Principles of RPD designing

The following presentation is a compilation of RPD designing data from Mccraken and Stewart. it also includes data from evidence-based literature and recent practices

1. Principles of Removable Partial Denture Design. 1

2. Learning Objectives Sr.no Topic Domain 1. Lever Principles Cognitive and Psychomotor 2. 3- Dimensional visualization of axis and forces exerted on a RPD Cognitive and Psychomotor 3. Classification of Support in RPD Designing Cognitive and Psychomotor 4. Support and Force Distribution in RPD Cognitive and Psychomotor 5. Factors to consider in Designing of RPD Cognitive and Psychomotor

3. Learning Objectives Sr.no Topic Domain 1. Systematics of RPD Designing Cognitive and Psychomotor 2. Components Of Removable Partial Denture Cognitive and Psychomotor 3. Designing Consideration of Components of Removable Partial Denture Cognitive and Psychomotor 4. Evidence Based Reports Cognitive and Psychomotor 5. Innovations Cognitive and Psychomotor 3

4. Contents Part 1 Terminologies Why the Need to design? The Lever Principle Mechanics Of Movement: Three Dimensional Thinking Forces Acting on RPD Factors Influencing Designing Of Removable Partial Denture Support and Force Distribution in Various Classes of RPD Factors Influencing Stress Transmitted to Abutment Teeth Principles of RPD design Philosophies Of RPD design Essential of RPD Designing

5. Contents Part-2 Systematics of RPD designing Major Connectors Direct Retainers Stabilizing components Guiding Planes Indirect Retention Stress Breaking Philosophy Implant Consideration in RPD Designing Evidence Based Studies Innovation 5

6. Common Observations Clearly indicate that the ability of living thing to tolerate force is largely dependent upon the magnitude or intensity of the force - Maxwell

7. Terminologies Removable partial denture prosthesis : Any prosthesis that replaces some teeth in a partially dentate arch. It can be removed from the mouth and replaced at will. ( GPT-8) A removable denture that replaces some teeth in a partially edentulous arch; the removable partial denture can be readily inserted and removed from the mouth by the patient (GPT- 9) (also called partial removable dental prosthesis.) Fulcrum Line in RPD : A theoretical line around which a removable partial denture tends to rotate.(GPT-9)

8. Lever : A rigid bar resting on a pivot, used to move a heavy or firmly fixed load with one end when pressure is applied to the other.(oxford dictionary) Wrought : worked into shape by artistry or effort. ( McCraken 6 th ed) Retentive fulcrum line : (GPT-9) 1. An imaginary line connecting the retentive points of clasp arms on retaining teeth adjacent to mucosa-borne denture bases. 2. An imaginary line, connecting the retentive points of clasp arms, around which the removable partial denture tends to rotate when subjected to dislodging forces.

9. Why the Need to design? The supporting structures are living tissues These tissues are subjected to force and thus the duration, direction frequency and magnitude of the force must be controlled. The potentially destructive forces must be minimized in order to limit the exerted force to the physiologic tolerance limit. The design of the removable partial denture requires mechanical and biologic considerations

10. The Lever Principle Fulcrum: Axis Around Which The Lever rotates Effort: Force applied to move the load Load: The object to be moved

11. Types of Lever Levers are classified by the relative positions of the fulcrum, effort and resistance (or load). Lever Of 1 st Order : Fulcrum in the middle: the effort is applied on one side of the fulcrum and the resistance (or load) on the other side, for example, a seesaw, a crowbar or a pair of scissors.

12. Lever of 2 nd order Resistance (or load) in the middle: the effort is applied on one side of the resistance and the fulcrum is located on the other side, for example, a wheelbarrow, a nutcracker, a bottle opener or the brake pedal of a car. Load arm is smaller than the effort arm.

13. Lever of 3 rd Order Effort in the middle: the resistance (or load) is on one side of the effort and the fulcrum is located on the other side, for example, a pair of tweezers or the human mandible. The effort arm is smaller than the load arm.

14. Mechanical Advantage Mechanical Advantage = Effort arm More the mechanical advantage more the output force Class 1 may be less than equal to or more than 1 Class 2 is always greater than 1 Class 3 is always less than 1 Resistance Arm

15. Mechanics Of Movement: Three Dimensional Thinking The three fundamental plane and the three fundamental axes as related to human head

16. The Sagittal Plane and the Mediolateral axis Divides the head into right and left half The axis runs mediolaterally The movement along this axis is mediolateral

17. The Horizontal plane with Vertical Axis Divides the head into upper and Lower half The axis runs vertically The movement along this axis is along the vertical axis

18. The Frontal plane and the anteroposterior axis. Divides the head into anterior and posterior half The axis runs antero-posteriorly The movement along this axis is along the anteroposterior direction

19. The force is split into vectors in X,Y and Z Axis

20. The 3 Fulcrum Lines Rotation in Sagittal Plane (denture movement toward or away from the supporting ridge). Rotational movement around this fulcrum line is the greatest in magnitude, but is not necessarily the most damaging. The resultant force on the abutment is mesio -apical or disto -apical,

21. A second fulcrum line lies in the frontal plane and extends through the occlusal rest on the terminal abutment and along the crest of the residual ridge on one side of the arch. This fulcrum line controls the rotational movements of the denture in the frontal plane (i.e., a rocking movement over the crest of the ridge). The resultant forces are more nearly horizontal and are not well resisted by the oral structures. Therefore, these forces can be moderately damaging and should be given thorough consideration in the design process.

22. The third fulcrum is located in the vicinity of the midline, just lingual to the anterior teeth. This fulcrum line is oriented vertically and controls rotational movement in the horizontal plane (i.e., the flat, arcuate movements of the prosthesis). Due to its orientation, the force resulting from this movement is almost entirely horizontal. Consequently, these forces can be extremely damaging and should receive significant attention during the design process.

23. Forces acting on Denture bases.

24. Factors Influencing Designing Of Removable Partial Denture Relationship of arch/es to be restored with each other Types of Major connector to be used based on existing and correctable situations Whether the denture will be entirely tooth borne . If one or more distal extension bases are involved. Material to be used for the framework and the bases Type of Replacement teeth to be used Need for abutment restoration. Patients past experience with a removable partial denture and the reason for making a new denture. Periodontal condition of the remaining teeth, need for splinting. Method to replace anterior teeth using RPD/FPD

25. Kennedy’s Classification of Removable Partial Denture (1925) Permits immediate visualization of the partially edentulous arch. The incidences of occurrence follows as class1> class2> class3

26. Support and Force Distribution In RPD Tooth supported prosthesis- Like a conventional FPD a class III RPD is entirely tooth supported . The forces are directed along the long axis of the abutment tooth and are transmitted to the associated periodontal ligament. Off-axial loading in these type of Dentures is minimum.

27. Combined Tooth- Tissue Supported Prosthesis Synge and DeVan stated that the mucoperiosteum of the residual ridge offers only 0.4% of the support provided by periodontal ligament

28. Differences Between The Two Main Types Aspects Class I and II Class III Type of support Derive maximum support from soft tissue Derive Support From Abutment Impression Technique There is need to record the anatomic and functional form Only anatomic impressions are needed Indirect Retention There is a need for indirect retention to prevent rotation along the retentive fulcrum line Terminal abutments are present which provides resistance to rotation Need To Reline Tissue changes are anticipated and so there may be a need to reline the denture Generally there is no need to reline the denture and metal bases are preferred. Requirement for Direct Retention To resist vertical displacement It also must dissipate tissue ward force equally to the abutment Direct retainers are needed but majorly for retentive purposes.

29. Factors Influencing Stress Transmitted to Abutment Teeth & Ridge Length of edentulous span Quality of Ridge Support Clasp Flexibility Clasp Design Material used in Clasp Construction Surface Characteristics of the abutment Occlusal harmony

30. Length Of Edentulous Span Longer the edentulous span greater is the leverage transmitted to the transmitted to the abutment teeth. A sincere effort must be made to retain an abutment teeth terminally to the edntulous space, if possible en-dosseous implants also can offer valuable service. Longer the edentulous span more will be the mechanical advantage, more will be the force delivered to the abutment tooth

31. Quality of ridge support Large well formed ridges are more favourable as compared to thin knife edged ridges. Broad ridges with parallel sides Thickness and health of periosteum also plays a vital role. A healthy mucoperiosteum approximately 1mm in thickness is capable of bearing a greater functional load than is thin, atrophic mucosa

32. Clasp Flexibility More flexible is the clasp, less is the load transfer to the abutment. Wrought wire clasps are more flexible then cast metal clasps Increased Flexibility decreases the resistance to displacement and allows more destructive non-axial forces

33. Clasp design A clasp is always passive in its completely seated position In a cast circumferential clasp only the retentive arm must be flexible A clasp must be designed in such a way that during insertion and removal the reciprocal arm must come in contact at the area of greatest bulge in order to stabilize the tooth when the retentive arm passes over it Refinement of the framework is accomplished by using disclosing wax, as the framework is seated wax is displaced.

34. Length of the clasp Flexibility is directly proportional to the length of the clasp, more flexible the clasp lesser the stress on the abutment Where D = deflection, P = applied force, L = length, E = modulus of elasticity, w = beam width, and t beam thickness =

35. Material used in Clasp Construction Clasp constructed of a chromium based alloy will normally exert a greater load on abutment than with a gold based alloy, all other factors being equal. To make a cobalt chromium alloy more flexible the diameter should be decreased.

36. Principles of Design (A. H Schmidt 1953) Planning and designing removable partial dentures Schmidt, Arthur H. Journal of Prosthetic Dentistry , Volume 3 , Issue 6 , 783 - 806

37. Philosophy of Design Philosophy of denture design are based upon approaches to force distribution. Stress Equalization Physiologic Basing Broad Stress Distribution

38. Stress Equalization Advocates the use of stress directors. Rigid connections between denture bases and direct retainers are damaging and thus stress directors to protect abutments. Advantages: The direct retainers are under less stress as the free base act independently. Stress directors minimizes tipping forces on abutment teeth. Limits bone resorption Disadvantages: Fragile assemblies Not cost-effective Require constant maintenance

39. Physiologic Basing The anatomy of edentulous bases must be recorded under functional loading. It also recognize that the prosthetic teeth and occlusal rest will be positioned above existing occlusal plane when not in function. Minimal number of direct retainers and minimal retention Advantages: Compression and recovery provides with a stimulating effect It is also believed that it requires less frequent relining and rebasing Minimal clasp assemblies gives a light weight prosthesis Reduction in force transmission to abutment Disadvantage: Premature contact during closure More vertical movement renders the indirect retainers useless. Not well stabilized under lateral forces

40. Broad Stress Distribution Trauma to the remaining teeth and residual ridge can be prevented by distributing forces over as many teeth and as much soft tissue areas as possible. This is accomplished by using additional rests and clasp assemblies. Advantages: Minimize lateral forces. Force distribution reduces force per unit area. No moving parts makes it less fragile. Disadvantage: The increased coverage may not be accepted by some patients. Oral hygiene may be compromised.

41. Essential of Removable Partial Denture Design.

42. Class III RPD Least complicated of all designs Does not require any functional impression The choice of clasp can be cast clasps or combination clasp The denture base is made with metal base unless rebasing is anticipated.

43. Class I RPD Need for registration of tissues in supportive form (use of metallic oxide, rubber base, silicone material) Dual Impressions Physiologic Impression McLean Hindels method Functional Reline Fluid Wax Technique Selected pressure technique Planning of Indirect retainers as far from the retentive fulcrum line as possible.

44. Class II RPD It is a combination of tooth supported and tissue supported restoration. The indirect retainers are to be place on the tooth borne side away from the fulcrum line. Cast clasps are made for the tooth borne side.

45. Two variations of Class II

46. Systematics of RPD Designing McCraken’s Removable Partial Prosthodontics 13th edition 47

47. Tooth Support Alveolar bone support to the abutment Crown and Root morphology Increasing the number of abutments will decrease the stress on any single abutment McCraken’s Removable Partial Prosthodontics 13th edition 48

48. Occlusal Rests Deepest portion of the rest seat Inter proximal rest seats are extended more lingually Minimal inter proximal reduction for minor connector The marginal ridge is lowered to by 1.5 mm L B Design of Occlusal Rests Prepared in sound enamel/ restorative material Direct forces along the long axis of the abutment Floor of preparation must form an angle of less than 90 degree with long axis Gently rounded contours McCraken’s Removable Partial Prosthodontics 13th edition 49

49. When Occlusal Rest seats are unavailable The three views of cingulum rests Lingual, Occlusal and proximal. The Rest Seat Preparation can be exaggerated by preparing it on a cast restoration McCraken’s Removable Partial Prosthodontics 13th edition 50

50. McCraken’s Removable Partial Prosthodontics 13th edition 51 Preparation- rounded notch at the incisal angle of a canine or on the incisal edge of an incisor, deepest portion being apical to the incisal edge. 2.5x 1.5 mm deep Least desirable More applicable to mandibular canine Can cause tipping movement of the teeth

51. Yuuji Sato(2003) carried out a 3-D finite element analysis; the clinical implications of the study was “The strength of the occlusal rest in the model tested increased with an increased width and thickness. On the basis of the other results of this study, it is recommended that over rounded or sharp inner line angles between the rest and minor connector be avoided, that the thickness of the minor connector be half the width of the rest, and that excessive rest inclination be avoided. ” McCraken’s Removable Partial Prosthodontics 13th edition 52

52. Ridge Support Support for the distal extension dentures comes primarily from the overlying soft tissue and the residual alveolar bone of the distal extension base area Six factors that decide effective ness of the tissue support Quality of the ridge Extent covered by the denture base The accuracy and type of impression registrations The accuracy of the denture base The design characteristics of component parts of the partial denture framework Occlusal load applied McCraken’s Removable Partial Prosthodontics 13th edition 53

53. Friable tissue Area covered without impingement Resistant to resorption Area Available Resistant to resorption Effective Support Cover maximal surface Select tissue which are resistant to resorption Extent covered by the denture base McCraken’s Removable Partial Prosthodontics 13th edition 54

54. The Accuracy And Type Of Impression Registrations Ridge tissues must be recorded in their resting as well as functional form. Three factors for acceptance of impression registration are Primary stress bearing area must be recorded in functional form. Tissues other then the stress bearing areas must be recorded in their anatomic form. Snow shoe principle McCraken’s Removable Partial Prosthodontics 13th edition 55

55. Occlusal Load Applied The applied occlusal load can be decreased by reducing the area of the occlusal table opposing the denture or natural teeth. Large teeth Vs Small teeth More Occlusal Force On Large Teeth As Compared To Small Teeth McCraken’s Removable Partial Prosthodontics 13th edition 56

56. Functional Form Vs Anatomic Form A denture base processed to functional form of impression is -Less irregular and provides greater area of coverage -More stable under rotating and torqueing forces Maintains occlusal relationship with opposing teeth under function Distributes occlusal load equitably Vs McCraken’s Removable Partial Prosthodontics 13th edition 57

57. Major Connectors Location Should be free of movable tissue Must not impinge the soft tissue Bony and Soft tissue prominences should be avoided by providing relief McCraken’s Removable Partial Prosthodontics 13th edition 58

58. Designing of Mandibular major connectors McCraken’s Removable Partial Prosthodontics 13th edition 59

59. Designing of Maxillary Major connectors ( Blatterfein 1953) McCraken’s Removable Partial Prosthodontics 13th edition 60

60. Minor Connectors 1. Joins clasp assembly to major connectors 2. Joins indirect retainer or auxiliary rest to the major connector 3. Joins the denture base to the major connector 4. Serves as an approach arm for a vertical projection or bar type clasp McCraken’s Removable Partial Prosthodontics 13th edition 61

61. Rigid Broad Bucco-lingually Thinner Mesio -distally Triangular cross section with thickest portion at lingual line angle of tooth & thinnest portion at buccal line angle of tooth. Rigid Must originate at butt joint from the major connector Must cross the gingiva abruptly Thickest portion cervically and thinner occlusal Straight path of insertion Minor Connectors Joining The Clasp Assembly To The Major Connector Minor Connectors Joining The Indirect Retainer To The Major Connector McCraken’s Removable Partial Prosthodontics 13th edition 62

62. A. B. C. D. E. F. Minor Connectors Which Join The Major Connectors To The Denture Base McCraken’s Removable Partial Prosthodontics 13th edition 63

63. It is the only minor connector which is not rigid. It is flexible as it aids in the deflection of the gingivally approaching clasps during seating It must not be used if soft tissue undercuts are present Minor Connectors Which Join The Gingivally Approaching Clasps To The Major Connector McCraken’s Removable Partial Prosthodontics 13th edition 64

64. Direct Retainers Design Rules for Cast Circumferential Clasp It originates from a portion of the framework that lies above the height of contour It follows cervically in an arcing fashion Only the terminal part of the clasp arm crosses the height of contour The reciprocal arm must be located at or slightly above the height of contour The retentive terminus is directed occlusally Should terminate at the mesial or distal line angles of the abutment A Cast circumferential claps must never be given on Mesio -facial undercut of terminal abutment of a distal extension RPD Disto -facial undercut of abutment distal to long span anterior edentulous space McCraken’s Removable Partial Prosthodontics 13th edition 65

65. Infrabulge Clasps Design Rules for Infrabulge Clasps The approach arm must not impinge on the soft tissues The approach arm should cross perpendicular to the free gingival margin The approach arm should never be designed to "bridge" an area of soft tissue undercut It must be uniformly tapered from origin to terminus The clasp terminus must be placed as apically as practical to counter lever like forces McCraken’s Removable Partial Prosthodontics 13th edition 66

66. Direct regainers in tooth supported Vs Tissue supported Tooth supported Tissue supported The function of the direct retainer is retention To resist vertical displacement It also must dissipate tissueward force equally to the abutment Mesial and distal under cuts can be safely engaged by suprabulge clasps Mesial undercut of the terminal abutment cannot be used for suprabulge clasps McCraken’s Removable Partial Prosthodontics 13th edition 67

67. Why to avoid engaging the mesiobuccal undercut in a distal extension space? McCraken’s Removable Partial Prosthodontics 13th edition 68

68. Reverse circlet clasp as an alternative McCraken’s Removable Partial Prosthodontics 13th edition 69

69. The vertical projection T-clasp engages a disto -facial undercut in a Class I partially edentulous arch The vertical projection I- Bar engages a facial undercut in a Class I partially edentulous arch Combination Clasp McCraken’s Removable Partial Prosthodontics 13th edition 70

70. RPI system Rest Guide Plane I- Bar mesioocclusal rest with minor connector placed in the mesio -lingual embrasure but not contacting abutment tooth A distal guiding plane extending from marginal ridge to junction of middle and gingival 3 rd of abutment tooth, prepared to receive proximal plate Located on Labial 1/3 The terminal tip is contact with the labial surface (2mm) Encirclement is provided by discontinuous engagement McCraken’s Removable Partial Prosthodontics 13th edition 71

71. Types of RPI DESIGNS The guide planes and proximal plate are in contact throughout the length of the tooth The guide planes and proximal plate are in contact only from marginal ridge to the middle third of the length of the proximal tooth. Bar clasp assembly in which the proximal plate contacts approximately 1 mm of the gingival portion of the guiding plane. During function, the proximal plate and the I-bar clasp arm are designed to move in a mesiogingival direction, disengaging the tooth. McCraken’s Removable Partial Prosthodontics 13th edition 72

72. The RPL System The RPA System The retainer has been described as one half T-bar or a modified T-bar clasp (L- Bar) The L-bar crosses the gingival margin of the abutment tooth in the shortest possible line, ascends to the survey line, and engages the distobuccal undercut Designed for mesially inclined abutment in cases of distal extension RPD The difference is in retentive arm. An Akers or circumferential clasp arm arises from superior portion of the proximal plate and extends around the tooth to engage the mesial undercut McCraken’s Removable Partial Prosthodontics 13th edition 73

73. Thomas J. Donahue (1988 ) stated factors that augmented the function of direct retaines they are as follows: 1. The duplication of direct retainer function by other prosthesis components 2. Physiologic adjustment of the framework to assure contacts with abutment teeth that are consistent with the design and intended functions of the components and that transfer stress in a manner those teeth are designed to accept 3. Intimate adaptation of denture bases to the residual mucosa, with recall visits to monitor this adaptation 4. Specific loading of the denture bases through selective placement of artificial teeth 5. Splinting of abutment teeth. Tsau -Mau Chou et al (1989 ) in a photoelastic study compared the load-transfer characteristics of various bilateral distal-extension removable partial denture designs embodying intracoronal attachments and clasp assemblies and concluded that The RPI clasp assembly generated the most uniform stresses. In general, intracoronal retainer frameworks produced higher stresses than did the clasp frameworks. McCraken’s Removable Partial Prosthodontics 13th edition 74

74. Mohammed M. Abd El‑ Khalik et al (2016) conducted a radiographic comparative study measuring the alveolar bone resorption around the terminal abutments at 6, 12 and 24 months (n=12) and concluded that Compound Aker clasp is better than the multiple circlet clasp assembly as it reduces abutment alveolar bone resorption regards broad stress distribution philosophy is considered for distal extension cases. Multiple Circlet Claps Compound Akers Clasp Vs Abd El.Khalik MM, El Mekawy NH, El- Kasaby SS. Mandibular kennedy class i partial denture management by broad stress distribution philosophy (radiographic assessment). J Indian Prosthodont Soc 2016;16:282-7 McCraken’s Removable Partial Prosthodontics 13th edition 75

75. Guiding Planes Proximal guide planes surface should be about one-half the width of the distance between the tips of adjacent buccal and lingual cusps. It must extend vertically about two third of the length of the enamel crown portion of the tooth from the marginal ridge cervically A guide plane must be situated on the abutment adjacent to the edentulous area McCraken’s Removable Partial Prosthodontics 13th edition 76

76. Placement of Guide Planes The guide planes must be placed on the proximal side of the abutment teeth bounding the edentulous space, More the number of guide planes= enhanced path of placement= cross arch resistance to horizontal rotational forces McCraken’s Removable Partial Prosthodontics 13th edition 77

77. The Exception Guide planes must not be placed on both sides of a lone standing abutment. The minor connectors which will be placed on such guide planes would exert undue stress on vertical displacement of the prosthesis THE LONE STANDING ABUTMENT McCraken’s Removable Partial Prosthodontics 13th edition 78

78. Template is generated by locking the guide pin in the most appropriate location The reach of the device is checked The template is checked intraorally The handpiece is attached to the device and guide planes are made Analyzing rod is attached and the prepared guideplanes are analysed Alexandre Luiz Souto Borges et al, A new intraoral device to facilitate preparation of the guide plane for removable dental prostheses, Journal of academy of general dentistry January 2012 volume 60 A new technique to prepare guide plane intraorally McCraken’s Removable Partial Prosthodontics 13th edition 79

79. Indirect Retainers An indirect retainers consists of one or more rests and the supporting minor connectors AN INDIRECT RETAINER SHOULD BE PLACED AT GREATEST PERPENDICULAR DISTANCE FROM THE FULCRUM LINE PASSING THROUGH THE REST SEATS OF THE TERMINAL ABUTMENT Incisors are the most effective regions, but they are not favourable for support and prone to uncontrolled tipping. Canine and mesio -occlusal surface of the first premolar provide best location McCraken’s Removable Partial Prosthodontics 13th edition 80

80. Various Edentulous Span With Prescribed Location For Indirect Retainers Kennedy’s Class I Kennedy’s Class II Kennedy’s Class III Kennedy’s Class IV McCraken’s Removable Partial Prosthodontics 13th edition 81

81. Forms of Indirect Retainers Auxiliary Occlusal Rests Canine Rests Canine Extension from Occlusal Rests Cingulum Bars and Linguo-plates Rests in modification areas Rugae support? Is Undesirable If Tooth Support Is Available, Palatal Horse Shoe Shape Major Connector McCraken’s Removable Partial Prosthodontics 13th edition 82

82. McCraken’s Removable Partial Prosthodontics 13th edition 83

83. Stress Breakers Steffel has classified the methods of treating distal extension conditions and stated the following philosophies Stress breaking philosophy : By the use of stress breakers Stress equalization philosophy : By physiologic basing Stress distribution philosophy : distributing forces over as many teeth and as much soft tissue as possible. McCraken’s Removable Partial Prosthodontics 13th edition 84

84. STRESS BREAKING can be achieved by: McCraken’s Removable Partial Prosthodontics 13th edition 85

85. Type 1 (Those utilizing hinge or movable joint ) Hinge type of joint Ball and socket type of joint McCraken’s Removable Partial Prosthodontics 13th edition 86

86. Type 2 ( Those utilizing flexible connection between direct retainer and saddle ) Lingual Bar connector with flexible distal extension Split Bar Major connector McCraken’s Removable Partial Prosthodontics 13th edition 87

87. THE E M GUAGE IS USED TO MEASURE THE AVAILABLE AREA FOR INCORPORATION OF INTRACORONAL ATTACHMENT McCraken’s Removable Partial Prosthodontics 13th edition 88

88. An Intracoronal Attachment McCraken’s Removable Partial Prosthodontics 13th edition 89

89. An Extracoronal Attachment Dalbo Attachmetnt McCraken’s Removable Partial Prosthodontics 13th edition 90

90. Implant Consideration in Treatment planning of RPD Survey Consideration: The Path of Insertion must be co-incident with the implant Location influenced by anatomic and opposing occlusal factors Need for sufficient interocclusal space for denture base, minor connector, denture tooth. Clasp assembly requirements if implant is used adjacent to tooth Incorporation of implant in retention of the prosthesis supplements the resistance derived from tooth engagement, however the tooth must also be involved as it supplements the implant stability McCraken’s Removable Partial Prosthodontics 13th edition 91

91. In a systematic review by De Freitas et al To assess clinical outcomes for mandibular implant-supported removable partial denture with distal extension. This review yielded 1751 records that were narrowed down to 5. The studies revealed implant survival rates ranging from 95% to 100% with one failure reported of 98 implants. The removable partial dentures associated with implant in mandibular free-end arches showed some complications and need of repair for relining, pitting of the healing abutment, replacement of resilient component of the attachment, damage in framework, screw loosening and damage in acrylic denture base. Patient satisfaction was evaluated through a five point questionnaire, and results ranged between 4.12 and 5.0, considering 1 as the least favourable situation. The literature review showed increase in patient satisfaction and high survival rates of implants associated with mandibular removable partial dentures with distal extensions. 92

92. Campos et al(2015) :A comparison between patients with bilateral distal extension post canine, treated with conventional RPD and Implant supported RPD, observations were made that the Oral health related Quality of Life significantly improved in Implant group as compared to the conventional group Karla Zancopé et al (2015): in a systematic review stated the clinical implication as the use of a partial removable dental prosthesis (PRDP) associated with dental implants to convert a Kennedy class I to class III denture does not decrease the implant survival rate and may ultimately benefit a patient’s satisfaction and masticatory abilities. This treatment could represent an option for resolving the problem of the intrusive movements of the PRDP and for reducing treatment costs. Ali Z et al (July 2018): in a meta-analysis involving treatment option for partially edentulous patients reached a conclusion that implant-supported fixed dental prostheses (FDPs) make greater improvements to oral health related quality of life ( OHRQoL ) than tooth supported FDPs or RPDs. They should also inform patients that although RPDs improve OHRQoL in the short term, these effects may be less noticeable in the medium term. 93

93. Some evidence based Queries What is the clinical evidence on the longevity of plastic partial dentures? 6 studies were found which addressed this question Survival rate of 83.6-100 % was found for a span of 5 years The main issues resulting in tooth loss from the investigations included in the studies was the progression of periodontal disease, secondary caries development, and tooth fracturing. The most common complication that was encountered was the development of caries. This result was found in the investigation by Behr et al CADTH RAPID RESPONSE REPORT, Longevity of Removable Prosthodontics: A Review of the Clinical Evidence, 10th April 2015 94

94. What is the clinical evidence on the longevity of metal partial dentures? The randomized controlled trial conducted by Stober et al.11 had an overall success rate of 87% for both prosthesis types after 72 months (77% in electroplated-RDP and 97% in Cast-RDP). Most of the complications were due to periodontal weakening which was evaluating by probing depth. Secondary caries and periodontal complication were primary cause of loss of abutment CADTH RAPID RESPONSE REPORT, Longevity of Removable Prosthodontics: A Review of the Clinical Evidence, 10th April 2015 95

95. Digital designing software Laith Mahmoud Abdulhadi , Hana Abbas Mohammed, Ahmed Laith Mahmoud Humam Laith Mahmoud, A new digital system to generate and draw framework design of removable partial dentures, Proceedings of ICERI 2013 Conference 18th-20th November 2013, Seville, Spain Fig.1 Snapshot of the first software interface. 96

96. Fig. 2 Designing the framework for unilateral free-end saddle. Laith Mahmoud Abdulhadi , Hana Abbas Mohammed, Ahmed Laith Mahmoud Humam Laith Mahmoud, A new digital system to generate and draw framework design of removable partial dentures, Proceedings of ICERI 2013 Conference 18th-20th November 2013, Seville, Spain 97

97. Helps In Saving Unconventional Design in the Database Laith Mahmoud Abdulhadi , Hana Abbas Mohammed, Ahmed Laith Mahmoud Humam Laith Mahmoud, A new digital system to generate and draw framework design of removable partial dentures, Proceedings of ICERI 2013 Conference 18th-20th November 2013, Seville, Spain 98

98. About the Software A new designing system for RPD had been presented and its suitability for professional use was approved. The limited input of parameters that have impacts on the RPD design might reduce its effectiveness in advanced training that includes the postgraduate students. Therefore, for the actual time its use is mainly for basic degree. It can be updated always with new cases and Interactive comparison can be done. It can enclose all the possible combinations of RPD (real and virtual). 99

99. Summary It is imperative to understand the RPD Design which will cater to the type of support. No component is to be added to a design which does not carry a purpose A combination of all the denture design philosophies yield better result. There is a need for further innovation in RPD therapy 100

100. References McCraken’s Removable Partial Prosthodontics 13 th edition Stewarts’s Clinical Removable Partial Prosthodontics 4 th Edition Thomas J. Donahue, Factors that augment the role of direct retainers in mandibular distal-extension dentures, JPD dec 1998 vol 60 number 6 Tsau -Mau Chou, Angelo A. Caputo, Dorsey J. Moore, Bin Xiao, Photoelastic analysis and comparison of force-transmission characteristics of intracoronal attachments with clasp distal-extension removable partial dentures, THE JOURNAL OF PROSTHETIC DENTISTRY, SEPTEMBER 19.39 VOLUME 92 NUMBER 3 Abd El.Khalik MM, El Mekawy NH, El- Kasaby SS. Mandibular kennedy class i partial denture management by broad stress distribution philosophy (radiographic assessment). J Indian Prosthodont Soc 2016;16:282-7. CAMPOS, Camila Heitor ; GONCALVES, Thais Marques Simek Vega ,GARCIA, Renata Cunha Matheus Rodrigues. Implant-Supported Removable Partial Denture Improves the Quality of Life of Patients with Extreme Tooth Loss.  Braz. Dent. J.  [online]. 2015, vol.26, n.5 , pp.463-467. 101

101. Placement of a distal implant to convert a mandibular removable kennedy class I to an implant-supported partial removable class III dental prosthesis: A systematic review zancopé , karla et al. Journal of prosthetic dentistry , volume 113 , issue 6 , 528 - 533.E3 Oral health-related quality of life after prosthodontic treatment for patients with partial edentulism: A systematic review and meta-analysis ali , zaid et al. Journal of prosthetic dentistry , volume 0 , issue 0 , De freitas , r. F., De carvalho dias , k. , Da fonte porto carreiro , a. , Barbosa, g. A. And FERREIRA, M. Â. (2012), mandibular implant‐supported removable partial denture with distal extension: a systematic review. Journal of oral rehabilitation, 39: 791-798. Alexandre Luiz Souto Borges et al, A new intraoral device to facilitate preparation of the guide plane for removable dental prostheses, Journal of academy of general dentistry January 2012 volume 60 CADTH RAPID RESPONSE REPORT, Longevity of Removable Prosthodontics: A Review of the Clinical Evidence, 10th April 2015 102

102. Thankyou 103