Relationships between Dental Roots and Surrounding Tissues for Orthodontic Miniscrew Installation

Transcription

1 Originl Article Reltionships between Dentl Roots nd Surrounding Tissues for Orthodontic Miniscrew Instlltion Kyung-Seok Hu ; Min-Kyu Kng b ; Te-Won Kim c ; Kyung-Ho Kim d ; Hee-Jin Kim e ABSTRACT Objective: To elucidte reltionships between the dentl roots nd surrounding tissues in order to prevent complictions fter plcement of miniscrew. Mterils nd Methods: Twenty humn mndibles nd mxills were used for this study. In the 200 sections of ech mndible nd mxill, nine items were mesured to investigte the reltionships between the dentl roots. Results: The interroot distnce incresed from nterior to posterior teeth nd from the cervicl line to the root pex in both the mxill nd the mndible. In the mxill, the gretest interroot distnce ws between the second premolr nd the first molr. In the mndible, the gretest interroot distnce ws between the first nd second molrs. The mxillry buccolingul bone width exceeded 10 mm from 7 mm (between cnine nd first premolr), 5 mm (between second premolr nd first molr), nd 4 mm (between first nd second molrs) bove the cervicl line. The mndibulr buccolingul bone width exceeded 10 mm from 7 mm (between second premolr nd first molr) nd 4 mm (between first nd second molrs) below the cervicl line. Conclusions: The sfest zone for plcement of miniscrew in the mxill ws between the second premolr nd the first molr, from 6 to 8 mm from the cervicl line. The sfest zone for plcement of miniscrew in the mndible ws between the first nd second molrs, less thn 5 mm from the cervicl line. (Angle Orthod. 2009;79:37 45.) KEY WORDS: Dentl root; Interroot distnce; Miniscrew; Compliction INTRODUCTION Roberts et l 1 were the first to use n endosseous dentl implnt s orthodontic nchorge; such endos Assistnt Professor, Division of Antomy nd Developmentl Biology, Deprtment of Orl Biology, Orl Science Reserch Center, BK21 Project, Humn Identifiction Reserch Center, Yonsei University, College of Dentistry, Seoul, Kore. b Reserch Assistnt, Division of Antomy nd Developmentl Biology, Deprtment of Orl Biology, Orl Science Reserch Center, BK21 Project, Yonsei University, College of Dentistry, Seoul, Kore. c Adjunct Professor, Division of Antomy nd Developmentl Biology, Deprtment of Orl Biology, Orl Science Reserch Center, BK21 Project, Yonsei University, College of Dentistry, Seoul, Kore. d Professor, Deprtment of Orthodontics, Yonsei University, College of Dentistry, Seoul, Kore. e Associte Professor, Division of Antomy nd Developmentl Biology, Deprtment of Orl Biology, Orl Science Reserch Center, BK21 Project, Humn Identifiction Reserch Center, Yonsei University, College of Dentistry, Seoul, Kore. Corresponding uthor: Dr Hee-Jin Kim, Room 601, Yonsei University, College of Dentistry, 134 Shinchon-dong, Seodemoon-gu, Seoul , Kore (e-mil: hjk776@yuhs.c) Accepted: Februry Submitted: August by The EH Angle Eduction nd Reserch Foundtion, Inc. seous implnts were pplied to clinicl orthodontics subsequently by Shpiro nd Kokich 2 nd by Roberts et l. 3 Dentl implnts, 4 minipltes, 5 nd miniscrews 6 hve been used s orthodontic nchorge, but the miniscrew type of nchorge is now the most widely used becuse of its low cost nd ese of implnttion. 7,8 In clinicl use, the erly orthodontic implnt provided orthodontic nchorge for simple tooth movements. Currently, orthodontic implnts re used for complex procedures such s distl movement of the molr, intrusion of the molr, nd tretment of n ectopic molr Most reserch relted to orthodontic implnts hs focused on the morphology of the miniscrew, including its type, shpe, dimeter, nd length, s well s its initil stbility. 3,13,14 In contrst, few studies hve evluted nd mesured ntomicl sites for sfe plcement of miniscrews in the interroot spces of the mxillry nd mndibulr rches. This prctice is probbly responsible for the prevlence of complictions such s hypersensitivity of the root, root frcture, nd lveolr bone frcture resulting from miniscrew insertion. The interrdiculr spce hs been investigted through the use of pnormic rdiogrphy, computed tomogrphy (CT), nd micro-ct. 7,8,15,16 However, pre- DOI: /

2 38 HU, KANG, KIM, KIM, KIM Figure 1. Sectioned specimens of the mxillry rch from 1 mm (upper left) to 10 mm (lower right) below the cervicl line. vious studies hve not fully chrcterized the ntomicl structures becuse of errors on the rdiogrphs, nd becuse investigtions were restricted to the molr region. The purposes of this study were to elucidte the reltionships between the roots nd surrounding structures nd to identify the optiml sites for miniscrewing. MATERIALS AND METHODS Cross sections of humn jws were nlyzed in 20 mndibles (17 mles, 3 femles; men ge, 63.3 yers; ge rnge, yers) nd 20 mxills (14 mles, 6 femles; men ge, 66.1 yers; ge rnge, yers). Resin blocks were produced by dehydrting the specimens with the use of conventionl method for 3 dys before infiltrting them with mixture of Technovit 7200 (No ; EXAKT Co., Norderstedt, Germny) nd 100% lcohol. The infiltrted smples were plced in n embedding mold nd were polymerized for 1 dy with light tht hd 450 nm wvelength in light-curing unit (520 light polymeriztion unit; EX- AKT Co). The resin blocks were cut serilly t 1 mm intervls from the cervicl line to the root pex with the use of mcrocutting nd bnd system (300CP; EXAKT Co). Imges of ech section then were obtined t resolution of 600 DPI with computer scnner (Perfection 3490 Photo; Epson Co., Shnghi, Chin) nd were stored in TIFF formt with high-qulity compression (Figures 1 nd 2). In ll, 200 sections of ech mndible nd ech mxill were prepred, nd the following items were mesured with n imge nlysis system (Imge-Pro Plus, version 4.0; Medi Cybernetics Co., Bethesd, Md, USA) fter stndrd clibrtion ws performed (Figure 3): Interroot distnce (buccl nd lingul) Buccolingul bone width Corticl bone thickness (buccl nd lingul) Mucosl thickness (buccl nd lingul) RESULTS The mesurements did not differ significntly with regrd to sex, ge, or side (P.05). Interroot Distnce The interroot distnce incresed from nterior to posterior teeth nd from the cervicl line to the root pex in both the mxill nd the mndible (Tbles 1 nd 2). In the mxill, the interroot distnce ws gretest between the second premolr nd the first molr. The interroot distnce from the centrl incisor to the

3 ANATOMICAL RELATIONSHIPS BETWEEN DENTAL ROOTS 39 Figure 2. Sectioned specimens of the mndibulr rch from 1 mm (upper left) to 10 mm (lower right) below the cervicl line. first premolr ws greter on the buccl side thn on the pltl side but ws similr on both sides between the first nd second premolrs. The interroot distnce from the second premolr to the second molr ws greter on the pltl side thn on the buccl side. In the mxillry nterior teeth, the interroot distnce exceeded 3 mm from 7 mm bove the cervicl line on the buccl side nd 9 mm on the pltl side. In the mxillry posterior teeth, the interroot distnce exceeded 3 mm from 3 mm bove the cervicl line on the buccl side nd 2 mm on the pltl side (Tble 1). The roots of the first nd second molrs penetrted the mxillry sinus t 8 to 9 mm bove the cervicl line in 5 of 25 cses (20%). In the mndible, the interroot distnce ws gretest between the first nd second molrs. In contrst to the mxillry rch, interroot distnces from the centrl incisor to the cnine nd from the second premolr to the second molr were greter on the buccl side thn on the lingul side. However, the interroot distnce from the cnine to the second premolr ws similr on both sides. In the mndibulr nterior teeth, the interroot distnce exceeded 3 mm from 9 mm below the cervicl line on the buccl side. In contrst to the mxillry rch, the spect of the region of the mndibulr posterior teeth vried. The interroot distnce exceeded 3 mm from 3 mm below the cervicl line (between first nd second premolrs), 7 mm (between second premolr nd first molr), nd 2 mm (between first nd second molrs). In the region of the posterior teeth, the interroot distnce ws smllest between the second premolr nd the first molr (Tble 2). Buccolingul Bone Width The mxillry buccolingul bone width incresed from nterior to posterior teeth nd from the cervicl line to the root pex. The buccolingul bone width exceeded 8 mm from 5 mm bove the cervicl line (from centrl incisor to cnine), 3 mm (from cnine to first molr), nd 1 mm (between first nd second molrs). The buccolingul bone width exceeded 10 mm from 7 mm bove the cervicl line (between cnine nd first molr), 5 mm (between second premolr nd first mo-

4 40 HU, KANG, KIM, KIM, KIM molr). The buccolingul bone width exceeded 10 mm from 7 mm below the cervicl line (between second premolr nd first molr) nd 4 mm (between first nd second molrs). In generl, the mndibulr buccolingul bone width ws nrrower thn the mxillry bone width (Tble 3). Figure 3. Mesurements of sectioned specimen. 1 indictes buccl interroot distnce; 2, lingul interroot distnce; 3, buccolingul bone width; 4, buccl corticl bone thickness; 5, lingul corticl bone thickness; 6, buccl mucosl thickness; nd 7, lingul mucosl thickness. lr), nd 4 mm (between first nd second molrs) (Tble 3). The mndibulr buccolingul bone width lso incresed from nterior to posterior teeth. This bone width ws gretest t 5 mm below the cervicl line from the centrl incisor to the cnine, nd it incresed from the cervicl line to the root pex in other regions. The buccolingul bone width did not exceed 8 mm in the nterior teeth region, but it did exceed 8 mm from 5 mm below the cervicl line (from cnine to second premolr) nd 2 mm (from second premolr to second Corticl Bone Thickness The mxillry buccl corticl bone ws thicker in the posterior teeth region thn in the nterior teeth region, but the difference (0.2 mm) ws smll nd the thickness did not chnge from the cervicl line to the root pex. The mxillry pltl corticl bone thickness ws similr to buccl corticl bone thickness from the nterior to posterior teeth regions. However, it incresed by bout 0.5 mm from the cervicl line to the root pex (Tble 4). The mndibulr corticl bone thickness incresed from nterior to posterior teeth regions nd from the cervicl line to the root pex. The chnge in bone thickness ws greter in the posterior teeth region thn in the nterior teeth region. The mndibulr corticl bone ws thicker on the lingul side thn on the buccl side in the nterior teeth region, nd on the buccl side thn on the lingul side in the posterior teeth region (Tble 5). The corticl bone thickness ws similr in the mndibulr nd mxillry rches in the nterior teeth region, but it ws greter in the mndibulr rch in the posterior teeth region. DISCUSSION The form (endosseous dentl implnt, miniplte, or miniscrew) nd size of orthodontic implnts hve chnged considerbly since Roberts et l 1 first used n implnt for orthodontic nchorge in 1984; the mini- Tble 1. Interroot Distnce of the Mxillry Teeth (unit: mm) Distnce From Cervicl Line, mm Teeth b CI-LI B P LI-C B P C-FP B P FP-SP B P SP-FM B P FM-SM B P Interroot distnce is t lest 3.0 mm. b B indictes buccl; C, cnine; CI, centrl incisor; FM, first molr; FP, first premolr; LI, lterl incisor; P, pltl; SM, second molr; nd SP, second premolr.

5 ANATOMICAL RELATIONSHIPS BETWEEN DENTAL ROOTS 41 Tble 2. Interroot Distnce of the Mndibulr Teeth (unit: mm) Distnce From Cervicl Line, mm Teeth b CI-LI B L LI-C B L C-FP B L FP-SP B L SP-FM B L FM-SM B L Interroot distnce is t lest 3.0 mm. b B indictes buccl; C, cnine; CI, centrl incisor; FM, first molr; FP, first premolr; LI, lterl incisor; P, pltl; SM, second molr; nd SP, second premolr. Tble 3. Buccolingul Bone Width of the Mxill nd Mndible (unit: mm) Distnce From Cervicl Line, mm Teeth c CI-LI Mx Mn LI-C Mx Mn C-FP Mx b b 10.1 b Mn FP-SP Mx b Mn b SP-FM Mx b 10.7 b 10.8 b 10.8 b 11.1 b 11.9 b Mn b 10.7 b 11.1 b 11.5 b FM-SM Mx b 12.3 b 12.7 b 13.2 b 13.6 b 13.8 b 14.0 b Mn b 11.0 b 12.0 b 12.9 b 13.3 b 13.4 b 13.1 b Buccolingul bone width is between 8.0 mm nd 9.9 mm. b Buccolingul bone width is t lest 10.0 mm. c C, cnine; CI, centrl incisor; FM, first molr; FP, first premolr; LI, lterl incisor; Mn, mndibulr; Mx, mxillry; SM, second molr; nd SP, second premolr. screw type is now the most widely used becuse of its low cost nd ese of implnttion. Miniscrews typiclly hve dimeters rnging from 1.2 to 2 mm nd lengths of 6, 8, nd 10 mm. 15 For instlltion of the miniscrew without dmge to the periodontl tissue nd dentl root, minimum clernce of 1 mm of lveolr bone round the screw is needed. 16 When the dimeter of the miniscrew nd the minimum clernce of lveolr bone re considered, the miniscrew cn be instlled sfely if t lest 3 mm of spce is vilble in the interrdiculr spce. Mny studies hve mesured the interroot distnce with the use of declcified specimens, pnormic rdiogrphy, CT, nd micro-ct. 7,8,15 17 The tissue cn deform during the declcifiction process, pnormic rdiogrphic imge cn be distorted, nd the border between the lveolr bone nd the cementum of the root is not cler on CT imges. Micro-CT solves these problems, but it cnnot be used to exmine mucos or the entire mxill nd mndible. Therefore, the most ccurte method is to exmine norml specimens tht re cut directly from untreted tissue. Heins nd Wieder 17 mesured the smllest interroot distnce between the premolr nd the molr in declcified specimens. They reported tht the distnce between the second premolr nd the first molr ws smllest, prticulrly in the cervicl third nd the middle third (distnce of 2.03 mm) nd between the first nd second molrs in the middle third (distnce of 1.05 mm). In the present study, it ws found tht the inter-

6 42 HU, KANG, KIM, KIM, KIM Tble 4. Corticl Bone Thickness of the Mxill (unit: mm) Distnce From Cervicl Line, mm Teeth CI-LI B P LI-C B P C-FP B P FP-SP B P SP-FM B P FM-SM B P B indictes buccl; C, cnine; CI, centrl incisor; FM, first molr; FP, first premolr; LI, lterl incisor; P, pltl; SM, second molr; nd SP, second premolr. Tble 5. Corticl Bone Thickness of the Mndible (unit: mm) Distnce From Cervicl Line, mm Teeth CI-LI B L LI-C B L C-FP B L FP-SP B L SP-FM B L FM-SM B L B indictes buccl; C, cnine; CI, centrl incisor; FM, first molr; FP, first premolr; L, lingul; LI, lterl incisor; SM, second molr; nd SP, second premolr. Tble 6. Mucos Thickness of the Mxill (unit: mm) Distnce From Cervicl Line, mm Teeth CI-LI B P LI-C B P C-FP B P FP-SP B P SP-FM B P FM-SM B P B indictes buccl; C, cnine; CI, centrl incisor; FM, first molr; FP, first premolr; LI, lterl incisor; P, pltl; SM, second molr; nd SP, second premolr.

7 ANATOMICAL RELATIONSHIPS BETWEEN DENTAL ROOTS 43 Tble 7. Mucos Thickness of the Mndible (unit: mm) Distnce From Cervicl Line, mm Teeth CI-LI B L LI-C B L C-FP B L FP-SP B L SP-FM B L FM-SM B L B indictes buccl; C, cnine; CI, centrl incisor; FM, first molr; FP, first premolr; L, lingul; LI, lterl incisor; SM, second molr; nd SP, second premolr. Tble 8. Sum of the Mxillry Buccolingul Bone Thickness nd Mucos Thickness Where Miniscrew Insertion Is Possible (ie, possible length of the miniscrew) (unit: mm) Distnce From Cervicl Line, mm Teeth CI-LI B P LI-C B P C-FP B P FP-SP B P SP-FM B P FM-SM B P B indictes buccl; C, cnine; CI, centrl incisor; FM, first molr; FP, first premolr; LI, lterl incisor; P, pltl; SM, second molr; nd SP, second premolr. root distnce is greter between the second premolr nd the first molr thn between the first nd second molrs; however, these distnces were greter thn in the previous study. Also, this study differed from the previous study in tht the smllest distnce between the first nd second molrs occurred in the cervicl third. This difference is probbly due to deformtion of tissue during the declcifiction process. Moreover, the sme difference ws evident in the mndible. The interroot distnce for CT dt ws greter thn for the dt obtined in this study in the nterior teeth region, nd it ws smller in the posterior teeth region in both the mxill nd the mndible. On CT, the border between the lveolr bone nd the cementum of the root is uncler becuse of their similr densities; hence the interroot distnce vries with the threshold used in CT. The buccolingul bone width is not influenced by this effect, nd it did not differ gretly between the CT dt nd dt reported in this study. The micro-ct dt differed gretly from the dt obtined in this study, but this difference might be due to the smll number of smples (only five). Sfe Zone for Miniscrew Instlltion In the mxill, it ws possible to plce miniscrew t lest 7 nd 9 mm from the cervicl line on the buccl nd pltl sides of the nterior teeth, respectively. In the posterior teeth region, the possible insertion site ws less thn 2 mm from the cervicl line. However, the possible insertion site on the buccl side between the first nd second molrs ws from 8 mm bove the cervicl line. In the mxill, the sfest zone for plcement of miniscrews ws between the second premolr

8 44 HU, KANG, KIM, KIM, KIM Tble 9. Sum of the Mndibulr Buccolingul Bone Thickness nd Mucos Thickness Where Miniscrew Insertion Is Possible (ie, possible length of the miniscrew) (unit: mm) Distnce From Cervicl Line, mm Teeth CI-LI B 5.6 L 5.5 LI-C B L 7.9 C-FP B L FP-SP B L SP-FM B L FM-SM B L B indictes buccl; C, cnine; CI, centrl incisor; FM, first molr; FP, first premolr; L, lingul; LI, lterl incisor; SM, second molr; nd SP, second premolr. nd the first molr t lest 6 mm bove the cervicl line (Tble 1). However, if miniscrew is instlled t lest 8 mm bove the cervicl line, it should be confirmed rdiogrphiclly whether the mxillry root hs penetrted the mxillry sinus. Insertion of miniscrews in the mndibulr nterior teeth region ws possible less thn 10 mm from the cervicl line. The possible insertion site between the first nd second premolrs, between the second premolr nd the first molr, nd between the first nd second molrs ws less thn 3, 7, nd 2 mm from the cervicl line, respectively. In the mndible, the sfest zone for plcement of miniscrew ws between the first nd second molrs less thn 5 mm from the cervicl line (Tble 2). In both the mxill nd the mndible, the shortest distnce from the corticl bone to line perpendiculr to the interroot distnce ws greter on the lingul side thn on the buccl side, with this difference incresing from the cervicl line to the root pex. This phenomenon is due to (1) the loction of both teeth more on the buccl side thn on the lingul side, nd (2) the increse in width of the jw from the cervicl line to the root pex. Therefore, it is considered sfer to insert miniscrew on the lingul side thn on the buccl side. Stbility nd Length of the Miniscrew The stbility of miniscrew is determined by its length nd by the corticl bone thickness. When the corticl bone is thicker nd the miniscrew is longer, the stbility of the miniscrew is incresed. Therefore, the instlltion of long miniscrew in the thick corticl bone re ws profitble for the stbility of the miniscrew. The llowble length of miniscrew is influenced by the buccolingul width of the jw nd the mucosl thickness. The thickness of the mxillry buccl mucos nd of the mndibulr buccl nd lingul mucos ws constnt in ll regions, t bout 0.7 mm. However, the thickness of the mxillry pltl mucos ws 1 to 2 mm nd 3 to 4 mm in the cervicl nd picl regions, respectively; this llows for use of longer miniscrew (Tbles 6, 7). The length of the miniscrew is decided by the interroot distnce, the buccolingul bone width, nd the mucosl thickness. Also, the interroot bone must be t lest 4 mm thick to llow plcement of miniscrew. 8 In the mxillry buccl instlltion, the regions for which n 8 mm miniscrew is recommended re found between centrl incisor nd cnine (from 9 mm bove cervicl line), between first nd second premolrs (from 3 mm bove cervicl line), nd between second premolr nd first molr (from 3 mm to 4 mm bove cervicl line). The regions for which miniscrew of 10 mm is recommended re locted between cnine nd first premolr (from 7 mm bove cervicl line), between second premolr nd first molr (from 5 mm bove cervicl line), nd between first nd second molrs (from 8 mm bove cervicl line). However, in the cse of pltl instlltion, the miniscrew should be 2 mm longer thn tht used in buccl instlltion becuse of pltl mucos thickness (Tble 8). In the mndible, the regions for which 6 mm miniscrew is recommended re between lterl incisor nd cnine (10 mm below cervicl line) nd between first nd second premolrs (from 3 mm to 4 mm below cervicl line). The regions for which n 8 mm miniscrew is recommended re between cnine nd first premolr (from 9 mm below cervicl line), between first nd second premolrs (from 5 mm to 8 mm below cer-

9 ANATOMICAL RELATIONSHIPS BETWEEN DENTAL ROOTS vicl line), nd between first nd second molrs (from 2 mm to 3 mm below cervicl line). The regions for which 10 mm miniscrew is recommended re between first nd second premolrs (from 9 mm below cervicl line), between second premolr nd first molr (from 7 mm below cervicl line), nd between first nd second molrs (from 4 mm below cervicl line) (Tble 9). A miniscrew my be longer in the mxillry rch thn in the mndibulr rch, wheres the corticl bone is thicker in the mndible thn in the mxill on both buccl nd lingul sides (Tbles 4 nd 5). This mens tht the stbility of miniscrew will be greter for the mndible thn for the mxill becuse it is more ffected by bone thickness thn by the length of the miniscrew. Miniscrews cn be plced oblique to the long xis of the teeth so s to increse corticl bone contct nd llowble miniscrew length, lthough this requires creful considertion of the mxillry sinus nd the mndibulr cnl. 15 We believe tht further investigtion is required regrding the sfety nd strength of such oblique plcement of miniscrews in ech region. CONCLUSIONS The sfest zone for plcement of miniscrew is between second premolr nd first molr, from 6 to 8 mm bove the cervicl line in the mxill, nd between first nd second molrs, less thn 5 mm from the cervicl line in the mndible. In the mxillry, the regions for which miniscrew of 8 mm is recommended re buccl instlltion between centrl incisor nd cnine (from 9 mm bove cervicl line), between first nd second premolrs (from 3 mm bove cervicl line), nd between second premolr nd first molr (from 3 mm to 4 mm bove cervicl line). In the mndible, the regions for which miniscrew of 8 mm is recommended re between cnine nd first premolr (from 9 mm below cervicl line), between first nd second premolrs (from 5 mm to 8 mm below cervicl line), nd between first nd second molrs (from 2 mm to 3 mm below cervicl line). ACKNOWLEDGMENTS This study ws supported by the Yonsei University fund 2007 ( ). REFERENCES Roberts WE, Smith RK, Zilbermn Y, Mozsry PG, Smith RS. Osseous dpttion to continuous loding of rigid endosseous implnts. Am J Orthod. 1984;86: Shpiro PA, Kokich VG. Uses of implnts in orthodontics. Dent Clin North Am. 1988;32: Roberts WE, Mrshll KJ, Mozsry PG. Rigid endosseous implnt utilized s nchorge to protrct molrs nd close n trophic extrction site. Angle Orthod. 1990;60: Herrero DB. Implnts s nchorge in orthodontics: clinicl cse report. J Orl Implntol. 1998;24: Umemori M, Sugwr J, Mitni H, Ngsk H, Kwmur H. Skeletl nchorge system for open-bite correction. Am J Orthod Dentofcil Orthop. 1998;115: Kyung SH, Choi JH, Prk YC. Miniscrew nchorge used to protrct lower second molr into first molr extrction sites. J Clin Orthod. 2003;37: Ishii T, Nojim K, Nishii Y, Tkki T, Ymguchi H. Evlution of the implnttion position of mini-screws for orthodontic tretment in the mxillry molr re by micro CT. Bull Tokyo Dent Coll. 2004;45: Schnell MA, Beck FM, Jynes RM, Huj SS. A rdiogrphic evlution of the vilbility of bone for plcement of miniscrews. Angle Orthod. 2004;74: Kyung SH, Hong SG, Prk YC. Distliztion of mxillry molrs with midpltl miniscrew. J Clin Orthod. 2003;37: Be SM, Kyung HM. Mndibulr molr intrusion with miniscrew nchorge. J Clin Orthod. 2006;40: Jeon JM, Yu HS, Bik HS, Lee JS. En-mss distliztion with miniscrew nchorge in Clss II nonextrction tretment. J Clin Orthod. 2006;40: Xun C, Zeng X, Wng X. Microscrew nchorge in skeletl nterior open-bite tretment. Angle Orthod. 2007;77: Odmn J, Lekholm U, Jemt T, Thilnder B. Osseointegrted implnts s orthodontic nchorge in the tretment of prtilly edentulous dult ptients. Eur J Orthod. 1994;16: Klokkevold PR, Nishimur RD, Adchi M, Cputo A. Osseointegrtion enhnced by chemicl etching of the titnium surfce: torque removl study in the rbbit. Clin Orl Implnts Res. 1997;8: Deguchi T, Nsu M, Murkmi K, Ybuuchi T, Kmiok H, Ymmoto TT. Quntittive evlution of corticl bone thickness with computed tomogrphic scnning for orthodontic implnts. Am J Orthod Dentofcil Orthop. 2006;129: (e7 e e7 721.e12). 16. Poggio PM, Incorvti C, Velo S, Crno A. Sfe Zones : guide for miniscrew positioning in the mxillry nd mndibulr rch. Angle Orthod. 2006;76: Heins PJ, Wieder SM. A histologic study of the width nd nture of inter-rdiculr spces in humn dult pre-molrs nd molrs. J Dent Res. 1986;65: