Influence Of Incremental Techniques On Initial Marginal Adaptation Of Large Occlusal Composite Restorations R. Haak*, M.J. Wicht And M.J. Noack (Dental School, University Of Cologne, Germany) Application modes of composite resins have been demonstrated to affect the marginal adaptation due to differences in interfacial stress build-up. Especially, when extended Class I cavities are restored, a high amount of marginal enamel fractures could be expected.   Purpose of this in vitro study was to evaluate marginal adaptation of large Class I situations filled with different layering techniques. 50 standardized occlusal cavities in extracted human molars were randomly assigned to five groups and incrementally restored with the adhesive system: Prodigy Condensable, Revolution, Optibond Solo.   Following layering techniques were used: two diagonal layers (2x D) , four diagonal layers (4x D), two horizontal increments (2x H), two horizontal layers and final marginal sealing (2x H/seal), bulk filling after lining with flowable composite (B/flow). Immediately after restoration replicas were taken and margins were quantitatively assessed by SEM (200x) using defined criteria.   mean values in % 2x D 4x D 2x H 2x H/seal B/flow marginal continuity 59 % 73 % 72 % 65 % 73 % marginal enamel fracture 36 % 11 % 24 % 33 % 23 %   One-way ANOVA revealed no differences for „marginal continuity“ (p>0.05) but for „marginal enamel fracture“ (p<0.01). Four diagonal composite layers (4x D) showed significantly less marginal enamel fractures than 2x D and 2x H/seal.   When restoring extended Class I cavities with unsupported enamel margins no application technique is able to avoid marginal fractures in the enamel. The amount of initial marginal gap formation is not of clinical concern, irrespective which layering technique was used.