title: Quantitative and qualitative assessment of anchorage loss during en-masse retraction with indirectly loaded miniscrews in patients with bimaxillary protrusion.
abstract: BACKGROUND
  This study provides vital insight in assessing anchorage loss when miniscrews are indirectly loaded.
  
  
  METHODS
  The study sample comprised 18 patients with bimaxillary protrusion (14 girls, 4 boys; mean age, 17.3 ± 4.6 years) selected from a database of 89 patients treated with miniscrews. All subjects who were selected required extraction of all first premolars and maximum anchorage. After initial leveling and aligning, miniscrews were placed between the first molar and the second premolar in all 4 quadrants and loaded by the indirect method at 3 weeks after placement with 200-g nickel-titanium alloy closed-coil springs for en-masse retraction. Mean treatment duration was 29.7 ± 6.8 months. Pretreatment and posttreatment lateral cephalograms were analyzed to measure the amount of anchorage loss, incisor retraction, and the incisors' angular change in reference to the pterygoid vertical reference line and were evaluated by the structural superimposition method.
  
  
  RESULTS
  The ratio of incisor retraction to molar protraction was 4.2 in the maxilla and 4.7 in the mandible. The first molars showed mean extrusion of 0.20 mm in the maxilla and 0.57 mm in the mandible; these were statistically insignificant. The mean angular change of the first molars was -2.43° in the maxilla and -0.03° in the mandible. The mean anchorage loss in reference to the pterygoid vertical was 1.3 mm in the maxilla and 1.1 mm in the mandible; these were statistically significant. Structural superimpositions showed mean change in molar position of 0.83 mm in the maxilla and 0.87 mm in the mandible, and 5.77 mm in the maxillary incisor and 5.43 mm in the mandibular incisor. These results were compared with the direct anchorage method reported in the literature.
  
  
  CONCLUSIONS
  Indirect miniscrew anchorage can be a viable alternative to direct anchorage.
authors.affiliation: Senior resident, Division of Orthodontics and Dentofacial Deformities, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Nitika
authors.initials: N
authors.lastname: Monga
authors.affiliation: Chief, Centre for Dental Education and Research; professor and head, Division of Orthodontics and Dentofacial Deformities, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India. Electronic address: opk15@hotmail.com.
authors.forename: Om Prakash
authors.initials: OP
authors.lastname: Kharbanda
authors.affiliation: Assistant professor, Division of Orthodontics and Dentofacial Deformities, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Vilas
authors.initials: V
authors.lastname: Samrit
mesh_terms: D000293:Adolescent; D000328:Adult; D001863:Bone Screws; D002508:Cephalometry; D005260:Female; D006801:Humans; D008297:Male; D008311:Malocclusion, Angle Class I / Q000628:therapy*; D009532:Nickel; D052280:Orthodontic Anchorage Procedures / Q000379:methods*; D019516:Orthodontic Space Closure / Q000379:methods; D009971:Orthodontics, Corrective / Q000379:methods; D012189:Retrospective Studies; D013997:Time Factors; D014025:Titanium; D014081:Tooth Extraction; D014087:Tooth Movement Techniques / Q000379:methods*; D016896:Treatment Outcome
chemical_list: D009532:Nickel; D014025:Titanium