Following eruption of a tooth into the oral cavity, enamel is thought to continue to calcify. The continued calcification and maturation of enamel is described as "post-eruptive enamel maturation." It is believed that an observed decrease in enamel pore size and increase in the calcification of enamel matrix over time can be attributed to this process. In recent years, there has been a significant increase in the number of adult patients seeking orthodontic treatment. Since orthodontic attachments are bonded directly to the etched enamel using composite resin, post-eruptive enamel maturation may affect the bonding process. The purpose of this study was to determine whether there were differences in bond strength between mature and newly erupted teeth when using both conventional and self-etching primer techniques for bonding orthodontic appliances. The nature of adhesive bond failure among the groups was also compared using an adhesive remnant index (ARI). Etched surfaces were examined under scanning electron microscopy (SEM) and representative photomicrographs were taken. Human premolars were collected and bonded randomly with either the conventional or self-etching technique. Brackets were debonded using an Instron testing machine in shear-testing mode. There were no statistically significant differences in the bond strengths between the self-etching primer and conventional etching groups. ARI scores showed differences between mature and newly erupted teeth. Mature teeth had more cohesive bond failures whereas newly erupted teeth had more adhesive failures at the enamel-composite resin interface. Scanning electron micrographs (SEMs) of self-etched enamel revealed smooth areas of resin with filler particles. Conventionally etched enamel had rougher surfaces. There were no differences in etch pattern of new versus mature enamel. Further research may be needed as new bonding materials and techniques become available to determine the effects, if any, of post-eruptive enamel maturation on their success.