Finite element study of the mandibular angle width changes in retrogression surgery by bilateral sagittal split ramus osteotomy / 中华整形外科杂志

0bjective@#To establish a three-dimensional finite element model of mandible and study the transverse displacement of proximal segment after Bilateral Sagittal Split Ramus Osteotomy (BSSRO) with different retrogression amounts during mastication.@*Methods@#DICOM data of a skull model were processed with MIMICS and ANSYS software, reconstructing the 3D model including the teeth and temporomandibular joint in order to simulate BSSRO and evaluate the transverse displacement of proximal segment with different retrogression amounts during mastication.@*Results@#The mean of proximal segment width change were 2.955 mm and 3.490 mm, when retrogression amounts of distal segmentwere 3 mm and 8 mm, respectively.No significant difference between the two groups were found (P=0.131). Meanwhile the displacement color scale of the 3D finite element models showed that the apparent transverse displacement distribution of the proximal segment was measured around the gonial area, decreased from the exterior to the interior.@*Conclusions@#The mandibular angle width was significantly expanded right after BSSRO. The masticatory muscle system and single cortical fixation system played an important role in expanding the width of proximal segment. However there was no correlation between the widening effect and retrogression amounts of distal segment of mandible.

Clinical research on the simulation accuracy of zygomatic reduction using an L-shaped osteotomy by Proplan CMF software / 中华整形外科杂志

Objective@#To evaluate the surgical prediction accuracy of Proplan CMF software for zygomatic reduction surgery using L-shaped osteotomy.@*Methods@#Pre-and-postoperative 1-year CBCT data of 26 patients with zygomatic arch hypertrophy were imported in Proplan CMF software during 2014 Jan. to 2016 Jun., the 3D models were reconstructed for simulation of L-shaped osteotomy, characteristic landmarks were selected and 3D point measurement system was established. The measurement result were analyzed by one-way ANOVA. Meanwhile, the overlap color grading charts of preoperative and simulated images were also observed.@*Results@#The facial width, bilateral zygomatic process angle and facial width index were [(128.56±2.72) mm, (106.87±2.53)°, (108.56±3.02)°and 1.41±0.03] in postoperative result, [(129.49±2.26) mm, (108.68±2.40)°, (108.85±3.02)°and 1.42±0.03]in simulated result and [(135.45±2.45) mm, (102.50±2.60)°, (103.41±2.56)°and 1.48±0.05] in preoperative result, with significant difference between preoperative and postoperative result, or between preoperative and simulated result (P<0.05), while no significance between postoperative and simulated result (P>0.05). The soft tissue zygomatic process distance was(153.25±2.58) mm in preoperative result, (150.23±2.76)mm in postoperative result , (149.36±3.27)mm in simulated result, with no significance between any of two groups result (P>0.05). The zygomatic process distance and bilateral zygomatic process tragal distance were (126.35±2.56) mm, (68.75±2.15) mm and(68.86±3.21) mm in postoperative result, showing significant differences compared with preoperative result [(120.16±3.18) mm, (74.58±3.19) mm and(76.14±3.15) mm] and simulated result [(118.86±3.45) mm, (73.85±3.57) mm and(76.87±2.58) mm] respectively(P<0.05), while zygomatic arch distance was not statistically different among the three groups(P>0.05). It indicated that predictive accuracy of facial width, facial width index, zygomatic process angle, soft tissue zygomatic arch distance was high but the soft tissue zygomatic process distance and zygomatic process tragal distance was relatively low. Meanwhile, the color overlay image showed that predictive accuracy was not good in the zygomatic region while the zygomatic arch area was high.@*Conclusions@#The predictive accuracy of Proplan CMF software for zygomatic arch hypertrophy is relatively high except for the zygomatic region. Further improvement of the CMF software is needed.

The research of SurgiCase CMF software in surgical simulation and prediction for mandibular asymmetry / 中华整形外科杂志

<p><b>OBJECTIVE</b>To evaluate the predictive accuracy of the SurgiCase CMF software in surgical simulation and prediction for mandibular asymmetry with 3-dimensional simulation and measurement.</p><p><b>METHODS</b>CBCT data of 27 patients with mandibular asymmetry were observed in CMF, and postoperative soft tissue physiognomy were predicted by simulating sagittal ramus osteotomy with or without genioplasty. The measurement parameters representing the symmetry of soft tissue were selected and the horizontal, coronal and sagittal planes were established. The results were analyzed by SPSS 19. 0. The overlap compared color grading charts were observed.</p><p><b>RESULTS</b>Angles between cheilions and the horizonta plane (Ch-Ch-FH) in the simulation and postoperative soft tissues are (2. 35 ± 1. 81)° and (1. 44 ± 1. 13)°. The angles constructed among subnasale, upper lip and lower lip (Sn-UL-LL) are (4. 02 ± 3. 05)° and (2. 59 ± 1. 64)°, showing statistically different (P < 0. 01, P < 0. 05), which means that predictive accuracy of the lip canting and lip vertical deviation is relatively low. Distance between gonioi and sagittal plane (Go'-MS), distance between gonion and pogonion (Go'-Pog') and angle betweer subnasale to menton and the horizontal plane (Sn-Me'-MS) are not statistically different, which mean! high predictive accuracy of mandibular angle and chin. By observing the overlap compared color gradin-) charts, the predictive accuracy is not good in the cheek, especially in the deviate side.</p><p><b>CONCLUSIONS</b>The predictive accuracy of CMF system for patients with mandibular asymmetry is relatively high, but it is not good in the lip and cheek. The software improvement is still necessary.</p>

Establishing a finite element model of the mandible containing the temporomandibular joint after bilateral-sagitta-split-ramus-osteotomy with internal fixation / 中国组织工程研究

BACKGROUND:Bilateral-sagitta-split-ramus-osteotomy (BSSRO) has become a conventional method to correct facial deformities, and the finite element method is a significant way to study biomechanics of the mandible and temporomandibular joint (TMJ) after BSSRO. OBJECTIVE: To establish a precise and high simulation model of mandible containing TMJ after BSSRO with internal fixation, which is the base to study the biomechanics of the mandible and TMJ after BSSRO. METHODS: Spiral CT scan was used to get the data of DICOM that were input into MIMICS to establish the three-dimensional model of the mandible. The three-dimensional model was wrapped into a single closed shel for mesh generation and conversion in ANSYS. Then, the model was input into the ANSYS software for temporomandibular joint reconstruction and simulation of BSSRO and internal fixation. RESULTS AND CONCLUSION: The three-dimensional finite element model of mandible containing TMJ after BSSRO was established using MIMICS and ANSYS. This model had biological similarity and geometric similarity in comparison with the human tissues. The model could undergo various internal fixations through antedisplacement, retroposition and rotational movement of the distal end. Based on different experimental purposes, the established model can apply a load to al parts to study changes in stress and displacement of different tissues after BSSRO and internal fixation, and it also can be used to study the effect of different fixation materials on the rear stability after internal fixation.

Localization of the centre of resistance in different osteotomy pattern for maxillary complex with cleft lip and palate / 中华医学美学美容杂志

Objective To explore the location of the centre of resistance for the maxillary complex in cleft lip and palate by the use of finite element analysis. Methods Combining spiral CT scanning technology with the three-dimensional finite element method, a three-dimensional FEM model of LeFort Ⅰ , Ⅱ , and Ⅲ complex and soft tissue in cleft lip and palate was developed for analysis. Anteriorly and inferiorly directed forces of 9.8N were applied at five different levels parallel to the functional occlusal plane and four different levels perpendicular to the functional occlusal plane, respectively.For each loading condition, horizontal and vertical displacements of different anatomic points in the complex and on the maxillary dentition were analysed. Location of the centre of resistance in different osteotomy complex were studied. Results The resistant center of the LeFort Ⅱ complex in cleft lip and palate was located on intersection between basis nasi and medium of apertura piriforms vertically,apex of the canine and posterior point of the first bicuspid horizontally. The resistant center of the LeFort Ⅲ complex in cleft lip and palate was located on intersection between anterior of the nasion and medium of apertura piriforms vertically, posterior point of the first molar and first bicuspid horizontally. Conclusion Knowledge of the resistant center of different osteotomy complex could establish a basis for biomechanical studies of craniofacial complex distraction osteogenesis in cleft lip and palate.