Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
129 Cards in this Set
- Front
- Back
|
Provisional characteristics
|
-protect the pulp y covering prepared tooth and providing thermal insulation
-protect margins and prevent leakage by forming seal with prepared tooth -maintain space by providing stable an interabutment relation and occlusal contacts -good shade and highly polished |
|
|
biological function of temporary
|
-protect pulp
-protect periodontal ligament -occlusal function -tooth position |
|
|
mechanical function of temporary
|
-functional loading
-resistance -retention -interabutment relation |
|
|
esthetics of temporary
|
-good contours
-color stability -translucency |
|
|
Types of Provisional
|
-Custom: direct or indirect
-Prefabricated: metal crowns, celluloid shells, polycarbonate crowns |
|
|
Custom Provisional
|
-fits only one patient
-negative reproduction mold made from u-shaped modified cast either silicone putty index or clear vacuum index -patients tooth form take preop and any resin can be used |
|
|
Ideal properties
|
-convenient handling
-biocompatibility -dimensional stability -ease of contouring -adequate strength -abrasion resistance -esthetic -ease of adding and repairing -chemical compatibility with luting cements |
|
|
Protemp
|
-self-cured bis acryl composite provsional material
-can produce homogeneous void-free mix -fracture resistant and good marginal adaptation -color stability??? even over the long term -inappropriate for long span bridge -A1,A2, B1, B3 |
|
|
Prefabricated Provisional
|
-stock aluminum cylinders
-anatomic metal crowns forms -clear celluloid shells -tooth colored polycarbonate crown forms -direct custom is the best option -accurate and efficient -prefabricated provisional are ideal in emergency situations -tooth to be restored must be situated properly |
|
|
FPD Provisional
|
-maintain positional relationship (M-D, F-L) of abutment teeth and the inter-abutment distance during fabrication of the permanent FPD
- keeps occlusion stable - enables patient to see what the final restoration wiill be like esthetics feeling etc |
|
|
Remember
|
-with bis-acryl composite resins, as long as the air-inhibited layer is intact, you can add additional material to it
-if its disturbed, you need bonding agent or use mechanical retention -if ZOE had contaminated the surface, you MUST remove the contamination by grinding, or subsequent additions will NOT set, ever |
|
|
Pontics
|
-saddle shaped pontics are NEVER used in FPD construction
-concavity of ths shape would not allow patient to clean beneath it -would result in severe periodontal inflammation and horrendou odor |
|
|
Custom Tray Fabrication
|
-what is a custom tray - a tray fabricated on a diagnostic cast specifically for given patient
-rationale: impression tray with uniform relief for impression material will result in a much more accurate final impression-important in FPD construction -due to more close fit of tray to teeth (2-3mm) uses less impression material (cost savings) than stock stray, is more rigid |
|
|
Technique
|
-draw extent of tray on cast
-block out soft tissue undercuts -adat two thicknesses base plate wax over teeth extend 2-3mm beyond gingiva of teeth remove wax to make 3 occlusal stops -thin coat of vaseline over wax -adapt triad and add stop areas trim to extension line, place handle and cure |
|
|
Impression
|
-must have recorded both preparations, the edentulous ridge and all the teeth in the arch,
-margins should be evident on both preps circumferentially -MUST have recorded unprepared root structure apical to margins |
|
|
Interocclusal record
|
-to allow oposing casts to be accurately articulated at some pre-determine position (CO or MI)
- multiple teeth in arch are reduced occlusally in FPD so you need the interocclusal record because you cannot hand articulate -wax: not accurate enoguh dimensionally unstable to ship -regisil good -ZOE paste: accurate but very rigid fractures easily -PMMA resin (GC Pattern resin): accurate, rigid but hard to manage |
|
|
Master cast
|
-no voids on margins
-measure 10-12 mm from gingival crest to proposed base -trimmed and base must be flat to prevent fracture when pindexing it -removeable dies |
|
|
PFM fixed partial dentures
|
-most commonly used
-provides good esthetics with excellent physical propertie and longevity |
|
|
Requirements for successful metal-ceramic restoration
|
1. accurate abutment castings and ease of casting
2. accurate soldering and ease of soldering 3. rigidity of the metal frame 4. ability of the porcelain to fuse to the metal 5. adequate strength of the final restoration 6. esthetic apearance 7. tissue tolerance 8. ease of repair |
|
|
PRIMARY Functions of Metal ceramic substructure
|
1.provides fit of the restoration to the prepared tooth
2. metal oxide formation to which the brittle porcelain can be attached for increased strength and support 4. restores the tooth's proper emeregence profile |
|
|
SECONDARY function of metal ceramic substructure
|
1. Metal occlusal and lingual articulating surface
-metal occlusion requires more conservative preparation -occluding surfaces can be easily adjusted and repolished intraorally 2. the metal axial wall can support the components of a removable parital denture 3. the axial surfaces can house attachements for fixed or removeable partial dentures |
|
|
Principles of substructure design
|
-are the occlusal contacts in metal or porcelain?
-are the centric occlusal contacts 1.5-2mm from the porcelain-metal junction -are the proximal contacts to be restored in metal or porcelain -are the cusp tips or incisal edges adequately supported by the metal substrcture with no more than 2mm unsupported orcelain -is the substructure thick enough to provide a rigid foundatio nfo rhte porcelain veneer? |
|
|
Framework design (full contour wax up and controlled cut back)
|
-predictable esthetic results ar einsured by waxing to anatomical contour
-incisal and labial indices are used to verify even cutback -the metal ceramic junction must be carefully placed to avoid areas of high stress near occlusal contacts -waxing to the anatomic contour ensure smooth transition from porcelain to metal |
|
|
Designing the cut back
|
-occlusal contacts are 1.5mm away from the metal porcelain junction
-location of metal ceramic interface varies, depending on materia chosen to contact adjacent and opposing teeth |
|
|
Occlusal contacts
|
-opposing restoration must be carefully planned so that contacting surfaces will be of the same material
-care is needed to minimize sliding contacts over the porcelain metal interface |
|
|
Different Pontic designs used
|
-saddle (ridge lap)
-modified ridge lap -hygienic -conical -ovate |
|
|
Anterior fixed partial denture substructure design
|
-basic design for anterior pontic: modified ridge lap
-allow maximum esthetics -permit proper cleaning of the convex lingual and gingival contours -uniform thickness of porcelain |
|
|
Posterior fixed partial denture substructure designs
|
-same design principles used for single-unit posterior restorations
-most widely used: modified ridge-lap -alternative design: conical |
|
|
Elastic Deformation
|
-deformation = load X length^3 / 4xElastic modulus X width x thickness^3
-&=Fl^3/4Ebd^3 -There is one unit of deflection (x) for a given span length -deflection will be 8 times as great (8x) if the span length is doubled when all the other variables are the same -defelction will be 27times if span length is tripled when all other variables are the same -8x deflection if the thickness is decreased by 1/2 if all other variables are the same |
|
|
Clinical Consideration
|
-a long span fixed partial denture on short mandibular teeth could have disappointing results
-longer pontic spans also have the potential for producing more torquing forces on FPD, especially on the weaker abutment -to minimize flexing caused by long and/or thin spans, pontic designs with a greater occlusogingival dimension should be selected -double abutments are sometimes used as a mean of overcoming problems created by unfavorable crown-root ratios and long spans |
|
|
biomechanical considerations
|
-the walls of the facial and lingual grooves counteract torque resulting from force applied ot the pontic
-the retainers on secondary abutments will be placed in tension when the pontics flex, with he primary abutments acting as fulcrums |
|
|
Classification of metal-ceramic alloys
|
-high gold: 80-85%
-high noble- minimum 60% noble elemetns; at least 40% gold -Noble- minimum 25% noble; no gold required -base metal - less than 25% noble; no gold required |
|
|
Specific requirements for metal ceramic alloys
|
-ability to produce surface oxide for chemical bonding with porcelain
-coefficient of thermal expansion slightly greater than the porcelain veneer -melting range higher than the fusing temp of porcelain -strength as any flexure of the metal substructure will lead to porcelain fracture -must not undergo distortion at the firing temp of porcelain (sag resistant) -porcelain compatibility |
|
|
connectors in fixed partial dentures
|
-join the individual retainers and pontics together
-rigid and nonrigid -esthetics dictates: no metal exposure, and deep cuts into proximal areas to create embrasures |
|
|
connector design
|
-size shape and position influence success of the prosthesis
-highly polished -not too large (plaque control, perio, esthetics) -not too small to prevent distrotion and fracture -should comply with anatomic interproximal areas -anterior connectors normally placed toward the lignual embrasure for esthetics -eliptical in shape in buccolingual cross section -if too large =plaque control is impeded |
|
|
Which is more important height or width?
|
-2x width will double the strength (1/2 width will decrease strength by 1/2)
-2x height will cube the strength (1/2 height will decrease strength by 1/8) |
|
|
connectors
|
-4mm of connector height is necessary
-connector ideally should be 1mm above gingiva and 1mm away from the opposing tooth -if there is less than 4mm of space, then a metal tissue contact should be created |
|
|
rigid connectors
|
1. cast connectors: waxed, invested and casted
2. soldered connectors: intermediate metal alloy whose melting temperature is lower htna the parent aloy 3. welded connectors: connection is created by melting adjacent surfaces with heat or pressure 4. loop connector: special type of connector used in case when an existing diastema needs to be maintained |
|
|
non rigid connectors
|
-they are a stress breaking mechanical union of retainer and pontic
-types: 1. dovetail (key-key way) 2. split pontic 3. cross-pin and wing |
|
|
indications for non rigid connectors
|
1. to overcome problems with intermediate or pier abutments 2. maligned abutments when it is impossible to prepare a common path of insertion
3. long span FPDs which can distort due to shrinkage and pull of porcelain 4. presence of mobile teeth which needs to be splinted 5. questionable distal abutments |
|
|
factors affecting a design of fixed partial denure including a pier abutment
|
-physiologic tooth movement
-arch position of the abutments (teeth in diff segments can move in diff directions) -retentive capacity of retainers (lease retentive retainer fails first) |
|
|
Abutment inclination
|
-path of draw
-tipped teeth: poor abutment, consider ortho uprighting |
|
|
Split pontic
|
-type of nonrigid connector
-attachment completely within the pontic -useful in cases with tilted abument -more conservative preparation -improved esthetics |
|
|
Cross-pin and wing
|
-type of nonrigid connector
-two piece pontic system where the two segments are rigidly fixed after the retainers have been cemented on the abutment preparations -good for use on abutment teeth with different long axis -path of insertion is made parallel to the long axis of each tooth |
|
|
Anatomy of dentin tubules
|
-15-20,000 per sq mm at DEJ
-45-65,000 per sq mm at the pulp -diameter of tubules: -.5-.9 microns at DEJ -2.0-3.0 microns at pulp -pathogenic bacteria have diameters less than .5mm |
|
|
Components of dentin
|
cellular component: odontoblasts and odontoblastic processes
ECM: collagen, Type I and III, hydroxyapatite Fluid component: dentinal fluid |
|
|
Dentinal smear layer
|
-5-50 microns in thickness
-smear plugs extend into dentinal tubules -tightly bound to underlying dentin -reduces dentinal fluid flow/permeability -provides barrier against bacterial penetration of dentinal tubules, therefore, pulpal protection -controversy as to whether to remove or not |
|
|
Mechanisms of Post-op sensitivity
|
-Hydrodynamic theory of dentinal sensitivity (Gysi, Brannstrom)
-Inflammatory theory (Nahri) |
|
|
Hydrodynamic Theory
|
-tubular network is patent, and cross-linked via branches
-tubules are filled with: fluid of pulpal origin, odontoblastic processes, neurons -bi-directional movement of dentinal fluid stimulates the neural receptors = pain -positive pulpal pressure (5-7 mm Hg) moves fluid outword -seal the tubles and stop fluid flow using bonding agents on etched dentin -exposed collagen following acid etching "hybrid" layer is formed |
|
|
inflammatory theory
|
-branching nerve axons exist with receptors in teh coronal and cervical pulp regions
-stimulation of dentin in coronal pulp could release neuropeptides in cervical pulp -neuropeptide release can result in neurogenic inflammation in cervical regions, thus affecting cervical sensitivity of tooth |
|
|
inflammation theory
|
-hovgaard found that replacement of old restorations in hypersensitive teeth improved treatment responses of dentin hypersensitivity in the cervical regions
-replace old restorations and seal dentin beneath new ones to reduce or inhibit post op sensitivity |
|
|
Etiology of Sensitivity: Tooth preparation
|
-results in smear layer
-generates frictional heat -remaining dental thickness (between prepared walls and pulp) key to its protective nature |
|
|
Cutting Efficiency of dental burs
|
-considerable heat is generated when high speed preparations are performed
-dentin has low thermal conductivity; potential for damage increases as the depth of the cavity preparation increases -carbide burs preare dentin and enamel more efficiently, and wih less heat than diamond burs -diamond prepared surfaces are 31% more retentive than carbide prepared surfaces for crown preparations |
|
|
tooth preparation
|
-always results in secondary dentin formation in a VITAL tooth
-local anesthetics (with epi) reduce pulpal blood flow up to 3 hours - may allow additional heat build up |
|
|
Dentin dessication
|
-from air blast
-from preparing teeth without coolant water spray -prophy of prepared tooth to remove temporary cement (use wet pumice) -may aspirate odontoblasts into tubules |
|
|
Osmotic Responses
|
-can result around leaking restorations or exposed root surfaces
-sugar, salt, acid solutions elicit response -concentrated CaCl2 solution excellent for detecting leakage -any exposed root surface is prone to osmotic response |
|
|
Bacteria/Bacterial Products
|
-viable bacteria can be retained in or colonize the dentinal smear layer, whether on the exposed root, exposed dentin, or prepared tooth surface
-induce both acute and chronic pulpal inflammatory responses -inflammation can be eliminated if bacteria can be successfully sealed from prepared dentin |
|
|
Microleakage: The Bacterial invasion
|
-to date, no restorative material provides a perfect "hermetic seal" of the prepared dentin (includes crowns, composites, etc)
-ooth/restoration interfacial gaps may vary from between 10-150 microns; clinician cannot detect discrepancies less than 40 microns -bacteria have diameters of .5 microns |
|
|
Thermal Responses
|
-raising pulp temp by 6 degrees celcius increases incidence of pulp death by 15%
-increases of 10 degrees celcius results in 95% incidence of pulp death -tooth prearation (5-20 degree celcius) -light curing units/bleaching lights (5-20degre) -heat of polymerization: PMMA resins, othe rprovisional materials (5-45 degrees) |
|
|
Heat generation during tooth prep and provisionalization is affected by:
|
-proximity to the pulp tiissues
-cutting efficiency of dental burs -amount of water coolant -exothermic setting reaction of dental materials (PMMA and comp resins) -use of light curing units |
|
|
Temperature rise in dental pulp
|
-autopolymerizing acrylic resin (5-45 degrees)
-composite resins (5-35 degrees) -dental visible curing lights (5-20 degrees) |
|
|
Managing Temp increases in the pulp
|
-use copious water spray as a coolant during tooth preparation procedures to provide external cooling of dentin/pulp
-let the pulp "cool" between consecutive light cure cycles -construct "indirect" temporaries -replace burs frequently |
|
|
Threaded pin/slot retention
|
-threaded pins placed within .7mm of pulp resulted in severe pulpal inflammation
-placed greater than 1.0 mm from pulp resulted in no inflammation -slot retention resulted in no inflammation, regardless of proximity to dental pulp |
|
|
Dentin exposure occurs due to
|
-tooth to restoration fracture
-occlusal wear -tooth brushing -cervical abfractions -chemical erosion via: -perio -periodontal root planing -excessive acid etching -gap formation at the tooth/restoration interface |
|
|
Treatment methods must not solely focus on reducing dentin fluid flow...
|
must also focus on protecting vital pulp tissues
|
|
|
treatment of root sensitivity
|
chemical:
-metallic ions -chlorhexidine varnishes -fluoride and fluoride varnishes -dentrifices non-traditional |
|
|
fluoride varnishes
|
--duraphat
-1ml contains 50mg sodium fluoride in alcoholic solution of natural resins -acts to provide a reservoir of fluoride for remineralization shown to reduce caries by 75% -apply with brush -no drying required -slow setting time -instruct patients not to eat hard food 3-4 hours after application |
|
|
Provisionalization
|
-cover all prepared dentin; dont leave margins short
-avoid exothermic materials, or make indirect provisionals -if longer than 4 weeks use, consider permanent cements |
|
|
tooth prep
|
-use water spray to cool dentin/pulp
-use sharp burs/diamonds -use high speed, light pressure -do NOT marginate crowns "dry" |
|
|
take home message
|
-vital teeth restored with full crowns or FPD are "at risk" for pulpal necrosis
-incidence of pulp death is probably time dependent but is 11-17% on avg - a vital pulp has an inherent ability to repair itself -proper clnical techniqe critical to successful outcomes - prior restorative history of the tooth may be important in overall outcome -"sealing" of prepared dentin has not been shown to raise or loewr the long term incidence of pulp damage subsequent to crown preparation and placement -use of a desensitizer may reduce crown retention, while a bonding agnet may enhance it (and work as well) |
|
|
Evaluation of Abutment Teeth
|
Restored
-periodontal and pulpal health -presence/absence of caries -conditions of existing restorations unrestored -healthy supraerrupted max molars mesially inclined mand molars rotated teeth specially max and mand premolars |
|
|
Pontic
|
-pontic is derived from the latin, pons, meaning bridge
-it is an artificial tooth on a fixed denture prosthesis that repaces a missing natural tooth, restores its function, and usually fills the space previously occupied by the clinical crown |
|
|
Requirements of pontics
|
1. restoration of function and esthetics
2. oral hygiene 3. biologically acceptable |
|
|
Pontic characteristics
|
-metal-ceramic, cast metal or all ceramic
-porcelain is the material that should touch the tissue -glazed or highly polished porcelain and gold with a mirror-like finish preferred for tissue contact -proper design is more important to cleanability and good tissue health than is the choice of materials |
|
|
Pontic contact
|
-tissue contact is entirely passive (pressure free); pressure indicating paste can be used
-passive contact should occur on KERATINIZED attached tissue |
|
|
Pontic facts
|
-if pontic encroaches on unattached mucosa, an ulcer will form
-contours of pontic cannot match those of the original tooth |
|
|
Class I edentulous ridge deformities
|
-loss of faciolingual ridge with normal apicocoronal height
|
|
|
Class II edentulous ridge deformities
|
-loss of ridge height with normal labiolingual dimensions
|
|
|
Class III edentulous ridge deformities
|
-loss of both ridge width and height
|
|
|
Available Ridge management techniques
|
1. socet preservations technique
2. full-thickness soft tissue grafts 3. pouch procedure 4. ridge augmentation 5. immediate pontic technique 6. orthodontic forced eruption |
|
|
Socet preservation technique
|
-bone graft material applied directly after the exraction of the tooth
|
|
|
Pouch Procedure
|
-ridges with horizontal loss of dimension
-involves subepithelial placement of a C.T. graft from the tuberosity -Garber & Rosenberg 1981 |
|
|
Immediate pontic technique
|
-spear 1999
-a way to maintain the interdental papilla following anterior tooth removal -provisional modified to prevent socket collapse -intimate natural emergence profile |
|
|
Pontic design classification
|
-depends onthe shape of the gingival side of the pontic
1. mucosal contact -ridge lap -modified ridge lap -ovate -conical 2. no mucosal contact -sanitary (hygienic) -modified sanitary |
|
|
Ideal pontic should be designed as
|
1. surfaces smooth, well finished and convex in all directions
2. pin-point pressure free contact 3. for posterior pontics--> occlusal table should be harmonious with opposing teeth 4. emergence profile and pontic length should be harmonious with adjacent abutment teeth |
|
|
Sanitary (hygienic) pontic
|
-no contact with edentulous ridge
-good access for oral hygiene -indicated for posterior mandibular teeth -contraindicated in esthetic zone or limited VDO -disadvantages 1. food entrapment 2. feels odd against tongue -seldom used -convex undersurface mesiodistally and buccolingualy -all metal is preferred material -3mm thickness -compromised mechanical strength when inadequate space |
|
|
Modified sanitary pontic (Perel's pontic)
|
-gingival portion shaped like an archway between the retainers
-concave mesiodistally -easy to clean -increased connector size -mechanical strength to prevent flexure |
|
|
Ridge lap (saddle) pontic
|
-concave intaglio surface
-proposed to enhance esthetics -not amenable to oral hygiene -not recommended |
|
|
Modified Ridge lap pontic
|
-overlaps the residual ridge on the facial side
-clear of ridge on the lingual side -recommended in highly esthetic location -moderately easy to clean -not enough air seal for speech -passive and compact contact on attached gingiva -convex intaglio surface -tissue contact should resemble letter (T) as viewed from gingival aspect |
|
|
Conical pontic
|
-egg-shaped, bulet-shaped
-limited use for thin ridges -in molars without esthetic requirements -point contact with the ridge -conves surfaces -good access for oral hygiene |
|
|
Ovate pontics
|
-most esthetically apeallling design
-used for maxillary incisors, canines and premolars -high smile line -conves tissue surfaces -good emergence profile -accessible to oral hygiene -ease of cleaning -require surgical preparation -not for residual defects |
|
|
Multiple pontic designs:
|
-pink porcelain to simulate interdental papilla
-reduces the number of surfaces and complexity of restoration -improves accessibility to oral hygiene -reduces tongue toys |
|
|
Tissue contacting pontics additional considerations
|
-pontic length/width
-location of finish lines -gingival embrasures -edentulous flange -lip support |
|
|
Periodontal conditions in patients treated with dental bridges
|
-the increase of index values (PI,GI) may be attributed to the accumulated effects of the presenc eof Sub-G margins and pontics
-increase in pocket depth should mainly be ascried to the presence of subgingival retainer margin |
|
|
Oral hygiene consideration
|
-toxins released from microbial plaque, which accumulate between the gingival surface of the pontic and the residual ridge cause tissue inflammation
-FPDs cannot be taken out -patient must be taught efficient oral hygiene techniques -proxy brushes, oral-B super floss and dental floss with a threader are highly recommended |
|
|
Summary for pontics
|
-contact tissue with pontic tips only when necessary. If tissue contact is indicated, it should be passive, and limited to as little surface area as possible
-passive contact should be on KERATINIZED attached tissue -ridge lap design should be avoided because the concave gingival surface of the pontic is not accesible to clean with dental floss |
|
|
key features of ideal tooth preparation
|
1. provide sufficient dimension of restorative material for strength and esthetics
2. provide sufficient remaining tooth structure to maintain integrity of tooth (prevent prep fracture) 3. provide adequate R&R form to help maintain the crown in the oral cavity |
|
|
retention form
|
-those features of tooth preparation that pevent removal of the prosthesis along its path of insertion (long axis of the preparation)
|
|
|
Resistance form
|
-those features of tooth preparation that prevent dislodgement of the prosthesis from forces directed apically or obliquely against the prosthesis (lateral forces of occlusion)
|
|
|
Biomechanical features of retention form
|
1. prep taper (convergence)
2. length of prepared axial walls 3. surface roughness of prep 4. surface area of prep 5. mechanical properties of cement 6. casting/tooth prep for cementation 7. retention grooves/boxes |
|
|
Biomechanical features of resistance form
|
1. prep taper (convergence)
2. length of prepared axial walls 3. retention grooves/boxes 4. occlusal/incisal tooth contours |
|
|
Prep taper
|
-potential rotation axis for prostheis: M-D and F-L
-dental arch dependent: buccaly in max, lingual in mand -anterior vs posterior tooth prep design -ideal taper vs. reality |
|
|
One might say
|
-that crowns with short axial walls might require more axial parallelism (less TOC) than those with long axial walls
|
|
|
Methods to improve R&R
|
-paralleling devices
-crown extension surgery -rapid ortho exrusion -modifications of existing tooth prep by re-prep or placement of various core foundation materials -cementation factors |
|
|
Modification of existing preparation
|
-conversion of chmafer to shoulder (increases parallelism)
-mesial distal grooves boxes = resists F-L displacement -F-L grooves/boxes (resists M-D displacement) -occlusal morphology -placement of core foundation materials |
|
|
Occlusal function
|
-if te rotational arch from facial to lingual margin passes through tooth structure, you have adequate resistance form; if it does not, you don't (and you need to consider modifying the preparation)
|
|
|
Grooves/Boxes
|
-anterior teeth, due to traingular shape when viewed in profile, primarily gain retention form from parallelism of M and D walls
-posterior teeth have greater prepared surface area than anterior teeth, are rectangular rather than triangular in profile, and thus possess more potential parallelism and R&R form |
|
|
Resistance grooves
|
-must draw with remaineder of preparation
-must be parallel to each other -must be 1mm coronal to the prepared margin -must be accurately impressed -must be incorporated within the PFM casting or ceramic coping to be effective -should be 1/2 depth of a 271 carbide bur (providing opposing walls) -grooves must be accurately impressed -lab MUST cast metal into grooves within the crown -add to lab Rx: " please do not block out rsistance grooves on mesial and distal walls- cast metal alloy into them" |
|
|
Cementation Factors
|
-cement selection (adhesive cements for situations with poor R&R form)
-dentin preparation to enhance adhesion surface roughenss (diamond) and dentin bonding agents -prosthesis preparation to enhance cement adhesion, dependent on crown type |
|
|
cement selection factors
|
-strength (shear, tensile, compressive)
-solubility -film thickness (ADA <25 microns) -adhesion to tooth structure -dentin preparation to enhance cement adhesion: diamond vs. carbide prep cleaning dentin surface etching/drying protocol use of dentin bonding agents prosthesis prep to enhance cement retention -microabrasion -silicoating or tin plating -adhesive cement selection -complete removal of "fit checker" |
|
|
Clinical areas of concern
|
-short clinical crowns
-over-tapered preparations -long span FPDs -severe occlusal wear |
|
|
summary for retention
|
-assess your prep prior to final impression
-improve R&R form with grooves, boxes, more parallel walls, improved cements, crown lengthening, and/or pin amalgam or composite resin core foundations, or elective endo with dowel/cores -think carefully about the stresses, rotationl axis, and/or forces the restorations will endure |
|
|
All ceramic FPD indications
|
-short spans (4 ntis) in anterior regions and 3 units in posterior
-when patient has allergy to metallic components of PFM FPDs -when patient demands no metal alloy in prosthesis |
|
|
contraindications to all ceramic FPD
|
-FPD spans >4 units (anterior) or >3 units posteriorily
-bruxers -occlusion related cervical wear -patients with large pulp chambers (young patients0 -abutment teeth with compromised R&R form |
|
|
Types of Gold restorations
|
-3/4 crowns
-7/8 crowns -veneers -pinledge restorations -full crowns |
|
|
Cast Gold Onlay
|
-spans gap between inlay (intracoronal) and full crown (extracoronal)
-more conservative than full coverage -by definition, caps all of the cusps of a posterior tooth -provides for less gingival irritation -virtually eliminates future tooth fracture |
|
|
indicatins for gold onlay
|
-a large, failing amalgam (or composite) that extends 2/3 distance from the central groove to the facial and lingual cusp tips
-gross wear form attrition -existing amalgam/composite with one or more fractured cusps |
|
|
Advantages gold onlay
|
-low creep- means no edge deterioration
-no corrosion- means no discoloration, as seen with amalgam |
|
|
diadvantages gold onlay
|
-not a conservative restoration vis a vis amalgam
-must get ride of undercuts -need extension for impression material, wax pattern and gold -cost |
|
|
outline, retention and resistance form
|
-extend central groove F/L to get beyond caries to solid tooth structure
-extend all faulty grooves |
|
|
Cutting Proximal boxes
|
-extend into proximal boxes w/out removing marginal ridges
-expose DEJ approximately .5mm -as you approach the mesial and distal gradually widen the facial and lingual to accomodate the proximal boxes -widening provides bulk for wax pattern and metal |
|
|
proximal boxes continued
|
-continue with 271 and cut roximal ditches
-approximately .8mm wide mesial/distal -mostly at expense of dentin |
|
|
occluso gingival depth
|
-should just break through underneath the roximal contact
-.5mm from adjacent tooth at gingival floor -measure externally from marginal ridge height |
|
|
Retention grooves
|
-especially appropriate for short tooth
-in proximal boxes -in long axis of tooth -.3mm into dentin -use 169L carbide bur |
|
|
gingival beveling
|
-remves weak enamel
-creates "lap-sliding" fit -creates 30 degree bevel at gingival margin, which is burnishable -.5-1.0 mm wide |
|
|
Counter Bevles
|
-prepared at 30 degrees to external enamel surface
-generous enough so that margin is beyond any opposing contact, including excursions -blended smoothly into proximal bevels |
|
|
counter bevel on facial cusps of maxillary premolars and molars
|
-for esthetic reasons, can only blunt and smooth facial margin
-diamond is held at a right angle to the facial surface of the tooth |
|
|
Collars
|
-added to enhance R&R form on overly weakened cusps
-especially centric holding cusps -all cusps can be collared if needed -exception: facial cusps of maxillary teeth -use 271 bur |
|
|
More on Collars
|
-2-3 mm high occluso/gingivally and .8mm in axial epth
-blend with proximal boxes -roll in occlusal aspect and round all sharp line angles -place facial bevel and blend with gingival bevel |
