Effects of low-intensity laser therapy on the stability of orthodontic mini-implants: a randomised controlled clinical trial

Objective: To investigate the effect of low-intensity laser therapy on mini-implant stability using resonance frequency analysis during canine retraction with fixed appliances.

Design: A split-mouth randomised clinical trial.

Setting: Subjects were recruited and treated in the outpatient clinic, Department of Orthodontics, Faculty of Dentistry, Cairo University.

Participants: Fifteen subjects with mean age 20.9 (±3.4) years who required extraction of maxillary first premolar teeth and mini-implant-supported canine retraction.

Methods: Thirty orthodontic mini-implants were inserted bilaterally in the maxillary arches of recruited subjects following alignment and levelling. Mini-implants were immediately loaded with a force of 150?g using nickel titanium coil springs with split-mouth randomisation to a low-intensity laser-treated side and control side. The experimental sides were exposed to low-intensity laser therapy from a diode laser with a wavelength of 940?nm at (0, 7, 14, 21 days) after mini-implant placement. Mini-implant stability was measured using resonance frequency analysis at (0, 1, 2, 3, 4, 6, 8, 10 weeks) after implant placement.

Results: A total sample of 28 mini-implants were investigated with 14 in each group. Clinically, both mini-implant groups had the same overall success rate of 78.5%. There were no significant differences in resonance frequency scores between low-intensity laser and control sides from baseline to week 2. However, from week 3 to 10, the low-intensity laser sides showed significantly increased mean resonance frequency values compared to control (P?>?0.05).

Conclusions: Despite evidence of some significant differences in resonance frequency between mini-implants exposed to low-intensity laser light over a 10 weeks period there were no differences in mini-implant stability. Low-intensity laser light cannot be recommended as a clinically useful adjunct to promoting mini-implant stability during canine retraction.     

微型种植体在口腔正畸中稳定性的研究进展

在口腔正畸治疗中,支抗对于正畸载荷的施加是必不可少的。微型种植体支抗作为当下最广泛应用的支抗手段,患者个体情况、支抗体本身设计、植入前准备、植入技术以及植入后加载都能影响植入的稳定性,而其稳定性又与正畸治疗的效率和质量息息相关。植入的失败不仅会增加患者的痛苦,还会提升治疗成本,延长治疗时间,阻碍正畸治疗的进程。通过对稳定性影响因素的研究,减少不利因素的产生,可以提升微型种植支抗的植入成功率,以达到更加专业、精准的正畸治疗。本文就微型种植体支抗的稳定性及其影响因素的研究进展作一综述。     

Effects of insertion angle and implant thread type on the fracture properties of orthodontic mini-implants during insertion

Objective:To determine the effects of insertion angle (IA) and thread type on the fracture properties of orthodontic mini-implants (OMIs) during insertion.Materials and Methods:A total of 100 OMIs (self-drilling cylindrical; 11 mm in length) were allocated into 10 groups according to thread type (dual or single) and IA (0°, 8°, 13°, 18°, and 23°) (n  =  10 per group). The OMIs were placed into artificial materials simulating human tissues: two-layer bone blocks (Sawbones), root (polymethylmethacrylate stick), and periodontal ligament (Imprint-II Garant light-body). Maximum insertion torque (MIT), total insertion energy (TIE), and peak time (PT) were measured and analyzed statistically.Results:There were significant differences in MIT, TIE, and PT among the different IAs and threads (all P < .001). When IA increased, MIT increased in both thread groups. However, TIE and PT did not show significant differences among 0°, 8°, and 13° IAs in the dual-thread group or 8°, 13°, and 18° IAs in the single-thread group. The dual-thread groups showed higher MIT at all IAs, higher TIE at 0° and 23° IAs, and longer PT at a 23° IA than the single-thread groups. In the 0°, 8°, and 13° IA groups, none of the OMIs fractured or became deformed. However, in the 18° IA group, all the OMIs were fractured or deformed. Dual-thread OMIs showed more fracturing than deformation compared to single-thread OMIs (P < .01). In the 23° IA group, all OMIs penetrated the artificial root without fracturing and deformation.Conclusions:When OMIs contact artificial root at a critical contact angle, the deformation or fracture of OMIs can occur at lower MIT values than those of penetration.     

A torque removal study on the primary stability of orthodontic titanium screw mini-implants in the cortical bone of dog femurs

The aim of this study was to biomechanically evaluate the primary stability of pure titanium orthodontic mini-implants, inserted into pre-drilled cavities of differing diameters. Mini-implants (1.2 mm diameter) were placed into 1.0 mm and 1.2 mm diameter cavities prepared in the mid-region of the bilateral hind leg femurs of anesthetized beagles. Removal torque strengths were measured immediately, 1, 3, 6, 9 and 12 weeks post-insertion of the implant. For mini-implants placed into 1-mm cavities, removal torque values decrease over the first 6 weeks (p<0.01), after which values remained static. Average values obtained immediately, 1, 3 and 6 weeks post-insertion were 10.98, 8.83, 7.20 and 5.12 Ncm, respectively . Immediately post-insertion, removal torque values of mini-implants placed in a 1.2-mm cavity, were 11-fold lower than those placed in 1.0-mm cavities, which then demonstrated a significant increase in strength from 3 weeks (1.35 Ncm) to 6 weeks (5.17 Ncm) post-insertion (p<0.01). Measurements 6, 9 and 12 weeks post-insertion were similar to those in the 1.0-mm cavity. Initial stability of titanium mini-implants is considered necessary for immediate and early use in orthodontics, and an implant without this initial stability should be replaced or isolated until it develops the appropriate stability supported by osseointegration.     

Impact of bone quality, implant type, and implantation site preparation on insertion torques of mini-implants used for orthodontic anchorage

Mini-implants are widely used as skeletal anchorage in orthodontics. To reduce implant loss rate, sufficient primary stability is required. This study quantitatively analysed the impact of bone quality and pre-drilling diameter on the insertion torque of five different mini-implants. Twenty pig bone segments were dissected and embedded in resin. The insertion torques of two different mini-implant types (Tomas Pin, Dentaurum, Germany, 8 and 10 mm; and Dual Top, Jeil, Korea, 1.6 mm × 8 and 10 mm plus 2 mm × 10 mm) were measured. After preparation of the implant sites using pilot drill diameters 1.0, 1.1, 1.2 and 1.3 mm, 30 implants were inserted into each bone segment. Five reference implants were inserted into each segment for comparison. Micro CT evaluated bone compacta thickness. Insertion moments of orthodontic mini-implants, and hence primary stability, varied strongly depending on compacta thickness, implant design, and pre-drilling at the implant site. The Dual Top consistently showed higher primary stability than the Tomas Pin. Insertion moments higher than 230 Nmm resulted in fractures in some cases. Compacta thickness, implant design and preparation of implant site affect the insertion torque of mini-implants for orthodontic anchorage. To avoid fractures and high bone stresses, optimum pre-drilling diameters should be chosen.     

错畸形正畸治疗后的稳定性研究

目的　本研究旨在探讨Ⅰ、Ⅱ类错畸形患者正畸治疗后牙的变化趋势 ,并探讨影响和预测牙变化的要关因素。以期为临床实践提供参考。方法　选取 11— 18岁之间的安氏Ⅰ ,Ⅱ类错畸形患者 72例。选择十项模型测量指标对牙变化进行评估。对所得数据采用配对t检验 ,多因素方差分析 ,多元相关分析。结果　保持后牙关系有向治疗前回复的趋势 ,但仍旧保持了大部分的治疗效果。各项指标的变化在拔牙与不拔牙之间 ,安氏Ⅰ ,Ⅱ类之间无差别。上尖牙间宽度较下尖牙间宽度更稳定。下尖牙间宽度保持后缩小明显且伴随下前牙拥挤增大。     

In vitro evaluation of insertion and removal torques of orthodontic mini-implants

This study evaluated the influence of bone cortical thickness on the maximum torque required for insertion and removal of orthodontic mini-implants of different shapes. Five different types of orthodontic mini-implants were examined Cylindrical 1 (CYM), Cylindrical 2 (CYI) and Cylindrical 3 (CYT) Conical 1 (CON), Conical 2 (COS). Insertion and removal torque tests were performed in mini-pig medullary bone (8 mm thick) and cortical bone 1, 2, 3 and 6 mm thick. A digital torque meter measured the torque forces; the maximum values of insertion and removal were obtained (N/cm). There were no statistically significant differences between the different implants in the torque forces required for insertion and removal from medullary bone (P > 0.05). During insertion into 1-2 mm cortical bone, COS, CON and CYT had torque values statistically higher, but CON had higher torque values compared with the others when 3-6 mm cortical bone was used (P < 0.05). The removal torque values were significantly lower for CYM and CYI. Conical type mini-implants require a greater torque force for insertion and removal compared with cylindrical types. Torque values were directly related to cortical thickness.     

骨密度对正畸支抗稳定性影响的临床研究

目的：研究骨密度对正畸支抗稳定性的影响。方法：选择进行正畸治疗,需要拔除4颗第一前磨牙及弱支抗矫治的安氏Ⅰ类错牙合的健康男性患者212名,年龄18-25周岁,其中支抗失控患者16名,支抗稳定患者196名,通过双能X线骨密度仪测定每位患者4颗第二前磨牙根尖区周围0.5 cm2范围区域的骨密度,并运用统计学方法进行对比分析。结果：经单因素方差分析,两组患者第二前磨牙区域骨密度值具有显著性差异（P<0.05）。结论：骨密度可能是影响正畸支抗稳定性的因素,在正畸支抗设计时应列为参考指标之一。     

正畸微种植体稳定性的临床共振频率分析

目的 用共振频率分析法评价正畸微种植体稳定性的临床变化规律,探讨合适的加载时机及加载对微种植体稳定性的影响。方法 选择上颌第一前磨牙减数并需要强支抗的正畸患者14例,分为延期加载组和择期加载组各7例。每例患者在上颌后牙左右颊侧牙槽骨区植入分体式微种植体各1颗,用Osstell种植体稳定性测量仪作共振频率分析,植入后即刻及每周记录微种植体的种植体稳定性系数（implant stability quotients,ISQ值）。延期加载组在第12周加载150 g水平牵引力之前,选出ISQ值稳定的时间点,以此作为择期加载组的加载时机,施加同样大小的正畸力。2组患者均随访至16周,采用SPSS 19.0软件包对数据进行方差分析和t检验。结果 28颗微种植体中,5颗在4周内发生松动而取出,剩余23颗在16周内保持稳定,其中12颗延期加载组微种植体的共振频率分析显示,ISQ值在植入即刻及第1周最高（21.48±5.25）,第2周到第5周逐渐下降,第6周后维持平稳 （11.26±3.36）。11颗择期加载组微种植体在第6周加载牵引力。从第6周至16周,2组微种植体无论加载与否, ISQ 值均无显著变化,2组间也无显著差异（P>0.05）。松动微种植体的初始ISQ值显著小于非松动组。结论 微种植体植入1周后稳定性下降,6周后趋于稳定。6周后加载正畸力对稳定性无影响,而初始稳定性差是微种植体失败的重要原因。     

Effects of placement angle and direction of orthopedic force application on the stability of orthodontic miniscrews

Objectives:To evaluate the influence of placement angle and direction of orthopedic force application on the stability of miniscrews.Materials and Methods:Finite element analysis was performed using miniscrews inserted into supporting bone at angles of 90°, 60°, and 30° (P90°, P60°, and P30°). An orthopedic heavy force of 800 gf was applied to the heads of the miniscrews in four upward (U0°, U30°, U60°, U90°) or lateral (L0°, L30°, L60°, L90°) directions. In addition, pull-out strength of the miniscrews was measured with various force directions and cortical bone thicknesses.Results:Miniscrews with a placement angle of 30° (P30°) and 60° (P60°) showed a significant increase in maximum von Mises stress following the increase in lateral force vectors (U30°, U60°, U90°) compared to those with a placement angle of 90° (P90°). In accordance, the pull-out strength was higher with the axial upward force when compared to the upward force with lateral vectors. Maximum von Mises stress and displacement of the miniscrew increased as the angle of lateral force increased (L30°, L60°, L90°). However, a more dramatic increase in maximum von Mises stress was noted in P30° than in P60° and P90°.Conclusion:Placement of the miniscrew perpendicular to the cortical bone is advantageous in terms of biomechanical stability. Placement angles of less than 60° can reduce the stability of miniscrews when orthopedic forces are applied in various directions.     

补骨脂对大鼠正畸后稳定性的影响

目的 探讨补骨脂素对大鼠正畸牙移动后牙周组织改建的影响。方法 选择36只8周龄雄性Wistar大鼠,将其随机分为实验组和对照组2组。在上颌左侧切牙和上颌左侧第一磨牙之间安装拉第一磨牙向近中的加力装置。加力21 d后去除装置,对2组进行药物灌胃处理。实验组大鼠灌服8 mg/（kg·d）补骨脂素溶液,对照组大鼠每天灌服等量生理盐水,连续灌服4周。在去除装置当天和第7、14、21、28天制取大鼠上颌石膏模型,3D扫描获得电子数据,测量并计算复发距离。灌药4周后,心脏灌注处死全部大鼠,分离上颌骨,分离大鼠磨牙及其周围的牙周组织,对切片进行H-E染色和BMP2、BMP4免疫组织化学染色。采用 SPSS 21.0 软件包对数据进行统计学分析。结果 拆除矫治器后,2组均有复发,实验组在第7、14、21、28天的复发率显著小于对照组（P<0.05）。2组复发速度均在第1周最快,第2、3、4周逐渐变慢,实验组在第1周复发速度显著小于对照组（P<0.05）,2组牙周膜和牙槽骨中均有BMP2、BMP4表达,实验组表达强度高于对照组（P<0.05）。结论 补骨脂素能够促进牙周组织中BMP2、BMP4的表达,加速牙周组织改建,有效抑制复发。     

Effects of different orthodontic adhesives and resin removal techniques on enamel color alteration

Objective: To investigate the color alterations in enamel following the use of different orthodontic bonding resins and adhesive residue–removal burs.Materials and Methods:Metal brackets were bonded to extracted human premolars (n  =  175) by using an etch-and-rinse adhesive system, a self-etch adhesive system (SEP), or a resin-modified glass ionomer cement (RMGIC). After 24 hours of photoaging, the brackets were removed and the adhesive residue on the tooth surfaces was cleaned with either a tungsten carbide bur or a Stainbuster bur. Tooth colors were measured with a spectrophotometer at baseline, after adhesive removal, and after additional photoaging. Color evaluation was made, and color differences induced by photoaging were calculated. Statistical evaluation was made using the Kruskal-Wallis test and the Mann-Whitney U-test, with Bonferroni correction.Results:All specimens showed discoloration at varying levels. The highest color change was observed in the etch-and-rinse adhesive/tungsten carbide bur group. When the etch-and-rinse and self-etch adhesives were used, adhesive-remnant removal with Stainbuster burs resulted in significantly lower discoloration. The type of bur did not affect the extent of enamel discoloration in the RMGIC group.Conclusions:Orthodontic treatment alters the original color of enamel, and both the adhesive system and the resin-removal methods are responsible for this change. When brackets are bonded with the etch-and-rinse system or the SEP, cleaning the adhesive residuals with Stainbuster burs is recommended for minimal change. RMGIC can be safely cleaned with tungsten carbide burs.     

Effects of predrilling on the osseointegration potential of mini-implants

Objectives:To determine a reliable method of drilling a pilot hole when using a self-tapping surface-treated mini-implant and to evaluate stability after placement.Materials and Methods:Implant sites were predrilled in 12 rabbits with two devices: a conventional motor-driven handpiece and a newly developed hand drill. Mini-implants were then inserted in a complete random block design. Samples were divided into 1-week and 6-week groups to investigate osseointegration capacity in relation to the two time intervals. Mechanical and histomorphometric assessments were performed.Results:Mechanical analysis revealed no difference in maximum removal torque or total removal energy between the motor-driven predrilling group and the hand-drilling group. No difference was found between the 1-week group and the 6-week group. Histomorphometric evaluation showed no difference in the bone-implant contact (BIC) ratio or the bone volume (BV) area. For the time interval, a statistically significant increase in BIC and BV area was found in the 6-week group when compared to the 1-week group.Conclusions:The osseointegration potential of the motor-driven predrilling method was not different from that of the manual predrilling method with the newly developed hand drill. Hand drilling may be an attractive predrilling method in preference to the conventional motor-driven pilot drilling.     

Angled-predrilling depth and mini-implant shape effects on the mechanical properties of self-drilling orthodontic mini-implants during the angled insertion procedure

Abstract Objective: To investigate the effects of orthodontic mini-implant (OMI) shape and angled-predrilling depth on the mechanical properties of OMIs during the angled insertion procedure. Materials and Methods: A total of 30 OMIs (self-drilling type, 7?mm in length) were allocated into six groups according to the OMI shape (cylindrical or tapered) and angled-predrilling depth (control, 1.5-mm and 4.0-mm angled-predrilling; predrilled with 1-mm-diameter drill-bit), as follows: C-con, C-1.5, C-4.0, T-con, T-1.5, and T-4.0 groups (N = 5 per group). The OMIs were installed at an angle of 60° in double-layer artificial bone blocks that simulated the cortical and cancellous bone (Sawbone?). Total insertion time (TIT), maximum insertion torque (MIT), total insertion energy (TIE), and inclination of the time-torque graph (INC) were measured. Results: Within the same shape group, angled-predrilling had a shorter TIT than did the control (control vs 1.5; control vs 4.0; all P < .05). MIT and TIE decreased in the order of control, 1.5-mm, and 4.0-mm angled-predrilling (control vs 1.5; 1.5 vs 4.0; all P < .05), but INC increased from control to 1.5-mm angled-predrilling and decreased from 1.5-mm to 4.0-mm angled-predrilling within the same shape group (control vs 1.5, 1.5 vs 4.0; all P < .05). The MIT of the tapered group was greater than that of the cylindrical group (C-con vs T-con, C-1.5 vs T-1.5; all P < .05, C-4.0 vs T-4.0; P < .01). In the same angled-predrilling depth, no differences were observed in TIE between the cylindrical and tapered groups (C-1.5 vs T-1.5, C-4.0 vs T-4.0; all P > .05). Conclusions: In angled-predrilling insertion of OMIs into thick cortical bone, tapered OMIs might be a better choice than cylindrical OMIs for increasing primary stability because of higher MIT and similar TIE values.     

结缔组织生长因子对正畸大鼠牙周组织改建的影响

目的:探讨结缔组织生长因子(connective tissue growth factor,CTGF)对大鼠正畸牙移动模型牙周组织改建的影响.方法:雄性SD大鼠45 只,牵引下颌第一磨牙近中移动制作大鼠牙移动模型.模型完成后,随机分为3 个实验组: CTGF组,生理盐水对照组及加力对照组,每组15 只.从0 d开始分别将CTGF及生理盐水每隔1 d注射到CTGF组及生理盐水对照组左侧下第一磨牙舌侧骨黏膜下,分别于干预后1、3、7、15、21 d每组各取3 只大鼠的牙周组织,制备组织切片,HE及免疫组化染色,计算机图像分析检测牙周组织中VEGF的表达状况.结果:正畸加力后,大鼠牙周组织中伴随牙周组织改建,牙周组织中VEGF表达增高.加力7 d牙周组织改建最为活跃,VEGF表达达到高峰期.CTGF干预治疗后,CTGF组加力后7、15 d VEGF表达强度增幅最高,CTGF组与对照组间差异有显著性.结论: CTGF干预可上调正畸大鼠牙周组织中VEGF表达,加速正畸牙周组织改建.     

正畸治疗影响成人鼻唇角变化的多元回归分析

目的探索正畸治疗对成人鼻唇角变化的影响。方法挑选125例Ⅰ类和轻度Ⅱ类成人患者,83例拔除第一双尖牙,42例不拔牙治疗,测量治疗前后鼻唇角以及有可能影响鼻唇角的软硬组织测量项目。根据鼻唇角改变值、治疗前上切牙突距大小分组,做多元回归分析,找出影响鼻唇角变化的相关因素。结果鼻唇角的变化与上唇突度改变正相关,治疗前上切牙突距在正常值以外时,其鼻唇角的变化与上切牙唇倾度的改变呈正相关。而正常者,其鼻唇角的改变与上切牙唇倾度无相关性。结论鼻唇角的改变与上唇突度有关,治疗前上切牙位置偏离正常越小,鼻唇角的变化越不明显。     

即刻负载对正畸用微型种植体的稳定性及周围组织的影响

目的 临床和组织学评价即刻负载连续的,持续的水平力于正畸微种植体的可行性及其对周围组织的影响.方法 32枚钛合金微型种植体放置于两只狗的上下颌骨颊侧的牙根间区,愈合在开放的环境下.研究组包括28枚微型种植体,即刻负载约200克的、连续的水平力持续,9周.4枚没有负载的微型种植体作为对照组.在负载开始及结束时,测量相互受力的微型种植体之间的距离,种植体周边袋.光学和荧光学显微镜检查脱钙和不脱钙的微型种植体周围组织的组织切片.结果 9周负载后,研究组有24枚微型种植体无松动,无X线阴影.研究组移位距离在上颌(0.93±0.32)mm,在下颌(0.66±0.45)mm.对照组微型种植体没有松动、移位、倾斜现象.组织学分析显示,在两组中均可见微型种植体与周围组织的骨性结合,其间没有软组织.骨结合可见于微型种植体在骨皮质区的任何部位.结论 微型种植体是有效的支抗工具,可以即刻负载.但是,由于有微移动,植入位置应该与生物器官有一定的距离.     

Effect of cortical bone thickness and implant placement torque on stability of orthodontic mini-implants

PURPOSE: To examine the relationship between cortical bone thickness, inter-root distance (horizontal space), distance from alveolar crest to the bottom of maxillary sinus (vertical space) at the prepared site, and implant placement torque and the success rate of mini-implants placed for orthodontic anchorage. MATERIALS AND METHODS: After computerized tomography examination, mini-implants 1.6 mm wide and 8 mm long were placed in the posterior alveolar bone. The mini-implant was judged a success when orthodontic force could be applied for at least 6 months without pain or clinically detectable mobility. The unpaired t test was performed to examine differences between the success and failure groups. The chi-square analysis or Fisher exact probability test was used to compare the implant success according to placement torque, location, and patient gender. P values less than .05 were considered significant. RESULTS: The subjects included 4 males (11 implants) and 28 females (76 implants) who ranged in age from 14.6 to 42.8 years. The success rate of the 87 implants was 87.4%. Cortical bone thickness was significantly greater in the success group (1.42 +/- 0.59 mm vs 0.97 +/- 0.31 mm, P = .015). The success rate was significantly higher in the group with an implant placement torque of 8 to 10 Ncm (100%) as compared to implants with higher or lower placement torques. The odds ratio for failure of the mini-implant was 6.93 (P = .047) when the cortical bone thickness was less than 1.0 mm relative to 1.0 mm or more. CONCLUSION: A relationship between stability after implant placement and the width and height of the peri-implant bone was not demonstrated. The prepared site should have a cortical bone thickness of at least 1.0 mm, and the placement torque should be controlled up to 10 Ncm.