The effect of post-polymerization methods and varying thicknesses on colour stability and flextural strength of denture base polymers produced with stereolithography (SLA) technique.

Abstract

Background: Limited information is available on the thickness and post-polymerization procedure of denture base resins produced by stereolithography (SLA). This study aims to assess the impact of varying thickness, post-curing durations, and temperature on the flexural strength and colour stability of 3D-printed denture bases.

Materials and methods: A total of 80 rectangular specimens, measuring 65 × 10 × 3 mm and 65 × 10 × 2 mm, were developed using 3D-printed acrylic resin. The 3D-printed groups were further categorised based on their thickness into two groups: 2 mm and 3 mm. Each of these four groups was then subdivided based on the post-curing temperature (60 °C and 80 °C) and post-curing duration (15 min and 60 min). To ensure colour stability, the specimens were placed in an incubator containing a coffee solution at a temperature of 37 degrees Celsius. To evaluate the flexural strength of the specimens, they were placed on a specialised jig with two supports that were 50 mm apart. The jig was securely attached to a universal testing machine. The spectrophotometer was used to measure the colour changes (ΔE00) of the specimens that underwent different post-curing procedures and were immersed in coffee. The data analysis involved the use of ANOVA and Tukey's post hoc tests, with a significance level (α) set at 0.05.

Results: The study's findings suggest that the flexural strength values exhibited an upward trend as the post-curing periods increased from 15 to 60 min and the temperatures rose from 40 °C to 80 °C. Group 2 and 4 showed the highest flexural strength (86 MPa and 95 MPa, respectively). Group 2 with less thickness than group 4 exhibited a better color stability and acceptable level of color change with ΔΕ00 = 2.59.

Conclusions: The study revealed that the specimens with a thickness of 3 mm, a post-curing period of 60 min, and a temperature of 80 °C exhibited the best flexural strength but the lowest colour stability compared to the other groups. Optimum results can be achieved by increasing the post polymerization time and temperature rather than increasing the thickness of the denture base. Because group 2, which has a thickness of 2 mm and is subjected to the same post-curing period, has acceptable clinical results in terms of both flexural strength and color stability.

Clinical trial number: Not applicable.