Objectives . The purpose of this study was to investigate, in dental neat resins, the effect of adding hyperbranched polymers (HBPs) on polymerization contraction ( C ), degree of conversion (DC) and elastic modulus ( E ).

Materials and methods . Neat resins were formulated with varying weight ratios of three different HBPs added at a reference matrix Bis-GMA/TEGDMA.

Raman micro-spectroscopy was used to determine the degree of conversion, volume contraction was determined by pycnometry and by means of a density column and elastic modulus was measured by a Dynamic Mechanical Analyzer (DMA). Data were submitted to analysis of variance (ANOVA).

Results

Organic matrix	Bis-GMA/TEGDMA/HBP % w/w	C (%) n = 3	DC (%) n = 3	E (GPa) n = 3
R	50/50/0	9.07 (0.36) a	65.2 (3.4) a	2.32 (0.27) bcde
HBP 1 – 5%	47.5/47.5/5	8.95 (0.06) ab	64.5 (3.4) a	2.51 (0.16) abd
HBP 1 – 10%	45/45/10	8.53 (0.18) c	65.8 (2.6) a	2.76 (0.03) a
HBP 1 – 20%	40/40/20	8.05 (0.15) e	68.3 (2.5) a	2.53 (0.14) abd
HBP 1 – 30%	35/35/30	7.49 (0.07) f	69.2 (1.6) a	2.21 (0.16) de
HBP 1 – 40%	30/30/40	7.03 (0.02) g	75.6 (1.3) b	1.77 (0.08) f
HBP 2 – 5%	47.5/47.5/5	8.78 (0.03) bc	66.4 (0.3) a	2.68 (0.08) ac
HBP 2 – 10%	45/45/10	8.60 (0.08) c	66.8 (1.0) a	2.78 (0.10) a
HBP 2 – 20%	40/40/20	8.26 (0.01) d	66.8 (1.1) a	2.46 (0.12) abd
HBP 2 – 30%	35/35/30	7.68 (0.04) f	67.0 (3.5) a	2.32 (0.14) bde
HBP 2 – 40%	30/30/40	7.05 (0.02) g	68.3 (2.9) a	1.26 (0.04) g
HBP 3 – 5%	47.5/47.5/5	8.67 (0.07) c	71.4 (0.3) a	2.51 (0.05) ab
HBP 3 – 10%	45/45/10	8.50 (0.07) c	67.9 (1.0) a	2.67 (0.25) ab
HBP 3 – 20%	40/40/20	8.02 (0.07) de	70.7 (1.1) a	2.53 (0.08) abd
HBP 3 – 30%	35/35/30	7.22 (0.14) g	70.5 (3.5) ab	2.16 (0.08) e
HBP 3 – 40%	30/30/40	6.51 (0.06) h	67.0 (2.9) a	1.61 (0.06) f

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