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Objective: This study compared the fatigue behavior of endodontic instruments manufactured with conventional NiTi alloy electropolishing, RaCe (FKG Dentaire, LaChauxdeFonds, Switzerland), with instruments manufactured with NiTi CM Wire subjected to thermomechanical treatment, in the manufacturing process, HyFlex CM (Coltène Whaledent, Cuyahoga Falls, Ohio, USA), both with similar geometry and dimensions in order to determine the influence of the manufacturing process in the fatigue resistance. Methods: The methodoly consisted of twenty HyFlex CM and RaCe instruments with D0 0.25 mm, taper 0.06 mm / mm, 25 mm length, both with triangular cross section. The fracture resistance was evaluated by static fatigue test, using a stainless artificial canal with 5mm of radius (86°), recording the time and calculating the number of cycles until fracture occurs (NCF). For statistical analysis the Student t test was used The fractured instruments surface was analyzed by SEM. Results: The NCF was significantly higher for HyFlex CM instruments in comparison with RaCe files (P˂0.05) being 1336% more resistant to fatigue. The analysis of the fractured surface by SEM showed ductile-kind morphological characteristics for both instruments and the absence of plastic deformation. Conclusion: HyFlex CM instruments present higher values of NCF. Thus, it can be concluded that the thermal treatment to which these instruments with CM Wire alloy are submitted makes them more resistant to fracture than Race instruments manufactured with conventional NiTi alloy electropolishing.

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Objective: Hyflex CM instruments were developed for debridement of the root canal system. The control-memory alloy recovers its shape on sterilization, thereby allowing instrument reuse. This study investigated the effect of shape recovery by sterilization on the fatigue life and crack formation of Hyflex CM NiTi instruments. Material and Methods: the cyclic fatigue test was performed in two groups: In the first, it was continuously performed to establish the fatigue life (group 1, n = 10); in the second, it was performed with outages of 30s to evaluate cracks' nucleation and propagation (group 2, n = 10). The test was performed using a stainless steel canal that was 1.5mm in diameter and 3.5mm in depth, with an arc of 9.42mm and radius of curvature of 6mm. The instruments were driven at 300 rpm. The fatigue time was recorded using a digital stopwatch (Technos). An electronic microscope (Quanta 250) was used to observe the crack formation and growth during the cyclic fatigue. Results: the autoclaved instruments endured 1196.67+214.63 cycles, and the non-autoclaved endured 1000+199.42 cycles until the occurrence of fracture. The t-student test (α=5%) revealed a significant difference. The cyclic fatigue test with pauses demonstrated a significantly longer cyclic fatigue life than the continuous cyclic fatigue test (p<0.05). Conclusion: as revealed by SEM images, cracks grow with an increase in the number of cycles to fracture (NCF). It can be concluded that the shape of Hyflex CM instruments recovered by autoclaving withstood significantly more NCF than non-autoclaved instruments (p<0.05), demonstrating an improvement of approximately 16%.

ResumoO controle de uma infecção endodôntica demanda um esforço concentrado de fatores gerais do hospedeiro e de medidas de tratamento a partir da compreensão da etiologia e patogênese das doenças endodônticas. Atualmente há uma tendência de se considerar as lesões perirradiculares como doença induzida por biofilme. Este artigo de revisão tem como objetivo apresentar o biofilme dentro do conceito de comunidade como unidade de patogenicidade. O conhecimento e a compreensão do conceito de comunidade são importantes, pois o aprimoramento do endodontista no campo da microbiologia é fundamental para o entendimento do processo infeccioso que se propõe a eliminar. Isto se justifica para poder elaborar estratégias que permitam tratar de forma previsível o dente acometido. BiOFiLmS AND THE PATHOGENESiS OF THE APiCAL PERiODONTiTiS AbstractThe control of an endodontic infection requires a concerted effort of general host factors and treatment measures based upon the understanding of the etiology and pathogenesis of endodontic diseases. Currently there is a tendency to consider apical periodontitis as a disease induced by biofilm. This review aims to present the biofilm within the concept of community as the unit of pathogenicity. Knowledge and understanding of the concept of community is important, because improving the endodontist in the field of microbiology is essential for a better understanding of the infectious process to be eliminated. Key words:Endodontic infection, Biofilm, Apical periodontitis, Bacterial pathogenicity.Recibido para publicación: 30 de marzo de 2011. Aceptado para publicación: 2 de mayo de 2011. iNTRODUÇÃOA endodontia é a disciplina envolvida com o controle e a prevenção das infecções pulpares e perirradiculares.1 Há uma tendência atualmente de se considerar as lesões perirradiculares como doença induzida por biofilme.2 O controle de uma infecção endodôntica demanda um esforço concentrado de fatores gerais do hospedeiro e de medidas de tratamento a partir da compreensão da etiologia e patogênese das doenças endodônticas. Apesar de fatores físicos e químicos estarem envolvidos, bactérias são o principal agente etiológi-co das doenças pulpares e perirradiculares, e elas exercem um papel importante na indução e perpetuação de processos inflamatórios na polpa dental e periápice. 4 Por isso, em polpa viva, todos os cuidados precisam ser tomados para evitar e prevenir a contaminação, enquanto que na necrose pulpar, como consequência desta, o ambiente endodôntico torna-se um habitat seletivo para o estabelecimento de uma microbiota mista, dominada por bactérias anaeróbias. Nos estágios finais do processo infeccioso, a organização bacteriana se assemelha a biofilme. 5,6 Este artigo de revisão tem por objetivo apresentar o biofilme endodôntico dentro do conceito de comunidade como unidade de patogenicidade. Comunidade como patógenoTradicionalmente, o estudo da etiologia das principais doenças da cavidade oral tem sido baseado em reducionismo. Sob a ótica reducionista, muitos profissionais da saúde e microb...