Indirect Restorations
Indications
Aesthetics
As part of treatment plan to help with construction of other prosthesis
Loss of tooth tissue
Patient factors
Medical history
Mouth opening
Mobility and manual dexterity
Finance
Oral hygiene and motivation
Tooth factors
Periodontal status
Endodontic status
Remaining structure
Remaining cuspal structure
Location of margins
Marginal ridges
Furcation
Clinical attachment loss
Pulp-capping (Barthel 2000)
45% fail in 5 years
80% fail in 10 years
Must endo before crown if pulp has been exposed
Papers
Bandish et al 2006
Reeh and Messer 1989
McDonald 2005
Gonzalez-lopez et al 2005
Loss of proprioception leading to overloading (Randow and Glantz 1986)
Location of remaining dentine is important: palatal wall plays major role in resistance to fracture (Ibrahim 2006)
Preparation
Materials
Shillingburg's principles
Preserve tooth structure
Create acceptable finish line
Reduction results in retentive restoration (NO LONGER ACCEPTED)
Encourage favourable tissue response
Rosenstiel's principles (examples)
Mechanical
Aesthetic
Biological
Retention form
Resistance form
Protect against fracture
Conserve tooth tissue
Minimal display of metal
Porcelain occlusal surfaces
Tooth structure removal (Edelhoff and Sorensen 2002)
PFM 20% more destructive than full gold crown
All ceramic less destructive than PFM
PFM 14 times more tooth removal than inlay
Inlays: least destructive
Retention
Resistance
Prevents removal of the restoration along the path of displacement
Prevents removal of the restoration in an oblique direction
Taper: Relationship of one wall of a preparation to the long axis of that prep
Ideal 3 degrees taper/6 degrees total occlusal convergence
Clinically achievable: 10-22 degrees total occlusal convergence
Path of placement
the specific direction in which a prosthesis is placed on the residual alveolar ridge,abutment teeth, dental implant abutment(s), or attachments
Posterior 3/4 crown: parallel to long axis of tooth
Anterior 3/4 crown: parallel to mid-third of labial surface
Longer prep improve resistance
Interfere with arc of casting
In short prep, grooves in axial walls improve resistance
Prep should follow anatomy
Choice
Porcelain fused to metal
Porcelain
Metal
Ceramics
Composite
Problems with evidence
Heterogeneity of methods
Technology advances faster than research
Survival of materials at 5 years (Pjetursson 2007)
Anterior teeth
Posterior teeth
All ceramic = PFM
PFM = Densely sintered alumina crowns = Reinforced glass cermamics
Slightly lower survival: InCeram, Glass ceramics