Prostaglandin mediated modulation of transforming growth factor-beta metabolism in primary mouse osteoblastic cells in vitro.

Prostaglandins and transforming growth factor-beta (TGF-beta) are both important local regulators of bone metabolism, but their actions on bone are complex. Prostaglandins mediate bone loss due to immobilization, but prostaglandin E2 (PGE2) treatment stimulates bone formation in vivo. TGF-beta may have both anabolic and catabolic effects on bone in vitro.

Mechanical stimulation by intermittent hydrostatic compression promotes bone-specific gene expression in vitro.

In a previous study of the cellular mechanism underlaying Wolff's law we showed that mechanical stimulation by intermittent hydrostatic compression (IHC) increases bone formation in cultured fetal mouse calvariae compared to non-stimulated cultures. To test whether mechanical stimuli may modulate bone-specific gene expression, we studied the effect of IHC on alkaline phosphatase (AP) expression and enzyme activity as well as collagen and actin mRNA levels in neonatal mouse calvariae and calvarial bone cells. Two cell populations, one resembling osteoprogenitor (OPR) cells and another resembling osteoblasts (OB) were obtained from calvariae by sequential digestion.

Mechanical loading stimulates the release of transforming growth factor-beta activity by cultured mouse calvariae and periosteal cells.

We have shown earlier that mechanical stimulation by intermittent hydrostatic compression (IHC) inhibits bone resorption and stimulates bone formation in cultured fetal mouse calvariae (Klein-Nulend et al., 1986, Arthritis Rheum., 29: 1002-1009).

Sensitivity of osteocytes to biomechanical stress in vitro.

It has been known for more than a century that bone tissue adapts to functional stress by changes in structure and mass. However, the mechanism by which stress is translated into cellular activities of bone formation and resorption is unknown. We studied the response of isolated osteocytes derived from embryonic chicken calvariae to intermittent hydrostatic compression as well as pulsating fluid flow, and compared their response to osteoblasts and periosteal fibroblasts.

Long-term in vivo study of plasma-sprayed coatings on titanium alloys of tetracalcium phosphate, hydroxyapatite and alpha-tricalcium phosphate.

In order to study the interaction of calcium phosphate coatings with bone tissue, coated titanium plugs of standard size were implanted in dog femora. The bone bonding and bone formation of hydroxyapatite, alpha-tricalcium phosphate (alpha-TCP) and tetracalcium phosphate plasma-sprayed coatings were evaluated by mechanical push-out tests and histological observations after 3, 5, 15 and 28 months of implantation. During this time all coating types degraded.

Effect of mechanical stimulation on the production of soluble bone factors in cultured fetal mouse calvariae.

Mechanical stimulation by intermittent compressive force (ICF) stimulates bone formation and inhibits bone resorption in cultured fetal mouse bone. Fetal bone tissue can produce autocrine factors that stimulate bone cell replication and matrix formation, and paracrine factors that increase the formation of osteoclast precursor-like cells from bone marrow. In the present study, we have tested whether ICF affects the production of such local factors in fetal mouse calvariae.

Necrotizing sialometaplasia: report of 12 new cases.

The clinical and histopathological findings of 12 new cases of necrotizing sialometaplasia are described.

Studies of the solubility of different calcium phosphate ceramic particles in vitro.

In vitro solubility tests of hydroxyapatite, tetracalcium phosphate or tricalcium phosphate particles were performed in lactate, citrate, Gomoris or Michaelis buffer with pH 6.2 or 7.2 and in aqua destillata.

Histological evaluation of biocompatible orthopaedic polymer.

The biocompatibility of biocompatible orthopaedic polymer implant materials was studied in subcutaneous and bony tissue of rats and rabbits. The tissue response was evaluated by histological techniques. No bone induction capacity of biocompatible orthopaedic polymer could be observed.

Tissue response to percutaneous implants in rabbits.

This study reports on certain aspects of wound-healing around percutaneous implants. Plasma-sprayed and dense hydroxylapatite, titanium, and carbon test implants were inserted into the tibia and the cranium of 12 rabbits. Four and 8 months after insertion, the animals were sacrificed and the implants with their surrounding tissues were processed histologically.

Intraoral adenoid cystic carcinoma: the role of postoperative radiotherapy in local control.

Fourteen cases of adenoid cystic carcinoma (ACC) of the intraoral salivary glands with positive surgical margins have been reviewed in order to determine the role of postoperative radiotherapy in local control. Since local control was obtained in all patients, postoperative radiotherapy seems an adequate treatment to deal with the problem of positive surgical margins at the microscopic level, in cases of intraoral ACC, making additional surgical treatment redundant.

Morphometric study of pseudoepitheliomatous hyperplasia in granular cell tumors of the tongue.

Several reports have mentioned the possibility of misdiagnosing pseudoepitheliomatous hyperplasia (PEH) of the overlying mucosa of a granular cell tumor as a squamous cell carcinoma (SCC). Because of this, morphometry was applied to five granular cell tumors with PEH and five well-differentiated SCC of the tongue. In addition, ten normal tongues have been examined.

Epithelial reaction to percutaneous implant materials: in vitro and in vivo experiments.

The major fact in determining percutaneous implant success is the formation of a stable skin-implant junction. However, the characteristics an implant material must meet to secure a durable percutaneous seal are still unknown. The objective of this study, therefore, is to gain more insight into the mechanisms underlying implant-skin reactions by means of in vitro cell culture and in vivo animal experiments.

Dental patients asking for a second opinion: what oral problems do they have?

The oral and dental problems of a group of 235 patients, who asked for a second opinion consultation, were surveyed. More than 80% of the group were regular dental attenders (once or more times a year); 70 patients were advised by their own dentist to visit the "second opinion" dentist. The oral problems were classified in eight categories.