Miniscrews in orthodontic treatment: Review and analysis of published clinical trials
ABSTRACT A systematic review of effects related to patient, screw, surgery, and loading on the stability of miniscrews was conducted.
Reports of clinical trials published before September 2007 with at least 30 miniscrews were reviewed. Parameters examined were patient sex and age, location and method of screw placement, screw length and diameter, time, and amount of loading.
Fourteen clinical trials included 452 patients and 1519 screws. The mean overall success rate was 83.8% + or - 7.4%. Patient sex showed no significant differences. In terms of age, 1 of 5 studies with patients over 30 years of age showed a significant difference (P <0.05). Screw diameters of 1 to 1.1 mm yielded significantly lower success rates than those of 1.5 to 2.3 mm. One study reported significantly lower success rates for 6-mm vs 8-mm long miniscrews (72% vs 90%). Screw placement with or without a surgical flap showed contradictory results between studies. Three studies showed significantly higher success rates for maxillary than for mandibular screws. Loading and healing period were not significant in the miniscrews' success rates.
All 14 articles described success rates sufficient for orthodontic treatment. Placement protocols varied markedly. Screws under 8 mm in length and 1.2 mm in diameter should be avoided. Immediate or early loading up to 200 cN was adequate and showed no significant influence on screw stability.
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ABSTRACT: In recent years, the skeletal anchorage through miniscrews has expanded the treatment options in orthodontics (Yamaguchi et al., 2012). We hereby present a modified method for tooth extrusion for cases where crown-lengthening surgery is contraindicated for aesthetic reasons. This modified method uses three orthodontic appliances: a mini-implant, an orthodontic wire, and a bracket. The aim of this case report was to increase the length of the clinical crown of a fractured tooth (tooth 23) by means of an orthodontic extrusion with the modified method of Roth and Diedrich.
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ABSTRACT: The aim of this animal study was to develop a model of orthodontic tooth movement using a microimplant as a TSAD in rodents. A finite element model of the TSAD in alveolar bone was built using μCT images of rat maxilla to determine the von Mises stresses and displacement in the alveolar bone surrounding the TSAD. For in vivo validation of the FE model, Sprague-Dawley rats (n = 25) were used and a Stryker 1.2 × 3 mm microimplant was inserted in the right maxilla and used to protract the right first permanent molar using a NiTi closed coil spring. Tooth movement measurements were taken at baseline, 4 and 8 weeks. At 8 weeks, animals were euthanized and tissues were analyzed by histology and EPMA. FE modeling showed maximum von Mises stress of 45 Mpa near the apex of TSAD but the average von Mises stress was under 25 Mpa. Appreciable tooth movement of 0.62 ± 0.04 mm at 4 weeks and 1.99 ± 0.14 mm at 8 weeks was obtained. Histological and EPMA results demonstrated no active bone remodeling around the TSAD at 8 weeks depicting good secondary stability. This study provided evidence that protracted tooth movement is achieved in small animals using TSADs.International Journal of Dentistry 09/2014; 2014:917535. DOI:10.1155/2014/917535
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ABSTRACT: Reçu le 2 mars 2012, accepté le 22 mars 2012) MOTS CLÉS : Orthodontie / Ancrage squelettique / Mini-implant RÉSUMÉ – Dans le domaine de l'ancrage squelettique, le recours aux mini-implants orthodontiques ne cesse de se développer. Cependant, le principal problème reste leur taux relativement élevé de perte de 16,4 %. Si l'on analyse les publications trai-tant des causes de perte d'implants, il s'avère que l'insertion de mini-implants plus importants en taille dans la région antérieure et médiane du palais aboutit à une grande stabilité ainsi qu'à un taux élevé de succès. De plus, la stabilité du couplage mini-implant/suprastructure est déterminante dans le succès. L'utilisation de mini-implants dont la tête possède un pas de vis interne permet la mise en place vissée stable de différents types d'abutments (piliers). Grâce à de longues plaques perfo-rées spéciales, il est possible de relier deux mini-implants entre eux et d'augmenter ainsi leur stabilité. Un système d'éléments préfabriqués permet l'élaboration rapide de différents types de mécaniques orthodontiques efficaces (systèmes mécaniques efficaces). ABSTRACT – Improvement of mini-implant stability in orthodontics. Orthodon-tists are continuing to increase the use of mini-implants as a source of skeletal an-chorage. However, the relatively high 16.4% rate of their failures remains a problem. An analysis of articles in the literature on the loss of mini-implants shows that larger size anchorage screws and plates inserted in the anterior and median regions of the hard palate are highly stable and, accordingly, contribute to a high rate of opti-mum orthodontic outcomes. It is the reliability of the mini-implant/skeletal structure couple that is the principal factor in this success. With mini-implants whose heads possess internal threads, orthodontists can attach different types of stable, screwed-in abutments. And with long plates with specifically designed perforations splinting two mini-implants together, orthodontists can further increase the stability of this ar-tificial anchorage. By employing a system with pre-fabricated components orthodon-tists can quickly create skeletal anchorage adaptable to the mechanics of different techniques.