Thermal degradation of universal composite resins

Objectives: G-aenial Universal Flo (GUF, GC) was developed under a unique concept called injectable composite resin. GUF shows high wear resistance because of high loaded and homogeneously dispersed nano filler. The purpose of this study was to investigate resistance to thermal degradation of GUF, especially wear resistance, compared with other universal composite resins.

Methods: GUF, Filtek Supreme Ultra (FSU, 3M ESPE), Herculite Ultra (HU, Kerr) and Tetric Evo Ceram (TEC, Ivoclar/ Vivadent) were examined in this study as universal composite resins. Each materials were filled into metal (contact area 2.1 mm diameter) mold in order to make specimens and cured according to the manufacturers' instructions. All specimens were divided into two groups, one group was stored in 37 degreeC water for 24 hours and performed 3-body wear test (Control, n=4). Another group was performed 3-body wear test after thermal cycle (5 degreeC /55 degreeC, 10,000 cycles, n=4). 3-body wear test was performed with original wear test machine for 100,000 cycles (load 0.84 MPa). The slurry mixture of PMMA and Glycerin was applied to contact area. The data was analyzed by one-way ANOVA (p<0.01). All specimens after 3-body wear test were also observed by scanning electron microscope (SEM). 

Results: GUF showed the lowest wear value after thermal cycle and there was no significant difference between control and after thermal cycle. However other universal composite resins showed higher wear value after thermal cycle. At condition of thermal cycle, increased cracks were observed with SEM on sample surface of FSU, HU and TEC.

Conclusions: These results suggested that GUF had higher durability against thermal degradation than other universal composite resins.

Wear value

	GUF	FSU	HU	TEC
Control (µm)	3.2 (1.6)	6.0 (1.8)	8.2 (0.8)	16.2 (3.5)
TC10000 (µm)	4.5 (0.6)	16.7 (1.2)**	16.8 (2.1)**	43.0 (7.8) **

^**: P<0.01