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Dynamic mechanical thermal analysis of two light-cured dental composites
Nazanin Emami1, Karl-Johan M Söderholm
1Division of Polymer Engineering, Luleå University of Technology, S-971 87 Luleå, Sweden. nazanin.emami@sirius.luth.se
Summary
Composite resin choice significantly impacts post-operative sensitivity. Z250 composite resin exhibits more efficient curing and lower stress development than Z100, independent of light irradiance.
Area of Science:
- Dental Materials Science
- Polymer Chemistry
- Biomaterials Engineering
Background:
- Clinical observations link certain composite resins to increased post-operative sensitivity.
- Material properties like elastic modulus and polymerization rate may explain these differences.
Purpose of the Study:
- To investigate the viscoelastic behavior of two light-curable composite resins (Z100 and Z250).
- To determine if significant differences in viscoelastic properties exist between Z100 and Z250 when light-cured at varying irradiance levels.
Main Methods:
- Two composite resins, Z100 and Z250, were tested.
- Specimens were light-cured at 250, 500, and 850 mW/cm² to achieve a constant energy density of 30 J/cm².
- Dynamic mechanical thermal analysis (DMTA) was employed to assess viscoelastic properties.
Main Results:
- Significant differences in transition temperatures and glass transition temperatures (Tg) were observed between Z100 and Z250.
- Z250 demonstrated a lower and narrower Tg compared to Z100.
- Z250 exhibited lower storage modulus values; irradiance did not significantly affect transition temperatures.
Conclusions:
- Z250 shows more efficient curing and a narrower glass transition range than Z100.
- Z250's lower storage modulus suggests reduced stress development within the tooth during curing.
- Material selection, not light irradiance, appears to be the primary determinant of stress generation during light curing.