Hardness and surface roughness of reline and denture base acrylic resins after repeated disinfection procedures

Enhancing mouthguard longevity: Impact of surface treatment against aging from brushing and disinfectant exposure

BACKGROUND/AIMS

The study aimed to assess the surface characteristics of sports mouthguards under mechanical stresses during cleaning, either by brushing or immersion in disinfectant solutions.

MATERIAL AND METHODS

Ethylene-vinyl acetate samples, 4 mm thick, were randomly assigned to cleaning methods: control (C-no cleaning), brushing with water (B.W), brushing with neutral liquid soap (B.S), brushing with toothpaste (B.T), immersion in distilled water for 10 min (I.W), immersion in 2.25% sodium hypochlorite solution for 10 min (I.SH), and immersion in sodium bicarbonate solution for 5 min (I.SB). All cleaning methods were applied for 28 days. Surface roughness average (Ra) and wettability were measured at baseline for the control group (n = 9), and after cleaning for all the other groups.

RESULTS

One-way ANOVA with Tukey tests (5% significance) indicated significant differences among groups (p < .05). The I.SB group had higher surface roughness than B.S and B.T (p < .05). B.W showed the lowest wettability, significantly lower than B.T, I.W, and I.SB (p < .05). I.SB exhibited the highest wettability, significantly different from sodium hypochlorite, neutral liquid soap, brushing with water, and control groups (p < .05). The sodium bicarbonate immersion group (I.SB) demonstrated greater statistical variation, displaying higher susceptibility to aging compared to brushing with neutral liquid soap.

CONCLUSION

Cleaning mouthguards with a toothbrush, water, and neutral liquid soap emerged as the most promising method, causing minimal surface changes in the material.

Effects of simulated long-term exposure to bottled, neutral pH electrolyzed oxidizing water on the properties of denture base resins

STATEMENT OF PROBLEM

Denture stomatitis can pose serious health risks, especially to older people. Chemical denture cleaning agents must be effective, yet not adversely affect the longevity of removable dentures. Ready-to-use (RTU) neutral pH electrolyzed oxidizing water (EOW) is an effective biocide against Candida albicans biofilms on denture resins, but the effects of daily disinfection with EOW on the physical and mechanical properties of resins have not been established.

PURPOSE

The purpose of this in vitro study was to investigate the effects of simulated long-term exposure to RTU EOW on the color, surface characteristics, and flexural strength of denture base resins.

MATERIAL AND METHODS

Heat-polymerized (HP), 3D printed (3D) and computer-aided design and computer-aided manufacture (CAD-CAM)-milled (CC) denture resin specimens (square: 20×20×3.3 mm; beam: 64×10×3.3 mm) were immersed in tap water (TW), RTU EOW (Neutral Anolyte ANK; Envirolyte; EOW), or a commercial denture cleaning tablet solution (Polident 3-Minute; Glaxo SmithKline; PD), mimicking a 5-minute once daily disinfection routine performed up to 3.0 years. Color and surface roughness were recorded (n=3, squares), and changes in color (∆E00) and surface roughness (∆Ra) were calculated. Flexural strength (n=12, beams) and surface hardness (n=18, beams) were measured with a universal testing machine. The fractured surfaces of specimens were examined by scanning electron microscopy and energy dispersive spectroscopy. Data were assessed by performing the Shapiro-Wilk or D'Agostino and Pearson normality tests. Two-way ANOVA or the Kruskal-Wallis test with a post hoc Tukey HSD or Dunn multiple comparisons (α=.05) was used for statistical analyses.

RESULTS

No significant changes were found in either color or surface roughness for HP, 3D, and CC resins after 1.5-year and 3.0-year immersion in any of the agents (P>.05). The surface hardness of 3D resins reduced by 14% with TW and by 23% with EOW and PD at 3.0 years. The flexural strengths of all 3 resins were unaffected by 3.0-year immersion (P>.05).

CONCLUSIONS

Simulated long-term immersion disinfection with RTU neutral pH EOW did not adversely affect the physical and mechanical properties of HP or CC denture resins.

Bonding Efficiency between Artificial Teeth and Denture Base in CAD/CAM and Conventional Complete Removable Dentures

A common challenge encountered with both traditional and digitally produced dentures involves the extraction of artificial teeth from the denture base. This narrative review seeks to present an updated perspective on the adherence of synthetic teeth for denture base materials, employing diverse methods. Dental technicians often employ chemical approaches and mechanical techniques (including abrasion, laser treatment, and abrasive blasting) to augment the retention of denture teeth. However, the efficacy of these treatments remains uncertain. In certain instances, specific combinations of Denture Base Resin (DBR) materials and artificial teeth exhibit improved performance in conventional heat-cured dentures following these treatments. The primary reasons for failure are attributed to material incompatibility and inadequate copolymerization. As new denture fabrication techniques and materials continue to emerge, further research is imperative to identify optimal tooth-DBR combinations. Notably, 3D-printed tooth-DBR combinations have demonstrated reduced bond strength and less favorable failure patterns, while utilizing milled and traditional combinations appears to be a more prudent choice until advancements in additive manufacturing enhance the reliability of 3D-printing methods.

Nanoparticle-Modified 3D-Printed Denture Base Resins: Influence of Denture Cleansers on the Color Stability and Surface Roughness In Vitro

This study aimed to evaluate the influence of denture cleansers on the color, stability, and surface roughness of three-dimensional (3D)-printed denture base resins modified with zirconium dioxide nanoparticles (nano-ZrO2). A total of 440 specimens were fabricated using one heat-polymerized resin, and two 3D-printed resins (NextDent and ASIGA). According to the nano-ZrO2 content, the specimens for each resin were divided into five groups (0%, 0.5%wt, 1%wt, 3%wt, and 5%wt). Each concentration was divided into four subgroups (n = 10) based on the immersion solution (distilled water, sodium hypochlorite, Corega, and Fittydent) and immersion duration (360 and 720 days). The color changes (∆E00) and surface roughness (Ra, µm) of each specimen were measured at different time intervals (base line, 360 days, 720 days) using a spectrophotometer and a non-contact profilometer, respectively. The results were statistically analyzed using ANOVA and a post hoc Tukey's test (α = 0.05). Sodium hypochlorite showed the highest significant color change of all the denture base resins (p < 0.001). The average value of ΔE00 for sodium hypochlorite was significantly higher than the values for the other solutions (Fittydent, Corega, and water) (p < 0.001). Color stability was significantly affected by immersion time for all types of solutions except Corega (p < 0.001). All of the tested immersion solutions (distilled water, sodium hypochlorite, Corega, and Fittydent) showed a significant increase in the surface roughness of all the denture base resins (p < 0.05). Surface roughness was substantially increased by immersion time for all types of solution except Fittydent (p < 0.001). Denture cleansers can result in substantial color change and affect the surface roughness of unmodified and nanoparticle-modified denture base resins. Therefore, the selection of denture cleanser and appropriate types of material is critical for denture longevity.

Effects of disinfectants on physical properties of denture base resins: A systematic review and meta-analysis

STATEMENT OF PROBLEM

The disinfection of removable dental prostheses and orthodontic appliances is essential to preventing transmission of pathogens. However, whether different disinfection solutions and durations affect the physical properties of denture base resins is unclear.

PURPOSE

The purpose of this systematic review and meta-analysis was to statistically analyze the influence of disinfectants on the physical properties of denture base resins.

MATERIAL AND METHODS

A systematic search in Medline, Embase, PubMed, and Cochrane Library databases was conducted to evaluate the effects of chemical disinfection on the physical properties of denture base resins such as surface morphology, roughness, hardness, and flexural strength. Of 1909 studies, 44 studies were included in the systematic review and 41 in the meta-analysis. Heterogeneity was analyzed by using I2 statistics. The influence of different disinfection solutions and durations on the physical properties was further analyzed, and the risk of bias evaluated. Statistical analyses were performed by using the RevMan 5.4 software program with the standardized mean differences (SMDs) and 95% confidence intervals (CIs).

RESULTS

Of the 44 included studies, 40 studies were assessed as having a low risk of bias, and 4 had an unclear risk of bias. Meta-analysis results showed that compared with the control, disinfection could not significantly affect surface roughness and hardness within 60 minutes of immersion in disinfectant solutions or flexural strength within 30 minutes (roughness: P=.79, I2=0%; flexural strength: P=.08, I2=0%; hardness: P=.05, I2=19%). In addition, the physical properties were not significantly affected when glutaraldehyde, chlorhexidine, and peracetic acid were repeatedly used for more than 30 minutes.

CONCLUSIONS

Most of the disinfectants did not reduce the physical properties of denture base resin within 30 minutes of immersion. Glutaraldehyde, chlorhexidine, and peracetic acid are recommended if longer immersion or repeated disinfection is required.

Anti-Microbial Effect of AgBr-NP@CTMAB on Streptococcus Mutans and Assessment of Surface Roughness Hardness and Flexural Strength of PMMA

Purpose

To investigate the inhibition of Streptococcus mutans (S.mutans) and its biofilm by AgBr-nanoparticles (NP) @CTMAB (cetyltrimethyl-ammonium bromide) and evaluate the changes in Polymethyl methacrylate (PMMA)'s surface roughness (Ra), microhardness, and flexural strength during prolonged immersion in AgBr-NP@CTMAB for application in the denture cleaning industry.

Patients and Methods

The antibacterial activity of AgBr-NP@CTMAB against S.mutans was measured colony formation assay, OD600 and laser confocal microscopy. Changes in the specimens' values for surface roughness, microhardness, and flexural strength (MPa) were measured after immersion solutions for 180 or 360 days.

Results

The AgBr-NP@CTMAB solution exhibited a robust antibacterial effect on planktonic S. mutans, with a minimum bactericidal concentration of 5 µg/mL. The 10 µg/mL AgBr-NP@CTMAB solution efficiently inhibited S. mutans biofilm formation. (2) No significant difference in surface roughness after immersion in AgBr-NP@CTMAB (10 µg/mL and 20 µg/mL) comparing with distilled water (P > 0.05) and Polident had significantly higher than distilled water (P < 0.05). There was a significant decrease in the surface hardness of the PMMA specimens that were immersed in the Polident compared with those in distilled water (P < 0.05). While, no significant differences in surface hardness after immersion in the AgBr-NP@CTMAB (P > 0.05). The result of flexural strength suggested that there was no statistically significant difference (P < 0.05) between AgBr-NP@CTMAB as well as Polident and water.

Conclusion

AgBrNP@CTMAB can efficiently inhibit the growth of plankton S.mutans and biofilm formation, without affecting the flexural strength, microhardness, or surface roughness of PMMA. Therefore, AgBrNP@CTMAB holds promise as a new denture cleaning agent.

Investigation of the Surface Roughness and Hardness of Different Denture Teeth Materials: An In vitro Study

Background

Surface roughness and hardness are key factors that influence the clinical performance and durability of denture teeth. Understanding variations in these properties among different denture teeth materials can assist in selecting the most suitable materials for optimal patient outcomes. This study aimed to investigate the surface roughness and hardness of four commonly used denture teeth materials: acrylic resin, composite resin, porcelain, and nanohybrid composite.

Materials and Methods

Ten specimens were prepared for each denture teeth material, resulting in a total of 40 specimens. Surface roughness was assessed using a profilometer, and measurements were recorded in micrometers (μm). Hardness was determined using a Vickers hardness tester, and results were expressed as Vickers hardness numbers (VHN). The surface roughness and hardness data were analyzed using appropriate statistical tests (e.g., analysis of variance), with significance set at P < 0.05.

Results

The results revealed significant differences in both surface roughness and hardness among the different denture teeth materials (P < 0.05). Acrylic resin exhibited the highest surface roughness (mean ± standard deviation: 3.45 ± 0.78 μm) and the lowest hardness (mean ± standard deviation: 45.6 ± 2.3 VHN). Composite resin demonstrated intermediate values of surface roughness (mean ± standard deviation: 1.87 ± 0.54 μm) and hardness (mean ± standard deviation: 65.2 ± 3.9 VHN). Porcelain demonstrated the smoothest surface (mean ± standard deviation: 0.94 ± 0.28 μm) and the highest hardness (mean ± standard deviation: 78.5 ± 4.1 VHN). Nanohybrid composite displayed surface roughness and hardness values similar to composite resin.

Conclusion

This study demonstrated significant variations in surface roughness and hardness among the different denture teeth materials evaluated. Acrylic resin exhibited the roughest surface and lowest hardness, while porcelain demonstrated the smoothest surface and highest hardness. Composite resin and nanohybrid composite exhibited intermediate values. These findings provide valuable insights for prosthodontic practitioners in selecting denture teeth materials based on specific clinical requirements, aiming to achieve optimal aesthetics, reduced plaque accumulation, and improved wear resistance.

Color stability, surface, and physicochemical properties of three-dimensional printed denture base resin reinforced with different nanofillers

Various materials have been introduced for the three-dimensional (3D) printing of dentures. In this study, the color stability and surface and physicochemical properties of 3D-printed denture base resins with four types of nanofiller particles were evaluated. Al2O3, ZnO, CeZr, and SiO2 nanofillers were added to a 3D printable denture base-resin matrix and subjected to digital light processing. The specimens were immersed in Coke, coffee, black tea, or distilled water for 6 days. For the assessment of color differences, 6 samples were analyzed using a spectrophotometer. In a separate investigation, surface properties of 10 samples were examined, while a different set of 6 samples was used to analyze water sorption and solubility. All experimental groups exhibited higher color stability in Coke than the control group. However, the groups containing ZnO and CeZr had lower color stability in coffee and black tea than the control group. Moreover, they had agglomerated nanofillers and lower gloss than the control group. Compared with that of the control group, the contact angle of the CeZr group and microhardness of the ZnO group were not significantly different. Water sorption was higher in the Al2O3 group, whereas the solubility of the experimental and control groups was not statistically significant. The results demonstrated the significant effect of ZnO and CeZr nanofillers on the color stability of the dentures when exposed to discoloring beverages. These results will facilitate the development of fillers that enhance the resistance of 3D printed denture base resins to discoloration in the oral environment.

Effects of various disinfectants on surface roughness and color stability of thermoset and 3D-printed acrylic resin

Denture cleansers are extensively utilized to inhibit the colonization of various Candida species. Currently, additive technology in denture fabrication has become more prevalent. This study aims to assess the impact of disinfectants on the surface roughness and color stability of distinct denture bases. Disc-shaped samples (N=66) were exposed to three different disinfectants: 0.5% sodium hypochlorite, 1% hydrogen peroxide, and 2% chlorhexidine. The samples underwent evaluation via spectrophotometry and profilometry, respectively. Data analysis was conducted utilizing analysis of variance (ANOVA) (p < 0.05). Within the heat-cured group, sodium hypochlorite resulted in the most notable change in surface roughness (0.2 μm), while chlorhexidine exhibited the least impact (0.001 μm), showing a significant difference (p <0.008). The color change (ΔE) for 3D-printed samples immersed in all disinfectants was higher compared to heat-cured samples. Among the heat-cured samples, chlorhexidine induced the highest ΔE (2.76), while sodium hypochlorite resulted in the lowest (ΔE = 1.44), and this difference was statistically significant (p <0.008). Chlorhexidine caused the most significant color alteration among the solutions, while sodium hypochlorite induced the most considerable changes in surface roughness.

Effects of disinfection with a vinegar-hydrogen peroxide mixture on the surface characteristics of denture acrylic resins

OBJECTIVE

This study aimed to investigate changes in the surface characteristics of two denture resins when disinfected with a vinegar-hydrogen peroxide (VHP) mixture.

MATERIALS AND METHODS

Microwave-polymerized or 3D printed acrylic resin disks were immersed for 900 min (simulating 90 daily uses) in the following solutions (N = 10): water; 0.5% sodium hypochlorite; hydrogen peroxide and water dilution (1:1 ratio); vinegar and water dilution (1:1 ratio); and VHP mixture. Surface roughness, Knoop microhardness, surface free energy, and scanning electron microscopic images were assessed before and after the immersions. Results were compared using the 2-way ANOVA for repeated measures and Tukey test, at 5% significance.

RESULTS

Surface roughness and microhardness did not differ (P > .05) among the solutions and times. Surface free energy and its dispersive component increased (P < .05) for all solutions. All solutions, except for water and VHP mixture, degraded microtopography.

CONCLUSIONS

The VHP mixture was not deleterious to conventional and 3D-printed resin surfaces.

CLINICAL RELEVANCE

Conventional and 3D printed resin dentures can be disinfected with a VHP mixture in a 1:1 ratio because this mixture does not substantially affect the surface characteristics after 90 daily immersions. On the contrary, sodium hypochlorite, hydrogen peroxide, and vinegar solutions, even in low concentrations, should be used with caution for denture disinfection because they may alter the resin microtopography over time.

Flexural strength, surface roughness, and biofilm formation of ceramic-reinforced PEEK: An in vitro comparative study

PURPOSE

This in vitro study aimed to compare flexural strength, surface roughness, and biofilm formation of ceramic-reinforced polyetheretherketone (PEEK) with conventionally heat-compressed and milled polymethylmethacrylate (PMMA) denture base materials.

MATERIALS AND METHODS

Thirty strips (6.4 mm × 10 mm × 3 mm) and 30 discs (10 mm × 1 mm) were fabricated from a heat-compressed PMMA, milled PMMA, and ceramic-reinforced PEEK, 10 each. One surface of each sample was polished to mimic the laboratory procedure for denture base materials. Strips were then subjected to a three-point bend test using a universal testing machine at a crosshead speed of 5.0 mm/min. An optical profilometer was used to assess the Ra value (mm) of the discs on polished and unpolished sides. Biofilm formation behavior was analyzed by measuring the colony-forming unit (CFU)/mL of Candida albicans on the unpolished surface of the discs. One-way ANOVA followed by Tukey multiple comparison tests were used to compare the flexural strength, Ra value, and biofilm formation of the studied materials (a = 0.05).

RESULTS

Ceramic-reinforced PEEK showed significantly higher flexural strength (178.2 ± 3.2 MPa) than milled PMMA (89.6 ± 0.8 MPa; p < 0.001) and heat-compressed PMMA (67.3 ± 5.3 MPa; p < 0.001). Ceramic-reinforced PEEK exhibited a significantly higher Ra value than the other groups on unpolished sides; however, the polishing process significantly reduced the Ra values of all studied groups (p < 0.05). There was no significant difference in C. albicans adhesion among the groups (p < 0.05).

CONCLUSION

The flexural strength of tested materials was within acceptable limits for clinical use as a denture base material. Ceramic-reinforced PEEK had the highest surface roughness; however, its similarity in biofilm formation to other groups indicates its clinical acceptability as denture base material.

Effect of different disinfection protocols on the surface properties of CAD-CAM denture base materials

STATEMENT OF PROBLEM

Which disinfection protocol provides optimal water contact angle and microhardness for computer-aided design and computer-aided manufacturing (CAD-CAM) polymethyl methacrylate (PMMA) materials is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of different disinfection protocols (1% sodium hypochlorite, denture cleanser gel, and effervescent tablet) on the water contact angle and microhardness of different CAD-CAM PMMA denture base materials by comparing them with a heat-polymerized PMMA.

MATERIAL AND METHODS

Disk-shaped specimens (Ø10×2 mm) were fabricated from 3 different CAD-CAM PMMAs-AvaDent (AV), Merz M-PM (M-PM), and Polident (Poli)-and a heat-polymerized PMMA (Vynacron) (CV) (n=21). Three disinfection protocols (1% sodium hypochlorite [HC], denture cleanser gel [GEL], an effervescent tablet [TAB]) were applied to simulate 180 days of cleansing. The water contact angle and microhardness of specimens were measured before and after disinfection and compared by using a 2-way ANOVA (α=.05).

RESULTS

For water contact angle, material (P=.010) and disinfection protocol (P=.002) had a significant effect. The material (P<.001), disinfection protocol (P=.001), and their interaction (P<.001) significantly affected the microhardness after disinfection. When the condition after disinfection was compared with that before disinfection, the water contact angle increased significantly in all material-disinfection protocol pairs (P≤.025), and microhardness increased significantly in all material-disinfection protocol pairs (P≤.040), except for GEL- (P=.689) or TAB-applied (P=.307) AV, HC-applied M-PM (P=.219), and TAB-applied Poli (P=.159).

CONCLUSIONS

The material and disinfection protocol affected the water contact angle of all tested PMMAs after disinfection, resulting in more hydrophobic surfaces for heat-polymerized or CAD-CAM PMMAs. The microhardness of heat-polymerized PMMA was less than that of all CAD-CAM PMMAs after disinfection, regardless of the protocol.

Effect of Different Disinfecting Agents on Surface Roughness and Color Stability of Heat-cure Acrylic Denture Material: An In Vitro Study

AIM

The current study aimed to determine the impact of three different disinfectants on the surface roughness and color stability of heat-cure acrylic denture material.

MATERIALS AND METHODS

Using a stainless-steel mold, disc-shaped wax patterns with dimensions of 10 mm in diameter and 2 mm thick (in accordance with ADA Specification No. 12) were created and prepared for a total of 75 acrylic samples. Dimensions of all 75 acrylic samples were checked with a digital Vernier caliper. About 25 samples of denture base material were immersed in three different chemical disinfectants: Group I: immersed in chlorhexidine gluconate solution, group II: immersed in sodium hypochlorite solution, and group III: immersed in glutaraldehyde solution. All samples were scrubbed daily for 1 minute with the appropriate disinfectant and submerged for 10 minutes in the same disinfectant. Between disinfection cycles, samples were kept in distilled water at 37°C. Color stability was measured using a reflection spectrophotometer. Surface roughness values were measured by a profilometer at baseline following 15 days and 30 days.

RESULTS

After 15 days, the color stability was better in chlorhexidine gluconate solution group (4.88 ± 0.24) than sodium hypochlorite solution (4.74 ± 0.18) and glutaraldehyde solution group (4.46 ± 0.16). The mean surface roughness was less in glutaraldehyde solution group (2.10 ± 0.19), followed by chlorhexidine gluconate solution group (2.48 ± 0.09) and sodium hypochlorite solution group (2.64 ± 0.03). After 30 days, the color stability was significantly better in chlorhexidine gluconate solution group (4.40 ± 0.02), followed by sodium hypochlorite solution (4.06 ± 0.16) and glutaraldehyde solution group (3.87 ± 0.17). The mean surface roughness was significantly lesser in glutaraldehyde solution group (2.41 ± 0.14), followed by chlorhexidine gluconate solution group (2.94 ± 0.08) and sodium hypochlorite solution group (3.02 ± 0.13).

CONCLUSION

In conclusion, the color stability was significantly better in chlorhexidine gluconate solution group than sodium hypochlorite solution and glutaraldehyde solution group. But the surface roughness was significantly lesser in the glutaraldehyde solution group, followed by the chlorhexidine gluconate and sodium hypochlorite solution group.

CLINICAL SIGNIFICANCE

The maintenance of the prosthesis requires the use of a denture disinfectant; therefore, it is crucial to select one that is effective but would not have a negative impact on the denture base resin's inherent characteristics over time. How to cite this article: Kannaiyan K, Rakshit P, Bhat MPS, et al. Effect of Different Disinfecting Agents on Surface Roughness and Color Stability of Heat-cure Acrylic Denture Material: An In Vitro Study. J Contemp Dent Pract 2023;24(11):891-894.

Effect of denture cleansers on color stability and surface roughness of denture bases fabricated from three different techniques: Conventional heat-polymerizing, CAD/CAM additive, and CAD/CAM subtractive manufacturing

PURPOSE

Denture base materials are commonly exposed to different denture cleansers which can affect their essential properties. This study aimed to assess the effect of denture cleansers on color stability and surface roughness of poly methyl methacrylate (PMMA) denture bases fabricated from different techniques: Conventional heat-polymerizing, CAD/CAM additive and CAD/CAM subtractive.

MATERIALS AND METHODS

In this in vitro study, 24 disc-shaped specimens were fabricated by the mentioned methods for each group. The initial color and surface roughness of specimens were recorded. The specimens were randomly divided into three subgroups (n = 8): a control subgroup (distilled water), and two experimental subgroups of bioactive oxygen tablet (Corega) and 1% sodium hypochlorite solution. Then they were immersed in the solutions simulating 180 days of clinical use. Color change (∆E) was measured by a spectrophotometer according to the CIE L*a*b* color space and the American National Bureau of Standards (NBS = 0.92 × ∆E). Final surface roughness was recorded by a profilometer and its change was calculated. The Kruskal-Wallis test followed by the Wilcoxon signed rank test were used for statistical analyses (α = .05).

RESULTS

The conventional and CAD/CAM subtractive groups showed an increase in surface roughness following immersion in hypochlorite solution (p < .05). After immersion in the solutions, the highest surface roughness was noted in the conventional group, and the lowest in the CAD/CAM additive group. The CAD/CAM additive group experienced a significant color change in hypochlorite solution (p < .05) and showed the highest color change while the CAD/CAM subtractive group showed the lowest color change in all denture cleanser solutions.

CONCLUSION

Although the CAD/CAM additive denture base resins had the lowest surface roughness after exposure to denture cleanser solutions, they showed significant color change, which should be taken into account. Using hypochlorite as a denture cleanser should be cautioned due to its negative effects on the surface roughness and color stability of denture base materials.

Adhesion of Conventional, 3D-Printed and Milled Artificial Teeth to Resin Substrates for Complete Dentures: A Narrative Review

BACKGROUND

One type of failure in complete or partial dentures is the detachment of resin teeth from denture base resin (DBR). This common complication is also observed in the new generation of digitally fabricated dentures. The purpose of this review was to provide an update on the adhesion of artificial teeth to denture resin substrates fabricated by conventional and digital methods.

METHODS

A search strategy was applied to retrieve relevant studies in PubMed and Scopus.

RESULTS

Chemical (monomers, ethyl acetone, conditioning liquids, adhesive agents, etc.) and mechanical (grinding, laser, sandblasting, etc.) treatments are commonly used by technicians to improve denture teeth retention with controversial benefits. Better performance in conventional dentures is realized for certain combinations of DBR materials and denture teeth after mechanical or chemical treatment.

CONCLUSIONS

The incompatibility of certain materials and lack of copolymerization are the main reasons for failure. Due to the emerging field of new techniques for denture fabrication, different materials have been developed, and further research is needed to elaborate the best combination of teeth and DBRs. Lower bond strength and suboptimal failure modes have been related to 3D-printed combinations of teeth and DBRs, while milled and conventional combinations seem to be a safer choice until further improvements in printing technologies are developed.

Effect of cigarette smoke and denture cleansers on the surface properties and color stability of CAD-CAM and conventional denture base resins

This study aimed to evaluate the hardness, roughness, and color stability of heat- and microwave-polymerized polymethyl methacrylate (PMMA), polyamide, and CAD-CAM PMMA resins when exposed to cigarette smoke (CS) and immersed in a denture cleanser (DC). Specimens of each resins were divided into four subgroups (n=10). The DC and CS+DC specimens were immersed in a DC; the CS and CS+DC specimens were exposed to CS; and the control (C) specimens were kept in distilled water. Hardness, roughness, and color measurements were performed. DC and CS significantly affected the roughness and color of all resins (p<0.05). However, these did not affect the hardness of the CAD-CAM PMMA resin (p>0.05). The CAD-CAM PMMA resin presented the lowest roughness, highest hardness, and lowest ΔE₀₀ values. While the roughness of all resins exposed to CS when immersed in DC decreased, the ΔE₀₀ values of the conventional PMMAs also decreased. Although this decreases were not significant, it may be advisable to use DC for smokers to decrease discoloration and roughness especially for conventional PMMAs resins.

Antifungal activity, mechanical properties, and accuracy of three-dimensionally printed denture base with microencapsulated phytochemicals on varying post-polymerization time

BACKGROUND

Studies on the antifungal activity, flexural strength, Vickers hardness, and intaglio surface trueness of three-dimensionally printed (3DP) denture bases with microencapsulated phytochemicals with respect to changes in post-polymerization time (PPT) are lacking.

METHODS

Specimens of various shapes and dimensions were fabricated with a 3DP denture base resin mixed with 5 wt% phytoncide-filled microcapsules. Each specimen was subjected to different PPT protocols of 5, 10, 20, and 30 min. Specimens without microcapsules with 5-min PPT were used as the negative control group. Cell colonies were counted to evaluate antifungal activity. Three-point bending and Vickers hardness tests were performed to measure the flexural strengths and hardness of the specimens. Fourier-transform infrared spectrometry was used to inspect the degree of conversion (DC). The intaglio surface trueness was measured using root-mean-square estimates calculated by superimposition analysis. A non-parametric Kruskal-Wallis test or one-way analysis of variance was performed (α = 0.05).

RESULTS

The specimens with microcapsules and 10-min PPT showed the highest antifungal activity among the tested groups. Compared with the positive control group (5-min PPT), the specimens with PPTs of 10 min or longer showed significantly higher mean flexural strength, higher DC, greater hardness, and better trueness (all, P < 0.05). Except for the difference in antifungal activity, no statistically significant differences were detected between the specimens subjected to 10-, 20-, and 30-min PPT.

CONCLUSION

The 3DP denture base filled with microencapsulated phytoncide showed different antifungal activity and physical properties on changing PPT. The 3DP denture base containing phytoncide-filled microcapsules at 5 wt% concentration and subjected to 10-min PPT exhibited sufficient antifungal activity as well as mechanical properties and accuracy within clinical acceptance.

Development of Phantoms for Multimodal Magnetic Resonance Imaging and Magnetic Particle Imaging

Phantoms are crucial for the development of imaging techniques based on magnetic nanoparticles (MNP). They serve as test objects to simulate application scenarios but are also used for quality assurance and interlaboratory comparisons. Magnetic particle imaging (MPI) is excellent for specifically detecting magnetic nanoparticles (MNP) without any background signals. To obtain information about the surrounding soft tissue, MPI is often used in combination with magnetic resonance imaging (MRI). For such application scenarios, this poses a challenge for phantom fabrication, as they need to accommodate MNP as well as provide MR visibility. Recently, layer-by-layer fabrication of parts using Additive Manufacturing (AM) has emerged as a powerful tool for creating complex and patient-specific phantoms, but these are characterized by poor MR visibility of the AM material. We present the systematic screening of AM materials as candidates for multimodal MRI/MPI imaging. Of all investigated materials, silicone (Dreve, Biotec) exhibited the best properties with sufficient MR-signal performance and the lowest absorption of MNP at the interface of AM materials. With the help of AM and the selection of appropriate materials, we have been able to produce suitable MRI/MPI phantoms.

Do denture cleansers influence the surface roughness and adhesion and biofilm formation of Candida albicans on acrylic resin? Systematic review and meta-analysis

PURPOSE

To evaluate the influence of denture cleansers on the surface roughness, Candida albicans adhesion, and biofilm formation on denture base acrylic resins.

STUDY SELECTION

Electronic databases and gray literature were searched using an individual search strategy. In vitro studies that evaluated the effects of immersion in denture cleansers on the surface roughness (µm) and antimicrobial activity (CFU/mL) on samples of heat-polymerized denture base acrylic resins were included.

RESULTS

After screening, 17 studies were included, and a qualitative synthesis was performed. After assessing the risk of bias, only nine studies were included in the meta-analysis. The meta-analysis results showed that the evaluated solutions (0.5% sodium hypochlorite, 1% sodium hypochlorite, alkaline peroxide, and natural substances) did not influence the roughness of the acrylic resin. However, in the qualitative analysis, it was not possible to confirm an association between roughness and C. albicans adhesion and biofilm formation on the acrylic resin samples.

CONCLUSION

Denture cleansers did not affect the surface roughness of denture base acrylic resins.

Effect of phytochemical-filled microcapsules with antifungal activity on material properties and dimensional accuracy of denture base resin for three-dimensional printing

BACKGROUND

Studies on the material properties and dimensional accuracy of three-dimensionally (3D) printed denture base containing microcapsules with antifungal phytochemicals are lacking.

METHODS

Two types of phytochemicals (phytoncide A and B) with antifungal activity were microencapsulated. The 3D-printed denture base specimens with minimum and maximum effective concentrations of microcapsules (6 and 8 wt% for phytoncide A; 15 and 25 wt% for phytoncide B) were prepared. The morphological changes of C. albicans on 3D-printed denture base with microcapsules was microscopically observed. The degree of conversion of 3D-printed denture base with microcapsules investigated. The microhardness and flexural strength values were also measured to evaluate the mechanical properties of 3D-printed denture bases. The dimensional accuracy (trueness) of the specimens with microcapsules was measured as root-mean-square values (RMS) for the whole, upper, and side surfaces of the specimens as well as their total height. For the degree of conversion, microhardness, and flexural strength values, the Kruskal-Wallis analysis and a post-hoc comparison using Mann-Whitney U test was performed. For the analysis of trueness (RMS), the one-way analysis of variance and a post-hoc comparison using Tukey's method was conducted (α = 0.05).

RESULTS

At both maximum and minimum effective concentrations of microcapsules, cell surface disruption or membrane breakdown of fungal cells were observed in the specimens. The groups with microcapsules (both phytoncide A- and B-filled) showed significantly lower microhardness and elastic modulus values than the control group (all, P = 0.001). For the trueness, all the RMS values of the whole, upper, and side surfaces of the specimens with microcapsules were less than 100 µm, although significantly higher than those without (all, P = 0.001). The mean flexural strength values of the groups with phytoncide A-filled microcapsule were higher than 65 MPa, not statistically different from that of the control group (all, P > 0.05). However, the groups with phytoncide B-filled microcapsules showed significantly lower values than the control (all, P = 0.001).

CONCLUSIONS

Within the limitations of this in-vitro study, the 3D-printed denture base containing 6 wt% of phytoncide A-filled microcapsules was clinically acceptable in terms of antifungal activity, dimensional accuracy, and flexural strength.

Comparison of the Effect of Denture Cleansers on Long-Term Water Sorption and Solubility of Polyetheretherketone with other Denture Base Materials

Objective: In this in vitro study, the effect of three denture cleansers (DCs) after immersion in a chemical solution applied to polyetheretherketone (PEEK) and other denture base materials (DBMs) on long-term water sorption and solubility was compared. Methods: Disk-shaped specimens (50±1.0-mm diameter and 0.5±0.1-mm thickness) were prepared from four DBMs (n=48). All specimens were randomly subdivided into four storage media groups (n=12): Corega tablet (CT), Protefix tablet (PT), 1% sodium hypochlorite (NaOCl) solution (SH), and control (distilled water, DW). Storage media were renewed thrice a day for 120 days and simulated for 1-year use of overnight immersion. Water sorption and solubility (µg/mm3) of DBMs before and after immersion in storage media were examined and obtained data were statistically analyzed using a multivariate analysis of variance, followed by multiple comparisons by a posthoc Tukey’s test (p

Effect of denture cleansers on the surface properties and color stability of 3D Printed denture base materials

OBJECTIVES

To evaluate the effect of denture cleansers on surface roughness, hardness and color stability of 3D-printed resins compared to heat-polymerized resins.

METHODS

Acrylic specimens (N=160) were prepared using one heat-polymerized (HP) and three 3D-printed denture base resins. Specimens per material were randomly divided into four groups (n = 10) according to immersion solutions as follows: distilled water (DW), sodium hypochlorite (NaOCl), effervescent tablet 1 or effervescent tablet 2. Color changes (∆E) were measured using a spectrophotometer. Surface roughness (Ra, µm) and microhardness were evaluated. The results were analyzed using one- and three-way ANOVA with Tukey's post hoc test (α = 0.05).

RESULTS

After 360 days of cleaning protocols, we observed a significant increase in the surface roughness of tested materials (P<0.001). Hardness values significantly decreased in all groups (P<0.001), except HP and ND specimens, cleaned with effervescent tablet 1 (P>0.05) and AS specimens with effervescent tablet 2 (P=0.051). According to the National Bureau of Standards (NBS) score, all denture base specimens had 'perceivable' to 'extremely marked' color change after immersion in NaOCl, while immersion in effervescent tablets 1 and 2 resulted in a 'slight' to 'marked' color change.

CONCLUSION

3D-printed denture bases exhibited changes in surface roughness, hardness and color of 3D-printed dentures similar to HP denture base material. The use of denture cleansers resulted in a time-dependent increase in surface roughness and a decrease in hardness. The color change was significant with NaOCl, while effervescent denture cleansers produced a minimal color difference.

CLINICAL SIGNIFICANCE

Denture cleansers seem to influence surface properties over time. The degree of impact is mainly dependent on the type of cleanser selected, regardless of the type of denture base material.

Evaluation of microhardness in two types of denture bases after using sodium hypochlorite and NatureDent disinfecting agents

Background. Chemical agents, in combination with mechanical methods, play an important role in reducing microbial plaque on denture surfaces. However, these methods might change the mechanical behavior of acrylic resins, including microhardness and surface roughness. This in vitro study investigated the effect of two disinfectants, i.e., water and sodium hypochlorite, on the microhardness of conventional heat-cured and TiO₂ nanoparticle-reinforced acrylic resins. Methods. Sixty acrylic resin specimens were divided into two groups, and the samples in each group were randomly assigned to three subgroups (n=10). Heat-cured specimens and 1 wt% TiO₂ acrylic resin were prepared and immersed in three solutions: water, a solution prepared with NatureDent pills, and 1% sodium hypochlorite for 30, 60, and 90 days. Microhardness tests were performed on each sample at each immersion stage. The data were analyzed using descriptive statistical methods, three-way and one-way ANOVA, repeated-measures t test, and Tukey HSD tests using SPSS 17. P values<0.05 were considered significant. Results. All three independent parameters, including resin, solution, and time, significantly affected microhardness (P<0.05). The microhardness of both specimen types, i.e., conventional heat-cured and TiO₂ nanoparticle-reinforced acrylic resins, immersed for 30, 60, and 90 days, was the highest and lowest in water and hypochlorite solutions, respectively. Regarding 90 days, the microhardness values of conventional heat-cured and TiO₂ nanoparticle-reinforced acrylic resins were 17.050±0.094 and 19.953±0.053 in water, 15.675±0.069 and 18.965±0.037 in hypochlorite, and 16.713±0.122 and 19.39±20.113 in NatureDent solutions, respectively. Conclusion. Disinfecting two types of acrylic resin specimens decreased their microhardness as a function of immersion time for up to 90 days in the three solutions. However, the magnitude of hardness lost was less for TiO₂ nanoparticles-reinforced acrylic resin.

Dimensional Stability of Elastomeric Impression Material After Disinfection Via Immersion and Microwave Irradiation

Aims:

This study aimed to evaluate and compare the dimensional stability of two elastomeric impression materials, namely polyvinyl siloxane (PVS) and vinyl siloxanether (VSE), subjected to chemical immersion and microwave irradiation for disinfection.

Materials and Methods:

Sixty discs of PVS and VSE impression materials each were prepared using a stainless-steel test die and ring in accordance with ANSI/ADA Specification No. 19. Twenty discs of each impression material were disinfected by chemical immersion for 10 min; another 20 discs were subjected to dry microwave irradiation for 3 min. The other 20 discs served as a control group. Dimensional stability measurements were then performed using an image analyzer at 20× magnification. The data were analyzed by one-way analysis of variance (α=0.05) and Bonferroni (post hoc) test for multiple comparisons to detect significant differences between the groups.

Results:

When subjected to microwave irradiation, both PVS and VSE showed dimensional changes, but the changes were within the limit of 1.5% set by ANSI/ADA (P<0.00). VSE showed markedly better results than PVS for both disinfection methods. The immersion disinfection method resulted in a higher average percentage of linear dimensional changes than both the microwave irradiation and the control for VSE and PVS impression materials.

Conclusion:

VSE exhibited excellent dimensional stability than PVS under both chemical immersion and microwave irradiation. Microwave irradiation using conventional microwave ovens can be used in clinical settings as an alternative to other disinfection techniques because the dimensional changes of the elastomeric impression materials subjected to microwave irradiation have been observed to be within the clinically acceptable limit set by the ANSI/ADA standard.

The Influence of Decontamination Procedures on the Surface of Two Polymeric Liners Used in Prosthodontics

Polymeric liners are materials commonly used in prosthodontics to reshape denture surfaces contacting the soft tissues of the oral cavity. The aim of the study was to determine the impact of different cleaning methods on two polymeric materials used in prosthodontics as non-adhesive permanent liners. The material for the research consisted of samples made from Mollosil Plus (Detax, Ettlingen, Germany)-direct polysiloxan liner; and Plastitanium (Pressing Dental, San Marino, Republic of San Marino)-an injection-molded liner. A total of 198 samples were made, 99 of each assessed material. They were exposed to different cleaning methods-a toothbrush, a toothbrush and soap, a toothbrush and toothpaste (BlendaMed, Procter&Gamble, Cincinnati, OH, USA), a toothpaste and denture cleaning paste (Protefix Hygiene Denture Paste, Queisser Pharma, Germany), denture cleansing tablets (Protefix Hygiene Cleaning Tablets, Queisse Pharma, Germany), and a disinfecting spray (Aftermat, Port Jefferson Station, New York City, NY, USA)-for 1 min, 5 min, 10 min, and 15 min. The image acquisition was performed with scanning electron microscopy and samples were analyzed for the homogeneity of their surfaces-the presence of holes, grooves, precipitate, and small and large separating pieces of the material marking departures from this homogeneity. For each type of damage, one point was given. Continuous data from two groups were compared with Mann-Whitney U testing. Due to a small sample size and distribution of variables other than normal, to compare more than two groups, Kruskal-Wallis testing with post hoc analysis (Dunn test with Bonferroni correction) was used. Categorical data were compared with the chi-square test and the Fisher's exact test. The Mollosil Plus material should be decontaminated with the use of a toothbrush or toothbrush with soap, while Plastitanium material should be disinfected. Plastitanium samples are more susceptible to damage during the decontamination procedures than Mollosil Plus.

Complete denture hygiene solutions: antibiofilm activity and effects on physical and mechanical properties of acrylic resin

BACKGROUND

Appropriated denture hygiene is a predictive factor for longevity of rehabilitation treatment and maintenance of the oral mucosal health. Although, disinfectant solutions are commonly used as denture cleansers, the impact of these solutions on acrylic resin-based dentures remain unclear.

OBJECTIVE

To evaluate, in vitro, the antibiofilm activity of complete denture hygiene solutions and their effects on physical and mechanical properties of acrylic resin.

METHODOLOGY

For antibiofilm activity measurement acrylic resin specimens were contaminated with Candida albicans, Candida glabrata and Streptococcus mutans. After biofilm growth, the specimens were assigned to the hygiene solutions: Distilled water (Control); 0.2% Sodium hypochlorite (SH); Efferdent Power Clean Crystals (EPC) and 6.25% Ricinus communis (RC). The viability of microorganisms was evaluated by agar plate counts. In parallel, physical, and mechanical properties of the acrylic resin were evaluated after simulating a 5-year period of daily immersion in the previously mentioned solutions. The changes in surface roughness, color, microhardness, flexural strength, impact strength, sorption and solubility were evaluated. Data were compared by ANOVA followed by the Tukey test or Kruskal-Wallis followed by the Dunn test depending on the distribution (α=0.05).

RESULTS

Regarding antibiofilm action, SH eliminated all microorganisms while EPC and RC exhibited moderate action against S. mutans (p=0.001) and C. glabrata (p<0.001), respectively. Relative to effects on the physical and mechanical properties of the acrylic resin, RC led to higher values of color change (p=0.030), hardness (p<0.001), surface roughness (p=0.006) and flexural strength (p<0.001). Moreover, RC induced the highest values of changes in solubility (p<0.001). EPC promoted greater changes in surface morphology, whereas immersion in SH retained the initial appearance of the acrylic resin surface. All hygiene solutions reduced the impact strength (p<0.05).

CONCLUSION

SH presented the most effective antibiofilm activity. In addition, changes on properties were observed after immersion in RC, which were considered within acceptable limits.

Anti candidal efficacy of commercially available triphala, neem, denture cleanser and natural aloevera leaf on heat polymerized acrylic resin

Aim:

The aim of the study was to evaluate the anticandidal efficacy of Triphala, aloe vera, Neem, and denture cleanser on heat polymerized acrylic resin.

Settings and Designs:

In vitro - experimental study.

Materials and Methods:

In this study, forty denture wearer patients were selected and were divided into four groups consisting of ten patients, namely, Group I, Group II, Group III, and Group IV, in which dentures were cleansed with denture cleanser (tablets), Triphala (churna), aloe vera (leaf), and Neem (tablets), respectively, and stored in copper containers. Swabs were collected from the dentures before and after the use of Denture cleanser, Triphala, aloe vera, and Neem. Thereafter, the swabs were cultured on Sabouraud dextrose agar and the total Candida counts (CFU/4 cm²) were determined.

Statistical Analysis Used:

One way ANOVA and Tukeys HSD post hoc test were used.

Results:

The pre- to post-reduction in mean Candida count was found highest in Denture cleanser followed by Neem, Triphala, and aloe vera. Further, both Denture cleaner and Neem showed statistically significant reduction (P < 0.001) in the mean Candida count when compared to Triphala and aloe vera. However, reduction in the mean Candida count of both Denture cleanser and Neem was found statistically similar (P > 0.05).

Conclusion:

The anticandidal efficacy of denture cleanser was found to be the highest. The cost-effective Neem can be used as anticandidal modality in place of denture cleanser.

Evaluating Polishability of Zirconia Impregnated PMMA Nanocomposite for Denture Base Application

Artificial biomaterials are being developed for use in denture base with symmetrical properties to restore the aesthetics and functionalities. The rough surface of denture base resin promotes the adhesion of microorganisms and plaque accumulation. This study aimed to explore the consequences of polishing times on the surface roughness of high-impact (HI) heat-polymerized PMMA denture base acrylic resin reinforced with zirconia nanoparticles (nanocomposite). Thirty specimens (25 ± 0.50 mm in diameter and 2 ± 0.10 mm thickness) were fabricated from HI PMMA by adding zirconia nanoparticles at different concentrations of (0 wt.%, 1.5 wt.%, 3 wt.%, 5 wt.%, 7 wt.%, and 10 wt.%). Specimens were divided into six groups (n = 5) and surface roughness (Ra) was measured before and after polishing with a standard protocol for one and two minutes. The addition of zirconia in PMMA at low concentrations (1.5 wt.%, 3 wt.%, and 5 wt.%) did not negatively affect the surface finish of the denture base composites following conventional polishing and remained below the clinically acceptable limit (0.2 µm). After one minute of polishing, only the 10 wt.% zirconia (0.17 ± 0.03 µm) demonstrated a substantial rise in median surface roughness, in comparison with the control group (0.11 ± 0.01 µm). It is concluded that the group containing 3 wt.% (0.10 ± 0.01 µm) of zirconia is the optimum concentration to obtain the best symmetrical surface finish after two minutes of polishing.

Evaluation of various denture cleansers on color stability and surface topography of polyetherketoneketone, polyamide, and polymethylmethacrylate

The aim of this study was to evaluate the effect of sodium perborate effervescent tablets and citric acid solution on the color stability and surface topography of a new generation of high-performance polymer polyetherketoneketone (PEKK), thermoinjection-molded polyamide, and polymethylmethacrylate (PMMA). Fifty disc-shaped specimens were fabricated (10 mm × 2 mm) from PEKK (P group), polyamide (D group), and PMMA (M group). These groups were divided into five subgroups (n = 10) according to the storage media. The test groups were immersed in the following solutions: distilled water (Control), Corega, Protefix, Perlodent, and Curaprox. The color stability values (ΔE) were measured using a spectrophotometer before and after immersion in distilled water and four different denture cleansers for 8 hr/day for 140 days. Topography alterations after treatments were assessed with scanning electron microscopy (SEM). Data were analyzed by one-way analysis of variance (ANOVA) followed by Tukey's Honest Significant Difference test. The p < .05 was considered significant. All denture cleansers increased the ΔE values relative to the baseline values in the M, D, and P groups (p < .05). The Perlodent denture cleanser demonstrated the highest ΔE value in all groups, which was unacceptable. Curaprox denture cleanser showed the lowest ΔE value in the M and D groups (p < .05). Curaprox in all groups showed a ∆E value less than 3.7. For patients who have PEKK- and polyamide-based prosthesis, the use of citric acid-based cleansers may be more recommended than sodium perborate-containing cleansers because of its clinically acceptable color changes on polymers in terms of color stability.

Assessment of surface roughness changes on orthodontic acrylic resins by all-in-one spray disinfectant solutions

Background. The disinfection of orthodontic acrylic resins might change the physical and mechanical properties of these materials. We aimed to investigate the impact of four different commercially available disinfectants on the surface roughness of acrylic resins used for orthodontic appliances.

Methods. Four disinfectant solutions (BirexSE, Opti-Cide3, COEfect MinuteSpray, and CaviCide Spray) were used to disinfect orthodontic acrylic resins using the spraying method. The resins were subjected to repeated disinfection protocols. Distilled water, also applied via spraying method, was used as a control. Surface roughness was scrutinized to examine the extent of surface topography changes by stylus profilometry. Data normality was evaluated via the Shapiro–Wilk test, followed by the Wilcoxon Signed-Rank test for non-parametric data or paired Student’s t-test for parametric data to compare intra-group differences in roughness before and after the use of the disinfectant solutions.

Results. Some of the disinfectants (BirexSE and CaviCide) resulted in significant changes in surface roughness values before and after the disinfection compared to the controls (P<0.05). The groups that were in contact with distilled water, Opti-Cide, and Coeffect did not exhibit significant differences in surface roughness before and after the intervention (P>0.05). However, from a clinical perspective, the resulting variations in surface roughness (<%0.15) induced by these solutions might not reflect clinically significant differences.

Conclusion. The use of disinfectant solutions is unlikely to harm the surface of orthodontic acrylic resins. Oral care providers need to be attentive to the interpretation and implementation of clinically significant changes in their evidence-based approach regarding potential material damages by disinfection sprays.

Effect of Disinfectants on Mechanical Properties of Orthodontic Acrylics

Objective

Infection control protocols in dentistry dictate that orthodontic acrylics have to be disinfected. No specific products for orthodontic acrylics are available. The objective of this study was to investigate the influence of chemical disinfectants on mechanical properties of orthodontic acrylics.

Materials and Methods

260 test specimens of two cold-curing orthodontic acrylics were manufactured. Three chemical disinfecting agents were tested: Impresept, D050 Instru-Gen, and Stammopur DR. Test specimens were stored in distilled water and divided into test groups. E-Modulus, flexural strength, macro hardness, micro hardness, average roughness, and colour change were measured.

Results

Disinfection agents showed no significant influence on E-modulus. Values ranged from 1783.80 ± 163.80 MPa (Forestacryl colourless) to 2474.00 ± 135.00 MPa (Orthocryl green) after storage in distilled water. Disinfection agents performed no significant influence on flexural strength. Values ranged from 18.64±1.59 N/mm² (Forestacryl colourless) to 25.64 ± 1.43 N/mm² (Orthocryl green) after storage in distilled water. Orthocryl colourless showed a reduction of the macro hardness after disinfection (Stammopur DR (p≤0.001), D050 Instru-Gen (p≤0.037)). Disinfection of Orthocryl green with D050 Instru-Gen (p<0.001) and Forestacryl colourless with Impresept (p≤0.001) led to a reduction of macro hardness. Micro hardness of Orthocryl colourless altered significantly after disinfection with D050 Instru-Gen (p≤0.001). Micro hardness of Forestacryl colourless increased (Impresept (p≤0.039)) and decreased (Stammopur DR (p≤0.006) Instru-Gen (p≤0.001)) after disinfection. Average roughness did not change significantly (Orthocryl colourless). Forestacryl colourless performed a significant change after disinfection with Stammopur DR (p≤0.05). This is also true for the disinfection of Orthocryl green and Forestacryl pink with Instru-Gen (p≤0.05). Disinfection performed no significant influence on colour change. ΔE-values were in a range of 1 to 2.

Conclusions

Some orthodontic acrylics disinfection caused significant changes of determined parameters. Changes were specific for the applied disinfectant and tested orthodontic acrylic. Further studies should verify the impact of long-term disinfection intervals. Thus, from manufacturers of orthodontic acrylics recommendations for appropriate disinfectants would be desirable.

Effect of Commercially Available Denture Adhesives on Microhardness of a Flexible Denture Base Material

BACKGROUND

Various clinical cases of thermopress denture base materials necessitate the use of denture adhesives to achieve proper retention and stability of the removable prosthesis. Therefore; the microhardness of these flexible materials as surface property and its' alterations due to the application of various denture adhesives are still crucial issues to be discussed.

AIM

This study aimed to investigate the impact of two commercially available denture adhesives (DAs) on microhardness of a flexible denture base material.

METHODS

A total of 30 duplicate disc specimens (DS) were fabricated from a thermoplastic injection moulded resin (TR). The obtained 30-disc specimens (DS) were stored in distilled water for seven days, and then their microhardness was measured using Knoop Hardness Test (KHN) under a 10 g load for 10 seconds. The denture adhesives were prepared, and 15 DS were immersed in Corega Super Cream, while the other 15 DS were soaked in Fitty Dent Cream. All DS were stored in distilled water at 37°C. After 30 days of immersion in DAs, microhardness of DS was again measured. T-test for paired observation was used to investigate any alterations in microhardness between the baseline and after 30 days of immersion in the DAs. Statistical analysis was performed with SPSS 20®, Graph Pad Prism® and Microsoft Excel 2016 with a significant level set at P ≤ 0.05.

RESULTS

Student`s t-test had revealed a significant difference between both groups after application of denture adhesive as a P value < 0.05. The obtained results showed that DA material type, flexible denture base material and their surface interaction provoke a statistically significant outcome on the mean microhardness.

CONCLUSIONS

DAs were found to affect the microhardness of thermoplastic injection moulded resin (TR); which may jeopardise the durability and serviceability of complete denture and patients' acceptance and comfortability.

Denture Liners: A Systematic Review Relative to Adhesion and Mechanical Properties

Purpose

The objective of this systematic review is to compare results concerning the properties of adhesion, roughness, and hardness of dental liners obtained in the last ten years.

Methods

Searches on the databases LILACS, PubMed/Medline, Web of Science, and Cochrane Database of Systematic Reviews were supplemented with manual searches conducted between February and April of 2018. The inclusion criteria included experimental in vitro and in vivo, clinical, and laboratory studies on resilient and/or hard liners, assessment of hardness, roughness, and/or adhesion to the denture base, and physical/mechanical changes resulting from the disinfection process and changes in liners' composition or application.

Results

A total of 406 articles were identified and, from those, 44 are discussed. Twenty-four studies examined the bond strength, 13 surface roughness, and 19 the hardness. Of these 44 studies, 12 evaluated more than one property. Different substances were used in the attempt to improve adhesion. Considering roughness and hardness, the benefits of sealants have been tested, and the changes resulting from antimicrobial agents' incorporation have been assessed.

Conclusion

Adhesion to the prosthesis base is improved with surface treatments. Rough surfaces and changes in hardness compromise the material's serviceability.

Effect of cleansers on denture base resins’ structural properties

Introduction:

We assessed the effect of different available denture cleansers on the roughness and hardness of polyetherketoneketone, thermoinjection-molded polyamide, and polymethylmethacrylate.

Materials and Methods:

A total of 150 disc-shaped specimens were fabricated (10 mm × 2 mm) from these three denture base resins, and divided into five subgroups ( n = 10) according to immersion procedures. One of these groups subjected to distilled water served as control, whereas other groups were subjected to daily cleansing with four denture cleansers (Corega, Protefix, Curaprox, and Perlodent) for 8 h a day for 140 days. The surface roughness and hardness values of specimens were recorded by measuring twice at baseline, and again after application of chemical solutions. Topography alterations after treatments were assessed with scanning electron microscopy. The data were subjected to statistical analysis and comparison among groups was done using Kruskal Wallis and Wilcoxon Signed Ranks tests. P-value <0.05 was considered significant.

Results:

The surface roughness of polyetherketoneketone, polymethylmethacrylate, and polyamide dentures was increased significantly by chemical solutions of denture cleansers. While the hardness value of polyetherketoneketone was not affected significantly after immersion in denture cleansers, those of polymethylmethacrylate and polyamide decreased significantly. Compared with Curaprox, the effervescent tablets significantly altered the surface hardness and roughness of polyamide.

Conclusion:

Denture cleansers can considerably alter the surface roughness and hardness of denture base resins and should be used carefully depending on the material.

Properties of an acrylic resin after immersion in antiseptic soaps: Low-cost, easy-access procedure for the prevention of denture stomatitis

Denture stomatitis triggered by Candida species requires better preventive measures. This study evaluated the physical and biological properties of a denture base acrylic resin after immersion in antiseptic soaps. Acrylic resin specimens were prepared and stored in distinct solutions for 0, 7, 14, 21, and 28 days. The solutions were as follows: DW: distilled water at 37°C (control group); DS: cycles of daily immersion in Dettol soap for 8 hours at room temperature, followed by immersion in distilled water for 16 hours at 37°C; PS: cycles of daily immersion in Protex soap, as described for the previous group; LS: cycles of daily immersion in Lifebuoy soap, as described for the DS group. The parameters evaluated at each time point were the following: biofilm formation capacity by Candida albicans and reduction of preformed fungal biofilms, cytotoxicity, surface roughness, hardness, and color change. For the fungal adhesion phase, the type of soap had a statistically significant effect (p = 0.0292), but after 24 hours, no differences were found between solutions or between storage times. Regarding the efficacy of biofilm reduction, there was a significant difference when the groups were compared to each other (p = 0.014). Dettol and Lifebuoy eliminated the preformed biofilm on the specimens. Moreover, all the soaps were classified as non-cytotoxic (on HaCaT cell line) because there was no difference in cell viability between the different groups, except after 21 days, when a decrease in cell viability occurred, regardless of the type of soap. Regarding the roughness, there was no statistically significant difference (p > 0.05) between the groups. Lifebuoy decreased resin hardness regardless of storage time (p = 0.003). After 21 and 28 days of storage, there was an increase in hardness value, regardless of the type of soap. The specimens’ color, according to the National Bureau of Standards values, ranged from 0.27 to 0.58 (i.e., imperceptible or mild color changes). In general, the disinfectant soaps were not able to prevent biofilm formation, but all the soaps were effective in reducing the preformed biofilm. In addition, all soaps were non-cytotoxic and did not change surface roughness, hardness (except Lifebuoy), and color (except Lifebuoy). Therefore, immersion in two antiseptic soaps (Protex and Dettol) may be a cheap and easy procedure for preventing denture stomatitis.

Superficial and Inner Examination of a Microwave-Irradiated Dental Acrylic Resin and Its Metal-Polymer Interface

The aim of this study is to conduct an extended surface and cross-section characterization of a denture base acrylic resin subjected to 500, 650, and 750 W microwave irradiation for 2, 3, and 5 min to assess its morphological modifications. A commercial heat-cured powder was polymerized according to the manufacturer's specifications and distributed into 20 circular samples. A stainless-steel wire was partially embedded in half of the discs, in order to investigate the metal-polymer interface. High-resolution scanning electron microscopy (SEM) imaging, white light interferometry, roughness measurements and Fourier transform infrared spectrometry were employed for morphological and structural evaluation of the irradiated polymer. Superficial adaptation was discovered after 5 min exposure at 500 W, 650 W, and 750 W, revealing significant roughness correction for 750 W. SEM characterization revealed the inner alteration of the resin for the 750 W protocol and a metal-polymer gap developed regardless of the irradiation conditions. The considerable temperature fluctuations that the samples were subject to during the experiments did not essentially change the poly(methyl-methacrylate) bond structure.

Evaluation of Surface Microhardness Following Chemical and Microwave Disinfection of Commercially Available Acrylic Resin Denture Teeth

INTRODUCTION

Denture disinfection is an indispensable procedure for preventing cross contamination and the maintenance of a healthy oral mucosa in patients rehabilitated with removable dental prosthesis. Nevertheless, they are known to cause changes in the physical and mechanical properties of denture base resins and acrylic resin denture teeth following immersion of a denture in a suitable chemical disinfectant solution or by undergoing microwave irradiation. One such mechanical property indicator for artificial tooth materials is hardness.

AIM

To assess the surface hardness of acrylic resin teeth of three different commercial brands (Ivoclar, Newace, Acryrock) following chemical (2% glutaraldehyde, 1% sodium hypochlorite) and microwave disinfections.

MATERIALS AND METHODS

Ten specimens of each of the three commercial brands were made for control and each simulated disinfection type and stored in distilled water at room temperature for 24 hours. After water storage, specimens were immersed in 2% glutaraldehyde and 1% sodium hypochlorite (one and three cycles) at room temperature for 10 minutes. Irradiation with microwave (one and three cycles) was done in domestic microwave for three minutes with the specimens immersed in 150 ml of distilled water. The specimens were stored in distilled water at room temperature for seven days after each disinfection cycle. Vickers hardness measurements were made using a hardness indenter under a load of 50 g force for 10 seconds. Data was subjected to repeated measure two-way ANOVA test and Tukey's test.

RESULTS

There were statistically significant differences for the variables disinfection, tooth, and cycle (p<0.05 for teeth & disinfectant interaction, p<0.05 cycle and disinfectant interaction). The mean surface hardness following one microwave disinfection cycle was lower than control, glutaraldehyde and sodium hypochlorite. Comparison among cycles revealed that microhardness was significantly decreased for three cycles of microwave disinfection.

CONCLUSION

It was concluded that there was no significant difference in microhardness when the teeth were subjected to chemical disinfection but three cycles of microwave disinfection produced decrease in the microhardness of different types of artificial teeth.

Impact of Denture Cleansing Solution Immersion on Some Properties of Different Denture Base Materials: An In Vitro Study

PURPOSE

To evaluate the effect of several denture cleansing solutions on the color stability, surface roughness, and flexural strength of three denture base materials.

MATERIALS AND METHODS

Twenty-seven specimens were prepared using heat-polymerized (HP) denture base material, 27 using autopolymerized (AP) denture base material, and 27 using visible-light-polymerized (VLP) denture base, creating a total of 81 specimens. The specimens were randomly divided into three groups (n = 27): the distilled water group (DWG), Corega group (CG), and Renew group (RG). Color changes (ΔE), surface roughness (Ra, nm), and flexural strength (MPa) of each specimen were measured using a spectrophotometer, an optical profilometer, and a universal testing machine, respectively. The results were statistically analyzed using a one-way ANOVA and a post hoc Tukey's test (α = 0.05).

RESULTS

The only statistically significant color change detected was in the VLP resin treated with Corega and Renew. There was a significant increase in the surface roughness of all denture resin groups after immersion in Corega. Immersion in Renew significantly increased surface roughness only in the HP and AP specimens. The only significant reduction in flexural strength was detected in the HP resin after immersion in Corega (p < 0.05).

CONCLUSIONS

Within the limitations of this study, it can be concluded that Corega has a significantly greater negative impact than distilled water on the flexural strength of HP resin base materials. Renew significantly increased the surface roughness of AP and HP, while Corega increased the surface roughness of all resin materials.

Effects of various denture cleansers on surface roughness of hard permanent reline resins

The aim of this study was to investigate the influence of denture cleansers on surface roughness (Ra, µm) of two hard permanent reline resins and a conventional acrylic denture base resin. Fifty specimens of each material, measuring 10 mm×2 mm were randomly divided into 1 control and 4 experimental subgroups (n=10). Surface roughness values were measured using profilometer before and after immersion in distilled water and in 4 different denture cleansers for 8 h for 140 days. The Kruskal Wallis and Wilcoxon Signed Ranks tests were used for comparison among groups with a significance level of α=0.05. Immersion in denture cleansers significantly increased the surface roughness of reline resins and the difference among the cleansers was statistically significant (p=0.059). Denture cleansers can cause significant surface roughness alterations on hard permanent reline resins and denture base resin where their effect may differ according to the selected resin material.

The Effect of Repeated Microwaving Disinfection on the Dimensional Stability of Acrylic Dentures

OBJECTIVE

The aim of this study was to evaluate the effect of repeated microwave disinfections on the dimensional stability of acrylic dentures.

MATERIALS AND METHODS

Three groups of dentures made of a heat polymerized acrylic resin were tested. I: dentures kept in water (control group). II: dentures microwaved daily while being immersed into water (wet disinfection). III: dentures microwaved daily without being immersed into water (dry disinfection).
Measurements were taken across three reference points, on two occasions: after curing and immersion in water for 24 hours, and one week later.
Data obtained were analyzed using one-way analysis of variance (ANOVA) and Scheffe's multiple range test.

RESULTS

The results showed that the microwave disinfection provokes dimensional changes of the same pattern (shrinkage). The dentures which underwent wet disinfection exhibited the greatest shrinkage (p<0.05).

CONCLUSIONS

Disinfection using microwave energy may cause dimensional changes (shrinkage) of complete dentures.
The microwave "dry disinfection" method can be safely applied in everyday practice since the dimensional changes which occurred seem to be of no clinical significance.

Effect of nanoscale particles incorporation on microhardness of polymers for oral prosthesis

Objectives:

This study aimed to evaluate the influence of the incorporation of pigments on surface hardness of four acrylic resins subjected to thermocycling and analyze their elemental composition using energy dispersive X-ray spectroscopy (EDS).

Materials and Methods:

Twenty-one discs of each resin were fabricated, whereas seven had no additive, seven had 3% of nanoscale pigments and last seven had 10% of them. The percentage was obtained by measuring the total weight of each resin disc. Besides, seven discs composed by only nanoscale pigments were also fabricated, totalizing 91 discs. The pigment was weighed by using an analytical balance (BEL Analytical Equipment, SP, Brazil). The surface hardness was measured through a hardness tester machine before and after thermocycling (5–55°C, for 2000 cycles). Data were analyzed by ANOVA and Tukey's test (P < 0.05). The chemical composition of the discs composed only by nanoscale pigments was analyzed with EDS test.

Results:

Hardness of all resins decreased after thermocycling. The lowest values were observed on the discs with 3% of nanoscale pigments and discs fabricated only with them. EDS showed the presence of titanium dioxide.

Conclusion:

Discs with 7% of pigments (after thermocycling) showed higher hardness values.

A Comparative Clinical Study of the Effect of Denture Cleansing on the Surface Roughness and Hardness of Two Denture Base Materials

AIM:

This study aimed to verify the influence of oral environment and denture cleansers on the surface roughness and hardness of two different denture base materials.

METHODS:

A total of sixteen identical removable disc specimens (RDS) were processed. Eight RDS were made from heat-cured acrylic resin (AR) and the other eight were fabricated from thermoplastic injection moulded resin (TR). Surface roughness and hardness of DRS were measured using ultrasonic profilometry and Universal testing machine respectively. Then the four RDS (two AR and two of TR) were fixed to each maxillary denture, after three months RDS were retrieved. Surface roughness and hardness of RDS have measured again.

RESULTS:

The surface roughness measurements revealed no significant difference (p >0.05) for both disc groups at baseline. However, both groups showed a significant increase in the surface roughness after three months with higher mean value for (TR) group. On the other hand, the (AR) group showed higher hardness mean value than (TR) group at baseline with no significant decrease in the hardness values (p >0.05) following three months follow-up period.

CONCLUSIONS:

Denture cleansers have an effect on the denture’s surface roughness and hardness concurrently with an oral condition which will consequently influence the complete dentures’ lifetime and patients’ satisfaction.

Effects of postpolymerization microwave irradiation on provisional dental acrylics: physical and mechanical properties

BACKGROUND

This study aimed to evaluate the effects of microwave irradiation on the physical and mechanical properties of poly(methyl methacrylate) (PMMA) provisional resins.

METHODS

Twenty bars and 20 disc-shaped specimens were fabricated for each selected provisional restorative material (Dencor and Duralay). Test groups were subjected to microwave irradiation (3 minutes at 600 W) after polymerization. Bar specimens were subjected to a flexural strength test. Disc-shaped specimens were used to evaluate microhardness. Backscattered Raman spectroscopy was employed for each group to define the degree of conversion of the monomer/polymer. The frequency bands corresponding to C = C and C = O groups were used to determine the conversion of methyl methacrylate (MMA) monomers into polymers. Glass transition temperature was determined using a differential scanning calorimeter.

RESULTS

Microwave irradiation of both tested autopolymerizing PMMA provisional materials resulted in a statistically significant increase in microhardness, degree of conversion and glass transition temperature values. Also, the results demonstrated a significant increase in flexural strength after postpolymerization microwave irradiation for the Dencor specimens.

CONCLUSIONS

It is concluded that mechanical and physical properties are positively influenced by microwave irradiation.

Evaluation of polymethyl methacrylate resin mechanical properties with incorporated halloysite nanotubes

PURPOSE

This study inspects the effect of incorporating halloysite nanotubes (HNTs) into polymethyl methacrylate (PMMA) resin on its flexural strength, hardness, and Young's modulus.

MATERIALS AND METHODS

Four groups of acrylic resin powder were prepared. One group without HNTs was used as a control group and the other three groups contained 0.3, 0.6 and 0.9 wt% HNTs. For each one, flexural strength, Young's modulus and hardness values were measured. One-way ANOVA and Tukey's test were used for comparison (P<.05).

RESULTS

At lower concentration (0.3 wt%) of HNT, there was a significant increase of hardness values but no significant increase in both flexural strength and Young's modulus values of PMMA resin. In contrast, at higher concentration (0.6 and 0.9 wt%), there was a significant decrease in hardness values but no significant decrease in flexural strength and Young's modulus values compared to those of the control group.

CONCLUSION

Addition of lower concentration of halloysite nanotubes to denture base materials could improve some of their mechanical properties. Improving the mechanical properties of acrylic resin base material could increase the patient satisfaction.

Effect of Disinfection on the Bond Strength between Denture Teeth and Microwave-Cured Acrylic Resin Denture Base

PURPOSE

Denture tooth debonding is a common complication for denture wearers; however, the effect of complete denture disinfection on bonding between denture teeth and acrylic resin remains unclear. The aim of this study was to evaluate the effect of disinfection methods on the bond strength between denture teeth and microwave-cured acrylic resin denture base.

MATERIALS AND METHODS

Three commercial brands of denture teeth (Trilux, Biolux, Vipi Dent Plus) and one microwave-cured acrylic resin denture base were tested. Each brand of denture teeth was divided into seven groups (n = 6; estimated by partial Eta squared). The specimenss of groups H and Cl were immersed in 1% sodium hypochlorite and 4% chlorhexidine digluconate for 7 days, respectively. In group Br, the specimens were subjected to toothbrush simulation under 200 g of force for 20,000 cycles. In groups Br-H and Br-Cl, the specimens were brushed and further disinfected with 1% sodium hypochlorite and 4% chlorhexidine digluconate, respectively. In control groups 1 (Co1) and 2 (Co2), the specimens were stored in distilled water for 50 ± 2 hours and 7 days, respectively. Shear bond strength testing was performed at the resin/tooth interface in a universal testing machine at a 1 mm/min crosshead speed. The failure pattern was quantified and classified into adhesive, cohesive, or mixed. Data were analyzed using two-way ANOVA and Tukey HSD test (α = 0.05).

RESULTS

Disinfection with 1% sodium hypochlorite (p = 0.031), brushing (p < 0.0001), and association of brushing with either 1% sodium hypochlorite (p < 0.0001) or 4% chlorhexidine digluconate (p = 0.01) reduced the bond strength between denture teeth and microwave-cured acrylic resin denture base. All commercial brands of denture teeth presented a similar bond strength (p > 0.05). The failure pattern was predominantly adhesive independent of the disinfection method and denture tooth brand.

CONCLUSIONS

Disinfection with sodium hypochlorite, brushing, and the association of mechanical and chemical methods reduced the bond strength between denture tooth and microwave-cured acrylic resin denture base.

Comparative evaluation of the effect of denture cleansers on the surface topography of denture base materials: An in-vitro study

Aims:

The aim was to evaluate and compare the effects of three chemically different commercially available denture cleansing agents on the surface topography of two different denture base materials.

Materials and Methods:

Three chemically different denture cleansers (sodium perborate, 1% sodium hypochlorite, 0.2% chlorhexidine gluconate) were used on two denture base materials (acrylic resin and chrome cobalt alloy) and the changes were evaluated at 3 times intervals (56 h, 120 h, 240 h). Changes from baseline for surface roughness were recorded using a surface profilometer and standard error of the mean (SEM) both quantitatively and qualitatively, respectively. Qualitative surface analyses for all groups were done by SEM.

Statistical Analysis Used:

The values obtained were analyzed statistically using one-way ANOVA and paired t-test.

Results:

All three denture cleanser solutions showed no statistically significant surface changes on the acrylic resin portions at 56 h, 120 h, and 240 h of immersion. However, on the alloy portion changes were significant at the end of 120 h and 240 h.

Conclusion:

Of the three denture cleansers used in the study, none produced significant changes on the two denture base materials for the short duration of immersion, whereas changes were seen as the immersion periods were increased.

Effects of thermal cycling on surface roughness, hardness and flexural strength of polymethylmethacrylate and polyamide denture base resins

BACKGROUND

The purpose of this study was to evaluate the effects of thermal cycling on the surface roughness, hardness and flexural strength of denture resins.

METHODS

Polyamide (PA; Deflex and Valplast) and polymethylmethacrylate (PMMA; QC-20 and Acron MC) denture materials were selected. A total of 180 specimens were fabricated and then divided into 3 groups. The first group (group 1) acted as a control and was not thermocycled. The second group (group 2) was subjected to thermocycling for 10,000 cycles in artificial saliva and 5,000 cycles in distilled water. The last group (group 3) was thermocycled for 20,000 cycles in artificial saliva and 10,000 cycles in distilled water. The surface roughness were measured with a profilometer. The hardness of the resins were measured with a Vickers Hardness Tester using a 100-gf load. The flexural strength test was performed using the universal test machine with a crosshead speed of 5 mm/min. Data were analyzed using statistical software. The results of the measurements in the 3 different tests were analyzed by Kruskal-Wallis test with Bonferroni correction. Multiple comparisons were made by Conover and Wilcoxon tests.

RESULTS AND CONCLUSIONS

There was a significant difference between the PMMA and PA groups in terms of surface roughness, hardness and transverse strength before and after thermal cycling (p&lt;0.001). Thermal cycling did not change the surface roughness, hardness and flexural strength values of either the PMMA or PA group (p&gt;0.001).