I have a problem with my character project. This is possibly due to some bad topology of the mouth area. I modelled a head and applied some materials and textures. Please note that the head and the mouth belong to the same mesh, but are not connected to each other. I find it easier to create mouth shapekeys this way. In material preview, the mouth blends seamlessly with the rest of the face, but in rendered view you can see a great visual gap between the two parts. Both parts are UV mapped to the same single texture file, using the same single material. I've tried merging the outermost vertices of the mouth with the ones on the face, but the result is the same. Is there a way I can blend the two parts and still have them look decent in a render, maintaining the same render quality as the rest of the head, considering I've already added some lights to the scene?
I'm using blender 2.83 and Eevee. This is how it looks like: