How to measure the depth of cure of composites according to ISO 4049?

The ISO4049 standard explains in detail how the depth of cure is measured and what is minimum depth that composites must have in order to comply with this standard. This simple procedure does not require sophisticated equipment and may be done in every dental office. It allows testing and comparison of materials and light curing units. Even if there is a radiometer to check the light intensity, it is recommended to measure the actual thickness of the composite cured by a a particular light curing unit.

Here is what we need:

1. composite
2. light curing unit
3. cylindrical moulds (6 mm thick and 4-5 mm in diameter), originally it should be stainless steel, but plastic straws cut into moulds of this size may be used as well
4. glass slab
5. Mylar strips
6. plastic filling instrument
7. spatula or scalpel

And here is the step-by-step procedure:

1. Place the mould on the glass slab and fill it with composite.

2.  Place the Mylar strip on top of the composite.

3. Light-cure the composite according the manufacturer's instructions (i.e. 40 s using a conventional or 20 s using a high-power halogen or LED light).

4. Discard the Mylar strip and remove the cured material from the mould.

5. Peel off the uncured material from the bottom side of the sample using the spatula or scalpel.

6. Measure the remaining thickness of the sample and divide this number by two. The ISO 4049 standard requires that the result should be at least 1.5 mm for non-opaque shades and 0.5 mm for opaque shades.

Refractive Index of Methacrylate Monomers & Polymers

It is my pleasure to share this post originally published by Esstech, Inc. www.esstechinc.com
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TECHNICAL BULLETIN:  Refractive Index of Monomers and Their Respective Polymers

The refractive index (RI) of photopolymers is an essential property for many applications.  For optical and coating applications, the RI can be related to the resultant gloss or clarity upon cure.  Within the dental industry, the refractive index of the organic polymer matrix, must match that of the inorganic filler and substrate in order to avoid obvious “lines” where the product is applied.

Various factors affect refractive index values.  The presence of conjugated ring structures contributes to increasing RI.  In general, larger molecular weight monomers have a tendency to possess a higher RI in comparison to their lower molecular weight counterparts.  Similar to this trend, high molecular weight functional groups like methacrylates have higher RI than their acrylate counterparts. Higher atomic weight atoms also seem to be predisposed to having higher RI.

Recognizing the importance of refractive index to our customers, Esstech has assembled RI data for a portion of our existing monomer products as well as their corresponding homopolymers.

Maintaining its position as an industry innovator, Esstech has also created functional, high refractive index materials.  Contact us to learn more about these novel materials and how Esstech can make a material to match your application.

 (P) 800-245-3800 / (P) 610-521-3800 / techsupport@esstechinc.com / www.esstechinc.com

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