fa Influence of the expansion screw height on the dental effects of the hyrax expander: A study with finite elements ارتودنسی Orthodontics پژوهشي Research <p> <strong>Introduction</strong></p><p>  Our objective was to evaluate the influence of the expansion screw height of a hyrax expander on the degree of dental inclination during rapid maxillary expansion by using the finite element method. </p><p> <strong>Methods</strong></p><p>  The hyrax expander and the maxillary arch were modeled by using Solidworks software (Dassault Systèmes, Paris, France). Three distinct finite element method models were created by simulating different screw heights relative to the plane that intersected the center of resistance of the maxillary first molars. These 3 relative positions were 10 mm below the maxillary first molars' center of resistance, at the same level as the maxillary first molars' center of resistance, and 10 mm above the maxillary first molars' center of resistance. The initial activation of the expanders was simulated, and tooth displacements for each finite element method model were registered in the buccolingual, corono-apical, and mesiodistal directions. </p><p> <strong>Results</strong></p><p>  The simulations tested showed that the 3 hyrax screw heights had different dental tipping tendencies. When the screw was simulated below the maxillary first molars' center of resistance, buccal tipping of the crowns and lingual tipping of the roots were registered. This tendency decreased when the screw was simulated at the same level as the maxillary first molars' center of resistance. However, when the screw was simulated above the maxillary first molars' center of resistance, the tipping tendency was inverted, with the crowns displaying lingual tipping and the roots displaying buccal tipping. </p><p> <strong>Conclusions</strong></p><p>  These findings might explain the importance of carefully planning the height of the hyrax expander screw, since, depending on this position, different tooth movements can be achieved. From an orthopedic perspective, the ideal screw position might be slightly above the maxillary first molars' center of resistance this would generate less dental tipping. </p><hr><p></p><p> <strong>Source: </strong>American Journal of Orthodontics & Dentofacial Orthopedics </p><p> <a href="http://www.ajodo.org/article/S0889-5406(12)01072-4/abstract" target="_blank"><font color="#0000ff">Full Text</font></a></p> 0 0 http://idai.ir/browse.php?a_code=A-10-32-1740&slc_lang=fa&sid=1 Rafael Marques de Sousa Araugio 10031947532846008196 10031947532846008196 No and former orthodontic resident, Pontifical Catholic University of Minas Gerais, Belo Horizonte, Brazil Jánes Landre 10031947532846008197 10031947532846008197 No School of Engineering, Pontifical Catholic University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil Diana de Lourdes Almeida Silva 10031947532846008198 10031947532846008198 No Mechanical Engineer, School of Engineering, Pontifical Catholic University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil Wellington Pacheco 10031947532846008199 10031947532846008199 No Department of Orthodontics, Pontifical Catholic University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil Matheus Melo Pithon 10031947532846008200 10031947532846008200 No Department of Orthodontics, Southwest Bahia State University, Jequié, Bahia, Brazil Dauro Douglas Oliveira 10031947532846008201 10031947532846008201 Yes Department of Orthodontics, Pontifical Catholic University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil