removable Partial denture

General idea about removable partial dentures definitions and categories. major and minor components of RPD, retainers and its design

1. Presented by Rusul N (Assistant Lecturer) Aseel A. R. (Lecturer ) Zydoon Hassan(Assistant Lecturer) Karbala university collage of dentistry, Department of prosthdontics Partial denture

2. Partial denture : a dental prosthesis that restores one or more but not all of the natural teeth and/or associated parts and that is supported in part by natural teeth and/or the mucosa. Partial denture construction : the science and techniques of designing and constructing partial dentures.

3. Types of Partial dentures 1-RPD 2-FPD

4. Indication for removable partial denture:

5. RPD is generally avoided in the following cases: -Patient with large tongue which tends to push the denture way . 2-Patient attitude:mentally retarded patients cannot maintain a removable prosthesis. 3-Poor oral hygiene

6. denture retention: the resistance in the movement of a denture away from its tissue foundation especially in a vertical direction 2:a quality of a denture that holds it to the tissue foundation and/or abutment teeth.

7. denture stability : the resistance of a denture to movement on its tissue foundation, especially to lateral (horizontal) forces. A quality of a denture that permits it to maintain a state of equilibrium in relation to its tissue foundation and/or abutment teeth . Support : Resistance to movement towards the tissues or teeth denture supporting structures: the tissues (teeth and/or residualridges ) that serve as the foundation for removable partial or complete dentures.

8. Components of a typical removable partial denture 1. Major connectors 2. Minor connectors 3. Rests 4. Direct retainers

9. 5. Stabilizing or reciprocal components (as parts of a clasp assembly) 6. Indirect retainers (if the prosthesis has distal extension bases) 7. One or more bases, each supporting one to several replacement teeth

10. Major Connectors The unit of a removable partial denture that connects the various parts of the denture. Its principal functions are to provide unification and rigidity to the denture

11. Requirements: are made of an alloy compatible with oral tissue are rigid & provide cross arch stability through the principle of broad distribution of stress . should be free of movable tissue

12. Bony and soft tissue prominences should be avoided during placement and removal. Relief should be provided to prevent its settling into areas of possible interference, such as inoperable tori or elevated median palatal suture Major connectors should be located and/or relieved to prevent impingement of tissue that occurs because the distal extension denture rotates in function

13. Maxillary Major Connectors : 1-Sigle palatal strap: Indication : CLIII or CLIII mod I Disadvantage:1-Cannot be used to connect anterior replacement. 2-Relief may be required over bony midline areas in some instances to prevent fulcruming over the overlying soft tissue. 3-posterior border should end before the junction of the soft & hard palate to avoid discomfort .

14. Single palatal bar(posterior palatal bar ):half oval cross section Indications:in CLIII cases when only one or two teeth are to be replaced on each side & the teeth anterior or posterior to the space can bear the load. Disadvantage:less than 8mm width is referred to as a bar the most objectionable because of discomfort.

15. Palatal plate-type connector also called anatomic replica palatal major connector Indication: 1-CLI 2- long distal extension cases & excessive ridge resorption . 3-the primary abutments are periodontally involved, requiring maximum stress distribution. 4-flabby tissue or where there is a shallow palatal vault this connector also provides greater stability and stress distributing characteristics.

16. - Combination Anterior-Posterior Palatal Strap: closed horse shoe -Indications:1-CLII Mod I long edentulous area &CLIV cases. 2-large inoperable tori. 3-when anterior & posterior abutment teeth are widely separated.

17. 5-Combination Anterior& posterior bar major connectors: 1-CLVI case. 2-long edentulous span in CLII Mod I. 3-when anterior & posterior teeth are widely separated. 4-large inoperable tori. 5-patient wants to avoid complete palatal plate.

18. 6-U-shaped Or "Horse-Shoe palatal connector sIndications : 1-large inoperable tori. 2-several anterior teeth to be replaced.

19. Mandibular Major Connectors: Tongue space Tongue space Periodental prob Functional impression

20. 2-Linguopalate ( lingual palate)

21. Indications 1-there is no space for lingual bar. Lingual frenum high, ioperable tori. 2-when most of posterior teeth are lost& additional indirect retention is required. 3-when one or more incisor teeth have to be replaced in the future the teeth added by attaching retention loop to them. 4-stabilize periodontally weakened teeth act as splint. 5-CLI cases in which the residual ridges have undergone excessive resorption , lingual plate will engage the remaining teeth to resist horizontal rotation. 6-step back design(modification of lingual plate) used in case of spaced anterior teeth.

22. - Subligual bar Indications: it can be used if the sulcus depth too little & a lingual bar cannot be placed with at least 4mm clearance from the free gingival margin

23. Cingulum bar thin narrow3mm metal strap located on cingula of anterior teeth, scalloped to follow interproximal embrasures with inferior & superior borders tapered to tooth surfaces. Originates bilaterally from the rest of adjacent principle abutment. Cannot be used when anterior teeth tilted lingually or there is wide diasthema because of metal display. has the disadvantage of food trap & periodontal problems . Indications : when a lingual plate or sublingual bar is indicated but the axial alignment of the anterior teeth is required excessive blockout of interproximal undercuts.

24. Labial bar: half pear shaped with bulkiest portion inferiorly located on the labial & buccal aspects of the mandible, superior border located at least 4mm inferior to labial & gingival margins, inferior border located at the juncture of attached & unattached mucosa. Indications :1-when lingual inclinations of remaining teeth cannot be corrected, preventing placement of lingual bar. 2-inoperable lingual tori or tissue undercut.

25. Part2 other component of RPD

26. Minor Connectors A unit of a partial denture which connects other components (e.g. direct retainer, indirect retainer , denture base, etc.) to the major connector . Functions 1. Provide unification and rigidity 2. Provide stress distribution by transferring stresses from the major connector to other parts of the partial denture and from the partial denture to the abutment teeth 3. Act as bracing elements through contact with guiding planes opposing the retentive arms. 4. Maintain a path of insertion via contact with guiding planes

27. Finishing line: the junction between metal & plastic portions of a RPD. An internal finish line is on the internal or tissue surface & is formed while preparing a cast for dublication . An external finish line is on the polished surface of a denture & is formed in the wax pattren Vertical finishing line Horizontal finishing line

28. Rests and Rest Seats Rest: A rigid component of a removable partial denture which rests on the occlusal , lingual or incisal surface of a tooth to provide vertical support for the denture. Although a rest is a component of a direct retainer (retentive unit, clasp assembly), the rest itself is classified as a supporting element due to the nature of its function. Rest seat : the prepared portion in a tooth or restoration created to receive the occlusal , incisal , cingulum , or lingual rest function: 1-maintains component in their planned position. 2-maintains established occlusal relationships by preventing settling of the denture. 3-ptrevents impingement of soft tissue. 4- directs & distributes occlusal load to abutment.

29. Types of Rest Occlusal rest Conventional occlusal rest Extended occlusal rest Interproximal occlusal rest Internal occlusal rest Lingual rest ( cingulum ) Incisal rest Implant as a rest

30. direct retainer A direct retainer is any unit of a removable dental prosthesis that engages an abutment tooth or implant to resist displacement of the prosthesis away from basal seat tissue. it is ususally composed of 1) retentive arm, 2)reciprocal (bracing) element arm, 3)rest and 4)minor connector. Requirement of direct retainer: Support Reciprocity Stability Retention Encirclement of greater than 180 of the tooth. Passivity

31. Types of Direct Retainers 1.the intracoronal retainer (precision attachment .) the intra-coronal retainer is either cast or attached totally within restored natural contours of an abutment tooth . it's typically composed of the prefabricated machined key and key way , with opposing vertical parallel walls , which serve to limit movement and resist removal of the partial denture through frictional resistance usually regarded as an internal or a precision attachment.

32. B. Extra coronal retainer Clasps designed without movement accommodation It also named subrabulge clasp or occlusally approach clasp since it approach the retentive undercut from the occlusal direction. Types of Circumferential clasps: Circumferential (Circle or Akers) clasp The ring clasp The embrasure clasp Back-action Clasp Multiple Clasp. Half and half clasp Reverse-action Clasp.(hair pin )

33. The embrasure clasp Indication In the fabrication of an unmodified Class II or Class III partial denture, no edentulous spaces are available on the opposite side of the arch to aid in clasping Back action Clasp used on premolar abutment anterior to the edentulous space

34. Reverse-action Clasp.(hair pin) Advantages: a. Allows use of undercut adjacent to edentulous space Disadvantages: a. Almost impossible to adjust b. Non-esthetic c. Difficult to fabricate so the upper portion of the retentive arm clears the opposing occlusion d. Covers extensive tooth surface and acts as a food trap e. Insufficient flexibility on short crowns due to insufficient clasp arm length

35. 2) Clasps Designed to Accommodate Functional Movement (RPI, RPA, and Bar Clasp ) Bar type a.The bar clasp is a cast clasp that arises from the partial denture framework and approaches the retentive undercut from gingival direction b. Retentive clasps are identified by shape of retentive terminal, i.e. T, Y, L, I, U, and S. Contraindications: a) deep cervical undercuts - food trap or impingements result b) severe soft tissue or bony undercuts c) insufficient vestibular depth for approach arm d) pronounced frenal attachments in area - impingement

36. The RPI clasp The rest is located on the mesio-occlusal surface of premolar and mesiolingual surface of canine. The proximal plate (essentially wider minor connector) is located on a guiding plane on th distal surface of the tooth. On premolar the proximal plate should be extended lingually so the distance between the proximal plate and mesio-occlusal rest less than mesodistal width of the tooth. Contraindications to the R.P.I. Clasp 1. Insufficient depth of the vestibule. (The inferior border of the I-bar must be located at least 4 mm. from the gingival margin.) 2. No labial or buccal undercut on the abutment 3. Severe soft tissue undercut 4. Disto-buccal undercut (less than 180° encircle

37. RPA clasps Mesial rest concept clasps have been proposed to accomplish movement accommodation by changing the fulcrum location the RPA consist of [rest, proximal plate, Akers] the Akers is used instead of I bar which arises from the proximal plate and end in mesiobuccal undercut , it used when there is insufficient vestibular depth or sever tissue under cut. Some advantages are (1) its interproximal location, which may be used to esthetic advantage. (2) increased retention without tipping action on the abutment. (3) less chance of accidental distortion resulting from its proximity to the denture border .

38. Part3 indirect retainer and design principles of RPD

39. Indirect retainer Is the component of R.P.D. that assist the direct retainers in preventing displacement of the distal extension denture base by functioning through lever action on the opposite side of the fulcrum line when the denture base moves away from the tissues in pure rotation around the fulcrum line.

40. Principles of Partial Denture Design 1. Utilize what's present.     2. Plan for the future 3. Minimize framework elements whenever possible. Cingulum rests can be designed to join proximal plates, rather than having separate minor connectors, whenever possible.

41. First step in the RPD design is Surveying What is Surveying? Surveying the cast include: 1-analysing the cast. 2- surveying the teeth. 3-surveying the soft tissue contour on the cast. -OBJECTIVES

42. Objectives of Surveying: 1.Locating soft tissue undercuts 2. Contouring wax patterns 3. Machining parallel surfaces 4. Blocking out undesirable undercuts 5. Placing intracoronal retainers 6. Recording the cast position

43. Denture Bases Use broad tissue base support. 2. Distal extension bases should be extended to the retromolar pads and the maxillary tuberosities as these structures provide comfort and a peripheral seal for retention.

44. Direct Retainers Minimize requirements for direct retention .Design retentive clasps tips to be ideally placed in the gingival 1/3 Consider caries susceptibility. The height of tooth If no retentive undercut can be found it is possible to prepare a small retentive area on the tooth.

45. Indirect Retainers Class I and Class II partial dentures often require indirect retainers. These should be as far from the primary fulcrum line as possible (90°), and placed on the opposite side of the fulcrum line from the denture base. They are normally not required for tooth-borne RPD’s. Major Connectors 1. Assess tori, height of floor of mouth, frenal attachments. 2. The posterior extensions of a maxillary distal extension framework should point to hamular notches. 3. Major connectors should have smooth continuous contours that flow into other elements of the partial denture.

46. Minor Connectors Where a cingulum rest is not adjacent an embrasure minor connector to an occlusal rest, cross the free gingival margin directly – do not use an embrasure minor connector. Cover the entire rest seat preparation, but do not wrap these minor connectors into embrasures

47. Distal Extension Case Considerations: 1. Use stress releasing direct retainers in distal extension cases. There are three axes of rotation for these partial dentures. If abutment teeth are locked into the frameworks they can be torqued in many directions. Stress-relieving clasps allow for some release of the teeth to minimize torquing potential.