The Effect of Dentinal Tubule Orientation on the Removal of Smear Layer By Root-Canal Irrigants - a Scanning Electron-Microscopic Study

WOS: A1990DF43200004PubMed ID: 212807

In vitro evaluation of the effects of the interaction between irrigating solutions, intracanal medication and Er:YAG laser in dentin permeability of the endodontic system Estudo in vitro dos efeitos da interação de substâncias irrigantes, medicação intracanal e laser Er:YAG na permeabilidade dentinária do sistema endodôntico

The purpose of this study was to evaluate in vitro the effects of different associations between irrigating solutions (EDTA-T and citric acid), intracanal medicament (NDP), and Er:YAG laser irradiation on dentin permeability. Fifty-one extracted single-rooted teeth were instrumented and divided into seven groups. Groups GI and GII had final irrigation with a demineralizing solution only (EDTA-T and citric acid, respectively). Groups GIII and GIV had final irrigation with EDTA-T and citric acid, respectively, plus an association of irrigating solution and Er:YAG laser. Groups GV and GVI had final irrigation with EDTA-T and citric acid, respectively, plus an association of intracanal medication and Er:YAG laser. Group GVII (control group) had final irrigation with distilled water. All root canals were filled with NDP associated with rhodamine B dye. After the experimental period, the samples were transversely cut into six 2.0 mm thick slices for subsequent reading using the ImageLab software. Analysis of the results allowed us to conclude that there were statistically significant differences (p < 0.05) between the groups as to the penetration of the dye-intracanal medication solution. Groups III and IV presented smaller values of dentinal permeability when compared to the other groups. The best results were obtained with the interaction between a demineralizing irrigating solution and the association of intracanal medicament and laser Er:YAG (groups V and VI). In these groups the observed penetration of the intracanal medicament plus dye solution in the apical third was, on average, 29% greater than in the other groups.<br>Este experimento teve como objetivo avaliar in vitro os efeitos da interação entre soluções irrigantes desmineralizadoras (EDTA-T e ácido cítrico), medicação intracanal (NDP) e laser Er:YAG na permeabilidade dentinária. Foram utilizados 51 dentes unirradiculares extraídos que, após o preparo químico-cirúrgico, foram divididos em sete grupos experimentais: grupos I e II - irrigação final com solução de EDTA-T e ácido cítrico, respectivamente; grupos III e IV - irrigação final com EDTA-T e ácido cítrico, respectivamente, mais a associação entre solução irrigante e laser Er:YAG; grupos V e VI - irrigação final com EDTA-T e ácido cítrico, respectivamente, mais a associação entre medicação intracanal e laser Er:YAG, e grupo VII (controle) - irrigação final com água destilada. Os canais radiculares foram preenchidos com o corante rodamina B solubilizado na medicação de uso intracanal NDP. Após o período experimental, as amostras foram cortadas transversalmente para posterior leitura com o software ImageLab. A análise dos resultados permitiu concluir que existiram diferenças estatisticamente significantes (p < 0,05) quanto à penetração da solução corante-medicação intracanal nos diferentes grupos. Os grupos III e IV apresentaram menores valores de permeabilidade dentinária quando comparados aos outros e, finalmente, os melhores resultados foram obtidos quando da interação entre a solução irrigante desmineralizadora e a associação medicação intracanal/laser Er:YAG (grupos V e VI). Nesses, constatou-se que a diferença de penetração da solução corante-medicação intracanal no terço apical foi, em média, 29% maior do que nos demais grupos

The smear layer:a phenomenon in root canal therapy.

WOS: A1995RM09200005PubMed ID: 8626198When the root canals are instrumented during endodontic therapy, a layer of material composed of dentine, remnants of pulp tissue and odontoblastic processes, and sometimes bacteria, is always formed on the canal walls. This layer has been called the smear layer. It has an amorphous, irregular and granular appearance under the scanning electron microscope. The advantages and disadvantages of the prescence of smear layer, and whether it should be removed or not from the instrumented root canals, are still controversial. It has been shown that this layer is not a complete barrier to bacteria and it delays but does not abolish the action of endodontic disinfectants. Endodontic smear layer also acts as a physical barrier interfering with adhesion and penetration of sealers into dentinal tubules, in turn, it may affect the sealing efficiency of root canal obturation. When it is not removed, the durability of the apical and coronal seal should be evaluated over a long period. If smear layer is to be removed, EDTA and NaOCl solutions have been shown to be effective, among various irrigation solutions and techniques, including ultrasonics, that have been tested. Once this layer is removed, it should be borne in mind that there is a risk of reinfecting dentinal tubules if the seal fails. Further studies are needed to establish the clinical importance of the absence or presence of smear layer