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rpd design

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									                                                                   DIAGNOSIS, TREATMENT PLANNING,
                                                                   DESIGN, TREATMENT SEQUENCING
                                                                   AND MOUTH PREPARATION
                                                                   !   Study cast surveyor
                                                                       !   Diagnosis
                                                                       !   Guiding and verify the appropriate tooth preparation

                                                                   !   Mouth preparation goal
                                                                       ! Support
                    REMOVABLE PARTIAL                                  ! Stabilization
                    DENTURE                                            ! Retention
                                                                       !   Harmonious occlusion

                                            CHATCHAI KUNAVISARUT
                                           CHANITA SUPA-AMORNKUL

AND MOUTH PREPARATION                                              AND MOUTH PREPARATION
!   Mouth preparation sequence                                     ! Take impression with alginate for ascertain the
    !   Proximal tooth surfaces                                      contour of abutment
        !   Parallel to guiding plane                              ! Take another impression for master cast
    !   Occlusal rest seats                                        ! Master cast
        !   Direct occlusal force along the long axis
                                                                       ! Survey
        !   Spoon shape
                                                                       ! Draw RPD framework design
    !   Retentive area
                                                                       ! Tripoding
        !   Resist dislodging force
    !   Reciprocal area

                                                                   KENNEDY’S CLASSIFICATION

                    CLASSIFICATION OF
                    PARTIALLY EDENTULOUS

                                               COMPONENT OF PARTIAL
                                               DENTURE DESIGN

                                MAJOR CONNECTOR
                                ! Join the components on one side of the arch with
                                  those on the other side
                                ! Rigidity " Distribution force

                                ! Not impingement subgingival


                                !   Design
                                    ! Symmetrical
                                    ! Cross midline at right angle
                                    ! Avoid torus
                                    ! Smooth and round contour
                                    ! Self cleansing
                                                                                           PALATAL BAR
! Palatal bar                                                           Narrow half oval with thickest point at the middle
! Palatal strap
                                                                        Interim application
! Anteroposterior palatal bar

! Horseshoe                                                             Uncomfortable
! Anteroposterior palatal strap

! Complete palate                                                       Little vertical support

                                                                        All support derive from remaining teeth

                                                                        Short span class III

                                                                        Should not place anterior to second molar

                     PALATAL STRAP                                           ANTEROPOSTERIOR PALATAL BAR

                                                                         Anterior bar = Palatal strap Posterior bar = Palatal bar

 Wide – thin band of metal                                               Join two bar with flat longitudinal element

 At least 8 mm. wide                                                     Rigidity

 Little interfere tongue                                                 Minimized soft tissue coverage

 Patient accept                                                          Uncomfortable

 Resistance to bending and twisting force                                Little support from palate

 Distribute stress                                                       Not the first choice

 Patient may complain of palatal coverage                                Support is not major consideration

                                                                         Widely separate abutment

                  HORSESHOE CONNECTOR                                           ANTEROPOSTERIOR PALATAL STRAP

 Thin metal band running along the lingual surface of remaining teeth
 and extending (6-8 mm.) on to the palatal tissue
                                                                         Indicated when replace numerous teeth or present of palatine torus
                                                                         Extensive length of border may irritation to tongue
 Replaced several anterior teeth
                                                                         Open area in palatal region at least 20x15 mm.
 Prominent median palatal suture line
                                                                         Good support from palate
 Inoperable torus
                                                                         Resistance to flexure
 Tendency to flex or deform
 Not good for cross arch stabilization

 More rigid connector cannot be used
                 COMPLETE PALATE
                                                             INDICATION OF MAXILLARY MAJOR
 Ultimate rigidity and support
                                                             Condition                         Major connector
  Posterior border extend to hard and soft palate junction
                                                             Weak periodontal support of       -Wide palatal strap
                                                             remaining teeth                   -Complete palate
  Anterior border cover cingular of anterior teeth
                                                             Adequate periodontal support of   -Palatal strap
 Greatest amount of tissue coverage                          remaining teeth                   -Ant.-post. palatal bar
                                                             Long span distal extension        -Ant.-post. palatal strap
 Replaced all posterior teeth
                                                                                               -Complete palate
                                                             Replaced anterior teeth           -Ant.-post. palatal strap
 Periodontal compromised
                                                                                               -Complete palate
 Distribution force to remaining teeth and tissue                                              -Horseshoe


 Extensive tissue coverage

                                                             MANDIBULAR MAJOR CONNECTOR
Condition                        Major connector             ! Lingual bar
Torus present                    -Ant.-post. Palatal strap   ! Lingual plate
                                 -Ant. -post. Palatal bar
                                                             ! Double lingual bar
                                                             ! Labial bar

•Very sparing use horseshoe connector
•Palatal bar is rarely indicated

                                                                                          LINGUAL PLATE
                        LINGUAL BAR

                                                             Half pear shape and thin piece of metal

   Indicate for all tooth support unless insufficient space   Scallop appearance

   At least 8 mm. between gin. margin and floor of mouth      Always support by rests

   Minimum contact with teeth and soft tissue                Insufficient vertical space for lingual bar

   Half pear shape                                           Splinting

                                                             Existing of mandibular tori
                                                             Exceptional rigidity
   Decrease plaque accumulate
                                                             More comfortable than lingual bar
   Need extreme care for design and construction
                                                             Extensive coverage
                                                                                   DOUBLE LINGUAL BAR

                                                                       Characteristics of both lingual bar and plate

                                                                       Join 2 bars with rigid minor connector

                                                                       Contact with remaining anterior teeth indicated

                                                                       Marginal gingival receives natural stimulation

                                                                       Horizontal stabilization

                                                                       Tendency to trap debris

                                                                       Not comfortable

                              LABIAL BAR
                                                                   MANDIBULAR MAJOR CONNECTOR
 Run across the mucosa on facial surface                           Condition                         Mandibular major connector
                                                                   Tooth support                     Lingual bar
 Indicated in the presence of a gross uncorrectable interference
                                                                   -Insufficient space               Lingual plate
 Half pear shape                                                   -Inoperative torus
                                                                   -High lingual frenum attachment
 Swing-lock                                                        -Reduced periodontal support in   -Modified lingual plate
                                                                   anterior teeth                    (step back design)
 Tipped remaining mandibular teeth                                 -Large interproximal space        -Double lingual bar

 Poor patient acceptance

 Distort lower lip


Condition                          Mandibular major connector
Replace all posterior teeth        Lingual plate

 • Labial bar is rarely indicated
                                                                                    MINOR CONNECTOR
MINOR CONNECTOR                                    TYPE OF MINOR CONNECTOR
! Join the remaining component of RPD to the       ! Join clasp to major connector
  major connector                                  ! Join direct retainers or auxiliary rest to major
! Distribute force to supporting teeth and oral      connector
  tissues                                          ! Join denture base to major connector
! Rigidity                                         ! Serve as approach arms for bar- type clasp

                                                           JOIN INDIRECT RETAINERS OR AUXILIARY REST
          JOIN CLASP TO MAJOR CONNECTOR                               TO MAJOR CONNECTOR

                                                   Right angle with the major connector
                                                   Gently curve junction
Locate on proximal surface
                                                   Positioned in lingual embrassure
Broad buccolingually but thin mesiodistally


                                                    Strong enough to anchor denture base
Open construction form ladder like network
                                                    Distal extension

Mesh construction
                                                    In maxillary arch, extend as far posterior as practical

Bead, wire or nail head components on metal base
                                                    In mandibular arch, extend two thirds the length of edentulous ridge

    Not required to be rigid

    Must not cross tissue undercut

                                                                       RESTS AND REST SEAT

                                                           PRIMARY REST
!   A rest that is part of a retentive clasp is referred   ! Prevent vertical movement
    to a primary rest                                      ! Transmit force to supporting tissue
                                                           ! Ball and socket joints
!   A rest that is responsible for additional support
    or indirect retention is called an auxiliary rest or
    secondary rest

AUXILIARY REST                                             MAJOR FORM OF REST
!   Indirect retainer in extension base                    ! Occlusal rest
!   Place anterior or posterior to the axis of rotation    ! Lingual or cingulum rest
                                                           ! Incisal rest
                OCCLUSAL REST                                         OCCLUSAL REST

   Triangular                                   Floor of rest seat slightly inclined toward the center of the teeth

                                                Deepest portion located near the center
   1/3 – 1/2 of mesiodistal diameter
                                                At least 0.5 mm. thick at thinnest point
   Approximate 1/2 of bucco lingual width
                                                1.0-1.5 mm. thick at the marginal ridge

       LINGUAL AND CINGULUM REST                                           INCISAL REST

Primarily used on maxillary canine          Frequently used in mandibular canine

V shape                                     Small V shaped notch

Ball and socket assembly                    Located approximately 1.5 to 2.0 mm. from the proximal
                                            incisal angle

                                            DIRECT RETAINER
                                            !   Engage abutment and resist dislodging forces
                                            !   Two type
                                                 !   Intracoronal direct retainer
                                                     !   Precision attachment
                                                     !   Semiprecision attachment

                                                 !   Extracoronal direct retainer
                                                     !   Retentive clasp
           DIRECT RETAINER                               !   Suprabulge
                                                         !   Infrabulge

                                                     !   Attachment
RETENTIVE CLASP ASSEMBLIES                                RETENTION
!   Structure of clasp assembly                           !   The quality of clasp that resists forces acting to
    ! Rest                                                    dislodge component from supporting tissue
    ! Retentive arm
    ! Reciprocal element                                  !   Depend on
    ! Minor connector                                         ! Type of clasp
                                                              ! Flexibility
                                                              ! Undercut

CLASP ARM FLEXIBILITY                                     RECIPROCATION
!   Depend on
    ! Length " increase
    ! Cross-sectional diameter "circular
    ! Longitudinal taper
    ! Clasp curvature " single plane
    ! Metallurgical properties of alloy "gold , wrought

                                                           The quality of clasp that counteracts lateral
                                                           displacement of an abutment when retentive
                                                           clasp terminate

RECIPROCATION ELEMENT                                     ENCIRCLEMENT
! Cast clasp                                              ! The characteristic of clasp that prevent
! Lingual plate                                             movement of abutment away from associated
! Combination of mesial and distal minor
                                                            clasp assembly
                                                          ! Contact over at least 180°

!   Prepared parallel to path of insertion
                                                                            LOCATION OF RETENTIVE CLASP
PASSIVITY                                                                   TERMINUS
!   Quality of clasp that prevent the transmission of                       !   Mesial or distal line angle
    the adverse forces to the associated abutment                           !   Facial surface better than lingual surface
                                                                                !   Length " Flexibility
                                                                                !   Contraindicated in premolar

           SIMPLE CIRCLET DESIGN (Aker’s clasp)                                                   REVERSE AKER DESIGN

    Widely used
                                                                            Undercut located adjacent to edentulous area
    Tooth support RPD
                                                                            Infrabulge clasp is contraindicated
    Engage undercut remote from edentulous area
                                                                            Kennedy class I ,II
    Half round cross sectional
    Disadvantages                                                           - Reduced strength
    - Increase circumference clinical crown                                 - Lack of rest adjacent to edentulous area
    - Increase tooth coverage                                               - Poor esthetic

                    MULTIPLE CIRCLET DESIGN                                                          EMBRASURE CLASP

                                                                                2 simple circlet joined at bodies
 2 simple circlet clasp joined at the terminal aspect of their reciprocal
elements                                                                        Used on no edentulous area side

Principle abutment is periodontal compromised                                   Insufficient tooth preparation results in

Disadvantage                                                                        Inadequate cross sectional dimension
- The same as simple circlet and reverse circlet
                                                                                    Compromised clasp strength
                         RING CLASP DESIGN

 Indicated on tipped mandibular molar

 Engage mesiolingual or mesiobuccal undercut

 Auxiliary bracing arm

 Distal and mesial –occlusal rest

 - Tooth coverage
 - Difficult correction

                                           Lingual   Buccal
 - Limit vestibular depth
 - Soft tissue undercut

             C-CLASP DESIGN (Back action clasp)                         WROUGHT WIRE CIRCUMFERENTIAL CLASP

                                                                   Combination clasp
                                                                   - Occlusal rest
                                                                   - Cast metal reciprocal arm
 “Fishhook” or “Hairpin” clasp                                     - Wrought wire retentive arm

 Simple circlet clasp with loop back retentive arm                 Circular cross sectional

 Sufficient crown height                                            Kennedy class I and II

 Disadvantage                                                      Mesiobuccal undercut
 - Insufficient flexibility
 - Tooth coverage                                                  Minimal tooth coverage
 - Esthetic compromised
                                                                   -Minimal stabilizing

                                                              INFRABULGE CLASP
                                                              !   Bar type
                                                              !   Flexibility
                                                                  !   Length
                                                                  !   Taper
                                                              !   More esthetics
                                                              !   T-clasp, modified T clasp, Y clasp and I bar
                                                                             DESIGN RULES
!   Disadvantage                                                             !   Approach arm
    ! Food accumulate                                                            !   must not impinge soft tissue
    ! Flexibility ! " Horizontal stability "                                     !   cross perpendicular to free gingival margin

                                                                             ! Uniformly tapered " Flexibility
                                                                             ! Terminate clasp positioned " Apically on the abutment
                                                                             ! Rigid minor connector " Bracing and Stabilization

                           T-CLASP DESIGN
                                                                                                         I-CLASP OR I BAR

Kennedy class I and II                                                           Contact area

Undercut locate adjacent edentulous area                                             2-3 mm. in height

O.01’’ undercut                                                                      1.5-2 mm. in width

Contraindication                                                                 Mesial rest
- Severe soft tissue undercut
- High of contour locate near occlusal surface                                   Kennedy class I and II

                                    A = Approach arm                             RPI
                          B= Vertical projection of approach arm                 - Mesial rest
                  C= Location where B cross perpendicular to free gingival       - Proximal plate
                               D=Point of first tooth contact
                             E=Terminus of the retentive clasp
                                                                                 - I bar
                                 F= Encirclement portion

                          MODIFIED T-CLASP                                                               Y-CLASP DESIGN

                                                                              Equivalent to T-clasp
 No retentive horizontal projection
                                                                              Mesial and distal projection terminate near occlusal surface
 Kennedy class I and II

 Undercut locate near adjacent edentulous area

 Canine and premolar

 - Improve esthetic compare with conventional T clasp
                                                                       INDIRECT RETAINER

                                                           INDIRECT RETAINER
                                                           ! Framework component that resists rotational
                                                             displacement of an extension base from the
                                                             supporting tissue
                                                           ! Require for Kennedy class I, II and IV


!   Occlusal dislodging forces
    !   Denture base move away from supporting tissue
    !   Anterior segment of major connector impinge upon
        underlining tissue
RETAINER                                               FORM OF INDIRECT RETAINER
! Position on the opposite site of fulcrum line        ! Auxiliary occlusal rest
! Perpendicular and far from fulcrum line              ! Cingulum rest
! Canine and premolar                                  ! Incisal rest

! Rest at each end of lingual plate

Distal Extension RPD
!   Direct retainer design


                                                       Indirect retainer

                                                  83                               84
  EXTENSION DENTURE BASE                           Impression technique
! Maximum border extension                         ! Final impression with custom tray and
! Accurate border detail                             elastomeric impression material
! Primary supporting area                          ! Altered-cast technique

! Form of the ridge under function


                                                          “Being excited about being wrong because
! Retentive arms should be on the same side               that means you’ve discovered something new”
! Dimpling

! Treatment denture

! RPD drawing
  - in paper
  - on the cast

                                                               THANK YOU


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