Filling material effects on root canal treatment outcomes of 83 canine teeth in cats using a taperless rotary file system

Abstract

Objectives

This study aimed to evaluate the clinical outcomes of root canal treatment (RCT) for canine teeth in cats by determining the optimal master apical file (MAF) size via a taperless rotary file system and comparing three different filling materials.

Methods

A total of 83 fractured canine teeth from 78 cats were treated with a taperless nickel–titanium file system. Three different filling materials were used: (1) a silicone-based sealer with a single gutta-percha (GP) cone; (2) a bioceramic sealer with a single GP cone; and (3) a bioceramic plug at the apex followed by a silicone-based sealer and a GP cone for the residual pulp canal. The MAF size was determined by enlarging the apical portion to three International Organization for Standardization sizes beyond the initial apical file. Treatment outcomes were classified as success, no evidence of failure and failure. Outcome-related factors were identified via multivariable logistic regression.

Results

The overall success rate was 91.6%. The bioceramic sealer showed the highest success rate (97%), followed by the bioceramic plug (95%) and the silicone-based sealer (83.3%). Overfill and pre-existing periapical lesions were significantly associated with reduced success. The overfill rates of bioceramic sealers and plugs were significantly lower than those of silicone-based sealers. The MAF size showed a significant positive correlation with body weight and a negative correlation with age.

Conclusions and relevance

A taperless file system could be used to facilitate precise apical shaping tailored to the fusiform anatomy of canine teeth in cats and thus improve treatment outcomes. These findings support the use of bioceramic sealers in a single-cone obturation technique and highlight the importance of achieving an optimal MAF size to enhance the success of RCT for canine teeth in cats.

Keywords

Root canal treatment master apical file size taperless file system sealer overfill

Introduction

Tooth fractures are the most common cause of pulp disease in cats. They account for 71.4% of the primary causes of periapical lesions (PALs).^1
–4 The canine teeth are the most frequently fractured in cats, with a fracture rate of 35.7%.⁵

The canine teeth of cats are anatomically characterised by the coronal end of the pulp chamber, which is located close to the most coronal tip of the crown; as such, the pulp is exposed in most cases of tooth fracture.^1
–3,6 If left untreated, tooth fractures can cause pulpitis due to pulp exposure, allowing bacteria to migrate through the pulp chamber ultimately causing infection and inflammation in periapical tissues and leading to periapical periodontitis.⁷

Root canal treatment (RCT) is a highly effective and less invasive treatment option for fractured canine teeth with pulp exposure in cats because it preserves tooth function while avoiding extraction-related complications, such as mandibular fractures, oronasal fistulas and soft tissue trauma caused by the remaining canine teeth.^3,8
–12 However, the success rate of RCT in cats is substantially lower than that in dogs.^3,8

One of the key factors contributing to the reduced success rate of RCT in cats may be the anatomical complexity of their canine teeth; it presents challenges in achieving proper canal shaping and determining an appropriate master apical file (MAF) size. Chrostek et al¹³ described the pulp cavities of feline canine teeth in the buccal view as typically fusiform, with a narrow coronal third, a broad middle third and tapering towards the apex. Because of this morphological characteristic, conventional tapered file systems often fail to establish sufficient mechanical contact with the middle and apical thirds of the canal; consequently, an adequate MAF size cannot be easily defined. Furthermore, a primary root canal is clearly observed within the apical delta in 48% of feline canine teeth.¹³ Although lateral canals are not identified in cats as they are in dogs, well-developed apical ramifications similar to those in canine teeth in dogs are frequently observed in cats.^13
–17 Therefore, the optimal MAF size for the apical portion should be accurately determined to enhance the effectiveness and long-term success of feline RCTs.¹⁸

After root canal shaping, various obturation techniques and filling materials have been introduced in veterinary endodontics.^2,11 Among them, silicone-based sealers have been widely used, whereas bioceramic sealers, known for their excellent sealing properties, antibacterial effects and biocompatibility, have been introduced more recently.^19
–22 In dogs, a previous study compared the effects of silicone-based sealers, bioceramic sealers and calcium hydroxide-based sealers on endodontic treatment outcomes.¹⁹ Another study has reported the treatment outcomes of bioceramic sealers in RCT for canine teeth of cats.⁶ However, no studies have compared the different types of sealers in RCT for cats.

In the present study, we evaluated the outcomes of RCT in 83 canine teeth from 78 cats obturated with three different filling materials: (1) a silicone-based sealer with a single gutta-percha (GP) cone; (2) a bioceramic sealer with a single GP cone; and (3) a bioceramic apical plug combined with a silicone-based sealer and a single GP cone in the remaining pulp canal. This study is the first to statistically assess whether different filling materials significantly affect treatment outcomes in cats. In addition, the influence of other clinical and radiographic variables – including pre-existing PALs, preoperative external inflammatory root resorption (EIRR), overfill and voids – was also analysed. Moreover, the MAF size for RCT of feline canine teeth using a taperless rotary nickel–titanium (Ni–Ti) file system was also evaluated to serve as a reference for endodontic veterinarians.

Materials and methods

Medical records and case selection criteria

The medical and dental records of 143 cats that underwent RCT on 156 canine teeth at May Veterinary Dental Hospital (MVDH) and Evichi Veterinary Dental Hospital (EVDH) between January 2015 and June 2024 were reviewed. Only the cats with intraoral radiographs taken under general anaesthesia at least 3 months after the initial RCT were included. As a result, 83 canine teeth from 78 cats met the inclusion criteria.

Sex (including neuter status), body weight, age at treatment and breed were documented. The detailed records of the condition of the affected tooth, the type of sealer used and the timing of follow-up evaluations were collected. Intraoral radiographs obtained preoperatively, immediately after RCT and at all follow-up examinations were also reviewed. The working length (WL) of the root canal and the MAF size were noted during the RCT using a taperless rotary file system, the LightSpeed Ni–Ti file system (LSX file system; Sybronendo).

Radiographic evaluation and diagnostic criteria

All digital radiographs (CR7 Vet Digital X-ray; iM3) were evaluated by two veterinarians of MVDH and EVDH. A PAL was defined as the widening of the periodontal ligament space at the apex, and the widest point of the space was measured. The presence or absence of PALs in all cases was documented.

The outcomes of RCT were classified as success, no evidence of failure (NEF) and failure according to European Society of Endodontology guidelines.²³ The treatment was considered successful if the periapical periodontal ligament space at the apex remained unchanged without development of a new periapical lucency, if a pre-existing PAL resolved and any preoperative EIRR, if present, stabilised. A case was categorised as NEF if the preoperative EIRR stabilised and the existing PAL remained the same or decreased in size but did not fully disappear. A case was deemed a failure if a new PAL developed after RCT or if preoperative EIRR progressed and the PAL increased in size compared with that in pretreatment radiographs.

RCT procedure

Access hole opening and WL determination

Direct access was obtained through the pre-existing fracture site by enlarging the coronal portion of the pulp canal with #1, #2 or #3 Gate Glidden burs (Mani). If the surface of the pre-existing fracture site was insufficient to create an adequately sized access hole, the crown height was reduced to an appropriate length. Next, #00 barbed broaches (Mani) were used to remove any vital pulp tissue from the entire canal. The WL was then measured using a #10 K-hand file, and the determined final WL was confirmed through intraoral radiography.

Canal shaping, irrigation and MAF size determination

While maintaining the WL, the root canal was shaped using #15 to #30 0.02 taper K-hand files. Sequential instrumentation with a taperless rotary Ni–Ti file system starting from #35 was performed using standard techniques. During the procedure, 17% EDTA gel (RC Prep; Premier Dental Products) was applied as a lubricant for each file during instrumentation.

Constriction at the apical portion of the pulp canal was assessed throughout the shaping process and the initial apical file (IAF) size was determined accordingly. The apical portion of the canal was further shaped to at least one and up to three International Organization for Standardization sizes larger than the IAF size but within a diameter range smaller than the access hole. The final file was designated as the MAF.

Between filing steps, the prepared canal was irrigated with 5.25% sodium hypochlorite and flushed with sterile saline. Finally, 17% EDTA solution (EDTA 17%; Dentaires SA) was applied for 1 min then the canal was rinsed with sterile saline and thoroughly dried using absorbent paper points.

Obturation techniques and sealers

Two obturation techniques with three different filling materials were used, and their influence on treatment outcomes was statistically compared and analysed. The techniques were as follows: (1) a single-cone technique using a silicone-based sealer (GuttaFlow 1 or GuttaFlow 2; COLTENE) for 30 teeth; (2) a single-cone technique using a bioceramic sealer (One-Fil; Mediculus) for 33 teeth; and (3) a combination technique through which the apical portion of the shaped pulp canal was filled with a bioceramic plug (OrthoMTA; Do Co) and the remaining space was obturated with a GP cone (Diadent) and a silicone-based sealer for 20 teeth (Figure 1). All GP cones used in this study were standard 0.02 taper cones commonly employed in routine RCT procedures.

Figure 1

Outcomes of root canal treatment after two different obturation techniques with three different filling materials. Single-cone techniques using (a) a silicone-based sealer and (b) a bioceramic sealer. (c) A combination technique using a bioceramic plug showing the compacted bioceramic paste (black asterisk) in the apical portion and the gutta-percha cone with the silicone-based sealer in the residual pulp canal (white asterisk). Glass ionomer (black arrowheads) was filled as intermediate layers and resin composite (white arrowheads) restored the access holes in all cases

The GP cone size was selected with reference to the ‘final apical size minus 50’ rule;²⁴ however, instead of directly applying the minus 50 value, multiple GP cones smaller than the MAF size were trial-fitted to the canal. The cone that best maintained the WL and provided adequate filling of the apical portion was ultimately selected. The final confirmation was achieved through intraoral radiography. For the bioceramic plug in the combination technique, bioceramic powder was mixed with sterile saline to obtain a paste with an appropriate consistency, which was then placed into the apical portion of the pulp canal. Vertical compaction was performed using paper points to ensure that the material was densely adapted and formed an effective apical plug. The remaining space was filled with a silicone-based sealer and a GP cone following standard obturation techniques.

The intermediate layer was filled with a glass ionomer (Ketac Fil Plus Aplicap; 3M GmbH) and the access site was restored using composite resin.

Follow-up evaluation

Follow-up after RCT comprised intraoral radiographs under general anaesthesia.

Statistical analysis

Data were statistically analysed using Jamovi (version 2.3.28.0) and Python (version 3.11.7) with the statsmodels (version 0.14.0), scikit-learn (version 1.2.2) and matplotlib (version 3.8.0) libraries. The associations of MAF size with age and body weight were examined using a generalised linear model (GLM) with a Gamma distribution and identity link function. The factors associated with overfill occurrence and RCT outcome were assessed via multivariable binary logistic regression. NEF and failure were combined into a single failure category for binary outcome analysis. Class frequency-based weighting was applied to account for class imbalance in binary outcomes. Odds ratios (ORs) with 95% confidence intervals and variable- and category-level P values were also reported. Model performance was evaluated using Nagelkerke’s R² and the area under the receiver operating characteristic curve (AUC). Results were considered statistically significant when P <0.05.

Results

Characteristics and summary of patients

A total of 143 cats were recorded to have undergone RCT for fractured canine teeth at MVDH and EVDH over 9 years. Among them, 78 cats (corresponding to 83 treated teeth) received at least one follow-up examination. The first follow-up evaluations were conducted between 3 and 36 months postoperatively (mean 7). Among the 83 teeth evaluated, 75 had one follow-up (3–36 months postoperatively), five had two follow-ups (3–72 months) and three had three follow-ups (4–48 months). The case with the longest follow-up period was examined 6 years postoperatively.

In total, 16 different cat breeds were included in this study. Among them, the domestic shorthair (42.3%) was the most common, followed by the Abyssinian (9.0%). Their age was in the range of 1–12 years (mean 4.2 ± 2.67) and their body weight was in the range of 2.7–8.3 kg (mean 5.0 ± 1.22). Of the 78 cats, 48 (61.5%) were neutered males, 29 (37.2%) were neutered females and one (1.3%) was an intact male, indicating a higher proportion of male cats. The distribution of the treated canine teeth was as follows: 36 (43.4%) maxillary right canines (#104); 42 (50.6%) maxillary left canines (#204); three (3.6%) mandibular left canines (#304); and two (2.4%) mandibular right canines (#404).

In the intraoral radiographs taken immediately after RCT, various obturated root canal shapes were observed. The length of the radiodense apex (from the apex to the terminus of the pulp canal) also varied (Figure 2).

Figure 2

Post-root canal treatment (RCT) radiographic images showing varying root canal morphology and length of the radiodense apex. (a) The longest radiodense apex measured from the apical terminus of the root canal to the root apex was 6.4 mm. (b) The youngest cat that underwent RCT was aged 12 months at the time of treatment. (c) A cylindrically shaped ribbon-like pulp canal of mandibular canine teeth and (d) a maxillary canine tooth obturated in a fusiform-shaped configuration. Overfilled silicone-based sealer (white asterisk) and bioceramic sealer (black asterisk) are also visible

Association between MAF size, weight and age at the time of treatment

The WL during the RCT of the canine teeth was in the range of 10–20 mm (mean 16.6). MAF size varied between #40 and #100 (mean #70) (Figure 3a). The GLM analysis showed that MAF size was significantly associated with both age and body weight (R² = 0.3090). This relationship is described by the following regression equation: MAF = 69.64−2.40 × age + 3.63 × body weight. In the analysis of the relationship between age and MAF size, MAF size decreased with ageing (OR = 0.09; P <0.0001) (Table 1, Figure 3c). Conversely, MAF size increased as body weight increased (OR = 37.86; P = 0.0005) (Table 1, Figure 3b).

Figure 3

Generalised linear model (GLM)-based analysis of master apical file (MAF) size in relation to age and body weight (BW). (a) A three-dimensional regression plane and its corresponding equation derived from a GLM are presented along with a scatter plot showing the distribution of MAF size in relation to body weight and age (R² = 0.3090). (b) Effect plot showing the association between BW and MAF size, adjusted for age. (c) Effect plot showing the association between age and MAF size, adjusted for BW. ISO = International Organization for Standardization

Table 1

Generalised linear model analysis of master apical file size associated with age and body weight

Variable	Coefficient	Odds ratio (95% CI)	P value
Age	−2.40	0.09 (0.04–0.20)	<0.0001
Body weight	3.63	37.86 (5.37–276.57)	0.0005

CI = confidence interval

Success rates

RCT had an overall success rate of 91.6% in 83 canine teeth. NEF was observed in 6% of cases, while failure was confirmed in 2.4%. Among the different sealers, the bioceramic sealer showed the highest success rate (97%), followed closely by the bioceramic plug (95%). Conversely, the silicone-based sealer had the lowest success rate of 83.3% (Figure 4).

Figure 4

Overall root canal treatment outcomes and success rates based on obturation techniques with different sealers. (a) The overall success rate was 91.6%. (b) The bioceramic sealer and the bioceramic plug showed similar success rates, whereas the silicone-based sealer had a relatively lower success rate. NEF = no evidence of failure

Association of success rate with sealers, pre-existing PALs, preoperative EIRR, overfill and void

The factors associated with the success of RCT were identified via multivariable logistic regression analysis (Table 2). The model performance was acceptable (Nagelkerke’s R² = 0.7456; AUC = 0.8966). The bioceramic sealer was significantly associated with a higher success rate than the silicone-based sealer (OR = 10.20; P = 0.002). The outcome of RCT of feline canine teeth was significantly associated with pre-existing PALs (OR = 0.03; P <0.001) and overfill (OR = 0.16; P <0.004). Conversely, the success rate was not correlated with preoperative EIRR (P = 0.498) or voids (P = 0.611). Pre-existing PALs at the time of treatment and overfill occurrence during the endodontic procedure contributed to the reduction in RCT success rate (Table 2).

Table 2

Binary logistic regression analysis of the factors associated with outcome

Variable	Category	Total (n)	Outcome (n [%])		Odds ratio (95% CI)	CategoryP value	VariableP value
Variable	Category	Total (n)	Success	Failure	Odds ratio (95% CI)	CategoryP value	VariableP value
Sealer	Silicone-based sealer	30	25 (83.3)	5 (16.7)	1.0 (Ref)	–	0.0010
	Bioceramic sealer	33	32 (97.0)	1 (3.0)	10.20 (2.44–42.63)	0.0015	–
	Bioceramic plug	20	19 (95.0)	1 (5.0)	1.90 (0.60–6.04)	0.2747	–
Pre-existingPAL	Absent	68	66 (97.1)	2 (2.9)	1.0 (Ref)	–	<0.0001
Pre-existingPAL	Present	15	10 (66.7)	5 (33.3)	0.03 (0.01–0.11)	<0.0001	–
Preoperative	Absent	78	73 (93.6)	5 (6.4)	1.0 (Ref)	–	0.4988
EIRR	Present	5	3 (60.0)	2 (40.0)	1.87 (0.31–11.36)	0.4980	–
Overfill	Absent	71	67 (94.4)	4 (5.6)	1.0 (Ref)	–	0.0024
	Present	12	9 (75.0)	3 (25.0)	0.16 (0.04–0.56)	0.0042	–
Void	Absent	68	64 (94.1)	4 (5.9)	1.0 (Ref)	–	0.6135
	Present	15	12 (80.0)	3 (20.0)	0.74 (0.23–2.39)	0.6113	–

CI = confidence interval; EIRR = external inflammatory root resorption; PAL = periapical lesion

Analysis of the factors influencing the incidence of overfill

The factors associated with overfill occurrence were identified via multivariable logistic regression analysis (Table 3). The model performance was acceptable (Nagelkerke’s R² = 0.3402, AUC = 0.7230). The use of bioceramic sealer (OR = 0.34; P = 0.006) and bioceramic plug (OR = 0.13; P <0.001) was significantly associated with a lower incidence of overfill than use of silicone-based sealers. Pre-existing PALs (P = 0.0949), preoperative EIRR (P = 0.2965) and void (P = 0.0561) were not significantly correlated with the incidence of overfill.

Table 3

Binary logistic regression analysis of the factors associated with overfill occurrence

Variable	Category	Total (n)	Overfill (n [%])		Odds ratio (95% CI)	CategoryP value	VariableP value
Variable	Category	Total (n)	Present	Absent	Odds ratio (95% CI)	CategoryP value	VariableP value
Sealer	Silicone-based sealer	30	8 (26.7)	22 (73.3)	1.0 (Ref)	–	<0.0001
	Bioceramic sealer	33	3 (9.1)	30 (90.9)	0.34 (0.16–0.73)	0.0057	–
	Bioceramic plug	20	1 (5.0)	19 (95.0)	0.13 (0.05–0.37)	0.0001	–
Pre-existingPAL	Absent	68	10 (14.7)	58 (85.3)	1.0 (Ref)	–	0.0877
Pre-existingPAL	Present	15	2 (13.3)	13 (86.7)	0.44 (0.17–1.15)	0.0949	–
Preoperative	Absent	78	10 (12.8)	68 (87.2)	1.0 (Ref)	–	0.2815
EIRR	Present	5	2 (40.0)	3 (60.0)	2.28 (0.49–10.70)	0.2965	–
Void	Absent	68	8 (11.8)	60 (88.2)	1.0 (Ref)	–	0.0514
	Present	15	4 (26.7)	11 (73.3)	2.48 (0.98–6.28)	0.0561	–

CI = confidence interval; EIRR = external inflammatory root resorption; PAL = periapical lesion

Discussion

In human teeth, a large apical foramen is prominently located at the root apex, accompanied by fewer apical ramifications. In addition, a wide array of non-apical ramifications, including secondary canals, accessory canals, lateral canals, recurrent canals, collateral canals and intercanal communications, are commonly observed.²⁵ Unlike human teeth, dog teeth do not have a large apical foramen. Instead, dogs have numerous apical ramifications that have diameters of less than 234.19 μm and are relatively more developed than those of humans. Among them, 85.44% have a diameter smaller than 50 μm.¹⁷ A distinctive feature of dog teeth is that the internal aspect of the apical region exhibits a ‘sieved plug’ configuration, indicating the presence of a natural apical stop formed by cementum.¹⁷ In the maxillary canine teeth of dogs, the mean number of apical ramifications is 38 ± 9.3, with a mean diameter of 35.95 ± 23.21 μm.^14,17 The incidence of non-apical ramifications in their mandibular first molars and maxillary fourth premolars is approximately 25.1%, which is notably lower than that in humans. These non-apical ramifications are secondary and lateral canals.²⁶

Anatomical studies of canine teeth in cats have revealed the absence of a large apical foramen but well-developed apical ramifications; consequently, patency similar to that in dogs cannot be established. In cats, prominent apical ramifications, which serve as the primary interface between the pulp cavity and periapical tissues, have been identified; however, no lateral or other non-apical ramifications have been observed.¹⁵ The mean number of apical ramifications is in the range of 7–12.5.^13,15 Interestingly, 48% of feline canine teeth exhibit a distinct primary root canal within the apical ramifications. Moreover, the root canal of canine teeth in cats generally presents a fusiform morphology characterised by a narrow coronal portion, a widened middle third and a gradual narrowing towards the apical end.¹⁵ Understanding these anatomical differences in the root canal systems of teeth in dogs and cats is necessary to optimise endodontic outcomes. Recognising species-specific features, such as the presence or absence of non-apical ramifications or the configuration of apical structures, can directly influence treatment strategies and success rates in veterinary endodontics. With the anatomical characteristics of canine teeth in cats, the use of a taperless file system for canal shaping may be the most advantageous approach to achieve the optimal MAF size while preserving the peri-cervical dentin around the access as much as possible.

Among the procedural stages of RCT, the foundational stage involves canal shaping. It is essential for mechanical debridement and useful for optimal irrigation and disinfection, thereby promoting the effective chemomechanical disinfection of the root canal.¹⁰ Given the distinct anatomical characteristics of canine teeth in cats, adequate apical shaping, particularly at the canal terminus, is likely a crucial determinant of endodontic success. In the present study, a definitive IAF was identified, and progressive apical enlargement was performed to establish an optimal MAF size tailored to each case. This deliberate approach to apical preparation potentially contributed to the observed success rate of 91.6%, which markedly exceeded the previously reported success rate of 49–64% of RCTs for canine teeth in cats.^3,6

In the present study, RCT was performed on 83 canine teeth in cats and the optimal MAF size for each case was determined. The measured MAF size was in the range of #40 to #100 (mean #70). The pulp cavity volume of teeth gradually decreases with age, and this characteristic correlates with age-related dentin deposition.^27,28 Furthermore, Soukup et al²⁹ reported an allometric relationship between tooth size and body weight. On the basis of these previous studies, the associations of MAF size with age and body weight were analysed separately to verify whether the determination of MAF size in the present study was conducted through evidence-based and rational criteria rather than the operator’s subjective judgement. The results revealed that the MAF size of canine teeth in cats was significantly related to age and body weight. Age was negatively correlated with MAF size (OR = 0.09; P <0.0001); thus, age-related reduction in pulp cavity volume, as reported in previous studies,^27,28 might subsequently contribute to the decrease in MAF size. Body weight was positively correlated with MAF size (OR = 37.86; P = 0.0005). Soukup et al,²⁹ having demonstrated that tooth size is correlated with body weight, suggested that an increase in tooth size could contribute to a corresponding increase in MAF size. These findings confirmed that MAF size was determined through a rational, evidence-based approach in the present study.

A recent study investigated the outcome of RCT using a bioceramic sealer in 50 canine teeth of cats and reported a success rate of 64%, a NEF rate of 28% and a failure rate of 8%.⁶ When success and NEF, which are broadly considered positive outcomes, were combined, the cumulative favourable outcome rate reached 92%. In the present study, the overall outcome of RCT for 83 canine teeth in cats showed a success rate of 91.6%, a NEF rate of 6.0% and a failure rate of 2.4%. Among the sealers used, the bioceramic sealer achieved the highest success rate (97.0%), closely followed by the bioceramic plug (95.0%). Conversely, the silicone-based sealer showed the lowest success rate at 83.3%, a difference that was statistically significant in favour of the bioceramic sealer. The notably lower NEF rate observed in the present study compared with a previous report may be explained by the lower proportion of treated teeth with pre-existing PALs (18%) and preoperative EIRR (6%) in this cohort vs approximately 50% PALs and 25% EIRR in the earlier study.⁶ The success rates in both studies remain markedly superior to those reported in an earlier study of 32 canine teeth treated with various shaping and obturation techniques, where the success rate was only 49%.³

Several studies on RCTs in dogs have conducted statistical analyses to evaluate the influence of various factors on treatment outcomes, such as pre-existing PALs, preoperative EIRR, overfill, voids and patient age at RCT. Pre-existing PALs are a significant predictor of lower success rates, whereas other factors have not consistently shown strong associations.^8,19,30 However, studies on RCT outcomes in cats remain limited in number and sample size; as such, definitive conclusions regarding the statistical relevance of these variables cannot be easily drawn. Strøm et al³ identified that preoperative EIRR and an age of 5 years or older at the time of treatment are significant risk factors that markedly increase the failure rate of RCT for feline canine teeth. By contrast, they found no significant associations in preoperative EIRR or obturation voids. However, in the present study, pre-existing PALs and overfill had significant negative effects on treatment success. The association between pre-existing PALs and reduced RCT success observed in this study was consistent with that in dogs.^8,19,30 Therefore, a similar biological effect likely occurred across species. Conversely, the negative effects of overfill on treatment outcome differed from those in dogs;^8,19,30 specifically, overfill has not been consistently associated with treatment failure in dogs.

Thorne et al⁶ found that overfill occurred in 7/50 feline canine teeth that underwent RCT. Among them, 29% were classified as successful, 71% had NEF and none was classified as a failure. Although no statistical analysis was performed, the proportion of overfilled cases was notably lower in the success group than in the NEF group. Similarly, the present study showed that overfill was significantly associated with reduced RCT success, suggesting a more definitive effect of overfill on RCT outcomes in canine teeth of cats. Furthermore, statistical analyses were performed to explore the relationship between overfill occurrence and variables such as the type of sealer used, pre-existing PALs, preoperative EIRR and obturation voids. Among them, only the type of sealer was significantly related to the overfill frequency. Specifically, the overfill rates of the bioceramic sealer and bioceramic plug groups were significantly lower than those of the silicone-based sealer group. Overfill can induce various adverse reactions, including inflammation, allergic responses and neurotoxicity, in the periapical region.^31
–34 However, cats cannot be easily diagnosed clinically, or these complications cannot be readily evaluated, because cats rarely exhibit observable signs of discomfort or pain resulting from such events. Therefore, the occurrence of overfilling should be minimised; from this perspective, bioceramic filling materials may provide a more favourable option.

Bioceramic sealers offer two major advantages over silicone-based sealers when used as root canal sealers. First, they exhibit excellent biocompatibility, which helps prevent rejection from the surrounding tissues.^35
–41 Second, they contain calcium phosphate components, which enhance their setting properties and facilitate the formation of a crystalline structure and chemical composition similar to apatite found in the teeth and bone. Subsequently, the adhesion between the sealer and root dentin is enhanced.^36,42 Moreover, the high pH (>11) of bioceramic sealers elicits potent antibacterial effects; as such, they effectively eliminate microorganisms within the root canal system.^43
–45 Bioceramic sealers also have lower cytotoxicity responses than other sealers.⁴⁶

A notable limitation of the present study is the reliance on conventional intraoral radiography alone for evaluating RCT outcomes. Recent evidence suggests that this method may not be as sensitive as cone beam CT (CBCT) in detecting and characterising periapical pathology. CBCT has shown a significantly higher detection rate of PALs after RCT in dogs compared with conventional intraoral radiography. Although radiographs tend to underestimate lesion size, CBCT findings closely align with microscopic analysis. These results suggest that CBCT may offer a more accurate assessment of RCT outcomes.^19,47,48 In addition, the earliest follow-up time point was 3 months postoperatively, and only eight teeth underwent more than one follow-up examination. These factors limited our ability to evaluate long-term treatment outcomes.

The present study showed that the bioceramic plug exhibited an RCT success rate of 95%, comparable with that of the bioceramic sealer (97%). However, the combination technique involving the precise placement of a solid, separate bioceramic plug into the apical portion of the root canal required greater operator experience and technical proficiency than the single-cone technique with a bioceramic sealer; thus, these requirements substantially influence clinical outcomes.^49
–51 These results collectively indicate the superior efficacy of bioceramic sealers in achieving favourable endodontic outcomes in the canine teeth of cats.

Conclusions

In this study, RCT using an optimal MAF size was performed on 83 canine teeth from 78 cats, and an overall success rate of 91.6% was obtained. Among the three filling materials used, the bioceramic sealer showed the highest success rate (97%). Pre-existing PALs and overfill were the factors that contributed to a reduced success rate. The incidence of overfill was significantly lower with the bioceramic sealer and plug than with the silicone-based sealer. Therefore, securing an optimal MAF size and using a bioceramic sealer in a single cone technique may ensure a high success rate in RCT of canine teeth in cats.

Footnotes

Accepted: 6 August 2025

Conflict of interest

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

This work was supported by the Korea Institute of Planning and Evaluation for Technology in Food, Agriculture and Forestry (IPET) through the Agriculture and Food Convergence Technologies Program for Research Manpower development funded by the Ministry of Agriculture, Food and Rural Affairs (MAFRA) (grant number: RS-2024-00398561).

Ethical approval

The work described in this manuscript involved the use of non-experimental (owned or unowned) animals. Established internationally recognised high standards (‘best practice’) of veterinary clinical care for the individual patient were always followed and/or this work involved the use of cadavers. Ethical approval from a committee was therefore not specifically required for publication in JFMS. Although not required, where ethical approval was still obtained, it is stated in the manuscript.

Informed consent

Informed consent (verbal or written) was obtained from the owner or legal custodian of all animal(s) described in this work (experimental or non-experimental animals, including cadavers, tissues and samples) for all procedure(s) undertaken (prospective or retrospective studies). No animals or people are identifiable within this publication, and therefore additional informed consent for publication was not required.

ORCID iD

Daehyun Kwon

Chun-Geun Kim

Gyumin Kim

Youngjin Jang

Se Eun Kim

Hyun Min Jo

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