This chapter outlines a holistic model of the tooth-preserving versus implant-replacement clinical decision-making process. Based on up-to-date evidence, the chapter discusses how site-specific elements of furcation involvement, pattern of bone loss, mobility of the tooth, and conditions of the restoration have significant impacts on tooth prognosis. The chapter deeply evaluates factors that affect treatment decisions systematically, of particular interest considering the age-related factors on each developmental stage of the patient’s life, the effects of smoking through dosing-dependent associations, and the far-reaching effects of bisphosphonate treatment and radiotherapy on treatment planning. The chapter also critiques the commonly used classification of prognosis and compares the general periodontal frameworks of the 2017 classification based on the tooth’s level of assessment models, specifically the McGowan evidence-based model, due to its clinical applicability. The diagnostic considerations and the prognostic implications of endo-periodontal lesions have special considerations of clear treatment pathways based on the original disease cause. The role of artificial intelligence in prognostic precision while classifying at-risk teeth gets a deeper look by offering better sensitivity to detect at-risk teeth using classical methods. The evidence-based model provides the clinician with a complex decision-making model that weighs biological capacity, functional needs, and patient-related concerns, emphasizing that dental implants are intended for the replacement of missing rather than existing teeth and should thus give way to preserving the patient’s own dentitions where possible.