Acrylic Polymethylmethacrylate Research Articles

Study on the characteristics of biopolymers in milling and 3D printing processing for prosthetic structures

Objectives. The experimental study aims to establish the suitability and reliability of milling and 3D printing processes for acrylic polymethylmethacrylate (PMMA) crown manufacturing by evaluating the internal structure and material integrity through CT scanning analysis and the mechanical properties through indentation experiments. Materials and methods. In the study, samples were made in the form of crowns obtained by milling from Telio CAD blocks (Ivoclar) and by 3D printing using Temp PRINT (GC) material. The samples were analyzed by CT microscanning with the high-resolution equipment Bruker μCT 1272 through which the structure, density and porosity of the materials were assessed. With a nanoindenter test system (G200 Keysight Technologies, Santa Rosa, CA USA) were analyzed the mechanical properties (modulus of elasticity, hardness, stiffness) of the materials of the two sample categories. Results. The results of the experimental study show that both the milling method and 3D printing offer fast and safe ways in obtaining crowns out of PMMA. Micro-CT scans reveal a predominantly uniform internal structure particularly for milling PMMA, with minor variations and localized porosity, indicating a higher level of reliability compared to 3D printing material. The modulus of elasticity values of 3D printing and milling materials are comparable, indicating their ability to provide stability and longevity in dental restorations. Indentation experiments have revealed that 3D printing material has superior rigidity and better resistance to deformation compared to milling material. The higher hardness of the milling material indicates that it has superior resistance to wear, abrasion and surface damage compared to 3D printing material, which provides an additional advantage in terms of long-term durability. Conclusions. The overall conclusion is that the selection of materials for optimal processing will take into account the suitability of the specific application and correlation with the observations of the study, which revealed that the 3D printing material exhibits rigidity and resistance to deformation, and the milling material wear-resistant.

Analysis of FS and Surface Roughness in Heat-Polymerized Poly Methyl Methacrylate Acrylic Resin Reinforced with Different Concentrations of Glass Fibers and Polypropylene Fibers: A Laboratory Study Using EDX and SEM

This study aimed to evaluate the flexural strength (FS) and surface roughness (Ra) of heat-polymerized poly methyl methacrylate (PMMA) acrylic resin reinforced with glass fibers (GF) and polypropylene fibers (PPF) in different concentrations. One hundred heat-cured PMMA resin samples were prepared and randomly allocated into five groups based on fiber reinforcement (n = 20). Group 1 had no fiber reinforcement, Group 2 had 0.5% silanized GF reinforcement, Group 3 had 1% silanized GF reinforcement, Group 4 had 0.5% silanized PPF reinforcement, and Group 5 had 1% silanized PPF reinforcement. Fatigue load was applied through artificial aging. FS testing of fifty samples was performed using a universal testing machine, and Ra was analyzed using an optical interferometric profilometer. Specimens were selected for SEM and EDX analysis. To find the differences among the studied groups, one-way analysis of variance and post hoc Tukey’s test were utilized. The results showed that Group 5 (1% PPF reinforcement) presented the highest fracture resistance (90.1±9.8 MPa), while the minimum FS scores were observed in Group 1 (no reinforcement) (59.2±7.1 MPa). Group 3 (1% GF reinforcement) exhibited the highest values of surface roughness (1.99±0.1992), whereas the lowest roughness scores were observed in Group 1. The study concluded that incorporating 0.5% PPF into the resin denture is a viable option for reinforcing the prosthesis without increasing surface roughness.

The effect of adding ZrO2 nanoparticles on the transverse strength and hardness of microwave-cured acrylic and heat-cured acrylic denture base materials

Background: One drawback of acrylic denture base materials is their liability to fracture, requiring methods to increase fracture resistance. Adding nanoparticles (NPs) represented one of these methods. Purpose: The objectives of this study are to evaluate and compare transverse strength and hardness when adding zirconium oxide nanoparticles (ZrO2 NPs) at concentrations of 0%, 3%, and 5% to heat-cured acrylic denture base materials (Ivoclare, Major) and to microwave-cured acrylic (Acron MC). Methods: Transverse strength was tested with a Universal Testing Machine (GESTER, Fujian, China), while hardness tests were conducted by using a Shore-D hardness durometer (Show, China). The 90 samples were prepared and then divided into three groups for each material. Attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy was used to analyze the microstructure. The samples were prepared following the manufacturer’s instructions for each material. Results: The results revealed that the addition of ZrO2 NPs (3%, 5%) improves the transverse strength and hardness of polymethyl methacrylate acrylic resin for both types (microwave-cured and heat-cured acrylic resins). The addition of ZrO2 NPs at 3% concentration shows the highest values for both transverse strength and hardness. The ATR-FTIR confirms no structural chemical changes with the addition of ZrO2 NPs. Conclusion: The study concludes that the incorporation of ZrO2 NPs (3%, 5%) into microwave-cured and heat-cured acrylic resins improves transverse strength and hardness.

Comparative Evaluation of Polymethyl Methacrylate and Thermoforming Crowns as Semipermanent Crowns in Primary Molars: An In Vivo Study.

The present randomized clinical trial is aimed at evaluating clinical efficiency of two different types of esthetic crowns-polymethyl methacrylate crowns and vacuum formed thermoformed crown as an alternative to full-coverage coronal restoration for deciduous molars. A total of 45 primary molars in pediatric patients were selected using randomization and split into three groups based on the technique used for preparation of crowns: group I-polymethyl methacrylate crowns; group II-thermoformed crown; and group III-stainless steel crowns (SSC). All crowns were clinically and radiographically evaluated at baseline, 1st month, and 3rd month for gingival health, retention, marginal integrity, proximal contacts, occlusion, alignment, and staining. The data was tabulated and analyzed by Statistical Package for the Social Sciences (SPSS) Version 23.0 software. The intergroup comparison was done by Kruskal-Wallis test, analysis of variance (ANOVA), and Mann-Whitney U test for continuous data. The intragroup comparison was done by Friedman test and Wilcoxon signed-rank test for categorical data. All p-values < 0.05 were considered statistically significant. With regard to the parameters of plaque score, gingival index score, occlusion, interproximal contacts, retention, alignment, and marginal adaptation, no statistical significance was noted between the three groups. However, with regard to the discoloration (staining) when the polymethyl methacrylate acrylic (PMMA) group was compared with thermoforming group, statistical significance was noted in 1st month with p-values of 0.04 and 0.03, respectively. On intragroup comparison, statistically significant values were obtained in SSC group for plaque score and thermoforming group for gingival index score. The study concluded that the PMMA and thermoforming crowns can be used as an alternative to SSC for restoring the primary molars as they showed equivalent results to that of standard SSC. Matha N, Kumar KS, Reddy BVT, et al. Comparative Evaluation of Polymethyl Methacrylate and Thermoforming Crowns as Semipermanent Crowns in Primary Molars: An In Vivo Study. Int J Clin Pediatr Dent 2024;17(S-1):S43-S54.

Enhanced antimicrobial efficacy of chlorhexidine-encapsulated halloysite nanotubes incorporated in presurgical orthopedic appliances: an in vitro, controlled study.

Presurgical infant's orthopedic appliances (PSIOs) play an increasingly crucial role in the interdisciplinary management of neonatal CLP, aiming to improve and maintain adequate nasolabial aesthetics, followed by primary lip/nasal surgery in both unilateral and bilateral CLP cases. The use of PSIOs in cleft lip and palate patients can lead to contamination with oral microflora, acting as a potential reservoir for infectious microorganisms. Acrylic surfaces might provide retention niches for microorganisms to adhere, and inhabit, which is difficult to control in immunocompromised patients, thus predisposing them to increased infection risks. The objective of this multi-assay in vitro study was to investigate the effects of incorporating chlorhexidine-loaded halloysite nanotubes (CHX-HNTs) fillers on the morphological, cytotoxic, release, and antimicrobial characteristics of self-cured acrylic polymethyl methacrylate (PMMA) material used in pre-surgical orthopedic appliances. Disk-shaped PMMA specimens were prepared with varying proportions of CHX-HNTs. A control group without any addition served as a reference, and four experimental samples contained a range of different concentrations of CHX-HNTs (1.0, 1.5, 3, and 4.5 wt%). The antimicrobial efficacy was assessed using an agar diffusion test against common reference microorganisms: Candida albicans, Staphylococcus aureus, Streptococcus pneumoniae, and Streptococcus agalactiae. Cytotoxicity was examined using the L929 cell line (mouse fibroblasts) through a (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide, MTT) cell viability assay. The release kinetics of CHX were monitored using UV-spectral measurements. The statistical analysis used a one-way ANOVA followed by Tukey's post hoc test. The integration of CHX-HNTs in PMMA exhibited a substantial dose-dependent antifungal and antibacterial effect against microorganisms at tested mass fractions (1.0 to 4.5 wt%). CHX release was sustained for up to 60 days, supporting prolonged antimicrobial activity. Furthermore, no significant cytotoxicity was determined in the L929 fibroblast cell line (control), indicating the biocompatibility of the CHX-HNTs-enhanced PMMA. Incorporating CHX-HNTs in PMMA successfully enhanced its antimicrobial properties, providing sustained CHX release and superior antimicrobial efficacy. These findings demonstrate the potential of antimicrobial nanoparticles in dental therapies to improve therapeutic outcomes. However, rigorous further clinical trials and observational studies are warranted to validate the practical application, safety, and efficacy. This study has the potential to make a major impact on the health of infants born with cleft lip and palate by helping to reduce the prevalence of infectious illnesses. The incorporation of CHX-HNTs into PMMA-based appliances is a novel promising preventive approach to reduce microbial infections.

Different Polymers for the Base of Removable Dentures? Part II: A Narrative Review of the Dynamics of Microbial Plaque Formation on Dentures.

This review focuses on the current disparities and gaps in research on the characteristics of the oral ecosystem of denture wearers, making a unique contribution to the literature on this topic. We aimed to synthesize the literature on the state of current knowledge concerning the biological behavior of the different polymers used in prosthetics. Whichever polymer is used in the composition of the prosthetic base (poly methyl methacrylate acrylic (PMMA), polyamide (PA), or polyether ether ketone (PEEK)), the simple presence of a removable prosthesis in the oral cavity can disturb the balance of the oral microbiota. This phenomenon is aggravated by poor oral hygiene, resulting in an increased microbial load coupled with the reduced salivation that is associated with older patients. In 15-70% of patients, this imbalance leads to the appearance of inflammation under the prosthesis (denture stomatitis, DS). DS is dependent on the equilibrium-as well as on the reciprocal, fragile, and constantly dynamic conditions-between the host and the microbiome in the oral cavity. Several local and general parameters contribute to this balance. Locally, the formation of microbial plaque on dentures (DMP) depends on the phenomena of adhesion, aggregation, and accumulation of microorganisms. To limit DMP, apart from oral and lifestyle hygiene, the prosthesis must be polished and regularly immersed in a disinfectant bath. It can also be covered with an insulating coating. In the long term, relining and maintenance of the prosthesis must also be established to control microbial proliferation. On the other hand, several general conditions specific to the host (aging; heredity; allergies; diseases such as diabetes mellitus or cardiovascular, respiratory, or digestive diseases; and immunodeficiencies) can make the management of DS difficult. Thus, the second part of this review addresses the complexity of the management of DMP depending on the polymer used. The methodology followed in this review comprised the formulation of a search strategy, definition of the inclusion and exclusion criteria, and selection of studies for analysis. The PubMed database was searched independently for pertinent studies. A total of 213 titles were retrieved from the electronic databases, and after applying the exclusion criteria, we selected 84 articles on the possible microbial interactions between the prosthesis and the oral environment, with a particular emphasis on Candida albicans.

Applied and computational investigation of plasticizing effects of dibutyl maleate on polymethyl methacrylate acrylic resin material

In this study, the amount of change in the glass transition temperature (Tg) of PMMA was analyzed by DSC by adding different ratios of dibutyl maleate (DBM) plasticizer to polymethyl methacrylate (PMMA), which is used as the main ingredient of prosthetics in dentistry. For this, liquid DBM was added to powdered PMMA at a rate of 2, 5, 8 and 15 % by mass, and polymerization was carried out at 100 °C. Mechanical tests such as impact resistance, transverse resistance and maximum flexion tests were applied to these prepared mixtures. It was observed that there was a significant parallelism between the Tg values calculated from the DSC curves and the mechanical tests. The Tg value of PMMA was reduced by approximately half with the addition of DBM plasticizer. Additionally, the chemical interaction between PMMA and DBM was analyzed in the light of the Density Functional Theory (DFT) calculations. The binding energy for the mentioned interaction was determined as 1.591 eV. After both species interacted with each other, the glass transition temperature of the formed complex system was theoretically also predicted through the quantitative structure-property relationship (QSPR) model. For theoretical prediction of Tg, the molecular traceless quadrupole moment Θ and the molecular average hexadecapole moment Φ, are used. The change determined as experimental in glass transition temperature as a result of the interaction between PMMA and DBM was supported with theoretical calculations. Experimental and theoretical data are in good agreement.

In vitro efficacy of synthetic lawsone derivative disinfectant solution on removing dual-species biofilms and effect on acrylic denture surface properties

Candida albicans (C. albicans) and Streptococcus mutans (S. mutans) biofilms involve in denture stomatitis. This study compared compound 1 to 2% chlorhexidine gluconate (CHX), Polident, and distilled water (DW) in biofilms reduction and effect on polymethylmethacrylate acrylic (PMMA) properties. The structure of lawsone (naphthoquinone derivative) was modified by the addition of an alkylnyloxy group to yield compound 1. Dual-species biofilms of C. albicans and S. mutans were developed on PMMA discs. The colony-forming unit count measured the number of residual biofilm cells after exposure to the test agents. PMMA discs were examined for color stability, surface roughness, hardness, and chemical structure after 28 days. At 3 min, compound 1 was less effective than CHX in reducing C. albicans (p = 0.004) and S. mutans (p = 0.034) but more effective than Polident in reducing C. albicans (p = 0.001). At 15 min, no viable cells were detectable for compound 1 and its effectiveness was comparable to CHX (p = 0.365). SEM showed fungal cell surface damages in CHX, compound 1 and Polident groups. Only color change was affected by time (p < 0.001) and type of test agent (p = 0.008), and only CHX reached a clinical perception level. Compound 1 is a promising agent for removing biofilm from the PMMA surface without substantially degrading surface properties.

Effect of microwave polymerization on the thermomechanical and surface properties of ocular prosthetic acrylic resins.

Polymerization conditions affect the physical-mechanical properties of acrylic resins used for craniofacial prostheses. The aim of this study was to evaluate the effect of microwave polymerization on the thermomechanical properties and surface morphology of ocular prostheses fabricated with polymethyl methacrylate (PMMA). PMMA discs were polymerized with microwave energy and with conventional heat polymerization (CHP) method. Ocular prostheses were fabricated to determine whether there were changes according to the polymerization method. The surface morphology and roughness were observed under SEM and AFM. The Vickers Hardness number (VHN) and flexural strength were measured. Thermal properties were evaluated with TGA/DSC, and chemical composition with FTIR. The PMMA acrylic resin polymerized with microwave energy showed a smooth surface with some relief areas. In the internal surface of the ocular prosthesis with microwave energy the PMMA is more compact. The mean roughness values were higher and statistically significant with CHP (P <0.05), while the surface hardness and flexural strength were higher with microwave energy (P <0.05). There were no changes in the calorimetry with either method, TGA showed an exothermic peak around 120°C with CHP method. PMMA polymerized with microwave energy improved the mechanical and surface properties of the ocular prostheses.

Strain measurement with multiplexed FBG sensor arrays: An experimental investigation

In conventional rock mechanics testing, radial strain measuring devices are usually attached to the sample's surface at its mid-height. Although this procedure provides a realistic picture of the lateral deformation undergone by homogeneous samples, however, this assumption may not be accurate if the tested rock has significant heterogeneity. Fibre Bragg Grating (FBG) sensors have recently been introduced to various rock testing applications due to their versatility over conventional strain gauges and radial cantilevers. FBG sensors have small size, multiplexing capability, and immunity to magnetic interference. The main objective of this study is to explore and understand the capabilities of FBG sensing for strain measurement during rock mechanics testing, including under confining. To do so, two limestone plugs (Savonnières limestone) and one acrylic Poly Methyl Methacrylate (PMMA) plug, all of 38 mm diameter, were prepared. The acrylic plug and one of the Savonnières samples plugs were subjected to Unconfined Compressive Strength (UCS) tests. The second Savonnières plug was subjected to a hydrostatic test up to 20 MPa confining at room temperature. FBG sensors of 125 μm cladding diameter with ceramics (Ormocer) coating were glued on the surface of each sample, spreading across the entire sample's height. Strain gauges and cantilever-type radial gauges were used on the samples submitted to UCS for comparison. Results show that radial strain measurements and calculated elastic properties derived from the FBG readings for samples are comparable to readings from the conventional strain gauges and cantilever-type devices. Apparent bulk moduli based on volumetric strain computed from FBG radial strain readings during the hydrostatic test on the Savonnières sample was consistent with benchtop measurements conducted on the Savonnières sample and another plug extracted from the same parental block, as well as published literature data. Moreover, variations in the calculated elastic properties are interpreted as evidence that the FBG sensors detected heterogeneities in the samples' inner structure, which can be seen in the density profiles computed from x-ray CT images. Such observation confirms the potential of the presented FBG sensors configuration for 3D strain mapping in rock mechanics tests.

Single geometry abutment for narrow and extra-narrow implant systems: Survival and failure modes

The use of identical prosthetic components for all implant diameters could reduce the production costs by companies and the complexity of component selection for the clinician and his team. However, it would imply in reduction of thickness of the cervical walls of tapered internal connection implants, which could compromise the reliability of narrow and extra-narrow implants. Therefore, this study aims to evaluate the probability of survival and failure modes of extra-narrow implant systems with the same internal diameter as standard-diameter implants using the same prosthetic components. It was used eigth different implant system configurations, including narrow (Ø 3.3 mm) (N) extra-narrow (Ø 2.9 mm) (EN) and extra-narrow-scalloped (Ø 2.9 mm) (ENS) implants, both with cementable abutments (Ce) or titanium bases (Tib) and one-piece implants (Ø 2.5 mm and Ø 3.0 mm) (OP) (Medens, Itu, SP, Brazil), comprising the following groups: OP 3.0; OP 2.5; N Ce; N Tib; EN Ce, EN Tib, ENS-Ce and ENS-Tib. The implants were embedded using polymethylmethacrylate acrylic resin in a 15 mm matrix. Standardized maxillary central incisor crowns were virtually designed and milled to fit on the different studied abutments and cemented using a dual self-adhesive resin cement. The specimens were submitted to SSALT (Step Stress Accelerated Life Testing) at 15 Hz in water until failure or suspension of the test, until a maximum load of 500 N. Fractographic analysis of the failed specimens were realized in scanning electron microscopy. All implant systems demonstrated high probability of survival (90–100%) for missions at 50 and 100 N and values of characteristic strength superior to 139 N. Failure modes were restricted to the abutment in all the implant configurations tested. Therefore, the use extra-narrow implants with standardized prosthetic components for different implant diameters is a viable option for the replacement of anterior teeth.

Different cavity disinfectant efficacy against S.mutans and shear bond strength of caries affected dentin bonded to resin restoration

AimsThe existing study aimed to assess the survival rate of S.mutans and shear bond strength (SBS) of resin adhesive restoration bonded to carious affected dentin (CAD) after using different cavity disinfectants (Chitosan, Fotoenticine®, and CO2 laser) in comparison to Chlorhexidine (CHX). Materials and methodsThe study included human mandibular molars assessed on International Caries Detection and Assessment System (ICDAS) score 4 and 5. The cusp part of the clinical crown was cut off until the reduction reaches the central fossa while being continuously supplied with water coolant till the tooth cementoenamel junction (CEJ). The root sections were embedded in polymethyl methacrylate acrylic resin followed by culturing S.mutans biofilm on the CAD surface. Specimens were arbitrarily allocated into four groups(n = 10) based on the type of disinfection. Group 1 (2% CHX), Group 2 (Chitosan), Group 3 (Fotoenticine), and Group 4 (CO2 laser). S.mutans survival rate was assessed and CAD was restored with a composite restorative material. Thermoocycling of the samples was performed and a universal testing machine (UTM) and Stereomicroscope were used to identify bond integrity and type of fracture. ANOVA and Tukey multiple comparison tests were used to assess SBS. Data on the survival rate of S. mutans were compared between groups using the nonparametric Kruskal-Wallis test ResultsOutcomes revealed that Group 1 (CHX) displayed the highest survival rate (0.65 ± 0.10). However, lowest survival rate was demonstrated by Group 3 (Fotoenticine) treated specimens (0.25 ± 0.06). It was also discovered that CHX unveiled highest bond strength values (21.48 ± 1.39 MPa). Nevertheless, Group 2 (Chitosan) showed lowest SBS (11.01 ± 1.00 MPa). Intergroup comparison analysis presented that group 1, and group 4 (Co2 laser) (17.76 ± 0.41 MPa) displayed no significant difference in their bond integrity achieved. (p > 0.05). However, group 3 (Fotoenticine) (16.28 ± 0.51 MPa) and group 2 demonstrated comparable outcomes of SBS. (p > 0.05) ConclusionThe use of CHX and CO2 lasers as disinfectants on the CAD surface resulted in a positive impact on the SBS of resin composite, according to the study's findings. However, it is worth noting that Fotoenticine exhibited better antimicrobial efficacy against S. mutans

Antimicrobial effect of silver nanoparticles on polypropylene and acrylic resin denture bases.

The investigation of the antimicrobial action of Ag solutions in different surfaces has been performed, however, there is little data on the direct addition of those particles to the polypropylene denture base. The aim of this study was to evaluate the antimicrobial effect of silver nanoparticles in Candida albicans and Streptococcus mutans colonization in acrylic resin and polypropylene denture bases. Twenty test bodies (10×13×3 mm) were fabricated with (heat-polymerized) poly methyl methacrylate acrylic resin (group 1), (heat-polymerized) poly methyl methacrylate acrylic resin with silver nanoparticles (group 2), polypropylene (group 3) and polypropylene with silver nanoparticles (group 4). Candida albicans and Streptococcus mutans colonization were performed. A colony count was performed in Colony Forming Unit (CFU/ml) and registered to calculate the arithmetical mean of the duplicate values of each sample. Data was analyzed by Lilliefors test and since samples did not present a normal distribution, Kruskal-Wallis for variance analysis with the value of significance set at p<0.05. For Candida albicans colonies, when comparing nano-Ag in polypropylene, there were statistical difference between groups 3 and 4. For the same type of growth in heat-polymerized PMMA resin with and without nano-Ag, no statistical differences were found. The presence of nanoparticles did not affect Streptococcus mutans growth in the heat-polymerized PMMA resin. Value differences of S. mutans were not significant for comparisons between groups 1-2 and 3-4. Silver nanoparticles presented antifungal activity against C. albicans in polypropylene surfaces, but not in the heat-polymerized PMMA resin. Silver nanoparticles did not present antibacterial activity against S. mutans in any of the analyzed surfaces. Key words:Removable Partial Denture, Candida, Streptococcus mutans.

The effect of thermo-cycling on fracture strength of 3D printing and PMMA interim prostheses

Aim of the study: This study compared the fracture resistance of three-dimensional printing (3D) interim restoration with that polymethylmethacrylate (PMMA), interim restoration.&#x0D; Materials and methods: In the present study upper molar (dentoform) tooth was prepared for full coverage crowns. The prepared model was digitally scanned by extra-oral scanner. Duplication of the master die into metal dies (chrome cobalt alloy). Totally, 40 samples were divided into two groups (20) using 3D printing (asiga dentatooth resin material), and (20) Polymethylmethacrylate PMMA (integra) resin material. Ten samples from each group were subjected to thermo-cycles (1250 cycles, 5-55 °C). The fracture resistance was then measured for all samples with a universal testing machine.&#x0D; Results: In SPSS, the mean ± Stander deviation values of fracture resistance were recorded for the acrylic PMMA group before thermo-cycling (1703.30 ±376.659 Newton) and after thermo-cycling (1460.30 ±364.260 Newton), while the mean ± Stander deviation values were recorded for 3D printing group before thermo-cycling (1972.50±399.181 Newton) and after thermo-cycling ( 2284.10±239.001Newton). It was found that 3D printing recorded a significantly higher fracture resistance mean than PMMA groups.&#x0D; Conclusion: 3D printing interim prostheses recorded higher fracture resistance compared with PMMA interim prostheses.

Multi-Objective Optimization of Nd: YAG Laser Drilling of Optical-Grade Acrylic Plate Using Taguchi-Based Grey Relational Analysis.

This study proposed an effective method for optimizing laser drilling processing (LDP) by using grey relational analysis (GRA) for multiple performance requirements. First, we developed a system using a Quantel Brilliant Neodymium-doped Yttrium Aluminum Garnet (Nd: YAG) laser with a pulse width of 5-6 ns and F-theta lenses to deliver a focused laser beam with a diameter of 0.2 mm. The developed system was first employed to drill holes in a 3-mm-thick optical-grade acrylic polymethyl methacrylate (PMMA) plate on a safe window with a high optical density and a grade of OD 7+ @ 950~1085 nm. To avoid errors in the experimental data due to unstable power, a laser power (energy) meter was used to measure the energy stability of the Quantel Brilliant Pulse Laser. Given the stability of 5.6%, this is an effective method for LDP. Four control factors were investigated, including laser pulse energy, repetition rate, focusing position offset, and drilling time. Then, nine experiments were performed using the Taguchi method with orthogonal arrays in L9 (34). The experimental results with multiple quality characteristics were measured and used to optimize the control factors by using GRA with equal weighting of the four qualities (roundness, Hillock ratio, taper, and HAZ). The results show that A1B3C1D1 is the optimal combination of the control factors, and the maximal variation of 0.406 is obtained from the control factor B (focusing position offset) which has the greatest contribution to the drilling time. We then performed confirmation experiment and obtained a better result from the combination of the control factors, A1B3C1D1. GRA helps us determine the best laser drilling parameters to meet the desired multiple drilling qualities.

EFFECT OF GINGER EXTRACT (ZINGIBER OFCINALE ROSC.) ON CANDIDA ALBICANS ON HEAT CURED ACRYLIC RESIN PLATE

Background: Denture bases that are often used in dentistry are heat cured polymethyl methacrylate acrylic resin or heat polymerized acrylic resin. Acrylic resin has a weakness, namely the surface of the acrylic resin that can trigger the growth of bacteria and Candida albicans. Candida albicans has an important role in the occurrence of denture stomatitis. Epidemiological studies show the prevalence of denture stomatitis is quite high, ranging from 30%-50% in denture users. Innovation is needed to inhibit the growth of Candida albicans on acrylic resin, one of which is the use of ginger extract. Ginger can be antifungal because of the content of phenols and essential oils.To determine the effect of ginger extract (Zingiber ofcinale Rosc.) on Candida albicans on heat cured acrylic resin. Methods: This research design was a post test only control group design with a total sample of 24 samples. There was 3 treatment groups and 1 control group. Statistical test used One-way ANOVA Welch with post hoc Games-Howell test. Results: The results showed that there was a significant effect of 25% and 50% ginger extract on Candida albicans on heat cured acrylic resin. The Shapiro-Wilk test got normal results and the homogeneity test got inhomogeneous results. The analytic test conducted used One-way ANOVA Welch with post hoc Games-Howell and the result showed a significant differences in the 4 test groups Conclusion: There was a significant effect of 25% and 50% ginger extract in inhibiting Candida albicans on heat cured acrylic resin with an average fungal count of 2 and 1.

The Antifungal and Antibiofilm Activities of Caffeine against Candida albicans on Polymethyl Methacrylate Denture Base Material.

Background: In this study, the effect of pure caffeine was established against Candida albicans (C. albicans) using different microbiological techniques. Methods: Broth microdilution and colony forming units (CFUs) assays were used to detect the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC). The Live/Dead fluorescent dyes were implemented to determine the yeast viability. Polymethyl methacrylate acrylic resin (PMMA) discs were prepared to evaluate caffeine’s effects against adherent C. albicans using microplate reader, CFUs, and scanning electron microscope (SEM). Results: caffeine’s MIC was detected around 30 mg/mL, while the MFC was considered at 60 mg/mL. In an agar-well diffusion test, the inhibition zones were wider in caffeine groups. The Live/Dead viability test verified caffeine’s antifungal effects. The optical density of the adherent C. albicans on PMMA discs were lower at 620 nm or 410 nm in caffeine groups. CFU count was also reduced by caffeine treatments. SEM revealed the lower adherent C. albicans count in caffeine groups. The effect of caffeine was dose-dependent at which the 60 mg/mL dose demonstrated the most prominent effect. Conclusion: The study reinforced caffeine’s antifungal and antibiofilm properties and suggested it as an additive, or even an alternative, disinfectant solution for fungal biofilms on denture surfaces.

Denture Base PMMA Resin Containing Vanillin Inhibits Biofilm Formation of Bacteria Associated with Malodor

Dentures are prosthetic device made of polymethyl methacrylate acrylic (PMMA) resin generally used by elderly people to replace their real teeth. However, the porosity and surface irregularities of acrylic resin are undesirable aspects of the denture base that can support colonization of oral microorganisms on the denture surface, particularly those associated with malodor. Oral malodor is a common and upsetting situation frequently found in denture wearers due to inadequate denture cleaning. A large number of strategies had been employed to minimize the potential bacterial pathogens, including mechanical brushing and using chemical agents. Therefore, we have developed denture PMMA resin containing vanillin and evaluated antimicrobial potential against four species of bacteria related to oral malodor. Denture base resin samples were prepared with dimensions of 10 mm x 10 mm x 1 mm. according to the amount of incorporating vanillin concentrations (0.1%, 0.5% and 1.0% w/w) and coated with saliva. Then, the biofilm formation of four species of bacteria (Porphyromonas gingivalis ATCC 33277, Aggregatibacter actinomycetemcomitans ATCC 33384, Fusobacterium nucleatum ATCC 25586, and Actinomyces viscosus ATCC 19246) was performed on resin samples in anaerobically condition for 48-72 h. Denture resin sample without vanillin was prepared in the same way and used as a control. The quantity of vital biofilm was assessed by WST Microbial Cell Counting Kit (Dojindo Molecular Technologies, USA). Kruskal-Wallis test followed by Dunn’s method were applied for statistical analysis. The results showed that in the groups of 0.5% and 1.0% w/w vanillin, significant decreases of biofilm mass were observed in all tested bacteria (P. gingivalis, A. actinomycetemcomitans, and F. nucleatum) compared with controls, except for A. viscosus. Approximately 30% to 38% bacterial biofilm reduction was demonstrated at 1.0% w/w vanillin on three species of bacteria, whereas 7% to 27% biofilm decreases were observed at 0.5% vanillin. No significant biofilm reduction was observed in A. viscosus. This conforms to our previous studies which revealed the antimicrobial properties of denture PMMA resin containing vanillin on respiratory pathogens and oral yeast. Denture base resin consisting of vanillin may be considered as a promising dental appliance for the use to prevent or solve the problem of oral malodor in patients who wear dentures.

Influence of Propolis Extract (Caffeic Acid Phenethyl Ester) Addition on the Candida albicans Adhesion and Surface Properties of Autopolymerized Acrylic Resin.

Background Denture stomatitis has been linked to the adhesion and proliferation of Candida albicans (C. albicans) on denture bases, which is a common and recurrent problem in denture wearers. The current study aimed to evaluate the effect of incorporating caffeic acid phenethyl ester (CAPE) into autopolymerized polymethyl methacrylate (PMMA) acrylic resin on C. albicans adhesion, surface roughness, and hardness as well as the correlation between tested properties. Methods Autopolymerized acrylic resin discs (N = 100, 50/C. albicans adhesion; 50/C. albicans surface roughness and hardness test) were fabricated in dimensions 15 × 2.5 mm, samples were categorized into 5 groups (n = 10) based on CAPE concentrations; unmodified (control), 2.5, 5, 10 and 15% wt of acrylic powder. Specimens were stored in distilled water for 48 h at 37°C. C. albicans adhesion was evaluated via direct culture method. Profilometer and Vickers hardness tester were used for surface roughness and hardness measurement. Post hoc Tukey's HSD with ANOVA test was performed to compare the difference of means amongst groups. P values were statistically significant at ≤0.05. Results The addition of 2.5% of CAPE to PMMA has significantly reduced C. albicans counts in comparison to higher CAPE concentrations (p < 0.001). As for surface roughness, it was noticed that it increased with increased CAPE concentrations (p < 0.0001). While surface hardness decreased as CAPE concentrations increased (p < 0.0001). All tested properties showed a significant difference amongst groups for C. albicans colony count and surface parameters. Conclusion The addition of 2.5% of CAPE to PMMA acrylic resin significantly decreased C. albicans count compared to higher CAPE concentrations. CAPE can be used as an adjunct in the prevention of DS by incorporating in the PMMA acrylic resin.

Effect of laser plasma on Nd:YAG laser drilling of acrylic plate with high optical density

Laser material processing (LMP) is used to replace traditional material processing techniques, such as material cutting, thin plate drilling, and surface processing. When a high-energy laser is projected onto a material, the temperature of the material increases rapidly, changing the characteristics of the material and making the material on the surface vaporize and peel off instantly. In this study, we developed a laser system using a Quantel Brilliant neodymium-doped yttrium aluminum garnet (Nd:YAG) with a wavelength of 1064 nm laser a pulse width of 5–6 ns, a beam diameter of the 6 mm, and 10 repetition rate (Hz) on the energy stability is within 5.60%, an F-theta lens is used to obtain a focused laser beam with a diameter of 0.2 mm. The developed system was employed to drill holes in a 3-mm-thick optical-grade acrylic polymethyl methacrylate (PMMA) plate with high optical density and 7 + safe windows. A laser-safe, flat-window, visible-light-transmitting (VLT) sample was used, and the material to be drilled was a PMMA plate. The laser beam must be focused on the center of the F-theta lens and must be aligned with the distance between the F-theta lens and the linear stage. The working distance was set to 300 mm. Furthermore, the diameter was adjusted to obtain the laser plasma effect; that is, the working distance was fixed. First, the characteristics of the laser plasma and the ability of the laser to penetrate optical-grade acrylic (PMMA) plates samples were studied. By changing the lifting position of the vertical axis and varying the working distance of the acrylic (PMMA) plates, the laser beam was targeted at different positions on the acrylic (PMMA) plates. To determine the optimal parameters for the drilling process, a pulsed laser output of 174.7 mJ/pulse (3000 pulses in 5 min) was focused on the hole. Results showed that the energy was 522.98 J/cm2; a laser energy density of 141.26–275.93 J/cm2 resulted in an acceptable heat-affected zone. The Nd:YAG pulsed laser can produce laser plasma that can increase the hole diameter by up to 50% because of the produced cavity gap. Various exit and entrance hole shapes can be achieved and thus employed for different applications, such as laser beam cutting.