Time-Dependent Volumetric and Porosity Changes of Bioceramic, Silicone Bioactive Glass-Based, and Epoxy Resin-Based Root Canal Sealers: A Micro-CT Analysis

Abstract

Objective

To evaluate and compare volumetric changes in sealers and porosity of root canals filled with bioceramic, silicone bioactive glass-based, and epoxy resin-based sealers over 60 days.

Materials and Methods

Eighty extracted mandibular premolars were instrumented with ProTaper Next files (size 40/06) and randomly assigned to five groups (n = 16), each canal filled with one of the following sealers: AH Plus Jet (AHP Jet), GuttaFlow Bioseal (GFB), CeraSeal (CS), EndoSequence BC (ES BC), and AH Plus Bioceramic (AHP Bioceramic). All canals were obturated using the matched single-cone technique. The change in sealer volume and porosity was assessed by micro-CT (n = 10/group) at 2, 30, and 60 days post-obturation. Scanning electron microscopy (SEM) evaluated interfacial adaptation at each time point (n = 2/group/time).

Statistical Analysis

Sealer volumetric changes, open, and total pores were normally distributed (Shapiro–Wilk test, p > 0.05). Two-way repeated measures ANOVA evaluated the interaction between sealer type and post-obturation time on sealer volumetric change and porosity. One-way ANOVA compared differences among sealers at each time point. Changes within each sealer over time were assessed using paired t-tests for two time points or repeated measures ANOVA with Bonferroni post hoc tests for comparisons involving three time points. Kruskal–Wallis and Friedman tests analyzed the closed pores.

Results

After setting, AHP Jet exhibited volumetric shrinkage, whereas bioceramic and silicone bioactive glass-based sealers showed volumetric expansion; however, statistically significant volumetric changes beyond 30 days were observed only for GFB (p = 0.011). Regarding porosity, bioceramic and bioactive glass-based sealers demonstrated significant reductions from 2 to 30 days (p < 0.05), with reductions observed across all time points in GFB (p < 0.05), whereas AHP Jet showed a significant increase over time (p < 0.05). SEM showed good sealer–dentine adaptation, and a more homogeneous interface was found in GFB and bioceramic sealers over time.

Conclusion

Within the limitations of this study, bioceramic and silicone bioactive glass-based sealers showed volumetric expansion and reduced porosity after obturation, whereas the epoxy resin-based sealer exhibited volumetric shrinkage with increased porosity.

Keywords

bioceramic - endodontics - micro-computed tomography - porosity - root canal sealer

Introduction

The long-term success of root canal treatment relies on a durable, three-dimensional filling within the root canal system that prevents reinfection and creates an appropriate environment for periapical tissue healing.[1] Due to the complexity of root canal anatomy, root canal sealers are used to provide a reliable seal by filling irregular spaces, lateral and accessory canals, and adhering to the dentine wall.[2] Among the critical properties of a root canal sealer, dimensional stability is important, as shrinkage can lead to gap formation and bacterial leakage,[3] while excessive expansion, though potentially improving adaptation, may exert stress on the root structure and risk fracture.[4]

The recent development of injectable premixed bioceramic sealers, such as Endosequence BC (ES BC; Brasseler, United States), CeraSeal (CS; Meta Biomed, Korea), and AH Plus Bioceramic (AHP Bioceramic; Dentsply Sirona, United States), is based on calcium silicate chemistry and offers ready-to-use formulations. Upon contact with tissue fluids, they form hydroxyapatite and calcium hydroxide, enabling chemical bonding to dentine and promoting healing.[5] These sealers exhibit superior physicochemical and biological properties, including biocompatibility, dimensional stability, high radiopacity, and antibacterial effects.[2] [6] GuttaFlow Bioseal (GFB; Coltene, Switzerland), a silicone-based material containing bioactive glass, promotes bonding and exhibits hydrophilic behavior, making it a promising alternative to traditional sealers.[7] [8] After setting, both bioceramic and silicone bioactive glass-containing sealers typically exhibit expansion due to continuous hydration reactions and absorption.[7] [9] [10] [11] Although this expansion may contribute to superior sealing ability,[12] [13] it also generates internal stress and risks root fracture.[14] Therefore, evaluating dimensional changes over time is essential to determine the clinical safety and performance of these materials.

Despite material advancements, residual porosity and interfacial gaps may still persist after obturation. These voids present clinical concerns, as they provide pathways for microbial colonization and migration toward the periapical region, potentially leading to treatment failure.[15] [16] The formation and distribution of such porosity are closely associated with the properties and volumetric changes of sealers.[3] Although previous studies have investigated the dimensional stability or porosity of root canal sealers, most evaluations have been limited to short observation periods or have focused on a single outcome parameter.[17] [18] Consequently, the time-dependent relationship between volumetric changes and porosity of different classes of root canal sealers remains insufficiently characterized.

Addressing this gap, the objective of this study was to evaluate the time-dependent volumetric changes and porosity of root canal fillings obturated with bioceramic, silicone bioactive glass-based, and epoxy resin-based sealers using micro-computed tomography (micro-CT). Accordingly, sealer behavior was assessed at early, intermediate, and longer-term time points following obturation to characterize time-dependent dimensional changes. The null hypotheses were that: (1) no significant differences would be observed among the sealers, and (2) no temporal changes would occur within each sealer group across the evaluation periods.

Materials and Methods

Experimental Design

A controlled multifactorial study was designed to investigate the effects of sealer type and post-obturation time on the volumetric changes of sealer and porosity. Two factors were evaluated: (1) sealer type: control AH Plus Jet (AHP Jet) and experimental (GFB, CS, ES BC and AHP Bioceramic; shown in [Table 1]); and (2) post-obturation time: 2 days (baseline after initial setting), 30 days (intermediate evaluation in accordance with ISO 6876:2001), and 60 days (longer-term assessment using an equivalent interval following the 30-day evaluation). All procedures were performed with a single operator to minimize technique-related variability.

Table 1 Root canal sealers, manufacturers, compositions, and LOT numbers

Sealer	Composition	Manufacturer	LOT number
AH Plus Jet (AHP Jet)	Paste A: epoxy resin, calcium tungstate, zirconium oxide, aerosil, iron oxide. Paste B: adamantane amine, dibenzyl-5-oxanonane, TCD-diamine, calcium tungstate, aerosil, and zirconium oxide.	Dentsply Sirona, USA	2301000708
GuttaFlow Bioseal (GFB)	Heptane, polydimethylsiloxane, bioactive glass ceramic, zirconia dioxide, nano-silver particle, paraffin oil, hexachloroplatinic and silicic acid, platinum catalyst, gutta-percha, zinc oxide	Coltene, Switzerland	M42977
CeraSeal (CS)	Zirconium dioxide, dicalcium and tricalcium silicate, tricalcium aluminate, and thickening agents	Meta Biomed, Korea	CSL2404271
Endosequence BC (ES BC)	Calcium silicates, calcium phosphate, zirconium oxide, filler, calcium hydroxide, and thickening agents	Brasseler, USA	23003SP
AH Plus Bioceramic (AHP Bioceramic)	Dimethyl sulfoxide, zirconium dioxide, tricalcium silicate, thickening agent, lithium carbonate	Dentsply Sirona, USA	KI230069

Sample Size Calculation

The sample size was calculated using G^*Power version 3.1.7 (Heinrich Heine University, Düsseldorf, Germany) for a two-way repeated measures ANOVA with five groups and three time points (2, 30, and 60 days). Based on standard conventions in biomedical research, parameters included a medium effect size of 0.25, α = 0.05, power = 0.80, correlation among repeated measures (r = 0.5), and nonsphericity correction (ε = 1). A minimum of nine specimens was required per group. To strengthen support subgroup analysis, 10 specimens per group were used. For scanning electron microscopy (SEM) evaluation, two teeth per group were included at each time point, resulting in a total of 80 teeth.

Sample Collection

Eighty single-rooted mandibular premolars extracted from orthodontic patients aged 15 to 25 years and disinfected in 0.1% thymol. Buccolingual and mesiodistal angulation radiographs evaluated root canal anatomy. Teeth with closed apices, root length 13 to 16 mm, a single canal with < 20 degrees curvature were included. Specimens with caries, resorption, and calcifications were excluded. Crowns were sectioned using a precision cutting machine with continuous water cooling to standard 13 to 13.5 mm root lengths. The root canal geometry at the sectioned surface was evaluated at 80× magnification with a digital microscope (Olympus, Tokyo, Japan) to exclude flattened canals.[19] Samples with an initial apical foramen larger than size 20 K-file were discarded to minimize canal volume variability.

Root Canal Preparation and Obturation

A size 15 K-file (Dentsply Maillefer, Switzerland) was inserted into the root canal until visible at the apical foramen. The working length was established by positioning the file 0.5 mm short of this point. Canals were prepared using ProTaper Next and X-Smart Endo motor (Dentsply Maillefer, Switzerland). The preparation started with X1 (17/04), followed by X2 (25/06), X3 (30/07), and finished with X4 (40/06). Following each file, the root canal was irrigated with 2 mL of 2.5% NaOCl (MDent, Thailand) using a 30-gauge needle. The smear layer was eliminated using 2 mL of 17% EDTA (MDent, Thailand), followed by 2 mL of 2.5% NaOCl, and finally rinsed with 10 mL of deionized distilled water.[20]

All roots were randomly divided into five groups (n = 16), according to the sealer: AHP Jet, GFB, CS, ES BC, or AHP Bioceramic. To remove excess irrigant while maintaining a moist canal environment suitable for bioceramic sealer hydration, the root canal was blot-dried with absorbent paper points,[21] then obturated using the matched single-cone technique. To standardize sealer delivery rate and needle position within the root canal, all sealers were delivered using a 24-gauge intracanal needle rather than manufacturer-provided tips until the canal was filled. Then, a prefitted 40/06 gutta-percha cone was coated with sealer and inserted to the established working length. During obturation, a gentle in-and-out motion in pecking motions was applied until the sealer puff was observed at the apical foramen, ensuring consistent sealer distribution along the canal walls. The excess gutta-percha was trimmed and slightly compacted, creating a cavity approximately 1 mm deep for subsequent restoration with glass ionomer cement (GC Asia, Japan). Radiographs were used to evaluate the obturation quality, and completely filled canals were included in the subsequent procedures. For sealer setting, samples were wrapped in moist gauze soaked with 2 mL of phosphate-buffered saline and stored at 37°C with 100% humidity.

Determination of the Volumetric Change of Sealer and Porosity

After obturation, 50 samples (n = 10/sealer) were scanned using micro-CT (Neoscan BVBA, Mechelen, Belgium) to assess the volumetric sealer and porosity distribution. Each sample was marked on the outer surface of the coronal region to ensure consistent orientation, then vertically mounted in a standardized position on a customized plastic cylinder for scanning at multiple axial levels. Scanning was performed at three time points: 2 days post-obturation to determine initial sealer and pore volume, 30 days to assess volumetric changes, and 60 days for final reassessment. The scanning was performed at 101 kV, 159 µA, 395 ms exposure time, 360 degrees reconstruction with a 0.2 degrees rotation step, and an isotropic resolution of 10 µm.[22] A 0.5 mm-thick copper filter was used to enhance image quality. Micro-CT parameters and scanning duration remained constant across all samples, generating 1,300 to 1,350 axial cross-sections per sample.

Following scanning, the 3D projection of samples was reconstructed using Dragonfly 3D software (Objective Research Systems, Montreal, Canada) with an image spacing of 10 µm. The root canal, beneath the glass ionomer restoration, was divided into apical, middle, and coronal regions. Based on the grayscale differentiation of dentine and filling materials, the root canal was located as the region of interest. Then the threshold values of root canal sealer, gutta-percha, and porosity were manually set within a range of 0 to 255 and verified by comparing raw and thresholded images. The segmentation and thresholding procedures remained consistent across samples for comparability. Following segmentation, the volume of sealer, gutta-percha, and porosity in each root region was quantified (mm³) using Dragonfly 3D software. The total pores were categorized as either open or closed pores based on their contact with dentine. Closed pores were defined as those located between the gutta-percha and sealer or within the sealer itself, without any contact with dentine. Open pores were determined as those situated between the dentine and either the sealer or gutta-percha.[23] For accurate classification, a comprehensive root canal image was reassessed to exclude the overlap between open and closed pores.

Quantitative analysis was performed to calculate the percentage of pores and the volumetric change of the sealer over time, using the following equations:

The percentage of pores was calculated using the formula:

Percentage of pores volume (%) = (Volume of pores/Volume of root canal) × 100%

The percentage change in sealer volume (Vc) was calculated as:

V_c = [(V₂ − V₁)/V₁] × 100%

Where V₁ represents the sealer volume at 2 days post-obturation, and V₂ represents the sealer volume at either 30 or 60 days post-obturation.

Analyzing the Adhesive Interface Quality

Following obturation, 30 samples were used for SEM analysis to assess the adhesive interface quality (n = 6/sealer). For each group, six samples were randomly allocated to three time points post-obturation (2, 30, and 60 days; n = 2/time point) to evaluate alterations in the adhesive interface. After completion of the designated storage, roots were horizontally sectioned using a 0.3 mm-thick diamond disc under water cooling. For each sample, three 1 mm-thick root slices at 2, 6, and 10 mm from the apex were obtained, corresponding to the apical, middle, and coronal regions. The coronal-facing surface of each slide was polished sequentially with 600-, 800-, and 1,500-grit sandpaper, followed by 2 minutes of ultrasonic cleaning to remove surface debris. Dehydration was performed according to standard SEM preparation protocol through sequential immersion in ethanol (25%, 50%, 75%, and 100%), followed by 24-hour storage in a desiccator.[24] Sections were mounted on aluminum stubs and sputter-coated for SEM analysis (SU3800, Hitachi, Japan). The root canal was divided into four equal regions: mesiobuccal, mesiolingual, distobuccal, and distolingual. Magnification was subsequently increased to 200 × , 600 × , and 1,000× for adhesive interface analysis in each region.

Data Analysis

Shapiro–Wilk test revealed that sealer volumetric change, open pores, and total pores distribution were normally distributed (p > 0.05). Two-way repeated measures ANOVA evaluated the effects of sealer type and post-obturation time interaction on sealer volumetric change and porosity. One-way ANOVA followed by Tukey and Games-Howell compared differences among sealers at each time point. Changes within each sealer over time were assessed using repeated measures ANOVA. Post hoc comparisons were conducted using paired t-tests for two time points and the Bonferroni test for comparisons involving three time points. Due to the nonparametric distribution, closed porosity was analyzed using the Kruskal–Wallis and Friedman tests.

Results

Statistical analyses revealed significant interactions between sealer type and post-obturation time on sealer volumetric change (p < 0.001) and total pores distribution (p = 0.04).

Volumetric Change of Root Canal Sealers

After setting, AHP Jet exhibited a volume reduction, while GFB, CS, ES BC, and AHP Bioceramic showed volume increases ([Fig. 1]). A significant difference in volumetric changes was found between sealers at both 30 and 60 days (p < 0.001). AHP Bioceramic exhibited the greatest volumetric expansion at both time points (1.47 ± 0.20% and 1.88 ± 0.53%, respectively), followed by GFB, CS, and ES BC. In contrast, AHP Jet showed volumetric shrinkage (−0.30 ± 0.15% and −0.36 ± 0.18%, respectively).

Fig. 1 Volumetric changes (V_C, %; mean ± SD) of different root canal sealers at 30 and 60 days post-obturation (n = 10/group). Different uppercase and lowercase letters indicate significant differences among sealers at 30 and 60 days, respectively (one-way ANOVA followed by Tukey and Games-Howell post hoc test, p < 0.05). Asterisk (^*) denotes a significant difference within the same sealer between time points (paired t-test, p < 0.05). AHP Jet, AH Plus Jet; GFB, GuttaFlow Bioseal; CS, CeraSeal; ES BC, Endosequence BC; AHP Bioceramic, AH Plus Bioceramic.

From 30 to 60 days, only GFB demonstrated a statistically significant volumetric increase (p = 0.011), while no significant changes were observed in AHP Jet (p = 0.114), CS (p = 0.123), ES BC (p = 0.188), and AHP Bioceramic (p = 0.051).

Alteration of Porosity Post-obturation

Across all time points, GFB demonstrated significantly higher both open and total porosity than CS and ES BC (p < 0.05). In terms of temporal progression, CS, ES BC, and AHP Bioceramic showed significant reductions in both open and total porosity from day 2 to 30 (p < 0.05), with no further changes thereafter ([Table 2]). GFB demonstrated a consistent and significant reduction across all time points (p < 0.05). In contrast, AHP Jet exhibited a significant increase in total porosity from day 2 to 60 (p < 0.05), with a significant increase in open pores observed only at day 60.

Table 2 Open, closed, and total pore volume (%) of different root canal sealers at 2, 30, and 60 days post-obturation

	AHP Jet	GFB	CS	ES BC	AHP Bioceramic
Open pores (mean ± SD)
2 d	1.65 ± 1.17ABa	2.65 ± 0.45Ba	1.09 ± 0.40Aa	0.99 ± 0.43Aa	2.11 ± 0.51Ba
30 d	1.78 ± 1.21ABab	2.23 ± 0.40Bb	0.92 ± 0.39Ab	0.81 ± 0.39Ab	1.63 ± 0.51Bb
60 d	1.87 ± 1.22ABb	2.15 ± 0.42Bc	0.84 ± 0.30Ab	0.77 ± 0.36Ab	1.51 ± 0.59Bb
Closed pores (median, IQR)
2 d	0.14 (0.22)	0.24 (0.51)	0.05 (0.50)	0.09 (0.43)	0.15 (0.17)a
30 d	0.18 (0.27)	0.20 (0.71)	0.05 (0.43)	0.12 (0.44)	0.09 (0.12)b
60 d	0.10 (0.14)	0.19 (0.72)	0.02 (0.52)	0.15 (0.43)	0.09 (0.11)b
Total pores (mean ± SD)
2 d	1.80 ± 1.16ABa	2.99 ± 0.56Ba	1.36 ± 0.71Aa	1.23 ± 0.64Aa	2.28 ± 0.53Ba
30 d	1.99 ± 1.20ABb	2.57 ± 0.57Bb	1.14 ± 0.64Ab	1.07 ± 0.63Ab	1.74 ± 0.55Ab
60 d	2.01 ± 1.21ABb	2.46 ± 0.55Bc	1.11 ± 0.61Ab	1.04 ± 0.60Ab	1.60 ± 0.60Ab

Abbreviations: AHP Bioceramic, AH Plus Bioceramic; AHP Jet, AH Plus Jet; CS, CeraSeal; ES BC, Endosequence BC; GFB, GuttaFlow Bioseal.

Note: Data are presented as mean ± SD for normally distributed variables and as median (interquartile range) for nonnormally distributed variables, according to the results of normality testing. Detailed descriptive statistics are provided in [Supplementary Table S1] (available in the online version only). In the same row, different superscript uppercase letters (A, B, C) indicate statistically significant differences between sealers, based on one-way ANOVA with the Games–Howell post hoc test (p < 0.05). In the same column, different lowercase letters (a, b, c) denote statistically significant differences among the three time points within the same sealer, as determined by repeated-measures ANOVA with Bonferroni correction for open and total pores, or by Friedman and Wilcoxon signed-rank tests for closed pores (p < 0.05).

A significant difference in closed pores was not observed among sealers across three time points (p > 0.05). Only AHP Bioceramic showed a statistically significant reduction in closed pores post-obturation (p = 0.037).

Micro-CT images corroborated the quantitative findings. GFB consistently exhibited high levels of open pores across all time points ([Fig. 2D–F]). A progressive reduction in porosity was observed in GFB, CS, ES BC, and AHP Bioceramic ([Fig. 2D–O]), whereas AHP Jet showed a gradual increase in both open and closed pores, most prominently at 60 days ([Fig. 2A–C]).

Fig. 2 The micro-CT images illustrate the alteration of the filling materials and pores at 2, 30, and 60 days post-obturation. Blue illustrates sealer; yellow illustrates gutta-percha, red illustrates open pores, and black illustrates closed pores. (A–C) Root canals were obturated using AHP Jet. (D–F) Root canals were obturated using GFB. (G–I) Root canals were obturated using CS. (J–L) Root canals were obturated using ES BC. (M–O) Root canals were obturated using AHP Bioceramic. AHP Jet, AH Plus Jet; GFB, GuttaFlow Bioseal; CS, CeraSeal; ES BC, Endosequence BC; AHP Bioceramic, AH Plus Bioceramic.

Adhesive Interface Observation

SEM evaluation revealed generally good sealer–dentine adaptation across all sealers. Porosities and interfacial gaps were more frequently observed in the coronal and middle thirds than in the apical third ([Fig. 3]), with GFB showing a higher prevalence of voids and gaps in representative sections ([Fig. 3F1, D3]). At the 30- and 60-day evaluations, specimens obturated with GFB, CS, ES BC, and AHP Bioceramic commonly exhibited a relatively homogeneous sealer–dentine interface. Because SEM analysis was performed on different specimens at each time point, these observations are qualitative and should be interpreted with caution when considering temporal changes.

Fig. 3 Representative SEM images of the adhesive interface in the distobuccal root canal region at apical, middle, and coronal thirds (1,000× magnification) at 2, 30, and 60 days post-obturation. (A–C) AHP Jet; (D–F) GFB; (G–I) CS; (J–L) ES BC; (M–O): AH Plus Bioceramic. Numbers 1, 2, and 3 denote 2-, 30-, and 60-day post-obturation time points, respectively. The black and yellow arrows indicate the presence of open and closed pores in the root canal, respectively. GP, Gutta-percha; DE, dentine; S, root canal sealer; AHP Jet, AH Plus Jet; GFB, GuttaFlow BioSeal; CS, CeraSeal; ES BC, Endosequence BC; AHP Bioceramic, AH Plus Bioceramic.

Discussion

The present study provides insight into the volumetric behavior and porosity characteristics of different root canal sealers following obturation, highlighting material- and time-dependent differences in dimensional stability and porosity. Accordingly, the null hypotheses were rejected.

The differences in open and total porosity among sealers highlight the role of material properties in maintaining root canal sealing. While total porosity reflects the overall void content, open porosity represents the pathways for bacterial penetration.[18] GFB exhibited the highest porosity, likely due to its limited wettability, low fluidity, short setting time, and gutta-percha particles that reduced dentine adaptation ([Fig. 3D1]).[10] [25] CS and ES BC with low viscosity, extended setting time, and high wettability enhance dentine adaptation and reduce pore formation ([Table 2]).[4] [23] [25]

This study provides new insights into sealer volumetric changes over 60 days post-obturation. Epoxy resin-based sealers are known to undergo polymerization shrinkage primarily during the early setting phase due to crosslinking between epoxide rings and amine.[26] In this study, AHP Jet exhibited volumetric reduction at 30 days (−0.30 ± 0.15%) with only a marginal additional decrease at 60 days (−0.36 ± 0.18%), suggesting that most shrinkage likely occurred during the initial polymerization stage, with minimal further dimensional change over time.[10]

With respect to calcium silicate-based sealers, the present findings demonstrate their volumetric behavior up to 60 days post-obturation. Although minor volumetric increases were observed in all bioceramic sealers at 60 days, these changes were not statistically significant compared with the 30-day evaluation, indicating relative volumetric stability beyond 30 days under the conditions of this study. Any early volumetric changes observed in calcium silicate-based sealers may be associated with hydration reactions initiated during the initial setting phase, in which residual moisture within the sealed root canal environment facilitates the formation of hydration products along the sealer–dentine interface.[27] [28] [29] Differences in material formulation, including relatively low dicalcium silicate content (7–15%), may also partly contribute to the observed long-term volumetric behavior.[11] [30] [31] Accordingly, mechanistic interpretations should be confined to early post-obturation reactions rather than progressive changes over time. Future studies employing dynamic fluid-exchange models may further clarify whether later-stage volumetric behavior differs under conditions allowing continuous moisture availability.

By comparison, GFB exhibited a significant volumetric expansion over time, observed at both 30 days (0.93 ± 0.31%) and 60 days (1.16 ± 0.37%). Although the polydimethylsiloxane matrix and gutta-percha components are dimensionally stable after setting, the presence of bioactive calcium silicate-based fillers may contribute to dimensional changes of GFB through hydration reactions initiated during the early post-obturation phase.[9] [10] Moreover, the relatively high open porosity observed in GFB ([Fig. 2D–F]) may permit internal redistribution of residual moisture within the material matrix, allowing delayed progression of hydration-related reactions rather than continuous external fluid uptake. This material-specific behavior may account for the significant volumetric increase observed between 30 and 60 days (p = 0.011).[9]

These material-specific volumetric changes were closely associated with corresponding alterations in porosity distribution across all groups (p < 0.05). Both GFB and bioceramic sealers exhibited reductions in open and total porosity after setting. This behavior may be attributed to sealer volume gain associated with crystallization and hydration reactions initiated by residual intracanal moisture during the early post-obturation phase,[9] [11] [28] [29] leading to progressive pore filling and closure. These findings are consistent with previous studies reporting porosity reduction in calcium silicate-based sealers over time.[18] [23] Conversely, AHP Jet demonstrated increased porosity, likely due to polymerization shrinkage and subsequent interfacial debonding, leading to marginal gap formation.[32]

Based on the findings, bioceramic sealers and GFB demonstrated expansion and a decrease in open porosity. These results are clinically relevant, as open pores can serve as potential pathways for reinfection. CS and ES BC may be suitable materials due to slight expansion and consistently low open porosity. However, prolonged contact between the apical foramen and the storage medium may influence the solubility behavior of calcium silicate-based sealers, potentially contributing to localized reappearance of porosity at the apical region over time ([Fig. 2L]).[17] The influence of root canal geometry on porosity distribution when using the matched single-cone technique has been previously reported. In wider canals or coronal regions, reduced hydraulic pressure during insertion of prefitted gutta-percha cones may be associated with less intimate sealer adaptation and a higher prevalence of porosity ([Figs. 2M–O] and [3F1, O1, B2, N2]).[33] [34]

This study has several limitations. As an in vitro investigation, it cannot fully replicate the clinical environment, particularly intracanal moisture dynamics and the absence of a periodontal ligament, both of which may influence stress distribution and material behavior. The presence of phosphate ions in phosphate-buffered saline promotes hydroxyapatite and calcium phosphate precipitation in calcium silicate-based sealers,[28] [29] potentially contributing to volumetric gain and porosity reduction and selectively favoring bioceramic materials over epoxy resin-based sealers; therefore, comparative outcomes should be interpreted with caution. Alternative storage media, such as deionized water, physiological saline, or artificial saliva, may provide a more balanced assessment of postsetting volumetric changes between materials.[13] In addition, the radiopacity of gutta-percha may have influenced micro-CT segmentation accuracy,[17] although consistent thresholding was applied to minimize this effect. SEM was used only to qualitatively illustrate sealer-dentine interfacial features; however, it is limited to 2D analysis, requires destructive sample preparation, and may introduce artifacts.[35] Accordingly, SEM findings should be interpreted as qualitative observations and should not be used to validate the micro-CT results. Finally, the greater volumetric expansion observed in GFB and AH Plus Bioceramic raises potential concerns regarding vertical root fracture,[4] warranting further long-term investigations under simulated clinical conditions.

Conclusion

The sealer volumetric changes following setting influenced the porosity distribution. Epoxy resin-based sealer showed shrinkage and increased porosity, while the bioceramic and silicone bioactive glass-based sealers reduced porosity due to their expansion.

Conflict of Interest

None declared.

Ethical Approval

This study protocol was approved by Khon Kaen University Ethics Committee, approval number [HE.672044].

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Publication History

Article published online:
13 February 2026