Bone and cortical bone thickness of mandibular buccal shelf for mini-screw insertion in adults

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1 Originl Article Bone nd corticl bone thickness of mndibulr buccl shelf for mini-screw insertion in dults Riccrdo Nucer ; Antonino Lo Giudice b ; Angel Mire Bellocchio b ; Pol Spinuzz b ; Alberto Cprioglio c ; Letizi Perillo d ; Giovnni Mtrese e ; Gincrlo Cordsco f ABSTRACT Objective: To nlyze the buccl bone thickness, bone depth, nd corticl bone depth of the mndibulr buccl shelf (MBS) to determine the most suitble sites of the MBS for mini-screw insertion. Mterils nd Methods: The smple included cone-bem computed tomogrphic (CBCT) records of 30 dult subjects (men ge yers) evluted retrospectively. All CBCT exmintions were performed with the i-cat CBCT scnner. Ech exm ws converted into DICOM formt nd processed with OsiriX Medicl Imging softwre. Proper view sections of the MBS were obtined for quntittive nd qulittive evlution of bone chrcteristics. Results: Mesil nd distl second molr root scn sections showed enough buccl bone for miniscrew insertion. The evlution of bone depth ws performed t 4 nd 6 mm bucclly to the cementoenmel junction. The mesil root of the mndibulr second molr t 4 nd 6 mm showed verge bone depths of mm nd mm, respectively. The distl root of the mndibulr second molr showed verge bone depths of mm nd 16.5 mm, respectively. All sites showed corticl bone depth thickness greter thn 2 mm. Conclusions: Specific sites of the MBS offer enough bone quntity nd dequte bone qulity for mini-screw insertion. The insertion site with the optiml ntomic chrcteristics is the buccl bone corresponding to the distl root of second molr, with screw insertion 4 mm buccl to the cementoenmel junction. Considering the corticl bone thickness of optiml insertion sites, predrilling is lwys recommended in order to void high insertion torque. (Angle Orthod. 2017;87: ) KEY WORDS: Mndibulr buccl shelf; Mini-screw; Mini-implnts; Skeletl nchorge; Extrlveolr orthodontic nchorge; Temporry nchorge devices Assistnt Professor, Deprtment of Biomedicl nd Dentl Sciences nd Morphofunctionl Imging, Section of Orthodontics, School of Dentistry, University of Messin, Messin, Itly. b Reserch Assistnt, Deprtment of Biomedicl nd Dentl Sciences nd Morphofunctionl Imging, Section of Orthodontics, School of Dentistry, University of Messin, Messin, Itly. c Associte Professor, Hed of Orthodontic Unit nd Chir of the Orthodontic Postgrdute Progrm, Deprtment of Surgicl nd Morphologicl Sciences, Section of Orthodontics, School of Medicine, University of Insubri, Vrese, Itly. d Associte Professor, Hed of Orthodontic Unit nd Chir of the Orthodontic Postgrdute Progrm, Multidisciplinry Deprtment of Medicl-Surgicl nd Dentl Specilties, Second University of Nples, Nples, Itly. e Associte Professor, Deprtment of Biomedicl nd Dentl Sciences nd Morphofunctionl Imging, Section of Orthodontics, School of Dentistry, University of Messin, Messin, Itly. f Full Professor nd Chir, Deprtment of Biomedicl nd Dentl Sciences nd Morphofunctionl Imging, Section of Orthodontics, School of Dentistry, University of Messin, Messin, Itly. INTRODUCTION Orthodontic mini-screws hve ttined widespred use recently, providing skeletl nchorge to improve orthodontic mechnics. 1 3 Mini-screws hve demonstrted good ptient cceptnce 4 nd reltively low filure rtes, reported t round 13.5%. 5,6 Primry stbility is key fctor for successful mini-screw plcement. 7 Antomicl fctors ffecting the stbility of mini-screws re bone chrcteristics (bone density, Corresponding uthor: Dr Riccrdo Nucer, c/o AOU Policlinico G. Mrtino, UOC di Odontoitri e Odontostomtologi, Vi Consolre Vleri 1, Messin, Itly (e-mil: riccrdo.nucer@gmil.com) Accepted: April Submitted: Jnury Published Online: June 09, 2017 Ó 2017 by The EH Angle Eduction nd Reserch Foundtion, Inc. DOI: /

2 746 NUCERA, LO GIUDICE, BELLOCCHIO, SPINUZZA, CAPRIOGLIO, PERILLO, MATARESE, CORDASCO bone depth, corticl bone thickness), soft tissue chrcteristics (mucos vs ttched gingiv, tissue thickness, mobility nd proximity to the frenum), nd the proximity of specific ntomicl structures (roots, nerves, vessels, sinus/nsl cvities). Different sites hve been used for mini-screw insertion: pltl bone, 7,8 the pltl side of the mxillry lveolr process, 9 the mndibulr retromolr re, 10 the infrzygomtic crest, 11 the mxillry nd mndibulr bucco lveolr corticl plte, 12 nd the posterior pltl lveolr process. 7 Recently, the mndibulr buccl shelf (MBS) hs been proposed 13 s suitble extr-lveolr mini-screw insertion site. The MBS is locted bilterlly in the posterior prt of the mndibulr body, buccl to the roots of the first nd second molrs nd nterior to the oblique line of the mndibulr rmus. To dte, no quntittive nd qulittive bone ssessment of the MBS hs been performed for miniscrew insertion. The im of this study ws to nlyze the buccl bone thickness, bone depth, nd corticl bone depth of the MBS to determine the most suitble sites of the MBS for mini-screw insertion. MATERIALS AND METHODS The smple of this retrospective study included cone-bem computed tomogrphic (CBCT) records of 30 subjects (men ge yers), including 15 mles (men ge yers) nd 15 femles ( yers) selected from the digitl rchive of privte prctice. The CBCT exms were performed between June 2012 to November 2015 nd were preselected if the exmined subjects fulfilled the following selection criteri: Cucsin subjects, ged between 20 nd 41 yers, with n bsence of periodontl disese, no metllic restortions in the first or second permnent mndibulr premolrs nd molrs, no missing teeth except for third molrs, no genetic syndromes or crniofcil dysmorphism, no history of fcil trum, nd no previous orthognthic surgery tretment. Seventy-six ptients fulfilled the selection criteri (35 mle nd 41 femle). The ptients were divided ccording to sex, nd ech of the two smples ws ordered by ge from the youngest to the oldest ptient. These two lists of ptients were used to ssign number to ech ptient from 1 to 35 for the mle list nd from 1 to 41 for the femle list. A rndom sequence genertor ( ws used to generte two lists of rndomized numbers of 35 nd 41 numbers, respectively. The first 15 numbers of both rndom lists were selected nd the corresponding CBCT exms were included in the study. According to this method, blnced block rndomiztion bsed on ptients sex ws pplied to select the included CBCT exms. The protocol of this study ws pproved by the humn reserch ethicl committee (Approvl No. 102/16). All CBCT exmintions were performed with the i-cat CBCT scnner (Imging Sciences Interntionl, Htfield, P) fter setting the cquisition prmeters s follows: 120 kv, 5 ma, nd 4- to 6-second exposure time. Ech exm ws converted to digitl imging nd communictions in medicine (DICOM) formt. DICOM files were processed using the OsiriX Medicl Imging 32-bit softwre (Pixmeo, Genev, Switzerlnd; www. osirix-viewer.com). The following procedure ws used to obtin proper view sections of the MBS for quntittive nd qulittive evlution of bone chrcteristics. Three preliminry reference lines were considered, s shown by the softwre interfce, corresponding to the three conventionl scn plnes (sgittl: yellow line; xil: violet line; nd coronl: blue line). These view scn plnes were reoriented ccording to the following method: the furction point of the right nd left first molr nd the furction point of the right second molr were identified nd the xil view scn plne ws reoriented in order to pss through these three furction points. In this reoriented xil scn plne, two points were identified t the center of the dentolveolr process t the level of the mesil root of the mndibulr first molr nd the distl root of the second molr. These points were used s references to reorientte the sgittl view scn plne section in order to identify the mesio-distl direction of the mndibulr lveolr process in the molr segment. Finlly, the coronl view scn plne ws reoriented in order to best fit the direction of the two-thirds coronl long xes of these four roots (Figure 1): mesil nd distl first molr roots, mesil nd distl second molr roots. This procedure identified four coronl view sections used to investigte the MBS bone chrcteristics. It ws repeted for both the right nd left sides. A modified version of the method reported in previous publictions 14,15 ws performed to identify specific prmeters evluting bone quntity nd qulity on ech coronl view section. This methodology included the following steps: Identifiction of the vestibulr cementoenmel junction (CEJ) on ech scn view root section; Evlution of the buccl totl bone thickness on two horizontl reference lines locted piclly t 6 mm (TotThick-t-6) nd 11 mm (TotTick-t-11) from the CEJ (Figure 2); nd Apico-coronl totl bone depth (corticl þ medullry bone) nd corticl coronl bone depth were mesured on two verticl reference lines bucclly locted

3 BONE THICKNESS OF MANDIBULAR BUCCAL SHELF 747 Figure 1. Softwre interfce; reoriented reference scn lines (sgittl: yellow line; xil: violet line; nd coronl: blue line) in order to best fit the direction of the long xes of the mesil root of the second left mndibulr molr. t 4 mm (TotDepth-t-4 nd CortDepth-t-4) nd 6 mm (TotDepth-t-6 nd CortDepth-t-6) from the CEJ (Figure 3). The corticl bone depth ws mesured considering only the coronl corticl plte becuse it ws ssumed tht only the corticl bone plte intercts with the miniscrew during mini-screw insertion. A set of eight mesurements ws tken for ech scn root plne ssessing the totl nd corticl bone depth in n picl direction (t 4 nd 6 mm from the CEJ bucclly) nd bone thickness in buccl direction (t 6 nd 11 mm from the CEJ piclly). All mesurements were tken by the sme expert opertor (AMB). Sttistics A preliminry nlysis ws run on 10 subjects to obtin dt for power nlysis evlution. The MBS bone thicknesses mesured on horizontl reference line piclly locted t 6 mm from CEJ (TotThick-t-6) of the mesil nd distl roots of the right second molr were compred, nd the difference in mens of 1.81 mm nd the stndrd devition (SD) of 2.47 mm were used s outcomes to perform the power nlysis clcultion. The results of the power nlysis indicted Figure 2. The bucco-lingul thicknesses of totl bone (corticl þ medullry bone) nd corticl bone were mesured on two horizontl reference lines piclly locted t 6 mm (TotThick-t-6) nd 11 mm from the CEJ (TotTick-t-11).

4 748 NUCERA, LO GIUDICE, BELLOCCHIO, SPINUZZA, CAPRIOGLIO, PERILLO, MATARESE, CORDASCO Tble 1. Descriptive Sttistics of Totl Buccl Bone Thickness Vlues of Different Root Sites Mesured on Two Horizontl Reference Lines t 6 mm Apicl to the Cementoenmel Junction (CEJ) (TotThick-t-6) nd 11 mm picl to the CEJ (TotTick-t-11). Dt Considered Suitble for Mini-Screw Insertion Are Lbeled with the Light Gry Color; the Dt Considered s Nonsuitble Are Lbeled with the Drk Gry Color Figure 3. The pico-coronl bone depth thicknesses of totl bone (corticl þ medullry bone) nd coronl corticl bone were mesured on two verticl reference lines bucclly locted t 4 mm (TotDeptht4 nd CortDepth-t-4) nd 6 mm (TotDepth-t6 nd CortDepth-t- 6) from the CEJ. tht in order to rech 80% of power it ws necessry to nlyze smple of 30 subjects. Preliminry dt nlysis of ll smples suggested norml distribution (Shpiro-Wilk test) nd equlity of vrinces (Levene s test). Descriptive sttistics were performed reporting men, SD, mximum nd minimum vlues for ech prmeter nd for ll root scn sections. The descriptive sttistics were used to perform preliminry evlution of the potentilly suitble sites for mini-screw insertion. The insertion sites were considered suitble if they presented minimum horizontl bone thickness of 5 mm (1.7 mm of root sfety distnce, 1.6 mm of screw dimeter, 1.7 mm of corticl buccl bone sfety distnce) nd minimum verge verticl bone thickness of 6 mm (which represents the minimum stndrd mini-screw length). The potentilly suitble sites were compred using inferentil sttistics to detect significnt bone thickness differences. Unpired t-tests were used to compre dt derived from different root scn sections. Pired t-tests were used to compre dt obtined from the sme scn root sections t different verticl loctions from the CEJ. In order to ssess the methodologicl error, view section identifiction nd mesurement of prmeters were repeted for 10 rndomly selected ptients 1 week prt. Pired t-tests nd intrclss correltion coefficients (ICCs) were used to ssess the intropertor relibility. The mgnitude of the rndom error ws ssessed using the Dhlberg formul. No differences (P,.05) were found between the two redings; First column bbrevitions: R1M-m indictes right first molr mesil root; L1M-m, left first molr mesil root; R1M-d, right first molr distl root; L1M-d, left first molr distl root; R2M-m, right second molr mesil root; L2M-m, left second molr mesil root; R2M-d, right second molr distl root; nd L2M-d, left second molr distl root. ll mesurements were highly relible, with the ICC vrying from 0.76 to Rndom error rnged from 0.5 to 0.9 mm. SPSS Sttistics softwre (version 17.0; IBM Corportion, Armonk, NY) ws used for ll sttisticl nlyses. The significnce levels for ll tests were set t P,.05. RESULTS Descriptive sttistics re reported in Tble 1 for totl bone thickness. Tbles 2 nd 3 report descriptive sttistics for totl bone depth nd corticl bone depth, respectively. In Tbles 1 nd 2, the dt cells reporting Tble 2. Descriptive Sttistics of Totl Bone Depth Vlues of Different Root Sites Mesured on Two Verticl Reference Lines t 4 mm Buccl to the Cementoenmel Junction (CEJ) (Tot-Depth-t-4) nd 6 mm buccl to the CEJ (TotDepth-t-6). Dt Considered Suitble for Mini-Screw Insertion Are Lbeled with the Light Gry Color; the Dt Considered s Nonsuitble Are Lbeled with the Drk Gry Color. The Abbrevitions in the First Column Are Explined in the Tble 1 Footnote

5 BONE THICKNESS OF MANDIBULAR BUCCAL SHELF 749 Tble 3. Descriptive Sttistics of Corticl Coronl Thickness Vlues of Different Root Sites Mesured on Two Verticl Reference Lines t 4 (CortDepth-t-4) nd 6 mm (CortDepth-t-6) buccl to the Cementoenmel Junction. The Abbrevitions in the First Column Are Explined in the Tble 1 Footnote CortDepth-t-4 CortDepth-t-6 Evluted Root Sites Men SD Min b Mx c Men SD Min b Mx c R1M-m L1M-m R1M-d L1M-d R2M-m L2M-m R2M-d L2M-d SD indictes stndrd devition; b Min, minimum; nd c Mx, mximum. Vs indictes versus. vlues considered suitble for mini-screw insertion re lbeled with the light gry color, nd dt considered nonsuitble re lbeled with the drk gry color. Tble 4 reports the results of the inferentil sttistics. DISCUSSION To the best of our knowledge, this is the first study in the literture tht investigtes the ntomic skeletl chrcteristics of the MBS for mini-screw insertion. The MBS potentilly offers some clinicl dvntges compred to dento-lveolr interrdiculr mini-screw insertion sites. The MBS extends bucclly with considerble mount of bone, nd this extension llows clinicins to insert mini-screws in n orienttion prllel to the long xes of the molr roots. 13 This insertion modlity could offer clinicl dvntges by voiding possible screw-to-root contct during nteriorposterior dentl movements long the dento-lveolr process. Another dvntge could be reduced risk of screw-to-root contct during insertion, considering tht screw-to-root contct is one of the most frequent cuses of filure. 16 This chrcteristic could help to explin the observtions by Chng et l., 13 who reported lower filure rtes compred to those ssocited with mndibulr interrdiculr mini-screw insertion. In order to properly insert mini-screw in the MBS, n understnding of the ntomicl bone chrcteristics of this insertion site is essentil. Upon preliminry evlution, minimum cutoff vlue of the buccl extension of the MBS for sfe mini-screw insertion ws considered to be 5 mm of buccl bone thickness (1.7 mm of root sfety distnce, 1.6 mm of screw dimeter, 1.7 mm of corticl buccl bone sfety distnce). Descriptive sttisticl dt showed tht the totl buccl bone thickness increses in the distl nd in the picl portions of the MBS. The mount of buccl bone thickness ws evluted t two different verticl levels: 6 nd 11 mm picl to the CEJ. Distl root of the second molr scn sections, on both the right nd left sides, were the only sections tht showed n verge of more thn 5 mm of totl buccl bone thickness 6 mm picl to the CEJ (Tble 1). Both the mesil nd distl second molr root scn sections on both sides (right nd left) showed enough buccl bone for mini-screw insertion t 11 mm picl to the CEJ. Significnt differences (P,.05) in buccl bone thickness were found between mesurements t 6 nd 11 mm (Tble 4). Inferentil sttistics lso reveled tht the distl root of the second molr site Tble 4. Inferentil Sttistics of Buccl Bone Thickness Dt of Right nd Left Second Molr. The Abbrevitions in the First Column Are Explined in the Tble 1 Footnote Right Second Molr Left Second Molr Evluted Root Sites R2M-m R2M-d L2M-m L2M-d TotThick-t (62.53) Vs** 5.57 (62.42) 4.25 (62.38) Vs** 5.63 (62.44) Vs* Vs* Vs* Vs* TotThick-t (62.02) Vs** 7.88 (61.71) 7.04 (61.65) Vs** 7.71 (61.69) TotDepth-t (63.64) Vs (NS) 8.81 (64.41) 8.44 (63.47) Vs (NS) 8.19 (62.8) Vs (NS) Vs (NS) Vs (NS) Vs (NS) TotDepth-t (66.33) Vs (NS) (67.44) 9.44 (65.96) Vs (NS) 9.34 (65.63) TotCort-t (64.86) Vs (NS) 6.07 (65.32) 5.45 (63.77) Vs (NS) 4.94 (63.35) Vs (NS) Vs (*) Vs (NS) Vs (NS) TotCort-t (66.6) Vs (NS) (68.08) 7.45 (66.68) Vs (NS) 6.99 (66.31) NS indictes not significnt. ** Significnt difference with P,.05 (unpired t-test); * Significnt difference with P,.05 (pired t-test).

6 750 NUCERA, LO GIUDICE, BELLOCCHIO, SPINUZZA, CAPRIOGLIO, PERILLO, MATARESE, CORDASCO showed significntly thicker bone compred to the mesil root of the second molr on both the left nd right sides (P,.05), signifying the region of the distl root of the second molr s sfer zone for insertion, compred to the mesil root (Tble 4). Other thn the chrcteristic of horizontl bone thickness, evlution of the corono-picl (verticl) bone depth dimension of the MBS is lso importnt in order to select the proper screw length. Dt showed tht the sites of the MBS with dequte bone depth on verge re t the mesil nd distl roots of the second molr. Evlution of the verticl bone depth dimension of the MBS ws performed t 4 nd 6 mm buccl to the CEJ (Tble 2). The mesil root of the mndibulr second molr showed verge bone depth dimensions of nd mm t 4 nd 6 mm buccl to the CEJ, respectively. The distl root of the mndibulr second molr showed verge verticl bone depth dimensions of nd 16.5 mm, respectively. These dt indicte tht the insertion sites evluted offer the opportunity to insert ny screw length commercilly vilble. The verge mount of bone depth dimension ws greter t 4 mm buccl to the CEJ compred to 6 mm buccl (Tble 2). However, no significnt differences were found compring bone depths between the 4- nd 6-mm insertion sites or between the mesil nd distl insertion sites of the second molrs (Tble 4). Only the bone depth difference mesured between the 4- nd 6-mm sites buccl to the distl right second molr ws found to be sttisticlly significnt (Tble 4); however, this difference would be cliniclly irrelevnt, considering the gret mount of vilble verticl bone depth t these loctions. The high stndrd devition of verticl bone dimensions t 6 mm buccl to the CEJ (TotDepth-t-6) of the mesil nd distl root scns of the mndibulr second molrs indictes the high ntomic vribility of the MBS. Minimum vlues t 6 mm buccl to the CEJ (Tble 2) were zero for ll the considered prmeters, indicting the presence of t lest one subject with reduced buccl extension of the MBS. The vribility of the MBS observed in this study emphsizes the importnce of preliminry clinicl evlution of potentil insertion sites on n individul bsis. Evlution of corticl bone thickness before miniscrew insertion is pproprite since pre-drilling my be indicted in order to improve primry stbility nd to void excessive insertion torque nd screw filure Corticl bone depth ws mesured (Tble 3) in order to evlute the necessity for pre-drilling in the MBS. All sites evluted displyed corticl bone thicknesses tht were greter thn 2 mm, with verge vlues t the distl root of the second molr of 5.5 mm mesured 4 mm lterl to the CEJ nd 8.72 mm mesured 6 mm Figure 4. Occlusl drwing of left mndibulr buccl shelf. A miniscrew representtion ws plced corresponding to the insertion site with the optiml ntomic chrcteristics. It is the zone of MBS djcent to the distl root of the second molr nd 4 mm buccl to the CEJ. lterl to the CEJ (Tble 3). These dt indicte tht pre-drilling is lwys recommended before mini-screw insertion in the buccl shelf in order to void excessive insertion torque. 16 One limittion of this study is tht it evluted only the bony ntomicl chrcteristics of possible MBS insertion sites. Evlution of the MBS periodontl soft tissue chrcteristics ws beyond the purpose of this study. However, in order to select the proper miniscrew insertion site, soft tissue should be considered, becuse mobility of the lveolr mucos cn ffect long-term mini-screw stbility. Moreover, this study evluted only Cucsins, nd the bony chrcteristics of the MBS could be different in other ethnic groups. Further studies re necessry to evlute MBS chrcteristics in different ethnic groups. However, the results of this study showed tht specific sites of the MBS (specificlly the distl root of the second molr) present gret mounts of bone tht my be dequte even when considering possible ethnic vritions. CONCLUSIONS Specific sites of the MBS offer enough bone quntity nd dequte bone qulity for mini-screw insertion. The insertion site of the MBS with the optiml ntomic chrcteristics is the buccl bone lterl to the distl root of the second molr, with screw insertion locted 4 mm buccl to the CEJ (Figure 4). For prticulr biomechnicl needs, it is possible to consider n insertion site lterl to the mesil root of

7 BONE THICKNESS OF MANDIBULAR BUCCAL SHELF 751 the second molr, but insertion will likely need to be more picl to ttin dequte buccl bone thickness. Becuse of ntomicl vrition mong individuls, potentil insertion sites should lwys be evluted on n individul bsis. Considering the corticl bone thickness of optiml insertion sites of the MBS, pre-drilling is lwys recommended in order to void high insertion torque. REFERENCES 1. Ppdopoulos MA, Trwneh F. The use of miniscrew implnts for temporry skeletl nchorge in orthodontics: comprehensive review. Orl Surg Orl Med Orl Pthol Orl Rdiol Endod. 2007;103:e6 e Nienkemper M, Puls A, Ludwig B, Wilmes B, Drescher D. Multifunctionl use of pltl mini-implnts. J Clin Orthod. 2012;46: Chndhoke TK, Nnd R, Uribe FA. Clinicl pplictions of predictble force systems, prt 2: miniscrew nchorge. J Clin Orthod. 2015;49: Zwwi KH. Acceptnce of orthodontic miniscrews s temporry nchorge devices. Pt Pref Adher. 2014;8: Ppgeorgiou SN, Zogkis IP, Ppdopoulos MA. Filure rtes nd ssocited risk fctors of orthodontic miniscrew implnts: met-nlysis. Am J Orthod Dentofcil Orthop. 2012;142: Ppdopoulos MA, Ppgeorgiou SN, Zogkis IP. Clinicl effectiveness of orthodontic miniscrew implnts: metnlysis. J Dent Res. 2011;90: Bumgertel S. Corticl bone thickness nd bone depth of the posterior pltl lveolr process for mini-implnt insertion in dults. Am J Orthod Dentofcil Orthop. 2011;140: Grcco A, Lombrdo L, Cozzni M, Sicilini G. Quntittive cone-bem computed tomogrphy evlution of pltl bone thickness for orthodontic miniscrew plcement. Am J Orthod Dentofcil Orthop. 2008;134: Poggio PM, Incorvti C, Velo S, Crno A. Sfe zones : guide for miniscrew positioning in the mxillry nd mndibulr rch. Angle Orthod. 2006;76: Poletti L, Silver AA, Ghislnzoni LT. Dentolveolr Clss III tretment using retromolr miniscrew nchorge. Prog Orthod. 2013;14: Bumgertel S, Hns MG. Assessment of infrzygomtic bone depth for mini-screw insertion. Clin Orl Implnts Res. 2009;20: Bumgertel S, Hns MG. Buccl corticl bone thickness for mini-implnt plcement. Am J Orthod Dentofcil Orthop. 2009;136: Chng C, Liu SS, Roberts WE. Primry filure rte for 1680 extr-lveolr mndibulr buccl shelf mini-screws plced in movble mucos or ttched gingiv. Angle Orthod. 2015;85: Brunetto M, Andrini Jd S, Ribeiro GL, Locks A, Corre M, Corre LR. Three-dimensionl ssessment of buccl lveolr bone fter rpid nd slow mxillry expnsion: clinicl tril study. Am J Orthod Dentofcil Orthop. 2013;143: Mrtin R, Cioffi I, Frell M, et l. Trnsverse chnges determined by rpid nd slow mxillry expnsion lowdose CT-bsed rndomized controlled tril. Orthod Crniofc Res. 2012;15: Kurod S, Ymd K, Deguchi T, Hshimoto T, Kyung HM, Tkno-Ymmoto T. Root proximity is mjor fctor for screw filure in orthodontic nchorge. Am J Orthod Dentofcil Orthop. 2007;131:S68 S Bumgertel S. Predrilling of the implnt site: is it necessry for orthodontic mini-implnts? Am J Orthod Dentofcil Orthop. 2010;137: Motoyoshi M, Yoshid T, Ono A, Shimizu N. Effect of corticl bone thickness nd implnt plcement torque on stbility of orthodontic mini-implnts. Int J Orl Mxillofc Implnts. 2007;22: Mrquezn M, Mttos CT, Snt Ann EF, de Souz MM, Mi LC. Does corticl thickness influence the primry stbility of miniscrews?: systemtic review nd metnlysis. Angle Orthod. 2014;84: Suzuki EY, Suzuki B. Plcement nd removl torque vlues of orthodontic miniscrew implnts. Am J Orthod Dentofcil Orthop. 2011;139: Wilmes B, Drescher D. Impct of insertion depth nd predrilling dimeter on primry stbility of orthodontic miniimplnts. Angle Orthod. 2009;79: Lim SA, Ch JY, Hwng CJ. Insertion torque of orthodontic miniscrews ccording to chnges in shpe, dimeter nd length. Angle Orthod. 2008;78: Heidemnn W, Gerlch KL, Grobel KH, Kollner HG. Influence of different pilot hole sizes on torque mesurements nd pullout nlysis of osteosynthesis screws. J Crniomxillofc Surg. 1998;26:50 55.