Biomechanical and Occlusal Factors Influencing the Longevity of Single-Unit Restorations: A Comprehensive Review

The long-term success of single-unit restorations is a key objective in restorative dentistry; however, failure rates remain significant due to multiple contributing factors, including inadequate tooth preparation, inappropriate material selection, bonding deficiencies, and occlusal mismanagement. This narrative review aimed to critically assess clinical studies and systematic reviews published between 2000 and 2024 that explored the biomechanical and occlusal determinants affecting the longevity of tooth-supported crowns. A structured search was performed using PubMed, Scopus, and Web of Science databases, supplemented by manual reference screening. Observations from the literature highlight several influential risk factors such as loss of tooth vitality, improper occlusal adjustment, bruxism, and poor margin design. Additionally, finite element analysis studies were reviewed to understand how material properties and preparation geometry influence stress distribution and fatigue. These findings highlight how small, well-considered decisions like refining occlusal contacts, choosing the right material, or adjusting the preparation design can make a meaningful difference in preventing complications. By drawing from the current evidence, this review reinforces the value of thoughtful, evidence-based clinical practices and points to specific areas where further research could help make single-unit restorations more reliable and long-lasting.