title: Forces and moments delivered by novel, thinner PET-G aligners during labiopalatal bodily movement of a maxillary central incisor: An in vitro study.
abstract: OBJECTIVE
  To evaluate whether overloading of teeth can be avoided by utilizing aligners with reduced thicknesses of 0.4 mm or 0.3 mm.
  
  
  METHODS
  The experimental setup included an acrylic maxillary jaw model with tooth 11 separated and fixed via a 3-D force-moment transducer to a hexapod for experimental movement. Aligners tested were fabricated on duplicate stone models using commercially available polyethylene terephthalate glycol (PET-G) foils with thicknesses between 0.5 and 0.75 mm, and novel 0.4-mm- and 0.3-mm-thick foils. With the test aligner seated, 11 was bodily displaced in a labiopalatal direction in the range of ±0.25 mm while all six force-and-moment components exerted on this tooth were registered.
  
  
  RESULTS
  With the thinnest commercially available 0.5-mm aligner, median forces of -7.89 N and 8.37 N were measured for the maximum 0.25-mm movement of 11 in a labial and palatal direction, respectively. In comparison, force values were 35% and 71% lower for the novel aligners with a thickness of 0.4 mm and 0.3 mm, respectively.
  
  
  CONCLUSIONS
  Novel "leveling" aligners with reduced thickness may reduce overloading of individual teeth during aligner therapy. Due to form instability of 0.3-mm aligners, we suggest a novel sequence of 0.4-0.5-0.75 mm for aligner systems using several foil thicknesses for load graduation within single setup steps. This would combine low stiffness of the initial aligner and relatively constant load increases throughout the treatment.
authors.forename: Fayez
authors.initials: F
authors.lastname: Elkholy
authors.forename: Falko
authors.initials: F
authors.lastname: Schmidt
authors.forename: Rudolf
authors.initials: R
authors.lastname: Jäger
authors.forename: Bernd G
authors.initials: BG
authors.lastname: Lapatki
mesh_terms: D003481:Cuspid; D006801:Humans; D007180:Incisor; D008437:Maxilla; D016382:Orthodontic Appliance Design; D014087:Tooth Movement Techniques
keywords: Aligner sequence; Aligner thickness; Force; Orthodontic aligner; Overloading