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RETENTIVE AREAS....

8:02 AM |

Retentive Areas........

q  Amount of desirable undercut …
q  0.01 inch-at the mesiobuccal distolingual line angle
                                 - gingival 3rd of the clinical crown
                                - when the cast chrome alloy is used for framework
                                                                                               
q  I bar design is used when the undercut is more on the center of the facial surface
q  If large molars or if gold is to be used instead of chrome , slightly deeper undercut is necessary
                           0.015 inches
q  If wrought wire combination is used
                          0.020inches (Coz of greater flexibility of the wrought wire )
q  Ideally, retentive clasps should be bilaterally opposed.
q  Similar retentive areas should exist on all principal abutment teeth
                                THE AMOUNT OF RETENTION SHOULD ALWAYS BE THE MINIMUM NECESSARY TO RESIST A REASONABLE DISLODGING FORCE

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Posted by Neeta

interferences

2:00 AM |


INTERFERENCES
q                  Certain areas of mouth may present interferences to easy insertion and removal of the prosthesis
q                  These interferences has to be identified with a surveyor and eliminated
Interferences can be dealt with by
q  Elimination – extraction , ablation
q  Alteration – disking , surgery, restoration
q  Avoidance -  modification of the design
q  Exploitation – using it as an undercut to help retain                                                                                          the prosthesis
Interferences in mandible
q  Lingual torus-
q  Lingually tipped teeth
q  Areas lingual to the retromolar pad
q  Tilting of the cast
q  Acrylic in the denture base can be relieved
q  Bony prominences at the facial surface of canines and premolars
q  Placement of denture base
q  Positioning  of approach arm of vertical projection clasp
Interferences in maxilla
q  Torus palatinus
q  Exostoses and undercuts ( buccal surfaces)
q  Buccally inclined teeth
q  Unilateral – tilting the surveying table away from the height of contour will lower the height of contour in the buccally tipped teeth
q  Bilateral-
q  Contouring of the enamel
q   Full crown restoration
q  Undercuts in anterior edentulous space

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Posted by Neeta

esthetics

2:00 AM |


ESTHETICS
q  To obtain optimum esthetics,
q  Metal components must be concealed as effectively as possible
q  Prosthetic teeth must be properly selected, contoured and positioned
IT IS RARELY POSSIBLE TO ACHIEVE THE OPTIMUM IN ALL FOUR FACTORS. ONE IS COMPROMISED AGAINST THE OTHER

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Posted by Neeta

dental surveyor

1:59 AM |


DENTAL SURVEYOR
Selecting path of insertion
q  Orient cast relatively horizontal to the cast holder
q  Place analyzing rod against abutments
q  Examine teeth to be clasped for favorable retentive undercuts
q  Anterior edentulous area for esthetic considerations
q  Proximal and lingual tooth surfaces  for guiding planes
q  Soft tissue undercuts that act as  interferences
q  Undercut  gauze is used to check for adequate and relatively equal undercut for retentive arms on all abutments. Alter the tilt of cast if required.
q  Tilt cast to obtain the most usable  compromise position. Final tilt should be rarely more than 10° from horizontal
q  Lock the cast in position
q  Tripod the cast
q  Mark the heights of contour
Hence, path of insertion is always parallel to the vertical arm of the surveyor and is determined by the tilt of the cast on the surveyor

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Posted by Neeta
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