Quartz 4

L1 Introduction to RPD

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Introduction to Removable Partial Denture12

Lecture Context

This lecture serves as the foundational presentation in a sequence addressing removable partial denture (RPD) therapy. It establishes the biological and functional rationale for tooth replacement while outlining the decision-making framework for selecting between fixed and removable prosthodontic options.

Overview of Removable Partial Dentures (RPD)

A Removable Partial Denture is a dental prosthesis that restores one or more missing teeth and associated structures in a partially edentulous arch. Unlike fixed bridges, these devices can be removed from the mouth and replaced by the patient.

Clinical Objectives

The primary goals of RPD treatment include:

  • Restoration of Function: Improving masticatory efficiency and speech.
  • Esthetics: Replacing missing anterior or posterior teeth to enhance facial appearance.
  • Preservation of Oral Health: Maintaining the integrity of the remaining teeth and supporting tissues by preventing migration or tilting of teeth adjacent to edentulous spaces.

Components and Design Considerations

Successful RPD therapy requires a comprehensive understanding of:

  • Support: How the prosthesis resists forces directed toward the basal tissue (tooth-supported, tissue-supported, or a combination of both).
  • Stability: Resistance to horizontal or rotational movements during function.
  • Retention: The ability of the prosthesis to resist displacement away from the tissues.

Masticatory System

Learning Outcome3

  • Discuss the importance of teeth for the digestive/masticatory system, aesthetics, phonetics, TMD
  • Discuss the impact of masticatory function on the mental health and cognitive function
  • Discuss bone remodeling after tooth loss
  • Provide the main reasons for tooth loss
  • Define and describe the Combination Syndrome
  • Discuss the indications, benefits and limitations of RPD

Mastication and Digestion

  • The acquisition, cutting and trituration of food
  • Loss of masticatory efficiency

Change in Diet

  • Consumption of fewer fruits and vegetables leads to fewer vitamins and a compromised immune system
  • Reduced fiber intake leads to stomach and intestinal problems
    • Dietary fiber serves as a crucial prebiotic, feeding beneficial probiotic bacteria in the gut; thus, masticatory deficiency compromises gut health and overall systemic function.

Importance of Teeth45678

Role of Saliva

  • Lubrication
  • Enzymes (amylase)
  • Buffering capacity

Overall Efficiency

  • Digestive efficiency
  • Nutrient extraction

Aesthetics

  • Lip and cheeks support
  • Maintenance of vertical dimension
    • Anterior tooth loss eliminates labial contour support, causing lip invagination and increased visibility of vertical labial wrinkles (rhytides).
    • In cases of significant alveolar resorption, an RPD with a labial flange may be necessary to restore facial contour where bridges are insufficient.

Phonetics and Pronunciation

  • Accurate pronunciation depends on various tooth-related contact points:
ClassificationSounds/Examples
Labialp, b, f, v, m
Dentalt, d, θ, ð, n
Palatal/Velark, g, x, ɣ, ŋ

Phonetic Characteristics:

  • Duration (D): Stop vs. Continuant
  • Voicing (V): Voiceless (-) vs. Voiced (+)
  • Nasal (~): Nasalized sounds

Occlusal Stability

Proper occlusal relationships provide guidance for lateral mandibular movements and protrusion, enabling bilateral chewing and balanced muscle contraction.

Occlusion and TMJ Health

  • Importance of good occlusion
  • Impact of occlusal changes:
    • Interferences
    • Premature contacts
    • Unbalanced muscle contraction
    • Temporomandibular disorders (TMD)

Psychosocial and Neurological Impact

  • Mental health

    • Tooth loss consequences
    • Low self-esteem and loss of confidence
    • Psychological problems

  • Cognitive dysfunction

    • Increased risk for dementia and Alzheimer’s disease

  • Regular sensory stimulation from mastication is essential for maintaining learning and memory functions in the aged hippocampus.

  • Decreased masticatory stimulation may reduce synaptic density in the cerebral cortex by decreasing sensory input.

  • Cerebellar functions are influenced by masticatory activity; increased cerebellar activity during chewing may improve certain motor functions.

Cognitive Dysfunction910

(Teixeira et al. 2014)

Factors in Cognitive Decline

External Factors

  • Reduction of masticatory function
  • Decrease in cerebral blood flow
  • Decreased metabolic activity in the brain

Intrinsic Factors

  • Periodontal disease
  • Chronic infection
  • Loss of teeth
  • Atrophy of brain
  • Deterioration of oral hygiene
  • Decline in swallowing function

Progression of Dementia

  • Core symptoms
  • Increased requirement for care
  • Behavioral and Psychological Symptoms

Pathological Cycle

A self-perpetuating cycle emerges where reduced masticatory function leads to dementia progression, which in turn causes a decline in oral hygiene and swallowing, leading to further tooth loss.

(Watanabe et. al 2015)

  • Maintenance of bone and soft tissues is dependent on the presence of teeth.
  • Tooth loss leads to a decrease in the quality, width, and height of the alveolar bone.
  • Immediate phase (3–6 months): Rapid remodeling occurs, precluding immediate definitive prosthesis fabrication.
  • Stabilization phase (12 months): Bone contours stabilize, though slow resorption continues throughout life.
  • Prosthetic Implications: Dentures must extend to maximum anatomical landmarks (e.g., retromolar pads) to distribute forces and prevent accelerated resorption.

Bone and Soft Tissue Maintenance11

Congenitally Missing Teeth

  • Hypodontia: 1 to 6 teeth absent
  • Oligodontia: More than 6 teeth absent
  • Anodontia: Absence of all primary or permanent teeth
  • Characteristics:
    • Can be partial or total (often associated with ectodermal dysplasia)
    • May affect primary dentition, permanent dentition, or both
    • Can be unilateral or bilateral

Reasons for Tooth Loss121314

  • Congenitally missing teeth

  • Caries

  • Periodontal disease

  • Congenitally missing teeth

  • Caries

  • Periodontal disease

  • Trauma

  • Oral and maxillofacial surgery

    • Oncologic treatment: Jaw resection and soft tissue loss following cancer therapy often require prosthetic replacement of both teeth and soft tissue volume.
  • There is a significant increase in tooth loss associated with ageing.
  • Global life expectancy has shown a steady upward trend from 1950 projected through 2050 (UN World Population Prospects).

Life Expectancy and Ageing15

Australian Statistics (2014)

  • Male life expectancy: 80.3 years
  • Female life expectancy: 84.4 years
  • Data from the Australian Bureau of Statistics confirms rising longevity since the late 19th century.

Clinical Viability

Increased longevity often brings systemic medical conditions or cognitive disorders that may contraindicate implants or complex fixed prosthodontics, making RPDs the only viable option.

  • Most people prefer not to have missing back teeth replaced.
  • This preference against replacement increases with age.

Need and Demand for Treatment1617

(Davenport, J. C et al: Br Dent J 2000)

  • Older people tend to find the usage of a Removable Partial Denture (RPD) more upsetting than younger patients.
  • Data indicates the proportion of patients who find RPD usage “Very upsetting” increases significantly in older age brackets (65 and over).
    • Treatment Need vs. Demand: "Need" is clinical judgment for health, while "Demand" is the patient's willingness to accept treatment.
    • ==Elderly patients demonstrate reduced adaptive capacity to new oral devices and require thorough counseling regarding long-term benefits.=

Tooth Loss Patterns18

=

I-nter-arch Differences

  • Maxillary teeth
  • Mandibular teeth

Intra-arch Differences

  • Posterior teeth
  • Anterior teeth

Combination Syndrome192021

Typical Presentation

  • A common clinical scenario involves a Maxillary Complete Denture opposing a Mandibular Removable Partial Denture (RPD).

Tolstunov, 2007, p. 139

Definition of combination Syndrome

“Combination syndrome (CS) is a dental condition that is commonly seen in patients with a completely edentulous maxilla and partially edentulous mandible with preserved anterior teeth. This syndrome consists of severe anterior maxillary resorption combined with hypertrophic and atrophic changes in different quadrants of maxilla and mandible” (Tolstunov, 2007, p. 139)

  1. Tolstunov L. Combination Syndrome: Classification and Case Report. Journal of Oral Implantology. 2007 Jun;33(3):139–51. doi:10.1563/1548-1336(2007)33%5B139:CSCACR%5D2.0.CO;2
Link to original

Pathological Changes

  • The syndrome involves specific degenerative changes in the oral tissues and bone structure when specific occlusal conditions are met.
  • Combination syndrome is also known as Kelly's syndrome
  • It can also occur when an edentulous maxilla opposes implant-supported anterior dentition
  • Edentulous maxilla is opposed by natural mandibular anterior teeth
  • Loss of bone from the anterior portion of the maxillary ridge
  • Overgrowth (hypertrophy) of the tuberosities
  • Extrusion of mandibular anterior teeth ()

Case Study: Posterior Mandibular Bone Loss from Inadequate Denture Extension

Radiographic evaluation (OPG) of a patient wearing a lower denture revealed severe bone loss in the posterior mandible because the denture base failed to extend onto the retromolar pads.

  • Masticatory forces concentrated in the mid-body of the mandible rather than being distributed to stress-bearing areas
  • Accelerated resorption compromised future prosthetic options and potential implant placement

Principle: Denture bases must extend to maximum landmarks to utilize available support area and minimize bone resorption, despite potential initial comfort advantages of shorter flanges.

  • Loss of alveolar bone and ridge height beneath the RPD bases
  • Decreased prosthetic space resulting from these changes, which complicates future rehabilitation

Clinical Features22

Case Study: Upper Edentulous with Lower Partially Dentate Presentation

A common clinical presentation involves patients requesting replacement of maxillary teeth while retaining only mandibular anterior teeth. Without posterior mandibular support:

  • Pressure concentrates on the anterior maxilla during function
  • Accelerated bone loss creates severe discrepancies between anterior and posterior alveolar ridge heights
  • Upper denture retention is compromised due to dislodgement of the posterior denture base when anterior contact breaks the peripheral seal and suction

Clinical Management: Patients must understand that acceptable upper denture retention requires bilateral balanced occlusion achieved through replacement of missing mandibular posterior teeth.

Prosthodontics2324

Objectives

  • Replace missing teeth and oral tissues
  • Restore and maintain form, function, appearance, and health

Fixed Prosthodontics

  • Replaces the coronal portion of teeth.
  • Rigidly fixed to remaining natural teeth or dental implants.

Removable Prosthodontics

  • Replacement of missing teeth and supporting tissues.
  • Designed to be removed and replaced by the patient.
    • Removable prosthodontics specifically addresses the rehabilitation of partially or fully edentulous patients using removable appliances.

Maxillofacial Prosthodontics

  • Replaces or restores lost or missing structures in the head and neck region.

Partial Edentulous Patients

Selection between fixed and removable options for partially edentulous patients depends on clinical indications and contraindications.

Assessment Criteria

Treatment planning requires a comprehensive assessment of the foundation quality of potential abutment teeth, the anatomy and distribution of edentulous spaces, and the patient’s oral hygiene status and plaque control capability. Additionally, consider patient cognitive function and the fact that patient expectations are often higher than achievable outcomes.

Fixed vs Removable252627282930

Contraindications for Fixed Partial Dentures (FPD)

  • Patient Age: Patients under 18 years old or elderly patients with low manual dexterity.
    • Ongoing bone and jaw development in young patients precludes fixed solutions
    • Elderly patients with low manual dexterity may be unable to perform adequate oral hygiene, such as flossing under pontics
  • Length of Span: Excessive length of the edentulous area.
    • Strict application of Ante's Law requires individual assessment for long spans
    • Poor oral hygiene, high caries risk, or uncontrolled periodontal disease are further contraindications for fixed options
  • Loss of Supporting Tissues: Significant loss of alveolar bone and soft tissue that requires replacement for aesthetics or lip support.
    • Fixed bridges cannot provide the labial flange support necessary for aesthetics when substantial bone resorption has occurred

Ante’s Law

  • The total root surface area (periodontal membrane) of the abutment teeth for a FPD must be equal to or greater than the root surface area of the teeth being replaced.

Indications for Removable Partial Dentures (RPD)

  • Long-span edentulous areas
  • Absence of a distal abutment tooth (distal extension cases)
    • Avoidance of distal cantilever bridges, which generate excessive torsion on abutment teeth risking mobility or fracture
  • Long-span edentulous area
  • No distal abutment tooth
  • Reduced periodontal support for remaining teeth
  • Need for cross-arch stabilization
  • Excessive bone loss
  • Limited manual dexterity
  • Survey crowns: Fixed restorations prepared specifically to support RPD retention (distinct from conventional bridges)

Classification of Removable Prosthodontics

  • Partial Dentures
    • Interim
    • Definitive
  • Complete Dentures

Clinical Verification

Prior to finalizing treatment plans, wax try-ins with acrylic teeth (without labial flanges) can verify whether sufficient lip support exists for fixed options. If support is inadequate, an RPD with a labial flange becomes necessary.

Interim RPD313233

Definition

  • A provisional prosthesis used to improve aesthetics and function until a definitive appliance can be delivered.

Indications

  • When the loss of additional teeth is inevitable.
  • During the healing process to provide function and protection.
  • As a carrier for treatment materials, such as soft tissue conditioners.

Soft Tissue Conditioning

Patients with old acrylic dentures often exhibit candidiasis (fungal infection). Treatment involves relining with soft tissue conditioner and antifungal medication to restore tissue health before final impressions, as inflamed tissues will change contour during healing.

- ==Immediate Partial Dentures are fabricated prior to tooth extraction and inserted immediately post-extraction to eliminate edentulous periods and stabilize the blood clot.==
- ==They maintain the position of adjacent and opposing teeth during the healing phase.==

Benefits

  • Simple to manufacture
  • Easy to repair or add teeth to
  • Useful in the early Control Phase of complex case management

Risks and Limitations

  • Requires patient adaptation
  • Potential to damage supporting structures
  • Poor retention
  • Mobility leading to compromised function, phonetics, or aesthetics
  • Limited longevity

Prosthetic Space Limitations

When vertical dimension loss is severe, acrylic dentures may be contraindicated because there is insufficient space for adequate acrylic thickness; metal frameworks are required in these instances.

Definitive RPD34

Benefits

  • Improved stabilization and retention
    • Utilizes diverse clasp designs, precision attachments, and semi-precision attachments engaging abutment teeth mechanically
  • Better distribution of functional loads
  • High aesthetic potential

Chrome Dentures (Cobalt-Chromium)

Metal backing: Thin metal frameworks placed lingual to anterior teeth when prosthetic space is limited; establishes contact points while minimizing bulk (incurs additional laboratory costs requiring treatment plan adjustment)

Risks and Challenges

  • Technically difficult and complex to design and fabricate
    • Requires meticulous planning, tooth preparation, and clinical execution beyond simple impression-taking
  • Uncertain longevity if not maintained
  • Potential to damage supporting tissues if poorly planned
    • When to avoid chrome: If abutment teeth lack sufficient periodontal support; acrylic dentures distribute forces more favorably in such cases
    • Longevity: Chrome dentures may last longer than acrylic, but poor planning can result in accelerated damage to abutment teeth, negating any longevity advantage
  • Significant financial and time investment
    • Chrome dentures involve higher laboratory fees and patient co-payments than acrylic alternatives
    • Treatment Planning Imperative: Clinicians must specify all technical requirements (e.g., metal backing, specific clasp types) to laboratories prior to fabrication and adjust fees accordingly

Publication Details

McCracken’s Removable Partial Prosthodontics
Thirteenth Edition

Authors:

  • Alan B. Carr
  • David T. Brown

Publisher:

  • Elsevier

Footnotes

  1. Original PDF page 1: L1 Introduction to RPD, p.1 ↩

  2. Original PDF page 34: L1 Introduction to RPD, p.34 ↩

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