James D. Kettering

In Vitro Bacterial Penetration of Coronally Unsealed Endodontically Treated Teeth

Forty-five root canals were cleaned, shaped, and then obturated with gutta-percha and root canal sealer, using a lateral condensation technique. The coronal portions of the root filling materials were placed in contact with Staphylococcus epidermidis and Proteus vulgaris. The number of days required for these bacteria to penetrate the entire root canals was determined. Over 50% of the root canals were completely contaminated after 19-day exposure to S. epidermidis. Fifty percent of the root canals were also totally contaminated when the coronal surfaces of their fillings were exposed to P. vulgaris for 42 days.

Bacterial leakage of mineral trioxide aggregate as a root-end filling material

Previous dye leakage studies have shown that mineral trioxide aggregate leaks significantly less than other commonly used root-end filling materials. This study determined the time needed for Staphylococcus epidermidis to penetrate a 3-mm thickness of amalgam, Super-EBA, Intermediate Restorative Material (IRM), or mineral trioxide aggregate (MTA) as root-end filling materials. Fifty-six single-rooted extracted human teeth were cleaned and shaped using a step-back technique. Following root-end resection, 48 root-end cavities were filled with amalgam, Super-EBA, IRM, or MTA. Four root-end cavities were filled with thermoplasticized gutta-percha without a root canal sealer (+ control), and another four were filled with sticky wax covered with two layers of nail polish (- control). After attaching the teeth to plastic caps of 12-ml plastic vials and placing the root ends into phenol red broth, the set-ups were sterilized overnight with ethylene dioxide gas. A tenth of a microliter of broth containing S. epidermidis was placed into the root canal of 46 teeth (40 experimental, 3 positive, and 3 negative control groups). In addition, 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 the test bacteria to penetrate various root-end filling materials was determined. Most samples whose apical 3 mm were filled with amalgam, Super-EBA, or IRM began leaking at 6 to 57 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative investigation of marginal adaptation of mineral trioxide aggregate and other commonly used root-end filling materials

This study investigated the marginal adaptation of mineral trioxide aggregate (MTA) as a root-end filling material, compared with commonly used root-end filling materials by scanning electron microscopy (SEM). Eighty-eight single-rooted freshly extracted human teeth were cleaned, shaped, and obturated with gutta-percha and root canal sealer. Following root-end resection and cavity preparation, the root-end cavities were filled with amalgam, Super-EBA, Intermediate Restorative Material (IRM), or MTA. Using a slow-speed diamond saw, 40 roots were longitudinally sectioned into two halves. Resin replicas of resected root ends of the remaining nonsectioned roots were also prepared. After mounting longitudinal sections of roots and resin replicas of resected roots on aluminum stubs, the distance between the test root-end filling materials and surrounding dentin was measured at four points under SEM. Examination of the original samples showed numerous artifacts in the longitudinal sections of the specimens. In contrast, the resin replicas of resected and filled root ends had no artifacts. Statistical analysis of data comparing gap sizes between the root-end filling materials and their surrounding dentin shows that MTA had better adaptation compared with amalgam, Super-EBA, and IRM.

Cytotoxicity of Four Root End Filling Materials

Leakage and scanning electron microscopic studies have shown that a mineral trioxide aggregate (MTA) used as root end filling material permits significantly less leakage and has better adaptation than other commonly used root end filling materials. Because these materials are in contact with the periradicular tissues, their cytotoxicity should be evaluated before in vivo tests. Using the agar overlay and radiochromium methods, the cytotoxicity of amalgam, Super EBA, IRM, and the MTA was evaluated. Statistical analysis of the data from the agar overlay technique shows that freshly mixed and set amalgam were significantly less toxic than the rest of tested materials (p< 0.00005). Fresh and set MTA ranked second when tested for cytotoxicity with this technique. Similar statistical tests revealed a significant statistical difference between the toxicity of freshly mixed and set materials after 24 h of incubation with radiochromium-labeled mouse L929 cells. The degree of cytotoxicity of fresh and set materials was MTA least toxic followed by amalgam, Super EBA, and IRM. Based on the results of the cell culture methods used in this study it appears that MTA is a potential root end filling material and warrants further in vivo evaluations.

The Antimicrobial Effect of MTAD: An In Vitro Investigation

Pulp and periradicular diseases are of microbial origin. To effectively clean the root canal system a disinfecting agent must be able to penetrate into difficult-to-reach areas and kill microorganisms with minimal damage to the host tissues. The purpose of this investigation was to test the ability of a mixture of a tetracycline isomer, an acid, and a detergent (MTAD) to kill Enterococcus faecalis and compare its efficacy to that of sodium hypochlorite (NaOCl) and ethylene diamine tetraacetic acid (EDTA). The zones of inhibition and minimum inhibitory concentrations were measured for these solutions. Measurement of zones of inhibition and determination of the minimum inhibitory concentrations showed that MTAD is as effective as 5.25% NaOCl and significantly more effective than EDTA (p < 0.0001). Furthermore, MTAD is significantly more effective in killing E. faecalis than NaOCl when the solutions are diluted (p < 0.0001). Measurement of the minimum inhibitory concentrations demonstrated that although MTAD is still effective in killing E. faecalis at 200x dilution, NaOCl ceases to exert its antibacterial activity beyond 32x dilution. EDTA did not exhibit any antibacterial activity. Based on the results of this study, it seems that MTAD is an effective solution in eradicating E. faecalis.

Factors associated with endodontic interappointment emergencies of teeth with necrotic pulps

Despite significant progress in the field of endodontics, the causes of interappointement emergencies are not well defined and are a subject of controversy. To delineate some of the major factors related to the incidence of these emergencies, information from the charts of 2,000 patients who had received root canal therapy for necrotic pulps was recorded and analyzed. One-half of the patients were those who had interappointment pain or swelling which required a nonscheduled emergency visit for urgent care. The other half were patients who reported no complications after cleaning and shaping of their root canals. The results of this study show that some factors, such as age, sex tooth type, presence of preoperative pain, presence of allergies, absence of periapical lesions, sinus tract stomas, retreated cases as well as those receiving prescribed analgesics, had significant effects on the incidence of endodontic interappointment emergencies. In contrast, presence of systemic diseases, use of intracanal medications, and penetration of the foramen with small instruments during length determination had no significant effect on the frequency of these emergencies.

Leakage Evaluation of Root End Filling Materials Using Endotoxin

Mineral trioxide aggregate (MTA) has been shown to possess excellent sealing ability when tested with dye, bacteria, and a fluid filtration technique. Endotoxin, a component of the cell wall of Gram-negative bacteria, has been proposed to play a role in the pathogenesis of periradicular lesions. This study used a modified Limulus Amebocyte Lysate test for the presence of endotoxin as a tracer and compared the sealing ability of Super-EBA, IRM, amalgam, and MTA. The results showed that MTA permitted less endotoxin leakage than IRM and amalgam at 1, 2, 6, and 12 wk (p < 0.05), and leaked less than Super-EBA at 2 and 12 wk (p < 0.05).

Identification and relative concentration of B and T lymphocytes in human chronic periapical lesions

Thirteen human dental periapical lesions were obtained, frozen, serially sectioned, and stained using the indirect immunoperoxidase technique for detecting the presence of B and T lymphocytes. All of the lesions had positive staining for both cells, and the number of T cells was greater than that of B cells in the same specimen.

Interleukin 1β in symptomatic and asymptomatic human periradicular lesions

Interleukin 1β (IL-1β) has been shown to be a potent mediator of bone resorption and has been implicated in resorption in periradicular lesions. In this study we compared the local concentrations of IL-1β in symptomatic and asymptomatic human periradicular lesions. Periradicular tissues from patients with symptomatic and asymptomatic lesions were obtained and stored at −70°C. Pulpal tissues from unerupted third molars and chronically inflamed gingival tissues were also obtained and used as negative and positive controls, respectively. Tissue samples were homogenized, and supernatants were assayed for IL-1β by the enzyme-linked immunosorbant assay. Significantly higher levels of IL-1β were found in symptomatic and asymptomatic lesions and inflamed gingival tissues compared with uninflamed pulp tissues. There was a trend toward higher levels of IL-1β in symptomatic lesions compared with asymptomatic lesions, but the difference was not significant. The results suggest that IL-1β may play a significant role in the pathogenesis of human periradicular lesions.

Efficacy of an alcohol-free chlorhexidine mouthrinse as an antimicrobial agent☆☆☆★★★♢♢♢

STATEMENT OF PROBLEM Antimicrobial mouthrinses have become an important part of comprehensive dental care. However, mouthrinses that contain alcohol have been shown to be detrimental to patients undergoing radiation therapy for head and neck cancer, to some immunocompromised patients, to families with small children, and to persons sensitive to alcohol. PURPOSE This study evaluated the effectiveness of alcohol-free, 0.12% chlorhexidine mouthrinse in reducing microbial levels when compared with commercially available 0.12% chlorhexidine (CHX) and essential oils mouthrinses. MATERIAL AND METHODS This study consisted of both in vitro and in vivo investigations. The double-blind study included 32 subjects randomly assigned to 3 groups, equalized according to the indices tested. One group (n = 11) received essential oils rinse; the second group (n = 11) received CHX; and the last group (n = 10) received the alcohol-free CHX. Subjects were asked not to use any mechanical means of oral hygiene for 21 days. The in vitro part of the study consisted of Streptococcus mutans strip tests. RESULTS Mean plaque scores for both CHX products decreased after 21 days, whereas the mean for the essential oils increased. Bleeding and gingival index scores for all 3 groups increased, which may be due to the initially healthy tissues of the participants. Relative microbial growth for S mutans for both the CHX products decreased to 0 after 21 days, whereas the counts for the essential oils group remained varied.