RESEARCH ARTICLE | VOLUME 2, ISSUE 1 | OPEN ACCESS DOI: 10.23937/2378-3664/1410012

Bio-Active Designer Materials and Dentures: from Design to Application

V Tamara Perchyonok1*, John Souza2, Shengmiao Zhang3, Desigar Moodley4 and Sias Grobler4

1VTPCHEM PTY LTD, Glenhuntly, Melbourne, Australia

2Department of Prothetics, TAFE Queensland, 66 Ernest Street, South Brisbane, 4101, Australia

3School of Material Science and Engineering, East China University of Science and Technology, China

4School of Dentistry, The University of Western Cape, South Africa

*Corresponding author: V Tamara Perchyonok, VTPCHEM PTY LTD, Glenhuntly, Melbourne, Australia.

Accepted: October 30, 2015 | Published: November 02, 2015

Citation: Perchyonok VT, Souza J, Zhang S, Moodley D, Grobler S (2015) Bio-Active Designer Materials and Dentures: from Design to Application. Int J Med Nano Res 2:012.

Copyright: © 2015 Perchyonok VT, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.



The present study aims to design and evaluate performance of chitosan based bio-active containing acrylic materials and investigations towards applicationfor the development of novel bio-active materials with build in capabilities for treatment and prevention of denture stomatitis and associated conditions in denture wearers in vitro.


The bio-active modified polymethyl methacrylate denture resins (PMMA) were prepared by dispersion of the corresponding component in glycerol and acetic acid with the addition of chitosan gelling agent. The release behaviors at physiological pH and also under acidic conditions and stability of the antioxidant-chitosan were also evaluated. Mechanical performance such as tensile strength and compressive strength were measured as well bio-adhesive studies were investigated in order to assess the suitability of these designer materials.


The bioactive modified PMMA hydrogels showed a high adhesive force and were only slightly swelled in the aqueous medium. Bioactive release suggested prolonged release of the therapeutic agent from the hydrogels. The hydrogels also had significant free radical defense capability.


In this study we demonstrated that the newly preparedbio-active modified PMMA resins are suitable novel bio-active materials capable of comparable performance with the conventional PMMA materials with additional benefit of therapeutic bioactive release as well as potential antimicrobial properties to be demonstrated in vitro.


Chitosan, Bio-active, PMMA, Drug delivery systems, Free radicals


Since first polymerized by Walter Bauer in 1936, acrylic resin denture base gradually took the place of traditional metal base and became most commonly used denture base material in clinical fabrication [1,2]. It is a combination of advantages, such as of its excellent esthetics, ease of processing and repair and being economical, rather than one excellent aspect that accounts for its wide usage [3], including its popularity in satisfying aestheticdemands and clearly defined processing method in dentistry application. However, this material is not ideal in every respect [4], especially when meeting with mechanical requirements of prosthesis. Fracture of acrylic resin denture base happens frequently because of the fatigue and chemical degradation of base material [3], which is reflected by a large number of denture repairs annually [5].

The surface of denture base acrylic resin is porous, and denture plague easily adheres to the surface of dentures [6]. The colonization of microorganisms on the denture base acrylic resin occurs rapidly and candida species adheres strongly to denture base materials.

Oral candidosis in the form of candida-associated denture stomatitis is a common disease in some 65 per cent of denture wearers [7]. Candida albicans and related species are believed to play a major role in initiating, maintaining and aggravating the disease. This is the further evidence by the fact that the denture stomatitis is often cured by antimycotic treatment [8].

Chitosan, which is a biologically safe biopolymer as well as an antioxidant, has been proposed as a bio-adhesive polymer and is of continuous interest to us due to its unique properties and flexibility in a broad range of oral applications reported by others and ourselves recently [9-11].

Lentinusedodes, known as shiitake mushroom, has received great attention due to positive health effects, including antitumour and hypocholesterolemic activity [12], related to the presence of β-glucans [13].

Propolis is a resinous substance produced by bees with antibacterial, antifungal, antiviral, and anti-inflammatory activities [14,15]. Propolis antibacterial activity is bacteriostatic and, in high concentration, bactericidal [16]. Propolis has antimicrobial activity against gram-positive bacteria, egS. aureus, but limited action against gram-negative bacteriaand also against some fungi, e.g., C. albicans [17,18].

The copaiba tree is native to Latin America and Occidental Africa [14]. There are more than 20 species of copaiba in Brazil, and the most commonly described effects are anti-inflammatory, analgesic, antibacterial and antitumoral activities [15-17].

The present study aims to design and evaluate performance of chitosan based bio-active containing acrylic materials and investigate applicationsfor the development of novel bio-active materialswith build in capabilities for treatment and prevention of denture stomatitis and associated conditions in denture wearers, while the performance of the material is not compromised in vitro.



Propolis Brazilian (Red, Natura Nectar), Copaiba Oil (Laboratorio Sao Lucas, Brazil) and Shiitake powder (Border herbal health, Australia) were purchased from a commercial supplier (Wholesale Chemist, QLD, Australia) and used without further purification. (-)-Epigallocatechin gallate (EGCG) from green tea, 95%, (-)-epicatechin gallate (ECG) from green tea, 98%, (-)-epigallocatechin (EGC) from green tea, 95%, (-)-epicatechin (EC), 90%, gallic acid (GA) purity not specified, 6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid (trolox), 95%, Folin-Ciocalteu reagent, ferric chloride, Tween-20 and 2,20-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS)were purchased from Sigma-Aldrich Company Ltd. (Australia).

Chitosan (Aldrich, Australia), glycerol (Sigma, USA), glacial acetic acid (E. Merck, Germany) were used as received. The degree of deacetylation of typical commercial chitosan used in this study is 87%. Chitosan with molecular weight 2.5 × 103 KD was used in the study. Gelatin in powder form was purchased from Shanghai Chemical Reagent Co., (Shanghai, China) with the number-average molecular weight (Mn) of about 8.7 × 104. The isoelectric point is 4.0-5.0.

Preparation of bioactive containing methyl methacrylate materials: general protocol

The bio-active containing gel was prepared by dispersion of 0.2 grams of commercially available bio-actives (Propolis (Red Brazilian), Copaiba oil or Shiitake powder) in glycerol (5% w/w) (1 ml) using a mortar and a pestle following the earlier reported generic protocol [16]. Ten milliliters of glacial acetic acid (2% w/w) was then added with continuous mixing to the mixture of 0.2 grams of commercially available bio-actives (Propolis (Red Brazilian), Copaiba oil or Shiitake powder) in glycerol (5% w/w) (1 ml) and finally chitosan (10% chitosan w/w) polymer was added and mixed well to form there quire gel and then mixed into a PMMA resin prior to setting. The amount of bioactive component such as propolis, copaiba oil or shiitake mushroom extract respectively was determined to be 0.2 grams of the prepared material (10 grams). The total phenolic concentration was quantified using Rocha et al [19] and described by Waterman & Mole [20] with some modifications.

Total phenol concentration in Propolis (Brazilian), Copaiba oil and Shiitake mushroom extract

Total phenols content was estimated by a colorimetric assay based on the same procedure realized by Rocha et al. [19] and described by Waterman & Mole [20] with some modifications. The samples were diluted in distilled water to obtain a concentration of 5 μg/mL of total phenols. The concentration of 5% v/v of Folin-Ciocalteu reagent and 10% v/v sodium carbonate (35% w/v) reagents were added to the samples. After the addition of the reagents, the solutions were kept in the dark at room temperature for 30 min and the absorbance was read at the wavelength of 760 nm in a mini 1240 UV - Vis spectrophotometer (Shimadzu Co., Kyoto, Japan). Gallic acid (Aldrich, Australia) was used as a standard. The analyses were performed in triplicate. The total flavonoids, total phenolics contents as well as the antioxidant activity results were statistically analyzed by the variance analysis (ANOVA) by the Prism 6 software. In all analyses, a 5% significance level was considered.

Swelling/Weight Loss Tests and Bioactive Release

The swelling/weight loss tests were performed when triplicates of each samples composition (approximately 2 cm2, weight normalized) were immersed in 2 mL of different fluids at 37°C for each time interval studied (1, 2, 4, 24, and 96 h). Two different media were used in accordance with the ISO 10993 - 9 standard. The first medium was Phosphate Buffered Saline (PBS, Sigma Aldrich), intended to mimic the inorganic phase of human plasma [17]. The other media was PBS with a reduced pH which was intended to simulate the local inflammatory environment of the wounds [15,18]. This is termed Solution pH 4.0. The pH was lowered using Lactic Acid (Sigma Aldrich). The fluid absorption of each sample was calculated according to equation (1) to obtain their swelling degree (SD). WS is the weight of the sample at each time interval (swollen weight) and WD is the dry weight before swelling [21]. After 4 days of immersion, the samples were dried and weighed in order to calculate their weight loss (WL) [equation (2)], where WD and WDS are the weight of the dried samples before and after swelling tests, respectively

Equation 1: SD = 100 × (WS-WD)/WD (%)

Equation 2: WL = 100 × (WS-WD)/WD (%)

To analyze the bio-active release (propolis (Brazilian), Copaiba oil and Shiitake mushrooms) based on the total phenolic concentration; the swelling media was analyzed after 1, 2, 24, and 96 h of immersion via UV - Vis spectrometer, from 300 to 800 nm, using polystyrene cuvettes [22]. For quantification of the amount of propolis released, a standard curve was created by diluting the original propolis in isopropanol resulting in several aliquots of known concentration, which were then analyzed in the same wavelength range. The area of the peak of these aliquots (of known concentration of bio-additive) was calculated and used to compare with those of the bio-additive released by the samples.

Tensile strength testing of the material

Tensile testing was conducted using Instron 5565. Following American Standardized Testing Materials Standard D3039, rectangular samples were approximately 6 - 8 mm in length, 1mm in width an 1 mm in thickness, and tested with a gauge length of 3.5 ± 0.4 mm [23]. Samples were elongated at a rate of 1% of gauge length per second. The cross-sectional area of samples was evaluated using Image J image analysis software [24].

Compressive strength

Compressive strength test samples were placed in the measuring apparatus in an appropriate manner and cross-sectional area of each sample (mm2) was determined. A compressive load (N) was applied at a crosshead speed of 1.3 mm/min [25]. The compressive strength (MPa) was measured at the sample fracture point.Mean, average, and mode in each group were calculated and normal distribution curve was evaluated. One-way ANOVA, followed by multiple comparison test (Scheffe's test), was used for statistical analysis. Statistical significance was set at P < 0.05.

Bio-adhesive investigation

Bio-adhesion studies were done using a Chatillon apparatus for force measurement [26]. This method determines the maximum force and work needed to separate two surfaces in intimate contact [26]. The hydrogels (0.1 g) were homogeneously spread on a 1 cm2 disk and then the disks were fixed to the support of the tensile strength tester using double sided adhesive. The bio active modified PMMA material was brought into contact with a slice of pig ear skin was established in order to imitate adhesion of the gel to the "oral mucosa prototype system" structure. After a preset contact time of 1 min under contact strength of 0.5 N, the 2 surfaces were separated at a constant rate of displacement of 1 mm/s. The strength was recorded as a function of the displacement, which allowed to determine the maximal detachment force, Fmax, and the work of adhesion, W, which was calculated from the area under the strength-displacement curve [26].


SEM Images

The single electron microscopy (SEM) images were obtained for selective bio-active modified PMMA resins to characterize the microstructure of the freeze-dried samples and are presented in figure 1 SEM observations of PMMA-based samples revealed a smooth surface with the formation of the valleys and crests, which could be attributed to the presence of some aqueous medium in the preparation of modified materials which is consistent with the SEM images previously reported for similar PMMA based materials.

Mechanical properties investigated

Compression test

The poly methyl methacrylate has adequate tensile and compressive strength for complete and partial dentures [27]. The compression behavior for composite prosthetic dentures represents the important mechanical properties specialization when using the polymer matrix materials. The compression strength values results obtained from compression tests are carried out for all bioactive prepared materials and results are summarized in the figure 2. The addition of the bioactive compounds such as Shiitake extract, Copaiba oil or Brazilian propolis had not influenced significantly the compression strength of the bioactive PMMA material. However upon incorporation of chitosan: bioactive combination (10% w/w) into the PMMA material the compressive strength of the new bioactive material was significantly lowered in comparison to the standard PMMA material. (Where Acr = PMMA resin materials)

Figure 1: SEM photographs of interior morphology of the selected gels under investigation for (a) Shiit/PMMA/Chi, (b) Cop/PMMA/Ch, (c) Pr/PMMA/Ch. View Figure 1

Figure 2: Comparison of compressive strength of bio-active denture materials. Where Acr = PMMA resin. View Figure 2

Tensile strength of the bioactive functionalized materials:

The tensile behavior for composite prosthetic dentures represents the important mechanical properties specialization when using the polymer matrix materials and is summarized in figure 3. The addition of the bioactive compounds such as Shiitake extract, Copaiba oil or Brazilian propolis had not influenced significantly the tensile strength of the bioactive PMMA material. However upon incorporation of chitosan-bioactive combination (10% w/w) into the PMMA material the tensile strength of the new bioactive material was significantly lowered in comparison to the standard PMMA material. The slight increase of tensile strength is probably due to the potential action interference of the bio-actives and their antioxidant capacity with the polymerization rates of the PMMA presence of chitosan as well as phenolic compounds which are capable to acts as the protective host of the excess of free radical formation and therefor the slight decrease in the tensile as well as compressive strength is observed. The results are basically consistent with the literature [28,29] and more detailed investigations into mechanistic interaction of chitosan/bioactive/PMMA resin are currently on the way in our laboratory.

Figure 3: Comparison of tensile strength of bio-active denture materials.
Where Acr = PMMA resin. View Figure 3

Swelling/Weight loss tests and bioactive release

The swelling characteristics of the bio-active modified materials at pH 7.0 and pH 4 are shown in figure 4a and figure 4b respectively. Swelling has not been affected significantly in case of either incorporation of bioactive or bioactive/chitosan did not increased in the case at either pH. No definite trend in swelling withcomposition was observed. Though PMMA is a hydrophobicpolymer, the acidic environment may hydrolyse the methacrylate group to some extent conferring hydrophilic nature to the copolymer.

Figure 4A: Swelling at pH = 4. View Figure 4A

Figure 4B: Swelling at pH = 7. View Figure 4B

Total phenolic concentration

On the basis of calibration curve for standard total phenolic concentration, the concentration of these bioactive compounds in the propolis (Brazilian, Red), Copaiba Oil and Shiitake mushroom powder sample used in the study was assessed and is summarized in figure 5.The results are consistent with the previously reported values for a hydroalcoholic extracts of the propolis, copaiba oil and shiitake mushroom powder in the literature [30-33]. It is well accepted in the literature that the biological activities for the bio-actives such as Propolis, Copaiba oil and Shiitake extracts for extracts for example are mostly due to the high levels of phenolic acids [30-36].

Figure 5: Total phenolic concentration of the bioactive extracts used in the investigation. View Figure 5

The amount of bio-actives (such as Brazilian propolis, Shiitake mushroom extract and Copaiba oil) release in swelling media was analyzed after 1, 2, 24, and 96 h of immersion (Figure 6). The propolis release by polymeric systems usually occurs in two steps: the release of certain amounts of propolis in the first day of swelling as well as a prolonged release in some cases [37,38]. A trend could be observed in all curves after 4 days of immersion: there was a high bioactive release in the initial hours and the cumulative release reached constant values up to 1 day of immersion. No prolonged release was observed.

Figure 6: Bioactive cumulative release profile of Ch/PMMA-bioactive samples. The Ch/PMMA-bioactive samples were immersed in (a) PBS and (b) Solution pH 4.0 and the bioactive (such as copaiba oil, propolis and shiitake extract delivered was quantified after regular intervals of time for 4 days.
Where Acr = PMMA resin. View Figure 6

Bio-adhesion of PMMA modified materials

Higher adhesiveness of the modified PMMA resins is desired to maintain an intimate contact oral mucosa and the prosthetic device such as full or partial denture, therefor bio-adhesion between the newly prepared modified bio-active containing PMMA was tested against pig ear skin structure and results are summarized in table 1 Chitosan hydrogels showed the highest adhesive force and the work of adhesion. This can be expected because of the well-known intrinsic bio adhesive properties of chitosan [39]. The adequate water absorption capacity together with the cationic nature, which promotes binding to the negative surface of skin structure, can also interpret this results.

Table 1: Bio-adhesion table. View Table 1


The first step for successful colonisation of mucosal surfaces or any other surface by C. albicans is adhesion [40]. Although among the functions of Propolis, the fungicidal property has already been shown, in this study, we aimed to verify its effectiveness in inhibiting the adhesion of C. albicans biofilm on a denture surface (Figure 7).

Figure 7: Surfaces of the materials after exposure to artificial saliva and oxygen as an in vitro model for the biofilm formation after 3 weeks of storage. a. Shiit/PMMA/Chi, b. Cop/PMMA/Ch, c. Pr/PMMA/Ch. View Figure 7


The reinforcement and bio-active addition of the copaiba oil, propolis (Brazilian) or shiitake mushroom extract of the tested PMMA dental resin resulted in no statistically significant increase of its compressive of tensile strength. The additional benefits of the functionalized bio-material as preventative measure for the biofilm formation as well as build in bio-active free radical defense capability of the materials make them ideal candidates for further development and application in the materials for prosthetic devices.


  1. Yli-Urpo A, Lappalainen R, Huuskonen O (1985) Frequency of damage to and need for repairs of removable dentures. Proc Finn Dent Soc 81: 151-155.

  2. Jagger DC, Harrison A, Jandt KD (1999) The reinforcement of dentures. J Oral Rehabil 26: 185-194.

  3. Nejatian T, Johnson A, Noort RV (2006) Reinforcement for denture base resin. Advanced Sciences and Technologies 4: 124-129.

  4. Kostoulas IE, Kavoura VT, Frangou MJ, Polyzois GL (2008) The effect of length parameter on the repair strength of acrylic resin using fibers or metal wires. Gen Dent 56: 51-55.

  5. DeBoer J, Vermilyea SG, Brady RE (1984) The effect of carbon fiber orientation on the fatigue resistance and bending properties of two denture resins. J Prosthet Dent 51: 119-121.

  6. Pfaller MA, Diekema DJ (2007) Epidemiology of invasive candidiasis: a persistent public health problem. Clin Microbiol Rev 20: 133-163.

  7. Blot S, Cankurtaran M, Petrovic M, Vandijck D, Lizy C, et al. (2009) Epidemiology and outcome of nosocomial bloodstream infection in elderly critically ill patients: a comparison between middle-aged, old, and very old patients. Crit Care Med 37: 1634-1641.

  8. Dimopoulos G, Paiva JA, Meersseman W, Pachl J, Grigoras I, et al. (2012) Efficacy and safety of anidulafungin in elderly, critically ill patients with invasive Candida infections: a post hoc analysis. Int J Antimicrob Agents 40: 521-526.

  9. Lockhart SR, Joly S, Vargas K, Swails-Wenger J, Enger L, et al. (1999) Natural defenses against Candida colonization breakdown in the oral cavities of the elderly. J Dent Res 78: 857-868.

  10. Perchyonok VT, Zhang S, Oberholzer T (2012) Towards Development of Novel Chitosan Based Drug Delivery Prototypes Devices for Targeted Delivery Drug Therapy at the Molecular Level in Aqueous Media. Curr Org Chem 16: 2437-2439.

  11. Perchyonok VT, Zhang S, Oberholzer T (2012) Alternative chitosan based drug delivery system to fight oral mucositis: synergy of conventional and bioactives towards the optimal solution. Curr Nanosci 8: 541-547.

  12. Perchyonok V Tamara, Reher Vanessa, Zhang Shengmiao, Nicolaas BJ, Sias GR (2015) Bioinspired-Interpenetrating Network (IPNs) Hydrogel (BIOF-INPs) and TMD in Vitro: Bioadhesion, Drug Release and Build in Free Radical Detection and Defense. OJST 5: 53-61.

  13. Tamara PV, Vanessa R, Shengmiao Z, Nicolaas BJ, Sias GR (2015) Bioactive-Functionalized Interpenetrating Network Hydrogel (BIOF-IPN): A Novel Biomaterial Transforming the Mechanism of Bio-Repair, Bio-Adhesion and Therapeutic Capability - An In Vitro Study. J Interdiscipl Med Dent Sci 3: 1.

  14. Tamara PV, Shengmiao Z, Nicolaas BJ, Sias GR (2014) Evaluation of tetracycline containing chitosan hydrogels as potential dual action bio-active restorative materials capable of wound healing: in vitro approach Biointerface. Res App Chem 4: 843-849.

  15. Rabea EI, Badawy ME, Stevens CV, Smagghe G, Steurbaut W (2003) Chitosan as antimicrobial agent: applications and mode of action. Biomacromolecules 4: 1457-1465.

  16. Miyake Y, Tsunoda T, Minagi S, Akagawa Y, Tsuru H, et al. (1990) Antifungal drugs affect adherence of Candida albicans to acrylic surfaces by changing the zeta-potential of fungal cells. FEMS Microbiol Lett 57: 211-214.

  17. Orgaz B, Lobete MM, Puga CH, San Jose C (2011) Effectiveness of chitosan against mature biofilms formed by food related bacteria. Int J Mol Sci 12: 817-828.

  18. Martinez LR, Mihu MR, Han G, Frases S, Cordero RJ, et al. (2010) The use of chitosan to damage Cryptococcus neoformans biofilms. Biomaterials 31: 669-679.

  19. Rocha BA, Rodrigues MR, Bueno PCP, Costa-Machado ARM, Vaz MMOL, et al. (2012) Preparation and thermal characterization of inclusion complex of Brazilian green propolis and hydroxypropyl-β-cyclodextrin: increased water solubility of the chemical constituents and antioxidant activity. J Therm Anal Calorim 108: 87-94.

  20. Waterman PG, Mole S (1994) Analysis of phenolic plant metabolites. Blackwell Scientific Publications, London.

  21. Carlson RP, Taffs R, Davison WM, Stewart PS (2008) Anti-biofilm properties of chitosan-coated surfaces. J Biomater Sci Polym Ed 19: 1035-1046.

  22. Martinez LR, Mihu MR, Tar M, Cordero RJ, Han G, et al. (2010) Demonstration of antibiofilm and antifungal efficacy of chitosan against candidal biofilms, using an in vivo central venous catheter model. J Infect Dis 201: 1436-1440.

  23. Sarac YS, Basoqlu T, Ceylan GK, Sarac D, Yapici O (2004) Effect of denture base surface pretreatment on microleakage of a silicone-based resilient liner. J Prosthet Dent 92: 283-287.

  24. Sarac D, Sarac YS, Basoglu T, Yapici O, Yuzbasioglu E (2006) The evaluation of microleakage and bond strength of a silicone-based resilient liner following denture base surface pretreatment. J Prosthet Dent 95: 143-151.

  25. Tugut F, Akin H, Mutaf B, Akin GE, Ozdemir AK (2012) Strength of the bond between a silicone lining material and denture resin after Er:YAG laser treatments with different pulse durations and levels of energy. Lasers Med Sci 27: 281-285.

  26. Al-Athel M, Jagger R, Jagger D (2002) Effect of ageing on the bond strength of a permanent denture soft lining material. J Oral Rehabil 29: 992-996.

  27. Takahashi JM, Consani RL, Henriques GE, Nobilo MA, Mesquita MF (2011) Effect of accelerated aging on permanent deformation and tensile bond strength of autopolymerizing soft denture liners. J Prosthodont 20: 200-204.

  28. Senna PM, Da Silva WJ, Faot F, Del Bel Cury AA (2011) Microwave disinfection: cumulative effect of different power levels on physical properties of denture base resins. J Prosthodont 20: 606-612.

  29. Minami H, Suzuki S, Ohashi H, Kurashige H, Tanaka T (2004) Effect of surface treatment on the bonding of an autopolymerizing soft denture liner to a denture base resin. Int J Prosthodont 17: 297-301.

  30. Burdock GA (1998) Review of the biological properties and toxicity of bee propolis (propolis). Food Chem Toxicol 36: 347-363.

  31. Bankova V, Christov R, Kujumgiev A, Marcucci MC, Popov S (1995) Chemical composition and antibacterial activity of Brazilian propolis. Z Naturforsch C 50: 167-172.

  32. Zhang Z, Guoying Lv, Pan H, Wu Y, Fan L (2009) Effects of Different Drying Methods and Extraction Condition on Antioxidant Properties of Shiitake (Lentinusedodes). Food Sci Technol Res 15: 547-552.

  33. Veiga VF Jr, Zunino L, Calixto JB, Patitucci ML, Pinto AC (2001) Phytochemical and antioedematogenic studies of commercial copaiba oils available in Brazil. Phytother Res 15: 476-480.

  34. Maeda T, Hong G, Sadamori S, Hamada T, Akagawa Y (2012) Durability of peel bond of resilient denture liners to acrylic denture base resin. J Prosthodont Res 56: 136-141.

  35. Goncalves LM, Del Bel Cury AA, Sartoratto A, Garcia Rehder VL, Silva WJ (2012) Effects of undecylenic acid released from denture liner on Candida biofilms. J Dent Res 91: 985-989.

  36. Uludamar A, Ozyesil AG, Ozkan YK (2011) Clinical and microbiological efficacy of three different treatment methods in the management of denture stomatitis. Gerodontology 28: 104-110.

  37. Pinto JR, Mesquita MF, Henriques GE, de Arruda Nobilo MA (2002) Effect of thermocycling on bond strength and elasticity of 4 long-term soft denture liners. J Prosthet Dent 88: 516-521.

  38. Bulad K, Taylor RL, Verran J, McCord JF (2004) Colonization and penetration of denture soft lining materials by Candida albicans. Dent Mater 20: 167-175.

  39. Rodger G, Taylor RL, Pearson GJ, Verran J (2010) In vitro colonization of an experimental silicone by Candida albicans. J Biomed Mater Res B Appl Biomater 92: 226-235.

  40. Garcia RM, Leon BT, Oliveira VB, Del Bel Cury AA (2003) Effect of a denture cleanser on weight, surface roughness, and tensile bond strength of two resilient denture liners. J Prosthet Dent 89: 489-494.