1 - Complex reconstructions

% Reduction in tooth stiffness from Endo/restoration

What are 6 factors that influence (And indicate) a direct restoration?

1. Retention and resistance

2. Cavity extension

3. Occlusion

4. Cusp restoration (active/inactive)

5. Root canal treated teeth

6. Socio-economic factors

(and other factors)

How can a root canal affect a tooth’s strength?

Loss of humidity and elasticity → Less resistance and more fractures. Fragility from structural loss makes the tooth harder to restore.

(Due to degradation of collagen fibres)

What strength of occlusal forces will cause tooth fracture?

More than 58 N/cm²

What can inadequate restorations of active cusps cause?

Fractures from occlusion

How do we restore active cusps if more than one cusp is affected?

Inlay or onlay

Do masticatory factors directly influence inactive cusps?

No

% Causes of failures of endodontically treated teeth?

What 3 things must restorations balance?

Function, Aesthetics, Longevity

What are 3 restorative options for endodontic teeth?

• Partial crowns & veneers - (when sufficient tooth structure remains)

• Full crowns - (widely used)

• Endocrowns - (suitable for molars)

What is a ferrule?

When we have at least 2mm of tooth structure above the bone.

In restorations of endo teeth, when is a post not preffered?

When a ferrule is present

What posts are favoured in endo teeth restorations?

Glass fibre posts better than metal (better stress distribution)

Bundled fibre posts are a promising innovation

What composites are reccomended for core build up when not using posts in endodontic tooth restorations?

High-filled bulk fill

Short-fiber-reinforced composites

What other factors influence a direct restoration?

• Complete isolation

• Inclined planes

• Fragile cusps and marginal crests (eliminate them)

• Cavitary base

• Contact points

• Matrix

What results from the absence of inclined planes?

Forces perpendicular to the main axis of the tooth that are harmful to the periodontum. Can also lead to break of cusp or dentinal wall.

What is septum syndrome?

Food impactation and gum inflammation from poor contact points

What is the purpose of a cavitary base?

Regularise surfaces, correct inclined planes without removing healthy dental tissue and isolate the pulp. (GIC better than compomer but both good)

Which materials release fluoride?

• GIC

• Compomer

(Ideal for use in children, and pit and fissure caries)

What are 5 desirable properties for a core material?

1. Compressive strength

2. Flexural strength

3. Biocompatibility

4. Easy to manipulate

5. Ability to bont to tooth, pins and posts

What are the key characteristics of amalgam?

High compressive strength and rigidity.

Not adhesive - needs mechanical retention (specific preparation)

What are 6 key aspects to consider before composite restoration of maxillary anterior teeth affected by wear?

1. Pattern of tooth surface loss

2. Interocclusal space availability

3. Space requirements for proposed dental restorations

4. Quantity and quality of dental hard tissue

5. Patients aesthetic demands

6. Speech

What are 5 important features when restoring maxillary incisors?

1. Height to width ratio for maxillary central incisor - 1.2:1

2. Incisal edge to lip line relationship and naso-labial angle

3. Morphology in frontal and lateral planes

4. Midline symmetry

5. Tooth shape respective to patient

What colour composite should you use to restore incisal edges?

Translucent

If the entire palatal surface of a tooth is eroded, what type of composite do we use?

First layers with dentin composite (dentin is exposed) and last layer with enamel composite (doesnt adhere to dentin)

Are glass ionomers, resin-reinforced glass ionomers, and most compomers weaker or stronger than tooth structure?

Significantly weaker - should be limited to use only where minimal tooth structure is missing and increased tooth strength and abutment retention aren’t required.

They have low flexural strength and fracture toughness

What are the materials of choice for high caries risk patients?

• Fluoride releasing materials

• GIC and RMGIC

What are the advantages of GIC?

1. Ion exchange adhesion

2. Continuing fluid reservoir

3. Acceptable aesthetics

4. Good wear factor on maturity

5. Low solubility on maturity

What are disadvantages of GIC?

1. Low fracture resistance

2. Can dehydrate in absence of saliva

What are the advantages of composite resins?

1. Excellent aesthetics

2. Excellent adhesion to enamel

3. Possible dentine adhesion

4. Polishable

5. Variety available for different uses

6. Chemical or light activation

7. Wear factor acceptable

8. Relatively inexpensive

What are the disadvantages of composite resins?

1. High risk of microleakage (compensatee with GIC base)

2. Difficult to restore coronal anatomy in extensive lesions

3. Longevity in large restorations may be relatively short

What are advantages of amalgam?

1. Relatively easy to handle

2. Relatively tolerant of poor placement techniques

3. Excellent longevity in medium to extensive-sized lesions

4. Relatively inexpensive

What are the disadvantages of amalgam?

1. Very poor aesthetics

2. Requires undue sacrifice of sound tooth structure

3. Difficult to restore full anatomical form

4. Wear factor too great for extensive restorations

5. Contains mercury

Decision tree for endodontically treated teeth (learn well)