Adhesion of Flowable Composites Bulk-filled in Posterior Class-I Cavities.
VAN ENDE A., DE MUNCK J., VAN LANDUYT K., PEUMANS M., POITEVIN A. and VAN MEERBEEK B.
Objectives: To evaluate the effect of bulk-filling of high C-factor posterior cavities on adhesion to cavity-bottom dentin.
Methods: A universal flowable composite (G-ænial Universal Flo, GC), a bulk-fill flowable base (SDR, Dentsply) and a conventional paste-like composite (Z100, 3M ESPE) were bonded (G-ænial Bond, GC) to standardized cavities (3.5x3.5mm; 8 teeth per group) with different C-factors, namely C=3.86 (Class-I cavity, 2.5mm deep, bulk-filled), C=5.57 (Class-I cavity, 4mm deep, bulk-filled), C=1.95 (Class-I cavity, 2.5mm, layer-filled in 3 increments) and C=0.26 (flat surface, bulk-build-up to 2.5mm using a mould). After 1-week water storage, the restorations were sectioned in 4 rectangular micro-specimens and subjected to a micro-tensile bond strength (µTBS) test. Fractured surfaces were analyzed light-microscopically and representative samples processed and further analyzed using SEM.
Results:
µTBS to cavity-bottom dentin
| 2.5mm cavity | 4mm cavity | 2.5mm cavity | flat surface |
G-ænial Universal Flo
| 12.1±15.0b,c (17/32)
| 0.0±0.0c (30/30)
| 37.3±10.0a (0/28)
| 39.8±13.7a (0/26)
|
SDR
| 27.3±9.7a,b (0/20)
| 31.8±14.0a (0/32)
| 33.9±11.8a (0/25)
| 41.5±7.3a (0/29)
|
Z100
| 0.0±0.0c (27/27)
| 0.0±0.0c (30/30)
| 31.4±14.5a,b (1/23)
| 29.7±7.2a (0/27)
|
µTBS expressed as mean±SD in MPa (ptf=pre-testing failure/n=number of specimens); different superscript letters indicate statistical significance (post-hoc multiple comparisons after Kruskal-Wallis test: p<0.05)
| ||||
Using the bulk-fill flowable base SDR, no statistical difference in µTBS was found between the 4 filling techniques tested. However, using the universal flowable composite and the conventional composite, the µTBS decreased significantly when Class-I cavities were filled in bulk (p<0.0001), even resulting in 100% pre-testing failures for the 4-mm deep cavities. However, when layer-filled or layer-built up onto a flat surface, no significant differences were found among all composites (p<0.05).
Conclusions: While the bond strength of the bulk-fill flowable base SDR to cavity-bottom dentin remained high using a bulk-filling technique, the conventional flowable and paste-like composite still required to be built up in layers.