PubMed · 3483768
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R Harndt. 1987. [Root canal length].. https://pubmed.ncbi.nlm.nih.gov/3483768/
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A new muffle model system is presented using the principle of internal indexing. The system is composed of a metal stand, four pins, and a single Teflon mold that is used for the investment of all teeth. This system is very precise, reproducible, and versatile. The sectioned specimens can easily be stored assembled, as opposed to previous systems that rely on external indexing.
The purpose of this study was to evaluate the efficacy of Er:YAG laser irradiation in removing debris and smear layer from prepared root canal walls. Thirty-six human extracted mandibular incisors teeth were divided into three groups. Group 1 (G1) was control specimens that were not lased. The teeth of group 2 (G2) and group 3 (G3) were irradiated by Er:YAG laser at different watt powers of 1 W and 2 W. The teeth were bisected and prepared for study in stereoscopic light microscope and SEM. Control specimens showed an amount of debris and heavy smear layer obscuring the dentinal tubules at all levels in the canals. The root canal walls irradiated by Er:YAG laser were free of debris, with an evaporated smear layer and open dentinal tubules. Statistical analyses showed significant differences (p < 0.01) in cleanliness smear layer between G1 and G2, and G1 and G3. However, there was no statistically significant difference between G2 and G3 in the cleanliness of the middle and apical one-third of the root canals. These results show Er:YAG laser is effective in removing debris and smear layer from root canal walls.
The effects of pulsed Nd:YAG laser irradiation with different laser initiators on the permeability and ultrastructure of the root canal wall dentin were investigated in vitro. Forty extracted human single-rooted teeth were randomly assigned to four groups. Group 1 teeth were not lased as a control. Group 2 specimens received four 10-s duration laser exposures for a total exposure of 40 s/canal. In group 3 specimens, the root canals were painted with black ink and then lased by the same method as group 2 teeth. In group 4 specimens, root canals were treated with 38% Ag(NH3)2F and then lased by the same method as group 2 teeth. Laser parameters were set at 2 W, 20 pps. After being placed in 0.6% rhodamine B solution for 48 h, the teeth were sectioned for study by stereoscope and scanning electron microscopy. Statistical analysis showed there were significant differences (p < 0.05) in dentin permeability in the apical areas between groups 3 and 1, 4 and 1, and 4 and 2. Scanning electron microscopic examination showed that laser treatment alone had no obvious effects on the root canal wall. The root canal surfaces prepared for by laser irradiation with black ink or 38% Ag(NH3)2F revealed melting, smear layer evaporation, and open dentinal tubules. Black ink was more effective than 38% Ag(NH3)2F as a Nd:YAG laser initiator.