The Impact of 3D Printer Accuracy
In previous posts we have covered the accuracy of various 3D printers on the dental market in great detail as it pertains to the dimensional trueness of a single, static 3D printed object. However, it is also important to understand how 3D printer accuracy impacts the clinical outcome of dynamic treatments like clear aligner therapy. When fabricating a series of clear aligners to incrementally align the teeth, the dimensional inaccuracy of each 3D printed model is compounded between aligner stages thereby making 3D printer accuracy an even more important consideration. Although the directionality of the error is not necessarily consistent, the magnitude of print inaccuracies between stages could be up to double that of single print. Thus, despite the dimensional error of even the least accurate 3D printers being well within the reported guidelines for accuracy for orthodontic casts of 300µm, the maximal error possible with clear aligners can approach and even exceed this limit with lower accuracy 3D printers.
In addition to the understanding the benefits of using more accurate 3D printers to manufacture clear aligners in-house, 3D print inaccuracies must be taken into consideration when designing maximal tooth movement velocities or activation rates for in-house clear aligner treatments. Since most quality 3D printers exhibit average dimensional inaccuracy on the order of 50-70µm, clinicians must account for the possibility of 0.1mm variance in the planned maximal activation rates. Based on the available data, it would be advisable to revise maximal tooth movement velocities down to 0.15-0.2mm of linear displacement per stage.
As in-house clear aligner software continues to evolve, machine learning and artificial intelligence will assist in the design of more effective movement staging and activations (as products like Invisalign are already doing), but the increased accuracy of 3D prints from quality 3D printing machines will always provide an advantage for clear aligner therapy.
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