Dentists have access to a wide variety of impression materials, ranging from elastic to rigid options. Among these, elastic materials are the most frequently used and include both hydrocolloids and elastomers. Hydrocolloids, such as alginate, and elastomers, including impression silicones, fall into two subcategories: addition silicones and condensation silicones.
Condensation silicones, also known as polydimethylsiloxanes or first-generation silicones, were first developed in the 1950s. They require an activator, which can be a liquid or a paste, to be manually mixed. Despite having short working times and less-than-ideal dimensional stability, condensation silicones offer benefits like excellent mechanical properties, low costs, and hydrophobicity.
Addition silicones, or polyvinylsiloxanes (second-generation silicones), were introduced in the 1980s. Their key distinction lies in their vulcanization process, where cross-linking between the vinyl groups of the polymer and silane groups occurs through a platinum salt catalyst. This results in superior dimensional stability due to the absence of reaction byproducts. Furthermore, addition silicones are easier to mix, often available in convenient self-mixing cartridges and automatic mixing systems.
It's important to note that techniques for achieving precise silicone impressions, using high-quality materials like those from Zhermack, are similar for both polydimethylsiloxanes and polyvinylsiloxanes. Dentists favor addition silicones for their dimensional stability, tear resistance, improved working times, self-mixing systems, and excellent wettability. These qualities allow for precision impression taking with minimal distortion upon removal and good compatibility with gypsum, characteristic of hydrocompatible polyvinylsiloxanes.
Patients also benefit significantly from the use of silicones. Research shows that impression materials can cause discomfort and increase psychological stress. Silicones, with their short working and setting times, help reduce this discomfort and minimize the time spent in the mouth when using fast-set impression materials.
Given their versatility, it's no wonder silicones are widely used in various dental applications. For instance, taking impressions for fixed and removable prostheses is made easier with high-fluidity addition silicones like Zhermack’s Elite HD+, which can reach difficult areas in the gingival sulcus. For implant-retained prostheses, radio-opaque and scannable addition silicones like Hydrorise Implant are ideal, providing precise three-dimensional recording of implant positions. Addition silicones are also recommended for duplicating master models in the lab with high precision.
In bite registration for fixed or removable prostheses, special addition silicones like Elite Transparent are invaluable. They allow for the reproduction of diagnostic wax-ups in a dimensionally stable manner, enabling the transfer of the fabricated project into the patient’s mouth accurately.
Therefore, it is evident that silicones, particularly addition silicones, are among the most widely used materials in dentistry due to their numerous advantages and remarkable versatility.
Davia - 1 month ago