Academic literature on the topic 'Miniscrew'

A thesis submitted to the College of Dental Medicine of Nova Southeastern University of the degree of Master of Science in Dentistry. Objectives. The purpose of this study was to determine the effect of pitch and thread depth of orthodontic miniscrew implants(MSI's) on stress generation. Methods. Quasi-three dimensional photoelastic models were created with MSI's embedded and then loaded with 60 and 104 grams respectively and evaluated under a full field reflection polariscope. The control MSI's (1.0mm pitch / 0.25mm thread depth) were compared to 3 experimental groups (n=10) which varied with only one design characteristic: Group 1 (0.75mm pitch), Group 2 (1.25mm pitch) and Group 3 (0.40 thread depth). The maximum shear stress (τmax) was calculated at 5 predetermined and standardized points. A two-way ANOVA was conducted to compare the means of τmax followed by a Tukey's post hoc (p<0.05). Results. No statistical differences were found for τmax between the control group and each of the 3 experimental groups except at point 4. At point 4, the control group was higher by an average of 5.05 and 7.1 MPa for the 60 and 104 gram loads respectively (p<0.05). No statistically significant differences were found for points 1, 2, and 5 for the 60 gram load and for points 1, 2, 3, and 5 for the 104 gram load. The mean τ max from highest to lowest was located at points 5<1< 2<4 <3 in both the 60 and 104 load steps. The variability in τmax at point 4 may have been due to its proximity to the neutral zone of the present loading conditions. Conclusions. As the orthodontic load was increased, maximum shear stress also increased for each of the four MSI designs used in this study. The results of this study suggest that, within limits, variation of pitch and thread depth of MSI's may not have a significant influence on the stress generation when loaded for orthodontic purposes. Photoelastic analysis has shown to be a viable option to evaluate mechanical properties of MSI'S.

Thesis (M.S.)--University of North Carolina at Chapel Hill, 2009.<br>Title from electronic title page (viewed Sep. 3, 2009). "... in partial fulfillment of the requirements for the degree of Master of Science in the School of Dentistry Orthodontics." Discipline: Orthodontics; Department/School: Dentistry.

Thesis (M.S.)--West Virginia University, 2008.<br>Title from document title page. Document formatted into pages; contains ix, 98 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 66-70).

December 2011. A thesis submitted to the College of Dental Medicine of Nova Southeastern University of the degree of Master of Science in Dentistry. Background: Temporary anchorage devices (TADs) provide a versatile means by which orthodontic anchorage can be established without the need for patient compliance and complex force systems. Their use is predicated on their ability to remain stable throughout the course of treatment in which they are needed. This has been shown to be the result of "primary stability" which is achieved through mechanical interlocking of the screw threads with the surrounding bone immediately upon placement. Therefore, evaluating the factors that can either enhance or detract from the primary stability of TADs can serve to improve the predictability of their success. Objectives: The objectives of this study were to describe how variations in synthetic cortical bone thickness and the angle of force applied in relation to the long axis of TADs affects their stability in terms of pull-out strength, and to ascertain the perspectives of practicing orthodontists in the state of Florida on their experiences with temporary anchorage devices with regards to success and failure. Methods: For the bench top study, 90 1.5x8mm long neck Orthotechnology Spider Screws were randomly allocated to 9 groups of 10 TADs each. The 9 groups were established based on both the thickness of synthetic cortical bone (1.0, 1.5, and 2.0mm) and the angle of force vector applied relative to the long axis of the TADs (45, 90, and 1800). Pull-out testing was carried out by applying a force to the TADs via a universal testing machine (Instron, Canton, MA) at a rate of 2.0mm/minute. Real-time graphical and digital readings were recorded, with the forces being recorded in Newtons (N). Each miniscrew was subjected to the pull force until peak force values were obtained. For the 450 and 1800 tests, the force registered at the time-point of pull-out, or screw head movement of 1.5mm within the synthetic bone blocks. The determination of 1.5mm of movement was made due the dramatically erratic deflection observed by the digital and graphical readouts at precisely this point. For the survey portion of this study, A customized survey was developed for this study. The survey was composed of 12 questions, some of which were obtained from a questionnaire that was created by Buschang et al.54 The additional questions were devised by the members of this research project, with the aim of answering questions regarding the clinical experiences that practicing orthodontists experienced with TADs. Results: For the bench top study: Implants placed in 2.0mm of synthetic cortical bone and pulled at an angle of 1800 had the highest pull-out strength among all groups (258.38N), while those placed in 1.0mm of synthetic cortical bone and pulled at an angle of 900 exhibited the lowest (67.11N). When evaluated separately, a cortical bone thickness of 2.0 mm displayed the highest pull-out forces for the three angles of force application, and 1800 angle of force displayed the highest-pull-out forces for the three cortical bone thicknesses. Conversely, 1.0mm of cortical bone thickness displayed the lowest pull-out forces for the three angles of force application, and 900 angle of force displayed the highest-pull-out forces for the three cortical bone thicknesses. For the survey: The most important factor associated with TAD failure was cited as placement location by 45.7% (n=16) of respondents, while root proximity was cited as the least important factor by 35.3% (n=12) of respondents. For the site from which practitioners indicated that they experience the greatest success, 81.8% cited the palate, while 51.9% responded that they experience the highest failure rates for the posterior maxilla (distal to the cuspids). Conclusions: A synthetic cortical bone thickness of 2mm and pull forces applied parallel to the long axis of TADs resulted in the greatest resistance to pull-out.

Aims: The aims of this study were to systematically review the evidence on miniscrews failure rate, their effectiveness in anchorage reinforcement, to assess the quality of reporting clinical trials in orthodontic literature in an observational study, to audit their use in the UK and to compare the anchorage effectiveness when measured against headgear and transpalatal arch in a randomised clinical trial. Methods: In two systematic reviews, databases were searched, data was extracted, the risk of bias was assessed and meta-analyses were performed when appropriate. In the observational study, clinical trials reports that were published in four major journals from 2008-2012 were identified and assessed against CONSORT checklist to evaluate the quality of reporting. The audit was a prospective multi-centre audit investigating the use of miniscrews in the UK. In a randomised clinical trial, orthodontic patients were randomly allocated into three groups (headgear, miniscrews or transpalatal arch). Digital models were measured to assess the anchorage loss. Results: The first systematic review and meta-analysis demonstrated that the failure rate of miniscrews was 14.1%(95% CI, 12-16.5). The data were obtained from 43 studies (16 clinical trials and 27 cohort studies). The second systematic review showed that overall mean difference in molar movement was 2.206mm in favour of miniscrews ( MD = - 2.20; 95% - 1.21 to -3.19) when compared with conventional anchorage methods. The data were obtained from seven clinical trials. The observational study assessed the reporting quality of 151 clinical trials and showed that clinical trials reports represented less than 5% of the articles published in four major journal and their reporting was suboptimal. The audit showed that none of the agreed standards were met except for infection/inflammation around the screw resulting in loss or removal in 5.6% of the cases while the standards were being below 20%. The miniscrew failure rate in this audit was 24.2%. The total number of placed miniscrews was 1072. The randomised clinical trial revealed no difference between headgear, transpalatal arch or miniscrews in regards to anchorage effectiveness. 51% of study models required to measure the primary outcome were missing. Conclusion: Based on the two systematic reviews, miniscrews have a modest failure rate and they are useful clinically to reinforce anchorage. Reporting clinical trials is suboptimal in orthodontic literature. The only item that met audit standards was failure due to infection/inflammation. The rest of the audit standards were not met. Recommendations are made to address these issues. In the clinical trial, no difference in anchorage effectiveness between headgear, transpalatal arch or miniscrews was found. The findings of this clinical trial should be interpreted with caution due to the missing data.

O objetivo deste trabalho foi avaliar a influencia da proximidade entre miniimplantes autoperfurantes e as raizes dentarias sobre a estabilidade destes dispositivos de ancoragem. A amostra consistiu de 40 mini-implantes inseridos entre as raizes do primeiro molar e segundo pre-molar superiores de 21 pacientes, como recurso de ancoragem para retracao anterior. A largura do septo no local de insercao (LSI) e a menor distancia da cabeca do mini-implante a raiz dentaria (MDR) foram mensuradas nas 40 radiografias pos-cirurgicas. Sob este aspecto, os miniimplantes foram divididos em duas categorias de grupos: de acordo com a largura do septo no local de insercao, grupos G1L (LSI3mm) e G2L (LSI>3mm), e de acordo com a proximidade do mini-implante a raiz adjacente, grupos G1P (MDR0mm) e G2P (MDR>0mm). A estabilidade dos mini-implantes foi avaliada mensalmente pela quantificacao do grau de mobilidade, e a partir desta variavel foi calculada a proporcao de sucesso. Tambem foi avaliada a influencia das seguintes variaveis sobre o grau de estabilidade: caracteristica do tecido mole no local de insercao, o grau de sensibilidade, a quantidade de placa, a altura de insercao e o periodo de observacao. As duas categorias de grupos foram comparadas quanto ao grau de mobilidade e proporcao de sucesso por meio do teste de Mann-Whitney e do teste Exato de Fisher, respectivamente. Adicionalmente, avaliou-se a influencia das demais variaveis sobre a estabilidade deste sistema de ancoragem atraves do teste t e do teste do Qui-quadrado. Os resultados obtidos demonstraram que não houve diferenca estatisticamente significante para o grau de mobilidade e proporção de sucesso entre os mini-implantes inseridos em septos do grupo G1L e G2L. A proximidade entre os mini-implantes avaliados e as raizes dentarias adjacentes (grupos G1P e G2P) tambem nao influenciou na estabilidade e proporcao de sucesso deste sistema de ancoragem. A proporcao de sucesso total encontrada foi de 90% e nenhuma variavel demonstrou estar relacionada ao insucesso dos miniimplantes. No entanto, observou-se maior sensibilidade nos pacientes cujos miniimplantes apresentavam mobilidade, e que a falha destes dispositivos de ancoragem ocorria logo apos sua insercao.<br>The purpose of this study was to evaluate the influence of the proximity between self-drilling miniscrews and dental roots on the stability degree. The sample consisted of 40 miniscrews inserted in the interradicular septum between maxillary second premolars and first molars to provide skeletal anchorage for anterior retraction. The forty post-surgical radiographs were used to measure the septum width in the insertion site (SWI) and the smallest distance between miniscrew head and dental root (SDR). In this regard, the miniscrews were divided in two categories of groups: according to the septum width in the insertion site, groups G1W (SWI 3mm) and G2W (SWI>3 mm), and according to the miniscrew dental root proximity, groups G1P (SDR0mm) and G2P (SDR>0mm). The mobility degree (MD) was monthly quantified to determine miniscrew stability, and the success rate of these devices was calculated. This study also evaluated the influence of following variables on the stability degree: soft tissue characteristics in the insertion site (attached gingiva, mucogingival junction and alveolar mucosa), sensitivity degree during miniscrew load, plaque amount around miniscrew, insertion height, and total evaluation period. All the groups were compared regarding mobility degree and success rate using t test and Fisher exact test, respectively. The results showed no significant difference in mobility degree and success rate between groups G1W and G2W. The miniscrew dental root proximity did not influence the stability and success rate of this anchorage system when G1P and G2P were compared. The total success rate found was 90% and no variable was associated with the miniscrew failure. Nevertheless, the results showed that greater patient sensitivity degree was associated to the miniscrews mobility and the failure of these anchorage devices happened in a short time after their insertion.

Depuis une dizaine d’années, l’essor des minivis d’ancrage orthodontique a été grandissant jusqu’à devenir, aujourd’hui, un outil incontournable dans l’arsenal thérapeutique de l’orthodontiste. Très peu d’études ont été publiées quant à la nature de la réponse tissulaire face à l’insertion et la mise en charge de ces minivis. De plus, une partie des patients concernés par l’orthodontie étant des adolescents, il serait intéressant de savoir si le tissu osseux en croissance est propice à l’utilisation de ces dispositifs. L’influence de la nature du matériau sur cette réaction tissulaire reste également à définir. L’objectif de cette étude a été d’évaluer la biointégration de deux systèmes de minivis orthodontiques présents sur le marché, l’un en acier chirurgical et l’autre en titane-aluminium-vanadium, en conduisant une analyse clinique, histomorphométrique et microtomographique chez le porc en croissance. Les résultats ont montré que la réponse osseuse se caractérise, dans un os en croissance peu compact, par un épaississement des travées osseuses au contact des dispositifs, probablement pour résister à la contrainte locale. Le tissu osseux en croissance permet la biointégration des minivis d’ancrage orthodontique, mais le taux de succès relativement faible observé implique l’adaptation des protocoles cliniques par une analyse préalable du ratio os trabéculaire/os cortical, une augmentation du délai avant mise en charge, et l’application de forces légères. La réponse tissulaire est similaire, quel que soit le système étudié. L’acier chirurgical, grandement utilisé en orthopédie, présente donc un intérêt en orthopédie dento-faciale, dans une indication temporaire<br>The miniscrew implants are increasingly used over the last decade in orthodontics and gradually replacing the use of extraoral forces because of their greater efficiency and because their effectiveness is not subject to patient compliance. Few studies seeking to understand the response to orthodontic anchorage devices at bone-tissue interface have been published over the last ten years. Despite the large use of miniscrews in teenagers, very few have included young subjects in their protocol. Furthermore, despite the use of stainless steel miniscrew implants, no studies have investigated biointegration of such devices. The aim of the present study was to evaluate tissue response to immediately loaded miniscrew implants (of Ti6Al4V and of stainless steel) in growing pigs in order to answer to the following questions: Is it possible to implant and load miniscrew implants in a growing bone? Does stainless steel devices present the same biointegration than titanium devices? A clinical evaluation, and histomorphometrical and micro-CT analyses were performed. Results showed that the growing bone seems compatible with the orthodontic anchorage. In the growing pig with low bone density areas, the trabecular thickness increase appears as the bone response to withstand the local strains induced by loaded orthodontic miniscrews. Stainless steel devices presented similar behavior to the Ti6Al4V devices in pigs. This study showed the possibility to place stainless steel miniscrew implants for orthodontic anchorage in growing models

碩士<br>長庚大學<br>顱顏口腔醫學研究所<br>97<br>ABSTRACT Introduction: The aim of this retrospective study was to compare treatment effects of various miniscrew anchorage setups for correction of bimaxillary protrusion. The influence of facial divergency on the miniscrew effects was also investigated. Methods: The sample consisted of 100 adult patients with Angle Class I or Class II bimaxillary protrusion who received extraction treatment and were divided into 4 groups according to the anchorage setups. Group 1 (n=25) received traditional anchorage preparation without miniscrews; group 2 (n=25) received two upper posterior miniscrews; group 3 (n=25) received two upper posterior and one or two anterior miniscrews; group 4 (n=25) received two upper posterior, two lower posterior and one or two anterior miniscrews. Pretreatment and posttreatment lateral cephalograms were superimposed. One-way ANOVA and Kruskal-Wallis tests were used to compare the treatment changes among the 4 groups. Results: Retraction of upper incisors was greater in groups 2, 3, and 4 than in group 1 (△U1-H: -4.8±2.9 mm vs. -8.9±2.9 mm, -7.4±1.7 mm, and -7.5±3.1 mm, p < 0.01). There was no significant difference in the upper molar horizontal anchorage loss among the 4 groups (△U6-H: 1.8±2.0 mm vs. 0.6±4.3 mm vs. 0.8±1.8 mm vs. 0.1±3.8 mm, p > 0.05). In hyperdivergent patients, groups 3 and 4 showed upward movement of Pogonion (△Pg-V: -0.8 and -1.2 mm, respectively), while group 2 showed downward movement instead (△Pg-V: 1.0 mm) (p < 0.05). Conclusions: In patients with bimaxillary protrusion, posterior miniscrews provided maximal retraction of upper anterior teeth. In hyperdivergent patients, combined use of posterior and anterior miniscrews provided favorable vertical control with counterclockwise mandibular rotation and facial height reduction.