The Influence of Contemporary Denture Base Fabrication Methods on Residual Monomer Content, Flexural Strength and Microhardness.

(1) Background: Digital technologies are available for denture base fabrication, but there is a lack of scientific data on the mechanical and chemical properties of the materials produced in this way. Therefore, the aim of this study was to investigate the residual monomer content, flexural strength and microhardness of denture base materials as well as correlations between investigated parameters. (2) Methods: Seven denture base materials were used: one conventional heat cured polymethyl methacrylate, one polyamide, three subtractive manufactured materials and two additive manufactured materials. High-performance liquid chromatography was used to determine residual monomer content and the test was carried out in accordance with the specification ISO No. 20795-1:2013. Flexural strength was also determined according to the specification ISO No. 20795-1:2013. The Vickers method was used to investigate microhardness. A one-way ANOVA with a Bonferroni post-hoc test was used for the statistical analysis. The Pearson correlation test was used for the correlation analysis. (3) Results: There was a statistically significant difference between the values of residual monomer content of the different denture base materials (p < 0.05). Anaxdent pink blank showed the highest value of 3.2% mass fraction, while Polident pink CAD-CAM showed the lowest value of 0.05% mass fraction. The difference between the flexural strength values of the different denture base materials was statistically significant (p < 0.05), with values ranging from 62.57 megapascals (MPa) to 103.33 MPa. The difference between the microhardness values for the different denture base materials was statistically significant (p < 0.05), and the values obtained ranged from 10.61 to 22.86 Vickers hardness number (VHN). A correlation was found between some results for the material properties investigated (p < 0.05). (4) Conclusions: The selection of contemporary digital denture base manufacturing techniques may affect residual monomer content, flexural strength and microhardness but is not the only criterion for achieving favourable properties.

Removable complete denture with a metal base: Integration of digital design and conventional fabrication techniques.

OBJECTIVE: Digitally-designed removable complete dentures are typically composed of a resin denture base without a metal framework. However, metal denture bases are preferable as resin bases are more susceptible to fracture. Therefore, this article introduces a unique technique that integrates computer-aided design (CAD) and conventional resin processing for the fabrication of removable complete dentures with a metal framework. CLINICAL CONSIDERATIONS: A maxillary complete denture with a metal base and a mandibular implant-retained overdenture reinforced with a metal framework were fabricated. The dentures were designed using CAD software and a tooth library. The denture bases were milled from wax disks, and artificial teeth were placed to complete the wax dentures. The metal frameworks were also designed using CAD software and produced via casting of printed resin patterns. Finally, conventional denture processing techniques were applied to obtain dentures with metal frameworks. CONCLUSIONS: A digitally designed, removable complete denture with a metal base can be successfully fabricated using the described technique, which merges digital design and conventional methods. This article demonstrates the feasibility and potential advantages of this innovative approach in denture fabrication. CLINICAL SIGNIFICANCE: The presented technique provides the following advantages: digital design features, precise space above implant overdenture attachments for a metal framework, convenience of esthetic evaluation with printed trial dentures, long-term data storage and duplication, reliable bond between the artificial teeth and denture base, and enhanced strength of the removable complete denture due to the metal reinforcement.

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

BACKGROUND: Flexible 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 METHODS: Acetal (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. RESULTS: AC 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. CONCLUSIONS: Biofilm 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.

Application of Laser Treatment in Adhesive Bonding of Liners to Polymethyl Methacrylate Denture Resins: A Systematic Review and Meta-Analysis.

Objective: This systematic review and meta-analysis aimed to assess the influence of laser treatment on adhesive bonding of liners to polymethyl methacrylate (PMMA) denture base resins. Methods: The focused question was: "Does the application of laser treatment (Intervention) influence the adhesive bonding strength (Outcome) of liners to PMMA denture base resins (Population) as compared with untreated or unconditioned surfaces (Control)?" In vitro and clinical reports as well as reports on influence of laser treatments on bonding strength of liners to PMMA denture resins in comparison with untreated surfaces were included. Reports without any control group[s], without any application of laser[s] for PMMA denture bases that did not utilize PMMA denture bases, and not evaluate bond strength of PMMA denture base resins were excluded. An electronic search was conducted on PubMed, Scopus, and Web of Science. Meta-analyses were performed for calculating the standard mean difference (SMD) with a 95% confidence interval (95% CI). Results: Nine of the 12 included studies found that laser irradiation treatment produced significant surface texture alterations of the PMMA denture base and improved the adhesion between the PMMA denture base and soft lining. According to the meta-analysis, tensile bond strength showed an SMD of -2.49% (95% CI: -3.89 to -1.08; p = 0.0005), suggesting a statistically significant difference between the control and test groups (i.e., favoring laser-treated samples than untreated samples). Regarding shear bond strength scores, the outcomes showed an SMD of -2.24% (95% CI: -3.79 to -0.69; p = 0.005), suggesting a statistically significant difference between the control and test groups (i.e., favoring laser-treated samples than untreated samples). Conclusions: Despite the high heterogeneity among the included studies, it can be concluded that laser treatment might improve the bonding strengths of liners to PMMA denture base resins as compared with untreated surfaces. To validate the aforementioned conclusions, further verification is required through the implementation of well-designed randomized controlled trials with large sample sizes.

Evaluation of Shear Bond Strength Between Denture Teeth and 3D-Printed Denture Base Resin.

PURPOSE: The aim of this study was to evaluate the bond strength between two types of artificial teeth with a 3D-printed denture base resin using different bonding agents. MATERIALS AND METHODS: Two types of artificial teeth were evaluated: 3D-printed (Cosmos TEMP) and prefabricated polymethylmethacrylate (Biotone) bonded to cylinders (2.5 mm in height and 5 mm in diameter) of 3D-printed denture bases (Cosmos Denture designing by Meshmixer and printed by Flashforge Hunter DLP Resin 3D Printer). Two combinations between denture base and artificial teeth were eveluated: Cosmos Denture - Biotone, n = 30, and Cosmos Denture - Cosmos TEMP, n = 30. For each combination, the specimens were randomly distributed according to the bonding agent: (1) autopolymerized acrylic resin-Duralay, n = 10; (2) 3D-printed resin Cosmos TEMP, n = 10; and (3) methylmethacrylate monomer (MMA) + 3D-printed resin Cosmos TEMP, n = 10, totaling 60 specimens. The application of MMA was done conditioning the tooth surface for 180 seconds; the other agents were applied on the same surface. The virtual design of the 3D-printed resin teeth was obtained by scanning the first maxillary molar of the prefabricated teeth as the same protocol of cylinders. The control group (n = 10) was a conventional heat-polymerized denture base resin (Lucitone 550) bonded to the prefabricated resin teeth (Biotone). The shear bond tests were performed by applying a perpendicular force to the artificial tooth - denture base resin, through a chisel at 1 mm/min until failure. Two-way ANOVA and Bonferroni post hoc tests (α = 0.05) were used for multiple comparisons. RESULTS: For the Biotone tooth, the bond strength was significantly higher using MMA + Cosmos TEMP (10.04 MPa), and similar to the control (11.84 MPa, p = 0.484). For the 3D-printed tooth (Cosmos TEMP), the bond strength using the agents Cosmos TEMP (9.57 MPa) and MMA + Cosmos TEMP (12.72 MPa) were similar to the control (11.84 MPa, p = 0.169 and p = 1, respectively), but different from each other (p = 0.016). CONCLUSIONS: From the results, it is recommended to use: MMA + Cosmos TEMP bonding agent for the Biotone tooth; and Cosmos TEMP or MMA + Cosmos TEMP bonding agents for the Cosmos TEMP tooth, both attached to the 3D-printed denture resin Cosmos Denture.

Effectiveness of disinfectant solutions associated or not with brushing on the biofilm control of a 3D printed-denture base resin

Abstract The formation of biofilm on denture bases is a recurrent clinical problem that favors the development of denture stomatitis. The effectiveness of a hygiene protocol in a 3D-printed denture base resin is still uncertain. Objective To evaluate of the effectiveness of immersion, associated or not with brushing in a soap solution, on the biofilm control of a 3D-printed denture base resin. Methodology Specimens of denture base resins [Cosmos Denture (COS) and Classico (CLA/control)] were contaminated in vitro with Candida albicans and immersed in sodium hypochlorite 0.25% (SH, alkaline peroxide) AP, chlorhexidine digluconate 2% (CD or PBS-Control), associated or not with brushing with 0.78% Lifebuoy soap. Roughness was evaluated before and after brushing and immersion. The effectiveness of the protocols was assessed by CFU/mL, cellular metabolism (XTT), scanning electron microscopy (SEM), and confocal scanning laser microscopy. Data were analyzed by T student, ANOVA/Welch, and Tukey/Gomes-Howell pos-hoc tests (α = 0.05). Results CLA showed greater roughness than COS. CFU/mL and XTT were higher in COS resin with a higher hyphae formation. Immersion in SH and CD eliminated CFU/mL and reduced XTT for both resins, associated or not with brushing. AP reduced CFU/mL only when associated with brushing. Conclusions The biofilm on the 3D-printed resin was thicker and presumably more pathogenic, regardless of its smoother surface. Immersions in SH 0.25% and CD 2% are effective hygiene protocols for both resins, associated or not with brushing. AP should be recommended when associated with brushing with a Lifebuoy 0.78% solution.

Effect of Denture Cleanser on the Physico-Mechanical Properties of Injection-Molded Thermoplastic Polyamides Denture Base Material: A preliminary Study.

Objectives: This study aimed to assess the color stability, surface roughness, and flexural properties of the injection-molded thermoplastic polyamide Vertex ThermoSens denture base resin following a 3-minute immersion in Polident 3-minute denture cleanser. Methods: Sixty specimens (Vertex ThermoSens) were processed and divided into two main groups (n = 30) based on the type of test. Group 1 was further subdivided into two subgroups (n = 15): the control group immersed in distilled water (G1DW) and the test group immersed in Polident cleanser solution (G1PD). Group 2 was divided into three subgroups: a non-immersed group (G2None), a group immersed in distilled water (G2DW), and a group immersed in Polident cleanser solution (G2PD). Color change (∆E) and surface roughness measurements were conducted for group 1, and flexural modulus (E) test was performed for group 2. The CIE Lab* formula was utilized to calculate ∆E. An optical 3D surface analyzer and a three-point bending test were employed for surface roughness and E assessments, respectively. Data were subjected to statistical analysis using a paired-sample t-test for differences within each group before and after immersion. Furthermore, independent-sample t-tests and one-way ANOVA were conducted to analyze differences between groups. A significance level of P < 0.05 was considered. Results: The results revealed a slight, statistically insignificant (P > 0.05) ∆E in all color components (L*, a*, b*) after immersion in distilled water. However, after immersion in the denture cleanser, only the L* component exhibited a statistically significant ∆E (P = 0.002), which was slight in magnitude. Additionally, a significant difference was found in the ∆E between G1DW and G1PD, with G1PD showing a higher change (P = 0.007). A significant increase in surface roughness after immersion was observed in G1PD (P = 0.017), with a notable difference between G1DW and G1PD. However, the E remained unaffected (P = 0.537). Conclusion: Denture cleansers have the potential to modify the properties of thermoplastic polyamide resin. Further research is needed to explore the clinical implications of these observed changes on denture performance.

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

PURPOSE: 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. MATERIALS AND METHODS: 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). RESULTS: 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. CONCLUSION: 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.

Algorithm for Designing a Removable Complete Denture (RCD) Based on the FEM Analysis of Its Service Life.

(1) Background: The paper addresses the computer simulation and prediction of the service life of the base of removable complete dentures (RCDs) under typical loads caused by biting and chewing food. For this purpose, the finite element method (FEM) was used. It is assumed that various blocks of teeth, such as incisors, canines, premolars and molars, are subjected to cyclic impacts during a human life. (2) Methods: Both symmetric and asymmetric mastication (two- and one-sided loads, respectively) cases were considered. The load level was assumed to be 100 N, which corresponds to the average muscular compression force of typical human jaws. (3) Results: The FEM analysis of the stress-strain state evolution for RCDs under cyclic loads was carried out. Maps of equivalent lines were drawn for the denture base in terms of its durability. A multi-axial criterion was implemented to determine the number of cycles prior to failure by the mechanism of a normal opening mode crack. The FEM-based assessment of the service life of RCDs enabled us to establish the critical stress concentration areas, thereby allowing for further planning for the correction of an occlusal scheme or teeth inclinations. As a result, the service life of RCDs under cyclic loading can be improved. (4) Conclusions: An algorithm for designing RCDs in the case of edentulism based on the FEM simulation using commercial software as part of the procedure is proposed.

Effects of Nanocrystal Cellulose from Bamboo on the Flexural Strength of Acrylic Resin: In Vitro.

The purpose of this study is to evaluate the effects of nanocrystal cellulose (NCC) from bamboo on the flexural strength of heat-cured acrylic resin. A total of 35 specimens (3.3 mm × 10 mm × 64 mm) were prepared and the specimens were divided into five groups of seven specimens each. Group 1 used conventional acrylic resin that was prepared based on the instructions of the manufacturer (0%). The filled NCC from bamboo fiber in four concentrations (0.25, 0.5, 1, and 2% w/w) was used in the four-reinforcing resin workpiece groups. The specimens were loaded until failure occurred on a three-point bending test machine. One-way analysis of variance and Dunnett's multiple comparison test at a 95% confidence level were used to determine the statistical differences in the flexural strength among the five groups. The results found that the average flexural strength of five specimen groups (0, 0.25, 0.5, 1, and 2% w/w) were 60.11 ± 2.4, 60.75 ± 2.18, 66.50 ± 5.08, 56.04 ± 0.31, and 48.05 ± 2.61 MPa, respectively. The flexural strength of 0.5 mg% w/w NCC-reinforced acrylic resin was significantly higher than the control group (p < 0.01). The reinforced NCC from bamboo fiber to acrylic resin improved the flexural strength properties.

Fracture toughness of conventional, milled and 3D printed denture bases.

OBJECTIVES: The aim of this study was to determine and compare fracture toughness (KIC) and work of fracture (WOF) of a conventional (C) denture base, using the notchless triangular prism (NTP) specimen KIC test, with CAD/CAM (milled, M) and 3D-printed (P) materials at 7 d and 90 d. METHODS: Lucitone 199 (C), Lucitone 199 CAD (M) and Lucitone Digital Print (P) (Dentsply, USA) were used to fabricate NTP specimens. Samples were stored in 37 °C water for 7 d (20/group) and 90 d (20/group) and conditioned in 23 °C water for 1 h prior to testing. For testing, samples were secured in custom-made jigs and loaded in tension until crack arrest/failure. The maximum-recorded load was used to calculate KIC. The results were analyzed by two-way ANOVA, Scheffé multiple mean comparisons (α = 0.05), independent t-tests and Weibull. WOF (in KJ/m2) was calculated by dividing the area under the load-displacement graphs by twice the corresponding crack-arrested cross sectional area of the fractured surfaces. RESULTS: The results have shown that: 1) the tested materials had significantly different KIC (P > C > M; p < 0.005) and WOF at both 7d and 90d; 2) ageing in 37 ºC water for 90 d resulted in a significant decrease of KIC in the C and M groups (p < 0.001) and of WOF in all groups. SIGNIFICANCE: The tested P denture base exhibited significantly higher KIC and WOF, suggesting that it could be more resistant to crack propagation than the C and M materials tested. Water storage for 90 d significantly decreased KIC of C and M materials and WOF of all.

Avaliação das propriedades de superfície, mecânicas e ópticas de resinas acrílicas de base de dentadura confeccionadas pelo método CAD-CAM com processo de envelhecimento e imersão em bebidas corantes / Evaluation of surface, mechanical and optical properties of denture base acrylic resins made by the CAD-CAM method with aging process and immersion in coloring drinks

O objetivo desse estudo foi investigar as propriedades de superfície, estabilidade de cor e propriedades mecânicas de resinas acrílicas para base de dentadura do método convencional, processada por micro-ondas, fresada e impressa 3D diante de diferentes tempos de envelhecimento e imersão em bebidas corantes. Além disso, realizar uma revisão sistemática para avaliar e comparar, através de estudos de ensaios clínicos, próteses totais fabricadas pelo método CAD/CAM com fabricadas convencionalmente, em termos de tempo clínico, manutenção, retenção, estabilidade, eficácia mastigatória, satisfação e qualidade de vida. Um total de 480 amostras redondas (10 × 3,3 ± 0,03 mm) foram confeccionadas para avaliação das propriedades de superfície e estabilidade de cor, divididas entre os quatro grupos principais de resinas e subdivididas em quatro tempos de análise (T0, T1, T2 e T3) e bebidas corantes (água, café, vinho e refrigerante cola), resultando um n = 10 para cada subgrupo. Um total de 160 amostras retangulares (64 × 10 × 3,3 ± 0,03 mm) foram confeccionadas para avaliação das propriedades mecânicas, divididas entre os quatro grupos principais de resinas e subdivididas em quatro tempos de análise (T0, T1, T2 e T3), resultando um n = 10 para cada subgrupo. A revisão sistemática seguiu os Itens de Relatório Preferenciais para Revisões Sistemáticas e Meta-Análises (PRISMA) e foi registrada no Registro Prospectivo Internacional de Revisões Sistemáticas (PROSPERO) (CRD42022296907). A busca eletrônica foi realizada nas bases de dados PubMed/MEDLINE, Web of Science e Scopus até dezembro de 2021. A questão formulada para população, intervenção, comparação e resultado (PICO) foi "Pacientes reabilitados com próteses totais com tecnologia CAD/CAM apresentam parâmetros clínicos semelhantes aos pacientes reabilitados com próteses totais convencionais?". A resina fresada apresentou os melhores resultados das propriedades de superfície diante do efeito do envelhecimento, enquanto que a resina impressa 3D apresentou resultados semelhantes as resinas tradicionais. A resina de Impressão 3D apresentou não ter propriedades ópticas adequadas diante do efeito do envelhecimento, enquanto que a resina fresada apresentou as melhores propriedades. As bebidas corantes não alteraram as propriedades de superfície das resinas, entretanto afetaram suas propriedades ópticas, principalmente a resina de impressão 3D e a processada por micro-ondas. A resina de dentadura fresada CAD/CAM apresentou propriedades mecânicas semelhantes as resinas tradicionais, enquanto que a impressa 3D não apresentou propriedades mecânicas adequadas para uso clínico à longo prazo. As próteses do método de fresagem apresentaram melhor desempenho clínico que as próteses convencionais, em termos de qualidade de vida, satisfação, retenção, estabilidade, tempo clínico e custo, enquanto que as de impressão 3D não apresentaram diferenças. Ambos os métodos do CAD/CAM apresentaram não haver diferenças da eficácia mastigatória em relação as próteses convencionais(AU)

The objective of this study was to investigate the surface properties, color stability and mechanical properties of acrylic resins for denture base of the conventional method, processed by microwave, milled and 3D printed in face of different aging times and immersion in coloring drinks. In addition, carry out a systematic review to evaluate and compare, through clinical trial studies, complete dentures manufactured by the CAD/CAM method with those manufactured conventionally, in terms of clinical time, maintenance, retention, stability, masticatory efficiency, satisfaction and quality of life. A total of 480 round samples (10 × 3.3 ± 0.03 mm) were made to evaluate surface properties and color stability, divided among the four main groups of resins and subdivided into four analysis times (T0, T1, T2 and T3) and coloring drinks (water, coffee, wine and cola), resulting in n = 10 for each subgroup. A total of 160 rectangular samples (64 × 10 × 3.3 ± 0.03 mm) were prepared to evaluate the mechanical properties, divided among the four main groups of resins and subdivided into four analysis times (T0, T1, T2 and T3), resulting in n = 10 for each subgroup. The systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and was registered in the International Prospective Registry of Systematic Reviews (PROSPERO) (CRD42022296907). The electronic search was performed in the PubMed/MEDLINE, Web of Science and Scopus databases until December 2021. The question formulated for population, intervention, comparison and result (PICO) was "Patients rehabilitated with complete dentures with CAD/CAM technology present clinical parameters similar to patients rehabilitated with conventional complete dentures?". The milled resin presented the best results of surface properties in the face of aging effect, while the 3D printed resin presented similar results to traditional resins. The 3D Printing resin did not have adequate optical properties due to the aging effect, while the milled resin showed the best properties. Coloring drinks do not change the surface properties of resins, but optical printing solutions, mainly 3D printing resin and microwave-processed resin. The CAD/CAM milled denture resin presented mechanical properties similar to traditional resins, while the 3D printed denture resin did not present adequate mechanical properties for long-term clinical use. The milling method prostheses showed better clinical performance than conventional prostheses, in terms of quality of life, satisfaction, retention, stability, clinical time and cost, while the 3D printing prostheses showed no differences. Both CAD/CAM methods showed no differences in masticatory efficiency in relation to conventional prostheses(AU)

Nanoparticle-modified PMMA to prevent denture stomatitis: a systematic review.

This systematic review aimed to evaluate the antifungal effectiveness of polymethylmetacrylate (PMMA) modified by nanoparticles (NPs) and to compare it with conventional acrylic resins for denture bases. The present study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Searches were performed using PubMed, SCOPUS, SciELO, EMBASE, and LILACS. Eligibility criteria were as recommended by PRISMA. The studies presented great variability regarding NP type, synthesis method, antifungal evaluation method, and antifungal effect. The most commonly used NPs were silver (AgNP) and zinc oxide (ZnONP), ranging in size from 10 to 100 nm. The incorporation methods were mechanical or agitated. Despite PMMA modification by ZnONP being shown in vitro to be a combination with the best antifungal effect, future studies are still needed to determine the minimum inhibitory concentration for Candida spp. and assess its biocompatibility before the protocol is clinically tested.

CLEANING OF REMOVABLE DENTAL PROSTHESES - A SYSTEMATIC REVIEW.

Objectives The aim of this systematic review was to provide an overview of the scientific evidence available from prospective clinical studies regarding denture hygiene interventions. Therefore, investigations addressing the efficacy of removing microorganisms and biofilms formed on the surface of removable dental prostheses (RDPs) and denture base materials in situ and their impact on the properties of denture base materials, such as color stability, surface roughness, and dimensional stability, were included. Methods A systematic literature search was conducted from June 1975-May 2020 and included articles published in English that have been indexed in the digital archives of PubMed and Cochrane (including PubMed, Embase, ICTRP, CT.gov). A complementary manual search of the initially retrieved studies was conducted. Inclusion criteria comprised prospective clinical trials with a minimum of ten participants investigating (1) approaches and methods to remove biofilms formed on the surface of RDPs and denture base materials in situ and/or (2) the influence of these biofilms on denture base materials. A total of forty-four studies were included in this systematic review, which was registered in the PROSPERO database (CRD42020189649). Results and Conclusions Data gathered from the systematic review indicate that the combined use of chemical and mechanical denture hygiene interventions is significantly more effective than single cleaning approaches. Only limited evidence is available from clinical studies regarding the effect of denture hygiene interventions on the properties of denture base materials.

Evaluation of physical properties of polyamide and methacrylate based denture base resins polymerized by different techniques.

AIM: This study aims to comparatively evaluate the flexural strength, internal adaptation, elastic modulus, and maximum deflection of a newly introduced, strengthened injection-molded semi-flexed polyamide resin (Deflex) and a conventional heat-cured resin containing cross-linking polymethyl methacrylate denture base polymers (QC-20). MATERIALS AND METHODS: A vinyl polysiloxane film replicating the gap between the denture base and the metallic master model of an edentulous maxilla was weighed using an analytical balance with an accuracy of 0.0001 g for the measurement of internal adaptation. The measurements were performed immediately after surface finishing. Seven rectangular test samples measuring 65 × 10 × 3.3 mm3 were set up for flexural strength test. Flexural strength test (three-point bending test) was performed using a universal machine under axial load at a crosshead speed of 5 mm/min. One-way ANOVA (α = 0.05) following by t tests was utilized in statistical analysis. RESULTS: The difference between the flexural strength of the denture base resins of Deflex and QC-20 was found to be statistically significant. The injection-molded resin demonstrated better internal adaptation compared to the conventional heat-polymerized resin. Evaluation of the physical test results revealed that the polyamide samples were more flexible than polymethyl methacrylate and did not break during flexural strength tests. CONCLUSION: Some properties of denture base resins, such as resin types, internal adaptation, and mechanical strength, may play a significant role in clinical performance of complete dentures and removable partial prostheses. Because of the superior flexural strength properties and internal adaptation characteristics, Deflex may prove to be a useful alternative to conventional denture base resin.

Bonding Behavior of Conventional PMMA towards Industrial CAD/CAM PMMA and Artificial Resin Teeth for Complete Denture Manufacturing in a Digital Workflow.

When applying a digital workflow, custom artificial resin teeth have to be integrated into a milled complete denture base, using polymethylmethacrylate (PMMA) applied with a powder-liquid technique. Debonding of denture teeth from dentures is reported to be a frequent complication. No evidence is provided as to which method of surface treatment may enhance the bonding strength. The bonding strength between artificial teeth and PMMA (Group A, n = 60), as well as between the PMMA and industrial PMMA (Group B, n = 60), was investigated following no treatment, monomer application, sandblasting, oxygen plasma, and nitrogen plasma treatment. Surface-roughness values and SEM images were obtained for each group. Shear bond strength (SBS) and fracture mode were analyzed after thermocycling. Within Group A, statistically significant higher SBS was found for all surface treatments, except for nitrogen plasma. In Group B, only nitrogen plasma showed a statistically lower SBS compared to the reference group which was equivalent to all surface treatments. Conclusions: Within the limitations of the present study, the monomer application can be proposed as the most effective surface-treatment method to bond custom artificial teeth into a milled PMMA denture base, whereas nitrogen plasma impairs the bonding strength.

Comparison of the Masticatory Force (with 3D Models) of Complete Denture Base Acrylic Resins with Reline and Reinforcing Materials.

The reinforcement of acrylic denture base remains problematic. Acrylic prosthesis fractures are commonly observed in prosthodontic practice and have not been reliably resolved. This study compared the resistance to masticatory force of acrylic bases of removable complete conventional prosthesis in 3D upper models. Forty acrylic base test specimens containing two types of reinforcement meshes (20 with glass fiber meshes (FIBER-FORCE®- Synca, Bio Composants MédicauxTM, Tullins, France), 20 with metal meshes (DENTAURUM®-Ispringen, Germany)), 20 with a conventional PMMA acrylic base (LUCITONE 199®-Dentsply Sirona, York, PA, USA), and 20 using a permanent soft reline material (MOLLOPLAST-B®-DETAX GmbH & Co. KG, Ettlingen, Germany) were tested-a total of 80 specimens. Half of the specimens were made for a low alveolar ridge and half for a high alveolar ridge. The data were analysed using one-way analysis of variance and Student's t-test for independent test specimens. In the high-alveolar-ridge group, the prosthesis reinforced with the glass fiber mesh was the most resistant to fracture, while in the low-alveolar-ridge group, the non-reinforced prosthesis showed the highest resistance masticatory force. Prostheses with the permanent soft reline material showed the lowest resistance to fracture in both high and low-alveolar-ridge groups. The results show that the selection of the right reinforcement material for each clinical case, based on the height of the alveolar ridge, may help to prevent prosthesis fractures.

Denture base polymers for analog and digital manufacturing: comparative study of the flexural strength, elastic modulus, and compressive strength of their mechanical properties / Polímeros para fabricación análoga y digital de bases de dentadura: un estudio comparativo de la resistencia flexional, módulo elástico y resistencia a la compresión de sus propiedades mecánicas

ABSTRACT Introduction: the emerging manufacture technologies for dental restorations have brought new materials with them, such as 3D-printing resins and CAD/CAM discs for the manufacturing of denture bases. Currently, there is no rigorous mechanical characterization for these materials in the literature, apart from the ones reported in technical datasheets. Method: samples for mechanical characterization were manufactured with a conventional heat cure acrylic, a CAD/CAM polymethyl methacrylate (PMMA) disc and two 3D-printing resins. The samples were tested in a universal testing machine, according to ISO 20795-1 for flexural strength and elastic modulus. Compression strength was also determined under dry conditions. The average value of each property was calculated (n = 5). One-way ANOVA and Tukey's multiple comparisons tests were used. Results: mean flexural strengths ranged from 78.35±2.99 to 87.48±4.47MPa, elastic moduli were between 2125.43±57.05 and 2277.72±58.46MPa, and compression strengths values ranged from 85.03±2.14 to 119.15±2.87MPa. Statistical analyses showed significant differences for flexural and compression strengths but did not show any difference for elastic moduli. Conclusions: all the tested materials met the minimum required specification for mechanical properties given by ISO 20795-1. From a mechanical point of view, the new materials for digital technologies, i.e., CAD/CAM disc and 3D-printing resins, are suitable for denture-base applications.

RESUMEN Introducción: con la aparición de nuevas tecnologías de manufactura han surgido nuevos materiales, como resinas de impresión 3D y discos CAD/CAM, todos empleados para fabricación de bases de dentadura. Actualmente no se cuenta con caracterizaciones mecánicas rigurosas para estos materiales, salvo lo expresado en fichas técnicas. Método: se fabricaron muestras para caracterización de propiedades mecánicas con un acrílico termopolimerizable convencional, un disco CAD/CAM de polimetilmetacrilato (PMMA) y dos resinas de impresión 3D. Se fallaron las probetas en una máquina universal de ensayos, según lo exigido por la norma ISO 20795-1 para el caso de la resistencia y módulo de flexión. La resistencia a la compresión también fue determinada. Se calculó el valor promedio de cada propiedad (n = 5). Se realizó un análisis de varianza de una vía y un análisis de Tukey para comparaciones múltiples. Resultados: los valores de resistencia a la flexión oscilaron entre 78.35±2.99 y 87.48±4.47MPa; el módulo de flexión estuvo en un rango entre 2125.43±57.05 y 2277.72±58.46MPa. La resistencia a la compresión fluctuó entre 85.03±2.14 y 119.15±2.87MPa. Los análisis estadísticos indicaron diferencias significativas para las resistencias a la flexión y compresión, pero no evidenciaron diferencias para el módulo de flexión. Conclusiones: todos los materiales evaluados cumplieron con la especificación mínima de propiedades mecánicas, dada por la ISO 20795-1. Desde el punto de vista mecánico, los nuevos materiales para las tecnologías digitales, discos CAD/CAM y resinas de impresión 3D, son aptos para su aplicación en manufactura de bases de dentadura.

Resistencia al impacto de dos acrílicos convencionales y dos de alto impacto para prótesis total / Impact resistance of two conventional and two high impact acrylics for dentures / Resistência ao impacto de dois acrílicos convencionais e dois acrílicos de alto impacto para próteses totais

Resumen Introducción y objetivo: las resinas acrílicas son los materiales idóneos para la elaboración prótesis totales, sin embargo, las caídas o golpes los hace susceptibles de fracturas. Conocer las propiedades y limitaciones de los acrílicos en nuestro entorno, nos permite realizar tratamientos con los mejores materiales. El objetivo de este estudio fue comparar la resistencia al impacto de dos acrílicos convencionales y dos de alto impacto para bases protésicas. Materiales y métodos: se realizaron 40 barras en cera para base para ser enmufladas de acuerdo con especificaciones de cuatro marcas de acrílicos (n=10), Lucitone199®, Masterdent acrylic resin, Veracril alto impacto® y convencional. La resistencia impacto se evaluó mediante la prueba de Charpy (Máquina ITC-XJU-22), con masa de péndulo de 0.237 Kg y fuerza de impacto de 1J. se realizó análisis estadístico por ANOVA a una vía y prueba de tukey. Resultados: los valores de resistencia al impacto fueron 16.5, 10.8, 9.3 y 5.9 KJ/m2 para Lucitone199®, Veracril alto impacto®, Veracril convencional® y Masterdent acrylic resin. Conclusiones: con las limitaciones de esta investigación, los acrílicos de alto impacto se pueden considerar como una alternativa más viable para la elaboración de prótesis totales ante los acrílicos convencionales, en busca de disminuir el riesgo de fracturas por accidentes o cargas repentinas de impacto.

Abstract Introduction and objective: acrylic resins are the ideal materials for the elaboration of dentures and removable prostheses, although the falls or blows make them susceptible to fractures. Knowing the properties and limitations of acrylics in our environment, allows us to carry out treatments with the best materials. The objective of this study was to compare the impact resistance of two conventional and two high impact acrylics for prosthetic bases. Materials and methods: 40 bars were made in base-wax and processed in muffles according to specifications of four trademarks of acrylics (n=10), Lucitone199®, Masterdent acrylic resin®, Veracril alto impacto® and convencional®. The impact resistance was evaluated by the Charpy test (Machine ITC-XJU-22), with a pendulum mass of 0.237 Kg and an impact force of 1J. One-way ANOVA and tukey test were performed for statistical analysis was performed. Results: the impact resistance values were 16.5, 10.8, 9.3 and 5.9 KJ / m2 for Lucitone199®, Veracril alto impacto®, Veracril convencional® and Masterdent acrylic resin®. Conclusions: with the limitations of this investigation, high impact acrylics can be considered as a more viable alternative for the elaboration of dentures compared to conventional acrylics, in order to reduce the risk of fractures due to accidents or sudden impact loads.

Resumo Introdução y objetivo: as resinas acrílicas são os materiais ideais para a elaboração de próteses totais, porém as quedas ou golpes os tornam suscetíveis a fraturas. Conhecer as propriedades e limitações dos acrílicos em nosso ambiente, permite realizar tratamentos com os melhores materiais.. O objetivo deste estudo foi comparar a resistência ao impacto de d ois acrílicos convencionais e dois de alto impacto para bases protéticas. Materiais e métodos: foram feitas 40 barras de cera para que a base seja silenciada de acordo com as especificações de quatro marcas de acrílicos (n=10), Lucitone199®, resina acrílica Masterdent, Veracril high impact® e convencional. A resistência ao impacto foi avaliada pelo teste de Charpy (Máquina ITC-XJU-22), com uma massa pendular de 0.237 kg e uma força de impacto de 1J. Foi realizada análise estatística ANOVA unidirecional e teste de tukey. Resultados: os valores de resistência ao impacto foram de 16.5, 10.8, 9.3 e 5.9 KJ/m2 para a resina acrílica Lucitone199®, Veracril high impact®, Veracril convencional® e Masterdent. Conclusões: com as limitações desta investigação, os acrílicos de alto impacto podem ser considerados uma alternativa mais viável para a elaboração de próteses totais em comparação aos acrílicos convencionais, a fim de reduzir o risco de fraturas devido a acidentes ou cargas de impacto repentinas.

Measurements of surface scale changes in different denture base materials by stereophotogrammetric technique.

Background. This study aimed to evaluate the surface scale changes in the denture base material using different polymerization techniques, such as heat-cure/pressure polymerization system and injection molding technique with the stereophotogrammetric technique. The function of a complete denture is related to the adaptation of its base to the supporting areas. Proper adaptation of the base depends on the stability and retention of dentures. The surface scale changes of dentures during processing and in service are of great importance since they affect the denture base material's fit. Methods. This study focused on the use of a computer-assisted stereophotogrammetric method for measuring changes in the volume of three different denture base resins of an edentulous maxillary ridge. A stone master model simulating the shape of an edentulous maxillary arch was used to prepare three groups of denture base resins. The stereophotographs were evaluated to determine the surface scale differences of maxillary jaws. Results. The results showed no significant differences between the denture borders for three denture base materials (P > 0.05). Conclusion. In the evaluation made using this technique, no significant difference was found in the different polymerization techniques in terms of surface scale changes for three denture base materials. Stereophotogrammetry, especially the digital stereophotogrammetric technique, has several useful research applications in prosthodontics.