Cone Beam ComputedTomography Updated

Technology for EndodonticDiagnosis

Randolph Todd, DMD

KEYWORDS

� Cone beam computed tomography � Radiographic diagnosis� 3-dimensional radiology � Radiographic outcome assessment� Root canal morphology � Endodontic diagnosis � Apical periodontitis

KEY POINTS

� Narrow field CBCT has many applications in Endodontics and reduces the negative effectsof anatomic noise, geometric distortion and technique sensitivity observed on 2D images.

� Narrow fieldCBCTprovidesearlier detectionof apical periodontitis thanconventional 2D radio-graphs providing improved diagnostic value, treatment efficiency and outcome assessment.

� Narrow field CBCT provides excellent image resolution at reduced radiation exposure ascompared to mid or large field of view CBCT.

� CBCT assists the practitioner to identify canal morphology, numbers of canals and relativepositioning even in the presence of calcific metamorphosis and dystrophic calcifications.

� Identification and treatment of lateral canals is supported by viewing their specific locationwith the use of narrow field of view CBCT before or during endodontic therapy.

INTRODUCTION

According to the Merriam-Webster dictionary, the term “diagnosis” is defined as:“the art or act of identifying a disease from its signs and symptoms.” In the field ofendodontics, dentists review a multitude of signs and symptoms to formulate theirdiagnosis. These include, but are not limited to: sensitivity to heat, sensitivity tocold, percussion, palpation, bite, swelling, caries, periodontal disease, presence of si-nus tracts, and unstimulated pain. In addition to these symptoms, tests are used toidentify variations from normal such as electric pulp tests,1 laser Doppler,2 and radio-graphs3 (first used in 1896 by Otto Walkhoff). In the early 1960s Seltzer and Bender4,5

identified several discrepancies using 2-dimensional (2D) radiographs for observing

Department of Endodontics, Stony Brook University School of Dentistry, Sullivan Hall, StonyBrook, NY 11794, USAE-mail address: drrandolphtodd@gmail.com

Dent Clin N Am 58 (2014) 523–543http://dx.doi.org/10.1016/j.cden.2014.03.003 dental.theclinics.com0011-8532/14/$ – see front matter � 2014 Elsevier Inc. All rights reserved.

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apical periodontitis (AP). These included: (a) a delayed appearance of radiographic ev-idence of AP until 40% cortical plate demineralization developed and (b) a lack of cor-relation between the size of the histologic defect and AP image.In addition, according to Durack and Patel, 2D radiographs are of limited value due

to the compression of 3-dimensional (3D) structures, geometric distortion, anatomicnoise, and temporal perspectives.4–6

Radiographs are used to identify the changes inside visually opaque objects.Although interpretations of these images are only part of the diagnostic process, thedental community places great emphasis on this information. In the early 1970s, Bry-nolf studied the benefit of using radiographs from multiple angles to increase theirdiagnostic value. She found that using 3 images improved diagnosis significantly.7

Later that decade, grave concerns developed. Many articles published supportedthe idea that reading dental radiographs was too subjective.8–10 To this concern,Orstavik and colleagues12 developed a guide to standardize apical observationscalled the Periapical Index. Despite these efforts, 2D radiographs were still limitedin diagnostic value due to the factors previously listed.4–6

Computer-assisted tomographic imaging or cone beam computed tomography(CBCT), a technology borrowed from medicine, previously focused on the need forbetter surgical guidance during implant placement.14 The principle of ALARA21 (AsLow As Reasonably Achievable) as related to radiation exposure and the lack of res-olution initially limited CBCT use in endodontics.15 A new area of research emerged,and old paradigms were shifting.17 These advances solved many of the listed 2D lim-itations.6,13 Specific applications of this technology developed and the Endodonticcommunity embraced them.18–20

The current narrow field of viewCBCTprovidesa 3D, low-radiation/high-resolution so-lution to many endodontic diagnostic and treatment problems.11 This article will displayspecific case scenarios and supporting literature for the application ofCBCT technology.

ROOTS: ANATOMIC NOISE HIDES ANATOMYCase #1: Maxillary Left First Bicuspid—Diagnosis: Pulpal Necrosis/Symptomatic ApicalPeriodontitis

Identification of root structure, curvature, and location are hampered in 2D radio-graphs by anatomic noise (Fig. 1).6 In this case, CBCT (Figs. 2 and 3) assisted with

Fig. 1. Preoperative 2D periapical x-ray, arrow pointing to hidden radicular anatomy“Anatomic Noise”.

Fig. 2. 3D CBCT sagittal view shows 2 buccal roots (arrow).

Fig. 3. 3D CBCT coronal view shows buccal and palatal roots (arrow).

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the preoperative identification of the presence, location, shape, and lengths of 3separate distinct roots. Note the accurate orientation, size, and location of apicalperiodontitis clearly observed on sagittal (see Fig. 2) and coronal views (seeFig. 3).16 Treatment is clearly supported by preoperative knowledge of rootanatomy.

CANALS: HIDDEN CANAL MORPHOLOGYCase #2: Mandibular Left First Molar, Diagnosis: Irreversible Pulpitis/SymptomaticPeriodontitis

Preoperative identification of the number, location, and length of canals is facilitatedwith a CBCT scan (Figs. 4–7). Successful endodontic treatment depends on treatingall canals (see Fig. 7).22 In tooth #19, a midmesial canal is observed on the preoper-ative axial scan (see Fig. 5) and verified clinically (see Fig. 6).

Fig. 5. 3D CBCT axial view 3 mesial canals (arrows).

Fig. 6. Axial view 3 mesial canals.

Fig. 4. Preoperative 2D view periapical x-ray.

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Fig. 7. Postoperative 2D periapical x-ray 3 mesial canals.

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CALCIFICATIONSCase #3: Maxillary Left Central Incisor Diagnosis—Pulpal Necrosis/Symptomatic ApicalPeriodontitis

Canal obliteration may represent dystrophic calcifications (DC, calcification of degen-erating or necrotic tissue pulp stones23) or calcific metamorphosis (CM, A process ofmineralization after trauma24) (Figs. 8–11). The mechanism for dentin deposition in CMhas been debated by the profession and is still unclear.25,26 It has been suggested thatthe severity of the injury may be related to the rate of deposition.27 The predominance

Fig. 8. Preoperative 2D periapical x-ray, arrow points to calcified root canal.

Fig. 9. 3D CBCT sagittal view, arrow pointing to visible canal.

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of literature suggests that despite the appearance of CM on a 2D radiograph, a narrowpulp canal space persists (see Figs. 9 and 10).26,28–30 With the development of CBCT,pretreatment identification and location of this narrow pulp space can facilitateminimally invasive treatment.

Fig. 10. Preoperative 3D CBCT axial view, arrow pointing to visible canal.

Fig. 11. Postoperative 2D periapical x-ray minimally invasive treatment.

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LATERAL CANALSCase #4: Maxillary Left Central Incisor Diagnosis—Pulpal Necrosis/Symptomatic ApicalPeriodontitis

Treatment of lateral canals requires pretreatment knowledge of their presence andlocation (Figs. 12–15).31 2D radiology does not provide adequate information to

Fig. 12. Preoperative 2D periapical x-ray.

Fig. 13. Preoperative 3D CBCT coronal view, arrow pointing to lateral canal exiting intolateral radicular defect.

Fig. 14. 3D CBCT sagittal view provides accurate measurement from apex to lateral canal(distance between arrows).

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Fig. 15. Postoperative 2D periapical x-ray, guttapercha cone in lateral canal.

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predictably locate and treat this entity.32,33 Successful endodontic treatment dependson the adequate debridement of bacteria from all spaces.31 CBCT technology assiststhe practitioner with identifying the specific location of lateral canals (see Figs. 13 and14). Overcoming the obstacle of identifying and locating lateral canals enhances theability to treat these difficult cases (see Fig. 15).34

BONE MORPHOLOGY IDENTIFIABLE ON CBCTFenestration Case #5

Identification of a fenestration can assist in planning apical surgery (Figs. 16–18).35

CBCT offers the opportunity to accurately evaluate an area of apical periodontitis

Fig. 16. 3D CBCT preoperative sagittal view—isolating buccal plate demonstrating fenestra-tion (arrow pointing to fenestration of Buccal Bone).

Fig. 17. 3D CBCT preoperative reconstructed view buccal plate demonstrating fenestration(arrow pointing to fenestration of buccal bone).

Fig. 18. Apical operative view, demonstrating fenestration observed after flap reflection(arrow pointing to fenestration of buccal bone).

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for size, volume, and location before surgery.36 Some studies find no value in apicalgrafting, while others advocate that the need for grafting is based on the volume ofthe space to be grafted.37 These studies suggest that larger lesions may not heal suc-cessfully from apical surgery without grafting, due to a lack of clot stability.38 CBCTcan be used to determine the volume of the apical periodontitis lesion. Future researchmay be able to identify the specific volumetric limits for clot stability and graft usage asopposed to the linear measurement currently used.

Dehiscence Case #6

Maxillary left second bicuspid—diagnosis: previously treated root canal/symptomaticapical periodontitis. In case #6 (Figs. 19–22), despite a careful and comprehensive ex-amination and periodontal probing, a vertical root fracture was clinically undetectable.The etiology for endodontic failure was ultimately identified with the use of a CBCT.Isolating the buccal plate defect on a coronal plane view assisted to identify the boneydehiscence (see Fig. 21). In this case, the vertical fracture was verified during the sur-gical exposure (see Fig. 22). Vertical fractures and cracks may not be visible on 3D

Fig. 19. Preoperative 2D periapical x-ray #13.

Fig. 20. 3D CBCT axial view (arrow pointing to buccal bone defect over vertical fracture).

Fig. 21. 3D CBCT sagittal view (arrows pointing to buccal bone dehiscence). The fracturemay not be visible on CBCT; look for the adjacent bone loss (arrows).

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Fig. 22. Surgical exposure of fracture and dehiscence (arrows). The fracture may not bevisible on CBCT; look for the adjacent bone loss (arrows).

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images. The Nyquest Theorem identifies the limitation of an image’s ability to identify acrack or fracture defect to equal twice the voxel size used to scan the object.39

IDENTIFYING CYSTS

A radicular cyst is a common odontogenic lesion of inflammatory origin. The ability todistinguish a cyst from a granuloma has been studied over the years.40–45 Variousstudies have suggested that the presence of an opaque lamina provides evidenceof a cyst. A study by Ricucci and colleagues46 refutes this theory. In support, oneonly needs to return to the findings of Seltzer, Bender, Bhaskar47 and more recentlyby Lalonde,40 to see that cysts, granulomas, and abscess all have a similar appear-ance on 2D radiographs. Conflicting studies have been published debating CBCT’seffectiveness to distinguish cysts from granulomas.48 In the following examples, oneobserves the lumen of the cyst42 as detected on CBCT (Figs. 23 and 24) but not visible

Fig. 23. 3D CBCT coronal view of apical periodontitis #5 with cystic lumen (arrow pointing toblack cystic lumen within gray apical defect).

Fig. 24. 3D CBCT sagittal view of apical periodontitis #5 with cystic lumen (arrow pointing toblack cystic lumen within gray apical defect).

Fig. 25. Threeviewsofan incisive canal cyst. (Data from Faitaroni LA,BuenoMR,CarvalhosaAA,et al. Differential diagnosis of apical periodontitis and nasopalatine duct cyst. J Endod2011;37(3):403–10.)

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on preoperative 2D image (Fig. 26). The question remains, however; if the lumen is notvisible, is it a granuloma? Further research is needed to clarify this issue.Case #7 Diagnosis: incisive canal cyst (Fig. 25).Case #8 Maxillary right first bicuspid—diagnosis: pulpal necrosis/asymptomatic

apical periodontitis radicular cyst (see Figs. 23, 24 and 26).

Fig. 26. Preoperative 2D image of apical periodontitis #5.

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Endodontic Recall

Endodontic healing has traditionally been verified clinically and radiographically. TheAAE 2005 definitions are described in Box 1.

Box 1

Definitions of endodontic outcomes

Healed—functional, asymptomatic teeth with no or minimal radiographicperiradicularpathosis

Nonhealed—nonfunctional, symptomatic teeth with or without radiographicperiradicularpathosis

Healing—teeth with radiographic periradicularpathosis, which are asymptomatic andfunctional, or teeth with or without radiographic periradicularpathosis, which aresymptomatic but whose intended function is not altered

Functional—a treated tooth or root that is serving its intended purpose in the dentition

Modified from Ingles’s Endodontics 6, chapter 32. Friedman S, editor. Treatment outcome: Thepotential for healing and retained function. p. 1162–232.

The outcome of endodontically treated teeth is heavily weighted on the observationof radiographic healing. The low predictive value49 of 2D radiography limits its useful-ness for evaluation of repair. 3D imaging expands the function of the recall examina-tion to include all periradicular tissues (cortical and medullary bone). The subsequentexamples apply current CBCT technology to discover the true status of all periradic-ular tissues.50 2D radiographs may indicate buccal or lingual plate healing but canmask the periradicular status. As noted by Orstavik, healing may take 1 to 4 years.45

Case #9: Healing—Diagnosis: Previously Treated Root Canal/Asymptomatic ApicalPeriodontitis

Nonsurgical retreatment was completed in 2 visits with Ca(OH)2 used as intravisitmedicament (Figs. 27 and 28). Patient returned for a 1-year routine recall (Fig. 29),asymptomatic. 2D radiographic examination revealed healed apex, while the 3Dradiograph (Fig. 30) exhibited possible reduction is size of asymptomatic apical peri-odontitis when compared with 3D preoperative images (see Fig. 28).

Fig. 27. Pre-operative 2D periapical x-ray.

Fig. 28. Pre-operative 3D.

Fig. 29. 1 year recall 2D periapical x-ray.

Fig. 30. 1 year recall 3D.

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Case #10: Healed—Diagnosis: Previous Root Canal Treatment (Missed Mesiobuccal)/Symptomatic Apical Periodontitis

Nonsurgical retreatment was completed in 2 visits (Figs. 31 and 32), with Ca(OH)2used as intravisit medicament. The patient returned 3 years after retreatment with

Fig. 31. Preoperative 2D periapical x-ray, 7/27/09.

Fig. 32. Postoperative 2D periapical x-ray, 8/27/09.

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continuous evidence of apical periodontitis on 2D radiograph. Surgical intervention(apicoectomy) was performed. One year and 18 months later, 2D (Figs. 33 and 34)and 3D screen shots exhibited healing of periradicular tissues.

Fig. 33. 1 year recall 2D periapical x-ray apicoectomy.

Fig. 34. 3D CBCT coronal view; note healed buccal plate and medullary bone (arrows).

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TRAUMA

Traumatic injuries to the dentition result in 1 of 3 outcomes. First, teeth may regain vitalresponses to tests due to revascularization. Second, teeth may remain nonresponsiveto vitality tests due to aseptic necrosis (without apical periodontitis), or third, teeth maybecome infected and develop acute or chronic apical periodontitis (Figs. 35–37).51,52

CBCT can help the clinician make an earlier diagnosis. Generally necrotic changes areevident within 3 months of the trauma.53,54 Early intervention of endodontic treatmentbased on clinical and radiographic evidence canhelp avoid tooth loss due to resorption.55

Fig. 35. 3D CBCT coronal view—fracture of anterior maxilla observed superior to canine andlateral incisor (arrows).

Fig. 36. 3D CBCT sagittal view of horizontal root fracture (arrows).

Fig. 37. 3D CBCT rendering of horizontal root fracture (arrow).

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Osseous Trauma: Case #11

A 45-year-old woman was hit in the face by a bus mirror and sustained a maxillaryfracture, avulsions and luxations of multiple teeth (see Figs. 35–37). The CBCT wasused to identify components of the maxillary fracture’s location andmorphology, ridgedefect height and width, and imaging of the temporomandibular joints.56,57

CONCLUSIONS

The previous examples identify the value of CBCT for Endodontics. Narrow fieldof view CBCT facilitates diagnosis, treatment and outcome assessment whileadhering to ALARA principles. Additional applications for this technology can be

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expected within the Endodontic field as a result of the explosion of research in theimaging field.

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