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What is Mushroom arch wire is used in and explain in detail?
Mushroom-shaped lingual arch forms
Natural variations in facial–lingual tooth dimensions are significant enough on the lingual  aspects to require routine first-order bends. Distal to the cuspids, mesial to the molars and  sometimes at the maxillary laterals.
Fujita introduced the concept of ‘mushroom-shaped  archwire’ in conjunction with the lingual appliance.