Abstract
The aim of this study was to investigate the influence of preheating and post-curing methods on diametral tensile strength (DTS), flexural strength (FS), knoop microhardness (KHN), and degree of conversion (DC) of an experimental fiber-reinforced composite (FRC). Specimens (30 wt% of 3-mm-short E-glass fiber, 22.5 wt% of methacrylated-based resin and 47.5 wt% of filler particles) were subjected to: P – photocuring at 1500 mW/cm2 for 40 s (control); P/M – photocuring and microwave post-curing (540W/5 minutes); P/A – photocuring and autoclave post-curing (120°C/15 minutes); PH-P – preheating (60°C) and photocuring; PH-P/M – preheating, photocuring and microwave post-curing; and PH-P/A – preheating, photocuring and autoclave post-curing. Specimens for DTS (Ø 3 x 6 mm) and FS (25 x 2 x 2 mm) were tested at Instron 5965. KHN employed a 50g load for 30s. DC was measured using FTIR spectroscopy. Statistical analysis employed: factorial analysis, normality test, one-way ANOVA and Tukey’s HSD test, independent T-test and the Dunnett test. Interaction between factors was not significant (P>0.05). Preheating promoted significantly higher values of FS and KHN (p = 0.0001). Post-curing promoted significantly higher values for KHN (p = 0.0001). For DTS (p = 0.066) and DC (p= 0.724) no statistical difference was found between groups. SEM images showed that preheating promoted better interaction between glass fibers and resin matrix. Preheating increased FS, KHN and DTS, and post-curing increased KHN. DC was not affected by both methods. Preheating and post-curing methods can be used to improve some mechanical properties of FRCs’ but degree of conversion remains unaffected.
Casts; Surgical
Means (MPa) and standard deviations (vertical bar) are shown. ANOVA comparisons revealed no differences between groups (p > 0.05). The Dunnett test revealed that preheating significantly (p < 0.05) increased the DTS compared with the control group. Equals capital letters show no statistically significant difference by ANOVA (p > 0.05). Different tiny letter show significant statistically difference by Dunnet test (p < 0.05).
Means (MPa) and standard deviations (vertical bar) are shown. T-tests revealed statistically significant differences between groups that were and were not preheated (p < 0.05) in each column (P × PH-P, P/M × PH-P/M, P/A × PH-P/A, and Total-without PH × Total-with PH). The Dunnett test revealed that the preheated groups (all of them) had significantly higher FS than the control group (p < 0.05). Different capital letters show no statistically significant difference by T-Test (p > 0.05) between each preheated and not preheated groups. Different tiny letter show statistically significant difference (p < 0.05) between preheated groups and control group by Dunnet test.
Means (KHN) and standard deviations (vertical bar) are shown. T-tests revealed statistically significant differences between groups that were and were not preheated (p < 0.05) in each column (P × PH-P, P/M × PH-P/M, P/A × PH-P/A and Total-no PH × Total-with PH). The Dunnett test revealed that all groups, except the PH-P group, had significantly higher KHN than the control group (p < 0.05). Different capital letters show statistically significant difference by T-Test (p > 0.05) between each preheated and not preheated groups. Different tiny letter show statistically significant difference between preheated groups and control group by Dunnet test.
Means (KHN) and standard deviations (vertical bar) are shown. Comparisons for the post-curing factor by ANOVA and Tukey test revealed differences (p < 0.05) between groups that were and were not post-cured. The Dunnett test revealed that all post-cured groups had significantly higher KHN than the control group (p < 0.05). Different capital letters show statistically significant difference by ANOVA and Turkey test (p < 0.05) between groups each column. Different tiny letters show statistically significant difference (p < 0.05) between between post-cured groups and control group by Dunnet test.
Means (%) and standard deviations (vertical bar) are shown. ANOVA comparisons revealed no difference between groups (p > 0.05). The Dunnett test revealed no differences compared with the control group (p > 0.05). Equals capital letters show no statistically significant difference by ANOVA and Dunnet tests (p > 0.05).
(A) At 500×, the P group revealed some remnants of the resin matrix at the fiber surfaces. (B) At 500×, the PH-P group revealed resins in intimate contact with glass fibers (arrows).
(A) At 530×, few resins remaining at the fiber surfaces were observed in the P/A group. (B) At 450×, the PH-P/A group revealed better interaction between the fibers and resin matrix with lots of remaining resin at the fiber surfaces.
(A) At 900×, the poor interaction between the fibers and resin matrix could be closely examined in the P/M group. (B) At 900×, the PH-P group showed remnants of resin adhered inwardly to the fiber surfaces (arrows).