|Year : 2018 | Volume
| Issue : 4 | Page : 54-57
Effects of disinfection procedures on surface roughness of hard chairside relining and denture base acrylic resins: An in vitro study
Chandrasinh Rajput1, Keval Shah2, Hiren Rana1, Bhagyashree Dave1, Yashpreet S Bhatia1, Rutu Shah1
1 Department of Prosthodontics and Crown and Bridge, College of Dental Sciences and Research Center, Ahmedabad, Gujarat, India
2 Department of Prosthodontics and Crown and Bridge, Pacific Dental College, Udaipur, Rajasthan, India
|Date of Web Publication||14-May-2019|
Dr. Chandrasinh Rajput
A/13 Manharnagar-1, Opposite Krishna Vidhyalay, Bapunagar, Ahmedabad-24, Gujarat.
Source of Support: None, Conflict of Interest: None
Objective: There is a concern that disinfection procedures may adversely affect the surface roughness of relining and acrylic denture base resins. Hence, this in vitro study was conducted to evaluate the effect of chemical and microwave disinfection on surface roughness of commonly used hard chairside relining (Ufi Gel hard and Kooliner) and acrylic denture base resins (Lucitone 199). Materials and Methods: Powder (polymer) and liquid (monomer) were mixed according to manufacturer’s instructions to prepare 20 specimens from each material. Specimens were divided into two control and two test groups. Surface roughness measurements (Ra, μm) were made after polymerization and water immersion (control groups) and after chemical and microwave disinfection (test groups). Measurements of roughness were statistically analyzed. Result: When compared with control groups, the surface roughness of all three types of materials evaluated were significantly increased (P ≤ 0.05) by both chemical disinfection (Ufi Gel hard, from 0.16 to 0.28 μm; Kooliner, from 0.18 to 0.29 μm; and Lucitone 199, from 0.14 to 0.26 μm) and microwave disinfection (Ufi Gel hard, from 0.16 to 0.26 μm; Kooliner, from 0.18 to 0.25 μm; and Lucitone 199, from 0.14 to 0.23 μm). For all three types of materials, specimens disinfected in microwave (Ufi Gel hard, 0.26 μm; Kooliner, 0.25 μm; and Lucitone 199, 0.23 μm) showed lower mean surface roughness values than those that were chemically disinfected (Ufi Gel hard, 0.28 μm; Kooliner, 0.29 μm; and Lucitone 199, 0.26 μm) but the difference was significant only for Kooliner (P = 0.015). Conclusion: The result of this in vitro study favored the use of microwave disinfection method as it had less adverse effect on surface roughness of materials compared to that of chemical disinfection.
Keywords: Denture base acrylic resin, disinfection, hard chairside reliner, residual monomer, surface roughness
|How to cite this article:|
Rajput C, Shah K, Rana H, Dave B, Bhatia YS, Shah R. Effects of disinfection procedures on surface roughness of hard chairside relining and denture base acrylic resins: An in vitro study. Int J Oral Care Res 2018;6:54-7
|How to cite this URL:|
Rajput C, Shah K, Rana H, Dave B, Bhatia YS, Shah R. Effects of disinfection procedures on surface roughness of hard chairside relining and denture base acrylic resins: An in vitro study. Int J Oral Care Res [serial online] 2018 [cited 2019 May 21];6:54-7. Available from: http://www.ijocr.org/text.asp?2018/6/4/54/253707
| Introduction|| |
Dental prostheses used by patients are exposed to normal oral microbial flora that includes bacteria, viruses, and fungi. Dental personnel adjusting or repairing these prostheses may therefore be at risk of contracting infections from prosthesis that has not been properly disinfected. Surface irregularities increase the likelihood of microorganisms remaining on the denture surface after the prosthesis has been cleaned. It has been observed that some disinfectant procedures may have an adverse effect on the roughness of acrylic resins.,, To prevent cross contamination, infection control procedures, such as chemical disinfection or microwave irradiation, are performed. Therefore, this study was conducted to investigate the effect of chemical disinfection and microwave irradiation on the surface roughness of two hard chairside reline resins and one heat-polymerizing denture base acrylic resin.
| Materials and Methods|| |
The materials used in this study along with their type, manufacturer, and batch number are presented in [Table 1]. Lucitone 199 was selected to represent the conventional polymethyl methacrylate heat-polymerizing acrylic resins, which are commonly used for the fabrication of denture bases.
Test specimens were produced in molds prepared by the investment of wax patterns in dental plaster within the flask. Sixty square patterns of 12×12×3mm dimensions were made of a modeling wax. Materials were mixed, packed, and polymerized according to manufacturer’s instructions.
After polymerization, the specimens were visually inspected for a smooth surface without voids or porosity. Immediately after polymerization, any flash was removed by polishing using progressively finer grades (600–1200) of silicon carbide paper (3M, São Paulo, Brazil) to obtain a smooth, flat surface. Square shape (12×12×3mm) of the specimens was chosen to ensure that the roughness measurements were made at the same locations on each specimen surface. Twenty specimens were produced for each material and divided into the following two controls and two experimental groups of five specimens each:
- Control ND: not disinfected
- Control WI: water immersion
- Experimental CD: chemical disinfection
- Experimental MD: microwave disinfection
Control group ND contained five specimens from each material in which surface roughness of hard reline resins was measured after polymerization but without disinfection, whereas for the heat-polymerized denture base acrylic resin, measurements were obtained after the specimens had been conditioned in distilled water at 37oC for 48h. These values were used as controls, as the patients will be wearing the relined denture bases soon after polymerization, without any effect of water sorption and disinfection.
In control group WI, the specimens were stored in 200mL of distilled water in a beaker at 37oC ± 2oC for 48h, and roughness was measured. This minimum volume of water was calculated by measuring the volume that would completely cover a maxillary complete denture in a standard pressure vessel. This time was chosen as being representative of the first recall appointment for adjustments after relining.
The specimens from test group CD were chemically disinfected by immersing in full strength Cidex (2% alkaline glutaraldehyde) for 20min at room temperature, whereas those from test group MD were disinfected by an unmodified domestic microwave oven (Intellowave; LG, Mumbai, India) followed by their placement in 200mL of sterile distilled water in a beaker. This beaker was later introduced on the rotation plate (two-dimensional turntable) in a microwave oven and irradiated at 650 W for 6min. The specimens were disinfected twice for 2 days to simulate the disinfection, which occurs, first when contaminated dentures are taken from the patient, and then again before the dentures are returned to the patient. Between two disinfection cycles, the specimens were stored in distilled water at room temperature.
The surface roughness (Ra, μm) was analyzed with a profilometer (SJ 201; Mitutoyo, Tokyo, Japan) with a diamond stylus (tip radius of 2 μm). A reading was obtained by the needle passing across a 0.8-mm length at 0.5mm/s to the nearest 0.01 μm., This procedure was repeated twice at the same position for a total of three readings. Therefore, three readings, each consisting of three lengths of 0.8mm, were obtained at each position, resulting in a total reading length of 2.4mm. An orientation jig was fabricated to position the stylus of the profilometer instrument to the same location on the specimen for repeated measurements. Surface roughness was measured at four positions, radially across each specimen, and a final Ra average was then calculated for that specimen.
All readings obtained were subjected to statistical analyses using the Statistical Package for the Social Sciences (SPSS), (IBM, Armonk, New York)/PC+ software to finalize the result. One-way analysis of variance (ANOVA) was conducted on the surface roughness data, followed by Tukey’s Honestly Significant Difference test for post hoc comparisons (α = 0.05). All statistical analyses were performed at a confidence level of 95%. In this study, P < 0.05 was considered as the level of significance.
| Results|| |
The results of the ANOVA of roughness data revealed that materials, disinfection methods, and their interactions were significant (P < 0.001).
When compared with control groups ND and WI, the surface roughness of all three types of materials evaluated was significantly increased (P ≤ 0.05) by both chemical disinfection (Ufi Gel hard, from 0.16 to 0.28 μm; Kooliner, from 0.18 to 0.29 μm; and Lucitone 199, from 0.14 to 0.26 μm) and microwave disinfection (Ufi Gel hard, from 0.16 to 0.26 μm; Kooliner, from 0.18 to 0.25 μm; and Lucitone 199, from 0.14 to 0.23 μm) [Table 2] [Figure 1].,
|Figure 1: Comparison of mean roughness values (Ra, µm) for different materials, evaluated after various disinfection methods|
Click here to view
From all three types of materials, specimens from group ND (Ufi Gel hard, 0.16 μm; Kooliner, 0.18 μm; and Lucitone 199, 0.14 μm) showed the lowest roughness values and specimens from group CD (Ufi Gel hard, 0.28 μm; Kooliner, 0.29 μm; and Lucitone 199, 0.26 μm) showed the highest roughness values when compared with other three groups but the differences were not significant for all materials [Table 2] [Figure 2].
|Figure 2: Comparison of mean roughness values (Ra, µm) after disinfection procedures for different materials|
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From all three types of materials, specimens from group MD (Ufi Gel hard, 0.26 μm; Kooliner, 0.25 μm; and Lucitone 199, 0.23 μm) showed lower mean surface roughness values than group CD (Ufi Gel hard, 0.28 μm; Kooliner, 0.29 μm; and Lucitone 199, 0.26 μm) but the difference was significant only for Kooliner (P = 0.015) [Table 2].
Comparison among materials revealed that the mean surface roughness of Lucitone 199 (group ND, 0.14 μm; group WI, 0.19 μm; group CD, 0.26 μm; and group MD, 0.23 μm) was lower than that of Ufi Gel hard (group ND, 0.16 μm; group WI, 0.20 μm; group CD, 0.28 μm; and group MD, 0.26 μm) and Kooliner (group ND, 0.18 μm; group WI, 0.20 μm; group CD, 0.29 μm; and group MD, 0.25 μm) in all groups but the differences were significant only in group ND (P < 0.05), and differences between the surface roughness of Ufi Gel hard and Kooliner were not significant except for group ND (Ufi Gel hard, 0.16 μm and Kooliner, 0.18 μm) where the difference was significant (P = 0.007) [Table 2].
| Discussion|| |
Surface roughness is an important characteristic of dental materials, and therefore, a direct correlation is present between the values of roughness and bacterial adherence. According to Allison and Douglas, smoother surfaces retain a smaller quantity of biofilm, thus avoiding the proliferation of microorganisms on the acrylic surface of dentures. Moreover, according to Yannikakis et al., the presence of pores may reduce the mechanical properties of acrylic resin as well as interfere in denture hygiene.
In this study, surface roughness of denture base resin Lucitone 199 and hard chairside liners Ufi Gel hard and Kooliner was increased after both chemical disinfection using Cidex (2% alkaline glutaraldehyde) and microwave procedures. Glutaraldehyde can alter the surface layer of acrylic resins and result in etched surface, thereby increasing the roughness after chemical disinfection, which is in accordance with the study conducted by Shen et al., where specimens exposed to Cidex solution revealed signs of deterioration on the surface of acrylic denture base resin.
The study also showed that the surface roughness of all three materials was increased after microwave disinfection possibly because of the high water temperature reached during the disinfection procedure, leading to alterations in the surface. Specimens of a heat-polymerized acrylic denture base material subjected to boiling or hot water were found to exhibit a breakdown of the surface layer, probably as a result of microcrazing of the surface with loss of integrity, as indicated by scanning electron microscopy observation., Also, increase in surface roughness and porosity could be due to monomer vaporization and continued polymerization of acrylic resins at elevated temperatures during the disinfection procedures. Another investigation by Sartori et al. also showed that the use of microwave energy can modify the surface texture of acrylic resins.
In this study, comparison between the four groups suggested that specimens from the group CD showed highest roughness values for all the three materials tested, which might be due to penetration of certain components of the Cidex, causing alteration of the surface morphology.
The surface roughness of each hard chairside reliners was higher than Lucitone 199 in all study groups. This may be related to the fact that the level of residual monomer in autopolymerized acrylic resins is higher on the surface layer. This is in accordance with a study by Braun et al. who found higher levels of residual monomer in self-cured acrylic resin in comparison with that in heat-cured materials. The high degree of polymerization of heat-cured acrylic materials could explain such phenomenon. Novais et al. suggested that autopolymerized resins have a high level of residual monomer, leading to greater degree of conversion and continuation of polymerization.
Some in vivo studies suggested a threshold surface roughness for bacterial retention (Ra = 0.2 μm), below which no further reduction in bacterial accumulation can be expected., According to the results from a study by Quirynen et al., an increase in bacterial colonization would be expected to occur on surface with Ra roughness values of 2.2 μm.
In this study, the mean roughness values of all specimens after chemical and microwave disinfection increased beyond the threshold limit value. These findings suggested that the rougher specimen surface after disinfection may render the surface more prone to the adhesion of microorganisms.
There are few limitations of this study. First, being a small sample-sized study. Second, we have used only Cidex as a chemical disinfectant, but a lot many other chemicals are also recommended for disinfection of prostheses. Effects of these chemicals on roughness of prostheses need to be evaluated.
| Conclusion|| |
Although the chemical disinfection of denture is a convenient and inexpensive method, certain components of the disinfectant solutions may penetrate the material and affect its mechanical and physical properties. The results of this in vitro study favor the use of the microwave disinfection method because it has less adverse effects on surface roughness of material, is easy to use, and is less time-consuming compared to that of chemical disinfection.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]