Chris H. Miller

Bacterial leakage of mineral trioxide aggregate as compared with zinc-free amalgam, intermediate restorative material, and super-EBA as a root-end filling material

Several dye leakage studies have demonstrated the fact that mineral trioxide aggregate (MTA) leaks significantly less than other root-end filling materials. The purpose of this study was to determine the time needed for Serratia marcescens to penetrate a 3 mm thickness of zinc-free amalgam, Intermediate Restorative Material (IRM), Super-EBA, and MTA when these materials were used as root-end filling materials. Fifty-six, single-rooted extracted human teeth were cleaned and shaped with a series of .04 Taper rotary instruments (Pro-series 29 files). Once the canals were prepared in a crown down approach, the ends were resected and 48 root-end cavities were ultrasonically prepared to a 3 mm depth. The teeth were then steam sterilized. Using an aseptic technique, under a laminar air flow hood, the root-end cavities were filled with amalgam, IRM, Super-EBA, and MTA. Four root-end cavities were filled with thermoplasticized gutta-percha without a root canal sealer and served as positive controls. Another four root-end cavities were filled with sticky wax covered with two layers of nail polish and served as negative controls. The teeth were attached to presterilized (ethylene oxide gas) plastic caps, and the root ends were placed into 12-ml vials of phenol red broth. Using a micropipette, a tenth of a milliliter of S. marcescens was placed into the root canal of each tooth. To test the sterility of the apparatus set-up, the root canals of two teeth with test root-end filling materials and one tooth from the positive and negative control groups were filled with sterile saline. The number of days required for S. marcescens to penetrate the four root-end filling materials and grow in the phenol red broth was recorded and analyzed. Most of the samples filled with zinc-free amalgam leaked bacteria in 10 to 63 days. IRM began leaking 28 to 91 days. Super-EBA began leaking 42 to 101 days. MTA did not begin leaking until day 49. At the end of the study, four of the MTA samples had not exhibited any leakage. Statistical analysis of the data indicated Mineral Trioxide Aggregate to be a most effective root-end filling material against penetration of S. marcescens.

The relationship ofBacteroides melaninogenicus to symptoms associated with pulpal necrosis

The canal contents of thirty-three cariously and traumatically exposed pulpless teeth were sampled with a special technique and cultured anaerobically for growth in prereduced thioglycollate and for Bacteroides melaninogenicus on selective blood agar plates. The presence of B. melaninogenicus was compared with the presence or absence of eight symptoms associated with pulpal necrosis and the presence or absence of growth in thioglycollate. B. melaninogenicus was found to be significantly related to pain, sinus tract formation and foul odor. Suggested relationships were found between the organism and the presence of apical sensitivity and local swelling. Growth in prereduced thioglycollate occurred more often from teeth in which B. melaninogenicus was present. With the sampling technique used, positive growth in the thioiglycollte ranged from 88 percent at the initial appointment to 72 percent at the fill appointment.

The effect of chlorhexidine gluconate irrigation on the root canal flora of freshly extracted necrotic teeth

Forty freshly extracted teeth with necrotic pulps were endodontically treated under simulated clinical conditions. Bacteriologic samples were obtained before during, immediately after, and 24 hours after instrumentation, irrigation, and medication either with 0.2 percent chlorhexidine gluconate or with sterile saline. There was a highly significant (p less than 0.0049) reduction in microorganisms in the chlorhexidine-treated specimens after the instrumentation and irrigation procedures. Further significant reductions were noted after intracanal dressing of the teeth for 24 hours with the chlorhexidine gluconate solution. The teeth treated with saline also demonstrated a generalized decrease in flora after the biomechanical procedures. However, there was an absolute increase in numbers of microorganisms for 80 percent of the uniradicular and 50 percent of the multiradicular specimens when no intracanal, antimicrobial dressing was applied. It was concluded that chlorhexidine gluconate in a 0.2 percent solution can be an effective antimicrobial agent when used as an endodontic irrigating solution and that as an intracanal, interappointment dressing, chlorhexidine helps to further reduce bacteria remaining within the root canal system.

In vivo evaluation of chlorhexidine gluconate solution and sodium hypochlorite solution as root canal irrigants

A comparison was made of the effectiveness of irrigation with 0.2% chlorhexidine gluconate solution and 2.5% sodium hypochlorite solution during the endodontic treatment of 60 asymptomatic, uniradicular teeth with necrotic pulps. The effects of the two irrigants were monitored through aerobic and anaerobic bacteriologic cultures, which were obtained at the beginning and end of each appointment. As an endodontic irrigant, sodium hypochlorite solution (2.5%) was significantly more effective as an antimicrobial agent than chlorhexidine gluconate solution (0.2%).

Inhibition of microbial adherence and growth by various glass ionomers in vitro.

This study measured the in vitro inhibition of growth and adherence of five oral bacteria by glass-ionomer materials. Disks were prepared from two cavity liners and four restorative class materials, by use of Teflon plates with circular wells, five mm wide and two mm deep. The bacterial species tested included: A. viscosus, S. mitis, S. mutans, L. casei, and S. sanguis. Growth inhibition studies were performed by the spreading of 0.1 mL of standardized inocula over agar plates produced with selective media, followed by the direct application of glass-ionomer disks onto the agar. On other plates, disks were placed onto uninoculated agars for 48 h, followed by bacterial inoculation. All agar plates were incubated under optimal growth conditions for each bacterial species. The four restorative materials were also placed aseptically into sterilized bovine incisors and placed into sucrose containing broth media, inoculated with S. mutans for three days. Adhering materials were disclosed and scored. An ion-exchange electrode was used to measure fluoride release over a seven-day period for all six glass ionomers. The two cavity liners and two of the restorative materials produced the largest growth inhibition zones by direct contact. No growth inhibition occurred when the specimens were allowed to come into contact with the agars prior to inoculation. All four restorative materials reduced bacterial accumulations on enamel surfaces by over 80%. Elevations in short-term fluoride release levels were positively correlated with growth inhibition.

The comparative antimicrobial effect of calcium hydroxide

The antimicrobial effectiveness of calcium hydroxide, camphorated paramonochlorophenol, and formocresol in root canals of extracted human teeth was compared. Canals in single-rooted teeth were enlarged and inoculated with Streptococcus mutans, Actinomyces viscosus, and Bacteroides gingivalis or Bacteroides fragilis. After treatment with a test agent and sealing and incubation for 1 hour, the canal contents were analyzed for the number of viable test bacteria and compared with that of inoculated teeth not treated with test agents. All test agents exhibited antimicrobial activity against all bacteria, with percent reductions in viable bacteria ranging from 64.3% to 100%. The combined data for Pulpdent paste and calcium hydroxide showed significantly higher antimicrobial activity than the combined data for camphorated paramonochlorophenol and formocresol for S. mutans and B. gingivalis or B. fragilis but showed no difference for A. viscosus.

Uptake and release of chlorhexidine by bovine pulp and dentin specimens and their subsequent acquisition of antibacterial properties

Bovine pulp and dentin specimens were treated with either a 0.02 or 1.00 percent solution of chlorhexidine for either 20 or 40 minutes. Culture determination of the acquisition of antibacterial properties by the treated specimens immediately and 1 week after the treatment was evaluated using the test organism Streptococcus faecalis. It was concluded that chlorhexidine is a potent antibacterial agent under the test conditions and that its use as an endodontic irrigating solution should be further evaluated.

A survey of sterilization practices in selected endodontic offices

Little information exists concerning the effect(s) office asepsis procedures can have on sterilization success in dental speciality offices. Therefore, 218 randomly selected private endodontic offices in five midwestern states were sent spore strips, use instructions, and a 16-question survey. The question-naire dealt with practitioner/auxillary training, continuing education practices, and office sterilization procedures. Offices returning “positive” spore strips were sent additional strips and guidelines for improving sterilizer performance. Survey data were compared with sterilizer type and spore killing results. A total of 139 sterilizers in 106 offices was monitored. Testing results indicated a 15.1% overall failure rate. Of the offices with sterilization failures, only 68.2% responded for retesting. However, all of the responding offices eventually achieved negative spore tests. Dry heat ovens were most likely to have a sterilization failure (p

Extracellular Dextran Hydrolase from Streptococcus mutans Strain 6715

Streptococcus mutans strain 6715 was shown to produce an extracellular dextranase with endohydrolytic α-(1→6)-glucan-6-glucanohydrolase activity. The enzyme degraded soluble polymers produced by some oral streptococci but did not disperse the streptococcal plaques tested. Enzyme levels in the culture supernatant were elevated in sucrose and sucrose plus glucose cultures but remained at basal levels in glucose and dextran plus glucose cultures.

The effect of sucralfate on the growth of cariogenic streptococci

Sucralfate, an aluminum salt of sucrose octasulfate, has been shown to be effective in reducing the discomfort of radiation therapy-induced oral mucositis. This study was done to determine whether sucralfate could be used as a nutritional source for dental caries-producing organisms. Three Streptococcus strains were cultured in a defined medium. Sucralfate powder was evaluated for its ability to be used as a carbohydrate food source by these organisms. The addition of sucralfate alone did not stimulate the organisms growth. The addition of sucralfate and glucose resulted in less growth than the addition of glucose alone. Increasing the sucralfate concentration from 1% to 10% in the glucose-containing cultures resulted in statistically significant growth inhibition (p less than 0.02). Sucralfate appears to have no cariogenic potential and may have some cariostatic potential.