Effect of increasing the vertical intrusive force to obtain torque control in lingual orthodontics: A three‑dimensional finite element method study.

Context: Biomechanical differences between lingual and labial orthodontics (LiO and LaO). Aims: To investigate the effects of intrusive forces in lingual technique during retraction treatment mechanics. Settings and Design: Intrusive forces act differently in both techniques because of the different location of force vectors in relation to the center of resistance. Increasing the vertical intrusive force is one of the methods routinely used to prevent the uncontrolled tipping and obtain bodily tooth movement in LaO. However, its effects in lingual technique need to be investigated to derive at an optimal treatment mechanics. Subjects and Methods: Finite element method which has been successfully used to simulate tooth movement and optimize orthodontic mechanics effectively was used in this study. An accurate model of the upper central and lateral incisors with the surrounding structures was developed, and the “ANSYS” version 7.0 software was used for analysis. Results: Intrusive forces as high as 3.6N was required to obtain translation in LiO that too in an undesirable direction. Efforts to obtain torque control by increasing the intrusive force only would not be successful. Conclusion: Forces that produce a translation in LaO tends to produce uncontrolled tipping in lingual technique. To obtain adequate torque control in lingual technique, a combination of the reduction in horizontal retraction forces, increased lingual root torque application, and increase in vertical intrusive forces is desirable.

Two Phase Orthodontic Treatment: A Case Report.

Myofunctional appliances become active through muscular forces that bring about the dentoalveolar and skeletal changes. Functional appliances can be both removable or fixed. Twin block appliance given by William Clark is one of the most popular functional appliance owing to its ease of fabrication for the orthodontist and its ease of wear for the patient. It is known to bring about both skeletal and dental changes and has been used extensively in Class II growing patients. This was a case report of a 12-year-old patient treated in two phases, first the functional phase using the twin block, followed by the second phase of fixed orthodontic appliance.

Intrusion of Overerupted Molars using Miniscrews and TMA Spring: A Case Report.

Over eruption of posterior tooth due to the loss of antagonist teeth causes occlusal and functional disturbances. To restore proper occlusion, intrusion of the overerupted tooth becomes essential before multidisciplinary reconstructive dental approaches can be initiated. Conventional orthodontic techniques do not intrude posterior teeth eff ectively, and almost all methods result in anterior extrusion rather than posterior intrusion. New absolute anchorages (miniscrews and miniplates) are said to make posterior tooth intrusion possible. Th is case report describes the treatment of a patient with supra-erupted maxillary right and left fi rst molars intruded with titanium molybdenum alloy spring and miniscrew anchorage. Th e results showed that the biological responses of the teeth and the surrounding bony structures to the intrusion appeared normal and acceptable. Periodontal health and vitality of the teeth were maintained throughout the treatment.