A study of the rheological properties of endodontic sealers.
OBJECTIVE
To test the hypothesis that there would be no statistically significant difference in viscosity-related measures of endodontic sealers or change in these with strain rate, internal diameter or powder : liquid ratio in a capillary system.


METHODS
Materials used were Apexit, Tubliseal EWT, Grossman's sealer and Ketac-endo. Viscosity-related measures were tested in a two-plate test, and in a capillary rheometer. The mean values (n = 12) for thickness and diameter of material formed between two glass plates were tested with one-way analysis of variance. Pressure was applied to a capillary rheometer at strain rates 5 and 10 mm min(-1) in tubes of internal diameter 0.6 and 1.2 mm.


RESULTS
Tubliseal EWT had a thinner film thickness than the other sealers (alpha = 0.05). The difference in diameter between Tubliseal EWT and the other sealers was significant apart from Apexit. Increased strain rate gave a significant increase (alpha = 0.05) in the flow of all sealers. Narrower tubes produced increased velocity, which was significant for all sealers, and reduced volumetric flow, which was significant for all sealers except Grossman's 2 : 1 (Wilcoxon signed rank test). Reduction in powder : liquid ratio of Grossman's significantly increased flow in narrow tubes and at higher strain rate (Mann-Whitney test).


CONCLUSIONS
There was a significant difference between the flow of Tubliseal EWT and the other sealers tested in the two-plate test; capillary flow was affected by sealer, internal diameter, strain rate and powder : liquid ratio. The null hypotheses were rejected.
Lacey
S
S
Department of Biomaterials and Conservative Dentistry, GKT Dental Institute, King's College London, Guy's Hospital, London Bridge, London, UK. susanna.lacey@kcl.ac.uk
Pitt Ford
T R
TR
Watson
T F
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Sherriff
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M
D002126:Calcium Hydroxide / Q000737:chemistry; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D011208:Powders / Q000737:chemistry; D011312:Pressure; D012212:Rheology; D012387:Root Canal Filling Materials / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014783:Viscosity; D015035:Zinc Oxide-Eugenol Cement / Q000737:chemistry
C074418:Apexit; D005899:Glass Ionomer Cements; C074934:Ketac Endo; D011208:Powders; D012387:Root Canal Filling Materials; D012996:Solutions; D015035:Zinc Oxide-Eugenol Cement; C045432:Grossman's sealer; C048769:tubliseal; D002126:Calcium Hydroxide