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

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

Influence of calcium hydroxide points on the quality of intracanal dressing filling Influência do uso de cones de hidróxido de cálcio na qualidade do preenchimento de canais radiculares com medicação intracanal

PURPOSE: The aim of this study was to evaluate, in vitro, the quality of calcium hydroxide [Ca(OH)2] paste filling (Ultracal, Ultradent) associated or not with Ca(OH)2-containing gutta-percha points (Calcium Hydroxide Plus PointsTM, Roeko) in curved root canals. MATERIAL AND METHODS: One hundred and twenty roots of extracted human teeth, randomly divided into three curvature ranges (mild - 0 to 14º; moderate - 15º to 29º; severe - >30º) were used. After chemomechanical preparation, the roots were assigned to 4 groups (n=30), according to the technique of intracanal dressing placement: group 1 - Ca(OH)2 paste was applied with a lentulo spiral; group 2 - Ca(OH)2 paste was applied with a lentulo spiral and a Ca(OH)2 point was inserted into the canal; group 3 - Ca(OH)2 paste was applied with a NavitipTM tip (supplied with Ultracal system); group 4 - Ca(OH)2 paste was applied with a NavitipTM tip and a Ca(OH)2 point was inserted into the canal. The roots were cleared and the quality of apical third filling was assessed by a calibrated experienced examiner. The specimens were examined under stereomicroscopy and scored 1 to 4 (i.e., from inadequate to complete root canal filling). The results were analyzed statistically by ANOVA and Duncan's post hoc test at 5% significance level. RESULTS: There were no statistically significant differences (p>0.05) among the curvature degrees in groups 1, 3 and 4. Severely curved roots in group 2 presented bordering significance (p=0.05). The groups that associated the use of Ca(OH)2 paste and points (2 and 4) showed better apical filling than the other groups, but this difference was statistically significant (p<0.001) only for roots with severe curvature. CONCLUSION: According to the results of this study, the curvature degree did not influence the quality of filling. The techniques that used Ca(OH)2-containing gutta-percha points yielded better filling of the apical third in roots with severe curvature.<br>OBJETIVO: O objetivo deste estudo foi avaliar, in vitro, a qualidade do preenchimento de canais radiculares curvos com a pasta de hidróxido de cálcio [Ca(OH)2] Ultracal (Ultradent), associada ou não a cones de guta-percha contendo hidróxido de cálcio (Calcium Hydroxide Plus PointsTM, Roeko). MATERIAL E MÉTODOS: Cento e vinte raízes de dentes humanos extraídos, aleatoriamente distribuídas em 3 faixas de curvatura (leve - 0 a 14º; moderada - 15º a 29º; severa > 30º) foram utilizadas. Após o preparo químico-mecânico, as raízes foram divididas em 4 grupos (n=30) de acordo com o método de aplicação da medicação intracanal: grupo 1 - aplicação da pasta de Ca(OH)2 com espiral de lentulo; grupo 2 - aplicação da pasta de Ca(OH)2 com espiral de lentulo, seguida da introdução de um cone de Ca(OH)2; grupo 3 - aplicação da pasta de Ca(OH)2 com a ponta NavitipTM (fornecida com o Sistema Ultracal); grupo 4 - aplicação da pasta de Ca(OH)2 com a ponta NavitipTM seguida da introdução de um cone de Ca(OH)2. As raízes foram diafanizadas e avaliadas quanto à qualidade do preenchimento do terço apical dos canais por um examinador calibrado. Os espécimes foram examinados em lupa estereoscópica e classificadas por escores de 1 a 4 (desde preenchimento inadequado até preenchimento total dos canais). Os resultados foram comparados através da análise de variância e teste post hoc de Duncan com nível de significância de 5%. RESULTADOS: Não se observaram diferenças estatisticamente significantes (p>0.05) entre os graus de curvatura dos grupos 1, 3 e 4 quanto ao preenchimento dos canais. A curvatura severa no grupo 2 apresentou significância limítrofe (p=0,05). Os grupos que associaram pasta e cones de Ca(OH)2 (2 e 4) apresentaram melhor preenchimento apical em relação aos demais grupos, porém essa diferença foi estatisticamente significante (p<0,001) somente para as raízes com curvatura severa. CONCLUSÃO: De acordo com os resultados deste estudo, o grau de curvatura não influenciou na qualidade do preenchimento. As técnicas que utilizaram cones de guta percha contendo Ca(OH)2 promoveram um melhor preenchimento do terço apical em canais radiculares com curvatura severa