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1Department of Pediatric Dentistry, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, College of Stomatology, Shanghai Jiao Tong University, 200011 Shanghai, China
2National Center for Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai Research Institute of Stomatology, 200011 Shanghai, China
*Corresponding Author(s):doctory0920@outlook.com (Shimin Zhao)
| History | Submitted: 27 January 2023 | Accepted: 27 March 2023 | Published: 03 March 2024 |
| Copyright: | ©2024 The Author(s). Published by MRE Press. |

Two-visit root canal treatment for children reduce the time of visits and the by-chair time in comparison with the three-visit root canal treatment. However, it is not clear whether two-visit root canal treatment increase the risk of complications. This study aimed to evaluate the clinical effects and post-operative pain intensity after the root canal treatment between two-visit and three-visit groups in primary molars from children.106 patients were screened for eligibility, of which 74 went back to the preservation visit. Therefore, 74 primary molars from 74 children that diagnosed with chronic pulp and periodontal tissue diseases in the clinics of pediatric dentistry were retrospectively analyzed, in which 37 in the two-visit group and 37 in the three-visit group. The total effective rate and postoperative pain intensity were assessed after treatment and all statistical data were carried out with SPSS software.The average age of children in the two-visit and three-visit groups was 6.4 and 7.0, respectively, with no significant difference (p = 0.056). The two-visit group consisted of 59.5% male and 40.5% female children, while the three-visit group consisted of 56.8% male children and 43.2% female children (p = 0.813). Two months after treatment, the total effective rate in the three-visit group was 97.30%, a little higher than that in the two-visit group (94.59%), but with no significant difference (p = 0.201). Besides, there was also no significant difference in pain intensity between the two-visit and three-visit groups (p = 0.692). Therefore, there were no significant difference of total effective rate and pain intensity in root canal treatment between the two-visit and three-visit groups in primary molars from children.
Cite this article
Binbin Yu, Shimin Zhao. The evaluation of effective rate and pain intensity of root canal treatment in primary teeth—a retrospective study. Journal of Clinical Pediatric Dentistry. 2024; 48(2): 88-92. doi: 10.22514/jocpd.2024.037
Childhood caries is considered as a severe public health problem among the worldwide. According to the data in the oral health epidemiology investigation of the third nations, the prevalence rate of caries in 5-year-old children were about 67% in China in 2005 [1]. When caries extended to inflammation or pulp necrosis, it could affect children’s growth and future dentition [2], and radical endodontic treatment is the last option to repair the tooth [3].
The main goal of root canal treatment is to maintain the integrity and health of the primary tooth until their physiological exfoliation [4]. This non-vital treatment contains procedure such as isolation of the tooth, access opening, extirpation of the pulp, root preparation, irrigants and drying of the root, as well as obturation of the canals and crown restoration [5]. During the treatment progress, non-reinforced zinc/oxide eugenol (ZOE), iodoform paste, and vitapex (a combination paste of iodoform and calcium hydroxide) are usually used to fill the canals. Single or multiple visits were used to complete the root canal treatment. During the progress, proper root canal shape should be obtained, so an efficient cleaning should be performed [6]. The engine-driven rotary nickel titanium (NiTi) files are commonly used in root canal preparation and could significantly increase the cleaning efficiency.
According to the review reported by M. B. McGuigan, the successful rate of the root canal treatment is over 90% after a range of periods [7]. The different outcome of root canal treatment can be attributed to inconsistencies in methodology and assessment criteria [8]. There are studies comparing the outcome of endodontic treatment carried out over single or multiple visits, and the results showed no significant difference between the two approaches [9]. The clinical end-points can be relied on the patient or clinician reporting. The European Medicines Agency (EMA) strongly stress the importance of patient-reported outcomes in the criteria for assessment of endodontic treatment [10]. The patient-reported outcomes classically included the survival, the function of teeth and the pain intensity.
Pain is a common short-term complication of root canal treatment, mostly appears in the first 24 h, which had significant influence on the quality of life [11, 12]. Studies have shown that the incidence rate of postoperative pain after root canal treatment range from 3 to 58% [13], and can reach as high as 80% in the first 24 h [14]. Postoperative pain is commonly attributed to acute inflammatory reaction in the periradicular tissues triggered by mechanical, chemical or microbiological injury [15]. Extrusion of debris and irrigating agent can induce postoperative pain and periradicular tissue damage in patients [16]. Previous studies have evaluated postoperative pain after root canal treatment, and demonstrates contrasting results [11, 17, 18]. However, there are no studies reporting the difference of pain intensity between two visits and three visits in the progress of root canal treatment.
Well-filled root canals are considered to provide a three-dimensional seal, which could be against bacteria ingress [19]. The success of root canal treatment was evaluated by clinically symptomless, radiographic healing, and the pain intensity. Therefore, this study aimed to evaluate the clinical effects and the pain intensity of patients in the three-visit and two-visit root canal treatment, in order to provide clinical treatment options for dentists.
106 patients were screened for eligibility, of which 74 went back to the preservation visit. Therefore, 74 primary molars from 74 children that diagnosed with chronic pulp and periodontal tissue diseases in the clinics of pediatric dentistry were retrospectively analyzed. Patients were enrolled from between August 2021 to November 2022.
① Patients that aged 4 to 11 years. ② Primary molar teeth that caries related to the pulp and the periodontal tissues. ③ Chronic apical periodontitis with or without gingival problems (swelling, redness or sinus tract) and the area of periapical radiolucency ≤1 cm. ④ Parents of patients had strong desire to preserve the affected tooth.
① Patients with other systemic diseases; ② Patients that were allergies to local anesthetic agents; ③ Tooth with mobility; ④ Patients whose tooth had been previously accessed or endodontically treated.
A single dentist with more than 5-year working experience performed all root canal treatments. The patients were divided into two groups according to the times of visit.
37 primary molars from 37 children were included in the two-visit group. After injections of 0.5 mL articaine hydrochloride and epinephrine tartrate injections for anesthesia, isolation of the tooth, the pulp was removed. Then the root canals were identified and prepared with WaveOne primary files (Dentsply Maillefer, Ballaigues, Switzerland), irrigated with normal saline (0.9% NaCl), and 2.5% sodium hypochlorite (NaOCl) in the 2 mL syringe. A total of 10 mL of 2.5% NaOCl was used for the irrigation of each tooth. The calcium hydroxide was put into the canal and the tooth was sealed temporarily with Glass Ionomer Cement during visits. About 1 week later, in the second visit, the Glass Ionomer Cement was removed and the irrigation was performed again. The root canals were dried and filled with vitapex (Neo Dental, Tokyo, Japan), and the tooth was sealed with resin and crown restoration.
37 primary molars from 37 children were included in the three-visit group. At the first visit, only the pulp was removed after anesthesia by 0.5 mL articaine hydrochloride and epinephrine tartrate injections as well as isolation of the tooth. Then calcium hydroxide was put into the canal and the tooth was sealed temporarily with Glass Ionomer Cement. At the second visit comes the preparation of the root canals with WaveOne primary files and large numbers of irrigation with 0.9% NaCl and 2.5% NaOCl, then the tooth was sealed with Glass Ionomer Cement. A total of 10 mL of 2.5% NaOCl was used for the irrigation of each tooth. The root canals were filled with vitapex and the tooth was sealed with resin and crown restoration in the third visit.
At follow-up, the outcome was categorized as: (1) Excellent prognosis; (2) Effective prognosis; (3) Invalid. Excellent prognosis refers to no abnormal mobility, no sensitivity to percussion, and healthy appearance of the soft tissue (no swelling, redness or sinus tract). Effective prognosis refers to no abnormal mobility, little percussion, and healthy appearance of the soft tissue (no swelling, redness or sinus tract). Invalid refers to persistent pain, swelling or gingival fistula [20, 21].
Postoperative pain intensity was registered during the treatment progress from the first to the end. Patients recorded pain intensity as none, slight, moderate and severe. Scores from 0 to 3 (0—none, 1—slight, 2—moderate and 3—severe) were attributed to each level of pain [11]. “0” indicates that children had no pain symptoms. “1” indicates that children have mild pain and can relieve without drug therapy. “2” indicates that there is moderate pain in the affected tooth, which can be relieved after drug treatment. “3” indicates that the affected tooth is in severe pain, with no relief after analgesic treatment.
All statistical data were carried out with SPSS 26 software (SPSS Inc., USA). The difference of age between the two groups was assessed using an unpaired t test. Chi square test was used to statistically assess the difference of gender, clinical effects and pain intensity between the two groups. p values < 0.05 were considered significant.
A total of 74 children, aged 4 to 11 years, were included in the study. They were allocated into two groups, two-visit and the three-visit group. The children in the two-visit group aged from 4.1 to 10.8 years, with an average age of 6.4. The children in the three-visit group aged from 4.8 to 10.0 years, with an average age of 7.0, which showed no significant difference with that in the two-visit group (p = 0.056) (Table 1). Besides, the results also showed no significant difference of gender distribution between the two groups. In detail, the two-visit group consisted of 59.5% male and 40.5% female children, while the three-visit group consisted of 56.8% male and 43.2% female children (p = 0.813) (Table 2).
| Age (yr) | Two-visit group | Three-visit group |
| Mean | 6.4 | 7.0 |
| SD | 1.34 | 1.38 |
| Min | 4.1 | 4.8 |
| Max | 10.8 | 10.0 |
| t-test | 1.941 | |
| p-value | 0.056ns | |
| SD: standard deviation; Min = Minimum; Max = Maximum; t = unpaired t test. ns: p > 0.05 (not significant). |
| Gender | Two-visit group | Three-visit group |
| Male | 22 (59.5%) | 21 (56.8%) |
| Female | 15 (40.5%) | 16 (43.2%) |
| χ2 | 0.056 | |
| p-value | 0.813ns | |
χ2: Chi square test; ns: p > 0.05 (not significant). |
After treatment, there were 27 teeth that was excellent prognosis, 8 effective and 2 invalid in the two-visit group, with total effective rate of 94.59%. The number of excellent teeth in the three-visit group was 33, with total effective rate of 97.30%. The effective and invalid teeth in the three-visit group was 3 and 1, respectively. Statistically, the results showed no significant difference of the effective rate in comparison with these two groups (p = 0.201) (Table 3).
| Group | Cases | Excellent | Effective | Invalid | Total effective |
| Two-visit group | 37 | 27 (72.97%) | 8 (21.62%) | 2 (5.41%) | 94.59% |
| Three-visit group | 37 | 33 (89.19%) | 3 (8.11%) | 1 (2.70%) | 97.30% |
| χ2 | 3.206 | ||||
| p-value | 0.201ns | ||||
ns: p > 0.05 (not significant). |
After treatment, the pain intensity of children was recorded. There were 10 children with 0 grade (no) pain after treatment and 23 with 1 grade (slight) pain which can relieve without analgesic therapy. 4 children had 2 grade (moderate) pain which can be relieved after analgesic therapy. In the three-visit group, there was 11 children with no pain, 24 with slight pain and only 2 had severe pain. There were no children with 3 grade (severe) pain both in the two-visit and three-visit groups. The pain incidence rate in the three-visit group was 70.27%, which was lower than that in the two-visit group (72.97%), but showed no significant difference (p = 0.692) (Table 4).
| Group | Cases | 0 | 1 | 2 | Pain incidence |
| Two-visit group | 37 | 10 (27.03%) | 23 (62.16%) | 4 (10.81%) | 72.97% |
| Three-visit group | 37 | 11 (29.73%) | 24 (64.86%) | 2 (5.41%) | 70.27% |
| χ2 | 0.736 | ||||
| p-value | 0.692ns | ||||
ns: p > 0.05 (not significant). |
Outcomes of root canal therapy has been the focus of investigation for many years [22]. Endodontic success is assessed in different functional activities after the treatment of tooth was finished over time [23]. Previous studies have shown that a host of factors contributed to the success or failure of root canal treatment. However, the fundamental biologic principle that determines clinically success of root canal treatment was still unchanged [22]. The present retrospective study was conducted to investigate the factors that can affect the therapeutic effect and the pain intensity of children after root canal therapy.
According to literature, the favorable outcome for root canal treatment can be up to 90% for those without pre-operative apical periodontitis, while 75–80% for those with pre-operative apical periodontitis [9, 24]. Bacteria and their by-products can be leak through the well-filled canal system even in the best root canal treatment [22]. Two types of clinical outcome assessment were applied in clinical medicine, patient or clinician-reported. The outcome in terms of periapical healing and post-treatment disease were the most important indicators for both patients and clinician [25]. However, the bulk of studies still focus on the clinician-reported end-points [26, 27]. This study investigated the outcome of root canal treatment from the perspective of patients. The outcome indicator includes tooth survival, disease exacerbation or an adverse clinical event [10].
Y.-L. Ng summarized the literature and showed that gender and age had no significant effect on the success rate of root canal therapy [9]. In this study, the gender and age of patients did not show significant difference between the two-visit and three-visit groups, which is consistent with previous studies. Besides, after completely irrigation and effective root canal preparation, the effective rate also showed no significant difference between the two-visit and three-visit treatment, implying that the times of visit is not the factor that affect the treatment outcome. Complete removal of pulp tissue or necrotic material are important for good prognosis of root canal treatment [28]. This can explain why the effective rate of two-visit treatment was not lower than the three-visit group even with little time of irrigating and disinfection, which suggesting that proper operation ensure the successful outcome.
Post-operative pain after root canal treatment may negatively affect the patient’s trust and compliance [29, 30]. The incidence of postoperative pain can be caused by many factors, such as age, gender, the instrumentation used in the root canal therapy, the choice of irrigating solution, the determination of working length, the use of analgesic agents, the times of treatment visits, as well as the obturation materials and techniques [13, 31]. Also, the presence of preoperative pain can influence the severity of postoperative pain [32]. This study demonstrated that the pain intensity of the two-visit and three-visit groups showed no significant difference. Maybe the post-obturation pain is related to the root canal filling technique rather than the times of visit.
As reported, the forcing of endodontic files can make a diversity of toxic debris outside the apical and generate pain [33]. Studies demonstrated that rotary nickel-titanium files used in the mechanical preparation can lead to less debris and irrigant extrusion apically, thus decreasing the incidence of postoperative pain [31]. A recent meta-analysis also showed that rotary instruments were associated with a lower rate of postoperative pain compared with reciprocating instruments [34]. In this study, the WaveOne files were used in both groups, in order to avoid the inconsistency between the two groups. Besides, the type of an irrigating during instrumentation can lead to different pain intensity, due to the flush debris, smear layer and bacteria out of the canal, which might cause reactions on the pulp and periapical tissues, leading to tissue necrosis [35]. The common irrigating solution used in the root canal therapy was normal saline (0.9% NaCl), NaOCl and hydrogen peroxide. Studies have reported that NaOCl is able to remove the organic portion of the smear layer but not the entire smear layer [36]. In this study, normal saline was alternated flush with 2.5% NaOCl in order to wash the remained debris thoroughly. The results of this study showed that there was no significant difference of pain severity between the two-visit and three-visit groups. Maybe, the protracted treatment just means increased technical difficulties in the progress, without improving the chance for successful healing [25]. The three-visit treatment enhanced the time of visits, the by-chair time and economic cost, which increase the burden of patients. This study showed that the treatment efficiency of root canal is able to solved upon thorough disinfection and elimination of microorganisms, regardless of the numbers of treatment visits [25].
However, there are also limits of this study. First, there should be larger sample sizes to make this study more convincing. Second, this study reported only limited periods after treatment, which might be acceptable for short-term outcome. Further studies still need long time follow up to investigate the outcome of root canal treatment.
The outcome of the root canal treatment in primary teeth showed no significant difference between the two-visit and three-visit groups, in terms of clinical effects and pain intensity.
Not applicable.
BBY—collected the data, and performed the writing. SMZ—conceived the idea and analyze the data. All authors read and approved the final version of the manuscript.
This study was approved by the institutional review board of the Shanghai Ninth People’s Hospital and was conducted in accordance with the ethical principles originating from the Declaration of Helsinki (SH9H-2023-T39-1). This was a retrospective study and the requirement for informed consent was therefore waived.
Not applicable.
This work was supported by Shanghai Sailing Program (21YF1424500) and National Natural Science Foundation of China (82103074).
The authors declare no conflict of interest.