Early treatment of Class III malocclusion with a tandem traction bow appliance

INTRODUCTION

The worsening of Class III malocclusion increases with age.^[1] A good facial balance can be obtained by modifying the maxillofacial growth and development with an early orthodontic intervention. Class III malocclusion is associated with sagittal malrelationship of the maxilla and the mandible, characterized by either deficiency and/or a backward position of the maxilla, or by prognathism and/or forward position of the mandible.^[2] Many treatment approaches can be found regarding orthopedic and orthodontic treatment of Class III malocclusion. These include intra- and extra-oral appliances such as a face mask, functional regulator, removable mandibular retractors, splints, Class III elastics, chin cup, and mandibular cervical headgear. The early orthopedic treatment of Class III malocclusions, at the beginning of mixed dentition, prior to growth spurt, provides facial balance, modifies the maxillofacial growth and development, and prevents a future surgical treatment by increasing the stability.^[3] The early Class III treatment has advantages such as it allows the eruption of canines and premolars in normal relation, eliminates the traumatic occlusion of incisors, which might lead to gingival recession, provides maxillary growth and improves the self-esteem of the child.^[2]

According to McNamara and Turley, rapid maxillary expansion (RME) enhances the protraction effect of the face mask by disrupting the maxillary suture. It is widely accepted that the midface deficient Class III patients should be treated before 7–8 years of age.^[4-6] RME along with facemask therapy is the most common orthopedic treatment protocol for Class III malocclusion. Although maxillary expander-facemask appliances achieve excellent orthopedic effects, they demand special patient compliance and are not as esthetic or comfortable due to their physical appearance and discomfort from the anchorage pads. The major problem with extraoral anchorage is of patient compliance, due to the appearance of the extraoral appliance. Considering this problem, Chun et al. in 1999 introduced the tandem traction bow appliance (TTBA) for the treatment of growing Class III patients.^[7] Klempner did some modifications in the appliance later on.^[8]

The case report presents an intraoral modified tandem appliance used for maxillary protraction to achieve clinically desirable results without relying much on patient co-operation.

CASE REPORT

A 10-year-old boy reported to the Department of Orthodontics and Dentofacial Orthopedics with a chief complaint of forwardly placed lower front teeth. On extraoral examination, he had a concave facial profile with retrognathic maxilla, obtuse nasolabial angle, protrusive mandible, and competent lips. Intraorally, he had angle’s Class I malocclusion, end-on canine relation on both sides, anterior crossbite, a unilateral crossbite on left side, and a reverse overjet [Figure 1].

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Figure 1

Pretreatment photographs

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The panoramic radiograph showed no missing teeth or pathologies. Cephalometric analysis indicated a skeletal Class III due to posteriorly positioned maxilla along with a horizontal growth pattern with retroclined lower incisors and a normal upper incisor inclination. The patient was in Fishman’s Stage II of growth status as per hand-wrist radiograph [Figure 2].

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Figure 2

Pretreatment orthopantomogram lateral cephalogram hand wrist X-ray

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Treatment progress

The patient was treated with TTBA. The upper assembly comprised a Hyrex with first molars banded and soldered with 1 mm thick stainless steel wire extending up to premolars for RME [Figure 3]. The facebow was modified to the shape of a traction bow. The precise position of the elastic hooks on the upper assembly, and the tubes on the lower first permanent molar determines the direction of force. The protraction hooks in the maxilla were placed distal to the permanent canines, so that the elastic force passes through the center of resistance of the maxilla. The expansion screw was activated half turn twice a day for 1 week followed by an activation of half turn once a day every alternate day until the desired amount of expansion was achieved. On both sides, a force of 400–450 g was applied bilaterally for 14–16 h per day.

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Figure 3

Tandem traction bow appliance

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Treatment results

The patient was assessed at an interval of 3, 5, and 9 months. Progress records taken after 9 months showed a favorable growth between the maxilla and the mandible and anterior crossbite correction[Figures 4 and 5]. Postprotraction cephalometric tracings revealed a forward movement of maxilla and counterclockwise tipping of the palatal plane. The ANB angle changed from − 8° to 1°. FMA opened from 26° to 27°. Slight labial tipping of the maxillary incisors was also observed. The point A also shifted anteriorly by 6 mm approximately [Table 1].

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Figure 4

Postfunctional photographs

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Figure 5

Postfunctional lateral cephalogram and orthopantomogram

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Table 1 Comparison of pre- and post-functional cephalometric values

Measurements	Pretreatment	Postfunctional
SNA (°)	75	83
SNB (°)	83	82
ANB (°)	−8	1
Effective length of maxilla (mm)	79	81
Effective length of mandible (mm) N⊥to A point (mm)	105 −10	104 −4
FMA (°)	26	27
Upper incisor to NA	30	34
IMPA (°)	87	89
Lower anterior facial height (mm)	54	58

IMPA – Incisor mandibular plane angle

DISCUSSION

The success of orthodontic treatment with a developing Class III malocclusion depends on the growth of individual and timing of orthodontic or orthopedic intervention. For patients with moderate to severe Class III malocclusions, the decision of whether to treat early or to wait is difficult until the end of growth. The incidence of Class III malocclusion was found to be 5% in whites and as high as 48% in Japanese.^[9] The prevalence in North and South India was approximately 3.4% and 0.3%, respectively.^[10] Takada et al. reported that the forward maxillary displacement with protraction was more favorable before or during the acceleration of a child’s pubertal growth spurt.^[6] Baccetti et al. reported that Class III treatment with maxillary expansion and protraction was effective in the maxilla only when it was performed before the peak (cervical Stage 1 or cervical Stage 2).^[11] However, patient might have to undergo a surgical procedure later after early orthopedic and orthodontic treatment. A combination of maxillary protraction and RME has been used to treat young Class III patients with the maxillary deficiency.^[5] The goal of combining RME with maxillary protraction was to disarticulate the maxilla from the surrounding bones connected by circum-maxillary sutures and to facilitate the forward movement of the maxilla.^[12] Maxillary protraction along the occlusal plane is accompanied by counterclockwise rotation of the palatal plane and downward and backward rotation of the mandible plane, which results in tentative improvement of the skeletal relationship.^[6] In this case report, postprotraction radiographs showed a counterclockwise tipping of the palatal plane and slight increase in the mandibular plane angle and lower facial height, thus leading to an overall improvement of the profile. A significant increase in ANB after TTBA treatment was due to the forward movement of the maxilla and the backward movement of the mandible.

Although maxillary expander-facemask appliances achieve excellent orthopedic effects, they demand special patient compliance and are not esthetic or comfortable due to their physical appearance and discomfort, and skin irritation from the anchorage pads. Chun et al. in 1999 defined TTBA as comfortable and more esthetic device than conventional appliances because it is removable and worn intraorally. Its design allows the patient to open the mouth freely.^[7] Tortop et al. compared the effects of the modified TTBA (MTTBA) and the facemask in treating patients with Class III malocclusion and found both appliances were found to be effective in the treatment of Class III malocclusion. Their skeletal and dental effects showed differences due to their design.^[13] Ngan et al. concluded that hybrid hyrax bone-anchored RPE appliance minimized the side effect encounter by tooth-borne RPE appliance for maxillary expansion and protraction and may serve as an alternative treatment appliance for correcting Class III patients with a hyperdivergent growth pattern.^[14]

CONCLUSIONS

Satisfactory correction can be obtained with MTTBA appliance in patients with skeletal and dental Class III malocclusion with an average or horizontal growth pattern. As the appliance is more esthetic compared with a conventional facemasks, it could be a good alternative for noncompliant patients.