Enhanced mechanical properties, anti-biofilm activity, and cytocompatibility of a methacrylate-based polymer loaded with native multiwalled carbon nanotubes.

OBJECTIVES: We aimed to optimize the mechanical and biological properties of a conventional methacrylate-based dental polymer by loading it with double- and triple-walled carbon nanotubes as growth (DTWCNTG). METHODS: A formulation of bisphenol A-glycidyl methacrylate and triethylene glycol dimethacrylate (mass ratio = 2:1) was mixed with DTWCNTG at concentrations of 0.0% (control), 0.001%, 0.005%, and 0.010%. The concentrations were physicochemical and morphologically evaluated, and antibacterial activity was assessed by seeding a Streptococcus mutans strain (ATCC 25175) on the experimental polymeric surfaces. Cellular survival and osteodifferentiation were evaluated in epithelial (HaCat) and preosteoblast cells (MC3T3-E1). RESULTS: The 0.001% DTWCNTG concentration yielded higher compressive strength, elastic modulus, flexural strength, flexural modulus, water sorption, and solubility than the control. The degree of conversion and color did not significantly change with a low amount of DTWCNTG incorporated into the polymer. Antibacterial activity significantly improved when tested on the 0.001% DTWCNTG discs. No groups showed cytotoxicity in a short-term analysis and adding DTWCNTG favored MC3T3-E1 mineralization over the control, particularly in the 0.001% formulation. SIGNIFICANCE: The micro-addition of 0.001% DTWCNTG confers mechanical resistance, antimicrobial properties, and bioactivity to methacrylate-based polymers without significantly compromising color. Incorporating DTWCNTG improved dental composite properties and could be a biomodified material for minimally invasive procedures.

Compósito odontológico carregado com nanotubos de carbono: caracterização e ensaios biológicos / Dental composite loaded with carbon nanotube: characterization and biological tests

Nanotubos de carbono (NTC) são materiais promissores ao melhoramento de compósitos odontológicos. Entretanto, a homogeneização e o comprometimento estético dessas associações ainda são um desafio. Além disso, até o momento, não foram exploradas composições capazes de induzir respostas teciduais endógenas de reparo. Neste sentido, este estudo teve como objetivo incorporar duas concentrações de NTC de paredes múltiplas (NTCPM), as growth, numa rede polimérica de metilmetacrilato no intuito de investigar as propriedades químicas, mecânicas e biológicas desse novo biomaterial. Produziu-se uma formulação Bis-GMA e TEGDMA (2:1) com 0%; 0,001%; ou 0,01% de NTCPM. Os compósitos foram caracterizados por meio de termogravimetria, espectroscopia no infravermelho com refletância total atenuada (FTIR-ATR), microscopia eletrônica de varredura (MEV). Testes de compressão, flexão, sorção-solubilidade (norma ISO 4049:2009), estabilidade de cor, grau de conversão, e microdureza foram aplicados aos diferentes grupos experimentais. Finalmente, ensaios antimicrobianos em S. mutans (ATCC 25175) (suspensão e biofilme) e ensaios em queratinócitos (HaCat) (citotoxicidade) e pré-osteoblastos (MC3T3) (citotoxicidade/diferenciação) foram utilizados para avaliação de citocompatibilidade e bioatividade. Utilizou-se luz LED (470 nm e 800 mW/cm2) para fotoativar os monômeros. De acordo com ANOVA seguido pelo post-hoc de Tukey, adotando um nível de significância de 5%, a resistência à compressão foi significativamente maior no grupo 0,001% (125,66 MPa) que no grupo controle (46,94 MPa). A resistência flexural foi significativamente maior no grupo 0,001% (51,74 MPa) quando comparado ao grupo 0,1%. Não houve variação nos valores de sorção, solubilidade e estabilidade de cor entre os grupos avaliados. O grau de conversão foi menor nos grupos com NTCPM quando comparado com o grupo controle, e a microdureza Knoop menor na concentração 0,001% quando comparada aos demais grupos. O exame superficial mostrou maior formação de aglomerados de nanotubos nas amostras mais concentradas. O grupo contendo 0,001% NTCPM apresentou atividade antibiofilme quando comparado com o grupo controle e 0,01%. Todas as concentrações apresentaram citotoxicidade nas HaCat após 7 dias, mas a incorporação de NTCPM favoreceu a mineralização de MC3T3 em relação ao controle. Concluiu-se que tanto as propriedades mecânicas como as biológicas apresentaram melhoras com a adição de baixa concentração de NTCPM (0,001%). A adição de 0,001% de NTCPM parece promissora para incorporação em compósitos odontológicos.

Carbon nanotubes (CNT) are candidates for the improvement of dental composites. However, the homogenization and aesthetic commitment of CNT' addition are still a challenge. Moreover, heretofore, there is no study investigating compositions capable of inducing tissue responses towards repair. In this sense, this study aimed to incorporate two concentrations of multiple walls CNT (MWCNT), as growth, in a polymeric network. The chemical, mechanical, and biologicals properties of this experimental biomaterials were assessed. A Bis-GMA and TEGDMA (2:1) base was produced with 0%; 0.001%; or 0.01% MWCNT. The composites were assessed using thermogravimetry, infrared spectroscopy with attenuated total reflectance (FTIR-ATR), scanning electron microscopy (SEM), and were also subjected to compression, bending, sorption-solubility tests in accordance with ISO 4049 :2009, color stability, degree of conversion, microhardness and also to antimicrobial assays in S. aureus (ATCC 25193) (halo formation), S. mutans (ATCC 25175) (biofilm adhesion) and biological assays in keratinocytes (HaCat ) (cytotoxicity) and pre-osteoblasts (MC3T3) (differentiation). LED light (470 nm and 800 mW / cm2) was used to light-cure the monomers. According to ANOVA followed by Tukey's post-hoc, adopting a significance level of 5%, the compressive strength was significantly higher for the 0.001% group (125.66 MPa) than control (46.94 MPa). Flexural strength was also more significant in the 0.001% (51.74 MPa) group than the 0.1% group. There was no significant difference in the values of sorption and solubility and color stability between the evaluated groups. The degree of conversion was lower in the groups with NTCPM when compared to the control group, however the Knoop microhardness was higher in the group with the highest concentration of NTCPM and lower in the group with the lowest concentration when compared to the control group. Despite not showing bacterial inhibition halo formation in any of the groups, the groups containing NTCPM showed a decrease in biofilm adhesion when compared to the control group. All groups shown cytotoxicity on HaCat, but the addition of MWCNT favored MC3T3 mineralization over control. It was concluded that both mechanical and biological properties improved with the addition of low concentration of MWCNT (0.001%). The addition of 0.001% MWCNT looks promising for incorporation in dental composites.

Maxillofacial Prosthetic Rehabilitation of Patients with Resection of Squamous Cell Carcinoma: A Report of Two Cases.

Maxillofacial prosthetic rehabilitation is almost always indicated after surgical treatment of affected individuals with oral cavity and pharynx cancers. Few articles have described in detail the technical sequence of maxillofacial prosthesis fabrication. The first case is a 56-year-old woman who was rehabilitated with pharyngeal obturator prosthesis after a partial maxillectomy, including soft palate, tonsil, oropharynx, and retromolar space regions. The second case is an 83-year-old man who was rehabilitated with hard palatal obturator prosthesis after a maxillectomy, including hard palate and nasal floor. In both cases, the patients complained of oronasal regurgitation and difficulty in chewing, swallowing, and speaking. A multi-professional approach including oral rehabilitation should be part of the treatment plan for individuals with oral and pharyngeal cancer after tumor resection.