Ralph V. McKinney

An Evaluation of Porous Alumina Ceramic Dental Implants

The fabrication, characterization, and clinical results of porous rooted alumina dental implants in animals are presented. Failures of all implants occurred in less than six months and were attributed to the presence of microporosity on the crown and cervical portion of the implant which prevented the establishment of an effective bialogical seal between the oral cavity and the alveolus.

Basement membrane changes under neoplastic oral mucous membrane. Ultrastructural observations, review of the literature, and a unifying concept.

This study explores the morphologic nature of the basement membrane under neoplastic oral mucous membrane. Of particular interest is the progression of changes associated with dysplasia, carcinoma in situ, and invasive carcinoma. On the basis of a critical review of the literature and our own ultrastructural observations, we present a unifying concept for the development of these basement membrane changes. This concept proposes that neoplastic epithelial cells may produce a collagenolytic enzyme which is released into the epithelial intercellular spaces. This enzyme permeates to the basement membrane, causes breaks in the basement membrane, and focal loss of stromal area contiguous with intercellular spaces. The neoplastic basal cells develop pseudopodia that eventually extend through the breaks in the basement membrane. This concept suggests that the basement membrane changes herald the progression of carcinoma in situ to invasive carcinoma.

Simultaneous Histological Preparation of Bone, Soft Tissue and Implanted Biomaterials for Light Microscopic Observations

Block specimens of formalin fixed bone, soft tissue and endosseous implanted biomaterials can be successfully embedded in polymethyl methacrylate by employing vacuum desiccation during the dehydration steps and refrigeration during the infiltration step. One-hundred-micrometer histological sections can be obtained from the cured polymethyl methacrylate blocks by cutting with a low concentration diamond wafering blade on a Buehler Isomet Circular Low Speed Saw using Buehler Isocut fluid. The sections can be readily stained and details of individual cells studied by light microscopy, thus allowing interpretation of the relationship between biomaterial and surrounding tissues. The advantage of this method is that it allows observations of the entire specimen in situ. The details of the procedure are presented.

The biologic response to the single-crystal sapphire endosteal dental implant: Scanning electron microscopic observations

T he use of endosteal dental implants has increased exponentially over the past decade as clinicians have applied new designs and different types of biomaterials. All materials used for endosteal implants have one region in common: the interface of the biomaterial with the oral mucous membrane as it passes through the soft tissues from bony crypt to the oral cavity. This soft tissue interface is analogous to the natural tooth dentogingival junction and is critical in the longevity of the implant. The purpose of this article is to present observations using scanning electron microscopy (SEM) on the soft tissue-biomaterial interface. For clarification of terminology, this region will be called the “biologic” or “per-perimucosal” seal.

Clinical, Radiographical, and Histological Evaluation of Porous Rooted Polymethylmethacrylate Dental Implants

Forty-three porous rooted polymethylmethacrylate (PMMA) dental implants were inserted into twenty-four dogs. Successful implants were maintained for up to three years. Histological sections with the implants in situ of implants revealed a soft tissue-implant interface similar to natural teeth. Bone and fibrous tissue ingrowth into the pores attached the implant to the bone. Failures were attrabuted to mechanical weakness of the implant, thin buccal cortical bone, and excessive implant-gingiva interface.

A Statistical Analysis of the Clinical Response to the Single-crystal Sapphire Endosseous Dental Implant in Dog Jaws

A statistical analysis was carried out an the clinical evaluatory data gathered from a two-year longitudinal study of the single-crystal sapphire endosteal dental implant in dog jaws. Statistically, the implants behaved either better than control molars (clinically), or in a manner similar to control molars. These data suggest an excellent prognosis for the single-crystal sapphire dental implant.

Maintenance of Long Junctional Epithelium in the Rat

The dynamics of the long junctional epithelium in rat gingivae were observed over a period of from three to six mo. In addition, the cellular dynamics of the epithelium were also evaluated at the end of three and six mo. The results of this study indicated that this model system cannot be used to study the long-term dynamics of long junctional epithelia. This study also indicated that the epithelial cuff increased in length with time, that it is a self-renewing tissue, and that long junctional epithelia may reduce in length with time due to sulcus deepening which was not related to subepithelial inflammation.

Scanning Electron Microscopy of Plasma Etched Implant Specimens

Following surface etching of previously processed plastic embedded specimens containing hard and soft tissues and implanted biomaterials with oxygen plasma, the fine structure of the tissues can be examined by scanning electron microscopy. One micrometer plastic orientation sections (with the implant removed in processing) and 110 microns histological sections (with the implant in situ) were examined. Direct comparison can be made between the scanning and histological observations. An examination in situ of oral tissues next to the biomaterial was also made, care being taken to minimize damage to the specimen. The fine structure of intracellular organelles was examined in detail. The method allows consecutive gathering of histological and ultrastructural data from the same plastic embedded specimen.

Effect of β-aminopropionitrile on lipid metabolism by bone cell cultures: Biochemistry and morphology

Abstract The effects of β-aminopropionitrile (BAPN) on [14C]acetate monitored by bone cells derived from newborn rat calvaria were examined by biochemical techniques and light and electron microscopic procedures. The effects of BAPN depends upon both concentration and time of exposure to the lathyrogen. BAPN tends to stimulate the incorporation of [14C]acetate into most lipids at lathyrogen concentrations up to 40 mM. At 100 mM the incorporation is significantly reduced. Prolonging the time of exposure generally enhances lipid synthesis. The major exception is the reduced synthesis of cholesterol esters. At BAPN concentrations higher than 5 mM, vesicles, which appear to be dilated endoplasmic reticulum, are formed in the cell cytoplasm. Further, the BAPN treated cells do not appear to adhere to each other in the same manner as untreated cells suggesting changes in the cell glycocalyx. This study demonstrates BAPN induced alterations in lipogenesis in cells which have the potential to calcify. These alterations suggest an increase in cell membrane area giving rise to the vesicles and dilated endoplasmic reticulum.

Effect of freezing and low temperature on in vitro bone lipid synthesis

Abstract 1. 1. Frozen-thawed bones failed to utilize acetate-C14, glycerol-C14, or inositol-H3 to any significant degree for lipid synthesis and incorporation of these substances by viable bones at 4 C was also minimal when compared to control bones. 2. 2. Choline-C14 and phosphate-P32 incorporation into lipids of experimental bones was 3. 3. Ethanolamine-C14 and serine-C14 utilization was significantly higher in frozen-thawed bones whereas incorporation of these two substrates at 4°C was diminished when compared to that at 37 C. 4. 4. The results support the importance of base exchange for incorporation of ethanolamine and serine into phospholipids and minimize the role of base exchange for choline or inositol incorporation.