Volume 39, Issue 11 , Pages 1074-1079, November 2010
Comparative evaluation of dento-alveolar distraction and periodontal distraction assisted rapid retraction of the maxillary canine: a pilot study
Article Outline
Abstract
Distraction osteogenesis is a biological process of new bone formation between the surfaces of the bone segments that are gradually separated by incremental traction. A recent innovative use of distraction osteogenesis in orthodontic tooth movement is to move individual tooth segments rapidly thus reducing orthodontic treatment time. Six patients, comprising two groups, were compared using two different surgical techniques: dento-alveolar distraction and periodontal distraction to bring about rapid canine retraction using an indigenously designed intra-oral distractor. The aim was to assess and evaluate the best approach to reduce the overall orthodontic treatment time by means of distraction osteogenesis. The patients were assessed at regular intervals with intra-oral periapical radiographs and lateral cephalograms for gauging the time required for retraction, canine tipping, anchorage loss and external root resorption. Dento-alveolar distraction was superior to periodontal distraction in all areas of assessment.
Keywords: dento-alveolar distraction, periodontal distraction, canine retraction, distraction osteogenesis
Distraction osteogenesis is a process of growing new bone by mechanical stretching of the pre-existing bone tissue. A recent innovative use of the distraction osteogenesis technique in the field of orthodontic tooth movement is to move individual tooth segments rapidly thus reducing orthodontic treatment time.
Conventional orthodontic treatment with either fixed or functional appliances relies on biological tooth movements, which can be achieved at a limited rate, so canine distalization takes about 6–8 months. In 1998, Liou & Huang12 concluded that the process of osteogenesis in the periodontal ligament during orthodontic tooth movement is similar to osteogenesis in the mid-palatal suture and suggested a new concept, which elicited rapid canine retraction in 3 weeks. Iseri et al.8 used a technique in which the dentoalveolus itself was designed as a bone transport segment for posterior movement.
The aim of this paper is to assess and evaluate the best surgical approach to reduce the overall orthodontic treatment time using distraction osteogenesis with an indigenously fabricated intra-oral tooth-borne distraction device.
Materials and methods
12 patients (7 males and 5 females) aged 17–22 years (mean age 20 years) and Angles Class I malocclusion with increased overjet were selected for the study. Six patients were selected for canine retraction in both maxillary quadrants using periodontal distraction (PD) and six using dento-alveolar distraction (DD); 12 canines in each group.
24 canine teeth were evaluated for root resorption using intra-oral periapical radiographs at 6 days, completion of retraction, 1 month, 3 months and 6 months (Figure 1, Figure 2). Assessment of canine tipping and anchorage loss in the sagittal and vertical plane was carried out using lateral cephalograms at completion of canine retraction and 3 months, respectively (Figure 3, Figure 4). All canines were assessed preoperatively for vitality and after removal of the distraction device, 6 months and 1 year postoperatively to prevent any false-positive responses; the probe was placed on the incisal one-third of the canine and the current increased gradually to observe for pain. The same distractor was used for both procedures. It was a custom-made; tooth-borne intra-oral device (Fig. 5) that consisted of an anterior segment soldered to the bands encircling the canine tooth and posterior segment to the first molar tooth with a sliding rod connecting them placed as apically as possible to minimise tipping. The device was compatible with orthodontic brackets and archwires. The sliding screw was activated using a screw wrench that brings about retraction of the canine. With every full turn in a clockwise direction, 0.5
mm of distraction was achieved.
Figure 1.
Postoperative intra-oral periapical radiographs for DD. Postoperative follow-up: (A) 6 days, (B) 12 days, (C) 3 months, (D) 6 months.
Figure 2.
Postoperative intra-oral periapical radiographs for PD. Postoperative follow-up: (A) 6 days, (B) 12 days, (C) 6 months.
Figure 3.
Preoperative and postoperative cephalograms for DD.
Figure 4.
Preoperative and postoperative cephalograms for PD.
Figure 5.
Distractor with screw wrench.
Technique for PD
Under local anaesthesia, the first premolar was extracted and a no. 4 round carbide bur was used to increase the depth of the premolar socket. The bone in the premolar socket was grooved vertically along the buccal and lingual sides, extending obliquely toward the base of the interseptal bone to weaken resistance. The interseptal bone was not cut through the distal aspect of the canine. This was followed by the oblique undermining groove (Fig. 6) connecting the vertical undermining grooves at the base of the prepared socket with a custom-made angled osteotome. The distractor was activated immediately after surgery. The rate of distraction was 0.5mm a day and the rhythm of distraction was 4 times a day.
Figure 6.
Technique for PD.
Technique for DD
Under local anaesthesia, the canine tooth was exposed with a mucosal incision, multiple monocortical holes were made around the canine root using a stainless steel round bur with copious saline irrigation medially and distally (Fig. 7). Apically, the holes were made 5mm above the canine root apex. A thin, tapered stainless steel bur was used to connect these holes. After extraction of the first bicuspid any possible bony interferences that might have been encountered during the distraction process were eliminated between the canine and second premolar teeth with preservation of palatal cortical shelves and the interdental bone. Fine osteotomes were used along the mesial aspect of the dento-alveolar segment to split the surrounding spongy bone around its root off of the palatal cortex and neighbouring teeth. There was a 2-day latency period before the distractor was activated. The rate of distraction was 0.5mm a day and the rhythm of distraction was 4 times a day.
Figure 7.
Surgical technique for DD.
In both groups minimal force was necessary for full mobilization of the transport bone disc. The distracted segments were kept passively after distraction for 12 weeks of consolidation.
Cephalometric measurements
The cephalometric planes used for the study are: PP, palatal plane, a line joining ANS to PNS; SN, anterior cranial base length, a line joining S to N; SV, perpendicular to SN plane through sella (S); U3L, long axis of the maxillary canine. The cephalometric measurements used are: maxillary first molar horizontal movement, distance between U6M and SV; maxillary first molar vertical movement, distance between U6M and PP; maxillary canine horizontal movement, distance between U3D and SV; change in inclination of canine, angle between U3L and SV.
Results
The results were ascertained by evaluating the two groups in four different parameters: time required in days, canine tipping, anchorage loss in sagittal and vertical planes, and root resorption where the number of sites per group was 12 (n=12). The mean and SD values of all the parameters in both the groups were statistically evaluated.
The time required for PD was 19.5±1.70 days and that for DD 12.5±0.50 days, which yielded a t-value of 9.68 (Table 1). This rapid retraction of the canines in both groups can be attributed to the surgical technique and the design of the distractor. Student's unpaired t-test revealed a highly significant difference between mean values of time required in days in the PD and DD groups (P<0.01).
Table 1. Parameters of study.
| Parameters | Group PD (n=12) | Group DD (n=12) | ‘t’ value | ‘P’ value |
|---|---|---|---|---|
| Mean±SD | Mean±SD | |||
| Time required (days) | 19.5±1.70 | 12.5±0.50 | 9.68 | <0.01 |
| Canine tipping left | 15.33±0.27 | 10.61±0.29 | 29.19 | <0.01 |
| Canine tipping right | 15.33±0.27 | ±0.22 | 32.96 | <0.01 |
| Anchorage loss | ||||
| Sagittal plane left | 0.24±0.045 | 0.32±0.043 | 3.2 | <0.01 |
| Sagittal plane right | 0.26±0.047 | 0.32±0.031 | 2.62 | <0.01 |
| Anchorage loss | ||||
| Vertical plane left | 0.65±0.048 | 0.55±0.035 | 4.29 | <0.01 |
| Vertical plane right | 0.66±0.045 | 0.56±0.032 | 4.44 | <0.01 |
| Root resorption | No. (%) | No. (%) | ‘t’ value | ‘P’ value |
|---|---|---|---|---|
| Yes | 1 (16.67%) | 0 | – | – |
| No | 5 (83.33%) | 6 (100%) | – | – |
The mean values of canine tipping (left and right side) showed a highly significant difference between the PD and DD groups (P<0.01) (Table 1). The mean values of anchorage loss for the left and right side in the sagittal and vertical planes revealed a highly significant difference between mean values in the PD and DD groups (P<0.01) (Table 1).
The vitality of the canines in both groups was checked before and after distraction with a 1-year follow-up. An electric pulp vitality tester found the canines were vital. The PD group showed no resorption of roots in 5 cases; 1 case had evidence of minimal root resorption. In the DD group there was no evidence of root resorption.
DD provides faster retraction of canines but the surgical procedure is more extensive than PD. PD accounted for more dental office visits than DD due to the rhythm of distraction. DD is a more superior option than PD to reduce the overall orthodontic treatment time by distraction osteogenesis.
Discussion
Distraction osteogenesis was introduced to maxillofacial surgery by McCarthy in 1992 when he first distracted the mandible. Ino et al.7 carried out an orthodontic treatment combined with corticotomy with placement of titanium miniplates in an adult patient, which reduced the orthodontic treatment time without any anchorage loss. Using the same concepts, Razdolsky et al.14 moved an ankylosed tooth by performing osteotomies around it, with the help of a custom-made distractor device. Liou et al.11 used interdental distraction osteogenesis to create a segment of new alveolar bone for the approximation of a wide alveolar cleft or fistula, and the reconstruction of a dento-alveolar defect. Gurgan et al.5 evaluated the alterations that occurred in the gingival dimensions of canine teeth following DD. Faber et al.2 showed that periodontal bone distraction resulted in periodontal bone regeneration, an excellent alternative for periodontal defects. Rapid canine retraction by distraction osteogenesis has become an excellent treatment for patients8, 10, 12, 13, 17.
The most time consuming stage of premolar extraction is canine retraction. In this study, with DD the authors achieved rapid canine retraction as there were no bony interferences or obstacles interfering with its movement. Other authors using DD8, 10 took 8–12 days to retract the canine. Comparable results were achieved by Sukurica et al.17 using DD (14.65±3.49 days). Gurgan et al.5 retracted canines in a mean record time of 10.36±1.93 days. Liou & Huang12 laid the foundation for PD and achieved canine retraction in a mean time of 21 days. In PD, retraction took a little longer than DD, the only obstacle was the interseptal bone that would be a hindrance in canine movement.
Various studies have been carried out to validate these techniques for rapid canine retraction. Kisnisci et al.10 who first carried out canine retraction by DD, observed no latency period, no consolidation period after surgery and distraction. Sukurica et al.17 also used DD but observed a 3-day latency period and a consolidation period of 1 week. Gurgan et al.5 observed a 3-day latency period but no consolidation period using DD for rapid canine retraction. In the present study, the authors observed a 3-day latency period with a consolidation period of 12 weeks for DD, while in PD there was immediate distraction with the same consolidation period. This allowed retraction of anterior teeth without the use of any additional appliances (extraoral or intra-oral) with minimal anchorage loss.
Usually treatments for patients involving premolar extractions need efficient posterior anchorage control. To minimise this anchorage loss, use of extraoral appliances or intra-oral appliances such as miniscrews and implants are commonly used, although none bring about effective rapid retraction of canines4. In this study both techniques retracted the canines much faster as well as maintained anchorage.
There is a ‘lag period’ of minimal tooth movement for 2–3 weeks with formation of hyalinised tissue before tooth movement proceeds12. If movement of teeth is not carried out before this time, anchorage loss ensues. In both PD and DD, the canines were retracted well before 2–3 weeks resulting in minimal anchorage loss sagittally and vertically. PD is technique sensitive; it is a blind procedure because access and visibility are difficult. If the osteotomy in the premolar socket is not adequate and complete, retraction of the canines takes longer which bypasses the lag period leading to anchorage loss. Sayin et al.16 observed a 0.56mm anchorage loss in the sagittal plane and 0.64mm in the vertical plane. The mesial movement of the first molar in the PD group was a mean 0.25mm, which is attributed to the surgical technique and the design of the distractor.
The DD technique gives excellent access, as all bony interferences are removed efficiently promoting retraction without any hindrances. Anchorage loss in the sagittal and vertical planes was not measured in any of the DD studies. The present comparative study using PD and DD yielded highly significant results giving the advantage to the finer surgical technique incorporating DD as the distractor used for both the techniques was the same.
External root resorption is initiated 2–3 weeks after the orthodontic force is applied and may continue for the duration of the force of application7, 15. An association between increased root resorption and the duration of the applied force has been reported. The duration of the applied force is an aggravating factor for root resorption and is more critical than the magnitude of the force1, 7, 15.
In the present study, in both groups, a distraction force of 0.5mm was used 4 times a day, which was high compared with other studies. The DD group showed no evidence of root resorption as the duration of force applied was for a mean period of 12.5±0.5 days, in the PD group the same force was applied for an extended mean period of 19.5±1.70 days. The negligible incidence of root resorption in the PD group is attributable to the minimal extended duration of the applied force. If the osteotomy performed for PD is incomplete or inadequate, the interseptal bone prevents the movement of the canine, increasing the duration of the distraction force applied, causing root resorption.
Canine tipping is related to the technique and the design of the distractor. The same distractor was used in both groups. Access for PD is poor and relies more on experience. Improper osteotomy of the interseptal bone initiates fractures in the interseptal bone16 adjacent to the apex of the canine indicating considerable resistance to the applied force causing tipping. The present study achieved highly significant results indicating that DD was a better technique than PD because it minimised canine tipping.
With both techniques, mucosal incisions and osteotomies were only made on the vestibular side of the alveolar bone and the gingival margin. The palatal mucosa and palatal bone remain untouched, thus maintaining adequate blood supply for the canine thereby preserving vitality.
Conflict of interest
None.
References
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PII: S0901-5027(10)00293-6
doi:10.1016/j.ijom.2010.06.012
© 2010 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.
Volume 39, Issue 11 , Pages 1074-1079, November 2010
