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

Comparative evaluation of the effects of laser and chemical denture disinfectants on the surface characteristics of CAD-CAM and conventional denture resins: An in vitro experimental study

PURPOSE

The purpose of this study was to assess the effect of Ga-Al-Ar diode, Nd:YAG lasers, and chemical disinfectants (NaOCl, vinegar, and Corega) on surface roughness (Ra) and hardness (VHN) of polymethylmethacrylate (PMMA), thermoplastic polyamide, milled and 3D-printed denture base resins.

MATERIALS AND METHODS

About 432 specimens of PMMA, thermoplastic polyamide, milled, and 3D-printed resins were divided into six subgroups (n = 18): distilled water (control:C), Ga-Al-Ar diode laser (L1), Nd:YAG laser (L2), 1% sodium hypochlorite (NaOCl), vinegar (AA), and Corega (CR). Each specimen's Ra and VHN were measured. Surface topography assessment was done using scanning electron microscopy (SEM). Analysis was done using ANOVA and post hoc Tukey's test (p = 0.05).

RESULTS

A significant difference was noted in Ra and VHN as affected by denture base materials, surface disinfectants, and their interaction (p < 0.001). Results showed a significant increase in Ra of PMMA with NaOCL (p < 0.001), AA (p = 0.005), and CR (p = 0.009), thermoplastic polyamide with L1 (p = 0.012), L2 (p = 0.015), NaOCL AA, and CR (p < 0.001 each), milled resin with AA NaOCL, and CR (p < 0.001 each), and 3D-printed resin with L1, NaOCl, AA (p < 0.001 each), and CR (p = 0.008). The VHN increased in PMMA with NaOCL (p < 0.001), AA (p = 0.044), and CR (p < 0.001), thermoplastic polyamide with L1 (p = 0.037), milled resin with L1, L2, and CR (p < 0.001 each), and 3D-printed resin with L1, NaOCl (p < 0.001 each), and decreased with CR (p = 0.007).

CONCLUSION

The tested properties showed variations affected by denture base material and surface disinfectants. Laser treatments induced smoother surfaces than chemical disinfectants. Laser improved the surface hardness of CAD-CAM resins, while chemical immersion improved that of PMMA.

Biofilm inhibition of denture cleaning tablets and carvacrol on denture bases produced with different techniques

OBJECTIVES

This study compares the biofilm inhibition effects of denture cleaning tablets, carvacrol, and their combined use against Candida albicans on denture bases produced with different techniques. Additionally, the surface roughness and contact angles of these denture bases were evaluated.

MATERIALS AND METHODS

Test samples were prepared from four different denture base materials (cold-polymerized, heat-polymerized, CAD/CAM milling, and 3D-printed). The surface roughness and contact angles of the test samples were measured using a profilometer and goniometer, respectively. For the evaluation of biofilm inhibition, samples were divided into 5 subgroups: Corega and carvacrol, separately and combined treatments, positive (inoculated with C. albicans) and negative control (non-inoculated with C. albicans, only medium). Biofilm mass was determined using the crystal violet method. An additional prepared test sample for each subgroup was examined under scanning electron microscopy (SEM).

RESULTS

The surface roughness values of the 3D-printed test samples were found to be statistically higher than the other groups (P < .001). The water contact angle of all test materials was not statistically different from each other (P > .001). Corega and carvacrol, separately and combined, significantly decreased the amount of biofilm on all surfaces (P < .0001). Treatment of corega alone and in combination with carvacrol to the 3D-printed material caused less C. albicans inhibition than the other groups (P < .001; P < .05).

CONCLUSIONS

The surface roughness values of all test groups were within the clinically acceptable threshold. Although Corega and carvacrol inhibited C. albicans biofilms, their combined use did not show a synergistic effect.

CLINICAL RELEVANCE

Carvacrol may be used as one of the disinfectant agents for denture cleaning due to its biofilm inhibition property.

Efficacy of denture cleansers on Candida albicans adhesion and their effects on the properties of conventional, milled CAD/CAM, and 3D-printed denture bases

OBJECTIVES

Evaluate the efficacy of denture cleaners on the adhesion of Candida albicans and their effects on the surface, optical, and mechanical properties of resins for conventional, milled, and 3D-printed denture bases.

MATERIALS AND METHODS

A total of 240 resin samples were made, 120 for testing Candida albicans adhesion, optical stabilities (ΔE00), roughness (Ra), hydrophilicity (°), surface free energy (Owens-Wendt) and 120 samples for testing Candida albicans adhesion, surface microhardness (Knoop), flexural strength and modulus of elasticity in a three-point test, in which they were divided into 3 groups of denture resin (n = 40) and subdivided into 5 cleaners of dentures (n = 8). Data were evaluated by two-way ANOVA and Tukey's test for multiple comparisons (α = 0.05).

RESULTS

Denture cleaners with an alkaline solution and dilute acid composition were those that showed the greatest effectiveness in reducing Candida albicans (P < 0.001), however 1% NaOCl significantly affected the properties of the resins (P < 0.05). Denture 3D-printed showed that the surface microhardness was significantly lower for all cleansers (P < 0.05).

CONCLUSIONS

Listerine demonstrated superior efficacy in reducing Candida albicans with minimal effect on denture properties, whereas 1% NaOCl had a significant negative impact on the properties. The mechanical properties were significantly lower in 3D-printed resin than in other resins for all denture cleansers.

CLINICAL RELEVANCE

Denture base materials are being sold to adapt to the CAD/CAM system, increasing the number of users of dentures manufactured with this system. Despite this, there is little investigation into denture cleaners regarding the adhesion capacity of microorganisms and the optical, surface and mechanical properties of dentures, thus requiring further investigation.

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.

Biofilm removal effect of diatom complex on 3D printed denture base resin

For patients who have difficulty in mechanical cleaning of dental appliances, a denture cleaner that can remove biofilm with dense extracellular polymeric substances is needed. The purpose of this study is to evaluate the efficacy of diatom complex with active micro-locomotion for removing biofilms from 3D printed dentures. The diatom complex, which is made by doping MnO2 nanosheets on diatom biosilica, is mixed with H2O2 to generate fine air bubbles continuously. Denture base resin specimens were 3D printed in a roof shape, and Pseudomonas aeruginosa (107 CFU/mL) was cultured on those for biofilm formation. Cleaning solutions of phosphate-buffered saline (negative control, NC), 3% H2O2 with peracetic acid (positive control, PC), denture cleanser tablet (DCT), 3% H2O2 with 2 mg/mL diatom complex M (Melosira, DM), 3% H2O2 with 2 mg/mL diatom complex A (Aulacoseira, DA), and DCT with 2 mg/mL DM were prepared and applied. To assess the efficacy of biofilm removal quantitatively, absorbance after cleaning was measured. To evaluate the stability of long-term use, surface roughness, ΔE, surface micro-hardness, and flexural strength of the 3D printed dentures were measured before and after cleaning. Cytotoxicity was evaluated using Cell Counting Kit-8. All statistical analyses were conducted using SPSS for Windows with one-way ANOVA, followed by Scheffe's test as a post hoc (p < 0.05). The group treated with 3% H2O2 with DA demonstrated the lowest absorbance value, followed by the groups treated with 3% H2O2 with DM, PC, DCT, DCT + DM, and finally NC. As a result of Scheffe's test to evaluate the significance of difference between the mean values of each group, statistically significant differences were shown in all groups based on the NC group. The DA and DM groups showed the largest mean difference though there was no significant difference between the two groups. Regarding the evaluation of physical and mechanical properties of the denture base resin, no statistically significant differences were observed before and after cleaning. In the cytotoxicity test, the relative cell count was over 70%, reflecting an absence of cytotoxicity. The diatom complex utilizing active micro-locomotion has effective biofilm removal ability and has a minimal effect in physical and mechanical properties of the substrate with no cytotoxicity.

Effects of three disinfection solutions on residual monomers released from resin nanoceramic CAD/CAM blocks

The aim of this study was to evaluate the effects of three disinfection solutions on the amount of monomers released from resin nanoceramic CAD/CAM blocks using high performance liquid chromatography (HPLC). Forty resin nanoceramic CAD/CAM (Cerasmart, GC, Japan) samples (12x14 × 2 mm) were divided into four groups; each group was disinfected using one of four solutions (Group 1: no disinfectant; Group 2: 70 % ethanol; Group 3: 2 % glutaraldehyde; and Group 4: 1 % sodium hypochlorite) for 5 min. Analysis of residual monomers (UDMA and Bis-EMA) amounts was performed using an HPLC instrument (Dionex Ultimate 3000, Thermo Fisher Scientific). After 30 days, the amounts of monomers found were as follows: 14.54 ppm for Group 1; 9.28 ppm for Group 2; 10.60 ppm for Group 3; and 2.76 ppm for Group 4 (the smallest monomer amount) (p < 0.001). Disinfection of indirect restorations prior to cementation can reduce the amount of residual monomers remaining from resin nanoceramic CAD/CAM blocks.

Effect of Denture Disinfectants on the Mechanical Performance of 3D-Printed Denture Base Materials

Denture care and maintenance are necessary for both denture longevity and underlying tissue health. However, the effects of disinfectants on the strength of 3D-printed denture base resins are unclear. Herein, distilled water (DW), effervescent tablet, and sodium hypochlorite (NaOCl) immersion solutions were used to investigate the flexural properties and hardness of two 3D-printed resins (NextDent and FormLabs) compared with a heat-polymerized resin. The flexural strength and elastic modulus were investigated using the three-point bending test and Vickers hardness test before (baseline) immersion and 180 days after immersion. The data were analyzed using ANOVA and Tukey's post hoc test (α = 0.05), and further verified by using electron microscopy and infrared spectroscopy. The flexural strength of all the materials decreased after solution immersion (p < 0.001). The effervescent tablet and NaOCl immersion reduced the flexural strength (p < 0.001), with the lowest values recorded with the NaOCl immersion. The elastic modulus did not significantly differ between the baseline and after the DW immersion (p > 0.05), but significantly decreased after the effervescent tablet and NaOCl immersion (p < 0.001). The hardness significantly decreased after immersion in all the solutions (p < 0.001). The immersion of the heat-polymerized and 3D-printed resins in the DW and disinfectant solutions decreased the flexural properties and hardness.