Removable Partial Dentures – The Tooth Tissue Junction

This program discusses the problems encountered with previous RPD designs and provides the basis for the employment of guide planes and proximal plates.  The benefits of parallel guide planes are presented with regards to retention, reciprocation and bracing provided by proximal plates are discussed and the design of the guide plane proximal plate interface is described. The various types of major connectors and design criteria for each is also presented.


The Tooth Tissue Junction – Major and Minor Connectors — Course Transcript

  • 1. The Tooth Tissue Junction Ting Ling Chang, Takahiro Ogawa and John Beumer III Division of Advanced Prosthodontics, Biomaterials and Hospital DentistryThis program of instruction is protected by copyright ©. No portion ofthis program of instruction may be reproduced, recorded or transferredby any means electronic, digital, photographic, mechanical etc., or byany information storage or retrieval system, without prior permission.
  • 2. RPI SystemThe Tooth Tissue Junction (Kratochvil)Mesial rest Proximal plate Tooth tissue junction “I” bar
  • 3. The Tooth Tissue Junction Kratochvil, 1963Basic Problem of previous designs  Acrylicresin at the tooth tissue junction  Acrylicresin is porous and harbors oral bacteria and retains plague  Space at tooth tissue junction  Impaction of food into the space  Hypertrophy of tissue into the space (arrow)
  • 4. Proximal plateDefinition A plate of metal in contact with the proximal surface (guide plane) of an abutment tooth.
  • 5. Proximal Plates vs Guide PlaneProximal Plate(the portion of the Guide planeRPD metal framework (Distal surface ofthat engages the abutment tooth)guide plane)
  • 6. The Tooth Tissue Junction Kratochvil, 1963Basic Problem of previous designs  Acrylicresin at the tooth tissue junction  Acrylic resin is porous and harbors oral bacteria and accumulation of plague  Space at tooth tissue junction  Impaction of food into the space  Hypertrophy of tissue into the space (arrow)
  • 7. The Tooth Tissue Junction Kratochvil RPD philosophySolution  Extend the prosthesis so that it contacts the entire proximal surface of the abutment tooth, eliminating all voids (ie. space)  Contact the tooth and tissue junction with metal
  • 8. The Tooth Tissue Junction Kratochvil RPD philosophyBenefits  Protect against food impaction  Prevent tissue hypertrophy between the tooth and prosthesis  The metal surface is nonporous and does not harbor oral bacteria  Plaque adherence is reduced
  • 9. The Tooth Tissue JunctionProximal plates – Design  It should extend 2 mm onto the edentulous mucosa  It should be fabricated of metal 2 mm  The metal is easily cleaned and does not harbor oral microorganisms
  • 10. Proximal Plates – Tooth Born RPD’s Additional benefits – Bracing and Retention Restores and maintains arch integrity in tooth-borne situations by anterior- posterior bracing action Enhances retention particularly when the proximal plates- guide planes are relatively parallel to one another
  • 11. Proximal platesAdditional Benefits – Restoration of arch integrity  The proximal plate in this case between the cuspid and premolar (arrow) helps restore the integrity of the dental arch, provides reciprocation for the retainer and helps prevent food impaction  The remaining teeth can therefore function as a unit in withstanding occlusal and lateral forces by distributing these forces more widely
  • 12. Proximal plates Additional Benefits – Restoration of arch integrityThe proximal plates restore the integrity of the dental arch. When lateralforces are applied the united dental arch can better distribute and absorbthese forces
  • 13. Proximal platesAdditional Benefits – Restoration of arch integrityThe proximal plates restore the integrity of the dental arch.When occlusal and lateral forces are applied in the extensionzone the united dental arch can distribute these forces morewidely.
  • 14. Proximal plates Additional Benefits – Restoration of arch integrityThe proximal plates restore the integrity of the dental arch. When lateralforces are applied the united dental arch can better distribute and absorbthese forces Courtesy Dr. T Berg
  • 15. Proximal platesAdditional Benefits – Restoration of arch integrityThe proximal plates restore the integrity of the dental arch.When lateral and occlusal forces are applied in the edentulousareas the united dental arch can better distribute and absorbthese forces Courtesy Dr. T Berg
  • 16. Proximal plates Additional Benefits-Reciprocation Act with other minor connectors in reciprocation of opposite retainers By extending the proximal plate around the lingual of the molar the tooth is properly encircled and the retainer is reciprocated
  • 17. Proximal plateDesign – Posterior teeth  Follow the curvature of the tooth  Extend to the self cleansing area on the facial and lingual side of the abutment
  • 18. Proximal plateDesign – Anterior teeth  Limitextension on the labial to enhance esthetics
  • 19. Minor connectorDefinition  The connecting link between the major connector or base of the removable partial denture and the other units of the prosthesis, such as the clasp assembly, proximal plates occlusal rests, or cingulum rests
  • 20. Minor connectors Design criteria They should be rigid Minor Connectors to Rests – The vertical components extending to the rests from the major connector should be at least 5.0 mm apart to reduce food entrapment. Consider lingual plate if the space is insufficient.
  • 21. Minor connectors Design criteria They should be rigid Minor Connectors to Rests – The vertical components extending to the rests should be at least 4-5.0 mm apart to reduce food entrapment. Consider lingual plate if the space is insufficient Courtesy Dr. A, Davodi
  • 22. Major Connectors,Definition:  A rigid part of the partial denture casting that unites the rests and other parts of the prosthesis across the arch.Maxillary  Circular Anterior-Posterior Connectors  Anterior palatal connectors  Central palatal connectorsMandibular  Lingual bar  Lingual plate
  • 23. Maxillary Major ConnectorsCriteria for selection  Location of the edentulous areas  The required amount of support  The required degree of rigidity  Patient preference  Anticipated loss of natural teeth  Location of the axis of rotation
  • 24. Maxillary Major ConnectorsCircular Anterior – Posterior ConnectorsFavored because they provide the best combination of rigidity and minimum bulk. Courtesy Dr. A, Davodi
  • 25. Maxillary Major Connectors Circular Anterior – Posterior ConnectorsThe anterior portion of the connector is positionedaccording to the treatment needs of the patient If the anterior teeth are to be replaced the connector should extend into the anterior edentulous area Courtesy Dr. GE King Courtesy Dr. GE King
  • 26. Maxillary Major Connectors Circular Anterior – Posterior ConnectorsThe anterior portion of the connector is positionedaccording to the treatment needs of the patient In some patients the anterior portion is extended to contact the anterior dentition to enhance bracing (resistance to lateral forces) and provide support
  • 27. Maxillary Major Connectors Circular Anterior – Posterior ConnectorsThe anterior portion of the connector is positionedaccording to the treatment needs of the patient If the anterior teeth are to be replaced the connector should extend into the anterior edentulous area Courtesy Dr. GE King Courtesy Dr. GE King
  • 28. Maxillary Major Connectors Circular Anterior – Posterior ConnectorsThe anterior portion of the connector is positionedaccording to the treatment needs of the patient If the anterior teeth are to be replaced the connector should extend into the anterior edentulous area Courtesy Dr. GE King Courtesy Dr. GE King
  • 29. Maxillary Major Connectors Circular Anterior – Posterior ConnectorsThe anterior portion of the connector is positionedaccording to the treatment needs of the patient In some patients the anterior portion is extended to contact the anterior dentition to enhance bracing (resistance to lateral forces) If the connector covers the lingual surfaces of the anterior teeth it must fit precisely and be thinned to avoid food impaction and allow for appropriate speech articulation.
  • 30. Maxillary Major Connectors Circular Anterior – Posterior ConnectorsWhen the anterior portion is extended to contact the anteriordentition, as shown in this patient example, indirect retention isprovided the RPD.
  • 31. Maxillary Major Connectors Circular Anterior – Posterior Connectors If anterior lingual coverage is not required the connector is designed well away from the teeth The borders of the connector should terminate in the valleys of rugai to minimize the junction between metal and mucosa. Courtesy Dr. A, Davodi
  • 32. Denture Base Connectors Design ConsiderationsPosition of the posterior bar of the connector  Anterior to the vibrating line  Should terminate adjacent but just short of the hamular notch region
  • 33. Maxillary Major Connectors Circular Anterior – Posterior Connectors The contours of the connector are thickest in the central portion of the casting and taper smoothly into the mucosa at the margins Contour the anterior connector as a strap, not as a bar, for less tongue annoyance/ Courtesy Dr. A, Davodi
  • 34. Central Palatal Connectors These are used for the replacement of one or two teeth unilaterally or bilaterally. Minimum width for rigidity is 8 mm The central portion must be thickened to at least 1.5 mm to ensure rigidity.
  • 35. Anterior Palatal Connectors Used in tooth borne RPD’s when anterior teeth are missing If the anterior palatal connector is used without the posterior component, a significant increase in bulk and surface area coverage is required. When using this kind of connector rigidity is required and the central portion of the connector needs to be at least 1.5 mm thick Courtesy Dr. GE King Courtesy Dr. GE King
  • 36. Anterior Palatal Connectors Used in tooth borne RPD’s when anterior teeth are missing If the anterior palatal connector is used without the posterior component, a significant increase in bulk and surface area coverage is required. When using this kind of connector increased rigidity is required and the central portion of the connector needs to be at least 1.5 mm thick Courtesy Dr. T Berg
  • 37. Anterior Palatal Connectors Used when a palatal torus precludes use of an anterior – posterior palatal connector If the anterior palatal connector is used without the posterior component, a significant increase in bulk and surface area coverage is required. When using this kind of connector increased rigidity is required and the central portion of the connector needs to be at least 1.5 mm thick. Courtesy Dr. T Berg Courtesy Dr. T Berg Courtesy Dr. T Berg
  • 38. Anterior Palatal Connectors Used when a palatal torus precludes use of an anterior – posterior palatal connector If the anterior palatal connector is used without the posterior component, a significant increase in bulk and surface area coverage is required. When using this kind of connector increased rigidity is required and the central portion of the connector needs to be at least 1.5 mm thick
  • 39. Maxillary Major Connectors Bead seal A light “V” shaped postdam at the borders (arrows) of the major maxillary connector, provides a dam, which prevents accumulation of food debris under the connectors.
  • 40. Complete Palatal CoverageIndications  Used when maximal mucosal bearing surface coverage is desired  Extension base RPD’s where abutments are not ideally positioned or are otherwise compromised  Posterior resin area enables relining Courtesy Dr. T Berg Courtesy Dr. T Berg Courtesy Dr. T Berg
  • 41. Major Connectors – Mandible Two types available  Lingual bar  Lingual plate Courtesy Dr. A, DavodiThe choice depends on two factors The anatomic space available The periodontal condition of the remaining teeth
  • 42. Major Connectors – MandibleLingual bar Preferred design  Less food impaction  Simple with minimal tissue contact  Less plaque accumulation
  • 43. Lingual Bar Design Criteria The bar should be 4mm in height and 2mm thick in order to provide Gingival Crest appropriate rigidity The superior portion of the bar 3 mm should be positioned at least 3mm away from the gingival crest. 4 mm Sufficient space (7-8 mm) must be available between the floor of the mouth (lingual frenum) in its elevated position and the gingival margins around the dentition.
  • 44. Lingual Bar Design Criteria Therefore the minimum amount of space between the floor of mouth and lingual frenum and the gingival crest required to fabricate a lingual bar of sufficient rigidity is 7-8 mm The space available is best determined clinically with a periodontal probe  The patient is instructed to elevate the tongue-floor of mouth and the measurement is made 3 mm 3-4 mm
  • 45. Major Connector Design-Mandible If a lingual bar extends posteriorly it should be at least 3-4mm away from the gingival margin to minimize food impaction If insufficient space is available posteriorly a lingual plate should be used 4 mm 3-4 mm
  • 46. Major Connectors – MandibleLingual plate Used when floor mouth contours are insufficient to accommodate a lingual bar Used to stabilize periodontally compromised teeth Courtesy Dr. A, Davodi
  • 47. Major Connectors – MandibleLingual plate Additional Benefits  Provides additional bracing  Enables replacement of anterior teeth Courtesy Dr. A, Davodi
  • 48. Major Connectors – MandibleLingual plate Additional Benefits  Provides additional bracing Courtesy Dr. A, Davodi
  • 49. Denture Base ConnectorsDefinition  That part of the framework to which the acrylic resin of the denture base is connectedFunction  Retain the acrylic resin of the denture base  Metal embrasure keeps resin away from abutment (arrow)
  • 50. Denture Base ConnectorsFunction  Retain the acrylic resin of the denture base  Provide strength to maintain rigidity throughout the prosthesisNote: Simple bars are rigid, easy tofabricate. Avoid meshwork
  • 51. Denture Base Connectors Design Considerations – Mandible Placement is dependent upon:  The space between the opposing dental arches  The position of the denture teeth In the mandible the connectors should be positioned on the crest and on the lingual side of the alveolar ridge Design- Establish a positive finish line between the acrylic resin of the denture base and the metal portion of the RPD framework. Courtesy Dr. A, Davodi
  • 52. Denture Base Connectors Design Considerations There should be 1 mm of space between the tissue surface of the connector and the tissue surface (arrow) to allow for sufficient thickness of acrylic resin  If the resin is thinner than 1mm it tends to fracture along the finish line and become separated from the metal framework
  • 53. Denture Base Connectors Design Considerations The junctional area between the major connector and the acrylic resin of the denture base must have sufficient bulk for strength in order to prevent fracture in this region It should be fan-shaped in the junctional area to provide sufficient bulk for strength
  • 54. Denture Base Connectors Design Considerations In the maxilla, there is often very little space between the tuberosity and the opposing retromolar pad of the mandible Therefore the connectors are designed away from this region as shown (arrows)
  • 55. Denture Base Connectors Design Considerations The connectors are not placed on the facial-buccal portion of the ridge, because they will interfere with the placement of the denture teeth Junctions between the acrylic resin and metal casting (finish lines) require bulk and must be made at 90 degree angle
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