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Restor Dent Endod
Restor Dent Endod
RDE
Restorative Dentistry & Endodontics
2234-7658
2234-7666
The Korean Academy of Conservative Dentistry

10.5395/rde.2024.49.e26
Research Article
Procedural errors detected by cone beam tomography in cases with indication for retreatment: in vivo cross-sectional study
https://orcid.org/0000-0003-2901-8928
Valverde Haro Henry Paul 12
https://orcid.org/0000-0003-0657-6011
Rupaya Carmen Rosa Garcia 2
https://orcid.org/0000-0002-9922-8202
Alves Flávio R. F. 3
1 Postgraduate Program in Dentistry, University of Grande Rio (UNIGRANRIO), Rio de Janeiro, RJ, Brazil.
2 Postgraduate Program in Dentistry, Cayetano Heredia University, Lima, Peru.
3 Department of Dental Research, Faculty of Dentistry, Iguaçu University (UNIG), Nova Iguaçu, RJ, Brazil.
Citation: Valverde Haro HP, Rupaya CR, Alves FRF. Procedural errors detected by cone beam tomography in cases with indication for retreatment: in vivo cross-sectional study. Restor Dent Endod 2024;49(3):e26.

Correspondence to Henry Paul Valverde Haro, DDS, MSc. Postgraduate Program in Dentistry, University of Grande Rio (UNIGRANRIO), Rua Professor José de Souza Herdy, 1160 Jardim Vinte e Cinco de Agosto, Duque de Caxias, RJ 25071-202, Brazil. endosolutionsec@gmail.com
8 2024
24 6 2024
49 3 e2624 4 2024
20 5 2024
05 6 2024
Copyright © 2024. The Korean Academy of Conservative Dentistry
2024
The Korean Academy of Conservative Dentistry
https://creativecommons.org/licenses/by-nc/4.0/ This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Objectives

This study aimed to investigate the frequency and type of endodontic procedural errors in cases indicated for retreatment through cone-beam computed tomography (CBCT) analysis.

Materials and Methods

The sample consisted of 96 CBCT scans, encompassing 122 permanent teeth with fully formed roots. Errors included perforation, instrument fracture, canal transportation, missed canals, and inadequate apical limit of filling. Additionally, potential risk factors were analyzed and subjected to statistical modeling.

Results

The most frequent procedural error observed was the inadequate apical limit of filling, followed by canal transportation, perforation, missed canal, and instrument fracture. Statistically significant associations were identified between various procedural errors and specific factors. These include canal transportation and root canal wall, with the buccal wall being the most commonly affected; missed canal and tooth type, particularly the palatine and second mesiobuccal canal canals; inadequate apical limit of filling and root curvature, showing a higher deviation to the mesial direction in severely curved canals; inadequate apical limit of filling and the presence of calcifications, with underfilling being the most frequent; canal transportation and periapical lesion, notably with deviation to the buccal direction; and the direction of perforation and periapical lesion, most frequently occurring to buccal direction.

Conclusions

CBCT emerges as a valuable tool in identifying procedural errors and associated factors, crucial for their prevention and management.

Cone beam computed tomography
Endodontics
Root canal therapy
Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro http://dx.doi.org/10.13039/501100004586 Conselho Nacional de Desenvolvimento Científico e Tecnológico http://dx.doi.org/10.13039/501100003593
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pmcINTRODUCTION

The primary goal of endodontic treatment is to reduce microbial load, aiming to eliminate the intracanal infection to levels compatible with the healing of the periapical tissues [1]. Nonetheless, 5%–20% of endodontic treatments result in post-treatment apical periodontitis, often attributed to anatomical variations that pose challenges and contribute to procedural errors [2]. These errors include perforations, instrument fractures, canal transportation, missed canals, and inadequate filling [34]. Factors such as root canal calcifications and pulp stones, occurring in 5.1% and 8% of cases, are commonly associated with procedural errors in endodontic practice [5].

The most common treatment alternative for cases with persistent periapical lesions is endodontic retreatment, particularly recommended for inadequately treated cases [6]. However, retreatments are challenging in cases presenting procedural errors. Therefore, meticulous treatment planning, with attention to detail, is crucial to the successful resolution of these cases. In this regard, cone-beam computed tomography (CBCT) stands out as a valuable tool for identifying endodontic procedural errors. The 3-dimensional (3D) nature and high-quality imaging of CBCT offer optimal conditions for error analysis. Despite the availability of this advanced imaging technology, it is noteworthy that several CBCT studies have predominantly examined individual procedural errors, thereby limiting a comprehensive understanding of the various factors influencing treatment outcomes [78].

The present study aimed to investigate the frequency and type of endodontic procedural errors in cases indicated for retreatment through CBCT analysis. Additionally, potential risk factors were analyzed and subjected to statistical modeling.

MATERIALS AND METHODS

This cross-sectional descriptive study received approval from the Institutional Research Ethics Committee (approval No. 209552).

Sample selection and evaluation

A sample calculation estimated the number of CBCT scans required to test pairwise associations between variables. This calculation took into account findings from similar prior studies [910]. Given the variability in these findings, 3 sample calculations were performed, each based on different assumptions: a weak association (r = 0.3), a moderate association (r = 0.55), and a strong association (r = 0.8). With a 5% alpha error and a 20% beta error, the minimum number of scans needed was estimated to be 85.

The sample consisted of 96 CBCT scans, encompassing 122 permanent teeth with fully formed roots and radiographic evidence of previous endodontic treatment, with retreatment indication. CBCT’s indications were based on the 7th and 8th recommendations of the AAE/AAOMR position statement [11]. The data collection occurred between January 1st, 2020 and June 30th, 2022. The scans were obtained using the GIANO HR CBCT equipment (NewTon, Imola, Italy), with FOV limited to 6 × 6 mm, a voxel from 68 to 300 μm, 16 mAs, 90 kVp, and a scan time in the Best Quality function of 16.8–3.6 seconds.

Two examiners underwent training and calibration under the guidance of an expert radiologist with over 10 years of experience in CBCT image measurement, interpretation, and diagnosis. This training was performed with a set of 20 CBCT scans and was focused on standardizing CBCT evaluation. CBCT evaluation was performed using Horos software version V3.3.6 (HOROS, Horos project, Annapolis, MD, USA). Scans were excluded if visualization difficulties due to artifacts were noted by at least 1 examiner. From an initial sample of 120 scans, 24 were excluded due to artifacts, resulting in the 96 that composed the final sample. Substantial agreement between observers was achieved (Kappa value of 0.90). In cases where there was no consensus in the evaluation, a joint review was conducted until consensus was reached.

Evaluation of procedural errors

1. Perforation and direction

The prevalence and direction of perforations were analyzed across the 3 tomographic sections, with greater emphasis on the axial and sagittal sections. The aim was to identify whether perforation occurred and its location within the root canal—whether buccal, distal, mesial, or palatal (Figure 1).

Figure 1 Dynamic cone-beam computed tomography analysis for identification of perforation in the right lateral incisor.

2. Instrument fracture

The frequency of instrument fracture was assessed, and the location of the instrument fragment within the root canal was identified (apical, middle, or coronal third). Special attention was given to analyzing sagittal and axial slices of the CBCT (Figure 2).

Figure 2 Dynamic cone-beam computed tomography analysis for identification of fractured instrument in lower left first molar.

3. Canal transportation

The filling material trajectory was compared with the canal direction, and any detected deviations were categorized as buccal, distal, mesial, or palatal. Evaluation involved analysis of sagittal, axial, and coronal sections of the CBCT (Figure 3).

Figure 3 Dynamic cone-beam computed tomography analysis for identification of canal transportation in upper right first molar.

4. Missed canal

Teeth images were analyzed for the occurrence of at least 1 untreated canal, defined as those without any evidence of filling material from the coronal orifice to the apex, and its association with the presence of apical periodontitis, primarily assessed on axial section images (Figure 4) [12].

Figure 4 Dynamic analysis of cone-beam computed tomography for identification of missed canal.

5. Apical limit of filling

The extent of filling was evaluated using a nominal scale: underfilled (> 2 mm short from the apex), overfilled, both understandable as inadequate, and adequate (0–2 mm short from the apex). Initial assessment was conducted on sagittal section images, with confirmation on axial slices (Figure 5).

Figure 5 Identification of (A) molar with an overfilled canal, (B) premolar at the appropriate level and (C) palatal canal of an underfilled upper molar.

6. Associated factors

Several associated factors were also evaluated: (a) presence of calcifications (Figure 6); (b) tooth type (anterior, premolars, and molars) (Figure 7); (c) periapical lesion, defined by disruption of lamina dura continuity and the presence of a radiolucent area around the root apex at least twice as thick as the normal periodontal ligament space (Figure 8); and (d) root curvature angle according to the Schneider’s method, modified by the inclusion of one more category (mild curvature) (Figure 9) [1314].

Figure 6 Identification of second mesiobuccal canal calcification in upper left first molar.

Figure 7 Identification of anterior, premolar and molar tooth type.

Figure 8 Identification of periapical lesion in upper right first molar.

Figure 9 Identification of type of curvature, (A) moderate, (B) severe and (C) straight.

Statistical analysis

The data were analyzed using Stata software v. 17 (StataCorp, College Station, TX, USA). Descriptive statistics were computed to understand the distribution of variables via univariate analysis. Absolute and relative frequencies were obtained and represented with tables. For inferential statistics, bivariate analysis was conducted between dichotomous qualitative variables utilizing χ2 and Fisher's analysis. These tests determined the association between endodontic procedural errors and associated factors. Response categories with counts less than 5 were collapsed to ensure statistical robustness.

RESULTS

The most frequent procedural error observed was the inadequate apical limit of filling (82.38%, n = 187), followed by canal transportation (68.72%, n = 156), canal perforation (63.44%, n = 144), missed canal (16.30%, n = 37), and instrument fracture (1.76%, n = 4). For a detailed prevalence of each procedural error, please refer to Table 1.

Table 1 Type and frequency of endodontic procedural errors per canal (n = 227)

Procedural errors	Values	
Perforation		
	Without perforation	83 (36.56)	
	Buccal	54 (23.79)	
	Distal	27 (11.89)	
	Mesial	39 (17.18)	
	Palatal	24 (10.57)	
Root canal transportation		
	No transport	71 (31.28)	
	Buccal	64 (28.19)	
	Distal	24 (10.57)	
	Mesial	42 (18.50)	
	Palatal	26 (11.45)	
Instrument fracture		
	No fracture	223 (98.24)	
	Middle third	4 (1.76)	
Missed canals		
	No missed canal	190 (83.70)	
	Single canal	1 (0.44)	
	Mesiobuccal	6 (2.64)	
	Mesiolingual	2 (0.88)	
	MB2	9 (3.96)	
	Distobuccal	5 (2.20)	
	Palatal	10 (4.41)	
	Buccal	4 (1.76)	
Root filling extension		
	Underfilled	114 (50.22)	
	Overfilled	33 (14.54)	
	Adequate	40 (17.62)	
	Unfilled	40 (17.62)	
Values are presented as number (%).

Statistically significant associations (p < 0.01) were identified between various procedural errors and specific factors. These include canal transportation and root canal wall, with the buccal wall being the most commonly affected; missed canal and tooth type, particularly the palatine and second mesiobuccal canal (MB2) canals; inadequate apical limit of filling and root curvature, showing a higher deviation to the mesial direction in severely curved canals; inadequate apical limit of filling and the presence of calcifications, with underfilling being the most frequent; canal transportation and periapical lesion, notably with deviation to the buccal direction in these cases; and the direction of perforation and periapical lesion, most frequently occurring to buccal direction. Conversely, no statistically significant association was found between endodontic procedure error and tooth quadrant (p > 0.05). Detailed frequencies are provided in the respective Tables 2, 3, 4, 5, 6.

Table 2 Procedural errors according to tooth type

Procedural errors	Tooth type	
Upper Incisors	Upper canines	Upper premolars	Upper molars	Lower incisors	Lower premolars	Lower molars	Total	
Perforation									
	Without perforation	13 (5.73)	2 (0.88)	19 (8.37)	34 (14.98)	0 (0.00)	1 (0.44)	14 (6.17)	83 (36.56)	
	Buccal	15 (6.61)	3 (1.32)	11 (4.85)	15 (6.61)	0 (0.00)	2 (0.88)	8 (3.52)	54 (23.79)	
	Distal	2 (0.88)	1 (0.44)	3 (1.32)	13 (5.73)	1 (0.44)	0 (0.00)	7 (3.08)	27 (11.89)	
	Mesial	9 (3.96)	0 (0.00)	4 (1.76)	15 (6.61)	0 (0.00)	2 (0.88)	9 (3.96)	39 (17.18)	
	Palatal	3 (1.32)	0 (0.00)	2 (0.88)	10 (4.41)	0 (0.00)	2 (0.88)	7 (3.08)	24 (10.57)	
	Pearson χ2 (1) = 0.6996 Pr = 0.403	
Root canal transportation									
	No transport	6 (2.64)	0 (0.00)	16 (7.05)	33 (14.54)	0 (0.00)	1 (0.44)	15 (6.61)	71 (31.28)	
	Buccal	19 (8.37)	4 (1.76)	14 (6.17)	16 (7.05)	0 (0.00)	2 (0.88)	9 (3.96)	64 (28.19)	
	Distal	2 (0.88)	1 (0.44)	2 (0.88)	12 (5.29)	1 (0.44)	0 (0.00)	6 (2.64)	24 (10.57)	
	Mesial	11 (4.85)	1 (0.44)	4 (1.76)	15 (6.61)	0 (0.00)	3 (1.32)	8 (3.52)	42 (18.50)	
	Palatal	4 (1.76)	0 (0.00)	3 (1.32)	11 (4.85)	0 (0.00)	1 (0.44)	7 (3.08)	26 (11.45)	
	Pearson χ2 (1) = 6.9223 Pr = 0.009	
Instrument fracture									
	Unfractured	42 (18.50)	6 (2.64)	39 (17.18)	85 (37.44)	1 (0.44)	7 (3.08)	43 (18.94)	223 (98.24)	
	Middle third	0 (0.00)	0 (0.00)	0 (0.00)	2 (0.88)	0 (0.00)	0 (0.00)	2 (0.88)	4 (1.76)	
	Fisher's exact = 1.000/1-sided Fisher's exact = 0.438	
Missed canals									
	Single canal	1 (0.44)	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)	1 (0.44)	
	Mesiobuccal	0 (0.00)	0 (0.00)	0 (0.00)	4 (1.76)	0 (0.00)	0 (0.00)	2 (0.88)	6 (2.64)	
	Mesiolingual	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)	2 (0.88)	2 (0.88)	
	MB2	0 (0.00)	0 (0.00)	0 (0.00)	9 (3.96)	0 (0.00)	0 (0.00)	0 (0.00)	9 (3.96)	
	Distobuccal	0 (0.00)	0 (0.00)	0 (0.00)	4 (1.76)	0 (0.00)	0 (0.00)	1 (0.44)	5 (2.20)	
	Palatal	0 (0.00)	0 (0.00)	7 (3.08)	3 (1.32)	0 (0.00)	0 (0.00)	0 (0.00)	10 (4.41)	
	Buccal	0 (0.00)	0 (0.00)	2 (0.88)	2 (0.88)	0 (0.00)	0 (0.00)	0 (0.00)	4 (1.76)	
	Pearson χ2 (1) = 7.3180 Pr = 0.007	
Root filling extension									
	Underfilled	19 (8.37)	4 (1.76)	15 (6.61)	47 (20.70)	1 (0.44)	2 (0.88)	26 (11.45)	114 (50.22)	
	Overfilled	13 (5.73)	0 (0.00)	6 (2.64)	11 (4.85)	0 (0.00)	3 (1.32)	0 (0.00)	33 (14.54)	
	Adequate	9 (3.96)	2 (0.88)	10 (4.41)	8 (3.52)	0 (0.00)	2 (0.88)	9 (3.96)	40 (17.62)	
	Unfilled	1 (0.44)	0 (0.00)	8 (3.52)	21 (9.25)	0 (0.00)	0 (0.00)	10 (4.41)	40 (17.62)	
	Pearson χ2 (1) = 0.5117 Pr = 0.474	
Values are presented as number (%).

Table 3 Procedural errors according to the type of root curvature

Procedural errors	Type of root curvature	
Straight (≤ 5°)	Mild (5°–10°)	Moderate (10°–20°)	Severe (25°–70°)	Total	
Perforation						
	Without perforation	60 (26.43)	7 (3.08)	5 (2.20)	11 (4.85)	83 (36.56)	
	Buccal	38 (16.74)	8 (3.52)	1 (0.44)	7 (3.08)	54 (23.79)	
	Distal	13 (5.73)	4 (1.76)	2 (0.88)	8 (3.52)	27 (11.89)	
	Mesial	19 (8.37)	10 (4.41)	1 (0.44)	9 (3.96)	39 (17.18)	
	Palatal	18 (7.93)	3 (1.32)	2 (0.88)	1 (0.44)	24 (10.57)	
	Pearson χ2 (8) = 15.3963 Pr = 0.052	
Root canal transportation						
	No transport	46 (20.26)	9 (3.96)	5 (2.20)	11 (4.85)	71 (31.28)	
	Buccal	49 (21.59)	7 (3.08)	1 (0.44)	7 (3.08)	64 (28.19)	
	Distal	11 (4.85)	4 (1.76)	2 (0.88)	7 (3.08)	24 (10.57)	
	Mesial	22 (9.69)	9 (3.96)	1 (0.44)	10 (4.41)	42 (18.50)	
	Palatal	20 (8.81)	3 (1.32)	2 (0.88)	1 (0.44)	26 (11.45)	
	Pearson χ2 (8) = 13.7770 Pr = 0.088	
Instrument fracture						
	Unfractured	146 (64.32)	31 (13.66)	11 (4.85)	35 (15.42)	223 (98.24)	
	Middle third	2 (0.88)	1 (0.44)	0 (0.00)	1 (0.44)	4 (1.76)	
	Fisher's exact = 0.612/1-sided Fisher's exact = 0.434	
Missed canals						
	No missed canal	131 (57.71)	25 (11.01)	7 (3.08)	27 (11.89)	190 (83.70)	
	Single canal	1 (0.44)	0 (0.00)	0 (0.00)	0 (0.00)	1 (0.44)	
	Mesiobuccal	1 (0.44)	3 (1.32)	0 (0.00)	2 (0.88)	6 (2.64)	
	Mesiolingual	1 (0.44)	1 (0.44)	0 (0.00)	0 (0.00)	2 (0.88)	
	MB2	1 (0.44)	2 (0.88)	0 (0.00)	6 (2.64)	9 (3.96)	
	Distobuccal	5 (2.20)	0 (0.00)	0 (0.00)	0 (0.00)	5 (2.20)	
	Palatal	6 (2.64)	1 (0.44)	2 (0.88)	1 (0.44)	10 (4.41)	
	Buccal	2 (0.88)	0 (0.00)	2 (0.88)	0 (0.00)	4 (1.76)	
	Pearson χ2 (1) = 7.2211 Pr = 0.007	
Root filling estension						
	Underfilled	67 (29.52)	18 (7.93)	5 (2.20)	24 (10.57)	114 (50.22)	
	Overfilled	24 (10.57)	6 (2.64)	1 (0.44)	2 (0.88)	33 (14.54)	
	Adequate	37 (16.30)	2 (0.88)	1 (0.44)	0 (0.00)	40 (17.62)	
	Unfilled	20 (8.81)	6 (2.64)	4 (1.76)	10 (4.41)	40 (17.62)	
	Pearson χ2 (6) = 23.7269 Pr = 0.001	
Values are presented as number (%).

Table 4 Procedural errors according to the presence of calcifications

Procedural errors	Calcification	
Yes	No	Total	
Perforation direction				
	Without perforation	8 (3.52)	75 (33.04)	83 (36.56)	
	Buccal	3 (1.32)	51 (22.47)	54 (23.79)	
	Distal	3 (1.32)	24 (10.57)	27 (11.89)	
	Mesial	2 (0.88)	37 (16.30)	39 (17.18)	
	Palatal	2 (0.88)	22 (9.69)	24 (10.57)	
	Pearson χ2 (1) = 0.5235 Pr = 0.469	
Root canal transportation				
	No transport	9 (3.96)	62 (27.31)	71 (31.28)	
	Buccal	3 (1.32)	61 (26.87)	64 (28.19)	
	Distal	1 (0.44)	23 (10.13)	24 (10.57)	
	Mesial	1 (0.44)	41 (18.06)	42 (18.50)	
	Palatal	4 (1.76)	22 (9.69)	26 (11.45)	
	Pearson χ2 (1) = 3.1882 Pr = 0.074	
Instrument fracture				
	Unfractured	18 (7.93)	205 (90.31)	223 (98.24)	
	Middle third	0 (0.00)	4 (1.76)	4 (1.76)	
	Fisher's exact = 1.000/1-sided Fisher's exact = 0.717	
Missed canals				
	No missed canal	7 (3.08)	183 (80.62)	190 (83.70)	
	Single canal	1 (0.44)	0 (0.00)	1 (0.44)	
	Mesiobuccal	1 (0.44)	5 (2.20)	6 (2.64)	
	Mesiolingual	1 (0.44)	1 (0.44)	2 (0.88)	
	MB2	6 (2.64)	3 (1.32)	9 (3.96)	
	Distobuccal	0 (0.00)	5 (2.20)	5 (2.20)	
	Palatal	1 (0.44)	9 (3.96)	10 (4.41)	
	Buccal	1 (0.44)	3 (1.32)	4 (1.76)	
	Pearson χ2 (1) = 28.7759 Pr = 0.000	
Root filling extension				
	Underfilled	5 (2.20)	109 (48.02)	114 (50.22)	
	Overfilled	2 (0.88)	31 (13.66)	33 (14.54)	
	Adequate	1 (0.44)	39 (17.18)	40 (17.62)	
	Unfilled	10 (4.41)	30 (13.22)	40 (17.62)	
	Pearson χ2 (3) = 19.6993 Pr = 0.000	
Values are presented as number (%).

Table 5 Endodontic procedure errors according to the presence of periapical reaction

Procedural errors	Periapical reaction	
Presence	Absence	Total	
Fenestration direction				
	Without perforation	67 (29.52)	16 (7.05)	83 (36.56)	
	Buccal	40 (17.62)	14 (6.17)	54 (23.79)	
	Distal	26 (11.45)	1 (0.44)	27 (11.89)	
	Mesial	32 (14.10)	7 (3.08)	39 (17.18)	
	Palatal	11 (4.85)	13 (5.73)	24 (10.57)	
	Pearson χ2 (4) = 20.6146 Pr = 0.000	
Root canal transportation				
	No transport	56 (24.67)	15 (6.61)	71 (31.28)	
	Buccal	51 (22.47)	13 (5.73)	64 (28.19)	
	Distal	23 (10.13)	1 (0.44)	24 (10.57)	
	Mesial	34 (14.98)	8 (3.52)	42 (18.50)	
	Palatal	12 (5.29)	14 (6.17)	26 (11.45)	
	Pearson χ2 (4) = 19.8368 Pr = 0.001	
Instrument fracture level				
	No fracture	174 (76.65)	49 (21.59)	223 (98.24)	
	Middle third	2 (0.88)	2 (0.88)	4 (1.76)	
	Fisher's exact = 0.219/1-sided Fisher's exact = 0.219	
Omission of root canals				
	No missed canal	144 (63.44)	46 (20.26)	190 (83.70)	
	Single canal	0 (0.00)	1 (0.44)	1 (0.44)	
	Mesiobuccal	6 (2.64)	0 (0.00)	6 (2.64)	
	Mesiolingual	2 (0.88)	0 (0.00)	2 (0.88)	
	MB2	9 (3.96)	0 (0.00)	9 (3.96)	
	Distobuccal	4 (1.76)	1 (0.44)	5 (2.20)	
	Palatal	8 (3.52)	2 (0.88)	10 (4.41)	
	Buccal	3 (1.32)	1 (0.44)	4 (1.76)	
	Pearson χ2 (1) = 2.0343 Pr = 0.154	
Root filling quality				
	Underfilled	89 (39.21)	25 (11.01)	114 (50.22)	
	Overfilled	25 (11.01)	8 (3.52)	33 (14.54)	
	Adequate level	27 (11.89)	13 (5.73)	40 (17.62)	
	Unfilled	35 (15.42)	5 (2.20)	40 (17.62)	
	Pearson χ2 (3) = 4.6713 Pr = 0.198	
Values are presented as number (%).

Table 6 Procedural errors according to dental quadrant

Procedural errors	Dental quadrant	
Upper right	Upper left	Lower left	Lower right	Total	
Fenestration direction						
	Without perforation	35 (15.42)	33 (14.54)	6 (2.64)	9 (3.96)	83 (36.56)	
	Buccal	16 (7.05)	28 (12.33)	1 (0.44)	9 (3.96)	54 (23.79)	
	Distal	10 (4.41)	9 (3.96)	4 (1.76)	4 (1.76)	27 (11.89)	
	Mesial	11 (4.85)	17 (7.49)	7 (3.08)	4 (1.76)	39 (17.18)	
	Palatal	7 (3.08)	8 (3.52)	3 (1.32)	6 (2.64)	24 (10.57)	
	Pearson χ2 (12) = 15.9915 Pr = 0.192	
Root canal transportation						
	No transport	27 (11.89)	28 (12.33)	5 (2.20)	11 (4.85)	71 (31.28)	
	Buccal	20 (8.81)	33 (14.54)	2 (0.88)	9 (3.96)	64 (28.19)	
	Distal	10 (4.41)	7 (3.08)	4 (1.76)	3 (1.32)	24 (10.57)	
	Mesial	14 (6.17)	17 (7.49)	7 (3.08)	4 (1.76)	42 (18.50)	
	Palatal	8 (3.52)	10 (4.41)	3 (1.32)	5 (2.20)	26 (11.45)	
	Pearson χ2 (12) = 11.7629 Pr = 0.465	
Instrument fracture						
	Unfractured	78 (34.36)	94 (41.41)	21 (9.25)	30 (13.22)	223 (98.24)	
	Middle third	1 (0.44)	1 (0.44)	0 (0.00)	2 (0.88)	4 (1.76)	
	Fisher's exact = 1.000/1-sided Fisher's exact = 0.566	
Missed canals						
	Single canal	61 (26.87)	81 (35.68)	19 (8.37)	29 (12.78)	190 (83.70)	
	Mesiobuccal	0 (0.00)	1 (0.44)	0 (0.00)	0 (0.00)	1 (0.44)	
	Mesiolingual	3 (1.32)	1 (0.44)	1 (0.44)	1 (0.44)	6 (2.64)	
	MB2	0 (0.00)	0 (0.00)	0 (0.00)	2 (0.88)	2 (0.88)	
	Distobuccal	5 (2.20)	4 (1.76)	0 (0.00)	0 (0.00)	9 (3.96)	
	Palatal	3 (1.32)	1 (0.44)	1 (0.44)	0 (0.00)	5 (2.20)	
	Buccal	6 (2.64)	4 (1.76)	0 (0.00)	0 (0.00)	10 (4.41)	
	Single canal	1 (0.44)	3 (1.32)	0 (0.00)	0 (0.00)	4 (1.76)	
	Fisher's exact = 0.266	
Root filling extension						
	Underfilled	43 (18.94)	42 (18.50)	13 (5.73)	16 (7.05)	114 (50.22)	
	Overfilled	10 (4.41)	20 (8.81)	0 (0.00)	3 (1.32)	33 (14.54)	
	Adequate	10 (4.41)	19 (8.37)	6 (2.64)	5 (2.20)	40 (17.62)	
	Unfilled	16 (7.05)	14 (6.17)	2 (0.88)	8 (3.52)	40 (17.62)	
	Pearson χ2 (9) = 13.5785 Pr = 0.138	
Values are presented as number (%).

DISCUSSION

In contemporary endodontics, the importance of CBCT to assess the quality of previous endodontic treatment is well recognized being probably the greater ally of the clinician to obtain accurate diagnosis and decision-making, especially in cases of posttreatment apical periodontitis [1213]. Using CBCT, the present study significantly advances the understanding of conditions associated with failures in endodontic procedures. By incorporating factors such as root canal anatomy, tooth type, presence of periapical lesion, and root curvature angle, this research highlights aspects often overlooked in similar studies, offering a detailed perspective on how these factors collectively impact endodontic outcomes [78]. This approach contributes to a more comprehensive understanding of endodontic procedural failures.

In this investigation, underfilling emerged as the most prevalent endodontic procedural error, affecting 50.22% of the cases. This finding aligns with previous research, including a study by Nascimento et al. [15] which identified insufficient filling of root canals as the predominant procedural error (52.47%). Similarly, a previous study found underfilled canals to be the most prevalent error (85.9%), with a statistically significant association noted in teeth exhibiting straight curvature (22.6%)—specifically, Vertucci type I—and the presence of a periapical lesion (77.3%) [16]. Moreover, a cohort study evaluating 1259 endodontically treated teeth observed that insufficient obturation, extending beyond or shorter than 2 mm from the apex, significantly reduced the odds ratio for treatment success [17].

Regarding associated factors, a higher prevalence of underfilled canals was observed in straight roots (29.52%), consistent with findings from a previous study, where underfilled canals were significantly more prevalent in teeth with straight canals (22.6%) [16]. Another factor associated with underfilled canals was the presence of periapical lesions, aligning with a previous study [18]. Inadequate filling allows bacteria and other microorganisms to invade the root canal or provide space for those that persist after treatment to proliferate, thereby maintaining or contributing to the development of post-treatment apical periodontitis [19]. The high prevalence of inadequate apical filling limits underscores several critical challenges in endodontic procedures. Technical difficulties in achieving an optimal apical seal. This issue is compounded by the clinician's skill and experience, as less experienced operators may struggle to prepare and thoroughly clean the apical region, jeopardizing the filling procedures.

Canal transportation, the second most prevalent error in our study (28.19%), demonstrated significant associations with the buccal wall of upper incisors, consistent with previous research [20]. The fact that the access cavities of upper incisors are angulated in the palatal direction, makes the buccal canal wall more susceptible to deviations and perforations. Studies have indicated that an apical transposition of more than 0.3 mm compromises the success of canal treatment and increases the risk of canal perforation [2122]. This should be considered a limitation of the present study since the degree of transportation was not evaluated, but only its presence or absence.

The prevalence of perforations was 23.79%, with significant associations observed between perforation direction towards the buccal wall and the presence of periapical lesions. Perforations become a contributing factor to the persistence or recurrence of infection. In addition, it may expose the tooth root to the oral cavity [23]. However, the present results should be analyzed carefully concerning the association of procedural errors with tooth type. For instance, incisors and canines are more susceptible to having more perforations to the buccal side, given the nature of the access cavity. Similarly, canal transportation tends to occur on the outside of the curvature. Therefore, some results depend on the nature of the tooth being analyzed.

Missed canals accounted for 16.29% of the cases, consistent with previous studies reporting percentages ranging from 12% to 23% [1213]. The most frequent missed canals were the palatal and MB2 from the upper molars, aligning with existing literature demonstrating a high prevalence of missed MB2 canals in the upper first and second molars [1213].

Our study revealed a statistically significant association between missed MB2 canals and severely curved upper molar roots, consistent with previous research, which emphasized the importance of 3D examinations in identifying curved canals that may be missed otherwise [24]. Conversely, missed palatal canals in upper premolars were associated with straight canals, in line with previous findings indicating a similar association in maxillary second premolars [25]. Besides, associations between missed palatal canals and the presence of calcifications were evident in the present study, highlighting the impact of calcifications on procedural errors. Notably, CBCT is an indispensable diagnostic tool for surgical and non-surgical retreatment cases, although its superiority varies depending on the specific condition being diagnosed.

Instrument fracture, despite being the least frequent error (1.76%) in the present study, poses challenges in diagnosis via CBCT, with periapical radiographs remaining the preferred diagnostic modality [26]. However, there is a growing trend among clinicians to rely on CBCT for making decisions regarding the management of fractured instruments [27].

CONCLUSIONS

In conclusion, underfilled canal was the most frequent error, especially in straight canals, irrespective of calcifications. Notably, canal transportation in upper incisors correlated with the buccal wall and the presence of periapical lesions. Missed canals were predominantly associated with severely curved mesiopalatal canals, palatal canals, and the presence of calcifications. Perforations were also frequent, particularly in cases with periapical lesions. CBCT emerges as a valuable tool in identifying procedural errors and associated factors, crucial for their prevention and management.

Funding: This study was supported by grants from Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brazilian Governmental Institutions.

Conflict of Interest: No potential conflict of interest relevant to this article was reported.

Author Contributions: Conceptualization: Valverde Haro HP, Rupaya CR.

Data curation: Valverde Haro HP.

Formal analysis: Valverde Haro HP.

Funding acquisition: Valverde Haro HP.

Investigation: Valverde Haro HP.

Methodology: Rupaya CR.

Project administration: Rupaya CR.

Resources: Valverde Haro HP.

Software: Valverde Haro HP.

Supervision: Rupaya CR.

Validation: Alves FRF.

Visualization: Valverde Haro HP.

Writing - original draft: Valverde Haro HP, Alves FRF.

Writing - review & editing: Alves FRF.
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