Enhance-L.C. is an orthodontic adhesion promoter. Our aim was to find out if this product is material-specific as stated by its manufacturers or whether its effects are similar when the promoter is used with other adhesive systems.In vitro study.Dental Clinic. University of Murcia, Spain, 2002.Enhance-L.C. was used with one of the manufacturer's recommended adhesives, Light-Bond, and with a second from another manufacturer, Transbond-XT. One hundred premolars were divided into four groups of 25 premolars: 1)Transbond-XT, 2) Transbond-XT/Enhance-L.C., 3) Light-Bond, 4) Light-Bond/Enhance-L.C.Shear bond strength was evaluated with a universal test machine and the adhesive remaining after debonding was determined using image analysis equipment.Enhance-L.C. did not significantly increase the bond strength of either of the two systems (P > 0.008). However, Light-Bond/Enhance-L.C. provided a bond strength significantly greater (P < 0.008) than Transbond-XT and Transbond-XT/Enhance-L.C. Light-Bond also left significantly (P < 0.05) less adhesive remaining on the enamel than Transbond-XT, whether or not either of the systems were used with Enhance-L.C.The use of Enhance-L.C with Light-Bond is to be recommended whenever extra bond strength is needed.