Indian Journal of Ophthalmology

REVIEW ARTICLE
Year
: 2017  |  Volume : 3  |  Issue : 1  |  Page : 1--3

Cone beam computed tomography in orthodontics


Sumreet Kaur Sandhu 
 Private Practitioner, Health First Multispecialty Clinic, New Delhi, India

Correspondence Address:
Sumreet Kaur Sandhu
Health First Multispecialty Clinic, Sector 19, New Delhi
India

Abstract

A new revolution in three-dimensional radiologic advances in dentistry was introduced in the year 1998, as cone beam computed tomography (CBCT). Over the years, it has become an increasingly popular technique in orthodontic diagnosis, treatment planning, and research. This rise in its popularity has been facilitated by the relative advantages of three-dimensional (3D) over 2D radiography. CBCT imaging involves only a minimal increase in radiation dose relative to combined diagnostic modern digital panoramic and cephalometric imaging. A combination of volumetric reconstruction and multiplanar views can provide the orthodontic clinician with skeletal hard tissue, soft tissue, dentition, and airway information. Despite many suggested indications of CBCT, scientific evidence that its utilization improves diagnosis and treatment plans or outcomes has only recently begun to emerge. This article provides a comprehensive review of the application of CBCT in orthodontics. The current indications for CBCT in standard orthodontic diagnosis include impacted teeth, cleft lip, and palate and skeletal discrepancies requiring surgical intervention, root resorption, supernumerary teeth, temporomandibular joint (TMJ) pathology, facial asymmetry, temporary anchorage devices, root morphology and angulation; alveolar boundary conditions; maxillary transverse dimensions and maxillary expansion, and vertical malocclusion. Advanced CBCT software applications can be used to quantify airway space in the cases of obstructive sleep apnea, perform superimpositions to semiquantitatively visualize changes over the hard and soft tissues, including the TMJ and airway.



How to cite this article:
Sandhu SK. Cone beam computed tomography in orthodontics.Saint Int Dent J 2017;3:1-3


How to cite this URL:
Sandhu SK. Cone beam computed tomography in orthodontics. Saint Int Dent J [serial online] 2017 [cited 2019 Oct 13 ];3:1-3
Available from: http://www.sidj.org/text.asp?2017/3/1/1/230201


Full Text

Cone beam computed tomography (CBCT) is an evolution of the original CT proposed by Hounsfield and Comark. The first CBCT scanner was built by Robles RA in 1982 for angiography purpose.[1] CT was available for three-dimensional (3D) dental imaging in the 1980s, but due to the high cost, limited access, and radiation exposure, its use was limited to management of craniofacial anomalies, complex surgeries, and other unique dental situations. CBCT can provide accurate assessment of the bone structure with a reduced image distortion due to patient movements, and increased X-ray efficiency leading to reduced radiation exposure due to the availability of choosing a field of view to suit the patients' requirements. CBCT relies on interpolation of the acquired data into units called voxels. The voxel is a 3D representation of the pixel. A number of studies have demonstrated the precision of linear measurements performed on CBCT images.[2],[3],[4] For these reasons, CBCT has made 3D imaging routinely accessible to the orthodontist.

The aim of this article is to provide a comprehensive overview of CBCT imaging, including its technique, advantages, and applications in orthodontics.

 Applications in Orthodontics



Impacted teeth

After third molars, maxillary canines are the second most commonly impacted teeth [5],[6] and are probably the most common indications for CBCT imaging in orthodontics. CBCT enhances the ability to localize impacted canines accurately, evaluate their proximity to other teeth and structures, determine the follicle size and the presence of pathology, estimate space conditions, assess resorption of adjacent teeth, assist in planning surgical access and bond placement, and aid in defining optimal direction for extrusion of these teeth into the oral cavity. The detection of abnormal anatomy of the root by CBCT, including dilacerated roots – particularly, in the buccolingual direction not seen in 2D radiographs – also may help determine the amount and direction that a dilacerated tooth can be moved or aid in the decision to extract.

Alveolar bone

This includes the depth, height, and morphology of alveolar bone relative to tooth root dimensions, angulation, and spatial position. Compromised or inadequate pretreatment boundary conditions as well as limited ability to adapt to tooth movement may restrict or interfere with the planned or potential tooth movement, as well as the final desired spatial position and angulation of the teeth. This measurement becomes important when evaluating the bone changes after retraction of teeth into extraction spaces, before the insertion of temporary anchorage devices (TADs) [Figure 1], and while planning multidisciplinary treatment for mutilated dentition, and also to evaluate the extent of bone condition in periodontally compromised dentitions and in patients with vertical growth patterns. Although CBCT provides accurate assessment of alveolar bone height, caution must be exercised in evaluating fenestrations owing to the high number of false positives in the determination of these defects.[2],[7]{Figure 1}

Cleft lip and palate

Radiographs of the dentition of cleft lip and palate (CL/P) patients [Figure 2] at an early age are needed to examine the volume of alveolar cleft, how much expansion and graft material is needed to fill the cleft, to assess the associated transverse deficiency of the maxilla and the number and morphology of the patient's teeth. While 2D radiographs have been used traditionally for this purpose, CBCT provides more accurate information on the numbers, quality and location of teeth in the proximity of the cleft site,[8] eruption status and path of canines in grafted cleft sites,[9] and diagnosing for implant placement.[10]{Figure 2}

Temporomandibular joint morphology and pathology

As expected, CBCT images provide clinicians with more accurate anatomic detail of the temporomandibular joint (TMJ) than do conventional 2D panoramic radiographs.[11] CBCT facilitates visualization of minor to overt osseous hard tissue changes and congruency of articulating surfaces resulting from pathology and adaptive processes and allows for accurate detection and evaluation of pathological changes.[12] CBCT has been shown to be more efficacious than conventional tomography and MRI in detecting osseous changes.[13]

Airway morphology

CBCT allows the clinician to measure both the volume and cross-section of the airway. Considerable interest in the airway measurements has risen in the recent past as the relationship of obstructive sleep apnea (OSA) to airway, and the effects of orthodontic treatment on OSA are being investigated.[14],[15] Initial investigations on airway patency, function, and disorders utilizing CBCT have provided preliminary answers, including dimensions of normal airway anatomy in adults,[16] relationship of 2D to 3D measurements,[17] differences in airway morphology in subjects with OSA and non-OSA,[18] the effects of extractions on 3D pharyngeal volume and structure,[19] and the consequences of rapid maxillary expansion (RME) and orthognathic surgery on airway dimensions.[20],[21]

Maxillary transverse dimension

Maxillary transverse deficiency is a common cause of malocclusions that are notable for posterior crossbites and are often accompanied by crowding and/or increased overjet. Correction of these occlusal and maxillary arch anomalies with RME is indicated in growing patients to widen the maxillary transverse dimension primarily through widening the mid-palatal suture. This goal of RME treatment in these cases is to re-establish the correct posterior transverse occlusion and increase the arch length to relieve crowding through skeletal expansion and/or dental tipping. CBCT has enabled more in-depth dissection of responses of bone and teeth to maxillary expansion than was possible through 2D radiography or study models.

Specifically, CBCT has been used to address two questions related to RME treatment, namely how expansion forces affect different regions of the maxilla and the effect of age on the relative magnitude of skeletal expansion versus dental tipping.[22],[23]

 Conclusions



Since its introduction, CBCT has become an increasingly important source of 3D volumetric information in clinical orthodontics. Although CBCT continues to gain popularity, its use currently is recommended in cases in which clinical examination supplemented with conventional radiography cannot supply satisfactory diagnostic information. This includes cases of impacted teeth, CL/P, and orthognathic or craniofacial surgery patients. CBCT on other types of cases such as supernumerary teeth, identification of root resorption caused by unerupted teeth, evaluating boundary conditions, TMJ degeneration, and progressive bite changes and for placement of TADs in complex situations can also be performed where there is likely to be a positive benefit-to-risk outcome. Orthodontists are advised to use their best clinical judgment when prescribing radiographs, including CBCT scans, to obtain the most relevant data using the least ionizing radiation possible.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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