An in vitro study using steel reference markers in the enamel of 120 permanent premolars was conducted to determine the amount of enamel lost during prophylaxis and during multiple bonding/debonding procedures. A prophylaxis procedure was carried out on eighty teeth. The procedure was standardized with respect to time, pressure, and revolutions of the prophy handpiece. Both bristle brush and rubber cup were used with four different prophylaxis pastes. The enamel loss with the bristle brush (14.38 micrometers) was significantly (p less than 0.01) greater than the loss with the rubber cup (6.9 micrometers). No significant differences were associated with the use of different pastes. Multiple bonding/debonding procedures were conducted with filled and unfilled resin adhesives. Following the initial bond, twenty of the teeth received prophylaxis and acid etching prior to subsequent bonds while the remaining twenty did not. Total enamel loss was 71.5 micrometers in the group bonded with a filled resin with prophylaxis and acid etching between bonds. This was significantly (p less than 0.01) greater than the amount lost (22.3 micrometers) by the group bonded with the same resin without prophylaxis and acid etching between bonds. Total enamel loss was 45.4 micrometers in the group bonded with an unfilled resin with prophylaxis and acid etching between bonds. This was significantly (p less than 0.01) greater than the amount lost (17.8 micrometers) by the group bonded with the same resin without prophylaxis and acid etching between bonds.