In precision impression-taking of fixed prostheses on natural teeth, the accuracy of the yield of the preparation end margin is vital. The most commonly used techniques involve the utilisation of elastomers.<\/p>\n
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Low viscosity products are usually preferred in the marginal area; nevertheless, the soft tissue still tends to constitute an impairment for sliding: for this reason, before beginning the process, the operator carries out temporary gingival displacement manoeuvres.<\/p>\n
The most common procedure for the displacement of soft tissues<\/strong> surrounding the abutment is based on the positioning of a cord (or more often two cords) which is commonly pre-impregnated with liquids to facilitate the process and maintain haemostasis.<\/p>\n Astringent<\/strong> liquids are doubtless the most widely used impregnating liquids in the dental industry, which is why our article focuses on these in particular. There are also impregnating liquids that contain<\/strong> vasoconstrictor molecules<\/strong> such as sympathomimetic amines and adrenaline, which could however cause local and systemic problems.<\/p>\n Astringent liquids are essentially split up into three different types<\/strong>, each with properties and possible critical aspects which you should be aware of for correct use.<\/p>\n Effective and biocompatible, its main flaw<\/strong> is that it can delay or block the additive reaction of certain impression materials, so a compatibility check between the two products is always advisable.<\/p>\n This category also includes potassium alum<\/strong>, a substance that is slightly less powerful than adrenaline but which tissues tolerate much more: it can even be left in the groove for 20 minutes without any adverse effects.<\/p>\n Overall, the advantages<\/strong> of these products are their haemostatic capacity, the potential reduced inflammation and the good retaining of the tissue displacement after the cord has been removed.<\/p>\n Implemented in concentrations that vary between 5 and 20-25%.<\/p>\n The advantages<\/strong> are essentially similar to those of aluminium sulphate. The drawback<\/strong> is the interference with the setting reaction of polyvinyl siloxanes and polyethers, an issue which can be remedied considerably though irrigation of the site after the cord has been removed.<\/p>\n Some authors suggest as an alternative not to impregnate the second cord in the double-cord technique.<\/p>\n Available in solutions with a concentration between 13 and 15-20%<\/em>, with quite a high degree of acidity, to such an extent that it may lead to temporary discolouration of the soft tissues.<\/p>\n For this reason, and also to guarantee the normal polymerization process of the elastomers, it is recommended that the cord be kept in situ for approximately 1-3 minutes<\/strong>, and then carefully remove all traces of the liquid before impression taking.<\/p>\n","protected":false},"excerpt":{"rendered":" In precision impression-taking of fixed prostheses on natural teeth, the accuracy of the yield of the preparation end margin is vital. The most commonly used techniques involve the utilisation of elastomers.<\/p>\n","protected":false},"author":1,"featured_media":550,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[38],"tags":[172,151,157],"class_list":["post-594","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-laboratory-en","tag-gingival-retraction","tag-methodologies","tag-prosthodontics"],"acf":[],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\tThe different types of astringent liquids<\/h2>\n
1. Aluminium sulphate<\/h3>\n
2. Aluminium chloride<\/h3>\n
3. Ferric sulphate<\/h3>\n