As dental material science and technology rapidly evolve and enable dentists to render more efficient treatment, an old challenge persists--preventing the formation of secondary caries at the restorative margin. Research has indicated that the existence of an acid-base resistant zone (ABRZ), which forms between the adhesive layer and the tooth, may have a preventive effect. The ABRZ is also known as super dentin, and the thickness of this zone is material dependent. Functional monomers such as 10-methacryloyloxyethyl dihydrogen phosphate and materials such as flowable composites used as luting agents may play roles in formation of the ABRZ. This article also includes a case study to illustrate the author's technique in helping to create the ABRZ.