Radiographic patterns of periosteal bone reactions associated with endodontic lesions.

Objectives: The formation of new bone by periosteum due to an insult is called periosteal bone reaction (PBR). This study assessed the cone beam computed tomography (CBCT) patterns of periosteal bone reactions associated with periapical inflammatory lesion (apical periodontitis/periapical rarefying osteitis). Materials and Methods: Twenty-two small field of view CBCT images of patients with PBR were selected from a database of a private practice limited to endodontics. The volume of the periapical inflammatory lesion, the presence of cortical fenestration, the distance of the root apices to the affected cortex, and the location, pattern, and longest diameter of the periosteal reaction were recorded. Statistical analysis was performed using Wilcoxon Ranksum, Fischer's exact, Spearman Correlation Coefficient, and paired t-test. Results: In all cases, periosteal bone reaction manifested as either parallel (90.9%) or irregular (9.1%). No correlation was found between periapical inflammatory lesion volume and the periosteal reaction's longest diameter (p > 0.05). Cortical fenestration was noted in 72.7% of the cases. In addition, the findings showed that periosteal reactions were located mostly on the buccal and were present 53.8% and 100% of the time in the mandible and maxilla, respectively. Conclusions: The periosteal reactions of endodontic origin had a nonaggressive form (i.e., parallel or irregular), and none of the lesions resulted in a periosteal reaction with an ominous Codman's triangle or spicule pattern.

The prevalence, characteristics, and risk factors of external cervical resorption: a retrospective practice-based study.

OBJECTIVES: External cervical root resorption (ECR) is a poorly understood and aggressive form of resorption. The purpose of this study was to examine the prevalence, characteristics, and risk factors associated with the occurrence of ECR in patients seeking endodontic care from private practice settings. MATERIALS AND METHODS: Records of 343 patients with 390 teeth diagnosed with ECR were identified from 3 private endodontic practices from 2008 to 2022. The patients' demographic information, systemic conditions, and dental history were recorded. The characteristics of the cases including Heithersay classification, pulpal and periapical status, and their management were documented. The association between case severity and potential predisposing factors was examined using chi-square analysis. RESULTS: The overall prevalence of ECR among patients seeking endodontic care was low (< 1%). However, there was a greater than twofold increase in the pooled prevalence from 2016 to 2021 (0.99%) compared to the data from 2010 to 2015 (0.46%). The most commonly affected teeth were anterior teeth (48.7%). Class II (30.0%) and class III (45.4%) defects were the most often identified. Patients with a history of trauma or orthodontic treatment were significantly more likely to be diagnosed with severe cervical resorption (class III or IV) (p < 0.05). CONCLUSIONS: There has been an increase in the prevalence of ECR in patients seeking endodontic care. A history of orthodontic treatment and traumatic dental mechanical injuries may predict the severity of resorption. CLINICAL RELEVANCE: The upward trend in the occurrence of ECR warrants close monitoring of the patients at high risk of developing the condition to facilitate early detection and management.

A retrospective study of initial root canal treatment failure in maxillary premolars via using cone-beam computed tomography.

BACKGROUND: This case-series study examined canal morphology and common factors for endodontic failure in maxillary first and second premolars that were referred for retreatment owing to clinical symptoms or radiographic signs. METHODS: Records were retrospectively searched using Current Dental Terminology codes to identify maxillary first and second premolars with endodontic failure. Periapical and cone-beam computed tomographic images were examined to determine Vertucci classifications and suspected factors related to treatment failure. RESULTS: A total of 235 teeth from 213 patients were included for evaluation. The following Vertucci classification of canal configurations were observed for maxillary first and second premolars: type I (1-1) (4.6% and 32.0%, respectively), type II (2-1) (15.9% and 27.9%, respectively), type III (2-2) (76.1% and 36.1%, respectively), type IV (1-2) (0% and 2%, respectively), and type V (3) (3.4% and 2%, respectively). More treatment failures were noticed in maxillary second premolars than first premolars and in females than in males. The 4 most common factors related to failure were inadequate filling, restorative failure, vertical root fracture, and missed canals. Missed canals were more frequently identified in maxillary second premolars (21.8%) than first premolars (11.4%) (P = .044). CONCLUSIONS: Multiple factors are associated with primary root canal treatment failures in maxillary premolars. Variations in canal morphology appear to be underappreciated in maxillary second premolars. PRACTICAL IMPLICATIONS: Maxillary second premolars have more complicated canal configurations than first premolars. Besides adequate filling, clinicians should give extra attention to anatomic variability in second premolars owing to higher failure incidence.

Efficacy of Different Solvents for Achieving Patency in Teeth Obturated Using Bioceramic Sealer.

INTRODUCTION: The retreatment of teeth obturated with bioceramic sealers has been shown to be challenging. The purpose of this study was to compare the efficacy of 10% formic acid (FA), 20% hydrochloric acid (HCl), and chloroform for achieving patency in teeth obturated with a bioceramic sealer. METHODS: Forty-five extracted single-canal teeth were instrumented and obturated 1.5 mm short of the working length using gutta-percha and EndoSequence BC Sealer (Brasseler USA, Savannah, GA). Two weeks later, gutta-percha was removed, and apical patency was attempted with a 10 C-file and a solvent (FA, HCl, or chloroform). The time to gain patency through EndoSequence BC Sealer was recorded. Five additional teeth were irrigated with the solvents, and scanning electron microscopy was used to evaluate the effect of solvents on the dentin. The Kruskal-Wallis and Mann-Whitney tests were used for statistical analysis. RESULTS: Patency was achieved in all canals, except for 1 in the chloroform group. Regarding the time to achieve patency, no significant difference was noted between chloroform and FA (P > .05). However, there was a significant difference between chloroform and HCl (P < .05) and between FA and HCl (P < .05). The erosion of dentinal tubules was more evident when HCl was used compared with the other irrigants. CONCLUSIONS: Twenty percent HCl was superior to 10% FA and chloroform in achieving patency in teeth obturated with EndoSequence BC Sealer. Regardless of the solvent used, patency may be achieved for most of the cases obturated with gutta-percha and EndoSequence BC Sealer.

Prevalence of Nonendodontic Diagnoses in Periapical Biopsies: A 6-year Institutional Experience.

INTRODUCTION: The purpose of this study was to identify nonendodontic periapical lesions (NPLs) mimicking endodontic pathosis, which are most frequently encountered by clinicians. METHODS: A retrospective study was conducted on biopsies obtained from 2015-2020 at Texas A&M College of Dentistry's oral pathology laboratory. The online database was screened for cases submitted as suspected endodontic pathology using specific key words. Histologic diagnoses were collected to determine the prevalence of NPLs that were originally thought to be of endodontic origin. The frequency and percentage of endodontic pathology and NPLs were documented. RESULTS: Among 6704 biopsies clinically diagnosed as endodontic lesions, 190 (2.8%) were histopathologically diagnosed as NPLs. The most frequent NPLs were odontogenic keratocytes' (n = 70, 36.8%), cemento-osseous dysplasia (n = 27, 14.2%), and dentigerous cysts (n = 22, 11.6%). Of all NPLs, 3.7% were malignant neoplasms, with the most common diagnosis being squamous cell carcinoma. Of 6514 endodontic histologic diagnoses, the prevalence of periapical granulomas and cysts was 60.2% (n = 3924) and 39.1% (n = 2549), respectively. CONCLUSIONS: Although most endodontic submissions are likely to be histologically diagnosed as periapical granulomas or cysts, the clinician should be aware that a small portion of these lesions may be nonendodontic in origin and possibly neoplastic in nature. Histopathologic evaluation of biopsied specimens is critical to achieve a proper diagnosis to ensure the appropriate management of patients.

Evaluation of Cone-beam Computed Tomography Artifacts Produced by Metal Objects Located Within and Outside the Field of View.

INTRODUCTION: Artifacts created by the presence of metal objects in the jaw negatively affect the cone-beam computed tomographic image quality. This study compares artifacts produced by metal objects outside of the field of view (FOV) in a small FOV CBCT image with those produced in a large FOV image in which the metal object is within the FOV. METHODS: We methodically placed 4 titanium implant-sized rods and 4 zirconium crown-sized disks on 1 side of a human cadaver mandible. Using the Accuitomo 170 CBCT machine (J Morita, Irvine, CA), a total of 18 scans (9 with a small FOV and 9 with a large FOV) were made. Ten axial slices from each scan were transferred to ImageJ software (National Institutes of Health, Bethesda, MD) for analysis. The mean standard deviation of all voxel values of a fixed region of interest (ie, uniform air located lingual to tooth #30) was compared between small and large FOV slices. Two blinded observers subjectively rated the images for diagnostic quality and the presence of artifacts. RESULTS: The Wilcoxon signed rank test showed that the standard deviation for both small and large FOV slices increases as the number of metal objects increases. The mean of the standard deviation for small and large FOVs is 3.6 and 2.5, respectively (P = .0000). Fifty-three percent of the small FOV slices had more artifacts in the subjective analysis. One hundred percent of the small FOV slices were rated as higher quality. CONCLUSION: Metal objects outside of the FOV in the contralateral quadrant do affect the quality of small FOV images. However, small FOV images have a higher resolution compared with large FOV images.

Nonclinical research areas of future importance for clinical therapies: Exploring the concepts of nonlinearity in dentistry.

Linear system analysis has been dominating medical and dental research, and most of the research achievements in these fields have come from applying a reductionist view of nature. However, biologic systems are fundamentally nonlinear with highly composite dynamics made up of numerous interacting elements and feedback loops, therefore studying them as linear models may not result in an accurate representation of their true features. The authors reviewed and utilized some of the principles of chaos and nonlinearity and extended them to clinical dentistry, from cracked tooth and flare-up after root canal procedures to the outcome of clinical treatments. Utilization of the concepts of chaos and sensitive dependence on initial conditions, and the concepts of self-organization, stigmergy, and fractals may help us to understand some of the puzzles that have not been solved by conventional linear models. The goal of this paper is to present some areas within nonclinical research that we believe will have important roles in the development of future clinical examination methods and therapies.

Severe Pain after Endodontic Surgery: An Analysis of Incidence and Risk Factors.

INTRODUCTION: The aim of this study was to determine the prevalence and characteristics of postoperative pain after endodontic microsurgery and to identify potential predictors for severe pain. METHODS: One hundred seventy-three patients who underwent endodontic microsurgery at a private practice were included in the study. The patients were asked to fill out a questionnaire to assess their postoperative pain levels for 5 days after surgery. The questionnaires were analyzed to record the changes in pain levels over time. The presence and size of preoperative lesions and bone thickness were determined on preoperative cone-beam computed tomographic scans. Statistical analyses were performed to identify predictors for developing severe pain after surgery. A binary logistic regression model was established to predict the occurrence of severe pain. RESULTS: Severe pain was most prevalent on day 1 (17.3%) and gradually decreased until a small increase on day 5. The average pain level also peaked on day 1 postoperatively and gradually decreased afterward. No significant difference was observed between patients who reported severe pain and those who did not report severe pain regarding tooth position (anterior vs posterior), lesion size, and presence of fenestration. However, sex, age, and bone thickness were all significant predictors of severe postoperative pain, with odds ratios of 2.8, 0.96, and 1.41, respectively. CONCLUSIONS: Severe pain was reported only in a small number of patients after endodontic microsurgery. Younger patients, females, and patients with thicker bone covering the apex are significantly more likely to develop severe pain.

Comparing dentinal tubule penetration of conventional and 'HiFlow' bioceramic sealers with resin-based sealer: An in vitro study.

This study compared the depth and percentage of dentinal tubule penetration for single-cone (SC) and warm vertical (WV) obturation techniques with two different bioceramic sealers (BC Sealer [BCS], BC Sealer HiFlow [BCSHF]) and an epoxy resin-based sealer (2Seal easymiX). Fifty canals were filled with BCS, BCSHF or resin-based sealer (RBS). Teeth in BCS and BCSHF groups were filled with SC or WV techniques, and teeth in the control group (RBS) filled with WV technique only. The roots were sectioned at 3 mm and 6 mm levels from the apex and evaluated with a confocal laser microscope. There was significantly greater depth and percentage of sealer penetration at the 6 mm section compared to 3 mm (P < 0.05). No statistically significant difference was found in sealer type or obturation technique at the examined levels (P > 0.05). In conclusion, dentinal tubule penetration was similar comparing BC Sealer, BC Sealer HiFlow and RBS using SC and WV techniques.

Retrograde Instrumentation of Surgically Resected Roots Using Controlled Memory Files: A Human Cadaver Study.

INTRODUCTION: The purpose of this study is to evaluate the amount of residual obturation material of retroinstrumented surgically resected roots using controlled memory files and to evaluate the incidence of adverse treatment outcomes. METHODS: Thirty maxillary anterior teeth in human cadavers were selected, and nonsurgical root canal treatment was performed on these teeth. A standardized 4-mm osteotomy and a 3-mm root resection with as close to 0° bevel as possible were made on each tooth. A microsurgical diamond tip was used to create a 1- to 2-mm starting point for each retropreparation. A 25/06 and 30/06 VTaper 2H were bent at about 90° angle to mimic the clinical and anatomic restrictions and used to create a retropreparation to a depth of 14 mm. Micro-computed tomography scans were taken and analyzed for volume and percentage of residual obturation material at 5 and 10 mm. In addition, the incidences of instrument separation and crack and ledge formation in the teeth were recorded. RESULTS: The median volume of residual obturation at 5 and 10 mm was 0.18 mm3 (interquartile range, 0.36 mm3) and 1.97 mm3 (interquartile range, 1.99 mm3), respectively. The overall incidence of file separation during retropreparation was 13.33% (4/30). Among the cases analyzed with micro-computed tomography, none showed crack or ledge formation. CONCLUSIONS: Retroinstrumentation of surgically resected roots using controlled memory files cleans the canal effectively with relatively low adverse treatment outcomes. Although this novel technique is limited in application, it is a safe and effective way to achieve a deep, clean retropreparation.

Comparison of a Dental Operating Microscope and High-resolution Videoscope for Endodontic Procedures.

INTRODUCTION: The purpose of this study was to compare a dental operating microscope (DOM) with a high-resolution videoscope (VS) in terms of depth of field (DOF), resolution, and effect on fine motor skills. METHODS: Two observers used test targets to measure the resolution and DOF of the DOM and the VS. In addition, 18 participants (12 dental students and 6 endodontic residents) performed an accuracy test on a manikin head using DOM, VS, or loupes. Each participant completed a posttest survey. RESULTS: The 3 magnifications of the DOM had higher resolutions and DOF (resolution: 32, 40.3, and 50.8 line pairs/mm; DOF: 15, 10, and 6 mm) than the VS (resolution: 20.1 line pairs/mm; DOF: 5 mm). Accuracy testing showed the DOM produced better results than the VS for both resident and student groups (P < .001); however, the VS was not significantly different than loupes. The residents performed better than the students using the DOM and the VS (P < .001). The students in general took 1.3 times longer than the residents to perform the accuracy test, irrespective of the magnification device used. The DOM and the VS required on average 1.9 and 2.8 times longer compared with loupes, respectively. Most participants reported a preference for the DOM with regard to visualization and ease of use. Comments also suggested that the VS has value in diagnosis and magnification in endodontics. CONCLUSIONS: Considering the findings from this study, the DOM stands out as the leading magnification tool in endodontics. However, the VS has potential in endodontic procedures and might be used as an adjunct to other visualization aids.

Periradicular Lesions in Cancellous Bone Can Be Detected Radiographically.

INTRODUCTION: The purpose of this study was to evaluate whether naturally occurring periradicular lesions confined to cancellous bone can be detected on periapical digital radiography and whether the size of the lesion had any effect on lesion detection. METHODS: One hundred twenty-nine roots were chosen based on cone-beam computed tomographic imaging and categorized as having no lesion, a lesion confined to cancellous bone, a lesion that encroaches on junctional corticocancellous trabeculae, or a lesion with cortical involvement. The largest buccolingual dimension of the lesions was measured on cone-beam computed tomographic imaging. Two observers separately viewed the corresponding periapical radiographs in their original version as well as in the edge-enhanced setting on MiPACS (LEAD Technologies Inc, Charlotte, NC). Observers were asked to evaluate and interpret the periapical radiographs as having a lesion present, absent, or "unsure." Evaluations of images were conducted at 2 times 1 week apart. Data were analyzed, and the level of significance was set at P = .05. RESULTS: Lesion size, not the degree of cortical involvement, significantly affected the observers' ability to accurately detect lesions. As the size of the lesion increased, the probability of correctly identifying a lesion increased (P = .0008). Lesions were correctly identified 97.6%, 94.1%, 91.6%, and 89.3% of the time, respectively, when in cortical bone, at the junction of corticocancellous bone, in cancellous bone, and when no lesion was present. Observers were "unsure" whether a lesion was present or absent 10.7% of the time. Only lesions in cortical bone significantly increased observers' certainty in making a diagnosis. CONCLUSIONS: This study concluded that lesions confined to cancellous bone can be detected radiographically at a high rate. Lesion size was positively correlated with correct lesion identification, whereas the degree of cortical involvement had no significant effect. This suggests that lesion size may be a better predictor for correct lesion identification than lesion location.

Comparison of optical performance among three dental operating microscopes: A pilot study.

INTRODUCTION: Two important aspects of the dental operating microscope (DOM) that factor into its overall effectiveness are resolution and depth of field. Therefore, the objective of this study was to evaluate and compare the resolution and depth of field of DOMs from three well-known manufacturers using standardized test targets. MATERIALS AND METHODS: A resolution test, using the 1951 USAF Hi-Resolution Target (Edmund Optics, Barrington, NJ), and a depth of field test, using the Depth of Field Target 5-15 (Edmund Optics, Barrington, NJ), were performed by two calibrated observers. Three DOM systems such as Seiler IQ (Seiler Instrument Inc., St. Louis, USA), Global G-Series 6 step (Global Surgical Corp., St. Louis, USA), and Zeiss Extaro 300 (Carl Zeiss Meditec AG, Oberkochen, Germany) were used to compare the resolution and depth of field. RESULTS: The Zeiss Extaro 300 showed the highest maximum resolution and maximum DOF (64 lp/mm and 17mm, respectively). The Seiler IQ showed the lowest maximum resolution and maximum DOF (35.9 lp/mm and 11 mm, respectively). CONCLUSION: Within the limitations of this study, the Zeiss Extaro 300 was superior in terms of resolution and depth of field as compared to the other two DOMs.

Dynamics of Bone Loss in Cases with Acute or Chronic Apical Abscess.

INTRODUCTION: Acute and chronic apical abscesses are 2 dramatic ways that periradicular tissues may react to pulpal infection and necrosis. Although both of these clinical states are the response to pulpal infection, their clinical manifestations are significantly different. It is not clear why the body responds to root canal infection in one way or another. The objective of this study was to evaluate the size and pattern of bone loss in patients with acute apical abscess (AAA) and chronic apical abscess (CAA) using cone-beam computed tomographic images. METHODS: Twenty-three cone-beam computed tomographic images of cases with AAA and 25 cases with CAA were selected and evaluated. The presence and location of fenestration and the volume and pattern of the periradicular lesions were recorded and compared between the 2 groups using the Fisher exact and Mann-Whitney U tests. RESULTS: One hundred percent of cases with CAA had cortical fenestration, but only 47% of cases with AAA had cortical fenestration (P < .05). The median volume of the lesions was 233 mm3 in the CAA group and 109 mm3 in the AAA group (P > .05). CAA cases, in comparison with the AAA group, had a relatively larger cortical disruptions. CONCLUSIONS: Cortical fenestration is fundamental for the development of CAA. However, periradicular lesions without evident cortical fenestration can still cause AAA and fascial space involvement.

Effectiveness of Gutta-percha/Sealer Removal during Retreatment of Extracted Human Molars Using the GentleWave System.

INTRODUCTION: The goal of endodontic retreatment is to address the etiology responsible for failure. In order to achieve this, the contents of the previous treatment must be removed. The aim of this study was to compare the effectiveness of the removal of residual obturation material (gutta-percha and sealer) using side-vented needle, EndoVac, and GentleWave (Sonendo, Inc, Laguna Hills, CA) irrigation protocols. METHODS: Thirty freshly extracted mandibular molars were instrumented to a master apical file size of 20.06, obturated using continuous wave of condensation and AH Plus sealer (Dentsply Tulsa, Tulsa, OK), restored, and placed in phosphate-buffered saline for 7 days. Teeth were retreated using a crown-down method to a master apical file size of 20.04. Radiographs and micro-computed tomographic images were obtained to confirm the presence of residual obturation material. Teeth were randomly divided among the following treatment groups: a side-vented needle, EndoVac, or GentleWave. Following strict irrigation protocols, postirrigation micro-computed tomographic scans were obtained and used to calculate the percentage of the residual obturation removed. RESULTS: GentleWave removed more residual obturation material (26%) than the side-vented needle (16%) and EndoVac (9%); the differences between the GentleWave group and the other 2 groups were not statistically significant (P > .05). The difference between the side-vented needle and EndoVac was statistically significant (P = .04). CONCLUSIONS: None of the irrigation techniques were able to completely remove all of the residual obturation material from the canals. The side-vented needle and the GentleWave groups were able to remove on average more residual obturation material than EndoVac; however, the differences were not significant.

Accuracy of 3-dimensional-printed Endodontic Surgical Guide: A Human Cadaver Study.

INTRODUCTION: Cone-beam computed tomographic (CBCT)-based 3-dimensional-printed surgical guides, such as those used in implant placement and orofacial surgery, allow for accurate planning and performance of surgical procedures. The objective of this study was to evaluate the accuracy of CBCT-designed surgical guides for use during endodontic surgery. METHODS: A split-mouth design was conducted using 48 roots in a cadaver model. In the experimental group, using information from the preoperative CBCT scans and digital impressions, surgical guides were designed using Blue Sky Bio (Grayslake, IL) planning software and printed using a Form 2 3-dimensional printer (Formlabs, Somerville, MA). The guides were designed to allow for surgical access at 3 mm from the apex of each root with depth control to the lingual or palatal surface of the root. In the control group, surgical access was completed "freehand" by visually approximating measurements from the CBCT scan only. The planned and postoperative CBCT images were superimposed, and the deviation of the surgical access point from the planned target was measured using Invivo software (Anatomage, San Jose, CA). A 2-tailed t test and the Fisher exact test were conducted to compare the deviation in the experimental CBCT-guided group versus the control CBCT-approximated freehand group. RESULTS: The mean deviation for the guided group (1.743 mm) was significantly less than that of the approximated freehand group (2.638 mm, P < .001). Only in 11 of the 24 samples of the control group was surgical access considered clinically successful (within the apical area of the root), whereas all 24 of the experimental samples were considered clinically successful. CONCLUSIONS: Using a CBCT-designed printed surgical guide is a more accurate method for access to the apical portion of the root during surgical endodontics compared with a "freehand" CBCT-approximated method.

A Novel Prefabricated Grid for Guided Endodontic Microsurgery.

INTRODUCTION: This study aimed to introduce a novel method using cone-beam computed tomographic (CBCT) imaging and prefabricated grids to guide apical access during endodontic microsurgery and to compare its accuracy with that of the nonguided method. METHODS: Forty-two roots from human cadaver jaws were selected. Twenty-one were randomly assigned to the experimental group (grid based) and their contralateral counterparts to the control group (nonguided). Preoperative CBCT images were used to design a drill path that intended to reach the palatal/lingual aspect of the roots without attempting to complete the osteotomy or to resect the entire root end. In the experimental group, prefabricated metal grids used during imaging and surgery acted as a reference in the design and drilling. Postoperative CBCT volumes were superimposed on the preoperative volumes, and the distances between the actual drill paths and the target points were measured. A dichotomized outcome of success versus failure was also recorded and compared. Statistical analysis was performed using the paired t test and Fisher exact test. RESULTS: The mean deviation of the drill paths from the target points was 0.66 mm ± 0.54 mm (mean ± standard deviation) for grid-based drilling and 1.92 mm ± 1.05 mm (mean ± standard deviation) for nonguided drilling (P < .001). Grid-based drilling was on average 1.27 mm (95% confidence interval, 0.81-1.72 mm) closer to the target point than nonguided drilling. The probability of successful drilling was also significantly higher with grids than without grids (P = .02). CONCLUSIONS: The proposed method of guided osteotomy and root-end resection using prefabricated grids was more accurate than the nonguided method.

Stress distribution in a tooth treated through minimally invasive access compared to one treated through traditional access: A finite element analysis study.

INTRODUCTION: The purpose of this study was to compare the stress distributions in the teeth treated through minimally invasive access (MIA) designs to those of the teeth treated through traditional straight-line access and their relationship to the final restoration using three-dimensional finite element analysis (FEA). MATERIALS AND METHODS: Four FEA models of an extracted mandibular first molar were constructed. An intact model served as the control, whereas the other three were prepared with either an MIA or traditional straight-line access. Simulated composite access fillings with or without a simulated gold crown were applied to the models, followed by application of an occlusal load of 100 N. Von Mises stresses in the teeth were then calculated and analyzed. RESULTS: Stress values within the dentin for baseline, MIA with composite filling, MIA with composite filling and crown, and traditional access with composite filling and crown were 10.14 MPa, 6.98 MPa, 11.79 MPa, and 16.81 MPa, respectively. Higher stress values indicate that the tooth is more prone to fracture. CONCLUSIONS: A traditional endodontic access cavity may render a tooth more susceptible to fracture compared with an MIA design.

Interobserver and Intraobserver Reliability of Cone-beam Computed Tomography in Identification of Apical Periodontitis.

INTRODUCTION: Accurate radiographic interpretation is of the utmost importance in the diagnosis and treatment of patients. Previous studies have indicated subjectivity in the radiographic interpretation of periapical tissues irrespective of using conventional radiography, digital radiography, or cone-beam computed tomographic (CBCT) imaging. No studies to date have evaluated the reliability of the interpretation of periapical tissues based on the size of periapical radiolucency (PAR). The purpose of this study was to assess the interobserver and intraobserver reliability of CBCT interpretation by observers from different specialties and different levels of experience when identifying PARs of various sizes. METHODS: Limited field of view CBCT scans were selected such that a variety of PARs with various sizes were included. Six observers with different levels of experience and fields of specialty evaluated periradicular tissues of 28 roots on the CBCT scans at 3 separate sittings each a month apart. RESULTS: The overall Fleiss kappa coefficient for interobserver reliability and intraobserver reliability was 0.88 and 0.85; the larger the PAR, the more reliable the radiographic interpretation. Increased experience level improved the intraobserver reliability. CONCLUSIONS: CBCT imaging appears to be a reliable method for the interpretation of PAR. The larger the PAR is the more reliable the radiographic interpretation.

Prevalence of Middle Mesial Canals and Isthmi in the Mesial Root of Mandibular Molars: An In Vivo Cone-beam Computed Tomographic Study.

INTRODUCTION: Many studies have investigated the morphology of the mandibular molar, but the prevalence of the middle mesial (MM) canal in the mesial root of the mandibular molar is still the subject of controversy. In addition, in previous literature, a true MM canal has not been clearly distinguished from an isthmus between the mesiobuccal and mesiolingual canals. Therefore, the objectives of this study were 2-fold: METHODS: Ninety limited field of view cone-beam computed tomographic scans were observed. One hundred twenty-two mature mandibular first and second molars with no previous root canal treatment, no root resorption, and intact crowns were retrospectively evaluated. Data regarding the sex, age, presence of MM canals, and number of root canals in the mesial root were recorded. RESULT: Of the 122 teeth, 20 (16.4%) had true MM canals. The prevalence of MM canals was 26% in first molars and 8% in second molars (P < .05). The frequency of isthmi in the mesial roots was 64.7%. The frequency of isthmi was higher in second molars, but the difference was not statistically significant (P > .05). CONCLUSIONS: This study showed a high prevalence of mandibular molars with MM canals or isthmi. The detection and biomechanical cleaning of these areas during nonsurgical or surgical root canal treatment are critical.