The accidental displacement of tooth roots into the mandibular canal is a serious complication during tooth extractions in oral and maxillofacial surgery, often resulting in direct damage to the structural and functional integrity of the inferior alveolar neurovascular bundle (IANB). This article reviews the anatomical features of the mandibular canal, the IANB, and adjacent tooth roots; identifies high-risk factors and anatomically vulnerable sites for root displacement; and outlines the clinical manifestations and radiographic characteristics of intraoperative root intrusion into the mandibular canal. Furthermore, management principles, surgical approaches and techniques, inferior alveolar nerve injury treatment, and prognostic considerations are discussed. The aim of this review is to provide a comprehensive clinical reference for improving surgical outcomes, and reducing postoperative complications.
Humans ; Tooth Extraction/adverse effects* ; Mandible/surgery* ; Tooth Root ; Mandibular Nerve/anatomy & histology* ; Postoperative Complications/prevention & control* ; Intraoperative Complications ; Mandibular Nerve Injuries/etiology*

It is a basic prerequisite for the successful completion of endodontic treatment to thoroughly understand the root canal space anatomy. With the development of dental devices in dentistry, the root canal morphology of the mandibular first premolars can be presented in more detail. Before conducting root canal therapy on the mandibular first premolar with complex root canal morphology, it should be necessary to evaluate the potential difficulties and risks for making an appropriate treatment plan. The present paper reviews the research progress on the diversities of root canal morphology in mandibular first premolars in recent years, and then makes technologic recommendations based on the morphology diversities.
Humans ; Dental Pulp Cavity/diagnostic imaging* ; Bicuspid/anatomy & histology* ; Mandible ; Tooth Root/anatomy & histology* ; Root Canal Therapy

OBJECTIVEThis study aims to identify the effects of corticotomy-assisted orthodontic premolar intrusion andevaluate the changes of root resorption and the alveolar bone.

METHODSBoth sides of the mandible of eight male Beagle dogswere randomly assigned into experimental and control groups. The third (P3) and fourth (P4) premolars were intruded withboth mini-screw implant anchorage (MIA) and corticotomy on the experimental side. By contrast, P3 and P4 were intrudedwith MIA alone on the control side. During pre-operation and after 2, 4, 8, and 12 weeks of orthodontic force applications,cone beam computed tomography was performed on every dog. The distance of tooth intrusion and root resorption of furcation, as well as the apex and height changes of the alveolar bone were measured and analyzed.

RESULTSThe intrusion distanceof premolars on the experimental side was greater than that on the control side (P < 0.05). The root of furcation and apex onboth sides occurred in root resorption, and the root resorption of the apex on the experimental side was lighter than that onthe control side after 12 weeks of force application (P < 0.05). The alveolar bone height decreased, and the height reductiondistance on the experimental side was greater than that on the control side after 8 and 12 weeks of force application (P < 0.05).

CONCLUSIONCorticotomy accelerates orthodontic molarintrusion and reduces root resorption.

Animals ; Bicuspid ; anatomy & histology ; Bone Screws ; Cone-Beam Computed Tomography ; Dogs ; Male ; Mandible ; Root Resorption ; Tooth Movement Techniques ; Tooth Root

The aims of the study were to investigate the incidence of C-shaped root canal systems in mandibular second molars in a native Chinese population using radiography and clinical examination under microscope and to compare the relative efficacies of these methods. For the recognition of C-shaped root canal system, 1 146 mandibular second molars were selected and examined. Teeth with C-shaped canal systems were categorized by using the radiographic classification criteria and the modified Melton's method. C-shaped canals were identified in 397 (34.64%) mandibular second molars by radiography (type I, 31.23%; type II, 38.29%; type III, 30.48%). Clinical examination showed that 449 (39.18%) cases exhibited C-shaped canal systems (C1, 22.94%; C2, 48.11%; C3a, 15.59%; C3b, 13.36%). As for the result of the radiographic and clinical combined examination, C-shaped root canals were found in 473 (41.27%) mandibular second molars (C1, 21.78%; C2, 45.67%; C3a, 16.70%; C3b, 15.86%). The incidence of C-shaped root canal diagnosed by radiographic method was statistically different from that by clinical examination and the combined examination (P<0.05). The study indicated a high incidence of C-shaped canal system in a Chinese population. The combination of microscopic and radiographic examination is an effective method in identifying the C-shaped root canal system.
Adult ; Aged ; Anatomic Variation ; Asian Continental Ancestry Group ; Chi-Square Distribution ; China ; Dental Pulp Cavity ; anatomy & histology ; diagnostic imaging ; Female ; Humans ; Male ; Mandible ; Microscopy ; Middle Aged ; Molar ; anatomy & histology ; Radiography, Dental ; Tooth Root ; anatomy & histology ; Young Adult

OBJECTIVETo investigate the anatomic features of the root apexes of permanent three-rooted mandibular first molars.

METHODSA total of 122 permanent mandibular first molars of Han Chinese patients were collected. Twenty three-rooted and 25 two-rooted molars were scanned by micro-CT and then reconstructed three-dimensionally. The apical anatomy of the tooth models were analyzed in software Mimics 10.01. The long and short diameters of the apical constriction (AC), the distances between AC, apical foramen (AF) and apex were measured. One-way ANOVA and LSD-t tests were used to compare the groups in relation to AC diameter and the distances between the AC, AF and apex.

RESULTSThe AF of the mesiobuccal (MB) canals most frequently presented at the distal side of the apex (10 cases in three-rooted and 6 cases in two-rooted group), and of the mesiolingual (ML) canals, most often at the lingual side (8 cases in each group). The AF of the distobuccal (DB) roots were frequently located at the distolingual (DL) side (10 cases), and those of the DL roots and distal canals of two-rooted molars were most often at the buccal (7 cases) and distal (11 cases) sides, respectively. The percentage of the "classical" singular AC was 53% (80/151). The average long(D) and short(d) diameters of the AC of the DB canals were (0.32 ± 0.09) mm and (0.25 ± 0.05) mm, respectively, significantly larger than the DL canals [D = (0.27 ± 0.08) mm, d = (0.22 ± 0.06) mm, P < 0.05] and the ML canals [D = (0.24 ± 0.06) mm, d = (0.19 ± 0.06) mm, P < 0.01). In three-rooted group, the mean distances between AC and AF, AF and apex, and AC and apex were (0.67 ± 0.32), (0.49 ± 0.28) and (1.01 ± 0.34) mm, respectively.

CONCLUSIONSThe AF of three-rooted mandibular molars frequently deviate from the root apex, and the AC of the DB canal is wider than those of the other canals. The mean distances between AC, AF and the apex suggest that root canal therapy should terminate at 1 to 1.5 mm short of the radiographic apex.

Asian Continental Ancestry Group ; Humans ; Imaging, Three-Dimensional ; Molar ; anatomy & histology ; diagnostic imaging ; Tooth Apex ; anatomy & histology ; diagnostic imaging ; Tooth Root ; anatomy & histology ; diagnostic imaging ; X-Ray Microtomography ; methods

Dental Pulp Cavity ; anatomy & histology ; Humans ; Male ; Maxilla ; Middle Aged ; Molar ; anatomy & histology ; Odontometry ; Tooth Root ; anatomy & histology

Constriction, Pathologic ; Humans ; Root Canal Obturation ; methods ; Root Canal Preparation ; methods ; Tooth Apex ; anatomy & histology ; pathology ; Tooth Diseases ; pathology ; therapy

We present a case of a patient with rare anatomy of a maxillary second molar with three mesiobuccal root canals and a maxillary third molar with four separate roots, identified using multi-slice computed topography (CT) and three-dimensional reconstruction techniques. The described case enriched/might enrich our knowledge about possible anatomical aberrations of maxillary molars. In addition, we demonstrate the role of multi-slice CT as an objective tool for confirmatory diagnosis and successful endodontic management.
Adult ; Asian Continental Ancestry Group ; China ; Dental Pulp Cavity ; anatomy & histology ; diagnostic imaging ; Female ; Humans ; Imaging, Three-Dimensional ; Maxilla ; Molar ; anatomy & histology ; diagnostic imaging ; Molar, Third ; anatomy & histology ; diagnostic imaging ; Root Canal Therapy ; Tomography, X-Ray Computed ; methods ; Tooth Root ; anatomy & histology ; diagnostic imaging

The aim of this study was to analyze the specific influence of root canal anatomy on the accessibility of working length during root canal therapy. Four hundred seventy-six root canal therapy cases (amounting to a total of 1 005 root canals) were examined. The anatomy risk factors assessed in each case included: tooth type (tooth location), root canal curvature, and root canal calcification, as well as endodontic retreatment. The investigation examined the correlation between each of these anatomic factors and the working length, with statistical analysis consisting of Chi-square tests and multiple logistic regression analysis. In an independent factor analysis, tooth type (tooth location), root canal curvature, canal calcification, and endodontic retreatment were determined to be the primary risk factors. In a multiple-factor regression model, root curvature and canal calcification were found to most significantly influence root canal working length accessibility (P<0.05). Root canal anatomy increases the difficulty of root canal preparation. Appropriate consideration of tooth anatomy will assist in accurate determination of preparation difficulty before instrumentation. This study alerts clinical therapists to anatomical factors influencing the working length accessibility, and allows for a direct estimate of success rate given in situ measurements of tooth factors during the root canal treatment procedure.
Chi-Square Distribution ; Dental Pulp Calcification ; pathology ; Dental Pulp Cavity ; anatomy & histology ; diagnostic imaging ; Humans ; Logistic Models ; Odontometry ; Radiography ; Retreatment ; Risk Factors ; Root Canal Preparation ; instrumentation ; Tooth Apex ; Tooth Root ; anatomy & histology

This experiment was aimed to shed light on the correlation and quantitative relationships between the width of bovine periodontal ligament (PDL) and the elastic modulus and, more over, between the width of bovine PDL and the capacity ratio of collagen fibers. The width and length of periodontal ligament of PDL were determined by stereomicroscope, and the elastic modulus by the materials testing systems. The collagen fibers in cross section of the specimen were stained with 1% Sirius Red F3B in saturated carbazotic acid, and the photo of stained PDL was collected by stereomicroscope. Image pro plus6.0 image analysis software was used to measure and calculate the capacity ratio of collagen fibers. It was found that there is a negative correlation between the width of bovine periodontal ligament and elastic modulus. The correlation coefficient is -0.21 and the simple linear regression model is Y = 71. 681-0.021x (Width of PDL); there is a positive correlation between capacity ratio of collagen fibers and elastic modulus. The coefficient correlation is 1.583 and the simple linear regression model is Y = -34.944 + 1.583x (The percentage of collagen fibers). Thus, the elastic modulus of bovine PDL increases while the width of bovine PDL decreases, and it increases while the capacity ratio of collagen fibers increases.
Animals ; Cattle ; Collagen ; chemistry ; Elastic Modulus ; Periodontal Ligament ; physiology ; Tensile Strength ; Tooth Root ; anatomy & histology