Chapter-I Direct Retainers in Removable Partial Dentures
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Questions and Answers

What is the definition of a direct retainer in a removable partial denture?

  • The component used to support the artificial teeth
  • The component used to resist vertical displacement and prevent dislodgment (correct)
  • The component used for aesthetics in a removable partial denture
  • The component used to connect the denture base to the framework

    • Which of the following may serve as forms of direct retainers?

  • Major connectors and minor connectors
  • Clasp assembly and precision attachment (correct)
  • Framework and artificial teeth
  • Base plate and occlusal surface

    • How are removable partial dentures mainly retained according to the text?

  • Chemical bonding to the tissues
  • Static electricity between the denture and tissues
  • Mechanical means of retention (correct)
  • Biological attachments to the oral mucosa

    • Why are physical forces less applicable to lower dentures compared to upper dentures?

    <p>Lower dentures have less surface area</p> Signup and view all the answers

    Which characteristic makes lower dentures less affected by physical forces?

    <p>Having less surface area</p> Signup and view all the answers

    What is the purpose of a direct retainer in a removable partial denture?

    <p>To hold the denture in place and prevent dislodgment</p> Signup and view all the answers

    What is the role of physiological means of retention in dentures?

    <p>Enhancing the peripheral border seal</p> Signup and view all the answers

    Which component is used to resist vertical displacement of a distant part of the denture?

    <p>Indirect retainers</p> Signup and view all the answers

    What is the purpose of intra-coronal retainers in dentures?

    <p>To serve as precision attachments</p> Signup and view all the answers

    How do direct retainers help accomplish primary retention in removable partial dentures?

    <p>By engaging tooth surface undercuts</p> Signup and view all the answers

    Which factor plays a significant role in denture retention according to the text?

    <p>Polished surface of the denture</p> Signup and view all the answers

    What is the function of extra-coronal retainers?

    <p>Engaging tooth surface undercuts</p> Signup and view all the answers

    What is a disadvantage of internal attachments for direct retainers?

    <p>They require preparation of the abutment teeth.</p> Signup and view all the answers

    Where do extra-coronal retainers, in the context of direct retainers, typically lie?

    <p>Outside the crown of a natural tooth abutment.</p> Signup and view all the answers

    Why shouldn't internal attachments be used in distal extension RPDs except with a stress breaking device?

    <p>Because they lack the stability needed without a stress breaking device.</p> Signup and view all the answers

    What is the primary function of a clasp in direct retainers?

    <p>To engage external surface of an abutment tooth below the height of contour.</p> Signup and view all the answers

    Why are extra-coronal attachments considered to be located outside the crown of abutment teeth?

    <p>To engage external surfaces below the height of contour and ensure proper retention.</p> Signup and view all the answers

    Study Notes

    Direct Retainers

    • Retention is the resistance of the RPD to vertical displacement away from the tissues.
    • The primary function of a direct retainer is to hold or keep the denture in place and prevent dislodgment.

    Types of Retention

    • Physical means of retention:
      • Adhesion, cohesion, and interfacial surface tension
      • Atmospheric pressure
      • Plastic molding of the tissues around the polished surfaces of the dentures
      • Gravity (in lower denture)
    • Note: The effect of physical forces is less applicable to lower dentures than upper denture.
    • Physiological means of retention:
      • Physiologic molding of the tissues around the polished surfaces of the denture
      • Neuromuscular control: patient's ability to control the denture with the lips, cheeks, and tongue
    • Mechanical means of retention:
      • Engagement of soft tissue undercut through the denture bases
      • Engagement of tooth surface undercut through the use of direct retainers
      • Frictional fit between the natural teeth and the denture and/or artificial teeth
      • Indirect retainers: components of RPD that are used to resist vertical displacement of a distant part of the denture

    Types of Direct Retainers

    • Intra-coronal retainers (internal attachment or precision attachment):
      • Developed by Dr. Herman E.S. Chayes in 1906
      • Require preparation of the abutment teeth
      • Have disadvantages such as losing frictional resistance with time, difficult to repair and replace, etc.
    • Extra-coronal retainers:
      • Classified into clasp retainers and extra-coronal attachments
      • Clasp retainers: metal projections of the RPD engaging external surface of an abutment in an area cervical to height of contour (undercut) to retain the RPD
      • Extra-coronal attachments: provide stimulation to the underlying tissues due to intermittent vertical massage

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    Description

    Learn about direct retainers in removable partial dentures which are essential for retention and preventing dislodgment. Understand the importance of sufficient retention to resist dislodging forces.

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