Objective: To analyze the internal anatomy of the maxillary first molar, to report the incidence of fourth root canals by comparing the efficacy of three diagnostic methods, Operating microscope, Cone beam computerized tomography and clearing technique.

Material methods: A sample size of 126 sound non carious, intact human maxillary 1st molar were taken for the study and were divided into three groups according of method of analysis of root canal system-(Group 1: operating microscope, Group 2: Cone beam computerized tomography, Group 3:clearing technique). Anatomical variation in form of additional canal in mesiobuccal root was analyzed for total incidence.

Results: For statistical analysis, Mean and Standard deviation were calculated for each group by using chi square test which revealed statistically significant difference between group 2 and 3 and non-significant difference between group 1 and group 2.

Keywords: Maxillary first molar, mesiobuccal second canal, operating microscope, Cone Beam Computerized Tomography.