Paper Topic:

Dental Materials

p Dental Impressions

A Brief Analysis of material characteristics and clinical techniques A dental impression is the negative replica of the oral tissues . A dental impression is got by recording details of the oral cavity into a suitable material . Such suitable recording material is called the impression material . Wax was one of the early materials used for taking oral cavity impressions . Several other materials have been used in the past and obviously research is also underway to find better materials Impression materials are used to obtain an exact replica of both

, soft and hard oral tissues . The area used to obtain an impression may vary from a single tooth to an entire dentition . A negative reproduction of the tissues is obtained by the impression . The impression is then filled with dental stone or other suitable material to obtain a positive cast The positive cast is removed after setting of the model material . The casts are used in fabricating restorations and prostheses and in evaluating dentition when orthodontic , occlusal or other problems are involved . The positive reproduction is referred to as a `model ' or `cast ' when it is associated with larger areas of oral tissues . The positive reproduction is called a `die ' when it is associated with single or multiple tooth preparations (Craig , Powers and Wataha Generally the unset impression material is brought to the mouth in a tray and applied to the treatment area . The impression material with the tray is removed from the mouth , after it is set . Based on the impression material used , the clinical impression technique and cast production procedures are varied

Ideal properties of an impression material

The physical properties of dental impression materials are selected such that it conforms to clinical procedure requirements and its suitability for contact with live tissues of the mouth . However , it is difficult to find an impression material which fulfills all requirements and therefore the best suited material for a corresponding situation can only be selected by the dentist . Some ideal properties of an impression material may be listed as follows

i ) The impression material should be capable of reproducing the oral tissues accurately

ii ) The material should have sufficient elastic properties to ensure that it does not permanently deform

iii ) The material should possess dimensional stability under humid conditions and during temperature changes associated with clinical procedures

iv ) The material must be strong so that it does not break or tear when removed from mouth

v ) It must have sufficient consistency , texture and compatibility with cast or die material

vi ) It should have adequate setting properties as per clinical requirements

vii ) The material should not contain any toxic ingredients and should be easy to use with minimum equipment

viii ) Should be economical and have adequate shelf life to ensure storage and distribution

ix ) The material should have an aesthetic color and a pleasant odor and taste

x ) The material should readily wet oral tissues and be readily disinfected without loss of accuracy

Accuracy and Dimensional Stability of impression materials

The...

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