Comparative evaluation of radiographic healing after nonsurgical endodontic treatment with and without irrigant activation: A randomized controlled trial

Abstract

Aim:

To compare the evaluation of radiographic healing after nonsurgical endodontic treatment with and without irrigant activation.

Materials and Methods:

Permanent anterior mandibular and maxillary teeth with associated periapical lesion were assessed for eligibility. Forty-eight patients were randomly split into three groups (n = 16) using allocation concealment method, and irrigation was performed in accordance with the allocated groups. The groups allocated were (a) sodium hypochlorite (NaOCl) irrigation with conventional syringe and needle, (b) NaOCl irrigation with sonic activation, and (c) NaOCl irrigation with ultrasonic activation. Root canals were medicated with calcium hydroxide for 14 days. In the second visit, after washing away the medicament and irrigation protocols, obturation was done with a bioceramic sealer with gutta-percha. The radiographic evaluation was done at 6 and 12 months of the treatment by taking intraoral periapical radiographs and periapical index (PAI).

Results:

The results revealed that both sonic and ultrasonic activation of 5.25% NaOCl showed a significant less PAI score when compared with conventional syringe and needle technique (Group I) and thus superior periapical healing in both sonic (Group II) and ultrasonic (Group III) groups.

Conclusion:

This study concluded that sonic and ultrasonic activation of 5.25% NaOCl led to maximum disinfection of canal systems and thus resulted in better healing of periradicular lesions than conventional syringe and needle irrigation technique.

INTRODUCTION

Microbial invasion and infection of the root canal system affect the onset and progression of periapical diseases. To treat endodontic periapical lesions, the root canal system must be free of bacteria and their by-products, and the risk of reinfection must be eliminated.[1]

Hand and rotatory devices are necessary during treatment to mechanically remove bacteria from the accessible parts of the primary root canal through direct mechanical cleaning action. However, even with careful mechanical preparations, many parts of the intricate root canal morphology remain uncleaned. Treatment failure or persistent periapical pathosis may result from residual pulp remnants, bacteria, and dentin debris, which may remain in these root canal system abnormalities.[2]

The result of endodontic treatment is dependent on effective irrigation. An optimal irrigant ideally must have a broad antimicrobial spectrum, induces endotoxin inactivation, and has the ability to avoid the formation of smear layer during instrumentation or dissolve one that has already formed. There are several irrigating and disinfecting solutions available, including normal saline, hydrogen peroxide, sodium hypochlorite (NaOCl) chlorhexidine, ethylenediaminetetraacetic acid (EDTA), Q-mix, mixture of tetracycline, acid, and detergent, tetraclean, and herbal irrigants.[3]

From the various irrigation techniques, conventional syringe and needle irrigation has been used since decades. However, this approach produces insufficient shear stress, has inadequate dentinal tubule penetration,[4] and delivers irrigant only 0–2 mm from the needle tip, which might allow residual bacterial species to survive even after root canal therapy.[5]

To overcome the limitations of conventional syringe and needle irrigation, activation approaches were introduced. Irrigant activation enhances surface contact between different solutions and causes motion within the irrigant solution.[6] The solution can be activated by gutta-percha cones, canal brushes, laser systems, negative pressure, or sonic/ultrasonic devices. Activated irrigant delivery methods have been shown to enhance irrigant penetration efficacy, increase canal debridement, diminish the risk of periapical extrusion, and promote the effective removal of the smear layer and microbiological biofilms.[7]

From various activation techniques, ultrasonic activation remains the most established technique which operates at a frequency of 40–45 kHz. Passive ultrasonic activation (PUI) is a noncutting method that utilizes the phenomenon of rapid fluid movement in circular motion around the activation point. Sonic activation (or endo activator) is another approach for activating irrigation systems. It works by using a flexible, noncutting soft polymer tip connected to a sonic handpiece to operate at lower frequencies (1000–6000 Hz).[8]

The success of nonsurgical endodontic treatment (NSET) can be measured by clinical and radiographic assessment. Success of criteria are depending on the absence of clinical signs and symptoms and by conventional radiographic measures of complete healing/presence of a normal periodontal ligament space.[9]

In endodontic research, three primary clinical outcome measures are frequently evaluated: the resolution of apical periodontitis, the efficacy of antimicrobial effectiveness, and severity of postoperative pain. Imaging techniques (two-dimensional [2D] and/or three-dimensional [3D]), clinical symptomatology, or both have been used for healing outcomes in endodontics. The periapical index (PAI), introduced by Ørstavik[13] in 1986, is a widely utilized assessment method for evaluating periapical status in 2D radiographic images, using a scale of five scores ranging from one (healthy) and five (severe periodontitis) for 2D radiographic examinations.[10]

The impact of irrigant activation on clinical outcome parameters remains partially unknown. Many previous studies have evaluated the effectiveness of ultrasonic activation on healing of periapical lesions and have presented mixed results. However, literature scares evaluating the effectiveness of sonic activation on healing of periapical lesions. Therefore, the objective of this study was to perform a randomized controlled trial to assess the radiographic healing of periapical lesions following NSET, comparing conventional syringe irrigation with sonic and ultrasonic activation of 5.25% NaOCl as the root canal irrigant. Null hypothesis (H₀): There is no significant difference in radiographic healing outcomes (as measured by PAI scores) among teeth treated with conventional syringe irrigation, sonic activation, or ultrasonic activation of 5.25% NaOCl.

MATERIALS AND METHODS

Forty-eight patients fulfilling the inclusion criteria were selected. Prior to the initiation, the ethical committee had previously authorized the protocol, and each patient provided written informed permission, and the study was officially registered with the Clinical Trials Registry of India (CTRI/2025/04/102950).

Selection criteria for patients

Patients between 18 and 50 years of age group with nonsignificant medical history and permanent single rooted maxillary and mandibular anterior teeth, which showed radiographic evidence of periapical bone loss with a periapical score of 3–5 (according to PAI scoring), were included.

Patients were excluded if they had a history of previous endodontic therapy, systemic disease, were pregnant or lactating, or were immunocompromised. Teeth were excluded if they presented with calcific degeneration, external or internal root resorption, mobility score >2, weeping canals, vertical or horizontal fractures extending below the cementoenamel junction, periodontal pockets >5 mm, or incompletely formed root apices.

CLINICAL STEPS

First treatment session

Oral cavity with experimental tooth was disinfected and the tooth was anesthetized, and a rubber dam was placed (Hygenic R Dental Dam Kit, Coltene Whaledent, Switzerland), after which the caries was excavated. The access opening was performed, and the patency of the root canal was verified using a size 10 K file (Mani, Inc. MDCI Ltd. Japan). Working length was determined and confirmed by radiological examination. If drainage was present, the canals were left open to allow drainage before starting biomechanical preparation. After the discharge ceases, biomechanical preparation was performed with 17% EDTA gel lubricant using an Endo motor (E-xtreme, Orikam Healthcare India Private Limited) with JIZAI Rotary files (Mani, Tochigi, Japan) with continuous motion at a rotation speed of 500 rpm and a torque of 3.0 N in a sequence: 25/0.14, 13/0.04 (300 rpm and torque 1.0 N), till 25/0.06 in maxillary anterior teeth, and till size 25/0.04 in mandibular anterior teeth. The canals were copiously irrigated with 2 ml of 5.25% NaOCl (Bharat Chemical, India) and 5 ml of normal saline (0.9% v/w, Infutec, India) alternatively in between each file. Patients were divided into three groups according to the final irrigation protocol:

• Group I (n = 16): 5.25% sodium hypochlorite irrigation with conventional syringe and needle: Irrigation of canals were done with 5 ml of 5.25% NaOCl with conventional syringe (Dispovan^®, India) and 27-gauge side-vented needle (Endo-rinse, Super Endo, India) maintained at a distance of 2 mm short of working length

• Group II (n = 16): 5.25% sodium hypochlorite irrigation with sonic activation. Irrigation of canals were done with 2.5 ml of 5.25% NaOCl and activated with sonic activator (EQ-S sonic activator, Metabiomed, India) with tip size 25/0.02 in vertical strokes 2 mm short of the working length for 30 s, followed by 30 s pause, and same procedure was repeated once again

• Group III (n = 16): 5.25% sodium hypochlorite irrigation with ultrasonic activation: Irrigation of canals were done with 2.5 ml of 5.25% NaOCl and passively activated with ultrasonic tip (Woodpecker Endo 3 Ultrasonic Endo Activator with tip size E73 for mandibular teeth and E74 for maxillary teeth) in vertical strokes in up and down direction 2 mm short of the working length without binding for 30 s, followed by 30 s pause, and same procedure was repeated once again.’’[12]

Final irrigation was done with 5 ml of 0.9% normal saline. Intracanal medicament of calcium hydroxide powder (Prevest DenPro, India) mixed with 0.2% chlorhexidine solution (Ammdent Dentochlor) was placed in the canal for 2 weeks and then temporization done with Cavit G (Orafil-G™, PREVEST DenPro, India).

Second treatment session

Patients were recalled after 2 weeks and then 0.2% chlorhexidine was used to disinfect the oral cavity and isolation of the tooth was done using a rubber dam. Final irrigant was 5 ml of 0.9% normal saline. If patients were asymptomatic, 10 ml of 17% EDTA (Orikam Healthcare India Private Limited) was used to remove the smear layer from the canals. After thoroughly irrigating the root canals with distilled water to get rid of any remaining EDTA, then dried with absorbent paper points. All canals were obturated using a single cone matched gutta-percha (25/0.06 in the maxillary anterior teeth and 25/0.04 in the mandibular anterior teeth) technique with a premixed bioceramic sealer (Bioactive RCS, Safe Endo, India) available in syringe form. Postendodontic composite restoration was done with a composite resin (Te-Econom Plus, Ivoclar Vivadent India Pvt. Ltd.). Patients were recalled, and radiographic evaluation of healing was done at 6 and 12 months by taking intraoral periapical radiographs and using PAI [Table 1].

Table 1.

Score criteria (periapical index given by Orstavik[13]et al. in 1986)

Score	Periapical index
1	Normal periapical structures
2	Small changes in bone structure
3	Changes in bone structure with some mineral loss
4	Periodontitis with well-defined radiolucent area
5	Severe periodontitis with exacerbating features

The treatment outcomes were defined as following:

• Healed: The clinical normalcy other than tenderness to percussion accompanied by radiographic PAI scores of 1 or 2. The lesion is no longer present or no periapical radiolucency

• Healing: The clinical normalcy other than tenderness to percussion accompanied by a reduction in the size of the periradicular lesion and PAI scores

• Diseased: The presence of clinical signs and symptoms accompanied by a PAI score of 3 or higher or an increase in the size of the periradicular lesion or increase in the PAI scores.[13]

Since the study was conducted as a double-blind trial, both the patients and the outcome assessors remained unaware of group assignments until the study concluded. However, due to the distinct nature of the treatment modalities, it was not feasible to blind the researchers to the allocation. Consequently, researchers were instructed to refrain from discussing the specific interventions with either the patients or the outcome assessors.

Sampling technique

Consecutive sampling was used to recruit eligible patients from the outpatient department until the required sample size was met.

Randomization

Computer-generated block randomization (block size of 6) was employed to assign participants to three groups.

Allocation concealment

Sequentially numbered, opaque, sealed envelopes were used. Each envelope contained the group assignment and was opened by the treating clinician only after access cavity preparation to prevent selection bias

Sample size estimation

Sample size estimation was done using G*Power software (version 3.0) SPSS version 21 (IBM, Chicago, IL, USA). Sample size was estimated for Chi-square test and goodness of fit tests: contingency tables were chosen. A minimum total sample size of 48 (divided into three groups, i.e., 16/group) was found to be sufficient for an alpha of 0.05, power of 80%, 0.5 as effect size (medium effect) size, based on a previous randomized controlled trial by Verma et al., which compared ultrasonic and conventional irrigation and reported significant differences in periapical healing measured by PAI scores[11] and four as degree of freedom.

RESULTS

The study was done to compare and evaluate the radiographic healing after NSET with and without irrigant activation.

Intragroup comparison

Intragroup comparison of mean PAI scores (at baseline, 6 months, and 12 months) among Group I, Group II, and Group III was done using Friedman test, which showed an overall statistically significant reduction in the mean PAI score. Post hoc pairwise comparisons (using Wilcoxon test) showed that the PAI score reduced significantly from baseline to 6 months and then from 6 months to 12 months, among Group I.

Intergroup comparison

The intergroup comparison of the mean PAI score at baseline was done using Kruskal–Wallis test. Overall, the difference in the mean PAI score at baseline, among the three study groups, was not found to be statistically significant [Table 2, Graph 1a, and Figure 1].

Table 2.

Intergroup comparison of mean periapical index score at baseline, 6 months and 12 months follow-up

	n	Mean	SD	P	Post hoc pairwise comparison
At preoperative
Group I (5.25% NaOCl with conventional syringe and needle	16	4.3750	0.80623	0.565 (NS)	NA
Group II (5.25% NaOCl with sonic activation)	16	4.1875	0.54391
Group III (5.25% NaOCl with ultrasonic activation)	16	4.2500	0.68313
At 6 months follow-up
Group I (5.25% NaOCl with conventional syringe and needle)	16	3.6875	1.07819	0.007 (significant)	Group I>Group II (P=0.006, significant) Group I>Group III (P=0.01, significant) Group II versus Group III (P=0.511, NS)
Group II (5.25% NaOCl with sonic activation)	16	2.6250	0.80623
Group III (5.25% NaOCl with ultrasonic activation)	16	2.7500	0.68313
At 12 months follow-up
Group I (5.25% NaOCl with conventional syringe and needle)	16	3.2500	1.06458	0.001 (significant)	Group I>Group II (P=0.007, significant) Group I>Group III (P=0.001, significant) Group II versus Group III (P=0.214, NS)
Group II 5.25% (NaOCl with sonic activation)	16	2.1250	1.02470
Group III (5.25% NaOCl with Ultrasonic activation)	16	1.7500	1.06458

Kruskal–Wallis test. NS: Nonsignificant, SD: Standard deviation, NA: Not available, NaOCl: Sodium hypochlorite

Graph 1.

(a) Intergroup comparison of mean periapical index score at baseline. (b) Intergroup comparison of mean periapical index score at 6 months. (c) Intergroup comparison of mean periapical index score at 12 months. (d) Intergroup comparison of success rate of the three groups

Figure 1.

Follow-up radiographs of Group I (conventional syringe and needle group). (a) Preoperative radiovisiography (RVG), (b) postoperative RVG, (c) 6 months of follow-up, (d) 12 months of follow-up

The intergroup comparison of the mean PAI score at 6 and 12 months was done. Overall, a difference in the mean PAI score at 6 and 12 months among the three study groups was found to be statistically significant. Post hoc pairwise comparisons were done using Mann–Whitney U-test. It showed that the mean PAI scores at 6 months and 12 months of Group II and Group III were significantly lower than that of Group I [Table 2, Graphs 1b and 1c, Figures 2 and 3].

Figure 2.

Follow-up radiographs of Group II (sonic activation group). (a) Preoperative radiovisiography (RVG), (b) postoperative RVG, (c) 6 months of follow-up, (d) 12 months of follow-up

Figure 3.

Follow-up radiographs of Group III (ultrasonic activation group). (a) preoperative radiovisiography (RVG), (b) postoperative RVG, (c) 6 months of follow-up, (d) 12 months of follow-up

Table 3 and Graph 1d show that the proportion of healed cases was 31.3%, 62.5%, and 81.3% among Group I, Group II, and Group III, respectively. The proportion of diseased cases was 43.8%, 12.5%, and 12.5% among Group I, Group II, and Group III, respectively. The intergroup comparison of treatment outcomes (healed, healing, or diseased) was done using Chi-square test. It showed that there was a statistically significant difference in the distribution of treatment outcomes between all three study groups. The frequency of diseased was significantly high among Group I as compared to Group II and Group III, and the frequency of healed was significantly high among Group II and Group III as compared to Group I.

Table 3.

Intergroup comparison of success rate of the three group

	t/t outcome			Total, n (%)
	Healed, n (%)	Healing, n (%)	Diseased, n (%)
Group
Group I (5.25% NaOCl with conventional syringe and needle)	5 (31.3)	4 (25.0)	7 (43.8)	16 (100.0)
Group II (5.25% NaOCl with sonic activation)	10 (62.5)	4 (25.0)	2 (12.5)	16 (100.0)
Group III (5.25% NaOCl with ultrasonic activation)	13 (81.3)	1 (6.3)	2 (12.5)	16 (100.0)
Total	28 (58.3)	9 (18.8)	11 (22.9)	48 (100.0)
P	0.04 (significant)

NaOCl: Sodium hypochlorite

DISCUSSION

Periapical endodontic lesions are caused by inflammatory response in the root apices of nonvital teeth.[14] The egress of bacteria and toxic chemicals from an infected root canal via apical, lateral, or furcal accessory canals causes pathologic alterations in the periradicular tissues.[15] Thus, the management of periapical lesions of endodontic origin is fundamentally based on thorough eradication of microorganisms from the root canal system. This disinfection process creates a biologically favorable environment which promotes the healing of periradicular tissues.[16]

The literature has suggested a number of methods to reduce the quantity of bacteria in the root canal system, such as the use of intracanal medications, irrigation protocols, and instrumentation techniques.[17] There are both in vitro and clinical evidence that mechanical instrumentation left significant parts of the root canal walls untreated. Thus, the majority of bacterial populations in infected root canals must be eliminated by chemical disinfection of the root canal system using irrigants.[18]

Intragroup comparison of the mean periapical index scores

In the present study, on intragroup comparison in Group I showed an overall statistically significant reduction in mean PAI score. The mean PAI score reduced significantly from baseline to 6 months and then from 6 months to 12 months among Group I. The possible reason for the decrease in the mean PAI score could be because of conventional endodontic therapy with a strict infection control. Another possibility for healing could be because of high concentration of 5.25% NaOCl used during the treatment as ability of NaOCl to dissolve organic tissue is directly proportional to its concentration therefore higher concentration of NaOCl could have contributed to healing. Berber et al. concluded that 5.25% NaOCl has a greater antibacterial activity inside the dentinal tubules.[19] Another major factor that determines the success of endodontic treatment is 3D obturation. According to the literature, root canal sealers with alkaline pH and bioactive characteristics are able to heal the apical area more effectively and prevent reinfection in root canals. Thus, in our study, bioactive RCS, which possesses high adherence to the dentinal wall and superior antibacterial capabilities, might have aided the healing process.[20]

In Group II, in which 5.25% NaOCl with sonic activation was used, the results revealed a reduction in the mean PAI scores from baseline to 6 months and then from 6 to 12 months, respectively. The possible reasons for the decrease in PAI score could be because of sonic activation of 5.25% NaOCl that operates using flexible polymer tips that improves irrigant penetration into lateral and accessory canals through acoustic streaming, removing biofilms and debris from the root canal space.[21] Arikan et al. (2024) concluded that sonic activation enhances the decontamination of the root canal anatomy that accelerates healing of periapical tissues.[22]

In Group III, in which 5.25% NaOCl with ultrasonic activation was used, it was found that there was a reduction in the mean PAI scores from baseline to 6 months and then from 6 to 12 months, respectively. The possible reasons for the decrease in the mean PAI score could be attributed to the fact that it aids in mechanical cleaning by raising the wall shear stress. Furthermore, it improves chemical debridement by acoustic microstreaming and acoustic cavitation, which involves the formation and distortion of bubbles. In addition, it ensures irrigant flow to remote parts of the complex root canal anatomy.[23] Verma et al. concluded that ultrasonic irrigation has the potential to enhance the predictability of successful outcomes in tooth with chronic apical periodontitis after endodontic treatment.[11]

Intergroup comparison at 6 months and 12 months

The intergroup comparison of the mean PAI score at 6 months and 12 months among three study groups was found to be statistically significant. Post hoc pairwise comparison showed that the mean PAI scores at 6 months and 12 months for Group II and Group III were significantly lower than that of Group I, suggesting superior outcomes/good periradicular healing in Group II and Group III when compared to Group I. However, there was no significant difference in the mean PAI score of Group II and Group III at 6 months and 12 months, indicating that both sonic and PUI showed similar results.

In this study, sonic activation showed a superior healing when compared to conventional syringe and needle irrigation at both 6 and 12 months. The possible reasons for the greater effectiveness of sonic activation could be because of the safe activation of 5.25% NaOCl with vigorous production of hydrodynamic phenomenon. In a well-shaped and fluid-filled canal, the hydrodynamic phenomena occur when a vibrating polymer tip causes fluid activation and intracanal waves. Sonic activation eliminates the smear layer, debrides uninstrumented areas of the root canal system, and dislodges biofilms from safe havens of the root canal system.[24] Sharawy and Ahme (2023) concluded that teeth with necrotic pulp and apical periodontitis treated by sonic activation showed favorable clinical and radiographic outcome.[25]

In this study, ultrasonic activation of 5.25% NaOCl showed superior results when compared to conventional syringe and needle irrigation technique. The possible reasons for the greater effectiveness of ultrasonic activation could be because of the fact that ultrasonic devices induce a 3D flow inside the root canal system. The rapid motion of an ultrasonic instrument and the resulting pressure changes in the irrigant may also give rise to acoustic cavitation.[26] Another reason for the superior performance of ultrasonic activation could be because of the temperature rise by ultrasonics which contribute to increase in antibacterial efficiency of NaOCl. In this, part of the ultrasonic energy is transformed to heat energy, which leads to an effective intracanal temperature of 45°C.[27] This temperature increase of NaOCl inside the root canal enhances its chemical reactivity and disinfecting potential.[28] Nakamura et al. concluded that ultrasonic activation was more efficacious than nonactivated irrigation for reducing the bacterial count in root canals of teeth with apical periodontitis.[29]

In the present study, both sonic and ultrasonic activation showed comparable results in periradicular healing at both 6 and 12 months. The possible reason for similar results could be attributed to irrigant activation of 5.25% NaOCl in both the groups, leading to maximum disinfection of root canal systems. The mechanism of action of both sonic and ultrasonic activation technique has been discussed earlier.

The H₀ was rejected based on the study results. Intergroup comparisons showed statistically significant differences in PAI scores at 6 and 12 months (P < 0.05). Specifically, both sonic and ultrasonic activation groups had significantly lower PAI scores compared to conventional irrigation.

There was no significant difference between sonic and ultrasonic groups. Thus, the alternative hypothesis that irrigant activation improves radiographic healing was supported. The rejection of H0 indicates that the choice of irrigation activation method does influence periapical healing outcomes in single-rooted teeth with apical periodontitis.

CONCLUSION

Therefore, within the limitations of this study, it can be concluded that activation of 5.25% NaOCl enhances antimicrobial activity and root canal cleanliness. In our study, both sonic and ultrasonic activation of 5.25% NaOCl showed a significant less PAI score when compared with conventional syringe and needle technique and thus superior periapical healing in both sonic and ultrasonic groups. Hence, 5.25% NaOCl when used with sonic and ultrasonic activation can be recommended as a potential endodontic disinfection regimen and for nonsurgical management of periapical lesions. However, further in vivo clinical studies are recommended for assessing periapical lesion healing based on volumetric measures using 3D/cone-beam computed tomography imaging.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.