Fixed & Removable Prosthodontics Quiz DES410

Fixed & Removable Prosthodontics

• Course code: DES410
• Lecturers: Dr. Christos Theocharides, Dr. Alexandros Panayiotou
• Exam format: 20 multiple-choice questions (MCQs), each worth 1 mark; 10 short-answer questions (SAQs), each worth 4 marks. MCQs will have 5 options, only one correct answer.
• SAQs are primarily clinical-based. Review year 3 notes and clinical guidelines.
• Read questions carefully before answering.

Crowns

• Indications:
  • Protect remaining tooth structure.
  • Alter aesthetics.
  • Modify crown form for removable partial dentures (act as abutments).
  • Change occlusal plane.
• Conservative to destructive crown materials:
  • Zirconia (monolithic)
  • All-metal crown
  • All-ceramic crown
  • Ceramo-metal crown
  • Porcelain fused to zirconia

Tooth Reductions

• A table presents recommended reductions for different crown types (zirconia, all-metal, all-ceramic, ceramo-metal, porcelain fused to zirconia) for occlusal (posterior) and incisal (anterior) tooth surfaces, as well as the axial surface.
• Maxillary teeth: Functional cusp is palatal
• Mandibular teeth: Functional cusp is buccal

Crown Preparation (Steps)

• Take shade of crown.
• Take 2-3 putty indices
• Use local anesthesia if required.
• Prepare the tooth (use indices as guides).
• Construct a temporary crown.
• Place retraction cord with a haemostatic agent.
• Take an impression.
• Place a temporary crown.
• Check occlusion and adjust if needed.
• Complete records and laboratory card.

One-stage Impression Technique

• Choose the appropriate tray.
• Apply adhesive to tray.
• Ensure undercuts are blocked.
• Ask your assistant to load the heavy bodied material into the tray (using the green/blue mixing tip).
• Simultaneously, syringe the lighter material around the tooth(s) (using the yellow tip).
• Place the loaded tray into the mouth and hold firmly until the impression sets.
• Remove, and rinse/disinfect according to the manufacturer's recommendations.

Inspection of Impression Quality

• Rinse under water to remove saliva/blood.
• Dry and check under light/magnification.
• Disinfect according to manufacturer recommendations.
• Check preparation margins' visibility.
• Ensure tooth morphology in impression matches that in the mouth.
• Check for air bubbles/drags.
• Ensure impression material hasn't detached from the tray.

Crown Cementation (Steps)

• Check lab work (fit and shade).
• Remove temporary restoration.
• Clean the prepared tooth.
• Try in the restoration.
• Check marginal fit, contact points, and occlusion.
• Check patient satisfaction with fit/appearance.
• Remove and clean both crown and tooth surfaces.
• Sandblast if required (aluminium oxide 50µm).
• Cement with appropriate cement.
• Check and remove excess cement.
• Recheck occlusion.

Cements or Luting Agents

• Soft (Temporary) Cements: Zinc Oxide with/without Eugenol, for provisional restorations and definitive restorations (if symptomatic/requires trial assessment).
• Permanent (Hard) Cements: Definitive cementation using conventional cements, acid-base reaction (resin cements), polymerization reaction (hybrid cements), or a combination of the above.

Choosing the Right Cement

• Weaker materials require stronger cements.
• Bonded cements distribute forces away from the tooth-restoration interface.
• Assess retention needed (preparation form, tapers, length of crown/walls).

Non-silicate Ceramics (e.g., Zirconia)

• Clinical problem with adhesion.
• Difficulty achieving adhesion to synthetic substrates or natural tissues when using traditional adhesive techniques.
• Current technologies address the problem, including surface modification to chemically functionalize the zirconia surface for better adhesive bonding.

Physical properties of Zirconia

• Composition and physical properties differ greatly from conventional silica-based materials (e.g. porcelain).
• Zirconia is not readily etched.
• Aggressive mechanical abrasion is needed to improve surface roughness.
• This can produce strength reducing flaws.

Recommended Cements for Zirconia

• 10-MDP (methacryloyloxydecyl dihydrogen phosphate) containing cements/primers (e.g. Panavia V5, SE Bond), SA Luting Cement, Scotchbond Universal adhesive.
• Metal/zirconia, Z-Primer, AZ Primer contain phosphoric acid to promote adhesion via chemical bond formation.

Some Important Tips

• Avoid contact with phosphoric acid on zirconia restorations during cementation.
• Don't clean tooth prep with prophy paste; use pumice and water instead.
• Consider resin-modified glass ionomer (RMGI) cement for zirconia restorations with near-optimum characteristics.
• Tooth prep should ideally be at least 4mm in height from the gingival margin to the occlusal table.
• Lack of parallelism in tooth prep walls should be up to, but not exceeding 20 degrees deviation from the tooth's long axis.

Permanent Cements

• Table providing details for different cement types, including recommended uses, primary strength, and primary weaknesses.

Articulating Papers

• Used to evaluate occlusal contacts.
• Different types of articulating paper available (normal-70-200microns, GHM-12-20microns, Shimstock-8microns)

Treatment Planning Process

• Emergency phase.
• Investigation/Stabilization phase.
• Rehabilitation phase.
• Maintenance/Monitoring phase.

Clinical Case Scenario

• Patient presents with acute pain in tooth #46 due to irreversible pulpitis and extensive caries and advanced periodontal disease.
• Discuss management phases (Emergency, Stabilization, Rehabilitation, Maintenance).

Common Errors Affecting Marginal Fit

• Tight proximal contacts.
• Casting blebs on fit surface.
• Over/under-crown extended margins.
• No die spacer.
• Impression distortion.

Checking Crown Fit

• Visual inspection (margins, direct/mirror view, magnification).
• Instrumental inspection (explorer probe, correct tip size/angle of approach, esp. for subgingival margins).

Types of Defective Margins

• Over-extended.
• Under-extended.
• Over-contoured.
• Open Margin.
• Description for each type (e.g. poor impression, surplus wax, poorly polished casting).

Evaluating Crown Fit Prior to Cementation

• Check proximal contacts (floss).
• Check marginal fit (explorer).
• Check aesthetics (shape/shade).
• Check occlusion (articulating papers).

Semi-precision Attachments

• (no further details provided about this in the scans).

Objectives of Modifying Abutment Tooth Contours

• Develop an acceptable path of insertion.
• Promote favorable biomechanical properties (retention, support, stability).
• Improve aesthetics
• Improve structural durability, particularly for heavily restored teeth.

Options for Replacing Teeth

• Removable: Acrylic, Cobalt Chrome, Valplast
• Fixed: Resin-bonded bridge, Implant, Conventional bridge

Factors Affecting Tooth Prognosis

• Patient Factors: Restorative status (endodontic, periodontal, structural integrity), medical/dental history, social factors, expectations, financial status, behaviour.
• Dentist Factors: Skills, post-graduate training, experience, available equipment and materials.

Prognosis (Details)

• Structural Integrity: Requires at least 1.5mm of ferrule for a fixed prosthesis, with dentin thickness > 1mm particularly for root treated teeth.
• Endodontic Integrity: A predictable outcome needs a healthy pulp or effectively cleansed/obturated root canal area.
• Periodontal Integrity: Higher bone loss and mobility lead to lower prognosis.

Strategic Value of a Tooth

• Aesthetic impact.
• Medical impact.
• Occlusal impact.
• Prosthodontic impact.
• Functional impact.
• Financial impact.

RCP (Re-organized Approach) and ICP (Intercuspal Position)

• Definition of CR (Centric Relation): Bilateral, unstrained mandible position, condyle and disc in superior anterior position in the glenoid fossa, and pure hinge-axis opening (first 20mm of incisal opening). RCP is initial tooth-to-tooth contact in CR.
• RCP: Reproducible position of the occlusion for multiple unit restorations in the fully dentate individual.
• ICP: Most tooth-to-tooth contact position. Used for placing restorations in line with the patient's normal occlusion. General Dentist use conformation in majority of their clinical cases (e.g. crowns, bridges).

Management of Teeth with Extensive Tooth Loss

• No details specific to this topic are provided in the scans.

Toothwear

• Clinical examination considerations (presenting complaint, medical/social/diet history).
• Extra-oral and intra-oral examinations. Identifying wear lesions; Sensibility tests; Radiographs. Prosthodontic assessment.

Types of Tooth Surface Loss

• Attrition.
• Abrasion.
• Erosion/Acid Dissolution.
• Abfraction.
• Caries.
• Iatrogenic.
• Trauma.

How to Manage Wear Cases

• Determining wear type (attrition vs. erosion).
• Monitoring/Treatment decisions needed.
• Restorative planning.
• Wax-ups using articulated study casts
• Materials to use.
• When a splint is needed.

Management of TSL (Tooth Surface Loss)

• Active monitoring, Splint Therapy, Composite Build-ups, Onlay Dentures, Crown and Bridges, Crowns with Dentures, Overdentures, Dentures, Implants
• Most conservative to least.

How to Manage Erosion

• Diet analysis and suggesting changes.
• Recommend fluoride toothpaste.
• Restore function/aesthetics using composite resin restorations.
• Plan restorations (lab-made indirect restorations for severe wear).
• Splints are not suitable for active erosion.

Management of Wear Cases (Specifics)

• Take articulated study casts in CR
• Make wax-ups
• Demonstrate to patient
• Putty index or plastic retainer

Role of Splints

• Test occlusal vertical dimension.
• Check patient in RCP.
• Treat TMD pain of muscle origin.
• Prevent toothwear.
• Assess partial/overdenture/onlay fit.

Posts & Cores

• Post: Metal or rigid restorative material in the root canal of a non-vital tooth.
• Core: Substructure replacing missing coronal structure, retaining the final restoration.
• Dental posts needed if natural tooth structure isn't sufficient to support the core.

How to Determine Ideal Post Length

• Minimum ferrule height: 1.5mm.
• 2-3mm requires indirect post.
• ≥4mm allows for a direct post.
• Molars: Consider Nayyar core instead of a post and core.

Differentiating between Post & Core Methods

• Indirect: Post & core fabricated in lab (typically using cast post).
• Direct: Post and core fabricated chairside (often using fiber composite post and bulk filled composite core).
• Wax or duralay for precise representation.

Tooth Restorability Index (TRI) and Clinical Decision

• TRI: Assesses remaining coronal tissue for retention/resistance (6 sextants, 0-3 score for each).
• Score 12+: Acceptable
• Score 9-12: Questionable/dependent on numbers of sextants scoring 3.
• Score <9: Unacceptable for plastic core, crown lengthening or cast post and core suggested. The Index is subjective to the clinicians assessment.

General Notes

• Ensure reading all lectures and lab sessions and refer to clinical guidelines. Revise using the lecture as a guide, with particular focus on some topics.