P.R. Wesselink

Limitations of previously published systematic reviews evaluating the outcome of endodontic treatment

The aim of this work was to identify the limitations of previously published systematic reviews evaluating the outcome of root canal treatment. Traditionally, periapical radiography has been used to assess the outcome of root canal treatment with the absence of a periapical radiolucency being considered a confirmation of a healthy periapex. However, a high percentage of cases confirmed as healthy by radiographs revealed apical periodontitis on cone beam computed tomography (CBCT) and by histology. In teeth, where reduced size of the existing radiolucency was diagnosed by radiographs and considered to represent periapical healing, enlargement of the lesion was frequently confirmed by CBCT. In clinical studies, two additional factors may have further contributed to the overestimation of successful outcomes after root canal treatment: (i) extractions and re-treatments were rarely recorded as failures; and (ii) the recall rate was often lower than 50%. The periapical index (PAI), frequently used for determination of success, was based on radiographic and histological findings in the periapical region of maxillary incisors. The validity of using PAI for all tooth positions might be questionable, as the thickness of the cortical bone and the position of the root tip in relation with the cortex vary with tooth position. In conclusion, the serious limitations of longitudinal clinical studies restrict the correct interpretation of root canal treatment outcomes. Systematic reviews reporting the success rates of root canal treatment without referring to these limitations may mislead readers. The outcomes of root canal treatment should be re-evaluated in long-term longitudinal studies using CBCT and stricter evaluation criteria.

Glucose reactivity with filling materials as a limitation for using the glucose leakage model

AIM To evaluate the reactivity of different endodontic materials and sealers with glucose and to asses the reliability of the glucose leakage model in measuring penetration of glucose through these materials. METHODOLOGY Ten uniform discs (radius 5 mm, thickness 2 mm) were made of each of the following materials: Portland cement, MTA (grey and white), sealer 26, calcium sulphate, calcium hydroxide [Ca(OH)(2)], AH26,Epiphany, Resilon, gutta-percha and dentine. After storing the discs for 1 week at 37 degrees C and humid conditions, they were immersed in 0.2 mg mL(-1) glucose solution in a test tube. The concentration of glucose was evaluated using an enzymatic reaction after 1 week. Statistical analysis was performed with the anova and Dunnett tests at a significant level of P < 0.05. RESULTS Portland cement, MTA, Ca(OH)(2) and sealer 26 reduced the concentration in the test tube of glucose significantly after 1 week (P < 0.05). Calcium sulphate reduced the concentration of glucose, but the difference in concentrations was not significant (P = 0.054). CONCLUSIONS Portland cement, MTA, Ca(OH)(2) and sealer 26 react with a 0.2 mg mL(-1) glucose solution. Therefore, these materials should not be evaluated for sealing ability with the glucose leakage model.

Polyethylene tubes as a model for the root canal

Polyethylene tubes, closed at both ends with casting wax and with four perforations in the middle, were implanted subcutaneously in rats and evaluated as a research model simulating the root canal. As controls, wax bars and unperforated tubes were implanted. Attention was given to the reaction of the tissue surrounding the perforated empty tube, the tissue reaction to polyethylene and casting wax, and to the displacement of the tubes.

Electronic determination of root canal length

Root canal length was measured in an experimental model composed of the severed halves of porcine mandibles, using an electronic device for locating the apical foramen. The measurements, each taken independently by two or three observers, were compared with radiographic working length determinations, and with direct visual measurements made after the teeth were extracted. Under the conditions of the experiment, electronic determination of endodontic working length did not compare favorably with radiographic determination of working length.

New terms for categorizing the outcome of root canal treatment

Dear Editor Various terms have been used to categorize the outcomes of root canal treatment. ‘Success’ and ‘failure’ are the most popular terms that are used, but ‘healing’ and ‘healed’ have been suggested (Friedman & Mor 2004). ‘Success’ means ‘the accomplishment of an aim or purpose’ (Oxford Dictionary). According to most endodontic textbooks, the purpose of root canal treatment is to prevent and eliminate apical periodontitis (AP) (Ørstavik & Pitt Ford 1998). Because the outcome of treatment is evaluated using the history provided by the patient at recall along with a thorough clinical examination and with radiographs, ‘success’ has been defined as the prevention and elimination of a periapical radiolucency and symptoms, with ‘failure’ being the development or persistence of AP and/or symptoms (European Society of Endodontology 2006). It has been demonstrated that bacteria cannot be removed completely from the canal system using current techniques in both primary root canal treatment and retreatments (Nair et al. 2005, Haapasalo et al. 2011). To conform to these limitations, the aim of root canal treatment should be restated as – ‘the minimization of the burden of root canal infection and the severity of AP’. It is well known that several years may be required for complete resolution of periapical radiolucencies (Ørstavik 1996), and thus a long follow-up time period is required, which reduces the recall rate. With a low recall rate, the reported success rates could be overor under-estimated (Ørstavik et al. 2004, Marquis et al. 2006, Wu et al. 2009). Sixty-three clinical studies (1922–2002) were selected in a review by Ng et al. (2007), the median recall rate was 52.7% and the lowest recall rate was 11% (Selden 1974). In the Toronto studies phases I, II and III, data of only 27% of the treated teeth were included in the final analysis in spite of several and various attempts to stimulate the participants to return for recall (Marquis et al. 2006). The problems of conducting clinical trials in mobile populations are well documented (Ng et al. 2007). In comparison with ‘success’ and ‘failure’, ‘effective’ and ‘ineffective’ are reasonable terms that should be considered. ‘Effective’ treatment is defined as the absence of symptoms and complete or partial resolution of the preoperatively existing periapical radiolucency 1 year following treatment. In cases where no preoperative lesion was present, ‘effective’ would mean that no lesion or signs/symptoms will develop after 1 year. ‘Ineffective’ treatment is defined as the development or enlargement of a radiolucency and/or the persistence/ emergence of symptoms and signs 1 year following treatment, and a timely retreatment should be suggested to the patient (Wu & Wesselink 2005). Asymptomatic teeth, where the size of the radiolucency does not noticeably change 1 year following treatment, should be placed into an uncertain category and monitored for a further period of one more year. Friedman & Mor (2004) suggested the use of ‘healed/ healing/ disease’ in place of ‘success’ and ‘failure’. The newly suggested term ‘effective’ would include the categories ‘healed’ and ‘healing’ and will not result in further treatment, whilst the term ‘ineffective’ at 1 year would mean the emergence or enlargement of the periapical radiolucency and/or symptoms and signs that will require intervention. A 1-year follow-up period is too short to judge a tooth as ‘diseased’ (Haapasalo et al. 2011) and this is why this term is not included in the present suggestion. The advantages of using ‘effective’ and ‘ineffective’ over previous terms to describe the outcome are the following: 1. shorten the follow-up period from 4 year to 1 year and thereby increase the recall rate and reduce the number of appointments and radiographs; 2. reduce the number of unnecessary retreatments indicated by adhering to previous definitions (Figdor 2002); and 3. the terms ‘effective’ and ‘ineffective’ relate directly to an indication for treatment and make clinical decisions easier and reproducible. We wish to initiate an open discussion on the issue of terms used to categorize the outcome of root canal treatment, beginning with this letter.

Reactions of the living organism to dead and fixed dead tissue.

Two series of experiments were conducted on the reactions of the living organism when in contact with dead and fixed dead tissue. The inflammatory reaction to necrotic tissue was less severe than the reaction to fixed necrotic tissue. The results led to the tentative conclusion that chronic periapical inflammation most likely is caused by living microorganisms.

Bisphosphonates and their clinical implications in endodontic therapy

This review gives an overview of the factors that may play a role in the development of osteonecrosis of the jaw in patients treated with bisphosphonates (BPs) and undergoing nonsurgical endodontic treatment as well as some recommendations for its prevention. BPs are a widely prescribed group of drugs for diverse bone diseases. The occasional but devastating adverse effect of these drugs has been described as bisphosphonate-related osteonecrosis of the jaw (BRONJ). As this condition is debilitating and difficult to treat, all efforts should be made to prevent its occurence in patients at risk. The main triggering event is considered to be dental extraction. Even though nonsurgical endodontic treatment appears to be a relatively safe procedure, care remains essential. After an overview of this class of drugs, the clinical presentation, epidemiology and pathogenesis of BRONJ, as well as the possible risk factors associated with its development after nonsurgical endodontic treatment will be described. Finally, several strategies will be proposed for the prevention of BRONJ during nonsurgical endodontic treatment.

Tissue reaction to implantation of unfixed and glutaraldehyde-fixed heterologous tissue

Renewed interest in the use of aldehydes in endodontics has made it necessary to find out if the antigenic properties of foreign proteins can be attenuated by glutaraldehyde fixation. Untreated and glutaraldehyde-fixed heterologous tissue was, therefore, implanted in rabbits. The local tissue reaction to the implants as well as the reaction in the lymph nodes draining the implant site was examined. The experimental results do not support the view that glutaraldehyde fixation, in the long term,attenuates the antigenic properties of proteins.

Release of endotoxin in an experimental model simulating the dental root canal.

The action of endotoxin on subcutaneous connective tissue was examined in an experimental model simulating the dental root canal. The local Shwartzman reaction was used as a tool to detect slight tissue alterations that might otherwise go unobserved. The experimental results warrent, in our opinion, the tentative conclusion that the primary toxicity of endotoxins has no major part in the initiation or maintenance of chronic periapical inflammation.

The correlation between fluid transport and push-out strength in root canals filled with a methacrylate-based filling material.

AIM To investigate the correlation between fluid transport and dislocation resistance in canals filled with a methacrylate-based filling material. METHODOLOGY The root canals in sixty-five single-rooted human teeth were prepared to size 40, 0.06 taper. Sixty roots were filled with a single-cone technique using RealSeal SE sealer and divided into 3 groups, whilst five roots served as fluid transport positive control. Group 1 (n = 20): correlation group. Specimens were consecutively tested with fluid transport for 90 min and thereafter with the push-out test at coronal and apical root levels. Group 2 (n = 20): push-out control. Specimens were only subjected to the push-out test at coronal and apical root levels. Group 3 (n = 20): fluid transport negative control. Specimens were totally covered with nail varnish. The correlation between fluid transport and dislocation resistance was assessed by Kendalls tau-b coefficient. The Mann-Whitney U-test was used to compare dislocation resistance between groups 1 and 2 and fluid transport between groups 1 and 3. Significance level was set at P < 0.05. RESULTS Kendalls tau-b correlation coefficients between fluid transport and dislocation resistance were weak, being coronally 0.139 (P = 0.444) and apically -0.080 (P = 0.658). No significant difference in dislocation resistance could be detected between groups 1 and 2 at both root levels (P = 0.052 and P = 0.336, respectively). CONCLUSION No significant correlation could be identified between fluid transport and dislocation resistance, meaning that the corono-apical sealing ability of a methacrylate-based root canal filling is independent of its adhesive properties as indicated by its dislocation resistance.