First, bonding was only achieved to the enamel, with the help of selective enamel etching with ortho-phosphoric acid, protecting dentin with bases. After this, bonding to enamel and dentin was attempted.
Primero sólo al esmalte, mediante el grabado selectivo de éste con ácido ortofosfórico, protegiendo la dentina con bases, después al esmalte y la dentina.