Denture Base Polymers Research Articles

Effect of curcumin on physico-mechanical properties of heat polymerized denture base resin

PurposeCurrent denture base resins lack adequate strength and antimicrobial properties, necessitating the exploration of alternative solutions. The purpose of this study was to evaluate the effects of curcumin incorporation on the physico-mechanical properties of heat-cured denture base resin, filling a gap in the literature regarding this correlation.MethodsHeat-cured denture base resin was supplemented with increasing concentrations of curcumin (CR). Groups were designated as CR-0 (0%), CR-0.05 (0.05%), CR-0.10 (0.10%), CR-0.50 (0.50%), and CR-1 (1%), based on the increasing concentrations of curcumin incorporated into the material. Physico-mechanical properties, including flexural strength, surface roughness, fracture toughness, impact strength, and color difference, were evaluated following the testing standards. Statistical analysis involved Kruskal-Wallis ANOVA followed by Dunn’s test for multiple comparisons, with significance set at P ≤ 0.05 and Bonferroni’s correction applied to p-values.ResultsFlexural strength peaked at 153.80 MPa in the CR-0.10 group, while surface roughness was lowest at 0.14 micrometers in the CR-0.50 group. Fracture toughness reached its highest value at 1.80 kJ/m^2 in the CR-0.05 group, and impact strength was greatest at 6.52 Joules in the CR-0.05 group. Additionally, color difference was least pronounced in the CR-0.50 group. Flexural strength, surface roughness, fracture toughness, impact strength, and color difference varied significantly among the control group and different curcumin concentrations (P < 0.05).ConclusionsIncorporating curcumin into denture base resin alters both optical and mechanical properties. Further research is required to validate the findings and determine the optimal curcumin concentration without compromising the material efficacy.

Evaluation of the Bond Strength of Acrylic Teeth to Denture Base after Various Chemical Surface Treatments: An In Vitro Study.

The purpose of the present study was to assess the bonding capacity and efficacy of acrylic teeth to denture bases following two different chemical surface treatments. A two-metal mold measuring 35 mm in length and 12 mm in diameter was created specifically for the investigation in order to standardize the wax pattern-based tooth attachment at 45°. Following standard protocol, 75 wax cylinder specimens were flasked, dewaxed, and surface treatment of teeth was done as follows with 25 samples in each group-group I: control group, group II: monomethyl methacrylate monomer group, group III: acetone group. The curing process was completed following the packing of the denture base material. The samples' shear bond strength was assessed using a universal testing machine. Every sample was taken out when it fractured, and the shear load (Newton, N) was noted. The significance of the variation in applied shear load was assessed using one-way analysis of variance (ANOVA) and post hoc ANOVA Tukey's honestly significant difference (HSD) test at the 5% level of significance. The maximum shear bond strength was found in the samples treated with acetone (183.21 ± 0.06) followed by samples treated with monomethyl methacrylate monomer (171.64 ± 0.12) and the control group (149.32 ± 0.04). A statistically significant difference was found between the different groups (p < 0.001). In conclusion, according to the current study's findings, acetone chemical surface treatment of acrylic teeth produced the strongest bond when compared with the control group and monomethyl methacrylate monomer. In prosthodontic practice, artificial teeth regularly de-bond and separate from the denture base. A weak interface is produced when certain clinical conditions, such as ridge prominence, cause excessive cutting of the acrylic teeth and base. Where the denture base polymer meets the teeth's highly cross-linked matrix, it de-bonds adhesively. Therefore, the bonding between the acrylic teeth and the denture base material can be improved by the chemical surface treatment. How to cite this article: Chaudhuri NG, Lahiri B, Francis NT, et al. Evaluation of the Bond Strength of Acrylic Teeth to Denture Base after Various Chemical Surface Treatments: An In Vitro Study. J Contemp Dent Pract 2024;25(6):514-517.

Post-processing of a 3D-printed denture base polymer: Impact of a centrifugation method on the surface characteristics, flexural properties, and cytotoxicity

ObjectivesTo investigate the impact of a centrifugation method on the surface characteristics, flexural properties, and cytotoxicity of an additively manufactured denture base polymer. MethodsThe tested specimens were prepared by digital light processing (DLP). A centrifugation method (CENT) was used to remove the residual uncured resin. In addition, the specimens were post-processed with different post-rinsing solutions: isopropanol (IPA), ethanol (EtOH), and tripropylene glycol monomethyl ether (TPM), respectively. A commercial heat-polymerized polymethyl methacrylate was used as a reference (REF). First, the values of surface topography, arithmetical mean height (Sa), and root mean square height (Sq) were measured. Next, flexural strength (FS) and modulus were evaluated. Finally, cytotoxicity was assessed using an extract test. The data were statistically analyzed using a one-way analysis of variance, followed by Tukey's multiple comparison test for post-hoc analysis. ResultsThe Sa value in the CENT group was lower than in the IPA, EtOH, TPM, and REF groups (p < 0.001). Moreover, the CENT group had lower Sq values than other groups (p < 0.001). The centrifugation method showed a higher FS value (80.92 ± 8.65 MPa) than the EtOH (61.71 ± 12.25 MPa, p < 0.001) and TPM (67.01 ± 9.751 MPa, p = 0.027), while affecting IPA (72.26 ± 8.80 MPa, p = 0.268) and REF (71.39 ± 10.44 MPa, p = 0.231). Also, the centrifugation method showed no evident cytotoxic effects. ConclusionsThe surfaces treated with a centrifugation method were relatively smooth. Simultaneously, the flexural strength of denture base polymers was enhanced through centrifugation. Finally, no evident cytotoxic effects could be observed from different post-processing procedures. Clinical significanceThe centrifugation method could optimize surface quality and flexural strength of DLP-printed denture base polymers without compromising cytocompatibility, offering an alternative to conventional rinsing post-processing.

Assessing the suitability of fused deposition modeling to produce acrylic removable denture bases.

To study the feasibility of using poly methyl methacrylate(PMMA) filament and fused deposition modeling (FDM) to manufacture denture bases via the development of a study that considers both conventional and additive-based manufacturing techniques. Five sample groups were compared: heat and cold cured acrylic resins, CAD/CAM milled PMMA, 3D-printed PMMA (via FDM), and 3D-printed methacrylate resin (via stereolithography, SLA). All groups were subjected to mechanical testing (flexural strength, impact strength, and hardness), water sorption and solubility tests, a tooth bonding test, microbiological assessment, and accuracy of fit measurements. The performance of sample groups wasreferred to ISO 20795-1 and ISO/TS 19736. The data was analyzed using one-way ANOVA. Samples manufactured using FDM performed within ISO specifications for mechanical testing, water sorption, and solubility tests. However, the FDM group failed to achieve the ISO requirements for the tooth bonding test. FDM samples presented a rough surface finish which could ultimately encourage an undesirable high level of microbial adhesion. For accuracy of fit, FDM samples showed a lower degree of accuracy than existing materials. Although FDM samples were a cost-effective option and were able to be quickly manufactured in a reproducible manner, the results demonstrated that current recommended testing regimes for conventionally manufactured denture-based polymers are not directly applicable to additive-manufactured denture base polymers. Therefore, new standards should be developed to ensure the correct implementation of additive manufacturing techniques within denture-based fabrication workflow.

Effect of Copper Oxide Nanoparticles Incorporation on the Mechanical and Surface Properties of Heat Polymerized Denture Base Resin: An In Vitro Study.

Effect of Copper Oxide Nanoparticles Incorporation on the Mechanical and Surface Properties of Heat Polymerized Denture Base Resin: An In Vitro Study.

In Vitro Study of the Surface Roughness, Hardness, and Absorption of an Injection-Molded Denture Base Polymer, Manufactured under Insufficient Mold Solidification

The current study sought to investigate the changes in surface hardness, roughness, and moisture absorption of the Vertex ThermoSens polymer (Vertex Dental, 3D Systems, The Netherlands) following immersion in artificial saliva for various periods (7, 14, and 28 days). A total of 60 rectangular specimens with dimensions of 20 mm in length, 20 mm in width, and 3 mm in thickness were made. Due to insufficient mold solidification, these specimens were made utilizing the injection molding process. A Mitutoyo Surftest 4 roughness meter (Mitutoyo, Aurora, IL, USA) was used to measure the surface roughness of the test materials. The ThermoSens polymer hardness was assessed using the Shor method and D—HSD scale, while absorption was measured with a Sartorius analytical balance. Results indicated the highest mean hardness after 28 days (M = 77.6) (Surface 1) and the lowest for the control group (M = 59) (Surface 2). The maximum surface roughness occurred in direction 2.2 pre-immersion (Ra = 2.88 μm) and 7 days post-removal (Ra = 2.95 μm). The control group exhibited the lowest absorption (Wsp = 1.524 mg/mm3), with the highest mean values over 28 days (Wsp = 1.541 mg/mm3). The elevated flask and plaster temperature slowed polymer solidification, resulting in longer macromolecules and improved mechanical properties and surface features.

In vitro evaluation of shape-memory hydrogels for removable dental prostheses and optimization of phase-transition temperature for intraoral use

Removable dental prostheses require periodic relining with the loss of intaglio surface fit because of mucosal shape changes over time. Therefore, a new material with high adaptability to tissue changes over time would be beneficial. This study focused on a shape-memory gel (SMG) that softens when heated, retains its shape when cooled, and returns to its original shape when reheated. The purpose was to optimize SMG for intraoral use by controlling the ratio of 2 acrylate monomers and to evaluate the changes in the shape memory and physical properties of SMG with temperature and to evaluate biocompatibility. SMG specimens were synthesized using the following mixing ratios of 2 monomers, docosyl acrylate (DA) and stearyl acrylate (SA): 0:100, 25:75, 50:50, 75:25, and 100:0. SMG specimens were photopolymerized using a fluorescent light-polymerizing unit. To evaluate shape memory as a function of temperature, permanent deformation was measured based on the standardized compression set test for thermoplastic rubber. For evaluation of the physical properties and cytotoxicity, a 3-dimensionally printed denture base material was used as the control material. All assessments were compared between the groups by using 1-way analysis of variance followed by the Tukey-Kramer multiple comparison test (α=.05). SMGs with a higher amount of DA maintained their compressed shape at room and intraoral temperatures. However, the SMG matrices softened and recovered their original shapes above 60°C. SMGs showed Shore A hardness equivalent to that of the denture-base polymer material at intraoral temperatures because of the high phase-transition temperature. The low water solubility of SMGs supported the biocompatibility test results. SMG, in which the phase-transition temperature was controlled by mixing acrylate monomers with different melting points, exhibited shape memory in the intraoral environment. The results indicate the feasibility of applying SMG for the fabrication of removable dental prostheses because of its high adaptability to tissue changes over time and biocompatibility.

The Effect of Exposure to Candida Albicans Suspension on the Properties of Silicone Dental Soft Lining Material.

While functioning in the oral cavity, denture soft linings (SL) are exposed to contact with the microbiota. Dentures can offer perfect conditions for the multiplication of pathogenic yeast-like fungi, resulting in rapid colonisation of the surface of the materials used. In vitro experiments have also shown that yeast may penetrate SL. This may lead to changes in their initially beneficial functional properties. The aim of this work was to investigate the effect of three months of exposure to a Candida albicans suspension on the mechanical properties of SL material and its bond strength to the denture base polymer, and to additionally verify previous reports of penetration using a different methodology. Specimens of the SL material used were incubated for 30, 60 and 90 days in a suspension of Candida albicans strain (ATCC 10231). Their shore A hardness, tensile strength, and bond strength to acrylic resin were tested. The colonization of the surface and penetration on fractured specimens were analysed with scanning electron and inverted fluorescence microscopes. Exposure to yeast did not affect the mechanical properties. The surfaces of the samples were colonised, especially in crystallized structures of the medium; however, the penetration of hyphae and blastospores into the material was not observed.

Effect of post-curing conditions on surface characteristics, physico–mechanical properties, and cytotoxicity of a 3D-printed denture base polymer

ObjectiveThis study aims to investigate the influence of post-polymerization (post-curing) conditions on surface characteristics, flexural properties, water sorption and solubility, and cytotoxicity of additively manufactured denture base materials. MethodsThe tested specimens were additively manufactured using digital light processing and classified into different post-curing condition groups: submerged in water (WAT), submerged in glycerin (GLY), and air exposure (AIR). An uncured specimen (UNC) was used as a control. The surface topography and roughness were observed. The flexural strength and modulus were determined via a three-point bending test. The water sorption and solubility were subsequently tested. Finally, an extract test was performed to assess cytotoxicity. ResultsDifferent post-curing conditions had no significant effects on the surface topography and roughness (Sa value). Various post-curing conditions also had no significant effects on the flexural strength. Notably, the flexural modulus of the WAT group (2671.80 ± 139.42 MPa) was significantly higher than the AIR group (2197.47 ± 197.93 MPa, p = 0.0103). After different post-curing conditions, the water sorption and solubility of the specimens met the ISO standards. Finally, all post-curing conditions effectively reduced cytotoxic effects. SignificancesPost-curing with different oxygen levels improved flexural properties, and flexural modulus significantly increased after the specimens were submerged in water. In addition, water sorption and solubility, and cytocompatibility were optimized by post-curing, irrespective of the post-curing conditions. Therefore, the water-submerged conditions optimized the flexural modulus of the 3D-printed denture base materials.

Evaluation of polymethyl-methacrylate and acetal denture base resins processed by two different techniques before and after nano-chlorohexidine surface treatment

BackgroundFlexible denture base polymers have gained popularity in modern dentistry however, their biofilm formation tendency, adversely affecting the oral tissue heath, remains a concern. Consequently, this study aimed to evaluate surface roughness and biofilm formation tendency of two types of denture base resins manufactured with two techniques before and after surface coating with chlorohexidine (CHX) NPs.Materials and methodsAcetal (AC) and Polymethyl-methacrylate (PMMA) resins manufactured by conventional and CAD/CAM methods were shaped into disk (10 X 10 X 1 mm). They were dipped for 8 h and 24 h in colloidal suspension prepared by mixing aqueous solution of CHX digluconate and hexa-metaphosphate (0.01 M). Surface roughness, optical density (OD) of microbial growth media and biofilm formation tendency were evaluated directly after coating. Elutes concentrations of released CHX were evaluated for 19 days using spectrophotometer. Three-way ANOVA and Tukey’s post-hoc statistical analysis were used to assess the outcomes.ResultsAC CAD/CAM groups showed statistically significant higher roughness before and after coating (54.703 ± 4.32 and 77.58 ± 6.07 nm, respectively). All groups showed significant reduction in OD and biofilm formation tendency after surface coating even after 19 days of CHX NPs release.ConclusionsBiofilm formation tendency was highly relevant to surface roughness of tested resins before coating. After CHX NPs coating all tested groups showed significant impact on microbial growth and reduction in biofilm formation tendency with no relation to surface roughness. Significant antimicrobial effect remained even after 19 days of NPs release and specimens storage.

Evaluation of the Linear Dimensional Stability of CAD/CAM Milled, 3-D Printed, and Heat-cured Denture Base Polymers Subjected to Thermocycling and Immersion in Artificial Saliva: An In vitro study

Evaluation of the Linear Dimensional Stability of CAD/CAM Milled, 3-D Printed, and Heat-cured Denture Base Polymers Subjected to Thermocycling and Immersion in Artificial Saliva: An In vitro study

Evaluation of Water Sorption and Solubility of 3D-Printed, CAD/CAM Milled, and PMMA Denture Base Materials Subjected to Artificial Aging

Background: This in vitro study aimed to investigate and evaluate the values of water sorption and water solubility of four types of denture base polymers—3D-printed NextDent 3D Denture + (NextDent, 3D Systems, Soesterberg, The Netherlands), CAD/CAM milled Ivotion Base (Ivotion Denture System, Ivoclar Vivadent, Schaan, Liechtenstein), PMMA conventional Vertex BasiQ 20 (Vertex Dental, 3D Systems, Soesterberg, The Netherlands), and conventional heat-cured BMS (BMS Dental Srl, Rome, Italy)—which were subjected to artificial aging. Materials and methods: 200 specimens were created (n = 50), dried, and weighed accurately. They were immersed in artificial saliva (T1 = 7 days, T2 = 14 days, T3 = 1 month) and re-weighed after water absorption. After desiccation at 37 °C for 24 h and then at 23 ± 1 °C for 1 h, samples were weighed again. Next, thermocycling (100 h, 5000 cycles, 5–55 °C) was performed, and the water sorption and solubility were re-measured. IBM SPSS Statistics 0.26 was used for data analysis, revealing a direct correlation between water sorption and material type. Thermocycling at 55 °C increased water sorption for BMS and Vertex BasiQ 20. In conclusion, NextDent’s 3D-printed resin had higher water sorption values throughout the study. Water solubility averages decreased over time, reaching the lowest in the 30-day period for CAD/CAM milled dental resin Ivotion Base. The artificial aging had no effect on Ivotion Base and NextDent’s water sorption. Thermocycling did not affect the solubility of the materials tested. The conducted study acknowledges the great possibilities of dental resins for additive and subtractive manufacturing for the purposes of removable prosthetics in daily dental practice.

Antifungal effects of eugenol on Candida albicans adherence to denture polymers.

The study's objective is to assess the adherence of C. albicans in different types of denture polymers and the effectiveness of eugenol and commercialized denture cleansers in the removal of C. albicans. Three types of denture base polymers (Lucitone® 199 (High-Impact PMMA), Impact® (conventional PMMA) and Eclipse® (UDMA)) and two hard denture reline materials (Kooliner® and Tokuyama® Rebase II Fast) were used in this study. Three hundred samples were prepared (6 × 2 mm disc shape) and divided into five groups of denture polymers (n=60) and further subjected into five treatment groups (Polident®, Steradent, distilled water, eugenol 5-minutes, and eugenol 10-min). Three samples were extracted from each treatment group for baseline data (n=12). Baseline data were used to calculate the initial number of C. albicans adherence. A 0.5 ml immersion solution from each specimen was cultured on YPD agar and incubated for 48 h at 37 °C. Visible colonies were counted using a colony counter machine (ROCKER Galaxy 230). The result showed that the denture base polymer significantly affected the initial adherence (p=0.007). The removal of C. albicans was also considerably affected by the denture base polymers and denture cleansers (p<0.05). Lucitone®, Tokuyama®, and Kooliner® denture base polymers immersed for 3 min in eugenol showed the best results of removal. This study's overall results showed that all denture polymers used as denture bases had an effect on C. albicans initial adherence and removal from the denture base, and eugenol is comparable to commercialised denture cleansers in reducing the number of attached C. albicans on denture base polymers.

Mechanical and spectroscopic investigation of novel f-MWCNTS/g-C3N4/TiO2 ternary nanocomposite reinforced denture base PMMA

In the present work, we report the fabrication, spectroscopic, and mechanical properties of the novel f-MWCNTS/g-C3N4/TiO2 (MGT-NCs) metal-free ternary nanocomposite reinforced denture base PMMA. The functionalised-MWCNTs were introduced into the graphitic carbon nitride (g-C3N4) nanopowders (NPs). The obtained high porous f-MWCNTS/g-C3N4 NPs were mixed with 10 wt% of TiO2 NPs previously hydrothermally synthesized. These prepared powders were characterized by XRD, FE-SEM, HR-TEM, FT-IR, and Raman spectroscopy to study the crystal structure and morphology. Using a mechanical blender 2 wt% of g-C3N4, MWCNT/g-C3N4, and MGT-NCs were sintered into PMMA heat-activated denture base polymer powder and mixed with monomer to fabricate the composites through heat curing. Three different varieties of composite specimens were prepared into flexural, impact, compression, and hardness testing standards. From the comparative assessment of results, it is found that novel MGT-NCs reinforced PMMA exhibited superior mechanical properties. The surface morphology of the fractured and compressed specimens was studied using the SEM analysis and found to have dimples and increased roughness compared to the pristine PMMA and g-C3N4, MWCNT/g-C3N4. Hence, the fabricated novel metal-free MGT-NCs can be used as a reinforcement material in PMMA denture bases to achieve a concurrent enhancement in both physical and mechanical properties.

Impact Strength Enhancement of PMMA base Denture Material by Fibre Addition

Prostheses used temporarily are flexible based on function. Given the paucity of empirical knowledge flexural strength of temporary resins, choosing the right material for their manufacturing is challenging. Dentures have been reinforced with partial fibres both during the production process and during repairs. Polymer's fiber-rich phase in the denture base can either form a distinct structure or the reinforcing fibres can be dispersed equally throughout the material. In this work, the static three-point flexural strength and modulus of denture base polymer reinforced with various fibre reinforcements were determined. PMMA base material can currently be strengthened by adding fibre reinforcement. The creation of bar-type specimens complied with standard 27 of the American National Standards Institute and the American Dental Association. After being immersed in artificial saliva at 37°C for 10 days, the specimens were broken under 3-point loading with a crosshead speed of 0.75 mm/min in a universal testing machine. The highest breaking weights were expressed in Newton’s. The mean flexural strengths were measured in MPa (n = 10 per group). Results were compared using variance analysis and Duncan's multiple ranges testing (P.05). Impact strength of The Glass and Natural fibre (Jute, Sugarcane, Banana etc.) group with 1% and 0.5% composition respectively composition have the maximum value. This group shows the maximum value of flexural strength, compression strength and tensile strength. The findings imply that fibres that are impregnated or re-impregnated strengthen the denture base polymer more than fibres that are not impregnated. When compared to the same amount of fibre reinforcement placed on the compression side, the fibre reinforcement applied on the tensile side produced much higher values for flexural strength and flexural modulus.

Impact of popular beverages on polyamides versus polymethyl methacrylate denture base materials colour stability: in vitro study

BackgroundChanging of different denture base materials colours could have a detrimental impact on patients' satisfaction and make them seek more frequent adjustments to their prosthesis; hence this study was conducted to investigate the colour stability of the conventional denture base polymer (PMMA) and polyamides.MethodsSpecimens of conventional PMMA and thermoplastic polyamides were constructed according to manufacturer instructions and utilized during the current study. For colour stability test a total of 80 specimens with dimensions of 40 mm (length) X 20 mm (width) X 0.8 mm (thicknesses), the specimens in this test were divided into two equal groups (n = 40) (PMMA specimens and polyamides specimens).ResultsWhen compared to polymethyl methacrylate denture base resin, polyamid denture base resin exhibited the greatest colour change (P 0.001). For 7 and 30 days, both materials had the greatest value in tea solution. One-Way ANOVA test P < 0.00001).ConclusionsWithin limitation of this in vitro study, we found that heat-cure PMMA resin has the significant higher colour stability when compared to the Polyamides after immersion in the tea, cola, coffee and distilled water solutions for 30 days.

Comparison of two surface sealants on surface roughness and color stability of a commercially available denture base material – An in vitro study

Comparison of two surface sealants on surface roughness and color stability of a commercially available denture base material. Metallic discs were invested in a denture flask using dental stone to prepare a mold space. The denture base polymer and monomer were mixed in a ratio of 3:1 by volume and processed to form disc disc-shaped specimen. All the samples were finished, polished and checked for surface roughness. Sealants were applied on denture base material and cured using light-curing unit. All the 120 samples were divided into Group I(n=60) – Lucitone 199 and Optiglaze, and Group II(n=60) – Lucitone 199 and Easy Glaze. All the specimens were further subdivided into three groups based on the solution they were immersed i.e, coffee (n=20), tea (n=20), and distilled water (n=20). The specimens were checked for surface roughness and color stability for one week, one month, two months, three months, and four months. Samples were checked for surface roughness using optical profilometer and colour change using a spectrophotometer. The surface roughness of all the samples was within the normal range and tea-stained higher compared to coffee samples for color stability. The study concluded that Optiglaze is a better sealant compared to Easy Glaze with better properties like less surface roughness and good color stability of commercially available denture base materials. All groups had surface roughness less than the plaque accumulation threshold (0.20 µm). Beverages affected color stability of commercially available denture base materials after the application of two different surface sealants.

Effects of layer thickness and build angle on the microbial adhesion of denture base polymers manufactured by digital light processing.

To investigate the effects of printing-layer thickness and build angle on the surface characteristics and microbial adhesion of denture base polymers manufactured by digital light processing (DLP). Specimens were additively manufactured using DLP. The specimens were printed with different printing-layer thicknesses (25, 50, and 100 μm) and build angles (0°, 45°, and 90°). Scanning electron microscopy was used to observe the surface topography, and the arithmetical mean heights (Sa) were measured. Moreover, the initial Candida albicans (C. albicans) adhesion to the specimens was evaluated using an adhesion test. Finally, two-way ANOVA and Tukey's multiple comparison tests were conducted. The results regarding the Sa values exhibited a statistically significant interaction (F (4, 45) = 90.77, P < 0.0001). The build angle has a significant impact on the surface topography. Furthermore, quantitative results revealed that the printing-layer thickness significantly affected C. albicans adhesion (F (2, 99) = 6.96, P = 0.0015). The surface roughness was significantly affected by the printing-layer thickness and the build angle. Additionally, the surface topography was mainly determined by the build angle. Furthermore, the adhesion of C. albicans to the DLP-printed denture surfaces was significantly affected by the printing-layer thickness but not by the build angle. Consequently, it is critical to decrease the thickness of the printing layer to produce digital dentures with optimal material properties.

Effect of Chitosan on the Mechanical Properties and Color Stability of Two Commercially Available Heat Cure Denture Base Resins: An In vitro Study

ABSTRACT Background: Chitosan is one of the new and promising biomaterials being used in dentistry. However, there are fewer studies available in the literature to estimate the mechanical properties of chitosan with heat polymerized denture base resin (DBR). This study aimed to evaluate the effect of incorporation of chitosan nanoparticles on flexural strength, fracture toughness, and color stability of two different types of heat cure DBR. Aim: The aim of the study is to evaluate the mechanical properties and color stability of two DBRs reinforced with different concentrations of chitosan. Materials and Methods: A total of 240 samples were made of DPI (n = 120) and Trevalon (n = 120) DBR. The samples of each type were divided into four groups depending on the concentration of chitosan-C 0, C 5, C 12.5, and C 20. Flexural strength and fracture toughness were estimated with a universal testing machine. Spectrophotometer was used to evaluate the color stability. Statistical Analysis: Results were compared with one-way analysis of variance, post hoc Tukey honest significant difference test, and Student’s t-test. Results: The results of the study showed that chitosan-reinforced DBR displayed enhanced mechanical properties. The test group with 5% chitosan nanoparticles had optimum mechanical properties among different test groups for both the DBR. The values for flexural strength and fracture toughness decreased with an increase in the percentage of chitosan. The addition of chitosan to DPI and Trevalon DBRs showed visible color change. Conclusion: The study concluded the Trevalon DBR with 5% chitosan showed the highest flexural strength and fracture toughness values. The addition of chitosan nanoparticles had no significant negative effects on heat-cure acrylic resin’s color change property. CLINICAL RELEVANCE TO INTERDISCIPLINARY DENTISTRY Gives knowledge about the mechanical properties as well as the physical properties of denture base resin which is beneficial for the dentists.

Post-processing of DLP-printed denture base polymer: Impact of a protective coating on the surface characteristics, flexural properties, cytotoxicity, and microbial adhesion.

To investigate the effect of a protective coating on the surface characteristics, flexural properties, cytotoxicity, and microbial adhesion of vat-photopolymerization additive-manufacturing denture base polymers. The specimens were additively manufactured using digital light processing (DLP). Specimen surfaces were coated with the same printed resin, and mechanical polishing was used for comparison. Surface topography, arithmetical mean height (Sa), and water contact angle values were measured. Furthermore, flexural strength (FS)/modulus and fractography were evaluated. Also, cytotoxicity was evaluated by an extract test. Finally, an adhesion test was used to investigate the adhesion of mixed oral bacteria to the specimens. The Sa values in the polished (0.26±0.08µm) and coated (0.38±0.14µm) groups were significantly lower than in the untreated (2.21±0.42µm) and control (2.01±0.37µm) groups. The coating treatment resulted in a higher FS compared to the untreated surface (p=0.0002). After the coating treatment, no significant differences were found in relative cell viability between the groups (p>0.05). The quantitative results showed significantly higher bacterial adhesion in the untreated group than in the polished (p=0.0047) and coated (p<0.0001) groups. The surface characteristics and flexural properties were optimized by the protective coating. Also, the protective coating did not adversely affect cytocompatibility. Moreover, the coating treatment could effectively decrease oral bacteria adhering to the surfaces. Therefore, the protective coating treatment can be a less time-consuming alternative to mechanical polishing as a post-processing procedure for the digital denture.