Korean J Orthod.  2019 Nov;49(6):349-359. 10.4041/kjod.2019.49.6.349.

Three-dimensional analysis of tooth movement in Class II malocclusion treatment using arch wire with continuous tip-back bends and intermaxillary elastics

• Lee JY
• Choi SK
• Kwon TH
• Kang KH
• Kim SC

• KMID: 2464198
• DOI: http://doi.org/10.4041/kjod.2019.49.6.349

Abstract

OBJECTIVE
The aim of this study was to analyze three-dimensional (3D) changes in maxillary dentition in Class II malocclusion treatment using arch wire with continuous tip-back bends or compensating curve, together with intermaxillary elastics by superimposing 3D virtual models.
METHODS
The subjects were 20 patients (2 men and 18 women; mean age 20 years 7 months ± 3 years 9 months) with Class II malocclusion treated using 0.016 × 0.022-inch multiloop edgewise arch wire with continuous tip-back bends or titanium molybdenum alloy ideal arch wire with compensating curve, together with intermaxillary elastics. Linear and angular measurements were performed to investigate maxillary teeth displacement by superimposing pre- and post-treatment 3D virtual models using Rapidform 2006 and analyzing the results using paired t-tests.
RESULTS
There were posterior displacement of maxillary teeth (p < 0.01) with distal crown tipping of canine, second premolar and first molar (p < 0.05), expansion of maxillary arch (p < 0.05) with buccoversion of second premolar and first molar (p < 0.01), and distal-in rotation of first molar (p < 0.01). Reduced angular difference between anterior and posterior occlusal planes (p < 0.001), with extrusion of anterior teeth (p < 0.05) and intrusion of second premolar and first molar (p < 0.001) was observed.
CONCLUSIONS
Class II treatment using an arch wire with continuous tip-back bends or a compensating curve, together with intermaxillary elastics, could retract and expand maxillary dentition, and reduce occlusal curvature. These results will help clinicians in understanding the mechanism of this Class II treatment.

Keyword

Tooth movement; Digital models; Tip-back bend; Intermaxillary elastic

MeSH Terms

Alloys
Bicuspid
Crowns
Decompression Sickness*
Dental Occlusion
Dentition
Female
Humans
Male
Malocclusion*
Molar
Molybdenum
Titanium
Tooth Movement*
Tooth*
Alloys
Molybdenum
Titanium

Figure

• 

  Figure 1 A, 0.016 × 0.022-inch (in) multiloop edgewise arch wire with continuous tipback bends; B, 0.016 × 0.022-in titanium molybdenum alloy ideal arch wire with compensating curve. Intermaxillary elastics (anterior vertical elastics; 3/16 in, 6.5 ounce [oz] and occasionally Class II elastics; 5/16 in, 6.5 oz) were used with these arch wires after alignment and leveling.

• 

  Figure 2 Three-dimensional virtual models. A, Pre-treatment; B, Post-treatment; C, Superimposition using the third medial rugae and the midline raphe as the reference area.

• 

  Figure 3 Angles between the maxillary occlusal plane and the Frankfort horizontal (FH) plane at pre-treatment (T0) and post-treatment (T1) were measured on lateral cephalometric radiographs. The angular difference between the occlusal planes at T0 and T1 of the three-dimensional (3D) virtual models was compared with that of the lateral cephalometric radiographs. If the angular difference between the 3D virtual model and the lateral cephalometric radiograph was greater than 5°, superposition of the 3D virtual models was reattempted to correct the error.18

• 

  Figure 4 Reference points, lines, and planes. A, Frontal view; B, Sagittal view; C, Occlusal view; D, Reference planes. 1, Facial axis (FA) point; 2, occlusal reference point: the point on the most occlusal side of the FA of the clinical crown; 3, mesial occlusal point; 4, distal occlusal point; 5, FA line: line between the FA point and occlusal reference point; 6, occlusal line: the line between mesiodistal occlusal points.

• 

  Figure 5 Linear measurements (mm). A, Anteroposterior displacement: the distance from the facial axis (FA) point to the coronal plane. When the tooth was located posterior to the coronal plane, the distance was taken to be negative. For the difference between pre- and post-treatment (T0–T1), positive means posterior movement and negative means anterior movement. Vertical displacement is the distance from the FA point to the horizontal plane. For T0–T1, positive means intrusion and negative means extrusion; B, Lateral displacement: the distance from the FA point to the midsagittal plane. For T0–T1, positive means medial movement and negative means lateral movement.

• 

  Figure 6 Angular measurements (°). A, Inclination. For the difference between pre- and post-treatment (T0–T1), positive means labioversion or buccoversion and negative means palatoversion; B, Angulation. For T0–T1, positive means distal crown tipping and negative means mesial crown tipping; C, Rotation. When the occlusal line was inclined inward and backward to the midsagittal plane, the angle of rotation was taken to be negative. For T0–T1, positive means distal-in rotation and negative means mesial-in rotation; D, Angles of anterior occlusal plane (AOP) and posterior occlusal plane (POP). When the AOP or POP was inclined forward and upward with respect to the horizontal plane, the angle of AOP or POP was taken to be negative. For T0–T1, positive means counterclockwise rotation and negative means clockwise rotation.

• 

  Figure 7 Schematic drawing of treatment results using arch wire with continuous tip-back bends or a compensating curve, together with intermaxillary elastics. We observed posterior displacement of the maxillary teeth and expansion of the maxillary arch with distal-in rotation of the first molar (A). There were distal crown tipping of the canine, second premolar, and first molar (B); and buccoversion of the second premolar and first molar (C). Reduced occlusal curvature was observed as a result of extrusion of the incisor and canine and intrusion of the second premolar and first molar (B). T0, Pre-treatment; T1, post-treatment; AOP, anterior occlusal plane; POP, posterior occlusal plane.

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