Impact of Aging on the Accuracy of 3D-Printed Dental Models: An In Vitro Investigation

Abstract

The aim of this in vitro study was to analyze the impact of model aging on the accuracy of 3D-printed dental models. A maxillary full-arch reference model with prepared teeth for a three-unit fixed dental prosthesis was scanned ten times with an intraoral scanner (3Shape TRIOS Pod) and ten models were 3D printed (Straumann P-Series). All models were stored under constant conditions and digitized with a desktop scanner after 1 day; 1 week; and 2, 3, and 4 weeks. For accuracy, a best-fit algorithm was used to analyze the deviations of the abutment teeth (GFaI e.V Final Surface®). Wilcoxon Rank Sum Tests were used for comparisons with the level of significance set at α = 0.05. Deviation analysis of the tested models showed homogenous intragroup distance calculations at each timepoint. The most accurate result was for 1 day of aging (3.3 ± 1.3 µm). A continuous decrease in accuracy was observed with each aging stage from day 1 to week 4. A time-dependent difference was statistically significant after 3 weeks (p = 0.0008) and 4 weeks (p < 0.0001). Based on these findings, dental models should not be used longer than 3 to 4 weeks after 3D printing for the fabrication of definitive prosthetic reconstructions.

Accuracy of 3-Dimensionally Printed Full-Arch Dental Models: A Systematic Review

“…Twenty-four studies included reference models as controls in their methodology design [ 6 , 7 , 34 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 55 , 56 , 57 ]. The controls included were a dental stone cast ( n = 8), a digital STL image of a dental stone cast ( n = 3), typodont digital STL image ( n = 7), typodont ( n = 1), prefabricated resin model digital STL image ( n = 2), patient intraoral scan image (2) or a dry human skull ( n = 1).…”

“…The three types of base designs used in the studies were horseshoe-shaped bases [ 4 , 34 , 36 , 37 , 38 , 39 , 41 , 43 , 49 , 50 , 51 , 55 ], regular American Board of Orthodontics (ABO) [ 35 , 38 , 44 , 46 , 47 , 49 , 52 , 54 , 57 ] and horseshoe-shaped with a transverse supporting bar [ 7 , 38 , 48 , 53 ]. Six studies did not specify their base design [ 6 , 19 , 40 , 42 , 45 , 56 ].…”

“…The majority of studies did not specify the postprocessing protocol ( n = 19/28) [ 6 , 19 , 34 , 35 , 36 , 40 , 41 , 44 , 45 , 46 , 47 , 48 , 50 , 51 , 52 , 54 , 55 , 56 , 57 ]. Nine studies reported their post-curing protocol for vat polymerisation techniques [ 4 , 7 , 37 , 38 , 39 , 42 , 43 , 49 , 53 ] which included cleaning the models with isopropyl alcohol [ 37 , 43 , 49 , 53 ], or ethanol [ 4 ] to remove uncured resin followed by curing with UV light. Three studies only used UV light to post-process SLA models [ 38 , 39 , 42 ].…”

“…Three studies only used UV light to post-process SLA models [ 38 , 39 , 42 ]. One study placed the SLA models in an ultrasonic bath followed by using light with wavelengths of 280–580 nm for post-curing [ 7 ]. Two studies reported that MJ and FFF did not require post-curing [ 37 , 38 ], and one study rinsed the MJ printed models in a bath of caustic soda to clean them [ 42 ].…”

“…Moreover, models acquired through vat polymerisation and material jetting are prone to shrinkage during the polymerisation stage as well as having stair-step surfaces due to the layering technique used in construction [ 6 ]. In addition, a recent study demonstrated that models exhibit dimensional changes postprocessing as they age with their dimensions reported to be significantly different after three-weeks of manufacturing [ 7 ].…”