The fracture resistance of 3D-printed versus milled provisional crowns: An in vitro study

Background CAD/CAM has considerably transformed the clinical practice of dentistry. In particular, advanced dental materials produced via digital technologies offer unquestionable benefits, such as ideal mechanical stability, outstanding aesthetics and reliable high precision. Additive manufacturing (AM) technology has promoted new innovations, especially in the field of biomedicine. Aims The aim of this study is to analyze the fracture resistance of implant-supported 3D-printed temporary crowns relative to milled crowns by compression testing. Methods The study sample included 32 specimens of temporary crowns, which were divided into 16 specimens per group. Each group consisted of eight maxillary central incisor crowns (tooth 11) and eight maxillary molar crowns (tooth 16). The first group (16 specimens) was 3D printed by a mask printer (Varseo, BEGO, Bremen, Germany) with a temporary material (VarseoSmile Temp A3, BEGO, Bremen, Germany). The second group was milled with a millable temporary material (VitaCAD Temp mono-color, Vita, Bad Sackingen, Germany). The two groups were compression tested until failure to estimate their fracture resistance. The loading forces and travel distance until failure were measured. The statistical analysis was performed using SPSS Version 24.0. We performed multiple t tests and considered a significance level of p <0.05. Results The mean fracture force of the printed molars was 1189.50 N (+/- 250.85) with a deformation of 1.75 mm (+/- 0.25). The milled molars reached a mean fracture force of 1817.50 N (+/- 258.22) with a deformation of 1.750 mm (+/- 0.20). The printed incisors fractured at 321.63 N (+/- 145.90) with a deformation of 1.94 mm (+/- 0.40), while the milled incisors fractured at 443.38 N (+/- 113.63) with a deformation of 2.26 mm (+/- 0.40). The milled molar group revealed significantly higher mechanical fracture strength than the 3D-printed molar group (P< 0.001). However, no significant differences between the 3D-printed incisors and the milled incisors were found (p = 0.084). There was no significant difference in the travel distance until fracture for both the molar group (p = 1.000) and the incisor group (p = 0.129). Conclusion Within the limits of this in vitro investigation, printed and milled temporary crowns withstood masticatory forces and were safe for clinical use.