Comparative study of orthopantomograph & cone beam computed tomography as pre-operative diagnostic tools for lower third molar surgery

Introduction Lower third molar surgery is a common and relatively uncomplicated procedure. Commonly indicated where there is infection, bony pathology, soft tissue pathology or damage to the adjacent tooth. Difficult surgical challenges and unpredictable surgical outcomes can be caused by wide variations in the position and anatomy of the mandibular third molar roots, and relationship of these roots to the mandibular canal containing the Inferior Alveolar Nerve (IAN) may at times present the surgeon with inadvertent crush injury, stretch injury or even severing of the inferior alveolar nerve. Appropriate imaging and treatment planning results in predictable surgical outcome. The relative relationship and proximidity of the mandibular third molar roots to the inferior alveolar canal can be predicted by several radiographic signs displayed on an orthopantomograph (OPG), including darkening of the roots, deflection of the roots, narrowing of the roots, dark and bifid roots, interruption of white line(s), diversion of the inferior alveolar canal and narrowing of the inferior alveolar canal. An OPG is however limited by depth of view, superimposed structures and distorted structures with positioning errors. Cone-Beam Computed Tomography (CBCT) is a radiographic imaging method which may provide the ability to predict more accurately the relationship of the root(s) to the inferior alveolar canal, and therefore a more predictable and favourable outcome. CBCT has been in use at Sydney’s Westmead Centre for Oral Health (WCOH) since 2006. The purpose of this study is to evaluate whether OPG alone or utilisation of OPG and CBCT together provides the more predictable outcome following surgery where there has been a close relationship of the roots to the inferior alveolar canal. Methods A retrospective study was performed of lower third molar cases that were managed at Westmead Centre for Oral Health, Westmead NSW, between November 2005 to August 2006 prior to CBCT (Group one) and November 2010 to August 2011 following CBCT (Group two). The study involved examination of de-identified pre-operative, operative and post-operative written records, as well as the OPG and relevant CBCT records. Relevant data was tabulated along with any associated complications in an excel spreadsheet. The variables within the data and the two groups were crosstabulated and analysed with a statistic software (SPSS). Results Total of 590 surgical cases were included in the study, with 265 in group one and 325 in group two. Post-operative complications totalled 9, where group one had 6 and group two had 3. Numbers with no post-operative complications totalled 581, with 259 for group one and 322 for group two. Discussion A two by two risk calculation demonstrated reduction of IAN complication by 50% with CBCT, with a risk ratio of 2.45 and risk difference of 0.0134. The numbers needed to be treated were calculated from there as 75. With CBCT, the superimposed structures can be eliminated and distortions minimised, via the mode of image scanning and digital software manipulation of the DICOM data set, so providing more depth of view and allowing a more accurate measurement of relative position between the roots of lower third molar teeth and inferior alveolar nerve. Coronal, sagittal, axial and panoramic views obtained from CBCT allow three-dimensional evaluation of the relationship between the roots of lower third molar teeth and inferior alveolar nerve. This may influence surgical techniques to provide more accurate and safer surgery or influence an alternative treatment plan such as coronectomy or leaving the impacted tooth in-situ. Safer outcome would not only benefit the patient and the surgeon, but may reduce costs to the institution, the community and the profession in terms of medico-legal liability and indemnity. One disadvantage of CBCT include the higher radiation dosage that the patient is exposed to when compared to OPG, but relatively lower radiation dosage than helical beam CT. Another disadvantage of CBCT is the high initial cost, as well as maintenance and replacement cost of each unit, whilst that of OPG remains relatively low. The cost effectiveness of CBCT needs to be considered, whereby an institution such as WCOH receives high numbers of external and internal referrals, which may justify these associated costs when weighted against the benefits to the patient and the surgeon by the 50% reduction in complications. Conclusion It can be concluded from the results that seventy five lower third molar surgeries are needed to be performed utilising CBCT as pre-operative diagnostic tools in order to reduce the incidence of inferior alveolar nerve complication by one. This study has been a retrospective study. A randomised prospective study would be the next step to verify the accuracy and demonstrate the benefits of CBCT

Jaw tissues segmentation in dental 3D CT images using fuzzy-connectedness and morphological processing

The success of oral surgery is subject to accurate advanced planning. In order to properly plan for dental surgery or a suitable implant placement, it is necessary an accurate segmentation of the jaw tissues: the teeth, the cortical bone, the trabecular core and over all, the inferior alveolar nerve. This manuscript presents a new automatic method that is based on fuzzy connectedness object extraction and mathematical morphology processing. The method uses computed tomography data to extract different views of the jaw: a pseudo-orthopantomographic view to estimate the path of the nerve and cross-sectional views to segment the jaw tissues. The method has been tested in a groundtruth set consisting of more than 9000 cross-sections from 20 different patients and has been evaluated using four similarity indicators (the Jaccard index, Dice's coefficient, point-to-point and point-to-curve distances), achieving promising results in all of them (0.726 ± 0.031, 0.840 ± 0.019, 0.144 ± 0.023 mm and 0.163 ± 0.025 mm, respectively). The method has proven to be significantly automated and accurate, with errors around 5% (of the diameter of the nerve), and is easily integrable in current dental planning systems. © 2012 Elsevier Ireland Ltd.This work has been supported by the project MIRACLE (DPI2007-66782-C03-01-AR07) of Spanish Ministerio de Educacion y Ciencia.Llorens Rodríguez, R.; Naranjo Ornedo, V.; López-Mir, F.; Alcañiz Raya, ML. (2012). Jaw tissues segmentation in dental 3D CT images using fuzzy-connectedness and morphological processing. Computer Methods and Programs in Biomedicine. 108(2):832-843. https://doi.org/10.1016/j.cmpb.2012.05.014832843108

A Cone Beam Computed Tomography Annotation Tool for Automatic Detection of the Inferior Alveolar Nerve Canal

In recent years, deep learning has been employed in several medical fields, achieving impressive results. Unfortunately, these algorithms require a huge amount of annotated data to ensure the correct learning process. When dealing with medical imaging, collecting and annotating data can be cumbersome and expensive. This is mainly related to the nature of data, often three-dimensional, and to the need for well-trained expert technicians. In maxillofacial imagery, recent works have been focused on the detection of the Inferior Alveolar Nerve (IAN), since its position is of great relevance for avoiding severe injuries during surgery operations such as third molar extraction or implant installation. In this work, we introduce a novel tool for analyzing and labeling the alveolar nerve from Cone Beam Computed Tomography (CBCT) 3D volumes

Assessment of bone loss adjacent to lower second molar in case of third molar impaction and other findings using Orthopantomography (OPG)

[eng] INTRODUCTION: Dental impaction is a pathological situation in which a tooth is totally or partially included in the jaw or maxilla bone. Different teeth are noticeably prone to impaction phenomena, including the canine and upper third molar, third molar, and lower canine. However, the lower third molar is considered the most common impacted tooth, accounting for 98% compared to other impacted teeth. It usually erupts between the ages of 17 and 24. The overall prevalence of impaction of the lower third molar is estimated to be around 24%, with no gender predilection between men and women. There are factors that cause a tooth to not erupt in the expected time, including lack of space, poorly positioned dental germs, abnormal eruption pathway, and alterations in jaw development. Mandibular third molar impaction has many complications in the adjacent soft tissue and second molar. Thus, pericoronitis is one of the consequences caused by impaction, which manifests itself as inflammation of the gum tissue that covers it. Other complications include distal caries, bone loss adjacent to the second molar, cystic formation, and neoplastic changes. The different positions of impacted mandibular third molars can complicate the maintenance of oral hygiene and control plate. Therefore, the periodontium manifests the formation of pockets that facilitate bone loss on the distal aspect of the second molar. In addition, the mandibular third molar is located near the inferior mandibular canal which contains the inferior alveolar nerve, the artery and the corresponding vein. Surgical extraction of such a tooth may pose a risk of nerve injury leading to dysesthesia or paresthesia. In addition, the third molar removal procedure can put pressure on the bone that can lead to fracture of the angle of the jaw. Finally, extraction can affect the lower 2nd molar. Therefore, clinical and diagnostic procedures are essential to address the position of the impacted tooth, the associated pathology, the proximity to the nerve canal, and the decision to intervene. Orthopantomography (OPG) is an imaging technique routinely used in the dental office, representing the jawbone and jaw in a single image. It has the advantage of exposing dental and bone changes in the oral cavity, including impacted teeth. Among the advantages of OPG are its speed and ease, especially the 2nd molar and the canal inside the realization, better patient cooperation and acceptance, complete coverage of dental arches and related structures (more anatomical structures can be seen on a panoramic film than in a full series of intraoral x-rays), simplicity, and low radiation exposure for the patient, compared to the most advanced imaging tool, cone beam computed tomography (CBCT). As impaction of the third molar is one of the dental pathologies that dentists frequently see, the determination of the position and relationship with nearby structures, especially the 2nd molar and the lower dental canal, can be predicted using OPG. HYPOTHESIS: Impaction of the third molar causes bone loss distal to the second molar, therefore there will be bone gain distal to the second molar after extraction of the third molar. OBJECTIVE: To determine the distal bone loss of the lower second molar associated with impaction of the third molar and to analyze its evolution after the extraction of the third molar.[spa] INTRODUCCIÓN: la impactación dental es una situación patológica en la que un diente se incluye total o parcialmente en el hueso de la mandíbula o del maxilar. Diferentes dientes son notablemente propensos a los fenómenos de impactación, incluyendo el canino y el tercer molar superior, el tercer molar y el canino inferior. Sin embargo, el tercer molar inferior se considera el diente impactado más común, representando el 98% en comparación con otros dientes impactados. Por lo general, entra en erupción entre los 17 y 24 años. La prevalencia global de impactación del tercer molar inferior se estima en torno al 24%, sin predilección de género entre hombres y mujeres. Hay factores que hacen que un diente no erupcione en el tiempo esperado, incluida la falta de espacio, los gérmenes dentales mal posicionados, la vía de erupción anormal y las alteraciones del desarrollo de la mandíbula. La impactación del tercer molar mandibular tiene muchas complicaciones en el tejido blando adyacente y en el segundo molar. Así, la pericoronaritis es una de las consecuencias causadas por la impactación, que se manifiesta como inflamación del tejido gingival que la recubre. Otras complicaciones incluyen la caries distal, la pérdida ósea adyacente al segundo molar, formación quística y cambios neoplásicos. Las diferentes posiciones de los terceros molares mandibulares impactados pueden complicar el mantenimiento de la higiene oral y la placa control. Por lo tanto, el periodonto manifiesta la formación de bolsas que facilitan la perdida oseas en la cara distal del segundo molar. Además, el tercer molar mandibular está ubicado cerca del canal mandibular inferior el cual contiene el nervio alveolar inferior, la arteria y la vena correspondiente. La extracción quirúrgica de dicho diente puede ejercer un riesgo de lesión nerviosa que conduzca a disestesia o a parestesia. Además, el procedimiento de extracción del tercer molar puede ejercer una presión sobre el hueso que puede conducir a la fractura del ángulo de la mandíbula. Finalmente, la extracción puede afectar al 2º molar inferior. Por lo tanto, los procedimientos clínicos y diagnósticos son esenciales para abordar la posición del diente impactado, la patología asociada, la proximidad al canal nervioso y la decisión de intervención. La ortopantomografía (OPG) es una técnica de diagnóstico por la imagen utilizada rutinariamente en el consultorio dental, que representa al maxilar y la mandíbula en una sola imagen. Tiene la ventaja de exponer los cambios dentales y óseos en la cavidad oral, incluidos los dientes impactados. Entre las ventajas de la OPG, se encuentran su rapidez y facilida, en especial el 2º molar y el canal dentro de realización, mejor cooperación y aceptación del paciente, cobertura completa de las arcadas dentales y estructuras relacionadas (se pueden ver más estructuras anatómicas en una película panorámica que en una serie completa de radiografías intraorales), simplicidad y baja exposición a la radiación para el paciente, en comparación con la herramienta de imagen más avanzada, la tomografía computarizada de haz cónico (CBCT). Como la impactación del tercer molar es una de las patologías dentales que los odontólogos ven con frecuencia, la determinación de la posición y la relación con las estructuras cercanas, en especial el 2º molar y el canal dentario inferior, se puede predecir utilizando OPG. HIPÓTESIS: La impactación del tercer molar causa pérdida ósea distal al segundo molar, por lo tanto, habrá ganancia ósea distal al segundo molar después de la extracción del tercer molar. molar impactado. OBJETIVO: determinar la pérdida ósea distal del segundo molar inferior asociada a impactación del tercer molar y analizar su evolución tras la extracción del tercer molar

Deep Segmentation of the Mandibular Canal: a New 3D Annotated Dataset of CBCT Volumes

Inferior Alveolar Nerve (IAN) canal detection has been the focus of multiple recent works in dentistry and maxillofacial imaging. Deep learning-based techniques have reached interesting results in this research field, although the small size of 3D maxillofacial datasets has strongly limited the performance of these algorithms. Researchers have been forced to build their own private datasets, thus precluding any opportunity for reproducing results and fairly comparing proposals. This work describes a novel, large, and publicly available mandibular Cone Beam Computed Tomography (CBCT) dataset, with 2D and 3D manual annotations, provided by expert clinicians. Leveraging this dataset and employing deep learning techniques, we are able to improve the state of the art on the 3D mandibular canal segmentation. The source code which allows to exactly reproduce all the reported experiments is released as an open-source project, along with this article

Inferior Alveolar Canal Automatic Detection with Deep Learning CNNs on CBCTs: Development of a Novel Model and Release of Open-Source Dataset and Algorithm

Featured Application Convolutional neural networks can accurately identify the Inferior Alveolar Canal, rapidly generating precise 3D data. The datasets and source code used in this paper are publicly available, allowing the reproducibility of the experiments performed. Introduction: The need of accurate three-dimensional data of anatomical structures is increasing in the surgical field. The development of convolutional neural networks (CNNs) has been helping to fill this gap by trying to provide efficient tools to clinicians. Nonetheless, the lack of a fully accessible datasets and open-source algorithms is slowing the improvements in this field. In this paper, we focus on the fully automatic segmentation of the Inferior Alveolar Canal (IAC), which is of immense interest in the dental and maxillo-facial surgeries. Conventionally, only a bidimensional annotation of the IAC is used in common clinical practice. A reliable convolutional neural network (CNNs) might be timesaving in daily practice and improve the quality of assistance. Materials and methods: Cone Beam Computed Tomography (CBCT) volumes obtained from a single radiological center using the same machine were gathered and annotated. The course of the IAC was annotated on the CBCT volumes. A secondary dataset with sparse annotations and a primary dataset with both dense and sparse annotations were generated. Three separate experiments were conducted in order to evaluate the CNN. The IoU and Dice scores of every experiment were recorded as the primary endpoint, while the time needed to achieve the annotation was assessed as the secondary end-point. Results: A total of 347 CBCT volumes were collected, then divided into primary and secondary datasets. Among the three experiments, an IoU score of 0.64 and a Dice score of 0.79 were obtained thanks to the pre-training of the CNN on the secondary dataset and the creation of a novel deep label propagation model, followed by proper training on the primary dataset. To the best of our knowledge, these results are the best ever published in the segmentation of the IAC. The datasets is publicly available and algorithm is published as open-source software. On average, the CNN could produce a 3D annotation of the IAC in 6.33 s, compared to 87.3 s needed by the radiology technician to produce a bidimensional annotation. Conclusions: To resume, the following achievements have been reached. A new state of the art in terms of Dice score was achieved, overcoming the threshold commonly considered of 0.75 for the use in clinical practice. The CNN could fully automatically produce accurate three-dimensional segmentation of the IAC in a rapid setting, compared to the bidimensional annotations commonly used in the clinical practice and generated in a time-consuming manner. We introduced our innovative deep label propagation method to optimize the performance of the CNN in the segmentation of the IAC. For the first time in this field, the datasets and the source codes used were publicly released, granting reproducibility of the experiments and helping in the improvement of IAC segmentation

Imaging in Third Molar Surgery: A Clinical Update

Third molar surgery is one of the most common surgical procedures performed in oral and maxillofacial surgery. Considering the patient's young age and the often-elective nature of the procedure, a comprehensive preoperative evaluation of the surgical site, relying heavily on preoperative imaging, is key to providing accurate diagnostic work-up, evidence-based clinical decision making, and, when appropriate, indication-specific surgical planning. Given the rapid developments of dental imaging in the field, the aim of this article is to provide a comprehensive, up-to-date clinical overview of various imaging techniques related to perioperative imaging in third molar surgery, ranging from panoramic radiography to emerging technologies, such as photon-counting computed tomography and magnetic resonance imaging. Each modality's advantages, limitations, and recent improvements are evaluated, highlighting their role in treatment planning, complication prevention, and postoperative follow-ups. The integration of recent technological advances, including artificial intelligence and machine learning in biomedical imaging, coupled with a thorough preoperative clinical evaluation, marks another step towards personalized dentistry in high-risk third molar surgery. This approach enables minimally invasive surgical approaches while reducing inefficiencies and risks by incorporating additional imaging modality- and patient-specific parameters, potentially facilitating and improving patient management

Enhancing Patch-Based Learning for the Segmentation of the Mandibular Canal

Segmentation of the Inferior Alveolar Canal (IAC) is a critical aspect of dentistry and maxillofacial imaging, garnering considerable attention in recent research endeavors. Deep learning techniques have shown promising results in this domain, yet their efficacy is still significantly hindered by the limited availability of 3D maxillofacial datasets. An inherent challenge is posed by the size of input volumes, which necessitates a patch-based processing approach that compromises the neural network performance due to the absence of global contextual information. This study introduces a novel approach that harnesses the spatial information within the extracted patches and incorporates it into a Transformer architecture, thereby enhancing the segmentation process through the use of prior knowledge about the patch location. Our method significantly improves the Dice score by a factor of 4 points, with respect to the previous work proposed by Cipriano et al., while also reducing the training steps required by the entire pipeline. By integrating spatial information and leveraging the power of Transformer architectures, this research not only advances the accuracy of IAC segmentation, but also streamlines the training process, offering a promising direction for improving dental and maxillofacial image analysis

Magnetic resonance imaging for preoperative diagnosis in third molar surgery: a systematic review

In recent years, magnetic resonance imaging (MRI) has made great strides through various technical improvements and new sequences, which have made it one of the most promising and leading imaging techniques in the head and neck region. As modern imaging techniques in dentistry aim to reduce radiation exposure, this systematic review evaluated the possibilities, advantages, and disadvantages of advanced imaging diagnostics using dental MRI and its evidence for clinical indications and limitations relevant to mandibular third molar (MTM) surgery. Two reviewers performed multiple database searches (PubMed MEDLINE, EMBASE, Biosis, and Cochrane databases) following the PICOS search strategy using medical subject headings (MeSH) terms, keywords, and their combinations. Ten studies were included in this systematic review. By providing high spatial resolution and excellent soft tissue contrast, black bone MRI sequences such as 3D Double Echo Steady State (DESS) and 3D Short Tau Inversion Recovery (STIR) imaging protocols have the potential to become a valuable alternative to cone-beam computed tomography (CBCT) in future dental clinical routines. Overall, radiation-free MRI represents another step toward personalized dentistry and improved decision-making that avoids ineffectiveness and minimizes risks in oral surgery by taking into account additional patient-side factors such as comorbidity, anatomical norm variations, and imaging biomarkers

Prophylactic removal of third molars: a risk-benefit analysis

The treatment of impacted third molars that have neither symptoms nor disease is controversial. One school of thought is that these teeth should be extracted before they do become symptomatic and/or diseased. A second school of thought advocates retaining these teeth until such time when they show evidence of developing symptoms or disease. The purpose of this review is to present the reasoning behind the two opposing schools of thought. Studies involving both the risks and the benefits of extracting and retaining asymptomatic, disease-free third molars were examined. There are studies to support the proponents of each school of thought. Proponents of removal are of the belief that many asymptomatic and disease-free impacted third molars eventually do become symptomatic and/or diseased, and do so when the patient is older. The morbidity and incidence of complications common to the procedure increase with age, and therefore proponents of removal prefer that surgery be performed at a younger age when the complications are less likely to be as severe or permanent. Those in support of retaining and monitoring these teeth are of the opinion that the status of these asymptomatic and disease-free impacted third molars may never change and therefore never require surgical intervention. They believe the increased complication rate and morbidity experience by some of the older surgical patients do not justify the routine removal of all asymptomatic, disease-free impacted third molars at an early age. Both groups recognize that when surgical intervention is employed, complications such as pain, swelling, alveolar osteitis, periodontal problems, temporomandibular joint disorders, nerve involvement, sinus communication, and financial stress are not uncommon. Ultimately, the clinician must consider the information presented in this review, and combine it with his/her academic knowledge and personal clinical experience to inform the patient of the risks and benefits of both treatment options. That way, the clinician and the patient together can decide the strategy for management of an asymptomatic, disease-free third molar