J Korean Acad Prosthodont.  2024 Oct;62(4):253-261. 10.4047/jkap.2024.62.4.253.

Effect of shell thickness on fracture strength of single implant provisional crowns fabricated by indirect-direct technique using 3D printing

• Hwang S
• Oh SC

• KMID: 2560755
• DOI: http://doi.org/10.4047/jkap.2024.62.4.253

Abstract

Purpose
. This study aimed to evaluate the effect of shell thickness on the fracture strength of provisional crowns fabricated by indirect-direct technique. Materials and methods. The study simulated the application of a provisional crown on a maxillary first molar implant abutment. A titanium metal die was milled by replicating a ready-made implant abutment. Using CAD software, shells for provisional crown was designed with varying thicknesses of 0.5 mm, 1.0 mm and 1.5 mm with different internal spaces for relining. These shells were 3D printed using photosensitive liquid resin and relined with PMMA resin to fabricate provisional crown specimens using indirect-direct technique. Ten specimens per each group were prepared. Fracture strength was measured by applying compressive loads vertically to the occlusal center of the specimens at a crosshead speed of 1.0 mm/min using a universal testing machine, and the maximum load value (N) at fracture was recorded. To compare the fracture strength between experimental groups, a one-way ANOVA followed by Tukey’s post hoc test was conducted (α=.05).
Results
. The fracture strength was observed in the following order: Group 1.5 (1504.5 ± 141.30 N), Group 1.0 (1420.2 ± 182.05 N), and Group 0.5 (1083.1 ± 178.90 N). Group 1.5 was not significantly different from group 1.0, but was significantly different from group 0.5, and group 1.0 was also significantly different from group 0.5. Conclusion. The fracture strength of provisional crowns fabricated by the indirect-direct techniques were significantly different depending on the thickness of the shell. The fracture strength of the indirect-direct method was significantly lower when the shell thickness was 0.5 mm compared to 1.0 mm and 1.5 mm. This finding indicates that the shell should not be too thin when fabricating provisional crowns using the indirect-direct technique.

Keyword

Temporary dental prosthesis; 3D printing; Fracture strength; PMMA