posterior crowns km
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Dr. Keyvan Moharamzadeh
Academic Unit of Restorative Dentistry
The University of Sheffield
Posterior Full-Coverage Crowns
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Aims
The reasons for crowning acompromised tooth
Design and biological considerations
Materials
Full coverage crowns: FGC, PFM,All-ceramic
Tooth preparations
Clinical Sta es
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The reasons to restore a
compromised tooth Restoring function (first) and
aesthetics (second)
Restoring structural integrity andresisting fracture
Integrating with other prosthesis
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The Compromised Tooth
Restoring function (first) andaesthetics (second)
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The Compromised Tooth
Restoring structural integrity andresisting fracture
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Endodontically treated
teeth Weakened tooth due to access
cavity preparation
Loss of Structural integrity
associated with loss of roof of the
pulp chamber
Loss of dentine elasticity
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Posterior Teeth
Cuspal protection is required if:
Loss of marginal ridgesLoss of substantial tooth structure
Heavily restored tooth(Panitvisai P et al., J Endod 1995)
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Posterior Teeth
Cuspal protection can be achieved by:
Adhesive restorations Cusp-coverage cast restorations
Full-coverage restorations
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The Compromised Tooth
Restoring function (first) andaesthetics (second)
Restoring structural integrity andresisting fracture
Integrating with other prosthesis
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Posterior Crowns
Design Considerations Is the tooth in function?
Appearance
Adjacent Teeth
Periodontal Tissues
Pulp Retention of the crown to the tooth
Materials
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Posterior Crowns
Periodontal Tissues Plaque control
Periodontal attachment
Alveolar bone levels
Status of periodontal disease
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Pulpal death following
crown preparationsAggressive insult to the tooth,
dentine and odontoblasts
Thermal damage
Local anaesthesia
Dessication Bacterial contamination
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Pulpal death following
crown preparations 10% - Hammerle 2000
19% - Saunders 1999 10% - Valderhaug 1997
6% - Jackson 1992
10% - Kerschbaum 1979 and 1993
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University of Graz
Austria
School of dentistry
Dep. of Prosthodontics
Gerwin Arnetzl
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Minimum of 0,7 mm dentine thicknesis recommended for pulpal protection
Gente 1995,Jde 1986, Robach 1982
0,7mm
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Courtesy G. Unterbrink
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A shoulder preparation of 1.2 mmResults in a remaining dentine width of 0.7 mm
only in50 % of maxillary molars
in all other premolars and molars theremaining dentine width is less than
0.7mm
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A 1.2mm shoulder crown preparationon a posterior tooth leaves 0.7mm
remaining dentine thickness
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Thermal
Chemical
Osmotic
Dessication
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Thermal
Chemical
Osmotic
Dessication
BacterialToxins
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Posterior Crowns
Materials
Balancing Functionand Aesthetics
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Posterior Crowns
MaterialsMetal
Metal-CeramicCeramic
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Posterior Crowns
MaterialsMetal (Full Gold Crown)
Minimal tooth reduction
Least aesthetic (? Not an issue)
Can be adjusted intra-orally (occlusion)
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Gold alloy types:
Type I (Soft) was hard enough to stand up to biting forcesbut soft enough to burnish against the margins of a cavitypreparation. It was used mostly for one-surface inlays.
Type II (Medium) was less burnishable but hard enough tostand up in small, multiple surface inlays that did not includebuccal or lingual surfaces.
Type III (hard) The most commonly used type of gold forall-metal crowns and bridges. A typical type III gold alloyincludes the following metals: Gold 75% Silver 10% Copper 10% Palladium 3% Zinc 2%
Type IV (Extra hard) was used for partial dentureframeworks but was not used in fixed prosthetics.
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Full Gold Crown
Donovan T, 2004: Retrospective clinicalevaluation of 1,314 cast gold restorationsin service from 1 to 52 years.
The survival rates at various time periods were97% at 9 years, 90.3% at 20 years, 94.9% at25 years, 98% at 29 years, 96.9% at 39 years,
and 94.1% for restorations in place > 40years. It appears that properly fabricated castgold inlays, onlays, partial veneer crowns, andfull veneer crowns can provide extremely
predictable, long-term restorative service.
http://www.ncbi.nlm.nih.gov/pubmed?term=Donovan%20T%5BAuthor%5D&cauthor=true&cauthor_uid=15597641http://www.ncbi.nlm.nih.gov/pubmed?term=Donovan%20T%5BAuthor%5D&cauthor=true&cauthor_uid=15597641 -
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Posterior Crowns
MaterialsMetal-Ceramic
Metal Core
Extensive buccal tooth reduction
Aesthetics at the cost of tooth tissue
Only the metal component can beadjusted intra-orally
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PFM alloy types:
High-noble alloys have a minimum of 60% noble metals (anycombination of gold, palladium, and silver) and a minimum of 40% byweight of gold. They usually contain a small amount of tin, indium, oriron which provides for oxide layer formation. These metals provide a
chemical bond for the porcelain. Noble alloys (gold, palladium, or silver) contain at least 25% by weight
noble metal. They have relatively high strength, durability, hardness, andductility.
Base-metal alloys contain less than 25% noble metal. They are muchharder, stronger and have twice the elasticity of the high-noble and
noblemetal alloys. Castings can be made thinner and still retain therigidity needed to support porcelain. They appear to be the ideal metalfor cast-dental restorations and were heavily used for PFM frameworksdue to their low cost and high strength characteristics. Unfortunately,nickel and beryllium, two of the most commonly used constituents ofbase-metal alloys can cause allergic reactions when in intimate contact
with the gingiva.
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Ceramic-Fused to metal Crown
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PFM crown
Pjetursson et al., 2007.A systematicreview of the survival and complicationrates of all-ceramic and metal-ceramicreconstructions after an observationperiod of at least 3 years. Part I: Singlecrowns.
In meta-analysis, the 5-year survival of all-ceramic crowns was estimated at 93.3% and95.6% for metal-ceramic crowns.
http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372http://www.ncbi.nlm.nih.gov/pubmed/17594372 -
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Posterior Crowns
MaterialsAll Ceramic
High strength ceramic core
Most aesthetic
Low edge strength
Requires extensive reduction
Intra-oral adjustment not possible
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All ceramic Crowns
Wang Xet al., 2012.A systematicreview of all-ceramiccrowns: clinical fracture rates inrelation to restored tooth type.
All-ceramic crowns demonstrated an acceptableoverall 5-year fracture rate of 4.4%irrespective of the materials used. Molar
crowns (8.1%) showed a significantly higher 5-year fracture rate than premolar crowns(3.0%), and the difference between anterior(3.0%) and posterior crowns (5.4%) also
achieved significance.
http://www.ncbi.nlm.nih.gov/pubmed?term=Wang%20X%5BAuthor%5D&cauthor=true&cauthor_uid=22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed/22930765http://www.ncbi.nlm.nih.gov/pubmed?term=Wang%20X%5BAuthor%5D&cauthor=true&cauthor_uid=22930765 -
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Principles of ToothPreparation for crowns
Preservation of tooth structure
Retention
Resistance
Structural durability
Marginal integrity
P i C
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Posterior Crowns
Retention of the crown Retention Form: Prevents
dislodgement of the crown in an
axial direction.
Resistance Form: Prevents
dislodgement of the crown due torotation from a lateral load.
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Tooth Preparation Design
Preparations should be well-definedand well-finished
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Tooth Preparation Design
Preparations should be well-defined andwell-finished
A clear finish line should be visible
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Tooth Preparation Design
Preparations should be well-defined andwell-finished
A clear finish line should be visible Ceramic margins should be a butt-joint rounded shoulder
- All Ceramic Crown -
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Contour togingiva
Shouldermargin
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Tooth Preparation Design
Preparations should be well-defined andwell-finished
A clear finish line should be visible Ceramic margins should be a butt-joint
rounded shoulder
Metal margins should have chamfermargins
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Chamfer margins
http://www.google.co.uk/url?sa=i&rct=j&q=chamfer+margin&source=images&cd=&cad=rja&docid=m-vagv_sEgStgM&tbnid=VFJhg_IveTC_zM:&ved=0CAUQjRw&url=http%3A%2F%2Fwww.technicdentallab.com%2Flava.asp&ei=B8kfUYTCFtGVswbRnYGwDw&bvm=bv.42553238,d.Yms&psig=AFQjCNEZ_zukXgFICW98kUO5wnHb6rKuYw&ust=1361123906528902 -
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Tooth Preparation Design
Preparations should be well-defined andwell-finished
A clear finish line should be visible Ceramic margins should be a butt-joint
rounded shoulder
Metal margins should have chamfer
marginsAll preparation line angles and point
angles are best rounded
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Tooth Preparation for All
Ceramic Crown
- All Ceramic Crown -
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Minimum occlusal reduction: 1.5mm
>2 mm inareas ofstress
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Occlusal reduction reflects the
morphology of the tooth and thefunctional pathways of the occlusion
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5 taper
Shouldermargin
Occlusalreduction:>1.5mm
>2 mm inareas ofstress
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Zone of retention
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Tooth Preparation for
PFM crown
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PFM crown prep
http://www.google.co.uk/url?sa=i&rct=j&q=pfm+crown+preparation&source=images&cd=&cad=rja&docid=0tSFYZHGZn-hDM&tbnid=tafO1cRdQRf_OM:&ved=0CAUQjRw&url=http%3A%2F%2Fwww.dentaljuce.com%2Ffruit%2Fpage.asp%3Fpid%3D106&ei=4tQfUYSGH6iP4gTimYDQCQ&bvm=bv.42553238,d.bGE&psig=AFQjCNF0rCiGqOhclU68gnVLLfciXkDmFw&ust=1361126919702959http://www.google.co.uk/url?sa=i&rct=j&q=pfm+crown+preparation&source=images&cd=&cad=rja&docid=0tSFYZHGZn-hDM&tbnid=z3h25lWGvXhQYM:&ved=0CAUQjRw&url=http%3A%2F%2Fwww.dentaljuce.com%2Ffruit%2Fpage.asp%3Fpid%3D106&ei=tNQfUbKVE7H24QTIpYCQBg&bvm=bv.42553238,d.bGE&psig=AFQjCNF0rCiGqOhclU68gnVLLfciXkDmFw&ust=1361126919702959 -
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PFM crown prep
http://www.google.co.uk/url?sa=i&rct=j&q=posterior+crown+preparation&source=images&cd=&cad=rja&docid=bCVfaJZdhl8iTM&tbnid=NcBOeWXljdmShM:&ved=0CAUQjRw&url=http%3A%2F%2Fdentistryandmedicine.blogspot.com%2F2011%2F07%2Fpfm-posterior-crown-restorations.html&ei=ydMfUeGALIfh4QSNpoD4DQ&bvm=bv.42553238,d.bGE&psig=AFQjCNFfu9lKTk-_j7m1AH2hO4EQ8VcuSg&ust=1361126691652584 -
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Tooth Preparation for Full
Gold Crown
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Full Gold Crown Prep
Posterior Crowns
http://www.google.co.uk/url?sa=i&rct=j&q=gold+crown+preparation+&source=images&cd=&cad=rja&docid=eEnG9rqSTdhI9M&tbnid=XBmEChIFFjndLM:&ved=0CAUQjRw&url=http%3A%2F%2Fwww.dentaljuce.com%2Ffruit%2Fpage.asp%3Fpid%3D417&ei=iNYfUamPIsrL4ATzg4HoDA&bvm=bv.42553238,d.bGE&psig=AFQjCNFMxbMm6D3REJPw8i2wG68GdhrF9Q&ust=1361127324841008 -
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Posterior Crowns
Clinical Stages-Phase I Pre-op clinical and radiographic
assessment
Further investigations, study models,diagnostic wax-up
Treatment Planning
Informed consent
Posterior Crowns
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Posterior Crowns
Clinical Stages-Phase II
Tooth build up (if necessary) and
Preparation Impression
Occlusal Record
Temporisation
Fabrication (Lab stage)
Posterior Crowns
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Posterior Crowns
Clinical Stages-Phase III Removal of temporary crown
Try-in of definitive crown
Cementation of definitive crown
Occlusal check
Review