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42 Cards in this Set
- Front
- Back
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WHat should the choice of material allow? |
- realisation of patients' cosmetic expectation, but not require excessive preps - facilitate optimum tissue response - take account of technical considerations - take account of opposite and adjacent contacts - be limited to those whoch satisfy relevant standards |
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Requirements of a good ECR material |
•Accuracyof fit.
•Strengthto resist occlusal forces. •Rigidityto avoid flexure and hence cement failure. •Thermalexpansion comparable to tooth.•Shouldnot attract plaque. •Biocompatibility |
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Types of metal materials |
essentially two types: - gold and palladium alloys (precious) - base metal alloys (non-precious) - nickel chrome, titanium |
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How to choose between precious and nono-precious? |
•Cost •Corrosionresistance •Strength,stiffness, hardness, ductility (clinical)–Low-stress bearing inlay vs Posterior bridge |
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What are the roles of gold, copper, silver in gold alloys? |
Gold •Gold adds to the color, tarnish andcorrosion resistance, and malleability of an alloy.Goldalso increases the density of an alloy. Copper •Copper is a strengthener and colorenhancer in Au-Ag-Cu crown and bridge alloys. Copper-rich Au-Ag-Cu alloys tendto have a "reddish" color. Silver •Silver is used in Au-Ag-Cu crownand bridge alloys to balance the reddening effect of copper. Silver-richAu-Ag-Cu alloys tend to have a "greenish" color. •Together with copper, it is used tocontrol the strength and hardness of crown and bridge alloys. |
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Pros and cons of base metal alloys |
•Have a higher modulus of elasticitythan noble alloys i.e. they are more rigid - Implies less flexing of , e.g., along span bridge •Major drawbacks are the need forvery carefully controlled casting conditions and of increasing concernBIOCOMPATIBILITY of dental alloys. |
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Biocompatibility issues with base metals |
•Grinding and casting fumes canresult in conjunctivitis, dermatitis and bronchitis (which may not expressitself for several years after exposure) •High levels of nickel arecarcinogenicMorecommonly, nickel is well known to cause contact dermatitis (a host response). |
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How and why is porcelain modified for PFM crown? What is the name of the alloy used at the LDI for PFM? |
•Inorder to more closely match thermal expansions, the porcelain is modified •Thebond to base metal alloys is not as good as that of the precious metals. Use V-Delta SF Role of palladium: - whiten gold - raise melting point and modulus, improve stength and hardness, lowers density - improves tarnish and corrosion resistance Role of indium: • strengthens andhardens both gold and palladium, and raises the thermal expansion of both. •Indium lowers the melting range ofboth gold and palladium, and contributes to the formation of the bonding oxide. |
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Pros and cons of PFM |
Pros •The coping distributes stressesand provides rigid support.–Inhibits propagation of cracks fromsmall faults at the ceramic/metal interface. •A good bond is achieved by: –Mechanical retention (roughness). –A direct chemical bond (iondiffusion) .–Mismatch of the coefficient ofthermal expansion (CTE) (metal higher than ceramic).•The mismatch in CTE createstangential compressive stresses in the ceramic. Cons •Absenceof light transmission, especially in cervical and proximal areas. •Reduceddepth of translucency. •Presenceof grey line at gingival margin.•Sensitivityor allergy to alloys. |
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Scale of porcelain and ceramics in terms of toughness and bend strength |
Weakest to strongest Conventional porcelain Glass-ceramic Glass infiltrated alumina High tech ceramics (far superior) |
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Whya are ceramics bettter than glasses? |
•Usuallya ceramic consists of a crystalline material in a glassy matrix - If a crack starts to propagate in the glass, the crystalline domainsdeviate the propagation - Thus the progression of the crackis hindered |
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What is aluminous porcelain? |
•Essentiallya high strength ‘core’ porcelain containing up to 50% fused alumina crystalsonto which a matched expansion veneer is baked. •Alumina,when added to porcelain, acts as a crackstopper, preventing cracks propagating through the material, thus increasingstrength. |
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What are glass ceramics? |
•Finegrained polycrystalline materials which are obtained from an initially glassyphase following a heat treatment cycle. •Largenumbers of fine crystals limit the propogation offlaws through the glass-ceramic which has far superior mechanical propertiescompared to the base glass. |
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Pros and cons of glass ceramics |
Pros •Nearnet shapes can be produced. •Almostzero porosity can be obtained. •Reproducibleproperties. •Moretooth-like than metal-ceramics and some porcelain restorations. Cons •Processingroute is not so suitable for incorporating variations of shade and stainingthat are important for an aesthetic restoration. |
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What is EMAX? |
•Designedfor crown and bridgework •Frameworkmaterial:–60% Lithium disilicate (main phase)–Lithium orthophosphate (secondary) Corematerial strength ~400 MPa •Layeringmaterial:–Fluoroapatite |
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Uses for EMAX? |
Inlay, Crowns, 3 unit conventional anterior bridge, onlay, veneers |
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What is transformational toughening? |
IDK, look up, see end of lecture |
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Define abutment, pontic, retainer |
Abutment: That part of a structure that directly receives the pressure, theabutments can either be natural teeth or abutment component in a dentalimplant. Pontic: An artificial tooth on a fixed dental prosthesis that replaces a missingnatural tooth, restores its function, and usually fills the space previouslyoccupied by the clinical crown Retainer: This is the part of the bridge which is cemented to theabutments. This could be in the form of a full crown, but can also be a ¾crown, an inlay/onlay or metal wing of a resin-retained bridge |
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Types of fixed bridge |
• Cantilever bridges: a fixed dental prosthesis in which the pontic iscantilevered i.e. is retained and supported only on one end by one ormore abutments. Fixed-Fixed bridges: a fixed dental prosthesis in which the pontic isretained and supported by two abutments, one either side of the pontic. Conventrional: retainer is a crown Resin retained: retainer is wing atached to abutment with resin cement |
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Design considerations for conventional bridge |
Occlusion: Keep pontic with light contact in ICP and no contact inlateral/protrusive movements. 2- Share the bridge occlusal guidance with the natural teeth if possible. |
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Indications and contraindications for conventional bridge |
) Heavily restored abutments. 2) Well motivated patient with excellentplaque control. 3) No active caries lesions. 4) Stable periodontium 5) Able to clean and maintain the bridgework 6) Small edentulous spaces 7) Replacement bridge Work 1) Unrestored abutments. 2) Poorly motivated. 3) Active Caries. 4) Active Periodontitis 5) Poor Manual Dexterity to cleanbridge 6) Large Edentulous Spaces 7)Contact Sports Player?? |
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Which teeth make best abutments? |
1, 3, and 6 |
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What are the clinical stages of a conventional bridge? |
Primary impression Diagnostic wax up on study model Abutment prep and master impression (temp crown) Bridge construction
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INdications and contra for resin retained bridge |
Indications for resin retained bridges 1) Sound, unrestored abutments. 2) Well motivated patient with excellent plaque control. 3) No active caries lesions. 4) Stable periodontium 5) Able to clean and maintain the bridge work 6) Small edentulous spaces Contraindications 1)Heavily restored abutments. 2) Lack of clinical crown height in the abutment teeth 3) Poorly motivated patient. 4) Active Caries. 5) Active Periodontitis. 6) Poor Manual Dexterity to clean bridge 7) Large Edentulous Spaces 8)Contact Sports Player?? 9) Bruxism and parafunctional habits |
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Design featurs for RRB |
• In most cases no preparation is advised to allow maximum bondingto the enamel layer.• Most recent research concluded that:“Resin-retained bridges made with minimal tooth preparation areshown to be superior in terms of longevity than those for which othertypes of tooth preparation is made. Patient satisfaction with theirtreatment was high” P.A King, BDJ 2015 Cover Maximal Surface Area of the Abutment tooth Use Rigid, Non-PreciousMetal Wing Retainers of atleast 0.7-0.8mm thickness Use Cantilever Designs for Adhesive Bridgework and keepthe pontics out of excursive contacts Canines and Molars can make ideal bridge abutments Avoid Fixed/Fixed Resin retained bridges - due to possibility of undetected bonding |
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Design consideratrions for RRB |
1- Occlusion: Keep pontic with light contact in ICP and no contact inlateral/protrusive movements. 2- Share the bridge occlusal guidance with the natural teeth if needed. 3- Discuss wax-up with patient specially in anterior bridgework. 4- Explain to the patient that metal wing might show through the abutment. |
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ADVS and dis of RBB? |
Advs Minimally invasive (Edelhoff 2002) Local? Tooth prep?• Quick (Verzijden1990)• Cheap• Easy??• High patient satisfaction Dis Vs Implants• Need to utilize abutment tooth• Vs Conventional bridgework• Limited span• Restricted ability to adjust tooth size/ alignment• Post-fit adjustment• Grey out of abutment tooth? |
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Success rate of bridges |
systematic reviews, success at 5 years: – RBBs 87.7% (Pjetursson BE et al 2008) – Conventional bridges 90% (Pjetursson BE et al 2007) – Implant retained single crowns 94.5% (Jung RE et al 2008) |
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Things to consider in case selection for RRB |
Abutment Tooth • Periodontal Support • Root formation • Clinical crown: – Size – Restored – Alignment Occlusal Assessment • Guidance • Inter-OcclusalSpace • Wear faceting |
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Considerations for RRB design |
Cantilever or fixed- fixed?Always cantilever!No double abutments! Exceptions:• Long spans• Post ortho? Retainer design• Maximum extensions Use of composite Base metal alloy 0.7mm thickness Pontics• Shade• Shape (ovate where aestheic) |
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How much tooth prep for RRB |
King et al 2014 – any more than minimal preparation is associated with a2.5x higher failure rate. Tooth preparation• Remove bulbosities to allow full extension• Remove fissure detail Does not aim to:• Create occlusal space• Provide grooves/ rest for retention Existing restorations• Replace• Extend into |
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What are the important points of cementation? |
Seating lugs -are they needed? • Moisture control - v important • Resin cement with a phosphate monomer– eg Panavia/ RelyX Ultimate– Consider need for opaquer - follow instruction!! |
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Why may a bridge fail? |
Biological complications – Patient selection and education– Super-Floss! • Technical complications – Structural damage Deterioration of aesthetics – Debonding – recement or remake? Has something changed?? • Is there parafunction?? |
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What is an immediate denture and immediate bridge? |
An immediate denture is one that isconstructed prior to the extraction of the natural teeth & insertedimmediately after their removal Immediate bridge - extracted tooth has root cut off, cleaned and sealed, then bonded on to neighbouring teeth with composite and ortho wire |
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WHy replace a tooth immediately? |
Aesthetic demand Drifting Over eruption |
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Ads and dis of immediate dentures |
ADS Noperiod without teeth, giving social & psychological advantages. Keeps a record of appearance, lip support,occlusal plane, OVD & type of occlusion. Aids in masticatory function. Helps speech. Maintains facial contour & muscle tone. Removable - Can be removed to clean both it andthe mouth - Can access the extraction socket- Can carry out permanentrestorations / preparations to adjacent teeth Made in laboratory – cuts downsurgery time Can repair Can re-fit as underlying mucosachanges following extraction Dis If constructed prior toextraction... May not fit May not be the right shade, shape etc Healing will change the shape ofthe underlying ridge Rarely a permanent solution = Increased number of visits= Increased cost Mucosal coverage= Plaque accumulation Patient acceptance Pressure on ridge increases bone resorption Removable therefore may be left outand allow tooth drifting |
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What is shortendedental arch? |
5 to 5 in each arch is adequate for masticatory function |
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INdications for remvable denture |
Many missing teeth? Prognosis of remaining teeth Young patient – still growing,large pulps Sports player Gross alveolar resorption |
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Indications and contra for fixed prosthesis |
More acceptable to the patient Directs forces axially Does not cover the gingival margin Better for restoring occlusion Periodontal splinting Ortho retention Public speaker etc Destruction of tooth tissue Good oral hygiene dexterity Longevity of bridge Periodontal implications if subgingival margins Cost |
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What is a fixed:maviable bridge? |
Similalar to F:F but connector is in two interconnecting parts •Toact as stress relief for minor retainer (movement must occur) •Toallow for different paths of insertion •Fixed end of bridge has rigid connector •Fixed end usually distal to pontic •Minor retainer houses moveable joint •Joint is slot and dovetail type |
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What generalfactors shouldbe taken into consideration before undertaking fixed prosthodontics? |
1 Patient attitude and motivation 2 Age 3 Sex 4 Occupation 5 General health 6 Confidence 7Appearance 1 Patient motivation - howimportant is it to replace the missing tooth 2 Biological age of patient / sex / occupation 3 Willingness to undertake the treatment 4 Attendance / accessibility 5 Cost 6 Physical ability to receive treatment 7 Psychological ability to have treatment – phobia 8 Patient expectations 9 Biological cost 10 Dentist and technician skills 11 Informed Consent |
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What are the local factors that affect the decision to use fixed prosthesises? |
1 Oral hygiene 2 Periodontal condition –progressive or stable / long term prognosis 3 Active caries / arrested caries /sound tooth 4 Existing restorations / crownheight / root configuration & length / recession / support of potential abutment teeth 5 Endodontic status of abutmenttooth – root filling acceptable or not 6 Apical pathology 7 Occlusion – space available /teeth over-erupted, drifted, rotated / guidance, contacts,interferences / parafunctional habits 8 Number of teeth to replace 9 Condition of alveolar bone inedentulous area |
