Kalpana stress breakers in rpd

Stress exerted against the teeth and their attachment apparatus by occlusal forces may be within the adaptive capacities of the tissues or else the tissues may not be capable of compensation and adaptation and the result is tissue destruction

1. Stress breakers in rpd Presented by: Dr. Kumari Kalpana Pg 2nd year

2. contents

3. Introduction Stress exerted against the teeth and their attachment apparatus by occlusal forces may be within the adaptive capacities of the tissues or else the tissues may not be capable of compensation and adaptation and the result is tissue destruction 3

4. Various approaches are been made to distribute the stress or forces acting on a partial denture between the soft tissue and teeth one among them is stress breaker. The stress breaker is suggested as a means to allow the base to move slightly with less strain to the abutments 4

5. DEFINITIONS 1 5 The Glossary of Prosthodontic Terms. J Prosthet Dent 2017 ;117(5S):e1-e105.

6. STRESS BREAKER : a device or system that relieves specific dental structures of part or all of the occlusal forces and redirects those forces to other load bearing structures or regions (GPT9) 6 The Glossary of Prosthodontic Terms. J Prosthet Dent 2017 ;117(5S):e1-e105.

7. Attachment: A mechanical device for the fixation, retention, and stabilization of a prosthesis A retainer consisting of a metal receptacle (matrix) and a closely fitting part ( patrix ); the matrix is usually contained within the normal or expanded contours of the crown on the abutment tooth/dental implant and the patrix is attached to a pontic or the removable dental prosthesis framework. 7

8. PRECISION ATTACHMENT : An interlocking device, one component of which is fixed to an abutment or abutments, and the other is integrated into a removable dental prosthesis in order to stabilize and/or retain it. (GPT-9) 8

9. Semiprecision Attachment : A laboratory fabricated rigid metallic extension ( patrix ) of a fixed or removable dental prosthesis that fits into a slot-type keyway (matrix) in a cast restoration, allowing some movement between the component 9

10. Types of stresses created on the abutment teeth In general there are three types of stresses on the abutment teeth

11. In all types of stress, the abutment becomes the fulcrum. To control these stresses and to distribute them between mucosa and the adjacent teeth requires a careful consideration of: 1] The condition of the teeth and mucosa 2] The impression techniques 3] The denture design 4] The distribution of stress between the mucosa and as many supporting teeth as possible 11

12. PHILOSOPHY OF Design

13. Philosophy of design Of the various philosophies relating to removable partial denture design, none is backed by overwhelming scientific evidence. They are the ideas of experienced dentists who have formulated rules for the design of removable partial dentures.

14. Nearly any removable partial denture design can be made to work successfully if respect for the physiologic limits of the supporting structures is observed. In partial denture design, the main concern is for prostheses that are partially supported by teeth and partially supported by soft tissues

15. Prostheses that are entirely supported by teeth are generally very straight forward. Because these partial dentures derive all of their support from the remaining teeth, a single impression may be used to record the teeth and soft tissues. The length in design, then, lies primarily in Class I and Class II arches and to some extent in Class IV arches. There is ongoing controversy about the design requirements for free end or extension base removable partial dentures (le, Class I, Class II, and long-span Class IV applications).

16. The debate centers upon the amount of support that should be derived from the edentulous ridge and that which should be derived from the remaining teeth. These philosophies are based upon three approaches to force distribution. These approaches may be described as follows: 1. Stress equalization 2. Physiologic basing 3. Broad stress distribution

17. Stress equalization The stress equalization approach to partial denture design emphasize that the vertical displaceability of a natural tooth is not as great as that of the soft tissues covering the edentulous ridge.

18. Forces applied to a removable partial denture are transmitted to the abutments. As a result, proponents believe that rigid connections between denture bases and direct retainers are damaging, and that stress directors are essential to protect the abutments

19. Stress directors may take several forms. The most commonly used stress directors are simple hinges interposed between the denture bases and the adjacent clasping assemblies. These hinges are designed to permit vertical movement of the denture bases without causing undue loading of the abutments. In addition, many of these devices can be adjusted to control the amount of vertical travel that is permitted.

20. Advantages Stress director designs usually call for minimal direct retention because the denture bases operate more independently than do those used in conventional removable partial denture applications. Theoretically, stress directors minimize the tipping forces on abutment teeth, thereby limiting bone resorption.

21. Disadvantages Stress directors are comparatively fragile and their incorporation into removable partial denture frameworks can be costly. These devices require constant maintenance and may be difficult or impossible to repair.

22. Physiologic basing Physiologic basing believe that there is a significant disparity between the apical displaceability of teeth and the compressibility of the soft tissues.

23. These practitioners believe that equalization can best be accomplished by recording the anatomy of the edentulous ridge in its functional form and ensuring that the associated denture base accurately reflects this anatomy. It can be accomplished by depressing the mucosa during impression-making procedures or by relining the denture base after it has been constructed.

24. This theory believe that denture bases formed over compressed tissues will show an increased ability to withstand vertical forces. These practicioners also recognize that the prosthetic teeth and occlusal rests will be positioned above the existing occlusal plane when the prosthesis is not in function

25. To permit vertical movement of the partial denture from its rest position to its functioning position, the number of direct retainers must be limited. Furthermore, these direct retainers must be designed to provide minimal retention.

26. Advantages Proponents of this theory believe that denture base movement occurring as a result of soft tissue compression and recovery exerts a physiologically stimulating effect on the tissues of the residual ridges. They also believe that this action promotes tissue health and reduces the necessity for frequent relining or rebasing procedures.

27. The minimal retention requirements associated with physiologic basing result in lightweight prostheses requiring minimal maintenance and repair. The forgiving nature of retentive clasps ( eg , combination clasps with wrought-wire retentive arms) produces a significant reduction in the forces transmitted to the abutment teeth. As a result, advocates of this theory believe that abutments are retained for longer periods.

28. Disadvantages Because the artificial teeth are slightly above the occlusal plane when the denture is not in function, there will always be premature contacts between the opposing teeth and the prosthesis during closure. This may be somewhat annoying to the patient and may result in some discomfort.

29. It is difficult to produce effective indirect retention because of the vertical movement of the denture and the minimal retention provided by the direct retainers. In addition to the foregoing factors, prostheses constructed in accordance with physiologic basing principles are not well stabilized against lateral forces. This is related to the minimal number of direct retainers used in conjunction with these designs.

30. Broad stress distribution Advocates of broad stress distribution believe that trauma to the remaining teeth and residual ridges can be prevented by distributing forces over as many teeth and as much of the soft tissue area as possible.

31. This is accomplished by using additional rests and clasp assemblies and by ensuring that the associated denture bases provide broad coverage

32. Advantages Proponents of this philosophy believe that forces transmitted to the supporting teeth and residual ridges may be minimized by distributing these forces over a greater number of teeth and a larger soft tissue area. Advocates of this philosophy also believe that increased contact with the remaining teeth and soft tissues minimizes the lateral forces on the remaining structures. The use of multiple clasp assemblies is not intended to increase retention.

33. In addition to the advantages already listed, proponents of this philosophy believe that the resultant prostheses are easier and less expensive to construct. There are no moving parts, so there is less danger of fracture and distortion. In addition, the rigid components minimize rotational movements and provide excellent horizontal stabilization.

34. Disadvantages The increased coverage provided by such prostheses may not be accepted by some patients. This coverage also may complicate oral hygiene. As a result, preventive dental programs must be instituted and oral hygiene must be carefully monitored.

35. synonyms 35

36. evolution 36

37. 1 Winders design Screw joint retention 2 Parr(1886) Extracoronal socket attachment 3 Stair Telescopic abutment restoration 4 Ash (1912) Split bar attachment system 37 1 2 3 4

38. Late 19 th century : Dr.Herman , ES Chayes “T shaped” Precision Attachment (1906) “H shaped” Chayes Attachment (1912) First attachment to be available in the general market 38

39. Stress management 39

40. Factors affecting magnitude of stress transmitted 40

41. Indications 41

42. contraindications 42

43. advantages Esthetics Retention incase of overdentures Stress director Cross arch stabilization Force closer to fulcrum thus less lateral forces 43

44. disadvantages Cost Maintenance Repair Experience of dentist & lab Additional chair & lab time 44

45. CLASSIFICATION OF ATTACHMENTS: Attachments are classified in a number of ways: Bases on the method of fabrication and tolerance of fit: 1. Precision (prefabricated attachments) 2. Semi precision (custom made) attachments:

46. Precision attachments are basically classified as follows ( Goodkind & Baker, 1976): Intracoronal Resilient Non-resilient Extracoronal Resilient Non-resilient

47. Based primarily on the function of the attachments: 1. Rigid: Any attachment employing a mechanical locking action with the use of clasps, lingual arms, springs, ball and sockets etc. The removable partial denture is held firmly in place and the abutment teeth are subjected to all of the forces in the mouth at all times. 2. Passive: An attachment that provides a free movement of the male when the abutment teeth are exposed to excessive forces. Such a passive retention mechanism has the effect of an automatic stress breaker.

48. Mensor’s classification : An attachment classification based on shape, design and primary area of utilization of attachment.

49. Classification by Harold Prieskel : 1. Intracoronal attachments : A. Those whose retention is entirely frictional With adjustment potential: Constant insertion and removal of the prosthesis will cause the attachments to wear, so that some form of adjustment is desirable. e.g.: a. Chayes attachment b. McCollum unit

50. Without adjustment potential: Lack of adjustment potential renders this type of unit unsuitable for removable prosthesis, as repeated insertion and removal will cause the attachment to wear. They are useful for joining a series of crowns without a common path of insertion.

51. B. Those whose retention is augmented by a mechanical lock. e.g.: Schatzmann unit.

52. Depending on the cross sections intra coronal attachments can be classified into 1. H-Shaped flanges : The external frictional flange of H-Shaped unit strengthens the attachment, without increasing the size of the female part. 2. T-shaped flanges : E.g. Chayes attachment. 3. Attachments with a circular cross section. They are suitable only for joining two sections of a fixed prosthesis.

53. Attachments with auxiliary retentive features: Auxiliary retentive features are incorporated in some attachments in an effort to provide more retention for a given frictional area although no extra stability is provided. A minimum of 4 mm vertical space is necessary: They are screw and tube attachment, key and keyway/ interlocks, Sectional dentures, bar connectors

54. H shaped attachment Single adjustment slot Mc Collum attachment An H shaped attachment indicated for fixed movable bridgework, removable partial dentures and distal extension partial dentures when cross arch stabilized. 56

55. Two adjustment slots Stern attachment H shaped configuration. This attachment is an intra-coronal, active friction grip attachment to which a distal hinge block has been added. Used as a stress breaker attachment and in fixed removal bridge work and RPDs. 57

56. Available as Rigid / Resilient Rigid crismani attachment Frictional grip Mechanical grip Crismani attachment These come in resilient and rigid forms. The rigid types are available with both friction and mechanical spring clip retention mechanisms. They come in intracoronal active friction grip as well as snap grip varieties. The hinged, resilient type attachment can be used in distal extension cases. 58

57. 2. Extracoronal attachments : a. Projection units : These units are attached to the proximal surface of a crown. E.g.: ASC -52. Those that provide a rigid connection. e.g.: Conex attachment. Those that allow play between the components. e.g.: Dalbo , Ceka attachment. b. Connectors : These units connect two sections of a removable prosthesis and allow a certain degree of play E.g.: Dalbo -fix used between a telescope crown and partial denture.

58. c. Combined units : The attachment features an extracoronally placed hinge type unit connected to an intracoronal attachment. E.g.: Schatzmann attachment consisting of an intracoronal section with a projection.

59. stabilex It is a bar with a double tube over which fits the secondary part containing two cross split cylinders as the frictional element These split pins are activated with a special key, which even the patient can use and with which the pins may also be unscrewed and replaced 61 Matrix Patrix Assembled

60. Patrix Matrix RESILIENT EXTRA CORONAL ATTACHMENT Dalbo / Dalla bona attachment These are known as Dalla bona slide block or Dalbo stud anchor. The Dalbo attachment is a good example of a ball and socket joint in which the ball is cantilevered off the abutment tooth and the socket is attached to the prosthesis. The wall of the metal socket has several small slits to provide a resilient entrance to the socket and offers some direct retention to the attachment when the socket engages the ball over its height of contour . They are useful when there is minimal vertical space available and rotation, resilience and retention are desired. 62

61. Rigid system Non-rigid system Stress breaker ROLE OF ATTACHMENTS AS STRESS BREAKER (Broken stress philosophy) 63

62. STRESS BREAKER DESIGNS (ASC-52) This is an example of an extracoronal resilient attachment that posses universal resilience. It consists of an extracoronal slide attachment with a spring activated universal hinge joint and adjustable retention. It is the smallest stress director in dentistry and is used for distal extension RPD’s. 64

63. Neys distal extension stress breaker Ney attachments are intracoronal snap grip attachments. Available in 2 basic designs, the familiar chayes with adjustable wings and the neyloc design with gingival retention feature. 65

64. Stud attachments are so called because of the shape of the male units that are usually soldered to the diaphragm of a post crown. They are among the simplest of all attachments. They can provide additional retention, stability and support. Few stud attachments are entirely rigid because of their small size. Gerber, Dalbo , Zest, ERA, Prosnap , Profix all are stud attachments. Gerber is the largest stud unit.

65. Dalla Bona It is a simple attachment, available in resilient, non-resilient and stress broken types. It is useful when there is minimal vertical space available and rotation resilience and retention is desired. It consist of a single piece male stud soldered to the coping and a single unit female processed within denture. 68

66. ROTHERMAN ECCENTRIC ATTACHMENT Advantages It is one of the smallest of stud attachments and hence requires very little space (average 1.6mm). It is available in nonresilient and resilient versions. Simple to use with adequate retention and ease of maintenance. Disadvantages : Chair –side insertion of keyway is difficult. 69

67. ZEST ANCHOR ATTACHMENT Consists of a metallic funnel shaped tube cemented into the root canal of the tooth and a polyethylene stud that is attached to the denture base. The head of the stud squeezes past the construction in the neck of the funnel to retain the denture on the tooth. It derives its retention from within the tooth 70

68. Cut section SCHUBIGER ATTACHMENT Patrix : threaded post / screw Matrix : recessed collar, cap nut / lock nut 71

69. Stud attachments have numerous applications: 1. Overdenture being relatively small they can provide additional stability, retention and support while the positive lock of certain units can maintain the border seal of the denture. 2. Non-vital partial denture abutments . The loads applied in these circumstances can be considerable, so one of the larger and stronger units is recommended. 3. For retention of a small tooth supported restoration with non-vital abutment.

70. bar 73

71. Gilmore clip system (1913) - metal bar with retaining sleeve / clip. Bar can be attached to the : Coping or crowns over the vital teeth Post coping on endodontically treated teeth Screwed down into the coping (implant system) 74

72. 75

73. Multiple sleeve bar joints Single sleeve bar joints BAR JOINTS 76

74. Round / circular Oval / egg shaped ‘U’ shaped / parallel sided bars Depending on cross section 77

75. Dolder bar Egg shaped bar in cross section Open sided sleeve Two sizes 3.5mm x 1.6mm, 3.0mm x 2.2mm Spacer – degree of movement 78

76. Sagittal rotation Rest position Vertical translation MOVEMENTS SEEN IN DOLDER BAR 79

77. ACKERMANN BAR Available in different cross section Circular cross section – can be bent in all planes A short extension of 5mm is carried behind the most distal root and the sleeve positioned on this section Prevents tendency for distal part to rise when sticky foods are chewed. This is recommended where bar is set an antero-posteriro curve to prevent hinge rotation and motion. Multiple sleeve bar joints are more versatile than single ones except bars that have slightly rigidity. 80

78. Cm bar It is similar to circular Ackermann bar with diameter of 1.9 and is of precious and semi-precious alloys, the latter recommended for long spans. 81

79. Hader bar Prefabricated plastic pattern are adapted to master cast according to its contour and cast in alloy of choice . Sleeves of plastic have to be replaced for adjustments, hence metal sleeves can be substituted. 82

80. Advantages of bar attachments : Rigidly splint the teeth Provides good retention, stability and support Provides cross arch stabilization Positioned close to the alveolar bone (exhibit less leverage) 83

81. Disadvantages : Bulk of bar Plaque accumulation Wearing Soldering procedure 84

82. magnet 86

83. Since 1950 To retain maxillofacial prosthesis Alu , Ni, Iron,Cobalt alloy (alnico) Limited use – larger size 1960 “use of rare earth element” – High field strength – Can be used in smaller size. Somarium cobalt (Sm-Co) (Joseph Becker Hoffer 1967) Neodymium iron boron ( Nd -Fe-B) – 20% stronger Somarium iron nitride – High magnetization Used for retention of mandibular overdentures (tooth and implant supported over dentures) 87

84. Gilling’s magnetic attachment (cobalt somarium alloy magnets) “Split pole paired magnets” Closed field magnetic system Magnetic retainer with magnets Magnetic keeper 88

85. Advantages of magnetic attachment : Smaller size and strong attractive force Produce constant force – constant retention Easy to incorporate into the prosthesis Automatic reseating Boon for elderly patients (Parkinsonism, arthritic patient) Less lateral force to the abutment tooth 89

86. Jackson magnetic attachment (cobalt somarium alloy magnets) Cemented in keeper Screwed in keeper 90

87. Disadvantages : Loss of retention due to corrosion or heat instability Requires encapsulation within inert alloys Cannot be repaired High cost Limited force transmission - Magnets can slide on their keepers. 91

88. Applications: 1. They act as relatively rigid connection between the implants to which they are attached by screws, which overcomes the divergence between the implants 2. Robust and effective retainers. 3. When employed to connect roots, the fact that the bar is close to the alveolar bone supporting the teeth results in far less leverage on the roots than if the occlusal rests had been employed. 4. Bar joints are applicable for over dentures constructions. 5. The design and construction of bar attachments can provide the denture with significant stability and retention.

89. 5. Auxiliary attachments a. Screw units b. Friction devices c. Bolts d. Hinge flanges

90. Swing-Lock Removable Partial Dentures In the Swing-Lock removable partial denture, first described by Dr J. Simmons in 1963, all or several of the remaining teeth are used to retain and stabilize the prosthesis against vertical displacement.

91. The prosthesis consists of a hinged buccal or labial bar attached to a conventional major connector. Retention and stabilization are provided by this bar. A Swing-Lock removable partial denture exhibits a hinged labial bar The labial bar is attached to the framework by a hinge mechanism (arrow) that permits it to open and close like a gate.

92. Locking mechanism in the open position Locking mechanism in the closed potion,(arrow).

93. The labial bar is generally designed with small vertical projection arms that contact the labial or buccal surfaces of the teeth gingival to the height of contour Vertical projections of the labial bar contact the remaining teeth

94. These vertical arms look like I- or T-bars and provide both retention and stabilization for the prosthesis. The labial bars can also be designed with acrylic resin retention components, in which case retention and stability are provided by an acrylic resin denture base attached to the labial bar. A labial bar also may include beads (arrows) to permit attachment of an acrylic resin veneer

95. This design is used if the vertical projection bars would produce a poor esthetic result or if extensive loss of gingival tissue has occurred and a resin gingival veneer is needed to improve appearance.

96. Advantages The primary advantage of the Swing-Lock concept is that it provides a relatively inexpensive method for using all or most of the remaining teeth for the retention and stabilization of a prosthesis. Alternatives to this type of treatment include (1) removal of the remaining teeth and (2) fixed splinting of the remaining teeth and construction of a conventional removable partial denture.

97. Disadvantages A Swing-Lock prosthesis can produce a relatively poor esthetic result for patients with short or extremely mobile lips. Obtaining perfect adaptation of a resin veneer is difficult because the path of insertion is dictated by the hinge movement of the labial bar.

98. The remaining teeth are grasped firmly by the prosthesis. A long distal extension base is likely to move toward the tissue under the forces of occlusion. This movement can tip the teeth grasped by the prosthesis

99. conclusion

100. It is critical that the appropriate attachment be utilized for each individual case situation. These classification systems aids in having a broader view about the type of attachment to be judiciously used since each clinical situation for which an attachment is intended will place specific demands that can be met, only if we have thorough idea about the diverse attachments available.

101. References

102. The Glossary of Prosthodontic Terms. J Prosthet Dent 2017 ;117(5S):e1-e105. Stewart, Rudd and Kurbker : Clinical Removable Partial Prosthodontics; 2nd ed., Euro America Inc , Publishers Tokyo,1997 Carr AB, Mc Givney and Brown DT: Mc Craken’s Removable Partial Prosthodontics; 11th ed.

103. Boitel HR. Precision attachments: an overview. In: Tylman SD, Malone WFP, eds. Tylman’s theory and practice of fixed prosthodontics. 7th ed. St Louis: The CV Mosby Co, 1978, chap 22. Zlataric . The Effect of Removable Partial Dentures on Periodontal Health of Abutment and Non-Abutment Teeth. JPeriodontology , 2002, 73: 137-144 Burns and Ward JE Review of attachments for RPD design Classification and selection IJP 1990; 3(1) : 90-102

104. Rudd KD, Morrow RM, Eissmann HF – Dental Laboratory Procedures – Removable Partial Dentures. St. Louis, Missouri: CV Mosby; 1986. Amit Khare , Sumit Makkar , Roshna T. Full Mouth Rehabilitation with Fixed and Removal Prosthesis using Extracoronal Attachments: A Clinical Report. People’s Journal of Scientific Research Vol. 4 (2), July 2011 Gerardo Becerra, Micheal Mac Entee . Classification of precision attachments. J Prosthet Dent 1987; 58 (3): 322-327.

105. Mensor MC. Classification and selection of attachments. J Prosthet Dent 1973; 29: 494-97. J. M. Sossamon . Spectrum of function- a classification system for attachments in removable prosthodontic therapy. QI 1986; 17 (3): 52-56. Dr. Prabhakar angadi et al. Precision attachments-applications and limitations. Journal of Evolution of Medical and Dental Sciences 2012; 1 (6): 1113-1121. Harold W. Preiskel . Over denture made easy. A Guide to Implant and Root Supported Prosthesis. 1996 Quintessence books; pgno ; 87.

106. Thank you