Wear and corrosion interactions on titanium in oral environment : literature review

The oral cavity is a complex environment where corrosive substances from dietary, human saliva, and oral biofilms may accumulate in retentive areas of dental implant systems and prostheses promoting corrosion at their surfaces. Additionally, during mastication, micromovements may occur between prosthetic joints causing a relative motion between contacting surfaces, leading to wear. Both processes (wear and corrosion) result in a bio-tribocorrosion system once that occurs in contact with biological tissues and fluids. This review paper is focused on the aspects related to the corrosion and wear behavior of titanium-based structures in the oral environment. Furthermore, the clinical relevance of the oral environment is focused on the harmful effect that acidic substances and biofilms, formed in human saliva, may have on titanium surfaces. In fact, a progressive degradation of titanium by wear and corrosion (tribocorrosion) mechanisms can take place affecting the performance of titanium-based implant and prostheses. Also, the formation of wear debris and metallic ions due to the tribocorrosion phenomena can become toxic for human tissues. This review gathers knowledge from areas like materials sciences, microbiology, and dentistry contributing to a better understanding of bio-tribocorrosion processes in the oral environment.(undefined

Bond strength of different endodontic sealers to dentin: push-out test

OBJECTIVE: The aim of this in vitro study was to evaluate the bond strength of different root canal sealers to dentin. MATERIAL AND METHODS: Forty extracted single-rooted human teeth were examined and the coronal and middle thirds of the canals were prepared with a 1.50 mm post drill (FibreKor Post System, Pentron). The teeth were allocated in two experimental groups, irrigated with 2.5% NaOCl+17% EDTA or saline solution (control group) and instrumented using Race rotary files (FKG) to a size #40 at the working length. Then, the groups were divided into four subgroups and filled with Epiphany sealer (Group 1), EndoREZ (Group 2), AH26 (Group 3) and Grossman's Sealer (Group 4). After 2 weeks of storage in 100% humidity at 37ºC, all teeth were sectioned transversally into 2-mm-thick discs. Push-out tests were performed at a cross-head speed of 1 mm/min using a universal testing machine. The maximum load at failure was recorded and expressed in MPa. RESULTS: Means (±SD) in root canals irrigated with 2.5% NaOCl and 17% EDTA were: G1 (21.6±6.0), G2 (15.2±3.7), G3 (14.6±4.5) and G4 (11.7±4.1).Two-way ANOVA and Tukey's test showed the highest bond strength for the Epiphany's group (p< 0.01) when compared to the other tested sealers. Saline solution decreased the values of bond-strength (p<0.05) for all sealers. CONCLUSION: Epiphany sealer presented higher bond strength values to dentin in both irrigating protocols, and the use of 2.5% NaOCl and 17% EDTA increased the bond strength values for all sealers

Somatic embryogenesis in white clover (Trifolium repens L.)

I White Clover (Trifolium repens L.) is an important perennial forage legume widely cultivated in Turkey and many other countries. It also helps in improving soil structure by fixing atmospheric nitrogen, and prevents soil erosion. The application of modern tissue culture techniques to this important plant should contribute to improvement in terms of production. Hypocotyls, epicotyl and cotyledon explants of a local ecotype of white clover were treated with various concentrations of Thidiazuron (TDZ) + Naphthalene acetic acid (NAA) and kinetin + NAA in MS medium to establish an efficient in vitro somatic embryogenesis system. High frequency of embryogenesis was observed on the MS medium containing 9.29 mM kinetin + 1.07 mM NAA (14.35embryos per explant) or 0.34 mM TDZ + 0.54 mM NAA (29.62 embryos per explant). It was concluded that embryogenesis was significantly influenced by the added plant growth regulators in the concentration-dependent manner;: Plantlets from the embryos were recovered on the MS medium and were transferred to a greenhouse, where they flowered and set fertile seeds

ADVENTITIOUS SHOOT REGENERATION FROM DIFFERENT EXPLANTS OF WILD LENTIL (LENS CULINARIS SUBSP. ORIENTALIS)

ABSTRAC

Adventitious shoot regeneration and micropropagation of Plantago lanceolata L.

Shoot regeneration from hypocotyl and cotyledon explants of Plantago lanceolata treated with various concentrations of Benzylaminopurine (BAP) and Indole 3 butyric acid in MS medium was significantly influenced by the amounts of BAP and IBA in concentration and explantdependent manner: Micropropagation was accomplished using various concentrations of BAP + IBA, kinetin + IBA and TDZ + IBA. Micropropagated shoots were rooted on the MS medium containing 2.69 mu M NAA. Plants were acclimatized and transferred to greenhouse, where they flowered and set seed