Surface changes in denture soft liners with and without sealer coating following abrasion with mechanical brushing

Gerodontology 2010; doi: 10.1111/j.1741‐2358.2010.00375.x Surface changes in denture soft liners with and without sealer coating following abrasion with mechanical brushing Aim: To evaluate the surface alterations of soft liners with or without sealer coating following abrasion with mechanical brushing. Methods: Thirty specimens were made of a methacrylate‐ (Coe‐Soft) and a siloxane‐based material (Ufi‐Gel SC), and 15 received two coatings of surface sealer. The specimens were submitted to a mechanical brushing‐dentifrice assay under 200 g of force at 250 cycles/min. Mechanical brushing was simulated for a period of 1 (1250 cycles) and 6 months (5000 cycles). Surface roughness (Ra parameter) was measured, and scanning electron microscopy (SEM) images were obtained. Ra data were analysed by anova for repeated measures and Bonferroni’s test (alpha = 0.05). Results: Ra increased from baseline to 6 months regardless of sealer coating. At baseline, only Coe‐Soft without sealer had a higher Ra than the other groups. After 1 month, the Ra of Coe‐Soft with sealer was three‐fold higher than the Ra at baseline; the other groups showed no significant increase of Ra. SEM images showed degradation of the soft liners over time, except for the Ufi‐Gel SC with sealer, which displayed minimum alteration of surface texture. Conclusion: Sealer coating reduced the surface degradation of the tested soft liners, but the protective effect was more pronounced for the siloxane‐based material.     

Biofilm formation of Candida albicans on the surface of a soft denture‐lining material

Background: Soft denture lining‐materials are more susceptible to microbial adhesion than hard denture base acrylic resin. Poor oral hygiene and Candida albicans infection are common among elderly denture wearers as these patients usually have difficulty in keeping them clean. Purpose: To evaluate the influence of the oral hygiene methods on the formation of a biofilm over a soft denture‐lining material. Material and methods: Twenty volunteers were randomly separated into two groups: G1 and G2. Ten volunteers performed daily hygiene of the prostheses with a soft toothbrush and toothpaste. The G2 performed a treatment identical to G1 but also immersed the prostheses in sodium hypochlorite 0.5% for 20 min, once a week. Quantification of the mean score values of biofilm formation at different times were statistically analysed using analysis of variance and Tukey’s test (α = 0.05). Results: G1 (0.65 ± 0.52) showed the lowest mean score values of biofilm formation. There was statistical difference between G1 and G2. The highest mean score values were found at 6 weeks (1.3 ± 1.08) and were statistically different from other times. Conclusion: The oral hygiene methods had a significant effect in the formation of the biofilm over a soft denture‐lining material.     

In vivo biofilm formation on a soft denture liner in elderly patients with controlled diabetes

doi: 10.1111/j.1741‐2358.2010.00428.x In vivo biofilm formation on a soft denture liner in elderly patients with controlled diabetes Objectives: This in vivo study evaluated the influence of controlled diabetes on biofilm formation on a soft denture liner in elderly patients. Background: Soft denture lining materials are more susceptible to microbial colonisation than denture base acrylic resins. Especially in the elderly, several predisposing factors may accumulate leading to an increased probability of biofilm development that may result in candidiasis, a significant clinical oral disease. Materials and methods: Volunteers wearing complete dentures were divided into two groups (n = 20): diabetic patients with controlled glycaemia, and healthy patients. In both groups, a silicone‐based soft liner was placed in a recess created at the base of the maxillary dentures. Subjects cleaned the prosthesis three times a day. Biofilm formed on the liner was quantified at various time points (baseline, two, four and six weeks). Data were analysed by two‐way repeated measures anova and Tukey’s test (α = 0.05). Results: There was no statistical difference in biofilm formation for any of the time points between controlled diabetes patients and healthy patients. Conclusion: The results suggest that the control of diabetes in elderly patients provides the same levels of biofilm formation when compared to healthy individuals.     

Effect of accelerated ageing and surface sealing on the permanent deformation of auto‐polymerising soft linings

doi: 10.1111/j.1741‐2358.2010.00419.x
Effect of accelerated ageing and surface sealing on the permanent deformation of auto‐polymerising soft linings Purpose: To compare the effects of different ageing methods on the permanent deformation of two permanent soft liners. Materials and methods: The materials selected were auto‐polymerising acrylic resin and silicone‐based reliners. Sealer coating was also evaluated. Sixty specimens of each reliner were manufactured (12.7 mm diameter and 19 mm length). Specimens were randomly distributed into 12 groups (n = 10) and submitted to one of the accelerated ageing processes. Permanent deformation tests were conducted with a mechanical device described within the American Dental Association specification number 18 with a compressive load of 750 gf applied for 30 s. All data were submitted for statistical analysis. Mann–Whitney test compared the effect of the surface sealer on each material and the permanent deformation of the materials in the same ageing group (p = 0.05). Kruskal–Wallis and Dunn tests compared all ageing groups of each material (p = 0.05). Results: The silicone‐based reliner presented a lower permanent deformation than the acrylic resin‐based reliner, regardless of the ageing procedure. The surface sealer coating was effective only for the thermocycled silicone group and the accelerated ageing processes affected only the permanent deformation of the acrylic resin‐based material. Conclusion: The silicone‐based reliner presented superior elastic properties and the thermocycling was more effective in ageing the materials.     

Effect of double flasking and investing methods on artificial teeth movement in complete dentures processing

doi: 10.1111/j.1741‐2358.2011.00494.x
Effect of double flasking and investing methods on artificial teeth movement in complete dentures processing Purpose: The aim of this study was to evaluate linear dimensional alterations of artificial teeth for complete dentures when using different investment and flasking techniques. Background: Dimensional changes in the vertical dimension may occur owing to changes in artificial teeth positioning caused by different investing and flasking techniques. Materials and methods: Thirty pairs of the complete dentures were manufactured and randomly divided into three groups (n = 10): (1) invested with type III stone in monomaxillary PVC flask; (2) invested with type III stone in bimaxillary PVC flask; and (3) invested with laboratory silicone in bimaxillary PVC flask. Dentures were polymerised by microwave, and 12 linear distances were measured before and after denture processing. Data were analysed by one‐way anova , considering manufacturing technique as the study factor. Tukey’s HSD was used as post hocanova (p = 0.05). Results: Most of the linear distances were comparable for all groups. All transversal maxillary and mandibular distances were higher for group 1 compared with groups 2 and 3 (p < 0.05), except the distance 3–6 for mandibular arch, in which no difference was found between groups (p < 0.05). Both maxillary diagonal distances were higher in group 1 (p < 0.05), and no differences were found among all groups for mandibular measurements. Conclusions: Double flasking technique independent on the investment material is shown to be the most effective method to reduce changes in artificial teeth positioning.     

Structural relaxation and physical ageing of starchy materials

The structural relaxation during the ageing of an amorphous maltose and a starch-sorbitol mixture was examined using a range of physical techniques. Heat capacity, measured by differential scanning calorimetry, showed an overshoot in the glass-transition region, the size of which was temperature and time dependent. Volume relaxation measurements were made at different ageing temperatures in the range T(g) -15 to -30 K. The volume decreased with increasing ageing time, in an essentially linear fashion with log time. The mechanical behaviour of the materials showed a progressive embrittlement on ageing. For both materials, the mechanical relaxation time increased with ageing, and the material became stiffer. Investigation of the effect of physical ageing on transport properties was also performed using conductivity measurements on a maltose-water-KC1 mixture. A decay in conductivity, which was almost linear with log time, was observed. The structural relaxation was modelled using the Tool-Narayanaswamy approach to describe the calorimetric data.     

Effect of different repair techniques on the accuracy of repositioning the fractured denture base

Objective: This study investigated the efficacy of different techniques for the union of fragments of a denture before repair and on the accuracy of the reposition. Materials and methods: For this study, 20 maxillary dentures made with Lucitone 550 heat‐cured resin were used. Points were determined with a scanner on the cusp of the teeth, as a measurement of the segments. After digitisation, each model was exported to the AUTOCAD R 14 program and two‐dimensional measurements of the distances between the marked points were made. After the initial analysis, the dentures were fractured into two segments using an impact test machine. For the repair, maxillary dentures were divided into two groups; in the first, the repair was carried out using Kerr’s sticky wax and in the second group, Super Bonder was used to join the fragments, with subsequent inclusion of DENTSPLY^® Repair Material resin. After the repair, the points of the maxillary dentures were measured again. The numerical values obtained were tabulated to compare the measurements before fracture and after the repair. For statistical analysis, analysis of variance was employed, using a single factor and double factor, followed by the Tukey test with a reliability of 95%. Results: The results demonstrated a statistically significant difference between the materials used to join the dentures for repair, where the dentures were joined with sticky wax presented a larger variation in the distances between the points. Conclusion: The variation in distances between the points is influenced by the agent of repair.     

Colonisation of soft lining materials by micro‐organisms

doi:10.1111/j.1741‐2358.2009.00300.x
Colonisation of soft lining materials by micro‐organisms Objective: This study evaluated the in vitro adherence of pathogenic micro‐organisms, Candida albicans, Staphylococcus aureus and Pseudomonas aeruginosa, to soft lining materials and their inhibitory effect on these micro‐organisms. Materials and Methods: To measure adherence, specimens of Molloplast B and Ufi Gel P were inoculated [10⁷ colony‐forming units per millimetre (cfu/ml)] with TSB media containing the micro‐organisms. To determine the number of micro‐organisms in the 10^?2–10^?5 dilutions, 25 μl of the suspension were transferred to plates of selective media. Colony counts of each specimen were quantified (cfu/ml). The surface roughness was measured with a perfilometer to assess the relationship between the adherence of micro‐organisms and surface roughness of each material. For the inhibition test, specimens of materials were placed in agar plates inoculated individually with the micro‐organisms. After 48 h, the inhibition zones around the specimens were measured. Results: None of the materials exhibited inhibition zones. The number of cfu/ml of S. aureus and P. aeruginosa were significantly greater than C. albicans for both materials. The Ufi Gel P exhibited greater adherence of C. albicans than Molloplast B. No correlation was observed between the adherence of micro‐organisms and surface roughness. Conclusion: The surface roughness of the materials is not the only factor governing micro‐organism adherence.     

In vivo assessment of the effect of an adhesive for complete dentures on colonisation of Candida species

doi: 10.1111/j.1741‐2358.2009.00345.x
In vivo assessment of the effect of an adhesive for complete dentures on colonisation of Candida species Objective: Denture adhesives have long been recognised by denture wearers as a useful adjunct to denture retention and stability. The objective of the present study was to evaluate, in vivo, the effect of a denture adhesive on oral quantities of Candida species by determination of absolute counts of colony‐forming units (CFU) per ml of saliva of individuals who use this denture adhesive for a period of 14 days. Materials and methods: Twenty‐four individuals were randomised in two equal groups of 12 (test and control), with the individuals of the test group using the adhesive for 14 days. Samples of saliva were collected from all individuals on days 0 (initial), 7 and 14. Aliquots of saliva were diluted and plated in duplicate on Sabouraud dextrose agar with chloramphenicol and incubated for 37°C for 48 h, the CFU/ml were counted in the individuals of each group and the data of each group were compared at the different time periods and analysed statistically by the non‐parametric Mann‐Whitney U‐test (α ≤ 5%). Results: There were no statistically significant differences between the test and control groups during the test periods. Conclusion: Within of the limitations of this study, the data suggested that the denture adhesive tested did not significantly alter the oral microbiota during the 14‐day trial period.     

Effect of amylose content on physical and mechanical properties of potato-starch-based edible films

The present study investigated the amylose content and the gelatinization properties of various potato starches extracted from different potato cultivars. These potato starches were used to prepare edible films. Physical and mechanical properties of the films were investigated. The crystallinity of selected native starches and edible films made of the same starches were determined by X-ray diffraction. The amylose content of potato starches varied between 11.9 and 20.1%. Gelatinization of potato starches in excess water occurred at temperatures ranging from 58 to 69 degrees C independently of the amylose content. The relative crystallinity was found to be around 10-13% in selected native potato starches with low, medium, and high amylose content. Instead, films prepared from the same potato starches were found to be practically amorphous having the relative crystallinity of 0-4%. The mechanical properties and the water vapor permeability of the films were found to be independent of the amylose content.     

Clinical and microbiological efficacy of three different treatment methods in the management of denture stomatitis

Gerodontology 2010; doi: 10.1111/j.1741‐2358.2009.00354.x
Clinical and microbiological efficacy of three different treatment methods in the management of denture stomatitis Objective: This study evaluated. the effect of mouthrinses and tissue conditioner on the clinical findings and microbial flora of 60 patients with Newton’s type II denture stomatitis (N2DS) Background: Denture stomatitis is a common problem in complete denture wearers. Materials and methods: Sixty patients with N2DS were included in this study and divided into three groups. Two groups of patients were instructed to rinse their mouth with the designated mouthrinses DioxiDent and Corsodyl twice daily for 1 min and to soak their dentures overnight in these solutions for 15 days. For the third group, tissue conditioner was placed in each of 20 patients’ existing maxillary dentures. Patients were evaluated both clinically and microbiologically at baseline and after 15 days. Palatal swabs and smears were taken from each patient before and after treatment and these samples were examined mycologically. The difference between Candida colonisation before and after treatment and the differences between pre‐treatment and post‐treatment clinical findings were assessed. Results: DioxiDent and Corsodyl showed an improvement in palatal inflammation and a decrease in Candida colonisation compared to Visco‐gel. Conclusions: The effectiveness of topical chlorine dioxide and chlorhexidine gluconate in the management of N2DS was demonstrated.     

In vitro and clinical evaluation of specific dentifrices for complete denture hygiene

Objectives: To study the physical properties of two experimental dentifrices for complete denture hygiene, their effect on denture biofilm removal and antimicrobial properties by means of a clinical trial. Materials and methods: The experimental dentifrices comprised two compositions. One was based on the addition of 1% chloramine T (D1) and the other on the presence of 0.01% fluorosurfactant (D2). Measurements of density, pH, consistency, rheological features and abrasiveness were conducted. Sixty complete denture wearers were randomly assigned to three groups and were instructed to brush their dentures with a specific toothbrush: (1) Water (control); (2) D1; or (3) D2. Each method was used for 21 days. Denture biofilm was disclosed by a 1% neutral red solution and quantified by means of digital photos taken from the internal surface. Microbiological assessment was conducted to quantify Candida sp. and mutans streptococci. Data were evaluated by one‐way anova and Tukey HSD, or Kruskal–Wallis (α = 0.05). Results: Both dentifrices decreased biofilm coverage when compared with the control group. D1 was the most efficacious treatment to reduce mutans streptococci, whereas D2 showed an intermediate outcome (anova , p < 0.040). No treatment influenced Candida albicans or non‐albicans species (Kruskal–Wallis, p = 0.163 and 0.746, respectively). Conclusion: It can be concluded that brushing complete dentures with the experimental dentifrices tested could be effective for the removal of denture biofilm.     

Evaluation of experimental cleanser solution of Ricinus communis: effect on soft denture liner properties

doi: 10.1111/j.1741‐2358.2010.00438.x Evaluation of experimental cleanser solution of Ricinus communis: effect on soft denture liner properties Objective: This study evaluated colour stability, hardness and roughness of soft denture liners after immersion in various cleansers. Materials and methods: Thirty specimens (14 mm × 4 mm) of Elite Soft Relining (ES) and Mucopren Soft (MS) were randomly immersed in distilled water at 37°C, sodium hypochlorite 1%, and an experimental Ricinus communis solution (RC) for 7, 15 and 183 continuous days. Results: anova (p < 0.05) and Tukey’s test indicated that after T7 (μ =8.79 ± 7.36); T15 (μ = 4.23 ± 2.62) and T183 (μ = 8.78 ± 3.16), MS presented a higher increase in hardness than ES. After T7, MS underwent an increase in roughness (μ = 0.09 ± 0.80); ES underwent a decrease (μ = ?0.08 ± 0.16). RC caused the smallest variation in roughness. After T15, both materials presented an increase in roughness. After T183, ES (μ = ?0.30 ± 0.48) presented a higher roughness variation than MS (μ = ?0.07 ± 0.32). Hypochlorite caused an increase in roughness (μ = 0.02 ± 0.19). Conclusion: After all periods ES presented higher colour alteration than MS; highest colour alteration was caused by hypochlorite. Both materials were more stable after immersion in RC.     

Relining of prosthesis with auto‐polymerizing hard denture reline resins: effect of post‐polymerization treatment on flexural strength

Background: It has been suggested that microwave irradiation and prosthesis immersion in hot water after its polymerization may improve mechanical and viscoelastic properties of acrylic resins. Purpose: This study was proposed to verify the influence of microwave post‐polymerization (PP) treatment over the flexural strength of thermo‐polymerizing acrylic resin specimens (QC‐20) relined or not with two different composition hard chairside auto‐polymerizing reliners [Kooliner (K) and New Truliner (NT)]. Materials and Methods: For this study, 50 specimens of 64 × 10 × 3.3 mm were polymerized and distributed into five groups. G1 (control) specimens without relining and PP; G2 specimens relined with K, without PP; G3 specimens relined with NT, without PP; G4 specimens relined with K, with PP (microwave irradiation with 650 W for 5 min); G5 specimens relined with NT, with PP. Tests were performed on a universal testing machine Instron 4411 with compression speed of 5 mm/min. Results: Specimens of K without PP did not show statistically different results (p < 0.05) when compared with control. However, when submitted to PP these specimens showed a significant increase in flexural strength. Specimens of NT showed the lowest flexural strength of all groups, with or without PP when compared with control and K groups. Conclusion: Microwave PP (650 W for 5 min) proved to be an effective method of improving the flexural strength of K relined prosthesis. However, it did not seem to affect NT specimens.     

Insertion and follow‐up of complete dentures: a literature review

Gerodontology 2010; 00; doi: 10.1111/j.1741‐2358.2010.00368.x Insertion and follow‐up of complete dentures: a literature review Objective: The aim of this study was to present the importance of clinical procedures related to insertion and follow‐up of complete dentures in elderly patients. Materials and Methods: The success of rehabilitation with complete dentures results from the accuracy of clinical and laboratorial procedures that makes the denture insertion an important step of treatment. Conclusion: The follow‐up and professional maintenance of function and hygiene facilitates long‐term efficiency.     

Oral health related quality of life of edentulous patients after denture relining with a silicone-based soft liner

doi: 10.1111/j.1741‐2358.2011.00503.x Oral health related quality of life of edentulous patients after denture relining with a silicone‐based soft liner Background: Knowledge of benefits caused by a treatment on quality of life is very relevant. Despite the wide use and acceptance of soft denture liners, it is necessary to evaluate the patient’s response about the use of these materials with regard to improvement in oral health related quality of life (OHRQoL). Objectives: The aim of this study was to evaluate the influence of denture relining in the OHRQoL of edentulous patients. Materials and methods: Thirty‐two complete denture wearers had their lower dentures relined with a silicone‐based material (Mucopren soft, Kettenbach, Germany) according to chairside procedures. OHRQoL was assessed before and after 3 months of relining by means of OHIP‐EDENT, and the median scores were compared by Wilcoxon test (p ≤ 0.05). Results: After 3 months of relining, participants reported significant improvement of their OHRQoL (p ≤ 0.01). Conclusion: Denture relining with a soft liner may have a positive impact on the perceived oral health of edentulous patients.     

Effect of pectate lyase bioscouring on physical, chemical and low-stress mechanical properties of cotton fabrics

The main objective of the present study was to meticulously investigate an inclusive set of physicochemical and handle properties (determined through Kawabata evaluation system) of bioscoured cotton fabrics. The application of a commercial pectinase preparation, Bioprep 3000L, for a range of concentrations and treatment times, could create a pectin-free textile with low wax content. Multiple regression analysis was used to describe the effect of enzymatic process variables on pectin and waxes removal. Comparison of fabrics' properties such as wettability, whiteness, crystallinity index, and dyeing behaviour, confirmed that bioscouring could be as much effective as the conventional alkaline process. Uncovering the relationship between the composition of materials and their physicochemical properties was attempted. The application of higher enzyme concentrations generated fabrics with improved low-stress mechanical properties. Bending and shear rigidity, compressional resilience, as well as, extensibility of enzymatically treated cotton fabrics could be efficiently predicted by means of a single independent variable, the crystallinity index.     

The effect of accelerated ageing on colour stability of visible light-cured (VLC) chairside denture liners

doi: 10.1111/j.1741‐2358.2011.00458.x
The effect of accelerated ageing on colour stability of visible light–cured (VLC) chairside denture liners Objective: The purpose of this study was to assess the colour stability of seven visible light–cured (VLC) hard and soft denture liners by an in vitro accelerated ageing test and compare them with two autopolymerised hard and soft liners. Materials and methods: Ten specimens of each material were fabricated. The initial colour was measured with a tri‐stimulus colorimeter. One set of five specimens was placed in distilled water at 37°C in the dark for 15 days, while the remaining were subjected to UV/visible light‐accelerated ageing initially for 24 h and then for 144 h. Colour change (ΔΕ) was calculated. Data were statistically analysed by anova , Tukey and t‐tests at α = 0.05. Results: All the liners showed clinically acceptable colour change (ΔΕ ≤ 6.8) in distilled water. The colour changes after ageing for Triad DuaLine, Lightdon U, Ufi Gel H and Light Liner Hard were clinically unacceptable (ΔΕ ≥ 6.8), whereas LightLiner Soft, Astron LC Soft, Triad Resiline and Flexacryl Soft presented slighter and clinically acceptable colour change (ΔΕ ≤ 6.8). Conclusion: Accelerated ageing affected significantly the colour stability of all denture liners tested except Astron LC Soft. Soft VLC denture liners were more colour‐stable than hard VLC liners.     

Assessment of changes in oral health‐related quality of life among patients with complete denture before and 1 month post‐insertion using Geriatric Oral Health Assessment Index

doi:10.1111/j.1741‐2358.2009.00323.x
Assessment of changes in oral health‐related quality of life among patients with complete denture before and 1 month post‐insertion using Geriatric Oral Health Assessment Index Objective: Geriatric Oral Health Assessment Index (GOHAI) is a 12‐item measure of “patient‐reported oral functional problems” intended for use in the assessment of the effectiveness of dental treatment. Design and Setting: As there is scanty literature available on GOHAI in the Indian population, the present study was undertaken to assess the changes in GOHAI before and 1 month after placement of dentures in completely edentulous patients reporting to a dental hospital at Indore, India. Measurements: The GOHAI questionnaire was completed by the examiner who interviewed the patients (n = 35) before placement of complete dentures and 1 month later. Mean, median values were calculated and the data were analysed using Wilcoxon signed‐rank test. Results: When overall mean was considered, the GOHAI scores increased from 27.48 to 30.19 (p = 0.002; highly significant). Conclusion: Patients reported improvement in functional changes after placement of complete dentures.     

The effect of sterilization on mechanical properties of soft tissue allografts

One major concern regarding soft tissue allograft use in surgical procedures is the risk of disease transmission. Current techniques of tissue sterilization, such as irradiation have been shown to adversely affect the mechanical properties of soft tissues. Grafts processed using Biocleanse processing (a proprietary technique developed by Regeneration Technologies to sterilize human tissues) will have better biomechanical characteristics than tissues that have been irradiated. Fifteen pairs of cadaveric Achilles tendon allografts were obtained and separated into three groups of 10 each. Three treatment groups were: Biocleanse, Irradiated, and Control (untreated). Each specimen was tested to determine the biomechanical properties of the tissue. Specimens were cyclically preloaded and then loaded to failure in tension. During testing, load, displacement, and optical strain data were captured. Following testing, the cross sectional area of the tendons was determined. Tendons in the control group were found to have a higher extrinsic stiffness (slope of the load–deformation curve, p = .005), have a higher ultimate stress (force/cross sectional area, p = .006) and higher ultimate failure load (p = .003) than irradiated grafts. Biocleanse grafts were also found to be stiffer than irradiated grafts (p = .014) yet were not found to be statistically different from either irradiated or non-irradiated grafts in terms of load to failure. Biocleanse processing seems to be a viable alternative to irradiation for Achilles tendon allografts sterilization in terms of their biomechanical properties.