Antero-posterior lingual sliding retraction system for orthodontic correction of hyperdivergent Class II protrusion
- Soon-Yong Kwon†1,
- Hyo-Won Ahn†1,
- Seong-Hun Kim1Email author,
- Young-Guk Park1,
- Kyu-Rhim Chung2,
- Cheol-Ho Paik3 and
- Gerald Nelson4
© Kwon et al.; licensee BioMed Central Ltd. 2014
Received: 20 January 2014
Accepted: 28 May 2014
Published: 5 June 2014
This report introduces a lingual bonded retraction system (Kinematics of Lingual Bar on Non-Paralleling Technique, KILBON) for efficient sliding mechanics combined with vertical control of the anterior and posterior teeth, which is suitable for Class II hyperdivergent patients.
Design and biomechanics of the KILBON System were described. Two adults with hyperdivergent class II malocclusion were treated with the KILBON system and temporary skeletal anchorage devices (TSADs) on the palate. The first patient was treated with conventional KILBON system on the upper arch and detailed with lingual appliances. The second patient showed the modified design of the KILBON when applied to a low palatal vault.
A large amount of intrusion and retraction of the anterior teeth and simultaneous intrusion of the posterior segment were achieved in short treatment time. Concomitant counterclockwise rotation of the mandible improved the esthetic profile. Periodontal support without dehiscence or bone loss was confirmed on anterior region in spite of large amount of retraction.
This report presented a lingual retraction system that provides simple and effective vertical and sagittal control of both anterior and posterior teeth. The biomechanics are dependable for correcting a dentoalveolar protrusion in a patient with Class II hyperdivergent skeletal pattern.
As esthetic concerns have increased in orthodontic fields, lingual appliances have become more sophisticated. Biomechanics for lingual orthodontics are not the same as for labial techniques [1, 2]. The most clinically challenging problem is torque control of the maxillary incisors during retraction [1, 3].
Several studies have introduced incisor retraction using lever arms combined with TSADs [4, 5]. However, when using TSADs combined with conventional lingual bonded appliances, unwanted side effects such as distal tipping of the posterior teeth or round tripping of anterior teeth are frequently occurred due to the friction .
Design and biomechanics
Skeletal Class II hyperdivergent malocclusion has always been a challenge in orthodontics because of the sagittal and vertical discrepancies. Ye R et al.  reported that the hyperdivergent skeletal Class II malocclusion in non-growing patients has a steeper cant of the occlusal plane, and an excessive height of the maxillary incisors. Successful treatment requires flattening of occlusal plane by intrusion of anterior teeth and avoiding any increase in vertical height of the molar . Conventional orthodontic treatment is likely to extrude the molars and rotate the mandible clockwise [11, 12]. On the other hand, the KILBON system achieved total intrusion of maxillary dentition using only two mini-implants.
The KILBON system produced a large amount of intrusion and retraction of the anterior teeth, in a relatively short duration. Previous CBCT study after retraction of anterior teeth by conventional orthodontic treatment revealed dehiscence of palatal bone and vertical alveolar bone loss due to insufficient alveolar remodeling . In our cases, alveolar bone remodeling, especially retraction of A point and the preservation of alveolar bone volume on pressure side, was achieved successfully. The teeth are grouped into three segments, so the orthodontic force is not concentrated on any individual tooth. Moreover, friction is minimal because the only site of friction during the sliding movement is between the posterior extension wire and the tube from the first molar. Labial flaring and round tripping of the incisors does not happen because the anterior teeth are not leveled and aligned before retraction. We do control the tube slot/guide wire using cephalogram and dental cast manually. Nowadays, Digital KILBON system was developed and we decide the exact tube slot position and angulation precisely using CAD/CAM method (Orapix, Seoul, Korea) .
The KILBON system can be further modified for effective vector control. If the patient has a low palatal vault, preliminary vertical force can be applied to the anterior teeth before retraction using an additional TSAD on the palatal rugae. Then the vertical height of the anterior teeth can be maintained by passive ligation between the TSAD and the lever arm during retraction. The clinician can also control the posterior intrusion with elastic modules between the molar splinting and the TSAD.
This report presented an esthetic antero-posterior lingual sliding retraction system that provides simple and effective vertical and sagittal control of both the anterior and posterior teeth using palatal TSADs (KILBON System). The biomechanics are excellent and dependable for correcting a dentoalveolar protrusion in a patient with a Class II hyperdivergent skeletal pattern.
Written informed consent was obtained from all patients for publication of this report and the accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal. In all cases, a medical indication for the respective treatment was present. The surgical procedure constitutes a routine treatment. The authors declare that no ethical approval was necessary.
We want to thank Kyung Won Seo, in masters program of Kyung Hee University in Orthodontic Department, for acquisition and analysis of data. This study was supported by the National Research Foundation of Korea funded by the Korea government (MEST) (no. 2012R1A5A2051388).
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