Objectives: Long-term stability of dental materials plays an important role in the clinical success of dental restorations. Properties are strongly influenced by water uptake, mechanical loading and thermal aging. The aim of this study was to compare flexural strength of five restorative composites after different aging conditions.
Methods: Composite specimens (see table, b: 2mm, h: 2mm, l: 25mm, n= 8 per group) were made of each material according to the manufacturer's instructions (polymerisation device: Translux Energy (Heraeus Kulzer, Germany), power:800 mW/cm2). Fracture force FF [N] was determined after 24hrs, combined storage (4 weeks) and thermal cycling (2x3000 cycles 5°/55° 2min each cycle, EGO chewing simulator, Germany) and mechanical loading (200 000 times with 20N, f= 5Hz, water bath 25°C, magnetic loading, Prematec F1000;Germany). Flexural strength FS [MPa] was calculated according to FS= (3xFFx20/2xbxh2) (EN ISO 4049). Statistics: one-way ANOVA (p=0.05).
Results:
Flexural strength FS [MPa] | 24hrs | mechanical loading in water | storage + thermal cycling | |||
material | mean | STD | mean | STD | mean | STD |
Herculite XRV Ultra (Kerr, USA)
| 106.5 | 11.3 | 101.0 | 14.9 | 76.0 | 8.4 |
Spectrum TPH 3 (Dentsply, USA) | 124.8 | 15.0 | 127.3 | 15.0 | 101.0 | 7.9 |
Tetric Evo Ceram (Ivoclar-Vivadent, Liechtenstein) | 103.3 | 5.1 | 85.7 | 4.6 | 67.2 | 4.4 |
Venus Pearl (Heraeus Kulzer, Germany) | 155.3 | 8.7 | 147.8 | 17.6 | 119.5 | 12.1 |
Estelite Sigma (Tokuyama, Japan) | 85.5 | 8.4 | 80.2 | 8.9 | 16.2 | 26.1 |
Mean and standard deviation (STD) of flexural strength (FS)
Conclusions: Significant different flexural strength values between the materials were found. Mechanical loading caused reduction of flexural strength for four materials. Significantly strongest decrease of flexural strength was found after combination of storage and thermal cycling.