Introduction to indirect restorations Flashcards
(26 cards)
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
How can a core be retained in non-vital teeth?
Pulp chamber and root canal space can be utilised to retain a core: posts, nayyar core
What are the contraindications for pt selection in providing indirect restorations?
- Irregular attendance
- Poor motivation
- Active disease: caries and periodontal disease
- Poor OH
- High caries risk
- Bruxist
What are the complications of indirect restorations?
- Tissue removal: sensitivity as more tubules are exposed, more susceptible to caries
- Restorative cycle: lifelong of replacing restorations
- Periodontal: margins can act as a plaque retention factor. Sub-gingival margin placement can impinge on the attachment of the periodontal soft tissues and cause inflammation and bone loss/recession
- Pulpal health: approx. 20% of crowned teeth undergo pulpal necrosis
- Leakage: poorly fitted restorations restorations result in exposure of cement, over time this undergoes dissolution and caries can result
- Occlusal problems: de-cementation, sensitivity, occlusal overload and mobility, TMJ problems
What are the stages in indirect restoration construction?
1st visit: H&E, radiographs, rx plan
2nd visit: restore any existing restorations in the mouth
3rd visit: a pre-op impression (temporary construction), opposing arch impression, bite registration, facebow registration, the impression of the preparation, shade, construction and cementation of temporary and check occlusion
Laboratory: pour models and articulate using bite and facebow registrations, section master die, construct restoration (lost wax technique, CADCAM, porcelain application), polish restoration, glaze (porcelain)
4th visit: remove temporary restoration, try in restoration (fit, occlusal contacts, shade). Always protect the airway with gauze, bisque try in - unglazed porcelain. Need an extra visit as we have to send back to the lab to glaze. Cementation, re-check occlusal contacts, cleaning instructions for pt.
5th visit - review pt
What impression material will be placed around the prep?
Light bodied addition silicone
What impression material will be placed to fill the tray?
Heavy bodied addition silicone
What is a luting cement?
A moldable substance used to seal the space between the tooth and the crown
Zinc phosphate, Zinc polycarboxylate, GIC, RMGIC luting cements are used for…
Conventional metal/metallo-ceramic crowns and bridges, metal inlays/onlays
Aesthetic composite resin (dual/chemical cure) luting cement is used for…
All ceramic full/partial coverage
