Is it just advertising hype or is it really as good as it seems? Let’s look at some of the pros and cons. First, let me start by saying that I started in dentistry as a laboratory technician. I graduated from lab school in 1987 and began working for a prosthodontist (Wikipedia). Having made thousands of crowns for a specialist and now having seated thousands as a dentist I am able to be a bit more critical about quality. It is the reason why I have an in house dental lab. I’ll try to be as objective as possible but…
ANY dentist who says he/she can make a crown as well as a well-trained dental technician ……. this may sound harsh but……. They are seriously uninformed!!
So, how does the same day crown work? The dentist gets the tooth ready in the same fashion as the conventional technique however instead of taking a mold of your teeth 3D pictures are taken and uploaded to the CAD (computer aided design) software where a virtual crown is designed. It is then up loaded to the CAM (computer aided mill) where it is carved out of a block, finished and finally put on the tooth! It is fantastic that we can even do this! I am impressed with where technology is going! The next technology break through is already happening with 3D printing! It will soon make the CAM milling obsolete! Go visit it on YouTube. It truly is fun and exciting stuff!!
So the question is… why haven’t we embraced the new technology?
Are we unwilling to pay the $100K+ it costs to get the CAD/CAM? Are we unwilling to train the needed staff? Am I fearful of change? If those were the excuses then I would GLADLY embrace the same day crown however, “a one visit crown compromises the esthetics and quality”, Dr. Ryne S Johnson (prosthodontist). Although it only requires ‘one visit’ it requires more office time’ for the patient.
So why is there a quality problem?
I met with a sales man in my office last month who was showing me the latest intraoral scanner on the market. We both compared the resolution of his software (digital pixels) to my own laboratory models (analogue) under our laboratory microscope. The digital resolution was nowhere near the handmade model. All of the sharp detail had been ‘rounded off’. The question is, why? Well, let’s think about this in a very simple way. The 3D image a dentist takes of your tooth is from a small camera (or multiple) on the end of a hand held wand. It goes in the mouth and taking multiple pictures. Accuracy. The software then stiches and resamples hundreds/thousands of pictures together into a 3D image. The problem? The software algorithms have to average out the multiple pictures and mesh them loosing detail. Going from analogue information to digital isn’t as easy as it would seem. This is why all of the detail had been rounded off when we were comparing it in my lab. This is fun technology when used on your current panoramic setting on your 2D camera but sadly at the 3D micron level accuracy is lost.
What does the research say??
Very few dental articles on this subject are true research articles. Most are advertisements made to look like articles until you look at the authors etc. But I have found a couple – one is by the University of Louisville published 5-2015 by Michael C. Guzelian that evaluated CAD/CAM vs handmade made porcelain veneers. The importance of this study is it is “double blinded”. This kind of study takes out the personal bias that is so common in most reports like the ones you see on the net. It has an interesting but predictable observation.
“There is a favorable perception and rapidly growing preference for digital impressions (and milling) in dental student communities compared to active clinicians!”
This is easy to understand since the generation of dental students and young doctors were born into technology and the “get it now” mentality gives way to the “old” hands on techniques. The laboratory skills required in dental school have been likewise reduced. Some schools only have a 2 crown laboratory requirement to graduate! So do you think a dentist with minimal laboratory background can evaluate the differences in quality? Of course not but it’s not their fault! They don’t know what they don’t know! Do you think that the schools go out and buy those high tech CAD/CAMS, or are they provided by suppliers who are getting the kids hooked on their technology so they need it after graduation? I don’t mean to be cynical but the writing is on the wall. Technology will win! However, as of today the conclusion of this double blind study is “digital impressions (CAD) with virtually-designed crown still underperforms against complete conventional technique, digital work flow requires substantial preparation design and milling improvements to compete with a conventional work flow involving current standards”. One further note that the research article doesn’t mention…The mills used in dental offices are not those used in the large commercial labs. Think of the dental office mill more like a hobby mill. The hand held intra oral cameras used in dental offices are also nowhere near the resolution of the fixed laser controlled environment units used in the commercial dental labs.
You don’t want your dentist or their assistant making a crown any more than you want a lab technician prepping your tooth. The time ‘lost’ and cost of equipment means no savings to the patient or improved quality. It is true that it can be a ‘one visit crown’ but at what cost? That is up to the patient to decide when they are objectively informed. I use digital 3D x-rays and software all of the time for surgery and I love the technology but even the best technology has its place it just doesn’t make a good crown…yetJ When it does it will be proudly be on display in our office!!!