7. ABUTMENTS IN FPD.pptxxxxxxxxxxxxxxxxxx

abutment selection in fpd

1. Abutments in FPD PRESENTED BY- ANUKRITY CHANDRA PG 2 ND YEAR. GUIDED BY – Dr. SUDHEER ARUNACHALAM Dr. TUSHAR TANWANI Dr. ANUPAM PURWAR Dr. SUDEEPTI SONI Dr. POOJA AGRAWAL

2. CONTENTS 2 Introduction Review of literature. Evaluation of abutment Biomechanical considerations S pecial types of abutment Conclusion References

3. 3 Introduction According to GPT 9 “ A tooth, a portion of a tooth, or that portion of a dental implant that serves to support and/or retain a prosthesis.”

4. 4 Primary abutment: Adjacent to edentulous space. Secondary abutment: Abutment remote from edentulous space. Intermediate abutment (pier abutment): A natural tooth located between abutments that serve to support a fixed or removable dental prosthesis

5. Review of literature Alijorah Al- sinaidi et al in 2013- stated that in subjects with FPDs the abutment teeth are more prone to plaque accumulation , gingival inflammation and development of periodontal pockets than the non- abutment teeth. The individual’s age and duration of insertion of the FPD can affect the periodontal condition of affected teeth. The abutment teeth with sub- gingivally placed crown margins are likely to have higher scores of plaque index than the abutment with supra-gingival crown margins. 5

6. Shivakshi chansoria and harsh chansoria in 2018 - stated that the abutment bear the stresses of mastication and the choice of abutment influences the prognosis of treatment. 6

7. Assessment of abutment teeth Root length and morphology. Pulp outline. Periodontal ligament space. Alveolar bone. Infrabony defects. Residual roots. Impacted or supernumerary teeth. The extent of present and past caries. Evaluate root canal filling 7

8. 8 Evaluation of abutment

9. 9 Every restoration must be able to withstand the constant occlusal forces to which it is subjected. All the forces that would normally be absorbed by the missing tooth are transmitted , through the pontic , connectors and retainers to abutment teeth.

10. 10 The factors influencing abutment selection. 1. Crown length. 2. Crown form. 3. Crown – root ratio. 4. Root configuration 5. Periodontal ligament area 6. Long axis relationship. 7. Arch form. 8. Span length.

11. Crown length Teeth must have adequate occluso -cervical crown length to achieve sufficient retention. Teeth with short clinical crown often do not provide satisfactory retention unless full coverage preparation are used or additional length is achieved periodontal surgery 11

12. Crown form Some teeth have tapered crown form, which interferes with preparation parallelism, necessitating full coverage retainers to improve their retentive and aesthetic qualities. Example- anterior teeth with poorly developed cingulum and short proximal walls and mandibular premolars with poorly developed lingual cusps and short proximal surfaces. 12

13. 13 Crown root ratio Physical relationship between the portion of tooth within alveolar bone compared with the portion not within the alveolar bone, as determined by radiograph. (GPT-9) The crown root ratio is measure of the length of tooth occlusal to alveolar crest of bone compared with the length of root embedded in the bone.

14. 14 Optimum -2:3 Minimum -1:1 (acceptable)

15. This ratio is determined by a comparison of the linear measurement of the portion of the tooth above the bone to that within the bone. Reynolds JM. Abutment selection for fixed prosthodontics . J. prosthet . Dent. 1968;19: 438-488. 15

16. Root configuration 16 Roots that are broader labiolingually than they are mesiodistally are preferable to roots that are round in cross section . Multirooted posterior teeth with widely separated roots will offer better periodontal support than roots that are converge, fuse or generally present with conical configuration.

17. A tooth with conical roots can be used as an abutment, if all other factors are optimal. Irregularly shaped, multiple roots offer better prognosis. A well aligned tooth will provide better support than a tilted one. Alignment can be improved with orthodontic treatment. 17

18. Periodontal ligament area The periodontal ligament area can be used as a scale or measurement to determine the potency of an abutment. This is an important point in the assessment of abutment’s suitability from a periodontal standpoint. 18

19. Periodontal ligament area 19 Root surface area or the area of periodontal ligament attachment of the root to the bone. The area of various root teeth have been reported by Japsen .

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21. 21 Tylman stated that two abutment teeth could support two pontics . Ante’s law by Johnston et al, the root surface area of the abutment teeth had to equal or surpassed that of the teeth being replaced with pontics . In FPD, for the observation that the combined pericemental area of all abutment teeth supporting a fixed dental prosthesis should be equal to or greater in pericemental area than the tooth or teeth to be replaced. GPT 9 In cases where the periodontal surface area seems inadequate, the use of multiple teeth for abutment may be indicated depending on other biomechanical factors.

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23. Long axis relationship The architecture of periodontal ligament is such that forces are withstand best when they are directed along the long axis of the tooth. A severely inclined tooth will not withstand forces as well as one that is erect. Inclined tooth as abutment - shorter edentulous span with less occlusal force. Common path for insertion - conventional FPD : less than 25 degree inclination 23

24. 24 Arch Form When pontics lie outside the inter abutment axis line, the pontics act as a lever arm, which can produce a torquing movement. Common problem in replacing all four maxillary incisors. SOLUTION Additional retention in opposite direction from the lever arm and at a distance from the inter-abutment axis equal to the length of the lever arm. The 1 st premolar is sometimes used as secondary abutments for a maxillary 4 pontic canine-to-canine FPD

25. Length of span ( laW of beam) The law of beams is an engineering principle that states that as the length of the span increases, the flexure of a system will be the increase in length to the power of three (cubed). 25

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27. Height of contour (law of beams) As the height of span decreases, the flexure of a system will be the increase in the length to the power of three (cubed) 27

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29. 29 Biomechanical considerations In addition to the increased load placed on the PDL by a long span FPD, Longer spans are less rigid. Bending or deflection varies directly with the cube of the length and inversely with cube of the occlusogingivally thickness of the pontic .

30. IDEAL ABUTMENT An unrestored caries free tooth is an ideal abutment. It can be prepared conservatively for a strong retentive restoration with optimum aesthetics 30

31. Endodontically treated abutments. Teeth in which the pulpal health is doubtful should be endodontically treated before initiating fixed prosthesis. Although a direct pulp caps may be acceptable ,a conventional endodontic treatment is normally preferred for cast restoration, especially where the later need for endodontic treatment would jeopardize the success of treatment. 31

32. Such endodontically treated teeth serve well as abutment with post and core foundation for retention and strength. Sometimes its better to remove badly damaged tooth rather than attempting endodontic treatment. Endodontically treated teeth cannot be selected for cantilever FPD 32

33. POST AND CORE 33

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35. Secondary abutments 35 Double abutments are sometimes used as means of overcoming problems created by unfavorable crown root ratio and long spans. Secondary abutment must have at least as much root surface area and as favourable a crown root ratio as primary abutment .

36. Indication. To increase retention of restoration. To increase area of supporting periodontal ligament and bone. Unfavourable crown root ratio. Long span FPDs Splint and stabilize periodontally compromised teeth. 36

37. 37 SPECIAL PROBLEMS Pier abutment A natural tooth located between terminal abutments that serve to support a fixed or removable partial denture. Completely rigid restoration is not Indicated.

38. 38 Nonrigid connectors for fixed partial dentures Shilinburg et al, JADA, Vol. 87, November 1973; 1195-1199 These movements of measurable magnitude and in divergent directions can create stresses in a long-span prosthesis that will be transferred to the abutments. Forces transmitted to terminal retainers as a result of middle abutment acting as a fulcrum, causes failure of weaker retainer.

39. 39 The retention on an anterior tooth is usually less because of its generally smaller dimensions. Because there are limits to increasing a retainers capacity to withstand displacing forces, some means must be used to neutralize the effects of those forces. use of non rigid connector, movement in a non rigid connector is enough to prevent transfer of stress from the segment being loaded to the rest of FPD.

40. 40 Non rigid connector on middle abutment tooth prevents its acting as fulcrum. Restrict to short span FPD key way - distal contours of pier a abutment key - mesial side of the distal pontic

41. 41 Non rigid connector transfer stresses to supporting bone rather than concentrating it in the connecctors .

42. 42 The long axis of the posterior teeth usually lean slightly in the mesial direction, and the vertically applied occlusal forces also produce some movement in this direction. A controlled study showed that nearly 98% of the posterior teeth measured tilt mesially when subjected to occlusal forces.

43. 43 Placement of the keyway on the mesial side, however, causes the keyway to be unseated during its mesial movements. In time, this could result in a pathologic mobility in the canine or failure of the canine retainer.

44. 44 Tilted molar abutments Discrepancy in long axis of molar and premolar makes it impossible to achieve common path of insertion 3rd molar tipped with tilted 2nd molar prevents complete seating of FPD

45. 45 If tilting is severe - Orthodontic treatment done Up righting 2nd molar. Extraction of 3rd molar to facilitate distal movement of 2nd molar. Temporary FPD post treatment to prevent relapse.

46. 46 Proximal half crown on distal retainer Three quater crown so that distal surface is uncovered.

47. 47 Telescopic crown A full crown preparation with heavy reduction is made to follow the long axis of the tlited molar. Inner coping: Fit the tooth preparation. Proximal half crown: Serve as retainer for FPD is fitted over the coping.

48. 48 Non rigid connector Full crown on molar with its path of insertion parallel to long axis of that tilted tooth. Box form placed in the distal surface of premolar to accommodate keyway. Non rigid connector on mesial surface of molar Greater tipping of the tooth .

49. 49 Canine replacement fixed partial denture Replacing canine – difficult because the canine often lies outside the interabutment axis. In maxillary canine – outward ( labially ) In mandibular canine – inward ( lingually )

50. So the support from secondary abutments will have to be considered. Edentulous spaces created by the loss of canine and any contiguous teeth is best restored with implants. 50

51. Impacted canine 51

52. 52 Cantilever fixed partial denture A cantilever fpd is one that has an abutment or abutments at one end only, with the other end of the pontic remaining unattached . Abutment teeth for cantilever FPDs should be evaluated for lengthy roots with favourable configuration, good crown root ratios and long clinical crowns. Generally cantilever FPDs should replace only one tooth and have at least 2 abutments

53. 53 Replacing a missing1 st premolar

54. 54 Replace molar when there is no distal abutment Most commonly this type of fixed partial denture is used to replace a first molar, although occassionally it is used to replace a second molar to prevent supereruption of opposing tooth.

55. IMPLANT ABUTMENTS An abutment is a component that is intermediate between the implant and the restoration and is retained to the implant by a screw or locking taper.. 55

56. Used as an attachment to retain a prosthesis.. During abutment selection on the basis of implant abutment connections, clinician should consider the topography of bone , available soft tissue characteristics and prosthetic component required particularly for aesthetic purpose,. 56

57. Questionable abutments. CLASSIFICATION General disorder Mineralization. amelogenesis imperfecta Dentinogenesis imperfecta Hypocalcification Internal resorption Congenital and growth deformities. Malformed dentition Malposed teeth 57

58. Local problems polycarious teeth periodontally involved teeth. occlusal plane correction Tilted teeth Wasting disease. 58

59. Treatment strategy Abutment with generalized mineral disturbance: full coverage restoration. success depends on supporting tissue response. Congenital growth deformities : 1 ST Line treatment; Orthodontics Interceptive periodontics Restorative dentistry 59

60. Malposed teeth Judicious teeth reduction. O rthodontics for minor tooth movement: require periodic occlusal adjustment. Telescopic crowns. Supra-erupted teeth Intentional RCT. Reduction to satisfactory occlusal plane . 60

61. 61 Conclusion Selecting a suitable abutment forms the preliminary treatment planning for FPD whose proper selection and preparation aids in long term durability of the restoration.

62. 62 References Shillingburg . Fundamentals of Fixed prosthodontics. 4 th ed. Tylman’s Theory and practice of fixed prosthodontics. 8 th ed. Rosenstiel , Land, Fujimoto. Contemporary Fixed prosthodontics. 3 rd ed. Stress distribution among periodontally compromised abutment : a comparative study using 3D FEAC. Rajkiran et al; cont clinical dent: oct-dec , 2012;3:4 Nonrigid connectors for fixed partial dentures Shilinburg et al, JADA, Vol. 87, November 1973; 1195-1199

63. Good morning

64. Metal and fibre posts If a Prefabricated metal post is used along with all ceramic restorations, colour and opacity of the post may lead to discolouration /shadowing of both gingiva and ceramic restoration. Metal free alternatives have been on the horizon for more than a decade now; these include carbon fibre posts and the aesthetic alternatives of quartz fibre as well as ceramic posts. Not only are metal posts are undesirable when aesthetics is of prime consideration as in all ceramic units; but is also a problem area where corrosion products are concerned. Biocompatibility is achieved to an excellent degree with the non-metal posts especially the ceramic, carbon fibre and quartz fibre posts. 64

65. 65 Replace molar when there is no distal abutment Forces on a full sized molar cantilever pontic place great stress on the mesial abutment. Cantilever fixed partial denture replacing a mandibular first molar, using both premolars as abutment teeth.to minimize stress on the abutments, the pontic is the size of premolar rather than a molar

66. Which developmental anomaly of tooth is best used as abutments. DILACERATION. - Refers to the angulation or a sharp bend or a curve anywhere along the root portion of a tooth. 66

67. How to calculate the degree tipping of a tooth The angle between the long axis of the tooth and a line perpendicular to the occlusal plane was used for measuring the degree of tipping. 67 Bars through the long axis of the teeth and perpendicular to the occlusal plane respectively show the reference lines used for measuring the degree of tipping

68. Tipped and upright molars in adults Molar inclined less than 10 degree in relation to the perpendicular to the occlusal plane to be normal upright tooth with regard to normal variations in the curve of spee . The molars tipped 30 degree or more relative to the perpendicular to the occlusal plane with or without mesial contact with the neighbouring tooth can opt for orthodontic treatment. 68

69. Preparation of key in non- rigid connectors. The recommended occluso -gingival height of connector is ideally 3-4 mm. it should be sufficiently large to prevent distortion/fracture during function. The main disadvantage of this system is need of increased tooth reduction on distal surface of ant abutment leads to over contouring of distal surface of mesial retainer. 69