Introduction
The first CT scanner was called the “EMI-Scanner” was installed in 1972 in England and was able to making tomographic sections of the
brain (1- 3).The first "whole body" CT scanners were installed in 1976. These scanners took several hours to acquire the raw data for a single "slice"
and took days to reconstruct a single image from this raw data. In the mid 1980's, the spiral or helical scanning was innovated. Later "multi-slice"
spiral CT scanners have being developed. Cone Beam CT was first introduced in the imaging of the dental and maxillofacial region in 1997. Nowadays
CBCT scanners are widely used for various indications (1, 3).
As a result of the constant scientific research in the medical imaging field, CT scanners, have been tremendously enhanced. The latest CBCT
are patient friendly, the scan time is eliminated, as well as the the effective patient dose compared to medical CT and the provided resolution is
getting higher. High resolution means that image quality is improved. Furthermore, the latest CBCT systems need some seconds to take and
reconstruct the images. Combined with sophisticated software programs they provide us with images in 3 orthogonal planes (axial, sagittal and
coronal) (3-6).
CBCT is a useful tool for imaging the craniofacial area that produces more realistic images that facilitate interpretation. All the previous
conventional and digital intraoral and extraoral procedures, as they were two dimensional (2D) projections, suffer from several limitations. These
limitations were magnification, distortion, superimposition and misrepresentation of structures. CBCT has achived a transition of dental imaging from
2D to 3D images. Moreover, the application of sophisticated software, contribute to the reestablishment of imaging sciences role. Now
Dentomaxillofacial radiology has been expanding from the diagnosis field to image guidance of operative and surgical procedures. As a consequence
the treatment outcome is enhanced (3-5, 7,8).
REFERENCES
1.Computed tomography: http://en.wikipedia.org (Retrieved August 2009).
2.Siemens Medical: Computed Tomography. Its History and Technology.
3.Calhoun PS, Kuszyk BS, David G. Heath DG, et al: Three-dimensional Volume Rendering of Spiral CT Data: Theory and Method. Radiographics. 1999;19:745-764.
4.Scarfe WC, Farman AG, Sukovic P: Clinical Applications of Cone-Beam Computed Tomography in Dental Practice. J Can Dent Assoc 2006;72(1):75–80.
5.Scarfe WC, Farman AG : Voxel Vision using Maxillofacial CBCT: Clinical Applications of the Maximum Intensity Projection http://www.aadmrt.com/currents/scarfe_farman_summer_07_print.htm (Retrieved August 2009).
6.Flygare L, Tsiklakis K, Whaites E, Horner K: Basic Principles for Use of Dental Cone Beam CT . Consensus Guidelines of the European Academy of Dental and Maxillofacial Radiology. January 2009.
7.Scarfe W.C, Farman AG: Cone beam computed tomography: A paradigm shift for clinical dentistry. Australasian Dental Practice; July/August 2007:102-110.
8.Boeddinghaus R, Whyte A: Current concepts in maxillofacial imaging. European Journal of Radiology 1008; 66:396–418.
Dental Clinical Applications of CBCT
As with any X-ray exposure, CBCT entails a risk to the patient. It is essential that any X-ray examination should show a net benefit to the patient, weighing the total potential diagnostic benefits it produces against the individual detriment that the exposure might cause. The efficacy, benefits and risk of available alternative techniques having the same objective but involving less (or no) exposure to X-rays should be taken into account (1).
In order that the justification process can be carried out, it is essential that selection of CBCT is based on the individual patient’s history and a clinical examination. The ‘routine’ use of CBCT on patients based on a generalised approach rather than individual prescription is unacceptable. A ‘routine’ (or ‘screening’) examination is defined as one in which a radiograph is taken regardless of the presence or absence of clinical signs and symptoms (1).
Choosing CBCT for a patient should also be based upon consideration of the prevalence of diseases, their rates of progression and the diagnostic accuracy of CBCT, compared with traditional techniques, for the application in question.Consulting guidelines facilitates the process of selecting radiographs (1).
Following a range of cases that the use of CBCT became apparent during the course of the systematic review.
1.The Developing dentition
Many children seek orthodontic treatment. Usually the treatment starts at the time period of mixed dentition stage. Orthodontic patients may present abnormalities in eruption pattern, tooth position or signs of crowding. Radiographs may be required to determine the presence, absence, position and condition of teeth (1).
Justification of X-ray examinations in children is especially important because of the higher risks associated with exposure in children. Traditional radiological examination of children undergoing orthodontic assessment includes a panoramic radiograph, supplemented by a lateral cephalometric radiograph in specific circumstances. Intra-oral radiographs are also used according to patient-specific needs (1).
In recent years, however, the availability of CBCT has led to this technique being used by some clinicians as a means of radiological examination. For assessment of facial bone shape, position and inter-relationships, there must be a high accuracy of measurements made with CBCT(1).
The applications of CBCT in assessment of the developing dentition for orthodontics will be considered under two broad headings: localised applications to answer a specific question and generalised application for examination of the entire dento-facial region (1).
1.1. Localised applications of CBCT for the developing dentition
1.1.1 Unerupted tooth localization
A frequent application of CBCT is for assessment of the position of an unerupted tooth, particularly where the tooth is impacted (1,3).
Impaction is defined as a failure of tooth eruption at its appropriate site in the dental arch within the normal period of growth based on clinical and radiographic assessment. Third molars are the most frequently impacted teeth, followed by the permanent maxillary canines (2).
Impacted third molar and related symptoms is a frequent problem that the dental practitioner has to deal with. In cases that the anatomy of the third molar is not extremely abnormal and the tooth in not correlated with the mandibular canal, surgical procedure is not a hazardous. In cases concerning the lower third molar in which there is a relationship between the roots and the mandibular canal, a careful preoperative evaluation is needed. In such cases the CBCT examination could provide us with valuable information that the conventional radiographic techniques could not, due to their limitations (3-5).
In particular, it is important to know the exact position and orientation of the impacted molar, as well as its relation with other anatomical structures, prior to the tooth removal, since there is a strong possibility to occur a permanent or temporary damage to the lingual of inferior alveolar nerve (4,5).
Also the CBCT allows for a more precise analysis of the extent of the pathology related to the impacted tooth. Consequently it is possible to design treatment strategies that would result in less invasive surgical intervention (1,3-5).
1.1.2 External resorption in relation to unerupted teeth
In cases of impacted teeth, an integral aspect of the assessment is often the accurate identification of any resorption of adjacent teeth (1,3).
Root resorption is defined as a condition of dental complication associated with either a physiological or pathological activity of the tooth resorbing cells, which results in loss of cementum and /or dentine. Root resorption is very difficult to treat and usually requires extraction of the affected tooth (2).
Such a situation is most often seen where maxillary canines are ectopic and incisor roots are suspected of having undergone resorption (1-3).
For the localized assessment of an impacted tooth (including consideration of resorption of an adjacent tooth) where the current imaging method of choice is conventional dental radiography, CBCT may be used when the information cannot be obtained adequately by lower dose conventional (traditional) radiography (1).
For the localised assessment of an impacted tooth (including consideration of resorption of an adjacent tooth), the smallest volume size compatible with the situation should be selected because of reduced radiation dose. The use of CBCT units offering only large volumes (craniofacial CBCT) requires very careful justification and is generally discouraged (1).
Clinical reports using 3-dimensional imaging have shown that the incidence of root resorption of teeth adjacent to impacted teeth is greater than previously thought (2,6).
1.1.3 Application of CBCT for orthodontics
CBCT allows the 3D visualization of the craniofacial skeleton. The overlay-free visualization of structural and anatomic relationships permit the accurate evaluation of the anatomic structures (6-8).
1.1.3.1 Cleft palate assessment
Where the current imaging method of choice for the assessment of cleft palate is MSCT, CBCT may be preferred where radiation dose is lower. The smallest volume size compatible with the situation should be selected because of reduced radiation dose (1).
CBCT in patients with cleft lip and palate is useful for preoperative evaluation of the borders of the cleft, for assessment of palatal bone thickness, as well as, for the clinical assessment of bone graft quality following alveolar surgery (7,8).
1.1.3.2 Tooth position and localization (see 1.1.1)
1.1.3.3 Resorption related to impacted teeth (see 1.1.2)
1.1.3.4 Measuring bone dimensions for mini-implant placement
The mini-implants have been widely used in orthodontic practice as temporary anchorage devices. Their diameter is ≈ 1.8 mm. They can be either immediate or delayed loading. They can be positioned in many areas of the alveolar bone. It is crucial to identify the ideal site for insertion of the mini-implants. Particularly, to reassure that the placement of mini-implants will be safe and won’t cause damage to anatomical structures or teeth. Consequently, the cortical bone thickness and bone pattern are important criteria in mini-implant selection and factors that affect their stability. CBCT scanners can provide information needed to locate the ideal site for insertion of the mini-implants like, the thickness of cortical bone, the location of the maxillary sinus or inferior alveolar canal, the exact locations of the roots the inter-root distance (9,10-14).
1.1.3.5 Rapid maxillary expansion
Rapid maxillary expansion treatments have been used widely to correct maxillary transverse deficiency problems in adolescents. Limitations of the two-dimensional (2D) cephalometric radiographs such as overlapping of structures leading to landmark identification errors and measurement errors obstruct the assessment of the skeletal and dental changes that occurs after the rapid maxillary expansion. The CBCT scanning technology overcomes these obstacles and provides superior reliability and greater accuracy in the evaluation of bone changes (15,16).
1.1.3.6 3-dimensional cephalometry
Lateral and frontal cephalometric radiographs are a valuable tool for pretreatment patient evaluation, monitoring treatment response, as well as for treatment outcome assessment Moreover, by identifying specific landmarks and calculating angular and linear dimensions in cephalometric radiographs is possible to predict the growth of the craniomaxillofacial complex (6-8,10,17).
With the conventional cephalometric techniques, complex 3D structures are projected onto a 2D plane. Consequently there are restrictions including superimposition of anatomical structures which obstacles the landmark identification, magnification and distortion. Also with conventional cephalometric techniques are not provided information concerning anatomical relationships in the coronal plane (8).
Concerning the 3D landamarks, according to recent research data, narrower slices should result in better measurement accuracy, decreasing the landmark identification errors (17).
CBCT allows the 3D visualization of the craniofacial skeleton, so accurate evaluation of the anatomic structures it’s achievable. Cross-sectional slices in all 3 views of space take full advantage of the 3D CBCT information. Moreover, from the evaluation of landmarks, lines, distances and angles CBCT allows the assessment of surfaces, areas and volume. In general, CBCT is very useful for selected orthodontic and surgical patients (6,8,17).
1.1.3.7 Airway assessment
The normal airway has been described as oval shaped with a larger lateral distance compared with the anterior posterior distance (18).
CBCT technology provides a major improvement for evaluation of the airway, allowing for 3-dimensional and volumetric analysis. Airway analysis conventionally has been carried out by using lateral cephalograms.
Three-dimensional airway analysis will be useful for the understanding of more complex conditions such as obstructive sleep apnea (OSA) and enlarged adenoids (2,6,7).
1.1.3.8 Age assessment
CBCT imaging has recently been explored for orthodontic applications, including dental age estimation (7).
Age estimation of living or deceased, children, subadults or adult individuals is important in several cases. Most of the age estimation methods are based on the evaluation of tooth development in cases of children or subadults, or on age -related changes like the pulp/tooth ratio, in cases of adults correspondingly. In particular, age estimation is important in forensic cases, since criminals usually pretend to be subadults, in order to benefit from the low. Moreover, dental age estimation is crucial for cases of unaccompanied asylum seekers with no official identification documents. Yang et al (2006) have create a software to calculate the pulp/tooth volume ratio based on the cone-beam CT tooth images. This was the first study concerning dental age estimation based on CBCT images. The results of the present study were promising although the research should be continued (19).
1.1.3.9 Investigation of orthodontic-associated paraesthesia
Although paraesthesia of the lower lip, may occur after orthognathic surgery to the lower jaw, removal of mandibular third molar, dento-alveolar surgery and following endodontic treatment, it is an uncommon complication during conventional orthodontic treatment. Since paraesthesia may be associated with malignant neoplastic disease, such as Burkitt’s lymphoma, multiple myeloma, central squamous cell carcinoma, and odontomas differential diagnosis is important (20-24).
The iatrogenic lower lip paraesthesia related with orthodontic treatment usually is temporary. In such cases the tooth apices and nerves are related. The relationship of bone, root apex and neurovascular canal can be evaluated only in CBCT images and not in 2D x-rays. The mental nerve paresthesia related to orthodontic treatment is rare since usually the distal root of 2nd lower molar and the neurovascular canal are not related (20-22).
REFERENCES
1.RADIATION PROTECTION: CONE BEAM CT FOR DENTAL AND MAXILLOFACIAL RADIOLOGY. Provisional guidelines 2009 (v1.1 May 2009). A report prepared by the SEDENTEXCT project sedentexct.eu (Retrieved August 2009).
2.Alqerban A, Jacobs R, Lambrechts P, Loozen G, Willems G: Root resorption of the maxillary lateral incisor caused by impacted canine: a literature review. Clin Oral Invest 2009; 13: 247–255.
3.Palomo J. M, Kan C H, Palomo LB, Hans MG: Three-Dimensional Cone Beam Computerized Tomography in Dentistry. Dentistry Today 2006; 25(11): 130-135.
4.Flygare L,Öhman A: Preoperative imaging procedures for lower wisdom teeth removal. Clin Oral Invest 2008;12: 291–302.
5.Scarfe WC, Farman AG, Sukovic P: Clinical Applications of Cone-Beam Computed Tomography in Dental Practice. J Can Dent Assoc 2006; 72(1):75– 80.
6.Kau C. H, Richmond S, Palomo J. M, Hans M. G: Current Products and Practice. Three-dimensional cone beam computerized tomography in orthodontics. Journal of Orthodontics 2005;32: 282–293.
7.Miracle AC, Mukherji SK: Conebeam CT of the Head and Neck, Part 2:Clinical Applications. Am J Neuroradiol 2009; 10.3174/ajnr.A1654
8.Kumar V, Ludlow JB, Mol A , Cevidanes L: Comparison of conventional and cone beam CT synthesized cephalograms. Dentomaxillofacial Radiology 2007; 36: 263–269.
9.Baumgaertel S, Hans MG. Buccal cortical bone thickness for mini-implant placement Am J Orthod Dentofacial Orthop 2009;136(2);230-235
10.Harrell W.E: Three-dimensional diagnosis & treatment planning: The use of 3D facial imaging and 3D cone beam CT in orthodontics and dentistry. Australasian Dental Practice. July/August 2007;102-113
11.Kim SH, Yoon HG, Choi YS, Hwang EH, Kook YA, Nelson G: Evaluation of interdental space of the maxillary posterior area for orthodontic mini- implants with cone-beam computed tomography. Am J Orthod Dentofacial Orthoped 2009;5: 635-641.
12.Gracco A, Lombardo L, Cozzani M, Siciliani G. Quantitative evaluation with CBCT of palatal bone thickness in growing patients. Prog Orthod
2006;2:164-174.
13.Gonzalez SM: Cortical bone thickness of the maxilla and mandible for mini-implant placement. Master Thesis University of Iowa 2008 (Retrieved August 2009 from http://ir.uiowa.edu/etd/36).
14.Christensen GJ: The ‘mini’-implant has arrived. JADA 2006; 137: 387-390.
15.Lagravèrea MO, Gordonb JM, Guedesc IH, Mird CF, Careye JP, Heof G, Majorg PW Reliability of Traditional Cephalometric Landmarks as Seen in Three-Dimensional Analysis in Maxillary Expansion Treatments. Angle Orthod. 2009;79:1047–1056.
16.Osorio F, Perilla M, Doyle DJ, Palomo JM: Cone Beam Computed Tomography: An Innovative Tool for Airway Assessment. Anesthesia and Analgesia 2008;106(6):1803- 1807.
17.de Oliveira A E, Cevidanesn LHS, Phillips C, Motta A, Burke B, Tyndall D: Observer reliability of three-dimensional cephalometric landmark identification on cone-beam computerized tomography. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;107:256-265.
18.Garrett BJ, Caruso JM, Rungcharassaeng K, Farrage JR, Kim JS, Taylor GD: Skeletal effects to the maxilla after rapid maxillary expansion assessed with cone-beam computed tomography.Am J Orthod Dentofacial Orthoped 2008;134(1):1-11.
19.Yang F,Jacobs R, Willems G: Dental age estimation through volume matching of teeth imaged by cone-beam CT. Forensic Science International 2006; 159S:S78–S83.
20.Erickon M, Caruso JM, Leggitt L: Newtom QR-DVT 9000 Imaging Used to Confirma Clinical Diagnosis of Iatrogenic Mandibular Nerve Paresthesia. JCDA 2003; 31: 843-845.
21.Krogstad O, Olmand G: Temporary paresthesia of the lower lip: a complication of orthodontic treatment. A case report. British Journal of Orthodontics 1997; 24:13–15.
22.Tang NC, Selwyn-Barnett BJ, Blight SJ: Lip paraesthesia associated with orthodontic treatment--a case report. Br Dent J. 1994;176:29-30.
23.Willy PJ, Brennan P, Moore J: Temporary mental nerve paraesthesia secondary to orthodontic treatment--a case report and review. Br. Dent.J.2004; 196:83-4.
24.Baxmann M: Mental paresthesia and orthodontic treatment. Angle Orthod. 2006 May;76:533-7.
1.2 Generalized application of CBCT For the developing dentition
Diagnosis and treatment planning of craniofacial anomalies involve the processes of visualization and analysis. In these processes, deviations from the norm, asymmetries and affected structures are realized for comprehensive treatment planning (1).
For complex cases of skeletal abnormality, particularly those requiring combined orthodontic/surgical management, large volume CBCT may be justified in planning the definitive procedure, particularly where MSCT is the current imaging method of choice (2).
There are patients with Craniomaxillofacial malformations that might be acquired or congenital. Acquired malformations are usually the result of trauma or the sequelae of surgical resection of tumours with no or inadequate primary reconstruction. There are several syndromes which present typical craniomaxillofacial deformities. Congenital or developmental malformations may be symmetric or asymmetric in nature (3).
CBCT combined with state-of-the-art orthodontic software programmes allows more accurate and relatively low dose analysis of symmetric maxillofacial skeletal and dental discrepancy. Also CBCT is useful for optimal evaluation of the extent of deformity (3).
The commonest causes of asymmetric deformity are under or over-activity of one of the condylar growth centres in the growing skeleton resulting in hypoplasiaor hyperplasia of the affected condyle. When unilateral condylar hypoplasia is suspected, hemifacial microsomia requires exclusion (3).Imaging plays an important role in the diagnosis of craniosynostosis (4).
The cervical spine is a structural feature often included in CBCT scans of the maxillofacial region, particularly with larger field of view protocols. It is not routinely imaged. However it is important to recognize that congenital anomalies of the cervical spine have been associated with osteogenesis imperfecta and with various craniofacial anomalies including Crouzon24 and Pfeiffer's25 syndromes, hemifacial microsomia26 and, in particular, Goldenhar's Syndrome (4).
REFERENCES
1.Enciso R, Shawa A, Neumann U, Maha J: 3D head anthropometric analysis In SPIE Medical Imaging, San Diego,California 2003.
2.RADIATION PROTECTION: CONE BEAM CT FOR DENTAL AND MAXILLOFACIAL RADIOLOGY. Provisional guidelines 2009 (v1.1 May 2009). A report prepared by the SEDENTEXCT project sedentexct.eu (Retrieved August 2009).
3.Boeddinghaus R, Whyte A: Current concepts in maxillofacial imaging. European Journal of Radiology 2008; 66:396–418.
4.Scarfe WC, Farman AG : Voxel Vision using Maxillofacial CBCT: Clinical Applications of the Maximum Intensity Projection http://www.aadmrt.com/currents/scarfe_farman_summer_07_print.htm (Retrieved August 2009).
2. Restoring the adult dentition
2.1. Dental caries diagnosis
CBCT should not be used as a routine method of caries detection and diagnosis (1). Where CBCT images include the teeth, care should be taken to check for caries when performing a clinical evaluation (report) (1).
According to some researchers CBCT has been evaluated for the detection of carious lesions and has shown better results than F-speed film in assessing the depth of proximal lesions (2).
2.2 Periodontal assessment
The diagnosis of periodontal diseases depends on a clinical examination. This may be supplemented by radiological examination if this is likely to provide additional information that could potentially change patient management or prognosis. Radiographs do not have a role in diagnosis of periodontal disease,but are used as a means of demonstrating the hard tissue effects of periodontal disease, particularly the bony attachment loss (1).
CBCT should not be used as a routine method of imaging periodontal bone support. CBCT may be useful in selected cases of infra-bony defects and furcation lesions, where clinical and conventional radiographic examinations do not provide the information needed for management. Where CBCT images include the teeth, care should be taken to check for periodontal bone levels when performing a clinical evaluation (report) (1).
2.3 Assessment of periapical disease
CBCT allow the clinician to diagnose the presence and expansion of periradicular lesions in each root of a multirooted tooth. This is not possible with the conventional techniques (3).
2.4 Endodontics
Radiographs are 2D representations of 3D structures, so it is impossible to reflect accurately the anatomy and morphology of the teeth. CBCT scanners overcoming the limitations of 2D techniques, produce images of high diagnostic quality. Consequently, CBCT images enable the visualization of the anatomic complexity, disturbances in the typical morphology ipresence of material in the root canal, and progression, regression and maintenance of apical periodontitis (4).
There are a number of Endodontic applications of CBCT.
2.4.1 Differentiation of pathosis from normal anatomy
Misinterpretation of the radiographs may be related to several factors, such as morphological variations, surrounding bone density, x-ray angulations, image contrast. The use of CBCT in endodontics is fundamental in aiding the identification of essential anatomic structures and periapical lesions. Moreover, CBCT images enable the clinician to identify anatomic and pathologic alterations, that where unattainable to evaluate, with 2D radiographs. This is of a major importance since the incidence of false-negative results has been reduced (4).
2.4.2 Relationships with important anatomical structures
The use of CBCT in endodontics is fundamental in the identification of essential anatomic structures and their relation with periapical lesions, as well the root apex (4).
2.4.3 Aiding management of dens invaginatus and aberrant pulpal anatomy
Malformed teeth might occur as a result of problems, like trauma, during the development of the teeth. Functional, orthodontic, or esthetic reasons necessitate endodontic and surgical treatment of these teeth (5).
Deviations from the normal teeth anatomy cause difficulties to diagnose and treatment. CBCT due to the amount of detailed information that can provide, and the visualization of root morphology in three dimensions leads to the accurate diagnosis, treatment planning and follow up of teeth with aberrant anatomy (5-10).
2.4.4 External resorption
Although the etiology of the resorption is unclear,several possible etiologic factors for root resorption have been identified, such as trauma. Root resorption is a frequent complication of dento-alveolar trauma. Types of root resorption that have been associated with traumatic injuries are, repair-related (surface), infection-related (inflammatory), ankylosis-related (osseous replacement) or extraradicular invasive cervical resorption. Prognosis is poor when resorption continues without diagnosis. The treatment and prognosis of the resorption is related to its location and extension. CBCT images are essential for the treatment planning since they allow the accurate visualization of the true extent of the lesion including location and severity of the root resorption. These parameters are not attainable with 2D images, particularly in early or mild resorption cases, due to many structures overlapping (10-14).
2.4.5 Internal resorption
Internal resorption is a structural change of the tooth that usually appear as a widening of the root canal. CBCT is a useful diagnostic tool that allows the accurate diagnosis and assessment of the resorption in order to determine the treatment complexity and expected outcome based on the location and extension of the root defect (10,12).
2.4.6 Lateral root perforation by a post
Iatrogenic root perforation may be caused by a post or by a fractured instrument. While 2D images provide inadequate information concerning the bucco-lingual dimension, CBCT images allow the three dimensional examination of the perforation. So the location and morphology of the perforation could be examined (15).
2.4.7Accessory canal identification
The high resolution of CBCT images makes it perfect in detecting accessory root canals. CBCT images allow the three dimensional examination of the root canals, so the exact location and the morphology of the accessory canal could be easily identified (10).
2.4.8 Root Fractures
Vertical root fractures are common in teeth with root canal treatment. Due to the limitations of 2D images such as superimposition, root fractures are not always visible. The high resolution of CBCT images confirm the presence and position of root fractures (10,16,17).
2.4.9 Surgical management of fractured instrument
The success of broken instrument removal from root canals depends on several factors such as, the length and site of the fragment. The high resolution of CBCT images allows accurate presurgical planning in cases of fractured instrument. In particular, CBCT will enable endodontists to clinically
simulate procedures, to select tools and techniques, and to perform a benefit/risk analysis before removal of a separated instrument (10,17).
2.4.10 Aiding surgical endodontic planning
Cone beam CT is helpful for diagnosis and treatment planning in endodontic surgery. In particular, allows the accurate evaluation of root morphology, the identification of the important anatomical structures of the area and their relation with periapical lesions (15,17).
2.5 Dental Trauma
Trauma to teeth and alveolar bone is a fairly common event faced by dentists in clinical practice. CBCT may be justifiable in the assessment of dento-alveolar trauma in selected cases, where conventional radiographs provide inadequate information for treatment planning (1). In particular CBCT images allow to identify dental root fractures, and the displacement of anterior maxillary teeth, luxation injuries, avulsion root resorption as a post-trauma complication (1,17,18).
REFERENCES
1. RADIATION PROTECTION: CONE BEAM CT FOR DENTAL AND MAXILLOFACIAL RADIOLOGY. Provisional guidelines 2009 (v1.1 May 2009). A report prepared by the SEDENTEXCT project sedentexct.eu (Retrieved August 2009).
2. Palomo J. M, Kan C H, Palomo LB, Hans MG: Three-Dimensional Cone Beam Computerized Tomography in Dentistry. Dentistry Today 2006; 25(11): pp 130-135.
3. Nakata K, Naitoh M, Izumi M, InamotoK, Ariji E, Nakamura H: Effectiveness of Dental Computed Tomography in Diagnostic Imaging of Periradicular Lesion of Each Root of a Multirooted Tooth: A Case Report. Journal of Endodontics 2006;32(6):583-587).
4. Estrela C, Bueno MR, Sousa-Neto MD, Pecora JD: Method for Determination of Root Curvature Radius Using Cone-Beam Computed Tomography Images Braz Dent J 2008; 19(2): 114-118.
5. Ballal S, Sachdeva GS, Kandaswamy D: Endodontic Management of a Fused Mandibular Second Molar and Paramolar with the Aid of Spiral Computed Tomography: A Case Report 2007;33(10):1247-1251.
6. Nair MK, Nair UP: Digital and Advanced Imaging in Endodontics: A Review. J Endodontics 2007; 33(1):1-6.
7. Rouas P, Nancy J, Bar D: Identification of double mandibular canals: literature review and three case reports with CT scans and cone beam CT. Dentomaxillofacial Radiology 2007; 36: 34-38.
8. De Vos W, Casselman J , Swennen G.R.J:Cone-beam computerized tomography (CBCT) imaging of the oral and maxillofacial region: A systematic review of the literature. International Journal of Oral and Maxillofacial Surgery 2009;38(6):609-625
9. Matherne RP, Angelopoulos C, Kulild JC, Daniel Tira D: Use of Cone- Beam Computed Tomography to Identify Root Canal Systems In Vitro.
J Endodontics 2008;34(1):87-89.
10. Cohenca, N, Simon J, Mathur A, Malfaz JM: Clinical indications for digital imaging in dento-alveolar trauma. Part 2: root resorption. Dental Traumatology 2006; 23(2):105-113.
11. Nakata K, Naitoh M, Izumi M, Ariji E, Nakamura H: Evaluation of Correspondence of Dental Computed Tomography Imaging to Anatomic Observation of External Root Resorption. J Endodontics 2009;35(11):1594-1597.
12. Patel S, Dawood A:.The use of cone beam computed tomography in the management of external cervical resorption lesions. Int Endod J. 2007;40(9):730-7.
13. Patel S, Dawood A, Wilson R, Horner K, Mannocci F. The detection and management of root resorption lesions using intraoral radiography and cone beam computed tomography - an in vivo investigation. International Endodontic Journal 2009; 42: 831-838.
14. Alqerban A, Jacobs R,Lambrechts P, Loozen G, Willems G: Root resorption of the maxillary lateral incisor caused by impacted canine: a literature review. Clin Oral Invest DOI 10.1007/s00784-009-0262-8
15. Tsurumachi T, Honda K: A new cone beam computerized tomography system for use in endodontic surgery. International Endodontic Journal, 2007;40: 224–232.
16. Hassan B, Metska ME, Ozok AR, van der Stelt P, Wesselink PR: Detection of Vertical Root Fractures in Endodontically Treated Teeth by a Cone Beam Computed Tomography Scan. Journal of Endodontics 2009; 35(5): 719-722.
17. Yuan G, Ove PA, Hongkun W, Xuedong Z: An Application framework of Three-dimensional reconstruction and measurement for endodontic research. Journal of Endodontics 2009; 35(2):269-274.
18. Miracle AC, Mukherji SK: Conebeam CT of the Head and Neck, Part 2: Clinical Applications. Am J Neuroradiol 2009; 10.3174/ajnr.A1654.
2.5 Surgical applications
2.5.1 Exodontia
Successful surgical planning of impacted teeth depends on accurate
localization, detecting the orientation, depth and angulation and appreciation of proximity and relationship to other anatomic structures. CBCT is of great value in the assessment of impacted teeth, providing the clinician with the ability to generate multiple 3D image projections at various angles with inherent image transparency (1).
For the localised assessment of an impacted tooth (including consideration of resorption of an adjacent tooth) where the current imaging method of choice is conventional dental radiography, CBCT may be used when the information cannot be obtained adequately by lower dose conventional (traditional) radiography (2).
Deeply impacted mandibular third molar teeth are often intimately related to the inferior alveolar canals, which may groove or perforate the roots, and be displaced and narrowed by them. Damage to the inferior alveolar nerve during extraction of impacted third molars results in permanent paraesthesia of the lower lip. Maxillary canines are also frequently impacted, as are supernumerary teeth, the commonest of which is the mesiodens, situated immediately adjacent to the midline nasopalatine canal, and frequently inverted (1-3).
2.5.2 Implant dentistry
In investigating an implant site, a surgeon requires information on bone volume and quality, topography and the relationship to important anatomical structures, such as nerves, vessels, roots, nasal floor, and sinus cavities (2,4). In 2002, a Working Group of the European Association of Osseointegration (EAO) devised consensus guidelines on imaging for implant dentistry (2,4). They did not include any comment on CBCT. They did, however, describe criteria for use of “cross-sectional imaging” (at that time, spiral tomography and conventional CT). The EAO guidelines made the following key points:
• Clinicians should decide if a patient requires cross-sectional imaging on the basis of the clinical examination, the treatment requirements and on information obtained from conventional radiographs.
• The technique chosen should provide the required diagnostic information with the least radiation exposure to the patient.
• “Standard” imaging modalities are combinations of conventional radiographs.
• Cross-sectional imaging is applied to those cases where more information is required after appropriate clinical examination and standard radiographic techniques have been performed.
The SedentextCt GDP recommends that the European Association for Osseointegration reviews its 2002 consensus guidelines on the use of imaging in implant dentistry to take into account the availability of CBCT (2).
The use of CBCT is not recommended as a routine imaging technique for all implant cases (2).
CBCT is justified for cross-sectional imaging prior to implant placement as an alternative to existing cross-sectional techniques where the radiation dose is shown to be lower (2).
The advantage of CBCT with adjustable fields of view, compared with conventional CT, becomes greater where the region of interest is a localised part of the jaws, as a similar sized field of view can be used (2).
While the emphasis has been on assessment of bone quantity, there is interest in bone quality assessment using CBCT. Current work by members of the SEDENTEXCT consortium suggests that density values from CBCT are variable and not reliable. The GDP considered that, in view of the wide variety of CBCT units and software available, they could not make a recommendation in support of quantitative bone quality assessment from CBCT (2).
Within the mandible, the critical structure is the inferior alveolar canal: if this is breached at implant placement, permanent paraesthesia of the lower lip may result. The inferior alveolar canal is usually visible, or its position can be inferred from aniche in the lingual cortex. The depth of the submandibular fossa can be assessed. If insufficient bone remains in the mandible, anterior implants can be placed mesial to the mental foramina, and these can be used to support an overdenture. The canal for the incisive artery, mesial to the mental foramina, must not be mistaken for the inferior alveolar canal (3-5).
Within the anterior maxilla, the degree of proclination of the alveolar ridge can be assessed, and the size of the nasopalatine canal and its relationship to the proposed implant site noted. If the labiopalatal width is narrow, a buccal bone graft may be placed prior to the first stage of implant placement. Within the posterior maxilla, alveolar bone width is usually adequate, but bone height is often markedly reduced. A maxillary sinus lift procedure, with placement of bone graft in a subperiostial position in the sinus floor, may be used to supplement bone height prior to implant placement. Therefore, antral disease and inferior antral septations should always be noted (3).
In conclusion, cross-sectional imaging techniques can be an invaluable tool during preoperative planning for dental implantation procedures since they provide us with information concerning all structures (the mandibular and alveolar bone morphology, the maxillary sinuses, incisive canal, mandibular canal, and mental foramina) particularly important in surgical planning for dental implantation. CBCT images have contribute to improved clinical success of implant prostheses and led to more accurate and aesthetic outcomes in oral rehabilitation (5-7).
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2.5.3 Bony pathosis
Occasionally, a dentist may be presented with a patient with an unusual bony lesion. Cysts, tumours and a wide range of esoteric lesions can present in the jaws causing symptoms and/or clinical signs; some may only be detected by chance on conventional radiography (2).
Where it is likely that evaluation of soft tissues will be required as part of the patient’s radiological assessment, the appropriate imaging should be conventional medical CT or MR, rather than CBCT (2).
Imaging of acute maxillofacial infection with OPG or intraoral images provide excellent evaluation of the lesion and helps to exclude an odontogenic cause for infection in most cases (3). CBCT is required for optimal evaluation of suspected serious or complicated maxillofacial infection. Information is provided concerning: the source of infection, the extent of the disease, the presence of an abscess and complications. In particular, CBCT provide us with information concerning the actual size of the lesion, its spatial relationship with anatomic landmarks and how far the lesion may extended from the oral cavity into the base of the skull, cervical, spine, paranasal sinuses or nasopharynx. Also, identifies the pattern and the content of a lesion. All these information provided by CBCT images, lead to a more accurate diagnosis between inflammatory lesions of the jaws (Osteomyelitis Bisphosphonates osteonecrosis, Osteoradionecrosis), cysts (Periapical, Follicular/Dentigerous, Keratocyst, Incisive canal, Stafne’s ,Traumatic bone, Residual), Odontogenic tumors ( Ameloblastoma, Odontoma, Cementoma, Pindborg tumor, Odontogenic Myxoma), non Odontogenic Tumors (Osteoma,Giant cell tumor/granuloma, Neurofibroma), other bening conditions (Fibrous Dysplasia, Thalassemia,), malignant lesions (Squamous cell Carcinoma, Metastatic tumors, Osteosarcoma – Chondrosarcoma, Mucoepidermoid carcinoma, Malignant Lymphoma,Ewing Sarcoma) and systemic disease manifestations in the jaws (Osteoporosis, Hyperparathyroidism) (3,10,11).
Concerning periapical lesions, CBCT cannot be used to distinguish scar tissue from an inflammatory granuloma. Therefore, one may question whether all CBCT detected radiolucencies are true lesions (8). According to a recent study, when a lesion was diagnosed by CBCT, 100% of the cases were periapically inflamed histologically (9).
Cysts mimic periapical lesions. In particular, some lesions in the jaws may present difficulties in the differential diagnosis with periapical lesions because they are relatively well-circumscribed radiolucent lesions. The most common are the non-endodontic odontogenic cysts such as, the lateral periodontal cysts, the odontogenic keratocysts, and the dentigerous cyst. The odontogenic keratocysts presents propensity for recurrence and aggressive behaviour. Among the other lesions are the non-odontogenic developmental cysts (as nasopalatine canal cyst and the Stafne’s cyst), the traumatic bone cysts and some forms of ameloblastoma (10).
Benign aggressive lesions includes, central ossifying fibroma, Pindborg tumour, Langerhans cell disease, osteoblastoma and the central odontogenic fibroma. The lesion that usually have been mistaken for periapical disease is the central giant-cell granuloma. The giant cell granuloma occurs more often in the mandible (anterior) and has the radiographic appearance of an irregular radiolucent area that may be unilocular or multilocular and tend to resorb the roots of adjacent teeth. Since these lesions are bening, misdiagnosis of these lesions would only result in a more extensive bone destruction.
Fibro-osseous lesions includes cemental dysplasia which is the most common sclerotic lesion of the jaws. Cemental dysplasia is considered one of the possible manifestations of cemento-osseous dysplastic/ reactive lesions of the jaws and is predominantly located in the mandible. The initial phase is always radiolucent and at this stage the distinction from periapical lesions may be difficult. A second stage shows a complex radiographic appearance with a progressive development of coalescent radiopacities; in the final stage the lesion is predominantly radiopaque. It is important to differentiate cemental lesions from odontomas and also important to distinguish cemental dysplasia from fibrous dysplasia, which is a generalized dysplastic condition. CBCT provide us the information that are crucial for the differential diagnosis and the treatment planning of these lesions (10).
A wide range of primary or metastatic malignant lesions may be located in the jaws. The presence of root resorption, irregular radiolucency, localized tooth mobility, anesthesia, tooth vitality and failure of the periapical lesion to resolve after root canal treatment are factors that are related with malignant lesions. Also the clinician must be aware that people who have metastases to the jaws often have vague or innocuous symptoms that can mimic dental infections (10-12).
2.5.4. Trauma
Trauma to teeth and alveolar bone is a fairly common event faced by dentists in clinical practice. CBCT may be justifiable in the assessment of dento-alveolar trauma in selected cases, where conventional radiographs provide inadequate information for treatment planning (2).
CBCT is an excellent tool for detecting radiographically occult fractures, or fractures suspected on the basis of secondary signs, such as a sinus air–fluid level, and for defining the displacements of fractures prior to surgical reduction and fixation (3).
The most common fractures of the maxillofacial region located to the nasal bone and are generally adequately assessed clinically or by plain radiographs. Lateral midfacial fractures including zygomatic complex fractures which are the second commonest facial fractures (after nasal fractures), are detecting more accurately with CBCT. Furthermore, CBCT is useful for detecting central midfacial fractures include naso-orbito-ethmoidal fractures, isolated maxillary fracture the classic Le Fort fractures (type I, a “floating palate”; type II a pyramidal fracture; and type III, complete craniofacial dysjunction) (3).
Mandibular fractures are common. They may be not seen clearly onOPG’s, so full evaluation requires CBCT scanning. Especially concening the condyle, which is not always clearly visualised, and CT may be necessary to demonstrate undisplaced fractures. CBCT may also reveal fractures of the condylar neck or head which can result in a characteristic post-traumatic deformity. Condylar fractures are frequently bilateral or associated with a contralateral body fracture (3).
CBCT imaging is useful also in preoperative characterization of mandibular and orbital floor fractures. In orbital floor fractures, although CBCT can demonstrate orbital content herniation, it lacks the contrast resolution to differentiate the tissue composition of the herniated materials. Lately, they have been used intraoperative C-arm CBCT systems in order to evaluate fractures of the zygomaticomaxillary complex. These navigated systems make possible the localization of bony fragments, the evaluation of screw anchorage and plate fittings (6).
2.5.5 Orthognathic surgery
Large volume CBCT should not be used routinely for orthodontic diagnosis. For complex cases of skeletal abnormality, particularly those requiring combined orthodontic/surgical management, large volume CBCT may be justified, particularly where MSCT is the current imaging method of choice (2).
CBCT images provide valuable information in cases of orthognathic surgery especially concerning patients with congenital deformities in the oral and maxillofacial region or malocclusions. Using CBCT images and DICOM (Digital Imaging and Communications in Medicine) compliant software, three-dimensional objects can be prepared by using preset intensity levels of soft and hard tissue. Once this is accomplished, the clinician canview the object’s skeletal or soft-tissue surfaces by themselves or together. CBCT images grate a potential to link equal pre-treatment expectations with posttreatment results (13).
2.5.6 Temporomandibular joint
CBCT images allow to view the temporomandibular joint complex without interference from surrounding dense temporal tissues (13).
The overwhelming majority of patients with symptoms and signs related to the temporomandibular joint (TMJ) are suffering from myofascial pain/dysfunction or internal disc derangements. Bony abnormality is not seen in the former and only occasionally in the latter. In such cases, radiographs do not add information of relevance to management. Where imaging of the TMJ disc is needed, Magnetic Resonance Imaging is the method of choice (2).
Other pathoses encountered in the TMJ include osteoarthrosis and rheumatoid arthritis. In both these conditions, there are often bony changes that may be detectable on conventional radiographs and CBCT. When considering the justification for CBCT, however, the clinician should consider whether the information obtained will alter the management of the patient. The identification of bony erosions, remodelling or deformity may be purely documentary and have no impact on treatment strategy (2,14).
Internal disc derangement (IDD) is common, and may be seen in asymptomatic temporomandibular joints. Longstanding IDD and the associated arthropathy may progress to osteoarthritis (OA), which is usually apparent on panoramic tomography and MRI, but is optimally visualised with CBCT. Fibrous and bony ankylosis, tumours and tumour-like conditions in the region of the TMJ include osteochondromas and synovial chondromatosis are also well seen with CBCT (3,6,13).
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