Tensile Bond Strength Of Resin To Dentin Treated With Kinetic Cavity Preparation (KCP) R.* Wischnewski, , B. Geitel, K.-R. Jahn, J.-F. Roulet (Department Of Operative And Preventive Dentistry, Charité, Humboldt-University Of Berlin, Germany) Usually the preparation of dental hard tissues is carried out with rotary instruments and therefore connected with some disadvantages. The so-called kinetic cavity preparation seems to be an acceptable alternative in some cases. The kind of the preparation of hard tissues influences the bond strength to the applied resin.   (a) The aim of this study was to test the tensile bond strength of resin to differently treated dentin surfaces   (b) The labial plane dentin surfaces of 200 human maxillary central incisors were differently treated. The variables of KCP-treatment were: particle size (27 and 50µm), air pressure (80 and 160psi) and the composite/bonder system Scotchbond Multi-Purpose + Z 100 (SBMP) and OptiBond Fl + Herculite XR (OB), respectively. The comparison group consisted of cut dentin samples etched by phosphoric acid over 15 seconds (control). Composite samples were bonded on all pretreated surfaces using a self-developed mold. Samples were stored at 20° in water for 24 hr and debonded in tension using an Instron at 0.05cm/min. The failure sites were qualitatively evalueted by SEM differentiating cohesive, adhesive and mixed fracture modes.   (c) Means (s.d.) of bond strength (MPa) are listed.   particle size / air pressure 27 / 80 27 / 160 50 / 80 56 / 160 control SBMP + Z100 3,91 (3,47) 3,75 (2,93) 5,31 (2,80) 2,68 (2,63) 8,10 (4,36) OB + Herculite 9,41 (4,07) 8,84 (4,34) 8,33 (2,79) 8,35 (2.62) 12,78 (3,80)   The bond strength values of the KCP-samples were significantly (Kruskal-Wallis-test) lower than those of the control group independently on the resin being used. Optibond/Herculite XR samples showed significantly better values than the SBMP/Z100 ones independently on conditions being used. There were no significant differences between the KCP-samples within the different resins which were used. As to the different fracture modes ahesive and mixed ones were predominant.   (d) Independently on the conditions being used the KCP-treatment of dentin deteriorates the tensile bond strength between dentin and resin compared with etched dentin samples. OptiBond + Herculite showed better results than Scotchbond Multi-Purpose + Z 100. Therefore we recommend the etching of dentin after KCP-treatment and the use of OptiBond + Herculite.