Interseptal bone reduction on the rate of maxillary canine retraction

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1 Originl Article Interseptl bone reduction on the rte of mxillry cnine retrction Chidchnok Leethnkul ; Surt Knokkulchi b ; Settkorn Pongpnich c ; Nrit Leepong d ; Chirt Chroemrtrote ABSTRACT Objective: To propose nd evlute novel surgicl pproch with miniml trum, termed interseptl bone reduction, combined with the use of conventionl orthodontic fixed pplince to ccelerte cnine retrction. Mterils nd Methods: A split-mouth design study ws conducted in 18 femle subjects (men ge, 21.9 yers) whose bilterl upper first premolrs were extrcted nd who subsequently received cnine distliztion. The extrction socket on the experimentl side ws deepened, nd interseptl bone distl to the mxillry cnine ws reduced in thickness using surgicl bur; conventionl extrction ws performed on the control side. The cnines were then distlized using elstomeric chins on both the lbil nd pltl sides, with net force of 150 g. The extent of cnine movement nd rottion ws determined from study models, nd the ngultion ws nlyzed bsed on lterl cephlogrms. Results: A Wilcoxon signed rnk test demonstrted tht the extent of cnine movement in the mesio-distl direction fter 3 months ws significntly greter on the experimentl side thn on the control side (5.4 nd 3.4 mm, respectively, P 5.002). However, there ws no sttisticlly significnt difference in cnine ngultion or rottion fter 3 months between the experimentl nd control sides. Conclusions: In combintion with the use of conventionl orthodontic pplinces, interseptl bone reduction cn enhnce the rte of cnine movement when interseptl bone is sufficiently reduced in both thickness nd depth following surgicl criteri. (Angle Orthod. 2014;84: ) KEY WORDS: Accelerted tooth movement; Mini-implnt; RAP; Surgicl pproch; Optimum force INTRODUCTION Associte Professor, Orthodontic Section, Deprtment of Preventive Dentistry, Fculty of Dentistry, Prince of Songkl University, Ht Yi, Songkhl, Thilnd. b Grdute Student, Orthodontic Section, Deprtment of Preventive Dentistry, Fculty of Dentistry, Prince of Songkl University, Ht Yi, Songkhl, Thilnd. c Assistnt Professor, Deprtment of Orl nd Mxillofcil Surgery, Fculty of Dentistry, Prince of Songkl University, Ht Yi, Songkhl, Thilnd. d Lecturer, Deprtment of Orl nd Mxillofcil Surgery, Fculty of Dentistry, Prince of Songkl University, Ht Yi, Songkhl, Thilnd. Corresponding uthor: Chidchnok Leethnkul, DDS, MSc, PhD, Associte Professor, Orthodontic Section, Deprtment of Preventive Dentistry, Fculty of Dentistry, Prince of Songkl University, Ht Yi, Songkhl 90112, Thilnd (e-mil: nokleethnkul@yhoo.com) Accepted: December Submitted: October Published Online: Mrch 4, 2014 G 2014 by The EH Angle Eduction nd Reserch Foundtion, Inc. Orthodontic tooth movement is process whereby the ppliction of force induces bone resorption on the pressure side nd bone pposition on the tension side. 1,2 The rte of biologic tooth movement in response to the ppliction of optimum mechnicl force is pproximtely 1 to 1.5 mm over 4 to 5 weeks. 3 Therefore, in cses of mximum nchorge premolr extrction, cnine distliztion usully tkes 6 to 9 months, leding to n overll tretment time of 1.5 to 2 yers. Mny ttempts hve been mde to shorten the durtion of orthodontic tretment; one such mechnicl mnipultion is dentolveolr surgery, which includes techniques such s distrction of the periodontl ligment, dentolveolr distrction osteogenesis, periodontlly ccelerted osteogenic orthodontics, nd other modified surgicl techniques. With these techniques, ctive orthodontic tretment cn be completed within less thn 1 yer. However, most of these techniques require flp surgery to perform invsive corticotomy or osteotomy nd the use of DOI: /

2 840 LEETHANAKUL, KANOKKULCHAI, PONGPANICH, LEEPONG, CHAROEMRATROTE Figure 1. Position of the surgicl guide wire, s shown introrlly. hevy orthodontic force to move teeth rpidly, which my increse the risk of periodontl problems nd pulpl vitlity loss over the longer term. Therefore, the study of less invsive dentolveolr surgicl pproches combined with the use of conventionl orthodontic pplinces with optimum force to ccelerte the rte of tooth movement is currently of significnt interest. The process of rpid tooth movement fcilitted by dentolveolr surgery hs been explined by vriety of mechnisms. For exmple, Liou nd Hung 4 stted tht the cnines could be rpidly distrcted fter dentolveolr surgery, s the first premolr extrction socket ws less resistnt nd not yet refilled by solid bone tissue, which tkes t lest 3 weeks to form. However, using this technique, the interseptl bone distl to the cnine, which ws surgiclly undermined to weken its strength, ws bent nd frctured by the hevy force generted by the distrction device. The im of this study ws to propose nd evlute novel surgicl pproch with miniml trum distl to the cnine combined with the use of conventionl orthodontic pplince with optimum force to increse the rte of mxillry cnine retrction. MATERIALS AND METHODS The study ws pproved by the ethicl committee of the Fculty of Dentistry t the Prince of Songkl University. Adult ptients receiving orthodontic tretment in the Orthodontic Clinic t the Dentl Hospitl, Prince of Songkl University, hd been indicted for mxillry first premolr extrction nd bilterl mxillry cnine distliztion nd demonstrted good orl hygiene, with probing depth vlues not exceeding 3 mm. This study ws split-mouth design in which the experimentl side ws llocted by rndomiztion. Ech ptient ws fitted with Roth s prescription predjusted edgewise brckets (3M Gemini metl brckets; 3M Unitek, Monrovi, Clif). The teeth were ligned nd leveled until complete on inch stinless-steel rchwire. Mini-implnts (#SH AbsoAnchor; Dentos, Degu, Kore) were plced between the roots of the second premolrs nd first molrs on both the left nd right sides bout 1 month before the surgicl procedure to observe the stbility of mini-implnts. Surgicl Procedure Trditionl extrction of the first premolr ws performed on one side s control, while extrction combined with interseptl bone reduction ws performed on the experimentl side. The surgicl procedure ws performed by two surgeons inside the extrction socket of the mxillry first premolr without flp surgery under locl nesthesi. The extrction socket ws deepened to the length of the cnine pex, nd the interseptl bone distl to the cnine ws reduced to 1 to 1.5 mm in thickness using round nd cylindricl crbide burs. If present, the interrdiculr septl bone of the socket ws lso removed. The first premolr extrction socket ws surgiclly widened in the buccopltl dimension long the curvture of the root of the cnine. The bur ws held prllel to the surgicl guide wire (Figure 1) nd dvnced buccopltlly, while the lveolr crest of interseptl bone ws left untreted (Figure 2). A peripicl rdiogrph ws tken prior to nd fter the surgicl procedure (Figure 3). Orthodontic Mechnics The mechnism for cnine distliztion consisted of power rm fbricted from inch stinless-steel rchwire ttched to the mesil end of ech cnine brcket, with the height of the hook pproximtely the sme s the verticl position of the mini-implnt, to produce vector force prllel to the occlusl plne. The power rm ws inserted into the

3 INTERSEPTAL BONE REDUCTION 841 Figure 2. Interseptl bone reduction technique: Dshed lines indicte the res of interseptl bone reduction. cnine brcket, nd n elstomeric chin ttched to the mini-implnt ws used to retrct the cnine. In ddition, lingul button (3M Unitek) ws plced on the pltl surfce of ech cnine nd first molr. Retrction force ws pplied on the pltl side by ttching n elstomeric chin (Alstik TM ; 3M Unitek) between the buttons of the cnine nd first molr. Both the lbil nd pltl chins were djusted to generte n pproximtely equl mgnitude of force, producing net force of 150 g with force guge (Figure 4). The durtion of the experimentl period ws 3 months; the ptients were scheduled for monthly exmintions, nd the elstomeric chins were replced t ech ppointment during the experimentl period. Mesurement of Cnine Movement The prmeters of cnine movement ssessed in this study included the extent of cnine movement, rottion, nd ngultion, which were determined from study models nd lterl cephlogrms. A series of models from ech subject ws used to ssess the chnge in the position of the cnines reltive to the stble lndmrk of the ipsilterl medin end of the third ruge for ech cnine. The initil model ws used for mking the pltl plug with reference wires nd for mesuring cnine movement nd rottion. 5 Peripicl rdiogrphs were tken every 4 weeks to determine the chnges in size of the periodontl spce nd extrction socket. Lterl cephlogrms were tken together with the ngultion-indicting wires before extrction of the first premolrs (T0) nd once gin fter cnine retrction for 3 months (T3) to evlute the chnge in cnine ngultion (Figure 5). The rdiogrphs were trced nd determined by single investigtor. Sttisticl Anlysis Ech liner nd ngulr mesurement on ech smple ws repeted twice t lest 4 weeks prt nd verged. Pired t-tests nd the Dhlberg s formul were used to determine the introbserver relibility. All vribles re presented s the men vlues. The Wilcoxon signed rnk test ws used to compre the extent of cnine movement between the experimentl nd control sides; P vlues of,.05 were considered sttisticlly significnt. Spermn rnk correltion nlysis ws pplied to identify ny correltions between potentil influencing fctors for cnine movement. RESULTS The smples included in this study were from 18 femle ptients. The men ptient ge t the strt of Figure 3. Peripicl rdiogrphs before (A) nd fter (B) extrction nd interseptl reduction.

4 842 LEETHANAKUL, KANOKKULCHAI, PONGPANICH, LEEPONG, CHAROEMRATROTE Figure 4. Mechnics used for cnine distliztion. tretment ws yers (rnge, yers). Dhlberg s error ws less thn 0.5, indicting introbserver relibility, nd pired t-tests indicted tht the two series of replicte mesurements by the sme investigtor were not significntly different. After clinicl observtion, the cnine on the experimentl side ws considered cliniclly significnt in four of the 18 cses. In one cse, the experimentl cnine contcted the second premolr within only 2 months, nd in nother three cses the experimentl cnines mde contct within 3 months, wheres the corresponding cnines on the control side were still in the middle of extrction spces (Figure 6). Neither periodontl problems nor discolortion of the experimentl cnine ws evident in ny cse. Figure 5. Angultion-indicting wires on the cnine brckets. Extent of Cnine Movement The verge extent of cnine movement per month, s mesured from the models, is presented in Figure 7. The extent of cnine movement in ech month ws greter on the experimentl side thn on the control side. The Wilcoxon signed rnk test demonstrted tht the totl extents of cnine movement in the first nd second months were significntly greter on the experimentl side thn on the control side (P 5.002). The verge ccumulted extent of cnine movement nd the rte of cnine movement in ech month, s mesured from the models, re shown in Figure 8. The ccumulted extent of cnine movement on the experimentl side ws greter thn tht of the control

5 INTERSEPTAL BONE REDUCTION 843 Figure 6. Exmple of cse between the experimentl (right) nd control (left) sides: cnine retrction ws complete within 3 months. (A) Before; (B) After. side throughout the experimentl period; however, the extent of cnine movement per month on the experimentl nd control sides ws significntly different. The rte of cnine movement per month ws significntly higher on the experimentl side thn on the control side, with verge vlues of 1.8 mm nd 1.1 mm, respectively. Rdiogrphic nlysis indicted tht the experimentl cnine tipped more distlly thn did the cnine on the control side; however, the Wilcoxon signed rnk test reveled tht the vlues for totl tipping nd tipping per millimeter of movement were not significntly different (P..05; Tble 1). Anlysis of the models demonstrted tht the cnine on the experimentl side rotted more significntly in totl thn did the cnine on the control side. However, there ws no significnt difference between the rottion per millimeter of movement between the control nd experimentl sides (P..05; Tble 2). Point-biseril correltion nlysis demonstrted tht the totl extent of cnine movement on the experimentl side ws strongly correlted with the presence of remining interseptl bone. However, the surgicl site (left or right) nd the two surgeons hd no significnt correltion with the totl extent of cnine movement (Tble 3). DISCUSSION A vriety of dentolveolr surgicl techniques hve been reported 4,6 9 to ccelerte the rte of tooth movement nd reduce the overll orthodontic tret- Figure 7. The verge extent of cnine movement (men 6 stndrd devition [SD], * P 5.002). Figure 8. The verge ccumulted extent of cnine movement (mm) 6 stndrd devition (SD) on the experimentl side nd control side (T1 nd T3; P 5.002, T2; P5.003).

6 844 LEETHANAKUL, KANOKKULCHAI, PONGPANICH, LEEPONG, CHAROEMRATROTE Tble 1. Medin Extent of Totl Tipping nd Tipping per Millimeter of Movement (in Degrees) for the Cnines on the Experimentl Side nd Control Side Control, u Experimentl, u Wilcoxon Signed- Rnk Test Totl tipping NS Tipping per mm NS NS indictes nonsignificnt. ment time. Using these techniques, ctive orthodontic tretment cn be completed within 1 yer. The mechnism of rpid tooth movement fcilitted by dentolveolr surgery hs been explined to be the result of number of different processes, including bending of the interseptl bone nd reduced bone resistnce, 4,7 dentolveolr block movement, 8 nd the regionl ccelertory phenomenon (RAP) fter bone injury, 9 which cn increse the bone turnover rte. In this study, we propose novel pproch to ccelerte the rte of mxillry cnine movement. We performed less invsive surgicl procedure without flp surgery, which is not much more invsive or complicted thn simple extrction for orthodontic tretment. To simplify clinicl prctice, we lso used conventionl orthodontic pplince insted of the custom-mde distrction devices employed in other studies 4,6 9 ; herein, n elstomeric chin ws employed with the ppliction of optiml force to move teeth within norml biologic limits. However, this pproch is verstile enough to be pplied to vrious types of brckets nd mechnics. Our surgicl intervention resembles the technique for distrction of the periodontl ligment presented by Liou nd Hung; however, buccl nd lingul verticl grooving of the interseptl bone ws not performed. During periodontl ligment distrction, verticl grooving is conducted to weken the interseptl bone; however, this technique contributed to frcture of the bone to be moved long with the cnine during distrction with the use of distrctor. In our study, we expected the surgicl procedure to reduce resistnce due to the bone nd promote lveolr bone bending during cnine retrction in the bsence of interseptl bone brekge. Additionlly, we expected tht the RAP would be initited s result of the lveolr surgery, which in turn would led to trnsient Tble 2. Medin Extent of Totl Rottion nd Rottion per Millimeter of Movement (in Degrees) for the Cnines on the Experimentl Side nd Control Side Control, u Experimentl, u Wilcoxon Signed Rnk Side Totl rottion ,.05 Rottion per mm NS NS indictes nonsignificnt. Tble 3. Correltion Between the Totl Extent of Cnine Movement nd Other Fctors Totl Extent of Cnine Movement R Vlue P Vlue Remining interseptl bone 0.926,.001 Surgeon NS Surgicl site NS NS indictes nonsignificnt; Spermn rnk correltion nlysis. osteoporosis on the experimentl side. As result of these mechnisms, we hypothesized the experimentl cnine should move fster thn the control cnine. As the RAP ws nticipted to occur following lveolr surgery, we used mini-implnts s n nchorge to minimize the risk of nchorge loss during cnine retrction. The results of this study demonstrte tht the rte of tooth movement on the control side (3.4 mm in 3 months) ws similr to the reported rte of biologic tooth movement rte using optimum force, which is pproximtely 1 to 1.5 mm in 4 to 5 weeks. 3 Sttisticl nlysis confirmed tht the ccumulted extent of cnine movement on the experimentl side ws significntly higher thn tht of the control side throughout the experimentl period (5.4 mm in 3 months). As is the cse with the periodontl ligment distrction technique, one possible explntion for the incresed rte of cnine movement observed fter our intervention my be reduced bone resistnce nd incresed lveolr bone bending, including the RAP. In the initil period fter the surgicl procedure, the remining interseptl bone on the pressure side ws resorbed. If enough interseptl bone ws surgiclly reduced, the entire bone could be completely resorbed within 1 month. Therefore, the experimentl cnine could be retrcted into the extrction socket, which ws not yet refilled by solid bone, 10 wheres the interseptl bone on the control side ws still being resorbed. In the study of Ren et l., 11 in which the interseptl bone ws undermined using distrction of the periodontl ligment technique combined with the use of 150-guge nickel-titnium coil spring to ccelerte the rte of tooth movement in dogs, histologicl nlysis demonstrted tht the undermined interseptl bone becme discrete s result of bone resorption during the third nd fourth weeks, nd the periodontium fused with the extrction socket. A similr mechnism my explin the rpid tooth movement in the experimentl group of this humn study. Moreover, bending of lveolr bone my be nother mechnism by which to explin the ccelerted cnine retrction observed in this study. Picton 12 demonstrted tht the bending of lveolr bone could constitute s much s 25% of initil tooth movement.

7 INTERSEPTAL BONE REDUCTION 845 In the third month, the rte of cnine movement ws not significntly different between the experimentl nd control sides. One possible explntion for this observtion my be tht fter tooth extrction, regenertive bone tissue refilled the extrction socket within 3 weeks nd becme resistnt nd solid within 3 months. 13 The more resistnt the bone tissue, the slower the rte of tooth movement expected. Additionlly, the RAP my decrese over time, s it is thought to pek t 1 to 2 months nd lst for bout 6 months fter the completion of the surgicl procedure. 14 Additionlly, in some cses, the cnine in the experimentl group could not move further, s there ws no more spce in which to move. However, if the study time ws lengthened, the result would hve been more obvious. Although interseptl bone reduction ws performed for 18 cnines on the experimentl side, the rte of cnine movement ws only considered to be cliniclly significnt in four subjects (ie, the cnine moved to contct the second premolr within 3 months). This could imply tht other fctors, prt from the mesiodistl thickness of the interseptl bone, my hve ffected the extent of cnine retrction in the other subjects. In terms of root ntomy, it is known tht the root of the cnine in the buccolingul dimension is greter thn tht of the first premolr. Hence, the first premolr extrction socket should be surgiclly widened to the width of the root of the cnine in the buccolingul dimension. Unfortuntely, the success of this procedure could not be determined from the peripicl rdiogrphs. Furthermore, the rte of cnine retrction my be limited by resistnce from the corticl bone. If the lbiolingul width of the cnine root is greter thn the width of the lveolr ridge between the cnine nd first premolr, the cnine cn only be distlized when the corticl plte is resorbed. Considertion of these fctors implies tht our surgicl technique is quite sensitive to cse selection, s is the cse with the periodontl ligment distrction technique. 15 Despite the incresed rte of cnine movement, it must be kept in mind tht the long-term effects of this technique on pulpl vitlity, root resorption, nd periodontl tissue were not investigted in this study. However, no subjects presented ny sign or symptom of pulp necrosis, root resorption, or periodontl defect fter tretment. CONCLUSIONS N Interseptl bone reduction combined with the use of conventionl orthodontic pplince with optimum force cn effectively ccelerte mxillry cnine retrction when the bone is sufficiently reduced in both thickness nd depth following surgicl criteri. N Antomicl structures, such s the mxillry sinus nd nrrowed lveolr ridge, my be limiting fctors for tooth movement fter this surgicl procedure; thus, pproprite cse selection must be mde. ACKNOWLEDGMENTS We would like to thnk the Grdute School, Prince of Songkl University, for grnt support; Assistnt Professor Dr Udom Thongudomporn for sttisticl dvice; nd Dr Nuengruti Yodthong for ll of the ssistnce. REFERENCES 1. Reitn K. Clinicl nd histologicl observtions on tooth movement during nd fter orthodontic tretment. Am JOrthod. 1967;53: Rygh P. Elimintion of hylinized periodontl tissues ssocited with orthodontic tooth movement. Scnd J Dent Res. 1974;80: Pilon JJGM, Kuijpers-Jgtmn AM, Mlth JC. Mgnitude of orthodontic forces nd rte of bodily tooth movement, n experimentl study in begle dogs. Am J Orthod Dentofcil Orthop. 1996;110: Liou EJ, Hung CS. Rpid cnine retrction through distrction of the periodontl ligment. 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