Graduate Medical Education Initiatives to Develop the Physician Workforce in Rural Wisconsin.

The physician shortage is an increasing concern across the nation. Wisconsin is seeing this shortage grow even more prominently in rural counties. In order to prepare a sufficient rural physician workforce, several state-funded programs are collaborating to monitor the number of rural graduate medical education (GME) opportunities available, assess the number of rural physicians needed to meaningfully reduce the shortage, and promote effective development and expansion of new and existing opportunities.

Fracture origins in twenty-two dental alumina crowns.

Objectives: The causes of in vivo fractures of all-ceramic dental crowns are not yet fully understood. The fracture origins often occur in the cervical margin in the approximal area, but the reason for this is unclear. The aim of this study was to evaluate the fracture origin of 22 of clinically-failed alumina crowns.

Strength and fracture origins of a feldspathic porcelain.

Objectives: To identify the strength limiting flaws in in vitro test specimens of a fine-grained feldspathic dental porcelain.

Methods: Four-point flexural strengths were measured for 26 test specimens. The fracture origin site of every test specimen was studied using stereoptical and scanning electron microscopy.

Fracture Toughness of Veneering Ceramics for Fused to Metal (PFM) and Zirconia Dental Restorative Materials.

Veneering ceramics designed to be used with modern zirconia framework restorations have been reported to fracture occasionally in vivo. The fracture toughness of such veneering ceramics was measured and compared to that of conventional feldspathic porcelain veneering ceramics for metal framework restorations. The fracture toughness of the leucite free veneer was measured to be 0.

Improving performance of dental resins by adding titanium dioxide nanoparticles.

Objective: The objective of this study is to improve the performance of dental resins by adding a small amount of titanium dioxide nanoparticles (TiO₂ NPs), which have outstanding mechanical properties and unique photoactivities.

Methods: Acrylic acid modified TiO₂ NPs (AP25) were prepared and added to a mixture of bis-phenol-A-dimethacrylate and triethylene glycol dimethacrylate (mass ratio 1:1) at seven mass fractions. Disks made of these resins were subjected to FTIR microspectroscopy, nanoindentation, microindentation, and 3-point bending to determine the degree of vinyl conversion (DC) modulus and hardness.

Effect of Calcium Hydroxide on the Fracture Resistance of Dentin.

An increased incidence of fracture has been reported in teeth where root canals were treated with calcium hydroxide. Edge chipping is one test used to measure the resistance of brittle materials to fracture. Presently, no studies have reported on edge chipping in teeth.

Fractographic analysis of a dental zirconia framework: a case study on design issues.

Fractographic analysis of clinically failed dental ceramics can provide insights as to the failure origin and related mechanisms. One anterior 6-unit all-ceramic zirconia fixed partial denture (FPD) (Cercon) has been clinically recovered and examined using qualitative fractography. The purpose was to identify the fracture origin and to state the reasons for failure.

Material properties and fractography of an indirect dental resin composite.

Objectives: Determination of material and fractographic properties of a dental indirect resin composite material.

Methods: A resin composite (Paradigm, 3M-ESPE, MN) was characterized by strength, static elastic modulus, Knoop hardness, fracture toughness and edge toughness. Fractographic analyses of the broken bar surfaces was accomplished with a combination of optical and SEM techniques, and included determination of the type and size of the failure origins, and fracture mirror and branching constants.

A practical and systematic review of Weibull statistics for reporting strengths of dental materials.

Objectives: To review the history, theory and current applications of Weibull analyses sufficient to make informed decisions regarding practical use of the analysis in dental material strength testing.

Data: References are made to examples in the engineering and dental literature, but this paper also includes illustrative analyses of Weibull plots, fractographic interpretations, and Weibull distribution parameters obtained for a dense alumina, two feldspathic porcelains, and a zirconia.

Sources: Informational sources include Weibull's original articles, later articles specific to applications and theoretical foundations of Weibull analysis, texts on statistics and fracture mechanics and the international standards literature.

Comparison of edge chipping resistance of PFM and veneered zirconia specimens.

Objectives: To investigate the chipping resistance of veneered zirconia specimens and compare it to the chipping resistance of porcelain fused to metal (PFM) specimens.

Methods: Veneered zirconia and PFM bar specimens were prepared in clinically relevant thicknesses. The specimen edges were chipped with different magnitude forces, producing chips of various sizes.

Fractographic failure analysis of a Procera AllCeram crown using stereo and scanning electron microscopy.

Objectives: Presentation of a methodological approach using stereo and scanning electron microscope examination for the failure analysis of an alumina all-ceramic premolar crown (Procera AllCeram).

Methods: The recovered part of a fractured Procera alumina crown was examined utilizing first a stereomicroscope and second a scanning electron microscope (SEM). The stereomicroscope analysis was performed at low magnifications with oblique lighting in order to enhance spatial relationships and gross detection of crack features.

Fractographic ceramic failure analysis using the replica technique.

Objectives: To demonstrate the effectiveness of in vivo replicas of fractured ceramic surfaces for descriptive fractography as applied to the analysis of clinical failures.

Methods: The fracture surface topography of partially failed veneering ceramic of a Procera Alumina molar and an In-Ceram Zirconia premolar were examined utilizing gold-coated epoxy poured replicas viewed using scanning electron microscopy. The replicas were inspected for fractographic features such as hackle, wake hackle, twist hackle, compression curl and arrest lines for determination of the direction of crack propagation and location of the origin.

Failure analysis of ceramic clinical cases using qualitative fractography.

Purpose: To educate dental academic staff and clinicians on the application of descriptive (qualitative) fractography for analyses of clinical and laboratory failures of brittle materials such as glass and ceramic.

Materials And Methods: The fracture surface topography of failed glass, glass fiber-reinforced composite, and ceramic restorations (Procera, Cerestore, In-Ceram, porcelain-fused-to-metal) was examined utilizing a scanning electron microscope. Replicas and original failed parts were scrutinized for classic fractographic features such as hackle, wake hackle, twist hackle, arrest lines, and mirrors.

Fractographic analyses of three ceramic whole crown restoration failures.

Objectives: Develop fractographic techniques to perform failure analyses of three ceramic whole-crown clinical failures.

Methods: Three clinical whole-crown failures of different ceramic material systems were studied. The systems included appropriate veneers applied to core materials of cold isostatically pressed alumina, injection molded alumina/alumina-magnesia spinel, and hot pressed lithium disilicate.

Effect of Loading Rate Upon Conventional Ceramic Microindentation Hardness.

The world standards for conventional ceramic hardness have varying requirements for control of loading rate during the indentation cycle. A literature review suggests that loading rate may affect measured hardness in some instances. In view of the uncertainty over this issue, new experiments over a range of indentation loading rates were performed on a steel, sintered silicon carbide, and an aluminum oxynitride.

Fracture Toughness of Advanced Ceramics at Room Temperature.

This report presents the results obtained by the five U.S. participating laboratories in the Versailles Advanced Materials and Standards (VAMAS) round-robin for fracture toughness of advanced ceramics.