Animal Experiment On Tooth Movement Through Periodontal Ligament Distraction And Dentoalveolar Distraction, And Meta-analysis Of Clinical Effect Of Tooth Movement Through Periodontal Ligament Distraction

In ordinary orthodontic tooth movement (OTM), teeth move in a speed of1mmper month. It takes6to8months to complete the step of canine distalization for theorthodontic patient who has the first premolar extracted. The course of treatment canbe largely shortened if the step of canine distalization can be achieved in a short time.In1998, according to the principle of distraction osteogenesis (DO), Eric Liou fromTaiwan extracted his patient’s first premolar and removed some alveolar bone todecrease the resistance in his clinical research. And then canine distalization wascarried out in a fast way by a custom-made, intraoral distraction device. And then theconcept of periodontal ligament distraction (PDLD) was proposed. In2002, RehaKisnisci from Turkey proposed a modified operation and named it dentoalveolardistraction (DAD). Since both methods were not present for a long time, reports arelimited and mainly about fundamental researches, like mechanism or the comparisonwith OTM. And direct comparison between PDLD and DAD was seldom seen. In theaspect of clinical researches, literatures about DAD are rare and not reported indomestic. Literatures about PDLD, which are from various regions including China,are relatively more than those about DAD, but the problem is the small sample researches and outcome-disaccord.Based on the above situation, the operation methods from Liou and Kisnisciwere taken for reference in this experiment. Repeatable animal model of PDLD andDAD tooth movement were built in beagle dog to compare the advantages anddisadvantages between them. Moreover, clinical study literatures and data werecollected and analysed by means of evidence based medicine (EBM) method toevaluate the clinical effect of PDLD objectivelyObjectives1. To compare the treatment effect of PDLD and DAD on rapid caninemovement.2. To assess the clinic effect and risk of PDLD on rapid canine retraction.Methods1.6beagles were included in a split mouth paired control experiment, with theoperation of PDLD or DAD carried out on one side of the mandibular randomly andDAD or PDLD on the other side. The distraction on both sides lasts for2weeks. Thelocations of teeth were measured and radiologic examinations were taken before andafter the operation and in the7th and14th days after the beginning of distraction. Thebeagle dogs were sacrificed after distraction and pathological observation wasperformed.2. PubMed, Medline, Cochrane library, EMbase, Science Direct, CBM, CNKI,WanFang Databases were searched to collect the literatures of clinical researchesabout PDLD for rapid canine retracted from the beginning of1998to the end ofMarch,2014. The quality of the included studies was evaluated and the data wasextracted by two reviewers independently, and meta-analysis was performed byRevMan5.2software. Results1. The movement of mandibular first premolar for PDLD is1.74mm±0.30mm inthe first week,2.16mm±0.27mm in the second week, and3.90mm±0.56mm in total.2. The movement of mandibular first premolar for DAD is2.14mm±0.22mm inthe first week,2.09mm±0.38mm in the second week, and4.23mm±0.59mm in total.3. The movement of anchorage teeth for PDLD is0.66mm±0.09mm, and forDAD is0.45mm±0.08mm.4. The first premolar’s displacement for PDLD between the first and secondweek has statistical differences(P＜0.01), and for DAD there is no significantdifference statistically(P＞0.05). The first premolar’s displacement between PDLDand DAD in the first week, second week and in total all have statistical differences(P＜0.01). The anchorage teeth’s displacement between PDLD and DAD in2weekshave statistical differences(P＜0.01).5. Radiologic examination shows that the movement of first premolar for PDLDis tipping, and for DAD is more bodily. No root apex absorption was found.6. Pathological examination shows that there’s no irreversible change in periodontal ligament and pulp. Osteogenesis was found in alveolar bone where thedistraction was carried out.7. Seven researches including84patients and149canines were identified.8. The results of meta-analysis of the data of tooth movement showedsignificantly changes in location of canine before and after PDLD [P＜0.01, MD＝5.36,95％CI(4.11,6.62)]. There are significant changes in inclination of the canine inmaxillary [P＜0.01, MD＝11.88,95％CI(9.28,14.47)], however the result of the onein mandible was not statistically significant[P=0.08], and the pooled effect showedstatistically significant[P＜0.01, MD＝11.43,95％CI(8.96,13.90)].9. The results of meta-analysis about the risk showed that there were nosignificant changes in location of first molars before and after PDLD [P=0.27, MD＝-0.60,95％CI(-1.67,0.47)]. The risk of apical root resorption of canine showedsignificant changes before and after PDLD [P＜0.01, RR＝15.40,95％CI(4.41,53.75)]. Conclusions:1. Both PDLD and DAD are able to move the tooth rapidly. In aspect of toothmovement effect, DAD is better. PDLD is of less injury.2. PDLD is able to retract the canine rapidly, with moderate incline of long axiswhich implies that the crown moves faster than the root, with increase of risk ofcanine’s apical root resorption, and without significant mesial movement of the firstmolar.