What Are Composite Resin Fillings and Why Are They Popular? Composite resin fillings are tooth-colored dental restorations used to repair cavities, cracks, or minor tooth damage. Dentists create them from a blend of resin and fine glass particles, allowing the filling to bond directly to the tooth structure. Because composite resin fillings closely match the natural color of teeth, they are a popular choice for patients who want a discreet…