reconfirm the actual incidence of a ML canal in both 1st and 2nd maxillary molars, effect of use of bur on incidence of perforations. Positional relationship between ML,MB canals and to the M and D of the root. Develop classification system of canal configuration .
•N= (51 1st , 32 2nd) maxillary molars.
•Teeth were stored in 10% formalin.
•Group 1: standard access and endo explorer only.
Group 2: they used same teeth in group 1. but deepened the ML groove using round bur (#8-2) until ML canal was found or groove reduced 2-3 mm. •Teeth mounted to a resin block, reference points to be reoriented in same position (Fig1). Crowns sectioned incrementally perpendicular to the long axis of MB root(1mm).
•Total of 10mm reduction, MB root was assessed for ML canal: Group3 (present) and Group4 (absent). •Thickness of dentin M, D to each canal, diameter and distance between MB and ML canals and movement of ML canal.
Most highlighted Results:
•95% of MB root in 1st and 2nd maxillary molars had 2 canals.
•The use of burs significantly affected locating ML canal.
•ML canal found within 1-3 mm distal to MB canal, but moves mesiolingually relative to the MB canal.
•Dentin in M and D was thicker in MB than ML canal.
Clinically, it appears that the greatest danger lies in a trifurcation perforation. However, careful use of a bur increased the incidence in locating the ML canal, in vitro, from 54.2 to 85.5% and should not lead to an increase in perforations.