By: Pamela Hanneman CDT
You have taken the time to plan the implant case ever so carefully. The design has been approved by the Dr. The case is on schedule and the milling was flawless. What could possibly go wrong now? You can just pop this zirconia in the furnace and finish the case up quickly in the morning. Just throw it in with that other tray that’s going up later….
Next morning you arrive to find a tray of beautiful zirconia crowns sintered to perfection………. except the one unit that was until now flawless and on schedule. Now it’s a mad dash to get it re-milled and sintered in a rush! “Rush I say!”
Stressed out Cam tech gets that milled ASAP and pops it in the furnace on a fast program. Few hours later the crown cools down and it looks just as bad as the one sintered previously.
“WHAT IS GOING ON!” “THIS ZIRCONIA IS TERRIBLE!” “THIS FURNACE IS BROKEN!”
Stop right there! The zirconia isn’t terrible and most likely your furnace isn’t broken. What really is happening is that you didn’t take the time to investigate what was truly going on. So, without understanding what happened you can’t fix the problem. You will not find resolution by doing exactly what you did the first time. We need a root cause. We need to step back and look at what we could have done wrong in the process. Sometimes this could be a lengthy process.
One size does not fit all when we talk about sintering zirconia. Not only does it differ by brand but by restoration type and design as well. Let’s look below at some of the results you may find.
I’m going to cut to the chase on this one. Based on my years of experience and visiting labs across the country, I can confidently tell you 98% of the time it is user error that causes sintering issues. We must understand how and when to use specific programs. We also need to maintain our equipment.
Always refer to the IFU.
- Each zirconia has a unique sintering program utilizing high temp and heat rate to achieve the desired esthetic result.
- There are typically 3 programs for each type of zirconia.
- Standard program
- Extended program
- Fast program
- Mixing zirconia that have different IFU’s will result in inconsistent results.
- Mixing units that are considered standard with units that should be handled on the extended program is going to again result in inconsistent firing. Either severely under or over fired.
Keys to success
- Calibrate your furnace as directed
- Clean heating elements if needed
- Learn to program your furnace
- Have pre-entered programs with explanations of when to use
- If you must fast sinter, increase your high temp at least 15 degrees Celsius above the IFU.
- If you must fast sinter, make your first heat rate faster but do not shorten the hold time or the second heat rate.
- Not all zirconia can fast sinter. Make sure it is recommended.
- Fast sintering shortens the life of your heating elements.