A systematic review and meta-analysis of the prevalence and global distribution of middle mesial canals in mandibular molars identified by CBCT.

OBJECTIVES: This systematic review and meta-analysis aimed to evaluate the prevalence of middle mesial canal (MMC) in permanent mandibular molars of different populations and regions based on cone-beam computed tomography (CBCT) studies. MATERIALS AND METHODS: PubMed, Scopus, Embase, Web of Science, and Open-Grey were searched up to October 2023 according to specific keywords. A hand search was conducted on the references of the included studies and articles from three peer-reviewed journals in endodontics. The main variable of interest was the prevalence of MMC. Additional data such as the total number of included cases, age and country of the population, CBCT device information, voxel size, and field of view details were also extracted. Extracted data were analyzed qualitatively with the JBI quality assessment checklist and quantitatively with STATA software. RESULTS: Of 32,793 studied teeth, the cumulative prevalence of MMC in both mandibular 1st and 2nd molars was 3.11% (95% CI: 2.00-4.44%). The subgroup analysis reveals a prevalence of 4.15% (95% CI: 2.69-5.89%) for mandibular 1st molars and 1.2% (95% CI: 0.2-2.83%) for mandibular 2nd molars. The highest prevalence of MMC in 1st molar was attributed to South Asia (11.24%) and Africa (6.61%). CONCLUSIONS: The prevalence of MMC varies among regions. Clinicians should be aware of the potential prevalence of MMC, particularly in mandibular first molars, as a missed MMC could result in endodontic failure. CLINICAL RELEVANCE: The presence of MMCs varies in different geographic regions (0% to 29.7%). Clinicians should always look for MMC when doing an endodontic treatment on mandibular molars, as the presence of this canal is not uncommon. We suggest searching for this canal as if searching for the second mesiobuccal canal of maxillary 1st molars.

Enhancing Coronal Adaptation of Root Canal Fillings with a Modified Single-Cone Obturation Technique: Two Case Reports.

The single-cone technique, also known as the hydraulic condensation technique, is widely employed in endodontics. However, the aforementioned method is presented with certain limitations; specifically concerning the coronal seal and the adaptation of the coronal third of a master gutta-percha (GP) with a round cross-section to the coronal dentinal walls of root canals with semi-round or oval cross-sections. Through two case reports, the current article introduces the coronal vertical condensation (CVC) technique; aiming to enhance GP adaptation to canal walls in similar scenarios. In fact, the coronal vertical condensation technique amalgamates the different aspects of warm vertical condensation and single-cone techniques. In CVC, following the placement of the master GP cone, an electrical heat carrier is inserted immediately a few millimeters apical from the canal orifice to remove the coronal portion of the master GP cone. Subsequently, a hand plugger is used to condense GP in the vertical dimension, and the coronal space is backfilled using melted GP. The implementation of CVC technique has demonstrated an improved coronal adaptation of GP with canal walls. The stated technique seems beneficial; especially in the obturation of severely curved canals or root canals with a final preparation shape of variable taper.

Prevalence and morphological features of molar-root incisor malformation in children attending a specialist paediatric dental unit.

BACKGROUND: Molar-root incisor malformation (MRIM) is a rare dental anomaly featuring constricted cervical margins and tapered, narrow root and pulp morphology, often associated with severe toothache and infection. AIM: The aim of this study was to determine the prevalence of MRIM in children seen in a specialist paediatric dental unit of a tertiary referral hospital and to describe the characteristics of affected individuals. DESIGN: This study was an audit of children attending from November 2020 to November 2021. Radiographs were used to identify individuals with MRIM, and clinical data were collated. In addition, histology and microcomputed tomography (microCT) imaging were performed on teeth extracted from an affected individual. RESULTS: The prevalence of MRIM was five cases of 1054 children examined (0.47% or 1:210). The permanent first molars were affected in all five children and the primary second molars in two children; all children had medical comorbidities and multiple exposures to general anesthesia before 4 years of age. In addition, histological and microCT analyses displayed numerous microchannels connecting the pulp chamber to the external surface of the tooth at the furcation. CONCLUSIONS: Molar-root incisor malformation is an uncommon dental anomaly affecting paediatric patients with multiple comorbidities and is characterized by porosities extending from the pulp chamber to the external tooth surface, predisposing the risk of bacterial ingress from the oral cavity into the pulp chamber. Early detection may prevent atypical odontogenic facial pain and infection.

Do zirconia single-retainer resin-bonded fixed dental prostheses present a viable treatment option for the replacement of missing anterior teeth? A systematic review and meta-analysis.

STATEMENT OF PROBLEM: Zirconia has been widely used in restorative dentistry because of its favorable strength and esthetics. However, its polycrystalline structure presents a challenge for resin bonding. Significant research into surface treatments of zirconia to improve bonding has been reported, yet a universally accepted protocol remains elusive. PURPOSE: The purpose of this systematic review and meta-analysis was to evaluate the performance of anterior single-retainer zirconia resin-bonded fixed dental prostheses (RBFDPs) and review the bonding protocols used in the published data. MATERIAL AND METHODS: An electronic search of English language literature was conducted in the PubMed and Ovid (MEDLINE) databases. Following the application of inclusion and exclusion criteria, the research was evaluated to assess the quantitative data. RESULTS: Of the included studies, 1 randomized controlled trial, 3 prospective cohort studies, and 2 retrospective cohort studies reporting on anterior single-retainer zirconia RBFDPs were evaluated. Over a 3- to 10-year period, the success rate of anterior single-retainer zirconia RBFDPs was over 80%. Although there were reports of debonds, this is a minor complication as rebonding is usually possible. Furthermore, catastrophic fractures of the entire prosthesis were rare. CONCLUSIONS: Evidence for the use of single-retainer zirconia RBFDPs as a suitable treatment option for the replacement of anterior missing teeth is considerable. Based on the findings of this systematic review and meta-analysis, a 2-step process comprising micromechanical retention using airborne-particle abrasion and subsequent resin-zirconia adhesion by the application of 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) can be recommended.

Remaining dentinal thickness after simulated post space preparation and the fit of prefabricated posts to root canal preparation shapes.

BACKGROUND: Post space preparation can increase the risk of experiencing perforation and root fracture. The authors assessed remaining dentin thickness after post space preparation and the fit of different prefabricated posts to root canal preparation systems in a theoretical model. METHODS: Ten datasets per type of tooth from cone-beam computed tomography were analyzed to determine the minimum root diameter from 5 through 13 mm from the apical foramen. The preparation shapes of 10 root canal preparation systems were calculated and compared with the root dimensions to determine the remaining dentin thickness. Eight post brands were compared with root dimensions to determine the areas where there was less than 1 mm dentin thickness. RESULTS: The average root canal preparation shape produced canal diameters of 0.57 mm at 5 mm from the canal terminus and 0.94 mm at 13 mm from the canal terminus. The mean post size tip diameter was 1.03 mm, which is larger than the dimensions of the average canal preparation. Post preparation would result in less than 1 mm of dentin thickness remaining in premolars, smaller roots of molars, and mandibular incisors. The area with less than 1 mm of dentin thickness was around the post tip. CONCLUSIONS: Endosequence Fiber Post (Brasseler USA), RelyX Fiber Post 3D (3M), and Rebilda (VOCO) were the better fitting posts with the root canal preparation shapes. PRACTICAL IMPLICATIONS: Many posts would result in less than 1 mm dentin thickness. Clinicians should use posts that fit their root canal preparations to minimize dentin removal.

Clinical efficacy of methods for bonding to zirconia: A systematic review.

STATEMENT OF PROBLEM: The polycrystalline nature of zirconia hinders its ability to bond to tooth structure. Consequently, durable bonding to zirconia has been challenging. In vitro studies have evaluated various methods of bonding to zirconia, but clinical data are sparse. PURPOSE: The purpose of this systematic review was to critically appraise clinical studies investigating the survival rate of resin-bonded zirconia fixed partial dentures (FPDs), inlay-retained zirconia FPDs, and zirconia veneers. MATERIAL AND METHODS: Searches were performed in MEDLINE, EMBASE, PubMed, Web of Science, Scopus, Cochrane Library, and Google Scholar. Clinical studies of over 12 months duration involving bonded zirconia restorations between 1990 and July 2018 were reviewed. All suitable studies were assessed for quality by using a "Questionnaire for selecting articles on Dental Prostheses". RESULTS: Eight studies were ultimately included. Three studies examined posterior inlay-retained FPDs with estimated survival rates of 12.1% at 10 years, 95.8% at 5 years, and 100% at 20 months. Five studies reviewed anterior, resin-bonded FPDs, all of which had a 3- to 10-year survival rate of 100%. Debonds occurred in all studies, but the prostheses could usually be rebonded. CONCLUSIONS: With correctly designed buccal and lingual coverage retainers and minimal if any veneering porcelain, zirconia-based, posterior, inlay-retained FPDs seem to have a high clinical survival rate. The role of bonding efficacy in this survival rate is unknown. Anterior, cantilevered, resin-bonded zirconia FPDs seem to have a high clinical survival rate. While these prostheses can debond, fracture of the entire prosthesis is unlikely, so they may be rebonded. To bond zirconia, the use of airborne-particle abrasion with 50-µm alumina (Al2O3) at 0.1 to 0.25 MPa in combination with a phosphate monomer-containing adhesive resin is recommended until further studies become available. Dental dam isolation is also recommended during zirconia bonding.

The effects of sodium hypochlorite and ethylenediaminetetraacetic acid on the microhardness of Mineral Trioxide Aggregate and TotalFill Bioceramic Putty.

This study aimed to evaluate the effects of 5% NaOCl and 17% EDTA on the Vickers microhardness of Mineral Trioxide Aggregate, MTA Angelus (MTAA), and TotalFill Bioceramic Putty (BCP) after 24 h and 8 days. Twenty-four samples of MTAA and BCP were tested for baseline microhardness at 24 h. They were divided into four subgroups (5% NaOCl or 17% EDTA, 24 h, 5% NaOCl or 17% EDTA at 8 days) and microhardness was evaluated at different time-points. Results were recorded and analysed statistically via one-way anova Kruskal-Wallis test and post hoc uncorrected Dunn's multiple comparison test. MTAA had a higher baseline microhardness than BCP. NaOCl reduced the microhardness of MTAA but increased that of BCP. EDTA reduced the microhardness for both materials at 24 h. At 8 days, EDTA reduced the microhardness of MTAA, while BCP exhibited an increase in microhardness. Enabling these materials to set for a week prior to exposure to irrigants improves their microhardness.

Rheological Characterization as an Alternative Method to Indentation for Determining the Setting Time of Restorative and Endodontic Cements.

This study explored an alternative approach using rheology to assess setting time. The following cements were tested: ProRoot® MTA (Dentsply, Tulsa, OK, USA), Biodentine® (Septodont, Saint Maur des Fosses, France), Fuji VII®, FujiVII® EP, and Fuji IX® (from GC Corporation, Tokyo, Japan), RealSeal SE™ Sealer (SybronEndo, Amersfoort, The Netherlands), AH 26® and AH Plus (both from Dentsply DeTrey, Konstanz, Germany). Freshly mixed cements were placed into a strain-controlled rheometer (1 rad·s-1 with an applied strain of 0.01%). From measurements of elastic modulus over time, the time taken to reach 90% of the plateau elastic modulus (designated as the setting time) was determined for each cement. In increasing order, the setting times were as follows: Fuji VII EP 3.3 min, Fuji VII 3.6 min, Fuji IX 3.7 min, ProRoot MTA 5.1 min, Biodentine 15.9 min, RealSeal 22.2 min, AH Plus 5933 min, and AH 26 5067 min. However, ProRoot MTA did not yield reliable results. The time to reach the 90% plateau elastic modulus correlates well with the setting time of glass ionomer cements and Biodentine. Using this approach gives much longer setting times for endodontic sealers than previously recognized.

Mineral Trioxide Aggregate-A Review of Properties and Testing Methodologies.

Mineral trioxide aggregate (MTA) restoratives and MTA sealers are commonly used in endodontics. Commonly referenced standards for testing of MTA are ISO 6876, 9917-1 and 10993. A PubMed search was performed relating to the relevant tests within each ISO and "mineral trioxide aggregate". MTA restoratives are typically tested with a mixture of tests from multiple standards. As the setting of MTA is dependent upon hydration, the results of various MTA restoratives and sealers are dependent upon the curing methodology. This includes physical properties after mixing, physical properties after setting and biocompatibility. The tests of flow, film thickness, working time and setting time can be superseded by rheology as it details how MTA hydrates. Physical property tests should replicate physiological conditions, i.e. 37 °C and submerged in physiological solution. Biocompatibility tests should involve immediate placement of samples immediately after mixing rather than being cured prior to placement as this does not replicate clinical usage. Biocompatibility tests should seek to replicate physiological conditions with MTA tested immediately after mixing.

Dental Material Choices for Pulp Therapy in Paediatric Dentistry.

OBJECTIVE: The purpose of this study was to assess the restorative choices for pulpal therapy by members of the Australian and New Zealand Society of Paediatric Dentistry (ANZSPD). METHODS: Members of the ANZSPD were sent an online survey asking about the procedures that they performed and their choice of dental materials. RESULTS: The respondents were 31 general dentists (GD) and 55 specialist paediatric dentists (PD). Materials used for indirect pulp capping included calcium hydroxide [Ca(OH)2] cement (CHC), glass ionomer cement or resin-modified glass ionomer cement (GIC/RMGIC), Ca(OH)2 paste (CHP) and mineral trioxide aggregate (MTA). Materials for direct pulp capping included MTA, CHP and CHC. Materials and techniques used for pulpotomy included MTA, ferric sulphate, formocresol and diathermy, CHP and CHC. GD and PD were similar in their choice of materials. However, there was no preferred product for pulp therapy. Most GD learnt how to use MTA from CPD lectures, while some PD learnt how to use MTA from their postgraduate training as well as CPD lectures. Many GD and PD did not have hands-on training from their education on how to use MTA (GD: 80%, PD: 43%). Most would like to attend hands-on MTA courses (GD: 86%, PD: 65%). CONCLUSION: There was no clear preferred product for the various types of pulp therapy in paediatric dentistry. Education appears to be the major barrier to the use of MTA rather than the cost of MTA.

A survey of various endodontic procedures related to mineral trioxide aggregate usage by members of the Australian Society of Endodontology.

This study aims to assess education on the use of mineral trioxide aggregate (MTA) and Biodentine among members of the Australian Society of Endodontology (ASE), a society of specialist endodontists (ED) and general dentists with an interest in endodontics (GD). The study also aims to compare the procedural preferences relating to perforation repair, apical barrier, root-end filling and regenerative endodontics. A structured online questionnaire was used, which sought details of the education in the use of MTA and the procedural steps involved in perforation repair, apical barrier, root-end filling and regenerative endodontics. Fisher's exact test was performed to compare the GD with ED. Responses were received from 208 out of 499 ASE members. Some 40% of the total respondents were ED. Almost all ED (98.8%) and some GD (39.8%) used MTA for perforation repairs. Likewise, almost all ED (96.3%) and some GD (42.7%) used MTA for apical barrier procedures. Lack of experience was more of a barrier to its use for GD (48.7%) than its high cost (31.6%). Few members used Biodentine. Significant differences exist in how MTA is used between GD and ED. Experience in handling MTA is a larger barrier to its widespread use in endodontics than its cost.

Clinical manipulation of mineral trioxide aggregate: lessons from the construction industry and their relevance to clinical practice.

Mineral trioxide aggregate (MTA) is based on ordinary Portland cement (with added radiopaque agents) and, thus, shares many of its features. Although MTA is reported to be difficult to handle clinically, concrete materials made using Portland cement are the foundation of the construction industry. In this paper, we summarize important lessons from the construction literature that are relevant to the successful use of MTA in clinical practice, including behaviour during storage, susceptibility to acidic environments, the effects of exposure of the setting material to moisture and interactions with substances that may interfere with the speed of setting and the quality of the end product.

D90: The Strongest Contributor to Setting Time in Mineral Trioxide Aggregate and Portland Cement.

INTRODUCTION: The setting times of commercial mineral trioxide aggregate (MTA) and Portland cements vary. It was hypothesized that much of this variation was caused by differences in particle size distribution. METHODS: Two gram samples from 11 MTA-type cements were analyzed by laser diffraction to determine their particle size distributions characterized by their percentile equivalent diameters (the 10th percentile, the median, and the 90th percentile [d90], respectively). Setting time data were received from manufacturers who performed indentation setting time tests as specified by the standards relevant to dentistry, ISO 6786 (9 respondents) or ISO 9917.1 (1 respondent), or not divulged to the authors (1 respondent). In a parallel experiment, 6 samples of different size graded Portland cements were produced using the same cement clinker. The measurement of setting time for Portland cement pastes was performed using American Society for Testing and Materials C 191. Cumulative heat release was measured using isothermal calorimetry to assess the reactions occurring during the setting of these pastes. In all experiments, linear correlations were assessed between setting times, heat release, and the 3 particle size parameters. RESULTS: Particle size varied considerably among MTA cements. For MTA cements, d90 was the particle size characteristic showing the highest positive linear correlation with setting time (r = 0.538). For Portland cement, d90 gave an even higher linear correlation for the initial setting time (r = 0.804) and the final setting time (r = 0.873) and exhibited a strong negative linear correlation for cumulative heat release (r = 0.901). CONCLUSIONS: Smaller particle sizes result in faster setting times, with d90 (the largest particles) being most closely correlated with the setting times of the samples.

Particle size changes in unsealed mineral trioxide aggregate powder.

INTRODUCTION: Mineral trioxide aggregate (MTA) is commonly supplied in 1-g packages of powder that are used by some clinicians across several treatments against the manufacturer's instructions. ProRoot MTA cannot be resealed after opening, whereas MTA Angelus has a resealable lid. This study assessed changes in particle size distribution once the packaging had been opened. METHODS: Fresh ProRoot MTA and MTA Angelus powder were analyzed by using laser diffraction and scanning electron microscopy and compared with powder from packages that had been opened once and kept in storage for 2 years. The ProRoot packet was folded over, whereas the MTA Angelus jar had the lid twisted back to its original position. RESULTS: After 2 years, ProRoot MTA powder showed a 6-fold increase in particle size (lower 10% from 1.13 to 4.37 µm, median particle size from 1.99 to 12.87 µm, and upper 10% from 4.30 to 34.67 µm), with an accompanying 50-fold change in particle surface area. MTA Angelus showed only a 2-fold increase in particle size (4.15 to 8.32 µm, 12.72 to 23.79 µm, and 42.66 to 47.91 µm, respectively) and a 2-fold change in particle size surface area. CONCLUSIONS: MTA reacts with atmospheric moisture, causing an increase in particle size that may adversely affect the properties and shelf life of the material. Smaller particles have a greater predisposition to absorb moisture. Single-use systems are advised.