Effects of low-dose irradiation on human osteoblasts and periodontal ligament cells

OBJECTIVE

To investigate the effects of dental x-ray on proliferation and mineralization in human primary osteoblasts as well as on proliferation and apoptotic potential in human periodontal ligament (PDL) cells.

DESIGN

Primary osteoblasts and PDL cells were irradiated with various doses of periapical radiography by repeated exposures and further incubated for 1, 3 or 7 days. Cell proliferation was assayed by BrdU incorporation. The effect of dental x-ray on mineralization in osteoblasts either before or after x-ray exposures was determined by Alizarin red staining. Both mRNA and protein expressions of BCL-2, an anti-apoptotic gene, and BAX, a pro-apoptotic gene, in PDL cells were analyzed by RT-qPCR and immunoblotting analysis, respectively.

RESULTS

Neither the proliferative nor the mineralization ability of irradiated osteoblasts was different from that of non-irradiated osteoblasts at any doses or time points. By contrast, there was a significant decrease in the proliferation of PDL cells on day 3 after repeated exposures to dental x-ray for 20 times (P < 0.05), whereas the ratio of BCL-2 to BAX mRNA and protein expressions in these irradiated PDL cells was significantly increased (P < 0.05).

CONCLUSIONS

Upon multiple exposures to dental x-ray used in intraoral radiography up to 20 times, there is no effect on the proliferation or the mineralization of osteoblasts, whereas the proliferative and apoptotic potentials of PDL cells are transiently decreased.

Reproducibility analysis of automated deep learning based localisation of mandibular canals on a temporal CBCT dataset

Preoperative radiological identification of mandibular canals is essential for maxillofacial surgery. This study demonstrates the reproducibility of a deep learning system (DLS) by evaluating its localisation performance on 165 heterogeneous cone beam computed tomography (CBCT) scans from 72 patients in comparison to an experienced radiologist's annotations. We evaluated the performance of the DLS using the symmetric mean curve distance (SMCD), the average symmetric surface distance (ASSD), and the Dice similarity coefficient (DSC). The reproducibility of the SMCD was assessed using the within-subject coefficient of repeatability (RC). Three other experts rated the diagnostic validity twice using a 0-4 Likert scale. The reproducibility of the Likert scoring was assessed using the repeatability measure (RM). The RC of SMCD was 0.969 mm, the median (interquartile range) SMCD and ASSD were 0.643 (0.186) mm and 0.351 (0.135) mm, respectively, and the mean (standard deviation) DSC was 0.548 (0.138). The DLS performance was most affected by postoperative changes. The RM of the Likert scoring was 0.923 for the radiologist and 0.877 for the DLS. The mean (standard deviation) Likert score was 3.94 (0.27) for the radiologist and 3.84 (0.65) for the DLS. The DLS demonstrated proficient qualitative and quantitative reproducibility, temporal generalisability, and clinical validity.

Comparing the pulp/tooth area ratio and dentin thickness of mandibular first molars in different age groups: A cone-beam computed tomography study

Context

Mandibular first molar frequently requires endodontic treatment. Understanding age-related changes in pulp-dentin complex and root canal morphologies is essential for successful endodontic and restorative treatments.

Aim

This study aimed to compare pulp/tooth area ratio (PTAR) and dentin thickness (DT) in mandibular first molars in different age groups through cone-beam computed tomography (CBCT) imaging.

Subjects and Methods

One hundred CBCT images of mandibular first molar were divided into five groups; age 20-29, 30-39, 40-49, 50-59, and 60 years old and older. Axial images were used to determine PTAR at Level A (furcation), Level B (between Levels A and C), and Level C (half distance between the furcation and apex of the root). The minimum DT of the distal wall of mesiobuccal (MB) and mesiolingual (MLi) canal and mesial wall of distal canal at 2 and 3 mm under the furcation was measured.

Statistical Analysis Used

Analysis of variance was used to determine differences among age groups.

Results

PTAR was determined to reduce as age increases, showing a significant difference among the age groups at Levels A, B, and C of both roots (P < 0.05). The minimum DT was found to increase with age, demonstrating a significant difference among the age groups of MB and MLi canal at 2 and 3 mm (P < 0.05). No statistically significant difference was observed in the mesial DT of distal canal.

Conclusions

The reduction of PTAR and the increasing DT were confirmed with advanced age.