Retention of streptococci to defined solid surfaces in the presence of saliva secretions

The initial surface retention of Streptococcus sanguis (G9B and ATCC 10556) and Streptococcus salivarius (ATCC 9758 and ATCC 13419) was examined using a well defined flow cell system. The microorganisms, known to be recovered from hard vs. soft tissue surfaces, respectively, were suspended in either Ringer solution, human parotid saliva (HPS), human submandibular and sublingual saliva (HSMSL), or mixed saliva. Microbial retention was evaluated on germanium prisms of low (20–25 mNm⁻¹) and medium (30–35 mNm⁻¹) critical surface tensions following distilled water rinse at 1 ml/min for 15 min. When suspended in only Ringer solution, the tested microorganisms showed patterns of generally high retention, that reflected the influence of both bacterial and substratum surface properties. However, in the saliva suspensions an overall reduction of retention was found with preferential retention to surfaces of medium critical surface tension for all bacteria. When comparing HPS and HSMSL as the suspending medium, a statistically significant observation was that smaller numbers of retained bacteria were recorded in the presence of HSMSL. The most frequently observed relationship between the tested salivas and numbers of retained cells was HSMSL < MIXED < HPS.     

Methodological aspects and quantitative adjuncts to computerized subtraction radiography

The methodology for the use of subtraction radiography in the study of human periodontal disease is described in detail to include: 1) design and fabrication of a system for taking standardized radiographs; 2) generation of interpretable subtraction images; 3) adjunctive, quantitative methods for analyses of digitized radiographic images; 4) reference standard for periodontally healthy individuals. Correct use of our system for taking standardized radiographs can provide a sufficient number of pairs of radiographs for the study of patients with severe periodontitis using subtraction radiography. Changes in bone mass observed on subtraction images can be quantified by measurement of their areas and their relationship to the alveolar crest.     

In vitro attachment of oral microorganisms to solid surfaces: evaluation of a controlled flow method

A flow cell method was modified to provide shear-controlled experimental conditions for monitoring initial attachment and detachment of oral microorganisms to solid surfaces. Whole unstimulated human saliva was collected and circulated at a flow rate of 1 ml/min, through a cell composed of two parallel test plates. Infrared-transparent plates of medium surface energy served as test substrata in these initial calibration experiments. The plates presented a similar distribution of polar forces and dispersion forces at the surface as that of human tooth enamel and some restorative dental materials. Internal reflection infrared spectroscopy verified the presence of deposited organic material. After saliva had been circulated through the flow cells for 15 min at 37 degrees C, sterilized distilled water was introduced at the same flow rate and time of exposure to remove unattached microorganisms. Morphologic characterizations and counts of adherent Gram-stainable microorganisms were performed using incident light microscopy. Three different surface zones corresponding to the inlet area, the middle area and the outlet area of the flow cell were analyzed, and compared with enumerations of microorganisms in the whole saliva samples. Numbers of attached microorganisms in the three zones followed predictions from the laminar flow conditions, with a positive correlation shown between total numbers of microorganisms in saliva and total numbers of microorganisms attached. Cocci and rods were the only morphotypes observed on the plates, and no significant difference could be detected between the percentage of cocci and rods attached in the three different zones.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tissue localization of Actinobacillus actinomycetemcomitans in human periodontitis. II. Correlation between immunofluorescence and culture techniques

Recent immunohistological studies have suggested that Actinobacillus actinomycetemcomitans is present in the gingival tissues in juvenile periodontitis lesions. The present study examined tissue bound A. actinomycetemcomitans by bacterial culture and immunohistological demonstration of antigen in tissue. A total of 14 periodontitis lesions were examined. Eleven biopsies were obtained from gingiva adjacent to A. actinomycetemcomitans infected pockets, while the remaining three control biopsies were obtained from gingiva adjacent to pockets where subgingival A. actinomycetemcomitans infection could not be detected. Each biopsy was hemisected, one half was used for immunofluorescence microscopic examination while the other half was processed for culture of A. actinomycetemcomitans. The latter section was surface-disinfected, repeatedly washed and then minced to release bacteria from within the tissues. Aliquots from the serial washings and the minced tissue suspension were cultured on medium selective for A. actinomycetemcomitans. Surface disinfection and serial washings gradually decreased cultivable A. actinomycetemcomitans in the washings aliquots. Following tissue disruption, an increase in colony-forming units of A. actinomycetemcomitans was seen from eight of the 11 test biopsies. This bacterium could not be detected in washings or minced tissue suspensions from the control biopsies obtained from lesions in which subgingival A. actinomycetemcomitans was previously not detected. A positive correlation was seen between the presence of A. actinomycetemcomitans antigens in the gingival biopsies and; (1) A. actinomycetemcomitans colony-forming units released from the minced tissues (r = 0.90, p = 0.000), as well as; (2) the colony-forming units from the periodontal pocket (r = 0.62, P = 0.017).(ABSTRACT TRUNCATED AT 250 WORDS)     

Analysis of site specific periodontal bacteria sampling schemes.

A great deal of controversy has existed in the periodontal literature as to whether the site or the subject should be the unit of analysis. Using the site as the unit of analysis assumes that observations of sites within the same subject are independent and ignores between subject variation. The purpose of this report is to evaluate the influence that the unit of analysis has on estimating the number of necessary site specific bacterial samples from each subject. The number of bacterial samples per subject was defined as the number of samples that would insure a clinician at a 95% confidence level that, if the bacteria were present in a subject, it would be discovered. From two data sets in which 20 to 30 bacterial samples were taken from each subject and data generated from a simulation, appropriate within-subject sample size was determined. In one data set the presence of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Bacteroides forsythus, and Prevotella intermedia was determined by indirect immunofluorescence. In the other data set the presence of A. actinomycetemcomitans, P. gingivalis, and P. intermedia was determined using DNA probes. Results of this study demonstrate that there is a large between subject variation in site specific bacterial prevalence, as indicated by an elevated intraclass correlation. Simulated data in this report demonstrated that the number of necessary bacterial samples per subject increased with increasing values of intraclass correlation. The number of necessary within subject samples also increased with decreasing prevalence rate. For A. actinomycetemcomitans, which had a low prevalence rate (0.11 to 0.18), the number of necessary samples per subject was very high (31 to 35).(ABSTRACT TRUNCATED AT 250 WORDS)