Many dentists currently use digital technology in their practice, with more converting from analogue to digital every year. In dentistry, 3D printing remains an emerging technology, with significant technological and cost obstacles or barriers that limit its wider adoption. Though there have been improvements made, 3D printers are still limited on the precision that is required for dental models and restorations.
Currently, accuracy has improved using resin-based printing methodologies including stereolithography (SLA) and digital light processing (DLP). With these technologies, printed layers of resin are solidified by a laser light source in SLA printers and a projector in DLP.
Continuous liquid interface production (CLIP) technology produces significantly less variation/better trueness from the reference model than a DLP printer; however, both printers exhibit a clinically acceptable level of accuracy (CLIP 35 and 45 microns, DLP 77 and 77 microns) for hollowed and solid bases. Clinically acceptable accuracy for fixed prosthodontics is 100 microns, and 200-300 microns for diagnostic models. Models manufactured by 3D printing method were significantly more accurate than the milling method.
Some current limitations on printing are:
- Cost of the equipment
- Cost of the materials
- Limitations in materials
- Restriction in build size
- Time of production
- Number of steps in the production (post processing)
- Quality of production
- Supporting structures required
- Health concerns (vapors) during production.
This scenario may be changing with the announcement of a new 3D printing technique called volumetric additive manufacturing (VAM). The new technique is called xolography and uses light to solidify objects from a liquid base. A rectangular sheet of blue light is projected through a volume of viscus resin, activating photo initiators dissolved in the resin. A second beam of red light then projects an image of the object to be printed into the plane of the light sheet, solidifying the resin where the two beams of light cross.
This high-speed process uses algorithms to control the cumulative light exposure with a dissolved oxygen system that prevents unwanted solidification. This process is repeated slice by slice until the object is complete. The process can produce a monolithic object with 100 micrometer scale features, which does not have the inaccuracies produced by the current layer-by-layer printing process. The volume of the item produced is currently limited to the depth the light can penetrate the resin.
Who knows how long this technology will take to make its way to dental applications, but this futuristic process and its ramifications could signal an accelerated end to analogue-based dentistry?
Robert Winter, D.D.S., is a member of Spear Resident Faculty.
Rungrojwittayakul O, Kan JY, Shiozaki K, et al. Accuracy of 3D Printed Models Created by Two Technologies of Printers with Different Designs of Model Base. Journal of Prosthodontics. 2019;29(2):124-128.
Jeong Y-G, Lee W-S, Lee K-B. Accuracy evaluation of dental models manufactured by CAD/CAM milling method and 3D printing method. The Journal of Advanced Prosthodontics. 2018;10(3):245.
Regehly M, Garmshausen Y, Reuter M, et al. Xolography for linear volumetric 3D printing. Nature. 2020;588(7839):620-624.