Diagnostic imaging for the purpose of identifying dental disorders in human dentistry has come a long way from the first dental radiograph in 1896, with the development of digital dental radiography in 1987 to the introduction of CBCT in 1998.1 Veterinary dental imaging can be challenging because there are a large variety of skull sizes and confirmations. By calculating the skull index, dogs can be categorized into brachycephalic, mesaticephalic, and dolichocephalic breeds.2 Currently in human dentistry, dental radiography is the main method used for the identification of gross lesions and bone loss in the interproximal space3; evaluation of the periodontal ligament space, lamina dura, and periapical region; and identification of the loss of tooth integrity. In veterinary dentistry, dental radiography currently represents the criterion-referenced standard imaging modality for the evaluation of periodontal and dental health.4,5 However, given that the brachycephalic skull configuration has inherent crowding and rotation of teeth, the interpretation of dental radiographs of brachycephalic dogs can be difficult.
During breeding selection for brachycephalic breeds, dogs with early ankylosis in the basicranial epiphyseal cartilage of the skull were chosen, which led to chondrodysplasia of the longitudinal axis of the skull.6 As a consequence, brachycephalic dogs have shortened maxillary and mandibular bones but have the same number of teeth as mesaticephalic and dolichocephalic dogs. In addition, small dogs have larger teeth in proportion to their jaw size.7 Both conditions lead to the predisposition (especially in small brachycephalic dogs) to developmental disorders of orofacial structures and a number of specific dental disorders, such as crowding, rotation of teeth, displacement of teeth, persistent deciduous teeth, partially erupted or unerupted teeth, odontogenic cysts, and aggravated periodontal disease.6,8–12
Whenever conventional radiography cannot supply satisfactory diagnostic information for human dentistry, especially for complex cases (eg, evaluation and treatment of cleft palate, unerupted teeth, or orthognathic surgery), CBCT is regarded as the method of choice.13 Through the use of advanced imaging software, CBCT can provide sagittal, dorsal, and transverse slices as well as serial transplanar reformation (cross sections) of each individual tooth, curved planar reformation (simulated distortion-free panoramic images), and indirect volume rendering in tooth and bone modes.
The objective of the study reported here was to determine whether dental disorders can be identified on dental radiographs and CBCT images and which of 3 CBCT modules had the highest diagnostic value regarding identification of dental disorders in small to medium-sized brachycephalic dogs. We hypothesized that CBCT, specifically serial CBCT slices and custom cross sections, would be better suited than dental radiography to aid in identification of predefined dental disorders in brachycephalic dogs.
Materials and Methods
Animals
Small to medium-sized brachycephalic dogs admitted to the Dentistry and Oral Surgery Service at the University of California-Davis for evaluation and treatment of oral pathological conditions between August 2014 and October 2015 for which full-mouth dental radiographs and CBCT scans of the skull were obtained were eligible for inclusion in the study. Nineteen client-owned dogs (12 males [11 castrated and 1 sexually intact] and 7 females [6 spayed and 1 sexually intact]) were included in the study. Breeds included French Bulldog (n = 4), Shih Tzu (3), Pekingese (3), Japanese Chin (3), Pug (2), English Bulldog (1), and Boston Terrier (1); there were also 2 mixed-breed dogs (Shi Tzu–Pekingese cross). Mean ± SD age of the dogs was 7.36 ± 3.65 years (range, 8 months to 14 years), mean body weight was 8.23 ± 5.13 kg (range, 2.2 to 25 kg), and mean skull index was 0.96 ± 0.09 (range, 0.81 to 1.14). Data for these dogs were reported in another study.14 Informed consent was obtained from each owner, and the study was conducted with approval of the University of California-Davis Institutional Animal Care and Use Committee and the Clinical Trials Review Board.
Image acquisition
Dogs were anesthetized, and dental radiography and CBCT were performed. Technical details of image acquisition and preparation before evaluation were described in another study.14 Because of the morphology of the skull of brachycephalic dogs and the consequential inconsistent orientation of teeth of those dogs, the axis of the skull was modified accordingly to create 13 standardized images for optimal evaluation of the dentition of brachycephalic dogs by use of CBCT reconstructed panoramic views (Figure 1).
Images of the 13 CBCT standardized reconstructed panoramic views, which are as follows: 1 = axis of the skull adjusted for angulation of the R maxillary P1 through P4, 2 = axis of the skull adjusted for angulation of the R maxillary C, 3 = axis of the skull adjusted for positioning of the R and L maxillary M1 and M2, 4 = axis of the skull adjusted for angulation of the L maxillary C, 5 = axis of the skull adjusted for angulation of the L maxillary P1 through P4, 6 = axis of the skull adjusted for the R maxillary quadrant, 7 = axis of the skull adjusted for angulation of the maxillary I1 through I3, 8 = axis of the skull adjusted for the L maxillary quadrant, 9 = axis of the skull adjusted for the R mandibular quadrant, 10 = axis of the skull adjusted for the R mandibular C, 11 = axis of the skull adjusted for angulation of the mandibular I1 through I3, 12 = axis of the skull adjusted for the L mandibular C, and 13 = axis of the skull adjusted for the L mandibular quadrant. Views were used to exploit the benefit of parallel imaging for the identification of dental disorders in brachycephalic dogs. C = Canine tooth. I1 = First incisor tooth. I2 = Second incisor tooth. I3 = Third incisor tooth. L = Left. M1 = First molar tooth. M2 = Second molar tooth. P1 = First premolar tooth. P2 = Second premolar tooth. P3 = Third premolar tooth. P4 = Fourth premolar tooth. R = Right.
Citation: American Journal of Veterinary Research 79, 1; 10.2460/ajvr.79.1.62
Image evaluation and scoring
Dental radiography (Rad method) and 3 CBCT software modules (reconstructed panoramic views [Pano method], serial CBCT slices and custom cross sections [Slices method], and tridimensional rendering [3-D method]) were evaluated separately for their usefulness in identification of 31 predefined dental disorders (Appendix). Each method was scored separately for each dental disorder by a third-year resident in a veterinary dentistry training program (SD), 2 board-certified veterinary dentists (BA and FJMV), and a board-certified human oral radiologist (DCH).
Whenever possible, dental disorders were defined in accordance with nomenclature of the American Veterinary Dental College.15 Qualitative scoring was used for each dental disorder, each imaging modality, and each tooth (0 if the disorder was absent or 1 if the disorder was present).
One observer was calibrated by the other investigators to ensure appropriate software handling and image scoring. Findings for all 4 methods were recorded by the calibrated observer without reference to each patient's medical record to limit biased interpretation. Final scores were obtained by consensus of the investigators, who agreed on 1 interpretation for each finding. After image evaluation was concluded, findings for the Rad and CBCT methods were compared to determine a point of reference.
The 31 dental disorders were grouped into 10 categories for statistical analysis. Those categories were missing teeth, abnormal eruption, rotation, abnormally shaped roots, abnormal number of roots, periodontitis, loss of tooth integrity, failure of the pulp cavity to narrow, periapical disease, and tooth resorption. Anatomic and developmental findings were calculated on the basis of a full set of the canine dentition, all other disorders were calculated on the basis of the number of present teeth.
Statistical analysis
Descriptive statistics and mean scores were reported as mean ± SD. Discordance of values for the Rad and 3 CBCT methods were compared to the point of reference and assessed by use of the McNemar χ2 test of marginal homogeneity for paired data. Overall accuracy, sensitivity, specificity, PPV, and NPV were calculated and reported along with the 95% CIs. Non-overlapping CIs reflected significant differences between these proportions at P < 0.05.
Results
Overall assessment
Sensitivity was highest, but not significantly different, for the Rad method when evaluating loss of tooth integrity. For 4 dental disorders (missing teeth, abnormal eruption, abnormally shaped roots, and periapical disease), sensitivity of the Rad method was higher, but not significantly different, compared with sensitivity for the Pano and 3-D methods. However, the Rad method had lower sensitivity than the Slices method for all dental disorders, except for 1 (loss of tooth integrity), and significantly lower sensitivity for the evaluation of abnormal tooth eruption, abnormally shaped roots, tooth resorption, and periodontitis.
Anatomic and developmental disorders
Results for the Rad and 3 CBCT methods were compared.
Missing teeth—Of the 798 teeth that should have been present according to the dental formula for dogs (I 3/3, C 1/1, P 4/4, and M 2/3), 110 (13.78%) were missing. Although all of these teeth were correctly identified by use of both the Rad and Slices methods, 5 additional teeth were found to be missing by use of the Rad method, although root remnants were actually present. For the Pano method, 11 teeth were falsely identified to be missing, and 4 teeth were falsely found to be present. For the 3-D method, 6 additional teeth were thought to be missing, whereas 3 were falsely found to be present as retained roots. Regardless of the imaging modality, sensitivity was high for all methods, with the lowest sensitivity for the Pano method (96.36%) and the highest for the Slices method (100%; Table 1). Accuracy was significantly higher for the Slices method than for the Pano and 3-D methods, and specificity and PPV were significantly higher for the Slices method than for the Pano method.
Ability to identify missing teeth in 19 brachycephalic dogs by use of dental radiography (Rad method) and 3 CBCT software modules.*
| Rad | Pano | Slices | 3-D | |||||
|---|---|---|---|---|---|---|---|---|
| Variable | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI |
| Accuracy | 99.12 | 98.20–99.65 | 98.12 | 96.92–98.94 | 100 | 99.54–100 | 98.87 | 97.87–99.48 |
| Sensitivity | 98.21 | 93.06–99.69 | 96.36 | 90.41–98.83 | 100 | 95.79–100 | 97.27 | 91.65–99.29 |
| Specificity | 99.27 | 98.20–99.73 | 98.40 | 97.07–99.16 | 100 | 99.31–100 | 99.13 | 98.01–99.65 |
| PPV | 95.65 | 89.65–98.39 | 90.60 | 83.43–94.98 | 100 | 95.79–100 | 94.69 | 88.33–97.82 |
| NPV | 99.71 | 98.83–99.95 | 99.41 | 98.40–99.81 | 100 | 99.31–100 | 99.56 | 98.61–99.89 |
Values reported are percentages.
The 3 modules were as follows: reconstructed panoramic views (Pano method), serial CBCT slices and custom cross sections (Slices method), and tridimensional rendering (3-D method). Differences in variables are significant (P < 0.05) for a method if the CI does not overlap with that of other methods.
Abnormal eruption—Fifty-six of 798 (7.02%) possible teeth were partially erupted or unerupted. The teeth most commonly partially erupted were the maxillary (n = 20) and mandibular (23) canine teeth. The most commonly unerupted teeth were the right and left mandibular first premolar teeth (n = 8). Three unerupted teeth were detected only by use of the Slices method, whereas those teeth appeared to be missing for the Rad, Pano, and 3-D methods. The 2 highest sensitivity scores were associated with the Rad method (80.70%) and Slices method (100%; Table 2). Accuracy, sensitivity, and NPV were significantly higher for the Slices method than for the other methods.
Ability to identify abnormal eruption of teeth in brachycephalic dogs by use of the Rad method and 3 CBCT software modules.*
| Rad | Pano | Slices | 3-D | |||||
|---|---|---|---|---|---|---|---|---|
| Variable | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI |
| Accuracy | 98.87 | 97.87–99.48 | 97.37 | 96.01–98.36 | 99.62 | 98.91–99.92 | 99.25 | 98.37–99.72 |
| Sensitivity | 90.00 | 80.73–95.27 | 75.95 | 64.78–84.55 | 96.34 | 88.94–99.05 | 93.98 | 85.88–97.76 |
| Specificity | 99.86 | 99.10–99.99 | 99.72 | 98.88–99.95 | 100 | 99.33–100 | 99.86 | 99.10–99.99 |
| PPV | 98.63 | 91.57–99.93 | 96.77 | 87.83–99.44 | 100 | 94.22–100 | 98.73 | 92.18–99.93 |
| NPV | 98.90 | 97.75–99.49 | 97.41 | 95.92–98.39 | 99.58 | 98.68–99.89 | 99.30 | 98.29–99.74 |
See Table 1 for key.
Rotation—Eighty-three of 798 (10.40%) possible teeth were rotated. Of the 83 rotated teeth, 62 were located among the right and left maxillary second, third, and fourth premolar teeth. Other teeth affected were the right and left mandibular second and third premolar teeth (n = 13), right and left maxillary first incisor teeth (5), right and left mandibular second molar teeth (2), and left mandibular third incisor tooth (1). For the Rad method, 72 (86.75%) rotated teeth were correctly identified, but only 60 (72.29%) rotated teeth were identified by use of the Pano method, whereas 79 (95.18%) were identified by use of the Slices method, and 78 (93.98%) were identified by use of the 3-D method. The Pano method was associated with the lowest sensitivity (75.95%); it was higher for the Rad method (90%), 3-D method (93.98%), and Slices method (96.34%; Table 3). Accuracy, sensitivity, and NPV of the Slices method were significantly higher than those of the Pano method.
Ability to identify rotation of teeth in brachycephalic dogs by use of the Rad method and 3 CBCT software modules.*
| Rad | Pano | Slices | 3-D | |||||
|---|---|---|---|---|---|---|---|---|
| Variable | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI |
| Accuracy | 98.62 | 97.55–99.31 | 98.25 | 97.07–99.04 | 100 | 99.54–100 | 96.87 | 95.41–97.96 |
| Sensitivity | 80.70 | 67.83–89.53 | 75.44 | 61.96–85.47 | 100 | 92.13–100 | 56.14 | 42.33–69.02 |
| Specificity | 100 | 99.36–100 | 100 | 99.36–100 | 100 | 99.36–100 | 100 | 99.36–100 |
| PPV | 100 | 90.40–100 | 100 | 89.76–100 | 100 | 92.13–100 | 100 | 86.66–100 |
| NPV | 98.54 | 97.32–99.23 | 98.15 | 96.83–98.94 | 100 | 99.36–100 | 96.74 | 95.15–97.83 |
See Table 1 for key.
Abnormally shaped roots—Sixty-five of 798 (8.15%) possible teeth had abnormally shaped roots (38 were dilacerated, 8 were divergent, 8 were convergent, 2 were concrescent, and 9 had fused roots). Although most mandibular teeth with abnormally shaped roots were detected by use of the Rad method and CBCT methods, 25 additional teeth with abnormally shaped roots among the right and left maxillary second premolar through second molar teeth (15 teeth with dilacerated roots, 9 with fused roots, and 1 with concrescent roots) were identified with the Slices method. Fourteen of these 25 abnormally shaped roots were also detected by use of the 3-D method, but none were detected by use of the Rad or Pano method. Of the 33 maxillary second molar teeth that were present, 9 (27.27%) had fused roots and 1 (3.03%) had concrescent roots; all 10 maxillary second molar teeth with abnormally shaped roots were identified only with the Slices method. Sensitivity of the Rad, Pano, and 3-D methods for use in identification of abnormally shaped roots was < 50%, whereas sensitivity for the Slices method was 98.46% (Table 4). Accuracy, sensitivity, and NPV of the Slices method were significantly higher than for the Rad, Pano, and 3-D methods.
Ability to identify abnormally shaped roots of teeth in brachycephalic dogs by use of the Rad method and 3 CBCT software modules.*
| Rad | Pano | Slices | 3-D | |||||
|---|---|---|---|---|---|---|---|---|
| Variable | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI |
| Accuracy | 95.86 | 94.24–97.14 | 94.49 | 92.67–95.97 | 99.87 | 99.30–100 | 95.49 | 93.81–96.82 |
| Sensitivity | 49.23 | 36.74–61.81 | 35.38 | 24.20–48.30 | 98.46 | 90.60–99.92 | 46.15 | 33.88–58.88 |
| Specificity | 100 | 99.35–100 | 99.73 | 98.91–99.95 | 100 | 99.35–100 | 99.86 | 99.12–99.99 |
| PPV | 100 | 86.66–100 | 92.00 | 72.50–98.60 | 100 | 92.95–100 | 96.77 | 81.49–99.83 |
| NPV | 95.69 | 93.94–96.97 | 94.57 | 92.66–96.01 | 99.86 | 99.12–99.99 | 95.44 | 93.65–93.76 |
See Table 1 for key.
Abnormal number of roots—Seventeen of 798 (2.13%) possible teeth had an abnormal number of roots. All teeth with an abnormal number of roots were correctly identified only by use of the Slices method (9 single-rooted teeth [8 right and left mandibular second molar teeth and 1 left mandibular second premolar tooth], six 3-rooted teeth [4 right and left maxillary third premolar teeth and 2 right and left mandibular second molar teeth], and two 2-rooted teeth [right and left maxillary fourth premolar teeth]). For the Rad and Pano methods, 1 rotated tooth was falsely identified as a single-rooted tooth, whereas 6 teeth with an abnormal number of roots were not identified by use of the Rad method, and 8 were not identified by use of the Pano method. For the 3-D method, all 3-rooted teeth except for 2 (right and left mandibular second molar teeth) were correctly identified. The 3-D and Slices methods had the highest sensitivity (88.24% and 100%, respectively; Table 5). Accuracy and sensitivity of the Slices method were significantly higher than those of the Pano method.
Ability to identify an abnormal number of roots of teeth in brachycephalic dogs by use of the Rad method and 3 CBCT software modules.*
| Rad | Pano | Slices | 3-D | |||||
|---|---|---|---|---|---|---|---|---|
| Variable | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI |
| Accuracy | 99.12 | 98.20–99.65 | 98.75 | 97.71–99.40 | 100 | 99.54–100 | 99.75 | 99.10–99.97 |
| Sensitivity | 64.71 | 38.62–84.74 | 47.06 | 23.86–71.47 | 100 | 77.08–100 | 88.24 | 62.25–97.94 |
| Specificity | 99.87 | 99.17–99.99 | 99.87 | 99.17–99.99 | 100 | 99.39–100 | 100 | 99.39–100 |
| PPV | 91.67 | 59.75–99.56 | 88.89 | 50.67–99.42 | 100 | 77.08–100 | 100 | 75.65–100 |
| NPV | 99.24 | 98.26–99.69 | 98.86 | 97.76–99.44 | 100 | 99.39–100 | 99.74 | 98.98–99.96 |
See Table 1 for key.
Periodontitis—Periodontitis was the most prevalent finding in the evaluated brachycephalic dogs (Figure 2). Of the 688 teeth that were present, 512 (74.42%) were affected by alveolar bone loss attributable to periodontal disease (208 [30.23%] teeth with mild horizontal or vertical bone loss; 143 [20.78%] teeth with moderate horizontal or vertical bone loss, furcation involvement, or both; and 161 [23.40%] teeth with severe horizontal or vertical bone loss, furcation exposure, or both). Compared with the point of reference, the extent of bone loss was underinterpreted for 272 teeth with the Rad method, 180 teeth with the Pano method, and 97 teeth with the 3-D method, and it was overinterpreted for 32 teeth with the Rad method, 100 teeth with the Pano method, and 133 teeth with the 3-D method. On the basis of the diagnostic imaging findings alone, indications for extraction of the 161 teeth because of severe periodontitis would have been missed for 72 (44.72%) teeth by use of the Rad method, 66 (40.99%) teeth by use of the Pano method, and 33 (20.50%) teeth by use of the 3-D method. For alveolar bone loss attributable to periodontal disease, the Rad method had the significantly lowest sensitivity (65.23%), whereas sensitivity was higher for the Pano method (84.93%), 3-D method (95.12%), and Slices method (100%; Table 6). Accuracy, sensitivity, and NPV for the Pano method were significantly higher than for the Rad method and were significantly higher for the 3-D method than for the Rad and Pano methods. Accuracy, sensitivity, and NPV were significantly highest for the Slices method. Specificity was significantly higher for both the Slices and Rad methods, compared with specificity for the Pano and 3-D methods. The PPV for the Rad method was significantly higher than for the Pano and 3-D methods; PPV was significantly highest for the Slices method.
Representative images obtained by use of dental radiography (Rad method; A) and 3 CBCT software modules (reconstructed panoramic views [Pano method; B], tridimensional rendering [3-D method; C], and serial CBCT slices and custom cross sections [Slices method; D]) and used for evaluation of periodontitis of the right maxillary second incisor tooth (arrow) of a brachycephalic dog. Although loss of alveolar bone (periodontitis) is visible on the dental radiographic view, various degrees of periodontitis can be seen on images for each of the 3 CBCT methods.
Citation: American Journal of Veterinary Research 79, 1; 10.2460/ajvr.79.1.62
Ability to identify periodontitis in brachycephalic dogs by use of the Rad method and 3 CBCT software modules.*
| Rad | Pano | Slices | 3-D | |||||
|---|---|---|---|---|---|---|---|---|
| Variable | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI |
| Accuracy | 76.57 | 73.47–79.47 | 85.96 | 83.36–88.30 | 100 | 99.54–100 | 91.10 | 88.91–92.99 |
| Sensitivity | 65.23 | 60.91–69.33 | 84.93 | 81.46–87.86 | 100 | 99.07–100 | 95.12 | 92.78–96.75 |
| Specificity | 96.85 | 93.91–98.46 | 87.80 | 83.32–91.25 | 100 | 98.35–100 | 83.92 | 79.02–87.87 |
| PPV | 97.38 | 94.90–98.71 | 92.54 | 89.68–94.68 | 100 | 99.07–100 | 91.37 | 88.58–93.55 |
| NPV | 60.88 | 56.21–65.36 | 76.60 | 71.60–80.99 | 100 | 98.35–100 | 90.57 | 86.23–93.68 |
See Table 1 for key.
The teeth most commonly affected by severe periodontitis were the mandibular incisor teeth (n = 35) and maxillary second through fourth premolar teeth (76). These teeth coincided with the areas of maximum crowding and represented the sites of the biggest disagreement among diagnoses between the Rad and Slices methods.
Endodontal disease—Of the 688 teeth that were present, 224 (32.56%) had signs of endodontal disease. The endodontal disease was characterized by loss of tooth integrity (n = 165), periapical disease (37), or failure of the pulp cavity to narrow (22).
Loss of tooth integrity—Of the 688 teeth that were present, 165 (23.98%) had loss of integrity of the crown, root, or both (Figure 3). Of these, 121 were limited to the crown and did not appear to involve the pulp cavity (107 attrition or abrasion and 14 uncomplicated crown fracture [including enamel fracture]), whereas 44 were associated with pulp exposure, root involvement, or both (2 complicated crown fracture, 1 uncomplicated crown-root fracture, 3 complicated crown-root fracture, and 38 root fracture [including retained tooth roots with a missing coronal segment]). None of the examined imaging techniques could be used to detect all findings, and there was no significant difference among the Rad and CBCT methods with regard to evaluation of loss of tooth integrity. Although 29 (23.97%) teeth with mild loss of integrity were missed with the Slices method and 23 (19.01%) were missed with the 3-D method, 8 (18.18%) dental fractures requiring treatment were missed with the Rad method and 11 (23%) were missed with the Pano method. However, the Rad method had the highest sensitivity (83.03%; Table 7).
Representative images obtained by use of the Rad method (A), Pano method (B), 3-D method (C), and Slices method (D) and used for evaluation of integrity of the left mandibular third incisor tooth (arrow) in a brachycephalic dog. A root fracture is not evident on the dental radiographic view but is apparent, to various degrees, on images for each of the 3 CBCT methods.
Citation: American Journal of Veterinary Research 79, 1; 10.2460/ajvr.79.1.62
Ability to identify loss of tooth integrity in brachycephalic dogs by use of the Rad method and 3 CBCT software modules.*
| Rad | Pano | Slices | 3-D | |||||
|---|---|---|---|---|---|---|---|---|
| Variable | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI |
| Accuracy | 96.49 | 94.97–97.66 | 95.36 | 93.67–96.71 | 94.74 | 92.95–96.18 | 95.74 | 94.10–97.03 |
| Sensitivity | 83.03 | 76.23–88.25 | 76.97 | 69.65–83.00 | 75.76 | 68.36–91.93 | 80.00 | 72.92–85.65 |
| Specificity | 100 | 99.25–100 | 100 | 99.25–100 | 100 | 99.25–100 | 99.53 | 98.50–99.88 |
| PPV | 100 | 96.60–100 | 100 | 96.34–100 | 100 | 96.28–100 | 97.78 | 93.14–99.42 |
| NPV | 95.76 | 93.86–97.12 | 94.35 | 92.25–95.92 | 94.04 | 91.90–95.66 | 95.04 | 93.03–96.51 |
See Table 1 for key.
Failure of the pulp cavity to narrow—Of the 688 teeth, 22 (3.20%) had failure of the pulp cavity to narrow, compared with the same tooth on the contralateral side. Use of the Rad method failed to identify 8 teeth, use of the Pano method failed to identify 7 teeth, use of the Slices method failed to identify 1 tooth, and use of the 3-D method failed to identify 3 teeth. Therefore, sensitivity was lowest for the Rad method (63.64%), whereas the Slices method had the highest sensitivity (95.45%; Table 8). There was no significant difference among the Rad and CBCT methods.
Ability to identify failure of the pulp cavity to narrow in teeth of brachycephalic dogs by use of the Rad method and 3 CBCT software modules.*
| Rad | Pano | Slices | 3-D | |||||
|---|---|---|---|---|---|---|---|---|
| Variable | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI |
| Accuracy | 99.00 | 98.03–99.57 | 99.12 | 98.20–99.65 | 99.87 | 99.30–100 | 99.62 | 98.91–99.92 |
| Sensitivity | 63.64 | 40.83–81.97 | 68.18 | 45.12–85.27 | 95.45 | 75.12–99.76 | 86.36 | 64.04–96.41 |
| Specificity | 100 | 99.39–100 | 100 | 99.39–100 | 100 | 99.39–100 | 100 | 99.39–100 |
| PPV | 100 | 73.24–100 | 100 | 74.65–100 | 100 | 80.76–100 | 100 | 79.08–100 |
| NPV | 98.98 | 97.92–99.52 | 99.11 | 98.08–99.61 | 99.87 | 99.17–99.99 | 99.61 | 98.78–99.90 |
See Table 1 for key.
Periapical disease—Periapical disease was associated with 37 of 688 (5.38%) teeth (6 with periapical lucencies, 24 with type 2 combined periodontal-endodontic lesions, 3 with widened apical periodontal ligament spaces, 2 with type 3 combined periodontal-endodontic lesions, and 2 with type 1 combined periodontal-endodontic lesions). All lesions could be identified only by use of the Slices method. Six (16.22%) teeth with periapical disease were missed by use of the Rad method, 12 (32.43%) were missed by use of the Pano method, and 10 (27.03%) were missed by use of the 3-D method. Sensitivity was highest for the Slices method (100%), followed by the Rad method (83.78%), 3-D method (72.97%), and Pano method (67.57%; Table 9). Accuracy was significantly higher for the Slices method than for the Pano method, and both sensitivity and NPV were significantly higher for the Slices method than for the Pano and 3-D methods.
Ability to identify periapical disease in brachycephalic dogs by use of the Rad method and 3 CBCT software modules.*
| Rad | Pano | Slices | 3-D | |||||
|---|---|---|---|---|---|---|---|---|
| Variable | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI |
| Accuracy | 99.25 | 98.37–99.72 | 98.50 | 97.39–99.22 | 99.87 | 99.30–100 | 98.62 | 97.55–99.31 |
| Sensitivity | 83.78 | 67.32–93.23 | 67.57 | 50.11–81.44 | 100 | 88.29–100 | 72.97 | 55.61–85.63 |
| Specificity | 100 | 99.37–100 | 100 | 99.37–100 | 99.87 | 99.15–99.99 | 99.87 | 99.15–99.99 |
| PPV | 100 | 86.27–100 | 100 | 83.42–100 | 97.37 | 84.57–99.86 | 96.43 | 79.76–99.81 |
| NPV | 99.22 | 98.22–99.68 | 98.45 | 97.23–99.16 | 100 | 99.37–100 | 98.70 | 97.54–99.34 |
See Table 1 for key.
Tooth resorption—Of 688 teeth, 163 (23.69%) were affected by tooth resorption (Figure 4). All lesions were detected in only 13 of the 19 dogs. Three dogs had 84 affected teeth (29, 29, and 26 teeth). The most common type of tooth resorption was root replacement resorption (n = 121), followed by external inflammatory resorption (18) and external surface resorption (5). Three teeth were affected by both external inflammatory resorption and root replacement resorption. Internal inflammatory resorption never occurred alone; it was associated with root replacement resorption in 9 teeth and occurred in combination with both external inflammatory resorption and root replacement resorption in 7 teeth.
Representative images obtained by use of the Rad method (A and E), Pano method (B and F), 3-D method (C and G), and Slices method (D and H) and used for evaluation of root resorption of the right maxillary second premolar tooth (arrow) in a brachycephalic dog with root replacement resorption (A through D) and a brachycephalic dog without resorption (E through H).
Citation: American Journal of Veterinary Research 79, 1; 10.2460/ajvr.79.1.62
Detection of all affected teeth was obtained only with the Slices method. Forty-one teeth with resorption were missed with the Rad method, 28 were missed with the Pano method, and 50 were missed with the 3-D method. Thus, sensitivity was lowest for the 3-D method (66.87%), but it was higher for the Rad method (74.85%), Pano method (80.37%), and Slices method (100%; Table 10). Accuracy, sensitivity, and NPV for the Slices method were significantly higher than for the Rad, Pano, and 3-D methods.
Ability to identify tooth resorption in brachycephalic dogs by use of the Rad method and 3 CBCT software modules.*
| Rad | Pano | Slices | 3-D | |||||
|---|---|---|---|---|---|---|---|---|
| Variable | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI | Estimated value | 95% CI |
| Accuracy | 94.74 | 92.95–96.18 | 96.12 | 94.53–97.35 | 100 | 99.54–100 | 93.36 | 91.40–94.99 |
| Sensitivity | 74.85 | 67.34–81.16 | 80.37 | 73.27–86.00 | 100 | 97.13–100 | 66.87 | 59.01–73.92 |
| Specificity | 99.84 | 98.98–99.99 | 99.53 | 98.50–99.88 | 100 | 99.25–100 | 99.53 | 98.50–99.88 |
| PPV | 99.19 | 94.89–99.96 | 97.76 | 93.10–99.42 | 100 | 97.13–100 | 97.32 | 91.79–99.31 |
| NPV | 93.93 | 91.78–95.55 | 95.18 | 93.19–96.63 | 100 | 99.25–100 | 92.13 | 89.79–93.98 |
See Table 1 for key.
Discussion
The present study revealed that CBCT provided more detailed and more accurate information than did dental radiography, thereby making CBCT better suited than dental radiography for use in diagnosing dental disorders in brachycephalic dogs. Although the Slices method had perfect scores of 100% for sensitivity, specificity, NPV, and PPV for 5 categories (missing teeth, abnormal eruption, abnormal number of roots, periodontitis, and tooth resorption), the 95% CI must be taken into consideration, especially for disorders with a low prevalence, to put these results into context.
We were able to correctly identify all missing teeth only by use of the Slices method, whereas retained tooth roots were missed or falsely found to be present by use of the Rad, Pano, and 3-D methods. The increased ability for the identification of retained deciduous roots or unerupted teeth by use of CBCT has been reported for humans.16,17 This likely is associated with the higher contrast and larger, density-related spectrum (ranging from white to black) displayed with the Slices method, compared with the gray scale depicted with dental radiographs or the Pano method or the color spectrum (ranging from white to orange) displayed with the 3-D method in tooth mode, which made it especially difficult when retained tooth roots or tooth fragments were also affected by resorption. However, partial overlap of anatomic structures or adjacent teeth as a result of crowding in brachycephalic dogs may also have played a role.
Mean age of dogs in the present study was 7.36 years, with the youngest dog being 8 months old. Thus, the 46 partially erupted and 10 unerupted teeth were more likely attributable to brachycephaly and crowding of teeth that blocked the natural eruption path, rather than to the age of the examined patients. The low sensitivity for the 3-D method was primarily attributable to the difficulty of discerning enamel from cementum and, therefore, identifying the cementoenamel junction in tooth and bone mode, whereas these structures were easily identified on dental radiographs and with the Pano and Slices methods. The ability to additionally define the exact height of the alveolar margin around each tooth by use of the Slices method might explain the clear advantage for that method over the Rad, Pano, and 3-D methods for evaluating the eruption of teeth.
To limit the number of views and the image adjustment time, the maxillary fourth premolar tooth was evaluated together with the maxillary second and third premolar teeth. Because of the curved nature of the maxillary alveolar margin in brachycephalic dogs, these teeth are not positioned in a straight line. For displaying the dentition on panoramic images with the CBCT software, the teeth to be evaluated must be included in a focal trough with a customizable path and thickness. When the curvature of the maxilla was followed by the focal trough during preparation of the panoramic images, some teeth that were rotated in relation to the long axis of the skull appeared realigned. In addition, the sometimes extreme curvature of the focal trough led to distortion of the images, which subsequently impaired the ability to correctly identify all rotated teeth with the Pano method.
The value of CBCT for use in the evaluation of tooth and root canal morphology in humans has recently been reported.18–23 Root dilaceration can be found both in the mesiodistal and linguobuccal or palatobuccal directions. However, by use of the Rad and Pano methods, only root dilaceration in the mesiodistal direction could be detected. The low detection rate with the 3-D method likely was attributable to the difficulty of precisely outlining the roots in tooth mode when the surrounding bone was thick and the inability to separate the roots from each other in areas of crowding. The higher diagnostic yield for the Slices method likely was attributable to the ability to exclude overlapping structures.
The Slices method had the highest sensitivity for detecting teeth with an abnormal number of roots, which supports results of a study24 conducted to compare CBCT with panoramic radiography for reliability in identifying roots of mandibular third molar teeth in humans. The increased difficulty of identifying an abnormal number of roots by use of the Pano method, compared with the Rad method, revealed that the benefit of true lateral imaging for the Pano method in the present study was outweighed by the higher resolution of dental radiographs.
Periodontal disease is one of the most common medical disorders in dogs.25,26 In the study reported here, most of the teeth affected by periodontitis were located in areas of crowding. In humans, crowding of teeth represents a cumulative risk potential for chronic inflammatory processes, such as periodontitis,27 which could at least partially explain why brachycephalic dogs often have more severe periodontal disease than do mesaticephalic or dolichocephalic dogs of the same age.
Lesions on the buccal or lingual aspect of a tooth cannot be clearly identified on intraoral radiographs.28 This might explain the reason that findings for the Slices method coincided with the point of reference because the bone level was easily detectable around the entire tooth or within the furcation area of teeth with multiple roots.
Studies29,30 conducted to compare the use of 2-D and 3-D images for identifying artificial bone defects have revealed that dental radiography has a sensitivity of 63% to 67% for the detection and classification of bone defects, whereas CBCT has a sensitivity of 80% to 100%, which agrees with the findings of the present study. The tendency to underinterpret the extent of bone loss on dental radiographs was likely associated with angulation of the beam leading to superimposition of the lingual or palatal and buccal alveolar bone margin and the inability to precisely identify the level of bone height in areas of crowding. For the Pano method, which is similar to a parallel beam technique, the bone level was more easily identified, compared with the ease of identification for the Rad method. However, the Pano method did not prove helpful in areas of crowding, likely because of superimposition. Severity of periodontitis was similarly both overinterpreted and underinterpreted by use of the 3-D method. A big disadvantage when evaluating 3-D images, which contributed to the lower sensitivity of the 3-D method for use in evaluating periodontitis, was the forcible stepwise adjustment of the level and brightness settings that influenced density of the depicted tissue. Because the settings were adjusted so that oral soft tissues would not be shown, the stepwise regulation likely led to density of thinner and softer bone also being ignored and therefore resulted in the tendency that alveolar bone loss would be overinterpreted and underinterpreted.
It is important to understand that the sensitivity of an imaging technique for use in detecting loss of tooth integrity is related to the severity of tooth damage and that diagnostic imaging should not be used as the sole method for evaluating pulp exposure but, instead, should always be used in combination with dental probing and charting. In the study reported here, the superior resolution provided by the Rad method aided in the detection of small crown defects, such as enamel fractures or mild attrition or abrasions that were commonly missed with the 3-D and Slices methods. The entire surface of the crown cannot be evaluated with the Slices method without increasing the thickness of the multiplanar reconstruction, which was not performed for the present study, and likely was the reason for the inability to identify these subtle crown defects. Most of the retained tooth roots that were missed by use of the Rad or Pano methods were located in areas of crowding and overlapping anatomic structures. The clear advantage of the Slices method is the ability to triangulate a retained tooth root (ie, simultaneously view the exact same point in 3 planes without any overlap of adjacent structures), which allows for the identification as well as the spatial localization of anatomic structures. The higher accuracy for the Slices method in the diagnosis of root fractures in the present study has been supported by findings for several human endodontic studies.31–34
Accuracy of CBCT for use in the identification of periapical disease has been established in human dentistry.35–41 Two studies42,43 of dogs, which compared findings for periapical radiography with CBCT findings and used histopathologic evidence as the criterion-referenced standard, revealed that use of dental radiography detected fewer periapical lesions than did use of CBCT and also underestimated their size. Although advanced periapical lesions are easily identified on dental radiographs, the diagnostic yield for dental radiography is less because of 2-D images, geometric distortion, and anatomic overlap. These disadvantages are eliminated by use of the Slices method because the orientation of the custom cross sections allows for an orthogonal view that is perpendicular to the long axis of the tooth root being investigated, which in turn provides highly detailed images of the area of interest without any superimposition.
In accordance with results of a previous study44 of dogs, external replacement resorption and external inflammatory root resorption were the most common types of tooth resorption in brachycephalic dogs of the present study. Use of CBCT as a diagnostic method for the evaluation of tooth resorption has been validated in human dentistry.45–49 Resorption of tooth substance can occur on any surface of a tooth, which makes dental radiography and the Pano method less suited for their detection as well as for their differentiation. External inflammatory resorption or root surface resorption can be mistaken for internal inflammatory resorption with both of these methods if they are located on the lingual, palatal, or buccal aspect of the tooth because they are displayed superimposed onto the pulp cavity. Possible advantages of the Slices method were in the ability to evaluate both the tooth surface and pulp cavity seperately and from every angle, and this was reflected in the highest sensitivity for the present study.
Limitations for the study reported here included the lack of histopathologic evidence of disease, which is an inherent problem with clinical studies. It is possible that certain lesions were missed by use of both dental radiography and CBCT, thereby falsely elevating or decreasing the reported accuracy of dental radiography, CBCT, or both. Additionally, the presence of lesions identified with use of CBCT but not with use of dental radiography (or vice versa) raised the question of validity for either of the diagnostic imaging modalities. The absence of definitive and objective methods (eg, information in a necropsy report) required that the evaluation method be determined by consensus of all 4 investigators.
Some dental disorders, such as an abnormal number of roots, periapical disease, or failure of the pulp cavity to narrow, had a low prevalence. Low prevalence influences the 95% CI for each statistical variable, which was extremely wide, and accuracy, which was high regardless of sensitivity because of the high number of true negative results, and apprehension about some of the results reported here may be justified.
In a clinical setting, findings on dental radiographs are combined with findings for periodontal probing and dental charting to compensate for some of the shortcomings of dental radiography. However, a comparison of CBCT and dental radiography combined with findings of periodontal probing and dental charting was beyond the scope of the study reported here.
For the study reported here, we qualitatively assessed the ability to identify dental disorders in brachycephalic dogs by use of dental radiography and 3 CBCT software modules. When all 3 CBCT software modules were used in combination, the diagnostic yield for CBCT was significantly higher than that for dental radiography in 4 of 10 categories (abnormal eruption, abnormally shaped roots, periodontitis, and tooth resorption) and higher, although not significantly so, in all dental disorders, except for 1 (loss of tooth integrity). Direct comparison of dental radiography and CBCT revealed that although resolution played an important role, the ability to obtain an unobstructed view of dental pathological conditions, as was obtained by use of the Slices method, resulted in a higher diagnostic yield for CBCT. In a clinical setting, 3-D images will help clinicians quickly get an overall impression of dental health and disease, whereas the Pano method will serve well for the evaluation of tooth integrity. However, the most detailed information can be gained by use of the Slices method.
Acknowledgments
Supported by the University of California-Davis Center for Companion Animal Health.
The authors did not have any conflicts of interest with the sources of materials or companies described in this manuscript.
The authors thank John Doval for assistance with the figures and Megan Loscar, Monica Calder, and Kimi Kan-Rohrer for preparation of the images for review.
ABBREVIATIONS
| CBCT | Cone-beam CT |
| CI | Confidence interval |
| NPV | Negative predictive value |
| PPV | Positive predictive value |
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Appendix
Predefined dental disorders evaluated in brachycephalic dogs by use of dental radiography and CBCT for each of 3 software modules.
| Anatomic or developmental disorders = Missing tooth, abnormal eruption, abnormally shaped root, abnormal number of roots, and rotation. |
| Periodontitis* (evident as alveolar bone loss) = VBL < 25%, VBL 25%–50%, VBL > 50%, HBL > 25%, HBL 25%–50%, HBL > 50%, furcation involvement, and furcation exposure. |
| Tooth resorption = External inflammatory resorption, internal inflammatory resorption, and external root replacement resorption. |
| Endodontal disease = Loss of tooth integrity (attrition or abrasion, uncomplicated crown fracture [including enamel fracture], complicated crown fracture, uncomplicated crown-root fracture, complicated crown-root fracture, and root fracture [including retained tooth roots with a missing coronal segment]), failure of the pulp cavity to narrow, and periapical lucency (P-E type 1 ill-defined, P-E type 1 well-defined, P-E type 2 ill-defined, P-E type 2 well-defined, P-E type 3 ill-defined, P-E type 3 well-defined, periapical lucency ill-defined, and periapical lucency well-defined). |
VBL < 25% and HBL < 25% = Mild periodontitis, which correlates with stage 2 periodontal disease.15 VBL 25% to 50% and HBL 25% to 50% = Moderate periodontitis, which correlates with stage 3 periodontal disease.15 VBL > 50% and HBL > 50% = Severe periodontitis, which correlates with stage 4 periodontal disease.15
HBL = Horizontal bone loss. P-E = Combined periodontal-endodontic lesion. VBL = Vertical bone loss.
