Surface Roughness Of Microfilled Composites
Write a short note on microfiled resin.
Answer:
They were developed to overcome the problems of surface roughness of conventional composites. The resin achieved the smoothness of unfiled acrylic direct filing resins and yet had the advantage of having filers.
Composition of Microfiled Resin:
- The smooth surface is due to the incorporation of microfilers. Colloidal silica is used as the microfilers.
- The problem with colloidal silica was that it had a large surface area that could not be adequately wetted by the matrix resin.
- Thus addition of even small amounts of microfiled results in the thickening of the resin matrix.
- The colloidal silica size is (0.02 to 0.04 mm)
- Filler content: With the inclusion of pre-polymerized filers, the filer’s content is 80 wt % or 70 vol %.
Properties of Microfiled Resin:
With the exception of compressive strength their mechanical properties are inferior to the other types of composites.
Compressive strength — 250 to 350 MPa
Tensile strength — 30 to 50 MPa (lowest)
Modulus of elasticity — 3 to 6 GPa (lowest)
Hardness — 25 to 30 KHN (lowest)
Thermal expansion
Coeffient — (50 to 60 × 10-6/°C)
Water sorption — 1.4 to 1.7 mg/cm² (highest among composites)
Esthetics — The higher resin content and presence of microfilers is responsible for the increased surfacesmoothness.
Clinical Consideration / Indication:
The microfiled composite is the resin of choice of aesthetic restoration of anterior teeth, especially in non-stress bearing situations.
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