– A method was developed to facilitate the estimation of S. mutans levels in saliva. Paraffin‐stimulated saliva was poured on a special slide coated with mitis‐salivarius‐sucrose agar. Two discs containing bacitracin (5 μg) were placed on the inoculated slide and the growth density of S. mutans around the bacitracin discs was scored after incubation in candle jars at 37°C for 48h. The obtained score values correlated well with the numbers of CFU of S. mutans per 1 ml of saliva estimated by a conventional method using mitis‐salivarius‐bacitracin agar. The experimental method was further tested by incubating the slides in an atmosphere created by CO2 generating tables that were placed into the cover tubes of the slides. These score values were similar to those after conventional incubation. The method is suggested for epidemiologic studies and in selecting persons at high risk for caries and in controlling the effectiveness of prophylactic measures of these patients.

No abstract

– Transferring actively growing bacteria or Streptococcus mutans ATCC 27351 into a xylitol‐containing reaction mixture caused distinct alterations in bacterial ultrastructure without notable effect on the total viability of the strain. Incubations in media containing 50 mg/ml of glucose, fructose, sucrose, lactose, sorbitol or mannitol as the primary carbon source did not affect bacterial ultrastructure. These fermentations were reflected biochemically in the amounts of insoluble glucans, as expected. A negative correlation was found between the cell mass and the lipoteichoic acid formation. But these aspects could not be visualized in the electron microscope. In the xylitol series, however, degrading cells and autolysis, intracellular vacuoles and lamellated formations in the cytoplasmic membrane were frequently seen independent of the concentration of xylitol in the reaction mixtures. In freeze‐fracturing replicas, however, the membrane intercalated particles of the cytoplasmic membranes seemed to be unaffected and like those in the controls. Minor ultrastructural changes in the fracture‐faces were detected. Despite the alterations in ultrastructure of the xylitol‐incubated bacteria, there was no difference in their viability when compared to the controls.

– The tightness of retrograde titanium screw fillings and retrograde amalgam fillings was compared in 17 human, single‐rooted teeth using Serratia marcescens bacteria in vitro. The root canals were subjected to instrumentation and irrigation, after which 2 mm was cut off from the apical end. Eight of the teeth were sealed using retrograde titanium screw fillings and nine using retrograde amalgam fillings. The teeth were suspended by means of wires in test tubes, with the crowns upwards and the roots immersed in trypticase soy broth. Suspensions of Serratia marcescens bacteria were placed in the root canals, and samples from the broth were plated daily. The bacteria penetrated the apical titanium screw seals in 2 to 7 days, and the retrograde amalgam fillings readily on the first day. Thus, the titanium screws seemed to provide a tighter seal. Staining with India ink showed that penetration had occurred at the tooth‐filling margin and that the instrumentation had not caused any fractures to the roots.

Abstract— The cytotoxicity of seven solutions used in root canal therapy was tested in human fibroblast and lymphoblast cultures. The amount of cell damage was assessed by measuring the release of 51Cr form labeled cells into the medium. The solutions, When applied at therapeutic concentrations, displayed high toxicity in vitro and difference in cytotoxicity were seen between different solutions. Generally, lymphoblasts were found to be more sensitive than fibroblasts. The cytotoxic profiles of the two cell types resembled each other except when 5% sodium bypochlorite or 0.2% Hibitance was used. When the criterion of total cell lysis was 50%51Cr release, The toxic concentrations of the solutions tested ranged between 1:25 and 1:900 (v/v) for fibroblasts. For lymphoblasts the corresponding concentration range was between 1:40 and 1:750. Despite technical simplicity and good reproducibility the 51Cr release method proved unreliable for testing the cytotoxicity of endodontic solutions. Because the methodological errors cannot be foreseen the 51Cr release method requires supproting evidence form other methods.