By Dr. Wally Renne
01 March 2023
We need to have an open honest discussion about 3D printed restorations. I have been printing definitive inlay, onlay, veneers and crowns for the past 28 months or so. I have just over 1000 restorations (mostly veneers, implant crowns and partial coverage onlays) and have had 2 fractures no debonds in this time. More importantly we have dramatically increased the quality of care for our patients. I will explain my reasoning for adopting these and some limitations.
But first, please let me take a moment to explain the difference between these materials, direct resin and milled resin like Tetric CAD, Cerasmart and the dreaded Lava Ultimate. And let me explain how I use these restorations in my practice. Please note this is not meant to be an exhaustive literature review.
Printed restorations are a way to do conservative indirect quadrants of Inlays and Onlays. A major upgrade to larger direct resins. Direct resins are great in certain indications however when they get large they become technique sensitive and are quite poor as a restorative solution. “Every time you add another surface to a direct resin, failure rate increases by 30-40%” (1).
We also know from a recent systematic review and Meta analysis that indirect Onlay restorations made of resin perform with the same success as ceramic, both dramatically better compared to direct resin(2). Two of the main reasons direct resins preform poorly is they have a poor degree of polymerization with around a 50% methacrylate conversion (3) and when they are cured in a tooth a large amount of force is placed on the tooth and adhesive layer due to polymerization shrinkage stress(4).
Contrastingly printed resins when properly cured can have up to 95% degree of polymerization (5) which explains the better wear characteristics (6,7,8) and we know indirect resins like printed restorations reduce shrinkage stress imparted on the tooth to almost zero( 4). It is a travesty in the USA that only 6% of dentist treatment plan Inlays and Onlays. This is largely due to cost of lab bills, difficulty temping and large cost of mills to make this single visit. Our patients deserve options. In Latin America, Europe and Asia more partial coverage indirect restorations are done then full coverage crowns. Not everything should be a filling or a crown, with nothing in between. I believe 3D printing will bring more conservative partial coverage to mainstream dentistry. It is certainly my favorite use of these printed restorations.
Based off of this and other evidence and following my printed restorations over time I charge the same for a printed Onlay or Inlay as I do for a ceramic Onlay and inlay. I am confident this is a great indication for these restorations. NOTE* you have to understand adhesive dentistry and partial coverage preparation for these to be nice.- [ ]
Another major application for me is implant crowns. Philosophically making implant crowns out of a polymer resin makes sense because implants lack a PDL space and the ability to absorb impact (9-17). This is opposite to the trend of making implant crowns out of zirconia. Natural teeth wear and are dynamic. Zirconia doesn’t wear at all, It is the immovable rock in the mouth. This can lead to hyperocclusion over time that may potentially result in implant failure (18-20).
We have high level of evidence that shows that 50% of all implant crowns next to a natural tooth end up with an open contact (21) With printed, you can simply unscrew the crown, sandblast the contact, add resin and cure. Milled composite was promised as an ideal material in these indication but failed through debonding. Interestingly composite crowns on implants manufactured using packable composite manufactured by Bicon as the Integrated abutment crown have great clinical success(22). This is because milled resin in contrast to direct resin and printed resin is completely devoid of free methacrylate to bond to and they suffer from debonding (23).
Studies show bond to printed resin is not only tenacious but actually increases over time (24). Based off of this and other evidence and my clinical knowledge, I charge the same for a printed implant crown as I do for a ceramic implant crown. NOTE* you have to understand how to finish and bond the printed restorations for them to be nice solutions.
Printed veneers. I love this application and use it almost daily in my practice as a lower cost alternative to ceramic. I still do plenty of ceramic veneers but printing has enabled me to do more conservative veneers on patients that normally wouldn’t have been able to afford veneers. I no longer do direct resin veneer. I charge half the cost for a printed veneer as I do for ceramic. They take me half the time to do. I do them single visit because 10 veneers can be printed in 10 minutes. NOTE* you have to know how to properly finish them or they look bad and don’t hold up.
Lastly, I use 3D Printed crowns as a lower cost crown. You can charge full fee with the recent code change. But me having it less expensive comes in handy for me when treating low income patients or even high income patients that need phased treatment. For example with full mouth reconstructions. Often I will do one arch in zirconia and the other in printed to buy them 5 or so years to slowly convert the remaining units to zirconia or emax. This enables me to still do both arches and not have to compromise occlusion by treatment of one arch only. Studies show that when opposing zirconia printed teeth wear less then even premium carded denture teeth. I am Fee for service.
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