Composite fillings a combination of resins and fine particles designed to mimic the color of natural teeth. Composite resins need to be bonded to the tooth surface to allow for adhesion. Inlays and onlays are indirect dental restorations, which means they are made outside of your mouth in a laboratory. An inlay or onlay is usually used when a cavity is too large for a simple filling.
Thus, Inlay is a ceramic dental restoration used for restoring natural dental crown when only the upper surface of the tooth is damaged, and it cannot be restored by a filling either cast into shape with gold or milled into shape with porcelain, whereas Onlay is a ceramic restoration is used for bigger dental crown damages, where along with the upper surface of the tooth we need to restore the lateral surface as well.