Better adaptation does not mean better sealing: an in vitro test of three sealers
The sealer with the greatest contact with dentine (92.3 percent) also had the greatest dye leakage (166 µm), while the bioceramic sealer with the weakest contact (59.9 percent) leaked the least.
The best contact with dentine came from the material that leaked most
An in vitro study published in PeerJ compared three endodontic sealers on 45 extracted single-rooted human teeth, divided into three groups of 15: AH Plus (epoxy resin, the reference material), NanoSeal-S (silicone, reinforced with silver nanoparticles) and Bio-C Sealer (premixed bioceramic).
The canals were instrumented with ProTaper Next and filled with the single-cone technique. Adaptation was measured as the percentage of contact area between sealer and dentine, by stereomicroscopy and image processing in ImageJ. Leakage was measured by dye penetration and viscosity with a Brookfield viscometer.
The results went in two directions. On adaptation, NanoSeal-S was best with 92.3 percent contact area, ahead of AH Plus (75.8 percent) and Bio-C Sealer (59.9 percent), with a statistically significant difference. On leakage the order was reversed: Bio-C Sealer had a median leakage of 0 µm, AH Plus 65 µm, and NanoSeal-S the most, 166 µm. Viscosity was lowest for NanoSeal-S, then AH Plus, then Bio-C Sealer.
In other words, the material that best filled the space along the canal wall also leaked the most dye. Low viscosity helps adaptation, but on its own it does not guarantee a seal.
Limitations
A laboratory study on extracted teeth, with the single-cone technique and 15 teeth per group. Dye penetration is an indirect measure of sealing and does not necessarily correspond to bacterial leakage in the mouth; this design says nothing about the clinical outcome of root canal treatment. For NanoSeal-S, as the authors note, little independent data is available.
For the practice
- A claim of perfect adaptation in manufacturer material is not the same as sealing. Ask for a measure of leakage as well, not only a microscopic image of the contact area.
- If you change sealer, change one variable at a time: the same instrumentation, the same filling technique, and only then judge the difference on follow-up radiographs.
- With newer materials that lack independent data, keep a conservative approach. In this test it was precisely the newest material that leaked most.