Cancer risk from low-dose ionizing radiation in dental imaging: A systematic review and meta-analysis

Abstract

OBJECTIVE: To evaluate the association between low-dose ionizing radiation from dental imaging (conventional radiography and cone-beam/medical CT) and cancer risk using contemporary epidemiological evidence. MATERIALS AND METHODS: This systematic review and meta-analysis followed PRISMA 2020 guidelines. PubMed, Scopus, and Web of Science were searched up to March 2026 for observational cohort and case-control studies assessing cancer risk after dental radiographic exposure. Risk of bias was assessed using Joanna Briggs Institute tools, causal inference with COSMOS-E guidance, and certainty of evidence with the GRADE framework. Random-effects models pooled adjusted Odds Ratios (ORs) and adjusted Hazard Ratios (HRs) with 95% confidence intervals (CIs). RESULTS: Among 1,883 records, 24 studies met inclusion criteria, and 19 were included in meta-analysis (415,887 participants). In the 16 case-control studies, thyroid cancer was significantly associated with dental imaging (OR = 2.21; 95% CI: 1.63-2.99), while central nervous system (CNS) tumors showed a non-significant elevation (OR = 1.31; 95% CI: 0.89-1.91). In the three cohort studies, thyroid cancer showed a small but significant association with conventional radiography (HR = 1.13; 95% CI: 1.01-1.26), and CNS tumors risk was moderately associated with CT scan exposure (HR = 1.54; 95% CI: 1.03-2.29). Certainty of evidence was rated low for thyroid cancer, and very low for central nervous system cancers, lymphoid cancer, oral cancer and salivary gland cancer due to risk of bias, inconsistency, and imprecision. CONCLUSION: Current evidence is insufficient to confirm an association between low-dose dental radiographic exposure and cancer. A small increased risk was observed, but certainty remains very low, highlighting the need for well-designed prospective research.