Influence of Repeat Pours of Addition Silicone Impressions on the Dimensional Accuracy of Casts

Making an impression represents a critical step in processing and fitting of a dental prosthesis. The definite impression should be accurate to fabricate restoration with ideal marginal fit, internal fit, interproximal contacts and occlusal contacts.The impression materials are used to register or reproduce the form and relations of the teeth and the surrounding oral tissues. Dimensional accuracy andstability are the primary requisites of an impression material. Accuracy of an impression depends on properties of impression materials like thermal contraction, polymerization shrinkage, presence of volatile by products, elastic recovery, bulk of material and impression technique use. Other factors which influence the accuracy of an impression are tray material, space between tray and tooth preparation, storage conditions, relaxation of stresses caused by the use of non-rigid trays, excessive seating pressure, too slow removal from the mouth or an impression removed before the polymerization is complete.
Addition Silicone

A variety of impression materials as silicones, polyether, polysulfide and alginate are available for crowns and fixed partial denture impressions. The addition-type silicone impression material i.e. polyvinyl siloxane is the most preferred material in the field of prosthodontics due to its favorable qualities, relative simplicity and reliability. Polyvinyl siloxane impression materials are reported to have precise detail reproduction, dimensional accuracy and stability, low creep, a relatively short setting time, moderate to high tear resistance and elastic recovery from undercut. The disadvantage of hydrophobicity of polyvinyl siloxane impression material has been overcome to some extent by addition of polyether carbosilane surfactants. Read more...........

Comments

Post a Comment

Popular posts from this blog

Harvesting Free Palatal Masticatory Mucosal Graft Using 3a Mucotome

Image
The technique of free autogenous gingival grafting (FGG) has undergone little modification since its introduction by Bjorn in Scandinavia in 1963 and by King and Pennel inthe United States in 1964. The technique is widely used to treat a variety of mucogingival problems such as insufficient or lack of attached gingiva, the presence of high frenum attachments, shallow fornix and denuded roots following gingival recession.  FGG can be procured from donor site using scalpels, gingivectomy knife or palatal shaving knife (Paquette knife). The donor site is frequently the palate, although the use of edentulous ridge areas, tuberosity and attached gingiva has also been described. Scalpel is most commonly used and conventional method for procuring gingival auto grafts. Gingivectomy knife, although not commonly used, also works on similar principle. Since the scalpel blade is straight and stiff and the palate is curved, repeated incisions to release the graft from underlying connecti
Read more

Dental Ailments may be risky for Cardiac Patients

Image
Patients that are suffering from cardiac t=disorders are susceptible to physical and mental stress. Dental ailments add to the stress further as these patients are unable to cope with the pain due to cardiac disorders. These patients may encounter medical emergencies in case of dental disorders and they may demand multi disciplinary approach to achieve the success. Additionally, the results of cardiac surgery may suffer if the oral cavity is not maintained well since there is always a fear of infection affecting the heart from the oral cavity. Hence, the cardiac surgeon has to refer surgical patients to a dentist for oral prophylaxis and to treat any oral infections before cardiac surgery to prevent infective endocarditis. PDF LINK
Read more

Non-Instrumented Silver Point Retreatment Using the GentleWave Procedure

Image
Apicoectomies are required for endodontically treated teeth instead of the preferred non-surgical endodontic therapy when biological or technical factors necessitate this therapy. These biological or technical factors may include, but are not limited to, non-healing periapical lesions, persistent clinical symptoms, separated instruments or silver points and the presence of long posts. Success rates for apicoectomies have been reported up to 78% with as many as 4% of endodontically treated teeth requiring this type of surgery. Although success rates are relatively high, once the tooth is no longer a candidate for non-surgical endodontic treatment, the alternatives in lieu of apicoectomy are limited to extraction with no replacement or replacement with a fixed prosthesis, removable prosthesis or implant. Read More>>>>>>>
Read more