2- b. Basic principles for designing Kennedy class II, III and IV Removable Partial Denture(RPD)

1-a. Basic principles for designing the removable partial denture (class I partial denture design)
Introduction.
Objectives and Functions of RPD.
Factors that affect RPD design.
Basic principles for designing Kennedy class I partial denture.
2- b. Basic principles for designing Kennedy class II, III and IV Removable Partial Denture(RPD)

1. 2 - Partial Denture Design b- Basic Principles for Designing Class II,III and IV removable partial denture

2. Basic Principles for Designing Class II,III and IV removable partial denture Dr. Amal Fathy Kaddah Professor of Prosthodontics, Faculty Dentistry, Cairo University

3. May you have enough happiness to make you sweet and satisfied, enough trials to make you strong and human , enough hope to make you happy and pleased.

4. Removable Partial Denture Design

5. The first step in a successful partial denture is to design and plan the case very carefully. The more time taken with this important step, the more secure and functional the resulting partial .

6. The prosthesis must be designed following the most favorable biomechanical principles, as the simple and proper design helps in reducing the harmful effects on the supporting structures

7. Objectives and Functions of RPD Preservation of the remaining structures Simplicity and rigidity Restore masticatory efficiency Restore Appearance and speech

8. Preservation of the remaining tissues without injury of the remaining oral structures. Restore the form and function Enhance psychological comfort Removable Partial Denture Design

9. Removable Partial Denture Design Dr. Mohamed Farouk

10. Factors that affect RPD design Are conditions and forces found in the patients mouth, that affect the partial denture design. Removable Partial Denture Design

11. Retention Reciprocation Support Indirect Retention RPD REQUIREMENTS Bracing and Stabilization A properly constructed partial denture must All should be within the physiological limits of the tissues involved

12. Principles of RPD design Are certain rules placed by the dentist to cope with the oral factors and achieve the biomechanical consideration of the design. Removable Partial Denture Design

13. Principles of RPD design Biological principles Mechanical principles

14. * Mechanical principles >>> related to resistance of forces and its application to object >> looseness of teeth, bon resorption…… etc Biomechanical principles of RPD design * Bio >>> biological principles pertaining to living systems >>> inflammation, Caries, bone resorption…. etc Removable Partial Denture Design

15. Principles of Kennedy Class II RPD design Tooth-mucosa support The difference of displaceability of the supporting tissues results in tissue-ward and tissue-away movements of the denture base with subsequent torque on the abutment.

16. Problems of support associated with free-end saddles is due to: Lack of posterior abutment Support is derived from both the residual ridge and abutment teeth Major support is obtained from the residual ridge If resorption occurs and relining of the denture is neglected further bone resorption occurs with subsequent torque acting on the abutments.

17. Kennedy class II partial dentures Designing class II partial dentures usually follow the same basic principles of class I partial dentures. The absence of a saddle on the other side of a class II partial denture complicates the retention of the appliance.

18. Thus, in class II RPD there are problems of : Support Retention Bracing and reciprocation Stabilization (tipping and rotational movements)

19. Factors influencing the effectiveness of tissue support of a distal extension base Contour and quality of the residual ridge (nature of the mucoperiosteun ). The Extent of area coverage by the denture base. Accuracy and fitness of the denture base. The accuracy and type of impression registration (anatomical or functional ). The Design characteristics of the components parts of the partial denture Framework. Total occlusal load applied.

20. Problems of unilateral distal extension bases can be reduced by: A- Load reduction and distribution. B- Addition retention must be provided on the side where the arch is complete. The clasp line should divide the denture into two equal halves. C- Using indirect retainer in case of class II without modification, to reduce lateral loading and rotational movement of the denture base. ? ? ? ? 10

21. How to minimize Strain on the residual ridge and the abutment teeth in class I and II Kennedy RPD ????? ? 9+8=17 Support: Flexible retention Need of indirect retention Bracing, stabilization and reciprocation .

22. Strain on the residual ridge is minimized through Broad tissue coverage and maximum extension of the denture base within the functional limits of muscular movements. Fitness and intimate adaptation of the denture base to the tissue. Functional basing: Muco -compression impression recording of the residual ridges. Improving the condition of the residual ridge e.g. correction of abusive condition of tori and hyperplastic tissues.

23. Use of small and narrow teeth to increase the masticatory efficiency and reduce the masticatory load. Harmonious occlusion and reducing the cusp angle of art. teeth. Leaving a tooth off the saddle. Placing the artificial teeth on the anterior two-thirds of the base (no 3 rd molar). Placement of occlusal rests away from the saddle. Providing Posterior Abutments A- Using an implant at the distal part of the ridge. B- Salvaging a hopeless badly decayed tooth (an overdenture abutments)

24. Correct choice of the abut. Tooth with sufficient alveolar bone support and crown and root morphology Placement of occlusal rests away from the saddle (6 benefits ????). Correct choice of direct retainer (flexible clasping). Using stress equalizing design . Strain on the abutment teeth is minimized through

25. 5 . Wide distribution of the load over the teeth: Strain on the abutment teeth is minimized through a- By placing additional rests, or b- by a splinting of one or more teeth, either by fixed partial dentures or by soldering two or more individual restoration together . 6- Using a Kennedy bar to distribute the lateral load on multiple teeth. XXXX

26. 7. Preparation and restoration of the abutment teeth to accommodate the most ideal design of PD this include a- Proper form of occ. rest seats b- Tooth prep. and modification to withstand the functional stresses ( guiding planes, ………..) 8. Providing Posterior Abutments a- Using an implant at the distal part of the ridge. b- Salvaging a hopeless badly decayed tooth , an overdenture abutment

27. 1- Direct retention 2- A double Aker clasp usually used on the dentulous side. 3- An indirect retainer should be provided to counteract rotation of the denture away from the tissues. I- Designing of class II partial dentures with no modifications

28. Direct retention is obtained either by : 1- Rigid clasping and rigid connection between the saddle and the retainer, In case of: Short edentulous span bounded by a strong abutment with healthy periodontium , and well formed edentulous ridge covered with firm mucosa of normal thickness. I- Designing of class II partial dentures with no modifications

29. This design is applied in long class II cases . ? ? I- Designing of class II partial dentures with no modifications Or Direct retention is obtained by: 2- Designs applying stress equalizing principles in long class II cases .

30. Stress Equalizing Design e.g . Clasps as RPI (flexible, Disengagement ), RPA , reverse Aker, RLS (Disengagement), back action, and reverse back action X clasps as well as combination clasp (wrought wire ( flexible) with casted clasp)

31. The clasps on abutments bounding the modification area provide retention, bracing and reciprocation together with indirect retention I- Designing of class II partial dentures with modifications

32. Tripoding configuration. Class II lower partial dentures with modification space. Rigid clasping I- Designing of class II partial dentures with modifications

33. Selecting Components for Designing Free Extension Removable Partial Dentures Denture base (Acrylic) Small and narrow teeth . Centric occlusion of teeth should coincide with centric relation Proximal Plate Contact approximately 1 mm of the gingival portion of the guiding plane in distal extension cases Occlusal Rest : Mesially placed ,Saucer-shaped, fit , strong not raise the vertical dimension of occlusion, the floor of the rest seat should inclined apically. Direct retention (Flexibility, disengagement). Indirect Retention, resist rotational movement of the base away from the saddle .

34. Restoration of the unmodified class III Fixed Bridges are usually the treatment of choice for short span bounded edentulous areas when abutments are strong and healthy and minimum bone loss exists . Bilateral Partial Dentures. Unilateral Partial Dentures. Principles of Kennedy Class III RPD design

35. A bilateral unmodified class Ill partial denture A unilateral class Ill partial denture XXXX I don’t recommend it.

36. 1- Denture base: Metallic denture base is designed to fit the static rather than the functional form of the ridge 2- Rests: rests are usually placed on the near zone of the abutment teeth to provide adequate support. Rest seats can be prepared in either a box-shaped or saucer-shaped configuration depending on the condition of the abutment teeth. 3-Clasps: Rigid clasping is usually required for class III cases bounded by strong abutments. The clasps are located on abutments bounding the edentulous span. A third clasp , which may either be an embrasure or a multiple clasp is used on the intact (dentulous) side. 4.Major connectors: A lingual bar for mandibular dentures. A palatal bar or palatal strap for maxillary major connector are usually used. I- Designing of class III partial dentures with no modifications

37. The tripod clasp configuration for class III partial denture Restoration of modified class III Principles of Kennedy Class III RPD design The quadrilateral clasp configuration for class III partial denture Class III cases having long edentulous spans and having modification are usually considered tooth-tissue supported dentures

38. These cases could also be restored by an Every denture which is a totally mucosa-borne denture.

39. For unilateral removable partial denture to be successful The buccal and lingual surfaces of the abutment tooth must be parallel to resist tipping forces. The clinical crown of abutment tooth must be long enough to resist rotational forces. Inhaled Should be used with caution Swallowed

40. Usually follow the same basic principles of class I partial dentures, and are considered as free-end partial dentures. As the edentulous area that crossing the midline lies anterior to the abutments. Principles of Kennedy Class V I RPD design

41. Fixed partial denture is the treatment of choice but removable restoration is preferred in children. The line of treatment of anterior edentulous areas differ depending on the age of the patient. Young patients are usually treated with a temporary appliance until a stable mouth condition is reached. Frequent inspections are necessary to detect the need for relining or rebasing the dentures.

42. Proper Location of I.R Spoon denture may be modified to improve retention by Adams Cribs or wire loops

43. Strain on the abutment teeth and the residual ridge is minimized through Broad tissue coverage and maximum extension of the denture base within the functional limits of muscular movements. Functional basing . Muco -compressive impression recording of the residual ridges. Improving the condition of the residual ridge e.g. correction of abusive condition of tori and hyperplastic tissues. Use of narrow teeth and harmonious occlusion. Leaving a tooth off the saddle. Placing the artificial teeth on the anterior two-thirds of the base. Correct choice of direct retainer. Using stress equalizing design. Using a Kennedy bar to distribute the lateral load on multiple teeth . XXXXX In Summary

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