Dental Impression for Viva Preparation

March 3, 2018
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COMMON VIVA QUESTION

Q25. Define impression?

Ans. A negative likeness or copy in reverse of the surface of an object; an imprint of the teeth and adjacent structures for use in dentistry.

Q26. Define a dental impression?

Ans. A negative imprint of an oral structure used to produce a positive replica of the structure to be used as a permanent record or in the production of a dental restoration or prosthesis.

Q27. What are the basic objectives of impression making?

Ans. The objectives of impression making are:

  1. Preservation of the alveolar ridge
  2. Retention
  3. Aesthetics
  4. Stability
  5. Support

Q28. What are the theories in impression making?

Ans. The theories in impression making are:

  1. Pressure technique/ functional pressure impression
  2. Non-pressure technique/minimal pressure
  3. Selective pressure technique

Q29. What are the techniques in impression making?

Ans. The techniques of impression making depends on:

  1. Amount of pressure used
  2. Open or closed mouth
  3. Hand manipulation/ functional movements
  4. Type of tray-using custom tray and prefabricated tray

Q30. What is a preliminary impression?

Ans. A negative likeness made for the purpose of diagnosis, treatment planning or the fabrication of a custom impression tray.

Q31. Define an impression tray.

Ans.  A receptacle into which suitable impression material is placed to make a negative likeness. A device that is used to carry, confine and control impression material while making an impression.

Q32. What is stock tray?

Ans. A metallic or a non-metalllic tray made from a preliminary cast recovered from a preliminary impression. It is used for making a final impression.

Q33. What is the custom tray?

Ans. An individualized impression tray made from a preliminary cast recovered from preliminary impression. It is used for making a final impression.

Q34. What should be the position, size and shape of the tray handle?

Ans. Anterior handle centered over the labial flange in the approximate position of the anterior teeth, height  20mm, 3-4mm thick.Posterior handles at first molar area, centre of the ridge, 20mm in height.

Q35.  What is the purpose of the tissue stops?

Ans. The tissue stops in the custom trays prevents the apical displacement of the tray while making the final impression and helps to reseat the custom tray during the final impression.

Q36. What are the materials used to fabricate a custom tray?

Ans. The materials used to fabricate the custom tray are:

  1. Acrylic resin
  2. Self cure
  3. Heat cure
  4. Light activated
  5. Shellac base plates

Q37. Define cast?

Ans. A life size likeness of some desired form. It is formed within or is a material poured into a matrix or impression of desired form.

Q38. What is preliminary cast?

Ans. A cast formed from a preliminary impression for use in diagnosis or the fabrication of a custom impression tray.

Q39. What is a diagnostic cast?

Ans. A life size reproduction of a part or parts of the oral cavity and/or facial structures for the purpose of study and treatment planning.

Q40. What is master cast?

Ans. A replica of the tooth surfaces, residual ridge areas and/ or other parts of the dental arch and/ or facial structures used to fabricate a dental restoration or prosthesis, which is also called final cast.

Q41. Define a die?

Ans. A positive reproduction of the form of a prepared tooth in any suitable substances.

Q42. What is the border seal?

Ans. The contact of the denture border with the underlying or adjacent tissues to prevent the passage of air or other substances.

Q43. What is border movement?

Ans. Mandibular movement at the limits dictated b anatomic structures,as viewed in a given plane.

Q44. What is the border tissue movements?

Ans. The action of the muscles and the other tissues adjacent to the borders of a denture.

Q45. What is the peripheral tracing/ border moulding?

Ans. The shaping of the border areas of an impression material by functional or manual manipulation of the soft tissue adjacent to the borders to duplicate the contour and size of the vestibule.

Determining the eextension of a prosthesis by using tissue function or manual manipulation of the tissues to shape the border areas of an impression material.

Q46. What are the material used for border moulding?

Ans. The material used for border moulding are:
1. Green stick compound

2. Putty consistency of elastomeric impression material

Q47. What is wash impression?

Ans. The impression that represents the completion of the registration of the surface or object.

Q48. What are the materials used for making final impression?

Ans. The materials used for making final impression are:

  1. Impression plaster
  2.  Zinc oxide-eugenol
  3. Light body consistency or addition silicone impession material
  4. Polyether impression material

Q49. What is record base?

Ans. An interim denture base used to support the record rim material for recording maxillomandibular records.

Q50. What are the requirements of record base?

Ans. Requirements of a record base:

  1. It should adapt to the basal seat area as the finished denture base
  2. It should have the same border form as the finished denture base
  3. It should be sufficiently rigid to resist biting forces
  4. It should be dimensionally stable
  5. It should permit its use as a base for setting up teeth
  6. It should have no undesirable colour

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Prosthodontics