The purpose of this study was to evaluate the marginal adaptation of two approximal ceramic insert systems before and after cementation to the cavities opened with ultrasonic tips. Proximal cavities with margins in enamel were prepared in a total of 40 intact molars using ultrasonic tips [SONICSYS approx tips (micro torpedo size #2 and #3, KaVo, Germany); Siplus Instrument approximal (U-shaped, Komet, Germany)]. The inserts of the similar sizes (n = 10) from two systems corresponding to the ultrasonic tips were placed in the cavities (SONICSYS Inlay, Vivadent, Germany; SDS-Inlay system, Schumacher Dental Systems, Germany), one on the mesial, the other on the distal side of the same molar. Marginal gap was measured before cementation. Following cementation (Tetric Flow, Vivadent, Germany) and thermocycling (5000 cycles, between 5-55*C) marginal quality was evaluated at the buccal and lingual walls, and pulpal floors of the proximal boxes under light microscope (x 150). ANOVA was used to analyze the data. The mean marginal gap of 25 µm (6 to 88 µm) recorded for SONICSYS inserts size #3 was not significantly different from that of SDS inserts of similar size [24 µm (6 to 78 µm)]. There was not a significant difference in marginal gap values between SONICSYS size #4 inserts (22 µm, 6 to 72 µm) and SDS inserts of similar size (34 µm, 6 to 104 µm) (p > 0.05). After cementation and thermocycling, five marginal discrepancies (less than 50 µm) for SONICSYS inserts size #3 and one for SDS size #2 inserts were found. One marginal microcrack for SDS inserts size #3 and four for SONICSYS size #4 inserts were observed. Comparison of mean gap values between the ceramic insert systems examined, revealed that marginal adaptation was better at the buccal and lingual proximal walls at both sizes from both systems than those at pulpal floors. Ceramic inserts placed in the cavities prepared with ultrasonic tips provide clinically acceptable marginal quality. Schlagwörter: ultrasonic tips, ceramic inserts, marginal adaptation, proximal cavities