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Incidence of Flare-Ups and Apical Healing after Single-Visit or Two Visits Treatment of Teeth with Necrotic Pulp and Apical Periodontitis after a Two-Year Control Period. A Randomized Clinical Trial

Jorge Paredes Vieyra, Fabian Ocampo Acosta, Seidi Karin Nevarez Osuna

Correspondence Address :

Jorge Paredes Vieyra
School of Dentistry
710E San Ysidro Blvd. suite "A" #1513, San Ysidro California 92173
USA
Email: jorgitoparedesvieyra@hotmail.com

Received on: March 20, 2018, Accepted on: March 27, 2018, Published on: April 11, 2018

Citation: Jorge Paredes Vieyra, Fabian Ocampo Acosta, Seidi Karin Nevarez Osuna (2018). Incidence of Flare-Ups and Apical Healing after Single-Visit or two visits Treatment of Teeth with Necrotic Pulp and Apical Periodontitis after a Two-Year Control Period. A Randomized Clinical Trial

Copyright: 2018 Jorge Paredes Vieyra, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Abstract
Aim to compare Incidence of flare-ups and apical healing after single-visit or two-visit treatment of teeth with necrotic pulp and apical periodontitis after a two-year control period.
Methodology: 110 teeth with a diagnosis of pulp necrosis and apical radiolucency at the apex. Working length was established with EAL and confirmed radiographically. M4 system with Flex-R files were used to complete canal preparation. Levels of discomfort were recorded and cases with severe postoperative pain and/or swelling were classified as flare-ups.
Results: Randomization allocated 50 teeth to one-visit and 60 teeth to two-visit treatment. Four teeth in the single-visit and nine in the two-visit group were lost to follow-up leaving 97 teeth that were evaluated at the 2-year follow-up period (46 single-visits, 51 two visits.
The occurrence of a flare-up was positively associated only with the treatment of previously symptomatic teeth with periradicular lesions (p=0.05). There was a significant difference regarding the occurrence of flare-ups when comparing treatment cases with retreatment cases (p=0.05). There was also no difference regarding the incidence of postoperative pain between treatment and retreatment (p > 0.01). Some level of postoperative pain occurred in 25.45% of the cases 23.76% of the treated teeth and 30% of the retreated teeth.
Postoperative pain was significantly associated with previously symptomatic teeth and apical periodontitis. (p= 0.05). Statistical analysis of the healing results did not show any significant difference between the groups (p=0.05).
Conclusions: This study gave evidence that a meticulously instrumentation and irrigation performed in a single-visit root canal treatment can be as successful as a two visit treatment. There was a significantly higher incidence of flare-ups in teeth that needed retreatment than in primary treatment.
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Introduction
Flare-up is a condition occurring within a few hours to a few days after a root canal treatment especially in teeth with necrotic pulp [1,2]. The AAE (2015) described flareup as an acute exacerbation of an asymptomatic pulpal and or periradicular pathos is after the initiation or continuation of root canal treatment.
Some etiological factors that have been suggested to play a role in flare-up including preoperative pain, pulp vitality and microbial infection, inadequate debridement and extrusion of debris and filling material into the periradicular area. Studies have reported a widely varying incidence of flare-ups ranging from 1.4% to 16% [3,4].
Periradicular periodontitis is an inflammatory disease comprising host responses to infection of the root canal system of the affected tooth [5]. Since the vast majority of endodontic problems are microbial in origin, removal of microorganisms is considered the most important step in root canal therapy [6,7].
Reduction of the microbial load as well as the disruption of biofilms are achieved by a combination of mechanical instrumentation, irrigation with tissue dissolving and microbicide solutions, and application of antimicrobial medicaments in the root canal between appointments [8].
The majority of studies reported significant reduction of bacteria with an increase in preparation size and irrigation [8,9]. On the other hand, [10] demonstrated that more than 30% of the root canal walls remained untouched even by modern rotary NiTi instrumentation techniques.
Mechanical debridement combined with antibacterial irrigation using 0.5% sodium hypochlorite can render 40-60% of the treated teeth bacteria negative [11,12]. In addition to mechanical debridement and antibacterial irrigation, dressing the canal with calcium hydroxide has been shown to increase the percentage of bacteria negative teeth to around 70% [9]. Singlevisit root canal treatment has become common practice and offers some advantages such as a reduced flare-up rate [13,14], reduced number of appointments and reduced cost.
It is understood that single-visit treatment is based on the clinical opinion that additional appointments would not improve the quality of care [15]. On the other hand, microbial eradication cannot be predictably maximized without calcium hydroxide dressing between appointments [16,17]. However, even though an interappointment dressing with calcium hydroxide decreases the bacterial count it does not assure total eradication of intracanal microbes [8].
Post-operative pain after an endodontic procedure is usually associated to the presence of periapical inflammation, which may be the result of over-instrumentation, over-filling, and passage of medicine or infected debris into the periapical tissues, damage of the vital neural or pulpal tissues or central sensitization [18].
The issue remains controversial since opinions vary greatly as to the relative risks and benefits of single-visit versus multiplevisits root canal treatment of teeth with necrotic pulp and apical periodontitis.
The purpose of this randomized controlled trial was a. To compare the incidence of flare-ups of single-visit versus two visits root canal treatment and retreatment of teeth with necrotic pulp and apical periodontitis and b. To relate the incidence of flare-ups to the clinical outcome after two years in terms of healing and disease. 

Materials and Methods

The institutional review board of the Facultad de Odontologia Tijuana Mexico approved the study protocol and all the participants were treated in accordance with the Helsinki Declaration (www.cirp.org/library/ethics/helsinki). The study started in February 2016 and ended in March 2018. The main inclusion criteria were: a) Radiographic evidence of apical periodontitis (minimum size ≥2.0 mm x 2.0 mm) and a diagnosis of pulpal necrosis confirmed by negative response to hot and cold tests and b) Need for retreatment. The author performed thermal pulp testing, and one certified oral surgeon verified radiographic interpretation.
Patient selection was based on the following criteria: 1) The aims and requirements of the study were freely accepted; 2) Treatment was limited to patients in good health; 3) Patients with symptomatic or asymptomatic teeth with necrotic pulps and apical periodontitis, with or without a sinus tract; 4) A negative response to hot and cold pulp sensitivity tests; 5) Presence of sufficient coronal tooth structure for rubber dam isolation, and 6) No analgesics or antibiotics were used five days before the clinical procedures began.
Exclusion criteria were patients without inclusion requirements or failure to obtain patient's authorization. Patients, were excluded if they were younger than 18 years old, pregnant, had a positive history of antibiotic use within the past month, suffered from diabetes, or other systemic diseases. Teeth with periodontal pockets deeper than 4 mm also were excluded of the study.
Once eligibility was confirmed, the study was explained to the patient by the authors, and the patient was invited to participate. After explaining the clinical procedures and risks and clarifying all questions raised, each patient signed a written informed consent form and was randomly assigned to either the one-visit or the two-visit group by using a block of random numbers generated by one of the investigators.
Randomization was performed before the clinical examination using the minimization method described by [16]. Three randomization factors were considered: tooth group, size of periapical lesion and pre and post-operative pain as a clinical symptom (Tables 1 and 2). Sample size was calculated using the method described by [17]. The minimum sample size per group was determined to be 50, based on power p ˂ 0.05, and the minimum clinically significant mean difference between groups was set at 0.5 units (standard deviation +/-.0 unit) by using the periapical index (PAI) scale described by [18,19].
One hundred and twelve of one hundred and twenty patients (63 women and 47 men), 18 to 60 years of age (mean = 55 years) with 110 eligible teeth consented to participate in the study. The study design is shown in Figure 1.
A medical history was obtained and a clinical examination performed. All teeth were asymptomatic with a diagnosis of pulp necrosis determined by hot and cold sensitivity tests and radiographically all teeth showed a small and irregular radiolucency at the tooth apex (Schick Technologies, Long Island City, NY, USA). Periodontal probing revealed no increased probing depth (> 3 mm) around any of the teeth. All of the clinical procedures were performed by the author.

Clinical Procedures

All treatment sessions were approximately 50 minutes in length to allow for acceptable time for completion of treatment and retreatment in one or two visits. The author performed all the clinical procedures.
Following local anesthesia with 2% lidocaine with 1:100,000 epinephrine (Septodont Saint-Maur des Fosses, France) and rubber dam isolation the tooth was disinfected with 5.25% NaOCl (Ultra bleach, Bentonville, AR, USA). Carious dentine was completely removed and endodontic access cavities prepared with sterile high-speed carbide burs # 331 (SS White. Lakewood, NJ, USA) and Zekrya Endo burs (Dentsply-Maillefer, Ballaigues, Switzerland).
Working length was established using the Root ZX (J Morita, Irvine, CA, USA) and confirmed radiographically. The root canals were negotiated and enlarged with hand instruments (Flex-R files, Moyco/Union Broach, York PA, USA) until reaching an ISO size #20 at working length. The coronal portions of the root canals were flared with sizes 2-3 Gates-Glidden burs (Dentsply Maillefer). Irrigation was performed using 2.0 mL 5.25% sodium hypochlorite following each step of instrumentation. The M4 Safety Handpiece E-Type (SybronEndo, Orange, CA, USA) with Flex-R files was used to complete root canal preparation to a size #60 for the anterior teeth and premolars and to a size #45 - #55 for molars. EDTA (Roth International Ltd, Chicago, IL, USA) served as a lubricant.
After completion of instrumentation, all root canals were irrigated with 2.5 mL 17% EDTA acid (Roth International) for 30 seconds followed by a final irrigation with 5.0 mL 5.25% NaOCl using the EndoVac irrigation system (Discus Dental, Culver City, CA, USA).
For the single-visit group, the root canals were dried with sterile paper points and obturated at the same appointment using lateral condensation of gutta-percha and Sealapex sealer (SybronEndo). Access cavities of anterior teeth were etched and restored with Fuji IX (GC Corp, Tokyo, Japan). For posterior teeth, a buildup restoration was placed using the same etching technique and Fuji IX.
For the two visits group, the root canals were dried and xmedicated with calcium hydroxide powder (Roth, International) with distilled water in a creamy consistency. The paste was prepared by using equal volumes of Ca(OH)2 powder and distilled water, and applied meticulously into the root canal using endodontic hand files.
The access cavities (occlusal/palatal surface) were sealed with Cavit (3M ESPE, Seefeld, Germany) and the quality of the calcium hydroxide powder filling was checked radiographically. Patients of the two visits group were scheduled for a second appointment to complete root canal therapy at least 1 week after the initial appointment. At the second appointment, the calcium hydroxide paste was removed with hand instruments and copious irrigation with distilled water followed by 2.5 mL 17% EDTA and a final rinse with 5.0 mL 5.25% NaOCl using the EndoVac irrigation system.
Following removal of the calcium hydroxide, the root canals were dried with sterile paper points, and obturation was performed with the same technique described for the single-visit group: Post treatment radiographs were taken and all teeth were restored with a Fuji IX buildup.
In re-treatment cases, after removal of the previous root canal filling using Gates Glidden burs, hand files and eucalyptol, root canal preparation was completed as described above.
The level of discomfort was rated as follows: no pain; mild pain, which was recognizable but not discomforting; moderate pain, which was discomforting but bearable (analgesics, if used, were effective in relieving pain); flare-up, which was difficult to bear (analgesics, if used, were ineffective in relieving pain). Cases with severe postoperative pain and/or the occurrence of swelling were classified as flare-ups and treated accordingly (Table 2). After completion of treatment, patients were instructed to return to their referring dentist for definitive restoration as soon as possible.
Two-Year Follow-Up
The healing results were clinically and radiographically evaluated 2 years postoperatively. All radiographs obtained preoperatively and at follow-up were coded blind and organized in random order.
Two pre-calibrated endodontists (author not included) independently evaluated all radiographs under moderate illumination at a light table using a 2x magnifying viewer equipped with a masking frame of the same size as the dental film. Before evaluation of the study images, each examiner graded a series of 10 radiographic images not associated with the study sample and representing a wide range of periapical bone densities.
To minimize false-positive diagnoses, observers used a strict definition of periapical disease [18]. In case of disagreement, joint re-evaluation was performed until a consensus was reached on all images. All radiographs were obtained by using the same digital imaging system (Schick Technologies).
The primary outcome measure for this study was classified by using a modification of Strindberg's criteria [20] used for assessment of radiographic healing. Teeth with symptoms of persisting periapical inflammation were scored as not healed, as were the cases with periapical radiolucencies that remained unchanged or increased in size (Table 3).
Teeth with a reduced periapical rarefaction were judged as uncertain. Teeth with complete restitution of the periodontal contours were judged as healed. In teeth with more than one root, the least favorable outcome was recorded.
The periapical index (PAI) scale described by [19] was used as a scoring system to evaluate radiographic healing (Walters 2004) as shown in Figure 2.
Secondary outcome measures were the presence of clinical symptoms or abnormal findings at the end or during a twoyears observation period (spontaneous pain, presence of sinus tract, swelling, mobility, periodontal probing depths greater than baseline measurements, or sensitivity to percussion or palpation) as shown in Table 2.
The overall incidence of postoperative discomfort was recorded and expressed as a percentage of the total number of teeth evaluated. The associations between the variables as well as the flare-up rates in both groups were compared. Incidence of postoperative pain was also calculated for each studied variable.
A chi-square test was used to test trends in contingency tables using SPSS v. 22 for windows. Statistical analysis was conducted at the 0.05 level of significance.
Results
Randomization allocated 50 teeth to single-visit and 60 teeth to two visits treatment. Four teeth in the single-visit and 9 in the two visits group were lost to follow-up leaving a total of 97 teeth that were evaluated at the 2-year follow-up period (46 singlevisit, 51 two visits; Figure 1 and Tables 1 and 3).
Incidence of flare-ups
The occurrence of a flare-up was positively associated only with the treatment of previously symptomatic teeth with periradicular lesions (p=0.05). There was a significant difference regarding the occurrence of flare-ups when comparing treatment cases with retreatment cases (p= 0.05). Moderate pain occurred in 5% of the treatment cases and 16.67% of the retreatment cases. Of the previously Asymptomatic/symptomatic teeth, the treatment was effective in completely eliminating pain in 73.76%, and in 60%, respectively, of the retreatment cases (Tables 2 and 3).
There was also no difference regarding the incidence of postoperative pain between treatment and retreatment (p > 0.01). Some level of postoperative pain occurred in 25.45% of the cases. 23.76% of the treated teeth and 30% of the retreated teeth.
Postoperative pain was significantly associated with previously symptomatic teeth and apical periodontitis. (p= 0.05). No other correlations were detected between the occurrence of a flare-up and postoperative discomfort and other clinical conditions. Data is summarized in Tables 2, 3 and 4.
Flare ups and apical healing
At the end of the study, 11 of the 46 teeth (11.34%) in the single-visit group and 8 (8.24%) of the 51 teeth in the twovisit group were classified as healed (Table 3). The number of cases classified as uncertain was higher (26) in the single-visit group (26.80%) as compared with 21 (21.64%) in the two visits group. One patient (single-visit group) presented with persistent draining sinus tracts at 24 months (presented with sinus tracts at the initial treatment appointment) as shown on Table 1.
The statistical analysis of the healing results did not show any significant difference between the groups (p=0.05).
Discussion
The purpose of this randomized study was to compare the flare-up rate of single-visit versus two-visit root canal treatment of teeth with necrotic pulp and apical periodontitis and the relation between flare-ups and apical healing after a two-year control period.
Our results agree with those from a recent study [21], which found that root canal treatments with postoperative
pain occurring shortly after treatment could result in longterm success whereas treatment without such pain may result in failure. Two other studies [8,9] reported that discomfort was the most common short-term outcome of root canal treatment procedures.
Unfortunately, the measurement of discomfort is fraught with hazards and opportunities for errors. It is necessary to rate the level of discomfort in categories arranged in advance and exactly described by authors [22]. Suggested accurate criteria to categorize patients pain [22].
The results of this study were similar to those reported by previous studies [23,24] where no significant differences in the occurrence of flare-ups were observed, when comparing singlevisit vs two visits root canal treatment. Found a significantly higher incidence of flare-ups in teeth that needed retreatment and were treated in one-visit than those with multiple-visit root canal treatment (Table 5) [24].
In our study two patients (2.5%) experienced a flare-up in teeth that had received primary root canal treatment, and 3 patients (10%) in retreatment teeth (Table 2). Flare-up occurred in 4.5% of the cases.
We found that previously symptomatic teeth with radiolucent areas were more susceptible to flare-ups. Our results are in agreement with the study by Torabinejad et al., [25]. A higher incidence of postoperative pain in teeth without periradicular lesions might be attributed to a lack of space for pressure release when periradicular bone resorption is absent [26].
Some studies have reported a significantly higher incidence of flare-ups in teeth that needed retreatment [1]. However, we found no correlation between the incidence of postoperative pain in cases of treatment or retreatment. We found more cases of flare-up in retreatment than in primary treatment. In contrast,
Walton and Fouad [2] found no significant difference in flare-up incidence between treatment and retreatment cases.
The incidence of postoperative pain and particularly of flareups was positively associated with the treatment of previously symptomatic teeth with periradicular lesions. Studies have shown that the presence of preoperative pain can significantly increase the probability of postoperative pain [1,2, AAE 2003]. There are conflicting results with regard to the influence of periradicular bone destruction on the incidence of postoperative pain.
Most studies on single visit endodontics have focused on postoperative pain and flare-up [26,27], despite the fact that pain has been shown to have no effect on long-term healing success [28,29].
Historically, several treatments strategies and interappointment dressings were used for infected teeth but over
the years the number of sessions has been reduced [30]. A two visits model using an inter-appointment dressing with calcium hydroxide has been proposed as a standard [30]. Several factors play an important role in the decision-making process between single-visit versus two-visit endodontics and the endodontic competence of clinicians becomes the overriding factor in determining the outcome of any treatment.
The probability that teeth treated in two visits with an interappointment dressing of calcium hydroxide would result in improved healing when compared with one-visit root canal therapy was not supported by the results of the present study. We did not attempt to balance the number of multi-rooted teeth in each group, although multi-rooted teeth with apical periodontitis have a lower possibility of complete healing when compared with
single-rooted teeth [31].
A determination of healed, not healed, or uncertain was made radiographically 2 years following treatment. However, since radiographic images of periapical bone lesions range from impossible or difficult to see to being easily seen false-positives were minimized in this study because periapical radiolucencies were recorded only when absolutely certain. Our results agree with Peters and Wesselink [14,32,33]. Two years is a practical standpoint considering the difficulty controlling patient dropouts over time [32].
Reported two randomized controlled trials that both compared radiographic periapical healing after root canal treatment of necrotic teeth completed in 1 visit or 2 visits [18]. There were no statistically significant differences in healing between the 2 groups as in the present study.
In this study we used the EndoVac, a negative pressure irrigation technique developed to avoid those adverse effects even when the needle was placed as far apically as the working length. Nielsen and Baumgartner [12] showed that there are significant differences in the cleaning effect at the apical 1 mm level using the EndoVac technique in comparison to a conventional positive pressure technique [34-39].
In the present study, age had no significant relationship with the rate of endodontic flare-up. Similar findings were also reported by Eleazer and Eleazer [31].
Conclusions
This study gave evidence that a meticulously instrumentation and irrigation performed in a single-visit root canal treatment can be as successful as a two visits treatment.
There was a significantly higher incidence of flare-ups in teeth that needed retreatment than in primary treatment. There was no significant difference in radiographic evidence of periapical healing between single-visit and two visits root canal treatment.
Acknowledgements
We thank Prof. Dr. Michael Hulsmann (Gottingen) for his valuable assistance in reviewing this manuscript. The authors deny any conflict of interests related to this study.

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Tables & Figures

Figure 1: Flow diagram of the progress of phases of the trial.


Figure 2: The PAI was used to evaluate radiographic healing.


Table 1: Distribution of teeth by Randomization Factors.


Table 2: Occurrence of postoperative pain and Flare up in different clinical conditions.


Table 3: Distribution of teeth according to outcome classification in the two experimental groups.


Table 4: Distribution by age and presence of Flare -up.


Table 5: Distribution of endodontic Flare-ups.
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