Diagnostic accuracy of cone-beam computed tomography scans with high- and low-resolution modes for the detection of root perforations
Purpose This study compared the diagnostic accuracy of cone-beam computed tomography (CBCT) scans obtained with 2 CBCT systems with high- and low-resolution modes for the detection of root perforations in endodontically treated mandibular molars. Materials and Methods The root canals of 72 mandibular molars were cleaned and shaped. Perforations measuring 0.2, 0.3, and 0.4 mm in diameter were created at the furcation area of 48 roots, simulating strip perforations, or on the external surfaces of 48 roots, simulating root perforations. Forty-eight roots remained intact (control group). The roots were filled using gutta-percha (Gapadent, Tianjin, China) and AH26 sealer (Dentsply Maillefer, Ballaigues, Switzerland). The CBCT scans were obtained using the NewTom 3G (QR srl, Verona, Italy) and Cranex 3D (Soredex, Helsinki, Finland) CBCT systems in high- and low-resolution modes, and were evaluated by 2 observers. The chi-square test was used to assess the nominal variables. Results In strip perforations, the accuracies of low- and high-resolution modes were 75% and 83% for NewTom 3G and 67% and 69% for Cranex 3D. In root perforations, the accuracies of low- and high-resolution modes were 79% and 83% for NewTom 3G and was 56% and 73% for Cranex 3D. Conclusion The accuracy of the 2 CBCT systems was different for the detection of strip and root perforations. The Cranex 3D had non-significantly higher accuracy than the NewTom 3G. In both scanners, the high-resolution mode yielded significantly higher accuracy than the low-resolution mode. The diagnostic accuracy of CBCT scans was not affected by the perforation diameter.
Determination of Root Canal Length Up to Perforation Area Using Different Electronic Apex Locators and CBCT Images Obtained at Different Voxel Sizes: A Comparative Ex Vivo Study.
OBJECTIVE
To compare the accuracy of electronic apex locators in the presence of blood and CBCT images obtained with two different voxel sizes (0.125 mm and 0.25 mm) in determining root canal length up to the perforation area.


METHODS
Forty extracted, single-rooted human teeth were selected and an artificial root perforation (0.4 ± 0.1 or 1.0 ± 0.2 mm diameter) was created in the middle third of the root. The actual root canal length up to the perforation area was determined under a stereomicroscope. CBCT images were obtained with a voxel size of 0.125 mm and 0.25 mm. The root canal length up to the perforation area was measured on CBCT images and recorded as the radiographic length. The teeth were embedded in alginate and root canal length up to the perforation area was measured using two different EALs (DentaPort ZX [Morita, Tokyo, Japan] and Gold Reciproc motor [VDW, Munich, Germany]) and recorded as the electronic length.


RESULTS
In teeth with an artificial root perforation 0.4 mm in diameter, the measurements obtained with DentaPort ZX were more accurate than with the Gold Reciproc motor (P ˂ 0.05), and on CBCT images, more accurate measurements were obtained with a voxel size of 0.125 mm compared to 0.25 mm (P ˂ 0.05). In teeth with an artificial root perforation 1.0 mm in diameter, the radiographic length was closer to actual length than the electronic length (P ˂ 0.05).


CONCLUSION
In artificial root perforations with a diameter of 0.4 mm, CBCT gives more reliable results than EALs. Both EAL and CBCT measurements were closer to actual length in artificial perforations that were 1.0 mm in diameter.
X-rays and photocarcinogenesis in hairless mice
It is well known that excessive X-ray radiation can cause non-melanoma skin cancers. With the increased incidence of sun-related skin cancer there is a need to investigate the combination of sunlight and X-rays. Immunocompetent C3.Cg/TifBomTac mice (n = 298) were divided into 12 groups. Mice were irradiated with 12, 29 or 50 kV X-rays. The mice received a total dose of 45 Gy. They were irradiated with 3 SED simulated solar radiation (SSR) either before or after irradiation with X-rays. The groups irradiated with X-rays alone, 0, 3, 9 and 10 mice (0, 12, 29 and 50 kV, respectively) developed squamous cell carcinoma. In the groups irradiated with SSR after X-rays the development of tumours was significantly faster in the 50 kV group than in the corresponding control group (175 vs. 194 days, p < 0.001). In the groups irradiated with SSR prior to the X-ray radiation the development of tumours was significantly faster in the 29 and the 50 kV groups than in the corresponding control group (175 vs. 202 days, p < 0.001 and 158 vs. 202 days, p < 0.001, respectively). In conclusion, X-ray radiation alone is a weak carcinogen in hairless mice. There is an added carcinogenic effect if X-ray radiation is given on prior sun-exposed skin or if the skin is sun-exposed after X-rays. We still believe that X-ray radiation is a safe and effective therapy for various dermatological diseases but caution should be observed if a patient has severely sun-damaged skin or has a high-risk sun behaviour.