Questions and Answers
What can occlusal problems lead to?
Tooth wear, fracture of tooth or restoration, restoration de bonding, bone resorption, gingival recession, tooth mobility, PDL sensitivity and pain.
What indicates an ideal bite in static occlusion?
Equal contacts on all cusp tips and fossa with heavier contacts posteriorly.
In dynamic occlusion, lateral excursion refers to moving the jaw to the ______ and ______.
right, left
Which of the following techniques is used to examine the location of contact points?
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What should you do before making any restoration?
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What factors are assessed in the periodontal considerations during tooth restorability evaluation?
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What is the definition of the ferrule effect?
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What are some endodontic considerations when assessing tooth restorability?
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Premature contacts are caused by low cusps.
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What can be added to hybrid ceramics to improve their properties?
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What is the strongest material used in dental ceramics?
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Which of the following is a disadvantage of all ceramic restorations?
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Porcelain layering includes Opaque, Dentine, and ______.
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What thickness is needed for incision reduction in all ceramic anterior crown preparation?
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What causes the porcelain to bond to the metal in metal-ceramic restorations?
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All ceramic restorations do not require any supporting metal structure.
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What should be done before cementing thin ceramics anteriorly?
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Match the following ceramics with their thickness requirements:
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What factors should be considered for a patient before dental treatment?
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The width of the remaining wall for Class 1 ferrule should be at least ____ mm for aesthetic margin.
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The ideal height of remaining tooth for Class 1 ferrule is ____ mm.
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Which treatment option is NOT a way to gain retention for extensively damaged teeth?
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When should you decide to crown a tooth?
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A patient with adequate tissue support is a good candidate for a removable partial denture (RPD).
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What is a consequence of losing balanced occlusion?
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Match the bridge classifications to their descriptions:
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What are indications for implants?
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Combining an implant and a natural tooth is recommended.
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What is necessary for checking the taper of a preparation?
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The optimum crown-to-root ratio is ____.
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Which finish line is used in all metallic restorations?
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What is the depth range for a chamfer finish line?
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What is the most destructive type of finish line?
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What materials can be used to layer the metal in prosthodontics?
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A beveled shoulder margin is used when gingival esthetics are not critical.
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Match the ceramic types to their characteristics:
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What should the connector thickness be for PFM bridges?
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The depth for heavy chamfer finish line is ______.
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What material is primarily used for dental implants?
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What type of ceramic is indicated when less than 50% of enamel remains?
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What are the two main ways ceramic can be fabricated?
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What structure should you choose towards the midline when determining a patient's midline?
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What is the indication for using PFM over all ceramic for long span bridges?
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What length should the maxillary incisors be established by?
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What is the position of lower incisors in relation to the maxillary incisors when saying the letter S?
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Which of the following is a contraindication for using PFM crowns?
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What type of smile line exposes all of the anterior teeth plus soft tissues?
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For posterior PFM crowns, the functional cusp should be reduced by ____ mm.
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Older patients tend to have high smile lines.
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What type of preparation should be used for anterior PFM crowns?
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The height to width ratio in the golden proportion is _____ (value).
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All ceramic bridges have a higher risk of fractures compared to PFM bridges.
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Match the following statements regarding veneers with their descriptions:
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What does metamerism refer to?
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What is a common disadvantage of using indirect veneers?
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Which shade guide is the only one approved by the ADA?
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What is the aesthetic consideration mentioned for shade selection?
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What should be done to prevent eye fatigue when choosing the shade of restoration?
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What affects the choice of posts when restoring a tooth?
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When preparing veneers, sufficient interproximal clearance is needed to place a _____ between adjacent teeth.
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The final color of the veneer is affected equally by the porcelain color and the cement color.
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Parallel-sided posts are more retentive than tapered posts.
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What is the recommended post length compared to the remaining coronal height?
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The optimal post diameter should not be greater than _____ of the diameter of the root.
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What is one advantage of having a post and core alone rather than a crown in one piece?
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Study Notes
Occlusion Examination
- Occlusal problems can result in tooth wear, fractures, restoration debonding, bone resorption, gingival recession, and tooth mobility.
- Ideal static occlusion (ICP/MI) requires equal contact on all cusp tips, with heavier contacts posteriorly.
- Premature contacts are caused by high cusps; deflective contacts occur from large cusps affecting mandibular movement.
- Use articulating paper (40 µm) for contact points and shimstock to assess contact heaviness.
- In dynamic occlusion, lateral excursion should show no working or non-working side interferences, except in complete denture patients.
- Protrusion analysis should have even contacts on anterior teeth and no posterior interferences, with adjustments avoided to prevent creating new interferences.
Assessing Tooth Restorability
- Begin with the removal of all caries and previous restorations.
- Evaluate remaining tooth structure, focusing on the ferrule effect both vertically and horizontally.
- Assess the crown-root ratio for structural integrity.
- Consider endodontic factors such as the complexity of root canal treatments, root canal morphology, and any pathogenic conditions affecting roots.
- Review periodontal health, including pocket depth, clinical attachment loss, bone loss, mobility, and presence of endodontic-periodontal lesions.### Patient Factors
- Presence of systemic diseases or risk factors like smoking impacts treatment choices.
Ferrule Effect
- Vertical measurement: Distance from the gingival margin to the top of the remaining wall measured using a probe at four locations (buccal, lingual, mesial, distal).
- Ideal Class 1 ferrule requires remaining tooth height of ≥ 2 mm.
- Class 2 ferrule acceptable with height of 0.5–2 mm, especially with post and core.
- Class 3 ferrule unacceptable with height < 0.5 mm.
Horizontal Ferrule
- Measurement at future crown margin level using gauge calipers or a probe.
- Minimum wall thickness must be preparation thickness + 1 mm.
- Aesthetic margin (AM) for metal-ceramic or all-ceramic; non-aesthetic margin (nAM) for metal only.
- Class 1: Wall width ≥ 2.2 mm (AM) or ≥ 1.5 mm (nAM).
- Class 2: Wall width ≥ 1.5 mm (AM) or ≥ 1 mm (nAM).
- Class 3: Wall width < 1.5 mm (AM) or < 1 mm (nAM).
- Margins: Chamfer width = 0.5 mm; Shoulder width = 1.2 mm.
Tooth Retention and Resistance
- Extensively damaged teeth can gain retention through ortho extrusion, crown lengthening, or RCT with post and core.
- Note: Ferric sulfate and aluminum chloride astringents can negatively affect bond strength of composite to dentin. Rinse with water if contact occurs.
Crown Decision Factors
- Crown placement is indicated when:
- Direct restoration is inadequate.
- Axial surfaces are weakened or restored.
- Tooth serves as an abutment for a bridge.
- Risk of tooth fracture is high.
- Subgingival margins may be necessary, but caution is required regarding biological width and impression quality.
Diagnosis & Treatment Planning for Restoration
- Comprehensive patient assessment includes medical history, clinical examination, and radiographs.
- Consider options: nothing, RPD, implants, FPD.
- Need to understand why to replace missing teeth: functional and esthetic restoration, occlusal stability, etc.
Bridge Classification Based on Preparation
- Conventional: Tooth structure is removed and replaced with a retainer.
- Minimal Preparation: Resin bonded bridge or Maryland bridge, preserving intact abutments.
- Hybrid: Combination of conventional and minimal prep retainers.
Treatment Planning for Missing Teeth
- Replace missing teeth options: implant, RBB, cantilever, 3-unit bridge.
- Dynamic equilibrium disrupted by tooth extraction may lead to further dental issues.
- Tilted teeth may cause occlusal interferences, requiring adjustments.
RPD and FPD Indications
- RPD: Indicated for cross-arch stabilization, bilateral spaces, ridge support.
- FPD: Indicated for a few missing posterior teeth, favorable abutments, and good inter-arch space.
- Avoid RPD in patients with tongue issues or xerostomia; avoid FPD in caries-active or periodontal diseases patients.
Resin Bonded Bridges
- Suitable for single missing incisor or premolar; typically temporary.
- Contraindications: deep bites, short clinical crowns, misaligned abutments.
Implants - Indications and Considerations
- Implants suitable when inadequate abutment teeth exist.
- Caution in combining implants with natural teeth due to differing responses to occlusal forces.
- Vertical forces are preferable for implants for better load distribution.
Abutment Assessment for Bridges
- Radiographs essential for evaluating periodontal support, pulp health, and restorability.
- Low crown-root ratios (C:R) acceptability may apply in specific conditions.
Biomechanical Principles of Tooth Preparation
- Conservation of tooth structure is paramount; excessive removal leads to complications.
- Retention affected by taper, length, and freedom of displacement parameters.
- Marginal integrity and structural durability of restoration are crucial for longevity and health.
Finish Lines
- Various types: Knife edge (conservative but plaque-retentive), chamfer (moderate retention), and shoulder (provides rigidity).
These aspects are essential for successful fixed prosthodontic treatment planning and implementation.### Finish Lines
- Chamfer finish line is used for all metallic restorations and the PFM's lingual portion; it's non-plaque retentive.
- Heavy chamfer features a rounded internal angle and a 90-degree cavo-surface angle, mainly for ceramic restorations.
- Shoulder finish line is employed in the facial portion of PFM and ceramic restorations, but the internal angle must be rounded.
- Beveled margin eliminates unsupported enamel, allowing for better cast metal margins against tooth structure.
- Knife edge is suitable for mandibular posterior teeth; it permits thin margins but is prone to distortion.
Common Mistakes in Finish Lines
- Discontinuity and roughness can be rectified using an enamel hatchet.
- Undercuts from improper taper can damage the margin.
- Insufficient proximal clearance may lead to lab-related damage during die preparation.
- Marginal lip occurs if the bur is inserted more than halfway into the margin.
Ideal Margin and Preparation Guidelines
- Ideally, margins should be supragingival, positioned 0.5 mm away from the gingiva.
- Complete stabilization phase including perio and caries control is required before restorations.
- Functional cusps require 1.5 mm of reduction, while non-functional cusps need 1 mm; bevel the functional cusp at 45 degrees.
- Lingual and proximal reductions should maintain a chamfer margin of 0.3-0.7 mm.
Dental Ceramics
- Ceramics are used to veneer metal or zirconia cores, applied directly to teeth, and for dentures.
- Porcelain contains feldspar, kaolin, and quartz.
- Fabrication involves either mixing powder and liquid or using pre-formed blocks/ingots.
Types of Ceramic Fabrication
- Sintering involves mixing powder and applying it onto a cast, followed by high-temperature firing.
- Slip casting uses a refractory material to duplicate a master cast, helping the ceramic to separate post-firing.
- Heat pressing and milling are other methods of creating ceramics.
Ceramics Strength and Aesthetics
- Ceramic strength varies with melting temperature: high melting for blocks, low melting for PFM, and ultra-low for aesthetic adjustments.
- Strength hierarchy: zirconia > lithium disilicate > feldspar; aesthetics hierarchy: feldspar > lithium disilicate > zirconia.
- Predominantly glassy ceramics offer translucency; opaque ceramics are formed from polycrystalline materials.
Strengthening Brittle Ceramics
- Techniques include glass infiltration, dispersion strengthening, and transformation toughening (specific for zirconia).
- Glassy ceramics are preferable when shade matching is unnecessary; opaque ceramics mask discolorations.
Glass Ceramics
- Feldspathic ceramics lie at the high end for translucency but have the lowest strength.
- Leucite ceramics are stronger than feldspathic due to added potassium oxide, while lithium disilicate provides high strength and translucency.
- Zirconia is the strongest option and is ideal when under 50% enamel remains.
Oxide Ceramics
- Alumina-based ceramics incorporate high crystalline content for opaqueness and are layered with feldspar.
- Zirconia ceramics, being 100% polycrystalline, are exceptionally strong but can damage opposing teeth.
Repairing and Adjusting Ceramics
- Repair of chipped ceramics may involve using hydrofluoric acid, silane coupling agents, and bonding agents.
- Adjustments to zirconia occlusion require sending restorations back for re-glazing.
Advantages and Disadvantages of All-Ceramic Restorations
- Advantages include high aesthetics and translucency, allowing for shade modification.
- Disadvantages consist of reduced strength due to brittleness, potential wear on opposing teeth, and the need for thicker connectors in bridges.
- Indications revolve around high aesthetic demands, while contraindications include unfavorable occlusal loads and insufficient tooth structure.
Porcelain Layering Technique
- Opaque layers (0.2 mm) mask the core color, dentine layers (1.5 mm) provide bulk, and incisal layers grant translucency.
- Each shade change demands an extra removal of 0.2 - 0.3 mm.
- Internal bleaching can be conducted prior to crown preparation on RCT teeth for better color matching.
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Description
This quiz covers essential concepts in fixed prosthodontics, including occlusion examination and assessing tooth restorability. Ideal for dental students and practitioners looking to refresh their knowledge in this specialized field. Test your understanding and apply these principles in practice.
