Avoid any contact of phosphoric acid with the zirconia restoration during the cementation process.
Do not clean the tooth preparations with prophy paste.
Use resin-modified glass ionomer (RMGI) cement for zirconia restorations when the tooth preparations have near-optimum characteristics.
1. RelyX Luting Plus - 3M ESPE
2. FujiCem 2 - GC America
FDA 510(K)Clearance for Abutments
Recently, the NADL gained clarification from the FDA that some of the abutments being produced by dental labs are not in compliance with their regulations. Here is a list of frequently asked questions and their answers to help clarify the issue.
Does the FDA have jurisdiction over labs?
Yes. The FDA is responsible for protecting public health by assuring the safety, effectiveness, quality and security of medical devices. This means the FDA has oversight over the manufacturing and sale of medical devices and as such, has responsibility for labs.
What is a 510(K)?
This is a clearance that a medical device manufacturer needs to market their products in the US. It claims” substantial equivalence” to a device that has already been cleared by the FDA called a “predictable device”. When a company submits their testing to the FDA, they are claiming to be the same as a device that has been previously cleared by the FDA and they name the predictable device and its 510(K) number in their submission.
What testing is required to get a 510(k) for implant abutments?
There is a standard protocol for testing that evaluates the strength of the overall system in worst-case conditions. Abutments have to be made at the most angled possible and tested under static and fatigue conditions. Manufacturers also have to describe the sterilization protocol and prove biocompatibility under separate, standardized testing protocols.
What does “tested under static and fatigue conditions” mean?
Static loading is subjecting the system” (abutment, screw and implant) to an increasing level of stress or force until it breaks. You measure the point at which it breaks and do that over many samples. Fatigue loading is designed to simulate the stresses the system will incur in the mouth. The system (again in “worse case condition”) is subjected to the equivalent of five million bite cycles and to ensure it survives. As with static, you test many samples to get good data.
What are the “worst case condition”?
The FDA will not allow abutments to correct over 30 degrees of angulation as there is no research to substantiate that such an angle would survive. The most angled abutment permitted by a system’s design parameters also represents worst-case for strength.
What is the FDA concerned about?
They are concerned about the abutment potentially damaging the implant or putting the patient at risk through going beyond acceptable limits. They want to ensure that abutments are designed and produced in a controlled manner that does not go beyond agreed upon limits and put patients at risk
What has changed to make this an issue?
Labs used to hand made most things but recently have purchased a lot of CAD/CAM technology to stay competitive. UCLA abutments were exempted under “custom” devices and while UCLA based had 501(k), the waxing and casting was manual so that process was considered “custom” or “one-off”. If a technician made a bad part, it was limited to that one bad part. With the technology labs have today, if it doesn’t have safety limits and isn’t validated, the process can produce hundreds or thousands of parts that are potentially risky for patients. The technology labs have invested in has made them more industrialized and therefore the FDA considers the risk to have gone up.
What can labs do to be in compliance?
A lab can order CAD/CAM abutments from a manufacturer who can prove 510(k) compliance with each interface. If a lab wants to manufacture their own abutments, the other options are:
If a lab is milling the entire abutment themselves-interface, emergence, margin and core, then they need to have a 510(k) for each interface they produce in each material they produce.
If a lab is using a blank which has a pre-milled interface, they need a 5109k) for each-interface they want to mill.
If a lab is using ti-bases and creating a CAD/CAM top to be cemented to it, even if they are using 510(k) cleared bases, they have to validate (test prove) to the FDA that the entire process (specific software, specific milling system, specific material to be used) produces parts that will survive worst cases conditions and has the right controls built into it to prevent an abutment that could cause a dangerous situation.
What are the risks to a lab if they continue to market uncleaned devices?
The FDA could send them a letter of non-conformity and demand they stop marketing and selling the non-cleared device. Failure to fix the situation could result in fines or having their business shut down.
What is the clinician’s responsibility?
They are ultimately responsible for the care of their patients. If they are using products that are not properly cleared, they are potentially risking the care of their patients and potentially putting their practice at risk by opening themselves up to liability.
What should a clinician do?
Talk with their labs about this issue. Ask them if the parts they are providing are FDA cleared and ask they provide documentation of that with their cases.
What is a clinician wants to research this for themselves?
The FDA has a database of 510(k)s that is accessible to the public: