Degree of Conversion and Hardness of a Silorane Based Composite

Objectives: The well-established relation between degree of conversion and hardness for methacrylate based composite resins is not the same for silorane based posterior filling material.

ObjectiveTo evaluate the effect of degree of conversion (DC) on microhardness of a composite resin based on silorane monomer (Filtek-LS, 3M-ESPE)
Methods: The specimens (n=10/gp, cilindrical 5x2mm, light-cured 1100 mW/cm2) were divided into 5 groups according to the energy amount obtained by the variation in the irradiation time (8, 12, 16, 20 and 24 J/cm2). The DC was performed using a FTIR (Excalibur 3100) and ATR (Miracle) in real time. Sixteen scans of spectra were performed (4cm-1/20 min). The Knoop Hardness Number (KHN) was performed (Durimet) in a total of 10 indentations/specimen botton (30s/25g).
The data were tested for normality and homogeneity and then subjected to ANOVA (5%).
Results: The data were presented on table. DC: p= 0.324; KHN: p< 0.001.

The Pearson regression test showed a strong correlation DC/KHN (p = 0.002, R2=0.976). The greater DC, higher KHN.
Conclusions: DC was not influenced by the energy, despite the trend of increasing conversion function of the energy amount has been observed. The progressive variation of the energy amount influences the increase of KHN. There is positive correlation between KHN and DC.