A comprehensive review of the literature on the biological effects from dental X-ray exposures

Development and validation of a questionnaire on radiation protection knowledge, attitudes, and practices among Moroccan dentists

PURPOSE

This study aimed to develop and evaluate the validity and reliability of dentists' radiation protection knowledge, attitudes, and practices (DRP-KAPs) questionnaire.

METHODS

This study was conducted using a stepwise approach. In the first step, items were generated to determine the relevant content and domains after a thorough literature review. In the second step, the content validity of the questionnaire was assessed by seven experts using face and content validity. The content validity index for relevance and clarity (I-CVI, S-CVI/Av, and S-CVI/UA) and the content validity ratio (CVR) were performed. Then, the questionnaire was pre-tested with 10 dentists for face validation. In the third step, reliability was assessed using internal consistency (Kuder-Richardson-20 (KR-20) and Cronbach's alpha) and test-retest (Kappa and intraclass correlation coefficient [ICC]) methods by filling out the questionnaire by 100 dentists practicing in the Rabat-Salé-Kénitra region, in Morocco.

RESULTS

The finalized DRP-KAPs questionnaire contains 41 items covering knowledge, attitudes and practices (KAPs). The I-CVIs, S-CVI/UA and S-CVI/AV and CVR values of the 41 items were ≥0.86 for each item, ≥0.82, ≥0.97, and ≥0.71, respectively. With regard to internal consistency reliability, the KR-20 coefficients for the knowledge and practice domains were 0.70 and 0.68, respectively, and the Cronbach alpha for the attitude domain was 0.73. The DRP-KAPs questionnaire has good reliability with the ICC coefficients for attitude items ranging from 0.57 to 0.95 and Kappa coefficients for knowledge and practice items ranging from 0.64 to 1 and 0.77 to 1, respectively.

CONCLUSION

The developed DRP-KAPs questionnaire was found to be a noteworthy tool for assessing radiation protection among dentists, with acceptable internal consistency, good ICC and Kappa coefficients, and good content validity indices.

Transfer Learning-Based Classifier to Automate the Extraction of False X-Ray Images From Hospital's Database

BACKGROUND

During preclinical training, dental students take radiographs of acrylic (plastic) blocks containing extracted patient teeth. With the digitisation of medical records, a central archiving system was created to store and retrieve all x-ray images, regardless of whether they were images of teeth on acrylic blocks, or those from patients. In the early stage of the digitisation process, and due to the immaturity of the data management system, numerous images were mixed up and stored in random locations within a unified archiving system, including patient record files. Filtering out and expunging the undesired training images is imperative as manual searching for such images is problematic. Hence the aim of this stidy was to differentiate intraoral images from artificial images on acrylic blocks.

METHODS

An artificial intelligence (AI) solution to automatically differentiate between intraoral radiographs taken of patients and those taken of acrylic blocks was utilised in this study. The concept of transfer learning was applied to a dataset provided by a Dental Hospital.

RESULTS

An accuracy score, F1 score, and a recall score of 98.8%, 99.2%, and 100%, respectively, were achieved using a VGG16 pre-trained model. These results were more sensitive compared to those obtained initally using a baseline model with 96.5%, 97.5%, and 98.9% accuracy score, F1 score, and a recall score respectively.

CONCLUSIONS

The proposed system using transfer learning was able to accurately identify "fake" radiographs images and distinguish them from the real intraoral images.

Multi-label dental disorder diagnosis based on MobileNetV2 and swin transformer using bagging ensemble classifier

Dental disorders are common worldwide, causing pain or infections and limiting mouth opening, so dental conditions impact productivity, work capability, and quality of life. Manual detection and classification of oral diseases is time-consuming and requires dentists' evaluation and examination. The dental disease detection and classification system based on machine learning and deep learning will aid in early dental disease diagnosis. Hence, this paper proposes a new diagnosis system for dental diseases using X-ray imaging. The framework includes a robust pre-processing phase that uses image normalization and adaptive histogram equalization to improve image quality and reduce variation. A dual-stream approach is used for feature extraction, utilizing the advantages of Swin Transformer for capturing long-range dependencies and global context and MobileNetV2 for effective local feature extraction. A thorough representation of dental anomalies is produced by fusing the extracted features. To obtain reliable and broadly applicable classification results, a bagging ensemble classifier is utilized in the end. We evaluate our model on a benchmark dental radiography dataset. The experimental results and comparisons show the superiority of the proposed system with 95.7% for precision, 95.4% for sensitivity, 95.7% for specificity, 95.5% for Dice similarity coefficient, and 95.6% for accuracy. The results demonstrate the effectiveness of our hybrid model integrating MoileNetv2 and Swin Transformer architectures, outperforming state-of-the-art techniques in classifying dental diseases using dental panoramic X-ray imaging. This framework presents a promising method for robustly and accurately diagnosing dental diseases automatically, which may help dentists plan treatments and identify dental diseases early on.

Attitudes and practices of radiation protection among Jordanian dental radiography practitioners

INTRODUCTION

Varying radiation protection practices have been documented in the literature. This study aims to evaluate the attitudes and practices of dental radiography practitioners towards radiation protection in Jordan, as no data currently explores their understanding and practices in this area.

METHODS

The survey involved 192 dental radiography practitioners. A cross-sectional, self-administered questionnaire containing 43 questions covered socio-demographic data, practices towards radiation protection, and attitudes.

RESULTS

The majority of participants were less than 40 years old (87.5 %), with 66.7 % working in private clinics and 53.6 % based in the capital city of Jordan. Nearly a quarter (26.5 %) of the practitioners used an X-ray tube voltage of 65-70 kVp; however, 14.6 % were unaware of the X-ray tube voltage used in their machines. Additionally, almost one quarter of the participants never or rarely used light beam positioning aids and available positioning guides in panoramic radiography practice. Only 33.3 % of practitioners consistently used lead aprons, with the main reasons for non-use being the weight of the apron or its unavailability. About 81 % of participants believed in spreading awareness about radiation protection and applying this knowledge in their daily practices.

CONCLUSIONS

The study found that the practitioners' practices were satisfactory to some extent, supported by a positive attitude towards radiation protection. The participants understand the importance of increasing their awareness and knowledge of radiation protection practices.

IMPLICATIONS FOR PRACTICE

The findings of this study highlight the need to improve radiation protection practices among dental radiography practitioners in Jordan by introducing standard dose protocols, supporting the transition to digital systems, establishing diagnostic reference levels, and encouraging the use of equipment over staff holding practices, and raising awareness about radiation safety.

Impacted mandibular third molars: a comparison of orthopantomography and cone-beam computed tomography imaging in predicting surgical difficulty

BACKGROUND

This study investigated the predictive value of orthopantomography (OPG) for the difficulty of extracting impacted mandibular third molars, in comparison with cone-beam computed tomography (CBCT).

METHODS

In this descriptive quantitative investigation, two oral and maxillofacial radiologists evaluated OPG and three-dimensional CBCT images according to the Pell-Gregory and Winter classifications. The results for the classification were compared using the chi-square test, and the prediction of difficulty was assessed using the Pederson scale, with a significance level of p< 0.05.

RESULTS

The study included 30 patients (14 men and 16 women), providing a total of 53 samples of impacted mandibular third molars. Of these, 30 (56.6%) were from the right side and 23 (43.4%) from the left. There was a statistically significant difference between the OPG and CBCT images concerning their relation to the mandibular ramus (p< 0.05). However, evaluations based on occlusal lines and angulation showed no significant differences (p> 0.05). According to the Pederson scale, significant differences were observed between OPG and CBCT in predicting extraction difficulty (p< 0.05).

CONCLUSION

CBCT offered a more accurate assessment of the surgical difficulty associated with mandibular third molars than OPG. OPG views frequently failed to adequately visualize the region of the mandibular ramus, influencing the perceived difficulty of mandibular third molar surgery. In certain cases, the use of CBCT imaging is crucial.

Development of Artificial Intelligence Models for Tooth Numbering and Detection: A Systematic Review

Dental radiography is widely used in dental practices and offers a valuable resource for the development of AI technology. Consequently, many researchers have been drawn to explore its application in different areas. The current systematic review was undertaken to critically appraise developments and performance of artificial intelligence (AI) models designed for tooth numbering and detection using dento-maxillofacial radiographic images. In order to maintain the integrity of their methodology, the authors of this systematic review followed the diagnostic test accuracy criteria outlined in PRISMA-DTA. Electronic search was done by navigating through various databases such as PubMed, Scopus, Embase, Cochrane, Web of Science, Google Scholar, and the Saudi Digital Library for the articles published from 2018 to 2023. Sixteen articles that met the inclusion exclusion criteria were subjected to risk of bias assessment using QUADAS-2 and certainty of evidence was assessed using GRADE approach.AI technology has been mainly applied for automated tooth detection and numbering, to detect teeth in CBCT images, to identify dental treatment patterns and approaches. The AI models utilised in the studies included exhibited a highest precision of 99.4% for tooth detection and 98% for tooth numbering. The use of AI as a supplementary diagnostic tool in the field of dental radiology holds great potential.

Sex estimation from maxillofacial radiographs using a deep learning approach

The purpose of this study was to construct deep learning models for more efficient and reliable sex estimation. Two deep learning models, VGG16 and DenseNet-121, were used in this retrospective study. In total, 600 lateral cephalograms were analyzed. A saliency map was generated by gradient-weighted class activation mapping for each output. The two deep learning models achieved high values in each performance metric according to accuracy, sensitivity (recall), precision, F1 score, and areas under the receiver operating characteristic curve. Both models showed substantial differences in the positions indicated in saliency maps for male and female images. The positions in saliency maps also differed between VGG16 and DenseNet-121, regardless of sex. This analysis of our proposed system suggested that sex estimation from lateral cephalograms can be achieved with high accuracy using deep learning.

Associated risks with periodontal x-rays or CBCT scans: Are there any?

Periodontal and implant radiography, mainly including intra-oral peri-apical and cone beam computed tomography images, are crucial in the diagnosis and treatment planning process. However, radiation safety concerns have been a chronic concern over the years, leading to uncomfortable situations. It is therefore crucial to understand the actual radiation exposure to determine if the patients' fear of necessary diagnostic exams is justified. In this perspective article, we aimed to provide concise information on dental imaging exposure, risks, and benefits, comparing them to that of absorbed radiation from daily life activities; and secondarily, to help periodontists choose the best option for each case and become more confident in addressing patients' concerns and providing a summary of safety guidelines as a reference for them.

Optimizing radiation safety in dentistry: Clinical recommendations and regulatory considerations

BACKGROUND

The value of dental radiographs to oral health care decision making must be balanced with radiation safety to minimize patient exposure and occupational risk of oral health care providers. This review summarizes recommendations and regulatory guidance regarding dental radiography and cone-beam computed tomography. An expert panel presents recommendations on radiation safety, appropriate imaging practices, and reducing radiation exposure.

TYPES OF STUDIES REVIEWED

A systematic search run in Ovid MEDLINE, Embase, and Cochrane Database of Systematic Reviews identified relevant topical systematic reviews, organizational guidelines, and regulatory reviews published in the peer-reviewed literature since 2010. A supplemental search of the gray literature (eg, technical reports, standards, and regulations) identified topical nonindexed publications. Inclusion criteria required relevance to primary oral health care (ie, general or pediatric dentistry).

RESULTS

A total of 95 articles, guidance documents, and regulations met the inclusion criteria. Resources were characterized as applicable to all modalities, operator and occupational protection, dose reduction and optimization, and quality assurance and control.

PRACTICAL IMPLICATIONS

Understanding factors affecting imaging safety and applying fundamental principles of radiation protection consistent with federal, state, and local requirements are essential for limiting patient ionizing radiation exposure, in conjunction with implementing optimal imaging procedures to support prudent use of dental radiographs and cone-beam computed tomographic imaging. The regulatory guidance and best practice recommendations summarized in this article should be followed by dentists and other oral health care providers.

Genotoxic and Cytotoxic Effects of Cone Beam Computed Tomography and Multidetector Computed Tomography on Exfoliated Buccal Epithelial Cells

Background

Cone beam computed tomography (CBCT) and multidetector computed tomography (MDCT) are frequently used in dental and maxillofacial problems. This study aimed to assess the genotoxicity and cytotoxicity effects of CBCT and MDCT radiographies on exfoliated buccal epithelial cells during dental examinations.

Methods

This prospective experimental study was conducted at Babol University of Medical Sciences (Babol, Iran) from March 2021 to April 2021. Buccal mucosa smears were collected bilaterally pre-exposure and 12 days after CBCT or MDCT examinations. To compare the frequency of micronuclei and other cytotoxic cellular changes such as pyknosis, karyolysis, and karyorrhexis, the paired sample t test and Wilcoxon test were used. In addition, independent sample t test, Mann-Whitney, and Chi square tests were used to investigate the differences between the imaging methods and between men and women. All statistical analyses were performed using the SPSS software, and P≤0.05 was considered statistically significant.

Results

The current study included 60 adult patients (30 patients in each group), ranging in age from 21 to 50 years. The micronuclei and the other cytotoxic cellular changes increased significantly after CBCT and MDCT radiographic examinations on the 12th day compared to the pre-exposure results (P<0.001). MDCT had statistically higher cytotoxic and genotoxic effects than CBCT (9.4%, 23.1%, and 40% higher values in micronucleus frequency, the mean frequency of micronuclei, and other cytotoxic changes, respectively). There were no significant differences between men and women in the two examination methods (P=0.46 and P=0.49, respectively).

Conclusion

Dental examinations with CBCT and MDCT can increase cytotoxicity and chromosomal damage in both men and women. Due to its lower radiation toxicities, CBCT can be recommended as an alternative to MDCT for dental examinations.

Effects of low-dose ionizing radiation on genomic instability in interventional radiology workers

Interventional radiologists are chronically exposed to low-dose ionizing radiation (IR), which may represent a health risk. The aim of the present study was to evaluate genomic instability by analyzing chromosomal aberrations, micronuclei, and 53BP1 DNA repair foci in peripheral blood lymphocytes of radiologists. Based on the IAEA guidelines on biodosimetry using dicentrics, the average protracted whole-body dose in radiologists were estimated. Since preleukemic fusion genes (PFG) are the primary events leading to leukemia, we also studied their presence by RT-qPCR and FISH. No significant difference in 53BP1 foci and incidence of PFG (MLL-AF4, MLL-AF9, AML1-ETO, BCR-ABL p190) was found in cells of interventional radiologists in comparison to controls. However, our results showed an increased frequency of micronuclei and various types of chromosomal aberrations including dicentrics in interventional radiologists. The average protracted whole body estimated dose was defined at 452.63 mGy. We also found a significantly higher amplification of the MLL gene segment and increased RNA expression in cells of interventional radiologists in comparison to controls. In conclusion, our results showed that long-term low-dose IR induces genomic instability in interventional radiologists.

Is micronucleus assay a suitable method for biomonitoring children exposed to X-ray? A systematic review with meta-analysis

PURPOSE

The aim of this study was to evaluate if the micronucleus test using oral epithelial cells is a suitable biomarker for biomonitoring children exposed to X-ray.

MATERIAL AND METHODS

A search was performed through the electronic databases PubMed/Medline, Scopus, and Web of Science, all studies published up to February 2022 that examined the relationship between exposure of children to radiographic examinations and micronucleus.

RESULTS

A total of 17 full-text manuscripts were screened for eligibility. Only two studies found a difference in micronucleus labeling. On the other hand, all studies showed that X-ray was able to induce cellular death in oral mucosa cells. Following the parameters of the Effective Practices in Public Health Project (EPHPP), five manuscripts reached moderate and strong scores, and four studies were categorized as weak at final rating. In the meta-analysis, statistically significant difference was detected in micronucleated cells in children before and after radiographic examinations (SMD = 0.96, 95% CI, 0.07-1.84, p = .04), with τ2=1.09; χ2=53.37, and p < .001.

CONCLUSION

Radiographic examinations in children can cause genotoxic and cytotoxic damage in the oral epithelium with a large effect size.

Application of Cone Beam Computed Tomography in Risk Assessment of Lower Third Molar Surgery

Risks of lower third molar surgery like the inferior alveolar nerve injury may result in permanent consequences. Risk assessment is important prior to the surgery and forms part of the informed consent process. Traditionally, plain radiographs like orthopantomogram have been used routinely for this purpose. Cone beam computed tomography (CBCT) has offered more information from the 3D images in the lower third molar surgery assessment. The proximity of the tooth root to the inferior alveolar canal, which harbours the inferior alveolar nerve, can be clearly identified on CBCT. It also allows the assessment of potential root resorption of the adjacent second molar as well as the bone loss at its distal aspect as a consequence of the third molar. This review summarized the application of CBCT in the risk assessment of lower third molar surgery and discussed how it could aid in the decision-making of high-risk cases to improve safety and treatment outcomes.

Prepolarized MRI of hard tissues and solid-state matter

Prepolarized MRI (PMRI) is a long-established technique conceived to counteract the loss in signal-to-noise ratio (SNR) inherent to low-field MRI systems. When it comes to hard biological tissues and solid-state matter, PMRI is severely restricted by their ultra-short characteristic relaxation times. Here we demonstrate that efficient hard-tissue prepolarization is within reach with a special-purpose 0.26 T scanner designed for ex vivo dental MRI and equipped with suitable high-power electronics. We have characterized the performance of a 0.5 T prepolarizer module, which can be switched on and off in 200 μs. To this end, we have used resin, dental and bone samples, all with T 1 times of the order of 20 ms at our field strength. The measured SNR enhancement is in good agreement with a simple theoretical model, and deviations in extreme regimes can be attributed to mechanical vibrations due to the magnetic interaction between the prepolarization and main magnets.

Informational content of two-dimensional panoramic radiographs and lateral cephalometric radiographs with respect to the bone volume of intraoral donor regions considering CBCT imaging

BACKGROUND

To test the hypothesis that cephalometric parameters in two-dimensional routine dental radiographs correlate with the bone volume of intraoral bone donor sites.

METHODS

One-hundred and eight radiographs [36 panoramic radiographs (PRs), 36 lateral cephalometric radiographs (LCRs), and 36 cone-beam computed tomography scans (CBCT)] of 36 patients (all three imaging techniques applied according to the needs of treatment planning), were analyzed individually. Cephalometric parameters (PR and LCR) were correlated with the bone volume measurement in three-dimensional CBCT scans in three intraoral donor sites (chin, mandibular retromolar region, and zygomatic alveolar crest).

RESULTS

The mean bone volumes measured for the chin were (3.10 ± 1.11 cm³ SD), the mandibular retromolar region (1.66 ± 0.54 cm³ SD), and the zygomatic alveolar crest (0.17 ± 0.04 cm³ SD). Cephalometric parameters were significantly correlated (all p-values < 0.05) with the bone volume in the chin and the mandibular retromolar region. The bone volume of the zygomatic alveolar crest exhibited no correlations (p > 0.05) with cephalometric parameters. However, it was significantly correlated (p < 0.01) with the mandibular retromolar bone volume. No gender-specific differences (p > 0.05) were observed concerning bone volumes in all bone harvesting regions. Nevertheless, the male population's interforaminal distance in the chin region was significantly higher (p = 0.001).

CONCLUSIONS

PRs and LCRs can be used at the initial stage of peri-implant augmentation planning to deduce conclusions about the bone volume in different intraoral bone donor sites. It can help describe indications and justify additional diagnostic options, such as three-dimensional radiologic techniques.

Cytotoxicity, genotoxicity, and immunohistochemical expression of p53 in the oral mucosal epithelium of adults following cone-beam computed tomography

This study sought to assess the cytotoxicity, genotoxicity, and immunohistochemical (IHC) expression of p53 in the oral mucosal epithelium of adults following cone-beam computed tomography (CBCT). This before-and-after observational study evaluated 30 patients (15 males and 15 females); mean age 35 years, who required CBCT. Exfoliating epithelial cells of the buccal mucosa were collected with a cotton swab immediately before and 10 days after CBCT. Following Papanicolaou staining, genotoxicity was evaluated by the micronucleus assay. The frequencies of pyknosis, karyorrhexis, karyolysis, budding and binucleation as cytotoxicity factors were also recorded. Expression of p53 was evaluated by IHC staining. Data were analyzed by paired samples t-test. Micronucleated cells, pyknosis, karyorrhexis, karyolysis, budding, cytotoxicity, and expression of p53 increased significantly after CBCT. CBCT exerts genotoxic and cytotoxic effects and leads to overexpression of p53 protein in the oral buccal mucosal cells.

Inductively Coupled Intraoral Flexible Coil for Increased Visibility of Dental Root Canals in Magnetic Resonance Imaging

OBJECTIVES

Accurate visualization of dental root canals is vital for the correct diagnosis and subsequent treatment. This work assesses the improvement of a dedicated new coil for dental magnetic resonance imaging (MRI) in comparison to conventional ones in terms of signal-to-noise ratio (SNR) and visibility.

MATERIALS AND METHODS

A newly developed intraoral flexible coil was used to display dental roots with MRI, and it provides improved sensitivity with a loop design and size adjusted to a single tooth anatomy. Ex vivo and in vivo measurements were performed on a 3 T clinical MR system, and results were compared with conventional head and surface coil images. Additional comparison was performed with a modified fast spin echo sequence and a constructive interference in steady-state sequence.

RESULTS

Ex vivo, an SNR gain of 6.3 could be achieved with the intraoral flexible coil setup, and higher visibility down to 200 μm was possible, whereas the external loop coil is limited to 400 μm. In vivo measurements in a volunteer resulted in an SNR gain of up to 4.5 with an improved delineation of the root canals, especially for the branch tissue splitting of the mesial root canal into mesial-buccal and mesial-lingual.

CONCLUSIONS

In summary, we showed the feasibility of implementing a wireless coil approach with readily available dental practice materials for sealing and placement. Highly improved MRI scans can be acquired within clinically feasible scan times, and this might provide additional medical findings to supplement available x-ray images.

Optical Coherence Tomography for Patients with Developmental Disabilities: A Preliminary Study

Dental radiographs are essential for diagnosis and treatment planning, but are sometimes difficult to acquire for patients with developmental disabilities (PDD). Optical Coherence Tomography (OCT) is a non-ionizing imaging modality that has the potential application as an alternative to dental radiographs for PDD. This study aimed to determine the feasibility of intraoral OCT imaging for PDD. Ten participants were recruited in the Dental Education in the Care of Persons with Disabilities (DECOD) Clinic to explore the utility of dental OCT. The prototype system (Yoshida Dental) creates in-depth and three-dimensional images of teeth. The participants indicated their degree of pain during imaging on the Wong-Baker FACES Pain Rating Scale, and the degree of discomfort after imaging on a visual analog scale. OCT can be used for patients with developmental disabilities with minimal levels of pain and discomfort, without ionizing radiation.

Plasma Proteins As Biodosimetric Markers of Low-Dose Radiation in Mice

Long-term exposures to low-dose radiation (LDR) may trigger several specific biological responses, including dysregulation of the immune and inflammatory systems. Here, we examined whether biodosimetry of LDR can be used to protect tissues from radiation or assess cancer risk. Mice were subjected to gamma-irradiation with repeated or single-dose LDR, and then the organ indices, peripheral hemogram, and blood biochemistry were analyzed. An antibody array was applied followed by enzyme-linked immunosorbent assay to evaluate the utility of multiple plasma proteins as biomarkers of repeated LDR in a murine model. LDR induced inapparent symptoms but slight variations in peripheral blood cell counts and alterations in blood biochemical indicator levels. Specific plasma proteins in the LDR groups were altered in response to a higher dose of irradiation at the same time points or a single-dose equivalent to the same total dose. Plasma levels of interleukin (IL)-5, IL-12p40, P-selectin, and serum amyloid A1 were associated with the LDR dose and thus may be useful as dosimetric predictors of LDR in mice. Estimating the levels of certain plasma proteins may yield promising biodosimetry parameters to accurately identify individuals exposed to LDR, facilitating risk assessment of long-term LDR exposure in individuals.

Biological effects of electron beam to target turning X-ray (EBTTX) on two freesia (Freesia hybrida) cultivars

Electron beam to target turning X-ray (EBTTX) is an emerging irradiation technology that can potentially accelerate the breeding process of plants. The biological effects of EBTTX irradiation on the two freesia cultivars (the red freesia and the purple freesia) were investigated by establishing an irradiation-mediated mutation breeding protocol. The germination rate, survival rate, plant height, leaf number and area, root number and length of the two freesia cultivars decreased following different irradiation doses (25, 50, 75, and 100-Gy). A high irradiation dose exhibited stronger inhibition effects on these plant growth parameters, and the survival rate of the two freesia cultivars was 0.00% following the 100-Gy irradiation treatment. The median lethal dose (LD₅₀) based on survival rates was 54.28-Gy for the red freesia and 60.11-Gy for the purple freesia. The flowering rate, flower number, and pollen vigor were significantly decreased by irradiation treatment. At 75-Gy irradiation, the flowering rate, flower number and pollen viability of the two varieties reached the minimum, exhibiting strong inhibitory effects. Meanwhile, 75-Gy irradiation significantly decreased the chlorophyll content and increased the malondialdehyde (MDA) content of the two freesia cultivars. Furthermore, as the irradiation dose increased, the changes in the micro-morphology of the leaf epidermis and pollen gradually increased according to a scanning electron microscope (SEM) analysis. These results are expected to provide useful information for the mutation breeding of different freesia cultivars and other flowering plants.

Estimation of x-ray radiation related cancers in US dental offices: Is it worth the risk?

OBJECTIVES

The objective of this study was to estimate the possible number of cancer cases produced during 2019 in US dental offices from radiography, estimate the possible reduction in those rates resulting from use of intraoral rectangular collimation and selection criteria, and determine the frequency and quality of website radiation risk information and informed consent forms.

STUDY DESIGN

An analysis of dental radiation examinations in 2014 to 2015 US national survey data, Nationwide Evaluation of X-ray Trends, and National Council on Radiation Protection and Measurements surveys was performed, in addition to an analysis of 2008 to 2020 Journal of Clinical Orthodontics national orthodontic surveys for radiographic examination frequencies. Lifetime attributable cancer risk estimates from US and European studies were used to generate the total dental and orthodontic office cancer totals. In total, 150 offices were examined online for the quality and frequency of risk information in websites and consent forms.

RESULTS

The 2019 estimate for all office cancers is 967. Collimation and selection criteria could reduce this to 237 cancer cases. Most cancers arise from intraoral and cone beam computed tomography examinations, with 135 orthodontic cancers over 21 months (average treatment time). Collimation and selection criteria could reduce this to 68. Only 1% of offices use collimators or informed consent for radiography. The website and consent information were of poor quality.

CONCLUSIONS

Dentists are not following selection criteria or using collimators according to guidelines. Up to 75% of cancer cases could be avoided.

Low-dose X-ray imaging may increase the risk of neurodegenerative diseases

The hypothesis presented here explores the possibility that X-ray imaging commonly used in dental practices may be a shared risk factor for sporadic dementias and motor-neuron diseases. As the evidence will suggest, the brain is ill-equipped to manage the intrusion of low-dose ionizing radiation (IR) beyond that which is naturally occurring. When the brain's antioxidant defenses are overwhelmed by IR, it produces an abundance of reactive oxygen species (ROS) that can lead to oxidative stress, mitochondrial dysfunction, loss of synaptic plasticity, altered neuronal structure and microvascular impairment that have been identified as early signs of neurodegeneration in Alzheimer's disease, Parkinson's, amyotrophic lateral sclerosis, vascular dementia and other diseases that progressively damage the brain and central nervous system. Although genes play a role in all outcomes, the focus here will be on the non-genetic processes at work. Common assumptions regarding the risks of low-dose IR will be addressed, such as: 1) comparing rapid, repeated bursts of man-made IR sent exclusively into the head to equivalent amounts of head-to-toe background IR over longer periods of time; 2) whether epidemiological studies that dismiss concerns regarding low-dose IR due to lack of evidence it causes cancer, heritable mutations or shortened life spans also apply to neurodegeneration; and 3) why even radiation-resistant neurons can be severely impacted by IR exposure, due to IR-induced injury to the processes they need to function. Also considered will be the difficulty of distinguishing the effects of dental X-ray exposure from similarly low amounts of background IR and where to find the evidence that they may, in fact, be responsible for neurodegeneration. Finally, the long-standing belief that whatever risks are inherent in dental radiography must be undertaken for the sake of oral health is challenged on two counts: 1) while dentists continue to drape their patients in lead-lined aprons, the most effective IR safety precautions are often ignored; and 2) there is an alternative dental imaging technology that does not use IR. While the thrust of this article will be on dental radiation and will touch on how age, gender, X-ray equipment and protocols may increase risk, chiropractic radiographs also will be considered because they focus exclusively on the central nervous system. If X-ray imaging is found to be associated with neurodegeneration, the risk-versus-benefit must be reevaluated, every means of reducing exposure implemented and imaging protocols revised.

Biodosimetry of Low Dose Ionizing Radiation Using DNA Repair Foci in Human Lymphocytes

Purpose: Ionizing radiation induced foci (IRIF) known also as DNA repair foci represent most sensitive endpoint for assessing DNA double strand breaks (DSB). IRIF are usually visualized and enumerated with the aid of fluorescence microscopy using antibodies to γH2AX and 53BP1. This study analyzed effect of low dose ionizing radiation on residual IRIF in human lymphocytes to the aim of potential biodosimetry and possible extrapolation of high-dose γH2AX/53BP1 effects to low doses and compared kinetics of DSB and IRIF. We also analyzed whether DNaseI, which is used for reducing of clumps, affects the IRIF level. Materials and Methods: The cryopreserved human lymphocytes from umbilical cord blood (UCB) were thawed with/without DNaseI, γ-irradiated at doses of 0, 5, 10, and 50 cGy and γH2AX/53BP1 foci were analyzed 30 min, 2 h, and 22 h post-irradiation using appropriate antibodies. We also analyzed kinetics of DSB using PFGE. Results: No significant difference was observed between data obtained by γH2AX foci evaluation in cells that were irradiated by low doses and data obtained by extrapolation from higher doses. Residual 53BP1 foci induced by low doses significantly outreached the data extrapolated from irradiation by higher doses. 53BP1 foci induced by low dose-radiation remain longer at DSB loci than foci induced by higher doses. There was no significant effect of DNaseI on DNA repair foci. Conclusions: Primary γH2AX, 53BP1 foci and their co-localization represent valuable markers for biodosimetry of low doses, but their usefulness is limited by short time window. Residual γH2AX and 53BP1 foci are more useful markers for biodosimetry in vitro. Effects of low doses can be extrapolated from high dose using γH2AX residual foci while γH2AX/53BP1 foci are valuable markers for evaluation of initial DSB induced by ionizing radiation. Residual IRIF induced by low doses persist longer time than those induced by higher doses.