Shaping and filling root canals during root canal re‐treatment

Re‐treatment of primary root canal treatment associated with post‐treatment disease has become an important component of daily endodontic practice. Basically, the management of cases requiring re‐treatment should comply with the general rules of primary root canal treatment namely accurate diagnosis, antiseptic treatment consisting of cleaning and shaping the root canals, followed by effective disinfection, canal filling, and a coronal restoration that prevents re‐infection. Nevertheless, re‐treatment represents a distinct treatment modality of its own, which in several respects differs from primary treatment of teeth with vital or necrotic pulps. The aim of this review is to present current knowledge on root canal preparation and filling during root canal re‐treatment.     

Restoring teeth following root canal re‐treatment

There have been many recent advances in the methods available for restoring root‐filled teeth that can equally be applied to re‐treatment cases. Most of these advances are related to adhesive techniques, composite resin materials, non‐metallic posts, and indirect ceramic materials. These new techniques and materials have enhanced the options available when restoring root‐filled teeth. However, the preservation of sound tooth structure is clearly the most significant factor influencing the survival of teeth following root canal re‐treatment. Although contemporary adhesive techniques will facilitate the preservation of valuable dentin in the re‐treated tooth, the degree of remaining sound tooth structure will ultimately be dictated by the extent of the existing restoration, carious and non‐carious tooth tissue loss, and iatrogenic tooth tissue loss caused during the previous endodontic and restorative procedures. There is a paucity of evidence in relation to the influence of specific restorative procedures on the outcome of root canal re‐treatment. In view of this, the following clinical trials are needed: a comparison of the survival of teeth following primary root canal treatment and re‐treatment; a comparison of the survival of root canal re‐treated teeth restored with different techniques (for example, fiber vs. metal posts); and a comparison of the survival of root canal re‐treated teeth with varying degrees of tooth structure loss.     

The concepts of evidence‐based periodontal plastic surgery: Application of the principles of evidence‐based dentistry for the treatment of recession‐type defects

The decision‐making process for the treatment of recession‐type defects is based on translation of the outcomes from randomized controlled trials and systematic reviews to clinical practice. Such an approach is capable of assisting researchers, clinicians, and patients to understand the mechanisms and effects of the treatment of different root‐coverage procedures, as well as turning treatment options into usable and predictable tools to be applied in dental practice. This review explores: (a) the aspects related to the etiology of gingival recession; (b) the history of periodontal plastic surgery procedures used to achieve root coverage; (c) the main findings, implications of research, and practice of root‐coverage procedures described from the current base of systematic reviews; (d) the role of the evidence produced in Latin American research centers; and (e) the outcomes of an individual patient data meta‐analysis of randomized controlled trials evaluating the role of root coverage and restorative procedures in achieving complete root coverage of noncarious cervical lesions. The findings of the current base of evidence clearly indicate that all of the main periodontal plastic surgery procedures lead to improvements in initial clinical parameters, but subepithelial connective tissue grafts, either alone or associated with coronally advanced flaps, result in superior complete root coverage, long‐term stability, and greater increase of keratinized tissue. Nonetheless, coronally advanced flaps, either associated with biomaterials (acellular dermal matrix grafts, enamel derivative proteins and xenogeneic collagen matrix) or used alone, provide satisfactory results and are suitable for use as secondary/alternative procedures to subepithelial connective tissue grafts.     

The Effect of Photodynamic Therapy in Root Canal Disinfection: A Systematic Review

Introduction

Effective root canal disinfection is a fundamental component of successful root canal treatment. Photodynamic therapy (PDT) has been proposed as a new adjunctive method for additional disinfection of the root canal system with the possibility of improved treatment outcomes. The aim of this systematic review was to investigate the effect of PDT on bacterial load reduction during root canal disinfection.

Methods

Two reviewers independently conducted a comprehensive literature search using a combination of medical subject heading terms and key words to identify studies relevant to the Population Intervention Control Outcome question. The selection of articles for inclusion was performed in 2 phases based on predetermined eligibility criteria according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Inter-reviewer agreement for each phase was recorded. The effect of PDT on bacterial load reduction during root canal disinfection was evaluated as the primary outcome variable during data extraction.

Results

The literature search provided 57 titles and abstracts. Three articles met the inclusion criteria and were selected for this systematic review. The reasons for study exclusion in each phase were recorded. Because of the heterogeneity in clinical indications and PDT protocols among the included studies, a meta-analysis could not be performed. All included studies showed a positive effect of PDT in the reduction of microbial load in root canal treatment ranging from 91.3%–100%.

Conclusions

Limited clinical information is currently available on the use of PDT in root canal disinfection. If supported by future clinical research, PDT may have efficacy for additional root canal disinfection, especially in the presence of multi–drug-resistant bacteria.     

Outcome of primary root canal treatment: systematic review of the literature - part 1. Effects of study characteristics on probability of success

AIMS: The aims of this study were (i) to conduct a comprehensive systematic review of the literature on the outcome of primary (initial or first time) root canal treatment; (ii) to investigate the influence of some study characteristics on the estimated pooled success rates. METHODOLOGY: Longitudinal clinical studies investigating outcome of primary root canal treatment, published up to the end of 2002, were identified electronically (MEDLINE and Cochrane database 1966-2002 December, week 4). Four journals (International Endodontic Journal, Journal of Endodontics, Oral Surgery Oral Medicine Oral Pathology Endodontics Radiology and Dental Traumatology & Endodontics), bibliographies of all relevant papers and review articles were hand-searched. Three reviewers (Y-LN, SR and KG) independently assessed, selected the studies based on specified inclusion criteria, and extracted the data onto a pre-designed proforma. The study inclusion criteria were: longitudinal clinical studies investigating root canal treatment outcome; only primary root canal treatment carried out on the teeth studied; sample size given; at least 6-month postoperative review; success based on clinical and/or radiographic criteria (strict, absence of apical radiolucency; loose, reduction in size of radiolucency); overall success rate given or could be calculated from the raw data. The findings by individual study were summarized and the pooled success rates by each potential influencing factor were calculated for this part of the study. RESULTS: Of the 119 articles identified, 63 studies published from 1922 to 2002, fulfilling the inclusion criteria were selected for the review: six were randomized trials, seven were cohort studies and 48 were retrospective studies. The reported mean success rates ranged from 31% to 96% based on strict criteria or from 60% to 100% based on loose criteria, with substantial heterogeneity in the estimates of pooled success rates. Apart from the radiographic criteria of success, none of the other study characteristics could explain this heterogeneity. Twenty-four factors (patient and operative) had been investigated in various combinations in the studies reviewed. The influence of preoperative pulpal and periapical status of the teeth on treatment outcome were most frequently explored, but the influence of treatment technique was poorly investigated. CONCLUSIONS: The estimated weighted pooled success rates of treatments completed at least 1 year prior to review, ranged between 68% and 85% when strict criteria were used. The reported success rates had not improved over the last four (or five) decades. The quality of evidence for treatment factors affecting primary root canal treatment outcome is sub-optimal; there was substantial variation in the study-designs. It would be desirable to standardize aspects of study-design, data recording and presentation format of outcome data in the much needed future outcome studies.     

Master apical file size – smaller or larger: a systematic review of microbial reduction

The purpose of this systematic review was to determine, in patients undergoing root canal treatment, whether apical enlargement of canals affected microbial reduction. A PICO (population, intervention, comparison and outcome) strategy was developed to identify previously published studies dealing with apical size of canal and microbial reduction. The MEDLINE, Embase, Cochrane and PubMed databases were searched. Additionally, the bibliographies of all relevant articles and textbooks were manually searched. Based on inclusion and exclusion criteria, two reviewers independently selected the relevant articles. Due to the variety of methodologies and different techniques used to measure outcome for master apical file enlargement, it was not possible to standardize the research data and to apply a meta‐analysis. Seven articles were identified that met the inclusion criteria. Five of the seven articles generally concluded that canal enlargement reduced bioburden in the root canal system. Two articles reported no difference in canals enlarged to size 25 or 40. The results of the systematic review confirmed that more evidence‐based research in this area is needed. With the limited information currently available, the best current available clinical evidence suggests that contemporary chemomechanical debridement techniques with canal enlargement techniques do not eliminate bacteria during root canal treatment at any size.     

Prevalence and nature of fungi in root canal infections: a systematic review and meta‐analysis

The role of bacteria in causing apical periodontitis has been widely established, whilst the role of other microorganisms is studied less thoroughly. This systematic review and meta‐analysis reviewed the literature for the prevalence and diversity of fungi in root canal infections. An extensive literature search was carried out in the Cochrane databases, EMBASE, MEDLINE, LILACS, SciELO and Web of Science. Additional studies were identified from six endodontic journals, four main endodontic textbooks and references of relevant papers. Selected clinical studies included sampling of necrotic pulps in permanent teeth and microbial analysis of these samples. Studies were critically appraised using the Joanna Briggs Institute Prevalence Critical Appraisal Checklist. Meta‐analysis was performed using MetaXL. The screening of 1041 titles and abstracts and full‐text reading yielded 54 studies. The overall prevalence of fungi in root canal infections was 7.5% (CI 95%: 3.6–11.8%) in the inverse variance fixed effect heterogeneity model. Candida albicans was the most frequently isolated species. Significant heterogeneity was observed (P < 0.001, I² = 85.04%). Subgroup analyses based on geographical location, period of publication, type of infection, state of general health, communication with the oral cavity, type of sample and identification method revealed no factor influencing the prevalence. Better standardized techniques and a comprehensive analysis will reveal a more detailed and accurate representation of the prevalence and nature of fungi in root canal infections.     

The probability of and factors influencing tooth survival following non‐surgical root canal treatment – a prospective study

Aim To investigate the probability of and factors influencing tooth survival following primary or secondary root canal treatment. Methodology This prospective study involved annual follow‐up of up to 4 years of primary (759 teeth, 572 patients) or secondary (858 teeth, 642 patients) root canal treatment in an Eastman cohort. Informed consent was obtained from the patients. Pre‐, intra‐ and post‐operative data were collected prospectively on customised proforma. Information about extraction of the root treated tooth was reported by the patient, the referring dentist or extracted from the patient's hospital medical records. The timing and reasons for extraction were recorded. Tooth survival was estimated and prognostic factors investigated using Cox regression. Clustering effects within patients were adjusted in all models using robust standard error. Results The 4‐year tooth survival after primary root canal treatment (95.4%) or secondary root canal treatment (95.3%) were similar. Fourteen prognostic factors were identified. Significant patient factors included: History of diabetes and systemic steroid therapy. Significant pre‐operative factors included: narrow periodontal probing depth; pain; discharging sinus; cervical root resorption; and iatrogenic perforation (for retreatment cases only). Significant intra‐operative factors included: iatrogenic perforation; patency at apical terminus; and extrusion of root fillings. Significant post‐operative restorative factors included: Presence of cast restoration or temporary restoration; presence of cast post & core; proximal contacts with both mesial and distal adjacent teeth; and terminal location of the tooth. The presence of pre‐operative pain had a profound effect on tooth loss within the first 22 months after treatment (HR = 3.1; P = 0.001) with a lesser effect beyond 22 months (HR = 2.4; P = 0.01). Patency at the apical terminus reduced tooth loss (HR = 0.3; P < 0.01) within the first 22 months after treatment but had no significant effect on tooth survival beyond 22 months. Extrusion of gutta‐percha root filling did not have any effect on tooth survival (HR = 1.1; P = 0.2) within the first 22 months but significantly increased the hazard of tooth loss beyond 22 months (HR = 3.0; P = 0.003). Conclusions The 4‐year tooth survival following primary or secondary root canal treatment was 95%; with fourteen prognostic factors common to both.     

Survival against the odds: microbiology of root canals associated with post‐treatment disease

Most periapical lesions resolve after root canal treatment of teeth with primary infections. Over the last decade there has been a renewed focus on post‐treatment apical periodontitis and its etiology. This review describes the microbiota associated with persistent post‐treatment infection, including microbial identification, ecology, and environmental selection. Compared with untreated teeth, the infection pattern in root canals with post‐treatment disease shifts to a resistant, mainly Gram‐positive community. The main challenge in root canal re‐treatment is access to the residual apical infection. Elimination of the microbial flora, or a dramatic reduction and sufficient ecological shift to allow host tissue healing, remains the biological goal.     

Root canal filling in primary molars without successors: Mineral trioxide aggregate versus gutta‐percha/AH‐Plus

The aim of this study was to compare the clinical and radiographical success of mineral trioxide aggregate (MTA) and gutta‐percha/AH‐Plus used as a root canal filling material in primary second molars without successors. A total of 16 patients (9 girls, 7 boys) aged 6–13 years (mean: 10.5) were selected and randomly distributed into the treatment groups. Children were recalled for clinical and radiographic examination at 6, 12, 18, 24 and 36 months. Differences in treatment outcomes were analysed using chi‐squared and Fisher's exact tests. Clinically, there was no significant difference in the success rates between the groups at the end of a 3‐year follow‐up period (MTA: 100%; Gutta‐percha/AH‐Plus: 70%) (P > 0.05). However, radiographically, there was a significant difference between the groups (MTA: 80%; gutta‐percha/AH‐Plus: 30%) (P < 0.05). The present study showed that MTA can be recommended for use in root canal treatment of primary molars without successors based on better radiographic success.     

Sub‐epithelial connective tissue graft for the management of Miller's class I and class II isolated gingival recession defect: A systematic review of the factors influencing the outcome

The aim of the present systematic review was to analyze the factors that affect the outcome of subepithelial connective tissue graft (SCTG) for managing Miller's class I and class II isolated gingival recession defect. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta‐Analyses) guidelines for systematic reviews were used. Quality assessments of selected articles were performed. Data on root surface condition, recession type defect, flap thickness, different flap designs, different harvesting techniques, presence/absence of the epithelial collar, graft thickness, flap tension, suturing techniques, and smoking‐related outcomes on root coverage were assessed. The SCTG procedure provides the best root coverage outcomes for Miller's class I and class II recession. The critical threshold of flap thickness was found to be 1 mm. Maximum root coverage was achieved by envelope and modified tunnel technique. SCTG with the epithelial collar does not provide additional gains than SCTG without the epithelial collar. The thickness of SCTG for root coverage was found to be 1.5‐2 mm. Greater flap tension and smoking adversely affect root coverage outcomes. Analysis of the factors discussed would be of key importance for technique selection, and a combined approach involving factors favoring outcomes of SCTG could be of clinical relevance in recession coverage.     

Outcome of primary root canal treatment: systematic review of the literature -- Part 2. Influence of clinical factors.

AIMS: (i) To carry out meta-analyses to quantify the influence of the clinical factors on the efficacy of primary root canal treatment and (ii) to identify the best treatment protocol based on the current evidence. METHODOLOGY: The evidence for the effect of each clinical factor on the success rate (SR) of primary root canal treatment was gathered in three different ways: (i) intuitive synthesis of reported findings from individual studies; (ii) weighted pooled SR by each factor under investigation was estimated using random-effect meta-analysis; (iii) weighted effect of the factor under investigation on SR were estimated and expressed as odds ratio for the dichotomous outcomes (success or failure) using fixed- and random-effects meta-analysis. Statistical heterogeneity amongst the studies was assessed by Cochran's (Q) test. Potential sources of statistical heterogeneity were investigated by exploring clinical heterogeneity using meta-regression models which included study characteristics in the regression models. RESULTS: Out of the clinical factors investigated, pre-operative pulpal and periapical status were most frequently investigated, whilst the intra-operative factors were poorly studied in the 63 studies. Four factors were found to have a significant effect on the primary root canal treatment outcome, although the data heterogeneity was substantial, some of which could be explained by some of the study characteristics. CONCLUSIONS: Four conditions (pre-operative absence of periapical radiolucency, root filling with no voids, root filling extending to 2 mm within the radiographic apex and satisfactory coronal restoration) were found to improve the outcome of primary root canal treatment significantly. Root canal treatment should therefore aim at achieving and maintaining access to apical anatomy during chemo-mechanical debridement, obturating the canal with densely compacted material to the apical terminus without extrusion into the apical tissues and preventing re-infection with a good quality coronal restoration.     

Single‐visit more effective than multiple‐visit root canal treatment?*

Data sources : Literature was searched using the Cochrane Controlled Trials Register (CENTRAL), Medline, Embase and HealthStar databases. Reference lists from identified articles were scanned and a further search made using names of authors of the identified articles. Papers that had cited these publications were also identified through the Science Citation Index to identify potentially relevant subsequent primary research. Study selection : Two reviewers scanned all titles and abstracts. An article was included if subjects had a no relevant medical history; subjects presented with mature teeth with infected necrotic root canals and radiographic evidence of periapical bone loss (as an indication of preoperative canal infection), all selected root canals had not received any endodontic treatment previously, participants underwent nonsurgical root canal treatment during the study, and the number of teeth showing radiographic evidence of healing was the outcome measure. Data extraction and synthesis : Data were abstracted by two reviewers. The principal measure of treatment effect was risk difference with the fixed‐effect method for combining study estimates being used to produce an overall estimate. Between‐study heterogeneity was assessed using standard x² test or Q‐statistic. Results : Only three randomized controlled trials (RCT) were identified and included in the review, covering a total of 146 cases. Sample size of all three studies was small. None demonstrated a statistically significant difference in healing rates. Risk differences (RD) of included studies were combined using the inverse variance‐weighted method (pooled RD, ‐6.3%; 95% confidence interval, ‐20.3 to +7.8). Conclusions : Based on the current best available evidence, single‐visit root canal treatment appears to be slightly more effective than multiple visits, that is, it had a 6.3% higher healing rate. The difference in healing rate between these two treatment regimens was not statistically significant (P= 0.3809), however.     

Master apical file size – smaller or larger: a systematic review of healing outcomes

The purpose of this systematic review was to determine in patients undergoing root canal treatment, whether apical enlargement affected the healing outcome. A PICO (population, intervention, comparison and outcome) strategy was developed to identify studies dealing with apical size of canal and healing outcome as measured clinically and radiographically. The MEDLINE, Embase, Cochrane and PubMed databases were searched. Additionally, the bibliography of all relevant articles and textbooks was manually searched. Based on inclusion and exclusion criteria, two reviewers independently selected the relevant articles. Four articles were identified that met the inclusion criteria. There were no studies that evaluated apical enlargement and healing outcome using cone beam computed tomography. The results of the systematic review confirmed that more evidence‐based research in this area is needed. With the limited information available, the best current available clinical evidence suggests that for patients with necrotic pulps and periapical lesions, enlargement of the apical size would result in an increased healing outcome in terms of clinical and radiographic evaluations.     

The influence of methodological variables on the push‐out resistance to dislodgement of root filling materials: a meta‐regression analysis

The aim of this systematic review was to evaluate the influence of several methodological variables on the push‐out resistance to dislodgment of root filling materials by a meta‐regression analysis of the literature. A systematic review was performed by searching the PubMed database using the terms ‘push‐out’ and ‘pushout’. Laboratory studies published before March 2015 were included. Two reviewers extracted data regarding country of origin, year of publication, tooth type, smear layer removal, root canal sealer, core material, obturation technique, sample storage, tooth portion, test machine load velocity and slice thickness. Pooled mean resistance to dislodgement of all groups from the included studies was used in a linear meta‐regression of random effects (α = 0.05). Of the 850 identified studies, 53 met the inclusion criteria. A meta‐regression of the 341 groups extracted from these articles was performed to analyse the influence of each variable on resistance to dislodgement (in MPa). The sealer, core material, obturation technique, slice thickness, storage time, load velocity and tooth portion significantly influence the results (P < 0.05). Irrigant solution and smear layer removal did not influence the resistance to dislodgement of the root filling materials (P > 0.05). Methodological variables such as sealer, core material, root filling technique, tooth type, tooth portion, slice thickness, storage time and load velocity influenced the resistance to dislodgment. The inclusion and standardization of all related variables could lead to a more comparable and reproducible analysis of the resistance to dislodgment of the root canal sealers.     

The effect of partially exposed connective tissue graft on root‐coverage outcomes: a systematic review and meta‐analysis

The aim of this systematic review was to compare the root‐coverage outcomes of using a partially exposed connective tissue graft (CTG) technique with a fully covered CTG technique for root coverage. An electronic search up to February 28^th, 2017, was performed to identify human clinical studies with data comparing outcomes of root coverage using CTG, with and without a partially exposed graft. Five clinical studies were selected for inclusion in this review. For each study, the gain of keratinized gingiva, reduction of recession depth, number of surgical sites achieving complete root coverage, percentage of root coverage, gain of tissue thickness, and changes of probing depth and clinical attachment level were recorded. Meta‐analysis for the comparison of complete root coverage between the two techniques presented no statistically significant differences. A statistically significant gain of keratinized tissue in favor of the sites with an exposed CTG and a tendency of greater reduction in recession depth were seen at the sites with a fully covered CTG. Based on the results, the use of a partially exposed CTG in root‐coverage procedures could achieve greater gain in keratinized gingiva, while a fully covered CTG might be indicated for procedures aiming to reduce recession depth.     

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.     

Efficacy of lasers as an adjunct to chemo‐mechanical disinfection of infected root canals: a systematic review

The aim was to evaluate the efficacy of various types of lasers used as an adjunct to chemo‐mechanical disinfection of infected root canals with the outcome measures ‘normal periapical condition’ or ‘reduction of microbial load’. PubMed, CENTRAL and ISI Web of Knowledge literature searches with specific indexing terms and a subsequent hand search were made with stated limits and criteria. Relevant publications were retrieved, followed by interpretation. The quality of each included publication was assessed as high, moderate or low. The initial search process yielded 234 publications. All abstracts of these publications were read, and the reference lists of relevant publications were hand‐searched. Ten articles were read in full text and interpreted according to a data extraction form. Five were included in the systematic review and were assessed. A meta‐analysis was impossible to perform because the included studies were heterogeneous with regard to study design, treatment and outcome measures. Positive effects were reported; however, no concluding evidence grade could be made because each included study was judged to have low quality, primarily due to lack of a power analysis, blinding and reproducibility. The evidence grade for whether lasers can be recommended as an adjunct to chemo‐mechanical disinfection of infected root canals was insufficient. This does not necessarily imply that laser should not be used as an adjunct to root canal treatment but instead underscores the need for future high‐quality studies.     

Aetiology,incidence and morphology of the C‐shaped root canal system and its impact on clinical endodontics

The C‐shaped root canal constitutes an unusual root morphology that can be found primarily in mandibular second permanent molars. Due to the complexity of their structure, C‐shaped root canal systems may complicate endodontic interventions. A thorough understanding of root canal morphology is therefore imperative for proper diagnosis and successful treatment. This review aims to summarize current knowledge regarding C‐shaped roots and root canals, from basic morphology to advanced endodontic procedures. To this end, a systematic search was conducted using the MEDLINE, BIOSIS, Cochrane Library, EMBASE, Google Scholar, Web of Science, PLoS and BioMed Central databases, and many rarely cited articles were included. Furthermore, four interactive 3D models of extracted teeth are introduced that will allow for a better understanding of the complex C‐shaped root canal morphology. In addition, the present publication includes an embedded best‐practice video showing an exemplary root canal procedure on a tooth with a pronounced C‐shaped root canal. The survey of this unusual structure concludes with a number of suggestions concerning future research efforts.