ABSTRACT Fifty freshly extracted human permanent mandibular single rooted premolar teeth were included. The anatomical crowns of the selected teeth were removed using a diamond disc and pulp tissue was extirpated using barb broaches. Working length was determined by subtracting 0.5mm from the length achieved with the tip of the trial file just visible at the apical foramen of each root canal in all the specimens. Biomechanical preparation was done in all the specimens in crown-down technique using ProTaper Next rotary file system. The master apical file was set to; X4 (Size 40 and 6% Taper). Specimens were randomly divided into 5 groups with 10 specimens per group. Group 1: Master Gutta-percha point coated with Bio-C sealer, Group 2: Master Activ GP point coated with Bio-C sealer. Group 3: Master Activ GP point coated with Activ GP sealer used as obturation materials with single-cone technique. Group 4 (Negative control): Root canals were not obturated. Group 5 (Positive control): Master Gutta-percha point without any root canal sealer used as obturation material. All canal orifices were sealed with restorative Glass ionomer cement. Specimens were then double coated with nail varnish, except at the apical 3mm of roots and were placed in petri dishes containing Indian ink dye for 48 hours. After removal from the dye, nail varnish was completely removed and specimens were longitudinally sectioned with a diamond disk. For each specimen, the half containing the most visible part of the entire root canal was selected and extent of linear dye penetration was measured using Stereomicroscope following Escobar’s criteria. The readings were recorded, tabulated and statistically analysed using One Way ANOVA and Tukey’s-Post hoc tests. Gutta-percha coated with Bio-C sealer used as root canal obturation material showed the maximum apical sealing ability compared to Activ GP with Bio-C sealer and Activ GP with Activ GP sealer. Activ GP with Activ GP sealer exhibited least or poor apical sealing ability.