RPD week 4
Card Set Information
RPD week 4
RPD week 4
♦ What are the types of rests for anterior teeth?
•Circular concave rests
♦ What is the type of anterior rests most commonly used for maxillary canines?
♦ How do you prepare the positive incisal rest seats?
1/3-1/2 width of incisal edge and sufficient clearance
Concave rest seat mesiodistally
Convex rest seat buccolingually
May create greater leverage on the tooth compare to cingulum rests when used improperly and is only used when the lingual anatomy of the tooth is not appropriate
♦ What are the roles of proximal plates?
1. Maintains arch integrity by producing bracing action.
2. Acts as retainers by frictional contact with the parallel guide planes on the teeth.
3. Guide a partial to seat along the path of insertion.
4. Provides reciprocation to a retainer
5. Protect against food impaction and tissue hypertrophy by adapting the guide plane at the tooth-tissue junction.
6. Facilitate a self-cleansing effect compared to the acrylic
♦ What must be considered to maintain the health in the area between soft tissue and abutment?
1. Impaction of food into the space.
2. Hypertrophy of tissue into the space.
3. A reduced bracing effect between the remaining teeth.
4. Increased periodontal involvement.
♦ What are the infrabulge and suprabulge retainers? Name representative retainers in each of the types?
♦ What are the advantages of I-bar retainers over the C-clasp retainers?
Minimal tooth contact
Minimal interference with natural tooth contour.
Maximum natural cleansing action.
Reduced display of metal for better esthetics.
Passive functional movement on the abutment adjacent to an extension-base
♦ What are the requirements to design the I-bar retainer?
To originate at a gingival area and cross the tooth-tissue junction at right angles.
To engage an undercut 0.01 inch or 0.25 mm. The
abutment needs to have the undercut around the
The tip of the I-bar should be located ideally within the cervical 1/3 or could be lower than the cervical ½.
The retention area should be at least 1 mm above the gingival margin
To extend in a straight line down (5-7mm) to create
sufficient flexibility; therefore, severe soft tissue undercut is a contraindication of I-bar Above the height of contour of the soft tissue
When no undercut found, a retentive area, or a dimple, can be created by a round bur, with an
approximately 1.5 mm diameter and an adequate depth depending on the contour of the abutment.
To be reciprocated by one of the following 3 structures
(1) a combination of a proximal plate and minor connector, Passive Active
(2) a passive retainer, or
(3) a plate.
Proximal Plates (a metal structure facing a guide plane): Fundamentals in guide plane preparation
1. The larger, the better bracing.
2. Curvilinear prep within the enamel.
3. Therefore, they can not always be prepared fully to the gingiva.
4. Preserve facial anatomy in the esthetic zone.
5. The more parallel each other, the more retention can be generated.
6. The more parallel each other, the longer bracing and retention last.
Which is first to prep, rests or guide planes ?