partial coverage restorations

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Introduction to Fixed Prosthodontics
Forth Year

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partial coverage restorations

  1. 1. • PARTIAL VENEER CROWNS
  2. 2. Definition “An extracoronal restoration that restores all but one coronal surface of a tooth or dental implant abutment, usually not covering the facial surface” GPT 8thEd,JPD July2005
  3. 3. Partial veneer crown Types : Post. teeth 3/4th crown Modified 3/4th 7/8th crown Reverse 3/4th Proximal ½ crown Ant.teeth 3/4th crown Pin-ledges Porcelain Laminates
  4. 4. Indications • Posterior Teeth that have lost moderate amount of tooth structure, provided buccal wall is intact • Commonly used as retainers for FPD’s • Where restoration or alteration of the occlusal surface is needed • Anterior partial veneer crowns can be used as retainers, to re-establish anterior guidance & to splint teeth.
  5. 5. Indications continued • Teeth with crown length that is average or that exceeds average • Teeth with normal anatomic crown form • Anterior teeth with adequate labio-lingual thickness
  6. 6. Contraindications • Short clinical crown • Retainers for long-span FPD’s • Rarely suitable for RC-treated teeth especially anteriors • Posterior-.RC-treated teeth where cusps are weakened • Active caries & periodontal diseases.
  7. 7. Contraindications continued • Deep cervical abrasion • Teeth with extensive core restoration • Bell shaped teeth • Thin teeth • Poorly aligned abutment
  8. 8. Advantages • • • • • • • Conservation of tooth structure Reduced pulpal & periodontal insult Access to supra-gingival margin is easy Better seating of the restoration Cement removal is simple Permits electric vital testing Good esthetic
  9. 9. Disadvantages • Less retention & resistance • Skillful preparation is critical to avoid metal display • Limited to fairly intact teeth
  10. 10. Principles Of Tooth Preparation 1.Preservation of tooth structure 2.Retention & resistance form 3.Structural durability of the restoration 4.Marginal integrity 5.Preservation of the restoration
  11. 11. Maxillary Premolar 3/4th Crown Occlusal Reduction  Mark the proposed location of the margin of the completed preparation  Depth grooves are made with a tapered carbide or narrow diamond.  Initial depth holes are placed in the mesial and distal fossae approximately 0.8 mm deep & centric cusp: 1.3mm.
  12. 12. b.Initial depth holes are connected by a guiding groove that extends through the central groove. Additional guiding grooves are placed on the lingual cusp similar to those for a complete cast crown . The depth cut placed on the triangular ridge of the buccal cusp becomes shallower as it approaches the cusp tip lingual
  13. 13. Recommended minimum clearance for reduction of a partial veneer crown preparation. c.Half the occlusal reduction is completed. Note the centric cusp bevel.
  14. 14. d. Occlusal reduction completed
  15. 15. E, After guiding grooves are placed in the lingual surface of the tooth parallel to the proposed path of withdrawal, the proximoaxial and linguoaxial reductions are initiated. Simultaneously a smooth and even-width cervical chamfer is created., Proximal and lingual axial reduction is performed with a round-tipped diamond. The proximal reduction is stopped short of the proposed location of the buccal margin.
  16. 16. F, When the axial reduction of the first half is considered acceptable, the other half can begin.
  17. 17. G, Proximal grooves are placed perpendicular to the prepared surface, and the buccal wall of each groove is flared to leave no unsupported enamel. The proximal flares are connected with a narrow contrabevel. After rounding of the line angles, the preparation is complete.
  18. 18. H, The interproximal clearance relative to adjacent teeth extends cervically as well as near the occlusal aspect of the buccal flares of the proximal grooves.
  19. 19. Groove placement • Done with tapered carbide bur • By 3 stages: 1.shallow occlusal template 2.extension to half length 3.Completion to full length
  20. 20. • Grooves should be placed as far facially as possible • Grooves are done first on the more inaccessible proximal surface • Length of the groove should be at least 4mm • Groove need not be deeper than 1mm at it’s cervical end • Groove should resist lingual displacement
  21. 21. Contd. • Walls of the grooves should not be undercut relative to the selective path of withdrawal • Walls should be flared towards intact buccal surface • 900 angle between lingual walls of proximal groove will resist lingual displacement • Buccal wall of each groove is flared to leave no unsupported enamel • Proximal flares are connected with a narrow contra bevel • 0.6mm clearance with adjacent teeth
  22. 22. Bucco-occlusal contra-bevel • Formed by connecting mesial & distal flares • It’s primary purpose to remove any unsupported enamel • If group function is planned, a heavier bevel will be needed • The bevel should remain within the curvature of cusp tip OCCLUSAL OFFSET When additional bulk is needed to ensure rigidity
  23. 23. Mandibular Premolar Modified 3/4th crown • Additional retention is required • Functional cusp bevels are placed on buccal cusp STEPS  0.8 mm depth holes  Depth holes connected by guiding groove
  24. 24. 1/2 the occlusal reduction completed Occlusal reduction & mesial 1/2 of axial surface completed
  25. 25. Axial reduction completed & proximal grooves prepared  Mesial groove has been flared & centric cusp chamfer placed
  26. 26. Facial view of complete prepn
  27. 27. 3/4th Prepn on a Mandibular Molar/PM • Location of occlusal finish line • No need for an offset on the lingual inclines of the buccal cusp
  28. 28. Reverse 3/4th Crown • Mandibular molar with intact lingual surface ,with severe lingual inclination • Occlusal offset on the buccal slopes of lingual slopes
  29. 29. THANK YOU

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