ABSTRACT
The aims of this investigation were to define the modified location of CRES and CROT in a maxillary central incisor with different alveolar bone heights. A three dimensional finite element model of the upper central incisor with its supporting structures was created using ANSYS software on a PIII computer. Five three dimensional models of an upper central incisor with 1 to 6.5 mm of alveolar bone loss were formulated and used by the author. Center of resistance and center of rotation were located for the various stages of alveolar bone loss. The results revealed that the moment/force ratio (at the bracket level) required to produce bodily movement increases in association with alveolar bone loss. Bone loss causes center of resistance movement towards the apex, but its relative distance to the alveolar crest decreases at the same time. Greater amounts of displacements of incisal edge and apex were observed with increased alveolar bone loss for a constant applied force. Center of rotation of the tipping movement also shifted towards the cervical line. Among the many differences between orthodontic treatment of an adolescent and an adult patient is the presence of alveolar bone loss in the adult cases. Alveolar bone loss causes change in center of resistance as a result of alteration in bone support. This necessitates modifications in the applied force system to produce the same movement as in a tooth with a healthy supporting structure.
ABSTRACT
Aim and objectives: To determine the shear bond strength of laser cured composite resin and compare with that of visible light cure resin and evaluate it’s clinical usefulness. Materials and methods: An argon laser with a wavelength of 488-500nm and a power density of 2.104 mW/cm2 and an optical diameter of 6mm with a curing time of 10 seconds was employed as against the visible light cure with a wave length of 450-500nm of the same optical diameter and curing time of 40 seconds and tested using a universal instron testing machine. Results: The bond strength between laser cured and visible light composite resin was not statistically significant. However the lesser curing time of laser reduces the chair side time. Conclusion: Laser curing of orthodontic brackets may not be a viable procedure due to the cost factor as the bond strength is clinically insignificant.
ABSTRACT
The potential challenge at the fag end of orthodontic treatment is to restore the tooth structure as was prior to the beginning of the treatment. The aim of the article is to give a proper insight into the methodology of debonding not only from the orthodontist’s point of view but also keeping in mind the general practitioners who follow the procedure. At times, cases which are very well treated end up with enamel fractures or tears during debonding. Among the several methods recommended, the simplest and most effective and popular method has been discussed in this article as a clinical tip.