This 3D dental illustration shows the difference between inlays and onlays as restorative treatments. An inlay is designed to fit within the grooves of the tooth to repair cavities or damage, while an onlay extends over one or more cusps to restore larger portions of the tooth structure. Both restorations are commonly fabricated from durable materials such as zirconia or porcelain and are bonded to the prepared tooth for strength and aesthetics.