Browsing by Author "Salgado, Helena"
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- Antimicrobial activity of a 3D-printed polymethylmethacrylate dental resin enhanced with graphenePublication . Salgado, Helena; Gomes, Ana T. P. C.; Duarte, Ana S.; Ferreira, José M. F.; Fernandes, Carlos; Figueiral, Maria Helena; Mesquita, PedroThe present study aimed to test, in vitro, the antimicrobial activity against Candida albicans and Streptococcus mutans and the surface roughness of a 3D-printed polymethylmethacrylate dental resin enhanced with graphene. A 3D-printed polymethylmethacrylate dental resin was reinforced with four different concentrations of graphene: 0.01, 0.1, 0.25 and 0.5 wt%. Neat resin was used as a control. The specimens were printed in a liquid crystal display printer. Disc specimens were used in antimicrobial evaluation, and bar-shaped specimens were used to measure surface roughness. The study of antimicrobial activity included the inhibition of the growth of C. albicans and S. mutans and their adhesion to the resin’s surface. Surface roughness increased with the increase in the graphene concentration. The growth inhibition of C. albicans was observed in the different concentrations of graphene after 24 h, with no recovery after 48 h. The specimens doped with graphene were capable of inactivating S. mutans after 48 h. The surface-adhesion studies showed that the density of microbial biofilms decreases in the case of specimens doped with graphene. Graphene, despite increasing the resin’s surface roughness, was effective in inhibiting the growth and the adhesion to the resin’s surface of the main inducers of prosthetic stomatitis.
- The antimicrobial effect of the incorporation of inorganic substances into heat-cured denture base resins - a systematic reviewPublication . Lima, Mariana; Salgado, Helena; Correia, André; Fonseca, PatríciaIntroduction: Polymethylmethacrylate (PMMA) is the most widely used denture base material due to its favourable properties. Several studies have tested the incorporation of anti-infective agents into PMMA as a strategy to prevent biofilm growth on the denture surface. This systematic review aims to evaluate the efficacy of incorporating inorganic antimicrobial particles into denture base resins in preventing antimicrobial growth, thereby identifying the most effective agents for enhancing PMMA’s antimicrobial properties. Materials and methods: This systematic review followed the PRISMA guidelines, and the research protocol was registered in PROSPERO. The search was performed by using Medical Subject Headings and free text combined with Boolean operators in PubMed/Medline® and in Cochrane® and a free text combination in Web of Science® Core Collection. Data regarding the inorganic particles studied, their antimicrobial effect, and the type of samples produced were collected and analysed. Results: After screening, a total of fifteen studies were included in this review. Most samples were disk-shaped and of varying sizes, and the most tested microbial strain was Candida albicans. Silver was the most used antimicrobial particle, followed by gold, titanium, and copper. Conclusions: Overall, incorporating inorganic particles into PMMA has produced promising antimicrobial results, depending on the concentration. Due to the high heterogeneity observed in the samples, more studies are recommended, particularly clinical trials.
- A different approach to analyzing the surface roughness of prosthetic dental acrylic resinsPublication . Quezada, Margarida Martins; Fernandes, Carlos; Montero, Javier; Correia, André; Salgado, Helena; Fonseca, Patrícia(1) Introduction: Apart from the polishing method, conventional or mechanized, the arithmetic mean roughness (Ra) is the most common metric to evaluate the surface roughness of denture base acrylic resins. An overview of the constraints related to this roughness parameter is highlighted in this study. This research introduces new parameters for accessing a functional analysis of surface roughness. (2) Materials and Methods: Five samples of CAD/CAM 3D-printed acrylic resins were prepared. Two polishing techniques, manual and mechanical, were applied. Surface roughness parameters were extracted from a profilometer reading: arithmetic mean height (Ra and Pa), skewness (Rsk and Psk), and kurtosis (Rku and Pku). (3) Results: Significant differences (p < 0.001) were found in the Ra distribution among the study samples, in contrast with the lack of significance in Pa values. Surface roughness parameters revealed an increased coefficient of variance (CV) value due to mechanized polishing across the specimens analyzed. Skewness and kurtosis indicate a more pronounced distribution with the manual polishing technique. (4) Conclusion: This preliminary study exhibits the influence of different polishing protocols on surface roughness parameters. The primary profile, skewness, and kurtosis should be assessed for the surface characterization of acrylic resins.
- Investigation of the effect of the same polishing protocol on the surface roughness of denture base acrylic resinsPublication . Quezada, Margarida Martins; Salgado, Helena; Correia, André; Fernandes, Carlos; Fonseca, PatríciaThis investigation aims to determine the effect of the same polishing protocol on the surface roughness (Ra) of different resins obtained by different processing techniques. Acrylic resins obtained by CAD/CAM technology overcame the disadvantages identified in conventional materials. A total of thirty samples (six of each resin): self-cured, heat-polymerized, injection molded, CAD/CAM 3D-printed and CAD/CAM milled were prepared. JOTA ® Kit 1877 DENTUR POLISH was used to polish the samples by two techniques: manual and mechanized, with a prototype for guided polishing exclusively developed for this investigation. The Ra was measured by a profilometer. The values were analyzed using ANOVA, Games-Howell post-hoc test and One-sample t-test, with p < 0.05. Manual polishing produces lower values of Ra compared to mechanized polishing, except for injected molded resins ( p = 0.713). Manual polishing reveals significant differences between the resin pairs milling/3D-printing ( p = 0.012) and thermopolymerizable/milling ( p = 0.024). In the mechanized technique only, significant differences regarding the R a values were found between the self-cured/3D-printed ( p = 0.004) and self-cured/thermopolymerizable pair resins ( p = 0.004). Differences in surface roughness values can be attributed to the inherent characteristics of the resin and the respective processing techniques.
- Mechanical and surface properties of a 3D-printed dental resin reinforced with graphenePublication . Salgado, Helena; Fialho, Joana; Marques, Marco; Vaz, Mário; Figueiral, Maria Helena; Mesquita, PedroObjectives: Commercial photocurable polymers used in dental additive manufacturing still have mechanical limitations. The incorporation of graphene may provide interesting advantages in this field. This study aimed to evaluate in vitro the effect of adding graphene nanoparticles to a 3D-printed polymethylmethacrylate dental resin in terms of surface roughness, flexural properties, and hardness. Methods: A 3D-printed dental resin (Dental Sand, Harz Lab) was loaded with four different graphene nanoplatelet (Graphenest) concentrations: 0.01wt%, 0.1wt%, 0.25wt%, and 0.5wt%. The neat resin was used as the control group. The surface roughness was measured with a contact profilometer using bar-shaped specimens (50x10x4mm). The flexural strength of specimens (80x10x4mm) from each group was calculated using the 3-point bending test in a Universal Test Machine. Hardness shore D was measured using a manual durometer on round-shaped specimens (12x6mm). Data were evaluated using the Kruskall-Wallis test followed by post-hoc Bonferroni corrected pairwise inter-group comparisons. Statistical significance was set at p<0.05. Results: Graphene improved 3D-printed PMMA resin hardness with statistical significance at a concentration of 0.01wt% (p=0.043). Surface roughness increased with graphene concentrations above 0.01wt%, with statistically significant differences at 0.25wt% (p=0.006) and 0.5wt% (p=0.005) concentrations. Flexural properties worsened with increased graphene concentrations, and these differences were significant in the concentrations of 0.25wt% (p=0.028) and 0.5wt% (p=0.006). Conclusions: The use of graphene as a mechanical reinforcement nanomaterial seems to be viable at low concentrations without prejudice to the surface roughness of a 3D-printed polymethylmethacrylate resin. (Rev Port Estomatol Med Dent Cir Maxilofac.
- Mechanical properties of polymethyl methacrylate as denture base material: heat-polymerized vs. 3D-printed — systematic review and meta-analysis of in vitro studiesPublication . Lourinho, Cláudia; Salgado, Helena; Correia, André; Fonseca, PatríciaThe synergy between dentistry and informatics has allowed the emergence of new technologies, specifically 3D printing, which has led to the development of new materials. The aim of this research was to compare the mechanical properties of dental base resins for 3D printing with conventional ones. This systematic review was developed using the PRISMA guidelines, and the electronic literature search was performed with the PubMed/MEDLINE, Web of Science—MEDLINE and EMBASE databases, until 30 April 2022. Two researchers selected the studies independently, and thus eight articles were found eligible for analysis. A meta-analysis was developed to estimate flexural strength. The Cohen’s kappa corresponding to this review was 1.00, and the risk assessment was considered low for the included studies. The 3D printing resin presented lower values of flexural strength and hardness compared with the heat-cured resin. Regarding impact strength, a lower value was recorded for the heat-cured resin compared with the 3D printing resin. Three-dimensional printing resins are viable materials for making prosthetic bases but need further clinical research.
- Propriedades mecânicas do polimetilmetacrilato de impressão 3D - revisãos sistemáticaPublication . Lourinho, Cláudia; Salgado, Helena; Correia, André; Fonseca, PatríciaObjetivos: Comparar as propriedades mecânicas das resinas de polimetilmetacrilato para impressão 3D com as da resina convencional, na confeção de bases protéticas, de modo a apresentar evidência científica de valor e elucidar os profissionais de saúde para que estes saibam adequar a utilização dos materiais disponíveis à situação clínica mais indicada. Materiais e métodos: Esta revisão sistemática teve por base as orientações PRISMA®. Foi realizada uma pesquisa nas bases de dados PubMed/MEDLINE®, Web of Science – MEDLINE® e EMBASE®, até 30 de abril de 2022. O protocolo de pesquisa foi registado no PROSPERO com o ID CRD42022296181. A seleção dos estudos foi realizada por dois investigadores independentes de acordo com critérios de inclusão e exclusão previamente definidos. A qualidade dos estudos foi avaliada através da checklist do Instituto Joanna Briggs para estudos quasi- experimentais (estudos experimentais não? randomizados) e a concordância entre investigadores foi determinada através do coeficiente de Kappa de Cohen. Foi realizada meta- análise para a resistência à flexão, com recurso ao software Comprehensive Meta?analysis ® (CMA versão 2.2.057). Selecionou? se o modelo de efeitos aleatórios. Resultados: Após a pesquisa foram identificados 93 artigos. Foi analisado o título de 55 artigos. Destes, 12 foram analisados pelo resumo e 10 pela leitura integral, resultando num total de 8 artigos elegíveis para integrar esta revisão sistemática. A resina de impressão 3D apresenta, na maior parte dos artigos, valores mais baixos de resistência à flexão e dureza, comparativamente à resina termopolimerizável. O forest plot que representa a análise estatística indica que os artigos que mencionam similitude de valores de resistência à flexão em ambos os grupos, sob o ponto de vista estatístico, não são relevantes. No que concerne à resistência ao impacto, os artigos apontam para valores mais baixos no caso da resina termopolimerizável, relativamente à resina de impressão 3D. Conclusões: As resinas de impressão 3D parecem ser materiais viáveis para a confeção de bases protéticas no que diz respeito às propriedades mecânicas avaliadas, mas carecem de mais investigação no sentido de simular as condições do ambiente oral e compreender o comportamento destes novos materiais a longo prazo.
- Técnica de polimento mecanizado na rugosidade de superfície de resinas acrílicasPublication . Quezada, Margarida; Salgado, Helena; Correia, André; Fonseca, PatríciaObjetivos: A presente investigação tem como objetivo avaliar a viabilidade de utilização de uma técnica de polimento mecanizado na rugosidade de superfície de resinas acrílicas para bases protéticas. Materiais e métodos: Um total de trinta provetes foram confecionados (seis de cada tipo de resina): autopolimerizável (Probase® Cold, Ivoclar Vivadent, Liechtenstein), termopolimerizável (Probase® Hot, Ivoclar Vivadent, Liechtenstein), termoplástica (iFlex, TCS®, USA), CAD/CAM de impressão 3D (V -Print dentabase, VOCO GmbH, Alemanha) e CAD/CAM de fresagem (CediTEC DB, VOCO GmbH, Alemanha). O grupo de estudo foi polido através do protocolo JOTA® Kit 1877 DENTUR POLISH (Jota AG, Rüthi, Suíça) com recurso a uma técnica mecanizada de polimento utilizando um gabarito para movimento controlado e condicionado, exclusivamente desenvolvido para este trabalho experimental. Quando aplicado o mesmo protocolo de polimento, este protótipo pressupõe a eliminação das variáveis relacionadas com o operador, de modo a que a rugosidade de superfície dependa exclusivamente das características intrínsecas da resina acrílica. O grupo de controlo não sofreu polimento. Após o polimento, os provetes foram emersos em água destilada durante 24h à temperatura de 37.ºC. A avaliação da rugosidade média (Ra) foi realizada com recurso a um perfilómetro de contacto. A significância estatística foi considerada para um valor de p<0,05. Resulta‑ dos: Os valores de rugosidade nas resinas de impressão 3D (p=0,004), termopolimerizável (p=0,003) e autopolimerizável (p=0,003) foram significativamente inferiores aos valores de rugosidade das respetivas resinas controlo. A análise bivariada de variância (ANOVA) revelou diferenças significativas na distribuição dos valores de rugosidade entre os grupos de resinas submetidas a polimento mecanizado (F=3,323; p=0,031). Verificaram -se apenas diferenças significativas face aos valorev port estomatol med dent cir maxilofac. 2022;63(S1):1-52 43 res de rugosidade entre os pares de resinas de impressão 3D e autopolimerizável (1,58µm±0,19 vs. 0,86µm±0,23; p=0,004) e termopolimerizável e autopolimerizável (1,58µm ±0,19 vs. 1,07µm ±0,25; p=0,004). Conclusões: Diferenças significativas entre o grupo de controlo e o grupo de estudo, assim como, entre pares de resinas permitem conferir viabilidade ao gabarito para movimento controlado e condicionado. Esta ferramenta de polimento mecanizado introduz uma nova abordagem de redução do efeito das variáveis do operador em estudos de rugosidade de superfície.
- The use of graphene for dental polymethylmethacrylate reinforcement - a systematic reviewPublication . Salgado, Helena; Fonseca, Patrícia; Vaz, Mário; Figueiral, Maria Helena; Mesquita, PedroObjectives: To produce a systematic review regarding the effect of graphene-reinforced polymethylmethacrylate used in dentistry on mechanical properties. Methods: Electronic databases (Pubmed/MEDLINE, Web of Science, Embase) were independently searched by two researchers for relevant studies published up to December 2021. An additional manual search was performed to identify relevant publications. The population, intervention, comparison, and outcome (PICO) question was “In dentistry, does graphene-reinforced polymethylmethacrylate offer better mechanical properties than conventional polymethylmethacrylate?”. The selection of articles was carried out according to the established inclusion and exclusion criteria, following the PRISMA flowchart. The inter-investigator reliability was assessed by Cohen's Kappa coefficient. The risk of bias was assessed using the Joanna Briggs Institute Critical Appraisal Checklist for Quasi-experimental Studies. Results: Six in vitro studies were included in the qualitative analysis. A total of 247 specimens were evaluated: 81 made of non-reinforced PMMA resin and 166 of PMMA reinforced with graphene. The mechanical properties evaluated were flexural strength, flexural modulus, hardness, biaxial flexural strength, and impact strength. These properties seem to improve with the addition of graphene in certain concentrations. The analysis of the risk of bias showed low risk. Conclusions: Within the limitation of this study, graphene seems to strengthen some mechanical properties of PMMA dental resin. However, more studies are needed to understand the ideal graphene concentration to improve resin's clinical performance.
- Utilização de resinas flexíveis em prótese removível - revisão sistemáticaPublication . Salgado, Helena; Teixeira, Beatriz; Correia, André; Fonseca, PatríciaObjetivos: O objetivo desta revisão sistemática é verificar se a confeção de bases protéticas em resina flexível termoplástica apresenta resultados mecânicos e físicos superiores, comparativamente com a resina acrílica convencional. Pretende? se desta forma criar evidência científica suficiente, para que os médicos dentistas sejam capazes de escolher qual o material mais indicado a cada caso, sempre com o objetivo de conferir um tratamento reabilitador que satisfaça as necessidades dos pacientes. Materiais e métodos: Após o registo do protocolo de pesquisa no PROSPERO, a mesma foi realizada utilizando as bases de dados PubMed/ Medline®, Cochrane® Library, Web of Science® e Scopus® onde foi efetuada uma combinação de termos MeSH e de texto livre com os operadores booleanos AND e OR. A questão de investigação foi elaborada segundo a estratégia PICO [A confeção de bases protéticas de próteses removíveis (P) em resina flexível termoplástica (I), comparativamente com a resina acrílica convencional (C), apresenta resultados mecânicos e físicos superiores (O)]. A seleção dos artigos foi realizada por dois investigadores independentes, segundo o fluxograma PRISMA, e a concordância avaliada pelo coeficiente kappa de Cohen, sendo posteriormente analisados e avaliados segundo os critérios de inclusão e exclusão estabelecidos. Resultados: Nos 10 estudos analisados nesta revisão foram avaliados 431 provetes, sendo 310 de resina flexível termoplásticas e 121 de resina acrílica convencional. Os estudos incluídos são in vitro e comparam as propriedades mecânicas e características físicas entre os diferentes tipos de resina. A confeção de bases protéticas removíveis em resina flexível termoplástica apresenta resultados mecânicos excelentes tais como a resistência à flexão, módulo de elasticidade, resistência ao impacto e resistência ao cisalhamento. Já no que se refere às características físicas: estabilidade de cor e rugosidade de superfície, as resinas flexíveis apresentam resultados inferiores em comparação com a resina acrílica convencional. Conclusões: A confeção de bases protéticas removíveis em resina flexível termoplástica apresenta resultados mecânicos excelentes, mas que aliados às fracas características físicas, podem não apresentar resultados superiores a longo prazo, comparativamente à resina acrílica convencional. No entanto, é necessária a realização de estudos clínicos a longo prazo, de maneira a investigar estas propriedades e características in vivo.