**Rest and Rest Seat** **Removable Partial Denture** Dr. Matsubara Dr. Matsubara **LEARNING OUTCOMES** * Discuss the importance of rest and rest seat * Describe the ideal features of rest seats (occlusal, lingual, incisal) * Determine the position of primary and secondary rests  Upon completion of this section, you should be able to: - Discuss the importance of rest and rest seat - Describe the ideal features of rest seats (occlusal, lingual, incisal) - Determine the position of primary and secondary rests Close-up photo of a hand holding a piece of chalk and writing on a green chalkboard. The text 'Learning Outcomes' and bullet points about rest seats are visible in the foreground, indicating an educational context related to dentistry or orthodontics. **The University of Western Australia** **Oral Health Centre of Western Australia** **DEFINITION** **REST:** * Component of a RPD in contact with tooth surface that provides vertical support and transmits occlusal load to abutments. * Rigid structure, * Part of the metallic framework **REST SEAT:** A prepared surface on the abutment to receive the rest The topography of the rest should restore the topography of the tooth before the rest seat preparation    #### Core Definitions - **Rest:** - A component of a Removable Partial Denture (RPD) in contact with the tooth surface. - Provides vertical support and transmits occlusal load to the abutments. - Consists of a rigid structure that is part of the metallic framework. - **Rest Seat:** - A prepared surface on the abutment tooth specifically designed to receive the rest. #### Functional Requirements The topography of the rest should restore the original topography of the tooth as it existed before the rest seat preparation. Clinical photograph showing a close-up of a metallic RPD framework (rest) seated on an abutment tooth. The red circle highlights the specific area where the rest contacts the prepared surface of the tooth. Schematic diagram illustrating a cross-section of a tooth with a prepared rest seat. A yellow outline represents the natural crown shape, while a red wedge-shaped area indicates the prepared space for the rest. Photograph or rendering of a dental cast showing multiple molar teeth, demonstrating the anatomical context of the occlusal surfaces and potential rest seat locations. FUNCTION OF REST **Primary** 1. To provide vertical support (Occluso-gingival direction) 2. To direct and distribute occlusal load to abutment teeth. **Secondary** 3. To maintain components in their positions, helping stabilization and retention: - neutralizing rotational movements 4. To maintain established occlusal relationships 5. To prevent impingement of soft tissues 7. To maintain the correct relationship clasp and abutment 8. To restore occlusal plane discrepancies   #### Primary Functions - Provide vertical support in the occluso-gingival direction. - Direct and distribute occlusal load to the abutment teeth. #### Secondary Functions - Maintain components in their planned positions to assist with stabilization and retention by neutralizing rotational movements. - Maintain established occlusal relationships. - Prevent impingement of soft tissues. - Maintain the correct relationship between the clasp and the abutment tooth. - Restore occlusal plane discrepancies. Clinical intraoral photograph showing a metallic cast partial denture framework (likely a cast clasp assembly) in the oral cavity. The metal structure is seated against the gingiva and tooth structures, demonstrating the physical appearance of a prosthesis component in situ. Schematic diagram illustrating the vertical support function of a rest. It depicts a cross-section with yellow blocks representing teeth and a pink block representing underlying tissue. A silver horizontal bar represents the major connector or denture base resting on the yellow blocks. Red arrows point upwards from the pink area to the interface, indicating the direction of occlusal load being transferred vertically through the rest onto the abutment teeth. **FUNCTION OF REST** <i>The University of Western Australia | Oral Health Centre of Western Australia</i> Directs and distributes occlusal load to abutment teeth * **Axial direction:** the most effective resistance is provided if the tooth is stressed along its long axis, without damaging the abutment **R** **F** Increased blood supply   #### Load Distribution and Axial Resistance Rests are designed to direct and distribute occlusal loads to the abutment teeth. - **Axial Direction:** The most effective resistance is provided when the tooth is stressed along its long axis. This orientation ensures support without damaging the abutment tooth. #### Physiological Effects - Increased blood supply **R** **F** Diagram illustrating the axial direction of occlusal load. It shows four panels: two depicting a crown with red arrows pointing upwards (axial force) and two showing lateral forces causing damage or stress on the abutment tooth structure. Cross-sectional anatomical diagram showing a tooth under occlusal load. Labels include 'R' indicating resistance along the long axis, 'F' indicating the applied force, and 'Increased blood supply' pointing to the periodontal ligament space. # Types of Rest and Rest Seat - **Location:** Occlusal, Lingual (cingulum) and Incisal - **Function:** Direct and Indirect *** **THE UNIVERSITY OF WESTERN AUSTRALIA** **Oral Health Centre** of Western Australia #### Classification of Rests - **Location:** Occlusal, Lingual (cingulum), and Incisal - **Function:** Direct and Indirect **Types of Rest and Rest Seat** Occlusal Rest and Rest Seat * Rounded triangular shape #### Basic Geometry - Rounded triangular shape # **Types of Rest and Rest Seat** ## **Occlusal Rest and Rest Seat** - Rounded triangular shape - Width (B/L) ½ inter-cusp distance   #### Dimensional Guidelines - Rounded triangular shape - Width (B/L): ½ inter-cusp distance Clinical photo of an occlusal rest seat preparation on a posterior tooth. The image shows the prepared occlusal surface with rounded triangular shape markings (purple dots) and visible grooves for retention. A ruler is placed beside the tooth for scale. Schematic diagram illustrating dimensions of an occlusal rest seat. The yellow area represents the occlusal surface, red area is the rest seat, X indicates inter-cusp distance (pink arrows), Y indicates rest width (blue arrows). Formula Y = X/2 shown below. # Types of Rest and Rest Seat ## Occlusal Rest and Rest Seat - Rounded triangular shape - **Width (B/L)** ½ inter-cusp distance - **M/D** equal or larger **B/L** size Z Y W **Z ≥ Y** **Z** = 1/3 **W** to 1/2 **W**  #### Proportional Relationships - Rounded triangular shape - **Width (B/L):** ½ inter-cusp distance - **Mesiodistal (M/D) Length:** Equal to or larger than B/L size **Mathematical Ratios:** - Z ≥ Y - Z = 1/3 W to 1/2 W - (Where Z represents M/D length, Y represents B/L width, and W represents the total width of the tooth) Labelled diagram of an occlusal rest and rest seat on a tooth. The yellow area represents the tooth with a red triangular shape indicating the rest seat. Dimensions are marked: 'W' (blue arrow) for buccolingual width across the tooth, 'Y' (blue arrow) for mesiodistal height of the rest seat, and 'Z' (green arrow) for the length of the rest seat along the occlusal surface. Text below specifies Z = 1/3 W to 1/2 W and Z ≥ Y. **Types of Rest and Rest Seat** **Occlusal Rest and Rest Seat** * Rounded triangular shape * Width (B/L) ½ inter-cusp distance * M/D equal or larger B/L size * Floor concave, rounded   #### Floor Morphology - Rounded triangular shape - Width (B/L): ½ inter-cusp distance - M/D: Equal or larger than B/L size - Floor: Concave and rounded Diagram illustrating an occlusal rest seat design. Shows a spherical object (representing the tooth or opposing surface) resting on a concave, rounded floor within a triangular-shaped structure. Red arrows indicate rotational movement around the contact point, demonstrating how the rounded triangular shape accommodates occlusal forces. Clinical photograph showing a close-up view of a dental restoration with an occlusal rest seat. The image displays a metallic component (likely part of a removable partial denture) seated in a prepared concave area on a natural tooth surface, illustrating the rounded triangular shape and concave floor mentioned in the text. # **Types of Rest and Rest Seat** --- ## Occlusal Rest and Rest Seat - Rounded triangular shape - Width (B/L) ½ inter-cusp distance - M/D equal or larger B/L size - Floor concave, rounded - Slightly inclined apically (less than 90°) --- **The University of Western Australia** | **Oral Health Centre of Western Australia**  #### Angulation - Rounded triangular shape - Width (B/L): ½ inter-cusp distance - M/D: Equal or larger than B/L size - Floor: Concave and rounded - Inclination: Slightly inclined apically (less than 90°) Labeled diagram of an occlusal rest and rest seat on a tooth. The image shows a cross-section of a molar with a red-colored rest seat located in the fossa area. A yellow arrow indicates the direction of force application (occlusal load). A vertical line represents the long axis of the tooth, and a horizontal line at the base of the rest seat indicates the floor of the seat, annotated with an angle symbol to demonstrate the 'slightly inclined apically' characteristic mentioned in the text. **# Types of Rest and Rest Seat** ## Occlusal Rest and Rest Seat * Rounded triangular shape * Width (B/L) ½ inter-cusp distance * M/D equal or larger B/L size * Floor concave, rounded * Slightly inclined apically (less than 90°)  #### Structural Summary - Rounded triangular shape - Width (B/L): ½ inter-cusp distance - M/D: Equal or larger than B/L size - Floor: Concave and rounded - Inclination: Slightly inclined apically (less than 90°) Labeled diagram of an occlusal rest and rest seat on a tooth model. The diagram shows a rounded triangular red rest seat positioned in the occlusal surface of the tooth. Yellow lines indicate dimensions: one vertical line representing the inter-cusp distance, and another horizontal line showing the width (B/L) of the rest seat as half the inter-cusp distance. A yellow arrow points to the floor of the rest seat, which is concave and rounded. Another yellow line indicates the slight apical inclination (less than 90°) of the rest seat. # Types of Rest and Rest Seat THE UNIVERSITY OF WESTERN AUSTRALIA Oral Health Centre of Western Australia Occlusal Rest and Rest Seat * Rounded triangular shape * Width (B/L) ½ inter-cusp distance * M/D equal or larger B/L size * Floor concave, rounded * Slightly inclined apically (less than 90°) * 0.5 mm thick at its point and 1.0 – 1.5 mm marginal ridge 1.0 – 1.5 mm 0.5 mm   #### Material and Clearance Requirements - Rounded triangular shape - Width (B/L): ½ inter-cusp distance - M/D: Equal or larger than B/L size - Floor: Concave and rounded - Inclination: Slightly inclined apically (less than 90°) - **Thickness Specifications:** - 0.5 mm thick at its point - 1.0 – 1.5 mm at the marginal ridge Diagram illustrating an occlusal rest on a tooth. The rest is highlighted in red and positioned on the marginal ridge of the tooth. Green arrows indicate the dimensions or orientation of the rest. Detailed diagram showing the cross-section of an occlusal rest seat. It highlights the thickness measurements: 0.5 mm at the point of the rest and 1.0 – 1.5 mm for the marginal ridge. Arrows and labels clearly indicate these dimensions. # Types of Rest and Rest Seat ## Enamel Thickness <table> <thead> <tr> <th></th> <th>Molar</th> <th colspan="2">Premolar</th> </tr> </thead> <tbody> <tr> <td rowspan="3">Superior</td> <td>1.25</td> <td>1.00</td> <td>1</td> </tr> <tr> <td>1.40</td> <td>1.25</td> <td>2</td> </tr> <tr> <td>1.25</td> <td>1.00</td> <td>3</td> </tr> <tr> <td rowspan="3">Inferior</td> <td>1.25</td> <td>1.10</td> <td>1</td> </tr> <tr> <td>1.50</td> <td>1.25</td> <td>2</td> </tr> <tr> <td>1.28</td> <td>0.80</td> <td>3</td> </tr> </tbody> </table>   #### Average Enamel Measurements (mm) | Arch | Position | Molar | Premolar | | :--- | :--- | :--- | :--- | | **Superior** | 1 | 1.25 | 1.00 | | | 2 | 1.40 | 1.25 | | | 3 | 1.25 | 1.00 | | **Inferior** | 1 | 1.25 | 1.10 | | | 2 | 1.50 | 1.25 | | | 3 | 1.28 | 0.80 | A green-colored table titled 'Enamel Thickness' displaying numerical data for Molar and Premolar teeth. The table is divided into two main sections: 'Superior' and 'Inferior'. Each section has three rows corresponding to positions labeled 1, 2, and 3 in the adjacent diagram. For Superior: Molar values are 1.25 (pos 1), 1.40 (pos 2), 1.25 (pos 3); Premolar values are 1.00 (pos 1), 1.25 (pos 2), 1.00 (pos 3). For Inferior: Molar values are 1.25 (pos 1), 1.50 (pos 2), 1.28 (pos 3); Premolar values are 1.10 (pos 1), 1.25 (pos 2), 0.80 (pos 3). A schematic line drawing on a teal background illustrating tooth enamel thickness measurements at different anatomical locations. Three numbered arrows indicate specific measurement points: Arrow 1 points horizontally outward from the buccal surface; Arrow 2 points vertically upward from the cusp tip; Arrow 3 points downward from the central fossa area. **Types of Rest and Rest Seat** **Enamel Thickness**  Enamel Thickness Enamel Thickness figure showing a dental anatomical illustration. On the left, a tooth with a red rectangular highlight and magnified inset reveals enamel structure; on the right, a cross-sectional view with blue shaded regions and grid lines demonstrates enamel layer thickness variations. # Types of Rest and Rest Seat ## Occlusal Rest and Rest Seat * **Rounded triangular shape** * Width (B/L) ½ inter-cusp distance * M/D equal or larger B/L size * Floor concave, rounded * Slightly inclined apically (less than 90°) * 0.5 mm thick at its point and 1.0 – 1.5 mm marginal ridge * Deepest part of the rest seat close to the long axis  #### Load Distribution - Rounded triangular shape - Width (B/L): ½ inter-cusp distance - M/D: Equal or larger than B/L size - Floor: Concave and rounded - Slightly inclined apically (less than 90°) - 0.5 mm thick at its point and 1.0 – 1.5 mm marginal ridge - **Deepest part of the rest seat:** Located close to the long axis of the tooth Labeled diagram of an occlusal rest seat on a tooth. The image shows a cross-section of a molar with the occlusal surface highlighted in yellow and the prepared rest seat area shaded red. A vertical yellow line indicates the long axis of the tooth, and a black arrow points to the depth of the rest seat preparation. # Types of Rest and Rest Seat ## Occlusal Rest and Rest Seat * **Rounded triangular shape** * **Width (B/L) ½ inter-cusp distance** * **M/D equal or larger B/L size** * **Floor concave, rounded** * **Slightly inclined apically (less than 90°)** * **0.5 mm thick at its point and 1.0 – 1.5 mm marginal ridge** * **Deepest part of the rest seat close to the long axis** * **Normal occlusal contact**   #### Functional Integration - Rounded triangular shape - Width (B/L): ½ inter-cusp distance - M/D: Equal or larger than B/L size - Floor: Concave and rounded - Slightly inclined apically (less than 90°) - 0.5 mm thick at its point and 1.0 – 1.5 mm marginal ridge - Deepest part of the rest seat close to the long axis - **Occlusion:** Maintain normal occlusal contact Diagram illustrating an occlusal rest seat on a tooth. The image shows a gray tooth with a red triangular rest area and a yellow concave floor, demonstrating the rounded triangular shape and dimensions described in the text. Diagram showing another view of an occlusal rest seat on a tooth. The image highlights the red rest area and the yellow floor, emphasizing the slightly inclined apical angle and normal occlusal contact as mentioned in the OCR context. **Types of Rest and Rest Seat** THE UNIVERSITY OF WESTERN AUSTRALIA | Oral Health Centre of Western Australia  Types of Rest and Rest Seat Clinical photograph of dental study models (upper and lower arches) demonstrating 'Types of Rest and Rest Seat'. The image shows teeth with red-colored rest seats prepared on the occlusal surfaces, likely illustrating different designs for removable partial dentures. # Types of Rest and Rest Seat  Clinical photograph of a lower dental cast showing a metal partial denture framework. The image demonstrates various types of rests and rest seats: a cingulum rest on the anterior tooth, an occlusal rest seat on a posterior molar, and minor connector extensions. Purple marking ink is visible in the prepared rest seat areas to highlight the contours. **Types of Rest and Rest Seat** Lingual or Cingulum Rest and Rest Seat • Cingulum of anterior teeth  - Cingulum of anterior teeth Lingual or Cingulum Rest and Rest Seat diagram showing an anterior tooth with a cingulum rest placement indicated by a checkered pattern on the cingulum area of the crown. The diagram illustrates the anatomical location for the lingual rest seat preparation. **Types of Rest and Rest Seat** Lingual or Cingulum Rest and Rest Seat * Cingulum of anterior teeth * Convex M/D  - Cingulum of anterior teeth - Convex Mesial/Distal (M/D) Diagram of a lingual or cingulum rest seat on an anterior tooth. The yellow shape represents the tooth viewed from the mesial-distal aspect, with a red curved area indicating the cingulum rest seat and a blue outline showing the convex M/D surface. **Types of Rest and Rest Seat** Lingual or Cingulum Rest and Rest Seat • Cingulum of anterior teeth • Convex M/D • Concave B/L, V shaped  - Cingulum of anterior teeth - Convex Mesial/Distal (M/D) - Concave Buccal/Lingual (B/L), V-shaped Lingual or Cingulum Rest and Rest Seat diagram showing the anatomy of an anterior tooth. The cingulum is highlighted in red, with a dotted line indicating the convex mesial/distal (M/D) surface and concave buccal/lingual (B/L) V-shaped rest seat. **Types of Rest and Rest Seat** Lingual or Cingulum Rest and Rest Seat * Cingulum of anterior teeth * **Convex** M/D * **Concave** B/L, V shaped * Floor less than 90° ****  - Cingulum of anterior teeth - Convex Mesial/Distal (M/D) - Concave Buccal/Lingual (B/L), V-shaped - Floor less than 90° Labeled diagram of a lingual or cingulum rest seat on an anterior tooth. The illustration shows a cross-section of the tooth with a purple vertical line indicating the long axis and a red concave area representing the V-shaped rest seat. A purple angle marker highlights the floor angle, which is described as less than 90°. Text annotations indicate convex mesial/distal (M/D) and concave buccal/lingual (B/L) surfaces. **Types of Rest and Rest Seat** **THE UNIVERSITY OF WESTERN AUSTRALIA** | **Oral Health Centre of Western Australia** **Lingual or Cingulum Rest and Rest Seat** * Cingulum of anterior teeth * **Convex M/D** * **Concave B/L, V shaped** * Floor less than 90° * Rounded, no sharp line angles * Minimum reduction 0.8 mm * Normal occlusal contact  #### Design Specifications - Cingulum of anterior teeth - Convex Mesial/Distal (M/D) - Concave Buccal/Lingual (B/L), V-shaped - Floor less than 90° - Rounded, no sharp line angles - Minimum reduction 0.8 mm - Normal occlusal contact Clinical intraoral photograph demonstrating a lingual or cingulum rest seat on an anterior tooth. The image shows the prepared cingulum area with a V-shaped concave floor and rounded line angles, consistent with the textual specifications for minimum reduction (0.8 mm) and convex mesial/distal walls. # Types of Rest and Rest Seat ## Lingual or Cingulum Rest and Rest Seat  Diagram illustrating Lingual or Cingulum Rest and Rest Seat types. Left panel shows a tooth with a rest seat where force F is applied at an angle causing potential lateral movement (red arrow). Right panel shows a properly prepared rest seat where force F is directed vertically along the long axis of the tooth (red arrow), demonstrating correct load distribution. # Types of Rest and Rest Seat ## Lingual or Cingulum Rest and Rest Seat  Educational diagram illustrating a Lingual or Cingulum Rest and Rest Seat. The image features a stick figure character labeled 'Rest' sliding down a red slide placed on the lingual surface of a tooth (shown as a white anatomical structure). Another stick figure character is shown near the bottom right, labeled 'Gingiva', representing the gum tissue area.   Clinical photo showing an intraoral view of a maxillary removable partial denture with metal framework. A black circle highlights the lingual cingulum rest on a premolar tooth. Magnified close-up figure (callout from main photo) showing a lingual or cingulum rest seat. A yellow arrow points to the concave metal rest seated within the preparation on the lingual surface of a tooth. **Types of Rest and Rest Seat** Lingual or Cingulum Rest and Rest Seat   Clinical intraoral photograph of the maxillary arch showing a lingual cingulum rest seat prepared on an anterior tooth (likely lateral incisor or canine). The preparation includes a concave depression on the lingual surface with visible margins. Adjacent teeth show existing restorations and caries. Close-up clinical procedure image demonstrating the placement or contouring of a lingual cingulum rest seat using dental instruments (matrix band and explorer or bur). The focus is on the lingual surface of an anterior tooth where the rest seat has been prepared. Types of Rest and Rest Seat Lingual or Cingulum Rest and Rest Seat  Clinical figure illustrating a Lingual or Cingulum Rest and Rest Seat. The left panel shows a close-up clinical photograph of the lingual surface of an anterior tooth with a red box highlighting the cingulum area; a pink arrow points from this region to the right panel. The right panel displays a radiographic view overlaid with a blue line tracing the contour of the rest seat preparation on the cingulum, demonstrating the proper anatomical location and shape for the rest. # Types of Rest and Rest Seat ## Lingual or Cingulum Rest and Rest Seat ### Lingual rest seat in composite   Lingual rest seat in composite Clinical photo showing a lingual or cingulum rest seat in composite on the lingual surface of an anterior tooth. The image displays the prepared tooth structure with the composite material forming the rest seat. Clinical photo showing a lingual or cingulum rest seat in composite on another anterior tooth. This image provides a different angle or view of the same type of dental preparation as the first photo. **Types of Rest and Rest Seat** Lingual or Cingulum Rest and Rest Seat Lingual rest seat in composite  Lingual rest seat in composite Clinical comparison image series demonstrating a lingual or cingulum rest seat in composite. The sequence includes: (left) original tooth anatomy; (center) diagrammatic overlay showing the preparation shape with red reference lines and blue shaded area indicating the rest seat geometry; (right) final clinical view of the prepared tooth. **Types of Rest and Rest Seat** Lingual or Cingulum Rest and Rest Seat Lingual rest seat in composite One single increment Sculpture **The University of Western Australia | Oral Health Centre of Western Australia**    #### Material Application - Lingual rest seat in composite - One single increment Sculpture Clinical photo showing a close-up of a dental restoration (lingual rest seat in composite) being sculpted. The image displays a white dental material being shaped into a curved form against a dark background, illustrating the 'One single increment Sculpture' technique mentioned in the OCR text. Clinical photo showing an intraoral view of teeth with a lingual rest seat in composite material on one tooth. A black outline highlights the cingulum area where the rest is placed. The surrounding gingiva and adjacent teeth are visible, providing context for the procedure. Clinical photo showing a close-up of a metallic instrument interacting with a tooth that has a lingual rest seat in composite. The instrument appears to be used for adjusting or finishing the restoration, demonstrating the final steps of the procedure. # **Types of Rest and Rest Seat** <div style="text-align: right; margin-right: 20px;"> THE UNIVERSITY OF WESTERN AUSTRALIA   |   Oral Health Centre of Western Australia </div> ## **Lingual or Cingulum Rest and Rest Seat** Multiple incisors should receive lingual rest to distribute the stress over a number of teeth  Multiple incisors should receive lingual rest to distribute the stress over a number of teeth. Clinical photo of a dental cast showing a partial denture with lingual rests on multiple anterior teeth. The image demonstrates the distribution of stress over several incisors using lingual or cingulum rests, as referenced in the accompanying text. # Types of Rest and Rest Seat ## Incisal Rest and Rest Seat   Types of Rest and Rest Seat Technical diagrams illustrating the design of an incisal rest and rest seat. The top row shows three line drawings: a flat occlusal view of a tooth with a cut-out for the rest (left), a side profile showing the depth of the preparation (middle), and another occlusal view with the rest shape indicated (right). Below these is a detailed cross-sectional diagram of a tooth showing dimensions labeled '1.5 mm' and '2.5 mm' to indicate the depth and width of the incisal rest seat preparation. Clinical intraoral photograph of a patient's dentition demonstrating multiple metallic rest seats placed on the incisal edges of both upper and lower anterior teeth. The metal components are visible as silver-colored fixtures embedded in the prepared enamel, consistent with the design principles shown in the accompanying diagrams. # Types of Rest and Rest Seat <div style="text-align:center; margin-top:40px;"> <span style="display:inline-block; vertical-align:top; width:250px; font-size:28px; font-weight:bold; margin-right:20px;"> Incisal Rest and Rest Seat <br><br> • Concave M/D<br>• Convex B/L </span> <span style="display:inline-block; vertical-align:top; width:350px; margin-left:20px;"> </span> </div>  #### Structural Contour - Concave Mesio-Distally (M/D) - Convex Buccal-Lingually (B/L) Diagram illustrating an Incisal Rest and Rest Seat. The image contains two panels: the top panel shows a yellow tooth cross-section with a grey incisal rest on the incisal edge, annotated with a vertical midline and an angled line indicating the path of insertion or seat geometry; the bottom panel shows another yellow tooth cross-section with a grey rest structure positioned along the labial surface. **Types of Rest and Rest Seat** Incisal Rest and Rest Seat - Concave M/D - Convex B/L - Floor less than 90° **Oral Health Centre of Western Australia**  #### Structural Contour and Angulation - Concave Mesio-Distally (M/D) - Convex Buccal-Lingually (B/L) - Floor angulation is less than 90° Diagram illustrating an Incisal Rest and Rest Seat. Shows a tooth with a green line representing the long axis of the tooth and a red line indicating the path of insertion or rest seat orientation. The angle between these lines is labeled <90°. The diagram visually supports the text description of 'Concave M/D', 'Convex B/L', and 'Floor less than 90°'. **Types of Rest and Rest Seat** Incisal Rest and Rest Seat **Concave M/D** **Convex B/L** **Floor less than 90°** **From L to B**  #### Preparation Orientation - Concave Mesio-Distally (M/D) - Convex Buccal-Lingually (B/L) - Floor angulation is less than 90° - Orientation from Lingual to Buccal Diagram illustrating an Incisal Rest and Rest Seat. The visual shows a yellow tooth cross-section with a grey rest seat structure positioned on the incisal edge. The diagram demonstrates the specific geometry described in the OCR text: Concave M/D (mesial-distal), Convex B/L (bucco-lingual), Floor less than 90°, and From L to B (labial to buccal). **The University of Western Australia Oral Health Centre of Western Australia** # Types of Rest and Rest Seat ## Incisal Rest and Rest Seat * Concave M/D * Convex B/L * Floor less than 90° * From L to B * Rounded, no sharp angles <img style="pointer-events: none; height: 100px; position: absolute; opacity: 0.9" src="https://example.com/path/to/image.png">   #### Preparation Refinement - Concave Mesio-Distally (M/D) - Convex Buccal-Lingually (B/L) - Floor angulation is less than 90° - Orientation from Lingual to Buccal - Rounded preparation with no sharp angles Schematic diagram illustrating an incisal rest seat. It shows a cross-section of a tooth surface (red hatched block) with a concave depression cut into it, designed to hold a spherical object (representing the rest). The visual demonstrates the 'Concave M/D' and 'Rounded, no sharp angles' properties mentioned in the text. Anatomical diagram showing a yellow tooth structure with a grey incisal rest placed on its edge. This illustrates the 'Convex B/L' curvature required for the rest seat to prevent dislodgement from side-to-side forces. Types of Rest and Rest Seat Incisal Rest and Rest Seat • Concave M/D • Convex B/L • Floor less than 90° • From L to B • Rounded, no sharp angles • 2.5 mm wide and 1.5 mm deep Diamond tapered bur The University of Western Australia | Oral Health Centre of Western Australia   #### Dimensions and Instrumentation - Concave Mesio-Distally (M/D) - Convex Buccal-Lingually (B/L) - Floor angulation is less than 90° - Orientation from Lingual to Buccal - Rounded preparation with no sharp angles - Dimensions: 2.5 mm wide and 1.5 mm deep - Instrument: Diamond tapered bur Labelled diagram of an incisal rest seat on a tooth. The outline shows the anatomical shape with specific dimensions marked: '2.5 mm' for width and '1.5 mm' for depth. Labels indicate orientation (M/D, B/L) and describe the floor angle as less than 90°, rounded edges, and directional flow from L to B. Clinical photo showing a dental procedure in progress. A diamond tapered bur is being used on a tooth within the oral cavity, demonstrating the preparation or shaping process related to the incisal rest seat described in the slide. # Types of Rest and Rest Seat ## Incisal Rest and Rest Seat **Lingual rest > Incisal rest** **Indication:** * Occlusal interference of lingual rest **Disadvantages:** * Aesthetic  Lingual rests are generally preferred over incisal rests. #### Indications - Used when there is occlusal interference with a lingual rest #### Disadvantages - Aesthetic concerns Clinical intraoral photograph demonstrating an incisal rest on a maxillary anterior tooth. The image shows the metal component of a removable partial denture clamping onto the incisal edge of the central incisor. This visual corresponds to the slide's text regarding 'Incisal Rest and Rest Seat' and illustrates the aesthetic disadvantage mentioned. # Types of Rest and Rest Seat ## Incisal Rest and Rest Seat **Lingual rest** > Incisal rest **Indication:** * Occlusal interference of lingual rest **Disadvantages:** * Aesthetic * Unfavorable Biomechanics  Lingual rests are generally preferred over incisal rests. #### Indications - Used when there is occlusal interference with a lingual rest #### Disadvantages - Aesthetic concerns - Unfavorable biomechanics Labeled diagram comparing 'Lingual rest' and 'Incisal rest'. The diagram features two sumo wrestlers leaning against vertical pillars to demonstrate force vectors. The left section depicts a wrestler leaning on the side of a pillar (representing a lingual rest) with an upward red arrow indicating lateral force; this is labeled 'Lingual rest'. The right section shows a wrestler pushing against the front face of a pillar (representing an incisal rest) with a downward red arrow indicating vertical force; this is labeled 'Incisal rest'. A central column illustrates the tooth anatomy. # Types of Rest and Rest Seat THE UNIVERSITY OF WESTERN AUSTRALIA | Oral Health Centre of Western Australia ## Incisal Rest and Rest Seat Lingual rest > Incisal rest **Indication:** * Occlusal interference of lingual rest **Disadvantages:** * Aesthetic * Biomechanical is not favorable * Occlusal interference  Lingual rests are generally preferred over incisal rests. #### Indications - Used when there is occlusal interference with a lingual rest #### Disadvantages - Aesthetic concerns - Biomechanical properties are not favorable - Potential for occlusal interference Clinical intraoral photograph showing an incisal rest on the lingual surface of a maxillary anterior tooth. The image demonstrates the metallic rest seat and its placement relative to adjacent teeth and gingival tissue. **Rest and Rest Seat** Function: Direct and Indirect retention Direct or Primary or Principal Rest • Adjacent or near the edentulous area • Part of the retentive clasp  #### Direct, Primary, or Principal Rests - Located adjacent to or near the edentulous area. - Functions as part of the retentive clasp assembly. Logo figure containing the crest and text for 'THE UNIVERSITY OF WESTERN AUSTRALIA' alongside the logo and text for 'Oral Health Centre of Western Australia'. # Rest and Rest Seat ## Function: Direct and Indirect retention ### Direct or Primary or Principal Rest - Adjacent or near the edentulous area - Part of the retentive clasp ### Indirect or Secondary or Auxiliary Rest - Part of a clasp or just the rest  #### Direct, Primary, or Principal Rests - Located adjacent to or near the edentulous area. - Functions as part of the retentive clasp assembly. #### Indirect, Secondary, or Auxiliary Rests - May be part of a clasp assembly or function as a standalone rest. Two labeled diagrams illustrating dental partial denture frameworks (metal clasps with yellow teeth). The left diagram shows a bilateral framework spanning an edentulous area in the anterior region. The right diagram shows a unilateral framework extending from posterior to anterior on one side. These visuals demonstrate the application of 'Direct or Primary Rest' adjacent to the edentulous area as described in the OCR text. # Rest and Rest Seat (The University of Western Australia | Oral Health Centre of Western Australia) **Function: Direct and Indirect retention** ### **Direct or Primary or Principal Rest** - **Adjacent or near the edentulous area** - **Part of the retentive clasp** ### **Indirect or Secondary or Auxiliary Rest** - **Part of a clasp or just the rest** - **Prevent the rotation of the denture** - **Distant from the fulcrum line**   #### Direct, Primary, or Principal Rests - Located adjacent to or near the edentulous area. - Functions as part of the retentive clasp assembly. #### Indirect, Secondary, or Auxiliary Rests - May be part of a clasp assembly or function as a standalone rest. - Designed to prevent the rotation of the denture. - Positioned distant from the fulcrum line. Diagram of a dental partial denture illustrating the concept of 'Direct or Primary or Principal Rest'. The image shows a metal framework with yellow artificial teeth. A clasp arm is positioned adjacent to the edentulous area (gap), demonstrating that it acts as part of the retentive clasp. Diagram of a dental partial denture illustrating the concept of 'Indirect or Secondary or Auxiliary Rest'. The image shows a metal framework with yellow artificial teeth and a long clasp arm extending away from the gap. This demonstrates how the rest prevents rotation of the denture and is located distant from the fulcrum line. Rest and **Rest Seat** Function: **Direct** and **Indirect** retention **The University of Western Australia** | Oral Health Centre of Western Australia  Function: Direct and Indirect retention Labeled dental diagram illustrating 'Rest and Rest Seat' function for direct and indirect retention. The image shows a partial upper denture with yellow teeth and a gray metal framework. Four red circles highlight specific rest seats on the occlusal surfaces of posterior teeth. Red arrows indicate force vectors or directional forces applied to these rests. Rest and Rest Seat Function: Direct and Indirect retention  Function: Direct and Indirect retention Labeled diagram of a partial denture showing the arch and metal framework. The diagram includes three red circles highlighting specific rest seats on yellow teeth to demonstrate direct and indirect retention. **Function: Direct and Indirect retention**  Function: Direct and Indirect retention Schematic diagram illustrating the 'Rest and Rest Seat' function for direct and indirect retention. The image displays a dental arch with yellow teeth on the left and a grey framework on the right. A red line runs diagonally across the structure, representing a fulcrum or axis of rotation. A blue curved arrow indicates rotational movement around this axis. A thick red arrow points to the specific area of contact between the metal rest and the tooth, highlighting the seat's role in stabilizing the denture against displacement. Rest and Rest Seat Function: Direct and Indirect retention  Function: Direct and Indirect retention Schematic diagram of a dental arch showing yellow teeth and grey framework components. Red arrows indicate force vectors related to 'Direct and Indirect retention' as per the text context. A blue curved arrow indicates rotational movement or displacement. **Rest and Rest Seat** Function: **Direct** and **Indirect** retention  Function: Direct and Indirect retention Labelled diagram of a maxillary removable partial denture. The image shows the metal framework and acrylic base with yellow artificial teeth in place. Red circles highlight specific areas on the posterior teeth where rests or rest seats are located. The diagram visually demonstrates the function of 'Direct and Indirect retention' as stated in the OCR context. **Rest and Rest Seat** Function: **Direct** and **Indirect** retention THE UNIVERSITY OF WESTERN AUSTRALIA | Oral Health Centre of Western Australia  Function: Direct and Indirect retention Labeled diagram of a dental partial denture illustrating the function of rests and rest seats. The image shows a metal framework (grey) with clasps engaging yellow artificial teeth on an arch. A red horizontal line indicates the axis of rotation or occlusal plane, while a large blue circular arrow demonstrates rotational movement. This visual supports the text context regarding 'Rest and Rest Seat' providing 'Direct and Indirect retention'. **Rest and Rest Seat** The University of **Western Australia** | Oral Health Centre of Western Australia Function: **Direct and Indirect retention**  Function: Direct and Indirect retention Labeled diagram of a maxillary partial denture demonstrating 'Rest and Rest Seat' function. The image shows yellow artificial teeth on a grey metal framework with clasps engaging the abutment teeth. A red line indicates the axis of rotation or force vector, while a blue curved arrow illustrates the movement associated with direct and indirect retention as described in the OCR text. **Rest and Rest Seat** **Function: Direct and Indirect retention**  Function: Direct and Indirect retention Diagram of a maxillary removable partial denture illustrating 'Rest and Rest Seat' function for 'Direct and Indirect retention'. The image shows yellow artificial teeth on a grey metal framework with clasps. A red line indicates the axis of rotation (fulcrum line), and a blue curved arrow demonstrates the downward movement of the denture base when dislodged. **Rest and Rest Seat** **Rest Distribution** Intercalated edentulous area - Adjacent to the edentulous area   - Adjacent to the edentulous area Cross-sectional schematic diagram illustrating 'Rest Distribution' in an 'Intercalated edentulous area'. The image shows a blue horizontal bar (representing a denture base) resting on two vertical supports. These supports have yellow tops and pink bases, representing teeth adjacent to the edentulous space (the gap between them). Gold triangles indicate the rest seats transferring force from the denture to the abutment teeth. Occlusal view schematic of a dental arch showing a partial denture framework. Yellow shapes represent remaining natural teeth, while grey metal components show the major connector and rests engaging the tooth surfaces. This visual demonstrates how the prosthesis distributes forces across multiple teeth rather than solely on the edentulous ridge. **Rest and Rest Seat** Rest Distribution Free-end edentulous area • Not immediately adjacent to the saddle.   - Not immediately adjacent to the saddle. Schematic diagram illustrating 'Rest Distribution' in a 'Free-end edentulous area'. The image shows two vertical yellow columns (representing abutment teeth) with silver rest seats at their tops. Above them is a blue bar representing the denture base. The text specifies this configuration applies when the area is 'Not immediately adjacent to the saddle', indicating the force distribution for a distal extension partial denture. Clinical illustration of a maxillary removable partial denture framework. It features yellow artificial teeth and metal components including rests on the posterior abutment teeth. This visual serves as a context example for the 'Rest and Rest Seat' topic discussed in the slide. Rest and Rest Seat Rest Distribution  Visual representation of 'Rest Distribution' showing a horizontal blue bar at the top and six vertical columns below. The columns are divided into two color segments: yellow on top and pink on bottom. The heights of the columns vary, suggesting different values or categories for rest distribution. Rest and Rest Seat **Rest Distribution**  Diagram illustrating 'Rest Distribution' under the topic 'Rest and Rest Seat'. The visual shows a blue horizontal bar representing a reference plane at the top. Below it are six vertical cylindrical structures (representing teeth or rest seats), colored pink at the bottom and yellow at the top, with varying heights relative to the blue bar. Some cylinders have silver caps on top. This appears to be a schematic representation of how rest distribution varies among different dental structures. # Rest and Rest Seat ## Rest Distribution  Bar chart titled 'Rest Distribution' under the section 'Rest and Rest Seat'. The chart displays five vertical bars representing different categories. Each bar is segmented into two colors: a pink lower portion and a yellow upper portion. The first three bars are of equal height, while the fourth and fifth bars are shorter. A blue horizontal bar appears above the main bars, possibly indicating a reference value or total sum. # **Rest and Rest Seat** Rest Distribution The University of Western Australia | Oral Health Centre of Western Australia  Diagram illustrating 'Rest Distribution' in a dental arch context. The image displays a schematic of an upper dental arch composed of rectangular blocks representing teeth arranged in a semi-circular arc. The top and middle sections of the arch are shown as empty dotted outlines, indicating resting positions or gaps. At the anterior (front) region of the arch, two pairs of solid blue rounded squares represent molars or premolars. Each pair consists of one square slightly overlapping another, with a red circle positioned at their interface, likely symbolizing occlusion points, rest seats, or specific contact areas relevant to the 'Rest and Rest Seat' topic. # **Rest and Rest Seat** **Thank you** Thank you [^1]: Original PDF page 1: [[L3 Rest and Rest Seat.pdf#page=1|L3 Rest and Rest Seat, p.1]] [^2]: Original PDF page 2: [[L3 Rest and Rest Seat.pdf#page=2|L3 Rest and Rest Seat, p.2]] [^3]: Original PDF page 3: [[L3 Rest and Rest Seat.pdf#page=3|L3 Rest and Rest Seat, p.3]] [^4]: Original PDF page 4: [[L3 Rest and Rest Seat.pdf#page=4|L3 Rest and Rest Seat, p.4]] [^5]: Original PDF page 5: [[L3 Rest and Rest Seat.pdf#page=5|L3 Rest and Rest Seat, p.5]] [^6]: Original PDF page 6: [[L3 Rest and Rest Seat.pdf#page=6|L3 Rest and Rest Seat, p.6]] [^7]: Original PDF page 7: [[L3 Rest and Rest Seat.pdf#page=7|L3 Rest and Rest Seat, p.7]] [^8]: Original PDF page 8: [[L3 Rest and Rest Seat.pdf#page=8|L3 Rest and Rest Seat, p.8]] [^9]: Original PDF page 9: [[L3 Rest and Rest Seat.pdf#page=9|L3 Rest and Rest Seat, p.9]] [^10]: Original PDF page 10: [[L3 Rest and Rest Seat.pdf#page=10|L3 Rest and Rest Seat, p.10]] [^11]: Original PDF page 11: [[L3 Rest and Rest Seat.pdf#page=11|L3 Rest and Rest Seat, p.11]] [^12]: Original PDF page 12: [[L3 Rest and Rest Seat.pdf#page=12|L3 Rest and Rest Seat, p.12]] [^13]: Original PDF page 13: [[L3 Rest and Rest Seat.pdf#page=13|L3 Rest and Rest Seat, p.13]] [^14]: Original PDF page 14: [[L3 Rest and Rest Seat.pdf#page=14|L3 Rest and Rest Seat, p.14]] [^15]: Original PDF page 15: [[L3 Rest and Rest Seat.pdf#page=15|L3 Rest and Rest Seat, p.15]] [^16]: Original PDF page 16: [[L3 Rest and Rest Seat.pdf#page=16|L3 Rest and Rest Seat, p.16]] [^17]: Original PDF page 17: [[L3 Rest and Rest Seat.pdf#page=17|L3 Rest and Rest Seat, p.17]] [^18]: Original PDF page 18: [[L3 Rest and Rest Seat.pdf#page=18|L3 Rest and Rest Seat, p.18]] [^19]: Original PDF page 19: [[L3 Rest and 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