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.

How to Choose Drug Dosage for Human Experiments Based on Drug Dose Used on Animal Experiments: A Review.

The orthodontic tooth movement is a biological response to orthodontic force. The biological response is very strongly-related to local bone metabolism. There is a strong evidence in the literature that bone metabolism can be altered by drugs. There are various studies published in dental journals on administration of drugs for the purpose of affecting orthodontic tooth movement both for augmentation of anchorage and to increase the rate of tooth movement. Most of these studies are animal studies. The aim of this article is to give insight to how to convert drug dose from animal studies to human trails. Dose per kilogram of body weight for one species is not the same for another species, it has to be converted first based on body surface area (BSA)normalization method. BSA correlates well across several mammalian species with several parameters of biology, including oxygen utilization, caloric expenditure, basal metabolism, blood volume, circulating plasma proteins, and renal function.

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.