The most important early manifestation of secondary caries is the color change of the filling. On the edge of the filling, there will be some symptoms that look and feel a little bit darker. Sometimes it may not be very dark, but only slightly discolored, and the color of the tooth is different from the white color after the filling, then it is considered to be in the early stage of secondary caries. Of course, it is necessary to go to the hospital and let the doctor examine the tooth surface with special dental instruments after professional examination. In some cases, it is even necessary to take an x-ray, which can also help to further confirm whether the tooth has formed secondary caries. Once the doctor finds the secondary caries, if it is still in the early stage, you should choose to remove the secondary caries early and then refill it to prevent the secondary caries from developing further and forming the damage to the tooth.