Heat-polymerized Acrylic Resin Research Articles

Improvement of the Adhesive Strength between Silicone-Based Soft Liner and Thermocycled Denture Base with Plasma Treatment

Purpose: The aim of this study was to investigate the effect of oxygen plasma treatment on the tensile bond strength of a silicone-based soft liner to a thermocycled denture base. Methods: 2 10×10×1 mm heat-polymerized acrylic resin blocks for X-ray photoelectron spectroscopy (XPS) analysis were prepared (one served as control, and another treated by oxygen plasma for 4 min). 30 (10×10×1 mm) acrylic resin blocks for contact angle measurement and 80 (8×10×30 mm) for tensile test were also prepared and equally divided into five groups: a control group and four experimental groups (exposure to oxygen plasma for 1min, 2 min, 3 min and 4 min, respectively). All blocks were thermocycled (5-55°C, 5000 cycles) before oxygen plasma treatment. After oxygen plasma treatment, the soft liner was processed between two blocks according to manufacturer’s instructions and polymerized. All specimens were submitted to a tensile test using a universal testing machine and results were statistically analyzed (ANOVA, p<0.05, Tukey’s HSD test). Results: The XPS analysis showed that the O/C ratio increased from 0.324 for the control group to 0.498 for the 4-min exposure group. With regard to water contact angle, the lowest value was obtained from the 4-min exposure group (37.32°). For the tensile test, the highest tensile bond strength was observed in the 4-min exposure group (1.998 ± 0.110 MPa) and the lowest was in the control group (0.831 ± 0.059 MPa). Conclusions: Oxygen plasma treatment was efficient in improving the tensile bond strength between siliconebased soft denture liner and thermocycled denture base.

The effect of two artificial salivas on the adhesion of Candida albicans to heat-polymerized acrylic resin.

PURPOSEXerostomia can diminish the quality of life, leads to changes in normal chemical composition of saliva and oral microbiata, and increases the risk for opportunistic infections, such as Candida albicans. Various artificial salivas have been considered for patients with xerostomia. However, the knowledge on the antifungal and antiadhesive activity of artificial saliva substitutes is limited. The aim of the present study was to evaluate influence of two artificial salivas on the adhesion of Candida albicans to the polymethylmethacrylate disc specimens.MATERIALS AND METHODSTwo commercial artificial salivas (Saliva Orthana and Biotene Oral Balance Gel) were selected. 45 polymethylmethacrylate disc specimens were prepared and randomly allocated into 3 groups; Saliva Orthana, Biotene-Oral Balance gel and distilled water. Specimens were stored in the artificial saliva or in the sterile distilled water for 60 minutes at 37℃. Then they were exposed to yeast suspensions including Candida albicans. Yeast cells were counted using ×40 magnification under a light microscope and data were analysed.RESULTSAnalysis of data indicated statistically significant difference in adhesion of Candida albicans among all experimental groups (P=.000). Findings indicated that Saliva Orthana had higher adhesion scores than the Biotene Oral Balance gel and distilled water (P<.05).CONCLUSIONIn comparison of Saliva Orthana, the use of Biotene Oral Balance Gel including lysozyme, lactoferrin and peroxidase may be an appropriate treatment method to prevent of adhesion of Candida albicans and related infections in patients with xerostomia.

The effect of aluminum oxide addition on the flexural strength of heat activated acrylic resin: An in vitro study

Aim: This study was done to investigate the effect of adding 5-20% aluminum oxide (Al 2 O 3 ) powder by weight on the flexural strength of heat-polymerized acrylic resin. Materials and Methods: A total of 50 specimens of heat-polymerized acrylic resin were fabricated and were divided into five groups (n = 10). Group A was the control group (unmodified acrylic resin specimens). The specimens of the remaining four groups i.e., Groups B, C, D and E were reinforced with Al 2 O 3 powder to achieve loadings of 5%, 10%, 15% and 20% by weight. Specimens were stored in distilled water for 1 week and the flexural strength of the specimens was tested in a universal testing machine (5 mm/min crosshead speed). Results were analyzed by one-way analysis of variance. Weibull analysis was used to calculate the Weibull modulus, characteristic strength and the required stress for 1% and 5% probabilities of failure. Results: The mean flexural strength values of the heat-polymerized acrylic resin were (in MPa) 92.01, 114.46, 116.77, 123.11 and 129.72, for Groups A, B, C, D and E, respectively. The flexural strength increased significantly with the incorporation of Al 2 O 3 . Conclusion: Al 2 O 3 fillers are potential components to be added in denture bases to provide increased flexural strength. Adequate flexural strength of denture base is quite essential for the longevity of the prosthesis.

Evaluating the efficiency of humic acid to remove micro-organisms from denture base material.

To evaluate the efficiency of humic acid substances on removing micro-organisms from denture base materials. Old denture wearer needs effective, easy-use and safe denture-cleaning material. Square-shaped, heat-polymerised acrylic resin specimens (n=550) were prepared and divided into five groups (n=110 for each) corresponding to the microbial contamination (Candida albicans, Staphylococcus aureus, Bacillus cereus, Enterococcus faecalis, Pseudomonas aeruginosa). Contaminated specimens were randomly assigned to the application of five different denture-cleaning agents as follows (n=20 for each): Kloroben, Corsodyl, Steradent, Corega, experimental solution with humic acid. Ten specimens were assessed as an experimental control carried out simultaneously for the treatment groups for each micro-organism. It was divided into two groups: negative control and positive control (n=5 for each). All acrylic specimens were incubated 37°C for 24h (for bacterial strains) and 37°C for 48h (for yeast strains). After incubation period, all brain-heart infusion broths (BHI) which contain disinfectant acrylic specimens were cultured on 5% sheep blood agar (for bacteria) and Sabouraud dextrose agar (SDA) for yeast using loop. The numbers of colony-forming units per millilitre (CFU/ml) were calculated. The results were analysed by Mann-Whitney U-test and Kruskal-Wallis tests (p=0.05). Corsodyl and Kloroben completely eliminated the adherence of all investigated micro-organisms (100%) and showed the highest removal activity compared with other cleaning agents (p<0.05). There was no statistically significant difference between Corsodyl and Kloroben (p≥0.05), and there was no statistically significant difference between Corega, Steradent and experimental solution (p≥0.05). Humic acid could be used as an alternative 'natural' solution for denture-cleaning agent.

The Effect of Repeated Microwaving Disinfection on the Dimensional Stability of Acrylic Dentures.

The aim of this study was to evaluate the effect of repeated microwave disinfections on the dimensional stability of acrylic dentures. Three groups of dentures made of a heat polymerized acrylic resin were tested. I: dentures kept in water (control group). II: dentures microwaved daily while being immersed into water (wet disinfection). III: dentures microwaved daily without being immersed into water (dry disinfection). Measurements were taken across three reference points, on two occasions: after curing and immersion in water for 24 hours, and one week later. Data obtained were analyzed using one-way analysis of variance (ANOVA) and Scheffe's multiple range test. The results showed that the microwave disinfection provokes dimensional changes of the same pattern (shrinkage). The dentures which underwent wet disinfection exhibited the greatest shrinkage (p<0.05). Disinfection using microwave energy may cause dimensional changes (shrinkage) of complete dentures. The microwave "dry disinfection" method can be safely applied in everyday practice since the dimensional changes which occurred seem to be of no clinical significance.

Effect of silver nitrate incorporation into heat polymerized acrylic resin on some mechanical properties

Background: Polymers are very rarely used in their form. These modifications are carried out in order to improve the properties of polymers.Recently silver have been used successfully as antimicrobial (medical and dental) biomaterials that can prevent caries and infection of implants Purposes: The aim of the present in vitro study is to evaluate the effect of addition of silver nitrate to acrylic resin in different concentrationsthrough several tests part of these are: The effect of this additive on impact strength, transverse strength, and tensile strength of AgNO3 – loaded resin, and to assess any effect of addition of silver nitrate on coloration of acrylic resin. Materials and methods: Different concentrations of silver nitrate (9.375, 15, 30, 60, 120, 150, 300, 600 and 900 ppm) were prepared from stock solution of 1000 ppm silver nitrate. The specimens were prepared in accordance with the manufacturer's instructions and the tested silver nitrate solution was added to the acrylic resin powder and monomer in a fixed volume (0.2ml). Controls devoid of silver nitrate were included. Results: Fourier transform infra-red confirmed that there was no chemical bond between the Poly methyl methacrylate and silver nitrate. There was insignificant increasing (P=0.05) in impact strength observed when compared with control group. In transverse strength test, significant reduction was show (P<0.001). While for tensile strength there was insignificant reduction with 9.375(P=0.05NS) and 15(P=0.42NS) ppm silver nitrate. However, it was significant above 15 ppm (P<0.001). Darkening of silver nitrate -loaded resins were shown to be started with concentration of silver nitrateof 300 ppm and above. Conclusions: The additions of silver nitrate to acrylic resins yield good color stability and mechanical properties, depending on the concentration of silver nitrate.

Effect of different palatal vault shapes and woven glass fiber reinforcement on dimensional stability of high impact acrylic denture base [Part I

Background: Change in palatal vault shape and Reinforcement of high impact acrylic denture base resin may in turn affect the dimensional accuracy of acrylic resin and affecting the fitness of the denture. The aim of study is to evaluate the effect of fiber reinforcement for high-impact acrylic resin denture base with different palatal vault shapes on linear dimensional change and effect of palatal vault shapes on linear dimensional changes of non-reinforced and fiber reinforced high impact denture base acrylic resin Material and method: Three different palatal vault shapes were prepared on standard casts using CNC (computer numerical control) machine. 60 samples of heat polymerized high impact acrylic resin maxillary denture base were fabricated onto each definitive cast according to manufacturer instruction. Samples divided into three main experimental groups represented the three different palatal vault shapes (20 samples for each main group); 1st rounded 2nd U-shaped and the 3rd groups V-shaped. Each main group divided into two subgroups (10 samples for each subgroup) representing non fiber reinforced high impact acrylic group as a control and the fiber reinforced high impact acrylic. The measurements of linear dimensional changes of denture bases done at two stages, 1st 24 hour after polymerization and 2nd measurement done after one month storage in distilled water at room temperature. Results and conclusion: Linear dimensional changes of high impact acrylic denture base not affected by glass fiber reinforcement p-value in all reference lines ≥ 0.05, while topographical change in maxillary vault shapes effects on the linear dimensional changes in woven glass fiber reinforced high impact acrylic denture base p-value < 0.05. Key words: High impact acrylic resin, topographical change in vault, woven glass fiber reinforcement.

Evaluation of Shear Bond Strength of Artificial Teeth to Heat Cure Acrylic and High Impact Heat Cure Acrylic Using Autoclave Processing Method

Debonding and fracture of artificial teeth from denture bases are common clinical problem, bonding of artificial teeth to heat cure acrylic and high impact heat cure acrylic denture base materials with autoclave processing method is not well known. The aim of this study was to evaluate the effect of autoclave processing method on shear bond of artificial teeth to heat cure denture base material and high impact heat cure denture base material. Materials and methods: Heat polymerized (Vertex) and high impact acrylic (Vertex) acrylic resins were used. Teeth were processed to each of the denture base materials after the application of different surface treatments. The sample (which consist of artificial tooth attached to the denture base at 45 degree) are consist of (80) artificial teeth from the same model of central incisor, they were prepared , treated and bonded to the conventional heat cured and high impact acrylic denture base material then processed. Control group (Group A 40 samples) in which acrylic resins PMMA cured by conventional water- bath processing technique (74°C for 1.5 hours then boil for 30 minutes),the group was subdivided to 20 samples heat cure acrylic and 20 samples high impact acrylic. Experimentalgroups (Group B 40 samples) in which acrylic resins was cured by autoclave at 121°C, 210KPa. For 30min.the group subdivided to 20 samples heat cure acrylic and 20 samples high impact acrylic. For each subgroup, the 20 samples were subdivided according to surface treatment into: 1-Five acrylic teeth without any surface treatment (control). 2- Five acrylic teeth with diatoric preparation (retention grooves). 3- Five acrylic teeth conditioned with thinner. 4- Five acrylic teeth with retention grooves and thinner. Results: Statistical analysis revealed that chemical and mechanical treatment of acrylic teeth improved the shear bond with heat cure and high impact acrylicalsoautoclave processing improvedthe shear bond with acrylic teeth in high impact acrylic. Conclusion: Autoclave polymerization is suggested as alternative method for processing denture base resins. Autoclave polymerization can be easily performed in laboratory conditions. In High Impact Acrylic, there were highly significant differences of autoclave processing technique compared with water bath regarding the shear bond

MİKRODALGA VE OTOKLAV POST-POLİMERİZASYON UYGULAMALARININ SERT BESLEME AKRİLİKLERİNİN BÜKÜLME DİRENCİNE ETKİSİNİN KARŞILAŞTIRILMASI

Purpose: To compare the effect of autoclave and microwave post-polymerization treatments on flexural strength of hard reline and heat-polymerized acrylic resins.Material and Methods: Hard chairside reline and heat-polymerized acrylic resin specimens (64x10x3.3 mm) were fabricated. 80 specimens with 4 subgroups for each acrylic (n=20) received post-polymerization treatment by microwave irradiation and two autoclave post-polymerization modalities (short and long). Specimens were subjected to flexural strength testing using 3-point bending with a crosshead speed of 5 mm/min. Two-way, one-way ANOVA and Tukey’s HSD tests were used for statistical analysis of data. Results: The microwave post-polymerization significantly increased the strength of heat polymerized acrylic resin and hard chairside reline resin specimens where its effect was significantly higher than the autoclave and control groups (p 0.05). Conclusion: Using autoclave, may be considered as a viable post-polymerization treatment alternative in order to increase the flexural strength of relined dentures.

Histopathological changes by the use of soft reline materials: a rat model study.

AimTo assess the histopathological changes of rat palatal mucosa exposed to soft reline materials.MethodsForty-five adult female Wistar rats with controlled living conditions and fed ad libitum were employed. Palatal appliances of heat-polymerized acrylic resin Lucitone 550 were manufactured and worn by forty animals during 14 days. Five animals did not use the appliances (G1) and were used to control the appliance influence. One experimental group (n = 10) used the appliances without any relining material (G2) to control the material effect. Three experimental groups (n = 10) received the following soft reline materials below appliances: Dentusoft (G3), Dentuflex (G4), and Trusoft (G5). Appliances from half of each experimental group(n = 5) was immersed in water bath at 55°C for 10 min before use. Animals were slaughtered and the palates were fixed in 10% buffered formalin. Hematoxylin and eosin stained sections of 5 µm were analyzed by computerized planimetry. Cellular compartment, keratin and total epithelial thickness, and basement membrane length were measured to histopathological description.Analysis of variance and Tukey post-hoc test were used to data examination(α = 0.05).ResultsFor heat-treatment groups, G4 showed less elongated ridges at the basal layer interface (p = 0.037) than G2. When comparing the conditions with and without heat-treatment, only G2 showed a significant decrease in the cellular compartment, keratin layer and total epithelium thickness (p<0.05).ConclusionThe post-polymerization for Lucitone 550 was an effective method to reduce the changes in the rat palatal mucosa. The soft reline materials tested did not cause significant histopathological changes in the rat palatal mucosa.

Investigation of the effect of different polishing techniques on the surface roughness of denture base and repair materials

The rough surface of denture base materials may cause plaque accumulation and staining. Thus,theeffectiveness of polishing techniques should be known. The purpose of this study was to compare the effects of chairside polishing kits and conventional laboratory techniques on the surface roughness of denture base and repair materials. Ninety-six specimens, 50 ±1 mm in diameter and 0.5 ±0.05 thick, were fabricated from heat-polymerized acrylic resin (HP), polyamide resin (PR), and autopolymerizing resin (AP) and submitted to grinding with a tungsten carbide bur. The specimens were divided into 4 groups according to the polishing technique used: control group without polishing, conventional laboratory polishing, polished with Acrylic Polisher HP blue kit, and polished with AcryPoint polishing kit. Surface roughness (Ra) was measured after polishing with a profilometer. Data were analyzed with a 2-way analysis of variance, and the Tukey honestly significant difference (HSD) test was performed to identify significant differences (α=.05). The polishing techniques significantly affected the Ra of denture base materials (P<.001). The highest mean averageRa was measured for the control group. The lowest Ra values were determined in specimens exposed to conventional laboratory polishing techniques. No significant differences were found between Acrylic Polisher HP blue and AcryPoint polishing kits (P>.05). Statistically significant differences were found in the Ra between the PR and both the HP and AP (P<.001); PR exhibited the highest Ra values. Conventional laboratory polishing was the most effective polishing technique. A significantly smoother surfacethan that of the specimens in the control group was produced with chairside silicone polishing kits.

Effect of surface treatments on the bond strength of soft denture lining materials to an acrylic resin denture base

Adhesive failure between acrylic resin and resilient liner material is commonly encountered in clinical practice. The purpose of this study was to evaluate the effect of different surface treatments on the bond strength of 2 different resilient lining materials to an acrylic resin denture base. Ninety-six dumbbell-shaped specimens were fabricated from heat-polymerized acrylic resin, and 3 mm of the material was cut from the thin midsection. The specimens were divided into 6 groups according to their surface treatments: no surface treatment (control group), 36% phosphoric acid etching (acid group), erbium:yttrium-aluminum-garnet (Er:YAG) laser (laser group), airborne-particle abrasion with 50-μm Al2O3 particles (abrasion group), an acid+laser group, and an abrasion+laser group. The specimens in each group were divided into 2 subgroups according to the resilient lining material used: heat-polymerized silicone based resilient liner (Molloplast B) and autopolymerized silicone-based resilient liner (Ufi Gel P). After all of the specimens had been polymerized, they were stored in distilled water at 37°C for 1 week. A tensile bond strength test was then performed. Data were analyzed with a 2-way ANOVA, and the Sidak multiple comparison test was used to identify significant differences (α=.05). The effects of the surface treatments and resilient lining materials on the surface of the denture base resin were examined with scanning electron microscopy. The tensile bond strength was significantly different between Molloplast B and Ufi Gel P (P<.001). The specimens of the acid group had the highest tensile bond strength, whereas those of the abrasion group had the lowest tensile bond strength. The scanning electron microscopy observations showed that the application of surface treatments modified the surface of the denture base resin. Molloplast B exhibited significantly higher bond strength than Ufi Gel P. Altering the surface of the acrylic resin denture base with 36% phosphoric acid etching increased bond strength.

Surface treatment with methyl formate-methyl acetate increased the shear bond strength between reline resins and denture base resin

Chemical surface treatment increases the shear bond strength (SBS) between hard reline resins (HRRs) and denture base resin. To evaluate the effect of methyl formate-methyl acetate (MF-MA), when used as a surface treatment agent, on the SBS between denture base resin and different HRRs. One hundred and twenty specimens of heat-polymerised acrylic resin denture base (Meliodent(®) ) were divided into 12 groups. These groups comprised denture base relined with three self-polymerised HRRs [Unifast trad(®) (UT), Tokuyama(®) RebaseII Fast (TR), Ufi gel hard(®) (UG)], and treated with their respective Bonding Agent (BA) or by MF:MA solutions at ratios of 35:65, 25:75, and 15:85 for 15 s. The SBS was measured using a Universal Testing Machine. The data were analysed using two-way anova and post hoc Tukey's analysis at p < 0.05. The highest SBS was in the UT treated with MF:MA at a ratio of 25:75 group, followed by UT treated with MF:MA at ratios of 15:85, 35:65, UT treated with BA, and all UG treated with MF:MA groups. The SBS of the UT treated with MF:MA at a ratio of 25:75 group was significantly higher than those of the groups treated with BA. The SBS of the UG treated with MF:MA groups was significantly higher than control. The TR groups treated with BA or MF:MA groups showed no significant difference in SBS. Surface treatment with MF-MA significantly enhanced the SBS of denture base resin and UT and UG compared to that of the groups treated with BA.

Effect of Titanium dioxide nanoparticles on the flexural strength of polymethylmethacrylate: an in vitro study.

To improve the flexural strength of polymethylmethacrylate (PMMA). To evaluate whether the incorporation of titanium dioxide nanoparticles in polymethylmethacrylate (PMMA) increases the flexural strength and to compare the different concentrations of titanium dioxide nanoparticles and its relation to flexural strength. Study was conducted in Sri Ramachandra University utilizing 40 specimens manufactured from clear heat polymerizing acrylic resin. Forty specimens of clear heat polymerizing acrylic resin of dimensions 65 Χ 10 Χ 3 mm as per ISO 1,567 standardization were fabricated and were grouped into A (CONTROL) with no titanium dioxide (TiO2) nanoparticles, B with 0.5 gms of TiO 2 nanoparticles, C with 1 gm of TiO 2 nanoparticles and D with 2.5 gms of TiO 2 nanoparticles added.The concentrations of titanium dioxide in each group were 1 wt%, 2 wt% and 5 wt%. Universal testing machine INSTRON was used to load at the center of the specimen with a cross head speed of 1.50 mm/min and a span length of 40.00 mm. ANOVA and multiple comparisons are carried out using the independent t-test. The ANOVA result shows that there is a significant difference between the groups with respect to the mean flexural strength. Highest mean flexural strength is observed in Group D, while the lowest is seen in Group A. Independent t-test revealed that there was a statistical significance between Group A and Group D (0.041) and between Group B and Group D (0.028). The results concluded that polymethylmethacrylate reinforced with different concentrations of titanium dioxide nanoparticles showed superior flexural strength than those of normal PMMA.

Evaluation of adhesion of reline resins to the thermoplastic denture base resin for non-metal clasp denture

This study aimed to evaluate the tensile and transverse bond strength of chairside reline resins (Tokuyama Rebase II, Mild Rebaron LC) to a thermoplastic acrylic resin (Acrytone) used for non metal clasp denture. The results were compared with those of a conventional heat polymerized acrylic resin (Paladent 20) and a thermoplastic polyamide resin (Biotone). The failure sites were examined by scanning electron microscopy to evaluate the mode of failure. As results, the bond strength of reline resins to a thermoplastic acrylic resin was similar to the value of a conventional heat polymerized acrylic resin. However, thermoplastic polyamide resin showed the lowest value. The results of this study indicated that a thermoplastic acrylic resin for non metal clasps denture allows chairside reline and repair. It was also found that the light-polymerized reline resin had better bond strength than the autopolymerizing reline resin in relining for a conventional heat polymerized acrylic resin and a thermoplastic acrylic resin.

Effect of Zirconium Oxide Nano-Fillers Addition on the Flexural Strength, Fracture Toughness, and Hardness of Heat-Polymerized Acrylic Resin

Purpose: The mechanical strength of polymethyl methacrylate (PMMA) remains far from ideal for maintaining the longevity of denture. The purpose of this study was to evaluate the effect of Zirconium oxide (ZrO2) nanofillers powder with different concentration (1.5%, 3%, 5% and 7%) on the flexural strength, fracture toughness, and hardness of heat-polymerized acrylic resin. Materials and methods: Zirconium oxide powders with different concentrations (1.5%, 3%, 5% and 7%) were incorporated into heat-cure acrylic resin (PMMA) and processed with optimal condition (2.5:1 Powder/monomer ratio, conventional packing method and water bath curing for 2 hours at 95。C) to fabricate test specimens of PMMA of dimensions (50 × 30 × 30 mm) for the flexural strength, fracture toughness, and (50 × 30 × 30 mm) were fabricated for measuring hardness. PMMA without additives was prepared as a test control. Three types of mechanical tests; flexural strength, fracture toughness and hardness were carried out on the samples. The recorded values of flexural strength in (MPa), fracture toughness in (MPa.m1/2), and hardness (VHN) were collected, tabulated and statistically analyzed. One way analysis of variance (ANOVA) and Tukey’s tests were used for testing the significance between the means of tested groups which are statistically significant when the P value ≤ 0.05. Results: Addition of Zirconium oxide nanofillers to PMMA significantly increased the flexural strength, fracture toughness and hardness. Conclusion: These results indicate that Zirconium oxide nanofillers added to PMMA has a potential as a reliable denture base material with increased flexural strength, fracture toughness, and hardness. According to the results of the present study, the best mechanical properties were achieved by adding 7%wt ZrO2 concentration.

Effect of repair resin type and surface treatment on the repair strength of heat-polymerized denture base resin

Acrylic resin denture fracture is common in prosthodontic practice. When fractured denture bases are repaired, recurrent fractures frequently occur at the repair surface interface or adjacent areas. The purpose of this study was to evaluate the effect of different surface treatments on the flexural strength of the acrylic resin denture base repaired with heat-polymerized acrylic resin, autopolymerizing resin, and light-polymerized acrylic resin. Ninety-six specimens of heat-polymerized acrylic resin were prepared according to the American Dental Association Specification No. 12 (65.0 × 10.0 × 2.5 mm) and sectioned into halves to create a repair gap (3.0 × 10 × 2.5 mm). The sectioned specimens were divided into 3 groups according to their repair materials. The specimens from each group were divided into 4 subgroups according to their surface treatments: a control group without any surface treatment; an experimental group treated with methyl methacrylate monomer (MMA group); an experimental group treated with airborne-particle abrasion with aluminum oxide particles of 250-μm particle size (abrasion group); and an experimental group treated with erbium:yttrium-aluminum-garnet laser (laser group). After the surface treatments, the 3 materials were placed into the repair gaps and then polymerized. After all of the specimens had been ground and polished, they were stored in distilled water at 37°C for 1 week and subjected to a 3-point bend test. Data were analyzed with a 2-way analysis of variance, and the Tukey honestly significant difference test was performed to identify significant differences (α=.05). The effects of the surface treatments and repair resins on the surface of the denture base resin were examined with scanning electron microscopy. Significant differences were found among the groups in terms of repair resin type (P<.001). All surface-treated specimens had higher flexural strength than controls, except the surface treated with the methyl methacrylate in the heat-polymerized group. A significant difference between the control and abrasion groups (P=.013) was found. The scanning electron microscopy observations showed that the application of surface treatments modified the surface of the denture base resin. The repair procedure with heat-polymerized resin exhibited significantly higher flexural strength than that of the autopolymerized and light-polymerized resins. In addition, the airborne-particle abrasion with aluminum oxide particles of 250-μm particle size improved the flexural strength of the specimens tested.

Evaluation of the properties of a tissue conditioner containing origanum oil as an antifungal additive

Adherence and colonization of Candida albicans on tissue conditioners is common and results in irritation of the denture-bearing mucosa. The purpose of this study was to investigate the antifungal activity and properties of a tissue conditioner by incorporating origanum oil. Origanum oil at varying concentrations was incorporated into a poly(methyl methacrylate) based tissue conditioner (Visco-gel), and its antifungal activity against Candida albicans was evaluated at 1 day and 1 week by using the agar punch well method. The adherence of Candida albicans, surface roughness, tensile strength, and bond strength of the tissue conditioner with an optimized origanum oil concentration were evaluated. The data were subjected to 2-way ANOVA (α=.05). Sixty vol% origanum oil in tissue conditioner (Visco-gel) showed a mean inhibitory zone of 21.00 ± 1.58 mm at 1 day and 13.44 ± 0.88 mm at 1 week. The control group showed 90 ± 6.80 yeast cells/mm(2) at 1 day and 165 ± 7.63 yeast cells/mm(2) at 1 week, whereas the group with origanum oil showed 16 ± 1.15 yeast cells/mm(2) at 1 day and 32 ± 4.00 yeast cells/mm(2) at 1 week. Surface roughness was less with the incorporation of origanum oil. Tensile strength at 1 day was 0.91 ± 0.52 N for the control group, whereas the group with origanum oil showed 0.16 ± 0.05 N. At 1 day, the bond strength of 3.97 ± 0.75 MPa was observed with control specimens, whereas tissue conditioner with origanum oil showed a bond strength of 3.73 ± 0.65 MPa. Within the limitations of this in vitro study, origanum oil can be used as an additive to tissue conditioner to reduce the adherence of Candida albicans without significantly affecting its bond strength to heat-polymerized acrylic resin.

High Performance Liquid Chromatographic Determination of Residual Monomer Released from Heat‐Cured Acrylic Resin. An In Vivo Study

Heat-polymerized acrylic resins are used in dentistry for complete denture fabrication. Despite the polymerization method, conversion of monomer into polymer is often incomplete with free or unreacted residual monomer remaining in the polymerized resin. The aim of this study was to determine the amount of residual monomeric methyl methacrylate (MMA) leaching in the saliva of patients wearing complete dentures in their postinsertion period. Thirty edentulous participants as first-time complete denture wearers (age 60 to 65 years) were selected. All the prostheses were fabricated using a similar standard technique with a heat-cured acrylic resin denture base material. Saliva samples were collected at time intervals of 1 hour, 1 day, and 3 days postdenture insertion. Participants were asked to discharge saliva every 30 seconds into a pre-weighed screw-capped container for a 5-minute period. MMA levels were measured using high performance liquid chromatography. Data were analyzed by ANOVA and Tukey-HSD. The maximum concentration of monomer released into saliva peaked 1 day after insertion of the complete dentures. The mean (SD) MMA content was 0.04 ± 0.01 (μg/ml) 1 hour after insertion, and 0.3 ± 0.09 (μg/ml), and 0.05 ± 0.01 (μg/ml) on the first and third days postinsertion, respectively. Although the released monomeric MMA was not at toxic levels, it could potentially sensitize complete denture patients or elicit an allergic reaction. The risk of the residual material as a primary irritant for a sensitizing reaction could be minimized by immersion of the denture in water for 24 hours before insertion.

Strength comparison of four techniques to secure implant attachment housings to complete dentures

Implant overdentures become thinner and weaker after direct transfer of implant attachment housings. While much has been published on denture repair, these data do not directly apply to implant overdentures because the introduction of a metal housing changes the character of the repair. It is desirable to make a strong repair to avoid prosthesis fracture. The purpose of this study was to compare the flexural strengths of 4 different methods for chairside direct transfer of implant attachment housings. Eighty 11.5 × 9.1 × 39 mm heat-polymerized acrylic resin blocks were processed, assessed for porosities, and polished. An 8.5 mm diameter hole was drilled to a depth of 5 mm in the center of each block. Attachment housings were set into the bases with 4 different repair materials: autopolymerized acrylic resin (APAR), light-polymerized acrylic resin (LPAR), autopolymerized acrylic resin with silanated attachment housings (APSAH), and light-polymerized acrylic resin with silanated attachment housings (LPSAH). Blocks were immersed in water for 30 days in an incubator. A 3-point bend test was done in a universal testing machine, and load to fracture was recorded (MPa). Results were compared with 2-way ANOVA (α=.05). APSAH had the highest mean flexural strength at fracture (863.1 ±87 MPa) as compared to APAR (678.4 ±72.4 MPa), LPAR (550.9 ±119.3 MPa), and LPSAH (543.2 ±100.8 MPa). A comparison among the 4 groups showed that there were significant differences in maximum flexural strength (P<.001). The mean maximum strength of autopolymerized acrylic resin groups was significantly higher than light-polymerized acrylic resin groups. Silanation increased strength significantly compared to nonsilanated groups. The flexural strength of autopolymerized acrylic resin with silanated attachment housings was significantly higher than autopolymerized acrylic resin alone, light-polymerized acrylic resin alone, or light-polymerized acrylic resin with silanated attachment housings. Autopolymerized acrylic resin produced stronger constructs than light-polymerized materials.