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# Experimental evaluation of initial tooth /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078

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### Experimental evaluation of initial tooth /certified fixed orthodontic courses by Indian dental academy

2. 2. Center of mass Each body has a point on its mass , which behaves as if the whole mass is concentrated at that single point. It is called the center of mass in a gravity free environment. Center of gravity The same is called the centre of gravity in an environment when gravity is present. www.indiandentalacademy.com
3. 3. Center of mass of a free body is the point through which an applied force must pass to move it linearly without any rotation. This center of mass is the free objects “Balance Point” The center of resistance is the equivalent balance point of a restrained body. Center of resistance of a tooth varies depending up on the - Root length & morphology - Number of roots - Level of alveolar bone support www.indiandentalacademy.com
4. 4. Center of resistance depending upon the level of alveolar bone. www.indiandentalacademy.com
5. 5. Review  Mathematical or physical models and finite element models  Cadavers have been used to test human teeth  In vivo measurements are needed to obtain more reliable results  Laser-holographic techniques and strain gauge techniques www.indiandentalacademy.com
6. 6. Aim  The purpose of this investigation was to determine the locations of the centre of resistance and the centre of rotation of a maxillary central incisor during retraction in human subjects. The relationship of the geometric parameters of the teeth and surrounding alveolar bone to the centre of resistance and centre of rotation will also be discussed. www.indiandentalacademy.com
7. 7. Method Schematic representation of system for measuring tooth movements. www.indiandentalacademy.com
8. 8. Lateral view demonstrating geometric relationship between level of force application and subject’s incisor www.indiandentalacademy.com
9. 9. Calculation of geometric position of centre of rotation. www.indiandentalacademy.com
10. 10. RESULTS Degree of tooth rotation as function of level of force application. Positive signs indicate lingual crown tipping and negative signs represent labial crown tipping. Centre of resistance is located at level of intersection of y-axis and line representing degree of tooth rotation www.indiandentalacademy.com
11. 11. Location of centre of resistance with respect to geometries of root and alveolar bone for each of 3 subjects (A, subject 1; B, subject 2; C, subject 3). www.indiandentalacademy.com
12. 12. Location of centre of rotation plotted along long axis of tooth corresponding to number of level of force application for each of 3 subjects (A, subject 1; B, subject 2; C, subject 3) www.indiandentalacademy.com
13. 13. DISCUSSION AND CLINICAL IMPLICATIONS  Burstone and Pryputniewicz (0.6 and 0.67)  Nikolai (0.45)  Tanne et al and Vollmer et al (0.76 and 0.58)  Labio-lingual inclination was not taken into consideration in those models, and labial and palatal alveolar bone attachments were thus positioned at the same level www.indiandentalacademy.com
14. 14. Therefore considered that the value of X/RP can be an indicator of the location of the centre of resistance with respect to the surrounding bony structures when incisors are retracted. www.indiandentalacademy.com
15. 15.  There seem to be other factors determining the location of centre of resistance, such as the amount or thickness of the alveolar bone and the periodontal ligament surrounding the tooth.  Even though only 3 subjects were studied, it is evident that the location of the centre of resistance depends on the palatal alveolar bone height and not on the labial alveolar bone height during anterior teeth retraction. This finding is of clinical significance for orthodontic tooth movement. www.indiandentalacademy.com
16. 16.  The effect of changes in the level of force application  Class II Division 1 malocclusions - controlled tipping  Class II Division 2 malocclusions  In cases of reduced palatal alveolar bone height, as with subject 1, the centre of resistance is located at a more apical position; therefore, a greater moment-to- force ratio is needed for any controlled movement of maxillary incisors during retraction. www.indiandentalacademy.com
17. 17. CONCLUSIONS  The location of the centre of resistance appears to depend more on the palatal alveolar bone height and very little on the labial alveolar bone height when anterior teeth are retracted.  The location of the centre of resistance of a maxillary central incisor was found at approximately two-thirds of the palatal alveolar bone height from the root apex. www.indiandentalacademy.com
18. 18.  A negative correlation exists between the palatal alveolar bone height and the moment-to-force ratio needed for any orthodontically programmed tooth movement such as controlled tipping, translation, and root movement during anterior retraction.  Further in vivo studies are needed to allow more accurate prediction of tooth movements based on applied force systems and total anatomical parameters, such as shapes of the root, surrounding bony structures, and the periodontal ligament, in addition to the labial and palatal bone levels. www.indiandentalacademy.com