Fracture resistance of ceramic brackets to arch wire torsional force / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to estimate the fracture resistance of commercially available ceramic brackets to torsional force exerted from arch wires and to evaluate the characteristics of bracket fracture. METHODS: Lingual root torque was applied to maxillary central incisor brackets with 0.022-inch slots by means of a 0.0215 x0.027-inch stainless steel arch wire. A custom designed apparatus that attached to an Instron was used to test seven types of ceramic brackets (n = 15). The torque value and torque angle at fracture were measured. In order to evaluate the characteristics of failure, fracture sites and the failure patterns of brackets were examined with a Scanning Electron Microscope. RESULTS: Crystal structure and manufacturing process of ceramic brackets had a significant effect on fracture resistance. Monocrystalline alumina (Inspire) brackets showed significantly greater resistance to torsional force than polycrystalline alumina brackets except InVu. There was no significant difference in fracture resistance during arch wire torsional force between ceramic brackets with metal slots and those without metal slots (p > 0.05). All Clarity brackets partially fractured only at the incisal slot base and the others broke at various locations. CONCLUSION: The fracture resistance of all the ceramic brackets during arch wire torsion appears to be adequate for clinical use.

Impact of Interhospital Transfer in Mortality of Critically Ill Patients

PURPOSE: Interhospital transfer of critically ill patients is often necessary for optimal patient care. However it is known that transport of critically ill patients has been associated with high rate of potentially detrimental complications. This study was designed to determine whether mortality of critically ill patients with interhospital transfers is different from critically ill patients with direct admissions. METHODS: The retrospective cohort study was conducted at an academic medical center with 3906 critically ill patients from 2003 to 2004, of whom 1652 were direct admissions and 2254 were interhospital transfers. Death within 48 hours in interhospital transfers and direct admissions were compared using univariate and multivariate regression analyses that adjusted for severity of illness. Severity of illness was measured using Simplified Acute Physiology Score (SAPS) II and Charles comorbidity score. To measure hospital performance standardized mortality ratio (SMR) was calculated by dividing observed mortality by SAPS II-predicted mortality. RESULTS: Death within 48 hours were not significantly higher for interhospital transfer patients than for directly admitted patients (7.5% vs 8.1%, p<0.05). But directly admitted patients had significantly higher SMR than transferred patients (0.94 vs 0.81, p=0.001). Finally, transferred patients with hepatic failure had significantly higher mortality rates (odds ratio=4.636) as compared with directly admitted patients, confirming the "transfer effect"for this patients' subgroup. CONCLUSION: Admission source is not an important determinant of outcome.