8Birn B, Rolling S. Premature loss of primary teeth. Frequency and results studied longitudinally in 186 children. J Tandlaegebladet, 1970,74(12) : 1301-1311.
9Owen DG. The incidence and nature of space closure following the premature extraction of deciduous teeth: a literature study. Am J Orthod, 1971,59( 1 ) :37-49.
10Bijoor RR, Kohli K. Contemporary space maintenance for the pediatric patient. N Y State Dent J, 2005,71 (2):32-35.
