Richard Komorowski

Antimicrobial Substantivity of Chlorhexidine-Treated Bovine Root Dentin

Previous studies have demonstrated antimicrobial substantivity in root canal dentin up to 7 days after treatment with chlorhexidine. This in vitro study assessed the antimicrobial substantivity of chlorhexidine-treated bovine root dentin over a period of 21 days. Sixty standardized bovine root sections were randomly divided into three equal groups, and their canals immersed in one of the following solutions: (i) sterile saline; (ii) 2.5% NaOCl; or (iii) 0.2% chlorhexidine (CHX). Half the specimens in each group were treated with the solution for 5 min and the other half for 7 days. After solutions were removed, the specimens were incubated at 37 degrees C in Brain Heart Infusion broth containing Enterococcus faecalis (ATCC 29212). A fresh inoculum was added to the broth every other day over a 21-day period. The canals were then enlarged with sterile burs, and the dentin shavings collected and cultured for the presence of cultivable bacteria in the dentinal tubules. Specimens treated with CHX for 7 days demonstrated significantly less dentin colonization by E. faecalis than the other specimens. CHX has potential as an intracanal medicament, if it can be applied for a period of at least 7 days.

In vivo model for assessing the functional efficacy of endodontic filling materials and techniques.

Endodontic fillings were challenged with bacterial ingress in mandibular premolars of 4 beagle dogs. Groups 1, 2, and 3 (n = 9), had canals filled with gutta-percha and sealer, gutta-percha alone, and sealer alone, respectively. After 2 wk, pulp chambers were inoculated with plaque. Group 4 (n = 9) and group 5 (n = 5) had canals either filled as in groups 1 to 3 or unfilled, respectively, but not inoculated. Group 6 (n = 5) had canals unfilled and inoculated. Teeth were radiographed periodically for 14 wk, dogs terminated, and jaw blocks retrieved and processed for light microscopic examination. Rarefying osteitis appeared in group 6 at 3 wk and in groups 2, 3, and 5 at 11 wk. Periradicular inflammation was none, mild, or severe. Occurrence of severe inflammation in groups 1 to 6 was 0, 11%, 33%, 0, 60%, and 100%, respectively. Groups 1 to 3 combined differed significantly from group 4 (repeated-measures ANOVA, p < 0.05). This model could be used to assess the functional efficacy of endodontic fillings in vivo.

Antimicrobial Substantivity of Bovine Root Dentin Exposed to Different Chlorhexidine Delivery Vehicles

Root canal dentin acquires antimicrobial substantivity after exposure to chlorhexidine gluconate (CHX) for 1 wk. Therefore development of a vehicle for delivery of CHX as an intracanal medication is desirable. This in vitro study assessed the efficacy of two CHX delivery vehicles, a controlled-release device and a gel, to affect antimicrobial substantivity of bovine root dentin. Sixty bovine incisor root specimens were prepared with standardized length (10 mm) and canal diameter (3.3 mm), and coated externally with nail polish. Specimens were divided into four equal groups and their canals medicated for 7 days with either: (i) an experimental controlled-release device containing 25% CHX that was immersed in sterile saline; (ii) 2% CHX gel; or (iii) Ca(OH)2 paste. Sterile saline was used as the positive control. After medication, the canals of the specimens were inoculated with Enterococcus faecalis for 21 days. Root canal dentin samples ranging in depth from 0.1 to 0.45 mm were then obtained using sterile round burs of ascending diameter. Each dentin sample was placed in a separate test tube containing Brain Heart Infusion broth and incubated for 24 h. The optical density (OD) of the broth was then measured spectrophotometrically at 540 nm. The positive control showed significantly higher mean OD values (one-way ANOVA and Tukeys Studentized Range Test; p < 0.001) than the three test groups. The CHX controlled-release device group showed significantly lower OD values than the Ca(OH)2 group; however only at dentin depths up to 0.2 mm. In contrast, the CHX gel group consistently showed significantly lower OD values than both the CHX controlled-release device and Ca(OH)2 groups. These results suggest that bovine root canals medicated with 2% CHX gel for 7 days acquire antimicrobial properties for at least 21 days.

In Vivo Resistance of Coronally Induced Bacterial Ingress by an Experimental Glass Ionomer Cement Root Canal Sealer

The resistance of an experimental sealer (KT-308) to bacterial ingress was assessed in six beagle dogs. In four mandibular premolars per dog, canals were prepared, filled with condensed gutta-percha and either KT-308 or Roth 801 cement (n = 24 roots), and the pulp chambers inoculated with plaque. Two additional premolars per dog were similarly root-filled, but not inoculated (n = 12 and 11, respectively). One incisor per dog was inoculated, but not root-filled (n = 6). Dogs were terminated after 6 months, and jaw blocks were retrieved and processed for light microscopic examination of the periapical tissues. Inflammation about the inoculated roots was significantly lower (p < 0.03) for KT-308 (17%) than Roth 801 cement (46%). Inflammation about the noninoculated roots did not differ significantly between KT-308 (8%) and Roth 801 cement (36%). This study demonstrated a better functional efficacy of KT-308 than of Roth 801 cement, and validated this in vivo model for assessment of root filling materials.

Ultrasonic root end cavity preparation assessed by an in situ impression technique

PROBLEM In vitro studies have demonstrated microfractures in resected roots after root end cavity preparation with ultrasonic tips. Such microfractures are of concern; however, they may be artifacts. OBJECTIVES To assess the incidence of microfractures after ultrasonic root end cavity preparation in situ. STUDY DESIGN Fifty-two roots in two cadavers were endodontically treated, the soft tissues excised, and the root ends exposed and resected. The resected root surfaces were replicated with polyvinylsiloxane impressions. Root end cavities were prepared with ultrasonic tips, then impressed a second time. The roots were retrieved; 25 were processed for direct SEM examination as were both the impressions of each root. The specimens were examined by stereomicroscope and scanning electron microscope. RESULTS In the impressions, the resected and prepared surfaces appeared irregular, but none demonstrated microfractures. In contrast, 15 retrieved roots showed microfractures. CONCLUSIONS Ultrasonic root end cavity preparation in situ did not cause root microfractures, and the impression technique could be clinically usable with minor modifications.