Surface Of Denture Base Research Articles

Effect of Duplication Techniques on the Fitting Accuracy of CAD-CAM Milled, 3D-Printed, and Injection-Molded Mandibular Complete Denture Bases.

Digital technology has been introduced in prosthodontics, and it has been widely used in denture duplication instead of a conventional denture duplication technique. However, research comparing different denture duplication techniques and how they affect the fitting accuracy of the denture base is scarce. The aim was to assess the impact of duplication techniques on the accuracy of the fitting surface of computer-aided design and manufacturing (CAD-CAM) milled, 3D-printed, and injection-molded complete denture bases (CDBs). This study involved fabricating a mandibular complete denture base with three marked dimples as reference marks (A, B, and C at the incisive papilla, right molar, and left molar areas) using a conventional compression molded technique. This denture was then scanned to generate a standard tessellation language (STL) file; after that, it was duplicated using three different techniques (milling, 3D printing, and injection molding) and five denture base resin materials-two milled CAD-CAM materials (AvaDent and IvoBase), two 3D-printed materials (NextDent and HARZ Labs), and one injection-molded material (iFlextm). Based on the denture base type, the study divided them into five groups (each with n = 10). An evaluation of duplication accuracy was conducted on the fitting surface of each complete denture base (CDB) using two assessment methods. The first method was a two-dimensional evaluation, which entailed linear measurements of the distances (A-B, A-C, and B-C) between reference points on both the scanned reference mandibular denture and the duplicated dentures. Additionally, a three-dimensional superimposition technique was employed, involving the overlay of the STL files of the dentures onto the reference denture's STL file. The collected data underwent statistical analysis using a one-way analysis of variance and Tukey's pairwise post hoc tests. Both evaluation techniques showed significant differences in fitting surface accuracy between the tested CDBs (p ˂ 0.001), as indicated by one-way ANOVA. In addition, the milled CDBs (AvaDent and IvoBase) had significantly higher fitting surface accuracy than the other groups (p ˂ 0.001) and were followed by 3D-printed CDBs (NextDent and HARZ Labs), while the injection-molded (iFlextm) CDBs had the lowest accuracy (p ˂ 0.001). The duplication technique of complete dentures using a CAD-CAM milling system produced superior fitting surface accuracy compared to the 3D-printing and injection-molded techniques.

Investigation the Effect of Different Oils as Separating Medium on Surface Roughness and Hardness of Tissue Surface of Flexible Denture Base

Background: Flexible dentures (thermoplastic material) are ideal alternatives to traditional methyl methacrylate dentures, since they not only give exceptional aesthetics and comfort, but also adapt to the continual movement of partially edentulous patients. During the manufacturing of acrylic denture base material, an effective separating medium must be used to separate the denture cleanly from the plaster to avoid direct contact between the denture base material and the mould surface.
 Objective: The goal of this study was to investigate the effect of several types of oil (glycerin oil, olive oil, and black castor oil) on the surface roughness and hardness of flexible denture base material compared with cold-mould seal separating medium.

Accuracy and retention of denture bases fabricated by injection molding, milling, and three-dimensional printing

Objective: To compare the accuracy and retention of denture bases fabricated by injection molding, milling, and three-dimensional (3D) printing fabricating, in order to provide some references for clinical practice. Methods: A maxillary edentulous jaw model made was used to duplicated 10 working casts. The casts were numbered and scanned. The wax pattern was designed by digital ways and conventional methods and then the denture bases were fabricated by injection molding, milling, and 3D printing. The tissue surface of experimental denture base was obtained using a dental laboratory scanner. The deviation between the tissue surface of the fabricated denture bases and the working model was evaluated. A digital force gauge was used to measure the traction force. Results: The milling group [(0.076±0.026) mm] was more accurate than the 3D printing group [(0.117±0.041) mm] (P<0.05) and the injection group [(0.120± 0.025) mm] (P<0.05). The accuracy of 3D printing group and that of injection group were not statistically significant (P>0.05). The milling group [(9.55±2.44) N] demonstrated greater retentive force than 3D printing group [(5.19±0.06) N] and injection molding group [(1.52±0.52) N] (P<0.05). Conclusions: The denture base fabricated by milling was more accurate and showed the greatest retentive force than the other groups. And 3D printing group showed better retentive force than the injection molding group. Both digital manufacturing methods can meet the requirements of clinical application.

Comparison of Tensile Bond Strength of Permasoft® and GC Reline Soft® Resilient Liners after Denture Base Surface Pretreatment

Objectives: The surface treatment of intaglio denture base surface by sandblasting followed by Methyl Methacrylate (MMA) monomer might enhance the bond strength of resilient liners. The purpose of this study was to evaluate and compare Tensile Bond Strength (TBS) of two resilient liners after surface treatment of Polymethyl Methacrylate (PMMA) resins by sandblasting and MMA monomer. Materials and Methods: One hundred and sixty PMMA resin blocks were randomly divided into eight groups of 20 blocks each based on type of resilient long term liner used (P=PermaSoft and G=GC Reline Soft) and the surface treatment performed (C=untreated Controls, S=Sandblasted, M=MMA monomer treated and SM=Sandblasted and MMA monomer treated: Group PC (PermaSoft untreated Controls), PS (PermaSoft Sandblasted), PM (PermaSoft MMA monomer treated) and PSM (PermaSoft Sandblasted and MMA monomer treated, GC (GC Reline Soft untreated Controls), GS (GC Reline Soft Sandblasted), GM (GC Reline Soft MMA monomer treated) and GSM (GC Reline Soft Sandblasted and MMA monomer treated). Each specimen was prepared by joining two PMMA resin blocks having standard dimensions of 10 × 10 × 40mm with either of the resilient liner of thickness of 10 × 10 × 3mm. The prepared 80 specimens were subjected to testing of TBS by universal testing machine. Also, the types of failure, whether adhesive, cohesive or mixed, were determined by stereomicroscope. One-way ANOVA followed by Tukey post hoc test was used to compare TBS of different surface treatment group with similar resilient liner. Student T-test was used to compare TBS of different resilient liner with similar surface treatment. The level of significance was set at 0.05. Results: There was highly significant difference in mean TBS of four surface treatment subgroups within both the groups (P&lt;0.001). The Tukey post hoc test showed significant difference (P&lt;0.05) between group PC=0.837 ± 0.120MPa and PSM=1.104 ± 0.234MPa; and GS=1.304 ± 0.261MPa and GM=2.053 ± 0.784MPa and highly significant difference (P&lt;0.001) between group PS=0.741 ± 0.103 MPa) and PSM=1.104 ± 0.234MPa); and GS=1.304 ± 0.261MPa) and GSM=2.176 ± 0.262MPa. The mean TBS of GC Reline Soft was significantly higher (&lt;0.001) than PermaSoft in various surface treatment groups. The overall modes of failures were predominantly cohesive type (63.75%) followed by mixed type (18.75%) and adhesive type (17.50%). Conclusions: All groups tested had mean bond strength values greater than the minimum acceptable standard (0.44MPa) for clinical application. MMA monomer treatment alone or in combination with sandblasting resulted in increase of the mean TBS whereas sandblasting resulted in decrease of the mean TBS of both PermaSoft and GC Reline Soft specimens.

Effect of post-rinsing time and method on accuracy of denture base manufactured with stereolithography.

PURPOSEThis in vitro study investigates the effect of different post-rinsing times and methods on the trueness and precision of denture base resin manufactured through stereolithography.MATERIALS AND METHODSNinety clear photopolymer resin specimens were fabricated and divided into nine groups (n = 10) based on rinsing times and methods. All specimens were rinsed with 99% isopropanol alcohol for 5, 10, and 15 min using three methods-automated, ultrasonic cleaning, and hand washing. The specimens were polymerized for 30 min at 40℃. For trueness, the scanned intaglio surface of each SLA denture base was superimposed on the original standard tessellation language (STL) file using best-fit alignment (n = 10). For precision, the scanned intaglio surface of the STL file in each specimen group was superimposed across each specimen (n = 45). The root mean square error (RMSE) was measured, and the data were analyzed statistically through one-way ANOVA and Tukey test (α < .05).RESULTSThe 10-min automated group exhibited the lowest RMSE. For trueness, this was significantly different from specimens in the 5-min hand-washed group (P < .05). For precision, this was significantly different from those of other groups (P < .05), except for the 15-min automated and 15-min ultrasonic groups. The color map results indicated that the 10-min automated method exhibited the most uniform distribution of the intaglio surface adaptation.CONCLUSIONThe optimal postprocessing rinsing times and methods for achieving clear photopolymer resin were found to be the automated method with rinsing times of 10 and 15 min, and the ultrasonic method with a rinsing time of 15 min.

Effect of Thermocycling on Surface Roughness and Shear Bond Strength of Acrylic Soft Liner to the Surface of Thermoplastic Acrylic Treated with Ethyl Acetate

Objective: To enhance bonding strength between thermoplastic denture base and acrylic soft liner through ethyl acetate surface treatment.Materials and Methods: Modifications of thermoplastic acrylic denture base surface were investigated with SEM. FTIR was used to detect whether there was a chemical bond between thermoplastic acrylic and the organic solvent. A total of 80 samples were prepared and divided into 20 samples for the surface roughness test and 60 samples for the shear bond strength test. Failure type was assessed visually.Results: Shear bond strength and surface roughness values of un treated samples were lower in comparison to surface treated groups; the greatest post thermocycling bond strength value was recorded for the samples treated with ethyl acetate following 1500 cycles.Conclusions: Bonding strength was improved following ethyl acetate surface treatment.

Phonetic contouring of polished surface of denture base for speech enhancement

The three main factors in complete denture construction are mechanics, esthetics, and phonetics. Out of which phonetics is generally given least importance as the tongue tends to adapt and patients tend to return to normal speech after a post insertion practice period of several weeks to several months. This may not be acceptable to certain group of people in accordance with their needs to speak socially or vocationally. An accurate approximation of palatal contours of a maxillary complete denture to patient’s tongue can improve intelligibility and decrease the post- insertion practice period. This article outlines a technique to replicate the patient’s palatal anatomy onto the polished palatal surface of a complete denture.

Fibrin Biopolymer Incorporated with Antimicrobial Agents: A Proposal for Coating Denture Bases.

The characteristics of the denture base surface, in combination with the oral environment, promote the colonization and development of Candida albicans biofilm, which is the main cause of denture stomatitis. This study evaluated the effectiveness of fibrin biopolymer with digluconate chlorhexidine or Punica granatum alcoholic extract to prevent C. albicans biofilm. Conventional heat polymerized and pre-polymerized poly(methyl methacrylate) (PMMA) circular specimens (10 × 2 mm) were fabricated (n = 504) and randomly divided into groups: no treatment (control—CT), fibrin biopolymer coating (FB), fibrin biopolymer with P. granatum (FBPg), or digluconate of chlorhexidine (FBCh) coating. The specimens were inoculated with C. albicans SC5314 (1 × 107 cells/mL) and incubated for 24, 48, and 72 h. Crystal violet and colony-forming unit assays were used to quantify the total biofilm biomass and biofilm-living cells. A qualitative analysis was performed using confocal laser scanning microscopy. Data obtained are expressed as means and standard deviations and were statistically analyzed using a three-way analysis of variance (α = 0.05). The FBPg and FBCh groups inhibited the growth of C. albicans biofilm in both PMMA materials analyzed, with FBCh performing better in all periods evaluated (p < 0.0001). The colony forming unit (CFU) assay showed that the FB group favored the C. albicans biofilm growth at 24 h and 48 h (p < 0.0001), with no differences with CT group at 72 h (p = 0.790). All groups showed an enhancement in biofilm development up to 72 h (p < 0.0001), except the FBCh group (p = 0.100). No statistical differences were found between the PMMA base materials (p > 0.050), except in the FB group (p < 0.0001). Fibrin biopolymer, albeit a scaffold for the growth of C. albicans, when combined with chlorhexidine digluconate or P. granatum, demonstrated excellent performance as a drug delivery system, preventing and controlling the formation of denture biofilm.

Mandibular residual ridge morphology in relation to complete dentures and implant overdentures-Part I: Predictors for perceived conventional denture stability.

There is lack of reliable predictors for success of conventional complete denture (CCD) therapy, which in turn might affect the effectiveness of subsequent implant-retained overdenture (IOD) therapy. To investigate relationships between digitally obtained geometrical mandibular residual ridge measures and perceived CCD-stability. 30 CCD wearing patients (67.9 ± 7.0 years) for whom a new set of CCDs was advised, were treated with new CCDs. Digitalized mandibular gypsum models were measured using the Geomagic Studio 2013 software. Data were obtained for (1) height, width, and cross-section surface area of the residual ridge at different locations (midline, premolar, and anterior edge of retromolar pad) and (2) denture base surface area. Scatter plots and multivariate regression analyses were used to investigate associations between the geometric data and denture base surface area, and correlated with denture stability scores (Spearman rank test). Scatter plots showed that best model fit for denture base surface area was mean ridge height (R2 = 0.906). Multivariate regression showed that height at premolar location (p = 0.001) had largest effect on denture base surface area (R2 = 0.796). Ridge morphology variables, except width at midline location, were significantly correlated with CCD-stability (p-values <0.05). CCD-stability was significantly correlated with denture base surface area (p ≤ 0.001). Residual ridge height at premolar location was most predictive for denture base surface area and perceived CCD-stability.

Evaluation of trueness in a denture base fabricated by using CAD-CAM systems and adaptation to the socketed surface of denture base: An in vitro study

Statement of problemComputer-aided design and computer-aided manufacturing (CAD-CAM) systems are increasingly used to fabricate removable complete dentures. However, comparisons and analyses of the trueness and adaptation of the socketed surface of denture bases produced by milling (MIL) and digital light processing (DLP) are lacking. PurposeThe purpose of this in vitro study was to evaluate and compare the trueness and socketed surface adaptation of denture bases fabricated by using additive and subtractive manufacturing. Material and methodsBased on a denture base standard tessellation language (STL) file, a total of 15 denture bases were produced by using DLP (horizontal and vertical direction) and MIL. The intaglio and cameo surfaces of the fabricated denture bases were scanned with a dental scanner. The scanned intaglio and cameo surfaces were overlapped with the corresponding reference denture base STL file for trueness evaluation. In addition, the ridge lap STL file of the diagnostic tooth arrangement, in which reverse normal was performed, was superimposed on the socketed surface of the denture base of all groups to evaluate adaptation. ResultsThe root mean square (RMS) values of trueness and adaptation showed statistically significant differences (P<.05). For the trueness RMS value of the intaglio surface of the denture base, the MIL-denture base (MDB) group had the lowest value of 150 ±6 μm, whereas the vertical denture base (VDB) of the DLP group was the largest with 328 ±4 μm. For the trueness RMS value of the cameo surface, the MDB group was the lowest with 50 ±1 μm, whereas the VDB group was the largest with 334 ±24 μm. For the adaptation RMS value of the socketed surface of the denture base, the MDB group was the lowest with 44 μm, whereas the VDB group was the largest with 117 ±2 μm. ConclusionsWithin the limits of this in vitro study, the MDB group showed better trueness and socketed surface adaptation than the DLP groups (HDB and VDB).

The effect of some antifungal agents and chlorhexidine on Candida albicans adherence on acrylic resin denture base surface (In vitro study)

The adherence of Candida albicans on acrylic resin denture base surface is co-nsidered as the first step in the pathogeni-city of candida–associated denture stoma-titis which is the most prevalent form of oral candidiasis in denture wearers. This study was an in vitro study aimed to eval-uate the anifungal effect of fluconazole, nystatin and chlorhexidine and their anti-adherent effect on Candida albicans cells that attached on the fitting surface of den-ture base. It was determined, using broth microdilution method at two concentra-tions for each drug, and the results were determined using spectrophotometer. All drugs had a highly significant antifungal effect on Candida albicans isolate at their two concentrations. The effect of saliva on the adherence of Candida albicans on the fitting surface of denture base was also considered. This study concluded the importance of saliva in increasing the microbial adherence; i.e., the mean number of adherent cells on ac-rylic resin samples in the absence of saliva was 7.4 + 1.9 cell/mm2 and with the pre-sence of saliva the number was 29.1 + 2.7 cells/mm2. The number of remaining adh-erent cells was counted using fluortescent microscope. The mean number of remain-ing cells which adhered on acrylic resin samples after the immersion in first con-centration fluconazole, nystatin and chlorhexidine for one hour respectively were 4, 5 and 2.6 cells/mm2 and for the second concentration/1 hour the numbers were 3.2, 4.1 and 1.7 cells/mm2 compared to the normal number of adherent cell 29.1 + 2.7 at p<0.01.

Current perspectives and the future of Candida albicans-associated denture stomatitis treatment.

Denture stomatitis (DS) is a multifactorial disease, but the proliferation of Candida albicans (C. albicans) is the main causative factor. Different modalities have been suggested for the prevention and treatment of DS. Among the different approaches that have been implemented to inhibit and control DS there are the topical application of antifungal agents, the surface modification of the denture base and the incorporation of antimicrobial agents into the denture base material. Antifungal agents can effectively control DS, but the recurrence of the disease is common. Accordingly, it has been suggested that coating the surface of the acrylic denture base may result in a decreased fungal adhesion. In recent years, nanotechnology has dominated the research, and several nanoparticles have demonstrated antifungal effects. Therefore, the aim of this article was to review the antifungal effects of the different methods that have been suggested for the prevention and/or control of DS as well as the antimicrobial activity of denture base acrylic resin additives, including nanoparticles. Studies reporting the incorporation of antifungal/antimicrobial agents into the polymethyl methacrylate (PMMA) denture base were included in this review. The PubMed, Web of Science, Google Scholar, and Scopus databases were searched for the articles published between January 2000 and December 2018 using the following key words: dental prosthesis, denture stomatitis, candidiasis, antifungal agents, biofilm formation, polymethyl methacrylate, and PMMA. The antimicrobial material incorporated into the resin may have a superior effect in preventing DS over simply coating the surface of the denture base. However, some antimicrobial fillers can have adverse effects on the physical and mechanical properties of the denture base resin.

The Effect of Essential Oils on Microbial Biofilm on Denture Base Surface

The Effect of Essential Oils on Microbial Biofilm on Denture Base Surface

A study to compare adhered oral flora to soft liner and conventional denture base surface in complete denture patients

Background: Denture base materials are subjected to sorption, a process of absorption and adsorption of liquids depending on the environmental conditions, also their fitting surface is subjected to microbial adhesion due to surface irregularities. Soft silicon liners are usually used with removable appliances to decrease load concentration on the hard and soft tissues. Silicon liners also undergo fluid sorption and microbial adhesion.Aim: This study was carried out to assess the effect of standardizing the oral hygiene conditions on the microbial load difference between conventional acrylic denture bases and silicon soft relining material (Mucopren soft) used to reline mandibular complete dentures in atrophied mandibles. Methods: Conventional complete dentures were constructed for 25 patients with flat atrophic mandibular ridges to be used for two weeks, salivary swabs were collected to evaluate oral flora attached on the fitting surface of the denture base and the buccal vestibule, soft liner was applied for all patients mandibular denture surfaces and the same approach was repeated after two weeks of the liner use. Results: Microbial load was found to be significantly higher in the fitting surfaces of the silicon soft liner, than in the conventional acrylic base fitting surfaces.Conclusion: Even under controlled oral conditions, Mucopren soft silicon liner incorporates greater microbial load than acrylic material thus, subjecting patients to numerous infections.

The effect of build angle on the tissue surface adaptation of maxillary and mandibular complete denture bases manufactured by digital light processing

Statement of problemThe effect of different build angles on the tissue surface adaptation of complete denture bases manufactured by digital light processing (DLP) is unclear. PurposeThe purpose of this in vitro study was to evaluate the effect of build angle on the tissue surface adaptation of DLP-printed complete denture bases. Material and methodsBoth maxillary and mandibular denture bases were virtually designed based on reference casts and fabricated by the DLP technique. For each arch, a total of 40 denture bases were fabricated with 4 different build angle conditions (90, 100, 135, and 150 degrees) and divided into 4 groups (90D, 100D, 135D, and 150D; 10 denture bases per group). The scanned intaglio surface of each DLP denture base was superimposed on the scanned edentulous area of the reference cast to compare the degree of tissue surface adaptation. Root-mean-square estimate, positive average deviation, and negative average deviation values were measured and displayed with a color deviation map. The Mann-Whitney test and Kruskal-Wallis analysis of variance were used for statistical analyses (α=.05). ResultsNo statistically significant differences were found for root-mean-square estimate values among any build angle groups in either the maxillary or mandibular arch. With the increase of build angles, the area of positive deviation in the maxillary arch moved from the palatal region to the posterior palatal seal area, and negative deviation became pronounced at the posterior tuberosity. In the maxillary arch, the 135D group showed favorable color distribution of surface deviation. In the mandibular arch, a positive deviation was detected at the labial slope to the crest of the ridge, whereas a negative deviation was observed at the buccal shelf and the retromolar pad. The 100D group showed favorable distribution of surface deviation in the mandible. ConclusionsIn both arches, the difference of overall tissue surface adaptation was not statistically significant in the 4 different build angles. However, the color deviation map revealed that the 135-degree build angle may be appropriate in the maxillary DLP-printed denture base and the 100-degree angle, in the mandibular denture base.

Effect of chitosan nanoparticles on the inhibition of Candida spp. biofilm on denture base surface

ObjectivesChitosan nanoparticles (ChNPs) have antifungal effects, however there is a lack of information about the effects of ChNPs against Candida biofilm on denture base surface. This study investigated the ChNPs effect against C. albicans biofilm adhesion and formation, and against Candida spp. biofilm on heat-cured acrylic resin. DesignThe ChNPs were synthetized (3800 μg/mL) and characterized by infra-red spectrophotometry and transmission electron microscopy. The minimum inhibitory/fungicidal concentrations (MIC/MFC) against Candida spp. were determined. The time-kill assay and changes on C. albicans micromorphology were evaluated. The % inhibition of ChNPs on C. albicans biofilm formation and reduction were investigated using 1 min and 8 h exposure. Candida biofilm was developed on resin surfaces and ChNPs were applied every 8 h for 5 days. After, fungal cells were counted (CFU/mL) and the surface roughness (Ra) and vickers microhardness (HV) of resin were analysed. For all experiments, sodium hypochlorite (NaOCl) was used as control. Data were analyzed by ANOVA, Tukey and paired t-tests (α = 0.05). ResultsThe MIC80% of ChNPs was 30.1 μg/mL. ChNPs at 4 MIC showed complete inhibition in the time-kill assays. Blastoconidia cells were predominant after ChNPs application. The % inhibition ChNPs on C. albicans was proportional to its concentration, regardless of the exposure time. ChNPs decreased the CFU/mL of Candida spp. and showed lower alteration of HV and Ra values of resin surface compared to NaOCl. ConclusionsThe ChNPs inhibited C. albicans biofilm, reduced Candida biofilm on resin and caused small changes in roughness and hardness of acrylic resin surface.

The Effect of Denture Base Surface Treatments on Tensile Bond Strength of Autopolymerizing and Heat Cure Silicone Resilient Liners

AbstractPurpose of this study was to evaluate the effect of sandblasting, monomer treatment and combined effect of sandblasting and monomer treatment of conventional denture base resin on tensile bond strength of heat and auto cure silicone soft liners. Two resilient liners Auto cure (Mollosil) and Heat cure (Molloplast- B) were selected. Fifty six samples with cross sectional area of 25 × 25 mm were prepared and divided into two groups (Group A heat cure and Group B auto cure). Each group was further divided into 4 subgroups (7 samples in each subgroup) dependent upon the surface pretreatment. Subgroup 1 was control group (no surface treatment), subgroup 2 samples were surface treated by sandblasting (250 μm alumina particles), subgroup 3 samples were treated with monomer (for 180seconds), subgroup 4 samples were given combined treatment with sandblasting and monomer. Resilient liners were processed between 2 poly methyl methacrylate surfaces, in the dimensions of 3 mm. Tensile bond strength was determined with Instron Universal testing machine, at a cross head speed of 5mm/min. The data were analyzed using one-way ANOVA, followed by Tukey HSD test (α = 0.05). Monomer and combined treatment significantly increased the tensile bond strength when compared with control. Sandblasting treatment significantly decreased the tensile bond strength when compared with control.

Effect of soft drink towards heat cured acrylic resin denture base surface roughness

Introduction: The absorption of fluid in the heat cured acrylic resin is able to cause the increase in surface roughness. Absorption of acidic fluid such as soft drinks can cause even higher increase of surface roughness. The objective of this study was to determined the effect of soft drinks towards heat cured acrylic resin denture base surface roughness. Methods: Specimens of this study were 32 pieces of specimen with the size of 12×12×3 mm. Sixteen pieces of specimens were kept in aquadest as a control group and 16 pieces of specimens were immersed in the soft drinks as the treatment group. Initial surface roughness was measured using surface roughness tester. The specimens were then immersed in both immersion media for 2 days. After immersion, the surface roughness of specimens were measured again. Results: Data obtained on the roughness measurements were analyzed using paired t test with the results of the analysis showed a significant difference (p&lt;0.05). Conclusion: It was concluded that there was increased in heat cured acrylic resin denture base surface roughness after immersed in soft drinks solvent.

Denture plaque microbiology in relation to removable denture hygiene methods

Introduction. Removable dentures, which constitute a reservoir of bacterial and fungal flora, can be an etiological factor responsible for generating local and systemic diseases. Plaque removal by applying mechanical and chemical methods is a basic principle of denture hygiene, it reduces the quantity of microorganisms and can play a role in the qualitative composition of bacterial biofilm. Aim of the study. To evaluate the impact of different denture hygiene methods on the composition of staphylococcal flora on the surface of denture base. Materials and methods. The study involved 62 patients of the Department of General and Transplantation Surgery and the Department of Prosthodontics. Each patient had a removable prosthesis. A thorough dental history with special emphasis put on denture hygiene methods was collected, swab from impression side of denture pate was sampled. Strains of the genus Staphylococcus were isolated and identified. Statistical analysis was conducted. Results. In the group of the examined patients, denture hygiene scheme based on toothbrush and toothpaste was most commonly used (53%). Bacterial strains of the genus Staphylococcus were found in 90% of subjects. The highest percentage of stains, including those with high pathogenicity (S.aureus, S.epidermidis, S.haemolyticus), were isolated in the subjects who used toothbrush and toothpaste and the lowest in those who regularly used mechanical and chemical denture cleaning methods. Conclusions. From a microbiological point of view, a combination of mechanical and chemical methods in regular denture hygiene, can help reducing the number of Staphylococcal strains. Patients, who receive an organ transplant should pay special attention to denture hygiene as microorganisms present on acrylic plate can pose a threat to their health and even life.

Evaluation of some physical properties of two permanent heat cure silicone soft lining materials

Background: Soft lining materials has a key role in modern prosthodontics because of their capability of restoring health of inflamed and distorted mucosa, but with two major problems; water sorption, solubility, and lack of bond to the underlying denture base materials. The aim of this study was to examine water sorption and solubility for two types of permanent heat cure silicone soft lining materials (Permaflex and Molloplast-B), applied for different types of acrylic denture base surface and stored in artificial saliva to evaluate the tensile bond strength. Materials and methods: Two types of permanent heat cure silicone soft lining materials was applied to different type of surfaces acrylic denture bases for tensile testing. Water sorption and solubility test was done according to ADA No. 12 specification for 1, 3, and 6 weeks intervals. Results: There was no significant changes in sorption and solubility with time of water storage from (1st-- 3rd week), for Permaflex soft lining materials, and significant decrease water storage from (3rd -- 6th week) for sorption only, and for Molloplast –B soft lining materials no significant changes for sorption of water storage from (1st–3rd– 6th week), solubility revealed a significant changes with time for water storage from (1st – 3rd – 6th week). Conclusion: This study indicated that heat cure soft lining materials shows some degree of water sorption and solubility, the lowest level was obtained by Permaflex soft lining material. Artificial saliva storage decrease the tensile bond strength for the two types of soft lining materials except for Permaflex sandblasted type of surface increase after artificial saliva storage.