4D Printing in Dentistry

Objectives: To introduce dental objects with smart behavior, that is, changing from static to functional. To produce dental objects with controlled self-folding criteria (i.e., changing their shape overtime in a controlled manner). To produce dental objects composed of microstructures and multi-materials with predefined dimensional changes, predetermined response to temperature/humidity and in known weights/proportions.
Methods: Dental 4D printing is governed by biological and thermomechanical considerations. It relies on 3D printing combined with selective photo-curing of copolymer networks to achieve variable flexibility, elasticity and elongation between different microstructures within the same object. This method allows the creation of dental object composed of different constituents with known interface bonds so that the object will be functional with smart, dynamic behavior. In the oral cavity, heat and humidity are always changing and many dental fillings or appliances failed to adapt with this changing environment, leading to undesired shrinkage and/or expansion.
Results: In December 2016, a patent was published on the use of 4D printing in clear aligners' orthodontics. Each aligner is composed of microstructures which undergo dimensional changes under the heat and humidity stimuli in the oral cavity. That is, clear aligners change their shape overtime in a controlled way. This change in shape carries the teeth to targeted position and in predefined angulation which ends by alignment (Figure 1).
Conclusions: 4D printing has been used in industry, and by considering some biological and thermomechanical issues, it can be used in dentistry and medicine as well. 4D printing can allow for the production of functional dental objects. This application can serve orthodontics, implant dentistry, restorative dentistry and TMJ research.