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What is Highest incidence of extra canal is seen in which tooth? and explain in detail?
More than 70 percent of maxillary first molar has shown the occurrence of second mesiobuccal canal, and this is found to be the most common reason for retreatment of maxillary molars. 
If seen through Dental operating microscope(DOM), approx. 90-95% cases show extra mesiobuccal canal (MB2).