Indications and Contraindication of Fixed Partial Dentures

Indications and Contraindication of Fixed Partial Dentures

Question 1. Diagnostic aids in fixed Partial Denture.

Important diagnostic aids are:

• Diagnostic casts
• Radiographs.

Diagnostic casts

Articulated diagnostic casts

• Aid in planning treatment procedures
• Provide information about static and dynamic relationships of the teeth
• Helps to view several aspects of the occlusion not detectable within the confines of the mouth.

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Read And Learn More: Fixed Partial Denture Short Essay Question And Answers

Diagnostic cast impression can be made of irreversible hydrocolloid and poured into dental stone.

Advantages of diagnostic cast

• Changing the arch relationship before orthognathic procedures
• Changing the tooth position prior to orthodontic procedures
• Modifying the occlusal scheme before attempting any selective occlusal adjustment
• Trial tooth preparation and waxing can be done before fixed restorative procedures
• The selection of an optimum path of withdrawal of a fixed partial denture can be assessed.

Radiographic examination

• Periapical radiographs
• Bitewing radiographs
• Panoramic films
• In the case of temporomandibular joint (TMJ) disorders:
  • Transcranial exposure
  • Serial tomography
  • Arthrography
  • CT scanning
  • Magnetic resonance imaging.

Periapical radiographs

• Importance of periapical radiographs:
• Knowing the extent of bone support, quality of supporting bone
• Detailed root morphology of each abutment tooth
• Width of periodontal ligament space
• Bone resorption (vertical, horizontal)
• Inclination of teeth
• Continuity of lamina dura
• Pulpal morphology and previous endodontic treatment
• Any periapical pathology can be evaluated
• Evaluation of crown–root ratio
• Evaluation of the shape, length, and direction of the root
• Helps in checking for the periodontal situation of the abutment tooth, as widening or thickening of lamina dura, occlusal prematurities, or trauma can cause thickening.

Bitewings

Evaluation of caries on proximal surfaces and secondary caries on previous restorations.

Panoramic films aid in

• Evaluation of bone resorption, pattern of bone resorption, and quality of bone support
• To check for the presence of retained root tips, impacted tooth
• To determine the thickness of soft tissue on the ridge in an area of pontic placement
• They do not provide a detailed view for assessing bone support, root morphology, or caries.

Question 2. Importance of diagnostic casts.

• A diagnostic cast should be an accurate reproduction of the teeth and adjacent tissues, poured in dental stone, because of its strength and abrasion resistance
• The impression for the diagnostic cast is made with irreversible hydrocolloid (alginate) in a perforated impression tray
• It is a life-size reproduction of a part or parts of the oral cavity or facial structures for the purpose of study and treatment planning.

Importance of diagnostic casts

• Diagnostic casts permit viewing of the occlusion from the lingual and buccal aspect
• To analyze the existing occlusion in case of needed occlusal adjustment and occlusal reconstruction
• Aids in diagnostic wax-up, to determine the occlusion before definitive treatment is begun
• Diagnostic casts help to survey the dental arch as a whole
• Helps in surveying the cast to determine existing soft tissue undercuts, and parallelism of teeth as for overdenture cases
• Aids in mouth preparation decisions, as to the removal of soft tissue undercuts
• Helps to show and discuss the case with the patient regarding the treatment plans, needed corrections, and problems, if any
• Aids to select and fabricate trays
• If needed, can duplicate diagnostic cast in case an undercut has to be blocked
• Diagnostic casts may be used as a constant reference
• In areas where alterations are required as in soft tissue or hard tissues, a rough alteration can be mocked on the duplicate cast to assess the outcome.

Question 3. Advantages, disadvantages, indications, and contraindications of fixed partial dentures.

Fixed Partial Dentures Advantages

• Movements for a fixed partial denture are less compared to a removable partial denture
• Psychologically better accepted than removable partial denture
• Acts as a splint
• Less lateral forces are transmitted to the abutment tooth compared to a partial denture abutment
• Can use weak abutment if other abutments are strong
• Esthetically better with more comfort to the patient
• Better functioning of the prosthesis with good perception
• Less bone resorption compared to removable prostheses.

Fixed Partial Dentures Disadvantages

• It can weaken a strong abutment tooth if the other abutment support is weak
• It is an irreversible treatment
• Preparation of a sound tooth will make the patient think twice before agreeing to go for a fixed prosthesis
• Adequate preparation with good occlusal clearance is required or a fixed prosthesis can fail
• If restoration is over contoured, it can cause periodontal problems.

Indications for fixed bridges

• The selection of prosthesis depends on biomechanical, periodontal, esthetic, and financial factors:
• In tooth bounded situations when a single tooth is missing
• In the case where the abutment tooth on either side can support the number of teeth missing
• If the abutment tooth is periodontally sound
• To maintain space in orthodontic cases
• If the edentulous span is short and straight
• To restore the missing tooth in order to prevent the adjacent tooth from drifting into the space
• To restore the mouth to complete function free of interferences.

Fixed Partial Dentures Contraindications

• Unfavorable crown–root ratio
• Large edentulous space
• Edentulous space with no distal abutment
• Bilaterally edentulous with no distal abutment
• Grossly tipped teeth (more than 22°)
• Periodontally weak teeth
• Teeth with short clinical crowns
• Severe bone resorption
• Young age with a large pulp chamber and lack of total eruption
• Large tongue
• Extensive caries with poor oral hygiene
• Financially poor patients
• If the patient cannot maintain oral hygiene
• In the case of parafunctional habits—with excessive force load on the abutment tooth.

Question 4. Importance of radiologic examination in crown and bridge prosthesis.

Different types of radiographic examinations are as follows:

• Periapical radiographs
• Bitewing radiographs
• Panoramic films
• In the case of temporomandibular joint (TMJ) disorders:
  • Transcranial exposure
  • Serial tomography
  • Arthrography
  • Computed tomography scanning
  • Magnetic resonance imaging.

Crown and Bridge Prosthesis Importance

• Knowing the extent of bone support, quality of supporting bone
• Detailed root morphology of each abutment tooth
• Width of periodontal ligament space
• Bone resorption (vertical, horizontal)
• Inclination of teeth
• Continuity of lamina dura
• Pulpal morphology and previous endodontic treatment
• Any periapical pathology can be evaluated
• Evaluation of crown–root ratio
• Evaluation of the shape, length, and direction of the root
• Helps in checking for the periodontal situation of the abutment tooth, as widening or thickening of lamina dura, occlusal prematurities, or trauma can cause thickening.

Bitewings

Evaluation of caries on proximal surfaces and secondary caries on previous restorations.

Panoramic films

They aid in

• Evaluation of bone resorption, pattern of bone resorption, and quality of bone support
• To check for the presence of retained root tips, impacted tooth
• To determine the thickness of soft tissue on the ridge in an area of pontic placement
• They do not provide a detailed view for assessing bone support, root morphology, or caries.
• Radiographs are important tools in the assessment to determine the success of the prosthesis after evaluating the abutment tooth, the proximity of the pulp chamber, the residual ridge support of the pontics, and for good aesthetic replacement of the pontics.

Question 5. Questionable abutments.

Are abutment teeth that can be retained after periodontal and endodontic treatment which otherwise are hopeless teeth.

It is possible to retain a tooth with a hopeless prognosis by highly specialized and complex treatment methods.

Selection of questionable abutments

• An abutment tooth that is periodontally weak yet can be used as multiple splinted abutment teeth, along with non-rigid connectors or intermediate abutments
• Tooth with gross caries, which can be used as abutment after endodontic treatment
• Abutment tooth with large restorations
• Abutments that are malaligned, tilted, or mesially drifted tooth
• Abutments that cannot withstand forces of a long edentulous span
• Abutments that are grossly attrited due to parafunctional habits
• Abutments with reduced bone support.

Assessment of abutment teeth

Periodontally weak tooth

• A tooth with slight mobility.
• Tooth with recession and furcation involvement.
• A tooth with gingival and periodontal pathology.

Some teeth can be saved and used as abutments by:

• Good oral hygiene measures before and after treatment
• Scaling, polishing, and root planing for initial periodontal pathology
• Mobile tooth that can be stabilized by splinting
• Gingival recession can be corrected by flap surgeries
• Osseous defects can be corrected by ridge augmentation methods/guided tissue regeneration techniques.

Abutment tooth requiring endodontic treatment

• After testing for pulp vitality, if pulpal health is doubtful endodontic treatment should be carried out.
• An endodontically treated abutment with a post and core foundation for retention and strength can serve as good abutment support.
• Failures occur with short roots and teeth with less coronal tooth structure.

Abutments with large restorations

For abutments with large restorations extending to cervical areas, the retainer margin should be placed subgingivally.

Abutments that are malaligned, tilted, or mesially drifted tooth

Mesially drifted tooth closing the pontic space is not an ideal abutment (mesially tilted second molar).

This can be treated by:

• Modified preparation designs.
• Non-rigid connector.
• By uprighting the tilted abutment orthodontically.
• Malaligned occlusion as supra-erupted, the tilted tooth needs to be occlusal corrected.
• A well-aligned tooth provides better support than a tilted one.

Abutments that cannot withstand forces of a long edentulous span

The longer the edentulous span length, the greater the flexing of the prosthesis under occlusal loads. This can cause fracture of a porcelain veneer, breakage of a connector, loosening of a retainer, or unfavorable soft tissue response.

Treatment method

• A mock preparation is done on the diagnostic cast to check the feasibility.
• If the abutments cannot withstand the occlusal load or if periodontally weak abutments are present then an implant-supported prosthesis or a fixed and removable prosthesis need to be used.
• Pontics and connectors should be of adequate thickness and of high strength and rigidity.
• If the restoration is overcontoured then maintenance of oral hygiene is difficult.

Replacing multiple anterior teeth

• Missing four mandibular incisors can be replaced with canines as abutments
• A single incisor present is best removed, as it cannot withstand the forces
• Multiple edentulous spaces are best restored with a combination of fixed and removable partial dentures.

Abutments that are grossly attrited due to parafunctional habits

During the application of load, the abutment teeth should not drift or become mobile as in a multiple-unit restoration. The dislodging forces are in a mesiodistal direction.

These abutment teeth are generally attrited and sometimes with slight mobility and drifting. Only after a treatment appliance is given to reduce parafunctional activity should a restoration be given.

In case the clinical crown height is less than:

• Crown lengthening procedures or a subgingival finish line should be done.
• If chances of pulp exposure are present it should be endodontically treated.
• The favorable crown–root ratio is 1:1.
• Proximal boxes and additional grooves on the buccal and lingual surfaces are added to the preparations to produce greater resistance and structural durability.

Abutments with reduced bone support

After periodontal disease, the root surface area is reduced. There is excessive bone loss, which magnifies the forces on that tooth as a length difference between the clinical crown and root exists.

Other factors to be considered

Root shape and angulation

• When tooth support is borderline, short conical roots give less support.
• Divergent multiple roots give good support and can be used as abutments even if there is reduced bone support.
• A single-rooted tooth with an elliptic cross-section gives better support than a tooth with a circular cross-section.
• In the case of vertical and horizontal resorption, potential abutment teeth need to be carefully evaluated as related to root shape angulation and number of roots.

Good oral hygiene measures

Nyjnan and Ericsson used abutment teeth with reduced bone support and reduced root surface area of less than half that of the replaced teeth. They recalled patients and found no loss of attachment after 8–11 years.

With proper and meticulous root planning, plaque control during the observed period, and the occlusal design of the prostheses any questionable abutments can bring success to the long-term prognosis of fixed partial denture.