The effect of exposure to irrigant solutions on apical dentin biofilms in vitro

This study assessed the effectiveness of different concentrations of sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX) (Vista Dental Products, Racine, WI), and BioPure MTAD (Dentsply Endodontics-Tulsa Dental, Tulsa, OK). Intracanal contents were collected from 10 patients diagnosed with chronic apical periodontitis. The samples were cultured on hemisections of root apices to generate a polymicrobial biofilm. Each biofilm was separately immersed in 6% NaOCl, 3% NaOCl, 1% NaOCl, 2% CHX, 1% NaOCl followed by BioPure MTAD, and sterile phosphate buffered solution (PBS). SEM analysis showed 6% NaOCl and 3% NaOCl were capable of disrupting and removing the biofilm; 1% NaOCl and 1% NaOCl followed by MTAD were capable of disrupting the biofilm, but not eliminating bacteria; 2% CHX was not capable of disrupting the biofilm. Viable bacteria could not be cultured from specimens exposed to 6% NaOCl, 2 % CHX, or 1% NaOCl followed by BioPure MTAD. These results indicate that 6% NaOCl was the only irrigant capable of both rendering bacteria nonviable and physically removing the biofilm.

Invasion of vascular cells in vitro by Porphyromonas endodontalis

AIM

The objective of this study was to determine whether laboratory strains and clinical isolates of microorganisms associated with root canal infections can invade primary cultures of cardiovascular cells.

METHODOLOGY

Quantitative levels of bacterial invasion of human coronary artery endothelial cells (HCAEC) and coronary artery smooth muscle cells (CASMC) were measured using a standard antibiotic protection assay. Transmission electron microscopy was used to confirm and visualize internalization within the vascular cells.

RESULTS

Of the laboratory and clinical strains tested, only P. endodontalis ATCC 35406 was invasive in an antibiotic protection assay using HCAEC and CASMC. Invasion of P. endodontalis ATCC 35406 was confirmed by transmission electron microscopy.

DISCUSSION

Certain microorganisms associated with endodontic infections are invasive. If bacterial invasion of the vasculature contributes to the pathogenesis of cardiovascular disease, then microorganisms in the pulp chamber represent potential pathogens.

Cytotoxicity of endodontic materials

An in vitro cell culture model of human gingival fibroblasts and L-929 cells was used to measure the cytotoxicity of currently used root canal sealers Endomet, CRCS, and AH26 and root-end filling materials Amalgam, Gallium GF2, Ketac Silver, mineral trioxide aggregate (MTA), and Super-EBA. Cytotoxic effects were assessed using the MTT assay for mitochondrial enzyme activity and the CV assay for cell numbers. Using inserts culture and L-929 fibroblasts. All-Bond-2 was also evaluated. The statistical analysis of results showed that CRCS was the least cytotoxic sealer followed by Endomet and AH26. Among root-end filling materials, MTA was not cytotoxic; Gallium GF2 displayed little cytotoxicity; and Ketac Silver, Super-EBA, and Amalgam showed higher levels of cytotoxicity. All Bond-2 also displayed a high degree of cytotoxicity. CRCS was the best root canal sealer and MTA the best root-end filling material. The outcome was favorable also for Gallium GF2 as a retrofilling material.

The effect of post space preparation on the apical seal of root canal obturated teeth

The dental literature is contradictory about the quality of the apical seal as it relates to the length of remaining gutta-percha following post-space preparation. The purpose of this study was to compare apical leakage with varying remaining lengths of gutta-percha in an in vitro system. Fifty disarticulated single canal human mandibular premolar teeth were used in five experimental groups. All root canals were prepared 1 mm short of the apical foramen through a size 50 k-file and sequentially flared through a size 70 k-file. Four groups were obturated using gutta-percha with lateral condensation and Roth's 801 Elite Grade root canal sealer. Post-space preparation was accomplished by removing gutta-percha with heated pluggers so that the lengths of the remaining filling varied by increments of one millimeter between 3 and 7 mm. Specimens were covered with enamel paint leaving only the apical foramen exposed. All roots were then submerged in 1 percent methylene blue dye for two weeks, sectioned longitudinally, and measured for depth of dye penetration. No significant difference was found between the 4 and 5 mm groups or between the 6 and 7 mm groups. Significant difference (p less than .05) in leakage did exist between the 3, 4-5, and 6-7 mm groups, showing the least in the latter groups. The best apical seal was obtained when the maximum of 6 mm of gutta-percha remained.

A scanning electron microscopic investigation of accessory foramina in the furcation and pulp chamber floor of molar teeth

Observations of the pulp chamber floor and furcation surface of human maxillary and mandibular first and second molars were made with the scanning electron microscopic to determine the incidence, size, and location of patent accessory foramina. Accessory foramina on both the pulp chamber floor and the furcation surface were found in 36% of maxillary first molars, 12% of maxillary second molars, 32% of mandibular first molars, and 24% of mandibular second molars. Mandibular teeth had a higher incidence (56%) of foramina involving both the pulp chamber floor and furcation surface than did the maxillary teeth (48%).

Root canal anatomy of the human permanent teeth

Two thousand four hundred human permanent teeth were decalcified, injected with dye, and cleared in order to determine the number of root canals and their different types, the ramifications of the main root canals, the location of apical foramina and transverse anastomoses, and the frequency of apical deltas.

Root canal morphology of the maxillary first premolar

Four hundred maxillary first premolars were decalcified, injected with dye, cleared, and studied. The canal configurations were categorized as: 26% had one canal, 69% had two canals, and 5% had three canals at the apex. The relationship of canal configuration to number of roots per tooth was determined. Of the canals studied, 49.5% had lateral canals. They occured equally in all types of canals, were located mainly in the apical region, and exited from the main canal mostly in a palatal direction. Also, 11% of these canals extended from the floor of the pulp chamber to the furcation area. An accurate knowledge of the morphology of the pulp cavity is essential before endodontic procedure can be approached rationally. The frequency with which root canals unite should be considered during enlargement and filing procedures. The dentist also should be aware of the possible existence of bifurcated and double canals if root canal therapy should unexplainbly fail. A knowledge of these variations will assist the dentist in reaching conclusions when diagnosing and treating endodontic cases.

Root canal morphology of mandibular premolars

Four hundred mandibular first premolars and 400 mandibular second premolars were decalcified, injected with dye, and made transparent to determine the number of root canals, their type, the ramifications of the main root canal, the location of apical foramina and transverse anastomoses, and the frequency of apical deltas. The mandibular first premolar had one canal at the apex in 74.0% of the teeth, two canals at the apex in 25.5%, and three canals at the apex in 0.5% of the teeth. The mandibular second premolar had one canal at the apex in 97.5% and two canals at the apex in 2.5% of the teeth.