How to close an open crown contact by yourself
Need a porcelain furnace with a vacuum, some add-on porcelain, modeling liquid and a brush.
Need to know coefficient of thermal expansion (CTE) and firing temperature for your porcelain. Add-on material must have the same CTE and a lower firing temperature than the material you are adding to. eMax has CTE of 9 and a firing temperature of 820 degrees Celsius or higher. So can use VM-9 Add-On from Vita which has a firing temperature of 780 and a CTE of 9.
Mix with modeling liquid (or distilled water) to desirable consistency by adding powder to liquid, then apply. Do not let dry out. If it does dry out, it’s best to discard the mix because you’ll end up with a porous low quality porcelain after it’s fired.
Add to clean surface and overbuild to compensate for shrinkage. While you can re-glaze the area, it’s typically not needed as you can typically achieve the desired finish with polishing alone.