Research progress on the three-dimensional finite element analysis of bite opening / 口腔疾病防治

@#Deep bite is a common clinical malocclusion that has a great impact on patients’ facial aesthetics and oral function. Bite opening is the key step in the treatment of deep bite, playing a decisive role in the development of mandible and the progress of orthodontic treatment. Torque and tip control during the correction of deep bites is a hot topic in orthodontics. The three-dimensional finite element method can accurately simulate clinical processes and conduct dynamic stress analysis, which provides the basis of the biomechanical mechanism. This paper reviewed the finite element analysis of various orthodontic systems for bite opening to provide a reference for clinical application. The emergence of mini-implants provided a new idea for anchorage control in bite opening. Finite element studies found that high-positioned mini-implants are beneficial for bodily tooth intrusion and proposed the ideal position for force application. For the finite element simulation of the reverse curve archwire, it was found that the intrusion and inclination of the anterior teeth increased with the curve depth of the archwire. The application of clear aligners has also been flourishing, but these forces are still difficult to effectively control. Finite element studies on their attachment design and corresponding tooth movement may be helpful to open the bite quickly and effectively. However, the existing studies still have modeling limitations. The structural simplification, linearization and nonstandard parameter definition of the model reduce model accuracy. Additionally, the existing research mostly focused on initial tooth movement, and studies on long-term tooth movement after bone remodeling are lacking. These studies are needed in the future.

Three-dimensional finite element analysis of rapid movement canine tooth through reducing resistance and distracting procedures / 中华医学美学美容杂志

Objective To establish a three-dimensional finite element model of rapid canine tooth movement by reducing resistance and distracting procedures,and to discuss canine distal movement and force distribution of periodontium,and to provide theory basis for its clinical application.Methods Through 64-slice spiral scanning,temporomandibular joint (TMJ),the mandible,lower jaw denture section phantom DICOM data were obtained.Mimics software,Geomagic Studio 8.0 software,Unigraphics NX software,and Ansys11.0 software were mixed,and the three-dimensional finite element model were established under the conventional condition to move the canine (model 1 ),rapid canine movement through distracting osteggenesis of the periodontal ligament (model 2),rapid canine movement tooth movement through reducing resistance and distracting method (model 3),the strength were carried on three kind of models and the canine,the pericementum,the tooth socket bone stress distribution were observed.Results The biggest displacements on those three models occured in canine crown on 1/3,biggest displacement quantity:model 3 ＞model 2 ＞model 1,and the canine crown displacement reduced gradually from crown to the root point; in the model 1 most greatly equivalent stress mainly concentrated in the middle of distal alveolar crest,but in the models 2 and 3 most greatly equivalent stress centralism area shifted liguodistal alveolar crest.Conclusions In the process of canine distal movement,reducing bone resistance,can accelerate the tooth moving speed effectively and simultaneously,the canine has distal motion tendency.While under the action of force,the canine tends to move ligually with the canine distal movement,and thus appropriate measures should be taken to prevent canine lingual rotation in clinical work.

A study on the stress distribution of posterior fixed partial denture with various all-ceramic systems / 대한치과보철학회지

PURPOSE: The purpose of this study was to analyze stress distribution of all ceramic posterior fixed partial denture using a three dimensional finite element method. MATERIAL AND METHOD: A three dimensional finite element model was created to demonstrate all-ceramic posterior fixed partial denture and then this computer model measured the stress distribution of the all ceramic bridges which has a ceramic core materials such as Zirconia, IPS Empress 2, In-Ceram zirconia, Metal-Ceramic. Also the stress distribution was examined according to loading sites when force was applied to sites such as the central area of second premolar, the mesial connector of pontic, the central fossa of pontic, the distal connector of pontic, and the central fossa of second molar. RESULTS: 1. In all the materials of the core in this study, von Mises stress indicated that the stress increased as force was applied to loaded sites, just at those points, on the connector, and the margin in the area adjacent to the connectors. 2. The maximum principal stress was much higher in the lower part of the connectors than in any other region. 3. As the load was applied to the different locations, the research showed a consistent increase of stress in the lower connectors. The maximum value of the von Mises stress was two or three times greater when the load was applied directly to the connectors rather than indirectly through another stressed region. 4. In the case of In-Ceram zirconia, the stress in lower connectors was the highest of all the reference points, the stress showed 75% of all the maximum stress. Ziconia showed 72%, Metal-Ceramic 67% and IPS Empress 2 50%. 5. In the case of Ziconia, the stress was well dispersed in each reference point that the stress differences were smaller when compared to In-Cream ziconia.

The effects of posterior retraction on the displacement of the maxilla / 대한치과교정학회지

Three-dimensional finite element model was made from adult skull to find desirable direction of retraction force to treat skeletal class II malocclusion. The retraction force of 400g was applied to the first molar. The direction of the force application was 23degrees downward, parallel, 23degrees upward and 45` upward to the occlusal plane. The stress distribution and the displacement within the maxilla were analyzed by three-dimensional finite element method. The findings obtained were as follows: 1. Maxillary first molar was displaced posteriorly and inferiorly in 23degrees downward, parallel, 23degrees upward retraction but it was displaced posteriorly and superiorly in 45degrees upward retraction. 2. ANS, A point and prosthion were moved posteriorly and inferiorly and pterygornaxillary fissure was moved posteriorly and superiorly. Clockwise rotation of maxilla occurred when retraction force was applied. 3. The degree of clockwise rotation of maxilla was greatest when the force was applied 23degrees upward to the occlusal plane and was least when the force was applied 23degrees downward to the occlusal plane. 4. Large tensile stress appeared in maxillary first molar and alveolar bone and the infraorbital region of maxilla when the force was applied 23degrees downward to the occlusal plane. Tensile stress was smaller as the direction of force move upward. 5. Large compressive stress was appeared in maxillary first molar and infraorbital region in 45degrees upward case and large compressive stress occurred in the posterior part of maxilla as the retraction force was upward.

Effect of the depth and angle of the reverse-curve arch wires on the perpendicular force exerted to teeth / 实用口腔医学杂志

Objective:To analyze the perpendicular force on each tooth produced by the reverse-curve arch wires of various angles and depths using the method of 3-D finite element (3-D FEM) analysis. Methods:3-D FEM models of lower teeth, periodontal ligaments and alveolar bone as well as the 0.46 mm?0.64 mm inch stainless steel reverse-curve arch wires with different angles and depths were developed with the ANSYS finite element software, and the displacements of deformation of the reverse-curve arch wires were established on the models. Results:A ideal 3-D FEM was construct,including 2 709 elements and 1 969 nodes. The depth and angle of the reverse-curve arch wires produced obvious effect on the force exerted to teeth, and they could alter both the strength and the direction of the force. The force was mainly loaded on the canines, the second premolars and the molars, while less loaded on the incisors. Affected by the reverse-curve arch wires, the perpendicular force on the incisors were brought intrusively and on the molars were brought intrusively and distal upright; however, the canines and the bicuspids, in the perpendicular direction, moved along with the transformation of the angle and depth of the reverse-curve arch wires. When the angle of reverse-curve arch wires was fixed, the intrusive force on the incisors and molars was increased along with the increase of depth of the reverse-curve arch wires. Perpendicularly, the canines underwent a process from extrusion to intrusion, while the bicuspids were from intrusion to extrusion. When the depth of reverse-curve arch wires was fixed, the intrusive force on the incisors and molars was increased along with the increase of angle of the reverse-curve arch wires. The canines underwent a process from intrusion to extrusion.Conclusion:The variation of the angle and depth of the reverse-curve arch wires may produce evident effect on the force exerted to teeth.