Document Type : Original Article


1 Dept. of Orthodontics, Oral and Dental Diseases Research Center, Kerman University of Medical Sciences, Kerman, Iran.

2 Dept. of Orthodontics, Zahedan University of Medical Sciences, Zahedan, Iran.

3 Dentofacial Deformities Research Center, Research Institute of Dental Sciences, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

4 Dept. of Mechanical Engineering, Shahid Bahonar University of Kerman, Kerman, Iran.

5 Student of Mechanical Engineering, Shahid Bahonar University of Kerman, Kerman, Iran.

6 Student of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran.


Statement of the Problem: Various factors have been introduced to achieve normal occlusion. One of them is anterior teeth torque that has a significant effect on orthodontic treatment outcomes.
Purpose: The aim of this study was to investigate the effect of changes in anterior teeth torque on changes in the space occupied by six anterior teeth by using computer-aided three-dimensional interactive application (CATIA).
Materials and Method: In this experimental finite element study, acrylic teeth with pre-adjusted MBT braces were aligned and three-dimensional (3D) scans were made by 3Dscaner. In the CATIA software program, upper incisors’ torque was changed to -2, -4, -6, +2, +4 and+6 degrees and in the lower incisors to -1, - 3, -5, +3 and+5 degrees; the space was measured at 3 heights of maxillary incisor crowns and at incisal edges of mandibular incisors. Then maxillary incisors were then tapered and the measurements were made again. To evaluate the effect of tooth size, these procedures were carried out on teeth with +17% and -17% magnifications
Results: The results showed that by increasing anterior torque from 14.7 to 20.7 degrees in maxillary incisors, the space occupied by anterior teeth increased. Maximum changes were at cingulum height with 1.421mm. Reduction in anterior torque from 14.7 to 8.7 degrees resulted in a decrease in this space and maximum changes were observed in the cingulum height with 1.824mm. In the mandibular arch, a 10-degree change in anterior torque resulted in an -.752mm change in the space. Changes in the space occupied by anterior teeth was not significant in tapered and normal teeth in +6 and -6-degree torque (p Value= 0.78 and p Value=0.83).
Conclusion: By increasing or decreasing the incisors’ torque, the space occupied by anterior teeth increased and decreased, respectively. These changes were less in tapered teeth. Size variations had no significant effect on the results.


  • Dempster WT. Adams WJ DR. Duddles RA. Arrangement in the jaws of the roots of the teeth. J Am Dent Assoc. 1963; 67: 779-
  • Andrews LF. The six keys to normal occlusion. Am J Othod Dentofacial Orthop. 1972; 62: 296-
  • Dewel BF. Clinical observations on the axial inclination of teeth. Am J Orthod Dentofacial Orthop. 1949; 35: 98-
  • Nanda RS, Hussels W. Effect of maxillary incisor angulation and inclination on arch length. Am J Orthod Dentofacial Orthop. 1987; 91: 233-
  • O'Higgins EA, Kirschen RH, Lee RT. The influence of maxillary incisor inclination on arch length. Br J Orthod. 1999; 26: 97-
  • Hayashi K, Araki Y, Uechi J, Ohno H, Mizoguchi I. A novel method for the three-dimensional (3D) analysis of orthodontic tooth movement calculation of rotation about and translation along the finite helical axis. J Biomech. 2002; 35: 45-
  • Joch A, Pichelmayer M, Weiland F. Bracket slot and arch wire dimensions: manufacturing precision and third order clearance. J Orthod. 2010; 37: 24124-
  • Creekmore TD, Kunik RL. Straight wire: the next generation. Am J Orthod Dentofacial Orthop. 1993; 104: 8-
  • Mestriner MA, Enoki C, Mucha JN. Normal torque of the buccal surface of mandibular teeth and its relationship with bracket positioning: a study in normal occlusion. Braz Dent J. 2006; 17: 155-
  • Sarver DM. Principles of cosmetic dentistry in orthodontics: Part 1. Shape and proportionality of anterior teeth. Am J Orthod Dentofacial Orthop. 2004; 126: 749-
  • Peluso C KA. The axial inclination of central incisors and its effects on perception of facial profile. Am J Orthod Dentofacial Orthop.1998; 113: 87-93
  • Freeman JE, Maskeroni AJ, Lorton L. Frequency of Bolton tooth size discrepancies among orthodontic patients. Am J Orthod Dentofacial Orthop. 1996; 110: 242-
  • Johe RS, Steinhart T, Sado N, Greenberg B, Jing S. Intermaxillary tooth size discrepancies in different sexes, malocclusion groups, and ethnicities. Am J Orthod Dentofacial Orthop. 2010; 138: 599-
  • Nie Q, Lin J. Comparison of intermaxillary tooth size discrepancies among different malocclusion groups. Am J Orthod Dentofacial Orthop. 1999; 116: 539-
  • Othman S, Harradine N. Tooth size discrepancies in an orthodontic population. Angle Orthod. 2007; 77: 668-
  • Araujo E, Souki M. Bolton tooth size discrepancies among different malocclusion groups. Angle Orthod. 2003; 73: 307-
  • Bolton WA. Disharmony in tooth size and its relation to the analysis and treatment of malocclusion. Angle Orthod. 1958; 28: 112-130.
  • Basdra EK, Kiokpasoglou M, Stellzig A. The Class II Division 2 craniofacial type is associated with numerous congenital tooth anomalies. Eur J Orthod. 2000; 22: 529-
  • Uribe F, Nanda R. Treatment of Class II Division 2 malocclusion in adults: biomechanical considerations. J Clin Orthod. 2003; 37: 599-
  • Burstone CJ, Choy K. The Biomechanical Foundation of Clinical Orthodontics. 1st ed. Berlin: Quintessence Publishing Company, Incorporated; 2015. p.195.
  • Spena R. Upper and lower incisor torque and the Straight Wire Appliance. Eur J Clin Orthod. 2014; 2: 21–32.
  • Schaeffer A. Behavior of the axis of human incisor teeth during growth. Angle Orthod. 1949; 19: 254-
  • Reed A, Holdaway A. Soft tissue cephalometric analysis and its use in orthodontic treatment planing. Am J Orthod Dentofacial Orthop. 1983; 85: 1-28.