Prosthodontics: General Flashcards
Anatomy of a Bridge
- Abutment: the Tooth the bridge attaches to
- Retainer: Crown that attaches to abutment
- Pontic: FAKE TOOTH
- Connector: Connects retainer to pontic
Bridge: Poor Prognosis Scenarios
- Half or less bone support around abutment tooth
- Single retainer cantilever (posterior region)
- Multiple-splinted abutment teeth
- Nonrigid Connectors
- Intermediate Abutments=pier (aubtment tooth used to support a bridge all by itself, w/no adjacent teeth)
What teeth should not be used an abutment teeth in a bridge?
Compromised Endo Teeth
* removed dentin makes them weaker
Compromised Perio Teeth
* crown to root ratio=2:1
Bridges: Crown to Root Ratio
Ideal: 1:2
Realistic: 2:3
Minimum: 1:1
Poor: 2:1 (not used for abutments)
what should be done if replacing a maxillary canine w/a bridge
Splint central and lateral together
* prevent lateral drifting of the bridge
Ante’s Law
The PDL surface area of abutment teeth should be equal to or greater than the imaginary PDL SA of missing teeth
Abutment teeth PDL SA >/= Imaginary/Missing teeth PDL SA
Bridge: Splinting Teeth
Splinting: Distributes occlusal forces
Recommend when Ante’s Law is broken
* PDL SA of abutment tooth can’t support the bridge
If replacing a maxillary canine:
*splint central and lateral together
* prevent lateral drifting of the bridge
Bridge: Ideal Root Shape for abutment teeth
Roots:
* Divergent
* Multiple
* curved
* broad Roots
Partial Denture Indications
Distal Extension
Long Span edentulous space
Bone loss around Potential Abutments
Bridge or implant is too expensive
Complete Denture: Indications vs Contraindications
Indications
* all teeth are missing
Contraindications in maxillary whenCombination therapy
* Only mandibular anteriors are present
* cause severe damage to premaxilla
Overdenture: How many implants recommended for mandible vs maxilla
Mandible: 2 implants
Maxilla: 4 implants
Cement-Retained Implant: Pros vs Cons
Pros
* economical
* minor angle correction
* Easier in small teeth
Cons
* more chair time
* gets loose over time
* excess cement=peri-implantitis
Screw-Retained Implant: Pros vs Cons
Pros:
* Retrievability: crown removal
* good maintenance
* Access hole: Posteriors=Occlusal; Anteriors: Lingual
Cons:
* Screw loosens during function
Alginate
Aka Irreversible Hydrocolloid
* 1st choice for diagnostic casts
* Diatomaceous earth adds strength
* Trisodium Phosphate: Controls setting time
More bulk=less unwanted dimensional changes
Process of taking impressions with alginate and pouring up for diagnostic casts
Process:
remove tray: 2-3 mins
Pour impression within 15 mins
Casts set in 30-60 mins
Maxillo-Mandibular Relations (MMR)
CR
MI
Centric Relation (CR)
Condyles
* in the most anterior-superior position
* articulate the thinnest avascular portion of the discs
* against the articular eminences
Independent of teeth
Maximum Intercuspation (MI)
aka Centric Occlusion (CO)
Complete interdigitation of teeth
* independent of condyle position
CR Vs MI
CR=MI in only 10% of pts
* in 90%, they slide into each position
Casts are mounted in MI when MI can be maintained
* (Single fixed procedure-single crown or bridge)
Casts are mounted in CR when MI is impossible to maintain
* complete dentures
* multiple teeth being restored/replaced
What is the most reliable and reproducible jaw movement?
CR
Occlusal Harmony
Joint, Muscles, and Teeth MUST function in harmony
Bimanual Manipulation
most accurate method to get in CR
* Goal-Deprogram the jaw
What is Objective of a Facebow Record
Duplicate the relatinoship b/w
* maxilla –> skull
* mandible –> TMJ ratoational center
On the articulator
Facebow Types and describe each
Arbitrary Facebow:
* orients maxillary cast–> skull by external auditory meatus
* easier to use
Kinematic Facebow:
* placed on hinge axis of mandible
* more complex
Articular parts and corresponding anatomy
Upper Member: Maxilla
Lower Member: Mandible
Hinge Axis=TMJ
Nonadjustable Articulator
NO Full range of mandibular movement
* Shorter distance b/w hinge and teeth vs in patient
Result in:
* premature contacts
* incorrect ridge & groove direction of restorations
Semiadjustable Articulator
Can set:
Bennett Angle (15 degrees)
Horizontal Condylar Inclincation (HCI=30degrees)
Types:
Arcon:
* condyles are part of the lower member
* fossa are part of the upper member
* more anatomically accurate
Nonarcon:
* upper and lower membres are rigdily attached
* Not anatomically accurate
When casts are poured from alginate or elastomeric materials, they are more accurately mounted with what?
- Alginate –> wax records
- Elastomeric materials–>elastomeric materials (PVS) or ZOE paste
Disclusion: Define
Mandible protruded forward
Disclusion Types:
Condylar Guidance
Incisal Guidance
Canine Guidance
Anterior Guidance
Disclusion: Condylar Guidance
articular eminence slope
* varies among patients
* limits jaw movement
Represented by HCI on articulator
Posterior Determinant of occlusion
Disclusion: Incisal Guidance
pin and guide table on articulator
Anterior Determinant of occlusion
Disclusion: Canine Guidance
lateral movements, all posteriors disclude
* canines contact on working side only
Disclusion: Anterior Guidance
Incisal & Canine Guidance
Disclusion Summary:
During Protrusive
* incisal and condylar guidance provide clearance for all posterior teeth
During Lateral (excursive),
* canines on working side and condyle on balancing side provide clearnace
* for posterior teeth on balancing side
Guide Table
Anterior guidance must be preserved when restorany guiding surface of teeth
Mechanical Incisal Guide:
* insufficient info to reproduce lingual contours of maxillary anteriors
Custom Incisal Guide table
* made out of acrylic resin
* provids info needed
Mutual Protection:
Front teeth protect back teeth
* front teeth disclude posterior teeth during protrusive and lateral movements
Back teeth protect front teeth:
* back teeth have flat occlusal surfaces and strong root=protect anteriors from bite forces
Maxillary Labial Frenum
At or adjacent to midline
Maxillary Buccal Frenum
Either Side of Alveolar Ridge
Attach:
* orbicularis oris
* buccinator
Maxillary Labial Vestibule
Anterior to the 2 buccal Frena
Maxillary Buccal Vestibule
Posterior to buccal frenum to hamular notch
Hamular Notch
soft tissue
connects:
* distal end of maxilla
* pterygoid hamulus
Vibrating Line
Pt says AHH=Location
* from hamular notch to hamular notch
* 2mm away from fovea palatini
Buttery Fly Line
Junction b/w hard and soft palate
* anterior to vibrating line
Valsalva maneuver: butterfly line balloons down
* hold nose and try to blow through nose
Posterior Palatal Seal
part of denture that compresses soft tissue of palate=suction
Anterior Boundary=Butterfly Line
Posterior Boundary=Vibrating Line
Cornoid Notch
DB part of maxillary impression/denture
Pt moves jaw side to side during border molding
* Coronoid notch slides past DB region of impression
Pterygomandibular Raphe
Pt opens wide to capture on posterior part of impression
Connect:
* buccinator m.
* superior pharyngeal constrictor
What are the 2 most important movements for upper impressions?
Move the Mandible Left/Right
* coronoid process glides past the distobuccal corners of denture
Open mouth wide
* pterygomandibular raphe tightens and molds impression in back
Mandibular Labial Freenum
Attach:
* orbicularis oris
Mandibular Buccal Freenum
Attaches:
Orbicularis oris
Buccinator
Lingual Freenum
Mandible
Attaches:
Genoglossus
Mandibular Labial Vestibule
Anterior to buccal frena
Mentalis Muscle (Chin)=inferior border
Mandibular Buccal Vestibule
Posterior to buccal frena
Buccinator m=inferior border
Retromolar Pad
Mandible
marks the distal extension of edentulous ridge
* Ideally covered for support and retention (bc bone integrity is maintained)
Attaches:
* temporalis m.
* buccinator m.
* superior pharyngeal constrictor
* pterygomandibular raphe
Masseteric Notch
DB area on mandibular impression/denture (analogous to hamuler notch)
*Masseter contracts when the mouth closes against resistance
Have pt close against resistance to capture in border molding
* prevents masseter from impinging on overextended DB corner of denture
Alveolingual Sulcus
B/w mandibular alveolar ridge and tongue
2 S’s (Vertical S & horizontal S)
3 Regions:
Anterior Region
Middle Region
Posterior Region
Buccal Shelf
Main Support for Denture
* Perpendicular to occlusal forces
* lateral to posterior alveolar ridge
Attaches: Buccinator
Alveolingual Sulcus: Anterior Region
lingual freenum to premylohyoid fossa
* First curve in the S
* Sublingual gland sits above mylohyoid muscle
* Want shorter flange
Alveolingual Sulcus: Middle Region
premylohyoid fossa to distal end of mylohyoid ridge
* 2nd curve of S
Flange
* deflected medially away from the mandible
* due to mylohyoid ridge & contraction of mylohyoid medially
Alveolingual Sulcus: Posterior Region
Extends into retromylohyoid fossa
Mylohyoid
* attaches higher the more posterior you go, but posterior fibers are directed vertically
Flange
* longer and deflected laterally towards the mandibular ramus=3rd curve of S
* extension is limited by palatoglossus and superior constrictor muscles
Frenectomy
Complete removal of Freenum
High Freenum Attachment
* neart top of alveolar ridge
Most to least common:
Labial>Buccal>Lingual
Free Gingival Graft
widen band of keratinized tissue
* Below gingival margin
Requires revascularization from recipient bed
Graft=palate
*includes surface epithelium
* ideal thickness: 1-1.5 mm
Might Need for overdenture teeth
Hypermobile Ridge
Flabby edentulous ridges in anterior maxilla
Tx: tissue conditioner if inflamed
* electrosurgery or laser surgery if not effective, can also eliminate the vestibule
Epulis Fissuratum
Hyperplastic tissue reaction
* due to ill fitting denture or overextended flange
Fibrous Tuberosity
aka Pendulous Tuberosity
Large Tuberosities touch retromolar pads
* limits interarch space
Tx: Surgical excision
Papillary Hyperplasia
Multiple papillary projections on palate
* Etiology: Candidiasis
Combination Therapy:
* General
* Signs/Symptoms
Only have mandibular anterior teeth
* bone resorption in maxillary anterior
Signs/Symptoms:
* overgrowth of tuberosities (Fibrous tuberosities)
* Papillary hyperplasia in hard palate
* Extrusion of lower anterior teeth
* Bone loss under partial denture bases
Retained Root Tips
Residual RT (Non-RCT)-infection risk
Can be left if:
* intact lamina dura
* no radiolucency
Paget’s Disease
Etiology: Unknown
Dentures not fitting
* need to remake periodically
Alveoplasty
Surgical reshaping of alveolar bone
* sharp, spiny, or irregular ridges
Tori removal indications
Creates an undercut (lingual torus)
interferes w/posterior palatal seal (palatal torus)
Bone Augmentation
Horizontal>Vertical
* easier to restore horizontal ridge width vs height
VDR
Vertical Dimension of Rest
Distance b/w nose and chin at rest
* elevator and depresssor musccles are in equilibrium (PRP=Physiological rest position)
3mm of space b/w upper and lower premolars
VDO
Vertical Dimension of Occlusion
Distance b/w nose and chin when biting together
* =superior-inferior relationship b/w maxilla and mandible in MI
Interocclusal Space
VDR=VDO+ 3mm
the difference b/w VDR and VDO
* ideally 2-4 mm
Excessive VDO
- Fatigue of Muscles of Mastication
- Lips appear strained
- Gagging
Insufficient VDO
**Aged appearance-lower 1/3 of face
Angular Cheilitis
Christensen’s Phenomenon
Distal space b/w maxillary and mandibular occlusal surfaces when mandible is protruded
* posterior open bite
Camper’s Line
imaginary line from ala of nose to tragus of ear
Interpupillary Oline
imaginary line b/w pupils of eyes
Complete Denture: Plane of Occlusion
Maxillary wax rim parallel to:
* Camper’s line
* Interpupillary line
Complete Dentures: Balanced Occlusion
Simultaneous anterior and bilateral posterior contnacts in centric and eccentric movements
* aka Tripodization
* avoid anterior guidance to prevent dislodgement
On balancing side
* maxillary lingual cusps –>lingual incline of mandibular buccal cusps
On working side:
* maxillary lingual cusps –> facial incline of mandibular lingual cusps
* Mandibular Buccal cusps contact lingual incline of maxillary B Cusps
Complete Denture: Lingualized Occlusion
Only maxillary posterior lingual cusps contact mandibujlar posterior teeth
* prevent dislodgement
Bennet Concepts: Bennett Angle vs Shit vs Movement
Bennett Angle:
* nonworking side condyle angle: From anteriorly and medial to sagittal plane
* 15 degrees
Bennett Shift:
* Lateral movement of mandible towards working side during lateral excursions
Bennet Movement:
* lateral movement of both condyles towards working side
* TMJ Looseness
Factors that Favor Disclusion(seperation) of posterior teeth (NO ECCENTRIC CONTACTS)
*Anterior Guidance
*Posterior Guidance
* Cusp Anatomy
* Tooth arrangement
*Occlusal plane orientation
Horizontal=protrussive
Lateral=excursive
Curve of Spee
AP Curve
* load on long axis of each tooth
More mesial tilted as you move distal
Curve of Wilson
Mediolateral Curve– along posterior cusp tips
* Load on long axis of each tooth
More lingual tilt as you move distally
Support
Resistance to Vertical Seating Forces
Support for Upper and Lower arch and form the Denture POV
Upper:
* Palate
* Alveolar Ridge
Lower:
* Buccal Shelf (mainly)
* Retromolar Pad
Denture:
* Denture Base
Stability
Resistance to horizontal dislodging forces
Stability for Upper and Lower arch and form the Denture POV
Upper/Lower:
* Ridge Height
* Depth of Vestibule
Denture:
* Denture Flange
Retention
Resistance to vertical dislodging forces
Retention for Upper and Lower arch and form the Denture POV
Peripheral Seal
Adhesion
Attraction of Unlike Molecules
saliva to tissues, saliva to denture base
* best seal created by intimate contact of denture base to tissues
Occlusal Prematurities break retention
Cohesion
Clinging of Like Molecules
* Saliva to Saliva
Unfavorable: Thick ropy saliva
Favorable: Thin and water saliva=better retention
Surface Tension
Combo of adhesion and cohesion forces
* maintain film integrity
Water molecules are more attracted to each other than surrounding air
Overextension
Denture Flange is too long
* get sore spot or ulcer after wearing for a while
* Tx: Relieve denture and re-eval in a few weeks
* trim the denture basck where it impinges on tissue
Denture extends too far back (Posterior)
* denture teeth are set so far back-go up onto ramus
* occlusal forces dislodge denture
Underextension
Denture Flange is too short
* No retention
What is the best indicator for success of a denture?
Ridge
* provides all 3: stability, suppport, retention
* Wide braod ridge=Best
Heat Cured Acrylic
PInk Acrylic on Dentures
2 components:
* PMMA=polymer (powder)
* MMA=monomer (liquid)
Liquid component of Heat-Cured Acrylic contains
Methyl Methacrylate (MMA): Monomer
Hydroquinone: Inhibitor
* prevents polymerization of MMA
Glycol dimethacrylate: cross-linking agent
* Increases Rigidity
Dimethyl-p-toluidine: Activator
Powder Component of Heat-cured Acrylic contains:
Polymethyl Methacrylate (PMMA): powder
Benzoyl Peroxide: Initiator
Iron and Cadmium salts or organic dye: Pigment
Denture Processing: Problems
Always shrink
* more shrinkage if excess monomer
* Ideal monomer to polymer ratio: 1:3
Porosity
* due to underpacking with resin at processing or heated to quickly
What are the 2 materials used to make denture teeth?
Acrylic
Porcelain
Acrylic vs Porcelain Denture Teeth
Acrylic:
* Better retention: bond to acrylic resin of denture base (Better Bonding)
Porcelain:
more esthetic
* more stain and wear resistant
Brittle
wear opposing teeth
Mechanical retention
* Anteriors=Pins
* Posteriors=diatorics
What do you need to do if your taking an impression w/a hypermobile ridge?
Large relief in a tray
OR
perforate custom tray
to avoid displacing the ridge
What treatment should be done if a hypermobile ridge is inflamed?
Tx=Tissue Conditioner
* Electrosurgery or laser surgery if not effective
Epulis Fissuratum Treatment
Tissue Conditioner & Adjust Flange
What causes Papillary Hyperplasia?
due to:
* local irritation
* ill-fitting denture
* poor oral hygiene
* leaving dentures in all the time
What is the etiology of Papillary Hyperplasia?
Candidiasis
Papillary Hyperplasia: Treatment
Tx: OHI, leave dentures out at night, soak in 1% bleach and rinse thoroughly
When can you leave retained root tips?
Can be left if:
* intact lamina dura
* no radiolucency
Kennedy Class I
Bilateral Distal Extension
Kennedy Class II
Unilateral Distal Extension
Kennedy Class III
Unilateral Bounded Edentulous Space (BES)
Kennedy Class IV
Bilateral BES (Crosses Midline)
Applegate’s Rules
- Classify after All extractions
- Do not consider Missing 3rd molars
- Consider Abutment 3rd molars
- Do Not Consider Missing 2nd Molars
- Most posterior edentulous area determines classification
- Other edentulous areas=modifications
- extent of modification doesn’ t matter, only number
- Class IV can NOT have any modifications
Major Connector
central component of metal framework
* connects all components
Provides rigidity
Not placed on movable tissue (Only on palate or lingual aspect of alveolar ridge)
Maxillary Major Connectors: Types
Should cross midline at 90 degrees
Types:
* complete palatal plate
* Horseshoe
* Palatal Strap
Complete Palatal Plate
Most Rigid Maxillary Major Connector
When is a complete palatal plate for maxillay major connector indicated?
- all posterior teeth are missing bilaterally (Class 1)
- shallow palatal vault
- periodontally compromised teeth
- small mouth
- flat or flabby alveolar ridges
Horse Shoe major connector
Least Rigid Maxillary Major Connector
When is a horse shoe major connector indicated to use?
Large palatal torus
Palatal Strap
Maxillary Major Connector
* metal strap that goes from L to R
Beading
Only for Maxillary Major Connectors
0.5 mm round groove in the cast at the borders of the major connector
* Adds Strength
* maintains tissue contact=prevent food impaction
Lingual Bar
Mandibular Major Connector
* Lingual vestibule depth >/= 7mm
* simplest
* most common
Lingual Plate
Mandibular Major Connector
Indications
* Lingual vestibule depth < 7 mm
* anticipate more tooth loss
* Lingual Tori
* Bilateral Missing Posterior Teeth(Class 1)
Labial Bar
mandibular Major connector
* aka Swinglock
Indicated when:
* missing canine
* unfavorable soft tissue contour
* questionable perio prognosis
What are the different types of mandibular major connectors?
Lingual Bar
Lingual Plate
Labial Bar (Aka Swinglock)
Minor Connectors
connect major connectors to rests, indirect retainers, and clasps
Rest
Rigid extension of RPD framework
* contacts occlusal, lingual, or incisal surface of abutment tooth
Provides Support
* directs forces down long axis
Rest Seat
Prepped into occlusal, lingual or incisal surface of abutment tooth
* receive and support rest
Occlusal Rest
Spoon Shaped
* rounded, semicircular outline form
1/3 MD width
1/2 intercuspal width (B/L)
1.5 mm depth
Floor inclines apically toward center
* < 90 degrees w/vertical minor connector
Cingulum Rest
Inverted V or U Shape
2.5-3 mm MD Length
2 mm B/L Width (ledge)
1.5 mm Deep
What are the benefits of a cingulum rest?
Distribute occlusal load (good)
esthetics
strength–due to how close they are to major connector (Dont need minor connector)
When are cingulum rests contraindicated?
Mandibular Incisors
Incisal Rests
Rounded notch at incisal angle
* used as indirect retainer
* less favorable leverage than lingual rest
* not esthetic
2.5 mm MD Length
1.5 mm Depth
Proximal Plate
Metal plate that contacts proximal surface of abutment tooth
Guide Planes
path of insertion and removal
1/3 Buccolingual width
extends 2-3 mm down from marginal ridge
Indirect Retainer
Indirect retainer
* perpendicular and anterior to fulcrum line (Axis of rotation)
* fulcrum line=line through most distal rests
* anti-rotation of distal extension area
What does a Direct Retainer consist of?
Aka Clasp Assembly
Consists of:
Rest: Support
Minor Connector: Stability
Clasp Arms
* Retentive Clasp Arm: Retention
* Reciprocal Clasp Arm: Stability
Direct Retainer: Extracoronal Retainer vs Intracoronal Retainer
Extracoronal Retainer:
* more common
* conventional clasp design
* encircles tooth at least 180 degrees
Intracoronal Retainer:
* precision attachment
* key and keyway pattern
* most esthetic bc no clasps
Retentive Clasp
Originates from minor connector & rest
Contacts tooth below HOC/Survey Line
* Retention
Reciprocal Clasp
Aka Stabilizing Clasp
* Stability
Contacts tooth Above HOC/Survey Line
* not torqued by retentive clasp
Suprabulge vs Infrabulge Clasps
Suprabulge: Originate above survey line/HOC
Infrabulge: Orginate below survey line
Circumferential Clasp
Aka Akers Clasp
* Most commonly used
* rest seats adjacent to edentulous space
Ring Clasp
Suprabulge
undercut=adjacent to BES
* molars and MF undercut
Embrassure Clasp
Suprabulge
Rests on both teeth
* so clasps don’t wedge teeth apart
T-Bar
Infrabulge
* T-Bar
* Modified T-Bar (R Bar)
I-Bar
Infrabulge
- needs enough vestibular depth
- No Soft Tissue undercut
RPI
Type of Direct Retainer
* Rest, Proximal Plate, I bar
* M Rest
RPA
Aka RPC
Type of Direct Retainer
* Rest, Proximal Plate, Akers/Circumferential
Clasp Selection: General Rules
* BES vs Distal Extensions
BES:
* use Akers clasps
* rest seats adjacent to edentulous space
Distal Extensions: (order of preference)
1. RPI
2. RPA
3. Wrought Wire
Wrought Wire Indications
Periodontally Compromised tooth
Endo-Treated tooth
More Flexible
seperately positioned and sauntered onto framework
Less torque on teeth
Cobalt Chromium
Framework material
2.3% shrinkage
* causes irregularities & porosity
Cold-working (aka plastic deformation or work hardening)
* manipulate metal at ambient temp
* Main reason why clasps break
What are some examples of suprabulge clasps?
- circumferential (Akers)
- Ring
- Combination
- Embrasure
What are some examples of infrabulge clasps?
- I Bar
- T Bar
- Bar Type
- Y Type
Tooth Prep
Occlusal/Incisal reduction:
* Maintain Cuspal Anatomy
Functional Cusp Bevel:
* Secondary Plane
* maxillary: Lingual
* Mandibular: Buccal
* Posterior teeth Only
Axial Reduction
Margin/Finish Line
Occlusal Table
Traced from cusp tip to cusp tip
What do we do if theres a cavity interfering with this prep?
Remove All Decay
Core Build Up
3 Principles of Tooth Prep
Biologic: Health of Oral tissues
Mechanical: Integrity and durability of restoration
Esthetic: Appearance of restoration
Biologic Principle of tooth prep
Oral Tissues Health:
Mechanical Injury:
* thinnest gingival tissue: L Molars & B Premolars
Thermal Injury: How close to pulp
* use:
* Water spray
* sharp cutting instruments
* intermittent light pressure
Chemical Injury:
* soaked retraction cord
* certain cements
Bacterial Injury:
* leakage under crown
Mechanical Principle of Tooth Prep: Retention Form Vs Resistance Form
Most important principle
Retention Form:
* prevent removal of crown from long axis of tooth prep
* (what holds the crown on, trying to pull off)
Resistance Form:
* prevent removal of crown by apical, horizontal, or oblique forces(occlusal force)
Mechanical Principles of Tooth Prep: Taper
Aka Parallelism
*angle of convergence b/w opposite axial surfaces
* smaller the taper=more retention
* ideal= 6-10 degrees
Most operator control
Mechanical Principles of Tooth Prep: Height, Length, Width,
Height or Length:
* from occlusal/incisal to crown margin
* Incisors/premolars/Canines=3mm minimum
* Molars: 4 mm minimum
Width:
* MD or BL dimension of base
Mechanical Principles of tooth prep: Height to Base Ratio
Height is more important than width
* minimum ratio=0.4
* bigger ratio=taller prep=more tape
* smaller ratio= shorter prep, less retention
If you have a short clinical crown, what mechnical properties would you add to increase retention and resistance?
Buccal Grooves=Retention
Proximal Grooves=Resistance
What is the minimum metal thickness required for a Gold Crown?
Minimum Metal Thickness: (GOLD Crown)
* Margin=0.5 mm
* Non-contact areas=1.0 mm
* Contact areas=1.5 mm
What is the minimum porcelain thickness for an all ceramic crown?
Minimum Porcelain Thickness:
* 1.5 mm
What is the minimum and optimal PFM thickness?
Minimal PFM Thickness= Non-contact areas
* 1.5 mm (1.2 mm porcelain, 0.3 mm metal)
Optimal PFM Thickness= Contact Areas
* 2.0 mm (1.5 mm porcelain, 0.5 mm metal)
Reduction vs clearance
Reduction:
* amount of occlusal tooth structure removed
* Ideal=1.5-2 mm
Clearance:
* amount of space b/w prepped tooth and opposing
* ideal= 1.5-2 mm
Margin Location
Supragingival: Above gingival crest
* promotes periodontal health
* easier to clean
Equigingival:
* at the gingival crest
Subgingival:
* below the gingival crest
* more esthetic=anterior
What are the different types of margins?
Featheredge
Light Chamfer
Heavy Chamfer
Shoulder
Featheredge Margin
- Best marginal seal
Light Chamfer Margin
0.3-0.5 mm wide
Used for:
* Gold Crowns
* wide gold collars of PFM crowns
Heavy Chamfer Margin
1-1.5 mm wide
Used for:
* PFM crowns
* some all ceramic crowns
Lab will onvercontour crown if not given enough room
Shoulder Margin
1.0-1.5 mm wide
* maximizes esthetics-no metal shows
* Aggressive prep:
Used for:
* porcelain of PFM restorations
* All ceramic crowns
3/4 and 7/8 Crowns
Hybrid b/w onlay and full crown
* conserves tooth structure
* Less margin close to gingiva
* Easier to seat during cementation
* normally gold, but rare now
Crown: Occlusal Schemes
Occlusal Point contacts=broad and flat
* prevent wear
Cusp-marginal ridge: seen in
* class 1 occlusion
* unworn teeth
Cusp-fossa:
* class II malocclusion
Hygienic Pontic
Aka Sanitary
* Posterior Mandible
Good Hygiene: 2mm space b/w pontic and ridge
* Requires enough VDO/restorative space
Poor Esthetics: Not recommended for anteriors
Saddle Pontic
Aka Ridge-Lap
* never use
Bad Hygiene
Conical Pontic
Molars
* similar to hygienic but slightly best esthetics
Modified Ridge-Lap Pontic
Anteriors
* Good Esthetics
Ovate Pontic
Anteriors only
* superior/best esthetics
Requires:
* surgery
* good ridge
Bridge: Connector types
Rigid:
* either cast in 1 piece or soldered together
Nonrigid:
* can put together and take apart (puzzle pieces)
* use= No common path of insertion b/w abutments
Bridge: Connectors
connect retainer to pontic
PFM Bridges: 3 mm Height minmum
Tissue Management for impressions
Fluid Control: Saliva & GCF
* cotton rolls, suction
* Antisialogogues (atropine)
Tissue Displacement:
Retraction cords-stretch circumferential periodontal fibers
Impregnated cords: promote hemostasis
* AlCl=Hemodent
* FeSO4: Viscostat
* Epinephrine
Electrosurgery:
* contraindicated: pacemakers or insulin pumps
* electrode can’t contact teeth
What are the 2 categories of impression materials?
Aqueous Hydrocolloids
* water based
* mix powder w/water
Non-aqeuous Elastomers:
* not water based
* do not mix powder w/water
What are the different Aqeous Hydrocolloid Impression Materials?
Agar=Reversive Hydrocolloid
Alginate=Irreversible Hydrocolloid
Reverse Hydrocolloid
Aka Agar
* Aqueous Hydrocolloid
* High accuracy=duplicate casts
Temp changes
* Heat=softer
* Cool=Hardens
Irreversible Hydrocolloid
Aka Alginate
Most Innaccurate
Setting time: 3-4 mins
* Pour w/gypsum within 10 mins
Primary Ingredient: Diatomaceous earth
Active Ingredient: Potassium Alginate
For Irreversible hydrocolloids, how do you increase or decrease setting time?
Decrease setting time
* Hot water
* Less water
Increase Setting time:
* cold water
* more water
Imbibition vs Syneresis
Imbibition: Water Absorption
Syneresis: Water Loss
Avoid Both in Hydrocolloids (Alginate & Agar)
What are the different types of NOn-aqeous elastomers?
Polysulfide rubber
Condensation Silicone
Addition Silicone (PVS)
Polyether
Polysulfide Rubber
Water Byproduct
Moisture tolerant:
* hydrophobic
* Syneresis (most prone to drying out)
30-45 mins to pour up
Condensation Silicone
Alcohol Byproduct
* shrinks impression when evaporated
30 mins to pour
Polyether
Very stable, but easily influenced by water and humidity
* Hydrophilic
* Imbibition (swell up with water(
Very stiff-easy to break teeth on cast
60 mins to pour
Addition Silicone
aka PVS (Polyvinyl Siloxane)
No Byproducts
Best of everything:
* fine detail, elastic recovery, dimensional stability
- inhibited by sulfur in latex gloves and rubber dam
60+ mins to pour
Gypsum
Mined as: calcium-sulfate dihydrate
Manufactured w/heat to get rid of water= Calcium-sulfate hemihydrate)
Type 1-5
Type 1 Gypsum
Impression Plaster
* mount casts on articular
Type 2 Gypsum
Model Plaster
Model for:
* Mouth guards
* essix retainers
Study Models
Type 3 Gypsum
Dental Stone
- Microstone
- Removable prostheses
- Diagnostic casts
Type 4 Gypsum
Dental Stone
* High Strength/Low Porosity
* Low expansion
Best abrasion resistance
Least expansion & Gauging water
fabricate dies
Type 5 Gypsum
Dental Stone
* High Strength
* High Expansion
Fabricate dies
Gauging Water
extra water needed to to get a workable mix f material
does not chemically react with gypsum
Gypsum setting time & Mixing time
20 second vacuum mix or 30 sec hand spatual
Setting time=45-60 mins
Noble Metals
Gold
Platinum
Palladium
SILVER is not
Silver
Not Noble Metal
* causes greening of porcelain
Gold
Noble Metal
Tarnish corrosion resistance
Platinum
Noble Metal
Strength
* increases melting temp
Palladium
Noble Metal
Strength
Metal Alloy
Combine 2+ metals
* greater strength or corrosion resistance
High noble alloys vs Noble Alloys vs Base metal alloys
High Noble Alloys:
* >/= 60% noble–>at least 40%=Gold
Noble Alloys:
* >/= 25% noble
Base metal alloys:
* < 25% noble
Type 1-4 Gold
Type 1: 98-99% Gold (Pure Gold)
* soft
* Class V restorations ONLY
Type 2: 77% gold
* Medium
* onlays
Type 3: 72%
* Hard
* Crowns
Type 4: 69%
* Very hard
*RPD castings
* Post & Core
*Clasps
* Bridges
How to decrease setting time in Gypsum?
HOt water
Less water
Use slurry water
Increased spatula time
Compressive Strength
Resist fracture during compression
Ex: Occlusal forces
Tensile strength
Reesist fracture during pulling
Flexural Strength
Resist fracture during bending
Fracture Toughness
resist crack propagation
What material has the best fracture toughness?
Zirconia
Undergoes fracture toughening
* normal tetragonal particles–>monoclinic particles=resist crack propagation
Modulus Of elasticity
aka Elastic MOdulus
Measures stiffness or rigidity
SLope=Stress/Strain
Steeper the sloper the stiffer the material
Brittle
Fractures easily w/o substantial dimensional changes
ex: Porcelain
What material is brittle?
Porcelain
fractures easily w/o substantial dimensional changes
Ductility
Deforms easily under tensile strength
ex; Wire
What dental material is a good example of Ductility
wire
Malleability
Deforms easily under compressive stress
ex: gold
What dental material is a good example of malleablity
Gold
deforms easily under compressive stress
Percentage Elongation
Can be burnished
* contact stress > Yield strength
* ex: Gold
What material is a good example of percentage elongation?
Gold
Can be burnished
* contact stress > Yield strength
Coefficient of Thermal Expansion
change in size per temp change
* Higher CTE=more tendency to change
Comopsite> MetOl> Tooth> Ceramic
Desirable Mechanical Properties of a dental material
High Yield Strength:
* does not permanently deform
High Elastic MOdulus:
* does not flex
Casting Accuracy:
* gold is more accurate than base meetal
CTE close to tooth (11.4)
Biologic Compatability
Corrosino Resistance
Minimal wear of oopposing dentition
Provisional Crown Fabrication
3 M’s
1. Method:
2. Mold:
3. Material:
Provisional Crown Fabrication: Method
Direct:
* made in patients mouth
Indirect:
* on a cast
* prefabricated
Provisional Crown Fabrication: Mold
Prefabricated Crown: Different materials:
* polycarbonate
* aluminum
* Stainless steel
Cellulose acetate crown form
* transparent plastic material
Putty or shim
Provisional Crown Fabrication: Material
PMMA:
* indirect method
* exothermic
PEMA:
* not common
Bis-Acryl Composite
* Direct method
Provisional Cements
Contain Eugenol:
* inhibits polymerization of resin
REMOVE as much as possible
When making a PFM crown, what must be present for the porcelain to bond to the alloy/metal?
Monomolecular oxidative layer
PFM Crown: Porcealin Layers
IN to Out
Opaque Porcelain:
* masks dark oxide color
* porcelain-metal bond
Body/Dentin Porcelain:
* most of the shade
* builds up most of crown
Insical/Enamel porcelain:
* most translucent layer
PFM Crown: Porcelain-Metal Junction
Anterior teeth: Lingual
* only metal present
* conserve tooth structure
occlusal contacts >/= 1.5 mm away from porcealin-metal junction
PFM Failures
Adhesive Failures (B/w different materials)
Cohesive Failures: (B/w samer materials)
* porcelain-porcelain= VOIDS
* oxide-oxide if oxide layer is TOO THICK
* metal-metal never happens
All Ceramic Crowns: Types
Glass-infiltrated Ceramics
Ceramics w/no glass content
All Ceramic Crowns: Glass-infiltrated ceramics
etched w/hydrofluoric acid
* treated w/silanecoupling agent
* bonded to tooth
All Ceramic Crowns: Ceramics w/No Glass content
Zirconia or alumina
* luted to tooth with cement
Porcelain Veneer Prep
Intra-enamel prep: all in eaneml layer; only facial surface
Gingival 1/3 reduction: 0.3 mm
Facial Reduction: 0.5 mm
Incisal Reduction: 1-2 mm
Incisal edge: Shoulder Butt Joint (90)
Gingival margin: Chamfer
Maryland Bridge
Aka Resin-bonded bridge
* minimal prep
* PFM or porcelain
* bopnd to adjacent teeth
can experience Debonding
Munsell Color System
- Hue
- Chroma
- Value
Hue
Color Family
* red, blue, grreen etc
Chroma
color saturation or intensity
- dull graying blue or more vibrant pure blue
Value
Lightness or darkness
* most important
measured from 0(Black) to 100 (white)
* more towards 100=Light version of color
* More towards 0=Dark version of color
Metamerism
color appears different under different lighting
Fluorescence
Object emits visible light when in UV light
Opalescence
Translucent material
* Reflected light=appears blue
* transmitted light=red/orange
How to select proper shade and color for crowns?
- Chroma=Cervical 1/3 of crown
- Value=middle 1/3 of crown (most important)
- Hue=incisal 1/3 of crown
Characterization of a restoratoin
Reproduce natural defects
* can add more color and make darker but not reverse
Types:
* Staining
* Glazing
Staining vs Glazing
Staining:
* Lose Fluorescence
* Increase Metamerism
* Decreases VALUE=make darker
Glazing:
* surface porcelain fill in defects
Crown Delivery Steps
- Shade (esthetics)=confirm the sahde is what you selected
- Proximal Contacts: Open-send back; Heavy-adjust
- Margins
- Fit
- R&R Form
- Occlusion
- Contour (anatomical)
- Cement
Luting Agents
Aka Cements
6 types:
* Zinc Oxide Eugenol
* Zinc Phosphate
* ZInc Polycarboxylate
* Glass Ionomer
* RMGI
* Resin
Luting Agent: Zinc Oxide Eugenol
Temp cement
* soothes pulp
* Eugenol=inhibits polymerixation of resin
Luting Agent: Zinc Phosphate
Gold Standard
* Phosphoric acid=irritates pulp
* exothermic rxn: mix on child glass slab
Luting Agent: Zinc Polycarboxylate
Calcium Chelation
* minimal pulp irritation
Luting Agent: Glass Ionomer
Adheres to enamel and dentin
* releases Fl
Luting Agent: RMGI
most commmon used today
* Higher strength and lower solubility than GI
Do NOT use with all ceramic crowns
* except zirconia
Resin Cement
Most compressive strength
* bonds to dentin
Light cure, chemical cure or dual cure
* light cure=more color stable than dual cure
What are the possible crowns used today?
Zirconia (Ceramic but no silica (Glass))
Metal: (PFM or Gold)
Lithium Disilicate (aka emax; glass ceramic)
Feldspathic porcelain (Veeners)
What crowns do we use RESIN Cement vs Luting Cement?
Resin Cement: chemical bond dentin-bond-resin-silane-silica
* Lithium dilicate (emax)= dual cure resin cement
* Feldspathic porcelain (veneers)=light-cure resin cement
Luting Cement: (GI or RMGI)
* Zirconia (cermica but no silica/glass)
* Metal (PFM or Gold)
Ditching a die
expose margin of prep
Die spacer
room for cement
Why do long span PFM bridges fail?
Fracture
* due to porcelains low ductility