28 April, 2014 Avi Cohen – Director, Global Dental – Stratasys Ltd.
The assessment is intended for forward-thinking dental labs and dental production centers wishing to discover how the latest 3D Printing technologies which help them stay ahead of the competition, as well as understand the advantages of 3D Printing with compare to traditional milling techniques. This assessment will lay out the industry needs and considerations while thinking about applying the use of 3D printing to their dental production floor.
3D Printing Digital Solution vs. Traditional Milling
• Overall reproducibility and accuracy to detail is less than printed. Especially if the object to be milled has an area to be milled smaller than itself. In this case the software will use a milling strategy of creating extra space for the cutting tool. In this scenario the bur cuts away more material than is needed to compensate to make the crown fit. Areas such as this include incisal edges, marginal ridge of tooth preparation. This can takes away much needed room for porcelain when you are limited by the diameter of the cutting tool. In other words a cutting tool cannot mill something smaller than itself. Surface details of anterior teeth and fine grooves such as you would find on posterior teeth are not easily reproduced. In general the fewer the number of tools used the less detail the milling system can produce. Examples of systems with lower detail include Cerec, D4D and Katana.
• The overall quality and ability to mill complex shapes is dependent on the number of axis used. Most dental systems typically use is 2 to 3 axis. There are a few systems that use 5 axis but this will increase the initial cost of the system and its operating and maintenance costs.
• Higher operating and maintenance costs. Burs are very expensive and difficult to optimize how many units can be milled from a set of burs. Sometimes they break long before their estimated capacity or life expectancy. Burs may break during production and unless a technician is there during production to change the broken bur. Production will stop. This does not fully support the concept of lights out manufacturing. Burs add additional cost to the coping or crown. Laboratories need to keep burs in stock. Some systems require only 1 bur (Katana) while others such as Dent Mill or Roeters require 4 burs for their system. This really increases material cost per unit. Typical bur cost is $135.00 to $150.00 per bur each.
• Wasteful in material usage. You use more material than you actually need and throw most of it away. Disposal of material waste may be harmful to the environment. Milling also requires much longer process times because it needs to remove excess material to produce the final object. Milling requires good dust extraction system. The milling waste from dental stone or zirconium may be harmful to the working environment and is destructive to the milling machine. Milling requires extra attention to cleaning and maintaining extraction systems. Filters and expensive extraction systems add additional set up and maintenance costs. It may be harder to comply with OSHA guidelines.
• Frequent calibration needed which takes time and decreases daily production. Constant adjustments need to be made to keep the milling machine in calibration especially after changing burs when they break. This gets more complicated with systems using multiple burs (2 or more). The more burs used the longer and more frequent calibration is needed.
• Milling systems in general are more complicated to learn and operate.
• The materials used are not esthetic or useable for case presentations such as diagnostic work. This limits the dental solutions and hinders milling systems versatility.
• Most milling systems have various limitations while milling and are intended for crowns and bridge fabrication.
3D Printing Advantages
• Printing can reproduce complex shapes and do not require special strategies or use of special parameters to compensate for the size of the cutting tool. You can reproduce and print in exact detail the tooth or object as it was designed. You also have the choice of printing in 2 resolutions and in 2 different surface finishes. A glossy finish shows better anatomical detail. This is especially a big advantage with working with anterior teeth.
• 3D Printers are not limited in the traditional sense to milling axis with linear rotary instruments. Curves, holes and more complex shapes are easier and more accurately reproduced with 3D printing.
• Printers do not require burs. The nature of the printing itself gives excellent detail without the constraints of the size of the smallest bur. There is nothing to break or change. The need to order and keep burs in stock is eliminated. Fully support lights manufacturing without the worry of production stoppage because of bur breakage during overnight production runs.
• Printing reproduces the object to be printed exactly as designed without waste. Process times and material costs are reduced. No harmful dust or fumes are created to harm the working environment. The recycling program that Objet offers is easy for the laboratory to dispose of spent resin cartridges.
• You can print multiple parts at the same time. Crowns, dies and models can all be printed at the same time. Multiple models can be printed at the same time. Example: one can print 4 quadrant models U/L with crowns and dies in 1 hour and 35 minutes. There are new printing strategies with semi hollow models that greatly reduce material cost by nearly 50% while support material will increase slightly. Average milling time per unit is 8-10 minutes. However one can print 50 to 80 units in 56 minutes in high quality mode.
• Very easy to learn and operate. Requires very little training time.
• Both the VeroDentPlus and VeroGlaze have excellent and life like features lending additional dental solutions for the dental and ortho lab.
• Can print all solutions needed for typical laboratory needs with one system.