The aim of the study was to measure the solubility of three cements after thermocycling and simultaneous loading by the non-invasive microfocus-computertomography (µCT).
Methods:
39 all-ceramic crowns were divided randomly in three groups of 13 and cemented either with Relyx Unicem®, or Panavia® and or Variolink II®. The solubility was measured in 50 points perimetrically of each crown, before and after simultaneous thermocycling (10000 cycles, 5°C to 55 °C) and mechanical loading (1.2 Mio×50N, 30°angle to the tooth long axis). At each point the perpendicular was measured to the angular combination of the marginal gap and the extension error (called absolute marginal discrepancy), in 5 positions (L1-L5) from coronal to apical direction. The resolution of the µCT was 10µm. The measurements were analyzed by Hieronymus® software. By the µCT-orthoslices a 3-D projection of the cement and the adjacent tooth could be constructed. The statistical analysis was made with SPSS® software.
Results:
1. Unicem and Variolink showed a statistically significant solubility after simultaneous thermocycling and mechanical loading (Wilcoxon-Test, p<0.001).
2. Variolink showed statistically significant more solubility (variance analysis with repeated measurements, p< 0.05) than Unicem in three positions and than Panavia in one position.
3. The average solubility ranged from 5.9µm (Unicem), to 1.1µm (Panavia) and 34.4µm (Variolink)
Conclusions:
Unicem and Variolink showed statistically significant solubility. Due to the small amounts there seems to be no clinical relevance for Panavia and Unicem.