Clinical and Radiographic Outcome of Non-Surgical Endodontic Treatment Using Calcium Silicate-Based Versus Resin-Based Sealers—A Systematic Review and Meta-Analysis of Clinical Studies

The aim of this paper is to systematically analyse the effect of calcium silicate-based sealers in comparison to resin-based sealers on clinical and radiographic outcomes of non-surgical endodontic treatment in permanent teeth. Methods: The study was conducted according to the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions and Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statement. The literature search was performed using PubMed/MEDLINE, Cochrane Central Register of Controlled Trials, Web of Science, DOAJ and OpenGrey with no language restrictions. Two reviewers critically assessed the studies for eligibility. Grading of Recommendations, Assessment, Development and Evaluations (GRADE) was carried out to assess the evidence. Meta-analysis of the pooled data with subgroups was carried out using the RevMan software (p < 0.05). Results: Results from the included studies showed that there were no significant differences between the groups in the 24 h post-obturation pain levels (mean difference (MD), −0.19, 95% CI = −0.43–0.06, p = 0.14, I2 = 0%), but at 48 h (MD, −0.35, 95% CI = −0.64–0.05, p = 0.02, I2 = 0%), a significant difference was observed in favour of calcium silicate sealers. Furthermore, there were no significant differences between the two sealers due to risk of onset or intensity of postoperative pain, need for analgesic and extrusion of the sealer. The heterogeneity assessed using Q test between the included studies was 97% (I2). Conclusions: Within the limitations of this review, the paper shows that calcium silicate-based sealers exhibited optimal performance with similar results to resin-based sealers in terms of average level of post-obturation pain, risk of onset and pain intensity at 24 and 48 h. The observations from the included studies are informative in the clinical evaluation of calcium silicate-based sealers and provide evidence for the conduction of well-designed, controlled randomised clinical trials for a period of at least four years in the future.


Introduction
Elimination of microorganisms is one of the prime requisites for the success of root canal treatment. Three-dimensional (3D) obturation of the root canal system plays a vital role in sealing the root canal system in order to prevent recontamination and microbial invasion. However, complete elimination of microorganisms is impossible owing to the anatomical complexity within root canal systems [1,2]. In addition, suboptimal obturation would compromise the 3D seal and might lead to endodontic failure [3,4].
Gutta percha (GP) and root canal sealer are the two main components used to achieve the desirable 3D sealing of the root canal space [5]. An ideal root canal sealer should be capable of creating an effective bond to the GP and root canal walls to prevent microleakage at the interface [6,7]. Biocompatibility and bioactivity are essential properties for root canal sealers, as these materials are in close proximation with the surrounding tissues and affect the repair [8,9]. If the sealers are biocompatible and soluble in tissue fluid, minimal extrusions could be tolerated by the peri-radicular tissues [10]. However, this outcome might also slow down or impair the healing process, or, in some cases, induce local inflammation in the periapical region [10,11]. Therefore, the selection of biomaterials is important to avoid risks of postoperative failure for nonsurgical endodontic treatment [11,12].
Epoxy resin-based root canal sealers (RBSs) are considered as the gold standard due to their optimal physicochemical properties [13]. These sealers have widely been used for decades due to their low solubility and disintegration, with adequate dimensional stability [12]. However, Kim et al. [14] reported that resin-based sealers lack bioactive properties or osteogenic potential in comparison to calcium silicate-based sealers (CSBSs). The increase in Ca 2+ in CSBSs regulates osteoblast proliferation and differentiation [15][16][17][18]. These ions upgrade the expression of bone-associated proteins of osteoblasts [19]. Zayzafoon et al. [20] showed that the increase in extracellular Ca 2+ causes a considerable inflation of Ca 2+ concentration within the cell through the calcium channels, activating numerous targets including calcium/calmodulin (CaM)-mediated calcium/calmodulin-dependent protein kinase (CaMK). CaMK2 controls c-fos expression, which is an element of AP-1 transcription factor [21] and ultimately supports osteoblast differentiation. As a result, osteoblasts are induced to mineralise the new bone [22,23]. Therefore, calcium ions in the CSBSs encourage osteoblastic differentiation and bone formation [11]. Lee et al. [11] and Zhang et al. [12] demonstrated a similar phenomenon by showing that Ca 2+ in the CSBSs stimulates the expression of bone-associated proteins and is required for apatite genesis. Apatites then mediate osteoblastic activity to modulate and mineralise new bone via accumulation of apatite crystals [22].
Furthermore, Osiri et al. [24] showed that CSBSs along with the root filling material (Gutta Percha) bonded to the dentine walls and reinforced the prepared root canal system. The authors reported a fracture resistance similar to that of intact roots [24]. In addition, Atteia et al. [10] demonstrated significant improvement in the apical healing and lower dissolution rate with CSBSs when compared to RBSs. Supporting the above observations, Nagar et al. [25] reported that CSBSs showed a superior performance in comparison to RBSs in terms of clinical and radiographic parameters. Contradicting the above evidence, Graunaite et al. [23] stated that a total of 35% of the study population (n = 57 patients) was affected with postoperative pain when treated with the CSBSs. There were reported statistically significant differences between the mean values of the VAS scores for the RBS and CSB groups when assessed at 24 h, 48 h, 72 h and seven days post-obturation [23,[26][27][28].
Junior et al. [29] and Jamali et al. [30] published systematic reviews comparing the effect of CSBSs and RBS on clinical outcomes, which included five and four controlled randomised clinical trials, respectively. In addition, Mekhdieva et al. [31] evaluated the postoperative pain following warm vertical compaction technique using bioceramic sealer in comparison to cold lateral condensation. However, these reviews conducted previously evaluated only the intensity of post-obturation pain and failed to include parameters such as radiographic healing and absence of clinical symptoms, i.e., sinus healing, reduction in inflammation and absence of tenderness to percussion. In addition, there is still limited evidence in relation to potential clinical and radiographic effects of CSBSs when compared to the RBSs following root canal treatment. Therefore, there is a need for further evidence that combines the clinical and radiographic outcomes and presents consolidated data regarding the effect of calcium silicate-based sealers versus resin-based sealers following non-surgical root canal treatments. Therefore, this systematic review with meta-analysis was conducted to assess available literature on both the clinical and radiographic outcomes of CSBSs when compared to RBSs following non-surgical endodontic treatment in permanent teeth.

Protocol Development
This study was conducted in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statement ( Figure 1) and registered in PROSPERO (CRD42020197475 https://www.crd.york.ac.uk/prospero/record_email.php, accessed on 18 January 2020). The following focused question using PICOs format (Patient, Intervention, Comparison and Outcome) was proposed: "Are calcium silicate-based sealers effective in improving the clinical and radiographic outcomes of endodontically treated permanent teeth in comparison to resin based sealers?". that combines the clinical and radiographic outcomes and presents consolidated data regarding the effect of calcium silicate-based sealers versus resin-based sealers following non-surgical root canal treatments. Therefore, this systematic review with meta-analysis was conducted to assess available literature on both the clinical and radiographic outcomes of CSBSs when compared to RBSs following non-surgical endodontic treatment in permanent teeth.

Protocol Development
This study was conducted in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statement ( Figure 1) and registered in PROSPERO (CRD42020197475 https://www.crd.york.ac.uk/prospero/record_email.php) accessed on 18th January 2020. The following focused question using PICOs format (Patient, Intervention, Comparison and Outcome) was proposed: "Are calcium silicate-based sealers effective in improving the clinical and radiographic outcomes of endodontically treated permanent teeth in comparison to resin based sealers?".

Literature Screening and Study Selection
A comprehensive search was conducted in PubMed/MEDLINE, DOAJ, Cochrane Central Register of Controlled Trials and Web of Science to include studies published in all languages (without any limitations) until December 2021. Searches in the ClinicalTri-

Literature Screening and Study Selection
A comprehensive search was conducted in PubMed/MEDLINE, DOAJ, Cochrane Central Register of Controlled Trials and Web of Science to include studies published in all languages (without any limitations) until December 2021. Searches in the ClinicalTrials.gov database and in the references of the included studies (cross-referencing) were also conducted. Google, Greylit and OpenGrey were used to search grey literature. Medical Subject Headings (MeSH) terms, keywords and other free terms related to the PICO question were used with Boolean operators (OR, AND) to combine searches. The same keywords were used for all search platforms following the syntax rules of each database, and the search terms were modified according to the database (Table 1).

Screening Process
The search and screening processes were conducted by two authors. Analysation of the titles and abstracts was followed by full-text articles chosen for in-depth reading. The level of agreement, between the two reviewers, calculated by Cohen's kappa (k), was 0.92 for titles and abstracts and 0.94 for full texts. The third author was approached in case of any differences among reviewers.

Data Extraction
The following data were extracted from the included studies: author names, study design, age of participants, sample size, type of tooth, type of pulpal disease, method of pulp testing, method of root canal preparation, type and concentration of irrigant solution used, obturation technique, endodontic sealers used, medicament prescribed, outcome assessed, method of outcome assessment(s), time of evaluation and authors' conclusions.

Quality Assessment and Risk of Bias Analysis (ROB)
The quality of the selected studies was assessed using the Cochrane Collaboration Tool [34] for RCTs, including random sequence generation, allocation concealment, blinding of participants, incomplete outcome data, selective reporting and other biases. Methodological index for non-randomised studies (MINORS) was used for quality assessment of the included non-randomised comparative studies [35].

Statistical Analysis
Review Manager (RevMan) 5.3 (Version 5.3, Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, 2014) was used for statistical analysis. The primary outcome was measured as standardised mean difference (SMD) for the mean pain level. However, dichotomous data related to the risk of occurrence of post-obturation pain, the intensity of the pain and frequency of analgesic medicament intake were expressed as relative risks (RRs) at 95% confidence intervals (CIs), p < 0.05, using the random-effect model. Heterogeneity was assessed by the Q test, for p < 0.1, as well as by the I 2 test. Sensitivity analysis was conducted to assess the stability of the results.

Results
The initial electronic database search resulted in 1188 titles. After removal of duplicates and screening of the abstracts, a total of 93 relevant titles were selected by two independent reviewers (VC and AB). Out of these 93 articles, 44 were then chosen for the full-text evaluation, which also included articles through hand searching of the reference lists of the selected studies. Subsequently, a total of 20 studies were selected according to the inclusion and exclusion criteria.
Seventeen studies with inappropriate outcome variables, four studies with no intervention group, and three studies without comparison group were excluded.
A total of twenty studies were included in this review; however, eight studies were then excluded for the meta-analysis. Subsequently, the study by Ved et al. [37] was not considered for further quantitative analysis, as there were only radiographic assessments for the mean area change in the periapical lesion using the Image J software in pixels/mm 2 . Nagar et al. (2018) and Zavattini et al. (2020) analysed clinical (tenderness to percussion assessment, mobility) and radiographic outcomes. However, these authors reported the results in percentages for each group at 1, 3, 6 and 12 months. Therefore, these studies were also excluded from the meta-analysis, since the authors presented the changes in area for healing in percentages only. VAS scale for postoperative pain was also not reported. A study by Atteia et al. (2017) was excluded in the meta-analysis, as this study presented the mean and median values only comparing the effects of extruded CSBS and RBS on apical healing using digital radiography.
Among the studies that were not included in the quantitative analysis, one study demonstrated optimum healing of the apical lesion following the use of bioceramic sealer in comparison to resin-based sealer after 6 and 12 months post-root canal treatment [37]. In addition, Zavattini et al. [38] demonstrated a high percentage of success rate with the group using the bioceramic sealer in comparison to the resin-based group. However, the authors failed to find statistically significant differences between the two groups. Nagar et al. [25] concluded bioceramic sealer was most efficient in comparison to the MTA, resin-based and zinc oxide eugenol sealers. Similarly, Atteia et al. [10] recorded high observations of 1.67 with Totalfill in comparison to 1.2 with AH Plus sealers (using Mann-Whitney U-test) with respect to complete healing following the RCTs. Using a Student t-test, the authors also reported a statistically significant difference (p ≤ 0.001) in the digital radiodensity of bioceramics (mean value 37.46), which increased at 12 month recall in comparison to the resin based sealers (mean value 19.73). It was concluded that increased radiodensity and low solubility of bioceramics after 12 months might be indicative of their osteoinductive and osteoconductive potential [10]. Figure 2 shows the quality assessment of the included studies. The main shortcomings were related to allocation concealment, blinding of participants and outcome assessment. The random sequence generation was unclear in three studies [25,37,40], and two studies reported incomplete outcome data [25,37]. MINORS was used for quality assessment of two non-randomised comparative studies [38,41] that presented scores of 21 and 22, respectively, demonstrating low risk of bias (Table 4). This is in accordance with the globally accepted score between 21-24 for non-randomised studies [35].

Risk of Bias (ROB) and Quality Assessment
Financial support was disclosed only by three studies [36,38,39], which might indicate a funding bias. The items are scored 0 (not reported), 1 (reported but inadequate) or 2 (reported and adequate). The global ideal score is 16 for non-comparative studies and 24 for comparative studies. * For study with control group.  The items are scored 0 (not reported), 1 (reported but inadequate) or 2 (reported and adequate). The global ideal score is 16 for non-comparative studies and 24 for comparative studies. * For study with control group.

Quantitative Analysis
A total of eight studies [23,[26][27][28]36,[39][40][41] fulfilled the inclusion criteria for quantitative analysis. The studies which included more than one type of CSBS group [27,28] or more than one type of obturation techniques as a study group [40] were analysed separately and were considered as different studies.

Mean Pain Levels
The meta-analysis (Figure 3

Quantitative Analysis
A total of eight studies [23,[26][27][28]36,[39][40][41] fulfilled the inclusion criteria for quantitative analysis. The studies which included more than one type of CSBS group [27,28] or more than one type of obturation techniques as a study group [40] were analysed separately and were considered as different studies.

Risk of Occurrence of Pain
The meta-analysis (Figure 4) was carried out according to the postoperative time intervals of 24, 48 h and seven days between the patients treated with the CSBS and RBS [23,26,27,36,40]. There was no significant difference in the risk of occurrence of pain at 24

Intensity of Pain
The meta-analysis ( Figure 5) failed to demonstrate any differences for the intensity of post-obturation pain for a period of 24 and 48 h., then seven days ( Table 5). The severity of pain was measured as mild and moderate [26,27,36,40].

Intensity of Pain
The meta-analysis ( Figure 5) failed to demonstrate any differences for the intensity of post-obturation pain for a period of 24 and 48 h., then seven days ( Table 5). The severity of pain was measured as mild and moderate [26,27,36,40]. Table 5. Observations for the intensity of pain after 24, 48 h and seven days.

Discussion
Based on the levels of evidence given by the Oxford Centre for Evidence-based Medicine [43], this systematic review and meta-analysis of clinical trials provides level 1 evidence for assessing post-obturation effect of CSBSs as compared to RBSs. In addition, Grading of Recommendations, Assessment, Development and Evaluations (GRADE) was carried out to assess the evidence available for this study. The overall results of the meta-

Discussion
Based on the levels of evidence given by the Oxford Centre for Evidence-based Medicine [43], this systematic review and meta-analysis of clinical trials provides level 1 evidence for assessing post-obturation effect of CSBSs as compared to RBSs. In addition, Grading of Recommendations, Assessment, Development and Evaluations (GRADE) was carried out to assess the evidence available for this study. The overall results of the meta-

Discussion
Based on the levels of evidence given by the Oxford Centre for Evidence-based Medicine [43], this systematic review and meta-analysis of clinical trials provides level 1 evidence for assessing post-obturation effect of CSBSs as compared to RBSs. In addition, Grading of Recommendations, Assessment, Development and Evaluations (GRADE) was carried out to assess the evidence available for this study. The overall results of the meta-analysis displayed that the CSBSs showed performance superior or similar to the conventional RBS for parameters such as post-obturation pain level, risk of occurrence, intensity of pain at 24 and 48 h and need for analgesic drug intake within 24 h.
Success with non-surgical root canal treatment is attained by the removal of microorganisms from the canals followed by 3D obturation to prevent reinfection. Clinical and radiographic parameters to evaluate endodontic success include absence of pain, inflammation and other symptoms, absence of sinus tract, retained function and radiological evidence of a normal periodontal ligament space around the root. [44,45]. Sathorn et al. [46] and Wong et al. [47] reported incidence of post-obturation pain between 3 and 58% in patients, with the highest being on the first and second day [36]. This might be due to the composition of the sealer or obturation material. In cases of sealer extrusion, this could cause localised inflammatory response affecting the healing process in the periodontium, which could be related to the possible release of chemical irritants by sealers [12,36]. In addition, many studies suggested that micro-organisms are not completely eliminated during root canal treatment and become the major factor in initiation, development and persistence of apical periodontitis [48][49][50].
The results for the primary outcome, i.e., post-obturation pain, showed no significant difference between the two evaluated sealer groups. However, Graunaite et al. [23] and Fonseca et al. [26] in their respective studies showed that the delayed setting time of AH Plus sealer might affect its biocompatibility and trigger the potential for cytotoxic by-products to be released before the final setting, leading to periapical inflammation that might result in post-obturation pain [23,28]. In addition, Lodienė et al. [51] and Zhang et al. [52] demonstrated significant differences in cytotoxicity levels between the RBS and CSBSs. However, such differences were not observed, as there was no correlation between sealer extrusion and postoperative pain [23,26,28,36,39]. There were statistically no significant differences in the mean pain intensity levels, need for analgesic drug intake and occurrence of post-obturation pain between the CSBS and RBS at any of the assessed time points (24 h. up to seven days). However, the mean pain levels were lower in the CSBSs in comparison to RBSs at 48 h. This could be due to the limited contact of these sealers within periapical tissues [29]. In addition, the presence of tissue fluids might dilute the concentration of toxic substances; therefore, inflammatory response might not be activated [29,33].
In all studies except that of Tan et al. [36], the scores for post-obturation pain at 1, 3 and 7 days were recorded using numerical values between 0 and 10 according to the VAS scale and then converted to a verbal scale-"no pain", "slight pain", "moderate pain", and "severe pain"-to assess the intensity of pain. In addition, the number of visits required to complete the root canal treatment and level of complexity of each treatment were not standardised. These factors can cause an outcome reporting bias in the results. Root canal sealers would aim to fill all irregularities within the root canal system if these materials have the desired rate of flow. In this respect, excessive flowability might increase the risk of sealer extrusion [26]. Fonseca et al. [28] stated that the unintentional extrusion of each sealer was recorded and confined to the region immediately adjacent to the portal of the canal exit. Fonseca et al. [26] reported a higher rate of extrusion for the Sealer Plus BC (MKLife Medical and Dental Products, Porto Alegre, Brazil) (59.74%) in comparison to the AH Plus sealer (28.13%). However, this was reversed in the study by Tan et al. [36], where the AH Plus sealer (65%) showed a higher rate of extrusion in comparison to the Sealer Plus BC (48.7%). The meta-analysis reported that there was no significant difference in the extrusion of sealers irrespective of their types. Even though a high rate of extrusion was observed (59.74% Sealer Plus BC; 28.13% AH plus), the VAS using pain perception ranging from 0-10 showed no report of pain by the patients, thus confirming that there is no association between sealer extrusion and post-obturation pain.
The success rates of these two sealers were measured according to the absence of pain, inflammation, absence of sinus tract, retained function, normal width and continuity of the periodontal ligament space on radiographs, along with the evidence of apical healing, i.e., improved radiodensity. Nagar et al. [25] and Ved et al. [37], using the SmartpasteBio BCS, and Atteia et al. [10], with Totalfill BCS, showed significant improvements in the clinical parameters after 1, 3, 6 and 12 months when compared to the RBS. In addition, complete apical healing, a slower rate of resorption and improved radiodensity assessed radiographically favoured the CSBs group in comparison to the RBS. Increased radiodensity and low solubility rate of the extruded CSBs indicate that these sealers act as osteoinductive and osteoconductive materials that accelerate healing and adsorb more minerals from the surrounding tissue. However, Nagar et al. [25] failed to provide the details of instrumentation and obturation techniques, which could influence the incidence of postoperative pain. These authors also mentioned using pre-and postoperative CBCT scans only for the CSBs group, whilst only digital periapical radiograph was used for the RBS.
The review included 12 clinical studies published between 2013 and 2021. The ages of the participants were above 18 years, with a mix of both genders. The selection bias was minimised by performing sensitivity analysis on quantitative results by excluding the studies with vital teeth [36]. In addition, the participants on any medicines that could possibly interfere with the post-obturation effect of sealers were excluded from this systematic review. However, a few studies failed to mention achieving apical foramina patency [23], which, if achieved, favours the occurrence of unintentional sealer extrusion [26]. Obturation technique for both sealers differs, as these materials were used according to the manufacturers' instructions. A few included studies [25] failed to mention the cleaning and shaping or obturation technique used.
A Cochrane systematic review by Manfredi et al. [53] concluded that there is lack of evidence suggesting one treatment regimen is better than the other. In this respect, Tan et al. (2021) failed to mention the number of visits required to complete the treatment [36]. In this current review, to rule out the effect of different visits, only single-visit RCT studies were included in the sensitivity analysis. This analysis affirmed the fact that although the exclusion of the studies reduced the RRs and heterogeneity, the overall results remain unaltered.
Furthermore, methodological heterogeneity was noticed due to the location of study, methodology, sample size, number and experience of clinicians performing the procedures and diagnosis, method of root canal preparation and obturation, visits required to complete RCT, marking on the scale used for assessing pain and radiographic techniques. A randomeffects model instead of a fixed-effects model for meta-analysis was used to address this heterogeneity. The sensitivity analysis performed using a fixed-effects model for the study outcomes showed unchanged overall results.
Inter-study variability and inconsistency within studies are identified as limitations in this systematic review. The clinical heterogeneity among the included studies could not be avoided. Individual analyses for tooth types (incisors, canines, premolars and molars), age, gender and number of visits required to complete the treatment were considered in the included studies. In addition, although the studies assessed postoperative pain, the reported data regarding the sealer extrusion and lack of standardisation in the pain relief doses were not comparable to perform the meta-analysis. Only a small number of articles and participants were included for quantitative analysis due to the limited evidence. However, six out of twelve studies demonstrated acceptable methodological validity, exhibiting a low risk of bias [23,[26][27][28]36,39,40]. Two studies disclosed the presence of external funding. The funding was received for the sealers used in both studies [36,38]. It could be speculated that the possibility of a funding bias in such cases cannot be overlooked.
Previously published systematic reviews and meta-analysis [29][30][31] evaluated the postoperative pain at different time intervals, with a maximum of only seven days. Junior et al. [29] were unable to perform meta-analysis for sealer extrusion and doses of medications i.e., Ibuprofen. Jamali et al. [30] included articles published in English only, which could lead to selection and selective outcome reporting biases. In addition, Mekhdieva et al. [31] failed to provide a clear description of the inclusion and exclusion criteria used for their study. This current systematic review is the first meta-analysis to assess the effect of CSBSs vs. RBSs on the clinical as well as radiographic outcomes when used for root canal treatment in permanent teeth.
Future randomised clinical trials evaluating postoperative pain and periapical and bone healing with different pulp and periodontal status at varying time intervals at least up to four years are required [54]. In addition, the CONSORT [55] or PRIRATE [56] recommendations need to be followed. Standardising the use of numerical rating scales (0-10 cm) to analyse pain intensity is preferred, as the more levels a tool has, the more sensitive it is, to the point that it could detect even a small change in pain intensity [57].

Conclusions
The overall results of the present systematic review and meta-analysis demonstrate that the CSBSs presented acceptable performance with similar results to the gold standard RBSs in terms of mean post-obturation pain level, risk of occurrence and intensity of pain at 24 and 48 h, as well as for analgesic drug intake within 24 h and extrusion of sealer.
However, the included studies have shortcomings that were presented in this current review. Therefore, further well-designed, controlled randomised clinical trials for a period of at least four years are required to provide high-quality evidence.