We report here that actin filaments in vitro exist in two populations with significantly different shrinkage rates. Newly polymerized filaments shrink rapidly, primarily from barbed ends, at 1.8/s, but as they age they switch to a stable state that shrinks slowly, primarily from pointed ends, at approximately 0.1/s. This dynamic filament stabilization runs opposite to the classical prediction t...

OBJECTIVE To ascertain the efficacy of polymerization of self-etching dental adhesives in different solvent evaporation conditions. MATERIAL AND METHODS Four self-etching adhesive systems were studied. Two of them are classified as mild two-step self-etching adhesives (Clearfil SE Bond, Protect Bond) and the other two are strong one-step systems (Xeno III, ADP-Prompt-L-Pop). The influence of ...

The aim of this study was to evaluate the effect of different curing methods on the stress generated by the polymerization shrinkage of a restorative composite in two moments: immediately after light exposure and after 5 min. Photoactivation was performed using two different light sources: (1) xenon plasma arc (PAC) light (1,500 mW/cm2 - 3s) and (2) a quartz-tungsten-halogen (QTH) light with th...

The aim of this study was to evaluate the viscoelastic properties of novel low-shrinking composites and compare them to those of packable composites. Six materials were tested: Clearfil Majesty Posterior (CM), ELS Extra Low Shrinkage (EL), Filtek P60 (FP), Filtek Silorane (FS), Prodigy (PR) and Surefil (SU). Static and dynamic testing was performed and materials were tested dry and wet at diffe...

Adhesive layer is an essential part of tooth colored restorations which play an important role in decreasing the microleakage between the tooth and restoration material after polymerization shrinkage. The purpose of this study was to evaluate the effect of deferent adhesive system of bonding agent on microleakage of nanocomposite resin in class II cavities. Two different types of adhesive syste...

OBJECTIVES Different light curing units are used for polymerization of composite resins. The aim of this study was to evaluate the degree of conversion (DC) and temperature rise in hybrid and low shrinkage composite resins cured by LED and Argon Laser curing lights. MATERIALS AND METHODS DC was measured using FTIR spectroscopy. For measuring temperature rise, composite resin samples were plac...

Silica in industrial production processes is precipitated by mixing an acid and an inorganic precursor. In this aqueous solution, silica particles form due to a polymerization reaction and agglomeration and, finally, build a gel. Thereafter, the reaction continues, and the gel network shrinks with the expulsion of the enclosed pore liquid. This slow process is known as “natural syneresis” and s...

Crosslinked polymer samples of a wide range of triacrylates, tetraacrylates, pentaacrylates and of their corresponding methacrylates were prepared by u.v. photopolymerization of the monomers using 2,2dimethoxy-2-phenyl-acetophenone as a photoinitiator. The monomers studied varied in rank, pendant group size and structure, and functionality or number of double bonds. The reaction kinetics was fo...

The present studies were aimed at the development of monomers for dental resins, for which the authors substituted the 8 Cl atoms in P4N4Cl8 with hydrophobic groups (Ph, TF and OF) and a polymerizing group (EMA), and bulk-polymerized them in order to examine their physical properties. Attention was focused on the relationship between the number of substituted hydrophobic groups and the mechanic...