Physical and mechanical properties of various resins for additively manufactured definitive fixed dental restorations: Effect of material type and thermal cycling

Abstract

Statement of problem

Although additive manufacturing (AM) has facilitated the fabrication of resin-based definitive restorations, knowledge of the effects of artificial aging on their physical and mechanical properties is lacking.

Purpose

The purpose of this in vitro study was to investigate the effects of material type and thermal cycling on the translucency, surface roughness, microhardness, and flexural strength of AM resins marketed for definitive restorations.

Material and methods

Bar-shaped (25×2×2 mm) and disk-shaped (Ø10×2 mm) specimens from 4 different AM resin groups Crowntec (CT), Tera Harz TC-80DP (TH), VarseoSmile Crown plus (VS), and Permanent (CB) were prepared. The specimens were randomly distributed to 2 groups: (1) nonaged (stored in distilled water at 37 °C for 24 hours) and (2) aged (thermocycled for 10 000 cycles at 5 °C to 55 °C). For each specimen, the degree of conversion (DC) was determined using Fourier transform infrared spectroscopy. Color coordinates of the specimens were measured to calculate relative translucency parameter (RTP) values. Surface roughness (Ra) was measured with an optical profilometer, and Vickers microhardness values (VHN) were obtained. Flexural strength (σ) and elastic modulus (E) values were obtained by using the 3-point bend test. Scanning electron microscopy (SEM) was used to analyze the fractured surfaces. The data were statistically analyzed using factorial analysis of variance (ANOVA), followed by Tukey post hoc analyses and paired t tests (α=.05).

Results

Both DC and RTP were significantly affected by material type (P<.001). The highest and lowest DC values were reported in CT and CB, respectively. None of the tested resins exceeded clinical thresholds of ΔRTP. The material type also had a significant impact on Ra (P<.001). VHN was significantly affected by material type (P<.001) and aging (P<.001). CT had the highest value, while TH had the lowest value, regardless of the aging condition. In addition, the σ and E were significantly affected by both material type (P<.001) and aging (P≤.002).

Conclusions

The material type of the AM resins significantly impacted on their DC, RTP, Ra, VHN, σ, and E values. Thermal cycling of the tested resins also significantly affected their VHN, σ, and E values. No interactions were observed between material type and aging.