SUMMARY OBJECTIVES: The transition from face-to-face to remote teaching is yet to be fully understood. In clinical training, traditional teaching must prevail because it is essential for the acquisition of skills and professionalism. However, the responses of each school to the pandemic and the decision on when to resume clerkship rotations were mixed. In this study, we aimed to analyze whether the time to resume clerkship rotations was associated with the performance of the students by using a multi-institutional Progress Test. METHODS: This is a cross-sectional study conducted at nine different Brazilian medical schools that administer the same annual Progress Test for all students. We included information from 1,470 clerkship medical students and analyzed the time of clinical training interruption as the independent variable and the student’s scores as the dependent variable. RESULTS: The comparisons of the students’ scores between the schools showed that there are differences; however, they cannot be attributed to the time the clerkship rotations were paused. The correlation between the schools’ average scores and the time to resume clerkship rotations was not significant for the fifth year (r= -0.298, p=0.436) and for the sixth year (r= -0.440, p=0.240). By using a cubic regression model, the time to resume clerkship rotations could explain 3.4% of the 5-year students’ scores (p<0.001) and 0.9% of the 6–year students, without statistical difference (p=0.085). CONCLUSIONS: The differences between the students’ scores cannot be attributed to the time when the schools paused the clerkship rotations.

Resumo Bactérias estão relacionadas a diferentes doenças bucais, como a cárie dentária e a doença periodontal. Assim, o controle e/ou erradicação de microrganismos e seus subprodutos é primordial para o sucesso dos tratamentos. Uma alternativa para diminuir a carga bacteriana é a utilização de extratos vegetais utilizados na medicina popular. A citotoxicidade e ação antimicrobiana de extratos de Cariniana rubra Gardinerex Miers, Senna martiniana H.S. Irwin & Barneby, Anadenanthera colubrina (Vell.) Brenan e Spiranthera odoratissima St. Hil. contra cepas de Streptococcus mutans, Enterococcusfaecalis, Staphylococcus aureus, Escherichia coli, Agartibacter actinomycetencomitans e Candida albicans foram investigados. A citotoxicidade foi avaliada nas concentrações de 1, 10, 40, 80, 100 e 1000 μg/mL por meio do teste MTT. Aqueles com citotoxicidade aceitável tiveram a ação antimicrobiana medida pelo teste XTT. Cariniana rubra Gardinerex Miers apresentou os maiores resultados de citototoxicidade, enquanto Spiranthera odoratissima St. Hil. obteve os melhores resultados, mas todos os extratos apresentaram citotoxicidade aceitável em diferentes concentrações. Os extratos vegetais apresentaram maior atividade contra A. actinomycetencomitans: Anadenanthera columbrina (Vell.) Brenan (80,52%) a 40 μg/mL, Spiranthera odoratissima St. Hil (78,48%) em 1 μg/mL, Senna martiniana H.S. Irwin & Barneby (73,28%) na concentração de 40 μg/mL e Cariniana rubra Gardinerex Miers (70,50%) em 10 μg/mL. Todos os extratos analisados apresentaram citotoxicidade aceitável em diferentes concentrações e foram promissores na inibição dos microrganismos patogênicos estudados.

Abstract Bacteria are related do different oral diseases, such as dental caries and periodontal disease. Therefore, the control or/and eradication of microorganisms and their by-products is primordial for the success of their treatment. An alternative for decrease bacterial load is the use of plant extracts used in popular medicine. The cytotoxicity and antimicrobial action of extracts of Cariniana rubra Gardiner ex Miers, Senna martiniana, Anadenanthera colubrina (Vell.) Brenan and Spiranthera odoratissima St. Hil. against strains of Streptococcus mutans, Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Aggregatibacter actinomyces- tencomitans and Candida albicans were investigated. Cytotoxicity was assessed at concentrations of 1, 10, 40, 80, 100 and 1000 μg/mL by means of the MTT test and compared to a control group with untreated cells. Those with acceptable cytotoxicity had the antimicrobial action measured by the XTT test. As a positive control, sodium hypochlorite was used. Cariniana rubra Gardiner ex Miers had the highest citototoxicity results while Spiranthera odoratissima St. Hil. had the best results, but all extracts showed acceptable cytotoxicity at different concentrations. The plant extracts showed higher activity against A. actinomycetencomitans: Anadenanthera columbrina (Vell.) Brenan (80.52%) at 40 μg/mL, Spiranthera odoratissima St. Hil (78.48%) in 1 μg/mL, Senna martiniana (73.28%) in the concentration of 40 μg/mL and Cariniana rubra Gardiner ex Miers (70.50%) in 10 μg/mL. All extracts analyzed showed acceptable cytotoxicity at different concentrations and were promising for inhibition of the pathogenic microorganisms studied.

Resumo A resposta de defesa do hospedeiro ao desafio microbiano que emerge do sistema de canais radiculares leva à periodontite apical. Os objetivos deste estudo foram avaliar a expressão de citocinas pró e anti-inflamatórias e Óxido Nítrico (NO) por macrófagos após interação com Enterococcus faecalis no modo: planctônio e de biofilme desalojado; biofilme intacto estimulado por hidróxido de cálcio (CH), CH e clorexidina ou Pasta Tri Antibiótica (TAP). Para isto, a cultura de macrófagos originados de monócitos do sangue periférico de humanos (N=8) foi exposta aos diferentes tipos de bactéria por 24 horas. Então, a quantificação da produção de of Fator de Necrose Tumoral- alfa (TNF-α), interleucina (IL)-1β, IL-6, IL-10 e NO por macrófagos se deu por meio do Luminex xMAP e reação de Greiss, respectivamente. Além dos potenciais efeitos terapêuticos desses compostos, sua atividade antimicrobiana contra E. faecalis também foi testada através microscopia confocal. Os dados dos experimentos foram analisados através do teste de Kruskal-Wallis com Dunn`s post hoc (α < 0.05). Bactéria em modo de biofilme desalojado se mostrou mais agressivo ao sistema imune que as bactérias planctônicas e controle negativo induzindo a maior excreção de NO e TNF-α. Em relação ao biofilme intacto, a atividade antimicrobiana mais fraca ocorreu no grupo de CH. Os grupos CHX e TAP aumentaram significativamente a porcentagem de bactérias mortas na mesma extensão. Interessantemente, o biofilme por ele mesmo não induziu a liberação de citocinas pro-inflamatórias - exceto por NO - enquanto que o biofilme tratado com TAP ou pastas a base de CH aumentaram os níveis de IL-6; e TNF-α e IL-1 β respectivamente. Em contraste, os níveis da potente citocina anti-inflamatória (IL-10) foram aumentados pelo grupo TAP.

Abstract The host defense response to microbial challenge emerging from the root canal system leads to apical periodontitis. The aim of this study was to evaluate the expression of inflammatory cytokines and Nitric Oxide (NO) by macrophages after interaction with Enterococcus faecalis in the: plankton and dislodged biofilm mode; intact biofilm mode stimulated by calcium hydroxide (CH), CH and chlorhexidine (CHX) or Triple Antibiotic Paste (TAP). For this purpose, culture of macrophages from monocytes in human peripheral blood (N=8) were exposed to the different modes of bacteria for 24 hours. Subsequently, the cytokines, such as, Tumor Necrotic Factor- alfa (TNF-α), interleukin (IL)-1β, IL-6, IL-10; and NO were quantified by Luminex xMAP and Greiss reaction, respectively. In addition to the potential therapeutic effects of the intracanal medication, their antimicrobial activity against Enterococcus faecalis biofilm were also tested in vitro by confocal microscopy. The experiments` data were analyzed by the Kruskal-Wallis test with the Dunn post hoc test (α < 0.05). Bacteria in dislodged biofilm mode were shown to be more aggressive to the immune system than bacteria in plankton mode and negative control, inducing greater expression of NO and TNF-α. Relative to bacteria in intact biofilm mode, the weakest antimicrobial activity occurred in Group CH. In Groups CH/CHX and TAP the percentage of dead bacteria was significantly increased to the same extent. Interestingly, the biofilm itself did not induce the release of pro-inflammatory cytokines - except for NO - while the biofilm treated with TAP and CH based pastes enhanced the levels of IL-6 and TNF-α; and IL-1 β, respectively. In contrast, the levels of a potent anti-inflammatory (IL-10) were increased in Group TAP.

Abstract Background: Qualea grandiflora (QG) (Vochysiaceae), also known as "pau-ferro", "pau-terra" or "pau-de-tucano", is a very common deciduous tree in the Brazilian Cerrado used in traditional medicine to treat inflammations, ulcers, diarrhea, and infections. There are reports in the scientific literature that demonstrate the medicinal effects of the bark and leaf of the QG. However, studies involving this plant are rather imited. Aim of the study: To perform the phytochemical analysis of the QG hydroalcoholic extract (HAE) of leaves, and to investigate it effects on fibroblast and preosteoblasts. Methods: Phytochemical analysis was done by HPLC-DAD. Murine NIH/3T3 fibroblasts and MC3T3-E1 preosteoblasts cell lines (ATCC) were used for the experiments. Cell viability was assessed by the MTT colorimetric assay and the expression of MMP-14 and HIF-1α by immunofluorescence. Results and conclusion: The following compounds were identified by HPLC-DAD, such as quinic acid, ethyl galate, ellagic acid derivatives as O-methylellagic acid O-galloyl, O-methylellagic acid O-deoxyhexoside, galloyl derivatives, flavonol glycoside as kaempferol-O-deoxyhexoside, quercetin-O-deoxyhexoside, myricetin-O-deoxyhexoside and the pentacyclic triterpene arjunglucoside. Cell viability results demonstrated no cytotoxic effects in the studied concentrations. We found in QG HAE some compounds with therapeutic properties that can increase the expression of MMP-14 and HIF-1α, in fibroblasts and preosteoblasts. These data suggest that QG HAE has an action on these two molecules widely involved in physiological conditions, such as collagen remodeling, bone development and growth and pathological processes as HIF signaling in cancer metastasis.

RESUMO As propostas de ensino atuais envolvem estratégias de ensino que auxiliam e incentivam a construção do conhecimento, fazendo com que o aluno seja um participante ativo do processo de aprendizagem, e têm sido alvo de diversas pesquisas. Este artigo relata, aula a aula, uma sequência didática realizada com alunos em fase inicial de formação, aplicada à primeira turma do curso de Ciências Médicas da USP – Bauru, que propõe em seu projeto pedagógico o Aprendizado Baseado em Problemas (PBL) como principal estratégia de ensino. Nesta sequência didática, utilizamos atividades experimentais investigativas. A característica principal de uma sequência didática que inclui atividades investigativas é seu processo evolutivo gradual, com o objetivo de entrelaçar a perspectiva científica e as concepções dos estudantes por meio de atividades de ensino-aprendizagem bem planejadas, contextualizadas e empiricamente adaptadas ao raciocínio do aluno. O objetivo deste trabalho é compartilhar uma vivência assertiva da aplicação de uma sequência didática de caráter investigativo contextualizada, que envolveu conceitos que foram desde as propriedades químicas mais simples das biomoléculas/íons até a associação e discussão de um caso clínico hipotético envolvendo proteinúria. Essa fisiopatologia consiste na excreção de proteína na urina, principalmente albumina, e ocorre quando há algum dano nos rins. Sendo assim, a dosagem da fração proteica na urina (albuminúria) é utilizada principalmente para detecção precoce de doença renal crônica e pode ser também um instrumento para o diagnóstico de doenças cardiovasculares. Portanto, deve-se estar atento aos possíveis elementos interferentes e às variadas causas de erros inerentes a esse exame. Desta maneira, por meio de um recurso didático que envolve atividades experimentais investigativas contextualizadas, tendo como questão problematizadora um caso de proteinúria, pudemos nos reaproximar de conceitos específicos e valorizar os saberes procedimentais e atitudinais, o que é importante para os alunos nesta fase de formação. Nesta proposta, os alunos foram protagonistas do processo de aprendizagem, no qual puderam levantar e testar suas hipóteses, interligando conhecimentos e adquirindo habilidades e competências específicas, o que possibilitou uma reflexão sobre a importância dos fundamentos e aplicações das ciências básicas. O propósito das sequências didáticas investigativas e contextualizadas é formar sujeitos autônomos, que saibam tomar decisões e trabalhar emequipe, seguros e críticos, compreendendo como os saberes científicos evoluem e estão relacionados.

ABSTRACT Current teaching proposals involve teaching strategies that seek to assist and encourage the construction of knowledge by the students, turning them into active participants during the learning process and these have been the subject of several researches. This article reports a didactic sequence carried out with students of applied training for the first year Medical Sciences USP – Bauru, and proposes, as part of its pedagogical design, Problem Based Learning (PBL) as the main teaching strategy. In this didactic sequence we used experimental investigative activities. A didactic sequence that includes investigative activities can be characterized as a gradual evolutionary process, with the objective of intertwining the scientific perspective and the students’ conceptions, through well-planned teaching and learning activities contextualized and empirically adapted to the student’s reasoning. The objective of this work is to share an assertive experience of the application of a contextualized research didactic sequence that involved concepts ranging from the simplest chemical properties of biomolecules and ions to the association and discussion of a hypothetical clinical case involving proteinuria. Its pathophysiology consists of the excretion of protein in the urine, mainly albumin, and occurs when there is some damage to the kidneys. Therefore, the dosage of the protein fraction in urine (albuminuria) is mainly used for the early detection of chronic or acute kidney disease and can also be an instrument for the diagnosis of cardiovascular diseases. Therefore, one should be aware of the possible interferences and the various causes of errors inherent to this examination. In this way, through a didactic resource involving contextualized research experimental activities, having proteinuria as the key problem, we were able to re-approximate specific concepts and to value procedural and attitudinal knowledge, which is important for students in this training phase. In this proposal, the students were protagonists of the learning process, where they were able to raise and test their hypotheses, interconnecting knowledge, acquiring specific skills and competences, allowing reflection on the importance of fundamentals and applications of the basic sciences. The purpose of the investigative and contextualized didactic sequences is to form autonomous subjects, who know how to make decisions and work in teams and have a sound and critical understanding of how scientific knowledge evolves and is related.

Abstract Bone development and healing processes involve a complex cascade of biological events requiring well-orchestrated synergism with bone cells, growth factors, and other trophic signaling molecules and cellular structures. Beyond health processes, MMPs play several key roles in the installation of heart and blood vessel related diseases and cancer, ranging from accelerating metastatic cells to ectopic vascular mineralization by smooth muscle cells in complementary manner. The tissue inhibitors of MMPs (TIMPs) have an important role in controlling proteolysis. Paired with the post-transcriptional efficiency of specific miRNAs, they modulate MMP performance. If druggable, these molecules are suggested to be a platform for development of “smart” medications and further clinical trials. Thus, considering the pleiotropic effect of MMPs on mammals, the purpose of this review is to update the role of those multifaceted proteases in mineralized tissues in health, such as bone, and pathophysiological disorders, such as ectopic vascular calcification and cancer.

Abstract Objectives: The aim of this study was to assess the effect of Myracrodruon urundeuva All. and Qualea grandiflora Mart. leaves hydroalcoholic extracts on viability and metabolism of a microcosm biofilm and on enamel demineralization prevention. Methodology: Microcosm biofilm was produced on bovine enamel using inoculum from pooled human saliva mixed with McBain saliva, under 0.2% sucrose exposure, for 14 days. The biofilm was daily-treated with the extracts for 1 min. At the end, it was analyzed with respect to viability by fluorescence, CFU counting and extracellular polysaccharides (phenol-sulphuric acid colorimetric assay) and lactic acid (enzymatic assay) production. The demineralization was measured by TMR. The data were compared using ANOVA or Kruskal-Wallis (p<0.05). Results: M. urundeuva All. at 100, 10 and 0.1 μg/mL and Q. grandiflora Mart. at 100 and 0.1 μg/mL reduced biofilm viability similarly to positive control (chlorhexidine) and significantly more than the negative-vehicle control (35% ethanol). M. urundeuva at 1000, 100 and 0.1 μg/mL were able to reduce both lactobacilli and mutans streptococci CFU counting, while Q. grandiflora (1000 and 1.0 μg/mL) significantly reduced mutans streptococci CFU counting. On the other hand, the natural extracts were unable to significantly reduce extracellular polysaccharides and lactic acid productions neither the development of enamel carious lesions. Conclusions: The extracts showed antimicrobial properties on microcosm biofilm, however, they had no effect on biofilm metabolism and caries protection.

Resumo O objetivo deste estudo foi avaliar in vitro o efeito antimicrobiano de uma bandagem oral bioadesiva de quitosana com clorexidina para o tratamento de infecções dos tecidos orais. Cinco bandagens de diferentes composições foram testadas: Quitosana 5% (G1); Quitosana 5% ± clorexidina a 0,2% (G2), Quitosana 5% ± clorexidina a 0,6% (G3), Quitosana 5% ± clorexidina a 1,0% (G4) e Quitosana 5% ± clorexidina a 2,0% (G5). Foram testados também 5 tipos de géis nas seguintes composições: Gel de Quitosana 5% (G6), Gel de clorexidina a 0,2% (G7), Gel de clorexidina a 2,0% (G8), Gel de Quitosana 5% ± clorexidina a 0,2% (G9) e Gel de Quitosana 5% ± clorexidina a 2,0% (G10). A ação antimicrobiana das amostras foi testada contra Candida albicans e Streptococcus mutans por meio do antibiograma, medindo o halo de inibição. Os dados foram analisados pelo teste de Kruskal-Wallis e ANOVA a um critério seguido pelo teste de Tukey (p<0,05). A membrana com 2,0% de clorexidina (G5) e os discos contendo gel com 2,0% de clorexidina (G8) apresentaram os maiores halos de inibição para os dois microrganismos, com diferença estatisticamente significativa em relação aos demais grupos testados (p=0,008) apenas nos resultados de inibição de C. albicans. Todas as outras formulações de membranas e géis apresentaram halo de inibição, mas sem diferença estatisticamente significativa. A bandagem oral bioadesiva de quitosana com gel de 2% de clorexidina foi a mais efetiva em inibir os microrganismos testados.

Abstract This study aimed to evaluate in vitro the antimicrobial effect of a bioadhesive chitosan-based oral membrane with chlorhexidine for local treatment of infections in the oral tissues. Five oral membranes of different compositions were tested: 5% chitosan (G1); 5% chitosan ± 0.2% chlorhexidine (G2), 5% chitosan ± 0.6% chlorhexidine (G3), 5% chitosan ± 1.0% chlorhexidine (G4), and 5% chitosan ± 2.0% chlorhexidine (G5). Also, five gel types were tested according to the following compositions: 5% chitosan gel (G6), 0.2% chlorhexidine gel (G7), 2.0% chlorhexidine gel (G8), 5% chitosan gel ± 0.2% chlorhexidine gel (G9), and 5% chitosan gel ± 2.0% chlorhexidine gel (G10). The antimicrobial action of the samples was tested against Candida albicans and Streptococcus mutans through antibiogram by measuring the inhibition halos. Data were statistically analyzed by Kruskal-Wallis and one-way ANOVA followed by Tukey test (p<0.05). The 2.0% chlorhexidine membrane (G5) and the disks containing 2.0% chlorhexidine gel (G8) showed the greatest inhibition halos for both microorganisms, with statistically significant difference when compared to others tested groups (p=0.008) only for Candida albicans inhibitions results. All the other formulations of membranes and gels showed inhibition halos, but without statistically significant difference. The bioadhesive chitosan-based oral membrane with 2% chlorhexidine and 2% chlorhexidine gel were the most effective in inhibiting the tested microorganisms.

The main aim of this study was to develop scaffolds based on alginate, chitosan and hybrid fibers with and without glycerol. The scaffolds developed underwent assessments for tensile property, swelling ratio and weight loss, cellular viability, degradation and biomineralization, as well as DSC/TGA thermal analysis. Tenacity values showed that use of glycerol and the interaction between alginate and chitosan as a hybrid fiber were associated with increasing tenacity values. In the swelling and weight loss study, the scaffolds containing glycerol presented lower weight loss and higher water absorption values in all scaffolds, compared to scaffolds without glycerol, indicating that glycerol acted as a stabilizer. None of the alginate, chitosan and hybrid scaffolds, with or without glycerol, decreased cell viability. On the third day of the biomineralization assay, chitosan without glycerol indicated the presence of apatite crystals. The degradation study showed that glycerol may have acted as a stabilizer.

ABSTRACT A/J and 129P3/J mice strains have been widely studied over the last few years because they respond quite differently to fluoride (F) exposure. 129P3/J mice are remarkably resistant to the development of dental fluorosis, despite excreting less F in urine and having higher circulating F levels. These two strains also present different characteristics regardless of F exposure. Objective In this study, we investigated the differential pattern of protein expression in the liver of these mice to provide insights on why they have different responses to F. Material and Methods Weanling male A/J and 129P3/J mice (n=10 from each strain) were pared and housed in metabolic cages with ad libitum access to low-F food and deionized water for 42 days. Liver proteome profiles were examined using nLC-MS/MS. Protein function was classified by GO biological process (Cluego v2.0.7 + Clupedia v1.0.8) and protein-protein interaction network was constructed (PSICQUIC, Cytoscape). Results Most proteins with fold change were increased in A/J mice. The functional category with the highest percentage of altered genes was oxidation-reduction process (20%). Subnetwork analysis revealed that proteins with fold change interacted with Disks large homolog 4 and Calcium-activated potassium channel subunit alpha-1. A/J mice had an increase in proteins related to energy flux and oxidative stress. Conclusion This could be a possible explanation for the high susceptibility of these mice to the effects of F, since the exposure also induces oxidative stress.

ABSTRACT The aim of this study was to evaluate the effect of ethanolic "aroeira" (Myracrodruon urundeuva) extract on the viability of human gingival fibroblast. For this, fibroblasts (2x103 cells/well) were plated in a 96-well plate and incubated for 24 h; the medium (Eagle's medium modified by Dulbecco - DMEM) supplemented with 10% fetal bovine serum was replaced by DMEM with different ethanolic extract concentration (0, 0.1, 1, 10, 100, and 1000μg / mL). The fibroblast viability was analyzed after 48,72, and 96 h by the neutral red capture test and violet crystal. The "aroeira" extract, at high concentrations (100 and 1000 µg/mL) caused decrease in both cellular viability tests (p<0.05). However, dilutions between 0.1 and 10 µg/mL did not affect the viability of the cells. It was concluded that "aroeira" extract was able to change the gingival fibroblast viability, and this effect was concentration dependent.

Resumo O objetivo deste estudo foi verificar se o uso do óxido de zircônia como radiopacificador de um cimento experimental à base de silicato de cálcio (WPCZO) levou a citotoxicidade. Os fibroblastos foram tratados com diferentes concentrações (10 mg/mL, 1 mg/mL e 0,1 mg/mL) dos cimento diluídos em meio Eagle modificado por Dulbecco (DMEM) durante períodos de 12, 24, e 48 horas. Os grupos testados foram: cimento Portland (WPC), cimento Portland branco com óxido de zircônio (WPCZO) e MTA Angelus branco (MTA). No grupo controle as células não foram tratadas. A citotoxicidade foi avaliada por meio da mitocondrial-atividade (MTT) e ensaio de densidade celular (cristal violeta). Todos os cimentos apresentaram baixa citotoxicidade. Em geral, na concentração de 10 mg/mL, houve um aumento na viabilidade desses grupos tratados com WPC e WPCZO quando comparado com o grupo controle (p <0,05). Um perfil semelhante para os valores de absorvância foi observado entre os grupos: 10 mg/mL apresentaram um aumento da viabilidade em relação ao grupo controle. Por outro lado, as concentrações menores apresentaram uma viabilidade semelhante ou inferior em comparação com o grupo controle, em geral. Um novo material odontológico composto de cimento à base de silicato de cálcio com 20% de óxido de zircônio, como o radiopacificador, apresentou baixa citotoxicidade e pode ser explorado como um material promissor para retrobturações.

The aim of this study was to verify whether the use of zirconium oxide as a radiopacifier of an experimental calcium silicate-based cement (WPCZO) leads to cytotoxicity. Fibroblasts were treated with different concentrations (10 mg/mL, 1 mg/mL, and 0.1 mg/mL) of the cements diluted in Dulbecco's modified Eagle's medium (DMEM) for periods of 12, 24, and 48 h. Groups tested were white Portland cement (WPC), white Portland cement with zirconium oxide (WPCZO), and white mineral trioxide aggregate Angelus (MTA). Control group cells were not treated. The cytotoxicity was evaluated through mitochondrial-activity (MTT) and cell-density (crystal violet) assays. All cements showed low cytotoxicity. In general, at the concentration of 10 mg/mL there was an increase in viability of those groups treated with WPC and WPCZO when compared to the control group (p<0.05). A similar profile for the absorbance values was noted among the groups: 10 mg/mL presented an increase in viability compared to the control group. On the other hand, smaller concentrations presented a similar or lower viability compared to the control group, in general. A new dental material composed of calcium silicate-based cement with 20% zirconium oxide as the radiopacifier showed low cytotoxicity as a promising material to be exploited for root-end filling.

The aim of this study was to establish the more accurate protocol for fibroblast cell viability using MTT assay. NIH/3T3 fibroblasts were seeded at the following cell densities: 3.125x10³; 1.156x10(4); 3.125x10(4); 1.156x10(5) and 3.125x10(5) cells/cm². Following 24h of seeding, MTT was added to the wells. After 4h of the MTT addition, different solvents were added to solubilize the formazan crystals: 1) HCl/SDS group- 20% SDS and 0.01 M HCl; 2) EtOH/ HAc group-50% ethanol and 1% acetic acid; 3) DMSO group- 99.5% dimethyl sulfoxide; and 4) PropOH group- 99.5% isopropanol. The absorbance values were measured using a spectrophotometer at 570 nm. The data were analyzed by 2-way ANOVA (p<0.05) and showed that the absorbance average varied according to the number of cells and solvents: HCl/SDS (0 to 0.13), EtOH/HAc (0 to 0.22), DMSO (0.76 to 1.31) and PropOH (0.66 to 1.04). The DMSO and PropOH groups presented the most appropriate protocols for NIH/3T3 fibroblasts cell viability, especially at the density of 1.156x10(4) cells/cm².