Rests & Rest Seats Rests & Rest Seats
Mar 28, 2015
Rests & Rest SeatsRests & Rest Seats
RestRest A rigid component resting in a recessed A rigid component resting in a recessed
preparation on the occlusal, lingual or preparation on the occlusal, lingual or incisal surfaceincisal surface
Provides vertical supportProvides vertical support
Rest SeatRest Seat
Portion of a tooth prepared to receive a Portion of a tooth prepared to receive a restrest
FunctionsFunctions
Direct forces along long axis of abutmentDirect forces along long axis of abutment
FunctionsFunctions SUPPORT - prevents denture base from SUPPORT - prevents denture base from
moving cervically & impinging gingivamoving cervically & impinging gingivaSlides down inclineSlides down incline
Fractured abutment, no rest seatFractured abutment, no rest seat
Major connector imbeds into tissueMajor connector imbeds into tissue
FunctionsFunctions
Maintain a clasp -tooth relationshipMaintain a clasp -tooth relationship
FunctionsFunctions
Prevent extrusion of abutmentsPrevent extrusion of abutments Provide reference for relines or Provide reference for relines or
impressionsimpressions
FunctionsFunctions
Act as indirect retainerAct as indirect retainer Prevents rotation (Class I or II RPDPrevents rotation (Class I or II RPD’’s s
only)only)
Preparation of Rest SeatsPreparation of Rest Seats
Light pressure Light pressure High-speed handpieceHigh-speed handpiece +/- Waterspray+/- Waterspray Minimal heat is generatedMinimal heat is generated
Preparation of Rest SeatsPreparation of Rest Seats
Keep in enamelKeep in enamel No anesthesiaNo anesthesia
Preparation of Rest SeatsPreparation of Rest Seats
Occlusal Rest SeatsOcclusal Rest Seats Diamonds Diamonds
8801- 0148801- 014 38006 -13538006 -135
8801- 0148801- 014
Rest Seat FormRest Seat Form
Smooth flowing outline form (i.e. no Smooth flowing outline form (i.e. no sharp line angles)sharp line angles)
Occlusal Rest Seat FormOcclusal Rest Seat Form
Rounded triangular shape Rounded triangular shape Apex near center of toothApex near center of tooth
Occlusal Rest Seat FormOcclusal Rest Seat Form
Base of triangle should be one third the Base of triangle should be one third the bucco-lingual width of the toothbucco-lingual width of the tooth
Occlusal Rest Seat FormOcclusal Rest Seat Form
Marginal ridge must be lowered and Marginal ridge must be lowered and rounded 1-1.5mmrounded 1-1.5mm Bulk of metal to prevent fractureBulk of metal to prevent fracture
Occlusal Rest Seat FormOcclusal Rest Seat Form
Floor inclined towards the center Floor inclined towards the center Angle formed by rest and minor Angle formed by rest and minor
connector should be less than 90connector should be less than 9000
Occlusal Rest Seat FormOcclusal Rest Seat Form
Deepest portion is centralDeepest portion is central
Occlusal Rest Seat FormOcclusal Rest Seat Form
Floor should be concave or spoon shaped Floor should be concave or spoon shaped ball-&-socket jointball-&-socket joint
Prevents horizontal stresses & torquePrevents horizontal stresses & torque
Occlusal Rest Seat FormOcclusal Rest Seat Form
Directs the occlusal forces along the long Directs the occlusal forces along the long axis of the toothaxis of the tooth
Prevent orthodontic movementPrevent orthodontic movement
““PositivePositive”” Rest Seats Rest Seats
Explorer tip will not slide off the rest seatExplorer tip will not slide off the rest seat
Avoid UndercutsAvoid Undercuts
Must draw along path of insertionMust draw along path of insertion
Occlusal Rest Seat MovieOcclusal Rest Seat Movie
Occlusal Rest Seat FormOcclusal Rest Seat Form
Conventional FormConventional Form
Occlusal Rest Seat FormOcclusal Rest Seat Form
Adjacent ToothAdjacent Tooth Rest not flared to facial line angleRest not flared to facial line angle Lingual flared more - space for minor Lingual flared more - space for minor
connectorconnector
Double Embrasure Rest Seat Double Embrasure Rest Seat FormForm Adjacent teeth, the form is also modifiedAdjacent teeth, the form is also modified Flared more dramatically on facial and Flared more dramatically on facial and
lingual line angleslingual line angles
Double Embrasure Rest Seat Double Embrasure Rest Seat FormForm Provides space for the retentive & Provides space for the retentive &
bracing armsbracing arms Ensure all line angles are smoothedEnsure all line angles are smoothed
Lingual Rest SeatsLingual Rest Seats
Usually the canine, due to its well-Usually the canine, due to its well-developed cingulumdeveloped cingulum
When canine is not available, an incisor When canine is not available, an incisor may be usedmay be used
Cingulum Rest Seat FormCingulum Rest Seat Form
Inverted Inverted ““VV ”” < 90< 9000
Cingulum Rest Seat FormCingulum Rest Seat Form
Slightly rounded to avoid sharp line Slightly rounded to avoid sharp line anglesangles
Test as Test as ‘‘positivepositive’’ with explorer tip with explorer tip 1mm depth1mm depth
Correct PreparationCorrect Preparation
Preparation Too HighPreparation Too High
Preparation Too LowPreparation Too Low
Preparation of Rest SeatsPreparation of Rest Seats
Cingulum Rest Seats & Cingulum Rest Seats & Guiding PlanesGuiding Planes Long, medium Long, medium
diameter cylindrical diameter cylindrical diamond diamond 8837K-0148837K-014
8837K-0148837K-014
Cingulum Rest PreparationCingulum Rest Preparation
Do not create an enamel undercutDo not create an enamel undercut Cylindrical bur along the long axis of the Cylindrical bur along the long axis of the
toothtooth
Cingulum Rest Seat MovieCingulum Rest Seat Movie
Cingulum Rest Seat PlacementCingulum Rest Seat Placement
Place in sound tooth structure or Place in sound tooth structure or restorationsrestorations
Not on amalgam restorationsNot on amalgam restorations If not prominent or large pulpIf not prominent or large pulp
Use different toothUse different tooth Bonded rest seatBonded rest seat Onlay or crownOnlay or crown
Maxillary Cingulum Rest SeatsMaxillary Cingulum Rest Seats
Avoid opposing occlusionAvoid opposing occlusion
Maxillary Cingulum Rest SeatsMaxillary Cingulum Rest Seats
1.5 - 2.0 mm clearance for metal1.5 - 2.0 mm clearance for metal Check with articulated modelsCheck with articulated models
Bonded Cingulum RestsBonded Cingulum Rests
Flat emergence profileFlat emergence profile Pumice, rinse, etch, bond using rubber Pumice, rinse, etch, bond using rubber
damdam Ensure cervical composite well adaptedEnsure cervical composite well adapted
Composite Bonded Rest Seat FormComposite Bonded Rest Seat Form
CorrectCorrect OvercontouredOvercontoured OvercontouredOvercontouredOpen marginOpen margin
Bonded Rest Seat MovieBonded Rest Seat Movie
Round Lingual Rest Seat FormRound Lingual Rest Seat Form
Mesial of the canine teeth when typical Mesial of the canine teeth when typical cingulum rest contraindicatedcingulum rest contraindicated Large restorationLarge restoration Lack of clearance with the opposing teethLack of clearance with the opposing teeth Poor cingulumPoor cingulum
Round Lingual Rest Seat FormRound Lingual Rest Seat Form
Spoon shaped, similar to occlusal rest seatSpoon shaped, similar to occlusal rest seat More difficult due to the incline of the More difficult due to the incline of the
lingual surface lingual surface Easily incorporated into crownsEasily incorporated into crowns
Incisal Rests Incisal Rests Inferior mechanically & estheticallyInferior mechanically & esthetically Lingual rest is nearer to the center of Lingual rest is nearer to the center of
rotationrotation Less torquing potentialLess torquing potential
Bring to Seminar Rooms:Bring to Seminar Rooms:
Ball burnisher if you have oneBall burnisher if you have one Boxof casts with prepartions on themBoxof casts with prepartions on them Any typodonts for checking of guiding Any typodonts for checking of guiding
plane preparations (Surveyor needed for plane preparations (Surveyor needed for checking)checking)