Section 24 - RPD Design

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Section 24 - RPD Design

  1. 1. Section 24 - RPD DesignHandoutAbstracts001. Henderson, D. Major connectors for mandibular removable partial dentures: Design andfunction. J Prosthet Dent 30:532-548, 1973.002. Boero, E. and Forbes, W. G. Considerations in design of removable prosthetic devices withno posterior abutments. J Prosthet Dent 28:253-263, 1972.003. Berg, T. A. and Caputo, A. A. Anterior rests for maxillary removable partial dentures. JProsthet Dent 39:139-146, 1978.004. Becker, C. M. and Bolender, C. L. Designing swing-lock partial dentures. J Prosthet Dent46:126-132, 1981.005. Kratochvil, F. J. and Caputo, A. A. Photoelastic analysis of pressure on teeth and bonesupporting removable partial dentures. J Prosthet Dent 32:52-61, 1974.006. Jacobson, T. E. and Krol, A. J. Rotational path removable partial denture design. J ProsthetDent 48:370-376, 1982.007. Firtell, D. N. and Jacobson, T. E. Removable partial dentures with rotational paths ofinsertion: Problem analysis. J Prosthet Dent 50:8-15, 1983.008. Zarb, G. A. and Mackay, H. F. Cosmetics and removable partial dentures. J Prosthet Dent46:360-368, 1981.009. Wagner, A. G. and Traweek, F. C. Comparison of major connectors for removable partialdentures. J Prosthet Dent 47:242-245, 1982.010. Schulte, J. K. and Smith, D. E. Clinical evaluation of swing-lock removable partialdentures. J Prosthet Dent 44:595-603, 1980.011. Demer, W. J. An analysis of mesial rest-I-bar clasp designs. J Prosthet Dent 36:243-253,1976.012. Yalisove, I. L. Crown and sleeve-coping retainers for removable partial prosthesis. JProsthet Dent 16:1069-1085, 1966.013. McArthur, D. R. Canines as removable partial denture abutments. Part II. Rest and undercutlocation for retainers. J Prosthet Dent56:445-450, 1986.
  2. 2. 014. Parr, G.R. and Gardner, L.K. The removable partial denture design template. CompendContin Educ Dent 8:594-602, 1987. Section 24: RPD Design (Handout)Classification Systems ( a historical look) Parr1. Cummer(1921)- one of 1st classification systems in American literature. Based on teethremaining or teeth lost. Said 131,072 combinations of RPD when Max and MN archesconsidered along with all 32 teeth2. Skinner- based on relationship between abutment teeth and supporting alveolar ridge3. Bailyn- a two tier system: looks at anterior saddle( anterior to premolars) and posterior saddle(posterior to canine) areas; designated as A or P. Class I, II, III determined by number of teethmissing teeth in the span between the abutments.4. Kennedy(1925)-Applegate Class I: Bilateral distal extension Class II: A unilateral distal extension Class III: A unilateral tooth supported Class IV: Anterior edentulous span crossing the midline Purpose of Kennedy classification system. - Immediate visualization of tooth lost. - Immediate differentiation between tooth-borne and tissue supported RPDs. - Communication among dentists and lab. - Universally understood.Principles of RPD Design ( Henderson, Boero, Berg, Zarb, Wagner, Kapur)QUESTION: HOW CAN WE DESIGN AN RPD SO THEY ARE SAFE AND AS STRAIGHTFORWARD AS POSSIBLE AND STILL SATISFY THE REQURIMENTS OF SUPPORT,STABILITY, RETENTION, FUNCTION AND ESTHETICS?Support (tooth or tissue) Rests( McArthur, Berg) "Anterior teeth by virtue of their crown and root orientation tend toexert a cantilever effort on supporting bone and periodontal membrane when receiving occlusalloads." Berg. If this is true how can we design anterior rest ? Is one design better(e.g., flat, V,half moon) Surveyed Crowns ( Yalisove)Stability Major Connector Minor Connector
  3. 3. Axis of Rotation (All RPDs are like a ship- they pitch, roll and yaw)- Three axes to be concerned with in RPD design. Can’t eliminate these but must accommodatethem.How? Vertical- "fish-tailing " of a KI RPD side–to–side Horizontal- rotation about a fulcrum line delineated by the distal most rests in a KI RPD Longitudinal – rotation about the crest-of–the–ridge lineForce Distribution (Berg, Boero, McArthur) - How are forces acting upon the RPD? - How do you control these forces?How does one avoid a type 1 lever system in an RPD?Esthetics ( Zarb)- Fixed v RPD when to use RPD? a. Edentulous span too long for FPD b. Significant alveolar ridge loss and mid third of face must be supported c. Cleft palate and other maxillofacial defects d. Very young patientDesign Principles- Do no harm- No clasps showing- Be retentive.Advantages of RPD- Not irreversible- Limited tooth structure removed- No pulpal necrosis.- Can always go to fixed.Terms1. Fulcrum Line a. A theoretical line around which an RPD tends to rotate b. The length of the fulcrum (lever arm) determines the amount of force transferred to theabutment tooth.. c. Through the most distal abutment (rest), on either side of the arch, multiple fulcrum linescan exist.2. Inclined Plane- what an RPD can act as if not properly supported by well-defined rests andgood tissue support.Philosophy for Extension Partial Dentures ( Kratochvil, Demer)
  4. 4. Bonus question: What are Roach, Kratochvil, Krol and Demer’s contributions to the RPIsystem? Roach-gave the system its name, bar went into a DF undercut; Krat-located I bar tomidfacial; Krol- modified the distal proximal plate; Demer – reviewed and analyzed the system.RPI( Roach) DemerIndicationsContraindications- High survey line- Severe tissue undercut- No midfacial or MF undercut- Insufficient region of attached tissueAdvantagesDisadvantagesParts of RPI systemRest (support) - Located on mesial. Why?I –bar (retention)Must disengage when rotation occurs around an anterior point.Minimal contact on toothProximal plate( reciprocation) extends slightly to distalProper height Krol- 2-3 mm occlusal-gingivally Below HOC. Why Kratovil- " physiological adjustment" What does this mean? Importance? How doesKratochvil’s proximal plate differ from Krol’s RPA (Eliason)Unconventional RPD Designs ( Firtell, Jacobsen, Becker,Schulte)Rotational Path (Jacobsen, Firtell) Indications Tilted abutment teeth Esthetics Do no want clasps showing- decrease number of clasps Contraindications Distal extensions Lingualy tilted abutment teeth Advantages Decreased no. of clasps Less components to distort Disadvantages Technique sensitive Classes: Category I: Characteristics of - Seat rest associated with rigid connector 1st and rotate 2nd segment into place
  5. 5. - Can be AP or PA but will replace posterior teeth Category II: - Lateral paths and AP replacing anterior teeth Six Biomechanical Requirements of: - Retention- rigid retentive component (minor connector) - Bracing/Stability- intimate contact of parallel rest seat walls, tissue surface of minorconnector, contacting proximal surface abutment - Support-rest ( 1.5-2.0mm deep, > ½ F-L width, dovetail shaped) - Reciprocation- not required since rigid retainer shows passivity in relationship to abutmentduring and after seating - Encirclement – contact of rest and minor connector - PassivitySwing –Lock (Becker, Schulte) Indications Compromised periodontal condition of teeth Multiple missing abutment teethSummary (Kapur) "The periodontium is the testing ground of all restorative procedures." Doyou agree with this statement? Why or why not? - Abstracts -24-001. Planning removable partial dentures. J Prosthet Dent 12:524-535, 1962.Purpose: To discuss planning the treatment for a removable partial dentureMaterials and methods: NoneResults: NoneDiscussion: A fixed partial denture is the treatment of choice whenever it may be used. If aremovable partial denture is to be used it should meet the following requirements. (1) preservethe alveolar ridges and remaining teeth, (2) provide desirable facial expressions, (3) correctocclusion, (4) restore and preserve occlusion and masticating efficiency that had been lost. In planning four items take precedence (1) bilateral distribution of stresses, (2) various typesof retainers, (3) cosmetic effect, (4) function. Splinting of abutment teeth may be necessary to add to the stability and life of the RPDabutment.Conclusions:(1) The biologic response of tissue to stress depends upon the tolerance of the tissue.(2) Partial dentures should be designed for bilateral distribution of stresses.(3) The type of retainer which will function best in all respects is the one which should beemployed in any specific location.(4) The location of the teeth remaining and available for support and the way they are used aremuch more important than the number of teeth remaining.(5) Splinting of teeth by clasping in sequence is effective for adding stability to a restoration andavoiding the overworking of abutment teeth.
  6. 6. (6) Modern periodontal procedures which are saving teeth are making partial denture serviceincreasingly necessary.(7) Removable partial dentures can effectively stabilize loose teeth so that they will grow firmagain.(8) Elastic clasp are more efficient for retention and less traumatizing to abutment teeth thanclasp which lack resiliency.(9) Removable partial dentures move slightly under functional loads.(10) Teeth splinted together by fixed restoration provide strong abutments.(11) It is the responsibility of the dentist to plan and design removable partial dentures.24-002. Boero, E. and Forbes, W. G. Considerations in design of removable prostheticdevices with no posterior abutments. J Prosthet Dent 28:253-263, 1972.Abstract not available at this time ...........24-003. Berg, T. A. and Caputo, A. A. Anterior rests for maxillary removable partialdentures. J Prosthet Dent 39:139-146, 1978.Abstract not available at this time ...........24-004. Becker, C. M. and Bolender, C. L. Designing swing-lock partial dentures. JProsthet Dent 46:126-132, 1981.Abstract not available at this time ...........24-005. Thompson W.D. Kratochvil, F.J. and Caputo, A.A. Valuation of Photoelastic stressPatterns Produced by Various Designs of Bilateral Distal Extension Removable PartialDentures. J Prosthet Dent 38:261-273,1977.Purpose: To compare the forces exerted on the supporting structures of abutment teeth by sevenRPD designs using a photelastic model.Methods & Materials: A model was fabricated with plastic teeth extending to the first premolars.Another plastic was used for PDL and another for bone. Seven RPD frameworks of variousdesign were fabricated. Each design was loaded in a photoelastic testing apparatus.Results: Anterior positioning of rests provides better vertical load transfer. The least favorabledesigns all had mesial undercuts and distal rests. The most favorable designs were mesial restwith an I bar or wrought wire combination clasp.Conclusion: A retainer with a mesial rest and a buccal I bar or a wrought wire and cast lingualarm exhibited the most favorable distribution of vertically applied forces. Distal rests tend tomove the clinical crown distally and the root mesially at the apex, resulting in horizontal forcesin bone. Placing rests more anteriorly provides an axis of rotation that directs applied forces in amore vertical direction. The distal rest with circumferential retainers developed greaterhorizontal forces within the supporting structures.24-006. Jacobson, T. E. and Krol, A. J. Rotational path removable partial denture design. JProsthet Dent 48:370-376, 1982.
  7. 7. Abstract not available at this time ...........24-007. Firtell, D. N. and Jacobson, T. E. Removable partial dentures with rotational pathsof insertion: Problem analysis. J Prosthet Dent 50:8-15, 1983.Abstract not available at this time ...........008. Zarb, G. A. and Mackay, H. F. Cosmetics and removable partial dentures. J ProsthetDent 46:360-368, 1981.Abstract not available at this time ...........24-009. Wagner, A. G. and Traweek, F. C. Comparison of major connectors for removablepartial dentures. J Prosthet Dent 47:242-245, 1982.Abstract not available at this time ...........24-010. Schulte, J. K. and Smith, D. E. Clinical evaluation of swing-lock removable partialdentures. J Prosthet Dent 44:595-603, 1980.Abstract not available at this time ...........24-011. Demer, W. J. An analysis of mesial rest-I-bar clasp designs. J Prosthet Dent36:243-253, 1976.Abstract not available at this time ...........24-012. Yalisove, I. L. Crown and sleeve-coping retainers for removable partial prosthesis.J Prosthet Dent 16:1069-1085, 1966.Abstract not available at this time ...........24-013. McArthur, D. R. Canines as removable partial denture abutments. Part II. Restand undercut location for retainers. J Prosthet Dent 56:445-450, 1986.Abstract not available at this time ...........24-014. Parr, G.R. and Gardner, L.K. The Removable partial denture design template.Compend Contin Educ Dent 8:594-602, 1987.Abstract not available at this time ...........

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