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.

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)

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.

Denture applicators with 125I seeds for treatment of palatal malignant tumors / 中国医师杂志

Objective:To explore the clinical application and curative effect of brachytherapy of denture applicators with 125I seeds in the treatment of palatal malignant tumor. Methods:Thirty patients with palatal malignant tumor who underwent surgical resection in Shandong Provincial Hospital from February 2012 to January 2020, and brachytherapy was performed with applicator additional 125I seeds 2 weeks after surgery. All patients were followed up for treatment effect and adverse reactions. Results:All patients wore 125I seeds denture base denture applicator well, no 125I seeds displacement and loss. 30 patients had 10-60 months of follow-up, among which 1 patient received palliative treatment with 125I seeds denture applicator alone died after 10 months of follow-up; 1 patient with adenoid cystic carcinoma recurred after 2 years of follow-up and underwent surgical treatment again; the rest patients did not see tumor recurrence or metastasis. The side effects, pronunciation and chewing function were improved in patients ( P<0.05). Conclusions:For patients with palatal malignant tumor, postoperative 125I seeds denture applicator can effectively prevent tumor recurrence and metastasis, reduce complications, and improve the quality of life.

Nanopartículas de prata em bases de próteses de PMMA para controle de atividade microbiana / Silver nanoparticles in PMMA prosthesis bases to control microbial activity

Objetivo:Avaliar in vitro a atividade de Staphylococcus aureus e Candida albicans em bases de próteses convencionais à base de polimetilmetacrilato de metila com nanopartículas de prata incorporadas a sua composição. Métodos: Foi realizado um estudo experimental laboratorial com resinas acrílicas autopolimerizáveis comercialmente disponíveis, Vipi Flash/VIPI e JET/Clássico. Foram confeccionados 80 corpos de prova, divididos em 16 grupos (n = 5), referentes ao tipo de resina, tratamento (incorporação e imersão na solução de nanopartículas de prata) e microrganismo inoculado. As nanopartículas foram sintetizadas com ácido polimetacrílico, nitrato de prata e irradiadas com luz ultravioleta de baixa potência (~8W) por 6 horas, e as suas concentrações idealizadas pelo método de microdiluição em placas para determinação da concentração mínima inibitória frente aos microrganismos selecionados. Verificou-se ação bactericida e fungicida com concentração inicial de 25% e após fator de diluição 12,5%. Resultados: Houve dificuldade de incorporação das nanopartículas na resina acrílica, que pode decorrer da alteração da proporção 3:1 recomendada pelo fabricante ou pela redução ou inativação da ação da nanopartícula de prata pela interação com o polimetilmetacrilato. VIPI com inclusão de nanopartícula obteve menor aderência de biofilme de Candida albicans. Conclusão:A nanopartícula de prata mostrou-se eficaz na sua ação de controle de Candida albicans e Staphylococcus aureus no método de imersão, entretanto, a sua ação antimicrobiana foi comprometida após inclusão nas resinas acrílicas.

Aim:To perform an in vitro evaluation of the activity of Staphylococcus aureus and Candida albicansin conventional prosthesis bases, based on methyl polymethylmethacrylate with silver nanoparticles incorporated into the composition. Methods: An experimental laboratory study was carried out using commercially available self-curing acrylic resins, Vipi Flash/VIPI and JET/Clássico. Eighty specimens were manufactured and divided into 16 groups (n = 5), referent to the resin brand, treatment (incorporation and immersion in the silver nanoparticle solution), and inoculated microorganism. The nanoparticles were synthesized with polymethacrylic acid and silver nitrate, and were irradiated with a low power (~ 8W) ultraviolet light for 6 hours. Their concentrations were idealized by the method of microplate dilution to determine the minimum inhibitory concentration when compared to the selected microorganisms. Bactericidal and fungicidal activities were identified with an initial concentration of 25% and a subsequent dilution factor of 12.5%. Results:It was difficult to incorporate the AgNPs into the acrylic resin, which may well have resulted from the change from the 3:1 proportion recommended by the manufacturer or by reducing or inactivating the action of the silver nanoparticle by interaction with polymethylmethacrylate. VIPI with the inclusion of nanoparticles obtained a lesser Candida albicans biofilm adherence. Conclusion: Silver nanoparticles were effective in controlling Candida albicans and Staphylococcus aureus in the immersion method; however, the antimicrobial activity was compromised after inclusion in acrylic resins.

Effects of denture cleansers on denture material properties ­an observational case­control study / Efectos de los limpiadores de prótesis dentales sobre las propiedades del material: un estudio observacional de casos y controles

Everyday use of denture cleansers to prevent microbial colonization on dentures can affect the properties of the denture base material. Limited literature is available on the effects of denture cleanser on reinforced resins. This study aimed to evaluate and compare the effect of denture cleanser on the flexural and impact strength of conventional and reinforced heat cure acrylic resins. Materials and Methods: Rectangular shaped specimens were prepared for flexural and impact strength as per ISO 1567. The denture base resins used included conventional, high impact, nylon fiber reinforced and glass fiber reinforced heat cure acrylic resins. They were further categorized into subgroups A and B depending on immersion in distilled water or denture cleanser (3.8% sodium perborate based). The flexural strength and impact strength of specimens were measured. The study design is a observational case-control study. SPSS version 25 statistical analysis software was used, and the STROBE statement checklist was followed. Results: The mean flexural strength was highest for glass fiber reinforced heat cure resin followed by conventional heat cure resin, high impact heat cure resin and nylon reinforced heat cure resin, respectively. The mean impact strength was highest for high impact heat cure resin followed by glass fiber reinforced heat cure resin, conventional heat cure resin, and nylon fiber-reinforced resin respectively.Conclusion: All the denture base resins tested exhibited a decrease in flexural and impact strength following use of a denture cleanser.

El uso diario de limpiadores para prótesis dentales para prevenir la colonización microbiana en las prótesis puede afectar las propiedades del material base de estas. Existe literatura limitada sobre los efectos de los limpiadores de prótesis sobre resinas reforzadas. Este estudio tuvo como objetivo evaluar y comparar el efecto de un limpiador de prótesis sobre la resistencia a la flexión y al impacto de las resinas acrílicas de curado con calor convencionales y reforzadas. Material y Métodos: Muestras de forma rectangular se prepararon para testear la resistencia a la flexión y al impacto según ISO 1567. Las resinas de base de prótesis utilizadas fueron resinas acrílicas convencionales, de alto impacto, y de curado térmico reforzadas con fibra de vidrio o nylon. Posteriormente se clasificaron en los subgrupos A y B según la inmersión en agua destilada o limpiador de prótesis (3,8% de perborato de sodio). Se midieron la resistencia a la flexión y la resistencia al impacto de las muestras. El diseño del estudio fue de un estudio observacional de casos y controles. Se utilizó el software de análisis estadístico SPSS versión 25, y se siguió la guía de la declaración STROBE. Resultado: La resistencia a la flexión fue más alta para la resina de curado por calor reforzada con fibra de vidrio seguida de la resina de curado por calor convencional, la resina de curado por calor de alto impacto y la resina de curado por calor reforzada con nylon, respectivamente. La resistencia al impacto fue más alta para la resina de curado por calor de alto impacto seguida de la resina de curado por calor reforzada con fibra de vidrio, la resina de curado por calor convencional y la resina reforzada con fibra de nylon, respectivamente. Conclusión: Todas las resinas de base de prótesis probadas exhibieron una disminución en la resistencia a la flexión y al impacto después del uso de un limpiador de prótesis.

Surgical and nonsurgical treatment of papillary hyperplasia: A case report / Tratamiento quirúrgico y no quirúrgico de la hiperplasia papilar inflamatoria: Reporte de Caso

Dentures with dental plaque predispose recurrent hyperplasia on the palatal mucosa. Surgical procedures for the treatment of inflammatory papillary hyperplasia involve postsurgical discomfort and morbidity. This repot describes clinical and histologic aspects of a patient with severe akantolitic inflammatory papillary hyperplasia. The palatal mucosa was treated with a surgical bur with a low-speed handpiece. A new removable denture was performed and adapted. A follow-up of 4 years showed staility of health at palatal mucosa. Patient referred low discomfort and morbidity when using bur technique. Control of removable denture was critical for long-term healing and soft tissue stability.

Las prótesis dentales con placa bacteriana predisponen a la hiperplasia recurrente en la mucosa palatina. Los procedimientos quirúrgicos para el tratamiento de la hiperplasia papilar inflamatoria implican molestias y morbilidad posquirúrgicas. Este reporte describe los aspectos clínicos e histológicos de un paciente con hiperplasia papilar inflamatoria acantolítica severa. La mucosa palatina fue tratada con una fresa quirúrgica con una pieza de mano de baja velocidad. Se realizó y adaptó una nueva prótesis parcial removible. Después de un seguimiento de 4 años, se encontró estabilidad de la salud de la mucosa palatina. El paciente se refirió a la baja incomodidad y morbilidad al usar la técnica de la fresa. El control de la prótesis parcial removible fue crítico para la cicatrización a largo plazo y la estabilidad de los tejidos blandos, evitando la recidiva de la hiperplasia papilar inflamatoria.

Antibacterial activity and effects of aromatic derivatives on denture base polymerization

This study assessed the effect of copolymerization on the microbiota of the oral cavity. The plant extraction was converted into aromatic derivatives, which were added to methyl methacrylate monomer. Fourier transform infrared spectroscopy spectra showed no negative effects of these additives on the polymerization process. All the assayed derivatives displayed some degree of antibacterial activity.

Injection Shrinkage аnd Water Sorption of Some Thermoplastic Dental Materials

Objective: To evaluate the change of diameter of different injection-molded thermoplastic materials. Material and Methods: Four thermoplastic injection-molded materials were analyzed (Bre.flex 2nd edition, Vertex ThermoSens, Perflex Biosens and Polyan IC). A total of 432 test samples were made in the form of an "hourglass". All samples were divided into three groups: Group I (Control) - consisting of 36 test samples for each type of material, that was not exposed to artificial aging or a wet environment; Group II - consisting of 36 test samples for each type of material, that were artificially aged through dehydration; Group III - specimen were subjected to artificial aging without dehydration. The diameter of each specimen was measured with a digital caliper. Data were analysed using the Student's t-test. Results: Regarding to shrinkage, the samples from the Bf Control group have a mean value of 1.56 mm and was observed a shrinkage of the injection-molded polyamide material within 0.25%. The comparison between the samples from Group II and Group III showed statistically significant differences (p<0.001). There were no significant differences between groups for Thermosens and Biosens (p>0.05). The comparison between Group II and Group III for Polyan IC samples shows that Group III has a higher arithmetic mean value (p<0.01). Conclusion: Shrinkage of the polymers during the injection process is present in all materials. The thermocycling and the storage in a dry or in a wet environment of the samples results in a change of the diameter in almost every single type of material.

Retention force and wear characteristics of three attachment systems after dislodging cycles

Abstract Several attachment systems for mandibular implant-supported overdentures are currently available and studies are required to understand their mechanical properties. The objective of this study was to evaluate the retention force and wear characteristics of three attachment systems in a simulation of the cyclic dislodging of implant-supported overdentures. Thirty samples were fabricated and divided into 3 groups: 1-O-ring; 2-Mini Ball; and 3-Equator. A mechanical fatigue test was applied to the specimens using a servo-hydraulic universal testing machine performing 5500 insertion/removal cycles (f=0.8 Hz), immersed in artificial saliva. Retention force values ​​were obtained before and after 1500, 3000, and 5500 cycles using a speed of 1 mm/min and a load cell of 1 kN. One specimen from each group was randomly selected and analyzed by scanning electron microscopy. Two-way repeated measures ANOVA and the Bonferroni post hoc test were used for statistical analyses (α=0.05). The O-ring system remained stable during all periods tested and exhibited significantly lower retention force values than the Mini Ball and Equator systems. The Mini Ball system exhibited a significant increase in retention force after the mechanical test (baseline=21.04±3.29N; 5500 cycles=24.01±3.30N).The Equator system exhibited a significant decrease in retention force after each period tested, but the values were higher than the other systems. The type of attachment was found to influence retention force in different ways after mechanical tests. The Equator system exhibited the highest retention force values. The Mini Ball and Equator matrices produced deformation and wear on the surfaces without breakage of the polyamide rings.

Resumo Vários sistemas de encaixe para sobredentaduras mandibulares implantossuportadas estão atualmente disponíveis e estudos são necessários para entender as suas propriedades mecânicas. O objetivo deste estudo foi avaliar a força de retenção e as características de desgaste de três sistemas de encaixe por meio de uma simulação de deslocamento cíclico de sobredentaduras implantossuportadas. Trinta amostras foram fabricadas e divididas em 3 grupos: 1-O-ring; 2-Mini Ball; e 3-Equador. Um teste de fadiga mecânica foi aplicado aos espécimes utilizando uma máquina de teste universal servo-hidráulica com 5500 ciclos de inserção/remoção (f = 0,8 Hz), imersos em saliva artificial. Os valores da força de retenção foram obtidos antes e após 1500, 3000 e 5500 ciclos utilizando uma velocidade de 1 mm/min e uma célula de carga de 1 kN. Um espécime de cada grupo foi selecionado aleatoriamente e analisado por microscopia eletrônica de varredura. O teste de Análise de Variância a dois fatores para medidas repetidas e o teste de comparações múltiplas de Bonferroni foram utilizados para análises estatísticas (α = 0,05). O sistema de O-ring permaneceu estável durante todos os períodos testados e apresentou valores de força de retenção significativamente menores do que os sistemas Mini Ball e Equator. O sistema Mini Ball apresentou um aumento significativo na força de retenção após o teste mecânico (controle = 21,04 ± 3,29N; 5500 ciclos = 24,01 ± 3,30N). O sistema Equator apresentou uma diminuição significativa na força de retenção após cada período testado, mas os valores eram maiores do que os outros sistemas. O tipo de sistema de encaixe influenciou na força de retenção de diferentes maneiras após testes mecânicos. O sistema do Equador exibiu os maiores valores de força de retenção. As matrizes dos sistemas Mini Ball e Equator produziram deformação e desgaste nas superfícies sem ruptura dos anéis de poliamida.

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

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

A new method for evaluating the retentive efficacy of different denture adhesives

Aim: The aim of this study was to evaluate a new method for measuring the retention values of different denture adhesives. Methods: The adhesive strength values of three different commercial denture adhesives (Corega powder, Corega adhesive tape and Ultra Corega cream) were evaluated using three different moisturizing agents (distilled water, artificial saliva and natural saliva). The adhesive test was performed on a universal testing machine, after applying the adhesive products to acrylic resin specimens, under two different test conditions (wetting or dipping). Tensile bond strength values in MPa were obtained for each denture adhesive presentation and test condition. Viscosity of the denture adhesives mixed with the different moisturizing agents was determined using a rotary rheometer. Maximum viscosity values were analyzed using the one-way ANOVA test. Tensile bond strength data was analyzed using Kruskal-Wallis and the Tukey's test. Pooled data of each denture adhesive presentations for all test conditions was also carried out. Correlation between viscosity and pooled tensile strength values was analyzed through linear regression analysis. A significance level of α=0.05 was set for all analyses. Results: Results showed that statistically higher adhesion strength was obtained with tape and cream adhesives when using natural saliva as moisturizing agents (p<0.05). The adhesive strength values obtained with the dipping method were similar to those obtained with the conventional wetting method. The denture retention strength was influenced by both the denture adhesive type and moisturizing agent used. Conclusion: The dipping method showed to be a reliable test capable to simulate the oral conditions and should be better explored in further studies

Long-term microwaving of denture base materials: effects on dimensional, color and translucency stability

Abstract While the combined effect of microwave irradiation with cleansing solutions on denture base materials has been investigated, the effects of only using microwave irradiation and, more importantly, in a long-term basis, was not studied yet. Objective The purpose of this study was to evaluate the effect of a long-term repeated microwaving on the dimensional, color and translucency stability of acrylic and polyamide denture base materials. Material and Methods Thirty two specimens (32 mm x 10 mm x 2.5 mm) from polyamide (Valplast) and PMMA (Vertex Rapid Simplified) denture base materials were made. Eight specimens from each material were immersed in distilled water (control) and 8 were subjected to microwave exposure at 450 W for 3 minutes for a period simulating 224 days of daily disinfection. Linear dimension, color change (ΔE*) and translucency parameter (TP) were measured at baseline and after certain intervals up to 224 cycles of immersion, using a digital calliper and a portable colorimeter. The results were analysed using two-way repeated measures ANOVA to estimate possible differences among predetermined cycles and material type. Regression analysis was also performed to estimate the trend of changes with time. Statistical evaluations performed at a significance level of 5%. Results Data analysis showed significant changes in length at baseline with an increasing number of cycles (p<0.05) and a significant interaction of cycle-material (p<0.001). The ΔΕ* parameter was significantly higher with a higher number of cycles (p<0.001), but it did not vary between materials (p>0.05). TP decreased similarly in both materials following microwave action but in a significantly higher level for Valplast (p<0.001). Conclusions The results indicated that long-term repeated microwaving affects linear dimensional, color and translucency changes of both materials. Differences between PMMA and polyamide material were noted only in dimension and translucency changes.

Determination of the effective anticandidal concentration of denture cleanser tablets on some denture base resins

Abstract Objective Although the effectiveness of chemical cleansing against Candida albicans biofilm has been shown, the effective concentration of denture cleanser tablets has not been studied. The aim of this study was to assess the effect of three denture materials against Candida albicans biofilm and to determine effective concentrations of denture cleanser tablets. Material and methods The surface-roughness of Acron-hi™, QC-20™ and Deflex™ (n=45 per resin) resins was standardized by using a profilometer and their contact angle or surface free energy was calculated. C. albicans biofilm was formed on all three resins and were treated with Polident 3 min™, Corega™ and Fittydent™ cleanser solutions at various concentrations and both resin-biofilm and cleanser-biofilm interest were determined by using a MTT protocol according to the European Committee on Antimicrobial Susceptibility Testing's antifungal susceptibility testing (AFST-EUCAST). Scanning electron microscopy was used to compare the efficacy of different resin materials against C. albicans biofilm. Anticandidal activity and surface free energy statistical parameters were calculated by using 3-way and 1-way ANOVA, respectively (p<0.05). Results Polident 3 min™ and Corega™ tablets significantly inhibited (p<0.05) the proliferation of C. albicans against all denture resins at 27-37 mg/mL. Scanning electron microscopy results indicated that there was no significant difference among resin specimens regarding biofilm formation on dentures. We failed to find a significant relationship between surface free energy and the anticandidal effect of resin types. However, the polarity value of the resins was statistically associated with their anticandidal activity. Conclusions The polarity of the resins, the concentrations of tablets and the chemical content of the cleanser may directly affect C. albicans biofilm formations. Polident 3 min™ and Corega™ tablets should be suggested for patients who use any denture resin types, whereas the Fittydent™ tablet should only be proposed for those who use Deflex™, when two tablets are dropped into 150 mL water.

Comparison of adaptation and microstructure of titanium upper complete denture base fabricated by selecting laser melting and electron beam melting / 中华口腔医学杂志

Objective@#To fabricate Ti alloy frameworks for a maxillary complete denture with three-dimensional printing (3DP) technique, such as selective laser melting (SLM) and electron beam melting (EBM), and to evaluate the microstructure of these frameworks and their adaptation to the die stone models.@*Methods@#Thirty pairs of edentulous casts were divided into 3 groups randomly and equally. In each group, one of the three techniques (SLM, EBM, conventional technique) was used to fabricate Ti alloy frameworks. The base-cast sets were transversally sectioned into 3 sections at the distal of canines, mesial of first molars, and the posterior palatal zone. The gap between the metal base and cast was measured in the 3 sections. Stereoscopic microscope was used to measure the gap. Three pieces of specimens of 5 mm diameter were fabricated with Ti alloy by SLM, EBM and the traditional casting technology (as mentioned above). Scanning electron microscope (SEM) was used to evaluate the differences of microstructure among these specimens.@*Results@#The gaps between the metal base and cast were (99.4±17.0), (98.2±26.1), and (99.6± 16.1) μm in conventional method; (99.4 ± 22.8), (83.1 ± 19.3), and (103.3 ± 13.8) μm in SLM technique; (248.3±70.3), (279.1±71.9), and (189.1±31.6) μm in EBM technique. There was no statistical difference in the value of gaps between SLM Ti alloy and conventional method Ti alloy group (P>0.05). There was statistical difference among EBM Ti alloy, conventional method Ti alloy and SLM Ti alloy group (P<0.05). The SLM Ti alloy showed more uniform and compact microstructure than the cast Ti alloy and EBM Ti alloy did.@*Conclusions@#SLM technique showed initial feasibility to manufacture the dental base of complete denture. The mechanical properties and microstructure of the denture frameworks prepared by SLM indicate that these dentures are appropriate for clinical use. EBM technique is inadequate to make a complete denture now.

A preliminary study on the forming quality of titanium alloy removable partial denture frameworks fabricated by selective laser melting / 中华口腔医学杂志

Objective@#To evaluate the processing accuracy, internal quality and suitability of the titanium alloy frameworks of removable partial denture (RPD) fabricated by selective laser melting (SLM) technique, and to provide reference for clinical application.@*Methods@#The plaster model of one clinical patient was used as the working model, and was scanned and reconstructed into a digital working model. A RPD framework was designed on it. Then, eight corresponding RPD frameworks were fabricated using SLM technique. Three-dimensional (3D) optical scanner was used to scan and obtain the 3D data of the frameworks and the data was compared with the original computer aided design (CAD) model to evaluate their processing precision. The traditional casting pure titanium frameworks was used as the control group, and the internal quality was analyzed by X-ray examination. Finally, the fitness of the frameworks was examined on the plaster model.@*Results@#The overall average deviation of the titanium alloy RPD framework fabricated by SLM technology was (0.089±0.076) mm, the root mean square error was 0.103 mm. No visible pores, cracks and other internal defects was detected in the frameworks. The framework fits on the plaster model completely, and its tissue surface fitted on the plaster model well. There was no obvious movement.@*Conclusions@#The titanium alloy RPD framework fabricated by SLM technology is of good quality.

Clinical study of custom abutment and digital provisional crown in implant denture gingival formation / 中国基层医药

Objective To analyze the effect of custom abutment and computer aided design and computer aided manufacturing(CAD/CAM) provisional crown on gingival shaping around the implant,and to research the main effect of the custom abutment in the formation of gingival.Methods According to the wishes of patients,fifteen patients were divided into two groups.Gingival molding used CAD/CAM in the observation group(n=7) to design and make custom abutment and provisional crown.The control group(n=8) used the prefabricated abutment and the hand-made self-curing resin temporary crown.Immediately after inserting of final insertion and three months later,pink esthetic score(PES) was calculated in both two groups.Results The labial gingiva curve of the observation group was (1.93±0.27)points,which was higher than (1.56±0.51)points of the control group,there was significant difference between the two groups(t=2.496,P0.05).The PES score of the observation group was (8.50±1.09)points,which was higher than (7.75±1.13)points of the control group,but the difference was not statistically significant(P>0.05).Conclusion The effect of the custom abutment on curvature of facial mucosa is significant.The combination of custom abutment and digital provisional crown can achieve better soft tissue stability and ideal aesthetic effect in a short time.

Removable partial or complete dentures exposed to beverages and mouthwashes: evaluation of microhardness and roughness / Próteses parciais e totais removíveis expostas a bebidas e enxaguatórios bucais: avaliação da microdureza e rugosidade

Purpose: To evaluate microhardness and roughness of denture base polymethylmethacrylate resinn exposed to acid beverages and mouthwashes. Material and method: Rectangular samples (n=80) were prepared from poly (methyl methacrylate) (PMMA). They were divided into 8 groups and had the initial microhardness and Knoop roughness measured. Samples of each group were immersed for 10 min into a test solution (coffee, lemon juice, chlorhexidine gluconate, red wine, cola-based soft drink, vinegar or antiseptic with and without alcohol) and after stored in artificial saliva for 23 h and 50 min, completing a period of 24 h. This procedure was performed for 14 consecutive days and after this period the microhardness and surface roughness measurements were made again. Data were statistically analyzed using ANOVA non parametric, Kruskal-Walis and the Dunn´s test for microhardness and the t-Student and ANOVA for roughness. Result: For microhardness there were found statistically significant differences among the chlorhexidine gluconate solution, antiseptic without alcohol and cola-based soft drink. For roughness was observed that the mean values between the initial period and after immersion in the test products differed statistically in all groups, without difference among groups. Conclusion: The microhardness of poly(methyl methacrylate) was affected by continue exposition to chlorhexidine gluconate, antiseptic without alcohol and cola-based soft drink. The roughness of poly(methyl methacrylate) is negatively influenced by the exposure to all tested products. It may be concluded that both, microhardness and roughness, were affected by the treatments.

Objetivo: Avaliar a rugosidade e microdureza de uma resina acrílica utilizada para base de prótese quando submetidas a diferentes bebidas e enxaguatórios bucais. Material e método: Oitenta amostras retangulares foram confeccionadas com polimetilmetacrilato, e separados em 8 grupos. As amostras foram avaliadas quanto à microdureza e rugosidade (Knoop) superficiais e imersas por 10 minutos em um dos seguintes produtos: café, suco artificial de limão, gluconato de clorexidina, vinho tinto, refrigerante a base de cola, vinagre e antissépticos com e sem álcool. Após a imersão nas soluções, as amostras foram acondicionados em saliva artificial por 23 horas e 50 minutos, completando o período de 24 horas. Esse procedimento ocorreu por 14 dias consecutivos e após esse período outras mensurações de microdureza e rugosidade foram realizadas. Os dados obtidos foram analisados estatisticamente pela ANOVA não paramétrico, Kruskal-Walis e teste de Dunn para a microdureza e ANOVA e t-student (alfa=5%) para rugosidade. Resultado: Para microdureza foram encontradas diferenças significativas entre os grupos onde houve imersão em clorexidina, antisséptico sem álcool e refrigerante de coca-cola. Para a rugosidade foi observado que a media entre os valores antes e após a imersão nos produtos diferiu estatisticamente em todos os grupos, porém sem diferença entre eles. Conclusão: A microdureza do polimetilmetacrilato foi afetada pela exposição ao gluconato de clorexidina, antisseptico sem álcool e refrigerante à base de coca-cola. A rugosidade da superfície do polimetilmetacrilato foi afetada por todos os produtos estudados.

Study on interface compatibility and fracture resistance of polyglycidyl methacrylate pre-impregnated quartz fiber reinforced polymethyl methacrylate denture base resin / 北京大学学报(医学版)

Objective: To explore the reinforcement of polyglycidyl methacrylate ( PGMA ) pre-impregnated quartz fiber mesh in denture base materials by investigation of interface compatibility and fracture resistance .Methods: 1-layer, 2-layer, 3-layer PGMA pre-impregnated quartz fiber meshes , electrolyzed cobalt-chromium alloy mesh and cobalt-chromium alloy mesh conditioned by metal primer were integrated in polymethyl methacrylate ( PMMA) resin by sandwich embedding method .Block sam-ples of 5 groups were prepared (40 mm ×15 mm ×2 mm).Fracture resistance was determined in a 3-point bending test at 2 mm/min.Scanning electron microscope (SEM), micrographs were taken from the fractured surfaces to analyze the bonding interface compatibility .Results: The group of 3-layer PGMA pre-impregnated quartz fiber mesh presented the highest elastic modulus of 6 406 MPa and flexural strength of 227 MPa among the five groups , while the 1-layer and 2-layer expressed the similar elastic modulus and flexural strength to the pure PMMA group .The metal groups demonstrated better mechanical properties, while the metal surface conditioner played much better .The metal surface conditioner pre-impregnated cobalt-chromium alloy and PGMA pre-impregnated quartz fiber mesh showed compatible in-terface with PMMA.Conclusion:The mechanical properties were improved by the increasing of the fiber by adding the more meshed .Although the benign interface did help the compatibility , the quantity of the fibers played an important role in the strength .