Ciente de que o principal objetivo do tratamento endodÃntico consiste na eliminaÃÃo de microorganismos e evitar a reinfecÃÃo dentro do canal radicular, e que as infecÃÃes sÃo polimicrobianas e difÃceis de serem eliminadas, o preparo biomecÃnico alÃm de ser primordial para a desinfecÃÃo, à incapaz de erradicar todos os microorganismos. EntÃo, utiliza-se da medicaÃÃo intracanal como coadjuvante ao tratamento, reduzindo a microbiota endodÃntica e favorecendo o reparo da lesÃo periapical. Contudo, esta dissertaÃÃo à constituÃda de dois artigos e propÃe-se, mediante uma revisÃo de literatura, apresentar e discutir as medicaÃÃes intracanais mais utilizadas atualmente na Endodontia â hidrÃxido de cÃlcio e clorexidina, e, por meio de uma pesquisa, avaliar o efeito antibacteriano do preparo biomecÃnico e de uma pasta à base de hidrÃxido de cÃlcio associada ou nÃo à clorexidina a 2 %, como medicaÃÃo intracanal, no tratamento de dentes necrosados apÃs trauma, bem como verificar a presenÃa dos microorganismos Fusobacterium nucleatum e bacilo pigmentado negro no interior do canal radicular desses dentes. De acordo com os critÃrios de inclusÃo, a amostra constituiu-se de 14 incisivos necrosados apÃs trauma. As coletas microbiolÃgicas foram adquiridas apÃs a abertura coronÃria (C1), preparo biomecÃnico (C2), medicaÃÃo intracanal (C3) e 72h depois da retirada da medicaÃÃo (C4). Mediante sorteio, oito pacientes utilizaram como medicaÃÃo intracanal o hidrÃxido de cÃlcio e seis pacientes a pasta de hidrÃxido de cÃlcio associada à clorexidina a 2 %. As coletas foram realizadas introduzindo sequencialmente trÃs cones de papel absorvente estÃril, de diÃmetro compatÃvel com o do canal radicular, no interior deste por aproximadamente um minuto e transferidas para um tubo contento um fluido reduzido para transporte e levadas ao laboratÃrio para processamento microbiolÃgico. Os resultados foram avaliados pelos testes Friedman, Conover-Inman e Kruskall-Wallis (p<0.05). Os microorganismos foram encontrados em 100 % dos canais radiculares, das amostras iniciais (C1), enquanto na C2 foram detectados em apenas 3/14 (21.4 %) das amostras, resultando numa reduÃÃo do nÃmero de unidades formadoras de colÃnias, estatisticamente significante (p<0.001) entre C1 e C2. O mesmo nÃo ocorreu quando comparados C2 com C3, C2 com C4 e C3 com C4, independentemente da medicaÃÃo. Foi constatada em C1 a predominÃncia de cocos Gram-positivos (8/14) e negativos (9/14), representando 57.1 % e 64.3 %, respectivamente. Na C2 sà foram detectados morfotipos bacterianos positivos, num total de 3/14 (21,4 %) de cocos Gram-positivos e 2/14 (14.3 %) de bacilos Gram-positivos. O microorganismo Fusobacterium nucleatum e o bacilo pigmentado negro foram observados em 8/14 (57.1 %) e 3/14 (21.4 %), respectivamente, das amostras iniciais, sendo apenas o primeiro encontrado em 1/6 (16.1 %) amostras, apÃs a utilizaÃÃo do hidrÃxido de cÃlcio. Concluiu-se que o preparo biomecÃnico de dentes necrosados apÃs trauma, utilizando NaOCl a 2.5 %, desempenha seu papel em reduzir significantemente a microbiota dos canais radiculares, porÃm o hidrÃxido de cÃlcio ou a sua associaÃÃo com clorexidina a 2 % possuem efeito antibacteriano limitado, nÃo sendo capazes de prevenir o recrescimento de bactÃrias apÃs seu uso como medicaÃÃo intracanal. / Aware that the main objective of endodontic treatment is the removal of microorganisms and the prevention of re-infection inside the root canal, and that the infections are polymicrobial and difficult to eliminate, the biomechanical preparation is essential for disinfection, though it is unable to eradicate all microorganisms. The intracanal medication is used as an adjunct to treatment, reducing the endodontic microbiota, and favoring the repair of periapical lesions. However, this dissertation consists of two papers and it is proposed, through a written review, to examine and discuss the intracanal medications most frequently used at present in endodontics - calcium hydroxide and chlorhexidine. Further, through research, to evaluate the antibacterial effect of biomechanical preparation and a calcium hydroxide based paste containing or not 2% chlorhexidine, as intracanal medication in the treatment of necrotic teeth after trauma, as well as to verify the presence of the microorganisms Fusobacterium nucleatum and black-pigmented bacilli inside the root canal of teeth. According to the inclusion criteria, the sample consisted of 14 incisors necrotic after trauma. The microbiological samples were acquired before (S1) and after biomechanical preparation (S2), after intracanal medication (S3) and 72 hours after removal of medication (S4). Selected at random, eight patients used calcium hydroxide as intracanal medication and six patients the calcium hydroxide based paste containing 2% chlorhexidine. The samples were collected sequentially, inserting three sterile absorbent paper cones with a diameter compatible with the root canal, and after a minute the paper points were removed and placed in a tube containing a reduced transport fluid, and sent to the laboratory for microbiological evaluation. The results were analyzed by the Friedman, Conover-Inman and Kruskal-Wallis tests (p <0.05). Microorganisms were found in 100 % of root canals in the initial samples (S1), while in S2 were detected in only 3 out of the 14 samples (21.4 %), resulting in a reduction in the number of colony forming units, a statistically significant result (p <0.001) between S1 and S2. No statistically significant reduction was observed when comparing S2 with S3, S2 with S4, and S3 with S4, regardless of the medication used. It was found that in S1, there was a predominance of Gram-positive cocci - 8 out of 14 (57.1 %) and Gram-negative cocci - 9 out of 14 (64.3 %). In S2 only Gram-positive bacterial morphotypes were detected, in 3 out of 14 samples (21.4 %) of Gram-positive cocci and 2 out of 14 (14.3%) of Gram-positive bacilli. The microorganisms Fusobacterium nucleatum found in 8 of the 14 samples (57.1%) and the black-pigmented bacilli found in 3 of the 14 (21.4%) of the initial samples, and were found in only one out of 6 (16.1%) samples taken after the use of calcium hydroxide. It was concluded that mechanical preparation of necrotic teeth after trauma, using 2.5% NaOCl, plays its role in significantly reducing the microbiota of root canals, but the calcium hydroxide, or the calcium hydroxide based paste containing 2% chlorhexidine, have a limited antibacterial effect, not being able to prevent the re-growth of bacteria after its use as an intracanal medication.