Objectives: Achievement of adequate early bond strength is necessary to withstand both short-term and long-term forces on composite restorations. The purpose of this study is to evaluate behavior of bond strength to dentin immediately, at 6 hr, 12 hr, 24 hr, 48 hr and 1 month after bonding using two different adhesive systems; self-etching primer and total-etch.
Methods: The occlusal surfaces of caries-free extracted molars were removed to expose a dentin surface and randomly divided into 12 groups (N=8). First six groups were etched with Ultra-etch (Ultradent) and the remaining groups were primed with Peak SE primer (Ultradent) before application of the adhesive Peak LC (Ultradent) and composite (Filtek Supreme Plus, 3M ESPE). Shear bond strengths were recorded at a crosshead speed of 0.5mm/min (Instron) immediately after bonding, at 6 hr, 12 hr, 24 hr, 48 hr and 1 month after aging in 37°C artificial saliva.
Results: Dentin bond strength of total-etch system did not show significant increase with time (p > 0.05). Samples treated with self-etch primer showed significant increase in bond strength after 48 hour (p = 0.0316). Self-etch samples exhibited higher dentin bond strength than total-etch samples at 48 hour (p=0.0254) and 1 month (p=0.049).
Table 1. Mean Bond Strength ± Standard Deviation (MPa)
| Self-Etch | Total-Etch |
Immediate | 23.04 (±7.79) | 18.94 (±6.29) |
6 hour | 25.58 (±4.31) | 19.26 (±5.03) |
12 hour | 25.82 (±7.50) | 20.11 (±3.74) |
24 hour | 29.40 (±5.96) | 22.90 (±7.13) |
48 hour | 31.76 (±6.72) | 23.76 (±6.06) |
1 month | 32.72 (±7.77) | 23.97 (±8.46) |
Conclusions: The samples treated with self-etching primer showed great increase in dentin bond strength over 48 hour period; however, total-etch samples did not. Overall, self-etch samples showed significantly higher dentin bond strength than total-etch samples at 48 hour and 1 month.