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.
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, L iou & H uang 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. I seri et al. 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 ( Figs 1 and 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 ( Figs 3 and 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.
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 0.5 mm a day and the rhythm of distraction was 4 times a day.
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 5 mm 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 0.5 mm a day and the rhythm of distraction was 4 times a day.
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.
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.
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).
|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|
|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|
|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|