When a tooth is too damaged and weak to support a tooth filling but not damaged enough for a dental crown, Inlays or Onlays will be the best treatment option. Large dental filling can weaken the remaining structure of the tooth, causing the tooth to break, crack or eventually need a root canal. Inlays and Onlays are made of a strong porcelain material that replaces the damaged part of the tooth without touching the healthy side of the tooth.