New In-Office Capabilities
Q&A with James F. Simon, DDS, MEd,
Inside Dentistry interviews James F. Simon, DDS, MEd, director of the Division of Esthetic Dentistry and a professor in the Department of Restorative Dentistry at the University of Tennessee Health Science Center College of Dentistry in Memphis, Tennessee
Inside Dentistry (ID): What are some of the most exciting and impactful developments in indirect restorative dentistry right now?
James F. Simon, DDS, MED (JS): What excites me the most is the quality of the restorations that we can achieve with the help of CAD/CAM. With the ability to fabricate precise inlays and onlays, we can provide conservative restorations instead of cutting all of the teeth down for crowns. Because we do not need to fabricate temporaries and we can deliver restorations in one appointment, we can maximize the conservation of tooth structure and avoid the unnecessary removal of enamel. I can bond to enamel much better than to anything else.
ID: For cases that need to be sent to the laboratory, what new developments are allowing them to provide better esthetics and strength?
JS: Laboratories have a wide variety of exceptional new materials because manufacturers continue to improve their products. Although dentists may be restricted to a limited amount of materials for in-office milling, laboratories often have many different options and are up-to-date on the latest developments. In addition, laboratories are the best equipped to capitalize on new staining and glazing materials because that is an area that requires extensive training and talent, and many private practitioners prefer to leave this step to them.
ID: What do dentists need to know about the newest materials on the market?
JS: Knowing the preparation requirements for any material being used is absolutely necessary. The old adage of "garbage in, garbage out" applies. Dentists must be knowledgeable about their materials. Whenever a new milling machine is acquired, proper training should include a review of preparations because each material's preparation requirements are extremely critical to the success of the end result. Then, on the back end, dentists must also know what each material needs in terms of cementation or bonding and the steps necessary to make that process effective. Many restorative failures are attributed to the under-reduction of teeth or the improper seating of restorations with the wrong material.
ID: How can CAD/CAM equipment help a practice's bottom line?
JS: Some dentists say the technology is too expensive, but in the long run, these systems are one of the few products they can purchase that increase revenue. A milling machine can turn what would be a $150 laboratory bill into a $20 charge for a block. Also, patients do not want to come back for a second appointment. They do not like being stuck with a needle or wearing a provisional, and their time is as valuable to them as ours is to us. They might even be willing to pay a bit more for the opportunity to receive a single-visit crown.
ID: What impact can intraoral scanners have if a dentist is not milling in-house?
JS: A full mouth impression with vinyl polysiloxane in a stock tray can cost $18 to $35 per impression, so dentists can save money on the front end by scanning. In addition, the scan is more accurate, and the laboratory can turn the case around in a more timely manner-often in 2 days instead of 2 weeks.
ID: Does CAD/CAM always provide more accuracy than analog processes?
JS: Oftentimes, it depends on the preparation. If the preparation is bumpy, a human can wax to that better than a machine can mill to it. CAD/CAM is a tool that can improve accuracy, but human intelligence is still a needed asset.
ID: What education is required in order to mill crowns effectively in-house?
JS: A basic education is necessary, but learning the process is not as difficult as some believe. It bothers me when clinicians say that they do not want to become involved with CAD/CAM because the restorations break, look bad, etc. Many of these dentists just do not want to learn the software or change their workflow and their scheduling process to accommodate single-visit dentistry. Again, the preparation is the key to everything: with a good preparation, the fit of a single-visit crown should be better than that of a crown from a laboratory.
ID: Are there any general guidelines that you would suggest regarding when a case can or should be fabricated chairside versus when it should be sent to a laboratory?
JS: That usually depends on the dentist's skill level and desire to do the work involved in the case. I prefer not to fabricate anterior restorations, because I do not want to take the time to achieve the necessary esthetics required by an anterior tooth. However, having the patient in the chair can offer an advantage over using the laboratory, depending on the degree of shade-matching and other information you provide to the laboratory. Lithium disilicate is a popular chairside material, but it is not recommended for use as bridge material in the molar area, despite some dentists' ability to place it there successfully when there is enough connector area for strength. Also, certain materials may limit the length of bridges that can be fabricated chairside.
ID: What trends do you expect to see develop or continue in the future?
JS: Many schools have incorporated CAD/CAM into their curricula, so graduating students are looking for practices that have that capability. Among dentists who already have purchased CAD/CAM equipment, many are achieving a higher return on investment with the help of younger dentists who join their practices. In addition, practitioners who have avoided the technology will need to become involved with CAD/CAM to make their practices more attractive when they want to sell.
ID: How do you envision the evolving role of 3D printing?
JS: Once a material is identified that is durable enough to be used in the mouth long-term and the speed of the machines increases to a certain level, the advantage will be the ability to make restorations that are given their multicolored characteristics from the inside. This could eliminate the need for some surface staining, which has a tendency to wear off over time. These restorations could potentially be very esthetic. Although it would be easier to fabricate these restorations in-office because staining and glazing would not be necessary, the dentist would still need a discerning eye to detect and reproduce the subtleties of the different colors in the tooth. Unfortunately, I do not know how long it will be before we have a printed material that is capable of withstanding the rigors of a human chewing on ice, pencils, etc.