Beeinflussung des Verbunds von Dentin und Kompositinlays durch das Befestigungsprotokoll

Aim of the study The aim of this in vitro study was to investigate whether the dentin bonding behavior of resin composite inlays is affected by the following parameters: 1. Choice of adhesive system (Syntac® or AdheSE® Universal) 2. Choice of luting composite with either solely light-curing (Venus® Flow) or dual-curing properties (Variolink®) 3. Additionally, separate light-curing of the adhesive 4. Duration of curing time Material and methods Fifty extracted human, caries-free and unfilled third molars were randomly assigned to ten groups (n=5). Class-I cavities with a size of 4x4x4 mm were cut. Subsequently, resin composite inlays were fabricated with the resin composite Venus® Diamond. All cavities were etched for 15 seconds with 36 % phosphoric acid while the associated inlays were sandblasted. These were then luted according to the group allocation as follows: Group 1: Syntac® (Heliobond not cured), Venus® Flow, curing time 60 s Group 2: Syntac® (Heliobond not cured), Venus® Flow, curing time 120 s Group 3: Syntac® (Heliobond not cured), Venus® Flow, curing time 240 s Group 4: Syntac® (Heliobond not cured), Venus® Flow, curing time 60 s Group 5: Syntac® (Heliobond cured), Venus® Flow, curing time 120 s Group 6: Syntac® (Heliobond cured), Venus® Flow, curing time 240 s Group 7: Syntac® (Heliobond not cured), Variolink® DC, no curing Group 8: Syntac® (Heliobond not cured), Variolink® DC, curing time 240 s Group 9: Adhese® (cured), Venus® Flow, curing time 240 s Group 10: Adhese® (cured), Variolink® DC, curing time 240 s Supergroup A: Syntac® Classic, groups 1 to 8 Supergroup B: AdheSE® Universal, groups 9 to 10 Supergroup C: no seperate light-curing of the adhesive, groups 1, 2, 3, 7, 8 Supergroup D: seperate curing of the adhesive, groups 4, 5, 6, 9, 10 The polymerization was carried out with a light-curing unit at a wavelength of 400-500 nm. To ascertain the values of composite and dentin adhesion, teeth were cut into 1 x 1 mm beams with a precision saw. Beams were then subjected to the microtensile test. The results of the test were analyzed and compared with the statistical software SPSS. Finally, the dentin composite interface and the hybrid layer were examined by scanning electron microscopy and evaluated for their quality. Results AdheSE® Universal showed a significantly stronger bond than Syntac®. The mean value of the composite-dentin bond was 3.37 MPa (± SD 5.39 MPa) in the AdheSE® group, while it was 0.30 MPa (± SD 1.3 MPa) in the Syntac® group. The highest bond value achieved was also found in the Adhese® Universal Group with a maximum of 23.39 MPa (p<0.05). Comparisons of Group 3 with Group 8 and Group 9 with Group 10 showed no significant differences in the adhesion values (p>0.05). Venus® Flow and Variolink® DC achieved similar results in these groups. The average adhesion of the group in which the adhesive was cured separately was 1.47 MPa (± SD 3.80 MPa); and thus significantly higher than in the group without isolated curing of the adhesive (p<0.05). Here the bond average was 0.37 MPa (± SD 1.49 MPa). The adhesion bond values of the following groups did not differ significantly from one another despite different polymerization times: Groups 1, 2 and 3; Groups 4, 5 and 6; Groups 7 and 8. Conclusion Within the limits of this study, the following findings can be noted: For resin composite inlays with a layer thickness ≥ 4 mm, AdheSE® achieved significantly better bond strength results than Syntac®. For composite inlays with a thickness of ≥ 4 mm, no predictable adequate polymerization through the resin is possible; therefore the composite-dentin bond is insufficient below such inlays. This could not be compensated for either by long polymerization times of up to 240 seconds or by dual-curing luting composites. Accordingly, it does not make any difference whether purely light-curing or dual-curing luting composites are used under composite inlays with a layer thickness of ≥ 4 mm. Different polymerization times do not change the adhesive performance. The separate curing of the adhesive leads to a significantly stronger bond in both adhesive systems used (p<0.05).