9 RESTSPrevent vertical movement of partial into tissue
10 The term rest designates any component of the framework that is placed on a tooth. It must be in a PREPARED REST SEAT. It limits the movement of the prosthesis in a gingival direction and transmits forces to the long axis of the teeth.Contact on a tooth surface incline without a rest seat could result in tooth movement converting the RPD to an ORTHODONTIC APPLIANCE.
11 1o SUPPORT Rests Transmits forces through long axis of tooth Transmits forces through periodontal ligamentStabilizes against rotational forces
13 Rest seats can be located on the occlusal and incisal sufaces of a tooth as well as the cingulum and in some instances the marginal ridges of canines.
14 REST AREA - REST SEATThat portion of the tooth selected and prepared to receive an occlusal, incisal, marginal ridge or cingulum / lingual rest.The portion of the tooth structure or of a restoration in a tooth prepared so it is spoon shaped on posterior teeth and V, U or hook-shaped on some anterior teeth, into which seats the metallic rest of a removable partial denture framework.
15 DESIGN CHARATERISTICS OF RESTS 1. Large enough to fit a casting to2. Forms acute angles with minor connectors -prevents tooth from moving away frompartial3. Does not interfere with occlusion
26 Occlusal Rests Rounded triangular shape-”teaspoon” Approximately one-third width of toothMarginal ridge should be lowered to permit bulk of metal for strength.Floor of rest apical to marginal ridge.No sharp edges or line angles.Angle formed by minor connector and rest should be less than <ninety degrees.
41 Cingulum Rests Most effective on maxillary canines. Slightly rounded inverted “V” shape.When mandibular canines / incisors are utilized a rounded ledge at the level of the cingulum can serve as a rests.Care must be taken to avoid enamel undercuts.
47 Incisal RestsPrepared in form of rounded notch at incisal angle of canine or incisal edge of incisor.Should be approximately 2.5 mm wide and 1.5 mm deep.Notch is beveled both labially and lingually.