Jarosław Żmudzki

Antifungal Activity of Denture Soft Lining Material Modified by Silver Nanoparticles—A Pilot Study

Soft liner materials in oral cavity environments are easily colonized both by fungi and dental plaque. These factors are the cause of mucosal infections. The microorganism that most frequently colonizes soft liner materials is Candida albicans. Colonization occurs on the surface of materials and within materials. A solution to this problem might involve modification of soft liner materials with silver nanoparticles (AgNPs). In this article, we present results showing the antifungal efficacy of silicone soft lining materials modified with AgNPs. The modification process was conducted by dissolving both material components (base and catalyst) in a colloidal solution of AgNPs and evaporating the solvent. Composites with various AgNP concentrations (10, 20, 40, 80, 120 and 200 ppm) were examined. The in vitro antifungal efficacy (AFE) of composite samples was 16.3% to 52.5%.

Sorption, solubility, bond strength and hardness of denture soft lining incorporated with silver nanoparticles.

The colonization of denture soft lining material by oral fungi can result in infections and stomatitis of oral tissues. In this study, 0 ppm to 200 ppm of silver nanoparticles was incorporated as an antimicrobial agent into composites to reduce the microbial colonization of lining materials. The effect of silver nanoparticle incorporation into a soft lining material on the sorption, solubility, hardness (on the Shore A scale) and tensile bond strength of the composites was investigated. The data were statistically analyzed using two-way ANOVA and Newman-Keuls post hoc tests or the chi-square Pearson test at the p < 0.05 level. An increase in the nanosilver concentration resulted in a decrease in hardness, an increase in sorption and solubility, a decrease in bond strength and a change in the failure type of the samples. The best combination of bond strength, sorption, solubility and hardness with antifungal efficacy was achieved for silver nanoparticle concentrations ranging from 20 ppm to 40 ppm. These composites did not show properties worse than those of the material without silver nanoparticles and exhibited enhanced in vitro antifungal efficiency.

One versus two implant-retained dentures: comparing biomechanics under oblique mastication forces.

The results from clinical tests of single implant-retained dentures (SIDs) are quite promising. However, the biomechanics of SIDs are still insufficiently determined. The aim of the study was to compare the implant loads and pressures beneath one and two implant-retained dentures (TIDs) under oblique mastication forces. The finite element method was used to conduct a model analysis in order to compare loading of the denture attachment onto the implant that accompanies oblique mastication forces in the cases of SIDs and TIDs. The possibility of a denture detaching and sliding on the mucous membrane surface was simulated. The SID solution faced a more remarkable tilt in the direction of the mastication forces, a higher pressures on the mucous membrane surface, and higher implant loadings. The hingelike restraints in the TID favored utilization of the support in the posterior area. The higher pressure values for the SID can be confusing and could lead to inaccurate conclusions about the acceptability of the SID. In the TID, the same areas of the mucous membrane were persistently loaded, independent of the occlusal force direction. In contrast, in the SID the full freedom of rotational movement enhances alternating use of the mucous membrane. This finding explains the more frequent sores in the mucous membrane beneath the TID than beneath the SID.

Biomechanical factors related to occlusal load transfer in removable complete dentures

Owing to economic conditions, removable dentures remain popular despite the discomfort and reduced chewing efficiency experienced by most denture wearers. However, there is little evidence to confirm that the level of mucosal load exceeds the pressure pain threshold. This discrepancy stimulated us to review the current state of knowledge on the biomechanics of mastication with complete removable dentures. The loading beneath dentures was analyzed in the context of denture foundation characteristics, salivary lubrication, occlusal forces, and the biomechanics of mastication. The analysis revealed that the interpretation of data collected in vivo is hindered due to the simultaneous overlapping effects of many variables. In turn, problems with determining the pressure beneath a denture and analyzing frictional processes constitute principal limitations of in vitro model studies. Predefined conditions of finite element method simulations should include the effects of oblique mastication forces, simultaneous detachment and sliding of the denture on its foundation, and the stabilizing role of balancing contacts. This review establishes that previous investigations may have failed because of their unsubstantiated assumption that, in a well-working balanced occlusion, force is only exerted perpendicular to the occlusal plane, allowing the denture to sit firmly on its foundation. Recent improvements in the simulation of realistic biomechanical denture behavior raise the possibility of assessing the effects of denture design on the pressures and slides beneath the denture.

Influence of Model Discretization Density in FEM Numerical Analysis on the Determined Stress Level in Bone Surrounding Dental Implants

Influence of mesh density on the results of FEM model analysis of mechanical biocompatibility of dental implants has not been presented yet. Taking advantage of the Ansys v.11 software, carried out was an analysis in the linear elastic range level of stresses in bone tissue surrounding standard osseointegrated implant of complete denture, with a decreasing size of elements (thetragonal type SOLID 187) adjacent to cortical bone/implant interface,respectively 0.5, 0.3 and 0.1. Equivalent Huber-Mises’ stress value in the zone that is exposed to effort the most, and is located close to the edge of implant insertion into the cortex bone significantly increases along with mesh density from app. 60 MPa to 120 MPa for opposite models, because of the lack of convergence of stresses at this singularity point. Increase of mesh density leads to an overestimation of loading stresses values and furthermore to an unjustified increase of pillars’ diameter. At the other hand, too large elements might lead, through an underestimation of loading stress level, to overloading atrophy of bone tissue or to implant loss.

Strength analysis of a three-unit dental bridge framework with the Finite Element Method

PURPOSE The aim of the study was to analyse the strength of a prosthetic bridge with variable geometry in the connectors between the span and the retention elements on the pillar teeth crowns. METHODS Research was carried using the Finite Elements Method (FEM) on a model of the bridge in the anterior teeth arch in the field 21-22-23, obtained using a contact scanner and computer aided design (CAD) system, with four different cross-sectional areas of the connectors: 4.0, 5.0, 5.5, and 6.0 mm2. For that purpose, the impact of the properties of selected metal alloys on the deflection of the prosthesis was analysed. RESULTS On the basis of the analyses, it was found that when the loading force acted obliquely, the stress was 19% higher compared to the stress with a loading vertical force. In the case of connectors with the smallest cross-sectional area, the stress exceeded permissible value (with safety factor n = 2) for one of the alloys. CONCLUSIONS Deflection of the bridges tested changed depending on the connector cross-section and the elastic modulus of the selected material.

Effect of Storage in Distilled Water for Three Months on the Antimicrobial Properties of Poly(methyl methacrylate) Denture Base Material Doped with Inorganic Filler

The colonization of poly(methyl methacrylate) (PMMA) denture base materials by pathogenic microorganisms is a major problem associated with the use of prostheses, and the incorporation of antimicrobial fillers is a method of improving the antimicrobial properties of these materials. Numerous studies have demonstrated the initial in vitro antimicrobial effectiveness of this type of material; however, reports demonstrating the stability of these fillers over longer periods are not available. In this study, silver sodium hydrogen zirconium phosphate was introduced into the powder component of a PMMA denture base material at concentrations of 0.25%, 0.5%, 1%, 2%, 4%, and 8% (w/w). The survival rates of the gram-positive bacterium Staphylococcus aureus, gram-negative bacterium Escherichia coli and yeast-type fungus Candida albicans were established after fungal or bacterial suspensions were incubated with samples that had been previously stored in distilled water. Storage over a three-month period led to the progressive reduction of the initial antimicrobial properties. The results of this study suggest that additional microbiological tests should be conducted for materials that are treated with antimicrobial fillers and intended for long-term use. Future long-term studies of the migration of silver ions from the polymer matrix and the influence of different media on this ion emission are required.

Use of finite element analysis for the assessment of biomechanical factors related to pain sensation beneath complete dentures during mastication

Statement of problem. The pain commonly suffered by denture wearers during mastication is not documented in the objective biomechanical criteria for the pressure pain threshold. Purpose. The purpose of this finite element analysis study was to determine whether the pressures developed beneath a removable mandibular complete denture during mastication would exceed the average pressure pain threshold in patients for whom the denture foundation had an acceptable load‐bearing capacity. Material and methods. A patient with an acceptable load‐bearing denture foundation was modeled with finite element analysis. The denture/mucosa interface was modeled as a sliding or detaching interface. A convex mandibular residual ridge, resilient mucosa, and denture were modeled in computer‐aided design (CAD) software using curves and cross sections. A unilateral vertical occlusal load of 100 N was assumed only for model verification, and an oblique mastication load of 141 N was assumed for simulated mastication with balanced articulation. The nonworking‐side occlusal contact was simulated in 2 situations: prompt nonworking‐side occlusal contact and delayed nonworking‐side occlusal contact by setting an initial distance of 0.1 mm or 1 mm between the denture and a flat solid above the nonworking side. Results. The denture was held to the mucosa under vertical force and a maximum pressure of 203 kPa. The denture was tilted under an oblique mastication load and achieved stability through nonworking‐side occlusal contact. This means that the denture was supported not only by the denture foundation but also by the nonworking‐side occlusal contact and had a downwardly directed stabilizing reaction force. The denture was weakly supported on the delayed nonworking‐side occlusal contact compared with the prompt nonworking‐side occlusal contact and weakly supported on the denture foundation. In delayed nonworking‐side occlusal contact, the pressure beneath the denture was 783 kPa (>pressure pain threshold) compared with 484 kPa (<pressure pain threshold) in prompt nonworking‐side occlusal contact. Despite the lower reaction force of the foundation in delayed nonworking‐side occlusal contact, the pressure beneath the denture increased, indicating a reduction in the load transfer area due to the inclined position of the denture. Friction on the mucosal surface was over 14‐fold higher for the delayed nonworking‐side occlusal contact. Conclusions. The pressure beneath a removable mandibular complete denture exceeded the average pressure pain threshold and was supported with a large slide, which produced friction. Although the value of the load on the occlusal side did not change, the pressure under the denture increased and the force of nonworking‐side occlusal contact decreased because of increasing distance to nonworking‐side occlusal contact.

Relevance of Tongue Force on Mandibular Denture Stabilization during Mastication: Relevance of Tongue on Denture Stabilization

PURPOSE Tongue activity, involving stereognosis of denture position, food bolus distribution, and direct denture pressing, can affect the stability of removable mandibular dentures. Knowledge of details of tongue activity in patients with removable dentures could contribute to the development of training methods to improve bilateral mastication. The hypothesis of this study was that tongue force improves mandibular complete denture stabilization on the atrophied foundation during mastication load transfer with a typical balanced occlusion. MATERIALS AND METHODS Finite element analysis was used to assess the effect of tongue activity on denture stability, which was evaluated with objective biomechanical criteria. Denture movement (displacement), sliding distance on the mucosal surface, and pressure on the foundation during occlusal load transfer were considered with and without additional tongue forces. RESULTS Tongue force in the canine zone of the balancing flange contributed to a slight reduction in the sliding distance. An adverse effect of tongue force on the working side and in the posterior zone of the balancing side was found. CONCLUSIONS Despite the lack of substantial improvement in stability with the addition of tongue forces, tongue action that contributes to a slight reduction in sliding may help reduce common frictional trauma resulting from cyclic movement during chewing. The beneficial impact of tongue force shown in earlier work under conditions of complete adherence of dentures to the foundation indicates a benefit of using adhesives.

Computer Aided Alternative Methods of Dental Implants Placement

Final product of computer aided dental implants placements is an object created by means of Rapid Prototyping (RP) – surgical template. An essential condition that makes utilization of this special technique possible is computer tomography (CT), which has to be carried out first. Radiation might be in some cases inadvisable, not possible or not necessary. In this work presented are possibilities of using standard CAD techniques for the purposes of planning and assisting of dental implantology treatment based on introduced into a CAD software prosthetic foundation topography and a standard panoramic radiograph.