Review a Comprehensive Article on Longitudinal Evaluation of Oral Microbial Changes and Radiation-Induced Dental Caries in Head and Neck Cancer Patients

Abstract

Radiotherapy is an essential treatment modality for head and neck cancers; however, it is frequently associated with significant oral complications, particularly radiation-induced dental caries. Emerging evidence suggests that radiotherapy not only impairs salivary gland function but also induces substantial alterations in the oral microbiome. Longitudinal studies have demonstrated that oral microbial changes may become evident within 2–3 weeks of treatment initiation, characterized by an increased prevalence of cariogenic microorganisms such as Streptococcus mutans and Lactobacillus species, along with a reduction in beneficial commensal bacteria including Neisseria, Rothia, and Streptococcus sanguinis. These microbial shifts are often accompanied by decreased microbial diversity, persistent xerostomia, and salivary dysfunction, creating an acidic oral environment that promotes enamel demineralization and accelerates caries progression. In addition, opportunistic fungal organisms, particularly Candida albicans, may increase during and after radiotherapy, further contributing to oral dysbiosis and oral complications. This review summarizes the longitudinal microbial changes associated with radiotherapy, examines their role in the pathogenesis of radiation-induced dental caries, and discusses current preventive and therapeutic strategies. Understanding these dynamic microbial alterations may facilitate early intervention, improve oral health outcomes, and support the development of personalized preventive approaches for head and neck cancer patients undergoing radiotherapy.