Please forward this diagnosis and treatment planning in complete denture pdf screen to sharedip-23229134225. A custom dental model or cast. It is made by placing an appropriate material in a stock or custom dental impression tray which is designed to roughly fit over the dental arches. Impression material is of liquid or semi-solid nature when first mixed and placed in the mouth.
The required type of material for taking an impression and the area that it covers will depend on the clinical indication. These impressions will generally lead to a denture that is most stable during function but not at rest. Dentures are at rest most of the time, so it could be argued that mucostatic impressions make better dentures, however in reality it is likely that tissue adaption to the presence of either a denture made with a mucostatic or a mucocompressive technique make little difference between the two in the long term. Another type of impression technique is selective pressure technique in which stress bearing areas are compressed and stress relief areas are relived such that both the advantages of muco static and muco compressive techniques are achieved. Wash impression”- this is a very thin layer of low viscosity impression material which is used to record fine details. Usually it is the second stage, where the runny impression material is used after an initial impression taken with a more viscous material. When taking impression for provision of crown and bridge work, the preparation border needs to be accurately captured by the light bodied impression material.
For this reason, the gingival tissues need to be pushed away from the preparation margin in order to make it accessible to the impression material. Mainly composed of β-calcium sulphate hemihydrate, impression plaster has a similar composition and setting reaction to the casting material with an increase in certain components to control the initial expansion that is observed with Plaster of Paris. Additionally, more water is added to the powder than with the casting material to aid in good flow during impression taking. If a special tray is to be used, impression plaster requires 1-1. 5mm spacing for adequate thickness. Impression compound has been used for many years as an impression material for removable prostheses. Although its use has recently declined with the advent of better materials.