Introduction
The purpose of this study was to test the null hypothesis that duration of orthodontic treatment can be significantly reduced by accelerating canine retraction using dentoalveolar distraction (DAD).
Methods
Thirty-six maxillary canines of 19 patients comprised the DAD group, and 28 canines of 14 patients were included in the distalization group (DG). The initial mean ages were 15.8 ± 1.96 years for the DAD group and 16.02 ± 2.8 years for the DG. A custom-made, rigid, tooth-borne intraoral distraction device was used for the DAD group, and intraoral elastics were applied for canine distalization in the DG. Six skeletal and 11 dental variables were measured for the cephalometric evaluation.
Results
Canine retraction was 7.9 ± 1.49 mm in 11.8 ± 1.3 days and canine distal tipping was 11.48° ± 4.37° after DAD; the canines were distalized 5.29 ± 2.01 mm and tipped 13.64° ± 9.54° in 200 ± 57 days in the DG. The rates of posterior canine movement were 0.67 ± 0.14 mm per day after DAD and 0.03 ± 0.01 mm per day in the DG. No significant first molar anchorage loss was observed after DAD, although the DG showed some vertical and sagittal first molar movement.
Conclusions
We failed to reject the null hypothesis. DAD can reduce the duration of orthodontic treatment time by accelerating canine retraction in extraction patients without undesirable side effects.
Highlights
- •
Effect of dentoalveolar distraction osteogenesis (DAD) on canine retraction was evaluated.
- •
Patients with conventional (intraoral elastic) canine distalization served as controls.
- •
DAD decreased canine retraction time with no molar anchorage loss.
A shorter orthodontic treatment duration has a positive impact on a patient’s lifestyle and can also be desirable to prevent possible harmful side effects. Various factors have been suggested for prolonged treatment duration such as malocclusion characteristics, treatment method, patient cooperation, impacted maxillary canines, and earlier initiation of orthodontic treatment.
Extraction treatment on average was found to require more treatment time to complete than did nonextraction treatment. Mavreas and Athanasiou concluded that there are indications that extraction treatment lasts longer than nonextraction therapy. Alger found that the treatment of nonextraction patients finished 4.6 months faster than for those in whom he extracted teeth for orthodontic treatment. Vig et al examined 5 practices to determine whether a systematic relationship existed between the relative frequency of extraction treatments and the duration of active appliance therapy; their findings showed that extraction treatment had a longer duration than nonextraction therapy. Skidmore et al suggested that extractions have a significant effect on treatment duration that is independent of their association with more complex cases.
Nonextraction orthodontic techniques including miniscrew and orthodontic implant-supported distalization methods have become popular during recent years. However, patients with severe or moderate crowding still require treatment based on tooth extractions. Tooth extractions can also be beneficial for some problems including caries, periodontitis, endodontic problems, or even some developmental defects that are not within the orthodontist’s control.
Various surgical procedures have been used to reduce the orthodontic treatment or the canine distalization duration including alveolar surgery, distraction osteogenesis, corticotomy, and piezosurgery. The dentoalveolar distraction (DAD) technique was introduced in 2001; rapid tooth movement is achieved within the principles of distraction osteogenesis. The dentoskeletal effects of this technique have previously been reported with a small sample and no control group. The aim of this clinical prospective study was to test the null hypothesis that the duration of orthodontic treatment can be significantly reduced by decreased canine retraction time using DAD. The rate of tooth movement and the effects of DAD on dentoalveoler and skeletal structures were evaluated, and these effects were compared with a conventional canine distalization group.
Material and methods
A priori power analysis was completed by G*Power (version 3.1.9.2; Franz Faul, Kiel, Germany) software. Based on a 1:1 ratio between the groups, a sample size of 17 canines in each group would give 90% power to detect significant differences at a significance level of α = 0.05. This prospective study consisted of 33 patients (13 boys, 20 girls). Thirty-six maxillary canines of 19 patients (8 boys, 11 girls) comprised the DAD group, and 28 canines of 14 patients (5 boys, 9 girls) were included in the distalization group (DG). Mean ages in the DAD group and the DG were 15.8 ± 1.96 and 16.02 ± 2.8 years, respectively ( Table I ). Inclusion criteria for both groups were the following: (1) permanent dentition, (2) first premolar extractions indicated for correcting the existing dental malocclusion (to eliminate overjet or crowding), and (3) no history of systemic disease causing medical difficulty after tooth extractions or any surgical intervention.
| Group | Patients (n) | Canines (n) | Mean age (y) | Retraction time (d) | Rate of tooth movement |
|---|---|---|---|---|---|
| DAD | 19 | 36 | 15.8 ± 1.96 | 11.8 ± 1.3 | 0.67 ± 0.14 mm/d |
| DG | 14 | 27 | 16.02 ± 2.8 | 200 ± 57 | 0.03 ± 0.01 mm/d |
The treatment procedure was explained in detail to all patients and parents, and informed consent was obtained before surgery. This research project was approved by the ethics committee at the University of Ankara in Turkey.
The DG consisted of 7 Class I, 5 Class II Division 1, and 2 Class III patients. Fixed orthodontic appliances were used in all DG patients; 120 g of horizontal intraoral elastic force was used for canine distalization. The magnitude of force was measured at each appointment and arranged with a gram gauge. The patients were ordered to change the elastics daily. Lateral cephalometric, panoramic and periapical films were taken before fixed orthodontic treatment and after canine-second premolar contact was achieved. The mean distalization duration for the DG was 200 ± 57 days. No intraoral or extraoral appliance was used for maintaining anchorage during canine retraction.
The DAD group consisted of 4 Class I, 14 Class II Division 1, and 1 Class III patients. Lateral cephalometric and panoramic films were taken before and after DAD and, in 11 patients, after fixed orthodontic therapy. One-sided DAD was achieved in 2 patients, and bilateral DAD was done in 17 patients. The total number of canines of the DAD group was 36. The periapical films were obtained before DAD, during DAD, and after DAD.
A custom-made, rigid, tooth-borne intraoral distraction device was used for DAD. The device was made of stainless steel and had a distraction screw and 2 guidance bars ( Fig 1 , A ). The patient or the parent turned the screw clockwise with a special apparatus for distal movement of the canine. The canines and the first molars were banded with 0.06 × 1.80-in band material, and an impression was obtained when the canine and first molar bands were placed on the teeth. The distractor was then soldered to the bands on the dental cast with consideration of both the biomechanical principles of tooth movement and the rotation center of the canine. The distractor was positioned buccally at the highest position permitted by the soft tissue to minimize tipping ( Fig 1 , B ).
The surgical procedure of DAD was described previously. Surgery was performed under local anesthesia. Briefly, a vestibule flap was opened without touching the gingival margin of the canines and neighboring teeth. Complete vertical and horizontal osteotomies at a distance of 3 to 5 mm from the apex and the roots were performed to mobilize the alveolar segment. Then the first premolar was extracted, and the buccal bone was removed between the outlined distal bone cut of the canine and the second premolar with a round bur. The palatal shelf was preserved, but the apical bone near the sinus wall was removed to leave an intact sinus membrane to prevent interferences during canine retraction. Osteotomes were used on the vestibule side of canines to split the surrounding bone around its root from the palatal cortex and neighboring teeth. The transport dentoalveoler segment included the buccal cortex and the underlying spongy bone that envelopes the canine root, leaving intact palatinal cortical plates and the bone around the apex of the canine ( Fig 2 , A ).
The device was cemented on the canine and the first molar immediately after the surgical procedure, and no other appliance was placed on the other teeth during the distraction procedure ( Fig 2 , B ). The device was activated intraoperatively by several millimeters and set back to its initial position to ensure the mobility of the transport segment. The incision was closed with absorbable sutures, and a nonsteroidal anti-inflammatory drug and an antibiotic were prescribed for 5 days. The duration of the surgical procedure was approximately 30 minutes for each canine. The patients were also instructed not to brush their teeth to prevent trauma around the surgical site for 3 days. A 0.2% chlorhexidine gluconate rinse was prescribed twice a day during the distraction procedure.
Distraction was initiated after 3 days of latency. The distractor was activated twice per day, in the morning and in the evening, for a total of about 0.8 mm per day. DAD was finished when the canines came into contact with the second premolars or the necessary amount of movement was achieved. The distractor was then removed, and fixed orthodontic treatment was immediately initiated with the leveling of both dental arches. Ligatures were placed under the archwire between the distracted canine and the first molar and kept for at least 3 months after the DAD procedure to prevent mesial movement of the canine ( Figs 3-6 ). A meticulous oral hygiene program was initiated before and after the DAD and during fixed appliance orthodontic therapy; it was controlled by a periodontologist with monthly appointments.
The stages of DAD treatment were the following.
- 1.
Dentoalveolar distraction.
- 2.
Initiation of fixed appliance orthodontic treatment on both dental arches with 0.018-in stainless steel brackets, an 0.008-in ligature wire between the first molar and the canine, a 0.014-in nickel-titanium wire for leveling, and a 0.016-in nickel-titanium wire for leveling (if necessary).
- 3.
A 0.016 × 0.016-in stainless steel wire with reverse closing loops for incisor retraction and torque control.
- 4.
A 0.017 × 0.025-in stainless steel wire for the finishing phase.
- 5.
End of orthodontic treatment.
The stages of the DG treatment were the following.
- 1.
Initiation of fixed appliance orthodontic treatment on both dental arches with 0.018-in stainless steel brackets, a 0.014-in nickel-titanium wire for leveling, a 0.016-in nickel-titanium wire for leveling, and a 0.016-in stainless steel wire for leveling.
- 2.
Canine distalization with horizontal intraoral elastic force.
- 3.
A 0.016 × 0.016-in stainless steel wire with reverse closing loops for incisor retraction and torque control.
- 4.
A 0.017 × 0.025-in stainless steel wire for the finishing phase.
- 5.
End of orthodontic treatment.
A comfort/patient satisfaction survey was used; discomfort levels between the 2 study groups were similar.
Panoramic films and periapical radiographs of the canines and first molars were taken to evaluate root structures. Root resorption scores were detected according to the root resorption scale modified from the study of Sharpe et al using panoramic and periapical radiographs.
In the DAD group, tooth vitality tests were used before DAD, after fixed orthodontic treatment, and at the sixth month of retention in patients whose orthodontic fixed therapies were finished. Electric pulp testing was done with Digitest (model D626D; Parkell Electronics Division, Edgewood, NY), and thermal stimulation was provided with chloraethyl spray (IG Sprühtechnik, Wehr, Germany). No pulpal sensibility test was performed in teeth with restorations because of possible incorrect responses. Tooth vitality was scored as positive or negative according to the response to both electric and pulpal tests.
Lateral cephalometric films were obtained under standardized conditions (the film-focus distance was 155 cm, and the distance from the midsagittal plane to the film was 12.5 cm). Fourteen anatomic reference points were digitized with a computer program, Purpose on Request Digitizer Input Output System. Six skeletal and 11 dental variables were measured ( Table II and Fig 7 ).
| Measurement | Description |
|---|---|
| NSL | Anterior cranial base; line between sella (s) and nasion (n) |
| NL | Nasal line; line between anterior nasal spine (sp) and posterior maxilla (pm) |
| NLv | Perpendicular vertical line constructed from sp point of nasal line |
| ML | Mandibular plane; line between menton (me) and tangent menton (tg.me) |
| ILs | Long axis of the central incisors—line between incisal edge (is) and apex (as) of maxillary central incisors |
| CLs | Long axis of the maxillary canines-line between tip (uc) and apex (uca) of canines |
| MLs | Long axis of the maxillary molars—line between the tip (ms) and apex (msa) of the mesiobuccal cusp of the maxillary first molars |
| s n ss (°) | Angle between NSL and subspinale |
| NSL/NL (°) | Nasal line angle in relation to anterior cranial base |
| s n sm (°) | Mandibular prognathism |
| NSL/ML (°) | Mandibular inclination in relation to anterior cranial base |
| ss n sm (°) | Sagittal intermaxillary relationship |
| NL/ML (°) | Mandibular inclination in relation to the nasal line |
| Overbite (mm) | Vertical distance between the incisal edges of the most prominent maxillary and mandibular central incisors |
| Overjet (mm) | Sagittal distance between the incisal edges of the most prominent maxillary and mandibular central incisors |
| NL/ILs (°) | Maxillary incisor inclination—angle between the long axis of the first incisors in relation to NL |
| NL/CLs (°) | Maxillary canine inclination-angle between the long axis of the canines in relation to NL |
| NL/MLs (°) | Molar inclination in relation to the NL |
| NLv-is (mm) | Sagittal position of the maxillary incisors in relation to the NLv |
| NLv-uc (mm) | Sagittal position of the maxillary canines in relation to the NLv |
| NLv-ms (mm) | Sagittal position of the maxillary first molars in relation to the NLv |
| NL-is (mm) | Vertical position of the maxillary incisors in relation to the NL |
| NL-uc (mm) | Vertical position of the maxillary canines in relation to the NL |
| NL-ms (mm) | Vertical position of the maxillary first molars in relation to the NL |
Statistical analysis
The initial descriptive statistics are presented in Table III . Intergroup changes and intragroup differences were evaluated with 2-sample t tests and paired t tests, respectively.
| DAD group (mean ± SD) | DG (mean ± SD) | Difference ( t test) | |
|---|---|---|---|
| Maxillary measurements | |||
| s n ss (°) | 79.09 ± 3.90 | 80.25 ± 3.40 | NS |
| NSL/NL (°) | 9.58 ± 2.94 | 9.06 ± 3.06 | NS |
| Mandibular measurements | |||
| s n sm (°) | 73.72 ± 5.43 | 77.93 ± 3.63 | ∗ |
| NSL/ML (°) | 38.73 ± 7.86 | 35.13 ± 5.07 | NS |
| Maxillomandibular measurements | |||
| ss n sm (°) | 5.36 ± 4.28 | 2.33 ± 3.68 | ∗ |
| NL/ML (°) | 29.16 ± 6.43 | 26.07 ± 4.35 | NS |
| Overbite (mm) | 2.94 ± 2.28 | 2.93 ± 2.35 | NS |
| Overjet (mm) | 7.17 ± 2.77 | 4.27 ± 2.86 | ∗ |
| Dentoalveoler measurements | |||
| NL/ILs (°) | 110.74 ± 6.75 | 112.05 ± 7.02 | NS |
| NL/CLs (°) | 103.53 ± 6.74 | 106.88 ± 9.94 | NS |
| NL/MLs (°) | 88.23 ± 5.89 | 95.75 ± 7.76 | † |
| NLv-is (mm) | 2.65 ± 2.79 | 1.85 ± 2.02 | NS |
| NLv-uc (mm) | 9.11 ± 4.05 | 10.14 ± 4.05 | NS |
| NLv-ms (mm) | 31.05 ± 4.11 | 30.32 ± 4.30 | NS |
| NL-is (mm) | 31.22 ± 2.45 | 29.29 ± 2.06 | ∗ |
| NL-uc (mm) | 27.15 ± 3.87 | 25.84 ± 4.32 | NS |
| NL-ms (mm) | 26.12 ± 3.06 | 24.62 ± 2.21 | NS |
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