Abstract
Background and Objectives: the study was conducted to evaluate the levels of stress produced in and around implants when placed at different sites for retraction and intrusion of maxillary anteriors. The other objective was to evaluate stress levels produced at implant bone interface when mini implants were placed at different angulations at the same site. Materials and Methodology: Finite element model of the maxilla and maxillary dentition was constructed using the CT skull of subject used in the study. All the accessories used like mini-implants, stainless steel wire, coil springs etc were scanned separately for obtaining detailed anatomic features. The force was given between retraction hook and mini -implant using NITI closed coil spring for intrusion and retraction of maxillary anterior teeth. The basic mechanical factors i.e. the stresses developed in mini implant, the angle of insertion of the mini implant into the bone surface were analyzed. Finite Element model was generated by Hyper mesh 9.0 software. Analysis was carried out by using Ansys 12.1 software. Results and Conclusion: All the set objectives were accomplished at the end of the study which included complete closure of extraction space by retraction and intrusion in the models. The following conclusions were drawn: The least stress was seen on an implant at middle third, when inserted at an angle of 800 to the bone surface, with application of 50-100mg of intrusive force on anterior implant and 200 gms of retractive force on posterior implant.
Highlights
Retraction force was given to anteriors by NITI closed coiled springs which were connected to implants and hooks
Model No: III (Figure 7) From above image the following observations are made: a) Maximum vonMises on the implant is observed at the neck region in both implants during retraction (Red in color) b) Minimum Von-misses of the implant is observed on the middle third to apex region (Blue in color) c) The color band at the bottom indicates the deformation values at different level of the bone and implant for e.g. The color dark red indicates the vonMises stresses developed value=3.2 MPa
From above image the following observations are made: a) Maximum vonMises stresses on the implant are observed at the neck region in both implants during retraction (Red in color) b) Minimum vonMises stresses of the implant are observed on the middle third to apex region (Blue in color) c) The color band at the bottom indicates the stresses values at different level of the bone and implant for e.g. The color dark red indicates the vonMises stresses developed value=(0.6-1.9Mpa)
Summary
Teeth during orthodontic treatment are subjected to forces and moments which always generate reciprocal forces of the same magnitude but opposite in direction. This is relevant where such an action is favorable tooth movement and the reaction is unwanted tooth movement. To avoid these unwanted tooth movements, the reciprocal forces must be re-directed which can be achieved by reinforcing an orthodontic anchorage. Objectives: the study was conducted to evaluate the levels of stress produced in and around implants when placed at different sites for retraction and intrusion of maxillary anteriors. The following conclusions were drawn: The least stress was seen on an implant at middle third, when inserted at an angle of 800 to the bone surface, with application of 50-100mg of intrusive force on anterior implant and 200 gms of retractive force on posterior implant
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