An evaluation of the effect of curing systems and water storage on the fracture toughness of two types of composite resin filling materials with different organic matrix composition : in vitro study

Abstract EN

Background : Chipping and bulk fracture are major contributors to clinical failures of composite restorations.

Fracture toughness (KIC) quantifies susceptibility for fracture.

Halogen light curing units have some specific drawbacks, such as decreasing light output with time.

This may result in a low degree of monomer conversion of the composite, which is undesirable, as it can adversely affect mechanical properties including fracture toughness.

This study was conducted to evaluate the effect of conventional light cure unit (Astral is – 5), light emitted diode (Radii) and water storage on the fracture toughness of packable composite (Filtek P60) and microfilled hybrid composite(Glacier).

Materials and Methods : KIC was determined by preparing 128 single – edge notched beam test specimens (2X4X20 mm with a 3mm long notch on one edge).

The composite specimens were cured by Astral is – 5 or Radii and were subjected to 3 – point bending test (without aging), after 1 day, 7 days, and 28 days storage in distilled water.

Student t – test followed by ANOVA (P<0.01) were used to analyze the results.

Results : The fracture toughness values were highly significant when using Radii light cure unit (for both types of composites), and the fracture toughness values for P60 composite were highly significant.

Conclusions : Water aging from 7 days to 28 days didn't produce significant effect in the fracture toughness values for P60 composite, but it led to a highly significant reduction in the fracture toughness values for the Glacier composite.

Resin containing Bis – GMA showed higher fracture toughness values than UDMA based resin.