Recap: RPD Workflow (No audio recording: Was given in person in CSSL) *The University of Western Australia* #### Session Overview Recap: RPD Workflow Note: No audio recording available as this session was delivered in person in the Clinical Dental School Simulation Laboratory (CSSL). Questions: **Why do you place a rest seat on 11 and 21?**  #### Rationale for Anterior Rest Seats Why do you place a rest seat on 11 and 21? Clinical diagram of the maxillary arch showing anatomical structures. Two red lines indicate a specific plane or path across the dental arch, with blue dots marking rest seats on teeth 11 and 21. A yellow curved arrow illustrates rotational movement along the right side of the arch. The image is associated with the question: 'Why do you place a rest seat on 11 and 21?' **Questions:** • Why do we use 17 and 27 as abutment teeth? Do they provide direct retention?  #### Posterior Abutment Selection - Why do we use 17 and 27 as abutment teeth? - Do they provide direct retention? Labeled diagram of the maxillary dental arch showing teeth with blue dots indicating abutment positions. A red horizontal line spans across the occlusal surfaces of teeth 17 and 27, representing an occlusal plane or path of insertion. A yellow curved arrow in the center indicates rotational movement around this axis. The question text at the bottom asks why teeth 17 and 27 are used as abutments and whether they provide direct retention. Questions: Explain this lower RPD design, particularly the placement and function of retentive components  #### Mandibular RPD Design Analysis Explain this lower RPD design, particularly the placement and function of retentive components. Diagram of a lower RPD (Removable Partial Denture) design. The diagram shows the dental arch with several teeth and highlights specific areas in red and blue, indicating retentive components such as clasps and rests. Labels 'M' are visible near the highlighted regions, possibly referring to minor connectors or other structural elements. **Diagnostic models/ preliminary examination** **Stewart’s Clinical REMOVABLE PARTIAL PROSTHODONTICS Fourth Edition** --- **Importance of Diagnostic Treatment Phase** Many failures in removable partial denture treatment can be traced to inadequate diagnosis and incomplete treatment planning. Therefore, a thorough, properly sequenced treatment plan is essential to successful removable partial denture therapy. The formulation of an appropriate treatment plan requires careful evaluation of all pertinent diagnostic data. Information must be obtained from patient interviews, radiographic evaluation, oral examination, **diagnostic mounting of casts**, **preliminary survey and design procedures**, and appropriate consultations with medical and dental specialists. Too often, the design of a removable partial denture is **determined after all other phases of patient treatment have been completed**. This approach generally results in failure. Decisions regarding teeth to be **retained**, **surgical procedures to be employed**, and **restorations to be placed** must be made with the ultimate **design of the prosthesis in mind**. Hence, survey and design procedures must be considered key elements in the diagnostic phase of treatment. **The University of Western Australia** You need to know (FOR EACH TOOTH): • Endodontic prognosis • Periodontal prognosis • Restorative prognosis Surveying of diagnostic models: Once you have done your control phase, which teeth will be present? Control Phase → Secondary Impression: All definitive restorations in place, all guide planes and rest seats are completed Restorative Phase →  #### Importance of Diagnostic Treatment Phase Many failures in removable partial denture (RPD) treatment can be traced to inadequate diagnosis and incomplete treatment planning. A thorough, properly sequenced treatment plan is essential and requires the evaluation of: - Patient interviews - Radiographic evaluation - Oral examination - Diagnostic mounting of casts - Preliminary survey and design procedures - Consultations with medical and dental specialists Decisions regarding teeth to be retained, surgical procedures, and restorations must be made with the ultimate design of the prosthesis in mind. Survey and design procedures are key elements in the diagnostic phase and should not be delayed until other treatments are completed. #### Clinical Assessment Requirements For each tooth, the following must be determined: - Endodontic prognosis - Periodontal prognosis - Restorative prognosis #### Surveying and Workflow 1. **Control Phase**: Determine which teeth will remain after initial treatment. 2. **Surveying**: Perform on diagnostic models following the control phase. 3. **Restorative Phase**: Complete all definitive restorations, guide planes, and rest seats. 4. **Secondary Impression**: Taken once the restorative phase is finalized. A vertical flowchart diagram illustrating the sequence of removable partial denture treatment phases. It consists of two blue downward-pointing arrows connecting three labeled stages: 'Control Phase' at the top, followed by 'Restorative Phase' at the bottom. The diagram visually represents the progression from surveying diagnostic models to secondary impressions. **Kennedy Class I and II** Stewart's Clinical REMOVABLE PARTIAL PROSTHODONTICS Fourth Edition THE UNIVERSITY OF WESTERN AUSTRALIA **I. Kennedy Class I and Class II partially edentulous arches** A. **Direct retention** 1. Retention should not be considered a primary objective of removable partial denture design. The main objectives should be the restoration of function and appearance, the maintenance of comfort, and the preservation of remaining oral structures. 2. Although clasp assemblies are largely responsible for direct retention, they are supplemented by close adaptation of the framework to properly prepared guiding planes on the remaining teeth. Proper extension and adaptation of one or more denture bases also contribute to retention of a removable partial denture. B. **Clasps** 1. The practitioner should use the **simplest clasps** that will satisfy the design objectives. 2. All clasps should have good **stabilizing qualities**, remain passive until activated by functional stresses, and accommodate a minor amount of movement without transmitting torque to the associated abutment teeth. 3. Clasps should be strategically positioned in the arch to achieve the greatest possible control of applied forces. a) A Class I prosthesis usually requires only two clasp assemblies. One clasp assembly should be located on the most posterior tooth on the right side of the arch. The remaining clasp assembly should be located on the most posterior tooth on the left side of the arch (Fig 7-61). (1) If a distobuccal undercut is present, an **infrabulge clasp** (T or ½ T) is preferred (Figs 7-62 and 7-63). **RPIs** (2) If a mesiobuccal undercut is present, a wrought-wire clasp is indicated (Figs 7-64 and 7-65). A **cast circumferential clasp** should not be used. (3) The reciprocal elements must be rigid. These components may be in the form of bracing arms or lingual plating (Figs 7-66 and 7-67). b) A Class II prosthesis should usually have three retentive clasp assemblies (Fig 7-68). (1) The **distal extension side** should be designed with the same considerations as described for a Kennedy Class I arch. (2) The opposite side of the arch should have two retentive clasp arms: one as far posterior and one as far anterior as tooth contours and esthetics permit (Fig 7-69). If a **modification space** is present, it is most convenient to clasp the teeth adjacent to the edentulous space (Fig 7-70). (a) The type of clasp and position of the retentive undercut can be selected for convenience. In most instances, circumferential clasps should be used. (b) Rigidity is required for all reciprocal elements. Reciprocation may be provided via bracing arms or lingual plating. <div style="text-align: center;">Kennedy Class I removable partial denture usually requires only two clasp assemblies. One clasp assembly is located on the most posterior tooth on the right side of the arch (**red arrow**). The remaining clasp assembly is located on the most posterior tooth on the left side of the arch (**white arrow**).</div> --- **Fig 7-61** A Kennedy Class I removable partial denture usually requires only two clasp assemblies. One clasp assembly is located on the most posterior tooth on the right side of the arch (red arrow). The remaining clasp assembly is located on the most posterior tooth on the left side of the arch (white arrow).  #### Direct Retention Principles - Retention is not the primary objective; the main goals are restoration of function/appearance, comfort, and preservation of oral structures. - Direct retention is provided by clasp assemblies, supplemented by: - Close adaptation of the framework to prepared guiding planes. - Proper extension and adaptation of denture bases. #### Clasp Design and Selection - Use the simplest clasps that satisfy design objectives. - Clasps must have good stabilizing qualities, remain passive until activated, and accommodate minor movement without transmitting torque to abutments. - **Kennedy Class I Configuration**: - Usually requires only two clasp assemblies. - Positioned on the most posterior tooth on both the right and left sides of the arch. - If a distobuccal undercut is present: Use an infrabulge clasp (T, ½ T, or RPI). - If a mesiobuccal undercut is present: Use a wrought-wire clasp (do not use a cast circumferential clasp). - Reciprocal elements (bracing arms or lingual plating) must be rigid. - **Kennedy Class II Configuration**: - Usually requires three retentive clasp assemblies. - **Distal extension side**: Designed using the same principles as Class I. - **Opposite side**: Two retentive clasp arms—one as far posterior and one as far anterior as possible. - If a modification space exists, clasp the teeth adjacent to the space. - Circumferential clasps are typically used for convenience on the non-extension side. - All reciprocal elements must be rigid. Clinical photo of a Kennedy Class I removable partial denture on an upper cast. The image demonstrates the placement of two clasp assemblies as described in the text: one on the most posterior tooth on the right side (indicated by a red arrow) and one on the most posterior tooth on the left side (indicated by a white arrow). **Stewart’s Clinical REMOVABLE PARTIAL PROSTHODONTICS Fourth Edition** **The University of Western Australia** **Kennedy Class I and II** **Not for free end edentulous area** **C. Rests** 1. Abutments should be selected to provide maximum support for a prosthesis. 2. Rest seats should be prepared so that forces will be directed within the long axes of the abutments. 3. In most instances, rests should be placed adjacent to the edentulous space(s). **D. Indirect retention** 1. Indirect retention should be employed to neutralize unseating forces. a) Each indirect retainer should be **located as far from the fulcrum line as is practical**. Indirect retainers should not be placed more anterior than the canines. b) **Two indirect retainers should generally be used in a Class I design**, whereas **one indirect retainer is generally adequate in a Class II design**. The indirect retainer in a Class II design should be located on the side **opposite** the distal extension base (Fig 7-71). c) Indirect retainers should direct forces within the long axes of the associated teeth. 2. **Lingual plating may be used to augment indirect retention**. It is important to remember that lingual plating must be supported by appropriate **rest–rest seat combinations**. **E. Major connectors** 1. The practitioner should select the simplest connector that will accomplish treatment objectives. a) **The major connector must be rigid.** b) The major connector must not impinge on gingival tissues. 2. In the maxillary arch, a broad major connector may be used to derive additional support from the hard palate. The greater the palatal coverage, the greater the support that may be derived. **F. Minor connectors** 1. Minor connectors must be rigid. 2. Minor connectors should be positioned to enhance comfort, cleanliness, and the placement of artificial teeth. **Fig 7-68** *A Kennedy Class II removable partial denture should have three clasp assemblies. One of these should be located adjacent to the distal extension area (red arrow). The remaining clasp assemblies should be located on the opposite side of the arch and should be positioned with regard to structural and esthetic considerations (white arrows).*  #### Rests and Support - Select abutments to provide maximum support. - Prepare rest seats to direct forces within the long axes of the abutments. - Rests should generally be placed adjacent to edentulous spaces (not for free-end edentulous areas). #### Indirect Retention - Used to neutralize unseating forces. - **Placement**: Located as far from the fulcrum line as practical (not more anterior than the canines). - **Class I Design**: Generally requires two indirect retainers. - **Class II Design**: Generally requires one indirect retainer, located on the side opposite the distal extension base. - **Lingual Plating**: May augment indirect retention but must be supported by appropriate rest–rest seat combinations. #### Connectors - **Major Connectors**: - Must be rigid and not impinge on gingival tissues. - Maxillary arch: Broad connectors can derive additional support from the hard palate. - **Minor Connectors**: - Must be rigid. - Positioned for comfort, cleanliness, and ease of artificial tooth placement. Clinical photograph of a maxillary cast showing a Kennedy Class II removable partial denture. The image includes red and white arrows pointing to specific clasp assemblies on the prosthesis, illustrating their placement relative to the edentulous area. **Kennedy Class I and II** **Stewart's Clinical REMOVABLE PARTIAL PROSTHODONTICS Fourth Edition** **THE UNIVERSITY OF WESTERN AUSTRALIA** G. Occlusion 1. If possible, maximum intercuspation should coincide with centric relation. 2. A harmonious occlusion should be established. All eccentric movements should be dictated by, or occur in harmony with, the remaining natural teeth. 3. Prosthetic teeth should be selected and positioned to minimize stresses on the prosthesis. a) The practitioner may choose to place fewer teeth and/or teeth that are narrower buccolingually. b) Prosthetic teeth should be placed over the crest of the residual ridge when possible. c) Prosthetic teeth should display sharp cutting edges and ample escapeways. H. Denture bases 1. Denture bases should be designed to provide broad coverage. This permits the distribution of forces over a greater area and minimizes the probability of stress concentration. a) Border extensions must not interfere with functional movements of the surrounding tissues. b) Selective pressure impressions are recommended for extension base areas of Kennedy Class I and Class II arches. 2. The external (ie, cameo) surfaces of a denture base should enable the patient to exercise maximum neuromuscular control. #### Occlusion - Maximum intercuspation should coincide with centric relation if possible. - Establish harmonious occlusion where eccentric movements are dictated by or in harmony with natural teeth. - **Prosthetic Tooth Selection**: - Use fewer or narrower teeth (buccolingually) to minimize stress. - Place teeth over the crest of the residual ridge. - Ensure sharp cutting edges and ample escapeways. #### Denture Bases - **Coverage**: Provide broad coverage to distribute forces and minimize stress concentration. - **Extensions**: Borders must not interfere with functional tissue movements. - **Impressions**: Selective pressure impressions are recommended for extension base areas. - **Cameo Surfaces**: External surfaces should enable maximum neuromuscular control. Kennedy Class III **Stewart’s Clinical** **REMOVABLE PARTIAL** **PROSTHODONTICS** Fourth Edition THE UNIVERSITY OF WESTERN AUSTRALIA **II. Kennedy Class III partially edentulous arches** A. Direct retention 1. Because these prostheses are entirely tooth borne, the trasmission of harmful forces to the abutment teeth and residual ridges can be minimized. 2. Positions of the retentive undercuts on individual abutment teeth are not critical. B. Clasps 1. **Quadrilateral positioning of direct retainers** is considered ideal (Fig 7-72). 2. Tooth contours, soft tissue contours, and esthetics should be considered, and **the simplest possible clasps should be selected.** In most instances, simple circlet clasps are chosen. 3. Reciprocals should be rigid. C. Rests 1. When possible, rests and/or rest seats should be positioned adjacent to the edentulous space(s). 2. Rests should be used to support major connectors and lingual plating. Fig 7-72 In a Kennedy Class III application, four clasp assemblies (arrows) are considered ideal.  #### Direct Retention and Clasps - Class III prostheses are entirely tooth-borne, minimizing harmful forces to abutments and ridges. - Undercut positions on individual abutments are not critical. - **Quadrilateral Positioning**: Four direct retainers are considered ideal. - **Clasp Selection**: Use the simplest possible clasps (usually simple circlet/circumferential clasps). - Reciprocals must be rigid. #### Rests - Position rests and rest seats adjacent to edentulous spaces when possible. - Use rests to support major connectors and lingual plating. Clinical photograph of a dental cast showing a maxillary arch with four red arrows pointing to the locations of clasp assemblies on abutment teeth. The caption below reads: 'Fig 7-72 In a Kennedy Class III application, four clasp assemblies (arrows) are considered ideal.' Kennedy Class III Stewart's Clinical REMOVABLE PARTIAL PROSTHODONTICS Fourth Edition THE UNIVERSITY OF WESTERN AUSTRALIA **D. Indirect retention** 1. Indirect retention is usually not required in Kennedy Class III applications. 2. In many instances, Kennedy Class III arches display bilateral tooth loss (ie, Kennedy Class III, Modification 1). If one or both of the posterior abutments are used solely for vertical support and not for retention, the entire design must satisfy the requirements described for Kennedy Class I or Class II arches. **E. Major and minor connectors** 1. Major and minor connectors must be rigid and must meet the same requirements described for Kennedy Class I and Class II arches. **F. Occlusion** 1. The requirements for occlusion are the same as for Kennedy Class I and Class II arches. **G. Denture bases** 1. Functional impressions are not required. Because these prostheses are entirely tooth borne, anatomic impressions are indicated. 2. Coverage of the residual ridge areas should be determined by appearance, comfort, and the avoidance of food impaction. #### Indirect Retention - Usually not required for Kennedy Class III applications. - **Exception**: In bilateral tooth loss (Class III, Mod 1), if posterior abutments are used only for vertical support (not retention), the design must follow Class I or Class II requirements. #### Connectors and Occlusion - **Connectors**: Major and minor connectors must be rigid and meet the same requirements as Class I and II designs. - **Occlusion**: Requirements are identical to those for Kennedy Class I and II arches. #### Denture Bases - **Impressions**: Functional impressions are not required; anatomic impressions are indicated as the prosthesis is tooth-borne. - **Coverage**: Determined by appearance, comfort, and the avoidance of food impaction. **Kennedy Class IV** Stewart's Clinical REMOVABLE PARTIAL PROSTHODONTICS Fourth Edition **III. Kennedy Class IV partially edentulous arches** A. The movements of removable partial dentures fabricated for Kennedy Class IV arches and the stresses trasmitted to the associated abutment teeth are unlike those seen in Kennedy Class I, Class II, and Class III applications. B. The arrangement of presthetic teeth to satisfy esthic and phonetic requirements may place these teeth anterior to the ridge crest. This may result in "tipping" of the prosthesis and application of rotational forces to the associated abutments. Every effort should be made to minimize these stresses. To accomplish this, the following guidelines should be observed. 1. Every effort should be made to preserve the hard and soft tissue components of the anterior edentulous ridge. 2. If possible, a central incisor or other tooth should be retained to serve as an intermediate abutment or as an overdenture abutment. Rotation of the prosthesis can be minimized by retaining serviceable teeth. This may serve to minimize harmful forces. 3. A quadrilateral configuration of direct retainers is considered ideal (Fig 7-73). For mechanical purposes, the anterior clasp as-semblies should be placed as far anterior as possible,** and the posterior clasp assemblies should be placed as far posterior as possible. C. The major connector should be rigid,** and broad palatal coverage should be used in the maxillary arch. D. **Indirect retention** should be located as far posterior to the fulcrum line as possible. 1. An ideal quadrilateral configuration of clasp**ing may preclude the need for additional indirect retainers. E. A functional impression may be indicated if the edentulous area is extensive.  #### Biomechanical Considerations - Stresses in Class IV arches differ from Class I, II, and III. - Anterior placement of prosthetic teeth for esthetics/phonetics can cause "tipping" and rotational forces. - **Guidelines to Minimize Stress**: 1. Preserve hard and soft tissue of the anterior edentulous ridge. 2. Retain teeth (e.g., central incisors) to serve as intermediate or overdenture abutments to minimize rotation. #### Design Principles - **Direct Retention**: A quadrilateral configuration is ideal. - Anterior clasp assemblies: Place as far anterior as possible. - Posterior clasp assemblies: Place as far posterior as possible. - **Major Connector**: Must be rigid; broad palatal coverage is preferred for the maxillary arch. - **Indirect Retention**: Should be located as far posterior to the fulcrum line as possible. - An ideal quadrilateral clasp configuration may eliminate the need for additional indirect retainers. - **Impressions**: A functional impression may be indicated if the edentulous area is extensive. Clinical photograph of a maxillary (upper) dental cast demonstrating the placement of direct retainers for a Kennedy Class IV removable partial denture. The image shows four red arrows pointing to clasp assemblies: two anteriorly placed on the canine/first premolar region and two posteriorly placed on the molar region, illustrating the ideal quadrilateral configuration described in the text. RPI Clamps    RPI Clamps Labelled diagram of a dental clasp assembly (labeled A). The image shows a posterior tooth with a metal framework engaging the undercut. It demonstrates the mechanical setup for an RPI or similar clasp design. Labelled diagram showing the three components of a mesial rest clasp assembly: Support (rest), Stabilization (proximal plate), and Retention (retentive arm). A circle highlights the area of engagement on the tooth. Close-up view (labeled E) of the retentive arm engaging the buccal undercut of a tooth. An arrow labeled 'Buccal' indicates the direction of force or movement. Questions: Stewart’s Clinical **REMOVABLE PARTIAL** **PROSTHODONTICS** Fourth Edition THE UNIVERSITY **WESTERN AUSTRALIA** Located at end of lever arm Rest seat (away from edentulous area) Very poor stability Although indirect retention is not as critical in a Class II arch as in a Class I arch, it is still required. If there is a modification space on the tooth-supported side of the arch, abutment teeth on both sides of the space should be rested. The fulcrum line will run through the most posterior abutment on the tooth-supported side and the terminal abutment on the distal extension side (Fig 4-41). The most anterior abutment on the tooth-supported side, with its rest and clasp assembly, may be located far enough anterior to the fulcrum line to serve as the indirect retainer. However, a definite rest seat positioned farther anteriorly may increase the effectiveness of indirect retention (Fig 4-42). If there is no modification space on the tooth-supported side of the arch, the practitioner should identify the most posterior tooth with favorable contours for clasping (Fig 4-43). This places the fulcrum line in a posterior position and allows the indirect retainer to be positioned farther from this axis of rotation. To develop a desirable clasping configuration, a third abutment should be located on the tooth-supported side as far anteriorly as is practical. The chosen abutment must display suitable contours for clasping, and the resultant clasp assembly should not interfere with esthetics. This clasp assembly may serve as the indirect retainer if it is located far enough anterior to the fulcrum line. • Why do you place a rest seat on 11 and 21?  #### Indirect Retention in Class II Arches Although indirect retention is not as critical in a Class II arch as in a Class I arch, it is still required. If there is a modification space on the tooth-supported side of the arch, abutment teeth on both sides of the space should be rested. - **Fulcrum Line Dynamics**: The fulcrum line will run through the most posterior abutment on the tooth-supported side and the terminal abutment on the distal extension side. - **Indirect Retainer Placement**: The most anterior abutment on the tooth-supported side, with its rest and clasp assembly, may be located far enough anterior to the fulcrum line to serve as the indirect retainer. However, a definite rest seat positioned farther anteriorly may increase the effectiveness of indirect retention. #### Arches Without Modification Spaces If there is no modification space on the tooth-supported side of the arch, the practitioner should identify the most posterior tooth with favorable contours for clasping. - **Axis of Rotation**: This places the fulcrum line in a posterior position and allows the indirect retainer to be positioned farther from this axis of rotation. - **Abutment Selection**: To develop a desirable clasping configuration, a third abutment should be located on the tooth-supported side as far anteriorly as is practical. - **Criteria**: The chosen abutment must display suitable contours for clasping, and the resultant clasp assembly should not interfere with esthetics. This clasp assembly may serve as the indirect retainer if it is located far enough anterior to the fulcrum line. #### Design Considerations - **Lever Arm**: Located at end of lever arm. - **Rest Seat**: Positioned away from edentulous area. - **Stability**: Very poor stability. #### Review Questions - Why do you place a rest seat on 11 and 21? Annotated diagram of a maxillary dental arch demonstrating indirect retention principles. The image displays a pink gum line with white teeth on the left side and edentulous space on the right. Red diagonal lines form a fulcrum line running through the posterior abutment (labeled 'Located at end of lever arm') and terminal abutment. Blue shaded areas on specific teeth indicate rest seats positioned away from the edentulous area. A yellow curved arrow indicates rotational movement around the fulcrum, labeled 'Very poor stability' to the left. Questions: <br> **ed** **sp** <br> **Fig 7-73** Four clasp assemblies (**arrows**) should be used in Kennedy Class IV applications. Two clasp assemblies should be placed as far anterior as possible. The remaining clasp assemblies should be placed as far posterior as possible. <br> * Why do we use 17 and 27 as abutment teeth? Do they provide direct retention?   #### Kennedy Class IV Applications Four clasp assemblies should be used in Kennedy Class IV applications. - **Anterior Placement**: Two clasp assemblies should be placed as far anterior as possible. - **Posterior Placement**: The remaining clasp assemblies should be placed as far posterior as possible. #### Review Questions - Why do we use 17 and 27 as abutment teeth? - Do they provide direct retention? Labeled diagram of a maxillary occlusal view showing the dental arch. A red horizontal line is drawn across the palate indicating an axis of rotation. Blue dots mark abutment teeth (17 and 27). A yellow curved arrow indicates rotational movement around this axis. Clinical photograph of a maxillary cast showing four clasp assemblies indicated by red arrows. The caption states these are used in Kennedy Class IV applications, with two placed anteriorly and two posteriorly. # Questions: **Kennedy Classification** **How many clasps?** **What do we do for free-end saddle?** **Major connector?** <img>Diagram showing a lower removable partial denture design** **Combination clasp** A retentive clasp arm made of wrought wire can flex more readily in all directions than can the cast half-round clasp arm. Thereby, it may more effectively dissipate those stresses that would otherwise be transmitted to the abutment tooth. Only the retentive arm of the circumferential clasp, however, should be made of wrought metal. Reciprocation and stabilization against lateral and torquing movements must be obtained through use of the rigid cast elements that make up the remainder of the clasp. This is called a combination clasp because it is a combination of cast and wrought materials incorporated into one direct retainer. It is frequently used on the terminal abutment for the distal extension partial denture and indicated where a mesiobuccal but no distobuccal undercut exists, or where a gross tissue undercut, cervical and buccal to the abutment tooth, exists. * Explain this lower RPD design, particularly the placement and function of retentive components  #### Combination Clasp Mechanics A retentive clasp arm made of wrought wire can flex more readily in all directions than can the cast half-round clasp arm. Thereby, it may more effectively dissipate those stresses that would otherwise be transmitted to the abutment tooth. #### Structural Components Only the retentive arm of the circumferential clasp should be made of wrought metal. Reciprocation and stabilization against lateral and torquing movements must be obtained through use of the rigid cast elements that make up the remainder of the clasp. This is called a combination clasp because it is a combination of cast and wrought materials incorporated into one direct retainer. #### Indications for Use - Frequently used on the terminal abutment for the distal extension partial denture. - Indicated where a mesiobuccal but no distobuccal undercut exists. - Indicated where a gross tissue undercut, cervical and buccal to the abutment tooth, exists. #### Design Analysis Questions - **Kennedy Classification** - **How many clasps?** - **What do we do for free-end saddle?** - **Major connector?** - **Explain this lower RPD design, particularly the placement and function of retentive components.** Labelled diagram of a lower removable partial denture (RPD) design. The image displays the dental arch with several teeth and shows the placement of retentive components on the abutment teeth. Specifically, it illustrates a combination clasp on the right side (mesiobuccal undercut) and another retentive component on the left side. The major connector is visible in the center. **Figure 13-23** Kennedy Class II, modification 1_, where the molar abutment has a guarded prognosis. **A**, Anterior abutment of the modification space has a clasp assembly that accommodates for potential future loss of the distal molar while currently providing adequate support, stability, and retention. **B**, Premolar clasp assembly comprises a mesial rest, a distal guide plane, and a wrought-wire retainer design, which will accommodate future distal extension movement. **C**, Buccal view shows guide-plane contact and a wrought-wire location that is appropriate for a distal extension. **Questions:** • Explain this lower RPD design, particularly the placement and function of retentive components **McCracken's** **Removable Partial Prosthodontics** * **A** * **B** * **C** THE UNIVERSITY OF WESTERN AUSTRALIA    #### Kennedy Class II, Modification 1 Design This design addresses a molar abutment with a guarded prognosis. - **Anterior Abutment (Modification Space)**: Features a clasp assembly that accommodates for potential future loss of the distal molar while currently providing adequate support, stability, and retention. - **Premolar Clasp Assembly**: Comprises a mesial rest, a distal guide plane, and a wrought-wire retainer design. This configuration is intended to accommodate future distal extension movement. - **Buccal View Considerations**: Shows guide-plane contact and a wrought-wire location that is appropriate for a distal extension. #### Review Questions - Explain this lower RPD design, particularly the placement and function of retentive components. Schematic diagram of a lower removable partial denture (RPD) framework. The illustration shows the arrangement of abutment teeth with clasp assemblies and the major connector spanning the edentulous span. Specific areas are highlighted in red and blue to denote different components or zones relevant to the design. Clinical photograph labeled 'B' showing an occlusal view of a dental cast with a metal retainer assembly on the premolar region. The image demonstrates the placement of the mesial rest, distal guide plane, and wrought-wire retainer design mentioned in the caption. Clinical photograph labeled 'C' showing a buccal view of the same dental cast. This perspective highlights the guide-plane contact between the tooth and the prosthesis, as well as the location of the wrought-wire component appropriate for a distal extension. **How would you design this?** A case series on the basic concept and design of removable partial dentures: support and bracing considerations Jun Takebe  How would you design this? A case series on the basic concept and design of removable partial dentures: support and bracing considerations Clinical photograph of a lower cast demonstrating the design of a removable partial denture. The image shows the metal framework and clasps (retainers) seated on the posterior teeth, with the anterior portion showing the acrylic base. The label 'a' is positioned above the image. # How would you design this? The mandibular major connector was designed as a lingual plate, with rest proximal plate I bar (RPI) clasps as direct retainers on the right side of the mandibular first premolar and left side of the mandibular second premolar as abutment teeth (Fig. 1a, c). A rest was also applied to the left first premolar as an indirect retainer (Fig. 1a, c). A case series on the basic concept and design of removable partial dentures: support and bracing considerations Jun Takebe    #### Mandibular Major Connector and Direct Retainers The mandibular major connector was designed as a lingual plate. Direct retainers utilized were Rest Proximal plate I-bar (RPI) clasps on the following abutment teeth: - Right mandibular first premolar - Left mandibular second premolar #### Indirect Retention A rest was applied to the left first premolar to serve as an indirect retainer. Clinical photo (labeled 'a') showing a mandibular dental cast with the lingual plate major connector and RPI clasp assembly on the right side. The metal framework is visible over the ridge. Clinical photo (labeled 'b') showing a removable partial denture frame from an occlusal view, displaying the metal construction of the major connector and clasps. Clinical photo (labeled 'c') showing a mandibular dental cast with the complete removable partial denture in place. The lingual plate and clasps are visible on both sides of the arch, demonstrating the full design including the indirect retainer on the left first premolar. <sub>a</sub> How would you design this? **A case series on the basic concept and design of removable partial dentures: support and bracing considerations** Jun Takebe  How would you design this? A case series on the basic concept and design of removable partial dentures: support and bracing considerations Clinical photograph of a lower dental cast (mandibular arch) showing teeth and the alveolar ridge. The image includes handwritten markings on the model and is labeled with the letter 'a' above it, as part of a case series on removable partial denture design. # **How would you design this?** ## A case series on the basic concept and design of removable partial dentures: support and bracing considerations Jun Takebe The completed final denture was a lingual plate major connector made of resin material, wrought wire clasps of the right lateral incisor, double Akers clasps of the left first and second premolars as direct retainers, and embrasure hooks of the left canine as indirect retainers.    #### Final Denture Components The completed final denture featured the following components: - **Major Connector**: Lingual plate made of resin material. - **Direct Retainers**: - Wrought wire clasps on the right lateral incisor. - Double Akers clasps on the left first and second premolars. - **Indirect Retainers**: Embrasure hooks on the left canine. Clinical photo (labeled 'a') showing a maxillary cast with a resin lingual plate major connector. The image demonstrates the support structure for the removable partial denture. Photo (labeled 'b') of the completed acrylic denture base showing metal clasps on the left side and an embrasure hook on the right lateral incisor area. Intraoral clinical photo (labeled 'c') showing the final denture in place, demonstrating wrought wire clasps on the right lateral incisor and double Akers clasps on the left premolars. How would you design this? <a>Dental cast showing removable partial denture design with occlusal rests and broad base coverage</a> A case series on the basic concept and design of removable partial dentures: support and bracing considerations Jun Takebe  How would you design this? Dental cast showing removable partial denture design with occlusal rests and broad base coverage. Clinical photograph of a lower dental cast showing the design for a removable partial denture. Visible features include occlusal rests on remaining teeth and broad base coverage on the edentulous ridge. Two yellow rectangular areas obscure specific details or branding information. **How would you design this?** A case series on the basic concept and design of removable partial dentures: support and bracing considerations Jun Takebe The mandibular major connector was designed as a Kennedy bar, and retentive arms were intended for the right second and first premolars as direct retainers. Furthermore, retentive arms were designed for the right canine as indirect retainers.  #### Major Connector and Retentive Elements - **Major Connector**: Designed as a Kennedy bar. - **Direct Retainers**: Retentive arms intended for the right first and second premolars. - **Indirect Retainers**: Retentive arms designed for the right canine. Composite figure demonstrating the design of a removable partial denture in three stages: (a) a master cast showing the prepared tooth anatomy with occlusal coverage and yellow rectangular overlays indicating the major connector area; (b) the laboratory view of the finished prosthesis featuring a Kennedy bar major connector and retentive arms engaging the right second and first premolars; and (c) an intraoral clinical photograph displaying the appliance seated on the mandibular arch. How would you design this? A case series on the basic concept and design of removable partial dentures: support and bracing considerations Jun Takebe  How would you design this? Clinical photograph labeled 'a' showing an upper cast of a maxillary arch with missing teeth. The image is relevant to the case series on removable partial denture design, illustrating support and bracing considerations. **How would you design this?** The maxillary major connector was designed as a palatal plate, with RPI clasps having cingulum rests on the canines as direct retainers on both sides. These clasps were installed to provide frictional retention on the lingual and distal axial surfaces of the abutment teeth. A case series on the basic concept and design of removable partial dentures: support and bracing considerations Jun Takebe    #### Major Connector and RPI Clasp Design The maxillary major connector was designed as a palatal plate. Direct retainers consisted of RPI clasps with cingulum rests on the canines of both sides. These clasps were installed to provide frictional retention on the lingual and distal axial surfaces of the abutment teeth. Clinical photo (labeled 'a') showing an occlusal view of a maxillary cast. It displays the dental arch with natural teeth and red markings on the buccal shelf areas indicating the extension for a major connector. Clinical photo (labeled 'b') displaying a metal framework component against a blue background. This is the palatal plate design featuring RPI clasps and cingulum rests on the canines, as described in the OCR text. Clinical photo (labeled 'c') showing the final removable partial denture seated in a patient's mouth. The image demonstrates the fit of the palatal plate and the retention provided by the clasps on the abutment teeth.  Clinical photo of a maxillary dental cast (study model) showing the upper jaw anatomy. The image displays two anterior teeth at the top and several posterior teeth along the right side. A distinct black rectangular defect or missing tooth area is visible in the central region of the palate. The image is labeled with the letter 'a' above it and serves as an example for designing a removable partial denture. # How would you design this? The maxillary major connector was designed as a palatal plate and was used to continuously extend to come into contact with the axial surface of the residual tooth. Cingulum rests for the left central and lateral incisors as direct retainers, Akers clasp with cingulum rest for the left canine as indirect retainer, Akers clasp with occlusal rest for the distal second premolar as indirect retainer, and double Akers clasps with occlusal rests for the distal first molar and mesial second molar as indirect retainers were installed. --- **A case series on the basic concept and design of removable partial dentures: support and bracing considerations** Jun Takebe    #### Major Connector and Tooth Contact The maxillary major connector was designed as a palatal plate, extending continuously to come into contact with the axial surface of the residual teeth. #### Retainer and Rest Specifications - **Direct Retainers**: Cingulum rests for the left central and lateral incisors. - **Indirect Retainers**: - Akers clasp with cingulum rest for the left canine. - Akers clasp with occlusal rest for the distal second premolar. - Double Akers clasps with occlusal rests for the distal first molar and mesial second molar. Clinical photo of a maxillary cast showing the design layout for a removable partial denture. The image displays an acrylic base with artificial teeth and metal framework components (clasp arms) extending towards the residual ridge area. Close-up clinical photo of the fabricated metal framework component (palatal plate). It shows the polished metal structure designed to extend continuously to contact the axial surface of the residual tooth, along with the clasp assembly on the left side. Intraoral clinical photo demonstrating the installed removable partial denture in the patient's mouth. Visible features include the palatal plate major connector, cingulum rests on the anterior incisors, and Akers clasps on the posterior abutment teeth as described in the text. **How would you design this?** Denture will end at 6s A case series on the basic concept and design of removable partial dentures: support and bracing considerations Jun Takebe  How would you design this? Denture will end at 6s. Clinical photograph of a maxillary dental cast showing an edentulous arch with remaining teeth. The image is labeled 'a' at the top. Visible anatomical features include the residual ridge and specific remaining teeth: a molar on the left side and a cluster of posterior teeth (molars/premolars) on the right side. A text annotation to the right states 'Denture will end at 6s', indicating the distal termination point for the prosthesis design. How would you design this? **A case series on the basic concept and design of removable partial dentures: support and bracing considerations** Jun Takebe The maxillary major connector was designed as a palatal plate, with Akers clasps for the right molars as direct retainers, a cingulum rest for the left canine as a direct retainer, and Akers clasp for the left first premolar as an indirect retainer and that for the first molar as a direct retainer    #### Maxillary Design Specifications - **Major Connector**: Palatal plate. - **Direct Retainers**: - Akers clasps for the right molars. - Cingulum rest for the left canine. - Akers clasp for the first molar. - **Indirect Retainer**: Akers clasp for the left first premolar. Clinical photograph (labeled 'a') showing the occlusal view of a maxillary cast with a removable partial denture framework. The image displays the palatal plate major connector and metal clasps engaging the right molar teeth. Clinical photograph (labeled 'b') showing the buccal/labial view of the removable partial denture prosthesis on a model. It highlights the pink acrylic base, artificial teeth, and the metal framework including Akers clasps on the left side. Clinical photograph (labeled 'c') showing the intraoral fit of the finished removable partial denture in a patient's mouth. The appliance is seated against the natural dentition, demonstrating the coverage and retainer placement. [^1]: Original PDF page 1: [[L10 RPD guide.pdf#page=1|L10 RPD guide, p.1]] [^2]: Original PDF page 2: [[L10 RPD guide.pdf#page=2|L10 RPD guide, p.2]] [^3]: Original PDF page 3: [[L10 RPD guide.pdf#page=3|L10 RPD guide, p.3]] [^4]: Original PDF page 4: [[L10 RPD guide.pdf#page=4|L10 RPD guide, p.4]] [^5]: Original PDF page 5: [[L10 RPD guide.pdf#page=5|L10 RPD guide, p.5]] [^6]: Original PDF page 6: [[L10 RPD guide.pdf#page=6|L10 RPD guide, p.6]] [^7]: Original PDF page 7: [[L10 RPD guide.pdf#page=7|L10 RPD guide, p.7]] [^8]: Original PDF page 8: [[L10 RPD guide.pdf#page=8|L10 RPD guide, p.8]] [^9]: Original PDF page 9: [[L10 RPD guide.pdf#page=9|L10 RPD guide, p.9]] [^10]: Original PDF page 10: [[L10 RPD guide.pdf#page=10|L10 RPD guide, p.10]] [^11]: Original PDF page 11: [[L10 RPD guide.pdf#page=11|L10 RPD guide, p.11]] [^12]: Original PDF page 12: [[L10 RPD guide.pdf#page=12|L10 RPD guide, p.12]] [^13]: Original PDF page 13: [[L10 RPD guide.pdf#page=13|L10 RPD guide, p.13]] [^14]: Original PDF page 14: [[L10 RPD guide.pdf#page=14|L10 RPD guide, p.14]] [^15]: Original PDF page 15: [[L10 RPD guide.pdf#page=15|L10 RPD guide, p.15]] [^16]: Original PDF page 16: [[L10 RPD guide.pdf#page=16|L10 RPD guide, p.16]] [^17]: Original PDF page 17: [[L10 RPD guide.pdf#page=17|L10 RPD guide, p.17]] [^18]: Original PDF page 18: [[L10 RPD guide.pdf#page=18|L10 RPD guide, p.18]] [^19]: Original PDF page 19: [[L10 RPD guide.pdf#page=19|L10 RPD guide, p.19]] [^20]: Original PDF page 20: [[L10 RPD guide.pdf#page=20|L10 RPD guide, p.20]] [^21]: Original PDF page 21: [[L10 RPD guide.pdf#page=21|L10 RPD guide, p.21]] [^22]: Original PDF page 22: [[L10 RPD guide.pdf#page=22|L10 RPD guide, p.22]] [^23]: Original PDF page 23: [[L10 RPD guide.pdf#page=23|L10 RPD guide, p.23]] [^24]: Original PDF page 24: [[L10 RPD guide.pdf#page=24|L10 RPD guide, p.24]] [^25]: Original PDF page 25: [[L10 RPD guide.pdf#page=25|L10 RPD guide, p.25]] [^26]: Original PDF page 26: [[L10 RPD guide.pdf#page=26|L10 RPD guide, p.26]] [^27]: Original PDF page 27: [[L10 RPD guide.pdf#page=27|L10 RPD guide, p.27]] [^28]: Original PDF page 28: [[L10 RPD guide.pdf#page=28|L10 RPD guide, p.28]]