Restoring a broken tooth with composite can be challenging. It is important to understand the optical properties of enamel and dentine and how this relates to the composite you are using. The enamel is primarily inorganic and high in value (brightness) whereas the dentine is predominantly formed of organic content and is high in chroma (actual colour).
This is important because when we are restoring a class IV cavity we can opt for a separate enamel and dentine composite shades. When we layer the restoration with the correct composites in the ideal ratios we can emulate the natural tooth quite closely giving us a good aesthetic outcome.
You can think of the restoration as a sandwich - the palatal surface is formed out of the enamel shade, the majority of the cavity is formed out of the dentine shade and then the final buccal layer is the enamel shade.
If we get the proportions of enamel and dentine wrong we can end up with an unaesthetic result. For example if we use too much enamel shade and too little dentine shade the restoration can appear too grey (lacking chromacity). If we use too much dentine shade and too little enamel shade the restoration can appear dull and lifeless as it lacks value.
The evidence suggests we should aim to have our final enamel layer at a thickness of 0.5mm. So how do we calibrate to get 0.5mm thickness space for our final layer? There are numerous techniques such as using a William’s probe once the dentine layer has been placed to check there is 0.5mm space left for the enamel layer or assessing with pre-fabricated putty stents and measuring the residual space.
One way we think works well and thought you would like to hear is by using the LM-Arte Misura instrument. You use the instrument when placing your dentine layer. Place the thin portion of the instrument on the unrestored surface so the thicker region of the instrument is compressing your dentine layer. By moving the instrument left and right to compress and adapt the dentine will leave 0.5mm of space for your enamel layer of composite ensuring you get the right thickness of composite in your enamel layer, and optimise the aesthetics!
LM-Arte Misura
How to hold instrument against tooth to compress dentine layer to correct thickness
This is a great article if you want to learn more:
https://fahl.com.br/wp-content/uploads/2019/08/sj.bdj_.2016.944-2.pdf