Effect of oral exposure on chemical, physical, mechanical, and morphologic properties of clear orthodontic aligners

The dental industry is heavily committed to developing more esthetic solutions for orthodontic treatments. Invisalign is a system of transparent orthodontic aligners introduced as an alternative to conventional orthodontic fittings with brackets and metal wires. This study aimed to assess the chemical, physical, mechanical and morphologic changes in these polymeric aligners after exposure to the oral environment. Twenty-four Invisalign orthodontic aligners were equally divided into 2 groups: an in vivo aged group in which patients used aligners for 14 days and the reference group, unexposed to the oral environment. Different experimental techniques were used to study the chemical structure, the color changes and translucency, the density and subsequent volume of the aligners, mechanical properties, surface roughness, morphology and elemental composition. The data were subjected to several statistical analyses. Clear orthodontic aligners exhibit chemical stability but undergo a statistically significant optical change in color and translucency. There was a gradual increase in the water absorption rate and the dimensional variation of the polymer, indicating a strong correlation among these factors. The mechanical properties of the polymer showed a statistically significant decrease in its elastic modulus and hardness. There was a slight tendency toward increased surface roughness of the material, but no statistical differences were found between reference and aged groups. The surface morphology of the used aligners demonstrates microcracks, distortions and biofilm formation. Intraoral aging adversely affected the physical, mechanical, and morphologic properties of the Invisalign appliance.

Effect of the rigid segment content on the properties of segmented polyurethanes conjugated with atorvastatin as chain extender.

Segmented polyurethanes were prepared with polycaprolactone diol as soft segment and various amounts of 4,4´-Methylenebis(cyclohexyl isocyanate) and atorvastatin, a statin used for lowering cholesterol, in order to obtain SPU with different content of rigid segments. Polyurethanes with 35% or 50% of rigid segment content were physicochemically characterized and their biocompatibility assessed with L929 fibroblasts. High concentrations of atorvastatin were incorporated by increasing the content of rigid segments as shown by FTIR, Raman, NMR, XPS and EDX. Thermal and mechanical characterization showed that polyurethanes containing atorvastatin and 35% of rigid segments were low modulus (13 MPa) semicrystalline polymers as they exhibited a glass transition temperature (Tg) at -38 °C, melting temperature (Tm) at 46 °C and crystallinity close to 35.9% as determined by DSC. In agreement with this, X-ray diffraction showed reflections at 21.3° and 23.6° for PCL without reflections for atorvastatin suggesting its presence in amorphous form with higher potential bioavailability. Low content of rigid segments led to highly degradable polymer in acidic, alkaline and oxidative media with an acceptable fibroblast cytotoxicity up to 7 days possibly due to low atorvastatin content.

Toxicity and inflammatory response in Swiss albino mice after intraperitoneal and oral administration of polyurethane nanoparticles.

In this work in vivo experiments were conducted in order to characterize the biocompatibility of polyurethane nanoparticles (PU-NPs) after intraperitoneal (i.p.) and oral administration. Additionally, ex vivo assays were performed to assess human blood compatibility as well as in vitro assays to assess protein binding. Our results indicated that administration of three different concentrations of PU-NPs induced a significant increase in visceral fat accumulation after oral dosing. In addition, fat tissue of mice intraperitoneally treated with the highest concentration of nanoparticles showed diffuse mononuclear inflammatory infiltrate in the fat tissue. Histopathological assessment showed inflammatory infiltrate and hepatocyte vacuolization in the liver, inflammatory infiltration and vascular congestion in the lung and glomerular necrosis in the kidney. Hepatic enzymes related with liver function were significantly increased in both groups of mice treated with PU-NPs. The PU-NPs did not affect the human blood cells number as well as coagulation time but showed a susceptibility to bind in proteins commonly found in the blood stream. In addition, increased amounts of pro inflammatory cytokines in vivo, as well as ex vivo in human cells were observed. Further studies to establish the consequences of long-term exposure to PU-NPs are warranted.

Evaluation of the cytotoxicity of elastomeric ligatures after sterilisation with 0.25% peracetic acid.

INTRODUCTION: Sterilisation using peracetic acid (PAA) has been advocated for orthodontic elastic bands. However, cane-loaded elastomeric ligatures can also become contaminated during processing, packaging, and manipulation before placement in the oral cavity and are therefore susceptible, and possible causes, of cross-contamination. AIM: To test the hypothesis that 0.25% peracetic acid (PAA), following the sterilisation of elastomers, influences the cytotoxicity of elastomeric ligatures on L929 cell lines. MATERIALS AND METHODS: Four hundred and eighty silver elastomeric ligatures were divided into 4 groups of 120 ligatures to produce, Group TP (latex natural, bulk pack, TP Orthodontics), Group M1 (Polyurethane, bulk pack, Morelli), Group M2 (Polyurethane, cane-loaded, Morelli) and Group U (Polyurethane, cane-loaded, Uniden). Of the 120 ligatures in each group, 100 were sterilised in 0.25% PAA at time intervals (N = 20) of 1 hour, 2 hours, 3 hours, 4 hours and 5 hours. The 20 remaining elastomeric ligatures in each group were not sterilised and served as controls. Cytotoxicity was assessed using L929 cell lines and a dye-uptake method. Analysis of variance (ANOVA), followed by the Tukey post hoc test (p < 0.05) determined statistical relevance. RESULTS: There was a significant difference between TP, Morelli and Uniden elastomerics (p < 0.05), but no difference between the two types of Morelli elastomerics at the 1 hour time interval. In addition, there was a significant difference between Group CC and the other groups assessed, except between Groups CC and TP at the 1 hour time interval. The non-sterilised elastomeric ligatures showed similar cell viability to that observed after 1 hour of standard sterilisation. CONCLUSION: PAA did not significantly influence the cytotoxicity of elastomeric ligatures after a sterilisation time of 1 hour and is therefore recommended for clinical use.

Histopathological reaction over prosthesis surface covered with silicone and polyurethane foam implanted in rats.

PURPOSES: To evaluate whether polyurethane foam leads more intense foreign-body reaction than silicone foam. To compare the vascularization of the capsules surrounding the foam implants. To investigate if the capsule of polyurethane foam implanted has greater amount of collagen than that of silicone foam. METHODS: Sixty-four young male Wistar rats were allocated into two groups: polyurethane foam and silicone foam. Subcutaneous discs were implanted into the dorsum of the animals in both groups. The capsules were assessed 28 days, two months, three months and six months postoperatively. Microscopic analysis with H&E stain was performed to evaluate the acute and chronic inflammatory process, foreign-body reaction and neovascularization. The analysis with picrosirius red was performed using the ImageProPlus software, to measure the number of vessels and collagen types I and III. RESULTS: There were no statistical differences between the two groups regarding the acute and chronic inflammatory processes. All rats from the polyurethane group, in all times, exhibited moderate or intense foreign-body reaction, with statistic significant difference (p=0.046) when compared with the silicone group, in which the reaction was either mild or nonexistent at two months. Vascular proliferation was significantly different between the groups at 28 days (p=0.0002), with the polyurethane group displaying greater neovascularization with H&E stain. Similar results were obtained with picrosirius red, which revealed in the polyurethane group a much greater number of vessels than in the silicone group (p=0.001). The collagen area was larger in the polyurethane group, significantly at 28 days (p=0.001) and at two months (p=0.030). CONCLUSIONS: Polyurethane foam elicited more intense foreign-body reaction when compared with silicone foam. The number of vessels was higher in the capsules of the polyurethane foam implants 28 days after the operation. The capsule of the polyurethane foam implants showed a greater amount of collagen than that of the silicone foam implants.

Novel experimental cements for use on the dentin-pulp complex.

This aim of this study was to evaluate the physicochemical and biological properties of novel experimental cements (Hybrid, Paste and Resin) based on synergistic combinations of existing materials, including pH, diametral tensile strength (DTS) and cytotoxicity comparing them with mineral trioxide aggregate (MTA - Angelus®) and a glass ionomer cement (GIC) developed at our laboratory. For the physicochemical and biological tests, specimens with standard dimensions were produced. pH measurements were performed with digital pH meter at the following time intervals: 3, 24, 48 and 72 h. For the DTS test, cylindrical specimens were subjected to compressive load until fracture. The MTT assay was performed for cytotoxicity evaluation. Data were analyzed by ANOVA and Tukey's test (α=0.05). Paste group showed pH values similar to MTA, and Hybrid group presented pH values similar to GIC (p>0.05). The tested materials showed pH values ranging from alkaline to near neutrality at the evaluated times. MTA and GIC showed similar DTS values. The lowest and highest DTS values were seen in the Paste and Resin groups, respectively (p<0.05). Cell viability for MTA and experimental Hybrid, Paste and Resin groups was 49%, 93%, 90% and 86%, respectively, when compared with the control group. The photo-cured experimental resin cement showed similar or superior performance compared with the current commercial or other tested experimental materials.

Histopathological reaction over prosthesis surface covered with silicone and polyurethane foam implanted in rats / Reação histopatológica sobre a superfície de próteses cobertas por espuma de silicone e poliuretano implantadas em ratos

PURPOSES: To evaluate whether polyurethane foam leads more intense foreign-body reaction than silicone foam. To compare the vascularization of the capsules surrounding the foam implants. To investigate if the capsule of polyurethane foam implanted has greater amount of collagen than that of silicone foam. METHODS: Sixty-four young male Wistar rats were allocated into two groups: polyurethane foam and silicone foam. Subcutaneous discs were implanted into the dorsum of the animals in both groups. The capsules were assessed 28 days, two months, three months and six months postoperatively. Microscopic analysis with H&E stain was performed to evaluate the acute and chronic inflammatory process, foreign-body reaction and neovascularization. The analysis with picrosirius red was performed using the ImageProPlus software, to measure the number of vessels and collagen types I and III. RESULTS: There were no statistical differences between the two groups regarding the acute and chronic inflammatory processes. All rats from the polyurethane group, in all times, exhibited moderate or intense foreign-body reaction, with statistic significant difference (p=0.046) when compared with the silicone group, in which the reaction was either mild or nonexistent at two months. Vascular proliferation was significantly different between the groups at 28 days (p=0.0002), with the polyurethane group displaying greater neovascularization with H&E stain. Similar results were obtained with picrosirius red, which revealed in the polyurethane group a much greater number of vessels than in the silicone group (p=0.001). The collagen area was larger in the polyurethane group, significantly at 28 days (p=0.001) and at two months (p=0.030). CONCLUSIONS: Polyurethane foam elicited more intense foreign-body reaction when compared with silicone foam. The number of vessels was higher in the capsules of the polyurethane foam implants 28 days after the operation. The capsule of the polyurethane foam implants showed a greater amount of collagen than that of the silicone foam implants.

OBJETIVOS: Avaliar, em relação ao uso de próteses, se a espuma de poliuretano apresenta maior reação de corpo estranho no organismo ao ser comparada com a espuma de silicone. Se há diferenças na vascularização das cápsulas formada ao redor das duas espumas implantadas. Se as cápsulas dos implantes de espuma de poliuretano apresentam quantidade maior de fibras colágenas ao serem comparadas com as da espuma de silicone. MÉTODOS: Utilizou-se 64 ratos albinos da linhagem Wistar, distribuídos em dois grupos de 34, grupo espuma de poliuretano e grupo espuma de silicone e receberam implantes discóides subcutâneos em seu dorso. Foram analisadas as cápsulas peri-implante com 28 dias, dois, três e seis meses após a introdução. A análise microscópica com H&E considerou as variáveis: inflamação aguda, inflamação crônica, reação de corpo estranho e neoformação vascular. A análise da coloração com picrosirius-red usando ImageProPlus considerou o número de vasos e colágeno tipo I e tipo III. RESULTADOS: Em relação à inflamação aguda e crônica, não foram encontradas diferenças estatísticas nos dois grupos. Todos os animais do grupo poliuretano, em todos os momentos, apresentaram reação de corpo estranho moderada ou intensa e foi encontrada diferença estatística significativa (p=0,046) ao serem comparados com o grupo silicone, cuja reação era ausente ou discreta aos dois meses. A neoformação vascular apresentou diferenças significativas nos dois grupos, aos 28 dias (p=0,0002); o grupo poliuretano com H&E apresentava quantidade maior de vasos neoformados e o mesmo ocorrendo com o picrosirius, cujo número de vasos era maior que no grupo silicone (p=0,001). A área de colágeno em todos os momentos foi maior no grupo poliuretano, sendo significativa com 28 dias (p=0,001) e com dois meses (p=0,030). CONCLUSÕES: A espuma de poliuretano apresentou maior reação de corpo estranho no organismo do que a espuma de silicone. A quantidade de vasos foi maior na cápsula da espuma de poliuretano com 28 dias após o implante. Aos 28 dias as cápsulas dos implantes de espuma de poliuretano apresentaram quantidade significativamente maior de colágeno do que as de espuma de silicone.

Novel experimental cements for use on the dentin-pulp complex

This aim of this study was to evaluate the physicochemical and biological properties of novel experimental cements (Hybrid, Paste and Resin) based on synergistic combinations of existing materials, including pH, diametral tensile strength (DTS) and cytotoxicity comparing them with mineral trioxide aggregate (MTA - Angelus®) and a glass ionomer cement (GIC) developed at our laboratory. For the physicochemical and biological tests, specimens with standard dimensions were produced. pH measurements were performed with digital pH meter at the following time intervals: 3, 24, 48 and 72 h. For the DTS test, cylindrical specimens were subjected to compressive load until fracture. The MTT assay was performed for cytotoxicity evaluation. Data were analyzed by ANOVA and Tukey's test (α=0.05). Paste group showed pH values similar to MTA, and Hybrid group presented pH values similar to GIC (p>0.05). The tested materials showed pH values ranging from alkaline to near neutrality at the evaluated times. MTA and GIC showed similar DTS values. The lowest and highest DTS values were seen in the Paste and Resin groups, respectively (p<0.05). Cell viability for MTA and experimental Hybrid, Paste and Resin groups was 49%, 93%, 90% and 86%, respectively, when compared with the control group. The photo-cured experimental resin cement showed similar or superior performance compared with the current commercial or other tested experimental materials.

O objetivo deste estudo foi avaliar propriedades físico-químicas e biológicas de novos cimentos experimentais (Híbrido, Pasta e Resinoso) baseado na combinação sinérgica de materiais existentes, incluindo pH, resistência à tração diametral (RTD) e citotoxidade, comparando-os ao MTA (Angelus®) e a um cimento de ionômero de vidro (CIV) desenvolvido em nosso laboratório. Para a realização dos testes físico-mecânico e biológico, foram confeccionados espécimes com dimensões padrão. O teste de pH foi realizado por meio de pH-metro digital nos tempos: 3, 24, 48 e 72 h. Para o teste de RTD, espécimes cilíndricos foram submetidos a carga compressiva até sua fratura. Para avaliação da citotoxidade, utilizou-se o teste MTT. Os dados foram analisados utilizando ANOVA e teste de Tukey (α=0,05). O grupo Pasta apresentou valores de pH semelhantes ao MTA, assim como o grupo Híbrido seguiu os parâmetros do CIV (p>0,05). Todos os materiais apresentaram valores de pH alcalinos ou próximosà neutralidade nos tempos avaliados. MTA e CIV apresentaram valores de RTD similares. Os menores e maiores valores observados foram do grupo Pasta e Resinoso, respectivamente (p<0,05). A viabilidade celular para os grupos MTA, Híbrido, Pasta, Resinoso, quando comparados ao grupo controle foi de: 49, 93, 90 e 86%, respectivamente. O cimento experimental Resinoso apresentou desempenho similar ou superior aos materiais comerciais e experimentais avaliados.

Genetic toxicology of dental composite resin extracts in somatic cells in vivo.

The aim of this study was to assess the potential genetic toxicity associated to nine aqueous extracts from dental composite resins (Charisma, Fill Magic, Fill Magic Flow, Durafill, TPH Spectrum, Concept, Natural Look, Filtek Z250 and Filtek P60) and one random extract. Homologous mitotic recombination, point and chromosomal mutation effects were determined in somatic proliferative cells of Drosophila melanogaster exposed to aqueous extracts of the clinically used composites. Reproducible increases in clone mutant spot frequencies induced by diluted extract of Fill Magic Flow were observed. These increments were exclusively associated to the induction of homologous recombination - a genetic phenomenon involved in the loss of heterozygosis. The other eight composite resins and the random extract had no statistically significant effect on total spot frequencies - suggesting that they are non-genotoxic in the somatic mutation and recombination test assay, which agrees with the applications they have in dentistry. These findings - supported by numerous studies showing a positive correlation between carcinogenicity in man and genotoxicity in the Drosophila wing spot test - point to the potential risks some composite resins pose to the health of patients and dentistry personnel.

Cytotoxicity of latex and non-latex orthodontic elastomeric ligatures on L929 mouse fibroblasts.

This study investigated the cytotoxicity exists between latex and non-latex Orthodontic elastomeric ligatures. Six elastomeric ligatures (1 latex, 2 latex-free and 3 polyurethane) from different manufacturers were divided into 6 groups of 15 elastics each: A (Latex-free, American Orthodontics), M (Polyurethane, Morelli), G (Polyurethane,GAC International), Te (Polyurethane, Tecnident), TP (Natural latex,TP Orthodontics) and U (Latex-free,3M Unitek). The cytotoxicity assay was performed using cell cultures (L929 mouse fibroblast cell line), which were subjected to the cell viability test with neutral red ("dye-uptake") at 1, 2, 3, 7 and 28 days. Data were analyzed statistically by ANOVA and Tukey's test (α=0.05). No statistically significant differences (p>0.05) were observed between Groups M and Te in all experimental periods, except at 2 days. No significant differences (p>0.05) in cell viability were found either among Groups A, G, TP and U or between Groups M and Te at 24 h or among Groups CC, A, G, TP and U at 2 and 28 days. It may be concluded that latex-free elastomeric ligatures from American Orthodontics and Unitek trademarks induced less cell lysis compared to latex and polyurethane ligatures.

Cytotoxicity of latex and non-latex orthodontic elastomeric ligatures on L929 mouse fibroblasts

This study investigated the cytotoxicity exists between latex and non-latex Orthodontic elastomeric ligatures. Six elastomeric ligatures (1 latex, 2 latex-free and 3 polyurethane) from different manufacturers were divided into 6 groups of 15 elastics each: A (Latex-free, American Orthodontics), M (Polyurethane, Morelli), G (Polyurethane,GAC International), Te (Polyurethane, Tecnident), TP (Natural latex,TP Orthodontics) and U (Latex-free,3M Unitek). The cytotoxicity assay was performed using cell cultures (L929 mouse fibroblast cell line), which were subjected to the cell viability test with neutral red ("dye-uptake") at 1, 2, 3, 7 and 28 days. Data were analyzed statistically by ANOVA and Tukey's test (α=0.05). No statistically significant differences (p>0.05) were observed between Groups M and Te in all experimental periods, except at 2 days. No significant differences (p>0.05) in cell viability were found either among Groups A, G, TP and U or between Groups M and Te at 24 h or among Groups CC, A, G, TP and U at 2 and 28 days. It may be concluded that latex-free elastomeric ligatures from American Orthodontics and Unitek trademarks induced less cell lysis compared to latex and polyurethane ligatures.

Este estudo investigou a citotoxicidade entre ligaduras elásticas ortodônticas de látex e não-látex. Seis ligaduras elásticas de diferentes fabricantes (1 látex, 2 não-látex e 3 poliuretano) foram divididos em 6 grupos de 15 elásticos cada: Grupo A (látex-free, American Orthodontics), M (Poliuretano, Morelli), G (Poliuretano, GAC International), Te (Poliuretano, Tecnident), TP (látex natural, TP Orthodontics) e U (Látex-free, 3M Unitek). O ensaio de citotoxicidade foi realizado utilizando culturas de células (células da linhagem L929, fibroblastos de camundongo) que foram submetidos ao teste de viabilidade celular com vermelho neutro ("dye-uptake") em 1, 2, 3, 7 e 28 dias. A análise de variância (ANOVA), com comparações múltiplas e teste de Tukey foram empregados (α=0,05). Os resultados mostraram que não houve diferença estatisticamente significante entre os Grupos M e Te em todos os tempos experimentais (p>0,05), exceto em 2 dias. Não houve diferença estatisticamente (p>0,05) entre a viabilidade das células nos grupos A, G, TP e U ou entre os grupos M e Te em 24 h, ou entre os grupos CC, A, G, TP e U em 2 e 28 dias. Concluiu-se que as ligaduras elásticas látex-free das marcas American Orthodontics e Unitek induziram menor quantidade de lise celular comparado às ligaduras de látex ou poliuretano.

Avaliaçäo da toxicidade sistêmica da poliuretana derivada de óleo de mamona: resultados preliminares / Evaluation of systemic toxicity of polyurethane derivade castor-oil plant: preliminary results

Seguindo normatizações internacionais (ASTM), a avaliação toxicológica de um material polimérico derivado de óleo de mamona está sendo feita através da injeção sistêmica em camundongos albinos. Posteriormente, será feita a averiguação histopatológica de rins, fígado, baço e pulmões. Os sinais clínicos apresentados pelos animais após a injeção não revelaram aspectos de toxicidade

Abstract - The toxicological evaluation of a polymeric material from castor oil is being carried out by systemic injection in albino mice and by a subsequent histopathological analysis of their kidneys, liver, spleen and lungs. The animais have not developed clinicai signs of toxicity after the injection. Histopathological analysis of their organs were not concluded yet