title: Changes in incisor third-order inclination resulting from vertical variation in lingual bracket placement.
abstract: OBJECTIVE
  To test the null hypothesis that third-order measurements are not correlated to lingual incisor features seen on radiographs.
  
  
  METHODS
  The lateral headfilms of 38 untreated, norm-occlusion subjects without incisor abrasions or restorations were used for third-order measurements of upper and lower central incisors and assessment of the inclination of four sites suitable for lingual bracket placement with reference to the occlusal plane perpendicular. Lingual sections were determined by the tangents at the incisal fossa (S1), at the transition plateau between incisal fossa and the cingulum (S2), by a constructed line reaching from the incisal tip to the cingulum (S3), and by a tangent at the cingulum convexity (S4). Third-order angles were also assessed on corresponding dental casts using an incisor inclination gauge. Regression analysis was performed using the third-order measurements of both methods as the dependent variables and the inclination of the lingual enamel sections (S1, S2, S3, S4) as the independent variables.
  
  
  RESULTS
  The null hypothesis was rejected. For the most common bracket application sites located on the lingual shovel (S1 and S2), third-order inclination changes of 0.4-0.7 degrees are expected for each degree of change in the inclination of the lingual surface. The impact of bracket placement errors on third-order angulation is similar between sections S1 and S2 and the cingulum convexity (S4). Section S3 proved to be least affected by interindividual variation.
  
  
  CONCLUSIONS
  The third-order measurements are correlated to lingual incisor features. Accordingly, third-order changes resulting from variation in lingual bracket placement can be individually predicted from radiographic assessments.
authors.affiliation: Departmento of Orthodontics and Dentofacial Orthopedics, Center of Dentistry, Georg-August-University, Göttingen, Germany. mknoesel@yahoo.de
authors.forename: Michael
authors.initials: M
authors.lastname: Knösel
authors.forename: Klaus
authors.initials: K
authors.lastname: Jung
authors.forename: Liliam
authors.initials: L
authors.lastname: Gripp-Rudolph
authors.forename: Thomas
authors.initials: T
authors.lastname: Attin
authors.forename: Rengin
authors.initials: R
authors.lastname: Attin
authors.forename: Reza
authors.initials: R
authors.lastname: Sadat-Khonsari
authors.forename: Dietmar
authors.initials: D
authors.lastname: Kubein-Meesenburg
authors.forename: Oskar
authors.initials: O
authors.lastname: Bauss
mesh_terms: D000465:Algorithms; D002508:Cephalometry; D004955:Esthetics, Dental; D005260:Female; D006801:Humans; D007180:Incisor / Q000503:physiopathology*; D008297:Male; D003765:Models, Dental; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D012015:Reference Standards; D012044:Regression Analysis; D055815:Young Adult