Occupational Radiation Exposure in Dental Clinics Operating Within Industrial Facilities Constructed with Lightweight or Artificial Walls: Implications for Thyroid Health and Radiation Safety “Challenging the Assumption of Safety in Low-Dose Dental Radiology”

1. Introduction

Dental X-ray equipment is widely considered safe because manufacturers describe it as emitting low radiation doses, an assumption that is typically based on conventional clinical environments. Dental radiography is an essential part of routine dental care and is widely used for diagnosis, treatment planning, and follow-up. Common techniques include intraoral radiography, panoramic imaging, and cone-beam computed tomography (CBCT). All these methods rely on ionizing radiation and therefore represent a potential source of occupational exposure for dental healthcare workers and other nearby personnel, mainly through scattered radiation within the clinic environment [1,2].

Available studies indicate that occupational radiation doses in dentistry are generally low and usually remain below the recommended annual limit of 20 mSv when standard radiation protection measures are applied [2,3]. These findings are largely based on dental clinics with appropriate architectural shielding, controlled working areas, and compliance with radiation safety guidelines. However, exposure levels may vary depending on imaging modality, workload, operator position, and the structural characteristics of the clinic [4].

The thyroid gland is one of the most radiosensitive organs in the human body. Ionizing radiation can induce biological effects in thyroid tissue through DNA damage, oxidative stress, and inflammatory pathways [5,6]. Evidence from medical radiation workers and exposed populations suggests that repeated or chronic exposure may be associated with thyroid nodules, functional alterations, and an increased risk of thyroid cancer [6,7]. However, in occupational environments characterized by inadequate structural shielding and limited enforcement of radiation safety measures, occupational exposure levels may be underestimated, regardless of the nominal dose associated with dental imaging procedures.

This narrative review focuses on occupational radiation exposure in dental clinics operating within permanent industrial and corporate healthcare facilities constructed with non-standard, lightweight architectural materials, such as those commonly found in petroleum, mining, and large industrial organizations. These settings differ fundamentally from conventional healthcare facilities, as they may lack structural radiation shielding, personal dosimetry programs, and strict regulatory oversight, despite continuous long-term operation.

In facilities constructed with lightweight or artificial walls, scatter radiation may extend beyond the dental operatory and affect adjacent offices and workspaces. As a result, occupational exposure may not be limited to dental healthcare workers but may also involve administrative staff, technical personnel, and other employees working in proximity to dental imaging areas. These individuals are typically not considered radiation workers and are unlikely to be included in dosimetry programs or radiation safety training, further complicating risk assessment and protection.

In dental practice, occupational exposure results mainly from scatter radiation during imaging procedures. CBCT examinations, which are increasingly used in implantology, orthodontics, and maxillofacial diagnostics, generate higher radiation doses than conventional intraoral radiography and may contribute more substantially to scatter within the indoor environment [8,9,10]. Distance from the radiation source and the presence of effective structural shielding play a key role in reducing staff exposure [12].

Current radiation protection recommendations are based on the principles of justification, optimization, and dose limitation. These principles assume that dental clinics are designed with adequate wall thickness and appropriate lead or lead-equivalent shielding [1,13]. Less attention has been given to non-standard clinic designs, such as lightweight or modular constructions, where shielding performance may differ from conventional facilities.

Given the long professional lifespan of dental healthcare workers and other personnel working in proximity to dental imaging areas, as well as the radiosensitivity of the thyroid gland, chronic occupational exposure deserves careful evaluation. Accordingly, this review examines occupational radiation exposure in dental clinics, with particular emphasis on thyroid health risks and radiation safety gaps related to indoor exposure and architectural shielding.

The central message of this review is that the perceived safety of dental radiographic procedures is fundamentally dependent on adequate architectural radiation shielding. In clinics constructed with lightweight or artificial wall materials, particularly within industrial and corporate facilities, this assumption may fail, allowing scatter radiation to extend beyond the dental operatory despite the nominally low radiation output of dental imaging equipment.

2. Methodology

This narrative review summarizes published evidence on occupational radiation exposure in dental clinics and its possible effects on thyroid health. A narrative approach was chosen due to the heterogeneity of study designs, exposure assessment methods, and outcome measures in the available literature.

Relevant literature was identified through searches of PubMed, Scopus, and Web of Science, mainly covering publications from 2000 to 2025. Search terms included dental radiography, occupational radiation exposure, dental staff, cone-beam computed tomography, scatter radiation, radiation protection, and thyroid radiation effects. Reference lists of relevant articles were also screened to identify additional pertinent publications.

Peer-reviewed articles addressing occupational doses in dental practice, radiation exposure from dental imaging modalities, and biological effects of ionizing radiation on the thyroid were included. International radiation protection guidelines were also consulted to contextualize safety standards and occupational dose limits. Articles unrelated to dental or medical radiation exposure, focused exclusively on patient outcomes, or lacking sufficient methodological detail were excluded.

3. Scientific Background: Dental Radiation and Occupational Exposure

Dental radiography uses ionizing radiation to obtain diagnostic images of teeth and surrounding structures. Common techniques include intraoral radiography, panoramic imaging, and cone-beam computed tomography (CBCT). Occupational exposure in dental practice occurs mainly through scattered radiation rather than direct beam exposure [1,2]. Although radiation doses in dentistry are generally lower than in other medical imaging fields under standard clinical conditions, occupational exposure may become more relevant in settings where structural shielding is inadequate or radiation safety practices are inconsistently applied [3].

Several studies have shown that occupational doses for dental healthcare workers and other personnel working in proximity to dental imaging areas usually remain below recommended limits when radiation protection measures are properly applied [2,4]. However, exposure levels vary depending on imaging modality, workload, equipment type, and compliance with safety practices.

CBCT, in particular, produces higher radiation doses than conventional dental radiography and contributes more to scatter radiation within the clinic [9,10]. In facilities with lightweight or artificial wall construction, this increased scatter radiation may extend beyond the imaging room, potentially affecting adjacent indoor areas. The main characteristics of common dental imaging modalities and their relevance for occupational radiation exposure are summarized below in Table 1.

4. Occupational Exposure in Dental Clinics

Occupational exposure in dental clinics is influenced by clinic layout, wall materials, shielding quality, operator position, and the broader architectural context in which dental imaging is performed. Radiation scatter can penetrate surrounding areas if structural shielding is insufficient or improperly designed [6]. Standard radiation protection models assume adequate wall thickness and the presence of lead or lead-equivalent barriers, which may not always be the case in non-standard or lightweight clinic constructions [1,11]. In clinics constructed with lightweight or artificial wall materials, such as prefabricated panels or modular structures, scatter radiation may penetrate walls more easily than assumed in standard radiation protection models.

Measurements of scatter radiation have demonstrated that distance from the X-ray source and the use of protective barriers significantly reduce occupational exposure [10]. In clinics with limited space or inadequate shielding, dental staff and other personnel working in proximity to dental imaging areas may be exposed to higher cumulative doses, particularly during frequent CBCT use [10].

This risk may be particularly relevant in industrial and corporate healthcare facilities, where dental clinics are embedded within office or field environments and where radiation protection practices may not be routinely audited.

5. Mechanistic Pathways Linking Ionizing Radiation and Thyroid Dysfunction

Ionizing radiation affects biological tissues primarily through the generation of reactive oxygen species, leading to oxidative stress. These reactive molecules can damage DNA, proteins, and cellular membranes [5,12]. The thyroid gland is especially vulnerable because normal thyroid hormone synthesis already involves oxidative processes, increasing baseline oxidative stress within thyroid cells [5].

Radiation-induced oxidative stress may result in DNA strand breaks, mitochondrial dysfunction, and chronic inflammatory responses in thyroid tissue. Over time, these effects may contribute to thyroid nodules, altered hormone production, and increased susceptibility to malignant transformation [5,7]. Chronic occupational exposure under conditions of inadequate shielding may therefore have long-term consequences even in the absence of acute radiation injury.

6. Human Evidence from Occupational and Medical Radiation Studies

Epidemiological studies of medical radiation workers have reported associations between occupational radiation exposure and thyroid abnormalities, including nodules and increased cancer risk [3,7,14]. An overview of the available human evidence linking radiation exposure to thyroid-related outcomes is summarized in Table 2. Although most evidence derives from settings with better-characterized exposure levels, recent reviews suggest that chronic occupational exposure may affect thyroid structure and function [4,5].

Meta-analyses and pooled studies have demonstrated an increased risk of thyroid cancer following external radiation exposure, with risk magnitude influenced by dose, duration of exposure, and age at exposure [3,14]. Data specific to personnel with occupational exposure to dental imaging remain limited, highlighting the need for further investigation in this occupational group.

7. Occupational Risk Management and Regulatory Gaps

Radiation protection in dentistry is based on the principles of justification, optimization, and dose limitation [11,15]. Current guidelines emphasize equipment quality assurance, operator training, appropriate positioning, and structural shielding [15]. When these measures are applied, occupational doses are generally low.

However, existing regulations largely assume conventional, hospital-grade clinic designs and may not adequately address dental clinics embedded within industrial or corporate facilities constructed with non-standard architectural materials [6,16,17]. Limited guidance exists on radiation protection requirements for lightweight or modular clinics, where shielding performance may differ from traditional facilities. This represents a potential gap in occupational risk management.

In industrial and corporate settings, dental clinics may operate as permanent healthcare units without being subject to the same level of architectural radiation safety assessment applied in hospital environments. In such facilities, wall construction materials may lack verified lead-equivalent shielding, and the physical separation between dental imaging areas and surrounding offices may be insufficient. As a result, scatter radiation may extend beyond the dental operatory and affect adjacent indoor workspaces, exposing personnel who are not formally recognized as radiation workers. These structural and organizational shortcomings represent a fundamental gap in occupational radiation protection that cannot be mitigated solely through procedural or administrative measures.

8. Discussion and Recommendations

Dental radiographic equipment is generally regarded as safe because manufacturers describe it as emitting relatively low radiation doses in technical specifications and operator manuals. This has contributed to a widespread perception among dental practitioners that dental radiology is safe when used within conventional clinical environments [1,12]. This perception of safety is largely based on dental clinics operating within conventional buildings constructed with thick concrete or masonry walls that provide substantial passive radiation shielding [11]. In such environments, scatter radiation is effectively attenuated by structural materials, reinforcing the assumption of minimal occupational and environmental risk. However, this assumption does not hold in clinics constructed with lightweight or artificial wall materials. In these settings, even low-dose scatter radiation may penetrate surrounding structures and extend into adjacent indoor areas. Therefore, reliance on nominally low radiation output alone is insufficient to ensure safety when architectural shielding is inadequate.

Available evidence indicates that occupational radiation exposure in dental clinics is strongly influenced by the physical and architectural conditions under which dental imaging is performed [2,6]. While exposure levels are generally well controlled in conventional healthcare facilities with verified structural shielding, this assumption may not apply to clinics operating in environments with non-standard architectural design. In such settings, inadequate wall shielding and insufficient physical separation of imaging areas may permit scatter radiation to extend beyond the dental operatory, increasing the potential for unintended occupational exposure [10].

The high radiosensitivity of the thyroid gland, combined with long-term occupational activity in these environments, underscores the importance of prioritizing effective engineering controls as the foundation of radiation protection [3,4,5,14]. Verification of wall construction materials, assessment of lead-equivalent shielding, and appropriate spatial planning of dental imaging areas should be considered essential components of occupational risk management. Procedural measures and radiation safety training, while important, cannot compensate for deficiencies in structural radiation protection [11].

Future research should place greater emphasis on evaluating radiation transmission through lightweight or artificial wall materials commonly used in industrial and corporate facilities. Studies assessing indoor scatter distribution and long-term thyroid-related outcomes in personnel working within or adjacent to dental imaging areas are particularly needed to inform evidence-based updates to radiation protection guidelines [3,4,17,18].

8.1. Occupational Radiation Exposure in Permanent Industrial Healthcare Facilities with Non-Standard Architecture

In many industrial sectors, including petroleum and energy industries, permanent medical and dental clinics are integrated within administrative offices and field facilities constructed using lightweight or prefabricated materials. Although these clinics may operate continuously for decades, their architectural design often does not incorporate verified lead-equivalent shielding or adequate physical separation between dental imaging areas and surrounding workspaces [6,16,17].

As a result, scatter radiation generated during dental imaging procedures may penetrate surrounding structures and extend into adjacent indoor areas [8,9,10]. This exposure may affect not only dental healthcare workers but also other personnel working nearby who are not formally considered radiation workers. Existing radiation protection frameworks largely assume hospital-grade construction with inherent structural shielding and therefore may underestimate occupational and environmental exposure risks in these industrial settings [15,16,17]. Addressing this gap requires explicit consideration of architectural design and wall shielding performance in radiation protection guidance for dental clinics operating outside conventional healthcare facilities.

9. Conclusions

Dental radiographic equipment is generally designed to operate at relatively low radiation output and is considered safe when used within appropriately constructed clinical environments. However, this perceived safety is fundamentally dependent on the presence of adequate architectural radiation shielding. In dental clinics operating within industrial and corporate facilities constructed with lightweight or artificial wall materials, these assumptions may not be valid.

This review highlights that insufficient wall shielding and inadequate physical separation of dental imaging areas can allow scatter radiation to extend beyond the dental operatory, potentially affecting both dental healthcare workers and other personnel working in adjacent indoor spaces. Thus, reliance on nominally low radiation output alone is insufficient to ensure occupational safety when architectural shielding is inadequate.

The central message of this review is that effective radiation protection in dental practice must prioritize verified structural shielding and appropriate architectural design as the foundation of occupational safety. Regulatory frameworks, workplace safety policies, and future research efforts should explicitly address the performance of wall materials and spatial layout of dental imaging areas in non-hospital settings to prevent unintended occupational exposure.