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Microimplant screw anchoage Review

Comprehensive Review of Microimplant Screw Anchorage in Orthodontics

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Comparison of the intrusion effects on the maxillary incisors between implant anchorage and J-hook headgear AJODO May 2008, Toru Deguchi etal

Introduction: Recently, miniscrews have been used to provide anchorage during orthodontic treatment, especially for incisor intrusion. Miniscrews during incisor intrusion are commonly used in implant orthodontics. Traditionally, effective incisor intrusion has been accomplished with J-hook headgear. In this study, we compared the effect of incisor intrusion, force vector, and amount of root resorption between implant orthodontics and J-hook headgear. Methods: Lateral cephalometric radiographs from 8 patients in the implant group and 10 patients in the J-hook headgear group were analyzed for incisor retraction. The estimated force vector was analyzed in the horizontal and vertical directions in both groups. Root resorption was also measured on periapical radiographs. Results: In the implant group, significant reductions in overjet, overbite, maxillary incisor to palatal plane, and maxillary incisor to upper lip were observed after intrusion of the incisors. In the J-hook headgear group, significant reductions in overjet, overbite, maxillary incisor to upper lip, and maxillary incisor to SN plane were observed after intrusion of the incisors. There were significantly greater reductions in overbite, maxillary incisor to palatal plane, and maxillary incisor to upper lip in the implant group than in the J-hook headgear group. Estimated force analysis resulted in significantly more force in the vertical direction and less in the horizontal direction in the implant group. Furthermore, significantly less root resorption was observed in the implant group compared with the J-hook headgear group. Conclusions: The maxillary incisors were effectively intruded by using miniscrews as orthodontic anchorage without patient cooperation. The amount of root resorption was not affected by activating the ligature wire from the miniscrew during incisor intrusion.

Hyo-sang Park etal:Treatment effects and anchorage potential of sliding mechanics with titanium screws compared with the Tweed-Merrifield technique AJODO April 2008 • Volume 133 • Number 4, page 593

The purposes of this study were to quantify the treatment effects of titanium screws on en-masse retraction of 6 anterior teeth and to compare the anchorage potential of treatment with titanium screws with the Tweed-Merrifield technique, which requires patient compliance with a high-pull J-hook. Sixteen nongrowing patients (14 women, 2 men; ages, 22.5 ± 4.8 years) who had been treated orthodontically for bialveolar protrusion were selected. All patients had 2 maxillary first premolars extracted, 13 had mandibular first premolars extracted, and 3 had second premolars extracted. Maxillary titanium screws were placed in all patients to provide anchorage for retraction of 6 anterior teeth. Screws were placed in 8 patients to apply intrusive force to the mandibular posterior teeth. To compare the anchorage potential with a high-pull J-hook, 14 nongrowing patients (11 women, 3 men; ages, 22.9 ± 4.0 years) who were treated with the Tweed-Merrifield technique and had an excellent compliance with a high-pull J-hook were used. There was more anchorage loss of the maxillary posterior teeth in the Tweed-Merrifield group than in the titanium screw group. Both groups had excellent vertical control of the maxillary posterior teeth. There was a skeletal effect on the maxilla—reduction of A-point in the titanium screw group; this contributed to improvement of the facial profile. Treatment time in the titanium screw group was less compared with the Tweed-Merrifield technique. The success rate for the titanium screws was 87% in 25.6 ± 5.5 months. These results suggest that titanium screws can provide acceptable and reliable anchorage and might produce skeletal effects on the maxilla.

Yu-Chih Wang, Eric J.W. Liou. Comparison of the loading behavior of self-drilling and predrilled miniscrews throughout orthodontic loading. AJODO January 2008 • Volume 133 • Number 1, page 38

Introduction: A predrilled miniscrew, when used as a temporary anchorage device in the infrazygomatic crest of the maxilla, can be displaced under orthodontic loading. The purpose of this retrospective cephalometric study was to compare the loading behavior of predrilled and self-drilling miniscrews placed in the infrazygomatic crest of the maxilla.

Hyo-Sang Park, Youn-Ju Lee, Seong-Hwa Jeong, Tae-Geon Kwon. Density of the alveolar and basal bones of the maxilla and the mandible. AJODO January 2008 • Volume 133 • Number 1, page 30

            Objectives: The purpose of this investigation was to quantitatively evaluate density of the alveolar and basal bones of the maxilla and the mandible.

Osseointegration of miniscrews: a histomorphometric evaluation

European journal of orthodontics.Eur J Orthod.2007 Oct;29(5):437-42.

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.

Chen Y-H, Chang, H-H, Chen Y-J, Lee D, Chiang H-H, Yao C-C. Root contact during insertion of miniscrews for orthodontic anchorage increases the failure rate: an animal study. Clin. Oral Impl. Res. Oct, 2007

            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.

Choi, B. H., J. Li, et al. (2007). "Ingestion of orthodontic anchorage screws: an experimental study in dogs." Am J Orthod Dentofacial Orthop 131(6): 767-8.

            INTRODUCTION: Sharp-edged foreign bodies that are accidentally swallowed can become lodged in the stomach. This animal study was undertaken to determine the outcome of orthodontic anchorage screw ingestion. METHODS: We evaluated radiographs of 10 mixed-breed dogs that ingested 10 orthodontic anchorage screws and 10 reamers (1 screw and 1 reamer per dog). RESULTS: All orthodontic anchorage screws and all but 2 reamers were spontaneously passed within 7 days. CONCLUSIONS: Further investigation is needed to determine whether the results of our animal study agree with clinical findings.

Cornelis, M. A., N. R. Scheffler, et al. (2007). "Systematic review of the experimental use of temporary skeletal anchorage devices in orthodontics." Am J Orthod Dentofacial Orthop 131(4 Suppl): S52-8.

            INTRODUCTION: Our aim was to review the experimental literature to determine what is known about functional and morphological tissue reactions around orthodontically loaded temporary skeletal anchorage devices. METHODS: The PubMed electronic database and the reference citations in published articles were searched to the end of April 2006. The inclusion criteria were animal studies about orthodontically loaded skeletal anchorage consisting of metallic bone plates or screw implants of 2.2 mm diameter or less. Data on healing time, force application, stability, side effects, and osseointegration were collected by 2 independent readers. RESULTS: Eight articles met the selection criteria. The healing times ranged from 0 to 12 weeks, and the amount of force varied from 25 to 500 g. Implant stability was generally achieved without severe side effects. Direct bone-screw contact was reported to be 10% to 58%, and osseointegration increased with loading time. Nevertheless, no significant difference in bone-screw contact was found between loaded and unloaded screw implants, or between tension and pressure sides of loaded implants. CONCLUSIONS: This review highlights some positive experimental findings that apply in clinical practice. However, questions concerning optimal force systems, surgical techniques and placement, and healing times remain. Future research should be well controlled and based on standardized protocols to test specific hypotheses.

Gelgor, I. E., A. I. Karaman, et al. (2007). "Comparison of 2 distalization systems supported by intraosseous screws." Am J Orthod Dentofacial Orthop 131(2): 161 e1-8.

            INTRODUCTION: The aim of this study was to compare the effects of 2 distalization systems supported by intraosseous screws for maxillary molar distalization. METHODS: Forty subjects with skeletal Class I dental Class II malocclusion were divided into group 1 (8 girls, 12 boys) and group 2 (11 girls, 9 boys). An anchorage unit was prepared by placing an intraosseous screw in the premaxillary area of each subject. To increase the anchorage in group 2, we used an acrylic plate resembling the Nance button around the screw. The screws were placed and immediately loaded to distalize the maxillary first molars or second molars when they were present. Skeletal and dental changes were measured on cephalograms, and dental casts were obtained before and after distalization. RESULTS: The average distalization times were 4.6 months for group 1 and 5.4 months for group 2. On the cephalograms, the maxillary first molars were tipped 9.05 degrees in group 1 and 0.75 degrees in group 2. The mean distal movements were 3.95 mm in group 1 and 3.88 mm in group 2. On the dental casts, the mean distalization amounts were 4.85 mm for group 1 and 3.70 mm for group 2. In group 1, the maxillary molars were rotated distopalatally to a moderate degree, but this was not significant in group 2. Mild protrusion of the maxillary central incisors was also recorded for group 1 but not for group 2. However, there were no changes in overjet, overbite, and mandibular plane angle measurements for either group. CONCLUSIONS: Immediately loaded intraosseous screw-supported anchorage units were successful for molar distalization in both groups. In group 2, side effects such as molar tipping and rotation were smaller, but distalization times were longer and hygiene was poorer.

Hedayati, Z., S. M. Hashemi, et al. (2007). "Anchorage value of surgical titanium screws in orthodontic tooth movement." Int J Oral Maxillofac Surg 36(7): 588-92.

            The aim of this study was to evaluate the clinical stability and anchorage value of titanium screws in orthodontic tooth movement. Nine patients, who needed maximum anchorage for canine retraction, were selected. Records of 10 patients with similar malocclusions who had received conventional treatment were used as controls. In the maxilla and mandible 27 mini-screws, diameter 2mm and length 9 or 11mm, were used. At the end of the first stage of orthodontic treatment the first premolar teeth were extracted after taking a lateral cephalometric radiograph. After 1 week, a retraction force of 180g was applied to the canines. The second cephalometric X-rays were taken and evaluated after the completion of canine retraction (mean duration of 23.2 weeks). Results were analysed using Fisher Exact, Wilcoxon signed ranks and paired t-tests. Displacement of the first molars and screws before and after treatment showed no significant changes in either the vertical or horizontal plane. The first molar movements in the study and control groups were only significant in the antero-posterior plane in both maxilla and mandible. Of the 9 screws in maxilla and 18 screws in mandible, 2 and 3 screws showed clinical failure, respectively. The failed screws were replaced by other screws that withstood the applied force until the end of treatment. In conclusion, titanium screws can be used reliably as a form of anchorage.

Kuroda, S., Y. Sugawara, et al. (2007). "Clinical use of miniscrew implants as orthodontic anchorage: success rates and postoperative discomfort." Am J Orthod Dentofacial Orthop 131(1): 9-15.

            INTRODUCTION: In this study, we evaluated the clinical usefulness of miniscrews as orthodontic anchorage. We examined their success rates, analyzed factors associated with their stability, and evaluated patients' postoperative pain and discomfort with a retrospective questionnaire. METHODS: Seventy-five patients, 116 titanium screws of 2 types, and 38 miniplates were retrospectively examined. Each patient was given a questionnaire that included a visual analog scale to indicate discomfort after implantation. RESULTS: The success rate for each type of implant was greater than 80%. The analysis of 79 miniscrews with a 1.3-mm diameter showed no significant correlations between success rate and these variables: age, sex, mandibular plane angle, anteroposterior jaw-base relationship, control of periodontitis, temporomandibular disorder symptoms, loading, and screw length. Most patients receiving titanium screws or miniplates with mucoperiosteal-flap surgery reported pain, but half of the patients receiving miniscrews without flap surgery did not report feeling pain at any time after placement. In addition, patients with miniscrews reported minimal discomfort due to swelling, speech difficulty, and difficulty in chewing. CONCLUSIONS: Miniscrews placed without flap surgery have high success rates with less pain and discomfort after surgery than miniscrews placed with flap surgery or miniplates placed with either procedure.

Kuroda, S., Y. Sugawara, et al. (2007). "Anterior open bite with temporomandibular disorder treated with titanium screw anchorage: evaluation of morphological and functional improvement." Am J Orthod Dentofacial Orthop 131(4): 550-60.

            Skeletal anterior open bite is one of the most challenging malocclusions to correct because it is difficult to establish absolute anchorage for molar intrusion with traditional orthodontic mechanics. In addition, patients with anterior open bite sometimes have signs and symptoms of temporomandibular disorders (TMD). In this article, we report the successful treatment of a patient with severe skeletal anterior open bite and TMD; we used titanium screw anchorage. The patient, a woman, age 19 years 11 months, had an open bite of -4.0 mm and increased anterior lower facial height. The titanium screws were implanted in the mandible, and intrusion force was provided with elastic chains for 6 months. After active treatment for 36 months, her mandibular first molars were intruded about 3.0 mm, and good occlusion was achieved. Her retrognathic chin and convex profile were improved both by upward rotation of the mandible and advancement genioplasty with vertical reduction. After treatment, the TMD signs and symptoms were reduced, and improvements of both function and occlusion were achieved. Molar intrusion with titanium screw anchorage might be a useful treatment option to improve function, occlusion, and facial esthetics in patients with severe anterior open bite and TMD.

Kuroda, S., K. Yamada, et al. (2007). "Root proximity is a major factor for screw failure in orthodontic anchorage." Am J Orthod Dentofacial Orthop 131(4 Suppl): S68-73.

            INTRODUCTION: The purpose of this study was to evaluate root proximity as a risk factor for the failure of miniscrews used as orthodontic anchorage. METHODS: We used dental radiographs and 3-dimensional computed tomography images to examine 216 titanium screws in 110 patients. Each screw was classified according to its proximity to the adjacent root. Category I, the screw was absolutely separate from the root; category II, the apex of the screw appeared to touch the lamina dura; and category III, the body of the screw was overlaid on the lamina dura. If the orthodontic force could be applied to the screw for 1 year (or until completion of orthodontic treatment), we recorded the screw anchorage as a success. RESULTS: The screws had a high success rate--above 80%. Screws placed in the maxilla had a significantly higher success rate than those in the mandible. There was a significant correlation between success rate and root proximity. There were significant differences in the success rates between categories I and II, I and III, and II and III. Although screws in all 3 categories in the maxilla and categories I and II in the mandible showed high success rates above 75%, screws in category III in the mandible had a low success rate of 35%. CONCLUSIONS: The proximity of a miniscrew to the root is a major risk factor for the failure of screw anchorage. This tendency is more obvious in the mandible.

Kuroda, S., T. Yanagita, et al. (2007). "Titanium screw anchorage for traction of many impacted teeth in a patient with cleidocranial dysplasia." Am J Orthod Dentofacial Orthop 131(5): 666-9.

            INTRODUCTION: Cleidocranial dysplasia (CCD) is a rare inherited skeletal dysplasia, often with prolonged retention of deciduous teeth and several impacted permanent successors and supernumerary elements. METHODS: This article demonstrates the usefulness of titanium screws for orthodontic anchorage to induce eruption of the impacted teeth in a patient with CCD. A boy, aged 10 years 11 months, had a number of impacted permanent teeth. After the supernumerary teeth were extracted and the incisors were surgically exposed, 2 titanium screws were placed in the palate without incisions or flap surgery. After implantation, a lingual arch appliance was placed, and orthodontic load began 4 weeks after surgery with an elastic chain. RESULTS: After 4 months of traction, 3 impacted incisors had erupted into the mouth. CONCLUSIONS: This new method for retraction of impacted teeth can reduce the patient's treatment time and psychological stress. Treatment with titanium screws for traction of impacted teeth might be a new treatment strategy for managing CCD patients.

Massif, L., L. Frapier, et al. (2007). Orthod Fr 78(2): 123-132.

            The recent introduction of the new systems of intraosseous anchorages called mini-screw, allowing an immediate loading, has revolutioned the clinical and biomechanical approach of anchorage in orthodontics. Trans-gingival insertion by a manual screwdriver is done easily and most frequently without before-hole. The goal of this experimental study is to show that the realization of a before-hole limits the intraosseous constraints during screwing. This having short-term effects on the primary stability of the mini-screws and long-term effects on their maintenance. Materials and methods: two self-drilling and self-tapping mini-screws Aarhus((R)) Medicon of 1.6 and 1.3 mm diameters are screwed with a manual screwdriver, without then with a before-hole, in a plate of cortical bone fixed on a sensor measuring the forces and the couple. Results: the realization of a before-hole in the cortical bone significantly decreases the maximum vertical force (FVM) at the beginning of screwing (p < 0.0001) and the maximum screwing couple (CVM) at the end of the screwing (p < 0.0001), this independently the diameter of the screw. Conclusion: screwing without before-hole led to the alteration of the osseous surface layer caused by micro fractures which limit the possibilities of blocking of the mini-screws. L'introduction recente des nouveaux systemes d'ancrages intra-osseux appeles mini-vis, permettant une mise en charge immediate, a revolutionne l'approche clinique et biomecanique de l'ancrage en orthodontie. L'insertion trans-gingivale par un tournevis manuel se fait aisement et le plus frequemment sans avant-trou. L'objectif de cette etude experimentale est de demontrer que la realisation d'un avant-trou limite les contraintes intra-osseuses lors du vissage, ceci ayant des consequences a court terme sur la stabilite primaire des mini-vis et a long terme sur leur maintien. Materiels et methodes : deux mini-vis auto-forantes et auto-taraudantes Aarhus((R)) Medicon de diametres 1,6 et 1,3 mm sont vissees avec un tournevis manuel, sans puis avec un avant-trou, dans une lamelle d'os cortical fixee sur un capteur mesurant les forces et le couple. Resultats : la realisation d'un avant-trou dans l'os cortical diminue significativement la force verticale maximale (FVM) au debut du vissage (p < 0,0001) et le couple de vissage maximal (CVM) en fin de vissage (p < 0,0001), ceci quelque soit le diametre de la vis. Conclusion : le vissage sans avant-trou conduit au delabrement de la couche osseuse superficielle par l'apparition de microfractures limitant les possibilites de blocage des mini-vis.

Mizrahi, E. and B. Mizrahi (2007). "Mini-screw implants (temporary anchorage devices): orthodontic and pre-prosthetic applications." J Orthod 34(2): 80-94.

            Mini-screw implants, often referred to as temporary anchorage devices (TADs), have become an accepted component of orthodontic treatment. The comparatively simple technique for the placement of these mini-screws is described with emphasis on the importance of correct site selection as well as an understanding of the possible complications that may arise. The application and description of appliances incorporating mini-screws are described with the aid of typodont models and clinical examples. While the technique is of primary relevance to orthodontists, the use of mini-screws as an aid for pre-prosthodontic tooth movement is also of relevance to prosthodontists. From the examples described in this paper, extrapolations can be made by individual clinicians to situations relevant to their particular treatment plans. Examples of appliances used in conjunction with mini-screws are described; however, depending on the requirements of individual malocclusions, these designs may be modified.

Papadopoulos, M. A. and F. Tarawneh (2007). "The use of miniscrew implants for temporary skeletal anchorage in orthodontics: a comprehensive review." Oral Surg Oral Med Oral Pathol Oral Radiol Endod 103(5): e6-15.

            Though not a novel therapeutic concept, the use of miniscrew implants to obtain absolute anchorage has recently become very popular in clinical orthodontic approaches. The mode of anchorage facilitated by these implant systems has a unique characteristic owing to their temporary use, which results in a transient, albeit absolute anchorage. The foregoing properties together with the recently achieved simple application of these screws have increased their popularity, establishing them as a necessary treatment option in complex cases that would have otherwise been impossible to treat. The aim of this comprehensive review is to present and discuss the development, clinical use, benefits, and drawbacks of the miniscrew implants used to obtain a temporary but absolute/skeletal anchorage for orthodontic applications. Topics to be discussed include classification, types and properties (e.g., biocompatibility, osseointegration, types of anchorage, screw head, and thread design), clinical applications, site and placement method selection, clinical procedures for implant insertion, and loading and removal processes. Lastly, the potential complications and the advantages and disadvantages accompanying their use are presented.

Gelgor, I. E., A. I. Karaman, et al. (2006). "Use of the intraosseous screw for unilateral upper molar distalization and found well balanced occlusion." Head Face Med 2: 38.

            BACKGROUND: The aim of this study was to present a temporary anchorage device with intraosseous screw for unilateral molar distalization to make a space for the impacted premolar and to found well balanced occlusion in a case. CASE PRESENTATION: A 13-year-old male who have an impacted premolar is presented with skeletal Class I and dental Class 2 relationship. The screw was placed and immediately loaded to distalize the left upper first and second molar. The average distalization time to achieve an overcorrected Class I molar relationship was 3.6 months. There was no change in overjet, overbite, or mandibular plane angle measurements. Mild protrusion (0.5 mm) of the upper left central incisor was also recorded. CONCLUSION: Immediately loaded intraosseous screw-supported anchorage unit was successful in achieving sufficient unilateral molar distalization without anchorage loss. This treatment procedure was an alternative treatment to the extraction therapy.

Graham, J. W. (2006). "Screw implant anchorage." Am J Orthod Dentofacial Orthop 130(4): 431; author reply 431.

Harzer, W., M. Schneider, et al. (2006). "Direct bone placement of the hyrax fixation screw for surgically assisted rapid palatal expansion (SARPE)." J Oral Maxillofac Surg 64(8): 1313-7.

Huja, S. S., J. Rao, et al. (2006). "Biomechanical and histomorphometric analyses of monocortical screws at placement and 6 weeks postinsertion." J Oral Implantol 32(3): 110-6.

            Maxillofacial screws are increasingly being used in orthodontics to provide anchorage for tooth movement. The objective of this study was to determine the biomechanical stability as well as the bone tissue response of screws at 6 weeks postinsertion in a canine model. Seven skeletally mature male dogs received 102 screws (2 x 6 mm or 2 x 8 mm) at predetermined sites. Twenty screws became loose or were lost during the 6-week undisturbed healing period. Forty-eight screws were randomized for mechanical testing and 34 for histology. Peak pullout strength was recorded and approximately 80-microm sections were examined for histomorphometric parameters. Statistical analyses were conducted by analysis of variance and Tukey-Kramer method. Mean +/- SE peak pullout strengths for the various sites ranged from 153.5 +/- 37.6 N to 389.3 +/- 32.5 N with no significant (P < .05) differences at immediate placement and 6 weeks postinsertion. Bone contact ranged from 79% to 95%. Histomorphometric analyses indicated higher bone formation rate in the mandible than in the maxilla and a gradient of decreasing turnover with increasing distance from the screw interface. These results provide the clinical orthodontist with an estimate of the holding power of these screws and an understanding of early biological healing response associated with self-drilling screws.

Kinzinger, G. S., H. Wehrbein, et al. (2006). "Molar distalization with pendulum appliances in the mixed dentition: effects on the position of unerupted canines and premolars." Am J Orthod Dentofacial Orthop 129(3): 407-17.

            INTRODUCTION: The pendulum appliance allows for rapid molar distalization without the need for patient compliance. Its efficiency has been confirmed in a number of clinical studies. However, the potential interactions and positional changes between the deciduous molars used for dental anchorage and the erupted and unerupted permanent teeth have yet to be clarified when this appliance is used for molar distalization in the mixed dentition. METHODS: Twenty-nine patients in the mixed dentition each received a modified pendulum appliance with a distal screw and a preactivated pendulum spring for bilateral distalization of the maxillary molars. The patients were divided into 4 groups based on dentition stages: patient group 1 (PG 1, n = 10) was in the early mixed dentition; patients had resorption of the distal root areas of the deciduous molars being used for dental anchorage, and the unerupted premolars were located at the distal margin of the deciduous molar root region. Based on radiographs taken before placement of the pendulum appliance, patient group 2 (PG 2, n = 10) was diagnosed as having a central location of the unerupted premolars. In the third group (PG 3, n = 4), the first premolars were already erupted and could be integrated into the dental anchorage, but the canines were not yet erupted. In the fourth group (PG 4, n = 5), the first premolars and both canines were fully erupted. RESULTS: Statistical analysis of the measured results showed significant differences in the side effects between PG 1 and PG 2. In patients being treated with pendulum appliances, the anchorage quality of the deciduous molars that were already partially resorbed in the distal root area was comparatively reduced. Consequently, the mesial drift of the deciduous molars and incisors was increased, without impairing the extent and quality of the molar distalization. Anchorage loss in the supporting area had no direct impact on the sagittal position of the unerupted premolars in the early mixed dentition. CONCLUSIONS: If permanent teeth have already started to erupt in the supporting area, additional space restrictions should be avoided in patients with critical topography, especially if there is little space for the unerupted canines. At this stage of the mixed dentition, premolar extraction or augmentation of the supporting area with extraoral headgear offers a therapeutic alternative to intraoral distalization appliances with exclusively dental anchorage.

Kircelli, B. H., Z. O. Pektas, et al. (2006). "Maxillary molar distalization with a bone-anchored pendulum appliance." Angle Orthod 76(4): 650-9.

            To obtain an effective and compliance-free molar distalization without an anchorage loss, we designed the bone-anchored pendulum appliance (BAPA). The aim of this study was to evaluate the stability of the anchoring screw, distalization of the maxillary molars, and the movement of teeth anterior to maxillary first molars. The study group comprised 10 patients (mean age 13.5 +/- 1.8 years) with Class II molar relationship. A conventional pendulum appliance was modified to obtain anchorage from an intraosseous screw instead of the premolars. The screw was placed in the anterior paramedian region of the median palatal suture. Skeletal and dental changes were measured on cephalograms, and dental casts were obtained before and after distalization. A super Class I molar relationship was achieved in a mean period of 7.0 +/- 1.8 months. The maxillary first molars distalized an average of 6.4 +/- 1.3 mm in the region of the dental crown by tipping distally an average of 10.9 degrees +/- 2.8 degrees . Also, the maxillary second premolar and first premolar moved distally an average of 5.4 +/- 1.3 mm and 3.8 +/- 1.1 mm, respectively. The premolars tipped significantly distally. No anterior incisor movement was detected. The BAPA was found to be an effective, minimally invasive, and compliance-free intraoral distalization appliance for achieving both molar and premolar distalization without any anchorage loss.

Koudstaal, M. J., K. G. van der Wal, et al. (2006). "The Rotterdam Palatal Distractor: introduction of the new bone-borne device and report of the pilot study." Int J Oral Maxillofac Surg 35(1): 31-5.

            Transverse maxillary hypoplasia, in adolescents and adults, is frequently seen as an acquired deformity and in congenital deformities patients and can be corrected by means of surgically assisted rapid maxillary expansion. Traditionally, the distractors for expansion are tooth-borne devices, i.e. hyrax appliances, which may have some serious disadvantages such as tooth tipping, cortical fenestration, skeletal relapse and loss of anchorage. In contrast, with bone-borne distractors most of the maxillary expansion is orthopedic and at a more mechanically desired level with less dental side effects. A new bone-borne palatal distractor has been developed. By activation the nails of the abutments plates automatically stabilizes the device and no screw fixation is necessary anymore. This new distractor is presented and the data of five acquired deformity and eight congenital deformity patients that were treated with this distractor are reported.

Ohashi, E., O. E. Pecho, et al. (2006). "Implant vs screw loading protocols in orthodontics." Angle Orthod 76(4): 721-7.

            OBJECTIVE: This systematic review presents the loading protocols applied when using implants and/or screws in orthodontic treatments. MATERIALS AND METHODS: Clinical trials which assessed the use of implants and/or screws for orthodontic anchorage and studies involving treatment on syndromic patients, surgery, other simultaneous treatments, or appliances (ie mini-plates) were considered. Electronic databases (Medline, Medline In-Process & Other Non-Indexed Citations, Lilacs, Pubmed, Embase, Web of Science, and All Evidence Based Medicine Reviews) were searched with the help of a senior Health Sciences librarian. Abstracts which appeared to fulfill the selection criteria were selected by consensus. The original articles were then retrieved and evaluated with a methodological checklist. References were also hand searched for possible missing articles. RESULTS: Eleven articles fulfilled the selection criteria established. Five studies involved the use of implants while six involved the use of screws for orthodontic purposes. An individual methodological analysis for each article was made. CONCLUSIONS: Loading protocols for implants involve a minimum waiting period of 2 months before applying orthodontic forces while loading protocols for screws involve immediate loading or a waiting period of 2 weeks to apply forces. Success rates for implants were on average higher than for screws.

Park, H. S., S. H. Jeong, et al. (2006). "Factors affecting the clinical success of screw implants used as orthodontic anchorage." Am J Orthod Dentofacial Orthop 130(1): 18-25.

            INTRODUCTION: The purposes of this study were to examine the success rates and find factors affecting the clinical success of screw implants used as orthodontic anchorage. METHODS: Eighty-seven consecutive patients (35 male, 52 female; mean age, 15.5 years) with a total of 227 screw implants of 4 types were examined. Success rates during a 15-month period of force application were determined according to 18 clinical variables. RESULTS: The overall success rate was 91.6%. The clinical variables of screw-implant factors (type, diameter, and length), local host factors (occlusogingival positioning), and management factors (angle of placement, onset and method of force application, ligature wire extension, exposure of screw head, and oral hygiene) did not show any statistical differences in success rates. General host factors (age, sex) had no statistical significance. Mobility, jaw (maxilla or mandible), and side of placement (right or left), and inflammation showed significant differences in success rates. Mobility, the right side of the jaw, and the mandible were the relative risk factors in the logistic regression analysis when excluding mobility, inflammation around the screw implants was added to the risk factors. CONCLUSIONS: To minimize the failure of screw implants, inflammation around the implant must be controlled, especially for screws placed in the right side of the mandible.

Philippot, R., P. Adam, et al. (2006). "[Survival of cementless dual mobility sockets: ten-year follow-up]." Rev Chir Orthop Reparatrice Appar Mot 92(4): 326-31.

            PURPOSE OF THE STUDY: We report a retrospective series of 106 total hip prosthesis with ten years follow-up. The purpose of this study was to analyze survival of cementless dual mobility sockets. MATERIAL AND METHODS: The series included 90 consecutive patients with 106 first-intention total hip prosthesis, all with cementless dual mobility sockets. All prosthesis (Novae-1 socket and Profil-1 stem, Serf) were implanted within a 6-month period. The stainless steal socket was coated with alumina and had two short anchorage studs and a superior mooring screw and a polyethylene retentive liner. The stem had a 22.2 mm chromium cobalt head. The main indication for arthroplasty was degenerative joint disease. Mean age at implantation was 56 years (range 23-87). All patients were seen for physical examination and x-rays every two or three years. We noted cup survival at ten years (actuarial method), defining surgical revision for cup replacement due to an aseptic cause as the endpoint. RESULTS: Twelve patients died during the 10-year follow-up and one was lost to follow-up. The Postel-Merle d'Aubligne score improved from 7.1 preoperatively to 15.8 at ten years. There were two isolated acetabular loosenings, two intra-prosthetic dislocations due to advanced wear of the polyethylene insert. The overall survival rate of the socket was 94.6% at ten years. There were no episodes of prosthetic instability in this series. DISCUSSION: This study demonstrates the good ten-year survival of the dual mobility socket, comparable to that of conventional prostheses. The absence of any case of prosthetic instability in this series confirms the good short-term and long-term stability of the dual mobility socket. Intraprosthetic dislocation, due to loss of the polyethylene retaining ring is the main limitation of this method. The incidence was however low (2% at ten years) and treatment was not a problem. We recommend using the dual-mobility socket as the first-intention implant for patients with a high risk of post-operative instability, but also recommend it for all patients aged over 70 years since instability is the leading cause of surgical revision after this age.

Rattanayatikul, C., K. Godfrey, et al. (2006). "Miniplates and screws in treatment of skeletal Class III malocclusion with missing posterior teeth. A case report." Aust Orthod J 22(2): 167-72.

            AIM: To describe the use of miniplates for temporary skeletal anchorage to distalise the entire lower dentition. METHODS: A 40 year-old woman presented with a skeletal Class III malocclusion and multiple missing maxillary and mandibular teeth. The treatment plan was to distalise the mandibular dentition. Two miniplates and screws in the mandibular retromolar region were used as temporary skeletal anchorage for Class I elastics. The entire lower dentition was distalised into a Class I incisor relationship with the miniplate and screw anchorage.

Wilmes, B., C. Rademacher, et al. (2006). "Parameters Affecting Primary Stability of Orthodontic Mini-implants." J Orofac Orthop 67(3): 162-174.

            AIM: Treatment options in orthodontics have been expanded by skeletal anchorage via mini-implants over the last few years. Sufficient primary stability is imperative to minimize implant loss rate. The aim of this study was to quantitatively analyze the factors influencing primary stability: bone quality, implant-design, diameter, and depth of pilot drilling. MATERIAL AND METHODS: Thirty-six pelvic bone segments (ilium) of country pigs were dissected and embedded in resin. To determine the primary stability, we measured the insertion torque of five different mini-implant types (tomas((R))-pin [Dentaurum, Ispringen, Germany] 08 and 10 mm, and Dual Top [Jeil Medical Corporation, Seoul, Korea] 1.6 x 8 and 10 mm plus 2 x 10 mm). Twenty-five or 30 implants were inserted into each pelvic bone segment following preparation of the implant sites using pilot drill diameters of 1.0, 1.1, 1.2 and 1.3 mm and pilot drill depths of 1, 2, 3, 6 and 10 mm. Five implants were inserted for reference purposes to establish comparability. Thicknesses of bone compacta were measured via micro-computer tomography. RESULTS: Insertion torques of orthodontic mini-implants and therefore primary stability varied greatly, depending on bone quality, implant-design, and preparation of implant site. Compared with the tomas((R))-pin, the Dual Top screw showed significantlygreater primary stability. Torque moments beyond 230 Nmm caused fractures of 9 Dual Top screws. CONCLUSION: Compacta thickness, implant design and implant site preparation have a strong impact on the primary stability of mini-implants for orthodontic anchorage. Depending on the insertion site and local bone quality, the clinician should choose an optimum combination of implant and pilot-drilling diameter and depth.

Yano, S., M. Motoyoshi, et al. (2006). "Tapered orthodontic miniscrews induce bone-screw cohesion following immediate loading." Eur J Orthod 28(6): 541-6.

            The aim of this study was to investigate the initial stability of tapered orthodontic miniscrews (T-type screws) after placement, the necessity of a healing period, and the propriety of immediate loading. Twenty male Wistar rats with a mean age of 20 weeks were divided into two groups. In the immediate-loading groups, straight orthodontic miniscrews (S-type screws) and T-type screws (five rats each) underwent experimental traction force for 2 weeks (W) immediately after placement. In the healing groups (S- and T-type, five rats each), force was applied for 2 W after a 6-W healing period. The right tibia in each rat was identified as the test limb, while the left tibia in each rat was used as the control group, and underwent no experimental force during the experimental period. The screw-to-bone contact was observed histologically and the bone-screw contact ratio was calculated. Scheffe's test was performed to compare the bone-screw contact ratio in each group using statistical software package (SPSS 8.0 for Windows). In the control group, the bone-screw contact ratio improved from 34.8 +/- 16.0 to 74.8 +/- 12.0 per cent with S-type screws in proportion to the experimental period (2 to 8 W, respectively). With the T-type screws in the test group, there was no significant difference between the immediate-loading and healing groups. In the immediate-loading group, the bone-screw contact ratio with T-type screws was significantly greater (82.3 +/- 15.0 per cent) than with the S-type screws (33.3 +/- 11.8 per cent; P < 0.05), suggesting that T-type screws can be used for orthodontic anchorage immediately after placement.

Youn, S. H. (2006). "Midline correction with mini-screw anchorage and lingual appliances." J Clin Orthod 40(5): 314-22; quiz 308.

Zhu, S. J., Y. H. Zhou, et al. (2006). "[Stability of upper molars with the application of implant anchorage]." Zhonghua Kou Qiang Yi Xue Za Zhi 41(1): 4-7.

            OBJECTIVE: To investigate the stability of upper molars with the application of micro-screw implant anchorage during orthodontic treatment. METHODS: Fifteen adult patients with severe maxillary protrusion were included. Upper first premolars were extracted and upper posterior anchorage was reinforced with micro-screw implant in all patients. The average treatment period to close the extraction space was 10.5 months. Cephalometric and cast analysis were carried out. RESULTS: During the treatment, the micro-screw implants kept stable in sagittal plane; neither the mesial-distal movement nor the rotation or tipping of the upper molars during the treatment was of statistic significance (P > 0.05); the edge of upper incisors was retracted by 6.99 mm on average, and no significant vertical change was observed (P > 0.05). CONCLUSIONS: Micro-screw implant could provide good anchorage control in the orthodontic treatment.

Asscherickx, K., B. V. Vannet, et al. (2005). "Root repair after injury from mini-screw." Clin Oral Implants Res 16(5): 575-8.

            Mini-implants and mini-screws are commonly used in orthodontics to provide extra anchorage. One potential insertion site is between the roots in the alveolar process, which results in a risk of damaging the roots of neighbouring teeth. In an animal-experimental study, 20 mini-screws (bracket screw bone anchors, BSBAs) were inserted into the mandible of five beagle dogs. Each dog received two BSBAs in each lower quadrant, between the roots of the second and third, and third and fourth premolars. Sequential point labelling was performed every 6 weeks with vital stains, and apical X-rays were taken every 6 weeks. Radiographic examination demonstrated damage at three roots because of insertion of the BSBAs. Histological examination at these three roots demonstrated an almost complete repair of the periodontal structure (e.g. cementum, periodontal ligament and bone) in a period of 12 weeks, following removal of the screws.

Asscherickx, K., B. V. Vannet, et al. (2005). Root repair after injury from mini-screw, Blackwell Synergy. 16: 575-8.

Carano, A., P. Lonardo, et al. (2005). "Mechanical properties of three different commercially available miniscrews for skeletal anchorage." Prog Orthod 6(1): 82-97.

            BACKGROUND: During the last 5 years, anchorage control with self-tapping miniscrews has become an important part of the clinical management of orthodontic patients. Yet, no studies have been performed for measuring mechanical properties of the currently available systems. OBJECTIVES: The purpose of this study is the evaluation of mechanical properties of three commercially available self-tapping screw systems used in orthodontic treatment. MATERIALS: three systems with a 1.5 mm diameter and 11 mm length screw (Leone, Firenze, Italy; M.A.S. Micerium, Avegno, Italy; Dentos, Korea) were examined. The results compared the resistance to bending, torque, pullout of each screw and the insertion moments needed to screw down each sample. CONCLUSIONS: All three miniscrews have mechanical properties that contribute to their safe use as skeletal anchorage in orthodontics. Although stainless steel has demonstrated to be more resistant to failure than titanium, its overall performance as material for miniscrews could be inferior to titanium. In order to facilitate the insertion, the asymmetric profile of the thread should be preferred to the symmetric cut. The ratio between the diameter of the drill and the diameter of the corresponding miniscrew is pivotal for the successful implantation and resistance of the miniscrews. Looking at the mechanical properties evaluated in this study, a cylindric shape of the screw is better than a conic one. The conic shape could be preferred in case the site of insertion is iterradicular and therefore limited to 2.5-3.5 millimetres.

Carano, A., S. Velo, et al. (2004). "Clinical applications of the Mini-Screw-Anchorage-System (M.A.S.) in the maxillary alveolar bone." Prog Orthod 5(2): 212-35.

            AIMS: anchorage control with self-tapping screws has become an important part of the clinical management of the orthodontic patients. Mechanical resistance and sites of insertion of miniscrews as orthodontic anchorage are critical to ensure successful outcomes. Aim of this clinical study was threefold: 1) to measure the mechanical resistance of the M.A.S., 2) to evaluate if the alveolar areas usually selected for mini-screws placement are adequate, 3) to illustrate the most frequent clinical application on the maxillary alveolar bone. METHODS: two methods were chosen to test these screws mechanically, representing two potential modes of failure during insertion or removal: torsional strenght and bending strenght. Three-dimension images of fifty maxillas have been retrieved from a group of 200 patients, age range between 20 and 40 years with a new type of tomogram called Newtom System. For each area mesio-distal and labio-lingual measurements from four horizontal cuts made at 2-5-8-11 mm below the bone-crest have been evaluated. RESULTS: the mean value of resistance to breakage in torsion is of 48.7 N.cm (around 5 Kg) for the miniscrew of 1.5 diameter, while the mean value of resistance to breakage in torsion is of 23.4 N.cm (around 2 Kg) for the miniscrew of 1.3 diameter.. The mean value of resistance to breakage in flexion is of 120.4 N (around 12 Kg) for the miniscrew of 1.5 diameter, while the mean value of resistance to the flexion is of 63.7 N (around 6 Kg) for the miniscrew of 1.3 diameter. On the maxillary alveolar bone the highest amount of bone was in mesio-distal dimension between 6 and 5 on the palatal side (minimum 1.9 mm at -11 mm cut; maximum 5.5 mm at -5 mm cut). The smallest amount of bone was in the tuber (minimum 0.2 mm; maximum 1.3 mm). Examination of the labio-palatal dimension demonstrated similar high thickness between 5-6 and 6-7 (minimum 3.7 mm at -11 mm cut; maximum 13.2 mm at -2 mm cut). The smallest amount of bone was recorded on the tuber (minimum 0.6 mm; maximum 4.1 mm). The following clinical applications are described: Closure of the extractions space, Symmetric intrusion of the incisors, Correction of the cant of the plane of occlusion and of the dental midline, Molar intrusion of one or two teeth, Molar distalization with the Distal Jet and miniscrews, Molar mesialization, Intermaxillary anchorage. CONCLUSIONS: the mechanical resistance of the miniscrews M.A.S. is suitable for their use in orthodontics. The best anatomical zones for their implantation are the interradicular spaces mesial to the first maxillary molars. From our experience to date, the miniscrews are a reliable and convenient system for skeletal anchorage when compared with other more invasive osseo-integrated systems.

Chen, F., K. Terada, et al. (2005). "Anchorage effect of various shape palatal osseointegrated implants: a finite element study." Angle Orthod 75(3): 378-85.

            The purpose of this study was to compare the anchorage effects of different palatal osseointegrated implants using a finite element analysis. Three types of cylinder implants (simple implant, step implant, screw implant) were investigated. Three finite element models were constructed. Each consisted of two maxillary second premolars, their associated periodontal ligament (PDL) and alveolar bones, palatal bone, palatal implant, and a transpalatal arch. Another model without an implant was used for comparison. The horizontal force (mesial 5N, palatal 1N) was loaded at the buccal bracket of each second premolar, and the stress in the PDL, implant, and implant surrounding bone was calculated. The results showed that the palatal implant could significantly reduce von Mises stress in the PDL (maximum von Mises stress was reduced 24.3-27.7%). The von Mises stress magnitude in the PDL was almost same in the three models with implants. The stress in the implant surrounding bone was very low. These results suggested that the implant is a useful tool for increasing anchorage. Adding a step is useful to lower the stress in the implant and surrounding bone, but adding a screw to a cylinder implant had little advantage in increasing the anchorage effect.

Gelgor, I. E., T. Buyukyilmaz, et al. (2004). "Intraosseous screw-supported upper molar distalization." Angle Orthod 74(6): 838-50.

            The aims of the present study were to investigate (1) the efficiency of intraosseous screws for anchorage in maxillary molar distalization and (2) the sagittal and vertical skeletal, dental, and soft tissue changes after maxillary molar distalization using intraosseous screw-supported anchorage. Twenty-five subjects (18 girls and seven boys; 11.3 to 16.5 years of age) with skeletal Class I, dental Class II malocclusion participated in the study. An anchorage unit was prepared for molar distalization by placing an intraosseous screw behind the incisive canal at a safe distance from the midpalatal suture following the palatal anatomy. The screws were placed and immediately loaded to distalize upper first molars or the second molars when they were present. The average distalization time to achieve an overcorrected Class I molar relationship was 4.6 months. The skeletal and dental changes were measured on cephalograms and dental casts obtained before and after the distalization. In the cephalograms, the upper first molars were tipped 8.8 degrees and moved 3.9 mm distally on average. On the dental casts, the mean distalization was five mm. The upper molars were rotated distopalatally. Mild protrusion (mean 0.5 mm) of the upper central incisors was also recorded. However, there was no change in overjet, overbite, or mandibular plane angle measurements. In conclusion, immediately loaded intraosseous screw-supported anchorage unit was successful in achieving sufficient molar distalization without major anchorage loss.

Huja, S. S., A. S. Litsky, et al. (2005). "Pull-out strength of monocortical screws placed in the maxillae and mandibles of dogs." Am J Orthod Dentofacial Orthop 127(3): 307-13.

            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.

Kawakami, M., S. Miyawaki, et al. (2004). "Screw-type implants used as anchorage for lingual orthodontic mechanics: a case of bimaxillary protrusion with second premolar extraction." Angle Orthod 74(5): 715-9.

            We present a case of bialveolar protrusion treated with second premolar extraction. The patient did not agree to placement of a visible labial appliance or to the use of a headgear. Therefore, a lingual orthodontic appliance was used, and titanium screws were placed into the buccal alveolar bone for orthodontic absolute anchorage and support of en masse retraction of the anterior teeth. Cephalometric superimposition and panoramic radiographs showed little anchorage loss and good occlusion at the end of treatment. Our results suggest that lingual treatment combined with a screw-type implant anchorage provides reliable and comfortable results for those seeking invisible treatment.

Kim, J. W., S. J. Ahn, et al. (2005). "Histomorphometric and mechanical analyses of the drill-free screw as orthodontic anchorage." Am J Orthod Dentofacial Orthop 128(2): 190-4.

            INTRODUCTION: Drill-free screws were developed to provide convenient orthodontic anchorage. The purpose of this study was to evaluate the effects of the drilling procedure on the stability of the screws under early orthodontic loading. METHODS: Thirty-two screws were inserted into the jaws of 2 beagles. The screws were divided into 2 groups of 16: the drilling group and the drill-free group. Screws in the drilling group were inserted into the site that had been drilled with a pilot drilling bur, and those in the drill-free group were inserted without drilling. A force of 200 to 300 g was applied using nickel-titanium coil springs 1 week after insertion. Twelve weeks after insertion, mobility was tested with Periotest (Siemens AG, Bensheim, Germany), and the screws with the surrounding bone were prepared for histomorphometric evaluation. RESULTS: Screws in the drill-free group showed less mobility and more bone-to-metal contact; they had more bone area compared with the drilling group, although bone osseointegration was generally found in both groups. CONCLUSIONS: With careful technique, drill-free screws can provide stable orthodontic anchorage.

Liou, E. J., B. C. Pai, et al. (2004). "Do miniscrews remain stationary under orthodontic forces?" Am J Orthod Dentofacial Orthop 126(1): 42-7.

            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.

Maino, B. G., G. Maino, et al. (2005). "Spider Screw: skeletal anchorage system." Prog Orthod 6(1): 70-81.

            The stability of the anchorage unit plays a very important role in orthodontic control. Controlled orthodontic movements such as retraction and/or protraction of teeth and intrusion of overerupted teeth are very difficult to achieve without patient cooperation and without causing undesirable reciprocal movement in the anchorage unit. The article describes characteristics, surgical procedure, and clinical use of the Spider Screw as an ideal non-dental and non-cooperation based anchorage system. The Spider Screws are self-tapping, titanium mini-screws with immediate loading capability. Their utilization involves a simple biomechanical principle combined with the utilization of minimum orthodontic mechanotherapy. Ideal orthodontic forces (in the range from 50 to 250 gr) can be applied to achieve the desired orthodontic movements. Complete osteointegration is neither expected nor desired with this anchorage system. The Spider Screw anchorage system can be used to support a variety of orthodontic movements specifically in clinical situations involving incomplete dental arches and limited cooperation as in many adult orthodontic cases. The ease of surgical placement combined with the reduced dimension of the Spider Screw diameter equally permits its use in clinical situations where anchorage recovery is necessary during treatment of complete dentitions in classical orthodontic therapy.

Seebeck, J., J. Goldhahn, et al. (2005). "Mechanical behavior of screws in normal and osteoporotic bone." Osteoporos Int 16 Suppl 2: S107-11.

            Fracture fixation in severe osteoporotic bone by means of implants that rely on screw anchorage is still a clinical problem. So far, a sufficiently accurate prediction of the holding capacity of screws as a function of local bone morphology has not been obtained. In this study the ultimate pullout loads of screws in the epi-, meta-, and diaphyseal regions of human tibiae were correlated to the cortical thicknesses and cancellous bone mineral densities at the screw axes determined from QCT densitometric data. Stepwise multiple linear regression showed that in regions with cortical thicknesses below 1.5 mm, cancellous density determined the ultimate pullout load (R2 = 0.85, p < 0.001), while in regions with cortices above 1.5 mm, cortical thickness alone significantly influenced the holding capacity of a screw (R2 = 0.90, p < 0.001). The findings of this study provide a basis for a bone morphology-related pre-operative estimation of the holding capacity of screws, which could help to improve their proper application in osteoporotic bone.

Travess, H. C., P. H. Williams, et al. (2004). "The use of osseointegrated implants in orthodontic patients: 2. Absolute anchorage." Dent Update 31(6): 355-6, 359-60, 362.

            Following the first article which explored the use of restorative implants in orthodontic patients which are later used to replace missing teeth, such as in hypodontia patients, this second paper examines the use of implants in orthodontics to provide 'Absolute Anchorage' after highlighting the standard orthodontic approaches to anchorage. It explains the advantages and disadvantages such methods give the specialist in treating full arch orthodontic patients over standard techniques used in modern orthodontics. Three different types of implant used in full arch orthodontic treatment are described in detail; the mid palatal implant, the OnPlant and the mini screw. The methods used in placing the implants and the techniques employed to gain the anchorage required are highlighted.

Keles, A., N. Erverdi, et al. (2003). "Bodily distalization of molars with absolute anchorage." Angle Orthod 73(4): 471-82.

            Palatal implants have been used over the last two decades to eliminate headgear wear and to establish stationary anchorage. In this case report, the stability of a palatal implant for distalization of molars bodily and for anchorage maintenance was assessed. The implant was a stepped screw titanium (4.5 mm diameter x 8 mm length), and it was placed in the palatal region for orthodontic purposes. A surgical template containing a metal drill housing was prepared. Angulation of the drill housing was controlled according to the radiologic tracing of the maxilla transferred to a plaster cast section in the paramedian plane. The implant was placed using a noninvasive technique (incision, flap, and suture elimination) and left transmucosally to facilitate the surgical procedure and to reduce the number of operations. The paramedian region was selected (1) to avoid the connective tissues of the palatine suture and (2) because it is considered to be a suitable host site for implant placement. After three months of healing, the implant was osseointegrated and orthodontic treatment was initiated. For molar distalization, the Keles Slider appliance was modified and, instead of a Nance button, a palatal implant was used for anchorage. The results showed that the molars were distalized bodily at five months, and no anchorage loss was observed. At the end of the treatment, the smile was improved, and an ideal Class I molar and canine relationship, an ideal overbite, and an ideal overjet were all achieved. In conclusion, palatal implants can be used effectively for anchorage maintenance and in space-gaining procedures. Use of a three-dimensional surgical template eliminated implant placement errors, reduced chair time, minimized trauma to the tissues, and enhanced osseointegration. This method can be used effectively to achieve distalization of molars bodily without anchorage loss.

Lin, J. C. and E. J. Liou (2003). "A new bone screw for orthodontic anchorage." J Clin Orthod 37(12): 676-81.

Maino, B. G., J. Bednar, et al. (2003). "The spider screw for skeletal anchorage." J Clin Orthod 37(2): 90-7.

Miyawaki, S., I. Koyama, et al. (2003). "Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage." Am J Orthod Dentofacial Orthop 124(4): 373-8.

            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.

Pierrisnard, L., F. Renouard, et al. (2003). "Influence of implant length and bicortical anchorage on implant stress distribution." Clin Implant Dent Relat Res 5(4): 254-62.

            BACKGROUND: Short implants present superior failure rates for everybody. PURPOSE: The aim of this theoretic study was to assess to what extent implant length and bicortical anchorage affect the way stress is transferred to implant components, the implant proper, and the surrounding bone. MATERIALS AND METHODS: Stress analysis was performed using finite element analysis. A three-dimensional linear elastic model was generated. All implants modeled were of the same diameter (3.75 mm) but varied in length, at 6, 7, 8, 9, 10, 11, and 12 mm (Branemark System, Nobel Biocare AB, Gothenburg, Sweden). Each implant was modeled with a titanium abutment screw and abutment, a gold cylinder and prosthetic screw, and a ceramic crown. The implants were seated in a supporting bone structure consisting of cortical and cancellous bone. An occlusal load of 100 N was applied at a 30 degrees angle to the buccolingual plane. RESULTS: With the selected model and bone properties, the coronal cortical anchorage was dominating, and the bone stress concentrated to that area. CONCLUSIONS: The maximum bone stress was virtually constant, independent of implant length and bicortical anchorage. The maximum implant stress, however, increased somewhat with implant length and bicortical anchorage.

Gotfredsen, K., T. Berglundh, et al. (2000). "Anchorage of titanium implants with different surface characteristics: an experimental study in rabbits." Clin Implant Dent Relat Res 2(3): 120-8.

            PURPOSE: To compare the anchorage of titanium implants with different surface roughness and topography and to examine histologically the peri-implant bone after implant removal. MATERIALS AND METHODS: Screw implants with five different surface topographies were examined: (1) turned ("machined"), (2) TiO2-blasted with particles of grain size 10 to 53 microns; (3) TiO2-blasted, grain size 63 to 90 microns; (4) TiO2-blasted, grain size 90 to 125 microns; (5) titanium plasma-sprayed (TPS). The surface topography was determined by the use of an optical instrument. Twelve rabbits, divided into two groups, had a total of 120 implants inserted in the tibiae. One implant from each of the five surface categories was placed within the left tibia of each rabbit. By a second operation, implants were installed in the right tibia, after 2 weeks in group A and after 3 weeks in group B. Fluorochrome labeling was performed after 1 and 3 weeks. Removal torque (RMT) tests of the implants were performed 4 weeks after the second surgery in group A and 9 weeks after the second surgery in group B. Thus, in group A, two healing groups were created, representing 4 and 6 weeks, respectively. The corresponding healing groups in group B were 9 and 12 weeks. The tibiae were removed, and each implant site was dissected, fixed, and embedded in light-curing resin. Ground sections were made, and the peri-implant bone was analyzed using fluorescence and light microscopy. RESULTS: The turned implants had the lowest Sa and Sy values, whereas the highest scores were recorded for the TPS implants. The corresponding Sa and Sy values for the TiO2-blasted implants were higher when a larger size of grain particles had been used for blasting. At all four observation intervals, the TPS implants had the highest and the turned implants the lowest RMT scores. The differences between the various TiO2-blasted implants were, in general, small, but the screws with the largest Sa value had higher RMT scores at 6, 9, and 12 weeks than implants with lower Sa values. The histologic analysis of the sections representing 6, 9, and 12 weeks revealed that fractures or ruptures were present in the marginal, cortical peri-implant bone. In such sections representing the TPS and TiO2-blasted implant categories, ruptures were frequently found in the zone between the old bone and the newly formed bone, as well as within the newly formed bone. CONCLUSIONS: The present study demonstrated that a clear relation exists between surface roughness, described in Sa values, and implant anchorage assessed by RMT measurements. The anchorage appeared to increase with the maturation of bone tissue during healing.

Melsen, B. and A. Costa (2000). "Immediate loading of implants used for orthodontic anchorage." Clin Orthod Res 3(1): 23-8.

            The healing around an immediately loaded screw was described and related to the bone type, manner of loading and observation time. In four adult macaca fasicularis monkeys, 16 titanium vanadium screws were inserted into the infrazygomatic crest and two in the symphysis region. Immediately after insertion, screws were loaded with 25- and 50-g Sentalloy springs extending to the canines. Following an observation period of 1, 2, 4 and 6 months, the screws and the surrounding bone were removed. Undecalcified serial sections perpendicular to the long axis were made and the degree of osseointegration studied. Two of the screws were lost immediately after insertion. Of the remaining screws, osseointegration was present around all, but two. The integration was independent of bone type, trabecular or cortical, but increased with time. Based on the results of this study, the use of screws described in the report can be recommended as anchorage units in cases where conventional anchorage is not possible.

Tosun, T., A. Keles, et al. (2002). "Method for the placement of palatal implants." Int J Oral Maxillofac Implants 17(1): 95-100.

            PURPOSE: Palatal implants have been used in the last 2 decades to eliminate headgear wear and to establish stationary anchorage. The aim of this investigation was to establish a method and easy protocol for palatal implant placement. MATERIALS AND METHODS: The study comprised 8 male and 15 female patients each having a 4.5 x 8-mm stepped screw titanium implant placed in the palatal region for orthodontic purposes. A surgical template containing metal drill housing was prepared. Angulation of the drill housing was controlled according to the radiologic tracing of the maxilla transferred to a plaster cast section in the paramedian plane. Implants were placed using a noninvasive technique (incision, flap, and suture elimination) and left transmucosally to facilitate the surgical procedure and reduce operations. The paramedian region was selected so as to avoid connective tissues of the palatine suture and because it was considered to be a suitable host site for implant placement. RESULTS: After 3 months of healing, all implants were osseointegrated and no implant was lost throughout the orthodontic treatment. DISCUSSION: Palatal implants can be used effectively for anchorage maintenance and space-gaining procedures. CONCLUSION: Usage of a 3-dimensional surgical template eliminated faulty implant placement, reduced chair time, and minimized trauma to the tissues while enhancing osseointegration.

Wehrbein, H., H. Feifel, et al. (1999). "Palatal implant anchorage reinforcement of posterior teeth: A prospective study." Am J Orthod Dentofacial Orthop 116(6): 678-86.

            A new orthodontic implant anchor system (Orthosystem) has been developed. This 1-piece device made from titanium consists of a screw-type endosseous section (lengths of 4 and 6 mm), a cylindrical transmucosal neck, and an abutment. Clamp caps with slots provide for attachment of square orthodontic wires (transpalatal bars) to the implant. The aim of the present prospective study was to evaluate the anchorage capacity of palatally inserted Orthosystem implants for anchorage reinforcement of posterior teeth. The sample consisted of 9 dental Class II patients (age 15 to 35 years) whose treatment plan included extraction of the maxillary first premolars. Each of the patients received 1 implant inserted into the center of the anterior palate. After a mean unloaded implant healing period of 3 months, transpalatal bars were inserted to connect the posterior teeth to the implant. Retraction of the canines and incisors was accomplished without the use of compliance-dependent headgear or Class II elastics. The degree of anchorage loss as well as the amount of canine and incisor retraction were evaluated by measurements of the casts and lateral cephalograms. The mean anchorage loss was 0.7 mm on the right side and 1.1 mm on the left (P <.05). The right and left canines were retracted 6.6 and 6.4 mm, respectively, and the mean overjet reduction was 6.2 mm. Because clinical assessment and postremoval histologic assessment both revealed stability of the short implant, the small anchorage loss was most likely from the deformation of the transpalatal bars by the orthodontic forces. Nevertheless, the treatment goal was achieved in all patients without the use of compliance-dependent auxiliaries. The clinical experience during and after implant insertion, active orthodontic treatment, retrieval of the implant, and subsequent wound healing are described.

Wehrbein, H., J. Glatzmaier, et al. (1997). "Orthodontic anchorage capacity of short titanium screw implants in the maxilla. An experimental study in the dog." Clin Oral Implants Res 8(2): 131-41.

            The aim of this study was to investigate experimentally the effect of long term orthodontic loading on the stability as well as on the peri-implant bone findings of short titanium screw implants (Bonefit, submersion depth 6 mm, phi 4 mm) inserted in regions with reduced vertical bone height. For this purpose, 6 maxillary premolars (1P1, 2P2, 3P3) were extracted from each of 2 foxhounds and reduction of alveolar bone height was performed by osteotomy. After a 16-week healing period, 8 implants (4 per dog) were inserted in the edentulous areas. Simultaneously, 2 implants (1 per dog) were positioned in the palatal suture (one-stage surgery). After an 8-week implant healing period, the fixtures in the P1/P2 areas (n = 4) and the palate (n = 2) were loaded (test implants) by means of transpalatal bars running anteriorly, fixed on the implants in the P1/P2 areas, and Sentalloy traction springs (approximately 2 N continuous force) inserted midsagittally between palatal implants and bars (force application period: 26 weeks). The fixtures in the P2/P3 areas served as controls (n = 4). Clinical measurements and histological evaluation revealed no implant dislocation of the loaded fixtures. These results suggest that short titanium screw implants inserted in the alveolar bone and palatal suture region retain their stability during long-term orthodontic loading, even following a relatively short unloaded implant healing period. Furthermore, it seems that long-term orthodontic loading may induce marginal bone apposition adjacent to the implants.