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This study examined the relationship between acetabular cartilage properties after hemiarthroplasty surgery and surgical variables including femoral head size and position. Nineteen sheep received unilateral hip arthroplasties and were euthanized one year post-operatively to harvest the femora and acetabula. Cartilage histology, biochemistry and material properties were determined from samples located in the superior load-bearing region. Femoral head size mismatch, leg length difference, anterior-posterior and medial lateral offset and anteversion were measured. In the acetabulum. substantial cartilage degradation occurred with widespread librillation and significant changes in the biochemical and material properties compared to the intact contralateral joint. Regression analyses on the surgical variables explained 75-80% of the changes in tissue biochemistry but did not explain the material changes. Head size mismatch and leg length difference were the most significant contributors of the five variables examined and therefore may be critical to successful outcome in hemiarthroplasty.

Summary Cartilage is a sex-hormone-sensitive tissue but the role of estrogen in the pathogenesis of osteoarthritis (OA) remains controversial. In this study, intrinsic material properties and thickness of articular cartilage of the knee joint of ovariectomized (OVX) and estrogen-treated sheep were measured. Skeletally mature ewes ( N =36, same breed, same housing, 4–5 years old) were divided into: sham treated (n=9), OVX ( N =13), OVX plus one estradiol implant (OVXE; N =10) and OVX plus two estradiol implants (OVX2E; N =4). Twelve months following sham procedure or OVX, sheep were euthanized and articular cartilage from a total of 216 points in the left femorotibial (knee) joints was tested for aggregate modulus, Poisson's ratio, permeability, thickness and shear modulus (six sites per sheep). When all of the sites in each knee were grouped together, OVX had a significant effect on articular cartilage. The sham cartilage of all sites grouped together had a larger aggregate modulus ( P =0.001) and a larger shear modulus ( P =0.054) than the OVX tissue. No statistically significant differences were seen for permeability and thickness between OVX, sham, OVXE and OVX2E. Differences existed in biomechanical properties at the different sites that were tested. Overall, no one location tended to be lowest or highest for all variables. This biomechanical study suggests that OVX may have a detrimental effect on the intrinsic material properties of the articular cartilage of the knee, even though the cartilage of the OVX animals appeared normal. Treatment with estradiol implants ameliorated these deleterious effects and may have helped maintain the tissue's structural integrity. Our study supports epidemiological studies of OA in women after menopause. The protective effect of estrogen and it's therapeutic effect remain to be further defined. This model may allow the relationship of estrogen and estrogen antagonists to be studied in greater detail, and may be valuable for the study of the pathogenesis and therapies of OA of postmenopausal women, particularly in its early stages.

This study sought to determine whether using sodium hypochlorite (NaOCl) as a pretreatment in bonding composite resins has a detrimental effect on bond strength. Previous studies have addressed pretreating dentin with NaOCl after etching; however, little research is available concerning pretreatment before etching. This study examines pretreating dentin with NaOCl prior to acid etching when fourth generation bonding systems are used. Thirty noncarious teeth were selected and sectioned horizontally at the occlusal third of the clinical crown. The teeth were divided into 3 groups (n = 10). Group 1 was the control group, with composite resin bonded to the dentin surface per manufacturer's instructions. Group 2 was pretreated with 6% NaOCl for 10 seconds; then, composite resin was bonded to the dentin as in Group 1. Group 3 was pretreated with 6% NaOCl for 20 seconds; then composite resin was bonded to the dentin as in Group 1. The specimens were stored in water for 24 hours, then thermocycled for 1000 cycles at temperatures of 5°C and 60°C. The specimens were shear tested until failure. According to the 1-way ANOVA testing (α = 0.05), using NaOCl as a pretreatment prior to etching with a specific fourth generation bonding agent does not affect bond strength.