Reline Resins Research Articles

The antimicrobial activity of an antiseptic soap against Candida Albicans and Streptococcus Mutans single and dual-species biofilms on denture base and reline acrylic resins.

To evaluate the effect of antiseptic soap on single and dual-species biofilms of Candida albicans and Streptococcus mutans on denture base and reline resins. Samples of the resins were distributed into groups (n = 9) according to the prevention or disinfection protocols. In the prevention protocol, samples were immersed in the solutions (Lifebuoy, 0.5% sodium hypochlorite solution and PBS) for 7, 14 and 28 days before the single and dual-species biofilms formation. Overnight denture disinfection was simulated. In the disinfection protocol, samples were immersed in the same solutions during 8 hours after the single and dual-species biofilms formation. Antimicrobial activity was analyzed by counting colony-forming units (CFU/mL) and evaluating cell metabolism. Cell viability and protein components of the biofilm matrix were evaluated using confocal laser scanning microscopy (CLSM). Data were submitted to ANOVA, followed by Tukey's post-test (α = 0.05) or Dunnett's T3 multiple comparisons test. In the prevention protocol, Lifebuoy solution effectively reduced the number of CFU/mL of both species. In addition, the solution decreased the cell metabolism of the microorganisms. Regarding disinfection protocol, the Lifebuoy solution was able of reduce approximately of 2-3 logs for all the biofilms on the denture base and reline resin. Cellular metabolism was also reduced. The images obtained with CLSM corroborate these results. Lifebuoy solution was effective in reducing single and dual-species biofilms on denture base and reline resins.

Bond strength of relined print and conventional denture base resins after aging

Objectives: To compare the bond strength of printed and conventionally produced denture base resins to reline resins after being submitted to a physical-chemical aging process. Methods: Sixty specimens (10×10×3.3 mm) of two printed (V-Print Dentbase and Denture 3D+) and one conventionally produced (Probase Hot) denture base resins were relined with two acrylic resins: Ufi Gel Hard C and Probase Cold (n=10). The specimens were submitted to 1000 cycles of thermal fluctuations (5-55ºC) and 28 days of pH cycles using pH=3 (8 h/day) and pH=7 (16 h/day). Then, the shear bond strength was evaluated (1 KN; 1 mm/min), and the failure mode was classified as adhesive, cohesive, or mixed type. Data were analyzed with Kruskal-Wallis and t-tests (=0.05). Results: Bond strength values ranged from 8.9 to 21.5 MPa. No statistically significant (p=0.07) differences were found between the bond strength of the three denture base acrylic resins. The reline resin did not significantly (p=0.07) affect the bond strength of the two printed resins. However, relining the Probase Hot with Probase Cold yielded a higher bond strength (p<0.001) than with Ufi Gel Hard C. Only the Probase Hot-Ufi Gel Hard C group revealed 100% of failures classified as adhesive type. Conclusions: The two printed denture base resins obtained similar bond strength to conventionally produced denture base resin after being submitted to thermal and chemical aging

Understanding the Mechanical, Surface, and Color Behavior of Oral Bioactive Prosthetic Polymers under Biodegradation Processes.

Changes in the properties of resin-based polymers exposed to the oral environment can emerge when chlorhexidine (CHX) is incorporated to develop bioactive systems for treating denture stomatitis. Three reline resins loaded with CHX were prepared: 2.5 wt% in Kooliner (K), 5 wt% in Ufi Gel Hard (UFI), and Probase Cold (PC). A total of 60 specimens were submitted to physical aging (1000 cycles of thermal fluctuations, 5-55 °C) or chemical aging (28 days of pH fluctuations in artificial saliva, 6 h at pH = 3, 18 h at pH = 7). Knoop microhardness (30 s, 98 mN), 3-point flexural strength (5 mm/min), and surface energy were tested. Color changes (ΔE) were determined using the CIELab system. Data were submitted to non-parametric tests (α = 0.05). After aging, bioactive K and UFI specimens were not different from the controls (resins without CHX) in mechanical and surface properties. Thermally aged CHX-loaded PC specimens showed decreased microhardness and flexural strength but not under adequate levels for function. The color change was observed in all CHX-loaded specimens that underwent chemical aging. The long-term use of CHX bioactive systems based on reline resins generally does not impair removable dentures' proper mechanical and aesthetic functions.

Using optical coherence tomography images to evaluate fungal growth in reline resins

As changes in hard or soft oral tissues normally have a microbiological component, it is important to develop diagnostic techniques that support clinical evaluation, without destroying microbiological formation. The optical coherence tomography (OCT) represents an alternative to analyze tissues and microorganisms without the need for processing. This imaging technique could be defined as a fast, real-time, in situ, and non-destructive method. Thus, this study proposed the use of the OCT to visualize biofilm by Candida albicans in reline resins for removable prostheses. Three reline resins (Silagum-Comfort, Coe-Comfort, and Soft-Confort), with distinct characteristics related to water sorption and fungal inhibition were used. A total of 30 samples (10 for each resin group) were subjected to OCT scanning before and 96 h after inoculation with Candida albicans (URM 6547). The biofilm analysis was carried out through a 2D optical Callisto SD-OCT (930 nm) operated in the spectral domain. Then, the images were preprocessed using a [Formula: see text] Gaussian filter to remove the noise, and then Otsu binarization, allowing segmentation and pixel counting. The layer’s biofilm formed was clearly defined and, indeed, its visualization is modified by water sorption of each material. Silagum-Comfort and Soft-Confort showed some similarities in the scattering of light between the clean and inoculated samples, in which, the latter samples presented higher values of light signal intensity. Coe-Comfort samples were the only ones that showed no differences between the clean or inoculated images. Therefore, the results of this study suggest that OCT is a viable technique to visualize the biofilm in reline materials. Because findings in the literature are still scarcely using the OCT technique to visualize biofilm in reline resins, further studies are encouraged. It should not contain any references or displayed equations.

Investigation of the effect of different surface treatments for preventing detachment of polyetheretherketone and titanium attachment matrix housings in overdentures: An in vitro study.

The attachment matrix housing (AMH) of implant overdentures is not chemically bonded with acrylic resins. Therefore, AMH may lose due to insertion and removal forces. This study aims to investigate the effects of different surface treatments to reduce the detachment of AMH and to compare the adhesion of the AMH used in implant-supported overdentures made of different materials with the reline acrylic resin. Titanium and polyetheretherketone (PEEK) AMHs were separated into four surface treatment groups; no treatment, airborne-particle abrasion (APA) applied, universal bond (UB) applicated, APA, and UB applicated. Eight millimeters in diameter and ten millimeters tall straws were used to restrain the reline acrylic resin prepared according to the manufacturer's instructions and the resin was injected onto the surface-treated AMH. After the polymerization was completed, the universal testing machine performed the tensile bond strength (TBS) test with a fishing line passed through the acrylic resins. TBS data were analyzed with two and one-way ANOVA and Tukey HSD post hoc tests (α =0.05). According to the two-way ANOVA results, titanium AMHs (103.78 ± 45.98 N) showed higher TBS than PEEK AMHs (67.81 ± 28.61 N). UB applicated titanium groups showed significantly increased TBS values. Using titanium AMHs may be a better choice in situations where clinical aesthetic expectations are unimportant for adhesion to reline acrylic resins. The UB resin significantly increased the bonding of the titanium AMHs with reline resins. The application of UB resin to titanium housings can be easily applied in a clinical situation and can reduce the detachment of the titanium AMHs.

Comparison of shear bond strength between various temporary prostheses resin blocks fabricated by subtractive and additive manufacturing methods bonded to self-curing reline resin

Comparison of shear bond strength between various temporary prostheses resin blocks fabricated by subtractive and additive manufacturing methods bonded to self-curing reline resin

Comparison of shear bond strength of CAD/CAM and conventional heat-polymerized acrylic resin denture bases to auto-polymerized and heat-polymerized acrylic resins after aging

BackgroundThe aim of this study was to investigate the shear bond strength of CAD/CAM and conventional heat polymerized acrylic resin denture bases bonded to self-cured and heat-cured acrylic resins after aging. Material and MethodsA total of 40 cubic specimens were fabricated from conventional heat-polymerized and CAD/CAM denture base resins. Denture base resin specimens in each group were divided into two subgroups (n=10) in which they were bonded to either a heat-cured (HC) or a self-cured (SC) reline resin. Subsequently, the specimens were subjected to thermocycling. Then the shear bond strength (SBS) of specimens was measured using the universal testing machine. After testing, modes of failure were examined using light microscopy. The results were submitted to statistical analysis. ResultsMann-Whitney test showed that in each group of denture base materials, specimens bonded to HC reline resin had significantly higher SBS than those bonded to SC reline resin (P<0.001). Conventional denture base bonded to HC resin exhibited the highest value of SBS. There was no statistically significant differences between the SBS of HC reline resin bonded to conventional and CAD/CAM with regards to SBS (P=0.218). However, the SBS of SC reline resin was significantly higher when bonded to CAD/CAM compared to conventional denture base resin (P<0.001). ConclusionsHeat-cured reline resin showed higher shear bond strength to both CAD/CAM and conventional heat-polymerized denture resin in comparison to self-cured reline resin. Although there was no difference between the bond strength of heat-cured reline resin to CAD/CAM and conventional denture base, self-cured reline material produced stronger bond with CAD/CAM denture base. Key words:CAD/CAM, shear bond strength, reline, denture base resin.

Effect of repair methods and materials on the flexural strength of 3D-printed denture base resin.

The aim of this study was to evaluate the flexural strength of a 3D-printed denture base resin (Cosmos Denture), after different immediate repair techniques with surface treatments and thermocycling. Rectangular 3D-printed denture base resin (Cosmos Denture) specimens (N = 130) were thermocycled (5,000 cycles, 5℃ and 55℃) before and after the different repair techniques (n = 10 per group) using an autopolymerized acrylic resin (Jet, J) or a hard relining resin (Soft Confort, SC), and different surface treatments: Jet resin monomer for 180 s (MMA), blasting with aluminum oxide (JAT) or erbium: yttrium-aluminum-garnet laser (L). The control group were intact specimens. A three-point flexural strength test was performed, and data (MPa) were analyzed by ANOVA and Games-Howell post hoc test (α = 0.05). Each failure was observed and classified through stereomicroscope images and the surface treatments were viewed by scanning electron microscope (SEM). Control group showed the highest mean of flexural strength, statistically different from the other groups (P < .001), followed by MMA+J group. The groups with L treatment were statistically similar to the MMA groups (P > .05). The JAT+J group was better than the SC and JAT+SC groups (P < .05), but similar to the other groups (P > .05). Adhesive failures were most observed in JAT groups, especially when repaired with SC. The SEM images showed surface changes for all treatments, except JAT alone. Denture bases fabricated with 3D-printed resin should be preferably repaired with MMA+J. SC and JAT+SC showed the worst results. Blasting impaired the adhesion of the SC resin.

The Effects Of Antimicrobial And Physical Properties Of Denture Soft Reline Material

Candida albicans(C. albicans) is one of the bacteria that resides in the oral cavity, and the ones living in medical and commercial denture resins, commonly cause diseases. Therefore, this study was conducted to confirm the antibacterial activity of C. albicans using a denture base resin containing peony extract with antibacterial properties.&#x0D; For the antibacterial effect, optical density and confocal laser microscopy were used. Contact angle measurements and color change measurements were performed to confirm the physical change of the material added with the antibacterial agent to the denture reline resin.&#x0D; As a result of the antibacterial test, the experimental group exhibited antibacterial activity against C. albicans. Compared to the optical density results, the results of the experimental group showed a significant difference. As a result of Fluorescent images showing (confocal laser microscope), the control group showed a lot of live bacteria, no bacteria appeared in the experimental group. All group did not show any physical changes. As a result of the contact angle measurement, the surface of the experimental group was changed to hydrophilic. In addition, there was no change in the color of the denture reline resin containing peony extract. In conclusion, it was confirmed that the peony extract contained antibacterial activity of the denture resin, and further studies should be conducted on various bacteria for denture base resin disinfection.

Antibacterial effects of soft denture reline resin containing natural extract

Candida albicans (C. Albicans) is one of the bacteria that reside in the oral cavity, and the ones living in medical and commercial denture resins, commonly cause diseases. Therefore, this study was conducted to confirm the antibacterial activity of C. Albicans using a denture base resin containing peony extract with antibacterial properties. Contact angle measurements and color change measurements were performed to confirm the physical change of the material added with the antibacterial agent to the denture reline resin. As a result of the antibacterial test, the experimental group exhibited antibacterial activity against C. Albicans. Compared to the optical density results, the results of the experimental group showed a significant difference. As a result of Fluorescent images showing (confocal laser microscope), the control group showed a lot of live bacteria, and no bacteria appeared in the experimental group. All group did not show any physical changes. As a result of the contact angle measurement, the surface of the experimental group was changed to hydrophilic. In addition, there was no change in the color of the denture reline resin containing peony extract. In conclusion, it was confirmed that the peony extract contained antibacterial activity of the denture resin, and further studies should be conducted on various bacteria for denture base resin disinfection.

Autopolymerized poly(methyl methacrylate) reinforced with alumina nanoparticles

Background/Aim. Mechanical properties, most significantly flexural strength of cold polymerized acrylic dental materials, used for denture reparation are lower compared to the equivalent hot polymerized materials. This paradox can be rectified by the application of alumina nanoparticles, which was the aim of this work. Methods. The liquid component of the commercial autopolymerized denture reline resin was modified with 0.05%, 0.2% and 1.5% (wt) 13 nm hydrophobic Al2O3. These mixtures, along with the unmodified liquid, were mixed with the powder component to form test specimens. Flexural modulus and strength were tested, while the results were statistically evaluated by the oneway ANOVA analysis followed by Tukey?s test. Differential scanning calorimetry, scanning electron microscopy and energy dispersive X-ray analysis were performed to assess the heat and fracture surface features. Results. A statistically significant increase in flexural modulus was obtained only for 0.2% nanoparticle content, while flexural strength was significantly increased for specimens modified with 0.05% and 0.2% nanoparticles. Moreover, the rise of nanoparticle content to 1.5% contributed the formation of agglomerates, giving unsatisfactory mechanical properties. Also, the rise in glass transition temperature was noted for the most effective 0.05 and 0.2% Al2O3 contents. Conclusion. The 0.2% 13 nm Al2O3 loading is the most effective in improving the tested mechanical properties of cold polimerized poly(methyl methacrylate) reline resin.

Effect of Different Surface Treatments of Resin Relined Fiber Posts Cemented With Self-adhesive Resin Cement on Push-out and Microtensile Bond Strength Tests.

When luting relined fiber posts with self-adhesive cement, the surface treatment of the posts influences the adhesion of the fiber posts to root dentin. This study evaluated the effect of surface treatment and silanization of resin composite on the bond strength of relined fiber posts cemented with self-adhesive resin cement. Push-out and microtensile bond strength (MTBS) tests were performed in this study. The endodontic treatment of 80 single-rooted bovine teeth was first performed in the push- out test segment, followed by weakening the intracanal walls by diamond bur. Then, the glass fiber posts were adapted with resin composite to fill the root canals, followed by photoactivation and resin surface conditioning according to four different experimental conditions: no conditioning as control, 10% hydrofluoric acid, 35% hydrogen peroxide, or air abrasion with alumina particle (all groups were subdivided into "with silanization" or "without silanization," thus totaling eight experimental groups). Self-adhesive resin cement was used for the post cementation. Four slices per tooth were obtained for the push-out tests. Next, 160 blocks of resin composite were first produced for the MTBS tests; their bonding surfaces were conditioned (as mentioned, ie, eight treatments), and they were cemented to each other. The 80 sets (n=10/treatment) were then cut into microbars (16/set): eight were immediately tested, while the other eight were thermocycled (12,000×) and stored (120 days) before MTBS. Failure modes and topographic analyses were performed after treatments. There was no statistically significant difference for the push-out results. In MTBS, surface treatment and silanization had a significant effect (p<0.001). Aging decreased bond strength for all groups. Considering the aged groups, air abrasion promoted the highest values and silanization improved bond strength for all treatments except air abrasion. The alumina particle air abrasion of the relining resin composite promoted the highest bond strengths when luting with self-adhesive resin cement.

Tensile bond strength of chairside reline resin to denture bases fabricated by subtractive and additive manufacturing

Tensile bond strength of chairside reline resin to denture bases fabricated by subtractive and additive manufacturing

EVALUATION OF POROSITY AND BIOFILM FORMATION IN RELINE RESINS THROUGH OPTICAL COHERENCE TOMOGRAPHY

Objective To evaluate the porosity and adhesion of mixed colony microorganisms in reline resins by means of optical coherence tomography (OCT). Study Design Two commercial brands of reline resins (Soft-Comfort and Coe-Comfort) were used, divided into 2 groups, and 10 samples were made for each group. Samples were submitted to OCT scanning before and after 96 hours inoculation with Candida albicans. The OCT images were composed of 2000 columns and 512 lines, obtained from a commercial model, Callisto SD-OCT (Thorlabs, USA), operating at 930 nm of central wavelength and 7 μm of axial resolution in the air. After the images were acquired, they were submitted to qualitative and quantitative analysis. Results It was possible to verify differences between OCT images before and after inoculation of microorganisms (MO). These differences suggest the observation of fluid absorption and presence of biofilm in the resins. As for the porosity, the Soft-Comfort resin presented higher values compared with the Coe-Comfort resin. Conclusions The OCT technique allows to evaluate the adhesion of microorganisms and porosity in reline resins. To evaluate the porosity and adhesion of mixed colony microorganisms in reline resins by means of optical coherence tomography (OCT). Two commercial brands of reline resins (Soft-Comfort and Coe-Comfort) were used, divided into 2 groups, and 10 samples were made for each group. Samples were submitted to OCT scanning before and after 96 hours inoculation with Candida albicans. The OCT images were composed of 2000 columns and 512 lines, obtained from a commercial model, Callisto SD-OCT (Thorlabs, USA), operating at 930 nm of central wavelength and 7 μm of axial resolution in the air. After the images were acquired, they were submitted to qualitative and quantitative analysis. It was possible to verify differences between OCT images before and after inoculation of microorganisms (MO). These differences suggest the observation of fluid absorption and presence of biofilm in the resins. As for the porosity, the Soft-Comfort resin presented higher values compared with the Coe-Comfort resin. The OCT technique allows to evaluate the adhesion of microorganisms and porosity in reline resins.

Beneficial Effects of Ethyl-Cyanoacrylate Coating Against Candida Albicans Biofilm Formation.

The aim of this study was to verify whether modifications made in a hard chairside reline resin by an ethyl-cyanoacrylate adhesive, ECA (Super Bonder®, Loctite, Itapevi, SP, Brazil) would be able to inhibit or reduce Candida albicans biofilm formation on its surface, comparing to a commercial surface sealant (BisCover®, Bisco, Schaumburg, USA). Reline resin specimens were fabricated and randomly divided into 6 groups (n=8): CG (control group), no surface treatment; ECA1, ECA coating on the surface before sterilization; ECA2, ECA coating after sterilization; ECA3, ECA incorporated in the resin bulk; DPE1, BisCover® coating before sterilization; DPE2, BisCover® coating after sterilization. Specimens were inoculated with C. albicans SC5314 (1x107 cells/mL) and incubated for 24 h. Then, the biofilm were stained with LIVE/DEAD® BaclightTM L7007 Kit and analyzed by Confocal Laser Scanning Microscopy. The images were evaluated by bioImageL® v.2.0 software and total biovolume (µm3), viable cells (%), and covered area (%) were calculated. Data were statistically analyzed by Kruskal-Wallis and Dunn tests (p<0.05). Results showed that ECA-coated groups presented better results, reducing C. albicans biofilm formation. Acquired images revealed that these groups (ECA1 and ECA2) presented a reduced number of cells, mostly in yeast form (less pathogenic), while the other groups presented higher number of cells, mostly in hyphae form (more pathogenic). Based on these findings, a beneficial effect of Super Bonder® coating reline resins surface could be demonstrated, suggesting a promising way to prevent fungal biofilm formation on dentures.

Adhesion potential of relining materials to polyamide and PMMA-based denture base materials: effect of surface conditioning methods

This study evaluated the bond strength of relining materials to different denture base materials polyamide and polymethylmethacrylate denture base materials after various surface conditioning methods. Denture base resin specimens (N = 128; n = 8 per group) (10 × 10 × 2.5 mm3) were fabricated out of injection-moulded thermoplastic polyamide resin (POL) (Deflex) and heat-polymerized polymethylmethacrylate (PMMA, Dura Dent) (HC). The specimens were randomly divided into 4 main groups according to different surface conditioning methods: (a) No conditioning, control (C), (b) grinding with green stone (G), (c) application of primer (V), (d) silica coating with Al2O3 particles coated with SiO2 (Rocatec) (R). Half of the specimens in each group received auto-polymerized hard relining resin (GC, GC Reline Hard) and the other half PMMA based relining resin (SC, Dura Dent). After thermocycling (×5000), the bonded specimens were tested under tensile forces (0.5 mm/min). Data (MPa) were analyzed using Mann–Whitney U and Kruskal–Wallis tests (alpha = 0.05). Bond strength of relining resins were significantly higher to PMMA than to POL, regardless of the conditioning method (p < 0.05). While R positively affected the bond strength results (p < 0.05) (4.99 ± 1.65–3.27 ± 1.31), application V or G did not show significant effect to POL-relining resin adhesion. After R conditioning, bond strength values were significantly higher in HC-GC group (7.48 ± 2.32) than POL-GC group (3.27 ± 1.31) (p < 0.05). Adhesion of auto-polymerized relining materials to thermoplastic polyamide or polymethylmethacrylate denture resins could be improved after surface conditioning with silica-coating.

Comparison of the Water Sorption and Solubility of Four Reline Acrylic Resins after Immersion in Food-Simulating Agents.

Objectives:Water sorption and water solubility adversely affect the mechanical properties and biocompatibility of the denture material. This study aimed to evaluate the water sorption and solubility of three direct hard reline acrylic resins and a heat-curing one after immersion in food-simulating agents.Materials and Methods:This study was performed on four groups of samples (n = 10 per group). The samples were made of three direct hard reline acrylic resins (TDV Cold Liner Rebase, Tokuyama Rebase II Fast, GC Reline Hard) and a heat-curing one (Meliodent). Each group was divided into four subgroups (n = 10) to undergo 7-day immersion in distilled water, 75% ethanol/water, 0.02 N citric acid, and heptane. Water sorption and solubility were calculated according to Oysaed and Ruyter formula. The statistical analyses were done by using SPSS software (version 22). Kruskal–Wallis H Test and Dunn's test were used to detect any significant difference among the groups (P < 0.05).Results:The median range of water solubility and water sorption values were −0.87–4.92 and 3.75–27.25 μg/mm3, respectively. The median solubility and sorption values of different resins differed significantly in the same solution (P < 0.05). Besides, immersion in different solutions caused significant differences in the median solubility and sorption values of each reline material (P < 0.05), except for Meliodent whose solubility was not significantly affected by different solutions (P = 0.16).Conclusions:Water sorption and solubility values of the tested hard reline resins were within the range of International Standards Organization 1567:1999. Given the low sorption and solubility values, these hard reline materials can be safely used in clinical situations.

Chlorhexidine loading of acrylic reline resins – Microhardness and flexural strength after thermal aging

Chlorhexidine loading of acrylic reline resins – Microhardness and flexural strength after thermal aging

Cytotoxicity of long-term denture base materials.

The aim of this study was to evaluate the cytotoxic effect of various denture base materials following four different aging periods. In total, 48 disc-shaped specimens per each group were prepared: Group I: acrylic resin polymerized in cool water and heated up to 100°C over 45 min and boiled for 15 min; Group II: acrylic resin polymerized under pressure in 40°C-45°C water bath for 10 min; Group III: autopolymerized hard relining resin Cold Liner Rebase; Group IV: autopolymerized hard relining resin Truliner; Group V: soft relining resin DentuSil. Then the specimens were stored in water for 24 h or 15 days, or thermocycled 2500 times or 10,000 times. Cytotoxicity was evaluated with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay using L929 cells after 72-h cell incubation. Cell viability percentages were counted and statistical analyses were performed. The results were also evaluated according to ISO standard 10993-5. All materials showed similar cell viability percentages following 24-h water storage and 2500 and 10,000 thermal cycles. Following 15-day water storage, a statistically significant difference was observed between the materials. Comparisons of the aging periods for each material showed statistically significant differences. Groups III and IV showed moderately cytotoxic effect following 15-day water storage. The remaining groups showed slightly cytotoxic or non-cytotoxic effect. Polymerizing acrylic resins under pressure can be an alternative to conventional polymerizing to ensure a faster denture repair while providing similar cell viability values. Heat-cured acrylic resins provide higher cell viability than hard chairside lining materials in a 15-day period.

Effects of relining materials on the flexural strength of relined thermoplastic denture base resins.

PURPOSEThe aim of this study was to evaluate the effects of relining materials on the flexural strength of relined thermoplastic denture base resins (TDBRs).MATERIALS AND METHODSFor shear bond strength testing, 120 specimens were fabricated using four TDBRs (EstheShot-Bright, Acrytone, Valplast, Weldenz) that were bonded with three autopolymerizing denture relining resins (ADRRs: Vertex Self-Curing, Tokuyama Rebase, Ufi Gel Hard) with a bond area of 6.0 mm in diameter and were assigned to each group (n=10). For flexural strength testing, 120 specimens measuring 64.0×10.0×3.3 mm (ISO-1567:1999) were fabricated using four TDBRs and three ADRRs and were assigned to each group (n=10). The thickness of the specimens measured 2.0 mm of TDBR and 1.3 mm of ADRR. Forty specimens using four TDBRs and 30 specimens using ADRRs served as the control. All specimens were tested on a universal testing machine. For statistical analysis, Analysis of variance (ANOVA) with Tukey's test as post hoc and Spearman's correlation coefficient analysis (P=.05) were performed.RESULTSAcry-Tone showed the highest shear bond strength, while Weldenz demonstrated the lowest bond strength between TDBR and ADRRs compared to other groups. EstheShot-Bright exhibited the highest flexural strength, while Weldenz showed the lowest flexural strength. Relined EstheShot-Bright demonstrated the highest flexural strength and relined Weldenz exhibited the lowest flexural strength (P<.05). Flexural strength of TDBRs (P=.001) and shear bond strength (P=.013) exhibited a positive correlation with the flexural strength of relined TDBRs.CONCLUSIONThe flexural strength of relined TDBRs was affected by the flexural strength of the original denture base resins and bond strength between denture base resins and relining materials.