Evaluation of polymethyl-methacrylate and acetal denture base resins processed by two different techniques before and after nano-chlorohexidine surface treatment.

BACKGROUND: Flexible denture base polymers have gained popularity in modern dentistry however, their biofilm formation tendency, adversely affecting the oral tissue heath, remains a concern. Consequently, this study aimed to evaluate surface roughness and biofilm formation tendency of two types of denture base resins manufactured with two techniques before and after surface coating with chlorohexidine (CHX) NPs. MATERIALS AND METHODS: Acetal (AC) and Polymethyl-methacrylate (PMMA) resins manufactured by conventional and CAD/CAM methods were shaped into disk (10 X 10 X 1 mm). They were dipped for 8 h and 24 h in colloidal suspension prepared by mixing aqueous solution of CHX digluconate and hexa-metaphosphate (0.01 M). Surface roughness, optical density (OD) of microbial growth media and biofilm formation tendency were evaluated directly after coating. Elutes concentrations of released CHX were evaluated for 19 days using spectrophotometer. Three-way ANOVA and Tukey's post-hoc statistical analysis were used to assess the outcomes. RESULTS: AC CAD/CAM groups showed statistically significant higher roughness before and after coating (54.703 ± 4.32 and 77.58 ± 6.07 nm, respectively). All groups showed significant reduction in OD and biofilm formation tendency after surface coating even after 19 days of CHX NPs release. CONCLUSIONS: Biofilm formation tendency was highly relevant to surface roughness of tested resins before coating. After CHX NPs coating all tested groups showed significant impact on microbial growth and reduction in biofilm formation tendency with no relation to surface roughness. Significant antimicrobial effect remained even after 19 days of NPs release and specimens storage.

Surface, mechanical and chemical properties of modified denture resin using natural biopolymer.

Objective: This laboratory study determined the surface, mechanical and chemical properties of polymethyl methacrylate (PMMA) denture resin reinforced with micron-sized Gum Arabic (GA) powder in different weight ratios. Methods: This laboratory study was conducted at the Dental Health Department of the College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia from November 2022 to February 2023. Three experimental denture resins were prepared by incorporating GA powder in heat-polymerized PMMA powder using different wt.% (5, 10, and 20 wt.%). While pristine PMMA served as the control group. A total of ten bar-shaped specimens with dimensions of 65 mm × 10 mm × 3.5 mm were prepared for each study group. The surface properties (micro CT and SEM evaluation), mechanical properties (Nanohardness, elastic modulus and flexural strength) and chemical properties (FTIR) were conducted. The data were statistically analyzed using the one-way analysis of variance and Tukey's post hoc tests (p<0.05). Results: The surface and bulk properties of experimental GA-reinforced PMMA resin materials deteriorated while the mechanical properties were also negatively altered using GA-based PMMA denture resin. A linear correlation was observed between weak mechanical properties and increasing wt.% of GA in denture resin. Conclusions: The incorporation of GA powder in denture resin might not be a viable option. The surface and mechanical properties of experimental PMMA composites were adversely affected compared to the control group.

Evaluation of Surface Topography of Heat Cure Acrylic Denture-base Resin before and after Reinforcement with Different Fibers Using Stylus-based Profilometer.

AIM: The aim of this in vitro study was to evaluate the effect of glass and nylon fiber reinforcement on surface topography of polymethyl methacrylate (PMMA) denture resin after polishing. MATERIALS AND METHODS: Stainless steel dies were used for preparation of specimens and were divided into three groups of 30 specimens each. Group A: Control group, Group B: PMMA reinforced with glass fibers, Group C: PMMA reinforced with nylon fibers. All specimens were finished and polished by a single operator to eliminate any inadvertent bias and ensure a constant pressure when polishing. The surface roughness of all the acrylic samples was measured with the help of profilometer (SURFCOM 130A). RESULTS: Glass-reinforced PMMA showed higher mean surface roughness (0.16817 µm) as compared to unreinforced PMMA (0.10203 µm). Nylon-reinforced PMMA showed lower mean surface roughness (Ra) of 0.09177 µm as compared to unreinforced PMMM (0.10203 µm). Glass-reinforced PMMA showed a higher mean surface roughness (Ra) of 0.16817 µm as compared to nylon PMMA (0.09177 µm). CONCLUSION: Reinforcement with glass and nylon fibers affects the surface roughness of the PMMA resin, i.e., glass fibers increase the surface roughness of PMMA resin, whereas nylon fibers slightly decrease the surface roughness of PMMA resin. Hence, the use of nylon fiber may be justified to obtain a denture with increased fracture resistance, acceptable esthetic properties, and better denture hygiene and plaque accumulation. CLINICAL SIGNIFICANCE: Two important parameters are essential for ensuring the durability of a restorative material, which include surface roughness and color stability. Surface roughness may be the major cause of discomfort for the patient and it may be associated with complications by promoting the deposition of biofilm and microbial growth. The use of nylon fiber increases fracture resistance and provides acceptable esthetic properties and better denture hygiene and plaque accumulation.

Shear bond strength between CAD/CAM denture base resin and denture artificial teeth when bonded with resin cement.

PURPOSE: The bond strengths between resin denture teeth with various compositions and denture base resins including conventional and AD/CAM purposed materials were evaluated to find influence of each material. MATERIALS AND METHODS: Cylindrical rods (6.0 mm diameter × 8.0 mm length) prepared from pre-polymerized CAD/CAM denture base resin blocks (PMMA Block-pink; Huge Dental Material, Vipi Block-Pink; Vipi Industria) were bonded to the basal surface of resin teeth from three different companies (VITA MFT®; VITA Zahnfabrik, Endura Posterio®; SHOFU Dental, Duracross Physio®; Nissin Dental Products Inc.) using resin cement (Super-Bond C&B; SUN MEDICAL). As a control group, rods from a conventional heat-polymerizing denture base resin (Vertex™ Rapid Simplified; Vertex-Dental B.V. Co.) were attached to the resin teeth using the conventional flasking and curing method. Furthermore, the effect of air abrasion was studied with the highly cross-linked resin teeth (VITA MFT®) groups. The shear bond strengths were measured, and then the fractured surfaces were examined to analyze the mode of failure. RESULTS: The shear bond strengths of the conventional heat-polymerizing PMMA denture resin group and the CAD/CAM denture base resin groups were similar. Air abrasion to VITA MFT® did not improve shear bond strengths. Interfacial failure was the dominant cause of failure for all specimens. CONCLUSION: Shear bond strengths of CAD/CAM denture base materials and resin denture teeth using resin cement are comparable to those of conventional methods.

Suitability of the new Aryl-Ketone-Polymer indicated for removable partial dentures: Analysis of elastic properties and bond strength to denture resin.

Elastic properties of Aryl-Ketone-Polymer (UAKP) and tensile bond strength (TBS) to denture resin (PalaXpress) were tested. Indentation modulus (EIT) and indentation hardness (HIT) were measured via Martens hardness (n=10 specimens) with 4.2±0.6 kN/mm2 and 261±8 N/mm2 respectively. TBS was tested in dependence of different adhesives (visio.link (VL), Adhese Universal (AU), All-Bond Universal (ABU), CLEARFIL UNIVERSAL BOND (CUB), G-Premio BOND (GPB), iBOND Universal (IBU), ONE COAT 7 UNIVERSAL (OCU), Scotchbond Universal (SBU) and without adhesive (CG), n=18/group) and the application of opaquer (n=9/group) after thermocycling (5°C/55°C, 10,000×). TBS was affected by the adhesive (η (P2=0.715, p<0.001) followed by the opaquer (ηP2=0.335, p<0.001). VL and CG showed highest TBS followed by AU and ABU. IBU and GPB resulted in lowest TBS. Opaquer increased TBS for all adhesives (p<0.05), except VL and CG (p<0.258). Elastic properties are well-suited for the indication of removable partial dentures. Bonding to denture resin is no limiting factor.

Development of long-term antimicrobial poly(methyl methacrylate) by incorporating mesoporous silica nanocarriers.

OBJECTIVE: Poly(methyl methacrylate) (PMMA) used as removable denture bases or orthodontic appliances has relatively poor antimicrobial properties, which accelerate oral infection and induce unfavorable odors. Mesoporous silica nanoparticles (MSNs) have been highlighted as a potential additive to overcome this issue because of their drug-loading capacity. Here, we present the long-term antimicrobial effect of MSN-incorporated PMMA with drug-loading capacity. METHODS: After the MSNs were characterized, MSN incorporation into chemically activated PMMA (0.5, 1, 2.5 or 5wt%) relative to the methyl methacrylate powder by mass was fabricated into a rectangular specimen (1.4×3.0×19.0mm) for a 3-point flexural test at a speed of 1mm/min or a disk (∅=11.5mm and d=1.5mm) for investigation of its antimicrobial effects. RESULTS: A typical spherical morphology with a well-ordered mesoporous structure of the MSNs was visualized and is beneficial for loading drugs and combining in matrixes. Among the tested levels of MSN incorporation in PMMA (0.5, 1, 2.5 or 5wt%), only 5wt% decreased the flexural strength (p<0.05), whereas the flexural modulus was not significantly decreased (p>0.05). The surface roughness and surface energy were increased with 2.5wt% or 5wt% incorporation. An anti-adherent effect against Candida albicans and Streptococcus oralis after 1h of attachment was only observed with 2.5 and 5wt% incorporation compared to a lack of MSNs (p<0.05). A long-term antimicrobial effect was observed for 2 weeks with 2.5wt% MSN-incorporated PMMA when amphotericin B was loaded into the MSNs on the PMMA surface. SIGNIFICANCE: The long-term antimicrobial performance after loading amphotericin B into the MSN-incorporated PMMA suggests the potential clinical usefulness of MSN-incorporated PMMA resin.

Antifungal Effect of Henna against Candida albicans Adhered to Acrylic Resin as a Possible Method for Prevention of Denture Stomatitis.

Denture stomatitis is a very common disease affecting the oral mucosa of denture wearers. The aim of this study was to measure the antifungal effect of henna against Candida albicans adhered to acrylic resin as a possible method for prevention of denture stomatitis. One-hundred-eighty acrylic plates were prepared of heat-cured acrylic denture resin. The specimens were divided into six groups of 30 samples each. The first group was only polymer and monomer following the conventional manufacturer instruction for processing complete dentures. The other five groups were processed by adding different concentration of Yamani henna powder (Harazi) to the polymer in a concentration of henna: polymer 1%, 2.5%, 5%, 7.5% and 10%, respectively. Samples were incubated in artificial saliva rich with Candida albicans at 37 °C, and the effect of henna on Candida albicans was evaluated in two different methods: semi-quantitative slide count and a culture-based quantitative assay (quantitative). Variation in the number of live Candida was observed with the increase in the concentration of Yamani henna powder. It was observed that the variation in live Candida, between control group and group B (concentration of Yamani henna powder was 1%), was statistically significant with a p-value of 0.0001. Similarly, variations in live Candida were significant, when the concentration of powder was 7.5% or 10% in contrast with control group and p-values were 0.0001 and 0.001 respectively. Adding henna to acrylic resin denture could be effective in controlling Candida albicans proliferation on the denture surface; however, its effects on the physical properties of acrylic resin denture need further studies.

Determination of Candida species nestled in denture fissures.

With the growing number of elderly individuals, Candida is occasionally recognised as a fungal cause of aspiration pneumonia. In addition, there are numerous investigational reports on oral candidiasis. However, there are currently no reports on Candida contamination of denture base materials. This study was conducted to investigate Candida species in the oral cavity, denture parts and oral lesions of older/elderly subjects with oral candidiasis. The Candida strains were isolated and the species identified. Candida was also cultured in a medium with sample of denture resin and observed under an electron microscope. The results demonstrated the presence of several Candida species in the lesions of the oral mucosa and the surface and inner portions of the dentures. The following species of Candida were detected: Candida albicans, Candida glabrata, Candida tropicalis and Candida parapsilosis. Using electron microscopy, the invasion of Candida was observed in the incomplete polymerized resin base material and/or through microcracks (fissures) that have a tendency to form in used dentures. It was concluded that Candida may be present on the surface as well as the deeper portions of dentures. In addition, it appeared necessary to consider denture and oral cavity cleaning and the risks of remaking old dentures.