2021, Number 4
Canine retraction with segmented arches alternative in patients with severe dental crowding: clinical case
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Language: English/Spanish [Versión en español]
References: 21
Page: 353-362
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ABSTRACT
Dental crowding is one of the most common abnormalities as the available space in the osseous base is less than the total sum of the teeth' size. The crowding can cause occlusal, periodontal, and aesthetic problems. These issues increase the necessity for a suiting orthodontic treatment. This reported clinical case aims to provide an effective treatment option to reduce the dental crowding, get a bilateral class I canine, correct intercuspation, and improve the smile and labial profile. The clinical case of a 16-year-old female patient is reported. She attends the FE-BUAP orthodontics clinic for not like her teeth. She presented a skeletal class II, hyperdivergent growth, orthognathic facial profile, convex labial profile, bilateral class I molar, and bilateral class II canine, with severe crowding in both arcades; she did not report any habits or joint problems. The treatment plan included extractions of dental organs 14, 24, 34, 44, and 41; 0.022" slot MBT appliances were placed, and it began the usage of TMA loop sectional arch wires 0.016" × 0.022". In addition, the phases of alignment and leveling, space closure, torque control, settling, and removable retention were continued. As a result, the planned objectives were met in one year and six months. The frictionless mechanic in root resorption does not differ significantly from the frictional mechanic. In conclusion, using sectional arch wires as an alternative for the canine distalization in patients with severe anterior crowding offers additional benefits by controlling the force, tip, torque, and the release of progressive crowding of the anterior incisors without permanent damage to the teeth and supporting tissues.INTRODUCTION
Dental crowding has been a problem for the population since immemorial time. Well-aligned teeth and a pleasant smile influence the patient's tooth function and self-esteem, while irregular teeth have negative connotations.1
Dental crowding is common in malocclusions and mainly the anteroinferior incisors.2 In 1975, when measuring the adjacent anatomic contact points of the lower-anterior incisors, Robert M. Little classified it into perfect alignment of 0 mm; minimum, of 1-3 mm; moderate, of 4-6 mm; severe, of 7-9 mm, and very severe, more than 10 mm.3
The treatment of the crowding is fundamentally orthodontic, and there are different ways to correct it depending on the crowding degree and the arcades shape. Some possible solutions are to place an expansor in arcades to repair the collapse and perform slight tooth wear between teeth to provide space; tooth extraction is resorted to when the dental crowding is so severe that it is not solved with these methods, mainly of the premolars.
Canine retraction after the first premolar removal is a general procedure. It should be done as a distalization body movement.4,5 These dental organs (DO) are of utmost aesthetic importance and mainly functional since they are responsible for canine disocclusions.
The differential space, anchorage control, axial inclination control, rotation control, and arc width must be considered.6 The space closure by the absence of first premolars can be achieved in different ways, such as frictional, in which the canine slides through an arc (lace back, elastomeric chain, closed coils of NiTi) and frictionless, through a retraction arc with sliding mechanics (sectional archwire).
The sectional archwire technique facilitates the creation of an optimum force system that meets the imperative biomechanical requirements for planned tooth movements.
Controlled canine retraction requires a biomechanical system to generate a predetermined force and a relatively constant moment-to-force ratio to avoid distal inclinations and rotations, where teeth move due to activation of the vertical closing loop, which are frictionless springs for the retraction of canines, providing a low deflection and a controlled moment, without exerting force in the anterior sector. The ratio of this moment and force is constant throughout the elastic range of activation of the spring.
This moment-to-force ratio is constant the higher the moment-to-force ratio, the greater the control.7-10 Therefore, the optimal orthodontic force has been defined as that which produces a maximum desirable biological response with minimal tissue damage, resulting in rapid teeth movement with little or no clinical discomfort.11 The loops make the wire more elastic and flexible, generating a lower but continuous force, mainly controlling the tip, and that this does not cause permanent damage to the teeth and supporting tissues.12,13
Another factor to consider is the types of wire, the most used for this effect are stainless steel and TMA.14 Compared to steel, TMA produces a lower force magnitude as it is a less rigid material.15,16
CLINICAL CASE REPORT
A 16-year-old female patient from San Martín Texmelucan, Puebla, Mexico, attends a consultation because she doesn't like her teeth. She presents a skeletal class II, hyperdivergent, orthognathic facial profile, convex labial profile, bilateral class I molar, and bilateral class II canine; she has severe crowding in the maxilla and mandibular. She does not report having any habits. On extraoral clinical examination, her frontal photograph (Figure 1A) shows a symmetrical and mesofacial patient. In her smile photograph (Figure 1B), the upper dental midline matches the facial midline (FML), and the lower one deviated 2 mm to the right concerning the FML. The profile picture (Figure 1C) features an orthognathic facial profile and a convex labial profile.
Intraoral studies: in the intraoral models and photographs analysis, the patient was diagnosed as bilateral class I molar and bilateral class II canine (Figure 1D-H), with severe dental crowding in both arcades (Figure 1I and J).
Radiographic studies: the initial lateral skull X-ray (Figure 2A) shows the skeletal class II hyperdivergent growth pattern. In the initial orthopantomography (Figure 2B), it can be observed that the upper and lower third molars are in formation and the presence of dilacerated roots. Clinically and imaging, periodontal disease is observed in the lower incisors and a compromise in the DO 41. Sagittal and surface cuts are performed to observe the vestibular cortical (Figure 2C-E), so the patient is sent a consultation with the periodontist, who gives an unfavorable diagnosis. It is worth mentioning that before and during orthodontal treatment, the patient was periodontal controlled to maintain her health.
Treatment: it consisted of an orthodontic phase starting with extractions of DO 14, 24, 34, and 44 because of the anterior crowding degree and 41 due to its periodontal involvement. During the alignment and leveling phase, it began using TMA loop sectional archwires 0.016" × 0.022" (Figure 2F-J) for canine distalization and the crowding release. Subsequently, the brackets of the lateral superiors and premolars were cemented by placing an arc of 0.016" NiTi, 0.016" × 0.022" NiTi with an open spring of DO 12 to 22, beginning with couple forces in DO 21 and later in DO 11 (Figure 2K-M).
Five months later, and once the upper crowding was released, the lower brackets were cemented with arch sequence 0.013", 0.014", 0.016" × 0.022", 0.017" × 0.025" NiTi, 0.017" × 0.025" SS with preplaced posts, with 12 mm NiTi closing springs, using the VPRO 5 device with high-frequency vibrations (120 Hz). After closing, a TMA inverse curve 0.017" × 0.025" was placed to flatten the curve of Spee. After removing the appliance, the patient was sent for prophylaxis and assessment of her periodontal status, presenting interproximal mud in the lower-anterior sector.
Final studies: the extraoral clinical examination was made after one year and six months of treatment, observing a harmonious labial profile with a broad smile (Figure 3A-C) and better self-esteem in the patient. A bilateral class I molar and canine are appreciated in the intraoral photographs, with an adequate alignment and release of the severe anterior dental crowding (Figure 3E-I).
Results: the objectives proposed in the treatment planning were satisfactorily achieved, reaching a bilateral class I molar and canine employing a sectional archwire with controlled and continuous force, and the severe crowding of both arcades was corrected, and the correct occlusal stability was provided.
In the final orthopantomography, compared to the initial one, it is observed that the crown-root ratio of the canines retracted with the sectional arch was maintained and that the upper and lower third molars and the DO 14, 24, 34, 44 and 41 were extracted (Figure 4G and H).
The patient finished the orthodontic treatment with concordance in the smile and harmony in the facial and labial profiles. Additionally, in the final lateral X-ray of the skull and the last lateral volumetric tomography (Figures 3D and 4J) compared with the initial ones (Figures 2Aand 4I), a skeletal class II relationship is observed, with a hyperdivergent growth and mainly a correction in the inclination of the upper and lower incisors. This description can be checked in the cephalometric superposition: initial (black) and final (red). It is also observed that the ANB increased by 1o, the mandibular plane rotated 2o anteriorly; the maxilla obtained a position posterior to the initial one, a slight anchorage loss of the molars, adequate inclination of the incisors, and convenient position of the soft tissues (Figure 5).
For the retention phase, circumferential retainers were placed in both arcades. Regarding treatment stability, we can observe that the objectives obtained after five months of appliance removal are still maintained (Figure 4A-F).
DISCUSSION
Non-extraction or extraction of teeth has been very controversial, especially when the available room in the osseous bases is smaller than the one of the teeth; however, extracting teeth in arcades with severe crowding is necessary to correct malocclusion, achieve proper aesthetics and occlusal stability, and reduce treatment time.17,18
In some cases removing a lower incisor helps gain space in the anterior segment of the mandible, improving the discrepancy between tooth size and arch length. Clinical criteria such as the periodontal condition of the teeth, the applied mechanics, and the aesthetic and functional alterations must also be considered.19
Another controversial issue after performing premolar extractions is the way for canine distalization by frictional or frictionless biomechanics. This issue could not be solved without knowledge of the optimal magnitude of force needed. Smith and Storey suggested a force of 150 to 200 g optimal for canine distalization in humans, generating approximately 160 g in frictionless biomechanics, with 1 mm apart. A force of 160 g was considered optimal for canine retraction.
In the friction method, a NiTi closed coil causes a relatively constant force of 160 to 200 g. However, the springs are sensitive to temperature and are known to produce variations in force.20
For root resorption, anchorage loss, or velocity, there is no significant difference between frictional and non-frictional techniques; however, the latter shows better control in rotations by distalizing the canine.20,21
CONCLUSIONS
Some clinical situations lead to the extractions of some dental organs due to different factors, such as caries, periodontal lesions, and, the main one, the dental crowding degree, whose primary purpose is to achieve class I canine. For this, it is essential to consider that the resistance center of the canines is generally in the 2/5 parts of the root, measured from the marginal alveolar crest to the apex, to carry out a dental movement.
In canine retraction, it is favorable to use light forces since they produce fewer unwanted effects, so using sectional archwires for canine distalization with severe anterior crowding without applying an initial force on the anterosuperior incisors is very beneficial, as is the clinical case presented, since the force, the tip and releasing of the dental crowding were controlled without permanent damage to the teeth and supporting tissues.
On the other hand, using TMA works ideally for canine retraction and generates less force than stainless steel, despite having the same mechanical characteristics.
REFERENCES
Heravi F, Shafaee H, Forouzanfar A, Zarch SH, Merati M. The effect of canine disimpaction performed with temporary anchorage devices (TADs) before comprehensive orthodontic treatment to avoid root resorption of adjacent teeth. Dental Press J Orthod. 2016; 21 (2): 65-72. doi: 10.1590/2177-6709.21.2.065-072.oar.
AFFILIATIONS
1 Residente. Maestría en Estomatología con opción terminal en Ortodoncia, Facultad de Estomatología, Benemérita Universidad Autónoma de Puebla. México.
2 Profesor. Maestría en Estomatología con opción terminal en Ortodoncia, Facultad de Estomatología, Benemérita Universidad Autónoma de Puebla. México.
CORRESPONDENCE
Miguel Ángel Casillas Santana. E-mail: miguel.casillas@correo.buap.mxReceived: Marzo 2020. Accepted: Junio 2020.