FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / A composiÃÃo quÃmica de oito marcas comerciais de cones de guta-percha foi determinada e seus resultados correlacionados com a capacidade de selamento apical. As marcas investigadas foram: (AnalyticÃ, DenstplyÃ, DiadentÃ, MetaÃ, ObturaÃ,OdusÃ, Tanarià e UltimateÃ). Os componentes dos cones de guta-percha (ZnO, BaSO4, guta-percha e ceras ou resinas) foram inicialmente obtidas pelo mÃtodo de Friedman at al 38. A composiÃÃo dos cones foi obtida por anÃlise gravimÃtrica, microanÃlise de energia dispersiva de raios-X, difraÃÃo de raios-X e anÃlise elementar. O polÃmero guta-percha foi caracterizado por analise tÃrmica (TGA e DSC), viscosidade intrÃnseca, cromatografia de permeaÃÃo em gel, infravermelho e ressonÃncia magnÃtica nuclear. O mÃtodo descrito por Friedman et al 38 foi apropriado para quantificar os componentes do cone como a guta-percha e ceras/resinas, mas superestimou a quantidade de sulfato de bÃrio e Ãxido de zinco. Um aumento na mÃdia de sulfato de bÃrio de 3,5% em relaÃÃo ao valor correto de sulfato de bÃrio e de 43,6% em relaÃÃo a massa do cone foi observado. Os cones de guta-percha contem em torno de 14,5 a 20,4% de guta-percha e de 62,8 a 84,3% de Ãxido de zinco. Sulfato de bÃrio nÃo foi determinado em trÃs dessas marcas (DentsplyÃ, Odusà e TanariÃ). As anÃlises de TGA mostraram que os resÃduos inorgÃnicos obtidos por essa tÃcnica à similar aos resÃduos inorgÃnicos observados na anÃlise gravimÃtrica. As fases cristalinas do polÃmero guta-percha foram identificadas por DSC. As marcas AnalyticÃ, DiadentÃ, MetaÃ, ObturaÃ, Odusà e Tanarià apresentaram picos endotÃrmicos caracterÃsticos da b guta-percha. Nas duas outras marcas o polÃmero esta presente na fase a. A determinaÃÃo da massa molar por anÃlise viscosimÃtrica mostrou valores similares para sete marcas variando de 1,0 x 105 a 1,6 x 105 g/mol, entretanto o polÃmero presente na marca Tanarià apresenta uma menor massa molar (5,6 x 104 g/mol). Resultado similar foi obtido por GPC. / The chemical composition of eight commercially available of gutta-percha cones brands was determined and the results correlated with the apical seal ability. These brands were: (AnalyticÃ, DentsplyÃ, DiadentÃ, MetaÃ, ObturaÃ, OdusÃ, Tanarià and UltimateÃ). The gutta-percha cones components (ZnO, BaSO4, gutta-percha, wax and resins) were initially obtained by Frideman et al 38 method. The composition of cones was obtained by gravimetric analysis, energy-dispersive X-ray microanalysis, X-ray diffraction and elemental analysis. The gutta-percha polymer was characterized by thermal analysis (TGA and DSC), intrinsic viscosity, gel permeation chromatography, infrared and nuclear magnetic resonance. The method described by Friedman et al 38 was appropriated to quantify gutta-percha and resin/wax components of cones, but led to overestimation of barium sulphate and zinc oxide. An average increase in the amount of barium sulfate of 3.5% in relation to the corrected BaSO4 mass value and of 43.6% in relation to cone mass was observed. Gutta-percha content range from 14.5 to 20.4% and zinc oxide from 62.8 to 84.3%. Barium sulphate was not detected in three of these brands (DentsplyÃ, Odusà and TanariÃ). TGA analysis shows that the inorganic residue obtained in this technique is similar of the inorganic residues observed in the gravimetric analysis. Crystal phases of gutta-percha polymer were identified by DSC. AnalyticÃ, DiadentÃ, MetaÃ, ObturaÃ, Odusà and Tanarià brands presents endothermic peak characteristic of b-guttapercha. In the other two brands the polymer is present in the a-phase. Molar mass determination by viscometric analysis shows similar values of seven brands in the average of 1.0 x 105 to 1.6 x 105 g/mol, however the polymer present in the Tanarià brand has lower molar mass (5.6 x 104 g/mol). Similar results were obtained by GPC. 11 The polymer present in the eight brands were analysed by IV and NMR, transpolyisoprene was identified as the main polymer component in the gutta-percha cones. The infiltration results of five brands (DentsplyÃ, TanariÃ, ObturaÃ, Odusà and Analyticà ) indicates that the small amount of gutta percha and also the presence of the a-phase in the Dentsplyà brand may be responsible for the high infiltration observed. A poor sealing ability was observed for brands with gutta-percha content lower than 16%.