Corrosion resistance assessment of nickel-titanium endodontic files with and without heat treatment.

OBJECTIVES: The aim of this study was to evaluate the corrosion resistance of heat-treated (Reciproc and WaveOne) and non-heat-treated (ProTaper and Mtwo) superelastic nickel-titanium endodontic files when immersed in a 5.25% sodium hypochlorite solution. MATERIALS AND METHODS: Anodic polarization curves were obtained with potential sweeps that began at the open circuit potential or corrosion potential (Ecorr). The pitting potential (Epit) was identified on the anodic polarization curve as the potential at which a sudden increase in current was observed. The micromorphology of the 28 tested files was analyzed before and after the electrochemical assay using scanning electron microscope (SEM). The data were analyzed using 1-way analysis of variance with the post hoc Bonferroni test (for Ecorr) and the Student t-test for independent samples (for Epit). RESULTS: The mean Ecorr values were 0.506 V for ProTaper, 0.348 V for Mtwo, 0.542 V for Reciproc, and 0.321 V for WaveOne files. Only WaveOne and Protaper files exhibited pitting corrosion, with Epit values of 0.879 V and 0.904 V, respectively. On the SEM images of the ProTaper and WaveOne files, cavities suggestive of pitting corrosion were detected. CONCLUSIONS: Signs of corrosion were observed in both heat-treated and non-heat-treated files. Of the evaluated files, WaveOne (a heat-treated file) and ProTaper (a non-heat-treated file) exhibited the lowest corrosion resistance.

Retention of Provisional Intraradicular Retainers Using Fiberglass Pins.

OBJECTIVES: The purpose of this study was to compare the retention properties between fiberglass pins with chemically activated acrylic resin and metallic intraradicular retainers often used for the purpose of temporary prosthetic retention. MATERIALS AND METHODS: Two mechanical tests, pushout and traction, were performed on specimens distributed in three groups (n = 10) for each test; two metal pins G1: Metalpin Ângelus and G2: Provisional Pivot Jon in addition to one fiberglass pin G3: Whitepost DC-E, FGM. One-way analysis of variance (ANOVA) followed by Tukey's post hoc test was used at the level of significance α = 0.05. RESULTS: The fiberglass pins (G3) showed higher values in the traction test than the metal pins (G1 and G2) with a statistically significant difference (P < 0.05); however, they performed similarly to the metal pin groups in the pushout test (P > 0.05). They also presented a lower occurrence of failure in the relining acrylic resin. CONCLUSION: The study pointed out the use of fiberglass pins as suitable alternatives for provisional intracanal metallic retainers.

Isolation and characterization of stem cells derived by human dental pulp from harvest based in rotary and manual techniques used in endodontic therapy / Isolamento e caracterização de células tronco da polpa dentária humana obtidas em instrumentação mecanizada e manual durante tratamento endodôntico

Objective: The aim of this study was to evaluate the impact on the isolation and characterization of stem cells from pulp tissues obtained through rotary instrumentation techniques compared to the manual technique. Material and Methods: Thirty permanent teeth were included, 15 of which were instrumented with rotational technique (Protaper SX) and other 15 with manual technique. Cells obtained were characterized by flow cytometry and proliferation was evaluated by the MTT assay. The plasticity was evaluated for adipogenic, osteogenic and odontogenic differentiations. Results: Cells isolated from the pulp of permanent teeth, by manual techniques, presented fibroblast morphology and were able to differentiate successfully. All lineages expressed CD29, CD73, CD90, CD105, CD146, CD166 and were negative for CD31, CD34 and CD45. MTT assay showing significantly increased proliferation of hDPSCs in 5 and 7 days of the culture. Conclusions: The present study demonstrated that manual instrumentation technique is one of the best candidates to harvest dental pulp tissue as the dental stem cell source due to ability effective expanded with less tissue invasion. The technique of rotational instrumentation proved to be very harmful to the tissues of the dental pulp, and we can't obtain cells using this technique. (AU)

Objetivo: O objetivo deste estudo foi avaliar o impacto no isolamento e caracterização de células-tronco de tecidos pulpares obtidos por meio de técnicas de instrumentação rotatória em comparação à técnica manual. Material e Métodos: Trinta dentes permanentes foram incluídos, 15 dos quais foram instrumentados com técnica mecanizada (Protaper SX) e outros 15 com técnica manual. As células obtidas foram caracterizadas por citometria de fluxo e a proliferação foi avaliada pelo ensaio MTT. A plasticidade foi avaliada quanto às diferenciações adipogênica, osteogênica e odontogênica. Resultados: células isoladas da polpa de dentes permanentes, por técnicas manuais, apresentaram morfologia de fibroblastos e foram capazes de se diferenciar com sucesso. Todas as linhagens expressaram CD29, CD73, CD90, CD105, CD146, CD166 e foram negativas para CD31, CD34 e CD45. O teste de MTT mostrou proliferação significativamente aumentada de hDPSCs em 5 e 7 dias da cultura. Conclusões: O presente estudo demonstrou que a técnica de instrumentação manual é um dos melhores candidatos para a colheita de tecido pulpar como fonte de células tronco dentárias devido à boa capacidade de proliferação celular com menor invasão tecidual. A técnica de instrumentação rotatória provou ser muito prejudicial para os tecidos da polpa dentária, e não possibilitou obter células. (AU)

Avaliação histomorfológica de maxilares humanos submetidos a enxerto ósseo autógeno e homógeno / Histomorphometric evaluation of autogenous and homogenous bone grafts on atrophic maxillary arches

O propósito deste trabalho foi avaliar, por meio de histomorfologia, quantitativa e qualitativamente os enxertos autógenos e homógenos realizados em maxilares atróficos cuja reabilitação oral visava à instalação de implantes dentários. Para o experimento, foram selecionados cinco pacientes que apresentavam maxilares atróficos para instalação de implantes. Desta forma, todos foram submetidos a procedimentos de enxertia óssea autógena e homógena, com exceção do paciente 2, que recebeu somente enxerto homógeno bilateral. Após o tempo de maturação dos tecidos enxertados (6 a 14 meses), foram colhidas amostras dos enxertos e estas foram preparadas pelas técnicas histológicas rotineiras para coloração com hematoxilina-eosina. Os resultados indicaram atividades osteogênicas em todas as amostras, com presença de células osteoprogenitoras em diferenciação e formação de camada osteoblástica, embora em estágios distintos de maturação tecidual. Entretanto, quando se comparou os potenciais osteogênicos de cada amostra e se traçou um paralelo entre o tempo de maturação óssea de cada enxerto e em cada paciente, observou-se que, independente do tipo de enxerto realizado e do tempo de maturação óssea, cada paciente apresentou potencial osteogênico semelhante para ambos os enxertos. Concluiu-se, ao término do trabalho, que a utilização de osso homógeno foi eficaz, induzindo mais rapidamente à remodelação óssea quando comparados com os enxertos autógenos. Somado a isso, o estágio de remodelação óssea esteve mais dependente da resposta orgânica individual de cada paciente do que propriamente do material utilizado na enxertia óssea.

The purpose of this study was to evaluate qualitatively and quantitatively autogenous and homogenous grafts performed in atrophic maxillary arches before dental implant placement. Five patients with atrophic jaws were selected and received autogenous and homogeneous bone grafts, except for patient 2, who received only bilateral homogenous grafts. After 6 to 14 months, samples were retrieved and stained with hematoxylin/eosin. The results indicated osteogenic activity in all samples, with differentiating osteoprogenitor cells and subsequent formation of osteoblastic layer, although in different stages of tissue maturation. However, when the osteogenic potential of each sample and time of maturation of bone graft were analyzed, it was observed that, regardless of the type of graft used and the time of bone maturation, all patients showed similar potential osteogenic activity in both graft types. We conclude that the use of homogenous bone was effective, leading to faster bone turnover when compared with autogenous grafts. Further, the stage of bone remodeling was more dependent on the response of each individual organism than on the material used in autogenous or homogenous bone graft.

Comparative study of the effect of ultrasound on the removal of intracanal posts.

This study sought to evaluate how ultrasound affected the removal of stainless steel and titanium posts that had been attached with two different resin cements. The crowns of 32 maxillary canines were removed, the roots were embedded in acrylic resin blocks, and the canals were treated endodontically. The specimens were randomly distributed into two groups (n = 16) according to the brand of cement and subdivided (n = 8) according to the type of post. The specimens were submitted to ultrasonic vibration applied perpendicularly to the long axis of the tooth for 60 seconds. Data were submitted to ANOVA and showed no significant statistical difference among the groups (p > 0.05). It may be concluded that the effects of ultrasonic vibration used to remove intraradicular posts were not significantly different when applied to stainless steel or titanium posts cemented with chemically or dual-activated resin cements.