Effect of heat generated root canal filling techniques on bond strength of NeoSealer Flo BC, AH Plus BC and BioRoot RCS to root dentin

Abstract

This study aimed to assess the effect of heat-generated root canal filling techniques—warm vertical compaction (WVC) and core-carrier (CC)—on the bond strength of bioceramic sealers (NeoSealer Flo BC, AH Plus BC, BioRoot RCS) compared with the resin-based sealer AH Plus. A total of 168 single-rooted mandibular premolars were prepared and randomly assigned to 12 groups according to sealer type and filling technique: hydraulic condensation (HC), WVC, or CC. Push-out bond strength was tested using a universal testing machine, and failure modes were analyzed. Two-way ANOVA was used for statistical comparisons (P = 0.05). The results revealed that AH Plus BC and NeoSealer Flo BC exhibited the highest mean bond strengths across techniques. Both AH Plus and BioRoot RCS showed significantly lower bond strengths (P ≤ 0.05) when used with WVC and CC. However, no significant difference (P > 0.05) was observed for AH Plus BC and NeoSealer Flo BC between WVC and CC. These findings indicate that bioceramic sealers, AH Plus BC and NeoSealer Flo BC, maintain their bonding performance under heat stress, suggesting potential clinical advantages when heat-based obturation techniques are used.

Introduction

Effective root canal disinfection, along with the implementation of three-dimensional filling techniques utilising biocompatible materials, is pivotal to achieving successful outcomes in root canal treatments¹. Various materials and techniques have emerged in recent years, specifically developed to fulfil this essential objective^2,3. In this context, researchers have devoted substantial efforts to refining root canal filling techniques, highlighting a profound commitment to innovation and continuous advancement within dentistry⁴.

Hydraulic condensation technique was once considered insufficient because of its drawbacks, including poor apical sealing and potential for leakage^2,5. The increased adoption of calcium silicate-based sealers (CSBSs) can be attributed to their numerous advantageous properties^5,6. However, it has been observed that applying heat plays a crucial role in minimising the sealer’s effectiveness porosity^7–9. This reduction occurs as the heat effectively evaporates the moisture contained within the sealer’s composition¹⁰. Thus, the porosity can compromise the seal and bond strength provided by root canal sealers. However, heat-generated techniques are expected to increase the adaptation to the canal walls and penetration into accessory canals (if present) and dentinal tubules¹¹.

CSBSs have garnered attention because of their biocompatibility, bioactivity, and dimensional stability¹². Studies showed that CSBSs are more biocompatible and have better sealing capabilities than resin-based sealers, which makes them a desirable option for root canal filling^13,14. In contrast to resin-based sealers, CSBSs exhibit hydrophilicity and remain unaffected by moisture¹⁵. CSBSs do not contract but experience minor expansion throughout the hardening process^16,17. CSBSs have been used with the hydraulic condensation technique, but literature shows they can be used with any root canal filling techniques^6,17.

BioRoot RCS (Septodont, France) is a powder–liquid CSBS that demonstrates lower cytotoxicity, reduced tissue accumulation, and notable antimicrobial activity compared with conventional sealers^3,18. Importantly, its chemical composition remains stable under heat application, supporting its suitability for various clinical techniques¹¹.

AH Plus Bioceramic sealer (Maruchi, South Korea) is a premixed CSBS containing tricalcium silicate, zirconium dioxide, dimethyl sulfoxide, and lithium carbonate^2,12. It is characterised by rapid setting, high washout resistance, and adequate radiopacity¹⁷. Previous studies have shown that warm vertical compaction does not adversely affect its physicochemical properties or bond strength to root dentin, indicating its heat resistance and compatibility with warm obturation techniques^6,18–20.

NeoSealer Flo (Avalon Nusmile, USA) is a premixed bioceramic sealer composed of tricalcium and dicalcium silicate, along with calcium aluminate–based compounds and tantalite as radiopacifiers²¹. Although its composition suggests favourable bioactivity and biocompatibility, the effects of heat-based obturation techniques on its bond strength to root dentin have not yet been investigated, highlighting a gap in the current literature.

Alberdi et al.⁶ reported that in Bio-C Sealer, CeraSeal, and BioRoot RCS, the heat generated by warm vertical compaction (WVC) and core-carrier (CC) techniques did not influence adhesion to dentin. According to Camilleri et al.¹¹, experimental Septodont sealer is recommended for obturations using cold laterally condensed gutta-percha, whereas MTA Fillapex and Apexit Plus were suitable with WVC root canal filling technique. Al-Hiyasat et al.¹⁸ found that warm vertical compaction technique decreased the bond strength of AH Plus but did not affect TotalFill BC sealer. Atmeh et al.¹⁹ demonstrated that the duration and temperature of heat application can alter the chemical structure of epoxy resin–based sealers, which may explain the reduced bond strength observed with AH Plus under heat generated root canal filling techniques. Similarly, Dewi et al.²⁰ reported that the heat-based technique did not negatively affect the bond strength of CSBSs, whereas AH Plus exhibited significantly lower bond strength. There are few studies about effect of heat on the bond strength of CSBSs and dentin. Thus, the aim of the present study was to compare the impact of heat generated root canal filling techniques (warm vertical and core-carrier) on the bond strength of NeoSealer Flo BC, AH Plus BC and BioRoot RCS to root dentin compared to AH Plus. The null hypothesis tested was that the type of sealer and obturation technique would not significantly affect bond strength.

Materials and methods

Specimen selection and initial preparation

The present study received approval from the Non-Interventional Ethics Committee of the Faculty of Health Sciences, Marmara University (Approval Number: 2024/54). All methods were performed in accordance with the relevant guidelines and regulations, including the ethical standards of the Declaration of Helsinki. Informed consent was obtained from all patients for the use of their extracted teeth for research purposes.

The materials and compositions used in the study are shown in Table 1. CSBSs (AH Plus BC; Maruchi, Wonju, South Korea; NeoSealer Flo BC; Avalon Biomed Inc., Bradenton, FL, USA; BioRoot RCS; Septodont, Saint-Maur-des-Fossés, France) and a resin-based sealer (AH Plus resin sealer; Dentsply Sirona, Bensheim, Germany) were evaluated. The sealers were combined with hydraulic condensation technique and heat generated root canal filling techniques: the warm vertical compaction and core-carrier.

Table 1.

Materials used in the study and composition declared by the manufacturer.

Material	Lot number	Manufacturer	Composition
BioRoot RCS	B13365	Septodont; Saint-Maur-des-Fosses Cedex, France	Powder-Liquid Powder: tricalcium silicate, zirconium oxide, and povidone Liquid: aqueous solution of calcium chloride and polycarboxylate
NeoSealer Flo	2020110502	(Avalon Nusmile, USA)	Tantalite (50%), tricalcium silicate (25%), calcium aluminate (25%), dicalcium silicate (10%), tricalcium aluminate (5%), calcium sulfate (1%), PEG *, grossite *
AH Plus Bioceramic	KI211103	(Maruchi, South Korea)	Zirconium dioxide (50–70%), tricalcium silicate (5–15%), dimethyl sulfoxide (10–30%), lithium carbonate (0.5%), thickening agents (< 6%)
AH Plus	2109000972	(Dentsply, Germany)	Paste A: diepoxide, calcium tungstate, zirconium oxide, aerosil, pigment (iron oxide) Paste B: 1-adamantane amine, N,N0 -dibenzyl-5-oxa-nonandiamine-1,9, TCD-diamine, calcium tungstate, zirconium oxide, aerosil, silicone oil

Inclusion criteria were defined as teeth with a single root canal, fully developed apex, and straight roots. Teeth that had undergone endodontic treatment, resorption defects, the presence of cracks or fractures, complex root canal anatomy, and any previous procedures were excluded from the study. All specimens were carefully examined under a stereomicroscope (Leica Microsystems, Wetzlar, Germany) at 20× magnification to detect the presence of cracks or fractures. 168 single-rooted mandibular premolar teeth extracted for reasons unrelated to this current study were used (such as periodontal or orthodontic indications). All teeth included in the study were extracted within the last 6 months prior to the experimental procedures. After extraction, the teeth were cleaned of soft tissue debris and stored in distilled water until use. The storage medium was changed weekly. The bucco-lingual and mesio-distal 2D radiographic images were taken to verify that the single-rooted teeth possessed only one root canal. After coronal access, apical patency of the canal was checked using an operating microscope with under 20× magnification (Leica Microsystems). A #10 K-file (Dentsply Maillefer, Ballaigues, Switzerland) was inserted into the root canal and positioned at the major apical foramen. The working length was determined by subtracting 1 mm from the measured length.

Root canal instrumentation

All samples were evaluated for apical root canal morphology according to the established procedure. The preparation diameter was gradually increased using Neolix EDM files (Neolix SAS, Évron, France), achieving a final apical taper of #40.04 (F4). The irrigation was performed with 2 mL of 3% sodium hypochlorite after each instrument application. This was followed by irrigation with 3 mL of 17% EDTA with ultrasonic activation for one minute using the UltraX ultrasonic irrigation system (Eighteeth, Changzhou, China) with a size 20 non-cutting polymer tip, positioned 1 mm short of the working length without contacting the canal walls, in accordance with the manufacturer’s recommended power setting. Subsequently, an additional 3 mL of 3% sodium hypochlorite was applied with ultrasonic activation for 1 min. The process was completed with a final rinse using 5 ml of sterile distilled water for 30 s. Irrigation was carried out using a 27-gauge side ported needle (Ultradent Products Inc., South Jordan, Utah, USA) to ensure effective delivery of irrigants. The canal was then dried with sterile #40 paper points before an F4 gutta-percha cone (Dentsply Maillefer) was selected and assessed for its fit with the master apical file.

Root canal filling procedures

A trained operator prepared all of the samples (A.A.). The teeth were numbered, and then samples were randomly allocated to subgroups using randomizer software (www.randomise.com). The teeth were then randomly divided into four groups of 42 each, according to the sealer type (NeoSealer Flo BC, AH Plus BC, BioRoot RCS, AH Plus). Each group was then divided into 3 subgroups (n = 14) according to the filling technique (HC, WVC, CC).

In the HC technique, the sealers were first applied to the root canal from the apex to the canal orifice with an intracanal tip for NeoSealer Flo BC and AH Plus BC groups. A thin layer of sealer was then coated onto the master cone, which was then carefully inserted into the canal until it reached the working length. For the BioRoot RCS and AH Plus groups, the root canals were obturated using a single master cone technique. A thin layer of sealer was applied onto the master cone, which was then carefully inserted into the canal until reaching the established working length. Then, the cone was removed from the coronal excess gutta-percha and vertically compacted using a Buchanan plugger (SybronEndo; Glendora, CA, USA).

For the WVC technique, the Calamus Dual heated Plugger M (Dentsply Maillefer) was operated at 200 °C and inserted 5 mm short of the working length, with heat applied for 2–3 s to soften the gutta-percha. Vertical condensation was performed using a cold Buchanan plugger, followed by backfilling of the middle and coronal thirds with thermoplasticized gutta-percha at the same temperature.

The Thermafil system utilises CC technique. The procedure begins with coating the canal walls with a sealer. According to the manufacturer’s instructions, GuttaCore obturators (#40) were heated in a ThermaPrep oven (Dentsply Maillefer) using the preset heating cycle, which provides a standardized temperature profile (approximately 130–150 °C) independent of obturator size. Once the obturator is inserted, any excess gutta-percha and carrier material above the canal opening is removed. Finally, the obturation mass is trimmed at the canal orifice for a precise finish.

Following radiographic imaging confirmation of proper canal filling, the samples were wrapped in gauze soaked in sterile distilled water and stored in an incubator set at 37 °C with 100% humidity for two weeks. This ensured the complete setting of the sealer.

Evaluation of bond strength

Using a water-cooled MicroDisc NH 6P cutting machine (DHUC, Buenos Aires, Argentina), each root was sectioned perpendicular to its long axis, 4 mm from the working length. A single slice, 1 mm thick and 4 mm coronal from the working length, was obtained from each specimen. The apical region of the slices was designated prior to the examination. Force was applied from the apical to the coronal regions of the sections to test them. Using a push-out bond test, a universal testing machine (Autograph AGS-X, Shimadzu, Kyoto, Japan) was used to analyse the obtained sections. For the purpose of ensuring that the pin diameter was verified to be approximately 0.80 times the filler diameter²⁹, the 0.8 mm diameter pin was used to apply a compressive force at a crosshead speed of 0.5 mm/min. The specimens were positioned with their apical portions facing the punch tip to avoid any structural interference that might result from root canal taper. The apical and coronal diameters of each slice were calculated under a stereomicroscope (Leica Microsystems).

The force required to dislodge the filling material from the dentin wall was measured in Newtons (N) and divided by the adhesion surface area (mm²) to determine the bond strength expressed in megapascals (MPa). The adhesion surface area was calculated using the following formula^26,27.

.

In this formula, R refers to the mean radius of the coronal canal, r denotes the mean radius of the apical canal, and h represents the thickness of the slice.

Analysis of failure modes

Following the completion of the push-out test, the sections were examined under a light microscope at 100× magnification. Photographs were taken, and the samples were categorized based on their failure modes. Adhesive failure was defined as the complete separation of the sealer from the dentin, indicating no adhesion between the two surfaces (Fig. 1a). Non-adhesive failures include cohesive failures (Fig. 1b) inside the sealer or mixed failures that combine cohesive and adhesive failures (Fig. 1c). The evaluation was carried out independently by two experienced examiners (S.Ö. and A.B.) who were blinded to the obturation technique and sealer type. Prior to assessment, all specimens were coded by an independent researcher not involved in the evaluation process to ensure blinding. Inter-examiner reliability was assessed using Cohen’s kappa coefficient to determine the level of agreement between the two evaluators. The agreement was interpreted according to established criteria, and a high degree of inter-examiner agreement was observed. In cases of disagreement, the examiners re-evaluated the specimens together and reached a consensus decision, which was used for the final analysis.

Fig. 1.

(a) Adhesive failure, (b) cohesive failure, (c) mixed failure.

Statistical analysis

Data normality was checked using the Shapiro–Wilk test. A two-way analysis of variance (ANOVA) was used for statistical analysis, with bond strength as the dependent variable and sealer materials and obturation techniques as independent variables. When significant differences were found, post hoc comparisons were performed using the Tukey test. Interactions between variables were also evaluated, and statistical significance was set at P = 0.05. The analysis was conducted using IBM SPSS Statistics software (IBM Corp., Armonk, NY, USA). Failure mode distribution was analyzed using the Chi-square test (P = 0.05).

Results

Figure 2 illustrates the mean push-out bond strength values observed in the study. A two-way ANOVA was performed to evaluate the effects of obturation technique and sealer type on push-out bond strength values. Both factors had a statistically significant effect (p < 0.001 for both). Effect size analysis revealed a large effect for the root canal filling technique (partial η² = 0.436). Sealer type demonstrated a very large effect size (partial η² = 0.570). The interaction between root canal filling technique and sealer type was also statistically significant (p < 0.05) and showed a moderate effect size (partial η² = 0.106), indicating that the effect of the filling technique on bond strength varied depending on the sealer used (Table 2). Estimated marginal means with 95% confidence intervals were calculated to facilitate the interpretation of the magnitude and clinical relevance of the observed differences between groups.

Fig. 2.

Mean and standard deviation (mPa) of the push-out bond strength of the root canal filling techniques with sealers.

Table 2.

Two-way ANOVA; push-out bond strength in relation to sealer type and root Canal filling technique. Df, degrees of freedom; F, F-statistic; sig: P value.

Source	Type III sum of squares	df	Mean square	F	Sig.	Partial eta squared
Root canal filling technique	43.263	2	21.632	60.238	< 0.001	0.436
Sealer type	74.090	3	24.697	68.774	< 0.001	0.570
Root canal filling technique * sealertype	6.711	6	1.118	3.115	< 0.05	0.106
Error	56.020	156	0.359
Total	1888.075	168
Corrected total	180.084	167

(a) R Squared = 0.689 (Adjusted R Squared = 0.667).

(b) Computed using alpha = 0.05.

WVC root canal filling technique group, AH Plus (2.01 ± 0.49 MPa) and BioRoot RCS (2.66 ± 0.53 MPa) demonstrated lower bond strength values compared to AH Plus BC (3.61 ± 0.56 MPa) and NeoSealer Flo BC (4.22 ± 1.00 MPa). There were no statistically significant differences among AH Plus BC and NeoSealer Flo BC groups in terms of bond strength to root dentin (P > 0.05).

In HC root canal filling technique group, AH Plus demonstrated lower bond strength values (2.78 ± 0.51 MPa) compared with AH Plus BC (4.22 ± 0.50 MPa), BioRoot RCS (3.95 ± 0.93 MPa), and NeoSealer Flo BC (4.39 ± 0.57 MPa). Similarly, in CC root canal filling technique group, AH Plus showed the lowest bond strength values (1.71 ± 0.38 MPa), whereas AH Plus BC (3.18 ± 0.37 MPa), BioRoot RCS (2.50 ± 0.31 MPa), and NeoSealer Flo BC (3.01 ± 0.63 MPa) exhibited higher bond strength values. No statistically significant differences were observed among AH Plus BC, BioRoot RCS, and NeoSealer Flo BC in either the HC or CC groups (P > 0.05).

For AH Plus and BioRoot RCS, both heat generated root canal filling techniques (WVC and CC) decreased bond strength to root dentin compared to HC technique. WVC and CC techniques were similar in bond strength to root dentin.

AH Plus BC and NeoSealer Flo BC present similar bond strength values to root dentin when used in HC and WVC techniques. However, AH Plus BC and NeoSealer Flo BC demonstrated lower bond strength values when used in CC technique compared to HC technique.

Failure mode analysis demonstrated an excellent inter-examiner agreement, with a Cohen’s kappa value of 0.96, indicating almost perfect concordance between the two blinded evaluators. Notably, the AH Plus/HC group exhibited a significantly different distribution of failure modes than the other groups (P ≤ 0.05). Within this group, adhesive and cohesive failures were predominantly observed, while WVC technique revealed a mix of cohesive and mixed failure modes. In contrast, CC technique was primarily characterised by mixed failure modes (Fig. 3).

Fig. 3.

Failure mode percentage distribution by group.

Discussion

Before engaging in root canal treatment, it is crucial to understand the various root canal filling techniques and their implications for the efficacy of root canal sealers^11,21,22. Despite the widespread use of calcium silicate-based sealers (CSBSs), existing literature lacks sufficient data regarding the influence of heat generated techniques on the bond strength of NeoSealer Flo BC. To the best of our knowledge, this is the first study to specifically investigate the performance of NeoSealer Flo BC when used with heat generated root canal filling techniques.

This study showed a statistically significant interaction between root canal filling techniques and sealer types, resulting in rejecting the null hypothesis. Notably, calcium silicate-based sealers (CSBSs), specifically NeoSealer Flo BC and AH Plus BC, exhibited superior bond strength compared to BioRoot RCS and the resin-based sealer AH Plus. These findings corroborate previous research highlighting the enhanced performance of CSBSs, attributing this superiority to their hydrophilic properties, dimensional stability, and heat resistance^24,25. Al-Hiyasat et al.¹⁸ also noted that CSBSs surpass resin-based sealers in effectiveness across cold and WVC techniques.

This study observed that the bond strength achieved with HC and WVC techniques did not present a significant difference for NeoSealer Flo BC and AH Plus BC. This suggests that NeoSealer Flo BC and AH Plus BC retain their structural integrity, even when subjected to heat. This finding is supported by Hadis and Camilleri¹⁶, who documented the heat resistance of AH Plus BC. Conversely, for BioRoot RCS and resin-based sealers, employing heat generated root canal filling techniques (WVC and CC) resulted in a significant decrease in bond strength when compared to the HC technique. This reduction may be attributed to the evaporation of water or the structural alterations induced by heat, particularly in the case of water-based sealers like BioRoot RCS¹¹. BioRoot RCS is a powder–liquid, water-based calcium silicate sealer whose setting reaction depends on hydration and the subsequent formation of calcium silicate hydrate and calcium hydroxide phases³. Exposure to elevated temperatures during warm vertical compaction or core-carrier techniques may accelerate water evaporation, disrupt the hydration process, and lead to increased porosity and microstructural discontinuities within the set material. These changes can compromise both the micromechanical interlocking and the chemical interaction with dentin, ultimately reducing bond strength^11,18. In contrast, NeoSealer Flo BC is a premixed, injectable calcium silicate-based sealer with a more stable formulation, incorporating organic vehicles and proprietary additives that regulate moisture availability and enhance dimensional stability during setting²¹. Its hydration reaction is less dependent on free water content and is therefore less susceptible to heat-induced dehydration. This difference in formulation and setting kinetics may explain why NeoSealer Flo BC demonstrated superior bond strength compared with BioRoot RCS under heat-based obturation techniques.

A recent study suggested that utilising the WVC technique adversely affects the bond strength of AH Plus when compared to the cold obturation technique; however, no noteworthy differences were observed regarding the CSBSs¹⁸. It is important to note that AH Plus is available in two distinct formulations. Paste A contains diepoxide, calcium tungstate, zirconium oxide, aerosil, and iron oxide pigment, while Paste B comprises dibenzyldiamine, aminoadamantane, and tricyclodecane-diamine. When the two pastes are combined for application, polyamines engage with epoxy resins, which disrupts the bond of the epoxide group and eventually induces the formation of polymers¹¹. Consistent with the current study’s findings, previous research has demonstrated that thermal influence plays a significant role in these processes¹⁸.

The current study found that adhesive failure was mainly linked to resin-based sealers used alongside the HC technique. Failure mode analysis provides insight into the integrity of the sealer–dentine interface and underlying bonding mechanisms. In the present study, adhesive failures were mainly associated with the resin-based sealer (AH Plus) used with the hydraulic condensation (HC) technique, indicating weaker interfacial adhesion to root dentin. In contrast, heat-based obturation techniques predominantly exhibited cohesive and mixed failure modes. While cohesive failures reflect fracture within the sealer, mixed failures suggest a balanced strength between the sealer material and the sealer–dentine interface, indicative of a more stable and integrated bonding system. In contrast, heat generated root canal filling techniques exhibited a higher prevalence of both cohesive and mixed failure types. In the case of NeoSealer Flo BC and AH Plus BC, significant mixed failure modes were observed regardless of the technique used. This finding suggests a more reliable performance across various clinical scenarios. These results align with the research conducted by Retana-Lobo et al.²⁵ and Alberdi et al.⁶, who also identified a predominance of mixed failures in CSBSs subjected to WVC root canal filling procedures.

WVC and CC tended to produce a more homogenous filling with reduced sealer content¹. While this may improve adaptability to canal walls and penetration into dentinal tubules^11,28, it also introduces a potential trade-off in bond strength for certain sealer types. The reduced sealer content in resin-based sealers could compromise their mechanical properties over time. Conversely, CSBSs (NeoSealer Flo BC and AH Plus BC) seem less affected by these changes, highlighting their suitability for heat-based techniques. Although NeoSealer Flo BC and AH Plus BC maintained higher bond strength values than BioRoot RCS and AH Plus under heat-based obturation techniques, a technique-dependent reduction in bond strength was observed. This reduction was less pronounced for premixed bioceramic sealers, suggesting greater resistance to thermal and mechanical stresses, whereas BioRoot RCS showed a more evident decrease in bonding performance. These findings indicate that, beyond statistical significance, the extent of bond strength reduction under heat-based techniques varies according to sealer formulation and should be considered when selecting obturation protocols in clinical practice.

Although both warm vertical (WVC) and core-carrier (CC) root canal filling techniques are classified as heat-based obturation techniques, the thermal dynamics and mechanical stresses they generate within the root canal differ substantially^12,25. In WVC, heat is applied in a controlled, intermittent, and localized manner, allowing gradual plasticization of gutta-percha while preserving the integrity of the sealer layer and maintaining continuous sealer–dentine contact¹¹. This controlled heat application appears compatible with the hydration-dependent setting reactions of calcium silicate-based sealers such as AH Plus BC and NeoSealer Flo BC. In contrast, the CC technique involves the insertion of a preheated obturator carrying a large mass of thermoplasticized gutta-percha, which delivers a more abrupt and volumetric heat transfer to the canal space^1,9. This sudden thermal exposure, combined with the hydraulic pressure generated during obturator insertion, may disrupt early-stage hydration and crystal nucleation processes critical for chemical bonding to dentine. Additionally, the carrier-driven flow of gutta-percha may mechanically displace the sealer from the canal walls, resulting in a thinner and less homogeneous sealer layer^6,9. Collectively, these thermal and mechanical factors may explain why AH Plus BC and NeoSealer Flo BC, despite demonstrating comparable bond strength under HC and WVC techniques, exhibited reduced bond strength values when used with the CC technique.

Push-out testing, as utilised in the present study, remains a widely accepted and reliable method for evaluating the bond strength of root canal sealers. Nevertheless, this method has inherent limitations, including potential variability related to sample preparation, dentine heterogeneity, and test conditions. To minimise these effects, strict standardisation protocols were applied, such as the use of single-rooted mandibular premolars with similar root dimensions and the precise calibration of push-out pins according to the root canal diameter, in line with the recommendations of Chen et al.²⁹. However, it should be acknowledged that push-out testing primarily reflects interfacial shear stress under static loading conditions and may not fully replicate the complex mechanical and thermal stresses encountered in the clinical environment. In addition, the in vitro nature of the study precludes the simulation of biological factors such as periodontal ligament support, moisture fluctuations, and long-term aging effects, which may influence sealer–dentine interactions over time. Another limitation of the present study is the absence of complementary analyses, such as microscopic evaluation of sealer penetration into dentinal tubules or chemical characterization of sealers following heat exposure. Such analyses could have provided further insight into the mechanisms underlying the observed bond strength values and the potential effects of thermal procedures on material integrity. Therefore, while the findings offer valuable comparative data under controlled conditions, they should be interpreted with caution, and future studies incorporating microscopic, chemical, and long-term aging assessments are warranted to enhance the clinical relevance of these results.

Within the limitations of this study, the following conclusions can be drawn:

1. NeoSealer Flo BC and AH Plus BC demonstrated greater push-out bond strength than alternatives.

2. The bond strength NeoSealer Flo BC and AH Plus BC exhibited comparable effects when utilising both the WVC and HC techniques.

3. Utilising WVC and CC root canal filling techniques may detrimentally affect the bond strength of resin-based sealers and BioRoot RCS. This observation highlights the complexities and potential drawbacks of these methods in endodontic procedures, suggesting careful consideration when choosing root canal filling techniques.

These findings suggest that NeoSealer Flo BC and AH Plus BC maintain superior bond strength across heat-generated root canal filling techniques, while resin-based sealer and BioRoot RCS may be more sensitive to specific techniques.

Author contributions

All authors contributed to the study conception and design. Data collection was performed by S.Ö., A.A. and A.B. Data analysis was performed by S.Ö. and H.A. The first draft of the manuscript was written by S.Ö. The manuscript was critically reviewed by HMMA, H.A. and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Funding

This research was not funded.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Consent for publication

All co-authors agreed to publication of the acquired data.

Competing interests

The authors declare no competing interests.