Biomechanical evaluation of different implant–abutment connections, retention systems, and restorative materials in the implant-supported single crowns using 3D finite element

This is an in silico study aimed to evaluate the biomechanical influence of different implant–abutment interfaces (external hexagon and Morse taper implants), retention systems (cement- and screw-retained), and restorative crowns (metal–ceramic and monolithic) using three-dimensional finite element analysis (3D-FEA). Eight 3D models were simulated for the maxillary first molar area using InVesalius, Rhinoceros, and SolidWorks and processed using the Femap and NEi Nastran softwares. Axial and oblique forces of 200 N and 100 N, respectively, were applied on the occlusal surface of the prostheses. Microstrain and von Mises stress maps were used to evaluate the deformation (cortical bone tissue) and stress (implants/fixation screws/crowns), respectively for each model. For both loadings, Morse taper implants had lower microstrain values than the external hexagon implants. The retention system did not affect microstrain on the cortical bone tissue under both loadings. However, the cemented prosthesis displayed higher stress with the fixation screw than the external hexagon implants. No difference was observed between the metal–ceramic and zirconia monolithic crowns in terms of microstrain and stress distribution on the cortical bone, implants or components. Morse taper implants can be considered as a good alternative for dental implant rehabilitation because they demonstrated better biomechanical behavior for the bone and fixation screw as compared to external hexagon implants. Cement-retained prosthesis increased the stress on the fixation screw of the external hexagon implants, thereby increasing the risk of screw loosening/fracture in the posterior maxillary area. The use of metal–ceramic or monolithic crowns did not affect the biomechanical behavior of the evaluated structures.

FAILURE ANALYSIS AND REDESIGNING OF INTERNAL FIXATION SCREWS

Its highly impossible for false proofing the super structures or mechanisms or the metallurgical methods after installation so they are perfectly engineered and dispatched only after a series of quality checks which has a proper methodology. If this is the scenario with the non living structure's components if they were engineered without errors. There must be some more intensity with the living organisms. living organisms are not engineered but the engineering of the ailments or aids which support the life of living organism must be error free and perfect also must be ready to use. In this context it's pity that there is no perfect operational procedure for internal fixation of fractures this thesis Is focused on that area and aimed to derive a reliable design of internal fixation screw which is designed in contrast with conventional screw This project is stimulation out from two case studies of operational failure implant removal.

Concomitant Partial Achilles Tendon Rupture and Lateral Luxation of the Superficial Digital Flexor Muscle Tendon in a Dog

The aim of this study was to report a posttraumatic partial Achilles tendon (AT) rupture associated with lateral luxation of the superficial digital flexor tendon (SDFT) in a Whippet. This article is a brief communication. A Whippet was presented with posttraumatic plantigrade stance and non-load-bearing lameness of the right pelvic limb. The objective findings consisted in partial AT rupture and SDFT lateral luxation. Surgical treatment ensued: tenorrhaphy of the torn tendons and calcaneo-tibial screw insertion for tarsal immobilization, followed by suturing of the SDFT retinaculum. A casting bandage was employed for additional immobilization. Nonetheless, a bandage complication prompted the premature removal of the fixation screw and casting wrap. Complete functional recovery was achieved by the 20th postoperative week. The simultaneous occurrence of SDFT luxation and partial AT tear has not been reported in the literature before. The long-term postoperative functional outcome was highly satisfactory.

Late removal of an upper third molar displaced into the infratemporal space using an intermaxillary fixation screw: a case report

Teeth displacement during extractions even tough rare are extremely unwanted, especially for infra temporal space. This accident generally necessitate additional treatment for their resolution, being either immediate or late. Several authors discribed surgical techniques for removal displaced teeth into the infratemporal space, varying according to the degree of displacement, being that in some of this cases, is necessary the utilization of complementary tools. This case describes the technique utilized for late removal of tooth 18 (upper right third molar) dislocated into the lower portion of the infratemporal space (confirmed by the Cone Bean Computer tomography Scan), exam was performed after the patient reported pain in the operated region and during mandibular movement too, with an interincisal opening maximum of 20 millimeters. The procedure was realized under local anesthesia by a conservative intraoral approach and aid of intermaxillary fixation screw to facilitate extraction. The patient recovered well, without complications, with remission of pain and restoration of mouth opening.

Integrating Finite Element Death Technique and Bone Remodeling Theory to Predict Screw Loosening Affected by Radiation Treatment after Mandibular Reconstruction Surgery

This study developed a numerical simulation to understand bone mechanical behavior and micro-crack propagation around a fixation screw with severe mandibular defects. A mandible finite element (FE) model was constructed in a rabbit with a right unilateral body defect. The reconstruction implant was designed to be fixed using six screws distributed on the distal and mesial sides. The element death technique provided in FE analysis was combined with bone remodeling theory to simulate bone necrosis around the fixation screw in which the strain value reached the overload threshold. A total of 20 iterations were performed to observe the micro-crack propagation pattern for each screw according to the high strain locations occurring in each result from consecutive iterations. A parallel in vivo animal study was performed to validate the FE simulation by placing specific metal 3D printing reconstruction implants in rabbits to compare the differences in bone remodeling caused by radiation treatment after surgery. The results showed that strain values of the surrounding distal bone fixation screws were much larger than those at the mesial side. With the increase in the number of iteration analyses, the micro-crack prorogation trend for the distal fixation screws can be represented by the number and element death locations during the iteration analysis process. The corresponding micro-movement began to increase gradually and induced screw loosening after iteration calculation. The strained bone results showed that relatively high bone loss (damage) existed around the distal fixation screws under radiation treatment. This study concluded that the FE simulation developed in this study can provide a better predictive diagnosis method for understanding fixation screw loosening and advanced implant development before surgery.