The overlooked potential of the Zeiss dental microscope in cosmetic and general dentistry
Having a long history of dentists in my family, the field has always been one of my main interests. Every time I go to the dentist, I would ask for a mirror so that I could see what goes on inside. On one of my visits, I saw that my dentist had just gotten a Zeiss microscope, which he used while operating on me. This time, instead of asking for a mirror, he switched on a screen and there it was. On the screen was exactly what he could see through the microscope. I was fascinated by the projection on the magnified image. Not only did I have a clearer view, but with the magnification, I could see all the miniscule details I never thought existed. Intrigued by this application of the microscope, I asked him if I could do an internship to observe the ways microscopes could be used in dentistry. He accepted it and at the end, I even got the chance to try the microscope myself and operate on models.
I first operated on the models only using loupes with 2.5x magnification, which are what most dentists use when operating. This was my first time using a dental turbine, and it took me a few trials on stone models to get used to wielding the turbine. Then I finally got my first real tooth-an extracted one-to drill. Using the loupes, I could see somewhat better than I could with my bear eyes. The task required immense concentration but also a great sense of space. Even with the loupes, I was not able to effectively gauge the depth. The magnification allowed me to get a better sense of depth than with my bare eyes, but I was not able to keep a consistent depth of 1.5mm (the recommended depth for onlays). Obviously, most of what is to blame for this is my lack of experience with the turbine, but I could barely tell the difference between 1mm and 3mm with the loupes. Though I was unable to gauge the depth, I was able to drill and flatten out the bottom of the hole, or so I thought.
After I finished drilling with the help of the loupes, I observed the samples through the microscope under 25x magnification. To my surprise, the surface I thought I successfully made flat and even was as bumpy as the skin of a toad, and there were some parts that were extremely shallow while others were too deep. In my opinion, the worst kind of failure is when you fail at something you think you did well. Though I could not get the right depth, I was confident that the hole I drilled was smooth and even, but I saw that I had completely failed.
The bottom of the tooth preparation appears to be smooth when viewed through a loupe (Left), but when viewed through the microscope (Right), you can see that it is rough and uneven.
I was astonished by the differences I saw when looking through a microscope but also wondered why such an extreme level of precision is necessary. It seemed almost perfect when I looked through the loupes, so I didn't quite understand the need for such accuracy. I learned that the smoothness of the hole is a crucial factor that determines the success of the treatment. Removing cavities is a two part treatment. On the first visit, the dentist removes the cavity and places a temporary filling after taking a mold of the tooth. The dentist sends the mold to a dental lab, where a technician constructs a permanent crown, inlay, or onlay. After the dentist receives the finished product, the patient returns for a second visit, where the dentist removes the temporary filling, replacing it with the permanent restoration. One of the factors that determine the quality and the durability of the restoration are the smoothness of the tooth. It would seem that having a rougher floor would be better because it offers a better grip, but in reality, this is a disadvantage that weakens the structural integrity of the restoration, making it much more prone to cracking. It is also important to smooth out the edges of the hole for the same reason. Having sharp corners rather than a smooth one causes pressure on the tooth and restoration to be unequally distributed. These sharp edges subject specific areas to a large amount of physical stress, increasing the likelihood of the restoration to crack.
After learning about the importance of smoothing out the hole, he let me continue operating on the same tooth, this time using the microscope. With this, I was able to operate with an astonishing increase of precision. Most of the roughness was gone, and I was able to flatten it out completely. I measured the depth afterwards using a periodontal probe (dental ruler) and saw that I did a decent job keeping the depth at 1.5mm throughout the entirety of the hole. More importantly, I was able to smoothen out all the rough edges, eroding the sharp corners into bullnose edges. All these factors increase the durability of the restoration.
These microscopes are typically used by endodontists, who require this level of precision to locate and maneuver through the narrow root canals. Very few general dentists currently use microscopes, partly due the costs and partly due to the disregard for such level of precision. Only through a microscope are most of these differences visible, yet precision is key. These technical are the main benefits of using the microscope, but there are substantial ergonomic benefits as well. The average dentist spends about 30 hours a week operating on patients, and in many cases, dentists may adopt positions that strain the back to get a closer look at patients. A meta-analysis conducted by Chikte found that there was a combined prevalence of thoracic-lumbar pain (Upper/middle back) in 53.9% of dentists and neck-pain in 41.4%1. This strain is reduced significantly when using the microscope as it allows the dentist to operate with a straight posture. Without the constant strain, dentists feel less stressed, so they can focus more on the operation, improving the quality of each treatment. This experience was fascinating. I had always pictured dentists as those doctors with funny looking glasses, but now, some have those glasses and the high tech microscopes. By experiencing some of the tasks that dentists perform regularly, I have gained greater insight into the field and learned that with constant innovations, unimaginable improvements to efficiency and accuracy can be achieved.
About the author
I am Jean-Luc Shimizu, a high school senior at the Awty International School. My father is in fact Dr. Shimizu and it was an amazing experience seeing the professional side of him. In my list of possible careers, dentistry is one that sits high in the ranks, so being able to consult with him basically any time I want is a gift I greatly appreciate.
1. Chikte UM, Khondowe O, Louw Q, Musekiwa A. A meta analysis of the prevalence of spinal pain among dentists. SADJ. 2011 Jun;66(5):214-8. PMID: 23193861.
Mr.Shimizu is looking through the microscope, focused on polishing up the dental preparation.
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Dr. Shimizu is an accredited member of the American Academy of Cosmetic Dentistry. There are only 404 dental professionals worldwide (Only six in Houston area) as of 2020 who have achieved this prestigious honor.