RESUMO
OBJECTIVE: To develop an antimicrobial orthodontic band cement for the prevention of white spot lesions using a novel process that generates silver nanoparticles (AgNP) in situ. MATERIALS AND METHODS: Twenty-seven groups of AgNP-loaded Opal Band Cement (OBC) and two control groups were formulated with varying concentrations of additional benzoyl peroxide (0.5, 1.0, 1.5, or 2.0 wt%) and 2,2-(p-Tolylimino) diethanol (0.5 or 1 wt%). Rockwell15T hardness and near-infrared FTIR were used to assess degree of cure, three-point bending was used to determine modulus and ultimate transverse strength (UTS), and Ag(+) ion release was measured for up to 4 months in vitro using atomic absorption spectroscopy. Antimicrobial activity against Streptococcus mutans and Lactobacillus acidophilus was tested in vitro by counting colony-forming units for up to 28 days. Biocompatibility was evaluated following ISO specifications 7405 (2008), 10993-3 (2003), 10993-5 (2009), and 10993-10 (2010). RESULTS: Most of the experimental groups had hardness, modulus, and UTS values similar to those of the control group. Ag(+) ion release was observed for all AgNP-loaded groups for up to 4 months. Increase in Ag loading increased Ag(+) ion release and in vitro antimicrobial effect. The biocompatibility of the optimal AgNP-loaded OBC was comparable to that of negative controls. CONCLUSION: A novel antimicrobial orthodontic band cement was developed that has comparable mechanical properties to controls, controlled and sustained Ag(+) ion release, significant bacterial inhibition in vitro, and excellent biocompatibility.
Assuntos
Antibacterianos/síntese química , Nanopartículas Metálicas/química , Braquetes Ortodônticos , Cimentos de Resina/síntese química , Prata/química , Antibacterianos/farmacologia , Carga Bacteriana/efeitos dos fármacos , Peróxido de Benzoíla/química , Materiais Biocompatíveis/síntese química , Materiais Biocompatíveis/química , Materiais Biocompatíveis/farmacologia , Cariostáticos/síntese química , Cariostáticos/química , Cariostáticos/farmacologia , Módulo de Elasticidade , Dureza , Humanos , Lactobacillus acidophilus/efeitos dos fármacos , Teste de Materiais , Metacrilatos/química , Maleabilidade , Polimerização , Cimentos de Resina/química , Cimentos de Resina/farmacologia , Prata/farmacologia , Espectrofotometria Atômica , Espectroscopia de Infravermelho com Transformada de Fourier , Espectroscopia de Luz Próxima ao Infravermelho , Streptococcus mutans/efeitos dos fármacos , Estresse Mecânico , Fatores de TempoRESUMO
UNLABELLED: Dual-cure (DC) resins are mainly used as cements due to high initial color (generally yellow) and large color shift (ΔE*) after polymerization as compared to light-cured resins. However, even as cements, this color shift is clinically unacceptable, especially when used to cement thin veneers. OBJECTIVE: To develop a novel DC initiator system with both lower initial color (less yellow, i.e., whiter) and smaller ΔE*. METHODS: The effect of using an allyl thiourea (T)/cumene hydroperoxide (CH) self-cure (SC) initiator system in combination with a photo-co-initiator, p-octyloxy-phenyl-phenyl iodonium hexafluoroantimonate (OPPI), in a commercial DC resin cement (PermaFlo DC, Ultradent Products, Inc.) was investigated. Initial color and ΔE* were assessed for 6 weeks in vitro under accelerated aging conditions (75°C water bath). Rockwell15T hardness was used to assess degree of cure (DoC) and the three-point bending test was used to assess mechanical properties. RESULTS: PermaFlo DC (control) was significantly harder than all experimental groups without OPPI but had up to three times higher initial color and four times greater color shift (ΔE*=27 vs. 8). With OPPI, hardness in the experimental groups increased significantly and several were comparable to the controls. Initial color and ΔE* increased slightly (ΔE*=9), but was still 3 times less than that of PermaFlo DC. DC samples containing OPPI had comparable modulus and ultimate transverse strengths to those of the controls. CONCLUSIONS: DC resins that use the T/CH initiator system are weaker but have extremely low color and ΔE*. The addition of OPPI increases DoC and mechanical properties to clinically acceptable levels and maintains extremely low color and ΔE*. SIGNIFICANCE: With this novel initiator system, DC resins potentially can now have comparable color and color stability to light-cure resins and be used in broader esthetic dental applications to improve color stability and reduce shrinkage stress in restorative composites.
Assuntos
Cor , Peróxido de Hidrogênio/química , Oniocompostos/química , Fotoiniciadores Dentários/síntese química , Cimentos de Resina/síntese química , Autocura de Resinas Dentárias , Tioureia/química , Análise de Variância , Dureza , Cura Luminosa de Adesivos Dentários , PolimerizaçãoRESUMO
UNLABELLED: Polymethyl methacrylate (PMMA) is widely used to treat traumatic head injuries (cranioplasty) and orthopedic injuries (bone cement), but there is a problem with implant-centered infections. With organisms such as Acinetobacter baumannii and methicillin-resistant staphylococcus aureus developing resistance to antibiotics, there is a need for novel antimicrobial delivery mechanisms without risk of developing resistant organisms. OBJECTIVES: To develop a novel antimicrobial implant material by generating silver nanoparticles (AgNP) in situ in PMMA. RESULTS: All PMMA samples with AgNP's (AgNP-PMMA) released Ag(+) ions in vitro for over 28 days. In vitro antimicrobial assays revealed that these samples (even samples with the slowest release rate) inhibited 99.9% of bacteria against four different strains of bacteria. Long-term antimicrobial assay showed a continued antibacterial effect past 28 days. Some AgNP-loaded PMMA groups had comparable Durometer-D hardness (a measure of degree of cure) and modulus to control PMMA, but all experimental groups had slightly lower ultimate transverse strengths. CONCLUSIONS: AgNP-PMMA demonstrated a tremendously broad-spectrum and long-intermediate-term antimicrobial effect with comparable mechanical properties to control PMMA. Current efforts are focused on further improving mechanical properties by reducing AgNP loading and assessing fatigue properties.