated on Sabouraud dextrose agar (SDA) at a temperature of 37°C for a duration of 24 hours. For the preparation of yeast suspensions, the cells were introduced into Sabouraud dextrose broth (SDB) and subsequently incubated for 18 hours at 37°C while undergoing agitation at 150 rpm. This process was aimed at achieving optimal cell density. The cell concentration was adjusted to 1 × 105 cells/mL within the SDB medium.

To initiate the adherence experiment, dental material disks were positioned within a 24-well tissue culture plate. Following this, 2 mL of MacFarland solution containing the yeast cell suspension was added to each well. The plates were then subjected to incubation at a temperature of 37°C with gentle shaking at 75 rpm for a duration of 90 minutes. Upon completing the incubation, the disks were carefully relocated to new wells and subjected to a triple wash with phosphate-buffered saline. This process was carried out to eliminate any cells that had not adhered. Following these procedures, microscopic examination of colony-forming units (CFUs) was conducted after an additional 24-hour incubation period at 37°C. The number of cells that had adhered was quantified and expressed as CFU/mL. For each of the three types of disks (a total of 240 disks), the procedure involving Candida application and subsequent adhesion was repeated as described above.13

Statistical Analysis

The data analysis involved the assessment of the Ra (roughness) of heat-cured resin, injection-molded thermoplastic resin, and CAD-CAM denture-base material. For this purpose, the data was collected and recorded. The software tools employed for the analysis were Statistical Package for the Social Sciences (SPSS) [International Business Machines (IBM) Corp. Released 2016. IBM SPSS Statistics for Windows, Version 24.0. Armonk, New York: IBM Corp.)] and Epi Info version 3.0 [Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, the United States of America]. To compare the quantitative data, statistical methods were utilized. Repeated measures analysis of variance (ANOVA) was applied when appropriate, along with one-way ANOVA. Furthermore, post hoc analysis using Tukey’s test was performed as needed to derive meaningful insights from the collected data. These analytical techniques facilitated a comprehensive understanding of the observed variations and relationships within the data.

RESULTS

The Ra of conventionally cured samples immersed in artificial saliva at baseline, 15, 30, and 45 days were 0.87 ± 0.01, 0.85 ± 0.02, 0.84 ± 0.02, and 0.83 ± 0.02 μm, respectively (p-value 0.087) (Table 1). Ra for injection-molded thermoplastic resin samples were 1.03 ± 0.01, 1.03 ± 0.04, 1.02 ± 0.03, and 1.00 ± 0.05 μm, respectively (p-value 0.055) (Table 2). Ra for CAD-CAM resin samples were 0.42 ± 0.01, 0.41 ± 0.02, 0.40 ± 0.03, and 0.40 ± 0.03 μm, respectively (p-value 0.55) (Table 3).

Table 1: Repeated measures of ANOVA for evaluation of the surface roughness (µm) of conventional heat-cured denture acrylic resin samples immersed in artificial saliva at different time intervals
Group N Mean Standard deviation (SD) 95% confidence interval (CI): lower 95% CI: upper F-value p-value
1Ai (0 days) 10 0.86 0.01 0.855 0.867 11.692 0.087
1Aii (15 days) 10 0.85 0.02 0.841 0.865
1Aiii (30 days) 10 0.84 0.02 0.823 0.857
1Aiv (45 days) 10 0.83 0.02 0.821 0.855
Table 2: Repeated measures of ANOVA for evaluation of the surface roughness (µm) of thermoplastic resin denture acrylic resin samples when immersed in artificial saliva at different time intervals
Group N Mean SD 95% CI: lower 95% CI: upper F-value p-value
1Bi 10 1.03 0.01 1.025 1.039 10462.77 0.055
1Bii 10 1.03 0.04 1.000 1.060
1Biii 10 1.02 0.03 1.003 1.053
1Biv 10 1.00 0.05 0.967 1.043
Table 3: Repeated measures of ANOVA for evaluation of the surface roughness (µm) of CAD-CAM denture-based resin samples immersed in artificial saliva at different time intervals
Group N Mean SD 95% CI: lower 95% CI: upper F-value p-value
1Ci 10 0.42 0.01 0.409 0.431 280.159 0.556
1Cii 10 0.41 0.02 0.402 0.434
1Ciii 10 0.40 0.03 0.378 0.430
1Civ 10 0.40 0.03 0.383 0.429

The Ra of conventionally cured samples in denture cleanser solution at baseline, 15, 30, and 45 days were 1.12 ± 0.011, 1.21 ± 0.008, 1.25 ± 0.011, and 1.56 ± 0.008 μm, respectively (p = 0.001) (Table 4). Ra for injection-molded thermoplastic resin samples was 1.31 ± 0.010, 1.45 ± 0.008, 1.76 ± 0.010, and 2.26 ± 0.014 μm, respectively (p = 0.001) (Table 5). Ra of CAD-CAM resin samples were 0.86 ± 0.016, 1.07 ± 0.008, 1.12 ± 0.008, and 1.18 ± 0.015 μm, respectively (p = 0.001) (Table 6).

Table 4: Repeated measures of ANOVA for evaluation of the surface roughness (µm) of conventional heat-cured acrylic resin samples when immersed in denture cleanser solution at different time intervals
Group N Mean SD 95% CI: lower 95% CI: upper F-value p-value
2Ai 10 1.12 0.01 1.118 1.134 317217.190 0.001*
2Aii 10 1.21 0.01 1.205 1.217
2Aiii 10 1.25 0.01 1.248 1.264
2Aiv 10 1.56 0.01 1.563 1.575

*p < 0.05 is statistically significant

Table 5: Repeated measures of ANOVA for evaluation of the surface roughness (µm) of thermoplastic acrylic resin samples immersed in denture cleanser solution at different time intervals
Group N Mean SD 95% CI: lower 95% CI: upper F-value p-value
2Bi 10 1.31 0.01 1.311 1.325 324584.607 0.001*
2Bii 10 1.45 0.001 1.445 1.457
2Biii 10 1.76 0.01 1.761 1.775
2iv 10 2.26 0.01 2.249 2.271

*p < 0.05 is statistically significant

Table 6: Repeated measures of ANOVA for evaluation of the surface roughness (µm) of CAD-CAM denture-based resin samples immersed in denture cleanser solution at different time intervals
Group N Mean SD 95% CI: lower 95% CI: upper F-value p-value
2Ci 10 0.86 0.01 0.856 0.880 246744.994 0.001*
2Cii 10 1.07 0.01 1.073 1.085
2Ciii 10 1.12 0.01 1.123 1.135
2Civ 10 1.18 0.01 1.170 1.192

*p < 0.05 is statistically significant

The mean growth of C. albicans on the conventional heat-cured denture acrylic resin samples when immersed in artificial saliva at different time intervals were 0.30 ± 0.04, 0.27 ± 0.04, 0.31 ± 0.05, 0.27 ± 0.06 (CFU × 105) mL at 0, 15, 30, 45 days, respectively, and result showed statistically nonsignificant results (p > 0.05). The mean growth of C. albicans on the flexible denture base resin samples when immersed in artificial saliva at different time intervals were 0.32 ± 0.05, 0.28 ± 0.04, 0.35 ± 0.07, 0.33 ± 0.06 (CFU × 105) mL at 0, 15, 30, 45 days, respectively, and result showed statistically nonsignificant results (p > 0.05). The mean growth of C. albicans on the CAD-CAM denture base resin samples when immersed in artificial saliva at different time intervals were 0.21 ± 0.04, 0.21 ± 0.02, 0.21 ± 0.04, 0.22 ± 0.04 (CFU × 105) mL at 0, 15, 30, 45 days, respectively, and result showed statistically nonsignificant results (p > 0.05) (Tables 7 to 9). However, when the samples were dipped in the denture cleanser solution, the adherence of Candida increased with increasing time intervals from baseline to 45 days. The values in heat-cured samples were 0.86 ± 0.15, 1.29 ± 0.10, 1.44 ± 0.12, 2.40 ± 0.09 (CFU × 105) mL (p < 0.05), for flexible denture base resin the values were 0.86 ± 0.15, 1.63 ± 0.19, 1.68 ± 0.17, 2.75 ± 0.11 (CFU × 105) mL, and for CAD-CAM denture base resin were 0.36 ± 0.12, 0.47 ± 0.04, 0.65 ± 0.07, 0.95 ± 0.05 (CFU × 10) mL (Tables 10 to 12).

Table 7: Repeated measures of ANOVA for evaluation of the C. albicans growth (CFU × 105) mL of conventional heat-cured acrylic resin samples immersed in artificial saliva at different time intervals
Group N Mean SD 95% CI: lower 95% CI: upper F-value p-value
1Ai 10 0.30 0.04 0.278 0.336 1018.56 0.054
1Aii 10 0.27 0.04 0.248 0.310
1Aiii 10 0.31 0.05 0.281 0.353
1Aiv 10 0.27 0.06 0.235 0.321
Table 8: Repeated measures of ANOVA for evaluation of the C. albicans growth (CFU × 105) mL thermoplastic resin samples immersed in artificial saliva at different time intervals
Group N Mean SD 95% CI: lower 95% CI: upper F-value p-value
1Bi 10 0.32 0.05 0.276 0.354 744.965 0.055
1Bii 10 0.28 0.04 0.250 0.314
1Biii 10 0.35 0.07 0.300 0.396
1Biv 10 0.33 0.06 0.292 0.372
Table 9: Repeated measures of ANOVA for evaluation of the C. albicans growth (CFU × 105) mL CAD-CAM denture-based resin samples immersed in artificial saliva at different time intervals
Group N Mean SD 95% CI: lower 95% CI: upper F-value p-value
1Ci 10 0.21 0.04 0.181 0.247 1555.655 0.072
1Cii 10 0.21 0.02 0.196 0.234
1Ciii 10 0.21 0.04 0.187 0.247
1Civ 10 0.22 0.04 0.192 0.262
Table 10: Repeated measures of ANOVA for evaluation of the C. albicans growth (CFU × 105) mL conventional heat-cured acrylic resin samples immersed in denture cleanser solution at different time intervals
Group N Mean SD 95% CI: lower 95% CI: upper F-value p-value
2Ai 10 0.86 0.15 0.755 0.971 5741.809 0.001*
2Aii 10 1.29 0.10 1.217 1.373
2Aiii 10 1.44 0.12 1.355 1.527
2Aiv 10 2.40 0.09 2.338 2.468

*p < 0.05 is statistically significant

Table 11: Repeated measures of ANOVA for evaluation of the C. albicans growth (CFU × 105) mL thermoplastic resin samples immersed in denture cleanser solution at different time intervals
Group N Mean SD 95% CI: lower 95% CI: upper F-value p-value
2Bi 10 0.86 0.15 0.759 0.967 5404.202 0.0001*
2Bii 10 1.63 0.19 1.495 1.763
2Biii 10 1.68 0.17 1.553 1.797
2iv 10 2.75 0.11 2.673 2.835

*p < 0.05 is statistically significant

Table 12: Repeated measures of ANOVA for evaluation of the C. albicans growth (CFU × 105) mL CAD-CAM denture-based resin samples immersed in denture cleanser solution at different time intervals
Group N Mean SD 95% CI: lower 95% CI: upper F-value p-value
2Ci 10 0.36 0.12 0.266 0.452 2963.199 0.0001*
2Cii 10 0.47 0.04 0.436 0.497
2Ciii 10 0.65 0.07 0.592 0.701
2Civ 10 0.95 0.05 0.914 0.995

*p < 0.05 is statistically significant

On comparing the three groups when immersed in denture cleansing solution on the basis of Ra and candida adherence using one-way ANOVA and post hoc test, it was found that flexible denture base resin samples depicted maximum Ra and candida adherence followed by heat-cured denture base resin and CAD-CAM resin samples (Tables 13 and 14).

Table 13: One-way ANOVA and post hoc test for the evaluation of surface roughness of different denture-based resin samples at various follow-up periods when immersed in a denture cleanser solution
Denture cleanser Heat-cured denture-based resin (μm) Injection-molded thermoplastic denture-based resin (μm) CAD-CAM denture-based resin (μm) F-value p-value Post hoc
Group 2 Group 2A Group 2B Group 2C
Mean SD Mean SD Mean SD
i at 0 days 1.12 0.01 1.31 0.01 0.86 0.01 3019.126 0.001* 2C < 2A < 2B
ii at 15 days 1.21 0.00 1.45 0.01 1.07 0.01 4639.304 0.001* 2C < 2 A < 2B
iii at 30 days 1.25 0.01 1.76 0.01 1.12 0.01 1069.910 0.001* 2C < 2 A < 2B
iv at 45 days 1.56 0.01 2.26 0.01 1.18 0.01 16872.797 0.001* 2C < 2 A < 2B

*p < 0.05 is statistically significant

Table 14: One-way ANOVA and post hoc test for the evaluation of the C. albicans growth in different denture-based resin samples at various follow-up periods when immersed in a denture cleanser solution
Denture cleanser Heat-cured denture-based resin (CFU/mL) Injection-molded thermoplastic denture-based resin (CFU/mL) CAD-CAM denture-based resin (CFU/mL) F-value p-value Post hoc
Group 2 Group 2A Group 2B Group 2C
Mean SD Mean SD Mean SD
i at 0 days 0.86 0.15 0.86 0.15 0.36 0.12 45.659 0.001* 2A, 2B > 2C
ii at 15 days 1.29 0.10 1.63 0.19 0.47 0.04 199.181 0.001* 2B > 2A > 2C
iii at 30 days 1.44 0.12 1.68 0.17 0.65 0.07 181.395 0.001* 2B > 2A > 2C
iv at 45 days 2.40 0.09 2.75 0.11 0.95 0.05 1137.369 0.001* 2B > 2A > 2C

*p < 0.05 is statistically significant

DISCUSSION

Dentures are prosthetic substitutes that facilitate the reproduction of the natural well-being of elderly patients and replace the usual function of dentition. Many researchers3,5,9,15 in the past have encouraged the concept that the Ra of dental materials plays a crucial role in the accumulation of microorganisms and staining. Preferably, to thwart the local infection and preliminary decomposition, the surface should have minimal irregularities recommended for the retention of microorganisms.

Bollen et al.15 stated that the minimum roughness for retention of dental plaque on dental materials is 0.2 μm. Lower than this value, no additional reduction in the accumulation of dental plaque will be anticipated. Higher than this value, a proportional rise in the accumulation of dental plaque might occur. In the present in vitro study, the Ra evidenced by all three groups while immersed in denture cleanser solution represented a value above 0.2 μm, yet it was lesser than the results documented by Zissis et al. (0.7–4.4 μm).18 The null hypothesis was rejected as CAD-CAM denture base resins were least affected by the action of denture cleanser and had less adherence to C. albicans when compared to heat-cured and thermoplastic resins.

Artificial saliva did not considerably increase the Ra values among the three different resin materials at varied time intervals. Also, the growth of Candida in all the samples in the control group remained unaffected even after an interval of 45 days.

The Ra values of conventionally heat-cured samples’ surface were 1.12 ± 0.011, 1.21 ± 0.008, 1.25 ± 0.011, and 1.56 ± 0.008 μm at 0, 15, 30, and 45 days, respectively, when immersed in denture cleansing solution, that is, Clinsodent, which consists of a peroxide-based cleansing solution. The Ra increased as the time interval increased from baseline to 45 days. As the Ra increased, the adherence of Candida to the conventional heat-cured samples also increased significantly. The outcomes observed in this study could potentially be linked to the duration of use, implying that alkaline peroxides might have been ineffective in eliminating the debris film present on the acrylic resins. This failure to remove the debris film could potentially contribute to an increase in the Ra value. These dissimilarities in results underscore the importance of not only considering the time and immersion intervals but also factoring in the specific type of cleanser utilized. This indicates that the effectiveness of the cleaning process might be influenced by the nature of the cleansing agent itself. These findings align with the research outcomes documented by Peracini et al.19 and Rodrigues Garcia et al.20 According to them, throughout the bracing interval of 180 days, alkaline peroxides raised the Ra of heat-cured resins.

The measurement of Ra of injection-molded thermoplastic denture-based resin samples was 1.31 ± 0.010, 1.45 ± 0.008, 1.76 ± 0.010, and 2.26 ± 0.014 μm at 0, 15, 30, and 45 days, respectively. There was an increase in Ra in polymeric amide resins as the time interval increased from baseline to 45 days. There was a statistically significant difference observed in Ra of the thermoplastic denture base resin samples. These results are consistent with the research conducted by Polychronakis et al.21 and Durkan et al.22 The researchers noted that the Ra of polymeric amide resin experienced an increase as a result of the effects of sodium perborate over a period of 30 days of exposure.

When the samples of three groups were compared after immersion in denture cleanser (Clinsodent) at baseline and an interval of 15, 30, and 45 days, the Ra and adherence of Candida was greatest in thermoplastic resin samples followed by heat-cured and CAD-CAM resin samples and the difference was statistically significant. One potential explanation for this could be attributed to the challenging nature of finishing and glazing thermoplastic denture base resins, stemming from their comparatively low melting temperature. As a result, these resins often present a textured surface. Abuzar et al.23 investigated the Ra of a thermoplastic denture base resin material (Flexiplast) in comparison with conventional heat-cured denture base resin (Vertex RS) and reported that thermoplastic resin samples had a rougher surface than conventional heat-cured resin, both before and after the polishing process. Furthermore, the pace at which processed polymeric amides cool down significantly affects their surface characteristics. It has been suggested that exceedingly slow cooling results in the formation of a relatively rigid material. However, this deliberate slow cooling process also tends to yield a surface that is rough in texture. Peracini et al.19 investigated that polymeric amide denture-based resins have fibrous and semi-flexible structures and also have low surface hardness when immersed in an alkaline peroxide solution for 6 days, which led to an increase in Ra of these denture-based resins. This finding is consistent with the results of the present study.

The CAD-CAM resin has the least amount of porosities as they are manufactured from homogenous blocks, resulting in decreased Ra and the least microbial adherence. A study conducted by Giti et al.24 arrived at the conclusion that conventionally cured PMMA displayed notably elevated Ra values compared to the digitally fabricated groups. This outcome was consistent with the findings reported by several other researchers, who also noted similar trends.22,25,26

Nassary Zadeh et al.27 noted that conventionallycured PMMA resins exhibited higher Ra values compared to modified methyl methacrylate resins and CAD-CAM PMMA blocks. They specifically observed the lowest Ra values in CAD-CAM PMMA blocks. This trend might be attributed to the formation of porosities, which are introduced through the manual mixture of liquid and powder during the mold packing process in the conventional group. These porosities, potentially created during hand mixing, could contribute to the higher Ra values seen in conventionallycured PMMA resins as opposed to the smoother surfaces found in modified methyl methacrylate resins and CAD-CAM PMMA blocks. A similar trend was visible in the adherence of Candida to the denture base resins; the least adherence was seen in CAD-CAM resin, followed by PMMA and thermoplastic denture base resins.

In a conducted study,28 the impact of denture cleansers on Candida biofilm development was investigated, specifically focusing on a polyamide resin (Flexite MP) and a PMMA resin (Acron MC). The findings of the study revealed that Candida biofilms displayed notably higher growth on polyamide surfaces in comparison to PMMA surfaces. This observation suggested that polyamide might provide a conducive environment for microbial colonization. The disparities in biofilm growth were attributed to the elevated presence of residual monomers within PMMA. These residual monomers led to variations in the surface charge of the resin, which subsequently influenced adhesion, ultimately inhibiting Candida growth.

A similar trend of low bacterial colonization was reported in the CAD-CAM group, as noted in a different study that compared bacterial colonization between CAD-CAM PMMA blocks and conventionally cured provisional materials. This shared observation suggests that CAD-CAM PMMA blocks exhibit a reduced tendency for bacterial attachment and growth in comparison to conventionally cured provisional materials.29

According to the present study’s findings, CAD-CAM resin samples were the least affected by denture cleansers with the least Ra and bacterial adherence. Future research is necessary, particularly on the three-dimensional printing of denture base resins, to confirm the long-term clinical performance of these materials. To fully comprehend the clinical performance of milled PMMA, a long-term assessment is also required. Thermocycling should be used in testing to see the effects of aging on examined parameters in future studies, and it was the limitation of the current study.

CONCLUSION

Within the limitations of the present in vitro study, it was concluded that all the denture base resins were affected by the usage of denture cleansers. CAD-CAM denture base resins were least affected by the use of denture cleanser and had the least Ra when compared with heat-cured and flexible denture base resins. Flexible denture base resin depicted the maximum Ra. Adherence of Candida was maximum on flexible denture base resin followed by heat cure and CAD-CAM resin.

REFERENCES

1. Suma K, Leoney A, Ali SA. Denture disinfectants used in prosthodontics - a review. Int J Contemp Med Res 2018;5(3):15–18.

2. Baba NZ. Materials and processes for CAD/CAM complete denture fabrication. Curr Oral Health Rep 2016;3:203–206. DOI: 10.1007/s40496-016-0101-3

3. Jain V, Babu J, Ahuja S, et al. Comparison of fungal biofilm formation on three contemporary denture base materials. Int J Experiment Dent Sci 2015;4(2):104–108. DOI: 10.5005/jp-journals-10029-1106

4. Shinawi LA. The effect of various denture cleansers on the colour stability of different denture base resins. Int J Pharm Res Allied Sci 2017;6(2):238–246.

5. de Freitas Fernandes FS, Pereira-Cenci T, da Silva WJ, et al. Efficacy of denture cleansers on Candida spp. biofilm formed on polyamide and polymethyl methacrylate resins. J Prosthet Dent 2011;105(1):51–58. DOI: 10.1016/S0022-3913(10)60192-8

6. M S, C S, George R, et al. Evolution of denture base materials from past to new era. IOSR J Dent Med Sci 2018;17(11):23–27.

7. Perea-Lowery L, Minja IK, Lassila L, et al. Assessment of CAD-CAM polymers for digitally fabricated complete dentures. J Prosthet Dent 2021;125(1):175–181. DOI: 10.1016/j.prosdent.2019.12.008

8. Janeva N, Kovacevska G, Janev E. Complete dentures fabricated with CAD/CAM technology and a traditional clinical recording method. Open Access Maced J Med Sci 2017;5(6):785–789. DOI: 10.3889/oamjms.2017.169

9. Barbeau J, Séguin J, Goulet JP, et al. Reassessing the presence of Candida albicans in denture-related stomatitis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2003;95(1):51–59. DOI: 10.1067/moe.2003.44

10. Prpić V, Schauperl Z, Ćatić A, et al. Comparison of mechanical properties of 3D-printed, CAD/CAM, and conventional denture base materials. J Prosthodont 2020;29(6):524–528. DOI: 10.1111/jopr.13175

11. Pires FR, Santos EB, Bonan PR, et al. Denture stomatitis and salivary Candida in Brazilian edentulous patients. J Oral Rehabil 2002;29(11):1115–1119. DOI: 10.1046/j.1365-2842.2002.00947.x

12. Batisse C, Nicolas E. Comparison of CAD/CAM and conventional denture base resins: a systematic review. Appl Sci 2021;11(13):5990. DOI: 10.3390/app11135990

13. Vojdani M, Giti R. Polyamide as a denture base material: a literature review. J Dent (Shiraz) 2015;16(1 Suppl):1–9. PMID: 26106628.

14. Fiore AD, Meneghello R, Brun P, et al. Comparison of the flexural and surface properties of milled, 3D-printed, and heat polymerized PMMA resins for denture bases: an in vitro study. J Prosthodont Res 2021;66(3):502–508. DOI: 10.2186/jpr.JPR_D_21_00116

15. Bollen CM, Lambrechts P, Quirynen M. Comparison of surface roughness of oral hard materials to the threshold surface roughness for bacterial plaque retention: a review of the literature. Dent Mater 1997;13(4):258–269. DOI: 10.1016/s0109-5641(97)80038-3

16. Sujitha K, Bharathi M, Lakshminarayana S, et al. Physical properties of heat cure denture base resin after incorporation of methacrylic acid. Contemp Clin Dent 2018;9(Suppl 2):S251–S255. DOI: 10.4103/ccd.ccd_172_18

17. Tripathi P, Phukela S S, Yadav B, et al. An in vitro study to evaluate and compare the surface roughness in heat-cured denture-based resin and injection-molded resin system as affected by two commercially available denture cleansers. J Indian Prosthodont Soc 2018;18(4)291–298. DOI: 10.4103/jips.jips_335_17

18. Zissis AJ, Polyzois GL, Yannikakis SA. Roughness of denture materials: a comparative study. Int J Prosthodont 2000;13(2):136–140. PMID: 11203622.

19. Peracini A, Davi LR, de Queiroz Ribeiro N, et al. Effect of denture cleansers on physical properties of heat-polymerized acrylic resin. J Prosthodont Res 2010;54(2):78–83. DOI: 10.1016/j.jpor.2009.11.004

20. Rodrigues Garcia RC, Joane Augusto de S Jr, Rached RN, et al. Effect of denture cleansers on the surface roughness and hardness of a microwave-cured acrylic resin and dental alloys. J Prosthodont 2004;13(3):173–178. DOI: 10.1111/j.1532-849X.2004.04028.x

21. Polychronakis NC, Polyzois GL, Lagouvardos PE, et al. Effects of cleansing methods on 3-D surface roughness, gloss and color of a polyamide denture base material. Acta Odontol Scand 2015;73(5):353–363. DOI: 10.3109/00016357.2014.967720

22. Durkan R, Ayaz EA, Bagis B, et al. Comparative effects of denture cleansers on physical properties of polyamide and polymethyl methacrylate base polymers. Dent Mater J 2013;32(3):367–375. DOI: 10.4012/dmj.2012-110

23. Abuzar MA, Bellur S, Duong N, et al. Evaluating surface roughness of a polyamide denture base material in comparison with poly (methyl methacrylate). J Oral Sci 2010;52(4):577–581. DOI: 10.2334/josnusd.52.577

24. Giti R, Dabiri S, Motamedifar M, et al. Surface roughness, plaque accumulation, and cytotoxicity of provisional restorative materials fabricated by different methods. PLoS One 2021;16(4):e0249551. DOI: 10.1371/journal.pone.0249551

25. Vojdani M, Bagheri R, Khaledi AAR. Effects of aluminum oxide addition on the flexural strength, surface hardness, and roughness of heat-polymerized acrylic resin. J Dent Sci 2012;7(3):238–244. DOI: 10.1016/j.jds.2012.05.008

26. Koroğlu A, Sahin O, Dede DO, et al. Effect of different surface treatment methods on the surface roughness and color stability of interim prosthodontic materials. J Prosthet Dent 2016;115(4):447–455. DOI: 10.1016/j.prosdent.2015.10.005

27. Nassary Zadeh P, Lümkemann N, Eichberger M, et al. Differences in radiopacity, surface properties, and plaque accumulation for CAD/CAM-fabricated vs conventionally processed polymer-based temporary materials. Oper Dent 2019;45(4):407–415. DOI: 10.2341/19-057-L

28. Kurt A, Erkose-Genc G, Uzun M, et al. The effect of cleaning solutions on a denture base material: elimination of Candida albicans and alteration of physical properties. J Prosthodont 2018;27(6):577–583. DOI: 10.1111/jopr.12539

29. Gantait S, Bhattacharyya J, Das S, et al. Comparative assessment of the effectiveness of different cleaning methods on the growth of Candida albicans over acrylic surface. Contemp Clin Dent 2016;7(3):336–342. DOI: 10.4103/0976-237X.188554

________________________
© The Author(s). 2023 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted use, distribution, and non-commercial reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.