Biological Basis of an Optimal Orthodontic Force
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The document discusses the biological nature of optimal orthodontic forces from various perspectives. It describes histological studies that show how bone cells respond to mechanical stress from orthodontic forces. The studies indicate periodontal ligament and alveolar bone marrow cells are most sensitive. Optimal forces are light, avoid ischemic damage, and allow time for tissue recovery. Finite element analyses show force distribution varies by tooth configuration. The concept of optimal force was first introduced in 1932 to mean below blood pressure to avoid tissue injury. Histology has provided insights into optimizing force magnitude, duration, and direction of tooth movement within alveolar bone.
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Biological Basis of an Optimal Orthodontic Force
- 1. The Biological Nature of an Optimal Orthodontic Force www.indiandentalacademy.com
- 16. Maxillary histology after Tx with SWA. Wherbein, Fuhrmann, and Diedrich, 1995 • A 19 yr old female after 19 mos Tx with SWA, including 2 mos torque with a 0.017 x 0.025” stainless steal arch wire. • Histologic findings of damage (bony dehiscences, fenestrations, and root resorption) were more pronounced than the radiographs would suggest. www.indiandentalacademy.com
- 24. Which bone cells are the main target for applied mechanical stress? www.indiandentalacademy.com
- 33. Conclusions • Bone cells respond readily in vivo to applied mechanical stress • This response depends upon variables such as stress magnitude, rate, distribution, and duration • Osteocytes are main target cells in orthopedics, while PDL and alveolar bone marrow cells appear to be the principal cell types sensitive to applied mechanical stress in orthodontics www.indiandentalacademy.com
- 34. Can orthodontic forces be optimized? www.indiandentalacademy.com
- 45. Conclusions • Understanding the biological effects of orthodontic forces and correlating them with clinical events may facilitate and promote the development and utilization of means to optimize mechanotherapy. • Magnets and electric currents are examples of such optimizing means. www.indiandentalacademy.com
- 46. A. Martin Schwarz was the first author to coin the term “optimal force” in orthodontics (1932) www.indiandentalacademy.com
- 50. Points worth remembering from Schwarz’s 1932 article • An optimal force does not exceed the blood pressure in the capillaries, thereby avoids ischemic injuries to dental and paradental tissues. • Orthodontic forces must be estimated and measured for each tooth. www.indiandentalacademy.com
- 54. A comment regarding orthodontic force distribution in jaws • Finite element analyses in the 1980s and 90s have revealed that the distribution of forces around orthodontically-treated teeth depends on the type of applied force and the configuration of the teeth and their surrounding tissues. • In every case, the distribution of these forces is never equal. www.indiandentalacademy.com
- 55. In the quest for an optimal orthodontic force, what have we learned from histological studies? www.indiandentalacademy.com
- 77. In the quest for an optimal orthodontic force, what have we learned from histological studies? • That the magnitude of the applied force is an important determinant of tooth movement. However, the effects of magnitude are influenced by other co- factors, such as mechanical principles, the duration of force application, and the specific anatomical details of the involved tissues. www.indiandentalacademy.com
- 96. Conclusions from Reitan and Rygh’s histological studies on the features of optimal orthodontic forces • They should be patient-friendly: cause minimal pain and discomfort, and move teeth efficiently to new correct positions. • They should be tissue- and cell-friendly: promote cell proliferation, differentiation, and activation, and evoke proper remodeling of paradental tissues. www.indiandentalacademy.com
- 97. Conclusions from Reitan and Rygh’s histological studies on the features of optimal orthodontic forces • Any type of tooth movement, i.e., intrusion, translation, etc., should result from the application of light forces, that do not harm or kill large numbers of PDL and alveolar bone cells, but rather strain them, while maintaining their vitality in both areas of compression and tension. www.indiandentalacademy.com
- 98. Conclusions from Reitan and Rygh’s histological studies on the features of optimal orthodontic forces • Tipping of teeth, especially uncontrolled tipping, may bring root apices into contact with compact plates of bone, thus increasing the risk for severe root resorption. • Interrupted forces are biologically better than continuously applied forces, because they provide time for recovery. www.indiandentalacademy.com
- 99. By subjecting the cells to either positive or negative hydrostatic pressures in vitro. Yousefian J, Shanfeld J, Davidovitch Z, 1995 www.indiandentalacademy.com
- 106. These results demonstrate that human PDL fibroblasts in culture respond to applied hydrostatic pressures, either positive or negative, within well defined numerical boundaries. It is, therefore, reasonable to assume that a similar situation exists in vivo. Orthodontic forces within this range may be defined as optimal or effective. www.indiandentalacademy.com
- 110. The Amalgamated Technique: A practical and effective method of moving teeth in an optimal fashion De Angelis V, 1975, 1980, 2004 www.indiandentalacademy.com
- 111. Fundamental principles of the Amalgamated Technique 1. Forces are light, continuous, and relatively non-traumatic (low load deflection rates due to the use of extra- slot torque). 2. Root movements are deliberate, non- redundant, and remain within the confines of the alveolar bone throughout treatment. www.indiandentalacademy.com
- 112. Fundamental principles of the Amalgamated Technique 3. Shortened treatment duration results in limited exposure to root resorbing cells. 4. Limits irreversible tissue changes even in individuals with compromised immune systems. www.indiandentalacademy.com
- 113. Radiographic images of damaged incisor roots following treatment with conventional Edgewise appliances www.indiandentalacademy.com
- 122. Observations • Periapical radiographs show incisor root shortening in the facial plane. This view usually does not reveal the reason for the root resorption. • Lateral cephalograms show it in the sagittal plane. This view exposes alterations in root-bone plate contacts, the leading etiology of root resorption. www.indiandentalacademy.com
- 123. Observations • An optimal orthodontic force avoids moving dental roots into surrounding plates of compact bone, or moving them redundantly, thereby preserving the roots’ length. • The Amalgamated Technique is capable of correcting malocclusions without causing tissue damage. It can, therefore, be classified as a biologically optimal method. www.indiandentalacademy.com
- 124. Conclusions • An optimal orthodontic force can thus be defined as one which is light, continuous or intermittent, moving the roots non- redundantly within the confines of the alveolar bone. • This kind of force is tolerable by patients, does not damage tissues, and moves teeth efficiently. www.indiandentalacademy.com