Effect of loading and syringing on void formation in automixed addition silicone elastomers

Abstract

The effect of loading and syringing on void formation in five automixed addition silicones was evaluated by determining the voids created in the first and second halves of material loaded and dispensed from a metal syringe. Impressions were made of a model with six stainless-steel cylinders. The voids were counted at a predetermined site on 3 separate days using a binocular microscope at x 7 magnification. Automixed addition silicones did not confirm the 'last out-fewer bubbles' phenomenon and specific loading and syringing technique did not appear to have a consistent effect on void formation in automixed elastomers.

Porosity and Color of Maxillofacial Silicone Elastomer

“…Furthermore, the silicone catalyst was thoroughly blended and incorporated into the silicone rubber, decreasing the number of unbounded particles within silicone, and forcing pores to the surface of the silicone. Mechanical mixing under vacuum has been investigated for bone cements 12 and elastomeric impression materials 1,6,11 . These reports suggested that such a technique reduced porosity and resulted in improved mechanical properties.…”

“…Mechanical mixing was effective in eliminating pores and voids, and mechanically mixed high‐viscosity materials had fewer pores than manually mixed materials 1,9 . Pore‐free mixtures were not possible to obtain, despite mechanical mixing under vacuum 8,10,32 . It is likely that formation of pores is affected by the high silicone viscosity, heat‐accelerated polymerization method, and the amount of catalyst used 2 …”

“…A material's mixing method, handling properties (manual vs. mechanical, with or without vacuum, and injection), along with its viscosity, greatly add to air bubble formation 6–8 . Mixing materials mechanically with the presence of air suction (vacuum) is effective in reducing pores, decreasing the number of unbounded particles within the mixture, and producing more homogeneous and dense mixtures 8–12 . Also, it saves more material than does manual mixing 13 …”

“…There have been no efforts to investigate maxillofacial silicone elastomer color under mixing methods due to limitations in methods of quantifying pores. The presence of pores within mixtures has been investigated by conducting invasive protocols of sectioning specimens into slices of controlled thickness, then investigating the slices using scanning electron microscopy 2 light or stereo microscopy 8,25 . Other protocols were noninvasive, using X‐ray microfocus computerized tomography (Micro‐CT) 4,7,26 in analyzing pores (number, size, volume, and percentage) of different materials including all‐ceramic crowns 26 and encapsulated glass ionomer cements 4 .…”

Estudo comparativo da alteração dimensional entre um silicone convencional e um de auto-mistura polimerizados por reação de condensação

“…Inicialmente para os silicones de adição a apresentação em um sistema de auto-mistura garantiu a diminuição no número de bolhas 6 , comuns à espatulação manual.…”