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Biomedical subjects

R W Phillips

Publications and source records attributed to R W Phillips.

At least 19 recordsLinked to original sources
PubMed1992

Proliferation of jejunal mucosal cells in rats flown in space.

To examine the effects of spaceflight on the proliferation and turnover of jejunal mucosal cells, we compared the percentages of mitotic cells present in the crypts of Lieberkühn in the proximal, middle, and distal jejunum in each of five rats flown on the COSMOS 2044 mission and in rats included in the vivarium, synchronous, and caudal-elevated groups. On the basis of the data obtained, there was no difference in mitotic indexes between animals in the flight and vivarium (ground control) groups. Thus it appears that the ability of jejunal mucosal cells to proliferate is not affected by microgravity conditions associated with spaceflight. Although the length of villi and depth of crypts were reduced in flight animals compared with those in the vivarium group, the observed reduction is probably attributable to changes in the connective tissue core of villi and is not likely due to an impairment of the proliferation and migration of jejunal mucosal cells.

Animals↗
PubMed1991

Report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry.

Subjects of the past decade in the dental literature are reflected in this year's Committee report. We note the decrease in the prevalence of caries, the influence of dental implants, the advancements in dental materials, and the continued efforts to control adhesive events in the oral cavity. This year we included comments from and about many significant review articles published this past year. The Committee continues to be concerned about the quality of some of the work reported and the quality of the reporting. We have attempted to select the distinguished work, that which provides new information to our profession. The subjects covered include pulp biology, caries prevention, periodontics, implants, craniomandibular function and dysfunction, occlusion, and dental materials.

Dental Bonding↗
PubMed1991

Barrett's esophagus. Natural history, incidence, etiology, and complications.

This article reviews the natural history of Barrett's esophagus. The pathology and etiopathogenesis are considered in detail, as are the symptoms and complications of this condition. The indication and efficacy of medical and surgical therapy are reviewed, and the question "Does regression of Barrett's metaplasia occur?" is posed.

Barrett Esophagus↗
PubMed1990

Report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry.

The growth in the dental literature continues to escalate, as evidenced by the publication of at least 326 new books in 1988 and 1989 and more than 20 new journals in 1989. There still appears to be undue emphasis on quantity instead of quality of research. This proliferation in the literature poses ever increasing difficulties to this Committee in filtering out the articles that are of particular interest to the members of the Academy and identifying those that are most likely to have a major impact on dental practice and service. The subjects covered include periodontics, caries and preventive dentistry, craniomandibular disorders, occlusion, pulp biology, ceramics, and restorative dental materials.

Dental Caries↗
PubMed1990

Effects of spaceflight on the proliferation of jejunal mucosal cells.

The mitotic indices, villus heights, and crypt depths were determined in each of three jejunal regions (proximal, middle, and distal) for five animals each in the flight, vivarium, and synchronous groups. Because of the rapid turnover of intestinal mucosal cells and the delay in recovering the flight animals, it is not known whether the proliferation of jejunal mucosal cells is affected by microgravity conditions associated with spaceflight. However, since there were no consistent differences between animals in the flight group and those in the synchronous and vivarium control groups, it appears that any effects of microgravity on the turnover of jejunal mucosal cells are short-lived. Thus, this study represents an initial step in determining the effects of microgravity on the proliferation and turnover of intestinal mucosal cells.

Animals↗
PubMed1989

In vitro degradation of cements: a comparison of three test methods.

Three in vitro tests were evaluated on the basis of their ability to predict the relative resistance of various types of luting cements to disintegration in the oral cavity. The tests were (1) weight loss, (2) reduction in size of cement films held between glass optical flats, and (3) reduction in transverse strength. Storage media evaluated were H2O and 0.1, 0.01, and 0.001 M HAc. These data were compared with previously obtained measurements on the in vivo disintegration rates of the same cements. The best correlation with in vivo disintegration was obtained by test No. 2 when the specimens were subjected to 0.01 M HAc.

Dental Cements↗
PubMed1989

Report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry.

Dental research continued to grow during 1988. Unfortunately the quality does not always parallel the quantity of publications. This report obviously does not encompass all of the literature but focuses on studies that are related to trends and to matters that are considered controversial. Likewise the particular interests of the members of the American Academy of Restorative Dentistry were taken into consideration. The subjects covered include periodontics, preventive dentistry, bulp biology, craniomandibular disorders, ceramics, color in restorative dentistry, and dental materials.

Dental Materials↗
PubMed1989

Adaptation of acrylic resin dentures as influenced by the activation mode of polymerization.

With the advent of newer methods of activation of the polymerization of denture base resins, there is a need to compare dentures constructed using various modes of activation such as heat, light, and microwave energy. This study compares the dimensional accuracy of a conventional heat-activated acrylic resin poly (methyl methacrylate) with a new pour resin, a visible light-activated resin, and microwave-activated acrylic resin, all polymerized for denture bases. All groups showed a processing contraction; the poorest-fitting group was processed in a brass flask and a water bath at 70-100 C, using a heat-activated resin (Acron); the relatively new light-activated resin (Triad) produced dentures of intermediate accuracy, as did Acupac 20, when either heat- or microwave-activated. The two best-fitting groups were prepared from an autopolymerizing resin (PERform) and the microwave-activated resin (Acron MC).

Chemical Phenomena↗
PubMed1989

Changing trends of dental restorative materials.

Esthetic dentistry evolved through advancements in dental materials and techniques. This article cites these trends, particularly the adhesive systems such as dentin bonding agents and polyacrylic acid based materials. In particular, the expanding role of glass ionomer cements is explored with attention to the various formulations and manipulative factors that influence performance. Also, a classification system for composite resins is offered with suggestions for proper selection.

Acrylic Resins↗