Older teeth showed less penetration of root-canal sealer, the material used to fill a prepared canal, into dentinal tubules, the microscopic channels inside dentine, in the apical third, the section nearest the root tip. The 30–40-year group had a maximum penetration depth of 1,458 micrometres, compared with 698 micrometres in the 60–70-year group. Its sectoral mean penetration depth was 738 micrometres, versus 183 micrometres in the older group. Total penetration area was also greater in the younger group, while measurements around the canal perimeter pointed in the same direction, with p less than 0.001.
That is an age-group association, not proof that ageing itself caused the difference. The study compared teeth from two donor-age bands. Randomization happened within each band: computer software assigned 20 specimens to each activation system, while the age groups themselves were set by donor age.
The two activation methods looked similar
For the activation question, the reported result was essentially a non-result. Ultrasonic activation, or UA, and SmartLite Pro EndoActivator, or SLP-EA, showed comparable sealer penetration across all evaluated variables. The narrative results reported no statistically significant activation-system difference, with p greater than 0.05. The age-group-by-activation interaction was also not statistically significant for any tested variable, suggesting that the age pattern did not depend on which system was used.
The comparison used 80 freshly extracted single-rooted human teeth. Forty came from donors aged 30 to 40 and 40 from donors aged 60 to 70. Radiography confirmed single canals and comparable anatomy, and specified dental and canal abnormalities were excluded. Within each age group, 20 teeth were assigned to UA and 20 to SLP-EA.
After standardized root-canal preparation and irrigation, the researchers labelled BC Universal Sealer with 0.01% sodium fluorescein and delivered 0.05 mL using a single-cone obturation technique. The dye made the sealer visible for imaging. Roots were sectioned 3 mm from the apex into slices 1.0 mm thick, plus or minus 0.1 mm, and examined by confocal laser scanning microscopy.
An image-analysis workflow excluded the central canal region, segmented the infiltrated areas and measured total penetration area both as an absolute value and relative to total canal area. It also calculated sectoral mean and maximum penetration depth. A perimeter analysis measured penetration at the canal wall and at 200 and 400 micrometres, giving the study a set of area, depth and perimeter readouts rather than a single measure.
To assess the data, the investigators checked normality with the Shapiro–Wilk test, used rank transformation for variables that were not normally distributed and then ran a two-way analysis of variance. The analysis tested activation system, age group and their interaction, with 0.05 as the threshold for statistical significance.
One number needs checking
One internal inconsistency makes the activation result harder to settle. For the P200 measure, the reported data list 0.045 under the Activation System p column and 0.052 in the adjacent effect-size column. The first value is below the study’s 0.05 threshold, yet the narrative results say there was no significant activation-system difference. The supplied analysis does not resolve whether the mismatch is a reporting or extraction error, so the P200 comparison needs verification rather than a confident reading.
The experiment’s scope is narrower than a clinical conclusion. It measured sealer penetration in extracted teeth, focusing on the apical third, and did not compare UA or SLP-EA with a non-activated protocol. Those design choices mean the study cannot by itself show that either system improves treatment success, or that greater fluorescent penetration equals better sealing. The missing non-activated group limits direct comparison with non-activation protocols.
What the researchers conclude
The authors interpret the findings as an age-related difference in apical-third penetration that was present with both UA and SLP-EA. For laboratory studies of root-canal materials, the result makes donor age an important design variable to account for alongside the activation method. That conclusion is strongest for the measured apical-third outcomes and the protocol used here; it should be kept separate from any claim about patient outcomes. The unresolved P200 entry leaves one part of the activation comparison open, but does not erase the reported age-group pattern. The authors report no commercial or associative conflict of interest.
Paper data and sources
Original title: Effect of irrigant activation systems and dentine ageing on sealer penetration into dentinal tubules
Authors: SANTAMARIA N, BASCONES J, GALLEGO-GARCIA C, GANCEDO-CARAVIA L
Journal/Repository: Brazilian oral research
Status: Peer-reviewed
First online: 2026-10-19
DOI: Not available
Original paper · Full text