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Considérations biomécaniques et cliniques dans le traitement des béances antérieures avec des mini-vis d’ancrage
Abstract
Lorsque des mini-vis d’ancrage sont utilisées pour le traitement non invasif des béances antérieures, le clinicien doit tenir compte de la biomécanique du
système de forces utilisé. L’ingression des dents postérieures maxillaires et mandibulaires permet de maximiser les changements squelettiques verticaux.
En comparaison avec une chirurgie bimaxillaire, cette approche est moins invasive, moins compliquée et moins coûteuse.
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Traditionally, orthodontic diagnosis and treatment have primarily involved the assessment of skeletodental relationships, with a particular focus on the mandibular dentition. Recently the focus has shifted towards the maxillary incisors as a starting point for facial esthetics with growing demands for facial esthetics. Three-dimensional maxillary incisor position (MIP) plays a pivotal role in improving facial esthetics in smiling and resting positions. With the advent of miniscrews, biomechanical force application in orthodontic treatment has become simpler due to absolute anchorage. Miniscrews allow clinicians to move teeth more precisely and easily in three dimensions according to the treatment plan, which was challenging or impossible with conventional biomechanics. Therefore, MIP using miniscrews should be a starting point for esthetic treatment planning.
Progressive condylar resorption, also known as idiopathic condylar resorption, is an uncommon, aggressive, degenerative disease of the temporomandibular joint (TMJ) seen mostly in adolescent girls and young women. This condition leads to loss of condylar bone mass, decrease of mandibular ramal height, steep mandibular and occlusal plane angles, and an anterior open bite. In 3 case reports, we review the pathogenesis of TMJ degen-erative disease and the clinical management of TMJ arthrosis. We emphasize that TMJ arthritic disease should be discussed in dental circles as a pathologic entity in the same way that orthodontists discuss arthritic disease in orthopedic circles. Regarding the degenerative pathology of the TMJ, treatment goals include restored function and pain reduction. The treatment methods used to achieve these goals can range from noninvasive therapy to minimally invasive and invasive surgery. Most patients can be treated noninvasively, and the importance of disease prevention and conservative management in the overall treatment of TMJ disease must be acknowledged. The decision to manage TMJ osteoarthrosis surgically must be based on evaluation of the patient's response to noninvasive treatments, mandibular form and function, and effect of the condition on his or her quality of life. (Am J Orthod Dentofacial Orthop 2019;156:531-44)
Cortical bone thickness and bone depth are important factors when placing an orthodontic mini-implant. The objective of this study was to investigate both variables for the palatal alveolar process.
Thirty dry human skulls were imaged by using cone-beam computed tomography technology. Two-dimensional slices bisecting the posterior interdental sites were generated, and cortical bone thickness and bone depth were measured at 4, 8, and 12 mm from the alveolar crest. Two-way repeated measures analysis of variance (ANOVA) was used to analyze the measurements.
Interdental site and measurement level had a significant impact on both cortical bone thickness and bone depth. Cortical bone thickness was typically greatest at the 8-mm measurement level and more anterior interdental sites. Bone depth decreased with higher measurement levels and was smallest at the most posterior-superior measurement points.
Cortical bone thickness and bone depth of the palatal alveolar process are, on average, favorable for the insertion of orthodontic mini-implants; however, some sites should routinely be avoided to prevent damage to the maxillary sinus unless 3-dimensional imaging is available.
The thickness of cortical bone is an important factor in mini-implant stability. In this study, we investigated the buccal cortical bone thickness of every interdental area as an aid in planning mini-implant placement.
From the cone-beam computed tomography scans of 30 dry skulls, 2-dimensional slices through every interdental area were generated. On these, cortical bone thickness was measured at 2, 4, and 6 mm from the alveolar crest. Intraclass correlation was used to determine intrarater reliability, and analysis of variance (ANOVA) was used to test for differences in cortical bone thickness.
Buccal cortical bone thickness was greater in the mandible than in the maxilla. Whereas this thickness increased with increasing distance from the alveolar crest in the mandible and in the maxillary anterior sextant, it behaved differently in the maxillary buccal sextants; it was thinnest at the 4-mm level.
Interdental buccal cortical bone thickness varies in the jaws. There appears to be a distinct pattern. Knowledge of this pattern and the mean values for thickness can aid in mini-implant site selection and preparation.