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Asymmetric Outer Bow Length and Cervical Headgear Force System: 3D Analysis Using Finite Element Method.

Geramy A, Hassanpour M, Emadian Razavi ES - J Dent (Tehran) (2015)

Bottom Line: A 2.5 N force in horizontal plane was applied and the loading manner of each side of the outer bow was calculated trigonometrically using data from a volunteer.The 15mm difference in outer bow length caused the greatest difference in lateral (=0.21 N) and distal (= 1.008 N) forces and also generated moments (5.044 N.mm).A difference range of 1mm to 15 mm of length in cervical headgear can be considered as a safe length of outer bow shortening in clinical use.

View Article: PubMed Central - PubMed

Affiliation: Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran ; Professor, Department of Orthodontics, Tehran University of Medical Sciences, Tehran, Iran.

ABSTRACT

Objectives: This study sought to assess distal and lateral forces and moments of asymmetric headgears by variable outer bow lengths.

Materials and methods: Four 3D finite element method (FEM) models of a cervical headgear attached to the maxillary first molars were designed in SolidWorks 2010 software and transferred to ANSYS Workbench ver. 11 software. Models contained the first molars, their periodontal ligament (PDL), cancellous and cortical bones, a mesiodistal slice of the maxillae and the headgear. Models were the same except for the outer bow length in headgears. The headgear was symmetric in model 1. In models 2 to 4, the headgears were asymmetric in length with differences of 5mm, 10mm and 15mm, respectively. A 2.5 N force in horizontal plane was applied and the loading manner of each side of the outer bow was calculated trigonometrically using data from a volunteer.

Results: The 15mm difference in outer bow length caused the greatest difference in lateral (=0.21 N) and distal (= 1.008 N) forces and also generated moments (5.044 N.mm).

Conclusion: As the difference in outer bow length became greater, asymmetric effects increased. Greater distal force in the longer arm side was associated with greater lateral force towards the shorter arm side and more net yawing moment.

Clinical relevance: A difference range of 1mm to 15 mm of length in cervical headgear can be considered as a safe length of outer bow shortening in clinical use.

No MeSH data available.


Related in: MedlinePlus

The 3D model of a slice of the maxillae containing the first molars, their PDLs, upper molar bands, spongy and cortical bones, and a cervical headgear with unequal outer bow lengths (the left outer bow is shortened)
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Figure 1: The 3D model of a slice of the maxillae containing the first molars, their PDLs, upper molar bands, spongy and cortical bones, and a cervical headgear with unequal outer bow lengths (the left outer bow is shortened)

Mentions: Five 3D finite element models of a mesiodistal slice of the maxillae were designed. The models contained upper first molars, their PDLs, cancellous bone, cortical bone, stainless steel molar bands fitted to molar crowns, and a cervical headgear. The difference in models was in the outer bow length in the cervical headgear, which was symmetric in the first model and asymmetric in models 2 to 4. The length difference (shortening of the left outer bow) was 5 mm (model 2), 10 mm (model 3), and 15 mm (model 4). Wire diameter was 1.6 mm in the outer bow and 0.9 mm in the inner bow (Figure 1). The last model was the same as the fourth one except for the molar teeth, which were replaced by two blocks. This replacement was done to simplify viewing the details of displacements occurred in headgear loading and to make an unforgettable image of the molar reaction (in the fourth model).


Asymmetric Outer Bow Length and Cervical Headgear Force System: 3D Analysis Using Finite Element Method.

Geramy A, Hassanpour M, Emadian Razavi ES - J Dent (Tehran) (2015)

The 3D model of a slice of the maxillae containing the first molars, their PDLs, upper molar bands, spongy and cortical bones, and a cervical headgear with unequal outer bow lengths (the left outer bow is shortened)
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4663312&req=5

Figure 1: The 3D model of a slice of the maxillae containing the first molars, their PDLs, upper molar bands, spongy and cortical bones, and a cervical headgear with unequal outer bow lengths (the left outer bow is shortened)
Mentions: Five 3D finite element models of a mesiodistal slice of the maxillae were designed. The models contained upper first molars, their PDLs, cancellous bone, cortical bone, stainless steel molar bands fitted to molar crowns, and a cervical headgear. The difference in models was in the outer bow length in the cervical headgear, which was symmetric in the first model and asymmetric in models 2 to 4. The length difference (shortening of the left outer bow) was 5 mm (model 2), 10 mm (model 3), and 15 mm (model 4). Wire diameter was 1.6 mm in the outer bow and 0.9 mm in the inner bow (Figure 1). The last model was the same as the fourth one except for the molar teeth, which were replaced by two blocks. This replacement was done to simplify viewing the details of displacements occurred in headgear loading and to make an unforgettable image of the molar reaction (in the fourth model).

Bottom Line: A 2.5 N force in horizontal plane was applied and the loading manner of each side of the outer bow was calculated trigonometrically using data from a volunteer.The 15mm difference in outer bow length caused the greatest difference in lateral (=0.21 N) and distal (= 1.008 N) forces and also generated moments (5.044 N.mm).A difference range of 1mm to 15 mm of length in cervical headgear can be considered as a safe length of outer bow shortening in clinical use.

View Article: PubMed Central - PubMed

Affiliation: Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran ; Professor, Department of Orthodontics, Tehran University of Medical Sciences, Tehran, Iran.

ABSTRACT

Objectives: This study sought to assess distal and lateral forces and moments of asymmetric headgears by variable outer bow lengths.

Materials and methods: Four 3D finite element method (FEM) models of a cervical headgear attached to the maxillary first molars were designed in SolidWorks 2010 software and transferred to ANSYS Workbench ver. 11 software. Models contained the first molars, their periodontal ligament (PDL), cancellous and cortical bones, a mesiodistal slice of the maxillae and the headgear. Models were the same except for the outer bow length in headgears. The headgear was symmetric in model 1. In models 2 to 4, the headgears were asymmetric in length with differences of 5mm, 10mm and 15mm, respectively. A 2.5 N force in horizontal plane was applied and the loading manner of each side of the outer bow was calculated trigonometrically using data from a volunteer.

Results: The 15mm difference in outer bow length caused the greatest difference in lateral (=0.21 N) and distal (= 1.008 N) forces and also generated moments (5.044 N.mm).

Conclusion: As the difference in outer bow length became greater, asymmetric effects increased. Greater distal force in the longer arm side was associated with greater lateral force towards the shorter arm side and more net yawing moment.

Clinical relevance: A difference range of 1mm to 15 mm of length in cervical headgear can be considered as a safe length of outer bow shortening in clinical use.

No MeSH data available.


Related in: MedlinePlus