title: E-space preservation.
abstract: OBJECTIVE
  To determine the relationship of E-space preservation with lingual holding arches to mandibular permanent second molar impaction.
  
  
  METHODS
  Two hundred consecutively treated patients undergoing nonextraction treatment for incisor crowding were entered into the study. Lower incisor crowding was assessed by the Little Irregularity Index. Treatment involved E-space preservation via a passive lingual arch placed prior to exfoliation of the second primary molar. Panoramic and cephalometric radiographs were analyzed for any significant relationship of mandibular permanent second molar impaction relative to molar angulation, spacing, growth pattern, and skeletal relationships.
  
  
  RESULTS
  Twenty-nine patients had at least one impacted second molar (14.5%). Of a possible 400 mandibular second molars, 34 were determined to be impacted (8.5%). Only the mandibular first molar-second molar angulation was found to be significant (P < .001). Pretreatment intermolar angulation of 24 degrees had a positive predictive value of 1.
  
  
  CONCLUSIONS
  Impaction of permanent second mandibular molars in patients undergoing nonextraction via E-space preservation with a passive lingual arch is 10 to 20 times more prevalent than that observed in the general population. Risk of impaction is best predicted by the pretreatment intermolar angulation between first and second permanent mandibular molars.
authors: Children's Hospital, Boston, MA 02115, USA. Andrew.Sonis@childrens.harvard.edu
authors: Andrew
authors: A
authors: Sonis
authors: Marc
authors: M
authors: Ackerman
references: J Am Dent Assoc. 1977 Jan;94(1):100-6
references: 264301
references: Am J Orthod Dentofacial Orthop. 2003 Mar;123(3):349-51
references: 12637908
references: Angle Orthod. 2009 May;79(3):422-7
references: 19413377
references: Am J Orthod. 1975 Nov;68(5):554-63
references: 1059332
references: Angle Orthod. 1978 Jan;48(1):39-48
references: 272130
references: ASDC J Dent Child. 2000 Jul-Aug;67(4):275-81, 231-2
references: 10997244
references: Oral Surg Oral Med Oral Pathol. 1985 Apr;59(4):420-5
references: 3858781
references: J Oral Pathol Med. 1991 Apr;20(4):159-66
references: 2061854
references: J Dent Res. 1950 Aug;29(4):440-7
references: 15436915
references: Am J Orthod Dentofacial Orthop. 2000 Oct;118(4):366-70
references: 11029729
references: Angle Orthod. 2005 Nov;75(6):904-11
references: 16448230
references: Angle Orthod. 2007 Sep;77(5):773-8
references: 17685771
references: J Clin Orthod. 1995 Feb;29(2):73-88
references: 8617843
references: Eur J Orthod. 2005 Dec;27(6):590-6
references: 16009666
references: Br J Orthod. 1988 Aug;15(3):199-203
references: 3262368
references: Angle Orthod. 2005 Sep;75(5):719-22
references: 16287223
references: Am J Orthod Dentofacial Orthop. 1997 Oct;112(4):449-56
references: 9345158
references: Br J Orthod. 1978 Apr;5(2):93-7
references: 284805
references: BMJ. 1994 Jul 9;309(6947):102
references: 8038641
references: J Clin Orthod. 2008 Nov;42(11):625-40
references: 19075377
references: Am J Orthod Dentofacial Orthop. 2000 Jan;117(1):81-5
references: 10629524
references: Angle Orthod. 1995;65(5):311-20
references: 8526289
references: Angle Orthod. 1975 Jul;45(3):153-8
references: 1056712
references: Am J Orthod Dentofacial Orthop. 2006 Jul;130(1):47-55
references: 16849071
references: J Can Dent Assoc. 2008 Jul-Aug;74(6):521
references: 18644237
references: Am J Orthod Dentofacial Orthop. 1987 Mar;91(3):242-51
references: 3469909
references: Am J Orthod Dentofacial Orthop. 2006 Dec;130(6):746-51
references: 17169737
references: Am J Orthod Dentofacial Orthop. 2003 Feb;123(2):138-45
references: 12594419