McCracken's Removable Partial Prosthodontics [PDF]

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Contents Implants as a Rest Support for Rests Lingual Rests on Canines and Incisor Teeth Incisal Rests and Rest Seats



PART I:  GENERAL CONCEPTS/TREATMENT PLANNING 1 Partially Edentulous Epidemiology, Physiology, and Terminology Tooth Loss and Age Consequences of Tooth Loss Functional Restoration with Prostheses Current Removable Partial Denture Use Need for Removable Partial Dentures



2 4 5 5 6 7



7 Direct Retainers



Managing Tooth Loss Over Time 8 Tooth-Supported Prostheses 9 Tooth- and Tissue-Supported Prostheses 10 The Phases of Partial Denture Service 12 Reasons for Failure of Clasp-Retained Partial Dentures14



8 Indirect Retainers



3 Classification of Partially Edentulous Arches 16



4 Biomechanics of Removable Partial Dentures 21



9 Denture Base Considerations



Biomechanics and Design Solutions 21 Biomechanical Considerations 22 Impact of Implants on Movements of Partial Dentures22 Simple Machines 23 Possible Movements of Partial Dentures 24



Functions of Denture Bases in Control of Prosthesis Movement Methods of Attaching Denture Bases Methods for Incorporating Dental Implants Ideal Denture Base Material Advantages of Metal Bases Methods of Attaching Artificial Teeth Need for Relining Stress-Breakers (Stress Equalizers)



29



Role of Major Connectors in Control of Prosthesis Movement30 Minor Connectors 45 Finishing Lines 50 Reaction of Tissue to Metallic Coverage 50 Major Connectors in Review 52



Role of Rests in Control of Prosthesis Movement Form of the Occlusal Rest and Rest Seat Extended Occlusal Rest Interproximal Occlusal Rest Seats Internal Occlusal Rests



93



Role of Indirect Retainers in Control of Prosthesis Movement 93 Factors Influencing Effectiveness of Indirect Retainers96 Auxiliary Functions of Indirect Retainers 96 Forms of Indirect Retainers 96



Requirements of an Acceptable Method of Classification17 Kennedy Classification 17 Applegate’s Rules for Applying the Kennedy Classification20



6 Rests and Rest Seats



67



Direct Retainer’s Role in Control of Prosthesis Movement67 Basic Principles of Clasp Design 68 Types of Direct Retainers 70 Criteria for Selecting a Given Clasp Design 71 Types of Clasp Assemblies 71 Implants as Direct Retainers 81 Analysis of Tooth Contours for Retentive Clasps 83 Amount of Retention 84 Other Types of Retainers 89 Internal Attachments 90



2 Considerations for Managing Partial Tooth Loss 8



5 Major and Minor Connectors



61 61 63 65



99 99 102 103 103 104 106 109 110



10 Principles of Removable Partial Denture Design112 Difference in Prosthesis Support and Influence on Design Differentiation Between Two Main Types of Removable Partial Dentures Essentials of Partial Denture Design Components of Partial Denture Design Implant Considerations in Design Examples of Systematic Approach to Design Additional Considerations Influencing Design



56 56 58 59 60 61



ix



112 113 115 117 122 122 125



x



Contents



11 Surveying



127



Description of Dental Surveyor 128 Purposes of the Surveyor 129 Factors that Determine Path of Placement and Removal133 Step-by-Step Procedures in Surveying a Diagnostic Cast 135 Final Path of Placement 138 Recording Relation of Cast to Surveyor 139 Surveying the Master Cast 140 Measuring Retention 140 Blocking out the Master Cast 141 Relieving the Master Cast 142 Paralleled Blockout, Shaped Blockout, Arbitrary Blockout, and Relief 144



12 Considerations for the Use of Dental Implants with Removable Partial Dentures 146 Physiologic Distinction Between Prostheses 147 Replacing Anatomy and Functional Ability 147 Strategically Placed Implants for Removable Partial Denture Stability and Improved Patient Accommodation 148 Movement Control With Selective Implant Placement148 Treatment Planning 149 Clinical Examples 149 Summary149 Acknowledgment149



PART II:  CLINICAL AND LABORATORY 13 Diagnosis and Treatment Planning



155



Purpose and Uniqueness of Treatment 155 Patient Interview155 Shared Decision Making 156 Clinical Examination156 Objectives of Prosthodontic Treatment 156 Oral Examination 157 Diagnostic Casts 161 Diagnostic Findings169 Interpretation of Examination Data 169 Infection Control 177 Differential Diagnosis: Fixed or Removable Partial Dentures 178 Choice Between Complete Dentures and Removable Partial Dentures 183 Clinical Factors Related to Metal Alloys used for Removable Partial Denture Frameworks 185 Summary187



14 Preparation of the Mouth for Removable Partial Dentures



188



Pre-Prosthetic Considerations in Partially Edentulous Mouths



189



Periodontal Preparation Optimization of the Foundation for Fitting and Function of the Prosthesis



15 Preparation of Abutment Teeth



193 200



206



Classification of Abutment Teeth 207 Sequence of Abutment Preparations on Sound Enamel or Existing Restorations 207 Abutment Preparations Using Conservative Restorations207 Abutment Preparations Using Crowns 209 Splinting of Abutment Teeth 213 Use of Isolated Teeth as Abutments 214 Missing Anterior Teeth 215 Temporary Crowns when a Removable Partial Denture is Being Worn 216 Fabricating Restorations to Fit Existing Denture Retainers216



16 Impression Materials and Procedures for Removable Partial Dentures Elastic Materials Rigid Materials Thermoplastic Materials Impressions of the Partially Edentulous Arch Individual Impression Trays



17 Support for the Distal Extension Denture Base Distal Extension Removable Partial Denture Factors Influencing the Support of a Distal Extension Base Anatomic form Impression Methods for Obtaining Functional Support for the Distal Extension Base



18 Occlusal Relationships for Removable Partial Dentures Desirable Occlusal Contact Relationships for Removable Partial Dentures Methods for Establishing Occlusal Relationships Materials for Artificial Posterior Teeth Establishing Jaw Relations for a Mandibular Removable Partial Denture Opposing a Maxillary Complete Denture



19 Laboratory Procedures



219 219 221 221 222 225



231 232 232 236 236



242 243 244 250 251



253



Duplicating a Stone Cast 253 Waxing the Removable Partial Denture Framework254 Spruing, Investing, Burnout, Casting, and Finishing of the Removable Partial Denture Framework258 Making Record Bases 266 Occlusion Rims 268



Contents Making a Stone Occlusal Template from a Functional Occlusal Record 270 Arranging Posterior Teeth to an Opposing Cast or Template 271 Types of Anterior Teeth 272 Waxing and Investing the Removable Partial Denture Before Processing Acrylic-Resin Bases273 Processing the Denture 276 Remounting and Occlusal Correction to an Occlusal Template 279 Polishing the Denture 280



20 Work Authorizations for Removable Partial Dentures283 Work Authorization 283 Definitive Instructions by Work Authorizations 285 Legal Aspects of Work Authorizations 288 Delineation of Responsibilities by Work Authorizations288



21 Initial Placement, Adjustment, and Servicing of the Removable Partial Denture 289 Adjustments to Bearing Surfaces of Denture Bases290 Occlusal Interference from Denture Framework 291 Adjustment of Occlusion in Harmony with Natural and Artificial Dentition 291 Instructions to the Patient 294 Follow-Up Services 296



PART III:  MAINTENANCE 22 Relining and Rebasing the Removable Partial Denture Relining Tooth-Supported and Tooth Implant– Supported Denture Bases Relining Distal Extension Denture Bases Methods of Reestablishing Occlusion on a Relined Removable Partial Denture



298 299 300 301



23 Repairs and Additions to Removable Partial Dentures



xi



304



Broken Clasp Arms 304 Fractured Occlusal Rests 306 Distortion or Breakage of Other Components— Major and Minor Connectors 306 Loss of a Tooth or Teeth not Involved in Support or Retention of the Restoration 307 Loss of an Abutment Tooth Necessitating its Replacement and Making a New Direct Retainer307 Other Types of Repairs 307 Repair by Soldering 307



24 Interim Removable Partial Dentures



310



Appearance310 Space Maintenance 311 Reestablishing Occlusal Relationships 311 Conditioning Teeth and Residual Ridges 311 Interim Restoration During Treatment 312 Conditioning the Patient for Wearing a Prosthesis 312 Clinical Procedure for Placement 313



25 Removable Partial Denture Considerations in Maxillofacial Prosthetics



315



Maxillofacial Prosthetics 315 Timing of Dental and Maxillofacial Prosthetic Care for Acquired Defects 316 Intraoral Prostheses: Design Considerations 322 Surgical Preservation for Prosthesis Benefit 322 Maxillary Prostheses 327 Mandibular Prostheses 330 Jaw Relation Records for Mandibular Resection Patients336 Summary336



Appendix A  Glossary



337



Appendix B  Selected Reading Resources



340



70



Part I  General Concepts/Treatment Planning



Support



Occlusal third Middle third



Stabilization Retention



Gingival third



A



Lingual



B



Occlusal



Occlusal third



Support Stabilization



Middle third



Retention



Gingival third



C



Buccal



 



Figure 7-5  A bar-type clasp on the mandibular premolar. A, Support is provided by the occlusal rest. B, Stabilization is provided by the occlusal rest and the mesial and distal minor connectors. C, Retention is provided by the buccal I-bar. Reciprocation is obtained through the location of the minor connectors. Engagement of more than 180 degrees of circumference of the abutment is accomplished by proper location of components contacting the axial surfaces. (The minor connector supports the occlusal rest, the proximal plate minor connector, and the buccal I-bar.)



fact that slippage along tooth inclines is always possible. The latter may be prevented by the use of a ledge on a cast restoration; however, enamel surfaces are not ordinarily so prepared.



TYPES OF DIRECT RETAINERS Mechanical retention of removable partial dentures is accomplished by means of direct retainers of one type or another. Retention is accomplished by using frictional means, by engaging a depression in the abutment tooth, or by engaging a tooth undercut lying cervically to its height of contour. Two basic types of direct retainers are available: (1) the intracoronal retainer and (2) the extracoronal retainer. The extracoronal (clasp-type) retainer is the most commonly used retainer for removable partial dentures.



The intracoronal retainer may be cast or may be attached totally within the restored natural contours of an abutment tooth. It is typically composed of a prefabricated machined key and keyway with opposing vertical parallel walls, which serve to limit movement and resist removal of the partial denture through frictional resistance (Figure 7-7). The intracoronal retainer is usually regarded as an internal, or precision, attachment. The principle of the internal attachment was first formulated by Dr. Herman E.S. Chayes in 1906. The extracoronal retainer uses mechanical resistance to displacement through components placed on or attached to the external surfaces of an abutment tooth. The extracoronal retainer is available in three principal forms. The clasptype retainer (Figures 7-8 and 7-9), the form used most commonly, retains through a flexible clasp arm. This arm



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Chapter 14  Preparation of the Mouth for Removable Partial Dentures



A



B



C



D



203



 



Figure 14-15  A, Diagnostic cast at an orientation best for all abutments considered. The buccal survey line is too close to the marginal gingival and the distal surface does not lend itself to guide-plane preparation. A surveyed crown is indicated. B, Abutment contours appropriate to clasp design (distal guide plane and mid-buccal 0.01 inch undercut) are produced in wax. C, Cast of abutment preparation provides buccal surface reduction adequate to replace with metal ceramic material at the required contour. Without careful consideration of survey line placement needs before and during preparation, it is easy to reproduce incorrect contours in finished crowns. D, Cast of a seated surveyed crown demonstrates desired contours for the clasp design chosen.



When there is proximal caries on abutment teeth with sound buccal and lingual enamel surfaces, in a mouth exhibiting average oral hygiene and low caries activity, a gold inlay may be indicated. However, silver amalgam or composite for the restoration of those teeth with proximal caries should not be condemned, although one must admit that an inlay cast of a hard type of gold will provide the best possible support for occlusal rests, at the same time giving an esthetically pleasing restoration. However, an amalgam restoration, properly condensed, is capable of supporting an occlusal rest without appreciable flow over a long period. The most vulnerable area on the abutment tooth is the proximal gingival area, which lies beneath the minor connector of the removable partial denture framework and is therefore subject to accumulation of debris in an area most susceptible to caries. Even when the removable partial denture is removed, these areas are often missed by the toothbrush, which allows bacterial plaque and debris to remain for long periods. Because of this unique removable partial denture concern, special attention should be paid to these



areas during patient education and follow-up. Even when a complete crown restoration is placed in this most vulnerable area, recurrent caries can occur. Caries risk is best managed through effective home care and professional follow-up procedures, rather than through the placement of restorations. All proximal abutment surfaces that are to serve as guiding planes for the removable partial denture should be prepared so that they will be made as nearly parallel as possible to the path of placement. Preparations may include modifying the contour of existing ceramic restorations, if necessary. This may be accomplished with abrasive stones or diamond finishing stones. A polished surface for the altered ceramic restoration may be restored by using any of several polishing kits supplied by manufacturers. When preparing abutments that will receive surveyed crowns, it is important to plan for the tooth reduction necessary to allow placement of sufficient restorative material for durability, contour, and esthetics, as well as the contours prescribed for the desired clasp assembly (Figure 14-15). This can be accomplished by first modifying the axial contours



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