**1. Introduction**

An endodontically treated tooth is more prone to vertical root fracture (VRF) due to multiple contributing factors, i.e., caries or trauma, access cavity preparation, root canal instrumentation, lateral condensation force during obturation, preparation of post space and functional occlusal loading, which leads to failure [1]. VRF is considered one of the most common complications of endodontic treatment, eventually leading to extraction of the tooth [2]. It can occur during or after the root canal treatment (RCT) due to compromised tooth structure. Therefore, reinforcement of the remaining tooth structure

**Citation:** Alkahtany, M.F.; Almadi, K.H.; Alahmad, F.A.; Alshehri, A.M.; AlSwayyed, A.A.; AlZahran, O.M.; AlHadan, A.; Almustafa, A.S.; Vohra, F.; Abduljabbar, T. Influence of Root Canal Sealers and Obturation Techniques on Vertical Root Fracture Resistance. An In Vitro Experiment. *Appl. Sci.* **2021**, *11*, 8022. https:// doi.org/10.3390/app11178022

Academic Editor: Bruno Chrcanovic

Received: 27 July 2021 Accepted: 24 August 2021 Published: 30 August 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

is considered as an important aspect of endodontic treatment [3]. Available literature revealed that bonding of root filling with the radicular dentin strengthens the tooth as well as increases its fracture resistance [4,5].

Cleaned and shaped root canals obturated with Gutta-percha (GP) and root canal sealer is considered as the gold standard [6]. GP lack the capability to reinforce the weakened root structure because of their low modulus of elasticity [7]. Therefore, a root canal sealer is considered as a joint between a canal and a filling material. An ideal root canal sealer should possess the property of filling the apical and lateral empty spaces and irregularities between GP points and root dentin walls [8]. Moreover, it was also assumed that sealer, which exhibits adhesion to the canal dentin, results in reinforcement of the tooth and increases the fracture toughness against the occlusal load by conserving the integrity at the sealer–dentin interface [9]. Therefore, multiple research methodologies have introduced different canal sealers [10].

Among different sealers used recently, AH Plus (resin-based root canal sealer) is considered as a material of choice for canal obturation due to ease of handling, good mechanical properties, wettability and excellent sealing property [11]. Furthermore, it also exhibits less polymerization shrinkage, low solubility, and a high degree of stability on storage [12]. Studies have suggested that AH Plus sealer results in increased fracture resistance of endodontically treated teeth [12,13]. However, a few studies presented contradictory findings [9,14].

TotalFill BC Sealer on the other hand is a calcium-silicate based bio-ceramic root canal sealer. It is dispensed in a premixed ready-to-use injectable form that sets in the presence of water, possesses excellent antimicrobial ability, higher pH, and exceptional biocompatibility. TotalFill BC sealer can easily penetrate the dentinal tubules due to presence of nanoparticles. In addition, it does not shrink while setting and demonstrates excellent physical properties. Available literature revealed that calcium silicate based sealer reinforces the tooth structure against the VRF and strengthens the tooth. A study conducted by Ghoneim et al. [15] and Sagsen et al. [ ˇ 16] showed that bioceramic-based sealer (BC sealer) has the potential to increase the root fracture resistance [17]. In contrast, Celikten et al. reported that BC sealer has a significantly lower mean value for fracture than the control group [18].

From the available indexed literature it was found that sufficient data related to the effect of AH Plus sealer on the fracture resistance of root canal treated tooth are available. However, data on the influence of TotalFill BC sealer on fracture resistance of root treated teeth in comparison to commonly used sealers are limited. Therefore, it was hypothesized that there will be no difference in fracture resistance of roots obturated with TotalFill BC Sealer and AH Plus sealer. It was also hypothesized that there will be no difference in root fracture resistance when two different obturation techniques, i.e., lateral condensation and single cone technique, are employed. Thus, the aim of the present study was to determine the fracture resistance of roots obturated with TotalFill BC Sealer and AH Plus sealer using lateral condensation and single cone techniques in comparison to untreated controls.

#### **2. Materials and Methods**

#### *2.1. Specimen Preparation*

A total of sixty freshly extracted single rooted mandibular premolars were collected over a period of 3 months. All the teeth were stored in Hank's balanced salt solution (HBSS) till further use. All the specimens were cleaned, sterilized and made ready to examine under stereo-microscope (Stemi 2000-C, Zeiss, Wetzlar, Germany) at 50× magnification in order to exclude teeth with open apices, root caries, cracks and/or fractured roots. Any tooth with a resorption defect or previous root canal treatment was excluded. A pre-operative radiograph was taken both buccolingually and mesiodistally to confirm the presence of a single canal. De-coronation was performed at the level of CEJ with the help of a high speed hand-piece with a wheel diamond bur in order to standardize 13 mm of root length. The methodology outline is presented in Figure 1.

**Figure 1.** Flow chart for study methodology.
