Hyperbranched polyesters and their application in dental composites:: Monomers for low shrinking composites

Using trimethylolpropane (TMP) and 2,2-bishydroxymethylpropionic acid (Bis-MPA), aliphatic hyperbranched polyesters (HBP) were synthesized, with a degree of branching of DB = 0.47 and a degree of polymerization of P-n = 16.5. Aromatic HBPs with repetitive units of 2,2-bis(4-hydroxyphenyl)pivaloniconic acid (BisPVA) lead to a higher DB=0.48 and P-n=30.5 compared to the aliphatic HBP. Reactive functionalization of the hyperbranched polymers teas achieved via esterification of mixtures of methacrylic acid and carboxylic acids. In this manner, i-butyke acid and methacryloyl terminated HBPs were obtained. They have a low viscosity ranging from 200 to 364 Pa*s and exhibit relatively tow volume shrinkage (1.9 to 3.6%) during photoinitiated cure. Dental composites with volume shrinkage of 0.5 to 1.5% have been prepared using these methacryloyl terminated HBPs in combination with a Ba/alumosilicate glass filler. Copyright (C) 2001 John Wiley & Sons, Ltd.