Dental Crowns and Tooth Reductions Quiz

Exam Format

• 20 multiple-choice questions (MCQs); 10 fixed, 10 removable; each worth 1 mark.
• 5 options per MCQ.
• Only one correct answer per MCQ.
• 10 short-answer questions (SAQs); 5 fixed, 5 removable; each worth 4 marks.
• Questions primarily focused on clinical aspects.
• Review year 3 notes and clinical guidelines.
• Read questions carefully before answering.

Crowns

• Indications for a dental crown:
  • Protect remaining tooth structure.
  • Improve aesthetics.
  • Modify crown form for removable partial dentures (as abutments).
  • Alter occlusal plane.
• Most conservative to most destructive crowns:
  • Zirconia (monolithic)
  • All metal crown
  • All ceramic crown
  • Ceramo-metal crown
  • Porcelain fused to zirconia

Tooth Reductions

• Data presented in a table format for different restorative materials.
• Shows differences in reduction amounts based on the restorative material, specific to occlusal (posterior) and incisal (anterior) areas.
• Materials listed from least to most destructive. ,

Crown Preparation (Steps)

• Take shade of crown (for porcelain or zirconia).

• Take 2–3 putty indices.

• Administer local anesthesia if needed.

• Prepare the tooth (using indices as guides).

• Construct temporary crown.

• Place retraction cord with hemostatic agent.

• Take impression.

• Place temporary crown.

• Check occlusion and adjust if needed.

• Complete records and laboratory card

One-Stage Impression Technique

• Choose appropriate tray.
• Apply adhesive on tray (follow manufacturer's recommendations).
• Ensure that any undercuts in the mouth are appropriately blocked (wax can be used).
• Have clinical assistant load heavy-bodied material into selected tray (use green/blue mixing tip).
• Simultaneously, syringe wash material (light-bodied) around the tooth(s) (use yellow mixing tip with yellow intra-oral tip).
• Place loaded tray in the mouth, hold firmly until impression sets.
• Remove impression, rinse, and disinfect according to manufacturer's instructions.

Inspection of the Quality of the Impression

• Rinse impression under water to remove saliva and blood.
• Dry impression using 3-in-1 and check under light magnification.
• Disinfect following manufacturer's recommendations.
• Check preparation margins for visibility.
• Verify that tooth morphology in the impression matches the relevant tooth.
• Inspect for air bubbles or drags.
• Confirm impression material is still attached to the tray.
• Send completed and inspected impression to the laboratory with relevant forms and supervisor's signature.

Crown Cementation (Steps)

• Check lab work, verifying proper fit and shade.
• Remove temporary restoration.
• Clean underlying prepared tooth.
• Try in the restoration.
• Evaluate marginal fit using a probe, checking contact points and occlusion.
• Confirm the patient is satisfied with the fit and appearance.
• Remove crown and clean both the crown and tooth surfaces.
• Sandblast the tooth surfaces with aluminum oxide (50µm) if indicated.
• Cement the crown using appropriate cement.
• Check and remove excess cement if necessary.
• Recheck occlusion after cementation.

Cements or Luting Agents

• Soft (Temporary) Cements: Zinc oxide with/without eugenol

  • For provisional restorations.
  • For definitive restorations (if symptomatic or needing trial assessment).

• Permanent (Hard) Cements:

  • Definitive cementation (conventional cements):
    • Acid-base reaction (Resin cements).
    • Polymerization reaction (Hybrid cements).
    • Combination of above reactions .

Choosing the Right Cement (Luting or Bonding)

• Weaker restorative material requires stronger cement to prevent forces from concentrating at the tooth-restoration interface.
• Bonded cements distribute forces away from the interface.
• Consider the required level of retention, the form, tapers, and length of crown walls .

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

• Zirconia-based components have challenges with adhesion to synthetic and natural tissues.
• Traditional adhesive techniques used with silica-based materials don't work well with zirconia.
• Surface modification of zirconia is critical for achieving adhesive bonding.
• Composition, and physical properties of zirconia differ from conventional silica-based materials such as porcelain.

Crown Preparation

• Procedures for various types of crown preparations.
• Steps and precautions for managing specific margin types during crown preparation.

Crown Fit Evaluation

• Check the crown's fit against the die before placement in the patient's mouth.
• Check proximal contacts using floss.
• Assess marginal fit using an explorer.
• Evaluate aesthetics.
• Check occlusion using GHM articulating paper.
• Critical order: Start with checking proximal contacts, marginal fit, and aesthetics to avoid conflicts with tight proximal contacts affecting other assessments.

Semi-Precision Attachments

• This section describes semi-precision attachments.

Objectives of Modifying Tooth Contours for Milled Crowns

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

Options for Replacing Teeth

• Removable options: Partial (Acrylic, Cobalt Chrome, Valplast), Complete (Acrylic, Cobalt Chrome).
• Fixed options: Resin-bonded bridge (minimally invasive), Implant (ideal but with cost implications), Conventional bridge (invasive).

Factors Affecting Tooth Prognosis

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

Prognosis

• Structural Integrity: Sufficient ferrule (1.5mm or greater) is needed for fixed prostheses; appropriate dentin thickness critical, especially after root canal treatment.
• Endodontic Integrity: Successful root canal treatment relies on healthy pulp or properly cleaned/obturated root canals.
• Periodontal Integrity: Bone loss and tooth mobility negatively impact prognosis.

Strategic Value of a Tooth

• Aesthetic impact.
• Medical impact.
• Occlusal impact.
• Prosthodontic impact.
• Functional impact.
• Financial impact.
• Important teeth like anterior teeth, teeth for lip support, and teeth in complex situations.

RCP and ICP

• RCP (Restorative Centric Relation): Bilateral, unstrained mandible position with superior anterior condyle position.
• Initial tooth-to-tooth contact in CR is the only useable repeatable occlusion.
• ICP (Intercuspal Position): Position of maximum mandibular intercuspation.
• Important for restorative procedures.

Management of Teeth with Extensive Tooth Loss

• This section describes management of teeth with extensive tooth loss.

Toothwear

• The section covers examination (presentation, medical/social history, diet, extra/intra-oral examination, 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 Cases of Toothwear

• Determining the wear type (attrition vs. erosion).
• Monitoring or treatment strategies.
• Planning restoration of original shape using articulated study casts and wax-ups.
• Identifying restorative materials.
• Determining when to use splints and the types of splints, and understanding their use.

Clinical Features of Attrition and Erosion

• Attrition: Flattened cusps, matching wear facets, excessive fracture of restorations, hypersensitivity, tooth surface loss unrelated to functional movements, masseteric hypertrophy/tenderness, prominent antagonized notching, limitation of mandibular movements, clicking or crepitus in temporomandibular joint, tongue scalloping.
  • Clinical presentation of attrition.
• Erosion: Smooth, shiny enamel, dentine, 'cupping' of amalgams, pronounced (or outstanding) 'cupping' characteristics observed.
  • Clinical presentation of erosion.

Management of Tooth Surface Loss (TSL)

• Most conservative: Active monitoring. Splint therapy. Composite Build-ups. Onlay dentures or crowns. Crowns with dentures.
• Intermediate-level approaches: Overdentures. Dentures.
• Least conservative: Implants (extractions) ,

Managing Erosion-Related Tooth Surface Loss (TSL)

• Diet analysis & suggested changes.
• Fluoride-containing toothpaste for repair and protection.
• Restore function and esthetics with composite resin restorations
• Restore worn-down teeth using indirect lab-made restorations.
• Note: Avoid splints in active erosion cases.

Managing Wear Cases

• Take articulated study casts and wax-ups.
• Present to patient.
• Create putty index/plastic retainer.
• Use composite to restore upper anterior teeth.

Role of Splints

• Testing for increase in occlusal vertical dimension.
• Assessing TMJ-related or muscle pain.
• Preventing tooth wear before and after restorative work.
• Checking suitability and fitting of partial dentures/overdentures/onlays for patients .

Posts and Cores

• Post: Rigid material (metal or other) placed in the root canal of a non-vital tooth.
• Core: Replaces missing coronal structure to support the final restoration.
  • Use posts to anchor the core/restoration to the root.
  • Assess amount of ferrule, which is critical to consider for the post design and to improve the long-term prognosis.

Choosing the Ideal Post Length

• Minimum ferrule height required (1.5mm).
• Consider indirect (laboratory-fabricated) posts for minimal ferrule or direct (chairside fabricated) posts for adequate ferrule.
• Molar teeth—alternative recommendations for core-type systems.

Indirect vs. Direct Post and Core Methods

• Indirect: Post and core fabricated in the laboratory.
• Direct: Post and core fabricated chairside (usually with fibre composite and bulk-fill composites).

Tooth Restorability Index (TRI)

• Description of the Index: Developed to assess tooth restorability, especially important for root-treated teeth and vital teeth, using a structured assessment based on defined parameters, including the amount of coronal/dentin tissue remaining.
• Tooth Segmentation: Divided into six equal sextants (2 proximal, 2 buccal, 2 lingual).
• Scoring: 0–3 score per sextant, with 0 being no axial wall or adequate dentin above finishing line, to 3 indicating adequate dentin for retention's resistance of the core or final restoration.
• Clinical Decisions Based on TRI Scores: Acceptable (12+ scores), Questionable and Dependent (9-12), and Unacceptable (<9 scores).

Overall Revision Guidance

• Review lectures, lab sessions, and clinical guidelines thoroughly.
• Use the specified revision lecture as a guide to focus review on specific topics.
• Be ready for additional questions on the specified topics.

Test your knowledge on dental crowns and tooth reductions with this comprehensive quiz. It covers clinical indications, types of crowns, and specific tooth reduction guidelines for various restorative materials. Review your year 3 notes and clinical guidelines to excel in this assessment.