Maintenance of the integrity of the abutment/implant interface is essential and is dependent on the abutment screw retaining a preload. Evaluation of this joint is usually done by manual assessment. The purpose of the current study was to determine whether the Periotest instrument could be used to evaluate abutment screw loosening. A custom-designed apparatus was constructed to measure abutment...

In this study, we characterized the rotational efficiency of the photo-driven Archimedes screw. The micron-sized Archimedes screws were fabricated using the two-photon polymerization technique. Free-floating screws trapped by optical tweezers align in the laser irradiation direction and rotate spontaneously. The influences of the screw pitch and the number of screw blades have been investigated...

Problems that screw cannot be inserted may occur in screw-rod fixation techniques such as Harms technique. We compared the biomechanical stability imparted to the C-2 vertebrae by four designed posterior screw and rod fixation techniques for the management of odontoid fractures. A three-dimensional finite element model of the odontoid fracture was established by subtracting several unit structu...

Various navigation systems are available to aid pedicle screw placement. The O-arm replaces the need for fluoroscopy and generates a 3-dimensional volumetric dataset that can be viewed as transverse, coronal, and sagittal images of the spine, similar to computed tomography (CT) scanning. The dataset can be downloaded to the Stealth system (Medtronic Navigation, Louisville, Colorado) for real-ti...

BACKGROUND Lateral mass screw fixation with plates or rods has become the standard method of posterior cervical spine fixation and stabilization for a variety of surgical indications. Despite ubiquitous usage, the safety and efficacy of this technique have not yet been established sufficiently to permit "on-label" U.S. Food and Drug Administration approval for lateral mass screw fixation system...

Ball screw drives are widely used as the motion delivery mechanism due to their high stiffness and high accuracy. As the speed and precision requirements from machine tools increase, the effects of the structural flexibility of the drives on controller performance are becoming increasingly significant. The vibrations adversely affect the positioning accuracy and performance of the drive. The na...

The relationship of stress generation upon placement of cement-retained or screw-retained implant restorations has not been thoroughly investigated. Passivity of fit and marginal discrepancies of screw- and cement-retained implant fixed partial denture (FPD) designs were determined using a photoelastic model of a partially edentulous posterior mandibular arch with 3 screw-type implants. Buccal ...

INTRODUCTION Pedicle screw fixation allows purchase of all three spinal columns without encroaching into the spinal canal improving fracture fixation, as well as deformity correction. Fortunately, neurologic injury associated with pedicle screw malposition is rare. CASE PRESENTATION A 19-year-old boy was surgically treated for severe right thoracic scoliosis associated with a Chiari Type 1 ma...

BACKGROUND Use of a pedicle screw at the level of fracture, also known as an intermediate screw, has been shown to improve clinical results in managing thoracolumbar(TL) fractures, but there is a paucity of powerful evidence to support the claim. The aim of this study was to compare outcomes between pedicle screw fixation combined with intermediate screw at the fracture level and conventional p...