Bone anchor systems for orthodontic application: a systematic review

This systematic review was performed to investigate the usefulness and clinical effectiveness of skeletal anchorage devices to determine the most effective bone anchor system for orthodontic tooth movement. Literature on bone anchorage devices was selected from PubMed and the Cochrane Library from January 1966 to June 2010. 55 publications regarding miniplates, miniscrews, palatal implants and dental implants as orthodontic anchorage were identified for further analysis. All bone anchorage devices were found to have relatively high success rates and demonstrated their ability to provide absolute anchorage for orthodontic tooth movement. Significant tooth movement could be achieved with low morbidities and good patient acceptance. The reported success rates for the four groups of anchorage systems were generally high with slight variability (miniplates 91.4–100%; palatal implants 74–93.3%; miniscrews 61–100%; dental implants 100%). It was concluded that bone anchorage systems can achieve effective orthodontic movement with low morbidities. The success rate is generally high with slight variability between miniplates, palatal implants, miniscrews and dental implants. Owing to the lack of randomized controlled trials, there is no strong evidence to confirm which bone anchor system is the most effective for orthodontic tooth movement.     

国产微型钛钉即刻负载正畸支抗临床应用初步研究

目的：评价国产微型钛钉支抗临床使用效果.方法：选取13例需拔除上颌双侧第一双尖牙并需使用最大支抗的患者为研究对象,在其双侧颧牙槽嵴第二双尖牙和第一磨牙间,植入国产微型钛钉各一枚,以其为支抗移动尖牙.利用尖牙到位前后的研究模、头侧位定位X片,计测尖牙移动速度及磨牙相对于参考平面的位移量.结果：移动尖牙的平均速度为1.05mm/月,与磨牙支抗无统计学差异;磨牙位移量平均为0.50mm,明显小于传统强支抗方式.结论：牙移动速度种植支抗与传统支抗无差别;种植支抗几为绝对支抗.     

自攻型微螺钉种植体支抗稳定性的临床研究

目的:研究自攻型微螺钉种植体加载正畸负荷后的稳定性。方法:本研究包括了15例成年患者,以植入上颌颧突的自攻型微螺钉作为前牙内收的颌内支抗。微螺钉植入2周后施力。加力前及加力后9个月分别拍摄X线头颅定位片,将头影测量片进行重叠,测量微螺钉的移位变化。结果:15例中6例患者的微螺钉伸出并向前移位(-0.5～1.5mm)。微螺钉头部平均向前移位0.4mm,有统计学意义(P<0.05)。结论:自攻型微螺钉种植体是一种稳定的支抗装置,但是在承载正畸负荷的过程中,并不保持绝对的稳定,部分微螺钉在正畸力作用下有移位。为了防止因种植体移位伤及临近的重要组织结构,建议自攻型微螺钉应植入在没有主要神经、血管通过的非齿槽骨区,或植入在齿槽间隔区,但种植体与牙根之间应留出2mm的安全距离。     

Orthopedic protraction with skeletal anchorage in a patient with maxillary hypoplasia and hypodontia

Multipurpose titanium miniplates were placed on the lateral nasal wall of the maxilla as anchorage for face mask protraction in an 11-year-old girl presenting with severe maxillary hypoplasia and hypodontia. Applying orthopedic forces directly to the maxilla resulted in an eight mm maxillary advancement. Intraosseous titanium screws were also placed on the palatal bone, near the alveolar crests, to provide anchorage for the expansion appliance. The maxilla was expanded from the median palatal suture, and seven mm of expansion was achieved across the buccal segments. No other tooth support was used for the expansion or the protraction of the maxilla.     

Osseointegration of miniscrews: a histomorphometric evaluation

Mini-implants and miniscrews are commonly used in orthodontics to provide additional temporary intraoral anchorage. Partial osseointegration represents a distinct advantage in orthodontic applications, allowing effective anchorage to be combined with easy insertion and removal. This article reports the histomorphometric findings of the osseointegration of bracket screw bone anchors (BSBAs). In an experimental animal study, four BSBAs were inserted in the alveolar process of the lower jaw in each of five male beagle dogs, aged 6.5 months from the same mother. Eleven screws were lost during the study, nine of them due to lack of primary stability. One screw was removed at the end of the examination period for evaluation of ease of removal. After 6 months, histological evaluation of the eight remaining screws was performed to evaluate the extent of osseointegration. All eight screws showed partial osseointegration (mean 74.48 per cent, standard deviation +/- 15.33 per cent). The amount of osseointegration was independent of loading time and location (anterior or posterior), as tested with an independent samples t-test (P > 0.05). Analysis of the data indicated that small titanium screws were able to function as rigid osseous anchors against an orthodontic load of 200 cN for 6, 12, 18, or 24 weeks after a minimal healing period or no healing period. These findings show that miniscrews, used for temporary anchorage in orthodontics, partially osseointegrate.     

Root contact during insertion of miniscrews for orthodontic anchorage increases the failure rate: an animal study

OBJECTIVES: Miniscrews and miniplates are increasingly being used for absolute anchorage during orthodontic treatment. However, potential problems of damaging adjacent roots and their consequences during mini-implant placement in the alveolar process have not been clearly described. MATERIALS AND METHODS: Animal experiments were used to evaluate the stability of miniscrews placed with intentional root contact. The root repair was evaluated after screw removal. Seventy-two miniscrews were surgically placed in the mandibular alveolar bone of six adult mongrel dogs with metabolic bone labeling at 3-week intervals. Miniscrews of the experimental group were placed so that they contacted the root of the adjacent teeth, were retained for different time durations, and were then removed. The insertion torque, clinical measurements, removal torque, and histological findings were analyzed. RESULTS: (1) miniscrews contacting the roots showed a significantly higher insertion torque than those without contact; (2) there was a significant difference in the removal torque measurements based on the mobility of miniscrews and the state of root contact; and (3) miniscrews contacting the root were at greater risk of failure. CONCLUSIONS: During placement of miniscrews in the aveolar process, increased failure rates were noticed among those contacting adjacent roots. Failed miniscrews appeared to be surrounded with a greater volume of soft tissue. When more inflammation was present, the adjacent roots seemed to experience more resorption. Nevertheless, the created lesion was repaired with a narrow zone of mineralized tissue deposited on the root surface, which was likely cellular cementum, and was mainly filled with alveolar bone, with the periodontal ligament space being maintained.     

Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage.

Recently, implant anchors such as titanium screws have been used for absolute anchorage during edgewise treatment. However, there have been few human studies reporting on the stability of implant anchors placed in the posterior region. The purpose of this study was to examine the success rates and to find the factors associated with the stability of titanium screws placed into the buccal alveolar bone of the posterior region. Fifty-one patients with malocclusions, 134 titanium screws of 3 types, and 17 miniplates were retrospectively examined in relation to clinical characteristics. The 1-year success rate of screws with 1.0-mm diameter was significantly less than that of other screws with 1.5-mm or 2.3-mm diameter or than that of miniplates. Flap surgery was associated with the patient's discomfort. A high mandibular plane angle and inflammation of peri-implant tissue after implantation were risk factors for mobility of screws. However, we could not detect a significant association between the success rate and the following variables: screw length, kind of placement surgery, immediate loading, location of implantation, age, gender, crowding of teeth, anteroposterior jaw base relationship, controlled periodontitis, and temporomandibular disorder symptoms. We concluded that the diameter of a screw of 1.0 mm or less, inflammation of the peri-implant tissue, and a high mandibular plane angle (ie, thin cortical bone), were associated with the mobility (ie, failure) of the titanium screw placed into the buccal alveolar bone of the posterior region for orthodontic anchorage.     

Primary failure rate for 1680 extra-alveolar mandibular buccal shelf mini-screws placed in movable mucosa or attached gingiva

Objective:To compare the initial failure rate (≤4 months) for extra-alveolar mandibular buccal shelf (MBS) miniscrews placed in movable mucosa (MM) or attached gingiva (AG).Materials and Methods:A total of 1680 consecutive stainless steel (SS) 2 × 12-mm MBS miniscrews were placed in 840 patients (405 males and 435 females; mean age, 16 ± 5 years). All screws were placed lateral to the alveolar process and buccal to the lower first and second molar roots. The screw heads were at least 5 mm superior to the soft tissue. Loads from 8 oz–14 oz (227 g–397 g, 231–405 cN) were used to retract the mandibular buccal segments for at least 4 months.Results:Overall, 121 miniscrews out of 1680 (7.2%) failed: 7.31% were in MM and 6.85% were in AG (statistically insignificant difference). Failures were unilateral in 89 patients and bilateral in 16. Left side (9.29%) failures was significantly greater (P < .001) compared with those on the right (5.12%). Average age for failure patients was 14 ± 3 years.Conclusion:MBS miniscrews were highly successful (approximately 93%), but there was no significant difference between placement in MM or AG. Failures were more common on the patient''s left side and in younger adolescent patients. Having 16 patients with bilateral failures suggests that a small fraction of patients (1.9%) are predisposed to failure with this method.     

A Comparitive Clinical Study Between Self Tapping and Drill Free Screws as a Source of Rigid Orthodontic Anchorage

Background and Objectives  

Self-tapping miniscrews are commonly being used as a temporary anchorage device for orthodontic purpose. A prerequisite for the insertion of these screws is the preparation of a pilot hole, which is time consuming and may result in damage to nerves, tooth root, drill bit breakage and thermal necrosis of bone. On the other hand the design of drill-free screws enables them to be inserted without drilling. The aim of this prospective study was to compare the stability and clinical response of the soft tissue around the self tapping and drill free screws when used for orthodontic anchorage for en mass retraction of maxillary anterior teeth.     

A radiographic evaluation of the availability of bone for placement of miniscrews

Monocortical screws are increasingly being used to enhance orthodontic anchorage. The most frequently cited clinical complication is soft tissue irritation. It is thus clinically advantageous for these miniscrews to be placed in attached mucosa. The purpose of this study was to (1) determine radiographically the most coronal interradicular sites for placement of miniscrews in orthodontic patients and (2) determine if orthodontic alignment increases the number of sites with adequate interradicular bone for placement of these screws. Sixty panoramic radiographs (n = 30 pretreatment, n = 30 posttreatment) of orthodontic patients were obtained from an archival database after Institutional Review Board approval. Selection criteria included minimal radiographic distortion and complete eruption of permanent second molars. Interradicular sites were examined with a digital caliper for presence of three and four mm of bone. If three or four mm of bone existed, then a vertical measurement from the cementoenamel junction (CEJ) to first measurement was made. In addition, the magnification error inherent in panoramic radiographs was estimated. Ninety-five percent confidence intervals were calculated for the vertical distances from the CEJ to the horizontal bone location. Bone stock for placement of screws was found to exist primarily in the maxillary (mesial to first molars) and mandibular (mesial and distal to first molars) posterior regions. Typically, adequate bone was located more than halfway down the root length, which is likely to be covered by movable mucosa. Inability to place miniscrews in attached gingiva may necessitate design modifications to decrease soft tissue irritation.     

MGBM system: new protocol for Class II non extraction treatment without cooperation

This article describes a method to treat Class II malocclusions with no patient cooperation. The technique involves converting the Class II molar relationship to a Class I in the initial phase of treatment by moving the maxillary molars distally with superelastic coils and wire. Anchorage is provided by a transpalatal bar attached to the first premolars and connected to 2 palatal miniscrews. Once the molars are positioned correctly, the palatal miniscrews are removed and miniscrews are inserted bilaterally in the buccal bone between the first molar and the second premolar. These miniscrews serve as the anchorage for the retraction of the premolars, canines and incisors.     

Mini-implant temporary anchorage devices: orthodontic applications

Skeletal anchorage, the concept of using the skeleton to control tooth movement, has been reported in the orthodontic literature since the early 1980s. Various forms of skeletal anchorage, including miniscrews, mini-plates, and intentionally ankylosed teeth have been reported in the literature. Recently, great emphasis has been placed on the miniscrew type of temporary anchorage device (TAD). These devices are small, are implanted with a relatively simple surgical procedure, and increase the potential for better orthodontic results. This article will present the indications of these devices along with clinical cases, discuss some of the common complications associated with these devices, and describe the placement and removal procedures for self-drilling TADs.     

Biomechanical considerations for total distalization of the maxillary dentition using TSADs

Class II malocclusions have traditionally been treated as nonextraction, extraction, or orthognathic surgery depending on the severity of the dental and skeletal discrepancies. To enhance function and improve esthetics with nonextraction treatment, functional appliances, tooth-borne molar distalization, and Class II elastics have been used, but they require patient cooperation and have drawbacks such as mesial movement of the anchor teeth, molar extrusion, and flaring of the incisors. Recently, with the application of temporary skeletal anchorage devices (TSADs) in patients with Class II malocclusions, clinicians have been able to achieve total distalization of the maxillary dentition without patient compliance and with less unwanted tooth movement. Before a clinician uses a TSAD, they must consider where to place it and what type to use for efficient, total arch distalization of the maxilla. TSADs such as miniscrews and miniplates can be inserted on the buccal and palatal sides for total arch distalization. When using them, the center of resistance of the entire maxillary dentition should be determined to obtain en masse movement of the maxillary dentition by a statically determinate force system. The treatment effects and the difference in biomechanics between buccal miniscrews and modified C-palatal plates (MCPPs) for total arch distalization of the maxilla are presented in this paper based on finite element and clinical studies. Additionally, a strategy for efficient total arch distalization with MCPPs is discussed along with considerations for the position of the second and third molars after total arch distalization.     

Removal torque of miniscrews used for orthodontic anchorage--a preliminary report

PURPOSE: Implant anchors such as miniscrews and miniplates have been loaded immediately for anchorage during orthodontic treatment. The purpose of this study was to measure the removal torque of immediately loaded miniscrews after clinical usage and to determine the possible factors associated with this value. MATERIALS AND METHODS: From 29 patients with malocclusions, 46 miniscrews were removed, and removal torque was measured with a torque gauge. Removal torque values were subjected to statistical analysis for possible association of different clinical characteristics. RESULTS: The mean removal torque value was 1.10 kg x cm, and removal torques for 50% of the implants were greater than 0.89 kg x cm (8.7 N x cm). Removal torque values were significantly higher in the mandible than in the maxilla. The removal torques of 15-mm and 17-mm miniscrews were significantly higher than those of 13-mm miniscrews. Therefore, the site of implantation and miniscrew length were important factors associated with removal torque. However, there was no significant correlation between the removal torque value and age, gender, healing time, or time in function. DISCUSSION: When miniscrews are used as anchorage for uprighting tipped molars, excessive torque in a counterclockwise direction may loosen them. From the measurements obtained in this investigation, miniscrews can sufficiently sustain an uprighting moment. CONCLUSION: The removal torque values of the majority of miniscrews in this study population when loaded immediately as orthodontic anchorage were greater than 0.89 kg x cm, and this was sufficient for these implants to fulfill their purpose as anchors in 3-dimensional tooth movements.     

Do miniscrews remain stationary under orthodontic forces?

Miniscrews have been used in recent years for anchorage in orthodontic treatment. However, it is not clear whether the miniscrews are absolutely stationary or move when force is applied. Sixteen adult patients with miniscrews (diameter = 2 mm, length = 17 mm) as the maxillary anchorage were included in this study. Miniscrews were inserted on the maxillary zygomatic buttress as a direct anchorage for en masse anterior retraction. Nickel-titanium closed-coil springs were placed for the retraction 2 weeks after insertion of the miniscrews. Cephalometric radiographs were taken immediately before force application (T1) and 9 months later (T2). The cephalometric tracings at T1 and T2 were superimposed for the overall best fit on the structures of the maxilla, cranial base, and cranial vault to determine any movement of the miniscrews. The miniscrews were also evaluated clinically for their mobility (0: no movement, 1: < or =0.5 mm, 2: 0.5-1.0 mm, 3: >1.0 mm). The mobility of all miniscrews was 0 at T1 and T2. On average, the miniscrews tipped forward significantly, by 0.4 mm at the screw head. The miniscrews were extruded and tipped forward (-1.0 to 1.5 mm) in 7 of the 16 patients. Miniscrews are a stable anchorage but do not remain absolutely stationary throughout orthodontic loading. They might move according to the orthodontic loading in some patients. To prevent miniscrews hitting any vital organs because of displacement, it is recommended that they be placed in a non-tooth-bearing area that has no foramen, major nerves, or blood vessel pathways, or in a tooth-bearing area allowing 2 mm of safety clearance between the miniscrew and dental root.     

Use of miniscrews as temporary anchorage devices in orthodontic practice. I--Introduction

AIM: To describe the use of miniscrews as temporary anchorage devices to facilitate mesial, distal and vertical orthodontic tooth movement. METHOD: The development of miniscrews and the direct and indirect application of forces from these devices are described. Case reports will be given in a second paper.     

一种新的种植体支抗技术在临床中的应用

目的使用新的微螺钉种植支抗方法远中移动整个上颌牙列。方法采用不锈钢质微螺钉种植体植入颧下嵴区（IZC），提供最佳骨性支抗，并大大简化操作的方法。结果采用新的微螺钉种植方法远中移动整个上颌牙列，在临床上获得成功。结论在IZC区使用不锈钢质微螺钉种植体作支抗，可直接实现整个上颌牙列的远中移动。     

Combined use of miniscrews and continuous arch for intrusive root movement of incisors in Class II division 2 with gummy smile

Adequate intrusion and torque control of the retroclined maxillary incisors are critical for the treatment of Class II division 2 (div2) malocclusion. In addition, anterior retraction via lingual root movement can be challenging. This case report demonstrates a combined use of miniscrews and continuous arch with additional torque for intrusion, retraction, and torque control of maxillary incisors in the Class II div2 with gummy smile. A 20-year-old woman presented with multiple issues, including impacted canine, lip protrusion, prolonged retained mandibular primary molar, and two missing maxillary premolars. In order to improve her facial profile and eliminate the need for prosthetic work, the mandibular primary molar and contralateral premolar were extracted. Two miniscrews were placed at the maxillary buccal alveolar bone to apply the posterosuperior force for retraction of anterior teeth, with additional labial crown torque on the arch wire. The results were the intrusion (4 mm) and lingual root movement (17°) of the maxillary incisors without anchorage loss of maxillary molars, flattening of the Curve of Spee, and Class I molar relation that were maintained after 50 months of retention period. The combined use of miniscrews and continuous arch could be a reliable and effective treatment modality for torque control and intrusion of retroclined maxillary incisors in the Class II div2 patient.     

Minor tooth movements using microimplant anchorage: case reports

For the treatment of extruded or tipped molars, various conventional techniques have been used. But those methods may lead to undesirable movement of the anchorage units and lengthen treatment time because of limited tooth-borne anchorage potential. Introduction of microimplants as orthodontic anchorage has expanded treatment possibilities because of their advantages. Some advantages are a less complex surgical procedure, decrease in cost, immediate loading, and their ability to be placed in any area of the alveolar bone. This article will illustrate clinical experiences in patients who were treated with the intrusion of overerupted molars, the up-righting of tilted molars, and other clinical applications for minor tooth movements. Anchorage control was achieved with the surgical insertion of titanium microimplants for immediate loading in the alveolar bone. When needed, minimal fixed appliances were used and orthodontic treatment was completed without any other complications.     

Pull-out strength of monocortical screws placed in the maxillae and mandibles of dogs.

BACKGROUND: Mini-implants can facilitate orthodontic tooth movement by serving as anchors. The purpose of this investigation was to determine whether the pull-out strength of screws in bone varies depending on the site of insertion in the maxilla or the mandible. MATERIALS: Fifty-six titanium screws (2 mm diameter, 6 mm length, Synthes USA, Monument, Colo) were placed in 4 beagle dogs (14 screws per dog) within 30 minutes after they were killed. The screws were inserted to obtain monocortical anchorage, at predetermined sites in the anterior, middle, and posterior regions of the jaws bilaterally. Two screws were placed in the posterior palate in each dog. The jaws were harvested, and bone blocks, each containing a screw, were prepared for mechanical testing. The bone/screw block was aligned on a custom-made fixture, and the maximum force (F max ) at pullout was recorded. Cortical bone thickness was measured after extraction of the screw. Statistical analyses to test for differences were conducted with ANOVA and Tukey-Kramer tests. RESULTS: Screws placed in the anterior mandibular region had significantly ( P < .05) lower F max (134.5 +/- 24N, mean +/- SE) than those placed in the posterior mandibular region (388.3 +/- 23.1N). Regression analyses suggested a weak (r = 0.39, P = .02) but significant correlation between F max and cortical bone thickness. CONCLUSIONS: The bone supporting monocortical screws would most likely withstand immediate loading and support tooth-moving forces.