title: Skeletal and dental response to rapid maxillary expansion with 2- versus 4-band appliances.
abstract: OBJECTIVE
  Banding a rapid palatal expansion (RPE) appliance to the 2 first molars has been proposed as an equivalent to the conventional 4-band RPE appliance. However, the dentoskeletal response to this treatment has not been evaluated.
  
  
  METHODS
  Twenty-eight subjects (aged 8-20 years) who required maxillary expansion were matched by age and randomly assigned to either a 2-band or a 4-band RPE group. Skeletal and dental responses were measured from standardized anteroposterior cephalometric and occlusal radiographs and dental casts before treatment (T1), at the end of expansion (T2), and at 1 year postexpansion (T3).
  
  
  RESULTS
  At T2, suture expansion was 2.5 times greater and arch perimeter was 6-fold larger in the 4-band than in the 2-band group. Both appliances displayed the typical "V" expansion of the suture and "reverse V" expansion of the dental arch. At T3, remineralization reduced the suture opening by 75%, but 95% to 99% of the dental reaction was maintained. The 2-band group demonstrated a significant inverse age-dependent correlation ( r = -0.795), with treatment failure beyond 12 years of age, whereas the 4-band group was age-independent.
  
  
  CONCLUSIONS
  The greater the skeletal resistance, the smaller the sutural response but the greater the dental response to RPE therapy. Four-band RPE is indicated when severe anterior crowding is accompanied by a tapered arch form, and 2-band RPE is recommended in the mixed dentition when mild crowding occurs with posterior constriction.
authors.affiliation: Department of Orthodontics, The Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Israel. davidom@post.tau.ac.il
authors.forename: Moshe
authors.initials: M
authors.lastname: Davidovitch
authors.forename: Stathis
authors.initials: S
authors.lastname: Efstathiou
authors.forename: Ofer
authors.initials: O
authors.lastname: Sarne
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Vardimon
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002508:Cephalometry / Q000706:statistics & numerical data; D002648:Child; D003724:Dental Arch / Q000033:anatomy & histology; D005260:Female; D006801:Humans; D008297:Male; D008437:Maxilla / Q000033:anatomy & histology; D008963:Molar / Q000503:physiopathology; D016382:Orthodontic Appliance Design; D009967:Orthodontic Appliances; D010155:Palatal Expansion Technique / Q000295:instrumentation*; D021362:Palate, Hard / Q000033:anatomy & histology; D018709:Statistics, Nonparametric; D016896:Treatment Outcome