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
<\/p>\n
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":[],"_links":{"self":[{"href":"https:\/\/magazine.zhermack.com\/en\/wp-json\/wp\/v2\/posts\/594","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/magazine.zhermack.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/magazine.zhermack.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/magazine.zhermack.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/magazine.zhermack.com\/en\/wp-json\/wp\/v2\/comments?post=594"}],"version-history":[{"count":1,"href":"https:\/\/magazine.zhermack.com\/en\/wp-json\/wp\/v2\/posts\/594\/revisions"}],"predecessor-version":[{"id":5991,"href":"https:\/\/magazine.zhermack.com\/en\/wp-json\/wp\/v2\/posts\/594\/revisions\/5991"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/magazine.zhermack.com\/en\/wp-json\/wp\/v2\/media\/550"}],"wp:attachment":[{"href":"https:\/\/magazine.zhermack.com\/en\/wp-json\/wp\/v2\/media?parent=594"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/magazine.zhermack.com\/en\/wp-json\/wp\/v2\/categories?post=594"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/magazine.zhermack.com\/en\/wp-json\/wp\/v2\/tags?post=594"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}The different types of astringent liquids<\/h2>\n
1. Aluminium sulphate<\/h3>\n
2. Aluminium chloride<\/h3>\n
3. Ferric sulphate<\/h3>\n