<prompt> For retraction of maxillary anteriors by 1 mm, space required is?1 mm2 mm0.5 mm1.5 mm  <response>: For every 1 mm of decrowding, same amount required for alignment. For every 1 mm of leveling the curve of spee, 0.5 mm space required in the arch. For every 1 mm of incisor retraction, 2 mm space required. 