title: Short- and long-term evaluation of mandibular dental arch dimensional changes in patients treated with a lip bumper during mixed dentition followed by fixed appliances.
abstract: OBJECTIVE
  To evaluate short- and long-term mandibular dental arch changes in patients treated with a lip bumper during the mixed dentition followed by fixed appliances, compared with a matched control sample.
  
  
  METHODS
  Dental casts and lateral cephalograms obtained from 31 consecutively treated patients before (T0) and after (T1) lip bumper, after fixed appliances (T2), and a minimum of 3 years after fixed appliances (T3) were analyzed. The control group was matched as closely as possible. Arch width, arch perimeter, arch length, and incisor proclination were evaluated. Repeated measures ANOVA was used to analyze changes in measurements over all four time points between treatment and control groups.
  
  
  RESULTS
  Arch widths and crowding were always significantly different except at T2-T1. At T1-T0, only crowding decreased 3.2 mm while intercanine, interpremolar, and intermolar widths increased by 3.8, 3.3, and 3.9 mm, respectively. Changes at T3-T2 showed a significant decrease of 2.1 mm for crowding and an increase of 3.5, 2.9, 2.7, and 0.8 mm for intercanine, interpremolar, and intermolar widths and arch perimeter, respectively. Finally, at T3-T0, the reduction in crowding of 5.03 mm was significant and clinically important in the treated group. The differences between intercanine, interpremolar, and intermolar widths were also significant (2.1, 3.8, and 3.6 mm, respectively). All those differences favored the treated group.
  
  
  CONCLUSIONS
  Mandibular dental arch dimensions were significantly changed after lip bumper treatment. At follow-up, all arch widths were slightly decreased, generating an increase of 0.4 mm in crowding, considered clinically irrelevant. Overall changes remained stable after an average 6.3-year follow-up.
authors.affiliation: a  Postgraduate Orthodontic Student, Multidisciplinary Department of Medical-Surgical and Dental Specialties, Second University of Naples, Naples, Italy.
authors.forename: Gaetana
authors.initials: G
authors.lastname: Raucci
authors.affiliation: b  Assistant Clinical Professor, Department of Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Camila
authors.initials: C
authors.lastname: Pachêco-Pereira
authors.affiliation: c  PhD Student, Orthodontic Graduate Program, Department of Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Maryam
authors.initials: M
authors.lastname: Elyasi
authors.affiliation: d  PhD Student, Multidisciplinary Department of Medical-Surgical and Dental Specialties, Second University of Naples, Naples, Italy.
authors.forename: Fabrizia
authors.initials: F
authors.lastname: d'Apuzzo
authors.affiliation: e  Professor and Orthodontic Graduate Program Director, Department of Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Carlos
authors.initials: C
authors.lastname: Flores-Mir
authors.affiliation: f  Associate Professor, Head of Orthodontic Unit and Chair of Postgraduate Program, Multidisciplinary Department of Medical-Surgical and Dental Specialties, Second University of Naples, Naples, Italy.
authors.forename: Letizia
authors.initials: L
authors.lastname: Perillo
mesh_terms: D002508:Cephalometry; D003724:Dental Arch; D003818:Dentition, Mixed; D006801:Humans; D008046:Lip; D008310:Malocclusion; D009967:Orthodontic Appliances; D010155:Palatal Expansion Technique
keywords: Dental arch dimensions; Lip bumper; Long-term; Mixed dentition; Stability