Role of finite element analysis for selection of single point fixation in zygomaticomaxillary complex fracture.

BACKGROUND: One-point fixation was superior to the two and three-points fixation in minimally displaced zygomaticomaxillary complex (ZMC) fracture regarding the cost, invasiveness, scaring, number of wounds, and operation time. Accordingly, this study aimed to predict which one-point fixation is the most stable in managing minimally displaced ZMC fracture. MATERIAL & METHODS: This study simulated the different one-point fixation approaches on three ZMC models after fracture reduction and application of all forces exerted on the fractured area. The findings were represented as stress impact on the ZMC fracture and plating system as well as the inter-fragments micro-motion. RESULTS: The von misses stresses of plates for the zygomaticofrontal, infra-orbital rim, and zygomaticomaxillary buttress model were (66.508, 1.285, and1.16 MPa) respectively. While the screws' von misses for the infraorbital rim, zygomaticofrontal, and zygomaticomaxillary buttress models were (13.8, 4.05, and 1.60 MPa) respectively. Whereas, the maximum principles stress at zygomaticofrontal, zygomaticomaxillary buttress, and infraorbital rim models were (37.03, 37.01, and 34.46 MPa) respectively. In addition, the inter-fragment micro-motion for zygomaticomaxillary buttress, infraorbital rim, and zygomaticofrontal models were (0.26, 0.25, and 0.15 mm) respectively. CONCLUSION: One-point fixation at zygomaticomaxillary buttress is the preferred point because it is exposed to low stresses, and the inter-fragment micro-motion is within the approved limit with the elements in the same direction of fixation which indicates the rigid fixation. In addition, it is less palpable and scarless. TRIAL REGISTRATION: clinical trial.gov (NCT05819372) at 19/04/2023.

Finite Element Analysis of the Stresses Induced by One-Piece and Two-Piece Dental Implants Supporting All-on-4 Implant-Supported Prostheses.

PURPOSE: To find out the difference in the stresses induced by one-piece monophasic and two-piece dental implants supporting All-on-4 implant-supported prostheses using finite element analysis. MATERIALS AND METHODS: Two finite element maxillary models were designed: In the two-piece model, two-piece dental implants were used, and in the one-piece model, one-piece dental implants were used. The dental implants were placed according to the All-on-4 treatment concept. The anterior implants were axially placed; however, the posterior implants were placed with a distal inclination of 15 degrees. In each model, the prosthetic superstructure was designed to be a titanium implant prosthesis with zirconia crowns. Three loading scenarios were applied in this study. The first scenario simulated biting function with a total load of 250 N. The second scenario simulated incision function in which 90-N horizontal static load was applied to the palatal surface of central incisors. The third scenario simulated biting in the presence of a cantilever. RESULTS: In the three loading scenarios, the stresses were higher in the two-piece model. Higher stress values were recorded posteriorly rather than anteriorly in both models. CONCLUSION: One-piece dental implants induce lower stress values compared with two-piece dental implants when used in All-on-4 implant-supported prostheses.

Stresses induced by one piece and two piece dental implants in All-on-4® implant supported prosthesis under simulated lateral occlusal loading: non linear finite element analysis study.

BACKGROUND: Correct choice of the implant design and the occlusal scheme is important for the success of implant supported restorations. So, the aim of the current study was to find out the difference in the stresses induced by the one piece dental implants designed to be used in the All-on-4® concept and the conventional two piece ones under simulated lateral occlusal schemes using nonlinear finite element analysis. METHODS: Two finite element models of the maxilla, implants, and prostheses were designed according to the All-on-4® concept. In the model TP, two piece dental implants were placed while in the model OP one piece dental implants were used. Two loading scenarios were applied to each model; the first one simulated a group function occlusal scheme while the second scenario simulated a canine guided one. RESULTS: The highest stress value was recorded in the model TP with the group function occlusion and the lowest stress value was in the model OP with the canine guidance occlusion. CONCLUSION: The one-piece dental implants can be concluded to induce less stress compared to the two piece dental implants when used in the All-on-4® implant supported prosthesis in the different lateral occlusal schemes. Canine guided occlusion can be concluded to cause lower stress values in comparison to the group function occlusal scheme.

The Stress Concentration and Biomechanical Properties of the Intraoral Distractors and the Extraoral Distractors Used in Treatment of Hemifacial Microsomia Patients: A Simulation Finite Element Analysis Study.

THE AIM OF THE STUDY: Finite element analysis of the stresses subjected to both the intraoral and the extraoral distractors devices used in the mandibular distraction of hemifacial microsomia patients. METHODOLOGY: Two models were included in the current study. The first model was an extraoral distractor and the second model was an intraoral distractor model. To generate the results in the simulated models; 2 vertical loads were applied (222.7 and 137.78 N) on the defective and normal side, respectively. RESULTS: The intraoral system observed lower stress (6.85 MPa) in the mandibular bone compared to the extraoral system (13.21 MPa). The intraoral distractor had a higher stress concentration on the distractor fixing screws (352 MPa) compared to the extraoral distractor fixing pins (15 MPa). The extraoral distractor had a higher displacement effect on the mandibular bone around the pins of 263.35 µm in comparison to the intraoral distractor effect which was 77.87 µm. CONCLUSIONS: Internal oral distractor provides a sort of stress shielding to the distracted bone and less displacement, so it is more advisable to be used in general. The external devices are advised only in extralong distraction distance because the distractor is subjected to lower stresses compared to intraoral counterparts.

The Stress Concentration and Biomechanical Properties of the Intra-oral Distractors and the Extra-oral Distractors Used in Treatment of Post Ankylosis Facial Asymmetric Patients: A Finite Element Analysis Study.

ABSTRACT: Assessment of stress and micromotions using finite element analysis along both the intraoral and the extraoral distractors devices used in the mandibular distraction of post temporomandibular joint ankylosis deformed mandible patients. The process of finite element analysis was carried out to assess distraction models. The first model was an extraoral mandibular distraction model and the second model was an intraoral mandibular distraction model. To analyze the stress state, 2 vertical loads were applied on the defective and normal side respectively by a 3D finite element ball model. The intraoral system observed lower stress (4.5 MPa) in the mandibular bone compared to the extra-oral system (11.5 MPa). The results revealed that the intraoral system observed higher stress on the distractor fixing points (392.21 MPa) compared to the extra-oral fixing points (12.62 MPa). The results revealed that the extra-oral system reflected higher displacement on the bone surrounding the screws of about 3720 µm compared to the intraoral system 1414.6 µm. Internal devices give better shielding to the bone and induce fewer stresses over the mandibular, so it is more advisable to be used. The external devices permit greater distraction length because the pins and the distractor main body are subjected to fewer stresses.