| buyer’s guide Dental resins in 3D printing—just the beginning: A buyers’ guide Dr George Freedman, Canada As 3D printing transforms the dental world, it is impera- tive for each dental practitioner to determine the specific formula for its productive integration into the practice. Regarding printers, their accuracy, speed, repeatability and ease of use are fundamental. The printing materi- als—resin, ceramic and/or metal—are absolutely crucial. As adoption of dental 3D printing is accelerating, and the myriad of its clinical and laboratory applications are rapidly expanding, the key to success lies in finding the best material for every specific task. Fortunately, there is a very large array of resin (and other) printing materials readily available to the practitioner. The first step in material selection is to correctly iden- tify the clinical problem which must be solved. There are three major classes of 3D-printed products: those that are used extra-orally (laboratory models), those that are used intra-orally on a temporary or intermittent basis (night guards, surgical guides and digital dentures) and those that are placed intra-orally on a permanent basis (crowns, bridges and other restorations). The earlier concerns about material biocompatibility have largely evaporated owing to the sheer number of regulatory compliant materials that are offered by nu- merous companies around the world. Their mechanical properties have been substantially improved over the past few years to offer greater structural strength and a higher resistance to functional wear. Restorative aes- thetics have also progressed significantly. With all these options available, the selection of a 3D printer that of- fers support for third-party materials is highly recom- mended. The most decisive considerations in the selection of 3D-printing resins are dependent on their intended clini- cal use, but should include biocompatibility, ease of use, predictable high quality, strength and accuracy. Intui- tively, differing application will demand differing proper- ties: – Permanent crown/onlay/veneer resins must offer high strength, accuracy, precise fit, multiple shades, low water sorption and a smooth finish for long-term res- torations and a low tendency to age, discolour and ac- cumulate plaque. – Digital denture resins require a good density with opti- mal flexural strength, compatibility with denture teeth, a smooth finish and a low tendency to age, discolour and accumulate plaque. – Flexible occlusal splint resins for occlusal guards and bleaching trays must offer easy polishability, comfort- able wearability, durability and preferably optical trans- parency. – Hard occlusal splint and night guard resins must be highly durable and fracture-resistant. They typically print clear and polish to a high optical transparency. Since these resins are used to produce long-term ap- pliances, they must resist discolouration and plaque accumulation. – Temporary crown and bridge resins (for provisional crowns, bridges, inlays, onlays and veneers) are re- quired to provide excellent marginal adaptation, strength, flexibility and aesthetics for up to one year intra-orally. – Surgical implant guide resins must be biocompatible and autoclavable. – Restorative model resins require high precision, reli- ability and reproducibility throughout the restorative dentistry process. The models and dies must be ac- curate and have crisp margins and precise contacts to deliver high-quality and timely results. – Orthodontic model resins must be fast-printing and highly accurate and offer a very smooth surface finish, ideal for aligner and retainer production. These and many, many more solution-focused printing resins are available. The practitioner must become very familiar with the properties of a reasonably limited range of resins and then apply this knowledge to the 3D-printing digital workflow to achieve maximal success in the treat- ment process. Resin cost is yet another parameter. Various resins have differing price points, but the difference between an average product and the best material may be a mere 20 %–30%. Considering that the resin material cost for a 3D-printed restoration represents 1 %–2% of the final fee to the patient, the dentist has every reason to use the best available material in every case. This is the key to clinical success. 48 3D printing 2 2023