WHAT ARE COMPONENTS OF RPD (REMOVABLE PARTIAL DENTURES)

🎯 KEY POINTS

🔹The fulcrum line is an imaginary line that joins the occlusal rests around which the prosthesis tends to rotate in function.

🔹Continuous gum denture is an artificial denture consisting of porcelain teeth and tinted porcelain denture base material fused to a platinum base.

🔹Fulcrum line is an imaginary line, connecting occlusal rests, around which a partial denture tends to rotate under functional stresses.

🔹The maxillary palatal strap should be a minimum of 8 mm in width.

🔹Bar clasp is also called vertical projection clasp, infrabulge clasp and roach clasp.

🔹Quasicingulum rest is given in the mandibular first premolar which has a rudimentary lingual cusp.

🔹The rest seat in the mesially inclined molar is prepared with the floor perpendicular to the long axis of the teeth.

🔹Rest seats should always be prepared in sound enamel whenever possible.

🔹Push type of retention is given by bar clasps.

🔹Pull type of retention is given by the reciprocal clasp.

🔹The clasp terminal should be placed below the height of contour of the tooth to act as a primary retainer.

🔹The amount of undercut required by the wrought clasp is 0.020 inch.

🔹The terminal third of the retention arm is the component of direct retainer which lies below the height of contour and provides retention to the prosthesis.

🔹Indirect retainer should be placed as far anterior or far from the saddle as possible to get best mechanical advantage.

🔹Porcelain teeth are mechanically retained in an acrylic base through diatoric holes.

🔍 DEFINITIONS:

🔺Rest Seat: The prepared recess in a tooth or restoration created to receive the occlusal, incisal, cingulum, or lingual rest’. (GPT 8th Ed)

🔺Direct Retainer: The component of a partial removable dental prosthesis used to retain and prevent dislodgement consisting of a clasp assembly or precision attachment’. (GPT 8th Ed)

🔺Indirect Retention: The effect achieved by one or more indirect retainers of a partial removable denture prosthesis that reduces the tendency for a denture base to move in an occlusal direction or rotate about the fulcrum line. (GPT 8th Ed)

🔺Fulcrum Line: An imaginary line, connecting occlusal rests, around which a partial removable dental prosthesis tends to rotate under masticatory forces. The determinants for the fulcrum line are usually the cross-arch occlusal rests located adjacent to the tissue-borne components. (GPT 8th Ed)

🔺Retentive Fulcrum Line: An imaginary line, connecting the retentive points of the clasp arms, around which the removable dental prosthesis tends to rotate when subjected to dislodging forces. (GPT 8th Ed)

🔍 COMPONENTS OF REMOVABLE PARTIAL DENTURE:
💡 Removable partial dentures (RPDs) consist of the following parts:

• Major connectors
• Minor connectors
• Rests
• Direct retainers
• Indirect retainers
• Denture base

📌 MAJOR CONNECTOR: A part of a removable partial denture which connects the components on one side of the arch to the components on the opposite side of the arch. (GPT 8th Ed)

⭐ TYPES OF MAXILLARY MAJOR CONNECTORS

(i) Single posterior palatal bar

(ii) Single palatal strap

(iii) Anteroposterior or double palatal bar

(iv) Horseshoe- or U-shaped connectors

(v) Closed horseshoe or anteroposterior palatal strap

(vi) Complete palate

⭐ TYPES OF MANDIBULAR MAJOR CONNECTORS:

(i) Lingual bar

(ii) Sublingual bar

(iii) Lingual plate

(iv) Kennedy’s bar or double lingual bar or continuous bar

(v) Labial bar

📌 MINOR CONNECTOR: The connecting link between the major connector or base of a removable dental prosthesis and the other units of the prosthesis, such as the clasp assembly, indirect retainers, occlusal rests, or cingulum rests. (GPT 8th Ed)

⭐ TYPES OF MINOR CONNECTORS:

💠Four types:
(i) Connector which Connects the Direct Retainers (Clasp Assembly) To the Major Connectors
(ii) Connector which Connects the Indirect Retainers To the Major Connectors
(iii) Connector which Joins the Denture Base To the Major Connector
(iv) Connector which acts as An Approach Arm in Bar-Type Clasp

📢 Minor Connector Which Joins the Denture Base to the Major Connector

👉 Three types:

• Lattice type
• Mesh type
• Nail head or bead shaped

📌 REST:A rigid extension of a fixed or removable dental prosthesis that prevents movement towards the mucosa and transmits functional forces to the teeth or dental implant. (GPT 8th Ed)

⭐TYPES OF RESTS

💠Two Types:

(i) Primary rests
(ii) Secondary rests

⭐ CLASSIFICATION OF RESTS:

(i) Based on Location on the Abutment

• Occlusal rest: Located on occlusal surface of the posterior teeth
• Cingulum or lingual rest: Located on the lingual area of usually maxillary canine
• Incisal rest: Located on the incisal edge of the teeth

(ii) Based On its Relation to the Direct Retainer

• Primary rest
• Secondary rest

📌 CLASP ASSEMBLY: The part of a removable dental prosthesis that acts as a direct retainer and/or stabilizer for a prosthesis by partially encompassing or contacting an abutment tooth-usage: Components of the clasp assembly include the clasp, the reciprocal clasp, the cingulum, incisal or occlusal rest, and the minor connector clasp’. (GPT 8th Ed)

⭐ COMPONENTS OF CLASP ASSEMBLY:

• Rest
• Body
• Shoulder
• Reciprocal arm
• Retentive arm
• Retentive terminal
• Minor connector
• Approach arm

📌 CIRCUMFERENTIAL CLASP or AKERS’ CLASP:A retainer that encircles a tooth by more than 180°, including opposite angles, and which generally contacts the tooth throughout the extent of the clasp, with at least one terminal located in an undercut area. (GPT 8th Ed)

⭐ TYPES OF CIRCUMFERENTIAL CLASP

• Simple circlet clasp
• Reverse circlet clasp
• Multiple circlet clasp
• Embrasure clasp or modified crib clasp
• Ring clasp
• Fishhook or hairpin clasp
• Onlay clasp
• Combination clasp
• Half and half clasp
• Back action clasp

📌 GINGIVALLY APPROACHING CLASP or BAR CLASP:A clasp retainer whose body extends from a major connector or denture base, passing adjacent to the soft tissues and approaching the tooth from a gingivo-occlusal direction. (GPT 8th Ed)

⭐ TYPES OF GINGIVALLY APPROACHING CLASP/ BAR CLASP

• ‘T’ clasp
• Modified ‘T’ clasp
• ‘Y’ clasp
• ‘I’ clasp

📌 RPI and RPA CONCEPT

✴️ RPI Concept:

• Consists of mesial rest, proximal plate and ‘I’ bar
• also called the self-releasing clasp.

✴️ RPA Concept:

• consists of mesio-occlusal rest, proximal plate and Akers’ clasp

⭐ Commonly Used Direct Retainers for Distal Extension RPDs:

• Kratochvil design (1963)
• Roach design (1934)
• Applegate design (1955)

📌 INDIRECT RETAINER : The component of a removable dental prosthesis that assists the direct retainers in preventing displacement of the distal extension denture base by functioning through lever action on the opposite side of the fulcrum line when the denture base moves away from the tissues in pure rotation around the fulcrum line. (GPT 8th Ed)

⭐ TYPES OF INDIRECT RETAINERS

i) Occlusal rest

ii) Canine rest

iii) Canine extension from the occlusal rest

iv) Lingual plate

v) Modification area

vi) Rugae area

📌 DENTURE BASE: The part of the denture that rests on the
foundation tissues and to which teeth are attached. (GPT 8th Ed)

⭐ METHODS OF REPLACING ANTERIOR TEETH WITH RPD:

• Acrylic teeth
• Porcelain teeth
• Interchangeable facings
• Tube teeth
• Reinforced acrylic pontics (RAPs)

⭐ METHODS OF REPLACING POSTERIOR TEETH WITH RPD

• Acrylic resin
• Porcelain
• Metal tooth
• Metal pontic with acrylic windows
• Tube teeth