Conditioning Of Enamel After Loss Of Fissure Sealant *B. Stephan, H. Lang, S. Brenneis, W.H.-M. Raab (Dept. Of Restorative And Preventive Dentistry, University Of Duesseldorf, Germany) The repair of (partially) lost pit and fissure sealants is still a problem in pediatric dentistry. The difficulty is to remove remaining portions of sealer completely and to condition the pretreated enamel sufficiently for a new sealing procedure. The purpose of this morphological study was to compare different methods of enamel conditioning after loss of fissure sealant and to investigate the effects on the treated enamel surface.   Freshly extracted caries-free teeth (n=50) were sealed with a transparent fissure sealant (Delton® transparent), thermocycled (4°C <-> 37°C<-> 55°C) and the sealing was removed using an ultrasonic device. The morphology of the teeth's surfaces were then assessed using epoxy resin replicas and investigated by scanning electron microscope. Afterwards the teeth were equally divided into 5 experimental groups: Gr. I - etching for 60 sec., Gr. II - pretreatment with an air-powder abrasive device and etching, Gr. III - irradiation with an Er:YAG laser (2Hz/ 60mJ for 1min.) followed by etching, Gr. IV - surface treatment using fine diamond burs plus etching and Gr. V - untreated /unetched teeth as control. Following these procedures the treated surfaces were analyzed again by scanning electron microscopy.   In all teeth great remnants of the sealant were found prior to treatment, especially at the bottom of deep fissures and on the cusp ridges. After the treatment teeth in groups I + II showed no decrease of sealing material but the sealer-free regions exhibited a normal etching pattern. Zones covered with powder residues were observed in group II. Teeth in group III showed a complete removal of the sealant, even in deep fissures. The enamel showed an etching pattern but surfaces were rough and exhibited structural damage (craters) due to laser irradiation. Treatment with fine diamond burs (group IV) resulted in significant reduction of sealing material (some remnants at the bottoms of the fissures), a normal etching pattern and less coarseness of enamel structure when compared to the laser samples.   Conclusions All investigated procedures resulted in either uncomplete removal of sealant remnants or removal of enamel at the teeth's surfaces. Due to the side effects of the invasive procedures it should be investigated if a sufficient re-bonding can be established by acid-etching of the sealer-impregnated enamel surface alone.