Optimal asymmetric thread for orthodontic microimplants: Laboratory and clinical evaluation

Objectives:To investigate the performance of microimplants incorporating a newly designed asymmetric thread.Materials and Methods:Three microimplants were compared. The control group comprised microimplants with the original v-shaped thread. The two experimental groups (Taper 1.0 and Taper 1.25) comprised prototype microimplants constructed with the new asymmetric thread; the Taper 1.25 specimens had a 1.25-mm-long and sharper tip, while the Taper 1.0 and control groups had a less sharp 1-mm tip. Two specially designed artificial bone blocks mimicking soft (maxillary) and hard (mandibular) bone were used to evaluate the microimplant insertion characteristics and postinsertion lateral stability. The peak insertion torque, insertion time, Periotest value (PTV), and torsional strength were measured. Then the microimplants were evaluated clinically over a 3-month period.Results:Significant differences in peak insertion torque, insertion time, and PTV were observed and favored the experimental groups. Although statistically insignificant, the clinical success rate was also higher in the Taper 1.25 experimental group than in the control group (87.2% vs 75.6%).Conclusions:The better performances of the experimental microimplant, under both laboratory and clinical conditions (although statistically insignificant in the latter), demonstrate the superiority of the new asymmetric thread.     

Optimal force magnitude loaded to orthodontic microimplants: A finite element analysis

Objective:To find an optimal force that can be loaded onto an orthodontic microimplant to fulfill the biomechanical demands of orthodontic treatment without diminishing the stability of the microimplant.Materials and Methods:Using the finite element analysis method, 3-D computer-aided design models of a microimplant and four cylindrical bone pieces (incorporating cortical bone thicknesses of 0.5, 1.2, 2.0, and 3.0 mm) into which the microimplant was inserted were used. Various force magnitudes of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, and 4.0 N were then horizontally and separately applied to the microimplant head as inserted into the different bone assemblies. For each bone/force assembly tested, peak stresses developed at areas of intimate contact with the microimplant along the force direction were then calculated using regression analysis and compared with a threshold value at which pathologic bone resorption might develop.Results:The resulting peak stresses showed that bone pieces with thicker cortical bone tolerated higher force magnitudes better than did thinner ones. For cortical bone thicknesses of 0.5, 1.2, 2.0, and 3.0 mm, the maximum force magnitudes that could be applied safely were 3.75, 4.1, 4.3, and 4.45 N, respectively.Conclusions: For the purpose of diminishing orthodontic microimplant failure, an optimal force that can be safely loaded onto a microimplant should not exceed a value of around 3.75–4.5 N.     

Light and transmission electron microscopic studies following frontal sinus obliteration with ionomer cement in cats

Osteoplastic frontal sinus surgery in combination with sinus obliteration can be performed for various indications, including chronic sinusitis, frontal sinus trauma and removal of osteomas. In an experimental study using cats, the mucous lining of the frontal sinus was removed, the nasofrontal duct sealed with semifluid ionomer cement and the cavity filled with Ionogran, a solid and porous bone substitute based on ionomer cement. Histological investigations up to 1 year after surgery showed increasing sinus obliteration by regenerating bone, starting from the sinus wall, and formation of connective tissue between the cement grains. There was no evidence for mucosal regeneration. Electron microscopic examination of the interface between the cement and connective tissue revealed mesenchymal cells, collagen fibers and areas of mineralization in close contact with the implant material. Newly formed connective tissue matrix in intimate contact with the cement was a good indication for biocompatibility of the material and is a possible explanation for the implant's solid adhesion to bone. The present findings indicate that lonogran is a suitable alloplastic material for experimental frontal sinus obliteration in cats.Adapted from a presentation of preliminary results reported at the 65th annual meeting of the German Society for Otorhinolaryngology — Head and Neck Surgery (Deutsche Gesellschaft für Hals-Nasen-Ohren-Heilkunde, Kopf- und Hals-Chirurgie), Chemnitz (Germany), 14–18 May 1994     

应用微种植体支抗不拔牙矫治重度牙列拥挤

目的：探讨采用微种植体非拔牙矫治重度牙列拥挤的临床效果及特点。方法：患者12例,均为安氏II类错,面型基本正常,上牙弓拥挤度〉8mm,在上颌颊侧牙槽骨共植入24枚微种植体,将Ni-Ti螺旋推簧置于上颌第二前磨牙与上颌第一磨牙之间,推磨牙远移,术前后行X线头影测量和模型分析。结果：12例重度拥挤患者治疗后均达到满意效果,牙列整齐,咬合关系正常,面型良好,治疗前后SNA、SNB、U1-NA未见明显变化（P〉0.05）,上颌第一磨牙平均远中移动距离5.48mm（P〈0.01）,其颊向移动距离及旋转角度无统计学意义。结论：应用微种植体推磨牙向远中能成功的非拔牙矫治重度牙列拥挤,种植体支抗在磨牙远移过程中,发挥了绝对强支抗作用。     

正畸微种植体支抗即刻加载的稳定性研究

目的 本研究通过观察即刻加载的微种植体支抗周围骨界面组织学变化,旨在探索即刻加载是否会影响微种植体支抗的稳定性.方法 本试验选用成年狗1只,16枚正畸用微种植体植入狗的下颌骨后即刻施加1.5 N力,施力9周后狗被处死.骨标本作病理切片后进行组织学观察和测量.结果 微种植体可以承受即刻加载的1.5 N正畸力而无松动.组织学观察显示骨-微种植体界面有骨组织沉积,没有纤维组织生成,即刻加载的正畸力没有影响骨细胞在微种植体表面的沉积.结论 在严格控制植入创伤、加载力量大小的前提下,微种植体的即刻加载是可行的.     

不同力值对正畸微螺钉种植体周围软组织形态的影响

目的建立正畸微螺钉种植体动物实验模型,通过种植体周围软组织组织学观察,反映不同力值对种植体周围软组织的影响,评价种植体的稳定性。方法全麻下狗上颌骨植入微螺钉种植体,按不同力值将微螺钉种植体分为4组,即刻加力2月后,透射电镜下观察各组种植体周围软组织的形态学变化,研究不同力值对种植体周围软组织的影响。结果各组均可观察到种植体周围软组织上有半桥粒形成,随着力值增加,胞浆内核糖体,分泌性小囊泡数量增加,张力细丝减少。结论加力力值增加将影响正畸微螺钉种植体周围软组织形成有效的生物封闭屏障作用,影响种植体的稳定性。     

磨牙后区微种植体支抗竖直下颌近中阻生第二磨牙的临床应用

目的探讨磨牙后区微种植体应用于下颌近中阻生第二磨牙竖直的正畸治疗方法,评估其效果。方法选择南京医科大学附属口腔医院正畸科2011—2014年门诊下颌第二磨牙近中阻生的患者13例23颗患牙,采用磨牙后区植入微种植体,牵引23颗患牙向远中移动,引导其竖直、萌出。结果 23颗阻生的下颌第二磨牙全部竖直萌出并建立良好的咬合。竖直治疗平均时间为6.5个月。结论磨牙后区微种植体支抗能简单有效地竖直下颌阻生的第二磨牙,并且可以控制磨牙的垂直向高度,避免对相邻牙齿产生不良影响。     

骨性Ⅲ类错群（牙合）者应用微种植支抗的临床研究

目的：比较应用微种植支抗与多曲方丝弓矫治骨性Ⅲ类错（牙合）患者软硬组织的变化,研究不同方法掩饰性治疗骨性Ⅲ类错（牙合）的临床矫治效果.方法：骨性Ⅲ类错（牙合）患者16例,8例应用微种植支抗牵引下牙列整体远中移动;8例多曲方丝弓代偿性治疗反（牙合）,运用Winceph8.0软件对矫治前、后软硬组织垂直向、矢状向的变化进行测量,应用SPSS13.0软件对矫治前、后各测量项目进行两样本配对t检验.结果：16例患者均获得较理想的治疗效果,达到正常覆（牙合）、覆盖和尖窝关系.矫治前后两组的∠L1-MP、∠L6-MP、L1c-Y轴及L6c-Y轴均明显减小,差异具有统计学意义（P＜0.05）;两组的UL-EL距离均增大,变化差异均无统计学意义（P＞0.05）;两组的LL-EL、L1r-Y轴、L6r-Y轴距离均减小,其中微种植支抗组变化差异具有统计学意义（P＜0.05）,多曲方丝弓组变化差异无统计学意义（P＞0.05）;微种植支抗组L6-MP距离减小,常规支抗组L6-MP距离增大,两组的变化差异均无统计学意义.结论：种植支抗可使下颌磨牙达到远中整体移动,切牙主要为倾斜移动,较好控制后牙垂直高度;多曲方丝弓通过远中竖直下颌磨牙获得间隙,牙齿以倾斜移动为主,较难控制后牙垂直高度;两种矫治方法均能达到改善软组织侧貌的治疗目的,但微种植支抗容貌改善效果更好;临床应用中应根据具体情况选择好适应证.     

不同表面涂层对兔微种植体支抗稳定性的影响

目的观察不同表面处理的微种植体支抗在骨质疏松家兔中的稳定性。方法制作去势新西兰大白兔模型（骨质疏松模型）,分组植入不同表面处理的微种植体。种植术后1个月,微种植体之间用镍钛拉簧100g交互牵引持续1个月后测量2枚种植体之间减少的距离,检测胫骨近端微种植体周1cm骨组织的骨密度。结果HA＋ZOL涂层的一组比HA涂层的微种植体的脱落率低,微种植体移动距离小,骨结合和骨密度显著性增高。结论局部用唑来膦酸可以提高种植体的稳定性,增加种植体的骨结合率。     

两种方法矫治骨性Ⅲ类错[牙合]前、后上气道变化的临床研究

目的探讨微种植体支抗与颌间Ⅲ类牵引矫治成人骨性Ⅲ类错[牙合]前后上气道矢状径的变化,为临床治疗提供参考。方法选取35例成人骨性Ⅲ类错[牙合]患者,利用直丝弓矫治技术矫治,微种植体组15例(A组):骨性Ⅲ类错[牙合]重度病例(垂直高角)选择配合微种植体支抗;颌间Ⅲ类牵引组20例(B组):骨性Ⅲ类错[牙合]轻、中度病例(垂直低角、均角)选择配合颌间Ⅲ类牵引,测量分析矫治前后的头颅定位侧位片。结果矫治后颅颌面测量指标的变化:A组蝶鞍中心鼻根点下牙槽座点构成的角(sellanasionsupramental angle,SNB角)减小(P<0.05),上牙槽座点鼻根点下牙槽座点构成的角(subspinalenasionsupramental angle,ANB角)增大(P<0.05);B组SNB角减小(P<0.05),蝶鞍中心鼻根点上牙槽座点构成的角(sellanasionsubspinale angle,SNA角)、ANB角、下颌平面角(anterior skull base planemandibular plane angle,SNMP角)增大(P<0.05)。矫治后上气道矢状径测量指标的变化:A组上气道矢状径舌咽段(TBTPPW)减小(P<0.05);B组上气道矢状径鼻咽第一段(PNSR)增大(P<0.05)。矫治后A组SNB减小、ANB增大的量大于B组,差异有统计学意义(P<0.05);A组上气道TB-TPPW减小的量大于B组,差异有统计学意义(P<0.05)。结论利用微种植体支抗矫治成人骨性Ⅲ类错[牙合],对上气道矢状径舌咽段产生消极影响。