A Paradigm Shift for Torsional Stiffness of Nickel-Titanium Rotary Instruments: A Finite Element Analysis

IntroductionThe aim of this study was to investigate the influence of mass and the polar moment of inertia on the torsional behavior of nickel-titanium rotary instruments to understand which parameter of cross-sectional design had a key role in terms of torsional resistance.MethodsFour different instrument models were designed and meshed using computer-aided engineering software (SolidWorks; Dassault Systems, Waltham, MA). Instrument models shared the same characteristics, except for cross-sectional design; triangle, rectangle, square, and hollow square geometry was selected. Finite element analysis was performed simulating a static torsional test using the FEEPlus internal solver (Solid Works). Von Mises stress and torsional load at fracture were calculated by the software. Linear regression analysis was performed to investigate the relationship of the polar moment of inertia, cross-sectional area, inner core radius, and mass per volume on the torsional resistance of nickel-titanium rotary instruments.ResultsThe polar moment of inertia positively affected the maximum torsional load with the highest level of correlation (R² = 0.917). It could be stated that the higher the polar moment of inertia is, the more maximum torsional load at fracture is present. Mass and cross-sectional area had a lower level of correlation compared with the polar moment of inertia (R² = 0.5533). According to this, 2 instruments with the same mass/mm and/or cross-sectional area could have different torsional resistance.ConclusionsThe polar moment of inertia can be considered as the most important cross-sectional factor in determining the torsional resistance of rotary instruments over metal mass and cross-sectional area.     

Spinal extradural solitary fibrous tumor with retiform and papillary features

We report a 66-year-old man with a spinal, extradural solitary fibrous tumor showing unique retiform and papillary architecture. The patient presented in May 2008 with worsening right-sided lower back pain and urinary frequency. Magnetic resonance imaging of the spine documented a heterogeneously enhancing dumbbell-shaped extradural lesion causing cord compression at T11/12 level. The tumor extended to the paravertebral soft tissue and invaded the right adjacent vertebral pedicles and laminae. An angiogram showed prominent vascular supply mainly from the right T11 radicular artery. The patient underwent surgery to relieve cord compression in May 2008 and a second operation following embolization with coils in October 2009. No recurrence was observed at the last neuroimaging follow-up in June 2012. The tumor was composed of vimentin, CD34, Bcl-2, and CD99-positive rounded or slightly elongated cells with scant cytoplasm and oval to spindle nuclei. Several pseudovascular spaces reminiscent of the rete testis were present, and several of them contained papillary projections. Cytologic atypia was minimal, and mitotic activity was low. Focal infiltration of the paraspinal adipose tissue was seen at microscopic level. To our knowledge, retiform and papillary features have never been reported in a solitary fibrous tumor.     

Repair of complete bilateral cleft lip with severely protruding premaxilla performing a premaxillary setback and vomerine ostectomy in one stage surgery

Background

The authors present a technique for selected cases of CBCL. The primary repair of the CBCL with a severely protruding premaxilla in one stage surgery is very difficult, essentially because a good muscular apposition is difficult, forcing synchronously to do a premaxillary setback to facilitate subsequent bilateral lip repair and, thus, achieving satisfactory results. We achieve this by a reductive ostectomy on the vomero-premaxillary suture.

Material and Methods

4 patients with CBCL and severely protruding premaxilla underwent premaxillary setback by vomerine ostectomy at the same time of lip repair in the past 24 months. The extent of premaxillary setback varied between 9 and 16 mm. The required amount of bone was removed anterior to the vomero-premaxillary suture. The authors did an additional simultaneous gingivoperiosteoplasty in all patients, achieving an enough stability of the premaxilla in its new position, to be able to close the alveolar gap bilaterally. The authors have examined the position of premaxilla and dental arch between 6 and 24 months. We did not do the primary nose correction, because this increased the risk of impairment of the already compromised vascularity of the philtrum and premaxilla.

Results

The follow-up period ranged between 6 and 24 months. None of the patients had any major complication. During follow-up, the premaxilla was minimally mobile. We achieved a good lip repair in all cases: adequate muscle repair, symmetry of the lip, prolabium and Cupid’s bow, as well as good scars.

Conclusions

To our knowledge, there are few reports of one stage surgery with vomerine ostectomy to repair CBCL with severely protruding premaxilla. Doing this vomerine ostectomy, we don’t know how it will affect the subsequent growth of the premaxila and restrict the natural maxillary growth. Applying this alternative treatment for children with CBCL and protruded premaxilla without any preoperative orthopedic, we can successfully perform, in a single-stage surgery, a good primary lip repair at our center. Further confirmations of this surgery with follow up and anthropometric studies of these patients during childhood and adolescence are required. Key words: Protruding premaxilla, bilateral cleft lip, vomerine ostectomy, one stage surgery, Millard II technique.     

Mycobacterium tuberculosis Gyrase Inhibitors as a New Class of Antitubercular Drugs

One way to speed up the TB drug discovery process is to search for antitubercular activity among compound series that already possess some of the key properties needed in anti-infective drug discovery, such as whole-cell activity and oral absorption. Here, we present MGIs, a new series of Mycobacterium tuberculosis gyrase inhibitors, which stem from the long-term efforts GSK has dedicated to the discovery and development of novel bacterial topoisomerase inhibitors (NBTIs). The compounds identified were found to be devoid of fluoroquinolone (FQ) cross-resistance and seem to operate through a mechanism similar to that of the previously described NBTI GSK antibacterial drug candidate. The remarkable in vitro and in vivo antitubercular profiles showed by the hits has prompted us to further advance the MGI project to full lead optimization.     

The ontogeny of the endocrine pancreas in the fetal/newborn baboon

Erratic regulation of glucose metabolism including hyperglycemia is a common condition in premature infants and is associated with increased morbidity and mortality. The objective of this study was to examine histological and ultrastructural differences in the endocrine pancreas in fetal (throughout gestation) and neonatal baboons. Twelve fetal baboons were delivered at 125 days (d) gestational age (GA), 140d GA, or 175d GA. Eight animals were delivered at term (185d GA); half were fed for 5 days. Seventy-three nondiabetic adult baboons were used for comparison. Pancreatic tissue was studied using light microscopy, confocal imaging, and electron microscopy. The fetal and neonatal endocrine pancreas islet architecture became more organized as GA advanced. The percent areas of α-β-δ-cell type were similar within each fetal and newborn GA (NS) but were higher than the adults (P<0.05) regardless of GA. The ratio of β cells within the islet (whole and core) increased with gestation (P<0.01). Neonatal baboons, which survived for 5 days (feeding), had a 2.5-fold increase in pancreas weight compared with their counterparts killed at birth (P=0.01). Endocrine cells were also found in exocrine ductal and acinar cells in 125, 140 and 175d GA fetuses. Subpopulation of tissue that coexpressed trypsin and glucagon/insulin shows the presence of cells with mixed endo-exocrine lineage in fetuses. In summary, the fetal endocrine pancreas has no prevalence of a α-β-δ-cell type with larger endocrine cell percent areas than adults. Cells with mixed endocrine/exocrine phenotype occur during fetal development. Developmental differences may play a role in glucose homeostasis during the neonatal period and may have long-term implications.     

Azygous continuation of the inferior vena cava with anomalous hepatic vein drainage

A 62-year-old woman was referred for evaluation of hypoxemia. Despite a resting SaO(2) of 89%, she was otherwise asymptomatic. The arterial blood gas on room air demonstrated a pO(2) of 58 mm Hg. Two shunt studies confirmed a shunt fraction of 25%. Echocardiogram with agitated saline demonstrated bubbles in the left atrium. Nuclear perfusion study revealed no uptake over the kidneys or brain. Computed tomography of the chest and cardiac magnetic resonance imaging confirmed the presence of a large shunt (azygous continuation of the inferior vena cava [ACIVC] with anomalous hepatic vein drainage). A large shunt fraction dictates either significant cardiac septal defect or an extracardiac shunt. The finding of ACIVC should prompt consideration of other vascular or cardiac abnormalities. The true incidence of isolated ACIVC is not known, as limited ACIVC may remain asymptomatic. However, the spectrum of vascular, cardiac and somatic abnormalities that may accompany ACIVC is quite varied.