Faculty Bibliography

A variety of microbiological diagnostic tests are available for clinicians to use for evaluation of patients with periodontal disease. Each one has its own unique set of advantages and disadvantages, and probably the most useful information for the clinician can be obtained using a combination of the various analytic methods. The tests appear to have their greatest utility when used on patients with chronic or aggressive periodontitis who do not respond favorable to conventional mechanical therapy. The major limitation of all microbiological tests is that the information obtained is relevant to the site sampled, and may not be representative of the microflora of the entire dentition. However, since it is often only specific sites that do not respond to initial therapy, knowing the constituents of the microflora that populate these sites is clinically relevant.

BACKGROUND: Our understanding of the complexity of the oral microbiota continues to improve as new technologies, such as the analysis of 16S rRNA bacterial genes, are utilized. Despite the difficult of cataloguing all microorganisms and determining their pathogenic potential, some species, mostly members of the resident oral microbiota, have been identified as likely periodontal pathogens. However, for microbial diagnosis to be of value, it needs to affect disease diagnosis and/or treatment planning as well as result in superior treatment outcomes and/or provide an economic benefit to the patient. RATIONALE: The purposes of this systematic review were to determine if microbial identification influences periodontal patient management and whether treatment outcomes are better compared to patients whose treatment plans are developed without this information. FOCUSED QUESTION: In patients with periodontal diseases, does microbial identification influence patient management compared to treatment prescribed without this information? SEARCH PROTOCOL: The MEDLINE database was searched for clinical studies in English from 1991 through 2002 by 2 investigators. Hand searches were performed on the Journal of Clinical Periodontology, Journal of Periodontology, Journal of Periodontal Research, Oral Microbiology and Immunology, and Periodontology 2000. In addition, directors of diagnostic laboratories were contacted about unpublished data. SELECTION CRITERIA: INCLUSION CRITERIA: Articles in which bacterial identification influenced patient treatment were preferred as were those reporting longitudinal data demonstrating a direct relationship between the presence or absence of certain bacteria and subsequent alterations in clinical variables. Because of the limited number of studies, all articles, including case reports, were considered. EXCLUSION CRITERIA: Review articles without original data were excluded, although references were examined for possible inclusion. Articles reporting data showing associations between certain microorganisms and disease or health that did not affect treatment were excluded. Clinical trials testing antibacterial agents for their ability to enhance mechanical debridement were not included since bacterial identification had little effect on drug selection or experimental group assignment. Articles dealing with implants rather than natural teeth were omitted. DATA ANALYSIS AND COLLECTION: The heterogeneity of the published data precludes any meaningful pooling of data or meta-analysis. The pertinent literature, including relevant variables of plaque, gingivitis, and bleeding on probing scores; probing depth; clinical attachment level; number of lost teeth; and microbial changes; and patient-centered outcomes including decrease in morbidity, reduced need for surgery, and duration and cost of treatment are summarized. MAIN RESULTS: 1. There was a lack of articles with a high evidence rating; most pertinent articles were either case reports or case series without controls. 2. Because reports were heterogeneous regarding study design, patient selection, and data collection, meta-analysis was not feasible and results are summarized in tabular format. 3. This report is based on a total of 24 studies, representing a total patient population of approximately 835. 4. Thirteen studies reported on microbiological identification as an aid in treatment planning. 5. Eleven studies reported a differential clinical response depending on the detection or lack of detection of specific organisms. REVIEWERS' CONCLUSIONS: 1. The published material suggests that microbiological monitoring may be useful in management of selected patients who do not respond to standard therapy. 2. Some practitioners consider microbial identification a valuable adjunct to managing patients with certain forms of periodontitis, although there is a lack of strong evidence to this effect. 3. Additional research is needed to address this issue.

Exposure to microgravity has been associated with several physiological changes in astronauts and cosmonauts, including an osteoporosis-like loss of bone mass. In-flight measures used to counteract this, including intensive daily exercise regimens, have been only partially successful in reducing the bone loss and in the process have consumed valuable work time. If this bone loss is to be minimized or, preferably, prevented, more effective treatment strategies are required. This, however, requires a greater understanding of the mechanisms through which bone metabolism is affected by microgravity. Various research strategies have been used to examine this problem, including in vitro studies using bone cells and in vivo studies on humans and rats. These have been conducted both in flight and on the ground, by strategies that produce weightlessness to mimic the effects of microgravity. Overall, the majority of the studies have found that marked decreases in gravitation loading result in the loss of bone mass. The processes of bone formation and bone resorption become uncoupled, with an initial transitory increase in resorption accompanied by a prolonged decrease in formation. Loss of bone mass is not uniform throughout the skeleton, but varies at different sites depending on the type of bone and on the mechanical load received. It appears that the skeletal response is a physiologic adaptation to the space environment which, after long space flights or repeated shorter ones, could eventually lead to significant reductions in the ability of the skeletal tissues to withstand the forces of gravity and increased susceptibility to fracture.

This study was undertaken to determine the direct effects of extracts derived from Porphyromonas gingivalis on bone formation and mineral resorption in an osteogenic/osteoclastic cell in vitro co-culture model. Osteogenic bone marrow derived stromal cells were isolated from 18-day old embryonic chickens, while osteoclastic cells were isolated from laying white Leghorn hens on calcium deficient diets. Osteoclastic cells (5 x 10(5)) were seeded onto mineral thin films and suspended above osteogenic cells (1 x 10(4)) already plated on the bottoms of tissue culture plate wells. Sonicated P. gingivalis 2561 extracts were prepared from whole bacterial cells and added in varying proportions (0 to 2 microg/ml) to the co-culture growth medium. These co-cultures, and appropriate mono-culture controls, were incubated for a further 4 days. Parameters of bone forming cell activity including alkaline phosphatase activity, calcium and inorganic phosphate accumulation were performed on the osteogenic cells. Mineral substrate resorption by osteoclastic cells was assessed morphometrically. In their respective mono-cultures, the addition of P. gingivalis sonicate to the culture medium had no effect on osteoclastic mineral resorption, but significantly inhibited osteogenesis (up to 45%; P <0.05). In co-cultures, however, the sonicate induced significant increases in mineral resorption (up to 70%; P <0.05), whereas bone forming cell activity was still inhibited, although to a significantly lesser extent than in mono-cultures (up to 25%; P <0.05). These results suggest that P. gingivalis sonicate induced up-regulation of mineral resorption may be mediated via osteogenic cells.

The processes involved in the regulation of bone cell metabolism are complex, including those implicated in bone cell coupling. This study was undertaken to develop a model that would permit real-time interaction between osteoclastic cells and osteoblasts in vitro. Osteogenic bone marrow stromal cells were isolated from 18-day-old embryonic chickens, while osteoclastic cells were isolated from laying White Leghorn hens on calcium-deficient diets. Osteoclastic cells (5x10(5)) were seeded onto mineral thin films and suspended above osteogenic cells (1x10(4)) already plated on the bottoms of tissue culture plate wells. The data showed that after 4 days of incubation there was up to a fivefold (P<0.05) reduction in all measured parameters of osteogenesis (mineralization, alkaline phosphatase activity and type I collagen production) in osteogenic cultures grown in the presence of osteoclastic cells. Similarly, osteoclastic cell-induced mineral resorption was reduced up to threefold (P<0.05). Co-culture effects on cellular responses could be manipulated by known antiresorptive agents (e.g., pamidronate) altering either the source or the age of osteoclastic cells. The results indicate that the co-culture model may be useful in the study of bone cell interactions.