Light-cured dental resins modified with silsesquioxanes.

SILVANA V. ASMUSSEN; CLAUDIA I. VALLO

Mar del Plata

Taller; 2º Taller de Organos Artificiales, Biomateriales e Ingeniería de Tejidos-; 2011

Facultad de Ingeniería-Universidad Nacional de Mar del Plata- INTEMA

ABSTRACT Methacrylate-based hybrid organic?inorganic materials have recently received considerable interest for the development of advanced dental composites in order to reduce the volumetric shrinkage during polymerization. Methacrylate-functionalized silsesquioxanes (SSQO) were synthesized by the hydrolytic condensation of 3-(methacryloxypropyl) trimethoxysilane (MPTMS) using dimethacrylate monomers as reactive solvent. Resins containing about 40 wt% SSQO resulted in incompletely condensed methacrylate-functionalized silsesquioxanes with a very large fraction of intramolecular cycles. The absence of higher molar mass oligómeros after prolonged storage periods is attributed to dilution of the reacting medium, which discourages bimolecular reactions that lead to polymer growth. 29Si NMR spectroscopy showed that the conversion in the polycondensation reaction was 0.96. Substitution of monomer with SSQO reduced the volumetric shrinkage during photopolymerization. The amount of leachable monomer detected in formulations containing SSQO was markedly reduced. This indicates that the unreacted monomer exists mainly as pendant chains instead of free leachable monomer. The presence of different proportions of SSQO in the methacrylate monomer resulted in no apparent change in the flexural modulus and in a modest decrease in the compressive yield stress of the polymerized materials. The markedly reduced levels of both volumetric shrinkage and extractable monomer make the SSQOs-modified resins very attractive for the manufacture of dental restorative composites.