Abutment evaluation /Fixed orthodontics teaching

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Abutment evaluation /Fixed orthodontics teaching

  1. 1. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. contents Need for evaluatioN factors to be coNsidered while abutmeNt evaluatioN  selectioN of abutmeNt teeth  coNclusioN  refereNces www.indiandentalacademy.com
  3. 3. Need for evaluatioN  Abutment--It is any tooth, root or implant which gives attachment and support to the fixed partial denture.  Abutment teeth are important to withstand the forces normally directed to missing teeth and those usually applied to itself. www.indiandentalacademy.com
  4. 4. aN importaNt step iN treatmeNt plaNNiNg  Identification of patient needs  Deciding what type of prosthesis  Decision to remove any teeth or not  Treatment of symptoms  Stabilization of deteriorating conditions such as dental caries, any periodontal disease  Definitive therapy and occlusal adjustment  Fixed prosthodontics---ABUTMENT EVALUATION  Follow up www.indiandentalacademy.com
  5. 5. factors to be coNsidered while abutmeNt evaluatioN www.indiandentalacademy.com
  6. 6. crowN-root ratio  It is a measure of the length of tooth occlusal to the alveolar crest of bone compared with the length of root embedded in the bone.  Optimum crown-root ratio for tooth to be used as an abutment is 2:3  Ratio of 1:1 is the minimum ratio acceptable .  Cases where ratio greater than 1:1 is possible- -if opposite dentition is made up of artificial teeth www.indiandentalacademy.com
  7. 7.  -if opposing dentition is composed of periodontally mobile teeth instead of sound teeth… www.indiandentalacademy.com
  8. 8. Root configuration www.indiandentalacademy.com
  9. 9. www.indiandentalacademy.com
  10. 10. www.indiandentalacademy.com
  11. 11. PDL AreA  Larger teeth have greater surface area and are better able to bear added stress,  When supporting bone has been lost because of periodontal disease, the involved teeth have a lessened capacity to serve as abutments  TYLMAN- two abutment teeth could support two pontics www.indiandentalacademy.com
  12. 12.  The root surface area of abutment teeth had to equal or surpass that of teeth being replaced with pontics --by Ante in 1926  According to this law, one missing tooth can be successfully replaced if the abutment teeth are healthy  Example – patient has lost first molar and second premolar - Four unit FPD is an acceptable risk as long as there is no bone loss from periodontal disease ANTe’S LAW www.indiandentalacademy.com
  13. 13. Ante’s law www.indiandentalacademy.com
  14. 14.  Because second molar and first premolar abutments have root surface areas approximately equal to those of missing teeth  If first molar and both premolars are missing ,then FPD is not considered a good risk because the missing teeth have a greater total root surface area than the potential abutments LIMITATION: Teeth with considerably reduced bone support can be successfully used as fixed partial denture abutments if oral hygiene is maintained www.indiandentalacademy.com
  15. 15. SeLecTION Of AbuTMeNT TeeTh  Replacement of single missing tooth  Replacement of several missing tooth  Replacement of special situations-  Pier abutment  Cantilever FPD  Canine FPD  Mesially tilted molar www.indiandentalacademy.com
  16. 16. rePLAceMeNT Of SINgLe MISSINg TOOTh 1. Cantilever FPD Example- lateral incisor pontic attached only to an extra coronal metal ceramic retainer on canine 2. Long term prognosis of single abutment cantilever is poor as it induces lateral forces on supporting tissues leading to tipping , rotation or drifting of the abutment - It can be resisted by multiple abutments teeth or using implant supported prostheses www.indiandentalacademy.com
  17. 17. ASSeSSMeNT Of AbuTMeNT TeeTh www.indiandentalacademy.com
  18. 18. eNDODONTIcALy TreATeD AbuTMeNTS  Used along with post and core foundations for retention and strength.  It can fail by 2 reasons: 1. If roots are short or 2. coronal tooth structure is less www.indiandentalacademy.com
  19. 19. Unrestored AbUtments  Unrestored abutment better than – prepared tooth  In case of prepared tooth prepare conservatively with optimum esthetics  In adult patients unrestored tooth can be safely prepared without jeopardizing the pulp as long as the design and technique of tooth preparation are wisely chosen www.indiandentalacademy.com
  20. 20. mesiAlly tilted second molAr TREATMENT : 1.UPRIGHT orthodontically 2.Space maintainer at the time of extraction 3.If cannot be corrected, it has been seen that less than 25 degree inclination can be accommodated 4.Designing with non rigid connector if parallel path of insertion is not obtained www.indiandentalacademy.com
  21. 21. www.indiandentalacademy.com
  22. 22. replAcement of severAl missing teeth www.indiandentalacademy.com
  23. 23. overloAding of AbUtment teeth  Forces due to parafunctional grinding and clenching should be eliminated for a perfect abutment.  Well formed ridge/Moderately resorbed ridge with favorable loading with respect to magnitude, direction. www.indiandentalacademy.com
  24. 24. direction of forces  Ideally a well fabricated FPD can distribute forces directing them in the long axis of abutment teeth  Potentially damaging lateral forces can be confined to the anterior teeth Where they are reduced by long lever arm????? www.indiandentalacademy.com
  25. 25. root shApe And AngUlAtion And root sUrfAce AreA 1. Divergent root > conical roots 2. Single root with elliptical cross section > circular cross section 3. Well aligned tooth > tilted tooth Root surface area—ante’s law www.indiandentalacademy.com
  26. 26. periodontAl diseAse  Horizontal bone loss from periodontal disease LEADS to loss of PDL supported root surface area o Example- because of conical shape of most roots, when one third of the root length has been exposed, half the supporting area is lost  Center of rotation moves apically  Lever arm increases – increased magnifying forces on supporting structure  Because of greater leverage associated with lengthened clinical crown www.indiandentalacademy.com
  27. 27. www.indiandentalacademy.com
  28. 28. Span length  Excessive flexing under occlusal loads can cause failure of a long span leading to 1. Fracture of porcelain veneer 2. Breakage of retainer or a connector 3. Unfavorable soft tissue response  LONGER THE SPAN ,GREATER THE FLEXING  Deflection varies directly with cube of length of pontic and inversely with the cube of occluso gingival thickness of pontic www.indiandentalacademy.com
  29. 29. Span length www.indiandentalacademy.com
  30. 30. Replacing Multiple anteRioR teeth  Problems with appearance and need to resist laterally directed tipping forces  In case of mandible, if a lone incisor remains, it should be extracted and only canine can be used as abutment  IN case of maxilla, both canine and premolar are used as abutments as because of the curvature of the arch, forces directed against a maxillary pontic will tend to tip the abutment teeth  In case of anterior bone loss, FPD cannot be used as it does not support missing tissues www.indiandentalacademy.com
  31. 31. concluSion  An abutment tooth is always evaluated so that it can bear forces of both missing teeth and those on itself.  Whenever possible ,an abutment should be a non mobile, vital tooth, if not then it should be endodontically treated and should possess good amount of coronal structure for retainer and surrounding tissues should be healthy . www.indiandentalacademy.com
  32. 32. RefeRenceS  Fundamentals of FPD by Herbert .shilinburg page(85-101)  Contemporary fixed prosthodontics by Stephen.rosenstiel page(82-102) www.indiandentalacademy.com
  33. 33. For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com

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