Assessment of guided versus non-guided endodontic microsurgery with root-end resection using different retrograde filling materials on operation time and lesion volume: A randomized controlled clinical study

Abstract

Background:

Guided microsurgery has been proposed to improve precision and reduce operation time, but its effect on bone healing remains unclear.

Aim:

To compare guided microsurgical root end resection and different retrograde filling materials versus non-guided endodontic microsurgery on operation time and lesion bone volume using cone-beam computed tomography (CBCT).

Subjects and Methods:

24 patients undergoing apicoectomy for anterior maxillary teeth were selected according to inclusion and exclusion criteria. Then they were randomly divided into two groups: Group A, receiving endodontic microsurgery without a surgical guide (n = 12), and Group B, utilizing a surgical guide (n = 12). Each of these groups was further subdivided into two smaller groups of six, based on the retrograde filling material used: Subgroup S1 for mineral trioxide aggregate (MTA)-Angelus and Subgroup S2 for Well-Root Putty. Operation time was recorded intraoperatively. Lesion volume was assessed using CBCT scans taken 1 week and 6 months after surgery. Data were analyzed statistically to evaluate differences among the groups.

Results:

The guided group showed a significantly shorter operation time (26–27.5 min) compared with the non-guided group (39–47 min), with no significant difference between retrograde filling materials. All groups exhibited a significant reduction in lesion volume at 6 months, with no significant intergroup differences.

Conclusion:

guided microsurgery effectively reduced surgical time but had no impact on bone lesion volume. MTA-Angelus and Well-Root Putty showed comparable clinical performance.

INTRODUCTION

Root canal therapy eliminates intracanal infection and prevents the spread of infection to the periapical tissues, reducing the risk of apical periodontitis.[1] Despite the high success rates achieved with modern techniques, failures still occur in 4%–15% of cases due to the anatomical complexity of the canal system and persistence of bacteria.[2] In such cases, orthograde retreatment is preferred; however, when periradicular pathosis persists, surgical intervention may be required.[3]

The advent of microsurgery has dramatically changed the management of periapical lesions. Surgical microscopes have greatly improved the accuracy and safety of microsurgical procedures by enabling smaller osteotomies, minimizing resection angles, and allowing for the detection of complex anatomical features such as isthmuses and lateral canals in the resected root.[4] Furthermore, the advent of cone-beam computed tomography (CBCT) imaging, computer-aided design/computer-aided manufacturing, and three-dimensional (3D) printing technology has enabled the fabrication of surgical guides that enhance accuracy during apicoectomy and allow safe and precise root-end resection in anatomically challenging cases.[5]

Moreover, the direct proportionality of the retrograde cavity sealing tightness and the amount of bacterial invasion, which subsequently contaminates the periapical tissues, affects the choice of root-end filling material and thus determines the surgical outcome. Therefore, the biomaterials must have a good marginal seal, adherence to root dentin, dimensional stability, and low porosity to minimize bacterial leakage.[1] The introduction of bioceramic-based materials represents an advancement in reparative dentistry.[6]

The first introduced calcium silicate was mineral trioxide aggregate (MTA) which became a preferable material due to its biocompatibility, low cytotoxicity, excellent seal, and good osteogenic properties. However, its clinical use is still limited by challenges in its handling and its long setting time.[6] Recent studies showed that fast-setting, putty-type calcium silicate–based materials offer better washout resistance and ease of use during surgery.[7] The material was designed to overcome several drawbacks, including its texture, manual mixing, setting time, and moisture contamination effect.[8]

Despite the proven accuracy and safety of guided endodontic microsurgery,[5] its effect on bone healing, lesion volume reduction, and its clinical efficiency, such as operation time, remains unclear. Furthermore, limited evidence exists comparing different bioceramic retrograde filling materials under guided and non-guided surgical approaches. Therefore, this study aimed to evaluate the effect of guided endodontic microsurgery on operation time and bone lesion volume in comparison with the nonguided technique, using two retrograde filling materials: MTA-Angelus and Well-Root PT. The null hypothesis stated that there is no significant difference between guided and non-guided microsurgery and between the different retrograde filling materials on treatment outcomes.

SUBJECTS AND METHODS

Ethical considerations

The study protocol for the current study was reviewed and approved by the Ethics Research Committee of the Faculty of Dentistry of Suez Canal University and was given an approval number (REC 379/2021). The protocol was further registered on ClinicalTrials.gov and was granted ID: NCT07184151. The study was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki, and all procedures were thoroughly explained to the participants, who provided written informed consent prior to their participation.

Study design, study settings, and sample size calculation

This randomized, prospective, parallel-group clinical study with an allocation ratio of 1:1:1:1 was conducted at the Department of Endodontics, Faculty of Dentistry, Suez Canal University. The trial compared guided and nonguided endodontic microsurgery on maxillary anterior teeth using two different retrograde filling materials (MTA-Angelus and Well-Root Putty), evaluating operation time and bone lesion volume by CBCT.

The sample size was determined based on the results of a previous study done by Hawkins et al.[9] which compared guided and traditional endodontic microsurgery techniques and reported substantial differences in surgical accuracy and operating time between groups. Accordingly, a large effect size was assumed (Cohen’s f = 0.8), and G*Power software version 3.1.7 (Heinrich Heine University Düsseldorf, Düsseldorf, Germany)[10] was used for a one-way ANOVA with a significance level of 0.05 and a power of 80%, resulting in a total of 24 patients (6 per group).

Patient selection

Patients’ eligibility was confirmed by the co-supervisor following comprehensive medical and dental history, clinical examinations, and preoperative CBCT evaluation. Patients between 18 and 60 years old were included if they had restorable, single-rooted maxillary anterior teeth with probing depth <4 mm, mobility <1 mm,[11] Eligible cases also included teeth with good endodontic and post-crown restorations, periapical radiolucency <10 mm³ without sinus tracts, obstructed canals, extruded filling materials, or separated instruments associated with apical periodontitis where retreatment was not possible. Patients were analgesic-free before surgery. On the other hand, exclusion criteria involved non-restorable teeth, patients with severe systemic diseases (ASA III or higher, including uncontrolled diabetes and significant cardiovascular disease), psychological disorders, pregnancy, poor oral hygiene, unfavorable anatomy, or insufficient periodontal support.

Randomization and blinding

Teeth eligible for apicoectomy were randomly allocated into two groups: Group A (nonguided microsurgical apicoectomy, n = 12) and Group B (guided microsurgical apicoectomy, n = 12). Each group was subdivided into two subgroups of six teeth based on the retrograde filling: subgroups S1 (MTA, Angelus, Londrina, Brazil) and Subgroups S2 (Well-Root Putty, Vericon Co., Chuncheon, Korea).

Using www.random.org, the main study supervisor generated the random sequence for the indicated teeth, giving each tooth a number between 1 and 24 and assigning it to any of the following groups: AS1, AS2, BS1, or BS2. The allocation list was securely kept by the same supervisor, who was not involved in the surgical procedures or outcome assessment and was responsible for informing the operator about the assigned cases to allow guide fabrication when required.

The operator of the current study was not blinded due to the inherent procedural differences, as he performed all surgical procedures. Participants, the outcome assessor, and the data analyzer were blinded. Root canal treatment was completed before surgery when necessary. All patients read and signed an appropriate informed consent document prior to participation.

Surgical procedure

Group A (nonguided microsurgical apicoectomy)

a preoperative CBCT was used to evaluate the periapical lesion, root end, and surgical plan. Procedures were performed under a surgical operating microscope (SOM, Labomed Prima, Lobo America Inc., Philadelphia, USA). After rinsing with 0.12% chlorhexidine and anesthetizing with 4% articaine (Inibsa dental, Barcelona, Spain), a full-thickness sulcular mucoperiosteal flap with two vertical releasing incisions was reflected. Osteotomy was conducted conservatively to create sufficient access for debridement and root-end procedures. Using bone curettes, the periapical lesion was enucleated with the goal to remove any diseased tissue from the periradicular bony lesion. A perpendicular root-end resection of 3 mm was done using a high-speed bur, followed by inspection under SOM to detect fractures or defects. A 3 mm Class I root-end cavity was prepared using ultrasonic diamond retro tips (E11, E10, Woodpecker, Guilin, China). The retrograde filling was selected according to the assigned subgroup: either hand-mixed MTA-Angelus or premixed Well-Root Putty. The selected material was then condensed and finished with a ball burnisher or moistened cotton pellet.

Wound closure was done with 4/0 polypropylene (Ethicon INC company, San Lorenzo, USA) interrupted sutures. Postoperative care instructions were explained to the patient, including the application of cold compresses, restricted oral hygiene in the surgical area to the use of antiseptic mouthwash only, and the intake of an analgesic if needed. Thereafter, the sutures were removed within 5–7 days following surgery.

Group B (guided microsurgical apicoectomy)

For surgical guide planning [Figure 1], an upper arch impression was initially obtained using alginate, followed by a more precise silicone impression with a custom tray to create study casts. These casts were then digitized with a scanner to generate STL files. The preoperative CBCT DICOM data were merged with the STL files within the implant planning software (R2GATE) to facilitate virtual surgical planning. Using the combined datasets, the osteotomy site, bevel angle, and a 3 mm apical resection level were planned digitally following microsurgical principles. A virtual cylinder representing the trephine bur (Trephine Bur 4, MCTBIO, Gyeonggi-do, Korea; outer diameter 4.0 mm, inner diameter 3.3 mm, 28 mm total length) was employed to define the dimensions, angulation, depth, and positioning of the guide port relative to the tooth anatomy and surgical access. The surgical guide was designed to cover the occlusal surfaces, ensuring stable intraoperative placement. The finalized guide design was exported as an STL file and fabricated using 3D printing technology. Prior to surgery, the guide’s fit was verified intraorally.

Figure 1.

Photographs showing guided surgical procedures (a) STL for study casts. (b and c) STL file merged with DICOM file in software for the surgical guide design. (d) Designed guide template (e) The trephine bur 4 (MCTBIO). (f) Study cast, Silicone impression, and guide. (g) Dental implant device. (h) putty retrograde filling. (i) Mineral trioxide aggregate filling. (j) bony window a (k) The root-end preparation. (l) The retrograde filling

During the surgery, the patient was anesthetized, followed by a full-thickness sulcular mucoperiosteal flap reflection with two vertically releasing incisions to expose the surgical field. After confirming the guide’s precise fit, soft tissues around the trephine site were retracted. A hollow trephine bur was rotated at 1200 rpm with maximum torque using an implant motor handpiece under sterile saline irrigation, incrementally cutting through bone, root end, and soft tissue with a light pecking motion to the preplanned depth. Upon removing the guide, root-end exposure was confirmed. Periapical curettage was completed to remove any pathological tissue. The design of the trephine bur allowed for precise resection; however, slight irregularities on the resected surface were sometimes present. When necessary, minor adjustments to flatten the resected surface were made. The remaining surgical steps, including retrograde cavity preparation, filling, wound closure, and postoperative instructions, followed the same protocol as described for the non-guided control group.

Outcomes assessment

Difference in operating time

The operating time was recorded for each resected root using a digital stopwatch. Timing started at the beginning of the osteotomy and ended upon completion of the retrograde filling procedure to reflect differences in surgical technique and to allow comparison of handling characteristics between the two retrograde filling materials. The time was measured in minutes by an independent observer who was not involved in the surgery.

Radiographic assessment

CBCT scans were performed for each patient at 1 week and 6 months postoperatively using a 5 cm × 5 cm field of view, 0.2 mm voxel size, 2–10 mA, and 60–90 kV. DICOM files were analyzed using Romexis Viewer (6.4.7.99 version, Planmeca Oy, Helsinki, Finland). An expert radiologist assessed the change in bone lesion volume in multiplanar views with 0.2 mm slice thickness. Standardization involved aligning X, Y, and Z reference lines along the root axis and aligning them in the middle and parallel to the long axis of the root related to the investigated lesion and intersecting it into two halves.[12]

Volumetric assessment of periapical lesions was performed using Planmeca Romexis software (6.4.7.99 version, Planmeca Oy, Helsinki, Finland) with a 0.2 mm slice thickness. Manual segmentation was carried out using the annotation tool and the free region grow icon in the software, whereby the lesion boundary was traced in sagittal slices to create a red-colored delineation of the cavity. This process was repeated for all slices until the entire lesion was segmented. The software’s “create region” option was then used for 3D reconstruction and automatic calculation of lesion volume in cm³.[13] Volumetric measurements were recorded at baseline and after 6 months, with the percentage reduction in lesion volume calculated and compared across all study groups [Figure 2].

Figure 2.

A cone-beam computed tomography image showing manual segmentation of postoperative cavity lesion (a) manual tracing the lesion cavity in different slice volume in sagittal view (b) 3D reconstruction of the lesion cavity with red colour by Romexis software to calculate the volume

Statistical analysis

Data were analyzed using IBM^® SPSS^® Statistics software (version 20.0; IBM Corp., Armonk, NY, USA). Mean and standard deviation were calculated for all variables. Normality was confirmed using Kolmogorov–Smirnov and Shapiro–Wilk tests; therefore, parametric tests were applied. The independent sample t-test was used for intergroup comparisons, and the paired sample t-test was used for intragroup comparisons over time. The level of significance was set at P ≤ 0.05.

RESULTS

Twenty-four teeth were identified to meet the inclusion criteria. The mean age was 32.92 ± 2.29 years in the non-guided group and 33.83 ± 2.51 years in the guided group, with no statistically significant difference between the two groups (P = 0.790). Regarding gender distribution, females represented 41.7% of the nonguided group and 16.7% of the guided group, while males accounted for 58.3% and 83.3%, respectively; the difference was not statistically significant (P = 0.089). The distribution of tooth types was comparable between the two groups, with no significant difference observed (P = 0.590).

The mean operation time in the non-guided group for the current study was (39–47 min) which decreased significantly in the guided group to 26–27.5 min (P ≤ 0.001, P = 0.011, P ≤ 0.05). While there was no significant difference between MTA and Well Root Putty within the same technique (P > 0.05) [Table 1].

Table 1.

The mean operation time for all the groups

Subgroup	Nonguided group (min)	Guided group (min)	Test value†	P †
S1 (MTA angelus)	47.00±6.36	27.33±3.01	6.85	<0.001*
S2 (WRP)	39.83±9.99	26.17±4.17	3.09	0.011*
Test value‡	1.48	0.56
P ‡	0.169	0.591

*Significance at P≤0.05, ^†Independent samples t-test was used for comparison between guided and nonguided groups within each subgroup, ^‡Independent samples t-test was used for comparison between S1 and S2 subgroups within the same technique. Values are expressed as mean±SD. WRP: Well-root putty, SD: Standard deviation, MTA: Mineral trioxide aggregate

For all tested groups, there was a significant reduction in the volume of cavity lesions after treatment at the 6-month follow-up compared with the 1-week assessment period in all groups. The mean percentage reduction in lesion volume at 6 months in the nonguided group (A) was 68.83% ±5.34 for the MTA-Angelus subgroup (S1) and 73.50% ±9.81 for the Well-Root Putty subgroup (S2), while in the guided group (B) it was 75.33% ±8.94 for the MTA-Angelus subgroup and 75.50% ±5.14 for the Well-Root Putty subgroup. Intergroup comparison revealed no statistically significant difference between guided and non-guided microsurgery in terms of percentage lesion volume reduction for either retrograde filling material (P = 0.546, P = 0.860, P > 0.05). Furthermore, intragroup comparison showed no statistically significant difference between MTA-Angelus and Well-Root Putty within the same surgical technique (P = 0.68, P = 0.987, P > 0.05) [Table 2].

Table 2.

Lesion volume changes with comparisons

Subgroup	Group	Volume at 1 week (cm3)	Volume at 6 months (cm3)	Reduction (%)	P† (1 week vs. 6 months)	P†† (Guided vs. nonguided)	P††† (S1 vs. S2)
S1 (MTA)	Nonguided	0.609±0.081	0.171±0.018	68.83±5.34	0.027*	0.546 (AS1 vs. BS1)‡	0.68 (AS1 vs. AS2)‡‡‡
S1 (MTA)	Guided	0.480±0.224	0.143±0.067	75.33±8.94	0.028*
S2 (WRP)	Nonguided	0.579±0.150	0.152±0.063	73.50±9.81	0.020*	0.860 (AS2 vs. BS2)‡‡	0.987 (BS1 vs. BS2)‡‡‡‡
S2 (WRP)	Guided	0.480±0.220	0.154±0.076	75.50±5.14	0.021*

*Significance at P≤0.05, ^†Paired sample t-test was used for comparisons between 1 week and 6 months, ^††Independent sample t-test was used for comparisons of Percentage of decrease in volume at 6 months between guided and nonguided groups within the same subgroup. (Intergroup comparison), ^†††Independent sample t-test was used for comparisons of percentage of decrease in volume at 6 months between S1 and S2 subgroups within the same technique (Intragroup comparison), ^‡Nonguided-MTA versus guided-MTA, ^‡‡Nonguided-well-Root PT versus guided-well-Root PT, ^‡‡‡Nonguided-MTA versus nonguided-well-Root PT, ^‡‡‡‡Guided-MTA versus guided-well-Root PT. Values are expressed as mean±SD. WRP: Well-root putty, SD: Standard deviation, MTA: Mineral trioxide aggregate

DISCUSSION

The management of periapical lesions highly developed with introducing microsurgery, digital technology, and CBCT imaging that allowed us to visualize the root apex and surrounding anatomical features in three dimensions prior to treatment, and allowed us to use templates like those used in implants for endodontics-guided access, canal location, and microsurgery.[4] This study employed surgical guidance to preplan apical access location and angulation, minimizing intraoperative adjustments. Dedania et al. reported a case in which a CBCT-based 3D-printed surgical template facilitated precise bone removal and apicectomy with minimal trauma, demonstrating the clinical utility of guided approaches in periapical surgery.[14] Ahn et al. suggested that guided approaches could expand the number of teeth that could be considered in surgery by reducing complications and minimizing surgical site size.[15]

The editorial by Singh highlights the emerging role of guided endodontic techniques and their potential to improve procedural accuracy and outcomes. Few studies have evaluated the accuracy of guided endodontic surgery.[16] Antal et al. reported minimal deviations during guided root-end resection using a trephine bur, with a mean angular deviation of 3.95°, an apex removal error of 0.19 mm, and an osteotomy depth error of 0.37 mm, concluding the technique is accurate even in posterior teeth.[5] Similarly, studies on cadaver models found that 3D-printed surgical guides provided more precise apical access than freehand surgery.[17]

In this study, MTA-Angelus and Well-Root PT were compared as root-end filling materials. MTA has long been considered the gold standard in endodontic surgery due to its excellent sealing ability, biocompatibility, mechanical properties, and regenerative effects on periradicular tissues.[7] It demonstrates a high success rate, exceeding 88.8%. However, newer bioceramic putties like Well-Root PT offer improved handling due to their premixed, user-friendly nature, minimizing mixing errors.[7] Although lacking the long-term track record of MTA, they are gaining popularity as promising alternatives with favorable clinical outcomes.[18]

Lesion bone volume was assessed after 6 months, following the approach described by Cohen et al.,[19] who investigated osseous regeneration following apicoectomy with various retrofilling materials. This provides an early, dependable indication of the healing dynamics and helps identify potential postoperative complications. In addition, recent advancements in surgical techniques and materials have contributed to generally higher success rates,[20] making it challenging to isolate the influence of individual variables. Hence, evaluating bone repair at an earlier phase can offer valuable insight into the rate and quality of tissue regeneration and may help distinguish approaches that facilitate faster recovery. However, longer follow-up may be needed to confirm complete and long-term success.[21]

In the current study, the mean operation time was 39–47 min in the non-guided group, decreasing significantly to 26–27.5 min in the guided group, with no significant difference between retrograde filling materials. These results align with Del Fabbro et al., who reported a mean of 42 min for root-end microsurgeries[22] and Liu et al., who achieved <23 min with guided apicectomy.[23] On the contrary, Wei et al. reported lesser time (5–15 min) using static guides,[24] and Tuk et al. noted a range from 25 min to 140 min.[25] The time reduction in guided surgery is attributed to accurate preoperative planning, elimination of intraoperative adjustments, and streamlined workflow, while variations between studies may relate to differences in measuring surgical time, operator experience, surgical site, lesion size, and facility resources.

This study assessed changes in lesion volume between 1 week and 6 months using CBCT. CBCT has become an indispensable tool in contemporary endodontic practice, particularly for the 3D assessment of periapical lesions and surgical planning. Previous studies have demonstrated the reliability of CBCT in evaluating periapical lesion characteristics, volume, and bone changes, thereby allowing a more accurate assessment of disease extent compared with conventional radiography.[26] CBCT has also been shown to assist in the differential diagnosis of periapical cysts and granulomas, improving preoperative decision-making and outcome assessment.[27] Moreover, studies examining lesion volume and bone radiodensity using CBCT provide detailed information about lesion size and bone radiodensity, which is critical for understanding lesion behavior and optimizing surgical approaches.[28]

The current study used the periapical lesion volume rather than simple linear size measurements because volumetric analysis provides a more comprehensive 3D assessment of lesion extent. 2D size measurements can underestimate the true lesion extent due to projection limitations and lack of depth information, whereas CBCT-based volume measurement captures the full spatial distribution of the lesion, improving accuracy in both diagnosis and monitoring of treatment outcomes.[29] For volumetric measurements, manual segmentation was employed due to its accuracy, despite being time-consuming and user-dependent.[30]

Results showed a significant decrease in the volume of the cavity lesion at the 6-month follow-up period in all groups. However, the effect of surgical technique and retrograde filling on cavity lesion volume was non-significant. There were only a few studies that dealt with postoperative volume of cavity lesions, and they may use different retrograde filling materials or surgical techniques. The results of the current study are in consonance with Karan and Aricioğlu (2020), who reported significant postoperative volume reduction and density increase across all groups, with no significant difference between MTA, PRF, and MTA + PRF. The highest density was in the MTA + PRF group, and the lowest volume value was obtained in the MTA and MTA + PRF groups.[31] Moreover, a study evaluating bone healing after endodontic microsurgery by Ramis-Alario et al. reported a significant reduction in lesion volume over 2 years with a radiographic healing rate of 6.2 mm³ per month.[32] Similarly, Eskandar et al. reported significant volume reduction over 1–4 years after microsurgery using MTA, RRM putty, or the lid technique, with no significant differences among groups.[33]

Several factors contribute to the positive impact of microsurgery and guided microsurgery on bone density and lesion volume following root-end surgery, including the precise removal of infected tissue, root resection, avoidance of needless trauma to nearby healthy tissues, enhanced root-end preparation with improved visualization, and the application of advanced biomaterials.[34] A recent review by Iqbal et al. reported satisfactory outcomes in the management of challenging endodontic cases and accepted bone healing, suggesting that the accuracy of guided surgeries promotes bone regeneration.[35]

Finally, it was concluded that guided microsurgery effectively reduced surgical time, and there was no significant difference between guided, nonguided microsurgery and the various retrograde filling materials in terms of the lesion volume reduction after surgery. The predominance of this partial healing is consistent with the expected intermediate phase of bone maturation before complete regeneration. This suggests that guided microsurgery may follow a similar biological healing pattern to conventional microsurgery, but with the potential advantage of improved precision and reduced surgical trauma. Finally, a larger sample size might have uncovered significant differences in outcomes of guided endodontic surgery. Moreover, a 3-month evaluation could offer additional information on early healing dynamics; extended follow-up periods could offer more comprehensive insights into the long-term success of the therapy.

CONCLUSION

Guided microsurgery reduced surgical time without affecting bone lesion volume. Clinical outcomes were comparable between MTA-Angelus and Well-Root Putty.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.