露龈笑患者上颌前牙区牙槽骨形态的研究

目的 通过锥形束CT(cone-beam computed tomography,CBCT)扫描测量露龈笑患者上颌前牙区牙槽骨,探讨露龈笑患者的牙槽骨解剖特征,为微种植钉的植入提供参考.方法 选取63例临床表现露龈笑的成年患者,CBCT扫描并三维重建.在距离牙槽嵴顶4 mm、6 mm、8 mm高度的3个层面上分别测量上颌前牙区相邻两牙根间的近远中向、唇腭向骨质厚度及唇侧皮质骨厚度.结果 在相邻两牙之间,近远中向牙根间的距离随测量高度的增加逐渐增加(P<0.05).中切牙与侧切牙间的牙根间距离最小(P<0.05).两中切牙间唇腭向根间骨厚度最薄(P<0.05).中切牙与侧切牙间、侧切牙与尖牙间的根间骨厚度差异无统计学意义(P>0.05).在相邻两牙之间,唇侧根间皮质骨厚度随测量高度增加而增加(P<0.05).两中切牙根间唇侧骨皮质最薄(P<0.05),侧切牙与尖牙间骨皮质厚度最厚(P<0.05).结论 牙根间近远中向骨厚度、唇腭向骨厚度和唇侧皮质骨厚度随高度增加而增加,且在侧切牙与尖牙间最厚.尖牙与侧切牙间的骨质区域可以考虑作为植入微种植钉的部位.     

基于CBCT的下颌第一磨牙区即刻种植相关的影像学研究

目的利用CBCT研究下颌第一磨牙区即刻种植适宜的植入位点、植入角度与植入深度,为术前数字化设计和临床操作提供参考依据。方法选取100例符合纳入标准的患者CBCT影像学资料,测量下颌第一磨牙区的牙槽骨厚度、颊侧及舌侧骨板厚度、牙根间隔宽度,同时测量下颌第一磨牙与下颌神经管及舌侧骨倒凹的关系,并进行统计学分析。结果由近中至远中,下颌第一磨牙的牙槽骨厚度及颊侧骨板厚度逐渐增大,舌侧骨板厚度逐渐减小;由牙槽嵴顶至根尖,牙根间隔宽度逐渐增大,最大为(5.00±1.42)mm;近中根、远中根、远舌根、牙根间隔顶至下颌神经管的距离分别为(7.47±2.38)mm、(7.19±2.49)mm、(9.59±1.94)mm、(15.90±2.39)mm;由近中至远中,下颌神经管颊侧及舌侧骨板最大厚度分别为(6.54±1.25)mm、(2.53±0.84)mm;下颌舌侧骨倒凹角度为(149.67±8.30)°,倒凹深度为(1.51±0.43)mm。结论在下颌第一磨牙区即刻种植前可通过CBCT规划合适的种植路径,注意避开下颌神经管和舌侧骨倒凹。若根尖至下颌神经管的安全距离足够,可从牙根间隔处植入,若安全距离不足,植入位点可偏近中舌侧,植入角度可适当舌倾。     

锥形束CT对微螺钉植入后牙安全区域的分析

目的通过锥形束CT（CBCT）测量上下颌后牙区不同高度牙槽骨近远中向及颊舌（腭）向的骨量,分析微螺钉种植体植入的安全区域。方法选取30例CBCT扫描的成人影像资料为研究对象,对颌骨进行扫描重建,从第前磨牙远中开始向后,在每个牙根间区域（包括上颌结节）距离牙槽嵴顶2、4、6、8、10 mm处,分别测量颊舌（腭）向宽度和近远中宽度。采用SPSS 16.0软件进行单因素方差分析和LSD法比较。结果1）上颌后牙区近远中骨量在同一高度不同位置间均存在统计学差异（P<0.05）,最大近远中骨量位于第二前磨牙和第一磨牙腭侧根间;颊腭向骨量在不同位置、高度间均有统计学差异（P<0.05）,最大颊腭向骨量位于第一磨牙和第二磨牙之间。2）下颌后牙区近远中骨量在不同位置、高度间均有统计学差异（P<0.05）,颊舌向骨量在同一位置不同高度间均存在统计学差异（P<0.05）,最大近远中骨量和最大颊舌向骨量均位于第一磨牙和第二磨牙之间。结论经CBCT获取了上下颌骨后牙段植入微螺钉种植体的安全区域,为后续临床应用提供了有价值的参考。     

Comparison of transverse analysis between posteroanterior cephalogram and cone-beam computed tomography

Objectives:To evaluate maxillary and mandibular alveolar and basal bone widths using cone-beam computed tomography (CBCT) and to verify the correlation between CBCT images and posteroanterior (PA) cephalograms.Materials and Methods:The CBCT scans and PA cephalograms were obtained from 20 men (age range  =  24.0–29.1 years; mean age  =  27.2 years; SD  =  2.8 years) and 20 women (age range  =  20.3–28.1 years; mean age  =  26.4 years; SD  =  3.2 years) with normal occlusion. On CBCT images, maxillary and mandibular bone widths were measured at three posterior sites and five bone levels. The differences between maxillary and mandibular bone widths were calculated and compared with conventional transverse width of PA cephalograms.Results:Statistically significant differences in maxillary and mandibular bone widths were detected at different levels and sites. Bone widths were significantly increased from the alveolar crest toward the basal bone in the maxillary molar and mandibular second premolar and molar areas. A statistically significant correlation was only found between CBCT images and PA cephalograms for maxillomandibular width at the first molar area.Conclusion:The results of this study suggested that three-dimensional assessment of maxillomandibular width is mandatory for the transverse analysis.     

跨下牙槽神经种植相关解剖结构的影像学测量及分析研究

目的 通过锥形束CT影像数据测量下颌第二磨牙处下颌神经管位置,分析跨下牙槽神经种植术的理论植入范围,为临床上使用该方法解决下颌后牙区种植骨量不足问题提供理论依据。方法 选取80例下颌第二磨牙缺失且缺牙区垂直骨高度<9 mm的患者CBCT图像,测量该处下颌神经管到颊侧骨皮质、舌侧骨皮质、牙槽嵴顶距离,并模拟跨下牙槽神经种植,测量种植体颊舌向倾斜的角度范围。结果 下颌第二磨牙处下颌神经管到颊侧骨皮质、舌侧骨皮质、牙槽嵴顶的距离分别是(6.913±1.222)、(2.859±0.891)、(7.991±0.783)mm,下颌神经管到颊侧骨皮质距离明显大于到舌侧骨皮质距离。75%的患者可行跨下牙槽神经种植术,模拟植入种植体颊舌向倾斜最小角度为19.360°±7.086°,最大角度为39.462°±6.924°。结论 下颌第二磨牙处下颌神经管明显偏向舌侧,保障了颊侧足够的骨量,多数下颌第二磨牙处无法垂直植入短种植体的患者仍可通过跨下牙槽神经种植术植入常规长度种植体。     

Buccolingual inclination of first molars in untreated adults: A CBCT study

Objective:To evaluate the buccolingual inclinations of maxillary and mandibular first molars in untreated adults.Materials and Methods:Fifty-nine subjects (14 males and 45 females; mean age, 41.2 years) with no missing teeth, no crossbite, and minimal crowding were included. For each subject, a CBCT was taken. The long axis of each first molar was determined, and the inclination of each molar was measured using the long axis and the floor.Results:One hundred seventeen out of 118 mandibular first molars measured had a lingual inclination, with a mean of 12.59° ± 5.47°. For the maxillary first molars, 107 out of 118 had a buccal inclination, with a mean of 4.85° ± 4.22°.Conclusions:There is a curvature to the inclinations of first molars in untreated adults, where the maxillary molars have a slight buccal inclination and mandibular molars have a slight lingual inclination.     

Accuracy of orthodontic miniscrew implantation guided by stereolithographic surgical stent based on cone-beam CT–derived 3D images

Objective:To develop surgical stents for cone-beam computed tomography (CBCT) 3-dimensional (3D) image-based stent-guided orthodontic miniscrew implantation and to evaluate its accuracy.Materials and Methods:Ten surgical stents were fabricated with stereolithographic appliances (SLAs) according to 3D CBCT image-based virtual implantation plans. Thirty self-drilling miniscrews were implanted at two to three positions on each side of the maxillary or mandibular posterior arches in three phantoms: 20 guided by 10 surgical stents in two phantoms (stent group) and 10 guided freehand in one phantom (freehand group). Six parameters (mesiodistal and vertical deviations at the corona and apex and mesiodistal and vertical angular deviations) were measured to compare variations between the groups.Results:No root damage was found in the stent group, whereas four of 10 miniscrews contacted with roots in the freehand group. In the stent group, deviations in the mesiodistal and vertical directions were 0.15 ± 0.09 and 0.19 ± 0.19 mm at the corona, respectively, and 0.28 ± 0.23 and 0.33 ± 0.25 mm at the apex, respectively; angular deviations in the mesiodistal and vertical directions were 1.47° ± 0.92° and 2.13° ± 1.48°, respectively. In the freehand group, the corresponding results were 0.48 ± 0.46 mm and 0.94 ± 0.87 mm (corona), 0.81 ± 0.61 mm and 0.78 ± 0.49 mm (apex), and 7.49° ± 6.09° and 6.31° ± 3.82°. Significant differences were found in all six parameters between the two groups (Student''s t-test, P < .05).Conclusions:3D CBCT image-based SLA-fabricated surgical stents can provide a safe and accurate method for miniscrew implantation.     

下颌颊棚区微螺钉解剖学植入区域位点锥形束CT测量分析

目的: 应用锥形束CT(CBCT)测量分析下颌颊棚区适合微螺钉解剖学植入的区域位点,为临床上安全植入微螺钉提供指导。方法: 收集2018年1月—2018年10月新疆喀什地区第一人民医院口腔科诊治的62例行正畸治疗患者的CBCT影像资料,对CBCT图像进行三维重建,分别测量在第一前磨牙和第二前磨牙间(A)、第二前磨牙和第一磨牙间(B)、第一磨牙和第二磨牙间(C)的牙槽嵴顶下方3 mm(D1)、6 mm(D2)、9 mm(D3)断层骨宽度。比较不同性别、左右两侧、不同位置骨宽度的差异。采用SPSS 22.0软件包对数据进行统计学分析。结果: 下颌颊棚区不同位置骨宽度在男、女之间,左右两侧之间均无统计学差异(P>0.05)。下颌颊棚区同一位置不同距离、同一距离不同位置骨宽度差异显著(P<0.05),第一磨牙和第二磨牙间距牙槽嵴顶9 mm处骨宽度最大,为(10.62±1.38)mm,第二前磨牙和第一磨牙间距牙槽嵴顶3 mm处骨宽度最小,为(2.65±0.38)mm。结论: 下颌颊棚区骨宽度在性别、左右两侧无显著差异,但下颌颊棚区不同解剖位点差异较大,自近中向远中有增加趋势。     

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

Objective:To analyze the buccal bone thickness, bone depth, and cortical bone depth of the mandibular buccal shelf (MBS) to determine the most suitable sites of the MBS for mini-screw insertion.Materials and Methods:The sample included cone-beam computed tomographic (CBCT) records of 30 adult subjects (mean age 30.9 ± 7.0 years) evaluated retrospectively. All CBCT examinations were performed with the i-CAT CBCT scanner. Each exam was converted into DICOM format and processed with OsiriX Medical Imaging software. Proper view sections of the MBS were obtained for quantitative and qualitative evaluation of bone characteristics.Results:Mesial and distal second molar root scan sections showed enough buccal bone for mini-screw insertion. The evaluation of bone depth was performed at 4 and 6 mm buccally to the cementoenamel junction. The mesial root of the mandibular second molar at 4 and 6 mm showed average bone depths of 18.51 mm and 14.14 mm, respectively. The distal root of the mandibular second molar showed average bone depths of 19.91 mm and 16.5 mm, respectively. All sites showed cortical bone depth thickness greater than 2 mm.Conclusions:Specific sites of the MBS offer enough bone quantity and adequate bone quality for mini-screw insertion. The insertion site with the optimal anatomic characteristics is the buccal bone corresponding to the distal root of second molar, with screw insertion 4 mm buccal to the cementoenamel junction. Considering the cortical bone thickness of optimal insertion sites, pre-drilling is always recommended in order to avoid high insertion torque.     

不同矢状骨面型后牙微种植体植入安全区研究

目的:CBCT探究不同矢状骨面型后牙区植入微种植体的安全区域特征.方法:纳入骨性Ⅰ、Ⅱ、Ⅲ类患者各20名的CBCT数据,运用InVivo 5.0软件重建,选择上下颌第一前磨牙远中至第二磨牙近中区域,分别测量距牙槽嵴顶2、4、6、8、10mm处的近远中向宽度,采用SPSS 19.0对测量结果进行统计学分析.结果:上颌距牙槽嵴高度4～8mm,下颌距牙槽嵴高度超过4 mm根尖间隔区域是安全适宜的微种植体植入部位.上颌第一前磨牙和第二前磨牙根间骨量在骨性Ⅰ、Ⅱ类组＞骨性Ⅲ类组(P＜0.05),其它测量部位各组间无统计学差异.下颌后牙区各根间骨量多数表现为骨性Ⅲ类组＞骨性Ⅰ、Ⅱ类组(P＜0.05).结论:上颌距牙槽嵴高度4～8 mm的第二前磨牙和第一磨牙间,下颌距牙槽嵴高度超过4 mm的第一和第二磨牙间的根尖间隔区域是相对安全的植入部位,不同骨面型存在一定差异.     

Root proximity of miniscrews at a variety of maxillary and mandibular buccal sites: Reliability of panoramic radiography

Objectives:To assess the root proximity and the insertion angles of miniscrews after miniscrew placement at a variety of maxillary and mandibular buccal sites using cone-beam computed tomography (CBCT) and to determine the differences in root proximity between CBCT and panoramic radiography (PR).Materials and Methods:This retrospective study included 50 patients (mean age, 22.0 ± 4.5 years) who underwent postoperative CBCT and PR after miniscrew placements for intermaxillary fixation in orthognathic surgery. Twelve miniscrews were placed in the buccal bone of each patient: at sites between the central incisor and lateral incisor (SII), sites between the canine and first premolar (SCP), and sites between the second premolar and first molar (SPM) on the right and left sides of the mandible and maxilla. The insertion angles were measured on CBCT, and the root proximity was assessed on CBCT and PR.Results:The mean vertical placement angles ranged from 84.27° to 95.12°, and the mean horizontal placement angles ranged from 90.93° to 101.1°. The rates of no contact between the root and the miniscrew were 68.0% in the SII, 50.5% in the SCP, and 57.8% in the SPM, which were significantly different (P = .000). The total concordance rate between PR and CBCT was 41.3%.Conclusions:Clinicians should use extreme caution during placement of miniscrews in the SCP. There are limitations on the use of PR for evaluating the root proximity of miniscrews.     

CBCT assessment of alveolar buccal bone level after RME

Objective:To evaluate the maxillary alveolar buccal bone levels after expansion with banded and bonded expanders, using cone-beam computed tomography (CBCT).Materials and Methods:The population sample consisted of 22 patients who required expansion during their comprehensive treatment; 10 patients (five males and five females) with a mean age of 13.5 years (CVMS 3) had bonded hygienic expanders, and 12 (six males and six females) with a mean age of 12.6 years (CVMS 3) had banded hyrax expanders. CBCT was taken both before (T1) and 6 months after last activation (T2). Measurements were made for buccal bone thickness (BT), buccal marginal bone level (MBL), and bone thickness level (BTL) at the right first molar (M_Rt), left first molar (M_Lft), right first premolar (PM_Rt), and left first premolar (PM_Lft). A mixed-design analysis of variance assessed differences between and within the groups. Post hoc t-tests were completed on significant analysis of variance results to determine where differences occurred.Results:Analysis of variance revealed no significant differences between or within the two groups. BT significantly decreased horizontally following rapid maxillary expansion. The amount of bone lost was −0.59 mm M_Rt, −0.72 mm PM_Rt, −0.50 mm M_Lft, and −0.57 mm PM_Lft (P < .003).Conclusions:There was no significant difference between or within the two groups. Buccal bone loss in the vertical dimension (MBL) only showed significance in the banded group for M_Rt (0.63 mm) and PM_LFt (0.37 mm) as evidenced by the paired t-test (P < .05).     

Transfer accuracy of vinyl polysiloxane trays for indirect bonding

Objective:To elicit the magnitude, directional bias, and frequency of bracket positioning errors caused by the transfer of brackets from a dental cast to the patient’s dentition in a clinical setting.Materials and Methods:A total of 136 brackets were evaluated. The brackets were placed on dental casts and scanned using cone beam computed tomography (CBCT) to capture 3-D positioning data. The brackets were then transferred to the patient’s dentition with an indirect bonding method using vinyl polysiloxane (VPS) trays and later scanned using CBCT to capture the final bracket positioning on the teeth. Virtual models were constructed from the two sets of scan data and digitally superimposed utilizing best-fit, surface-based registration. Individual bracket positioning differences were quantified using customized software. One-tailed t tests were used to determine whether bracket positioning was within limits of 0.5 mm in the mesiodistal, buccolingual, and vertical dimensions, and 2° for torque, tip, and rotation.Results:Individual bracket positioning differences were not statistically significant, indicating, in general, final bracket positions within the selected limits. Transfer accuracy was lowest for torque (80.15%) and highest for mesiodistal and buccolingual bracket placement (both 98.53%). There was a modest directional bias toward the buccal and gingival.Conclusion:Indirect bonding using VPS trays transfers the planned bracket position from the dental cast to the patient’s dentition with generally high positional accuracy.     

基于CBCT的下颌后牙区骨内重要解剖结构研究

目的利用锥形束CT（cone beam computed tomography,CBCT）软件分析系统NNTViewer对活体下颌骨三维影像重建测量,研究下颌神经管与邻近解剖结构之间的关系。方法选取100例CBCT影像资料,在下颌骨横截面上测量：①下颌第一前磨牙至同侧第二磨牙各牙牙根中点、根尖与颊舌侧骨壁的距离;②下颌神经管与每个后牙根尖之间及与之相对应的颊舌侧骨壁、牙槽嵴顶和下颌骨下缘的距离。结果下颌第一前磨牙至同侧第二磨牙各牙牙根与颊、舌侧骨壁之间的距离,在牙根中点处分别为1．26—5．02mm、3．74～4．45mm,在根尖处分别为3．85—9．23mm、5．43—7．94mm;下颌第二前磨牙至同侧第二磨牙各牙根尖与下颌神经管之间的距离为5．31～8．19mm。下颌第二前磨牙至同侧第二磨牙各牙根尖下方处的下颌神经管与颊、舌侧骨壁之间的距离分别为3．71～7．62mm、2．91～4．12mm,与牙槽嵴顶之间的距离为17．09-19．22mm,与下颌骨下缘之间的距离为8．22～9．28mm。结论下颌后牙（下颌第三磨牙除外）牙根及下颌神经管与颊侧骨壁之间的距离由前往后逐渐变大。下颌神经管距离第二磨牙远中根最近,距离第一磨牙两根最远;与牙槽嵴顶的距离,在第一磨牙处最大,第二磨牙处最小;与下颌骨下缘的距离,在第二磨牙处最大,第一磨牙近中根处最小。     

Transfer accuracy of 3D-printed trays for indirect bonding of orthodontic brackets:: A clinical study

ObjectivesTo evaluate the transfer accuracy of 3D-printed indirect bonding trays constructed using a fully digital workflow in vivo.Materials and MethodsTwenty-three consecutive patients had their incisors, canines, and premolars bonded using fully digitally designed and 3D-printed transfer trays. Intraoral scans were taken to capture final bracket positioning on teeth after bonding. Digital models of postbonding scans were superimposed on those of corresponding virtual bracket setups, and bracket positioning differences were quantified. A total of 363 brackets were evaluated. One-tailed t-tests were used to determine whether bracket positioning differences were within the limit of 0.5 mm in mesiodistal, buccolingual, and occlusogingival dimensions, and within 2° for torque, tip, and rotation.ResultsMean bracket positioning differences were 0.10 mm, 0.10 mm, and 0.18 mm for mesiodistal, buccolingual, and occlusogingival measurements, respectively, with frequencies of bracket positioning within the 0.5-mm limit ranging from 96.4% to 100%. Mean differences were significantly within the acceptable limit for all linear dimensions. Mean differences were 2.55°, 2.01°, and 2.47° for torque, tip, and rotation, respectively, with frequencies within the 2°-limit ranging from 46.0% to 57.0%. Mean differences for all angular dimensions were outside the acceptable limit; however, this may have been due to limitations of scan data.ConclusionsIndirect bonding using 3D-printed trays transfers planned bracket position from the digital setup to the patient''s dentition with a high positional accuracy in mesiodistal, buccolingual, and occlusogingival dimensions. Questions remain regarding the transfer accuracy for torque, tip, and rotation.     

下颌正中管的锥形束CT三维重建

目的 通过锥形束CT(CBCT)扫描对下颌正中管的存在与否、走向及其与周围组织的三维关系进行评估及测量,为颏下区手术的安全提供保障.方法 对100例患者的CBCT图像进行三维重建并测量.测量项目包括Mandibular Icisive Canal(MIC)的存在与否,MIC垂直向和水平向直径,MIC在下颌管起始点,第一前磨牙对应点,尖牙对应点,切牙对应点至牙根尖、下颌骨颊侧壁、舌侧壁、下颌下缘以及牙槽嵴顶的垂直距离.结果 100例CBCT中百分百可见MIC.MIC与颊侧骨板和舌侧骨板平均距离分别为3.52±0.54 mm和5.37±0.25 mm,与下颌骨下缘、牙根尖和牙槽嵴顶的平均距离为10.44±0.61、10.57±0.76及20.21±0.83 mm.MIC到下颌骨下缘的距离男性为10.70±0.43 mm,女性为10.17±0.63 mm,P<0.05,差异具有统计学意义.结论 MIC在CBCT中检出率高且走向各异.     

颧牙槽嵴区域骨密质厚度的锥形束CT测量分析

目的通过锥形束CT（CBCT）测量成年人与青少年的颧牙槽嵴区域骨密质厚度,评价两者的差异,为临床中微种植支抗钉在颧牙槽嵴的应用提供参考。方法采集30例患者口腔颌面部CBCT扫描数据,其中成年人、青少年各15例。分别测量颧牙槽嵴区域颊侧不同层面基准线（上颌第一磨牙近中颊尖顶所在水平线）上方13、15、17mm处骨密质厚度,并对测量数据进行统计源分析。结果成年人颧牙槽嵴区域骨密质厚度为（1．91±0．54）～（2．62±0．74）mm。在3个测量高度上,上颌第一、二磨牙间骨密质最厚,第一磨牙近颊根上方骨密质最薄。青少年颧牙槽嵴区域骨密质厚度为（1．30±0．51）～（3．08±1．01）mm。在不同测量高度上,上颌第二前磨牙与第一磨牙间骨密质最厚,最薄处则位于第二磨牙近颊根上方或第一磨牙远颊根上方。结论就骨密质厚度而言,成年人颧牙槽嵴区域微种植支抗钉的最佳植入点位于上颌第一、二磨牙间,青少年颧牙槽嵴区域微种植支抗钉的最佳植入点位于上颌第二前磨牙与第一磨牙间。成年人与青少年颧牙槽嵴区域各位点骨密质厚度均可为微种植支抗钉的稳定性提供了保障。     

Canal Transportation and Centering Ability in Long Oval Canals: A Multidimentional Analysis

IntroductionThe purpose of this study was to evaluate and compare the centering ability and canal transportation of the ProTaper Next (PTN; Dentsply Maillefer, Ballaigues, Switzerland) and Self-adjusting File (SAF; ReDent-Nova, Ra'anana, Israel) systems in long oval root canals using cone-beam computed tomography imaging.MethodsFifty-six fully formed single-rooted mandibular premolars were selected with a buccolingual canal size 2 to 2.5 times the mesiodistal size at 5 mm from the apex, ranging from a 0°–10° canal curvature with a 5- to 6-mm radius. The teeth were divided into 2 groups (n = 28) and prepared with PTN or SAF according to the manufacturers’ instructions. Cone-beam computed tomographic images were taken in the same position before and after instrumentation using modeling wax. The centering ability and canal transportation were calculated at 3, 6, and 9 mm from the apex in both mesiodistal and buccolingual directions. The mean and standard deviation were calculated, and the Student t test was used for comparative analysis.Resultssignificant difference for canal transportation was observed mesiodistally at 9 mm from the apex (P < .05) where the PTN shaved more dentin in 1 direction. A significant difference for the centering ability was observed at 6 mm buccolingually from the apex (P < .05) where the PTN was less centered in the canal compared with the SAF.ConclusionsBoth SAF and PTN were shown to be safe for being used in long oval canals. SAF resulted in less transportation at the coronal third in the mesiodistal direction and more centered at the middle third in the buccolingual direction compared with PTN.     

"Safe zones": a guide for miniscrew positioning in the maxillary and mandibular arch

The aim of this study was to provide an anatomical map to assist the clinician in miniscrew placement in a safe location between dental roots. Volumetric tomographic images of 25 maxillae and 25 mandibles taken with the NewTom System were examined. For each interradicular space, the mesiodistal and the buccolingual distances were measured at two, five, eight, and 11 mm from the alveolar crest. In this article, measurements distal to the canines are presented. In the maxilla, the greatest amount of mesiodistal bone was on the palatal side between the second premolar and the first molar. The least amount of bone was in the tuberosity. The greatest thickness of bone in the buccopalatal dimension was between the first and second molars, whereas the least was found in the tuberosity. In the mandible, the greatest amount of mesiodistal dimension was between first and second premolar. The least amount of bone was between the first premolar and the canine. In the buccolingual dimension, the greatest thickness was between first and second molars. The least amount of bone was between first premolar and the canine. Clinical indications for a safe application of the miniscrews are provided, as well as the ideal miniscrew features.