title: Effectiveness of bonded and vacuum-formed retainers: A prospective randomized controlled clinical trial.
abstract: BACKGROUND
  The objective of this prospective trial was to compare the clinical effectiveness of bonded retainers with vacuum-formed retainers, in terms of maintaining the results of orthodontic treatment in the lower arch up to 18 months post debond.
  
  
  METHODS
  This was a hospital-based, prospective randomized controlled clinical trial in which a total of 82 subjects were randomly allocated using a computer-generated number sequence to 1 of 2 groups, receiving either a vacuum-formed retainer (Essix Ace plastic (120 mm; DENTSPLY Raintree Essix, Sarasota, Fla) or a bonded retainer (0.0175 coaxial archwire (Ortho-Care, UK, Shipley, United Kingdom) bonded in place with Transbond LR (3M United Kingdom, Brachnell, United Kingdom) for the mandibular arch. Each number was placed in an opaque, concealed envelope and chosen randomly by the study subject; this determined the allocation group. Eligibility criteria included patients nearing debond after treatment with 0.022 × 0.028-in slot size preadjusted edgewise fixed orthodontic appliances whose pretreatment records and study models were available to confirm pretreatment labial segment crowding or spacing and who had clinically acceptable alignment at the end of treatment. The main outcome was to investigate the clinical effectiveness of the 2 types of retainers in terms of changes in incisor irregularity at 6 months of retention. The following measurements were recorded at each time point (6, 12, and 18 months) with a digital caliper: Little's irregularity index, intercanine width, intermolar width, arch length, and extraction site opening. Blinding was applicable only at debond because of the permanence of 1 intervention.
  
  
  RESULTS
  The 2 groups were well matched with respect to age, sex, clinical characteristics, and treatment plans. There was a statistically significant difference between the groups for changes in Little's irregularity index at 6 months, with the vacuum-formed retainer group showing greater changes than the bonded retainer group (P = 0.008). There was no statistically significant difference between the groups for changes in Little's irregularity index at 12 and 18 months.There were also no statistically significant changes at any time for intercanine width, intermolar width, arch length, or extraction site opening.
  
  
  CONCLUSIONS
  Some relapse is likely after fixed appliance therapy irrespective of retainer choice, and this is minimal in most patients at 6 months after debond. Bonded retainers have a better ability to hold the mandibular incisor alignment in the first 6 months after treatment than do vacuum-formed retainers.
  
  
  BACKGROUND
  Not applicable.
  
  
  METHODS
  The protocol was not published before trial commencement.
  
  
  BACKGROUND
  There is no funding or conflict of interest to be declared.
authors: Specialty registrar in orthodontics, Centre for Oral Growth and Development, Barts and the London School of Medicine and Dentistry, London, United Kingdom; postgraduate student in orthodontics, Institute of Dentistry, Queen Mary University, London, United Kingdom.
authors: Niamh
authors: N
authors: O'Rourke
authors: Specialty registrar in orthodontics, Centre for Oral Growth and Development, Barts and the London School of Medicine and Dentistry, London, United Kingdom; postgraduate student in orthodontics, Institute of Dentistry, Queen Mary University, London, United Kingdom.
authors: Hussein
authors: H
authors: Albeedh
authors: Senior clinical lecturer and consultant orthodontist, Centre for Oral Growth and Development, Barts and the London School of Medicine and Dentistry, London, United Kingdom.
authors: Pratik
authors: P
authors: Sharma
authors: Reader, honorary consultant orthodontist, and academic lead in orthodontics, Institute of Dentistry, Queen Mary University, London, United Kingdom. Electronic address: a.s.johal@qmul.ac.uk.
authors: Ama
authors: A
authors: Johal
mesh_terms: D001840:Dental Bonding; D003767:Dental Occlusion, Balanced; D005500:Follow-Up Studies; D006801:Humans; D016382:Orthodontic Appliance Design; D018704:Orthodontic Retainers; D011446:Prospective Studies; D014618:Vacuum