Diabetes mellitus (DM) is a global metabolic disorder characterized by chronic hyperglycemia resulting from impaired insulin secretion, insulin resistance, or both. Its prevalence continues to rise worldwide, with substantial morbidity linked to microvascular and macrovascular complications that influence overall health and the delivery of dental care. In dental practice, DM is clinically significant because it modifies host immunity, vascular function, inflammatory regulation, and tissue metabolism mechanisms that collectively increase susceptibility to oral infections and compromise healing. Common orofacial manifestations include increased risk and severity of gingivitis and periodontitis with alveolar bone loss, salivary gland dysfunction and xerostomia, oral mucosal lesions (including candidal infections and lichenoid reactions), dysgeusia, burning mouth symptoms, and, in severe settings, opportunistic deep fungal infections and osteomyelitis. These changes directly affect treatment planning across specialties. Prosthodontic management requires careful attention to salivary hypofunction, denture-related candidiasis, mucosal fragility, residual ridge resorption, and delayed wound healing, with emphasis on atraumatic techniques, hygiene reinforcement, and appropriate scheduling. Endodontic practice must consider the bidirectional relationship between apical periodontitis and glycemic control, the possibility of slower periapical healing, increased residual lesions, and the need for meticulous infection control and stress reduction to limit hyperglycemic episodes. Orthodontic therapy, particularly in patients with suboptimal glycemic control, demands thorough periodontal screening, the use of light physiological forces, close monitoring, and coordination with the patient’s medical team to reduce risks of infection, impaired healing, and hypoglycemic emergencies. This review synthesizes systemic and oral evidence to provide practical, clinically oriented recommendations for safe and effective dental management of patients with DM, with glycemic control and interprofessional collaboration as central determinants of favorable outcomes.