Dietary variation and mechanical properties of articular cartilage in the temporomandibular joint: implications for the role of plasticity in mechanobiology and pathobiology.

Due to their nature as tissue composites, skeletal joints pose an additional challenge in terms of evaluating the functional significance of morphological variation in their bony and cartilaginous components in response to altered loading conditions. Arguably, this complexity requires more direct means of investigating joint plasticity and performance than typically employed to analyze macro- and micro-anatomical phenomena. To address a significant gap in our understanding of the plasticity of the mammalian temporomandibular joint (TMJ), we investigated the histology and mechanical properties of condylar articular cartilage in rabbits subjected to long-term variation in diet-induced masticatory stresses, specifically cyclical loading.

Hydroxyapatite reinforced collagen scaffolds with improved architecture and mechanical properties.

Hydroxyapatite (HA) reinforced collagen scaffolds have shown promise for synthetic bone graft substitutes and tissue engineering scaffolds. Freeze-dried HA-collagen scaffolds are readily fabricated and have exhibited osteogenicity in vivo, but are limited by an inherent scaffold architecture that results in a relatively small pore size and weak mechanical properties. In order to overcome these limitations, HA-collagen scaffolds were prepared by compression molding HA reinforcements and paraffin microspheres within a suspension of concentrated collagen fibrils (∼ 180 mg/mL), cross-linking the collagen matrix, and leaching the paraffin porogen.

Effects of hydroxyapatite reinforcement on the architecture and mechanical properties of freeze-dried collagen scaffolds.

Freeze-dried collagen scaffolds reinforced with hydroxyapatite (HA) are of clinical interest for synthetic bone graft substitutes and tissue engineering scaffolds, but a systematic evaluation of the effects of the HA reinforcement weight fraction and morphology on the mechanical properties is lacking. Therefore, freeze-dried collagen scaffolds were reinforced with either HA whiskers or an equiaxed HA powder at 1:1, 1:2, or 1:4 collagen:HA by weight (which corresponded to approximately 28, 44, and 61 vol% HA, respectively) to investigate the effects of the HA reinforcement weight fraction and morphology on the architecture and compressive mechanical properties. All scaffolds exhibited a highly elongated linear pore structure containing 90%-96% porosity, which decreased with increased HA content, and a pore width of ∼50 μm.

The ecology of unhealthy places: violence, birthweight, and the importance of territoriality in structurally disadvantaged communities.

The present study tested the relationships between macro-level violence and birthweight in structurally disadvantaged communities in the District of Columbia. The study hypothesized that both rates of violence and violence "uncertainty" (the latter was operationalized as within-census tract residual change scores in violence), should be inversely associated with birthweight among all live singleton births in DC from 2000 to 2002. Using mixed models, the study found that (1) patterns of violence and violence uncertainty were significantly associated with birthweight among mothers residing in structurally disadvantaged communities, and (2) these findings held for Black and Hispanic, but not white, mothers.

Improved fatigue life of acrylic bone cements reinforced with zirconia fibers.

Poly(methyl methacrylate) (PMMA) bone cements have a long and successful history of use for implant fixation, but suffer from a relatively low fracture and fatigue resistance which can result in failure of the cement and the implant. Fiber or particulate reinforcement has been used to improve mechanical properties, but typically at the expense of the pre-cured cement viscosity, which is critical for successful integration with peri-implant bone tissue. Therefore, the objective of this study was to investigate the effects of zirconia fiber reinforcement on the fatigue life of acrylic bone cements while maintaining a relatively low pre-cured cement viscosity.

Effects of the reinforcement morphology on the fatigue properties of hydroxyapatite reinforced polymers.

The objective of this study was to examine the effects of the hydroxyapatite (HA) reinforcement morphology and content on the fatigue behavior of HA reinforced high density polyethylene (HDPE). To this end, HDPE was reinforced with 20 and 40 vol% of either HA whiskers or an equiaxed HA powder, and tested in four-point bending fatigue under simulated physiological conditions. The fatigue life, mechanical property degradation and failure surfaces were compared between experimental groups.

Personality, substance of choice, and polysubstance involvement among substance dependent patients.

The authors compared the association of several personality traits, drug of choice, and polysubstance involvement in 325 individuals (44% male) receiving treatment for substance dependence on heroin, cocaine, and/or alcohol. Measures included the Structured Clinical Interview for DSM-III-R, the MacAndrew Alcoholism Scale (MAC), the socialization scale of the California Psychological Inventory (CPI-Soc), the novelty seeking dimension of the Temperament and Character Inventory (TCI-NS), and the conscientiousness domain of the NEO Five-Factor Inventory (NEO-C). Analyses adjusted for demographic covariates, affective and antisocial personality disorder, and substance dependence severity.

Information is the key to patient empowerment.

Mr. Kane's paper examines the role of patients to ensure that they have both the knowledge and power to direct their health care choices. The evolving health care market place is discussed to emphasize the increased importance of individual involvement in health decision making.