Peak temperature, conversion and flexural strength of chairside reline resins

Objectives: This study evaluated the peak temperature (PT), degree of conversion (DC) and flexural strength (FS) of a denture base acrylic resin (Lucitone 550-L), three commercially available chairside reline resins (Kooliner-K; New Truliner-NT; Tokuyama Rebase II-TR) and three experimental chairside reline resins: A [based on Polyethyl methacrylate (PEMA) and Cyclohexyl methacrylate (CHMA)], B [based on PEMA and 1,4-Butanediol Dimethacrylate (BDMA)] and C [based on PEMA, CHMA and BDMA]. Methods: Three specimens (60x2.0 mm) were made for each material and the rise in temperature during polymerization was recorded, inside a stove at 37ºC, using a digital thermometer connected with a Type K (chromel-alumel) thermocouple. The degree of monomer conversion at 1640 cm^-1 was determined by Fourier transform infrared spectroscopy (FT-IR)/ATR spectrometry. Five specimens (10x4.0 mm) were made for each material and submitted to infrared spectroscopy (32 scans; resolution= 4.0cm^-1) 30 minutes after polymerization. In addition, 10 specimens (64x10x3.3 mm) were made for each material, immersed in distilled water at 37ºC, and submitted to FS testing (Span= 50 mm; 5.0 mm/min) 30 minutes after polymerization. Data were submitted to ANOVA and Tukey's test (a=0.05). Results:

	PT (ºC)	DC (%)	FS (MPa)
L	Not applicable	86.5 C	64.52 A
K	45.6	85.2 C	19.09 D
NT	41.7	97.4 A	9.93 E
TR	44.8	91.6 B	35.24 B
A	44.9	76.7 D	35.00 B
B	44.1	64.4 E	32.45 BC
C	43.3	65.7 E	30.34 C

Vertically, means (DC and FS) with the same letter were not statistically different at P<0.05.

Conclusions: All relining materials presented suitable PT for direct use in the oral cavity. Experimental resins produced higher FS and lower DC than the commercially available relining resins K and NT. All relining materials presented lower FS than L.

PhD scholarship granted by CAPES/Brazil