Immunohistochemical detection of matrix metalloproteinase-1 in the periodontal ligament of equine cheek teeth.

The hypsodont equine cheek tooth erupts continuously throughout life. The collagen fibers of the periodontal ligament (PDL) have to remodel constantly to allow the tooth to move in an occlusal direction. Remodeling of the collagen fiber bundles needs to be well-coordinated in order to maintain functional tooth support. The aim of this study was to examine the role of matrix metalloproteinase-1 (MMP-1) in the collagen remodeling of the equine PDL under physiological conditions. Specimens containing the PDL interposed between the dental cementum and the alveolar bone were taken from nine Warmblood horses at three designated horizontal levels: subgingival, middle, and apical. The expression of MMP-1 was detected immunohistochemically. MMP-1 was found to be present in the specimens of all horses. Immunopositive fibroblasts/fibrocytes were accumulated within individual single collagen fascicles. Our results suggest that MMP-1 induced collagen degradation plays a central role in the physiological remodeling of the equine PDL. The distribution of MMP-1 positive fascicles indicates well-directed remodeling which occurs as an asynchronous process, so that only single collagen fascicles are remodeled at the same time. Due to this remodeling of one fascicle at a time, the overall anchorage of the tooth is preserved at all times.

Primary culture of fibroblasts and cementoblasts of the equine periodontium.

Fibroblasts and cementoblasts in the periodontal ligament (PDL) of equine cheek teeth were harvested, and monocultures were obtained by means of a "selective detachment" procedure. Cells were characterized by morphological criteria and by immunostaining for vimentin, FVIII, pan-cytokeratin, smooth muscle actin, and pro-collagen. Cementogenic potential of the cells was determined by immunostaining for osteopontin and by histochemical detection of alkaline phosphatase. Equine periodontal fibroblasts (EPF) were spindle-shaped and polygonal. Equine dental cementoblasts (EDC) grew in cobblestone-like clusters. Both EPF and EDC stained positive for vimentin. Only EPF contained smooth muscle actin, pro-collagen, and alkaline phosphatase. Few EDC stained positive for osteopontin. The phenotypes of EPF and EDC and their specific expression of proteins corresponded to PDL fibroblasts and dental cementoblasts of other species. These results indicate the potential use of EPF and EDC in an adequate in vitro model of equine cementogenesis and equine periodontal remodeling.

The course of blood vessels in the hip joint capsule of the dog.

The course and the arrangement of capsular blood vessels in the joint capsule's wall, together with their extracapsular origins, were investigated using cleared specimens that had been injected with Latex, or Technovit, or India-ink in serum. Arteries enter areas of the joint capsule's wall near its femoral as well as coxal attachment. The intramural vascular network is arranged in layers which are assigned to the stratum fibrosum and stratum synoviale, with one or two intermediate, less distinct layers in between. The ramification in the network of the stratum fibrosum is mainly stellate. Circular anastomoses connecting the supplied areas are located in the capsule's periphery. In the stratum synoviale, the vascular network is made of close, elongated meshes in a circular extension.

Oxytalan fibres in the periodontal ligament of equine molar cheek teeth.

The distribution and arrangement of oxytalan fibres were examined in periodontal specimens of cheek teeth from seven horses. Oxidation prior to aldehyde fuchsin exposition permitted a selective staining of the oxytalan fibres, which are a distinct component of the elastic fibre system. On three horizontal levels of the periodontium--(a) subgingival, (b) middle third and (c) apical--two oxytalan fibre groups were shown histologically: 'blood vessel-related' and 'independent' oxytalan fibres. In levels a and b, both groups were arranged in a typical occluso-apical alignment along the reserve crown. Single oxytalan fibres deviated from their general course in order to attach to the cementum. In these cemental entheses the oxytalan fibres ran parallel to collagen fibre bundles. The interpretation of such morphological features emphasized the oxytalan fibres' capacity to improve the stability of periodontal blood vessel walls during masticatory movements. Level c, especially in regions next to the persisting epithelial root sheath, is the site of oxytalan fibre generation. This is a prerequisite for the facilitation of periodontal regeneration and reorganization during dental growth and eruption.

[Mechanical tests with polymethylmethacrylate in fresh specimens and specimens obtained from loosened prosthesis (author's transl)]. / Mechanische Untersuchungen an explantierten und frischen Knochenzementen.

Mechanical testing of specimen from fresh acrylic cement and from lossened prostheses between one and two years after implantation shows difference in compressive strength. Air bubbles, blood particles, and folds distinctly influence mechanical properties. Therefore, care should be taken to avoid these enclosures during implantation. But it is not the aging of the acrylic cement which presents the main problem in endoprosthetic fixation, but the cement-bone interface. Clinical experience and this mechanical study show that fracture of the acrylic cement is not due to primary fatigue of the material, but occurs secondarily after loosening of the bonding between bone and cement.