Impact of Thermal Cycling on Volumetric Stability of Endodontic Filling Materials

To evaluate the dimensional stability of root canal obturation materials under dynamic conditions by simulating ageing.

Forty extracted, single-rooted, human teeth were decoronated and randomly assigned to four experimental groups of 10 teeth each. Root canals were instrumented using the Reciproc R40 system and obturated using the single-cone technique in combination with one of four sealers: AH Plus, MTA Fillapex, TotalFill BC Sealer, or EndoREZ. All specimens underwent thermal cycling (9000 cycles between 5°C and 55°C) to simulate ageing. Each tooth was scanned using high-resolution micro-computed tomography (micro-CT) before and after thermal cycling. Volumetric changes of the filling materials were compared by analyzing the pre- and post-treatment scans in the apical 1 and 2-mm, and over the total canal volume.

At the apical 1-mm region, AH Plus exhibited the greatest expansion ( $0.016{\mathrm{mm}}^3$ ). EndoREZ, MTA Fillapex, and TotalFill BC Sealer showed significantly lower expansion ( $0.008,0.003,0.001{\mathrm{mm}}^3$ ) than AH Plus. In the apical 2-mm region, only TotalFill BC Sealer expanded significantly less than AH Plus, with a difference of 0.03 mm³.

Thermal cycling induced measurable expansion in all tested endodontic sealers, with the most pronounced effects observed in the apical region. AH Plus exhibited significantly greater expansion than the other materials. Controlled apical expansion may be clinically beneficial by improving sealer adaptation to dentinal walls and enhancing apical sealing without generating detrimental radial stresses. These findings underscore the clinical relevance of long-term volumetric stability under thermally dynamic conditions and suggest that sealer selection may influence the durability of the apical seal.