Preparation designs of ceramic inlays, onlays, overlays

Abstract

This thesis reviews preparation designs for ceramic inlays, onlays, and overlays in posterior teeth, focusing on biomechanical principles, material selection, and adhesive protocols in contemporary restorative dentistry. With the development of high-strength ceramics such as lithium disilicate and zirconia, together with CAD/CAM technology, minimally invasive indirect restorations have become predictable and widely used alternatives to full-coverage crowns. The classification of ceramic and ceramic-like materials is discussed to support appropriate clinical decision-making. Understanding material composition and mechanical properties is essential for selecting restorations capable of withstanding functional loads while meeting aesthetic demands. Indirect partial restorations are categorized as inlays, onlays, and overlays depending on cusp coverage. Preparation design plays a decisive role in their long-term success. Conservative designs that preserve enamel, maintain adequate ceramic thickness, incorporate rounded internal line angles, and ensure slight wall divergence provide improved stress distribution, enhanced fracture resistance, and reliable adhesive bonding. Evidence suggests that restricted cusp reduction often achieves sufficient mechanical performance while preserving more natural tooth structure compared to extensive coverage. Common preparation errors, including excessive taper, sharp internal angles, and inadequate reduction, may compromise restoration longevity. Advanced clinical techniques such as immediate dentin sealing (IDS), cervical margin relocation (CMR), and deep marginal elevation (DME) further improve adhesive predictability and allow management of deep or challenging margins. Overall, the success of ceramic inlays, onlays, and overlays depends primarily on proper preparation design, enamel preservation, correct material selection, and strict adherence to evidence-based adhesive protocols. When combined with modern digital workflows, these principles support durable, conservative, and biologically respectful rehabilitation of posterior teeth.