Utilização do grafeno para reforço do polimetilmetacrilato utilizado em Medicina Dentária - revisão sistemática

Objectives: 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.Objetivos: Realização de uma revisão sistemática para verificar a alteração do comporta mento mecânico do polimetilmetacrilato utilizado em dentária pela adição de grafeno. Métodos: Dois investigadores independentes efetuaram uma pesquisa em três bases de dados (Pubmed/MEDLINE, Web of Science, Embase) até 31 de dezembro de 2021. Realizou-se também uma pesquisa manual para identificar publicações relevantes. A pergunta de in vestigação definida foi “Em medicina dentária, o polimetilmetacrilato reforçado com grafe no apresenta melhores propriedades mecânicas do que o polimetilmetacrilato convencio nal?”. A seleção dos artigos seguiu o fluxograma PRISMA, considerando os critérios de inclusão e exclusão definidos. A concordância entre investigadores foi calculada pelo coe ficiente Kappa de Cohen. A qualidade dos estudos foi avaliada através da checklist do Joanna Briggs Institute para estudos quasi-experimentais. Resultados: Seis estudos in vitro foram incluídos na análise qualitativa. No total dos estudos analisados nesta revisão foram avaliados 247 provetes, 81 dos quais eram compostos por polimetilmetacrilato convencional e 166 por polimetilmetacrilato aditivado com grafeno. As propriedades mecânicas avaliadas foram: resistência à flexão, módulo de elasticidade, du reza, resistência à flexão biaxial e resistência ao impacto. Maioritariamente, estas proprie dades melhoraram com a adição de determinadas concentrações de grafeno. A análise da qualidade dos artigos demonstrou um baixo risco de viés. Conclusões: Considerando as limitações deste estudo, podemos concluir que o grafeno pa rece melhorar algumas propriedades mecânicas do polimetilmetacrilato utilizado em me dicina dentária. No entanto, mais estudos são necessários para se compreender a concen tração ideal de grafeno para se obter o melhor desempenho clínico das resinas protéticasinfo:eu-repo/semantics/publishedVersio

Retrospective evaluation of implant-supported overdenture treatments: prosthetic complications

Objectives: The objectives of this work are to determine the prevalence of prosthetic complications in implant-supported overdentures, and to compare the maintenance needs of retentive bar-clip and independent abutment systems.Methods: Thirty-seven patients, with 43 implant-supported overdentures (23 maxillary and 20 mandibular) with different retention systems (bar-clip and independent abutments), were clinically evaluated. The total number of maintenance visits and their causes were taken from the clinical file of patients and were evaluated retrospectively. Statistical analysis was done with IBM (R) SPSS (R) vs.22.0 software, considering alpha = 0.05 and using Fisher exact test, Mann-Whitney test and Spearman correlation.Results: Treatments with implant-supported overdentures present a high frequency of prosthetic complications: substitution of retainers (79.1%), overdenture repair or rebasing (53.5%), gingival hyperplasia (34.9%), tightening or fractured screws (20.9%), replacement of the prosthesis (16.3%), changing of retentive system (9.3%) and infrastructure fracture (4.7%). There are significant associations with bar system for gingival hyperplasia and for replacing clips, and with location in the maxilla for replacement of prosthesis and retainers. There are no differences between retentive systems for the number of annual visits.Conclusions: Prosthetic long-term evaluation of treatment with implant overdentures can provide useful guidance to the dentist in the selection of the number of supporting implants, the retentive system and the design of the removable prosthesis.info:eu-repo/semantics/publishedVersio

Effect of denture-related stomatitis fluconazole treatment on oral Candida albicans susceptibility profile and genotypic variability

Denture-related stomatitis (DRS) is the most common condition affecting removable-denture wearers, and Candida albicans the most frequent pathogenic agent. Systemic antifungal treatment is indicated but recurrences are frequent. The aim of this study was to characterize the oral load, fluconazole susceptibility profile and genotypic variability of oral C. albicans isolates from patients with DRS before (T0), immediately after fluconazole treatment (Tat) and after 6-months follow-up (T6m). Eighteen patients presenting DRS and treated with fluconazole were followed at the Faculty of Dentistry of Oporto University. Seventy C. albicans isolates were obtained and identified using standard cultural and biochemical multi-testing. Fluconazole susceptibility was tested by E-test®. Microsatellite-primed PCR was performed to assess the genotypic variability of C. albicans isolates. The patientsâ mean age was 58.0±3.2 years, and 55.6%/44.4% had total/partial dentures. Before treatment, 22.2%, 44.4% and 33.3% of the patients presented DRS type I, II or III, respectively. Fluconazole treatment healed or improved DRS in 77.8% of the patients, accompanied by an 83.5% reduction in oral C. albicans load. However, after 6-months, oral C. albicans load increased significantly and DRS severity was similar to the one observed before treatment. Moreover, the prevalence of patients presenting fluconazole resistant isolates of C. albicans increased significantly throughout the study: T0-5.6%, Tat-10.0% and T6m-42.9%. A change in the genotypic variability of C. albicans isolates was also verified, being mostly associated to fluconazole susceptibility profile change. In conclusion, fluconazole presents a good short-term DRS treatment efficiency, but may be associated to a long-term emergence of C. albicans fluconazole resistance. © Figueiral et al.; Licensee Bentham Open

Mechanical and surface properties of a 3D-printed dental resin reinforced with graphene

Objectives: 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

Antimicrobial activity of a 3D-printed polymethylmethacrylate dental resin enhanced with graphene

The 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.info:eu-repo/semantics/publishedVersio