Production tolerance of additive manufactured polymeric objects for clinical applications

• Two computer aided designs relevant to dentistry were utilized.
• Four additive manufacturing units produced 10 samples per design.
• Measuring equipment was validated.
• Accuracy and standard deviation was recorded for a total of 28 parameters.

ObjectivesTo determine the production tolerance of four commercially available additive manufacturing systems.MethodsBy reverse engineering annex A and B from the ISO_12836;2012, two geometrical figures relevant to dentistry was obtained. Object A specifies the measurement of an inlay-shaped object and B a multi-unit specimen to simulate a four-unit bridge model. The objects were divided into x, y and z measurements, object A was divided into a total of 16 parameters and object B was tested for 12 parameters. The objects were designed digitally and manufactured by professionals in four different additive manufacturing systems; each system produced 10 samples of each objects.ResultsFor object A, three manufacturers presented an accuracy of <100 μm and one system showed an accuracy of <20 μm. For object B, all systems presented an accuracy of <100 μm, and most parameters were <40 μm. The standard deviation for most parameters were <40 μm.SignificanceThe growing interest and use of intra-oral digitizing systems stresses the use of computer aided manufacturing of working models. The additive manufacturing techniques has the potential to help us in the digital workflow. Thus, it is important to have knowledge about production accuracy and tolerances. This study presents a method to test additive manufacturing units for accuracy and repeatability.

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