EA 157, Metrohm, Herisau, Switzerland.

In this article the question of the relevance and consequences of bacteria remaining in the tubules of root dentine after cleaning and shaping of the root canal space is addressed. A second aim is to discuss the necessity of clinical measures taken to eradicate those bacteria that are presumed to survive there. The available clinical and experimental evidence supports the use of antibacterial dressings in cases where the root canal space remains temporarily unobturated after removal of necrotic and infected pulp tissue. There is no evidence, however, that special measures should be taken to kill the bacteria in the dentinal tubules. Should time permit, a sound obturation technique immediately following the cleaning, shaping and disinfection phases allows the remaining bacteria in the tubules to be either inactivated or prevented from repopulating the (former) canal space. In the vast majority of cases, those bacteria appear not to jeopardize the successful outcome of root canal treatment.

Convective transport of water from the coronal to the apical end of obturated root canals was determined by the movement of an air bubble in a capillary glass tube connected to the apex of the experimental root section using a headspace pressure of 120 kPa (1.2 atm). Water transport through existing voids in the obturated canals could be measured reproducibly in this way. The root canals of 60 human maxillary canines were filled with gutta-percha and sealer by the cold lateral condensation technique. Thirty of these were first exposed to a small motile bacterium, Pseudomonas aeruginosa, growing in a reservoir at the coronal end of each root. After 50 days, two specimens allowed penetration of bacteria to a reservoir at the apical end. All the roots were then assessed quantitatively for convective transport of water. The results were divided into three defined categories: 39 obturated canals were in the 'bacteria tight' category, 14 canals in the 'slight leakage' and 7 canals in the 'gross leakage' category. The two specimens that showed bacterial penetration fell into the slight and gross leakage categories. The previous test for bacterial passage did not statistically influence the fluid transport pattern of these roots which was measured subsequently. These findings indicate that fluids transport through obturated root canals, most of which do not allow the passage of bacteria.

The review presented here covers metastatic local and systemic disease secondary to the accumulation of plaque or the formation of other pathogenic microbial depots in the mouth. At least 3 pathways may link oral infection to secondary disease, to wit metastatic infection due to transient bacteremia, metastatic immunological injury, and metastatic toxic injury. The available evidence is presented and examples are provided. They concern among others such divergent diseases as acute bacterial myocarditis, infective endocarditis, brain abscess, uveitis and iridocyclitis, trigeminal and atypical facial neuralgia, unilateral facial paralysis, fever of "unknown' origin, and neutrophil dysfunction.