Introduction
Orthodontic rectification of malocclusion is a tedious procedure and every patient wants to be treated in the shortest time frame with an esthetic treatment approach. Aligners are comfortable option for orthodontic treatment and have gained immense popularity over the last decade. In contemporary orthodontic practice, clear aligner therapy is frequently the preferred treatment, especially for patients with mild to moderate discrepancies who do not require extraction.1
For more severe cases, fixed appliances are needed since clear aligners therapy is less efficient.2 Premolar extraction is typically performed to rectify a tooth size arch length size disparity, to allow correction of the axial tilt of anterior teeth, or to correct the lower vertical height of the face. Spontaneous adjustment of dentition is induced in the space created by the extraction. Bourdet3 termed this adjustment “physiologic drift” and defined it as a natural adjustment of dentition following tooth loss. To alleviate the crowding of the anterior region, Alexander recommended postponing lower arch bonding so that the teeth could drift naturally.4 The maxillary first molars and canines migrate into the gap at a comparable rate, suggesting that molar mesial drift following premolar extraction may result in some molar anchorage loss. In instances where maximal molar anchorage control is required, this should be prevented as soon as possible following premolar extraction.5
This case report describes the effective orthodontic treatment of a young growing male patient with crowding in the upper and lower anterior region, by driftodontics in conjunction with a delayed fixed orthodontic therapy after four premolars extraction.
Case Presentation
Diagnosis
A 12-year-old male patient came to the orthodontic department, with the main concern being crowding in both the maxillary and mandibular anterior regions. Extra-oral clinical examination revealed mesocephalic head shape, mesoprosopic facial form with incompetent lips and acute nasolabial angle with orthognathic facial divergence, while intraoral examination depicted a Class I molar relationship on the right side and end-on molar relation on the left side with 5 mm of overjet and 2 mm of overbite, crowding in both upper and lower arches with crossbite in relation to the upper left first molar (26) (Figure 1 a, b). Lateral cephalometric analysis (Table 1) revealed a skeletal class I malocclusion (ANB, 2°) with hyper divergent growth pattern (SN-Go-Me, 42°), with proclined upper and lower incisors (U1 to N-A, 34°/7 mm, L1 to N-B, 26°/5mm).
Figure 2
Intra-oral photographs after 5 months of physiological drift following all first premolar extractions.
Table 1
Cephalometric analysis values of pre-treatment and post-treatment.
Treatment Objective
Our major goals, in this case, were to (a) level and align both upper and lower arches, (b) correct incisor inclinations, (c) achieve a bilateral Class I molar and canine relation, (d) achieve lip competency, (e) improve smile esthetics and (f) provide an aesthetic soft-tissue profile with optimum overjet and overbite.
Treatment progress
Since factors such as patient's age, profile, and arch discrepancy favor the physiological drift of dentition hence, extraction of all the first premolars was decided, and the patient was referred to the Department of Oral and Maxillofacial Surgery. The patient was recalled after two weeks of extractions. A transpalatal arch (TPA) was fabricated for anchorage and correction of crossbite. TPA was expanded by 2 mm and a buccal root torque on the upper right first molar (16) was given for anchorage, so that unilateral expansion of the upper left first molar (26) can be achieved. As we had planned to resolve the anterior crowding by driftodontics, the patient was recalled for evaluation every month. After 5 months, a substantial reduction in crowding was evident, which indicated the commencement of the fixed orthodontic treatment (Figure 2).
Pre-adjusted edgewise appliance (0.022”x0.028” slot MBT prescription, 3M Unitek) was bonded in both upper and lower arches. Leveling and alignment was initiated with 0.014” and completed using 0.016” and 0.016"×0.022" NiTi archwires. For the correction of anterior tooth inclination, 0.017"x0.025" and 0.019”x0.025” SS arch wires were used. Class 2 elastics were used on a 0.019"x0.025" SS wire on the left side for proper occlusion (Figure 3). Debonding was done after 10 months of overall treatment (5 months of Driftodontics followed by 5 months of active fixed orthodontic therapy), and fixed upper and lower lingual retainers were bonded.
Treatment Result
A good result was achieved only in 5 months of active fixed orthodontic therapy, the outcomes were a bilateral Class I molar and canine relationship with an ideal overjet and overbite. and an aesthetic improvement in facial profile (Figure 4 a, b). Post-treatment cephalometric analysis (Table 1) showed normal inclination of the upper and lower anterior teeth (U1 to N-A, 24°/3 mm, L1 to N-B, 23°/3mm), SN-Go-Me, 41°, IMPA, 88°, fair improvement in lip competency.
The superimposition of pre- and post-treatment cephalometric tracings is shown in Figure 5. The intra-oral images of the patient at 1-year follow-up (Figure 6) revealed a stable result.
Discussion
Force equilibrium is the prime factor that maintains the stability of dentition. To establish balance, the tongue's physiological force, along with biting force, drives the tooth forward until the posteriorly directed counter pressure from the lips stops it. Biting pressure from opposing teeth, pressures from neighboring teeth, or forces from the tongue, cheeks, and lips, along with some stabilizing forces from the periodontal ligament and alveolar bone, aid in the maintenance of this equilibrium. However, when a tooth is extracted, the aforementioned equilibrium is disrupted, and various modifications must occur in order to achieve a proper balance.
First-premolar extractions are usually required in patients with significant anterior crowding. In orthodontic therapy, physiologic drift is critical, which is used in several orthodontic procedures, such as the Alexander and PASS systems, to make treatment easier. Fei Teng et al.6 in their study found that tipping was the most common type of movement during physiological drift after extraction, supporting the theory that transseptal fibres play a significant role in physiological drift. Mandibular dentition has been the topic of previous clinical studies.7, 8 The researchers observed mesial movement of the first molar and distal movement of the canines, including tipping and translation, after the lower premolar extraction. According to Weber the mandibular canines moved distally by approximately 4.4 mm during the 2.5 years following the first premolar extraction.9 According to certain studies,10, 11 the mesial drift of the first molars took up just 1/3–1/4 of the first premolar extraction sites, whereas the distal drift of the canine was responsible for the majority of the gap closure. However, studies have revealed that the movement of these lower first molars is minimal, contributing for just a tiny portion of the premolar extraction gap closing during the drift.9, 12
Physiologic drift is not limited to the lower arch; in fact, only a few studies have looked at physiologic drift in the maxillary dentition, and even fewer have looked at it in orthodontics. Fei Teng et al.6 studied maxillary dentition and found that while the pattern of physiologic drift of maxillary teeth was comparable to that of mandibular teeth, the pace of drift was different. They concluded that drift length, age, and crowding before the extraction were important influences on physiologic drift, however, neither gender nor angle categorization had any effect on drift.6 The space created by the maxillary first premolar extraction reduced by an average of 0.792 mm/month following extraction, resulting in a 4-mm decrease over 6 months.6
The soft tissues that surround the teeth can alter their position, yet they stay stable in the stomatognathic system's equilibrium state of forces.13 In younger patients, extraction spaces tended to close rapidly, and crowding had a favorable effect on space closure. Jiang Ruoping et al.14 in their study found that physiological tooth movement for individual teeth started as early as 10 days after extraction, and the amount of teeth drift continuously increased over time, and the phenomenon being detected even 240 days after the extraction. They found that molar anchor loss was more in second premolar extraction cases as compared to first premolar extraction cases especially in the first 180 days after the extraction. Age-related tissue response,15 osteoclastic activity,16 and cell proliferation rate17 may explain the higher drift in the young population. Certain exogenous factors such as common prescription drugs, smoking and alcohol abuse influence tooth movement as well as physical drift.
Aligner therapy is expensive and many patients cannot afford it for orthodontic correction. The outcome of therapy depends on compliance. Whatever the aesthetic value of the aligner is, some patients especially the younger group do not like having a foreign object inside their oral cavity.
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