PubMed · 5270266
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G L Manning, R M Browne. 1970-02-17. Dentinoma.. https://doi.org/10.1038/sj.bdj.4802444
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The purpose of this pilot study was to investigate some of the clinical variables in ultrasonic endodontics. forty extracted human teeth with a single, straight root 21-25 mm in length were prepared using combinations of the following variables: hand or ultrasonic instrumentation; apical seat prepared to file sizes 35, 40, 45 or 50; 1 ml of water, 4% sodium hypochlorite or EDTAC as irrigant between each instrument size; three brands of ultrasound generator and inserts; a 'low', 'medium' or 'high' effective power output; a tuned or untuned circuit; post-instrumentation ultrasonic irrigation with either 4% sodium hypochlorite, EDTAC, or the two used in sequence. The specimens were viewed in a scanning electron microscope and scored for the presence or absence of a smear layer at levels < 1 mm, 5 mm and 10 mm from the apical seat. The most effective combination, as tested, was hand instrumentation to file size 40 with 1 ml EDTAC irrigation between each instrument size, supplemented by intermittent flush irrigation with EDTAC with ultrasound then 4% sodium hypochlorite with ultrasound. This technique left a minimum smear layer restricted to the apical seat. Other combinations of instrumentation and irrigation were not consistent in their effectiveness.
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.
In this study we evaluated the morphological aspect at scanning electron microscopy (SEM) and the degree of permeability of the dentinal surface after treatment with different detergent solutions, liners and cleansers. In particular we tested new potassium oxalate products. The results obtained with in vitro tests showed that many detergents, liners and cleansers are able to maintain almost unaltered the smear layer, causing small modifications for the diameter and the number of dentinal tubules which are partially exposed. The materials we used were able to deterge the dentinal surface, as demonstrated by SEM analysis, but one of them was able to stabilize and to protect the surface. All tested products, except potassium oxalate, caused an increase in dentinal permeability, proving to exercise a potential by damaging action towards the dentine and the pulpal tissue. Only DDS was able to reduce the dentinal permeability, causing the formation of calcium oxalate precipitates which occlude the dentinal tubules.