Effects of Post-Curing Heat Treatment of Resin Composites

Objectives: This study aimed to evaluate the effects of post-curing heat treatment (PCHT) on the surface roughness (SRO), gloss (GLO), and microhardness (MHA) of resin composites.
Methods: Composite discs (10mm diameter x 2 mm thick) were prepared from five composites: Gradia Anterior (GA/GC), Gradia X (GX/GC), Tetric N-Ceram (TC/Ivoclar), Neo Spectra ST (ST/Dentsply), and Estelite Asteria (EA/Tokuyama). Composite samples were light-cured with Valo (Ultradent) and polished with SiC abrasive papers (800-, 1200-, and 2000-grit) under water cooling. Afterwards, three measurements were performed for SRO, GLO and MHA (baseline values), using SJ-410 rugosimeter (Mitutoyo), Novo-Curve glossmeter (Rhopoint) and Knoop microhardness tester (Future-Tech FM Corp), respectively. The PCHTs consisted of microwave (samples immersed in water, 450 Watts, Electrolux ME28S) or Visio Beta Vario unit (15min + vacuum, Solventum). After PCHT, SRO (in µm), GLO (in GU) and MHA (in KHN) were measured again. The average of the three SRO, GLO and MHA measurements on each sample was calculated at the baseline and after post-curing. Data were analyzed using three-way (SRO and GLO) or two-way (MHA) ANOVA and post-hoc Tukey’s test (α=0.05).
Results: For most composites, SRO was not influenced by PCHT. Only GX and EA composites had their SRO reduced by PCHT. EA exhibited the highest GLO before and after PCHT, which increased the GLO for GA and GX. The PCHT using microwave increased the MHA for most composites, except for EA. No significant differences were observed in the post-curing performed with microwave or Visio Beta Vario unit regarding SRO, GLO and MHA evaluations.
Conclusions: PCHTs did not influence SRO and GLO for most composites, but PCHT using microwave increased MHA for most composites.