Optimal sites for orthodontic mini-implant placement assessed by cone beam computed tomography

Transcription

1 Originl Article Optiml sites for orthodontic mini-implnt plcement ssessed by cone bem computed tomogrphy Mon Mohmed Slh Fyed ; Pwel Pzer b ; Christos Ktsros c ABSTRACT Objectives: To determine (1) the optiml sites for mini-implnt plcement in the mxill nd the mndible bsed on dimensionl mpping of the interrdiculr spces nd corticl bone thickness nd (2) The effect of ge nd sex on the studied ntomic mesurements. Mteril nd Methods: The cone bem computed tomogrphy imges of 100 ptients (46 mles, 54 femles) divided into two ge groups (13 18 yers), nd (19 27 yers) were used. The following interrdiculr mesurements were performed: (1) Buccolingul bone thickness; (2) Mesiodistl spces both bucclly nd pltlly/lingully; nd (3) Buccl nd pltl/lingul corticl thicknesses. Results: In the mxill, the highest buccolingul thickness existed between first nd second molrs; the highest mesiodistl buccl/pltl distnces were between the second premolr nd the first molr. The highest buccl corticl thickness ws between the first nd second premolrs. The highest pltl corticl thickness ws between centrl nd lterl incisors. In the mndible, the highest buccolingul nd buccl corticl thicknesses were between the first nd second molrs. The highest mesiodistl buccl distnce ws between the second premolr nd the first molr. The highest mesiodistl lingul distnce ws between the first nd second premolrs. The highest lingul corticl thickness ws between the cnine nd the first premolr. The mles nd the older ge group hd significntly higher buccolingul, buccl, nd pltl corticl thicknesses t specific sites nd levels in the mxill nd the mndible. Conclusions: A clinicl guideline for optiml sites for mini-implnt plcement is suggested. Sex nd ge ffected the ntomic mesurements in certin res in the mxill nd the mndible. (Angle Orthod. 2010;80: ) KEY WORDS: Optiml sites; Mini-implnts; Interrdiculr dimensions; Corticl thickness; CBCT INTRODUCTION Mini-implnts hve become very populr type of orthodontic skeletl nchorge, which is reflected in the esclting number of studies ddressing this Lecturer, Deprtment of Orthodontics, Fculty of Orl nd Dentl Medicine, Ciro University, Ciro, Egypt. Visiting resercher, Deprtment Of Orthodontics nd Dentofcil Orthopedics, University of Bern, Bern, Switzerlnd. b Instructor, Deprtment of Orthodontics nd Dentofcil Orthopedics, University of Bern, Bern, Switzerlnd. c Professor nd Deprtment Chir, Deprtment of Orthodontics nd Dentofcil Orthopedics. University of Bern, Bern, Switzerlnd. Corresponding uthor: Dr Mon Mohmed Slh Fyed, Deprtment of Orthodontics, Fculty of Orl nd Dentl Medicine, Ciro University, Sry elmnil street, Ciro, Egypt (e-mil: monsfyed@yhoo.com) Accepted: Mrch Submitted: December G 2010 by The EH Angle Eduction nd Reserch Foundtion, Inc. subject. However, there is still no consensus in these studies bout the fctors tht influence the success of mini-implnts. A recent systemtic review could not prove n ssocition between the type of mini-implnt, ptient chrcteristics, plcement site, surgicl technique, nd orthodontic nd implnt mintennce fctors nd the success rtes of mini-implnts. 1 The present study focused on only one of these fctors: implnt plcement site. The most common implnt sites pper to be the plte, the pltl spect of the mxillry lveolr process, the retromolr re in the mndible, nd the buccl corticl plte in both the mxill nd the mndible. 2 7 Among the importnt fctors tht should be considered when choosing mini-implnt plcement sites re soft-tissue ntomy, interrdiculr distnce, sinus morphology, nerve loction, buccolingul bone depth, nd buccl nd lingul corticl thicknesses. Severl studies provide mesurements of the interrdiculr spces t the posterior mxill nd DOI: /

2 940 FAYED, PAZERA, KATSAROS Figure 1. Mxillry nterior region. (A) Mesurement of the buccolingul thickness. (B) Mesurement of the mesiodistl buccl nd pltl distnces. (C) Mesurement of the buccl nd pltl corticl thicknesses. Figure 2. Mxillry posterior region. (A) Mesurement of the buccolingul thickness. (B) Mesurement of the mesiodistl buccl nd pltl distnces. (C) Mesurement of the buccl nd pltl corticl thicknesses. Figure 3. Mndibulr nterior region. (A) Mesurement of the buccolingul thickness. (B) Mesurement of the mesiodistl buccl nd lingul distnces. (C) Mesurement of the buccl nd lingul corticl thicknesses.

3 OPTIMAL SITES FOR MINI-IMPLANT PLACEMENT 941 Figure 4. Mndibulr posterior region. (A) Mesurement of the buccolingul thickness nd the mesiodistl buccl nd lingul distnces. (B) Mesurement of the buccl nd lingul corticl thicknesses. mndible. It ws reported tht the volume of bone in the mxillry interrdiculr spce between the second premolr nd the first molr provides the optiml ntomic site for miniscrews in the mxill Poggio et l. 11 rnked the sfest sites vilble in interrdiculr spces in the posterior mxill nd reported tht the sfest ws between the first molr nd the second premolr 2 8 mm from the lveolr crest; for the posterior mndible it ws between the first nd second molrs. Hrdly ny dt re vilble concerning the interrdiculr spces of the nterior mxillry nd mndibulr res in spite of the fct tht mini-implnts cn lso be useful in the nterior region s nchorge for mesil movement of the posterior dentition or correction of the nterior verticl occlusion. 4,6 A limited number of studies hve investigted corticl bone thickness in the mxill nd the mndible. Most of these studies hve been crried out on smll smple or were limited to the posterior prt of the jws. The buccl corticl bone thickness seems to be greter in Tble 1A. Mens nd Stndrd Devitions of Mesurements of the Right Side of the Mxill Right Side Site Men SD Men SD Men SD Men SD Men SD Men SD 2-mm cut BL MD-B MD-P BC PC mm cut BL MD-B MD-P BC PC mm cut BL MD-B MD-P BC PC SD indictes stndrd devition; BL, buccolingul thickness; MD-B, mesiodistl distnce from the buccl side; MD-P, mesiodistl distnce from the pltl side; BC, buccl corticl thickness; nd PC, pltl corticl thickness.

4 942 FAYED, PAZERA, KATSAROS Tble 1B. Mens nd Stndrd Devitions of Mesurements of the Left side of the Mxill 1-1 Left Side Site Men SD Men SD Men SD Men SD Men SD Men SD Men SD 2-mm cut BL MD-B MD-P BC PC mm cut BL MD-B MD-P BC PC mm cut BL MD-B MD-P BC PC SD indictes stndrd devition; BL, buccolingul thickness; MD-B, mesiodistl distnce from the buccl side; MD-P, mesiodistl distnce from the pltl side; BC, buccl corticl thickness; nd PC, pltl corticl thickness. the mndible thn in the mxill Bumgertel nd Hns 15 studied 30 dry skulls nd found tht the thickness of the buccl corticl bone increses with incresing distnce from the lveolr crest in the mndible nd in the mxillry nterior re. The influence of ge nd sex in success of miniimplnts remins controversil. It seems tht corticl bone is thinner in femles mesil to the mxillry first molr 16 However, severl rticles reported no ssocition between sex nd implnt success. 1 Motoyoshi et l. 17 showed less implnt success in dolescents when the implnts were loded erly, wheres the success rtes were similr to tht in dults fter 3-month ltent period. The purpose of the present investigtion ws to determine the optiml sites of mini-implnt plcement in the nterior nd posterior mxill nd mndible bsed on mpping of the dimensions of the interrdiculr spces nd corticl bone thickness using cone bem computed tomogrphy (CBCT). In ddition, we wnted to elucidte the effect of ge nd sex on the studied ntomic mesurements. MATERIALS AND METHODS The smple consisted of three-dimensionl (3D) imges of 100 ptients (46 mles nd 54 femles; men ge, 20 yers) in whom there were 66 mxille Tble 2A. Mens nd Stndrd Devitions of Mesurements of the Right Side of the Mndible Right Side Site Men SD Men SD Men SD Men SD Men SD Men SD 2-mm cut BL MD-B MD-L BC LC mm cut BL MD-B MD-L BC LC mm cut BL MD-B MD-L BC LC SD indictes stndrd devition; BL, buccolingul thickness; MD-B, mediodistl distnce from the Buccl side; MD-P, mesiodistl distnce from the pltl side; BC, Buccl corticl thickness; PC, pltl corticl thickness.

5 OPTIMAL SITES FOR MINI-IMPLANT PLACEMENT 943 Tble 2B. Mens nd Stndrd Devitions of Mesurements of the Left Side of the Mndible 1-1 Left Side Site Men SD Men SD Men SD Men SD Men SD Men SD Men SD 2-mm cut BL MD-B MD-L BC LC mm cut BL MD-B MD-L BC LC mm cut BL MD-B MD-L BC LC SD indictes stndrd devition; BL, buccolingul thickness; MD-B, mesiodistl distnce from the buccl side; MD-L, mesiodistl distnce from the lingul side; BC, buccl corticl thickness; nd LC, lingul corticl thickness. Tble 3. Comprison Between Mesurements of Mles nd Femles in the Anterior Mxillry Region (Student s t-test) Mesurement Site Group Men SD Men Stndrd t P vlue 2-mm cut BL Mle Femle * MD-B Mle Femle MD-P Mle Femle BC Mle Femle PC Mle Femle mm cut BL Mle Femle * MD-B Mle Femle MD-P Mle Femle BC Mle Femle PC Mle Femle mm cut BL Mle Femle MD-B Mle Femle MD-P Mle Femle BC Mle Femle PC Mle Femle SD indictes stndrd devition;, confidence intervl; BL, buccolingul thickness; MD-B, mesiodistl distnce from the buccl side; MD-P, mesiodistl distnce from the pltl side; BC, buccl corticl thickness; nd PC, pltl corticl thickness. * P,.05, significnt.

6 944 FAYED, PAZERA, KATSAROS Tble 4. Comprison Between Mesurements of Mles nd Femles in the Posterior Mxillry Region (Student s t-test) Mesurement Site Group Men SD Men Stndrd t P vlue 2-mm cut BL Mle Femle MD-B Mle Femle MD-P Mle Femle BC Mle Femle PC Mle Femle mm cut BL Mle Femle * MD-B Mle Femle MD-P Mle Femle BC Mle Femle * PC Mle Femle mm cut BL Mle Femle * MD-B Mle Femle MD-P Mle Femle BC Mle Femle * PC Mle Femle SD indictes stndrd devition;, confidence intervl; BL, buccolingul thickness; MD-B, mesiodistl distnce from the buccl side; MD-P, mesiodistl distnce from the pltl side; BC, buccl corticl thickness; nd PC, pltl corticl thickness. * P,.05, significnt. nd 34 mndibles divided into two ge groups (13 18 yers nd yers) selected from n lredy vilble lrger smple of imges t the Rdiology Unit, Clinic of Orl Surgery nd Stomtology, University of Bern, Switzerlnd. Ptient dt were treted ccording to the recommendtions of the declrtion of Helsinki. Imges were tken with the 3D Accuitomo (J Morit Mnufcturing Corp, Kyoto, Jpn). Of the 920 imges screened, 780 were rejected ccording to the following exclusion criteri: Overlpping of crowns or roots of djcent teeth Periodontl disese (determined from rdiogrphic signs of lveolr bone resorption) Severe ectopic eruption (ie, bucclly blocked out cnines) Missing teeth (excluding third molrs) Mixed dentition (in the first ge group) or incomplete crown eruption Blurred or uncler imges The 3D imges were generted by the 3DX Accuitomo XYZ Tomogrph nd I-Dexil softwre (Morit, Tokyo, Jpn). Orthogonl tomogrphic imges were constructed using the I-Dexil. After 2 months of trining nd tril mesurements with 15 cses, the investigtor mde ll the mesurements. Four weeks lter, the sme investigtor remesured 10 rndomly selected cses to test for introbserver relibility. To minimize mesurement errors produced from nonstndrdized hed postures, ll imges were oriented using stndrdized protocol in which the pltl plne ws ligned prllel to the horizontl xis supplied by the softwre, nd the nsl septum ws ligned prllel to the verticl xis. The slicing ngle would be djusted ccordingly. Mesurements For ech interrdiculr spce in the mxill nd the mndible, from the second molr on one side to the

7 OPTIMAL SITES FOR MINI-IMPLANT PLACEMENT 945 Tble 5. Comprison Between Mesurements of Mles nd Femles in the Anterior Mndibulr Region (Student s t-test) Mesurement Site Group Men SD Men Stndrd t P vlue 2-mm cut BL Mle Femle MD-B Mle Femle MD-L Mle Femle BC Mle Femle LC Mle Femle mm cut BL Mle Femle MD-B Mle Femle MD-L Mle Femle BC Mle Femle LC Mle Femle mm cut BL Mle Femle MD-B Mle Femle MD-L Mle Femle BC Mle Femle LC Mle Femle SD indictes stndrd devition;, confidence intervl; BL, buccolingul thickness; MD-B, mesiodistl distnce from the buccl side; MD-L, mesiodistl distnce from the lingul side; BC, buccl corticl thickness; nd LC, lingul corticl thickness. second molr on the opposite side, the following mesurements were done t three different depths from the cementoenmel junction, tht is, t 2 mm, 4 mm, nd 6 mm. Mesiodistl distnce: These mesurements were tken both bucclly nd pltlly/lingully t the widest distnce between ech two djcent teeth. Buccolingul thickness: The thickness ws mesured from the outermost point on the buccl side to the outermost point on the pltl/lingul side t the middle of the distnce between ech two djcent teeth. Corticl bone thickness: Bucclly nd lingully/ pltlly, the distnce between the internl nd externl spects of the cortex in the middle of the interrdiculr distnce between ech two djcent teeth ws mesured. For ech ptient bout 195 distnces were mesured. These distnces were mesured using the millimetric ruler provided by the I-Dexil (Figures 1 through 4). Sttisticl Anlysis Descriptive nlysis ws used to obtin the men nd stndrd devition (SD) of ll the studied mesurements. Student s t-test ws used to determine the introbserver relibility. To simplify the comprtive nlysis, the dt were divided into two regions: nterior (from cnine to cnine) nd posterior (from the first premolr to the second molr bilterlly). Student s t-test ws used for comprisons between sexes nd ge groups; P,.05 ws considered significnt, nd P,.01 ws considered highly significnt. RESULTS Introbserver Relibility There ws no significnt difference (P..05) between the repeted mesurements of the 10 ptients.

8 946 FAYED, PAZERA, KATSAROS Tble 6. Comprison Between Mesurements of Mles nd Femles in the Posterior Mndibulr Region (Student s t-test) Mesurement Site Group Men SD Men Stndrd t P vlue 2-mm cut BL Mle Femle * MD-B Mle Femle MD-L Mle Femle BC Mle Femle LC Mle Femle mm cut BL Mle Femle MD-B Mle Femle MD-L Mle Femle BC Mle Femle LC Mle Femle mm cut BL Mle Femle MD-B Mle Femle MD-L Mle Femle BC Mle Femle LC Mle Femle SD indictes stndrd devition;, confidence intervl; BL, buccolingul thickness; MD-B, mesiodistl distnce from the buccl side; MD-L, mesiodistl distnce from the lingul side; BC, buccl corticl thickness; nd LC, lingul corticl thickness. * P,.05, significnt. Interrdiculr Dimensions Mesured Interrdiculr dimensions re reported in Tbles 1 nd 2: (ll expressed in millimeters t the 2-mm, 4-mm, nd 6-mm levels from CEJ). Generlly, ll the dimensions mesured incresed upon moving piclly nd posteriorly except for the mesiodistl distnces between the first nd second molrs. In the Anterior Mxill The highest buccolingul thickness ws found between the right centrl nd lterl incisor t the 6- mm level ( ), which decresed the more cervicl the mesurements were tken. The lowest buccolingul thickness ws between the centrl incisors t the 2-mm nd 4-mm level. The highest mesiodistl distnce from the buccl side between the centrl incisors t the 6-mm level ws , nd the lowest ws between the left centrl nd lterl incisor. The highest mesiodistl distnce from the pltl side nd buccl corticl thickness ws between the lterl incisor nd cnine t the 6-mm level ( ), nd ( ), respectively. The gretest pltl corticl thickness ws t the 6-mm level between the centrl nd lterl incisor ( ) nd the lterl incisor nd cnine ( ) nd ws greter in the nterior region thn in the posterior region. In the Posterior Mxill The highest buccolingul thickness ws found t the 6-mm level between the first nd second molrs ( ). The highest mesiodistl distnces, both bucclly nd pltlly, were found between the second premolr nd the first molr ( nd , respectively). A certin pttern ws found in the thickness of the buccl cortex: t the 2-mm level, the thickness ws between first nd second molrs, but it incresed to t 4 mm nd then decresed to t 6 mm. The highest pltl corticl bone thickness ws found between the

9 OPTIMAL SITES FOR MINI-IMPLANT PLACEMENT 947 Tble 7. Comprison Between Mesurements of the Two Age Groups (13 18 Yers nd Yers) in the Anterior Mxillry Region (Student s t-test) Mesurement Site Group Men SD Men Stndrd t P vlue 2-mm cut BL y y MD-B y y MD-P y y BC y y PC y y * 4-mm cut BL y y MD-B y y MD-P y y BC y y PC y y mm cut BL y y MD-B y y MD-P y y BC y y * PC y y * SD indictes stndrd devition;, confidence intervl; BL, buccolingul thickness; MD-B, mesiodistl distnce from the buccl side; MD-P, mesiodistl distnce from the pltl side; BC, buccl corticl thickness; nd PC, pltl corticl thickness. * P,.05, significnt. cnine nd the first premolr t the 6-mm level ( ). In the Anterior Mndible The highest buccolingul thickness, mesiodistl distnces lbilly nd lingully, nd corticl thicknesses both lbilly nd lingully were found between the lterl incisor nd cnine t the 6-mm level ( , , , , nd , respectively). The lowest mesured dimensions were found between the centrl incisors. In the Posterior Mndible The highest buccolingul thickness nd buccl corticl thickness were between the first nd second molrs ( , , respectively). The highest mesiodistl distnce from the buccl side ws found between the second premolr nd the first molr ( ), nd the highest mesiodistl distnce from the lingul side ws between the first nd second premolrs ( ). The thickest lingul cortex ws found between the cnine nd the first premolr ( ). Comprison Between Sexes Comprison between sexes ws significnt t P,.05 (Tbles 3 through 6). In the Mxill Anteriorly, mles hd significntly higher buccolingul thickness t the 2-mm nd 4-mm level from the CEJ. Posteriorly, mles hd significntly higher buccolingul nd buccl corticl thickness t the 4- mm nd 6-mm level from the CEJ. In the Mndible Anteriorly, there ws no significnt difference between sexes. Posteriorly, mles hd significntly

10 948 FAYED, PAZERA, KATSAROS Tble 8. Comprison Between Mesurements of the Two Age Groups (13 18 Yers nd Yers) in the Posterior Mxillry Region (Student s t-test) Mesurement Site Group Men SD Men Stndrd t P vlue 2-mm cut BL y y MD-B y y MD-P y y * BC y y PC y y mm cut BL y y MD-B y y MD-P y y BC y y ** PC y y ** 6-mm cut BL y y MD-B y y MD-P y y BC y y ** PC y y * SD indictes stndrd devition;, confidence intervl; BL, buccolingul thickness; MD-B, mesiodistl distnce from the buccl side; MD-P, mesiodistl distnce from the pltl side; BC, buccl corticl thickness; nd PC, pltl corticl thickness. * P,.05, significnt. ** P,.01, highly significnt. higher buccolingul thickness thn femles t the 2- mm level from CEJ. Comprison Between Age Groups Comprison between the two ge groups (13 18 yers) nd (19 27 yers) for ll the mesurements ws significnt t P,.05 nd highly significnt t P,.001 (Tbles 7 through 10). In the Mxill Anteriorly, the group ged yers hd significntly thicker pltl cortex t the 2-mm level from the CEJ nd higher buccl nd pltl corticl thicknesses t 6 mm. Posteriorly, the group ged yers hd significntly higher mesiodistl pltl distnce t the 2-mm level t the CEJ nd thicker buccl nd pltl cortex with highly significnt difference t the 4-mm nd 6-mm level from the CEJ. In the Mndible Anteriorly, there ws no significnt difference between the two groups. Posteriorly, the group ged yers hd significntly thicker lingul cortex t the 2-mm level from the CEJ. DISCUSSION Mny fctors could ffect the success rtes nd effectiveness of mini-implnts used for estblishing skeletl orthodontic nchorge. Some of these fctors re implnt relted (type, dimeter, nd length of the implnt), ptient relted (sex, ge, physicl sttus), surgicl relted (direction of mini-implnt plcement nd plcement torque), orthodontic relted (mgnitude nd timing of force), loction relted (peri-implnt bone quntity, corticl bone thickness, kertinized versus orl mucos), nd implnt-mintennce relted. 1 The exct role of these fctors, however, is not fully understood. 1 The present study investigted the

11 OPTIMAL SITES FOR MINI-IMPLANT PLACEMENT 949 Tble 9. Comprison Between Mesurements of the Two Age Groups (13 18 Yers nd Yers) in the Anterior Mndibulr Region (Student s t-test) Mesurement Site Group Men SD Men Stndrd t P vlue 2-mm cut BL y y MD-B y y MD-P y y BC y y LC y y mm cut BL y y MD-B y y MD-P y y BC y y LC y y mm cut BL y y MD-B y y MD-P y y BC y y LC y y SD indictes stndrd devition;, confidence intervl; BL, buccolingul thickness; MD-B, mesiodistl distnce from the buccl side; MD-L, mesiodistl distnce from the lingul side; BC, buccl corticl thickness; nd LC, lingul corticl thickness. ntomic dt gthered from 100 CBCT imges to determine the optiml sites for mini-implnt plcement by studying two elements tht re relted to the miniimplnt loction fctor: interrdiculr bone dimensions nd corticl bone thickness. Three-dimensionl mesurements of the interrdiculr spces t 3 verticl levels (2 mm, 4 mm, nd 6 mm) from the CEJ were performed. Introbserver relibility ws estblished for the mesurement method of this study. The vilbility of reltively lrge number of CBCT imges for this study llowed the reserchers to overcome the shortcoming of limited smple size in severl previous studies. 11,12,18 Most studies on this topic hve imed to determine the sfest sites for mini-screw plcement by focusing on the posterior region of the jws The fct, however, tht mini-implnts re often useful in the nterior region for spce closure 4 or correction of overbite problems 6 necessitted the evlution of the nterior region s well. To fulfill this objective in the present study, dt on interrdiculr distnces nd corticl bone thicknesses were provided for ll the teeth, both nteriorly nd posteriorly, to provide the clinicin with comprehensive ntomic mp of the mxill nd the mndible. In this study the CEJ ws selected s the strting point for the mesurements, unlike other studies 11,19 tht used the lveolr crest, which could be ffected by different periodontl problems. As it is dvisble to plce the mini-implnts in res of ttched gingivl, 20 the mximum level of mesurement in this study ws selected to be 6 mm from CEJ. Lim et l. 21 excluded levels higher thn 6 mm in their study on interrdiculr soft tissue for the sme reson. The results of this study showed consistent increse in the buccolingul thickness nd the mesiodistl distnces both bucclly nd pltlly/ lingully in most of the studied sites in the mxill nd the mndible when moving piclly nd posteriorly. One exception ws the mesiodistl buccl distnce between the mxillry first nd second molrs. The mens of the different mesurements in

12 950 FAYED, PAZERA, KATSAROS Tble 10. Comprison Between Mesurements of the Two Age Groups (13 18 Yers nd Yers) in the Posterior Mndibulr Region (Student s t-test) Mesurement Site Group Men SD Men Stndrd t P vlue 2-mm cut BL y y MD-B y y MD-L y y BC y y LC y y * 4-mm cut BL y y MD-B y y MD-L y y BC y y LC y y mm cut BL y y MD-B y y MD-L y y BC y y LC y y SD indictes stndrd devition;, confidence intervl; BL, buccolingul thickness; MD-B, mesiodistl distnce from the buccl side; MD-L, mesiodistl distnce from the lingul side; BC, buccl corticl thickness; nd LC, lingul corticl thickness. * P,.05, significnt. this study were found to be in greement with those obtined in other similr studies. 8,11,12,18 Limited dt re vilble in the literture describing the buccl corticl thickness. The results of this study showed tht in the mxill the buccl corticl thickness hd certin pttern: the thickness incresed s the cuts moved piclly from the CEJ to the 4-mm level, nd then they decresed gin t the 6-mm level. This is in greement with the study by Bumgertel nd Hns 15 on dry skulls. In the mndible, the thickness incresed grdully in the picl direction; the highest ws between the first nd second molr, nd the lowest ws between the centrl incisors. Monnert et l. 19 reported the lowest thickness between the lterl incisor nd cnine. Lingul nd pltl corticl bone thicknesses showed grdul increse s the cuts moved piclly. Bsed on the findings of the present study, the optiml site for mini-implnt plcement in the nterior mxill is the interrdiculr spce between the centrl nd lterl incisors nd between the lterl incisor nd cnine in the nterior mndible. These sites hd the highest buccolingul nd corticl thicknesses nd mesiodistl distnce. In the posterior region of the mxill nd the mndible the most suitble sites re between the second premolr nd the first molr nd between the first nd second molrs, which ws lso recommended in previous studies. 8,12,18 In the present study, mles hd significntly thicker buccolingul dimension nd buccl corticl thickness thn femles in both the mxill nd the mndible. Kim et l. 22 found no sttisticl difference between sexes in the interrdiculr mesurements of the posterior mxill, probbly becuse of the smll smple size (35 ptients). In the mxill, the older ge group (19 27 yers) hd significntly higher buccl nd pltl corticl thickness both nteriorly nd posteriorly. In the mndible, the older ge group hd significntly thicker lingul cortex. In the study by Swsty et l., 13 the ge group of yers hd significntly higher buccl corticl thickness in the mndible. In the present study more significnt differences were found between the sexes nd ge groups in the mxill thn in the

13 OPTIMAL SITES FOR MINI-IMPLANT PLACEMENT 951 mndible, which could be due to the difference in smple size. Thus, it would be expected tht miniimplnts plced in mles nd in those older thn 18 yers to hve higher success rtes becuse of the higher interrdiculr dimensions nd thicker corticl bone thickness, especilly in the mxill. CONCLUSIONS N The optiml site for mini-implnt plcement in the nterior region is between the centrl nd lterl incisors in the mxill nd between the lterl incisor nd the cnine in the mndible t the 6-mm level from the CEJ. At the buccl spect of the posterior region of both jws, the optiml sites re between the second premolr nd the first molr nd between the first nd second molrs. Pltlly, the optiml site is between the first nd second premolrs s it hs the dvntge of the highest corticl thickness. The more picl the site, the sfer the plcement. N The mles nd the ge group older thn 18 yers hd significntly higher buccolingul, pltl, nd buccl corticl thickness t specific levels nd sites in the mxill nd the mndible. ACKNOWLEDGMENT The uthors would like to thnk Dr. M. Bornstein, Hed of Rdiology Unit, Clinic of Orl Surgery nd Stomtology, University of Bern, Switzerlnd, for providing us with the ccess to the CBCT imges used in this study. REFERENCES 1. Reynders R, Ronchi L, Bipt S. Mini-implnts in orthodontics: systemtic review of the literture. Am J Orthod Dentofcil Orthop. 2009;135:564.e1 564.e Prk HS, Kwon OW, Sung JH. Nonextrction tretment of n open bite with micro screw nchorge. Am J Orthod Dentofcil Orthop. 2006;130: Roth A, Yildirim M, Diedrich P. Forced eruption with microscrew nchorge for preprosthetic leveling of the gingivl mrgin. J Orofc Orthop. 2004;65: Prk YC, Choi YJ, Choi NC, Lee JS. Esthetic segmentl retrction of mxillry nterior teeth with pltl pplince nd orthodontic mini-implnts. Am J Orthod Dentofcil Orthop. 2007;131: Knomi R. Mini-implnt for orthodontic nchorge. Am J Orthod Dentofcil Orthop. 1997;31: Xun C, Zeng X, Wng X. Microscrew nchorge in skeletl nterior open-bite tretment. Angle Orthod. 2007;77: Prk HS, Lee SK, Kwon OW. Group distl movement of teeth using microscrew implnt nchorge. Angle Orthod. 2005;75: Crno A, Velo A, Incorvti I, Poggio P. Clinicl ppliction of the mini-screw-nchorge-system (M.A.S.) in the mxillry lveolr bone. Prog Orthod. 2004;5: Crno A, Melsen B. Implnts in orthodontics. Prog Orthod. 2005;6: Prk HS. An ntomic study using CT imges for the implnttion of micro-implnts. Koren J Orthod. 2002;32: Poggio PM, Incorvti C, Velo S, Crno A. Sfe zones : guide for miniscrew positioning in the mxillry nd mndibulr rch. Angle Orthod. 2006;76: Deguchi T, Nsu M, Murkmi K, Ybuuchi T, Kmiok H, Tkno-Ymmoto T. Quntittive evlution of corticl bone thickness with computed tomogrphic scnning for orthodontic implnts. Am J Orthod Dentofcil Orthop. 2006;129:721.e7 721.e Swsty D, Lee JS, Hung JC, Mki K, Gnsky SA, Htcher D, Miller AJ. Anthropometric nlysis of the humn mndibulr corticl bone s ssessed by cone-bem computed tomogrphy. J Orl Mxillofc Surg. 2009;67: Prk J, Cho HJ. Three-dimensionl evlution of interrdiculr spces nd corticl bone thickness for plcement nd initil stbility for microimplnts in dults. Am J Orthod Dentofcil Orthop. 2009;136:314.e1 314.e Bumgertel S, Hns B. Buccl corticl bone thickness for mini-implnt plcement. Am J Orthod Dentofcil Orthop. 2009;136: Ono A, Motoyoshi M, Shimizu N. Corticl bone thickness in the buccl posterior region for orthodontic mini-implnts. Int J Orl Mxillofc Surg. 2008;37: Motoyoshi M, Mtsuok M, Shimizu N. Appliction of orthodontic mini-implnts in dolescents. Int J Orl Mxillofc Surg. 2007;36: Hu KS, Kng MK, Kim TW, Kim KH, Kim HJ. Reltionships between dentl roots nd surrounding tissues for orthodontic miniscrew instlltion. Angle Orthod. 2009;79: Monnert C, Restle L, Much JN. Tomogrphic mpping of mndibulr interrdiculr spces for plcement of orthodontic mini-implnts. Am J Orthod Dentofcil Orthop. 2009; 135:428.e1 428.e Melsen B. Mini-implnts: where re we? J Clin Orthod. 2005;39: Lim WH, Lee SK, Wikesjö UM, Chun YS. A descriptive tissue evlution t mxillry interrdiculr sites: implictions for orthodontic implnt plcement. Clin Ant. 2007;20: Kim SH, Yoon HG, Cho YS, Hwng EH, Kook YA, Nelson G. Evlution of interdentl spce of the mxillry posterior re for orthodontic mini-implnts with cone-bem computed tomogrphy. Am J Orthod Dentofcil Orthop. 2009;135: