Microstructural characteristics of human skin subjected to static versus cyclic pressures.

Pressure ulcers are generally associated with external pressures exceeding internal capillary pressures over bony prominences when the body cannot initiate motor movement to change positions. This investigation evaluated microstructural changes occurring in human skin, in vitro, exposed to static versus cyclic pressures, simulating those recorded for heels of human subjects on various pressure-relief mattresses. Morphological data are reported for tissues exposed to pressure in a bench-scale loading system. Dynamic (cyclic-relief) pressure induced parallel alignments of connective tissue collagen bundles, which themselves became differentially oriented to various degrees perpendicular to the surface of the tissue. Static pressure, with no relief, invariably produced alignment of the collagen bundles of the connective tissue parallel to both one another and to the compressed tissue surface. The precursor to pressure ulcer formation may be microstructural alignment in response to the pressure conditions on tissue.

Microstructural and mechanical characterization of human tissue at and adjacent to pressure ulcers.

This investigation evaluated the microstructural and mechanical properties of human skin at and adjacent to pressure ulcers (PUs). Healthy breast and leg tissue served as control tissue. The tissue was characterized through uniaxial tensile testing and histomorphometric analysis. The PU tissue had significantly fewer straight and wavy fibers, but the fibers present were significantly wider and longer than those found in the healthy control tissue. PU ulcer tissue tested in tension had significantly lower strains at peak stress, versus the control breast tissue. Tissue at and adjacent to PUs has undergone significant adaptation or remodeling, as a result of the pressure sustained by the tissue.

Immediate implantation of pure titanium implants into extraction sockets of Macaca fascicularis. Part II: Histologic observations.

The purpose of this study was to evaluate immediate implants with implants placed in ossified extraction (control) sites. Histologic observation of immediate and control implants showed similar levels of bone integration at the light microscopic level using ground-section and decalcified thin-section histologic methods. Both histologic methods provided similar information in relation to determination of hard and soft tissue components measured at the interface. The percentage of bone integration was similar in different anatomic regions of the oral cavity. Bone patterns peripheral to the interface region differed, suggesting that special consideration be given to implants placed in the posterior regions of the maxilla and mandible.

Immediate implantation of a pure titanium implant into an extraction socket: report of a pilot procedure.

The conventional osseointegration protocol calls for waiting up to 12 months for ossification of an extraction socket to heal before placing an endosseous implant. In this study the possibility of placing a pure titanium implant directly into an extraction socket immediately after extraction was investigated. A pure titanium Nobelpharma 10-mm implant was placed into a central incisor extraction socket of a stump-tailed monkey and allowed to heal for a period of 6 months, followed by functional loading of the implant. The implant was osseointegrated on a clinical and histological level. This pilot study suggests that pure titanium implants have the potential to integrate when placed immediately after extraction of the teeth and warrants further investigation.

Structural studies of human saliva.

Samples of mixed saliva and of parotid and sublingual/submandibular saliva fractions from four donors were subjected to instantaneous solidification in liquid nitrogen followed by sectioning in a microtome/cryostat. The sections were stained with hematoxylin-eosin, periodic acid-Schiff, Alcian blue, Oil-red-O, or Sudan Black B and then examined at the light-microscopic level. In all the sectioned samples several previously never described features were observed, the most pronounced of which were a loose overall network structure and collections of lipoid droplets often in a loose arrangement. In the mixed saliva sample sections many of the microorganism-like structures were observed in large bunches associated with epithelial cells and densely staining saliva components. The present method was tested in a series of experiments for possible errors.

Lectin histochemistry of ameloblastomas and odontogenic keratocysts.

The cell membrane carbohydrate components of 10 simple (follicular and/or plexiform pattern) and 5 acanthomatous ameloblastomas, one plexiform unicystic ameloblastoma, one soft tissue ameloblastoma and 11 odontogenic keratocysts were studied in paraffin-embedded tissues using horseradish peroxidase-conjugated lectins. The presence of glucose and mannose was demonstrated by intense labelling with Concanavalin ensiforme (Con A) in 73% of the ameloblastomas examined, while periodate oxidation of the specimens prior to Con A (PA/Con A) stained 53% of the cases. Ameloblastomas did not express receptors for Triticum vulgaris (WGA), Erythrina chrystagalli (ECA), Arachis hypogea (PNA), and Ulex europaeus (UEA-1). The plexiform unicystic ameloblastoma and the soft tissue ameloblastoma examined showed the same cell membrane glycoproteins as the simple and acanthomatous ameloblastomas. Forty-five per cent of the keratocysts demonstrated Con A reactivity from the basal to the keratinized layer, while 72% of these specimens showed positive PA/Con A reactivity from the parabasal to the keratinized layer. Staining with WGA, ECA, PNA, and UEA lectins also revealed the presence of N-Acetyl-glucosamine and fucose oligosaccharides in the plasma membrane of basal, spinous and keratinized cell layers of the odontogenic keratocysts. The distinct cell surface carbohydrate composition of the ameloblastoma and odontogenic keratocyst may be responsible for the differences in biological behavior in these conditions.

The use of animal models in research on dental implants.

The use of animal models in the study of dental implants has contributed greatly to our present understanding of the many different devices in use today. Animal testing plays a major role in assessing the safety and efficacy of dental implants. Standardized tests for determination of the toxicity and general biocompatibility responses of dental implants have been developed by the American Dental Association, the American National Standards Institute, and the Fédération Dentaire Internationale. To date, animal testing has shown the nature of soft tissue attachment to implants and the types of interfacial tissues within bone sites. There have been increased studies correlating animal tests with in vitro analysis and human studies. Additional development of testing remains to be accomplished to show the effects of function on host tissue and the long-term safety of dental implants.

Quantitative analysis of early in vivo tissue response to synthetic apatite implants.

Studies have shown synthetic calcium phosphates such as hydroxyapatite and beta tricalcium phosphate to be biocompatible in vivo. However, few studies have quantitated histological responses to the implants. The aim of this study was to develop a method for the quantitative assessment of tissue biocompatibility to ceramic materials in vivo and to use this method to compare noncarbonated and carbonated apatite implants. Synthetic sintered apatites of 0, 3, and 6% carbonate by weight were prepared and cut into implants 4 X 4 X 1 mm. These were placed 2 mm into the medial aspect of rat femurs. Following sacrifice at 4 weeks, the femurs were fixed in formalin, demineralized in formic acid, and embedded in glycol methacrylate. Sections were cut on an ultramicrotome set at 1.5 micron and stained with toluidine blue. A point counting technique using standard stereological grids and a low-power microscope was used to measure areas of new bone formation. The width of the connective tissue zone adjacent to muscle was measured using an image analyzer. All implants were well accepted by the host tissues judging from criteria of minimal inflammation and degree of fixation. Results showed an increase in new bone formed in the marrow cavity with increasing carbonate content. This may improve stability of the implant in the host bone, particularly during the initial healing period. A technique which should enable quantitative histological evaluation of different ceramic materials has been developed. The use of this method indicates that further studies are warranted to investigate carbonated apatite as an implant material.

Investigation of tissue/implant interactions during the first two hours of implantation.

The objective of this study was to determine whether detectable differences exist in the initial process of tissue incorporation of implant materials of different original surface energies. Our earlier work focused on materials implanted for days to months; the experiments reported here addressed the initial 2 hours of implantation. Surface-treated metal implants were placed in the fascial plane in the back of New Zealand white rabbits for 5 minutes to 2 hours. Prior to implantation, the metal plates were characterized by infrared spectroscopy, ellipsometry, and contact potential methods; the same analytical techniques, as well as scanning electron microscopy and contact angle measurements were applied to the explanted samples. No significant cellular adhesion was observed within the first 2 hours of implantation. Films rich in lipids and proteins were detected on the implants, however, within 5 minutes. There is good evidence for specific film differentiation as a function of differing initial substratum surface energies.

Quantitative bone remodelling resulting from the use of porous dental implants.

Histomorphometric analyses were used to quantitatively determine the patterns of bony ingrowth which resulted from the placement of porous-surfaced dental implants into the mandibles of Rhesus monkeys for up to 74 months utilizing a two-stage approach. Quantitative histopathologic evaluations were made using ground section microscopy. Implant stability resulting from bone remodelling and ingrowth occurred to varying degrees with all implants. Bone ingrowth occurred from medullary trabeculae and contact with the adjacent cortical plates. Quantitative histomorphometric analyses revealed that in only one case was the bone ingrowth into the available internal pores less than 45%. Minimal fibrous connective tissue ingrowth was observed in the implant crypts and was not thought to be due to micro-motion. The observed bone remodelling indicated a favorable prognosis for long-term implant performance.

The use of elemental microanalysis in verification of the composition of presumptive amalgam tattoo.

Routine histochemistry, special stains, and energy dispersive x-ray microanalysis (EDX) were used to analyze 15 cases of presumptive amalgam tattoo. Histologically, the fine, spherical, golden brown granules of amalgam were remarkably similar to hemosiderin and melanin granules, and routine and special stains were not always reliable in differentiating one from the others. EDX provided a simple, fast, inexpensive, and reliable method for identifying the precise elemental composition of the pigmented material.

Artifacts in oral biopsy specimens.

More than proper surgical technique is required to facilitate the proper diagnosis of an oral biopsy specimen. The proper preparation of the tissue for microscopic analysis depends on steps taken by the surgeon, assistant, and histotechnician to reduce the inclusion of artifacts. There are many ways that the exact interpretation of tissue specimens can be compromised. Unfortunately, many practitioners seem to be unaware of the extent of this problem, as well as how easily artifacts can be prevented.

Diagnosis and reconstruction of the human temporomandibular joint after trauma or internal derangement.

This study reviewed the standardized records of 1100 patients with the symptoms of temporomandibular joint syndrome. Of these patients, only 4.5 percent required surgical intervention. The remaining patients were found to have masticatory muscle spasm and were treated by conservative dental methods. Over half the surgical patients had significant macrotrauma to the jaws in their past history. In addition, electromyographic measurement of the masseteric silent period duration in these patients did not reveal muscle spasm. These factors further serve to differentiate the surgical patient from the patient with myofascial pain dysfunction. The patients selected for surgery demonstrated moderate to severe joint disease and required arthroplasty with partial meniscectomy. A surgical technique is presented demonstrating the reconstruction of the meniscus with silicone implant. This same surgical technique is studied in 10 monkeys, and their joints are examined histologically. The results of surgery reveal that 87 percent of the patients reported improvement 1 year after surgery. In all patients complaining of temporomandibular joint clicking or crepitus, surgery produced complete alleviation of these symptoms. The results of surgery were also associated with a 62 percent increase of jaw opening. Histologic evaluation of the human meniscal resections revealed that in addition to an anatomic displacement of the meniscus, there are also significant cellular changes. These changes consisted of calcification, a decrease in cellularity, hyperemia, and a decrease in elastin content.

Primates as a teaching model for biopsy.

It is our intention to poll former participants in this elective to determine their experience in biopsy of oral tissues in practice. To date, student critiques of this elective course have been positive; participants have strongly suggested that we continue this method of instruction. The use of animals can be justified by the fact that experience gained in this course is applicable to the serious problem of early detection of oral cancer. Curricula that include biopsy procedures will produce dentists who will be comfortable using this important diagnostic method in their practices. Studies indicate that more general dentists are utilizing biopsy. It is important that this trend be encouraged, and the use of the nonhuman primate in a course such as that described above is a positive step in this direction.

Surface properties determine bioadhesive outcomes: methods and results.

This investigation developed experimental evidence for the influence of different surface energy states on tissue incorporation of biomedical materials. Implants of two smooth metals, each with three different surface energy states, were placed in the subdermal fascial plane of the backs of New Zealand White rabbits and were allowed healing times of 10 and 20 days. The implant surfaces were thoroughly characterized by physical-chemical criteria prior to surgical placement and again following removal from the tissue capsules generated by the host animals. Quantitative histopathologic analysis, using standard morphometric criteria, of the adjacent tissues revealed up to a threefold increase of fibroblastic-fibrocytic cells against the initially scrupulously cleaned, high-surface-energy materials. The cells were flattened and active, producing tenacious bonds through a thin pre-adsorbed protein-dominated "conditioning" film, that could be broken only by cohesive failure in the tissue itself. In contrast, the lower-surface-energy materials typical of standard dental implants were "walled off" by a cell-poor, nonadhesive capsule with a fibrous interface separated from a thicker "conditioning" film by a lipid-rich mucus zone. The advantages of proper surface treatment to favor the desired degree of biological adhesion are apparent.

Fibroblastic activities post implantation of cobalt chromium alloy and pure germanium in rabbits.

Different preimplantation surface finishes were applied to surgical vitallium discs and germanium prisms implanted for 20 days within the back muscles of adult rabbits. Histopathologic analysis of the numbers of nuclei of active fibroblasts immediately adjacent to the implants was carried out. The mean apparent volume fractions (MAVF) for the subdermal implant sites were found to depend on the surface cleanliness of the implant, the cleanest or highest-surface-energy surfaces giving the highest MAVF values for active fibroblasts.

The hematopoietic defect of the jaws: a report of sixteen cases.

Biopsy of radiolucent lesions of the jaws has resulted in the identification of areas of hematopoiesis usually designated as focal osteoporotic marrow defects. The majority of the cases reported involve the posterior region of the mandible in a previous extraction site. Pain and swelling are not uncommon. Since the clinical and radiographic symptoms of hematopoietic defects resemble manifestations of other neoplastic and inflammatory diseases, it is important to continue to describe the properties of this interesting entity.