Evaluation of the Single-Tip Bioceramic Filling Procedure in Root Canal Treatment of Maxillary First Molars: A Clinical Study

Summary

This study compared the single-tip bioceramic filling and AH-Plus hot vertical compaction methods in treating second mesiobuccal canal root canals of maxillary first molars. The single-tip group showed higher optimal filling rates, shorter procedure time, and reduced postoperative pain, confirming it as a safe, effective, and efficient treatment option.

Abstract

This study aimed to assess the clinical efficacy of the single-tip bioceramic filling method in treating the second mesiobuccal canal (MB2) of maxillary first molars. Ninety-four patients requiring MB2 root canal therapy were randomly allocated to either an experimental group (n = 47) or a control group (n = 47) between January 2023 and December 2024. The experimental group was treated using the single-tip bioceramic technique, whereas the control group received AH-Plus hot vertical compaction. The primary outcome measures included filling quality, procedure time, postoperative pain at 24 hours and 7 days, and clinical efficacy at 6 months. The experimental group demonstrated a significantly higher optimal filling rate (P < 0.05) and shorter mean procedure duration, with comparable clinical success between both groups at 6 months. Additionally, patients in the experimental group experienced lower postoperative discomfort within 24 hours (P < 0.001). Overall, the single-tip bioceramic filling technique achieved equivalent clinical outcomes with improved procedural efficiency and patient comfort compared with the conventional AH Plus vertical compaction method. This simplified technique may represent a safe, effective, and time-efficient approach for MB2 canal obturation in maxillary first molars.

Introduction

Root canal therapy serves as the primary treatment approach for periapical diseases affecting the pulp¹, with the goal of thoroughly cleaning the root canal system and performing a three-dimensional hermetic seal to prevent reinfection². Maxillary first molars are the earliest permanent molars to erupt in the mouth³, which play a key role in maintaining a normal occlusal relationship, and root canal treatment is often required clinically due to caries, defects, and fissures.

The second mesiobuccal (MB2) canal is highly prevalent in maxillary first molars^4,5,6, with studies reporting a prevalence as high as 80.1% in the Emirati population using cone-beam computed tomography (CBCT). This highlights the importance of using advanced imaging modalities, such as CBCT, for accurate three-dimensional assessment of root canal anatomy, enabling reliable identification of MB2 canals during preoperative evaluation and thereby reducing the risk of missed canals and subsequent endodontic treatment failure⁷. A systematic review also confirmed that MB2 canals are present in approximately 68.2% of the cases, emphasizing the need for careful canal identification during clinical procedures⁵. Recent advances such as micro–computed tomography (micro-CT) have further enhanced the ability to visualize complex canal morphologies with superior clarity and precision, improving identification of MB2 and accessory canals.

According to the meta-analysis by Aung and Myint (2021), the sensitivity of CBCT for diagnosing second root canals in permanent teeth was 94%, while the specificity was 93.1%⁵. The maxillary first molar root canal system is more complex and exhibits substantial anatomical variability among populations. The second mesiobuccal canal (MB2) typically originates on the lingual aspect of the mesiobuccal canal and is positioned closer to the median plane of the tooth^8,9. Its canal orifice is often concealed, and anatomical variations such as isthmuses, inter-canal communications, and apical deltas contribute to the complex morphology of the maxillary first molar¹⁰.

The clinical success of bioceramic sealers in the single-cone technique for MB2 canals requires further investigation, particularly with long-term follow-up studies^11,12. While a high success rate (96.8%) is reported, the retrospective nature of the study and the lack of specific data on MB2 canal outcomes limit the generalizability of these findings⁸. The available literature lacks large-scale, prospective, randomized controlled trials specifically evaluating the long-term success of bioceramic sealers in MB2 canals. Many studies focus on the material properties of bioceramic sealers in vitro^13,14,15,16, providing valuable information about their biocompatibility and bioactivity, but these findings do not directly translate to clinical success rates in specific canal configurations. Further research is crucial to establish the long-term clinical effectiveness of this combination. The limited available evidence suggests a potential for success, but more robust studies are necessary to support widespread clinical adoption.

Altogether, although bioceramic sealers have good biological and sealing characteristics, the clinical performance of these sealants in complex canal systems, e.g., MB2, is under-researched. To fill this gap, the current study provides a comparison of the single-tip bioceramic filling procedure with the standard AH Plus hot vertical compaction process with respect to such clinical performance aspects as the quality of the filling, the time taken during the procedure, and the outcomes of the operations. The description of the specific experimental protocol used to assess these parameters is presented in the next section.

Protocol

This study was approved by the Medical Ethics Committee of the Second People’s Hospital of Yibin City. Written informed consent was obtained from all participants prior to enrollment in accordance with the Declaration of Helsinki. This work was supported by the 2023 Scientific Research Project of the Yibin Municipal Health Commission (Grant No. 2023YW014) and the Natural Science Foundation of Sichuan Province (Grant No. 2023NSFSC0546).

1. Study design and participants

This randomized controlled study involved 94 patients who received microscope-assisted root canal treatment for MB2 periapical disease affecting maxillary first molars at the Stomatology Center of the Second People's Hospital of Yibin City from January 2023 to December 2024. The study protocol was approved by the Medical Ethics Committee of the Second People's Hospital of Yibin City (Approval No. 2023-136-01, approved on June 12, 2023). Participants were randomly allocated to the experimental group (n = 47) or the control group (n = 47). Written informed consent was obtained from all participants prior to enrollment after a detailed explanation of the study objectives, procedures, and potential risks.

The inclusion criteria were as follows: (1) patients requiring root canal treatment of maxillary first molars; (2) imaging examination confirming apical foramen closure and complete root development, with radiographic evidence of unobstructed canal anatomy suggestive of root canal patency; (3) presence of apical radiolucency with a diameter ≤5 mm; and (4) provision of informed consent and willingness to cooperate with the treatment.

Exclusion criteria included extensive tooth defects and/or poor periodontal condition (as periodontal breakdown may alter root anatomy, compromise isolation, and affect accurate MB2 localization), previous root canal treatment requiring retreatment, tooth fractures, temporomandibular joint disorders (e.g., restricted mouth opening), and severe systemic diseases that could influence healing response, pain perception, or treatment outcomes.

2. Diagnostic and radiographic examination

Preoperative assessment included intraoral periapical radiography or CBCT, depending on clinical indication. While CBCT provides superior three-dimensional visualization of root canal anatomy, periapical radiographs were used as an initial screening tool, with CBCT employed selectively to enhance detection and assessment of complex canal morphology. Under a dental microscope, the pulp chamber and root canal anatomy were examined. The number and morphology of root canals were recorded, and MB, distobuccal, and palatal root canal systems were classified according to the Weine classification¹⁷.

3. Treatment procedure

Preoperative evaluation was performed for all affected teeth to assess restorability and case complexity based on clinical and radiographic findings, followed by rubber dam isolation. Under a dental microscope, all carious tissue and pulp remnants were removed. The working length was determined using an apex locator set at 0.5 reading and verified with periapical radiography. When necessary, ultrasonic instruments were employed to remove pulpal calcifications and canal obstructions, and passive ultrasonic irrigation (PUI) was used for irrigant activation using an ultrasonic tip placed short of the working length.

Root canal instrumentation was carried out using NiTi rotary files at 300 rpm and 2.0 N·cm torque, with sequential irrigation using 5 mL of 1% sodium hypochlorite (NaOCl) between each file, followed by a final rinse with 5 mL of 0.9% saline. After ultrasonic cleaning, the canals were dried using sterile paper points (size 30–40) until no visible moisture remained, after which a calcium hydroxide paste was applied as an intracanal medicament using a lentulo spiral. Patients were followed for 1–2 weeks until the treated tooth was asymptomatic, with no exudate or odor, before proceeding with root canal filling.

4. Control group

Root canal filling was performed using the AH Plus hot vertical compaction technique under a dental microscope. AH Plus sealer was applied, and a heated gutta-percha tip was compacted incrementally. The heat carrier was set to 180 °C and applied for 2–3 seconds per increment, maintaining an apical pressure of approximately 1.5 N to achieve dense compaction of the gutta-percha.

5. Experimental group

The single-tip bioceramic filling method was performed under a dental microscope. The sealant was injected into the canal until it reached the orifice, followed by the slow insertion of a single gutta-percha point to displace any air bubbles. Excess gutta-percha was removed at the orifice using a heat carrier, and compaction was performed.

For teeth in the control group, separate AH Plus hot vertical compaction was conducted for the MB and MB2 canals due to their proximity or fusion. In contrast, in the experimental group, simultaneous MB and MB2 filling was performed using the single-tip bioceramic technique, followed by orifice compaction.

Postoperative radiographs were obtained to assess the quality of obturation after the preparation of the pulp chamber and removal of excess sealer or gutta-percha. The total root canal filling time was recorded for both groups. All procedures were performed by a single experienced endodontist, and coronal restoration was completed within 1–2 weeks following root canal filling.

6. Observation indicators and evaluation criteria

1. Radiographic assessment of root canal filling
Postoperative apical X-rays were taken to assess the filling quality of the MB, MB2, distobuccal (DB), and palatal (P) root canals, based on established radiographic criteria evaluating filling length and homogeneity¹⁸. Radiographs were taken using a digital intraoral sensor (70 kVp, 8 mA, exposure time 0.25 s) and were analyzed using ImageJ software to measure filling length and homogeneity. The root canal filling was deemed optimal when the filling material was dense, displayed a continuous taper, and extended 0.5–2 mm from the apical foramen. Overfilling was characterized by the filling material extending past the apical foramen, whereas underfilling was identified when the filling material was positioned more than 2 mm from the apex or did not adequately seal the apical region.

2. Procedural time measurement
The total time needed to fill all four root canals in the maxillary first molars was documented for comparative analysis between the two groups. Procedure time was measured from the start of sealer application to the removal of excess gutta-percha at the canal orifice. Timing was recorded using a digital stopwatch operated by an independent observer to ensure consistency and minimize measurement bias.

3. Postoperative pain assessment
Patients were followed up at 24 h and 7 days postoperatively to assess pain levels using the Visual Analogue Scale (VAS), a validated tool for pain assessment¹⁹. Pain scores were self-reported via telephone by a blinded investigator using a standardized 10-point VAS form. Participants were advised to refrain from using analgesics unless pain was severe; any analgesic intake was recorded during follow-up. The VAS scores were categorized as follows: 0 points - No pain or postoperative discomfort; 1-3 points - Mild pain, with minimal discomfort; 4-6 points - Moderate pain, tolerable without medication; 7-10 points - Severe pain, requiring analgesics or emergency intervention.

4. Clinical efficacy evaluation
Clinical efficacy was evaluated at 6 months post-treatment according to established endodontic outcome criteria, based on radiographic and symptomatic improvements²⁰: (1) Significant improvement: Complete resolution of periapical pathology, with the disappearance of clinical symptoms and signs; (2) Effective: Considerable reduction in the radiolucent periapical lesion, with marked improvement in clinical symptoms; (3) Ineffective: No improvement or worsening of periapical radiolucency, with persistent or worsening clinical signs.
The treatment success rate was calculated as:
Treatment response rate = (significant improvement + Effective) X 100%
These outcome criteria were adapted from established clinical evaluation systems for endodontic treatment success¹⁷.

7. Statistical analysis

Data were analyzed statistically using SPSS 26.0. Normality of continuous variables was assessed. The mean plus or minus the standard deviation (x ± s) was used to display data that was normally distributed, and data from separate samples were also used. In order to compare the groups, t-tests were used. Data that did not follow a normal distribution were expressed as median (interquartile range) [M (Q1, Q3)], and group comparisons were performed using the Mann-Whitney U test.

Categorical variables were presented as frequencies and percentages [n (%)], and group comparisons were carried out using either Fisher's exact test or the chi-square (χ²) test, depending on what was relevant. Ordinal data were compared using the Mann-Whitney U test. The threshold for statistical significance was established at P < 0.05.

Results

Filling quality comparison

As shown in Table 1 and Figure 1, the overall filling quality differed significantly between the two groups. In the experimental group, 93.62% (95% CI: 88.2–97.0) of canals achieved an optimal fill, compared with 85.11% (95% CI: 78.0–90.6) in the control group. Overfilled canals were fewer in the experimental group (6.38% [95% CI: 3.0–11.8]) than in the control group (14.89% [95% CI: 9.4–22.0]). Statisti...

Discussion

The morphology of root canals in maxillary first permanent molars is notably intricate, especially within the MB roots, where the occurrence of MB2 canals exhibits significant variability across studies, with reported rates between 51% and 90%^11,13,14,15. This variability can be attributed to differences in race, age, detection methods, sample size, and the absence of a standardized definition ...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Apex Locator	J. Morita, Japan	Root ZX II	Determines working length of canals
Bioceramic Sealer (iRoot SP)	Innovate Biotech, China	IS-001	Root canal sealer for experimental group
Calcium Hydroxide Paste	Voco, Germany	2016	Used as intracanal medicament
Dental Operating Microscope	Zeiss, Germany	OPMI Pico	Used for enhanced visualization during MB2 canal location
Digital Radiography System	Carestream Dental, USA	CS 2100	Used for postoperative radiographs
Disposable Paper Points	Meta Biomed, Korea	DPP-30	For canal drying
Epoxy Resin-Based Sealer (AH Plus)	Dentsply Sirona, Germany	606.46.531	Sealer used in control group
Gutta-Percha Cones	Dentsply Sirona, Germany	GP-55	Used for obturation
Heat Carrier Tip	B&L Biotech, South Korea	Beta Mini	Used for vertical compaction at 180 °C
Hot Vertical Compaction Device	B&L Biotech, South Korea	Alpha II	For gutta-percha compaction
Image Analysis Software	National Institutes of Health (NIH), USA	ImageJ 1.53t	Used for radiographic evaluation
Intraoral Sensor	Carestream Dental, USA	RVG 5200	For digital image acquisition
Nickel–Titanium Rotary Files	Dentsply Sirona, Switzerland	ProTaper Gold	For canal preparation
Rotary Endodontic Motor	NSK, Japan	Endo-Mate DT	Used for NiTi rotary file operation
Rubber Dam Kit	Kerr, USA	1600	Isolation of operative field
Saline Solution (0.9%)	Baxter, China	07S060	Used as final irrigant
Sodium Hypochlorite Solution (1%)	Sigma-Aldrich, USA	425044	Irrigant used during instrumentation
Statistical Software	IBM Corp., USA	SPSS 26.0	Used for statistical analysis
Ultrasonic Scaler Unit	Dentsply Sirona, USA	Cavitron Select SPS	Used for ultrasonic cleaning of canals
Ultrasonic Tips	Dentsply Sirona, USA	Start-X #3	For canal debridement and MB2 troughing