Introduction to indirect restorations Flashcards
What is an indirect restoration?
Any type of restoration, which is constructed outside the mouth. Usually constructed in the laboratory.
What are the different types of indirect restorations?
Intra-coronal: fit within the contours of the tooth e.g. inlay, cast post
Extra-coronal: cover the outer surface of the tooth and recreate the external contour, either be full coverage (crown) or partial coverage (veneer)
Hybrid restorations: cover both the internal and external walls e.g. MOD inlay
Why do we use indirect restorations?
- To alter the contour/position/shade/occlusal contacts of the teeth
- To improve the appearance of teeth
- To restore the form and function of a tooth
- To protect teeth e.g. root canal treatment on a molar, this will require cuspal protection to sustain root fracture
- To replace missing teeth e.g. bridgework
What are the indications for extra-coronal restorations?
- Large cavities: difficult to achieve satisfactory occlusal morphology with a direct restoration
- When the remaining tooth tissue is at risk of fracture
- When a stronger material is required that will not wear down as quickly e.g. composite can wear down quickly
- Restoration of severely broken down/worn teeth
- Full coverage restorations may also be used to aid in denture retention
What are the principles of preparation for indirect restorations?
- Preservation of tooth tissue
- Retention form (features of prep that resist removal of restoration along the long axis of the tooth): taper of walls 5-8 degrees per wall, the diameter of the prep, height of the prep: longer prep, surface roughness
- Resistance form (features of the prep that prevent the restoration from being dislodged by lateral or rotational forces): add grooves
What are important properties when selecting the correct material?
Mechanical properties: modulus of elasticity, fracture strength, toughness, hardness, creep
Physical properties: optical properties like translucency, opalescence, fluorescence, surface texture
What are the problems of under-reduction?
Aesthetic and occlusal problems
Where must the margin of preparation be?
Always end on sound tissue and not on a direct restoration
Where should the location of the margins be situated?
Supra-gingival (best option for plaque control and periodontal health. Should always aim for this but may not be aesthetically acceptable on anterior teeth)
Juxta-gingival - the same level as gingival margin (for anterior teeth in aesthetic zones as this allows efficient plaque removal and does not encroach upon the periodontal tissues)
Which margin should be avoided and why?
Sub-gingival margin as this can result in periodontal inflammation and increased difficulty in impression taking and soft tissue management
What is a core?
A core is a restoration which is used to build up a broken down tooth prior to placement of an indirect restoration.
How are core restorations classified?
- Space filling core: if large amounts of coronal tissue remain remain, then the core may be required to block out undercuts or provide smooth axial walls
- Structural core: if little coronal tissue remains, the core will be required to retain the indirect restoration and form most of the preparation.
What materials are used for space-filling core?
GIC
RMGIC
Compomer
Composite
What material is used for structural core?
Amalgam (superior to composite as composite needs sufficient enamel to bond to)
How can the core be retained in vital teeth?
Undercuts, slots/amalgapins, pins, grooves, peripheral shelf, bonding
