Effect of cement space on 3D-printed fixed prostheses: an in vitro evaluation of accuracy and tensile strength

Abstract

ABSTRACT Objective: This in vitro study evaluated the internal adaptation and the influence of different internal cement space parameters on dimensional accuracy and tensile retention strength of 3D-printed provisional crowns. Methods: Three internal cement spaces (40 μm, 80 μm, and 120 μm) were digitally designed using MeshMixer software for a cylindrical abutment compatible with an implant-supported cementation post. Twenty specimens were printed per group. After standardized post-processing, specimens were internally scanned and STL files were analyzed using CloudCompare software to assess internal accuracy. Specimens were cemented onto abutment analogs and divided into two subgroups (n=10): storage in saline solution for seven days or thermocycling for 3,000 cycles between 5°C and 55°C. Tensile bond strength testing was performed to evaluate cementation stability. Results: The 120 μm group showed significantly greater internal distortion in total surface area and cervical third compared with the 40 μm and 80 μm groups (p<0.001). All crowns demonstrated clinically acceptable accuracy. Increased cement space significantly reduced tensile retention, with the 80 μm group exhibiting the highest bond strength. Thermocycling significantly reduced tensile strength in all groups. Conclusion: The 80 μm internal spacing showed superior accuracy, while thermocycling negatively affected the tensile strength of all 3D-printed provisional crowns, with the 120 μm group exhibiting the lowest tensile resistance.