The occurrence and progression of oral infectious diseases are, in essence, a process in which oral microecological imbalance leads to the formation of an oral infectious microecosystem, which subsequently drives tissue destruction. The oral infectious microecosystem is a pathological ecosystem with self-maintaining capacity, formed within infectious lesions through steady-state drift and structural remodeling of the healthy oral microecosystem under continuous perturbations from both intrinsic and extrinsic factors. It constitutes the common microecological foundation for diseases such as dental caries, periodontal disease, and pulpal and periapical diseases. From the perspective of systems ecology, this article deconstructs the oral infectious microecosystem into three dimensions: Living organisms, space, and environmental media. The living organism dimension encompasses microbial components including bacteria, fungi, viruses, and archaea, as well as the host cellular network. The spatial dimension includes the surface chemical characteristics of heterogeneous colonization interfaces, the habitat spectrum ranging from open, semi-closed to closed systems, and the physiological and pathological dynamic changes. The environmental media dimension covers the physiological-pathological shifts in parameters such as pH, oxygen partial pressure and redox potential, temperature and fluid flow, nutrient substrates, and mechanical environment. On this basis, this article systematically analyzes the bidirectional interactions and feedback coupling mechanisms among the three dimensions, elucidates the ecological essence underlying the establishment and maintenance of pathological steady states, and provides perspectives for future research directions, aiming to offer a theoretical reference for understanding the pathogenesis of oral infectious diseases from an ecological standpoint.