A survey of failed post-retained restorations

Survival of endodontically treated, post-restored teeth depends on a multitude of factors, all of which are practically impossible to include in a randomized, controlled clinical study. The purpose of this survey was to characterize and analyze reported failures of post-retained restorations to identify factors critical to failure and to type of failure. A questionnaire was mailed to private practitioners in Denmark with a request to complete the questionnaire whenever a patient presented with a failed post-retained restoration. Information was gathered on factors related to the patient, the tooth, the restorative materials, and the techniques. Two-hundred and sixty questionnaires were collected from 171 practitioners over a 3-year period. Functioning time until failure varied between 3 months and 38 years. Mean survival time until failure was 11 years. Of the failed restorations, 61% had functioned for 10 years or less. Fracture of the tooth was the most common type of failure reported, followed by loosening of the post and fracture of the post. Tapered posts implied an increased risk of tooth fracture compared to loosening or fracture of the post, and the relative risk of tooth fracture increased with the functioning time until failure. Fracture of the post was more common among male than female patients. On the basis of this survey of failed post-retained restorations, it was concluded that tapered posts were associated with a higher risk of tooth fracture than were parallel-sided posts

Surface-sensitive X-ray diffraction across the pressure gap

In this chapter surface-sensitive X-ray diffraction is introduced as an important crystallographic tool for the investigation of surfaces and nanostructures under high pressure reaction conditions and elevated temperatures which are relevant for industrial catalysis. After the introduction surface-sensitive X-ray diffraction methods are briefly explained and specialized instrumentation developed for the in situ investigation of surfaces and nanostructures across the pressure gap is presented combined with simultaneous measurement of the concentrations of reactants and products. In the following an overview of the experimental results is given: First the (near)-ambient pressure oxidation of 3d, 4d, and 5d transition metals is discussed which are relevant for oxidation catalysis. Afterwards catalytic reaction experiments in batch mode are reported, followed by an overview of current research using a flow reactor for surface-sensitive X-ray diffraction. Finally a perspective is given for future research directions