|Year : 2015 | Volume
| Issue : 2 | Page : 120-124
Histological evaluation of the root apices of failed endodontic cases
Camilla Nicole Pecora1, Jagan Kumar Baskaradoss2, Abdullah Al-Sharif3, Mansour Al-Rejaie4, Hussein Mokhlis5, Khalid Al-Fouzan6, Gabriele E Pecora1
1 Private practice, Rome, Italy
2 Department of Dental Public Health, School of Dental Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
3 Consultant, Director of Endodontic Board, Riyadh Military Armed Force Hospital, Riyadh, Saudi Arabia
4 Consultant Endodontist, King Saud Bin Abdulaziz University for Health Sciences, KAMC, National Guard Health Affairs, Riyadh, Saudi Arabia
5 Consultant, Department of Endodontics, Prince Sultan Military Medical City, Denal Clinics, Riyadh, Saudi Arabia
6 Consultant and Head of Endodontics Division, College of Dentistry, King Saud Bin Abdulaziz University for Health Sciences, KAMC, National Guard Health Affairs, Riyadh, Saudi Arabia
|Date of Web Publication||20-Apr-2015|
Consultant and Head Division, Endodontics, College of Dentistry, KSAU HS, King Abdulaziz Medical City, P.O.Box 22490, Riyadh 11426
Source of Support: None, Conflict of Interest: None
Aim: The aim of this histological study was to evaluate the different causes of the failures of the endodontic treatment. Materials and Methods: Adult patients who were referred for endodontic surgery and for whom root-end resection was considered suitable were invited to participate in this study. The inclusion criteria were: (1) Patients aged between 18 and 65 years; (2) teeth with apical periodontitis that was diagnosed radiographically; (3) the tooth could not be adequately and better managed by root-canal retreatment; and (4) the crown of the tooth was adequately restored. One hundred root apices were surgically removed together with the periapical pathological tissue from 92 patients (56 males and 36 women).Histological sectioning was performed on calcified specimens that were embedded in a suitable medium. Results: The causes of endodontic failure identified through histological evaluation were as follows: Presence of bacterial and debris into canals (51%), apex transposition and overfilling (3%), presence of the isthmus (21%), bacterial colonization of root surface (2%), untreated canals (11%), and filling material outside root canal (4%). There was no significant difference between the distribution of teeth and the causes of endodontic failures (P = 0.32). Conclusions: The present study demonstrated that the most common cause of endodontic failure is the insufficient cleaning of the root canal system. It also explores the effectiveness of histological evaluation of the root apex following root-end resection in exploring the causes of endodontic failures.
Keywords: Apical third, bacteria, debris, endodontic failure, histology
|How to cite this article:|
Pecora CN, Baskaradoss JK, Al-Sharif A, Al-Rejaie M, Mokhlis H, Al-Fouzan K, Pecora GE. Histological evaluation of the root apices of failed endodontic cases. Saudi Endod J 2015;5:120-4
|How to cite this URL:|
Pecora CN, Baskaradoss JK, Al-Sharif A, Al-Rejaie M, Mokhlis H, Al-Fouzan K, Pecora GE. Histological evaluation of the root apices of failed endodontic cases. Saudi Endod J [serial online] 2015 [cited 2019 Dec 5];5:120-4. Available from: http://www.saudiendodj.com/text.asp?2015/5/2/120/155450
| Introduction|| |
High standard of care is required to minimize the incidence of endodontic failures. , In the past, the success of root canal therapy was ascribed to the ability of the operator to effectively sterilize the root canal and achieve a hermetic apical seal. Of late, the focus has shifted to encourage comprehensive three-dimensional filling of the whole root canal space after thorough debridement. 
Numerous factors including the presence of extra-radicular and intra-radicular microbes, contributes toward endodontic failures. , Persistence of microbes in the apical portion of the root canal system has been reported to be one of the most common causes for endodontic failures.  Studies have demonstrated that bacteria located near isthmuses, ramifications, deltas, irregularities and dentinal tubules may sometimes be unaffected by endodontic disinfection procedures. , This may allow the micro-organisms to survive and, depending on several factors, induce failure.
It has also been suggested that certain intrinsic or extrinsic non-microbial factors may also contribute toward endodontic failures. Foreign body reaction in the peri-radicular tissues to cholesterol crystals precipitated from disintegrating host cells can be an etiological factor in non-resolving chronic inflammation.  Certain root-filling materials like talc-contaminated gutta-percha cones, can initiate a foreign body reaction if they are displaced into the peri-radicular tissues.  The cellulose component of paper points and cotton wool may contribute to failure of root canal treatment if they come in contact with the peri-radicular tissues. 
Diagnosis of endodontic failures is usually made based on the clinical presentation and radiologic evaluation. Most of the endodontic failures are located near the apical third, and it may not be possible to clearly define the lesion based on radiographs alone. , Histological evaluation after surgical apex resection would be able to provide a more accurate diagnosis of the status of the root apex.  The present study was designed to histologically determine the causes of endodontic failure from the apices of root-end resected teeth.
| Materials and methods|| |
This cross-sectional study was performed in the endodontic clinics at the College of Dentistry, King Saud Bin Abdulaziz University for Health Sciences (KSAU-HS), Riyadh, Saudi Arabia. Adult patients who were referred for endodontic surgery and for whom root-end resection was considered suitable were invited to participate in this study. Approval for the study was obtained from the Institutional Ethics Committee. The inclusion criteria included (1) patients aged between 18 and65 years; (2) teeth with apical periodontitisthat wasdiagnosed radiographically; (3) the tooth could not be adequately and better managed by root-canal re-treatment; and (4) the crown of the tooth was adequately restored [Figure 1]. Preoperatively, there was an assessment of the patient's medical condition, the general oral condition, percussion sensitivity and mobility of the affected tooth, the presence of pain, dental caries and restoration in the tooth, functioning of the tooth and the endodontic status. Exclusion criteria included (1) patients who were medically unfit for the study; (2)
presence of metallic restorations; and (3) presence of root resorption or fractures.
|Figure 1: Periapical radiographs of failed endodontic treatment in the right mandibular first molar showing periapicalradiolucency (a). A 6-month post-operative radiograph showing failed endodontic retreatment of the right mandibular first molar (b)|
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A convenient sample of 100 root apices that were surgically removed together with the periapical pathological tissue from 92 patients were histologically analysed. The surgical procedure was performed under local anesthesia and preoperatively the patient rinsed his/her mouth with an antiseptic mouthwash (chlorhexidinegluconate 0.2%). A buccalmuco-periosteal tissue flap was raised and sufficient bone was removed with a bur to expose the apex. The teeth were resected apically 3 mm from the root apex at a 90 o angle to the long axis of the root using a surgical microscope (Global, St.Louis, MO, USA) at 8X magnification. The root re-section was made with a tungsten carbide straight fissure bur mounted on contra-angle, high-speed handpiece (KavoDentale, Biberach, Germany) and with constant water irrigation to avoid overheating. Ultrasonic diamond tip (Spartan, Fenton, MO, USA) was used to prepare 3-mm retrograde cavities, which were filled with mineral trioxide aggregate (MTA) carried with the MAP system. Root ends were wrapped with wet gauze to facilitate MTA setting. The wound was closed and postoperative radiograph was taken to ensure adequate technical quality of the procedure. The patient was asked to take analgesics postoperatively and to use an antiseptic mouthwash twice a day for 1 week. After a week the sutures were removed.
All the surgical procedures were performed by a single calibrated endodontist. A pilot study, involving a similar surgical procedure was performed on five randomly selected teeth by the same endodontist. The surgical technique was evaluated for consistency by two experienced endodontists on the post-operative radiograph. The intra-examiner reliability was found to be good, with a kappa (k) value of 0.76.
The root apices were stored in 10% formalin and histologically evaluated. Histological sectioning were performed on calcified specimens embedded in methylmethacrylate (MMA) and on demineralized specimens embedded in LR White (Fluka, Buchs, Switzerland).Criteria of evaluation for failure were adopted from Rud et al.  All the patients were followed-up for a minimum of 12 months during which, all the teeth remained asymptomatic and showed radiographic evidence of healing [Figure 2].
|Figure 2: A 12-month post-operative radiograph of the right mandibular second premolar and first molar showing radiographic evidence of healing|
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All statistical analyses were carried out using SPSS 17.0 (Statistical Package for the Social Sciences for Windows® ; SPSS Inc., Chicago, IL, USA). Frequency distribution for all the categorical variables were obtained. χ2 test of significance was performed to determine the relationship between causes of failures and distribution of teeth.
| Results|| |
The study population consisted of 56 males (60.9%) and 36 females (39.1%), with a mean age of 49.2 years (SD ± 10.3). Of the apices of the teeth included in the study, 30 were from anteriors, 26 from premolars and 44 from molars. The causes of endodontic failures are shown in [Table 1]. The results indicated that the presence of bacteria [Figure 3] and debris [Figure 4] in the root canal were the most common causes for endodontic failures (51%). In addition, the presence of isthmus [Figure 5], untreated canals [Figure 6] and microfractures [Figure 7] also contributes toward endodontic failures. There was no significant difference (P = 0.32) between the distribution of teeth and the causes of endodontic failures [Table 2].
|Figure 3: Photomicrograph of the bacterial colonization in the root canal|
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|Figure 4: Photomicrograph of the debris outside the root canal at low power magnification (a) and at high power magnification (b)|
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|Figure 5: Cross-sectional photomicrographof the debris in the isthmus of root canalat low power magnification (a) and at high power magnification (b)|
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| Discussion|| |
Improvement in the techniques, as well as the introduction of new instruments, have positively raised the quality of endodontic treatment.  Instrumentations of the pulp chamber may leave debris in the root canal. , This debris increases the risk of bacterial contamination which may lead to the failure of endodontic treatment.  Debris may be compacted along the entire length of the canal surface and results in reduced adaptation of sealer and gutta-percha.
The high percentage of bacteria and the debris in the root canal shows that electronic apex locators and nickel titanium rotary instruments, together with vertical condensation of gutta-percha with cement, may not always be effective in the apical third of the root. Previous studies have shown that the number of bacterial cells persisting after instrumentation and irrigation with sodium hypochlorite is usually low in teeth with chronic periapical access.  Also, the use of bacteriostatic and bactericidal liquids, , have been reported to be successful in reducing the bacterial counts in the root canal space. , In the present study, the number of surviving bacteria was observed to be higher than those reported in other studies.  However, it must be mentioned here, that the histological findings from samples obtained during apical surgery may differ from findings obtained by teeth extractions. 
The high number of untreated canals provides evidence that despite the accuracy and the experience of the operators, it is difficult to detect calcified canals. It has been reported that the vertical condensation may induce microfractures in the apical dentin.  This can be an important reason for surgical failure especially if they go undetected. Also, the bacterial colonization of microfractures is difficult to detect with clinical and radiographical exploration alone. This finding reinforces the fact that clinicians have to be extremely careful while selecting the size of their spreaders and also the amount of pressure applied during the procedure.
Mandibular molars in our study constituted approximately one-third of the failures overall and 70% of the endodontic failures. This is similar to the study by Swartz et al.  which described significantly lower success rate while treating mandibular molars.
Another important finding of this study was the detection of untreated isthmus, present in 21% of the teeth. The isthmus is a narrow connection between two root canals and it usually contains pulp tissues.  This anatomic formation is a part of the root canal system and not a separate entity. Although the new endodontic techniques and instruments have improved the cleaning and the shaping capability, treating the isthmus with a non-surgical approach may still be challenging. Untreated isthmus was found in18 apices of the molars, two apices of the lower central incisors and one in a premolar. The complicated anatomy of the tooth and clinical error on the part of the treating dentist could explain the mismanagement of the isthmus. ,
Within the limitation of this study, it would be possible to recommend dentists to undergo adequate training prior to attempting endodontic procedures. But, good clinical skill alone may not be sufficient to ensure a successful outcome. The importance of correct case selection and a clear understanding of the biological basis of treatment must also be appreciated.
| Conclusions|| |
The present study demonstrated that the most common cause of endodontic failure is the insufficient cleaning of the root canal system. It also explores the effectiveness of histological evaluation of the root apex following root-end resection in exploring the causes of endodontic failures.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2]