Role of Cone Beam Computed Tomography in Diagnosis and Treatment Planning in Dentistry: An Update.

Accurate diagnosis and treatment planning are the backbone of any medical therapy; for this reason, cone beam computed tomography (CBCT) was introduced and has been widely used. CBCT technology provides a three-dimensional image viewing, enabling exact location and extent of lesions or any anatomical region. For the very same reason, CBCT can not only be used for surgical fields but also for fields such as endodontics, prosthodontics, and orthodontics for appropriate treatment planning and effective dental care. The aim and clinical significance of this review are to update dental clinicians on the CBCT applications in each dental specialty for an appropriate diagnosis and more predictable treatment.

INTRODUCTION

Wilhelm C. Röntgen discovered electromagnetism in 1895 in a wavelength range (the X-rays) which became a very important diagnostic tool.[1] This discovery unleashed a great source of knowledge of the human body breaking the constraints of medical science and enabling doctors to diagnose and treat pathologies accurately. It was after 14 years that X-rays were recognized in dentistry by Dr. Walkhoff, a dentist in Braunschweig, Germany. The discovery of X-rays was the basis for improved methods of scientific evaluation such as the cone beam computed tomography (CBCT). Interestingly, this technology took almost 40 years to evolve and become available for clinicians.

CBCT has evolved from CT scan; a technique invented in 1967 by the British engineer Godfrey Hounsfield.[2] The first prototype of clinical CBCT scanner was originally devised as a cost-effective and efficient method for obtaining cross-sectional three-dimensional (3D) images for radiotherapy and later (1982) for angiography.[3] CBCT's commercial availability was delayed for a decade and wasfirst introduced in Europe in 1998 and the US in 2001.[3] Columbia Scientific Inc., introduced 3D dental software in dentistry in 1988, and 2 years later, CBCT started to appear in dental research publications.[4] With CBCT's introduction in dentistry, dental clinicians could not only have profound knowledge of oral pathology but could also enhance the access to a detailed view of the underlying structures and their relations. This 3D image was groundbreaking since the process of decision-making became simpler and the recognition of the bony defects from different angles became easier.

The aim of this manuscript is to describe the CBCT function concept and its application in dental and maxillofacial conditions.

MATERIALS AND METHODS

This narrative review gathered literature from peer-reviewed articles published in indexed journals available in PubMed and other web-based resources. The article and literature used for this publication has been summarized in Table 1.

Table 1

Summary of literature used for this publication

APPLICATIONS IN DENTISTRY

Oral surgery

An oral surgeon can analyze the size, extent, and location of a tumor or cyst, its penetration into surrounding structures, and relation to vital structures such as nerves and blood vessels [Figure 1]. CBCT also helps in the assessment of impacted teeth and supernumerary in terms of its location and relation to vital structures.[5] The clinician can also detect changes in the bony deformities related to bisphosphonate-associated osteonecrosis of the jaw, bone grafts, and paranasal sinuses; in cases of obstructive sleep apnea, it helps to form a volume surface rendering of the windpipe.[5] CBCT has the ability to provide attention to details, thus, becomes the technology of choice for midface fracture cases e.g., gunshot wounds, orbital fracture management, interoperative visualization of the facial bones after fracture [Figure 2], and intraoperative navigation during surgical procedures.[678]

Figure 1

Destruction of the body – parasymphysis left mandibular region due to an intrabony tumor

Figure 2

Multiple fractures involving the naso-orbitoethmoidal region, bilateral Le Fort 2 and 3 levels and a bilateral high Le Fort 1 fracture along with a left parasymphysis fracture of the mandible

In cases of temporomandibular joint disorders and dysfunctioning related to trauma, pain, dysfunction, fibro-osseous ankylosis, detecting condylar cortical erosion, cysts, and visualization of soft tissue (ST), CBCT becomes the imaging device of choice.[9]

Implantology

CBCT provides a higher degree of predictability of implant placement because of its accuracy for evaluation. The clinician can evaluate the height and width of the bone present to place an implant [Table 2 and Figure 3]. In peri-implantitis cases, the amount of bone surrounding the implant can be assessed previous to probing, providing such important information as radiolucency.[1011]

Table 2

Cone beam computed tomography used in the treatment of implantology

Figure 3

Use of cone beam computed tomography in planning the tridimensional placement of four implants in the anterior zone

Orthodontics

An orthodontist can use CBCT for the assessment of the position of unerupted teeth, particularly for impacted ones, especially in cases of maxillary impacted canines where knowing exactly the tooth position results in accurate treatment planning [Figure 4]. The angulation is appreciated well in these 3D images, which would be difficult to appreciate on conventional radiographs even when taken in two different planes. It also helps in identification of any resorption of adjacent teeth (i.e., where maxillary canines are ectopic and incisor roots are suspected of having undergone resorption).[12]

Figure 4

Three-dimensional view of both maxillary and mandibular arches depicting amount of bone present, craters, furcation, and crestal bone loss

Other applications of CBCT in orthodontics are cleft palate assessment, resorption related to impacted teeth, rapid maxillary expansion, 3D cephalometry, surface imaging integration, airway assessment, age assessment, and investigation of orthodontic-associated paraesthesia.[13] In cases where mini-screw implants are placed for anchorage, CBCT is used to analyze bone dimensions and precise location of placement to minimize complications.[14]

Endodontics

CBCT can also be used for caries diagnosis since caries detection and depth evaluation in approximal and occlusal lesions are improved considerably. However, its application in endodontic-metallic restoration would produce artifacts reducing diagnostic accuracy.[15] CBCT imaging for caries should be limited to nonrestored teeth. Sensitivity may increase with CBCT but it should not be at the cost of specificity.[15] CBCT in endodontics can be used for identification and measurement of the extent of periapical lesions[16] and it also differentiates solid from fluid-filled lesions (e.g., periapical granulomas from cysts) using grayscale values in the lesions.[15] CBCT plays an important role in establishing successful endodontic therapy by identification of all root canals so that they can be accessed, cleaned, shaped, and obturated.[16] It helps in identification of prevalence of a second mesiobuccal canal (MB2) in maxillary first molars and also multiple and accessory canals (aberrant pulpal anatomy, e.g., dens invaginatus) in any other teeth.[15] It also helps in differentiation of pathosis from normal anatomy and relationships with important anatomical structures. CBCT also plays an important role in the diagnosis and management of root fractures, luxation and/or displacement, and alveolar fracture.[171819202122]

Periodontics

In periodontics, CBCT detects the amount of bone present, craters, furcation, crestal bone loss, fenestrations, and dehiscences [Figure 5]. In spite of its usefulness in this field, CBCT is not indicated as a routine method of imaging periodontal bone support. However, limited volume, high-resolution CBCT may be indicated in selected cases of infrabony defects and furcation lesions, where clinical and conventional radiographic examinations do not provide the information needed for management; thus, it may have a role to play in the management of complex periodontal defects for which surgery is the treatment option.[1315] CBCT can also be used within a period of 1 month for postoperative defect fill or bone density evaluation, which cannot be detected through normal radiographs, and it can also replace subtraction radiography.[15]

Figure 5

Both permanent upper canines are impacted with the crown facing toward the palatal aspect and the roots more toward the buccal aspect

CBCT can help in identifying bone defect size and early signs of periodontitis by assessing periodontal ligament space, measurement of gingival tissue, and the dimensions of the dentogingival unit.[23] This method is called ST-CBCT and helps to visualize and measure precisely distances corresponding to the hard and STs of the periodontium and dentogingival attachment apparatus. With ST-CBCT, gingival margin and the facial bone crest, gingival margin and the cementoenamel junction (CEJ), and CEJ and facial bone crest can be determined.[232425]

Forensic dentistry

CBCT can also be applied in the field of forensic dentistry for accurate age estimation for every person of the legal system (including those who have passed away). To estimate accurate age, tooth has to be sectioned to identify morphological changes; as with age, internal layers of the tooth (dentin, cementum, and pulp) illustrate physiological and pathological changes.[26] However, with CBCT, such aggressive methods are not required.[27]

SAFETY CONCERNS

It is paramount that as low as reasonably achievable (ALARA) principle is followed during diagnosis, as far as the radiation dose of CBCT imaging is concerned.[28] Use of CBCT for examination must be justified for each patient as the examination is dose dependent; i.e., higher doses of radiation may also be applied depending on the lesion to be examined, but higher radiation increases risks. Thus, CBCT should only be used when the question for which imaging is required cannot be answered adequately by lower dose conventional (traditional) radiography.[28] Therefore, it is necessary to ensure that patient doses are monitored on a regular basis and compared to agreed standards. Standard dose levels are normally referred to as diagnostic reference levels, and a dose of 4 mGy of SRL is recommended as the absorbed dose in air measured at the end of the spacer cone for a standard maxillary molar projection.[28]

By 1897, Kells reported that long exposures to X-rays caused a mild skin irritation, similar to sunburn, and early X-ray machines needed adjustment for each use so that the operator placed his hand between the actively radiating tube and the film plate. Kells took radiographs in this manner for 12 years, after which he developed cancerous tumors on his fingers. Thus, concerns about radiation exposure, especially when it is done once in a lifetime are inconsequential; furthermore, beyond 80 years of age, the risk becomes negligible because the latent period between X-ray exposure and the clinical presentation of a tumor would probably exceed the lifespan of a patient.[29] In contrast, the tissues of younger people are more radiosensitive and their prospective lifespan is likely to exceed the latent period. However, the ALARA principle should be kept in mind and should be followed with each exposure.

LIMITATIONS OF CONE BEAM COMPUTED TOMOGRAPHY IMAGING

While there has been enormous interest on CBCT, this technology currently has limitations too related to the “cone beam” projection geometry, detector sensitivity, and contrast resolution.[30] These parameters create an inherent image (known as noise) that reduces image clarity in such a way that current systems are unable to record ST contrast at the relatively low dosages applied for maxillofacial imaging; however, with advanced systems, it can be achieved.[30] Another factor that impairs CBCT image quality is image artifacts, such as streaking, shading, rings, and distortion.[31] Streaking and shading artifacts due to high areas of attenuation and inherent spatial resolution may limit adequate visualization of structures in the oral and maxillofacial region.[31]

Another limitation is the cost of the equipment and investment in the area where it is to be installed, as CBCT causes scattering of the radiation, especially when larger tissue is being evaluated, causing polydirectional Compton scattering. Thus, it needs lead barriers to be placed, adding to the investment.[31]

Another disadvantage is the poor quality in ST assessment.[13] The dynamic range of CBCT for contrast resolution can reach only 14-bit maximally.[32] To accurately read a ST phenomenon, a 24-bit contrast resolution is needed.[29] In addition, unlike multidetector CT, the Hounsfield units of tissue density are not calibrated on CBCT, which makes it unreliable to compare tissue density based on CT numbers generated from different CBCT units.[32]

CONCLUSION

From the aforementioned literature review, along with the advantages and disadvantages of CBCT, it seems that CBCT may not be the best imaging modality to evaluate STs; however, there are situations in which CBCT can help such as analysis of ST airway constrictions and obstructions for patients suffering from sleep apnea, other ST evaluations for orthodontic treatment and periodontal treatment,[3334] and detection of healed root fractures.[35] The development and rapid commercialization of CBCT technology has undoubtedly increased practitioners’ use of CBCT, as it is capable of providing accurate, submillimeter resolution images in formats enabling 3D visualization of the complexity of the maxillofacial region. It also provides clinicians with a modality that extends maxillofacial imaging from diagnosis to image guidance for operative and surgical procedures. Today, Wilhelm C. Röntgen's discovery through its evolution is providing diagnostic efficacy that can result in improved therapeutic efficiency in the medical and dental fields.

FINANCIAL SUPPORT AND SPONSORSHIP

Nil.

CONFLICTS OF INTEREST

There are no conflicts of interest.