Three Dimensional Finite Element Analysis Of Maxillary Protraction Using Labiolingual Arch And Implants

Objective: To build the physical model of four suturas which are related to the growth of maxilla in the three dimensional (3D) finite element modeling of maxillofacial bones. The models of labiolingual arch and implants maxillary protraction appliances are built and analyzed using 3D finite element method. To provide theoretical basis for reducing the adverse reaction of conventional oral appliances and improving the maxillary protraction. To introduce dental implants into maxillary protraction and to provide theoretical basis for increasing the type of indication of maxillary protraction and improving the effect of treatment.Method: A 16 years old volunteer with individual normal occlusion, good periodontium health condition and without diseases of temporo-mandibular joint was chosen to be the material of modeling. The 3-D finite-element model of the volunteer's maxillofacial bones was built using the CT scan combined with the ANSYS software. Finally we built the physical model of four suturas which are related to the growth of maxilla in the model of maxillofacial bones. Based on this model, the models of labiolingual arch and implants maxillary protraction appliances were built, respectively. The point of labiolingual arch traction was located between the maxillary canine and the adjacent of first premolar. The point of implants traction was located between the maxillary canine and the rootapex of first premolar. In both cases, the maxillary protraction was made at an angle of 20-30 degrees from the occlusion plane, according to the location of lower labium. The loads of these two models were both 800g. The Y-axis sagittal displacement and the z-axis coronair displacement of A point of maxillary, the upper anterior teeth, the sutura frontomaxillaris, the sutura zygomaticomaxillaris, the sutura temporozygomatica and the sutura pterygopalatine were calculated. The contour maps of stress distribution of the four suturas were also obtained. The displacement trend of maxilio-mandibular and the upper anterior teeth under the load of orthopedic force was evaluated, as well as the stress distribution of the sutura.Results: The 3D finite element model which contains 86575 nodes and 485915 units was built, as well as the physical model of the sutura frontomaxillaris, the sutura zygomaticomaxillaris, the sutura temporozygomatica and the sutura pterygopalatine. The sagittal-direction of maxillary: the maxillary moved forward and the maxillary anterior teeth tipped labially in the labiolingual arch model; the maxillary moved forward and the maxillary anterior teeth didn't tip labially in the implants model. The coronal-direction of maxillary: the maxillary moved upward, the upper dental arch moved upward, the maxillary rotated counterclockwisely in the labiolingual arch model; the maxillary moved downward, the upper dental arch moved downward, both the maxillary and the upper dental arch rotated clockwisely in the implants model. The in the labiolingual arch model: the stress distribution interval of the sutura frontomaxillaris is the biggest, the displacement of the maxillary bones which are connected with it is big; the stress distribution interval of the sutura zygomaticomaxillaris is smaller, the displacement of the maxillary and the cheekbone which are connected with it is bigger; the stress distribution interval of the sutura temporozygomatica is smaller, the displacement of the cheek bone and the maxillary is bigger, the z-axis displacement of sutura temporozygomatica is opposite to the cheek bone and maxillary; the stress distribution interval of the sutura pterygopalatine is big, but the displacement of itself is smaller, the maxillary which is connected with it is big. The implants model: the stress distribution intervals of the four suturas are bigger than the skeletal-dental model and the amount of the maxillary displacement is increased; the z-axis displacement direction of the sutura frontomaxillaris and the sutura zygomaticomaxillaris changed from upward to downward; the z-axis displacement of the sutura temporozygomatica tend to be upward, compare to the cheek bone and the maxillary which are connected with it; the stress distribution interval of the sutura pterygopalatine is increased and the amount of antedisplacement is increased.Conclusions:1. The physical model of the suturas which are related to the growth of the maxillary was built using the CT scan combined with the MIMICS and ANSYS software. The maxillofacial model which has high biological similarity, good editability was built. It can be rotated as will and we can edit any part of the model. The reliable model base was provided to the biomechanics study of maxillofacial bones. 2. After the in the labiolingual arch model was loaded, the maxillary moved forward, the upper anterior teeth tipped labially and the maxillary rotated counterclockwisely, which is in good agreement with the data of clinical research. The scientificity and accuracy of the model was proved by this result. The in the labiolingual arch maxillary protraction appliance is suitable to the cross bite and deep overbite Angle III patient.3. After the labiolingual arch model was loaded, the contour map of sutura stress distribution show that the sutura frontomaxillaris and the sutura zygomaticomaxillaris are important to the antedisplacement and counterclockwise rotation of the maxillary. The change of the sutura temporozygomatica and the sutura pterygopalatine are not obvious.4. After the implants model was loaded, the maxillary moved forward, the upper anterior teech didn't tip labially, the maxillary rotated clockwisely, which is in good agreement with the clinical data. The dental implant maxillary protraction appliance is suitable to the cross bite and open bite Angle III patient.5. After the implants model was loaded, the contour map of sutura stress distribution show that because the point of traction is changed, both the sutura frontomaxillaris and the sutura zygomaticomaxillaris make great impact to the antedisplacement and the rotation of the maxillary. The sutura temporozygomatica and the sutura pterygopalatine are not important to the antedisplacement and the clockwise rotation of maxillary. 6. Based on the clinical case analysis and the data obtained from this research, the in the labiolingual arch model maxillary protraction appliance provide less growth-simulating to the maxillary and the implants appliance provide more growth-simulating to the maxillary. The in the labiolingual arch model is suitable to the younger Angle III patient in the early period of dental transition. The implants appliance is suitable to the older Angle III patient who is in the later period of dental transition or early period of permanent teeth.