In vitro antiseptic properties of an ammonium compound combined with denture base acrylic resin

Background: Denture base acrylic resin is easily colonised by oral endogenous bacteria and Candida spp., and eventually by extra‐oral species such as Staphylococcus spp., Pseudomonadaceae or members of Enterobacteriaceae. This microbial reservoir can be responsive for denture related stomatitis and aspiration pneumonia, a life‐threatening infection especially in geriatric patients. However, the oral and denture hygiene of dependant elderly individuals is extremely poor. Objective: This in vitro study aimed to determine the per cent of a quaternary ammonium compound heat‐polymerised in acrylic resin necessary to obtain denture base displaying antiseptic properties. Design: Acrylic resin discs containing 2–50% ammonium polymer (Poly 202063A; 0% control) were soaked in artificial saliva for 4 weeks. Resin discs were incubated for 24 hours with Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa [37°C, brain–heart infusion (BHI) broth and phosphate‐buffered saline (PBS) buffer] and Candida albicans (30°C, Schaedler broth), in 15 ml (168 discs) and 600 μl (168 discs) of inoculum. Microbial growth was verified at t 0 hours and t 24 hours. Data were recorded as the mean of three colony forming unit (CFU) numerations. The borderline of antimicrobial effect was determined at 0.1% viable cells. Results: In 600 μl of PBS inoculum, resin specimens had a bactericidal effect (E. coli and S. aureus: 2%; P. aeruginosa: 10%) and a fungicidal effect (C. albicans: 50%). Long‐term stability and toxicity in vivo studies are now required. Conclusion: A 2% quaternary ammonium compound polymerised with a denture acrylic resin displayed antiseptic properties after a 4‐week soaking period in artificial saliva. Such antiseptic denture base could help geriatric patients to improve their oral health.     

Medical importance of biofilms in Candida infections

Many Candida infections involve biofilm formation on implanted devices such as an indwelling catheter, a prosthetic heart valve or a denture. Candida biofilms can be formed in vitro using several model systems. In the simplest of these, organisms are grown on the surfaces of small discs of catheter material or denture acrylic. Biofilms of C. albicans prepared in this way consist of matrix-enclosed microcolonies containing yeasts, hyphae and pseudohyphae, arranged in a bilayer structure. Candida biofilms are resistant to a range of antifungal agents in current clinical use, including amphotericin B and fluconazole. Current research suggests that multiple mechanisms are involved in biofilm drug resistance.     

Effectiveness of different cleaning agents on the adherence of Candida albicans to acrylic denture base resin

doi: 10.1111/j.1741‐2358.2010.00379.x
Effectiveness of different cleaning agents on the adherence of Candida albicans to acrylic denture base resin Objective:  To evaluate the ability of three alkaline peroxide‐type (Polident, Efferdent, Fittydent) and two mouth rinse cleaning agents (CloSYSII and Corsodyl) to inhibit Candida albicans on acrylic denture base resin. Background:  Appropriate routine cleaning of dentures is necessary to prevent denture stomatitis and maintenance of healthy supporting tissues. Materials and methods:  A total of 180 acrylic resin specimens (10 × 10 × 2 mm) were prepared and divided into six groups. Candida albicans was incubated on Sabouraud dextrose agar (SDA) at 37°C for 48 h. After dilution, a final yeast suspension of approximately 10 6 C. albicans per millimetre was prepared. Ten acrylic resin specimens for each group were placed in a sterile Petri dish covered with 20 ml of fungal suspension and incubated at 37°C for 90 min. Then, the specimens were immersed in 40 ml of the test solution at 37°C for 15, 30 and 60 min. Fungal cells adhering to acrylic resin surfaces were fixed in formaldehyde and counted microscopically. Results:  Mouth rinses showed the highest removal activity for all the treatment times and completely eliminated the adherence of C. albicans. Conclusions:  The use of mouth rinse may be a suitable method for cleaning dentures.     

Adhesion and surface-aggregation of Candida albicans from saliva on acrylic surfaces with adhering bacteria as studied in a parallel plate flow chamber

Adhesive interactions between Candida albicans and oral bacteria are generally thought to play a crucial role in the microbial colonization of denture acrylic, which may lead to denture stomatitis. This study investigated the influence of saliva on the adhesive interactions between C. albicans and Streptococcus sanguis or Actinomyces naeslundii on denture acrylic. First, bacteria were allowed to adhere to the acrylic surface from a flowing suspension, and subsequently yeasts were flowed over the acrylic surface. The organisms were assayed in the presence or absence of human whole saliva. All experiments were carried out in a parallel plate flow chamber and enumeration was done in situ with an image analysis system. In the absence of adhering bacteria, adhesion of C. albicans from buffer was more extensive than from saliva. However, in the presence of adhering bacteria, yeast adhesion from saliva was increased with respect to adhesion of yeasts from buffer, indicating that specific salivary components constitute a bridge between bacteria and yeasts. In all cases, yeast aggregates consisting of 3 to 5 yeast cells were observed adhering to the surface. A surface physico-chemical analysis of the microbial cell surfaces prior to and after bathing the microorganisms in saliva, suggests that this bridging is mediated by acid-base interactions since all strains show a major increase in electron-donating surface free energy parameters upon bathing in saliva, with no change in their zeta potentials. The surface physico-chemical analysis furthermore suggests that S. sanguis and A. naeslundii may use a different mechanism for adhesive interactions with C. albicans in saliva.     

Treatment protocol for denture stomatitis,prior to anatomical molding

doi: 10.1111/j.1741‐2358.2012.00661.x Treatment protocol for denture stomatitis, prior to anatomical molding Background: Microorganisms of the genus Candida have been recovered from complete dentures made of acrylic resin, with high numbers of colony forming units and species diversity, which can act as infectious agents causing chronic atrophic candidiasis (denture stomatitis). Objective: The objective of this paper is present a treatment protocol for chronic atrophic candidiasis (denture stomatitis). Materials and Methods: The work describes three cases of totally edentulous patients presenting palate stomatitis who were submitted for treatment associating denture rebasing with chemically‐activated acrylic resin, night immersion in 2.5% sodium hypochlorite and use of topical antifungals for two weeks. Results: In all cases, remission of the inflammatory process occurred. Conclusion: The proposed treatment protocol proved to be to be effective.     

Antimicrobial activity of [2-(methacryloyloxy)ethyl]trimethylammonium chloride against Candida spp

BackgroundCandida-associated denture stomatitis is the most common manifestation of oral candidal infection, caused mainly by Candida albicans. Several authors have attempted to add antifungal agents or antiseptics to denture temporary soft lining materials or to denture acrylic resins, without relevant results. Therefore, the investigation of a quaternary ammonium functionalized compound [2-(methacryloyloxy)ethyl]trimethylammonium chloride (MADQUAT), which copolymerizes with methacrylates and which could act as a fungal inhibitor, is of paramount importance.AimsTo evaluate the in vitro activity of MADQUAT against Candida species.MethodsThirty-one Candida strains were used to determine the in vitro antifungal activity of this compound. The minimum inhibitory concentrations and minimum fungicidal concentrations of MADQUAT and nystatin were determined.ResultsMADQUAT showed antifungal properties at concentrations of 6.25 to > 100 mg/ml, and fungicidal activity between 25 and > 100 mg/ml. The quantitative determinations of the fungistatic and fungicidal activity of MADQUAT showed fungistatic activity against all Candida albicans, Candida krusei and Candida parapsilosis strains, revealing fungicidal activity against some strains of the other species.ConclusionsMADQUAT has antifungal activity against Candida spp. Moreover, the sensitivity to this substance varies across the different species in terms of MIC values and fungicidal or fungistatic activity.     

Bond strength of denture teeth to acrylic resin: effect of thermocycling and polymerisation methods

Background: Failure of bonding between acrylic resin teeth and denture base material is a considerable problem for patients who wear complete dentures. Objective: The purpose of this study was to evaluate the bond strength between acrylic resins and resin denture teeth with different thermocycling and polymerisation methods. Materials and methods: Microwave‐polymerised (Onda‐Cryl), heat‐polymerised (Clássico) and autopolymerising (Jet) acrylic resins and resin denture tooth (Biotone) were used. The acrylic resins were polymerised according to the following: (A) microwave – fast cycle, Onda‐Cryl; (B) microwave – long cycle, Onda‐Cryl; (C) microwave – manufacturer’s cycle, Onda‐Cryl; (T) water bath – long cycle, Clássico; and (Q) bench polymerisation cycle, Jet. Twenty specimens were prepared for each polymerisation method. Ten were thermocycled, and 10 did not receive thermocycling. For the purpose of the study, a shear test was used. Data were analysed with the Kruskal–Wallis test and Dunn’s multiple comparisons test (p = 0.05). Results: Cycles B, C and T were similar (p > 0.05), and had statistically higher bonding values than cycles A and Q (p < 0.05) for the thermocycled and non‐thermocycled groups. For all cycles, there were no statistically significant differences between thermocycled and non‐thermocycled groups (p > 0.05), except for cycle Q (p = 0.0038). Conclusion: Thermocycling decreased the bond strength, but not significantly for microwave and heat‐polymerised cycles. Regarding the bond strength of denture teeth to acrylic resin, the fast microwave polymerisation cycle should be avoided when polymerising Onda‐Cryl acrylic resin. In addition, Jet acrylic resin is not adequate for use in denture repair.     

Effect of monomer treatment and polymerisation methods on the bond strength of resin teeth to denture base material

Background: The fracture between acrylic denture base material and artificial teeth is a common clinical occurrence in dental prosthodontic practice. Objective: To evaluate the bond strength between acrylic resins and resin denture teeth when submitted by two protocols of monomer liquid application on the tooth surface and using different polymerisation methods. Material and methods: Microwave‐polymerised (Onda‐Cryl), heat‐polymerised (Clássico) and autopolymerising (Jet) acrylic resins and a brand of resin denture teeth (Biotone) were used. The acrylic resins were polymerised according to the cycles: (A) microwave – fast cycle, Onda‐Cryl; (B) microwave – long cycle, Onda‐Cryl; (C) microwave – manufacturer’s cycle, Onda‐Cryl; (T) water bath – long cycle, Clássico and (Q) bench polymerisation cycle, Jet. Thirty specimens were prepared for each polymerisation method; 10 were packed with acrylic resin after 60 s of monomer liquid application on the tooth surface, 10 after 180 s and 10 without any monomer liquid application. For the purpose of the study, a shear test was used. anova and Tukey tests were performed to identify significant differences (α = 0.05). Results: The highest bond strength values were found for monomer surface treatments, regardless of the polymerisation cycles. The highest significant values were found for cycles B (15.4 ± 1.8 MPa), C (11.9 ± 4.9 MPa) and T (15.4 ± 2.6 MPa) for non‐treated and 60 s methylmethacrylate treated groups. Comparing the monomer liquid treatment, they did not differ significantly (p > 0.05), except for cycle A (p < 0.05). Conclusion: Chemical treatment using monomer on the tooth surface prior to the acrylic resin packing improved the bond strength between resin denture tooth and acrylic resin, regardless of monomer liquid treatment protocols. The microwavable resin, polymerised by fast cycle and autopolymerising resin should be avoided for processing denture and denture repairs, respectively.     

Survival analysis of mandibular complete dentures with acrylic‐based resilient liners

doi: 10.1111/j.1741‐2358.2012.00658.x Survival analysis of mandibular complete dentures with acrylic‐based resilient liners Objective: The purpose of this long‐term randomised controlled trial was to compare the longevity of dentures constructed using a conventional acrylic resin (CAR) to that of dentures constructed using an acrylic‐based resilient liner (ARL). Materials and methods: The follow‐up study was essentially carried out by annual telephone calls to each of the 67 participants. The Kaplan–Meier method and life‐table analysis were used for univariate analyses. The Cox proportional‐hazards test was used as a final model for statistically adjusting predictor variables such as sex, clinician type, mandibular denture type and age at denture delivery. Results: The denture type was likely to affect the survival time of the dentures, while the sex and clinician type were not. The group using acrylic‐based resilient denture liners had twice the risk of having shorter denture‐survival times than those using conventional acrylic resin dentures. Younger participants were likely to have a reduced risk of having shorter denture‐survival times than older participants. Conclusion: We conclude that mandibular complete dentures constructed using ARL are twice as likely as dentures constructed using CAR to have shorter denture survival times, mainly because of material deterioration.     

The effect of long‐term disinfection procedures on hardness property of resin denture teeth

doi: 10.1111/j.1741‐2358.2011.00520.x The effect of long‐term disinfection procedures on hardness property of resin denture teeth Objective: The aim of the study was to evaluate the effect of long‐term disinfection procedures on the Vickers hardness (VHN) of acrylic resin denture teeth. Material and methods: Five acrylic resin denture teeth (Vipi Dent Plus‐V, Trilux–T, Biolux‐B, Postaris‐P and Artiplus‐A) and one composite resin denture teeth (SR‐Orthosit‐O) were embedded in heat‐polymerised acrylic resin within polyvinylchloride tubes. Specimens were stored in distilled water at 37°C for 48 h. Measurements of hardness were taken after the following disinfection procedures: immersion for 7 days in 4% chlorhexidine gluconate or in 1% sodium hypochlorite (CIm and HIm group, respectively) and seven daily cycles of microwave sterilisation at 650 W for 6 min (MwS group). In the WIm group, specimens were maintained in water during the time used to perform the disinfection procedures (7 days). Data were analysed with anova followed by the Bonferroni procedure (α = 0.01). Results: Microwave disinfection decreased the hardness of all acrylic resin denture teeth (p < 0.001). Immersion for 7 days in 4% chlorhexidine gluconate or distilled water had significant effect on the hardness of the acrylic resin denture teeth A (p < 0.01), and 1% sodium hypochlorite on teeth T (p < 0.01). All disinfection procedures decrease the hardness of the composite resin denture teeth (p < 0.01). Teeth O exhibited the highest and teeth V the lowest hardness values in the control group (p < 0.01). Conclusions: Disinfection procedures changed the hardness of resin denture teeth.     

An ORMOSIL-Containing Orthodontic Acrylic Resin with Concomitant Improvements in Antimicrobial and Fracture Toughness Properties

Global increase in patients seeking orthodontic treatment creates a demand for the use of acrylic resins in removable appliances and retainers. Orthodontic removable appliance wearers have a higher risk of oral infections that are caused by the formation of bacterial and fungal biofilms on the appliance surface. Here, we present the synthetic route for an antibacterial and antifungal organically-modified silicate (ORMOSIL) that has multiple methacryloloxy functionalities attached to a siloxane backbone (quaternary ammonium methacryloxy silicate, or QAMS). By dissolving the water-insoluble, rubbery ORMOSIL in methyl methacrylate, QAMS may be copolymerized with polymethyl methacrylate, and covalently incorporated in the pressure-processed acrylic resin. The latter demonstrated a predominantly contact-killing effect on Streptococcus mutans ATCC 36558 and Actinomyces naselundii ATCC 12104 biofilms, while inhibiting adhesion of Candida albicans ATCC 90028 on the acrylic surface. Apart from its favorable antimicrobial activities, QAMS-containing acrylic resins exhibited decreased water wettability and improved toughness, without adversely affecting the flexural strength and modulus, water sorption and solubility, when compared with QAMS-free acrylic resin. The covalently bound, antimicrobial orthodontic acrylic resin with improved toughness represents advancement over other experimental antimicrobial acrylic resin formulations, in its potential to simultaneously prevent oral infections during appliance wear, and improve the fracture resistance of those appliances.     

Fatigue resistance of acrylic resin denture base material reinforced with E-glass fibres

doi: 10.1111/j.1741‐2358.2011.00548.x
Fatigue resistance of acrylic resin denture base material reinforced with E‐glass fibres Objective: The purpose of the study was to determine the effect of different forms and concentrations (2.5, 3, 4, 5% by volume) of glass fibres (chopped strand mat, continuous and woven) on fatigue resistance of acrylic denture base resin. Material and Methods: The fatigue resistance was measured by applying repeated three‐point bending deflection to the specimens, the cycle frequency of 1.05 g and magnitude of deflection of 2.0 mm. The number of loading cycles needed to cause a fracture in the test specimen was considered the fatigue resistance of the specimen. Results: The results of this study revealed that the addition of three different glass fibre forms at all concentrations to acrylic resin did not produce a statistically significant increase in the fatigue resistance (p ≥ 0.05). This study also revealed that there were significant differences (p < 0.05) between glass fibres forms used concerning the effects on the fatigue resistance. Conclusion: This study showed that the woven glass fibres had a definite superiority over the chopped fibres and the continuous fibres in regard to the fatigue resistance of the acrylic denture base resin.     

Correlation between factors associated with the removable partial dentures use and Candida spp. in saliva

doi: 10.1111/j.1741‐2358.2010.00390.x
Correlation between factors associated with the removable partial dentures use and Candida spp. in saliva Objectives: To correlate the presence and number of Candida spp. in the saliva of wearers of removable partial dentures retained with precision attachments with the proportion of metal/acrylic resin present in the dentures. Methods: Saliva samples from 40 removable partial denture wearers (test) and one paired sample of individuals, non‐wearers of any type of removable denture (control) were collected, seeded, and the colony forming units of Candida counted and identified. The metal/acrylic resin proportion of each denture was quantified, using silicone plates pressed over each denture. Results: Candida spp. was found in the saliva of 80% of the individuals in the test group and 65% of the control, with C. albicans being the most prevalent species. The test group presented with the highest number of colony forming units of Candida per ml of saliva, and there was weak correlation between this number and the metal and resin area of the denture (Pearson’s coefficient of correlation). Greater prevalence and a higher number of colony forming units of Candida per ml of saliva occurred in removable partial denture wearers (p = 0.04) with a weak positive correlation between the metal and resin area and the number of colony forming units of Candida per ml of saliva. However, this correlation was more significant for the area of resin.     

Influence of surface treatments on the flexural strength of denture base repair

doi: 10.1111/j.1741‐2358.2011.00454.x Influence of surface treatments on the flexural strength of denture base repair Objective: The purpose of this study was to evaluate the flexural strength of repairs made with autopolymerising acrylic resin after different treatments of joint surfaces. Material and Methods: Fifty rectangular specimens were made with heat‐polymerised acrylic resin and 40 were repaired with autopolymerising acrylic resin following joint surface treatments: group 1 (intact specimens), group 2 (chemical treatment: wetting with methyl‐methacrylate for 180 s), group 3 (abraded with silicon carbide paper), group 4 (abraded and wetting with methyl‐methacrylate for 180 s) and group 5 (without surface treatment). The flexural strength was measured by a three‐point bending test using a universal testing machine with a 100 Kgf load cell in the centre of repair at 5 mm/min cross‐head speed. All data were analysed using one‐way anova and Tukey HSD test for multiple comparisons (p < 0.05). Results: Among repaired specimens, groups 2 and 4 had 66.53 ± 3.4 and 69.38 ± 1.8 MPa mean values and were similar. These groups had superior flexural strength than groups 3 and 5 that were similar and had 54.11 ± 3.4 and 51.24 ± 2.8 MPa mean values, respectively. Group 1 had a mean value of 108.30 ± 2.8 MPa being the highest result. Conclusion: It can be concluded that the treatment of the joint surfaces with methyl‐methacrylate increases the flexural strength of denture base repairs, although the strength is still lower than that observed for the intact denture base resin. Abrasion with sandpaper was not able to influence the flexural strength of repaired denture bases.     

Inhibition of biofilms associated with dentures and toothbrushes by tetrasodium EDTA

AIMS: We examined the efficacy of tetrasodium EDTA in eradicating biofilms derived from salivary inocula or pure cultures of Candida albicans on discs of polymethyl methacrylate (PMMA) denture base or on toothbrushes that had been used normally for 4-8 weeks. Its efficiency in virus neutralization was also determined. METHODS AND RESULTS: Overnight (16 h) treatment with 4% (w/v) tetrasodium EDTA solution reduced salivary and C. albicans biofilm viable counts by > or =99%. Biofilm removal was confirmed using confocal laser scanning microscopy. Presence/absence of sucrose during biofilm formation had no effect on killing efficacy. Prolonged treatment of PMMA with tetrasodium EDTA did not influence subsequent formation of C. albicans biofilms or affect surface roughness of the PMMA, but it reduced subsequent biofilm formation from a salivary inoculum. Infectivities of herpes simplex virus and polio virus suspensions were reduced by >99.99% by treatment for 1 and 2 h, respectively. CONCLUSIONS: Tetrasodium EDTA solution efficiently disinfected toothbrushes and PMMA discs, with the detachment of biofilms, and rapidly neutralized both nonenveloped and enveloped viruses. SIGNIFICANCE AND IMPACT OF THE STUDY: Dentures and toothbrushes become contaminated by bacterial biofilms and by viruses. There is a need for disinfection methods that are rapidly effective, cost-effective, nontoxic and easily implemented. These studies indicate that tetrasodium EDTA solution has disinfection applications in the oral care field.     

Effect of pre-processing methods on bond strength between acrylic resin teeth and acrylic denture base resin

doi: 10.1111/j.1741‐2358.2011.00480.x
Effect of pre‐processing methods on bond strength between acrylic resin teeth and acrylic denture base resin Objectives: This study evaluated the effects of various pre‐processing methods on the bond strength between resin and denture teeth. Backgrounds: Debonding of acrylic resin teeth from denture base material is a problem for patients wearing complete dentures. Materials and Methods: Four experimental groups (n = 30) were investigated by subjecting tooth–resin bonding to tensile loading. Specimens were prepared and tested according to the methods of the International Standards Organization (ISO 22112:2005) using a special assembly. Four pre‐processing surface treatments of teeth were applied: (i) ST₁, no treatment applied (control); (ii) ST₂, wax solvent (Dewaks, Faber Kimya & Ilaç, Turkey); (iii) ST₃, boiling water followed by conditioning with methyl methacrylate (MMA) monomer (Meliodent, Bayer Dental, Germany); (iv) ST₄, boiling water followed by wax solvent agent and finally MMA monomer application. Bond strength test was performed using a universal testing machine. Results: All the strength values of the test groups were within clinically acceptable limits. The lowest values were from the ST₁ group and the highest values were in the ST₄ group. Conclusions: Wax elimination methods affected bonding strength. Application of wax solvent and MMA monomer to the ridge lap surfaces of the teeth gave the best results. In clinical practice, this application procedure may decrease the bonding failure of denture teeth.     

Flexural properties of repaired heat‐polymerising acrylic resin after wetting with monomer and acetone

doi:10.1111/j.1741‐2358.2009.00321.x
Flexural properties of repaired heat‐polymerising acrylic resin after wetting with monomer and acetone Objectives: Repair strength can be improved by treating fractured surfaces of a denture. Background: This study investigated flexural properties of heat‐polymerised acrylic resin specimens repaired with auto‐polymerising and visible light curing (VLC) resins after the repair surfaces were wetted with monomers or acetone. Materials and Methods: Fifty‐four specimens (65 × 10 × 2.5 mm) were prepared and 48 of them were sectioned to simulate denture fracture. Butt‐joint designed repair surfaces were wetted with heat‐, auto‐polymerising monomers and acetone for 180 s and repaired with auto‐polymerising and VLC resins. After repairs, specimens were subjected to three‐point bending test and flexural strength, strain, fracture load, modulus of elasticity and deflection values were recorded. Data were analysed with Student t and LSD tests (p ≤ 0.05). Results: Overall flexural strength, strain, fracture load and deflection values of specimens repaired with VLC resin were significantly higher than the specimens repaired with auto‐polymerising resin for all types of wetting agent (p < 0.05). Within the wetting agents, heat‐ and auto‐polymerising monomers produced the best mechanical properties, while wetting with acetone did not provide superior effect over both monomers. Conclusion: In clinical use, wetting the repair surfaces may result in stronger repairs. The use of bonding agent in VLC resin repairs in combination with wetting agent results in improved flexural properties.     

The effect of immersion cleansers on gloss,colour and sorption of acetal denture base material

doi: 10.1111/j.1741‐2358.2012.00657.x The effect of immersion cleansers on gloss, colour and sorption of acetal denture base material Objective: To study the effect of peroxide and hypochlorite cleansers on gloss, colour and sorption of acetal denture resins. Materials and methods: Pink acetal and thermoplastic acrylic resins were evaluated. Thirty‐five specimens 39 × 39 × 1.8 mm of each resin were prepared. Each group of specimens (n = 7) was then immersed into cleansers for 100 days. Group I immersed in tap water, Group II in Corega Extradent for 5 min, Group III in Corega Extradent for 8 h, Group IV in NitrAdine? Seniors for 15 min and Group V in NaOCl 5.25%. Gloss, colour and weight measurements were taken initially and after 100 days. Data subjected to two‐way anova and Tukey’s test at α = 0.05. Results: Acrylic resin showed reductions of glossiness from ?5 to ?15 and acetal from ?0.2 to ?6. Colour changes (ΔΕ*) ranged from 2.64 to 7.64 for acrylic and 2.77 to 26.54 for acetal resin. Sorption for acrylic ranged from 11.64 to 17.06 μg/mm³ and 9.18 to 24.79 μg/mm³ for acetal resin. The results of (ΔΕ*) and sorption showed an interaction between denture resins and cleansers. Conclusions: The gloss of acetal resin was less affected by water, peroxides and NaOCl 5.25% compared with acrylic resin. Acetal resin showed clinically acceptable (ΔΕ*) whereas acrylic resin unacceptable ones for water and peroxide solutions. The immersion of acetal resin in NaOCl 5.25% showed clinically unacceptable (ΔΕ*) and higher sorption and should be avoided or should be managed with care.     

Evaluation of Vickers hardness of different types of acrylic denture base resins with and without glass fibre reinforcement

doi: 10.1111/j.1741‐2358.2010.00435.x
Evaluation of Vickers hardness of different types of acrylic denture base resins with and without glass fibre reinforcement Objective: To evaluate the Vickers hardness of different acrylic resins for denture bases with and without the addition of glass fibres. Background: It has been suggested that different polymerisation methods, as well as the addition of glass fibre (FV) might improve the hardness of acrylic. Materials and methods: Five types of acrylic resin were tested: Vipi Wave (VW), microwave polymerisation; Vipi Flash (VF), auto‐polymerisation; Lucitone (LT), QC20 (QC) and Vipi Cril (VC), conventional heat‐polymerisation, all with or without glass fibre reinforcement (GFR) and distributed into 10 groups (n = 12). Specimens were then submitted to Vickers hardness testing with a 25‐g load for 30 s. All data were submitted to anova and Tukey’s HSD test. Results: A significant statistical difference was observed with regard to the polymerisation method and the GFR (p < 0.05). Without the GFR, the acrylic resin VC presented the highest hardness values, and VF and LT presented the lowest. In the presence of GFR, VC resin still presented the highest Vickers hardness values, and VF and QC presented the lowest. Conclusions: The acrylic resin VC and VW presented higher hardness values than VF and QC resins. Moreover, GFR increased the Vickers hardness of resins VW, VC and LT.     

Antimicrobial activity studies on a trypsin-chymotrypsin protease inhibitor obtained from potato

A 5.6 kDa trypsin-chymotrypsin protease inhibitor was isolated from the tubers of the potato (Solanum tuberosum L cv. Gogu) by extraction of the water-soluble fraction, dialysis, ultrafiltration, and C18 reversed-phase high performance liquid chromatography. This inhibitor, which we named potamin-1 (PT-1), was thermostable and possessed antimicrobial activity but lacked hemolytic activity. PT-1 strongly inhibited pathogenic microbial strains, including Candida albicans, Rhizoctonia solani, and Clavibacter michiganense subsp. michiganinse. Automated Edman degradation showed that the N-terminal sequence of PT-1 was NH2-DICTCCAGTKGCNTTSANGAFICEGQSDPKKPKACPLNCDPHIAYA-. The sequence had 62% homology with a serine protease inhibitor belonging to the Kunitz family, and the peptide inhibited chymotrypsin, trypsin, and papain. This protease inhibitor, PT-1, was composed of polypeptide chains joined by disulfide bridge(s). Reduced PT-1 almost completely lost its activity against fungi and proteases indicating that disulfide bridge is essential for its protease inhibitory and antifungal activity. These results suggest that PT-1 is an excellent candidate as a lead compound for the development of novel oral or other anti-infective agents.