Inflammatory and Immunological Basis of Periodontal Diseases

In its most common form, periodontitis is viewed as a chronic immunoinflammatory disorder of the tooth supporting tissues, shaped by host-microbiome disequilibrium, exaggerated immune activation, and impaired resolution mechanisms. This review explores the periodontal battlefield through its inflammatory and immunological lens, beginning with the transformation of the lesion from silent immune surveillance to sustained inflammation, connective tissue degradation, and alveolar bone loss. The classical Page and Schroeder model is used as a foundation but reinterpreted in light of current evidence derived from advanced molecular techniques. The immunological architecture is subsequently dissected through the involvement of its principal cellular players, acting in a dynamic battleground composed of saliva, crevicular fluid, epithelial barriers, and connective tissues. On the frontlines, neutrophils act as double-edged defenders, capable of both microbial clearance and bystander tissue damage. Like macrophages and dendritic cells, they also serve as strategic sensors and shapers of immunity, bridging innate and adaptive responses. Among these, the T cell arsenal includes inflammatory subsets such as Th1, Th17, and cytotoxic cells, balanced by regulatory T cells. B lymphocytes and plasma cells emerge not only as antibody producers but also as pro-inflammatory effectors, with growing evidence implicating autoreactive subsets in tissue damage, particularly in aggressive forms of the disease. Equally critical are the structural cells: gingival fibroblasts, which transition from matrix architects to immune-active contributors under stress, and osteocytes, recognized as mechanosensitive regulators of bone turnover and immune signaling. Alongside osteoblasts and osteoclasts, these elements form a fragile yet responsive osteoimmune axis that determines the trajectory toward either tissue homeostasis or destruction. The molecular arsenal fueling this conflict-cytokines, chemokines, complement, specialized pro-resolving mediators, neuropeptides, and matrix metalloproteinases-is also examined, highlighting how its dysregulation sustains chronic inflammation and drives structural breakdown. The review also explores how this localized immune conflict echoes systemically, contributing to broader immune activation and comorbidity. By reframing periodontitis as a prototypical immune-mediated disease, this work contributes to a deeper understanding of its pathogenesis and provides a framework for future research aimed at disentangling its immunological complexity and clinical heterogeneity for targeted diagnostic strategies and immune-based therapeutics.