Biomechanical analysis in mandibular advancement and occlusal plane rotation with finite element analysis.

We used finite element analysis to assess stress on the cortical bone and plate fixation system, as well as mandibular resistance after sagittal split ramus osteotomy with different mandibular advancements and rotations of the occlusal plane. Three-dimensional mandibular models were obtained, and 6mm and 12mm advancements were planned associated with linear, clockwise, and counter-clockwise rotation of the angle of the occlusal plane. Each model was then fixed with one or two 2.0mm system plates and secured with four monocortical screws. A total of 12 models were built and subjected to a vertical load in the lower central incisor ranging from 50N to 500N in 50N increments. Results showed that the 12mm advancement was associated with higher stress on the bone and plate surface. Additionally, the models fixed with two plates exhibited lower plate stress than those fixed with a single plate. Counter-clockwise rotation of the angle of the mandibular plane in the 6mm advancement caused more plate stress, which did not occur in the 12mm advancement. This analysis has shown that change in the occlusal plane in large mandibular advancements does not act as an additional stress factor. These findings can help to better understand the tensions on bone and plate surfaces in patients who need large mandibular advancements that are associated with a change in the occlusal plane, and will aid better surgical planning.

Biomechanical simulation of temporomandibular joint replacement (TMJR) devices: a scoping review of the finite element method.

The aim of this study was to perform a literature review on the use of finite element modeling (FEM) for the evaluation of the biomechanical behavior of temporomandibular joint replacement (TMJR) devices. An electronic search of online medical and scientific literature database was conducted using selected search terms. The search identified 307 studies, of which 19 were considered relevant to this study. Of the 19 selected studies, 10 (52.6%) investigated the influence of geometry and fixation methods, while two (10.5%) evaluated the behavior of artificial condyle-fossa structures. The TMJR devices assessed in these studies included TMJ Inc. (aka Christensen; 63.2%), Zimmer Biomet (15.7%), Stryker (10.5%), and a theoretical intramedullary condylar component (5.3%); 26.3% of the studies evaluated custom TMJR devices. Such studies provided important data on the distribution of strain and stress through TMJR structural components and surrounding bone by using different software systems and methods. The mean stress values were lower on a custom TMJR condyle-ramus component and the supporting bone than on the stock device. FEM proved to be an accurate and valuable biomechanical simulation tool for studying the current TMJR devices and should be considered a useful tool for the improvement and development of future joint replacement devices.

Evaluation of patients undergoing placement of zygomatic implants using sinus slot technique.

BACKGROUND: This study aimed to evaluate patients undergoing placement of zygomatic implants by Stella and Warner's technique, considering the survival rate of conventional and zygomatic implants, and assess the health of the maxillary sinuses and the level of patient satisfaction. METHODS: In this retrospective cohort study, 28 patients had received a combination of conventional and zygomatic implants (group I) and 14 were rehabilitated with only conventional implants (group II). RESULTS: The results showed that Stella and Warner's technique, thought to minimize the presence of the implant into the maxillary sinus, improving the emergence of the implant, proved to be effective, allowing a high survival rate of conventional and zygomatic implants (100 %). The follow-up period ranged from a minimum of 15 months to a maximum of 53 months after prosthetic rehabilitation (average of 34 months). No pathological changes were found on the periimplant tissues. Radiographs showed satisfactory bone levels in conventional implants of oral rehabilitation with zygomatic implants and a good positioning of the apex of the zygomatic implants in relation to the zygomatic bone. The tomographic findings revealed no characteristics of sinus disease. There were no cases of obstruction of the maxillary sinus ostium. CONCLUSIONS: The placement of zygomatic implants by Stella and Warner's technique proved to be a predictable technique with high implant survival rate in patients with atrophic maxilla and was not associated with sinus disease in the sample analyzed. However, a long-term follow-up is necessary to confirm the initial findings of this study.

In vitro mechanical assessment of 2.0-mm system three-dimensional miniplates in anterior mandibular fractures.

This study constituted a comparative assessment of the mechanical resistance of square and rectangular 2.0-mm system three-dimensional miniplates as compared to the standard configuration using two straight miniplates. 90 polyurethane replica mandibles were used for the mechanical trials. Groups 1, 2, and 3 simulated complete symphyseal fractures characterized by linear separation of the central incisors; groups 4, 5, and 6 simulated parasymphyseal fractures with an oblique configuration. Groups 1 and 4 represented the standard method with two straight miniplates set parallel to one another. Square miniplates were used in groups 2 and 5, and rectangular miniplates in groups 3 and 6. A universal testing machine set to a velocity of 10mm/min and delivering a vertical linear load to the first left molar was used to test each group. Maximum load values and load values with pre-established dislocation of 5mm were obtained and submitted to statistical analysis using a calculated reliability interval of 95%. The mechanical performances of the devices were similar, except in the case of rectangular plates used in the parasymphyseal fractures. The innovative fixation methods used showed significantly better results in the case of symphyseal fractures.