ABSTRACT
The current investigation proposes a novel method for simultaneous assessment of the electrochemical and structural fatigue properties of nickel-titanium shape memory alloy (NiTi SMA) wires. The design and layout of an in situ electrochemical cell in a custom-made bending rotation fatigue (BRF) test rig is presented. This newly designed test rig allows performing a wide spectrum of experiments for studying the influence of fatigue on corrosion and vice versa. This can be achieved by performing ex situ and∕or in situ measurements. The versatility of the combined electrochemical∕mechanical test rig is demonstrated by studying the electrochemical behavior of NiTi SMA wires in 0.9% NaCl electrolyte under load. The ex situ measurements allow addressing various issues, for example, the influence of pre-fatigue on the localized corrosion resistance, or the influence of hydrogen on fatigue life. Ex situ experiments showed that a pre-fatigued wire is more susceptible to localized corrosion. The synergetic effect can be concluded from the polarization studies and specifically from an in situ study of the open circuit potential (OCP) transients, which sensitively react to the elementary repassivation events related to the local failure of the oxide layer. It can also be used as an indicator for identifying the onset of the fatigue failure.
Subject(s)
Biocompatible Materials/chemistry , Dental Alloys/chemistry , Electrochemistry/instrumentation , Electrochemistry/methods , Equipment Design , Materials Testing , Microscopy, Electron, Scanning/methods , Models, Theoretical , Nickel , Orthodontic Wires , Orthodontics , Potentiometry/methods , Stress, Mechanical , Tensile Strength , TitaniumABSTRACT
OBJECTIVE: This study investigated a new technique for the bilateral sagittal split osteotomy (BSSO) by adding a new osteotomy line at the inferior border of the mandible in the Obwegeser-Dal Pont operation. MATERIAL AND METHODS: For this purpose a test system was designed and 100 pig mandibles were split to assess the test's reliability, to compare the torque necessary to split the mandible in both techniques and to record the fracture lines. The splitting technique was standardized, avoiding any contact with the inferior alveolar nerve. All outcomes were statistically examined by paired t-tests. RESULTS: By using the new technique, we demonstrated a decrease in the torque force required to split the mandible of 29.7% (t(69)=-12.68; p<0.05, paired t-test) compared to the Obwegeser-Dal Pont technique. The fracture lines were close to ideal. CONCLUSION: The additional osteotomy facilitates the BSSO technique and it reduces the likelihood of bad splits and damage to the inferior alveolar nerve in pig mandibles.
