Accuracy of Orthopantomography for Apical Periodontitis without Endodontic Treatment

Accuracy of Orthopantomography for Apical Periodontitis without Endodontic Treatment

Clinical Research Accuracy of Orthopantomography for Apical Periodontitis without Endodontic Treatment Cosimo Nardi, MD,* Linda Calistri, MD,* Silvia...

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Clinical Research

Accuracy of Orthopantomography for Apical Periodontitis without Endodontic Treatment Cosimo Nardi, MD,* Linda Calistri, MD,* Silvia Pradella, MD, PhD,* Isacco Desideri, MD,† Chiara Lorini, PhD,‡ and Stefano Colagrande, MD* Abstract Introduction: This study aimed to evaluate the diagnostic accuracy of orthopantomography (OPT) for the detection of clinically/surgically confirmed apical periodontitis (AP) without endodontic treatment using cone-beam computed tomographic (CBCT) imaging as the reference standard. Methods: One hundred twenty patients without endodontically treated AP (diseased group) were detected via CBCT imaging using the periapical index system. They were divided into groups of 10 each according to the size of the lesion (2–4.5 mm and 4.6–7 mm) and the anatomic area (incisor, canine/premolar, and molar) in both the upper and lower arches. Another 120 patients with a healthy root and periapex (healthy group) were selected. Each diseased and healthy patient underwent OPT first and a CBCT scan within 40 days of the OPT. The periapical index system was also used to assess AP by OPT. Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy for OPT images with respect to CBCT imaging were analyzed. The k value was calculated to assess both the interobserver reliability for OPT and the agreement between OPT and CBCT imaging. Results: OPT showed low sensitivity (34.2), negative predictive value (59.3), and diagnostic accuracy (65.0) and high specificity (95.8) and positive predictive value (89.1). Interobserver reliability for OPT was substantial (k = 0.71), and agreement between OPT and CBCT imaging was fair (k = 0.30). The best and worst identified AP were located in the lower molar area and the upper/lower incisor area, respectively. Conclusions: OPT showed high specificity and positive predictive value. However, overall, it was not an accurate imaging technique for the detection of untreated AP, especially in the incisor area. (J Endod 2017;-:1–7)

Key Words Apical periodontitis, cone-beam computed tomographic imaging, diagnostic accuracy, orthopantomography, panoramic radiography, periapical index

A

pical periodontitis (AP) Significance is a periapical bone Apical periodontitis is a very common and often lesion arising from an endasymptomatic clinical problem that has to be odontic infection determined treated, especially when anticancer therapy is by microorganisms peneexpected. Therefore, there should be a reliable trating into the root canal imaging technique available to detect apical up to the apex (1). The periodontitis. Can OPT fulfill this task? defense mechanism in the apical periodontium leads to resorption of the apical bone, which appears as a radiolucency around the root on radiographs (2, 3). AP is often asymptomatic and generally recognized by incidental findings during routine radiographic examinations using periapical radiography and orthopantomography (OPT) (4). These techniques have significant limitations because of 2-dimensional imaging of 3-dimensional structures, anatomic noise, superimposition, and geometric distortion effect (5–7). In addition, to be radiographically visible, periapical radiolucency should reach nearly 30%–50% of the bone mineral loss (8). For all these reasons, AP might be present even when it is not radiographically identified (9). This is especially the case if AP is confined within the cancellous bone, without the involvement of the cortical bone (10–12). Recently, cone-beam computed tomographic (CBCT) imaging has proven to perform well for the volumetric study of bone structures (13), including the detection of periapical bone lesions (14–16). Furthermore, CBCT imaging involves a low radiation dose compared with multislice computed tomographic imaging (17), is only moderately affected by metal artifacts (18), offers a high spatial resolution (0.075–0.4 mm isotropic voxel) (19), and allows accurate 2-dimensional/3dimensional measurements without distortion and magnification (20–22). Nevertheless, the routine use of CBCT imaging in endodontic practices is not justified (23). This imaging technique must be performed only in patients with unclear or contradictory clinical signs and symptoms using a small field of view (FOV) (24). Biopsy represents the only way to get a histologic confirmation of AP, but it is an invasive procedure and complications can occur. Therefore, definite indices based on the radiologic features of the periapical bone lesions are generally used to detect and classify AP in routine clinical practice (25–27). Only 1 article compared the accuracy of OPT and CBCT imaging for the assessment of AP (28) although it did not distinguish among lesions of different sizes. The aim of this retrospective study was to evaluate the diagnostic accuracy of OPT in the detection of clinically/surgically confirmed AP without endodontic treatment using CBCT imaging as the reference standard.

From the *Department of Experimental and Clinical Biomedical Sciences, Radiodiagnostic Unit n. 2 and †Department of Experimental and Clinical Biomedical Sciences, Radiotherapy Unit, University of Florence–Azienda Ospedaliero-Universitaria Careggi; and ‡Department of Health Science, University of Florence, Florence, Italy. Address requests for reprints to Dr Cosimo Nardi, Dipartimento di Scienze Biomediche Sperimentali e Cliniche, Radiodiagnostica 2, Universita di Firenze, AOU Careggi, Largo Brambilla 3, Firenze 50134, Italy. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2017 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2017.06.020

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Clinical Research Material and Methods Patients Between November 2011 and December 2016, we selected from our CBCT database all patients with at least 1 not endodontically treated radiolucent periapical bone lesion using the following key words: radiolucent periapical bone lesion, apical periodontitis, endodontically

treated, root canal treatment, and size (Fig. 1). One hundred twenty patients (67 women and 53 men) 22–84 years old (mean age = 57 years) were enrolled in the disease group. One AP lesion was selected for each of them. The clinical queries for the CBCT examinations were implant planning (76 patients), dental extractive planning (34 patients), and focal bone lesions (10 patients). This study was approved by the research ethics committee, and informed written consent was obtained

Records identified by CBCT database searching 247 patients with: - at least one not endodontically treated radiolucent periapical bone lesion from 2 mm to 7 mm - OPT carried out during the earlier 40 days - 51 patients without an endodontic infection clinically confirmed or a periapical infection surgically removed

196 patients with 272 clinically/surgically confirmed AP and assessed by two radiologists - 13 AP with no agreement on PAI values between the two radiologists

259 AP with concordant PAI values between the two radiologists

- 25 AP with PAI 2-3

234 AP with PAI 1 or PAI 4-5

72 canines/premolars

111 molars

16 upper arch, 2-4.5 mm

31 upper arch, 2-4.5 mm

49 upper arch, 2-4.5 mm

11 upper arch, 4.6-7 mm

13 upper arch, 4.6-7 mm

16 upper arch, 4.6-7 mm

14 lower arch, 2-4.5 mm

18 lower arch, 2-4.5 mm

33 lower arch, 2-4.5 mm

10 lower arch, 4.6-7 mm

10 lower arch, 4.6-7 mm

13 lower arch, 4.6-7 mm

51 incisors

Selection of AP: - only one lesion per patient - better visual assessment (i.e. high image quality without motion or metal artifacts) - shorter period of time between CBCT and OPT

10 AP for each arch and size

10 AP for each arch and size

10 AP for each arch and size

120 AP enrolled by CBCT by two radiologists, subsequently assessed by OPT by others three radiologists

Figure 1. A flowchart of the selection criteria for enrolling patients and AP.

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Clinical Research Hi-Res-Regular and Hi-Res-Enhanced by the producer, lasting 26 and 36 seconds and comprising 360 and 480 basis image frames, respectively. Furthermore, they had a small FOV (6  6 cm or 8  8 cm), 110 kV, and 7.1–14.3 mA. All CBCT volumes were reconstructed with a 0.15-mm isometric voxel size. OPT and CBCT images were displayed on a 20-inch medical monitor with a 3-megapixel Barco display (Barco, Kortrijk, Belgium) and 2048  1536 resolution. The software programs originally supplied with the systems were used for image evaluation.

Figure 2. Cutout OPT that shows both a tooth without the crown and the other structures within the range of 8 mm mesially and distally from the root apex.

from all patients. Moreover, 120 patients with a healthy root and periapex (ie, the control group [the healthy group without AP]) were selected using CBCT imaging also. They had the same mean age/sex and the same number/subdivision of the teeth as the diseased group. Each of the 240 patients (120 diseased and 120 healthy) underwent an OPT first and a CBCT scan within 40 days of the OPT.

Devices OPT was performed via the Orthoceph OC200 D (Instrumentarium Dental, Tuusula, Finland). It was a digital orthopantomograph with a rotation time of 17.6 seconds, 66 kV, and 4.5–6.8 mA. CBCT imaging was performed via the NewTom 5G (QR srl, Verona, Italy) equipped with a pulsed pyramidal X-ray beam (360 rotation), a very small focal spot (0.3 mm), and an amorphous silicon flat-panel detector (20  25 cm). The protocols used for imaging were named

Study Design and Assessment of AP The 120 AP lesions were divided into 60 lesions of the upper arch and 60 lesions of the lower arch. In each arch, 30 small lesions from 2.0–4.5 mm and 30 large lesions from 4.6–7.0 mm were selected. These, in turn, were divided into 3 groups of 10 in the incisor, canine/premolar, and molar areas, respectively. Finally, the lesions affecting the cortical bone were distinguished from those affecting only the cancellous bone. The 120 patients with AP had not received any root canal therapy; the presence of periapical infection was confirmed either clinically or surgically. AP was assessed using the periapical index (PAI) system of Ørstavik et al (25) applied to CBCT imaging (28). PAI is a 5-score scale based on periapical radiographs of histologically confirmed AP: 1, normal periapical structures; 2, small changes in bone structure; 3, changes in bone structure with some mineral loss; 4, periodontitis with a well-defined radiolucent area; and 5, severe periodontitis with exacerbating features. In the current study, a PAI of 2 and 3 and a PAI of 4 and 5 were grouped together. Therefore, our PAI system was divided into 3 scores: PAI 1, PAI 2 to 3, and PAI 4 to 5. In CBCT imaging, only PAI 1 and PAI 4 to 5, corresponding to the healthy group and diseased group, respectively, were selected. PAI scores of 2 to 3 were discarded to avoid unclear or poorly defined changes in the bone structure. AP was measured using a standardized and reproducible method (29). It was oriented 3-dimensionally to make the intersection between the sagittal and coronal planes coincide with the longitudinal axis of the interested tooth. The axial plane was automatically oriented perpendicularly to the other 2 planes. The dimensions of the AP lesions were recorded, taking into account the largest measurement observed in 1 of the 3 planes. Once all the diseased and healthy teeth were chosen on CBCT scans, the corresponding OPT images were electronically cut by means of the software originally supplied with the systems in order to display only the dental root (no crown should be shown) and surrounding tissues up to 8 mm mesially and distally from the root apex (Fig. 2). This was done to avoid the observers being influenced by an eventual crown treatment/disease or the overall status of the patient’s mouth. All 240 roots cut out from OPT were evaluated using the PAI system divided into 3 scores: PAI 1, PAI 2 to 3, and PAI 4 to 5. PAI 2 to 3 scores were included into AP as well as PAI scores 4 to 5. No image was

TABLE 1. True Positives, False Positives, True Negatives, and False Negatives for Orthopantomography (OPT) in Relation to Cone-beam Computed Tomographic (CBCT) Imaging CBCT imaging OPT Positive (PAI 2–3 + PAI 4–5) Negative (PAI 1) Total

Diseased (PAI 4–5), n (%)

Healthy (PAI 1), n (%)

Total

41 (34.1) 79 (65.9) 120 (100)

5 (4.2) 115 (95.8) 120 (100)

46 194 240

PAI, periapical index.

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Clinical Research TABLE 2. Sensitivity, Specificity, Positive Predictive Value (PPV), Negative Predictive Value (NPV), Diagnostic Accuracy, and Kappa Value for Orthopantomography in Relation to Cone-beam Computed Tomographic Imaging Anatomic area/lesion size

Sensitivity

Specificity

PPV

NPV

Accuracy

Kappa

Both arches Upper arch, incisive area Upper arch, canine premolar area Upper arch, molar area Lower arch, incisive area Lower arch, caninepremolar area Lower arch, molar area Small lesions (2–4.5 mm) Large lesions (4.6–7 mm)

34.2 15.0 35.0

95.8 95.0 100

89.1 75.0 100

59.3 52.8 60.0

65.0 55.0 67.5

0.300 0.100 0.350

20.0 15.0 60.0

95.0 85.0 100

80.0 50.0 100

54.3 50.0 71.0

57.5 50.0 80.0

0.150 0.000 0.600

60.0 20.0 48.5

100 95.8 95.8

100 70.6 85.3

71.4 70.6 78.8

80.0 70.6 80.0

0.600 0.193 0.495

Apical periodontitis were divided by the anatomic area and the size of the lesions.

discarded by OPT; no measurement of the size of the lesions was performed by OPT. In summary, 2 dental radiologists enrolled the 240 teeth/patients using CBCT imaging (120 diseased and 120 healthy) so that the diseased group had 10 AP lesions for each of the 3 anatomic areas (incisor, canine/premolar, and molar) in both the upper and lower arches and for each of the 2 sizes of lesions (2–4.5 mm and 4.6–7 mm). This was achieved in order to have unambiguous subdivisions of the lesions for each area and size.

Observers and Statistical Analysis All CBCT and OPT examinations were performed by the same technical staff with 10 years of experience in dental imaging to achieve standardization of the execution method. For both the diseased and healthy groups, each root of the selected tooth was assessed by OPT independently by 3 radiologists skilled in dental maxillofacial imaging (31, 18, and 12 years of experience, respectively). They were appointed over and above the 2 radiologists assigned to the selection of AP and were blinded to any information about both the patient and the PAI value of the CBCT examinations. The largest (ie, the most represented) OPT PAI value was taken when the opinion was not unanimous. An assessment in consensus was made if the 3 opinions differed from each other. Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy for OPT images with respect to the CBCT reference standard images were calculated. Moreover, the Cohen kappa value was calculated to assess the agreement between OPT and CBCT imaging. These analyses were fulfilled in the total sample and stratified for both the size and area of the lesions. In the whole sample, interobserver reliability for the OPT PAI system–categoric variable defined by the 3-score scale (PAI 1, PAI 2–3, and PAI 4–5) was also calculated using the Cohen kappa. Kappa values of 0.01–0.20, 0.21–0.40, 0.41–0.60, 0.61–0.80, 0.81–0.99, and 1 represented slight, fair, moderate, substantial, almost perfect, and

perfect agreement, respectively. A P value #.05 was considered to be statistically significant.

Results Observer/Device Agreement The Cohen kappa values showed a substantial agreement between the 3 observers (observer 1 vs observer 2: k = 0.63; observer 1 vs observer 3: k = 0.77; and observer 2 vs observer 3: k = 0.74). True positives, false positives, true negatives, false negatives, sensitivity, specificity, positive predictive value, negative predictive value, diagnostic accuracy, and kappa values for OPT images with respect to CBCT images are provided in Tables 1 and 2. Only specificity and positive predictive value had high values (95.8 and 89.1, respectively). Assessment of AP True positives (Table 3) were about one third of the cases (34.2%), of which slightly more than half were underestimated as PAI 2 to 3 (Fig. 3A–C). In the upper arch (Table 4), the true positives were 15.0%, 35.0%, and 20.0% in the incisor, canine/premolar, and molar area, respectively, and 0% (0/20) and 23.1% (3/13) for the small and large lesions affecting just the cancellous bone, respectively. In the lower arch (Table 5), the true positives were 15.0%, 60.0%, and 60.0% in the incisor, canine/premolar, and molar area, respectively, and 23.1% (6/26) and 61.2% (11/18) for small and large lesions affecting just the cancellous bone, respectively. Analysis of the Errors OPT generated 5 false positives, 4 of which were judged as PAI 2 to 3 and only 1 as PAI 4 to 5. Three of these false lesions were identified in the lower incisor area (Fig. 4). False negatives comprised about two thirds of the cases. Most of the AP lesions (43.0%, 34/79) were not recognized in the upper and lower incisor areas.

TABLE 3. Synopsis of the True Positives (Apical Periodontitis Judged as Periapical Index 4–5 and Periapical Index 2–3) by Orthopantomography according to the Anatomic Area, Size, and Bone Involvement of the Lesion Anatomical area

Lesion size

Bone resorption type

Dental arch

Incisor

Canine/premolar

Molar

Small (2.0–4.5 mm)

Large (4.6–7.0 mm)

Cortical

Cancellous

Upper arch Lower arch Both arches Total

15.0 15.0 15.0 34.2

35.0 60.0 47.5

20.0 60.0 40.0

10.0 30.0 20.0 34.2

36.7 60.0 48.3

39.2 56.7 47.9 34.2

7.5 33.3 20.4

Cone-beam computed tomographic imaging was used as the reference standard. Data are reported as percentage values.

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Figure 3. True positive. (A and B) Upper jaw CBCT imaging. AP of the size of 6.6 mm affecting the cortical bone (arrow) at the distobuccal root of the first molar. (C) In OPT, the distobuccal root of the first molar was superimposed on the mesiobuccal root of the second molar; despite the large size of the lesion and the involvement of the cortical bone, the AP appeared to be a small change in the bone structure with some mineral loss. Thus, it was underestimated as PAI 2 to 3.

Discussion OPT showed low sensitivity (34.2), negative predictive value (59.3), and diagnostic accuracy (65.0) and high specificity (95.8) and positive predictive value (89.1) in the detection of AP. Furthermore, the agreement between OPT and CBCT imaging was fair (k value = 0.30). The best identified AP lesions were the large lesions located in the lower canine/premolar and molar areas, whereas the upper and lower incisor areas were the most difficult to assess. Our results proved that the recognition of AP depended on both the anatomic area/size of the lesion and the involvement of the cortical bone. In the upper molar area, the air within the maxillary sinus, the presence of numerous roots not orthogonal to the X-ray beam, and the undulating morphology of the maxillary sinus floor in close connection with the root apex made it difficult to identify AP. These reasons

were only partly applicable to the premolar teeth and not applicable to the canine teeth, which explains the better diagnostic accuracy of AP in the upper canine/premolar area compared with the upper molar area. The AP lesions in the canine/premolar and molar areas were more identifiable in the lower arch compared with the upper arch because the roots in the lower arch were more orthogonal to the X-ray beam, there was no nasal/sinusal air, and there was a lower superimposition of the extraoral anatomic structures although the projection of the nerve foramen and canals can correspond to the periapical area. In the incisor area, the superimposition of the cervical spine and the skull base impaired the identification of the periapical area. The other structures that undermined the identification of AP were the nasal bone/cartilage/air and hard palate in the upper arch and, especially, the

TABLE 4. Assessment of the Upper Arch of the 60 Diseased Patients by Orthopantomography Upper arch Incisors

Canines/Premolars

Molars

2.0–4.5 mm

4.6–7.0 mm

2.0–4.5 mm

4.6–7.0 mm

2.0–4.5 mm

4.6–7.0 mm

OPT PAI

Cor

Can

Cor

Can

Cor

Can

Cor

Can

Cor

Can

Cor

Can

Total

1 2–3 4–5

2/2 0/2 0/2

8/8 0/8 0/8

2/4 1/4 1/4

5/6 1/6 0/6

1/3 1/3 1/3

7/7 0/7 0/7

1/4 2/4 1/4

4/6 1/6 1/6

4/5 1/5 0/5

5/5 0/5 0/5

6/9 2/9 1/9

1/1 0/1 0/1

46/60 9/60 5/60

Can, cancellous bone; Cor, cortical bone; PAI, periapical index. Cone-beam computed tomographic imaging was used as the reference standard. Apical periodontitis (AP) lesions were divided according to 3 anatomic areas (incisor, canine/premolar, and molar). Ten AP lesions with a size of 2.0–4.5 mm and 10 AP lesions with a size of 4.6–7.0 mm were evaluated for each anatomic area. AP lesions were additionally subdivided between those affecting exclusively the cancellous bone and those also involving the cortical bone.

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Clinical Research TABLE 5. Assessment of the Lower Arch of the 60 Diseased Patients by Orthopantomography Lower arch Incisors

Canines/Premolars

Molars

2.0–4.5 mm

4.6–7.0 mm

2.0–4.5 mm

4.6–7.0 mm

2.0–4.5 mm

4.6–7.0 mm

OPT PAI

Cor

Can

Cor

Can

Cor

Can

Cor

Can

Cor

Can

Cor

Can

Total

1 2–3 4–5

1/2 1/2 0/2

8/8 0/8 0/8

4/6 1/6 1/6

4/4 0/4 0/4

0/1 1/1 0/1

5/9 2/9 2/9

1/4 1/4 2/4

2/6 2/6 2/6

0/1 0/1 1/1

7/9 2/9 0/9

0/2 1/2 1/2

1/8 2/8 5/8

33/60 13/60 14/60

Can, cancellous bone; Cor, cortical bone. Cone-beam computed tomographic imaging was used as the reference standard. Apical periodontitis (AP) were divided according to 3 anatomic areas (incisor, canine/premolar, and molar). Ten AP lesions with a size of 2.0–4.5 mm and 10 AP lesions with a size of 4.6–7.0 mm were evaluated for each anatomic area. AP lesions were additionally subdivided between those affecting exclusively the cancellous bone and those also involving the cortical bone.

morphologic diversities of the mental fossa, simulating false lacuna bone images in the lower arch (Fig. 4). In fact, in the current study, the false positives amounted to 4.2%, 80% of which were located in the incisor area. This disagreed with Estrela et al’s study (28). They observed false positives in only 0.06% of the cases. OPT showed lower sensitivity in the detection of small lesions (2.0–4.5 mm) compared with large lesions (4.6–7.0 mm) because the smaller lesions were recognized less frequently than the larger ones, as already observed for periapical X-rays (30, 31). This indicated that the size of the periapical radiolucency was a key point in the detection of AP by OPT because small lesions were unlikely to amount to 30%–50% of bone mineral loss, which represents the required threshold for the radiographic identification of AP. Therefore, small lesions were not generally detected and could be mistaken for physiological lacunae of the cancellous bone, also taking into account the fact that the teeth in our study were not endodontically treated. The lower canine/premolar area for the small lesions and the lower molar area for the large lesions were the areas in which the AP

Figure 4. False positive. At the level of the periapex of the lower incisor, in the OPT the mental fossa simulated a radiolucent periapical bone lesion characterized by changes in bone structure with mineral loss.

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lesions were easier to identify. In the canine/premolar area, the limited buccolingual bone thickness facilitated the recognition of the small lesions because bone demineralization of 30%–50% was more frequently reached. On the contrary, bone mineral loss usually exceeded this threshold value in large lesions. Thus, the latter were easier to identify in the molar area than the canine/premolar area because of the lack of anatomic structures (mental fossa, canal, and foramen) that can be superimposed on the root apex. The root apex was placed more or less close to the cortical bone, and the different buccolingual bone thickness for the incisor, canine/premolar, and molar areas in the upper and lower jaws deeply influenced the percentage of bone demineralization, which is a prerequisite for AP detection. The cortical bone had a higher bone mineral content than the cancellous bone. Therefore, cortical bone involvement, for the same anatomic area and size of the lesion, resulted in easier detection of AP by OPT, as previously stated for periapical X-rays (10–12). The normal proximity of the root apex to the cortical bone in the upper arch caused a higher involvement of the upper cortical bone than the lower one. In contrast, the teeth of the lower arch had a smaller number of roots, which were usually mesiodistally oriented and located inside the cancellous bone, with no contact with the cortical bone. Our results proved that digital OPT was an imaging technique with a higher risk of underdiagnosis; 53.6% of true positives (only 34.2% in aggregate) were underestimated as PAI 2 to 3. The present study was compared with the only article that studied OPT and CBCT imaging for the assessment of AP. Estrela et al (28) used a conventional (ie, not digital) orthopantomograph and observed 45% of true positives, 84.9% of which were underestimated as PAI 2 or PAI 3. Nevertheless, 94.5% of the teeth investigated by Estrela et al were treated endodontically, whereas no root canal filling was enrolled in the current study. The agreement between the observers was substantial. We hypothesized that the lack of a higher grade of agreement could be caused by the assessment being performed by using electronically cut OPT small images. However, in our opinion, the visualization of the crowns in untreated roots, and especially the overview of the entire mouth, can influence the radiologic diagnosis of a healthy/diseased periapex. In addition, OPT is recognized as being a technique with poor reproducibility because of the difficulty in the patient’s positioning, morphologic variations of the periapical area, bone mineralization, X-ray angulations, and radiographic contrast, which influence OPT analysis (32, 33). In the current study, 2 different CBCT image acquisition modes (Hi-Res-Regular and Hi-Res-Enhanced) were used. We believe that this choice did not affect the result of the study because both modes provided high-resolution images at the highest mA values, and the voxel size used for all of the reconstructions was always the same and as small as possible. Our study was affected by several limitations. These were represented by the recruitment of periapical bone lesions only between 2 and 7 mm, JOE — Volume -, Number -, - 2017

Clinical Research discarding PAI 2 and PAI 3 in CBCT images, and examining just 3 anatomic areas (incisor, canine/premolar, and molar) for each arch. The enrollment of lesions smaller than 2 mm or larger than 7 mm should increase the false negatives and the true positives, respectively. OPT assessment of AP with CBCT PAI values of 2 or 3 should significantly increase the false negatives too because we considered that the majority of AP cases would be underestimated as PAI 1 (ie, the absence of a lesion). We hope that further works will analyze AP for each individually studied tooth, distinguishing completely radiolucent lesions from periapical radiolucencies surrounded by sclerotic tissue. Gathering a large number of untreated AP cases represents a real research challenge. At present, only 2 articles (34, 35) have focused merely on teeth without root canal treatments by comparing periapical X-rays and CBCT imaging. Another weakness was represented by the clinical/surgical diagnosis of the lesions and, therefore, the choice of CBCT imaging as a reference examination. However, histologic analysis of AP is very difficult to implement in clinical practice, and high-resolution CBCT imaging is currently considered the most accurate examination for the assessment of AP (25–27). Although in the present study OPT showed low sensitivity, negative predictive value, and diagnostic accuracy in the detection of AP, it cannot be replaced by CBCT imaging for any suspected periapical bone lesion for radioprotection reasons. An additional weakness was that we assessed OPT images in the most difficult conditions (ie, being unable to visualize the whole mouth). The scrap of OPT did not represent clinical reality. However, this was our choice. We did not want to be influenced by any dental treatment. In contrast, we wanted all the teeth investigated (ie, teeth with and without AP) to appear radiologically healthy. Two comparative studies are ongoing between untreated and treated AP and between the evaluation of the root only and complete OPT. In the follow-up of undetected AP by OPT before endodontic treatment, a topic of discussion for future research is which imaging technique is more appropriate among OPT, periapical X-ray, and high-resolution CBCT imaging with a small FOV.

Conclusions In our series, OPT showed high specificity and positive predictive value, mainly for AP greater than 4.5 mm located in the lower canine/ premolar and lower molar areas. However, OPT was not generally an accurate imaging technique for the detection of untreated AP because of low sensitivity and negative predictive value, especially for AP lesions smaller than 4.5 mm located in the upper and lower incisor areas.

Acknowledgments The authors deny any conflicts of interest related to this study.

References 1. American Association of Endodontists. Glossary of Endodontic Terms, 8th ed. Chicago: American Association of Endodontists; 2012. 2. Nair PN. New perspectives on radicular cysts: do they heal? Int Endod J 1998;31: 155–60. 3. Kakehashi S, Stanley HR, Fitzgerald RJ. The effects of surgical exposures of dental pulps in germ-free and conventional laboratory rats. Oral Surg Oral Med Oral Pathol 1965;20:340–9. 4. Bender IB. Factors influencing the radiographic appearance of bony lesions. J Endod 1982;8:161–70. 5. Wu MK, Shemesh H, Wesselink PR. Limitations of previously published systematic reviews evaluating the outcome of endodontic treatment. Int Endod J 2009;42: 656–66. 6. LeQuire AK, Cunningham CJ, Pelleu GB Jr. Radiographic interpretation of experimentally produced osseous lesions of the human mandible. J Endod 1977;3:274–6. 7. Katebzadeh N, Hupp J, Trope M. Histological periapical repair after obturation of infected root canals in dogs. J Endod 1999;25:364–8.

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8. Bender IB, Seltzer S. Roentgenographic and direct observation of experimental lesions in bone: I. 1961. J Endod 2003;29:702–6. 9. Bender IB, Seltzer S. Roentgenographic and direct observation of experimental lesions in bone: II. 1961. J Endod 2003;29:707–12. 10. Patel S, Dawood A, Mannocci F, et al. Detection of periapical bone defects in human jaws using cone beam computed tomography and intraoral radiography. Int Endod J 2009;42:507–15. 11. Huumonen S, Ørstavik D. Radiological aspects of apical periodontitis. Endod Topics 2002;1:3–25. 12. Stabholz A, Friedman S, Tamse A. Endodontic failures and re-treatment. In: Cohen S, Burns RC, eds. Pathways of the Pulp, 6th ed. St Louis: Mosby; 1994:692–3. 13. Liang X, Jacobs R, Hassan B, et al. A comparative evaluation of cone beam computed tomography (CBCT) and multi-slice CT (MSCT). Part I. On subjective image quality. Eur J Radiol 2010;75:265–9. 14. Cotton TP, Geisler TM, Holden DT, et al. Endodontic applications of cone-beam volumetric tomography. J Endod 2007;33:1121–32. 15. Lofthag-Hansen S, Hummonen S, Gr€ondahl K, Gr€ondahl HG. Limited cone-beam CT and intraoral radiography for the diagnosis of periapical pathology. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;103:114–9. 16. Nakata K, Naitoh M, Izumi M, et al. Effectiveness of dental computed tomography in diagnostic imaging of periradicular lesion of each root of a multirooted tooth: a case report. J Endod 2006;32:583–7. 17. Nardi C, Talamonti C, Pallotta S, et al. Head and neck effective dose and quantitative assessment of image quality: a study to compare cone beam CT and multislice spiral CT. Dentomaxillofac Radiol 2017;46:20170030. 18. Nardi C, Borri C, Regini F, et al. Metal and motion artifacts by cone beam computed tomography (CBCT) in dental and maxillofacial study. Radiol Med 2015;120: 618–26. 19. Watanabe H, Honda E, Tetsumura A, et al. A comparative study for spatial resolution and subjective image characteristics of a multi-slice CT and a cone-beam CT for dental use. Eur J Radiol 2011;77:397–402. 20. Kobayashi K, Shimoda S, Nakagawa Y. Accuracy in measurement of distance using limited cone-beam computerized tomography. Int J Oral Maxillofac Implants 2004; 19:228–31. 21. Ludlow JB, Laster WS, See M. Accuracy of measurements of mandibular anatomy in cone beam computed tomography images. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;103:534–42. 22. Pinsky HM, Dyda S, Pinsky RW. Accuracy of three-dimensional measurements using cone-beam CT. Dentomaxillofac Radiol 2006;35:410–6. 23. Kruse C, Spin-Neto R, Wenzel A, Kirkevang LL. Cone beam computed tomography and periapical lesions: a systematic review analysing studies on diagnostic efficacy by a hierarchical model. Int Endod J 2015;48:815–28. 24. American Association of Endodontists; American Academy of Oral and Maxillofacial Radiology. Use of cone beam-computed tomography in endodontics: 2015 update. Available at: http://www.aae.org/uAPoadedfiles/clinical_resources/guidelines_and_ position_statements/cbctstatement_2015update.pdf. Accessed January 1, 2017. 25. Ørstavik D, Kerekes K, Eriksen HM. The periapical index: a scoring system for radiographic assessment of apical periodontitis. Endod Dent Traumatol 1986;2:20–34. 26. Strindberg L. The dependence of the results of pulp therapy of certain factor. An analytic study based on radiographic and clinical follow-up examinations. Acta Odontol Scand 1956;14(Suppl 21):1–175. 27. Reit C, Grondahl HG. Application of statistical decision theory to radiographic diagnosis of endodontically treated teeth. Scand J Dent Res 1983;91:213–8. 28. Estrela C, Bueno MR, Leles CR, et al. Accuracy of cone beam computed tomography and panoramic and periapical radiography for detection of apical periodontitis. J Endod 2008;34:273–9. 29. Esposito S, Cardaropoli M, Cotti E. A suggested technique for the application of the cone beam computed tomography periapical index. Dentomaxillofac Radiol 2011; 40:506–12. 30. Sullivan JE, di Fiore PM, Koerber A. Radiovisiography in the detection of apical periodontitis. J Endod 2000;26:32–5. 31. Paurazas SB, Geist JR, Pink FE, et al. Comparison of diagnostic accuracy of digital imaging by using CCD and CMOS-APS sensors with E-speed film in the detection of periapical bony lesions. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000; 89:356–62. 32. Halse A, Molven O, Fristad I. Diagnosing periapical lesions: disagreement and borderline cases. Int Endod J 2002;35:703–9. 33. Molven O, Halse A, Fristad I. Long-term reliability and observer comparisons in the radiographic diagnosis of periapical disease. Int Endod J 2002;35:142–7. 34. Patel S, Wilson R, Dawood A, Mannocci F. The detection of periapical pathology using intraoral radiography and cone beam computed tomography – part 1: preoperative status. Int Endod J 2012;45:702–10. 35. Abella F, Patel S, Duran-Sindreu F, et al. Evaluating the periapical status of teeth with irreversible pulpitis by using cone-beam computed tomography scanning and periapical radiographs. J Endod 2012;38:1588–91.

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