Prosthodontics: General Flashcards
1
Q
Anatomy of a Bridge
A
- Abutment: the Tooth the bridge attaches to
- Retainer: Crown that attaches to abutment
- Pontic: FAKE TOOTH
- Connector: Connects retainer to pontic
2
Q
Bridge: Poor Prognosis Scenarios
A
- 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)
3
Q
What teeth should not be used an abutment teeth in a bridge?
A
Compromised Endo Teeth
* removed dentin makes them weaker
Compromised Perio Teeth
* crown to root ratio=2:1
4
Q
Bridges: Crown to Root Ratio
A
Ideal: 1:2
Realistic: 2:3
Minimum: 1:1
Poor: 2:1 (not used for abutments)
5
Q
what should be done if replacing a maxillary canine w/a bridge
A
Splint central and lateral together
* prevent lateral drifting of the bridge
6
Q
Ante’s Law
A
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
7
Q
Bridge: Splinting Teeth
A
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
8
Q
Bridge: Ideal Root Shape for abutment teeth
A
Roots:
* Divergent
* Multiple
* curved
* broad Roots
9
Q
Partial Denture Indications
A
Distal Extension
Long Span edentulous space
Bone loss around Potential Abutments
Bridge or implant is too expensive
10
Q
Complete Denture: Indications vs Contraindications
A
Indications
* all teeth are missing
Contraindications in maxillary whenCombination therapy
* Only mandibular anteriors are present
* cause severe damage to premaxilla
11
Q
Overdenture: How many implants recommended for mandible vs maxilla
A
Mandible: 2 implants
Maxilla: 4 implants
12
Q
Cement-Retained Implant: Pros vs Cons
A
Pros
* economical
* minor angle correction
* Easier in small teeth
Cons
* more chair time
* gets loose over time
* excess cement=peri-implantitis
13
Q
Screw-Retained Implant: Pros vs Cons
A
Pros:
* Retrievability: crown removal
* good maintenance
* Access hole: Posteriors=Occlusal; Anteriors: Lingual
Cons:
* Screw loosens during function
14
Q
Alginate
A
Aka Irreversible Hydrocolloid
* 1st choice for diagnostic casts
* Diatomaceous earth adds strength
* Trisodium Phosphate: Controls setting time
More bulk=less unwanted dimensional changes
15
Q
Process of taking impressions with alginate and pouring up for diagnostic casts
A
Process:
remove tray: 2-3 mins
Pour impression within 15 mins
Casts set in 30-60 mins
16
Q
Maxillo-Mandibular Relations (MMR)
A
CR
MI
17
Q
Centric Relation (CR)
A
Condyles
* in the most anterior-superior position
* articulate the thinnest avascular portion of the discs
* against the articular eminences
Independent of teeth
18
Q
Maximum Intercuspation (MI)
A
aka Centric Occlusion (CO)
Complete interdigitation of teeth
* independent of condyle position
19
Q
CR Vs MI
A
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
20
Q
What is the most reliable and reproducible jaw movement?
A
CR
21
Q
Occlusal Harmony
A
Joint, Muscles, and Teeth MUST function in harmony
22
Q
Bimanual Manipulation
A
most accurate method to get in CR
* Goal-Deprogram the jaw
23
Q
What is Objective of a Facebow Record
A
Duplicate the relatinoship b/w
* maxilla –> skull
* mandible –> TMJ ratoational center
On the articulator
24
Q
Facebow Types and describe each
A
Arbitrary Facebow:
* orients maxillary cast–> skull by external auditory meatus
* easier to use
Kinematic Facebow:
* placed on hinge axis of mandible
* more complex
25
Articular parts and corresponding anatomy
Upper Member: Maxilla
Lower Member: Mandible
Hinge Axis=TMJ
26
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
27
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
28
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**
29
Disclusion: Define
Mandible protruded forward
30
Disclusion Types:
Condylar Guidance
Incisal Guidance
Canine Guidance
Anterior Guidance
31
Disclusion: Condylar Guidance
articular eminence slope
* varies among patients
* limits jaw movement
Represented by HCI on articulator
Posterior Determinant of occlusion
32
Disclusion: Incisal Guidance
pin and guide table on articulator
Anterior Determinant of occlusion
33
Disclusion: Canine Guidance
lateral movements, all posteriors disclude
* canines contact on working side only
34
Disclusion: Anterior Guidance
Incisal & Canine Guidance
35
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
36
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
37
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
38
Maxillary Labial Frenum
At or adjacent to midline
39
Maxillary Buccal Frenum
Either Side of Alveolar Ridge
Attach:
* orbicularis oris
* buccinator
40
Maxillary Labial Vestibule
Anterior to the 2 buccal Frena
41
Maxillary Buccal Vestibule
Posterior to buccal frenum to hamular notch
42
Hamular Notch
soft tissue
connects:
* distal end of maxilla
* pterygoid hamulus
43
Vibrating Line
Pt says AHH=Location
* from hamular notch to hamular notch
* 2mm away from fovea palatini
44
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
45
Posterior Palatal Seal
part of denture that compresses soft tissue of palate=suction
Anterior Boundary=Butterfly Line
Posterior Boundary=Vibrating Line
46
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
47
Pterygomandibular Raphe
Pt opens wide to capture on posterior part of impression
Connect:
* buccinator m.
* superior pharyngeal constrictor
48
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
49
Mandibular Labial Freenum
Attach:
* orbicularis oris
50
Mandibular Buccal Freenum
Attaches:
Orbicularis oris
Buccinator
51
Lingual Freenum
Mandible
Attaches:
Genoglossus
52
Mandibular Labial Vestibule
Anterior to buccal frena
Mentalis Muscle (Chin)=inferior border
53
Mandibular Buccal Vestibule
Posterior to buccal frena
Buccinator m=inferior border
54
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
55
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
56
Alveolingual Sulcus
B/w mandibular alveolar ridge and tongue
2 S's (Vertical S & horizontal S)
3 Regions:
Anterior Region
Middle Region
Posterior Region
57
Buccal Shelf
Main Support for Denture
* Perpendicular to occlusal forces
* lateral to posterior alveolar ridge
Attaches: Buccinator
58
Alveolingual Sulcus: Anterior Region
lingual freenum to premylohyoid fossa
* First curve in the S
* Sublingual gland sits above mylohyoid muscle
* Want shorter flange
59
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
60
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
61
Frenectomy
Complete removal of Freenum
High Freenum Attachment
* neart top of alveolar ridge
Most to least common:
**Labial>Buccal>Lingual**
62
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
63
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
64
Epulis Fissuratum
Hyperplastic tissue reaction
* **due to ill fitting denture or overextended flange**
65
Fibrous Tuberosity
aka Pendulous Tuberosity
**Large Tuberosities** touch retromolar pads
* limits interarch space
Tx: Surgical excision
66
Papillary Hyperplasia
Multiple papillary projections on palate
* Etiology: **Candidiasis**
67
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
68
Retained Root Tips
Residual RT (Non-RCT)-infection risk
Can be left if:
* intact lamina dura
* no radiolucency
69
Paget's Disease
Etiology: Unknown
**Dentures not fitting**
* need to remake periodically
70
Alveoplasty
Surgical reshaping of alveolar bone
* sharp, spiny, or irregular ridges
71
Tori removal indications
Creates an undercut (lingual torus)
interferes w/posterior palatal seal (palatal torus)
72
Bone Augmentation
**Horizontal>Vertical**
* easier to restore horizontal ridge width vs height
73
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
74
VDO
Vertical Dimension of Occlusion
Distance b/w nose and chin when biting together
* =superior-inferior relationship b/w maxilla and mandible in MI
75
Interocclusal Space
VDR=VDO+ 3mm
the difference b/w VDR and VDO
* ideally 2-4 mm
76
Excessive VDO
* **Fatigue of Muscles of Mastication**
* Lips appear strained
* Gagging
77
Insufficient VDO
**Aged appearance-lower 1/3 of face
**Angular Cheilitis**
78
Christensen's Phenomenon
Distal space b/w maxillary and mandibular occlusal surfaces when mandible is protruded
* posterior open bite
79
Camper's Line
imaginary line from ala of nose to tragus of ear
80
Interpupillary Oline
imaginary line b/w pupils of eyes
81
Complete Denture: Plane of Occlusion
Maxillary wax rim parallel to:
* Camper's line
* Interpupillary line
82
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
83
Complete Denture: Lingualized Occlusion
Only maxillary posterior lingual cusps contact mandibujlar posterior teeth
* prevent dislodgement
84
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
85
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
86
Curve of Spee
AP Curve
* load on long axis of each tooth
More mesial tilted as you move distal
87
Curve of Wilson
Mediolateral Curve-- along posterior cusp tips
* Load on long axis of each tooth
More lingual tilt as you move distally
88
Support
Resistance to Vertical Seating Forces
89
Support for Upper and Lower arch and form the Denture POV
Upper:
* Palate
* Alveolar Ridge
Lower:
* Buccal Shelf (mainly)
* Retromolar Pad
Denture:
* Denture Base
90
Stability
Resistance to horizontal dislodging forces
91
Stability for Upper and Lower arch and form the Denture POV
Upper/Lower:
* Ridge Height
* Depth of Vestibule
Denture:
* Denture Flange
92
Retention
Resistance to vertical dislodging forces
93
Retention for Upper and Lower arch and form the Denture POV
Peripheral Seal
94
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
95
Cohesion
Clinging of Like Molecules
* Saliva to Saliva
Unfavorable: Thick ropy saliva
Favorable: Thin and water saliva=better retention
96
Surface Tension
Combo of adhesion and cohesion forces
* maintain film integrity
Water molecules are more attracted to each other than surrounding air
97
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**
98
Underextension
Denture Flange is too short
* No retention
99
What is the best indicator for success of a denture?
Ridge
* provides all 3: stability, suppport, retention
* Wide braod ridge=Best
100
Heat Cured Acrylic
PInk Acrylic on Dentures
2 components:
* PMMA=polymer (powder)
* MMA=monomer (liquid)
101
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
102
Powder Component of Heat-cured Acrylic contains:
Polymethyl Methacrylate (PMMA): powder
Benzoyl Peroxide: Initiator
Iron and Cadmium salts or organic dye: Pigment
103
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
104
What are the 2 materials used to make denture teeth?
Acrylic
Porcelain
105
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**
106
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
107
What treatment should be done if a hypermobile ridge is inflamed?
Tx=Tissue Conditioner
* Electrosurgery or laser surgery if not effective
108
Epulis Fissuratum Treatment
Tissue Conditioner & Adjust Flange
109
What causes Papillary Hyperplasia?
due to:
* local irritation
* ill-fitting denture
* poor oral hygiene
* leaving dentures in all the time
110
What is the etiology of Papillary Hyperplasia?
Candidiasis
111
Papillary Hyperplasia: Treatment
Tx: OHI, leave dentures out at night, soak in 1% bleach and rinse thoroughly
112
When can you leave retained root tips?
Can be left if:
* intact lamina dura
* no radiolucency
113
Kennedy Class I
Bilateral Distal Extension
114
Kennedy Class II
Unilateral Distal Extension
115
Kennedy Class III
Unilateral Bounded Edentulous Space (BES)
116
Kennedy Class IV
Bilateral BES (Crosses Midline)
117
Applegate's Rules
1. Classify after All extractions
2. Do not consider Missing 3rd molars
3. Consider Abutment 3rd molars
4. Do Not Consider Missing 2nd Molars
5. **Most posterior edentulous area** determines classification
6. Other edentulous areas=**modifications**
7. extent of modification doesn' t matter, only number
8. Class IV can NOT have any modifications
118
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)
119
Maxillary Major Connectors: Types
Should cross midline at 90 degrees
Types:
* complete palatal plate
* Horseshoe
* Palatal Strap
120
Complete Palatal Plate
**Most Rigid** Maxillary Major Connector
121
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
122
Horse Shoe major connector
Least Rigid Maxillary Major Connector
123
When is a horse shoe major connector indicated to use?
Large palatal torus
124
Palatal Strap
Maxillary Major Connector
* metal strap that goes from L to R
125
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
126
Lingual Bar
Mandibular Major Connector
* Lingual vestibule depth >/= 7mm
* simplest
* most common
127
Lingual Plate
Mandibular Major Connector
Indications
* Lingual vestibule depth < 7 mm
* anticipate more tooth loss
* Lingual Tori
* Bilateral Missing Posterior Teeth(Class 1)
128
Labial Bar
mandibular Major connector
* aka Swinglock
Indicated when:
* missing canine
* unfavorable soft tissue contour
* questionable perio prognosis
129
What are the different types of mandibular major connectors?
Lingual Bar
Lingual Plate
Labial Bar (Aka Swinglock)
130
Minor Connectors
connect major connectors to rests, indirect retainers, and clasps
131
Rest
Rigid extension of RPD framework
* contacts occlusal, lingual, or incisal surface of abutment tooth
Provides **Support**
* directs forces down long axis
132
Rest Seat
Prepped into occlusal, lingual or incisal surface of abutment tooth
* receive and support rest
133
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
134
Cingulum Rest
Inverted V or U Shape
2.5-3 mm MD Length
2 mm B/L Width (ledge)
1.5 mm Deep
135
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)
136
When are cingulum rests contraindicated?
Mandibular Incisors
137
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
138
Proximal Plate
Metal plate that contacts proximal surface of abutment tooth
139
Guide Planes
path of insertion and removal
1/3 Buccolingual width
extends **2-3 mm** down from marginal ridge
140
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
141
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
142
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
143
Retentive Clasp
Originates from minor connector & rest
Contacts tooth **below** HOC/Survey Line
* Retention
144
Reciprocal Clasp
Aka Stabilizing Clasp
* Stability
Contacts tooth **Above** HOC/Survey Line
* not torqued by retentive clasp
145
Suprabulge vs Infrabulge Clasps
Suprabulge: Originate above survey line/HOC
Infrabulge: Orginate below survey line
146
Circumferential Clasp
Aka Akers Clasp
* Most commonly used
* rest seats adjacent to edentulous space
147
Ring Clasp
Suprabulge
undercut=adjacent to BES
* molars and MF undercut
148
Embrassure Clasp
Suprabulge
Rests on both teeth
* so clasps don't wedge teeth apart
149
T-Bar
Infrabulge
* T-Bar
* Modified T-Bar (R Bar)
150
I-Bar
Infrabulge
* needs enough vestibular depth
* No Soft Tissue undercut
151
RPI
Type of Direct Retainer
* Rest, Proximal Plate, I bar
* M Rest
152
RPA
Aka RPC
Type of Direct Retainer
* Rest, Proximal Plate, Akers/Circumferential
153
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
154
Wrought Wire Indications
Periodontally Compromised tooth
Endo-Treated tooth
More Flexible
seperately positioned and sauntered onto framework
Less torque on teeth
155
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**
156
What are some examples of suprabulge clasps?
* circumferential (Akers)
* Ring
* Combination
* Embrasure
157
What are some examples of infrabulge clasps?
* I Bar
* T Bar
* Bar Type
* Y Type
158
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
159
Occlusal Table
Traced from cusp tip to cusp tip
160
What do we do if theres a cavity interfering with this prep?
Remove All Decay
Core Build Up
161
3 Principles of Tooth Prep
Biologic: Health of Oral tissues
Mechanical: Integrity and durability of restoration
Esthetic: Appearance of restoration
162
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
163
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)
164
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
165
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
166
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
167
If you have a short clinical crown, what mechnical properties would you add to increase retention and resistance?
Buccal Grooves=Retention
Proximal Grooves=Resistance
168
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
169
What is the minimum porcelain thickness for an all ceramic crown?
Minimum Porcelain Thickness:
* 1.5 mm
170
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)
171
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
172
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
173
What are the different types of margins?
Featheredge
Light Chamfer
Heavy Chamfer
Shoulder
174
Featheredge Margin
* **Best marginal seal**
175
Light Chamfer Margin
0.3-0.5 mm wide
Used for:
* **Gold Crowns**
* wide gold collars of PFM crowns
176
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
177
Shoulder Margin
1.0-1.5 mm wide
* maximizes esthetics-no metal shows
* Aggressive prep:
Used for:
* porcelain of PFM restorations
* **All ceramic crowns**
178
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
179
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
180
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
181
Saddle Pontic
Aka Ridge-Lap
* never use
Bad Hygiene
182
Conical Pontic
Molars
* similar to hygienic but slightly best esthetics
183
Modified Ridge-Lap Pontic
Anteriors
* Good Esthetics
184
Ovate Pontic
Anteriors only
* superior/best esthetics
Requires:
* surgery
* good ridge
185
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
186
Bridge: Connectors
connect retainer to pontic
PFM Bridges: 3 mm Height minmum
187
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
188
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
189
What are the different Aqeous Hydrocolloid Impression Materials?
Agar=Reversive Hydrocolloid
Alginate=Irreversible Hydrocolloid
190
Reverse Hydrocolloid
Aka Agar
* Aqueous Hydrocolloid
* High accuracy=duplicate casts
Temp changes
* Heat=softer
* Cool=Hardens
191
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
192
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
193
Imbibition vs Syneresis
Imbibition: Water Absorption
Syneresis: Water Loss
Avoid Both in Hydrocolloids (Alginate & Agar)
194
What are the different types of NOn-aqeous elastomers?
Polysulfide rubber
Condensation Silicone
Addition Silicone (PVS)
Polyether
195
Polysulfide Rubber
**Water Byproduct**
Moisture tolerant:
* hydrophobic
* Syneresis (most prone to drying out)
30-45 mins to pour up
196
Condensation Silicone
**Alcohol Byproduct**
* shrinks impression when evaporated
30 mins to pour
197
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
198
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
199
Gypsum
Mined as: **calcium-sulfate dihydrate**
Manufactured w/heat to get rid of water= **Calcium-sulfate hemihydrate)**
Type 1-5
200
Type 1 Gypsum
Impression Plaster
* mount casts on articular
201
Type 2 Gypsum
Model Plaster
Model for:
* Mouth guards
* essix retainers
Study Models
202
Type 3 Gypsum
Dental Stone
* Microstone
* Removable prostheses
* Diagnostic casts
203
Type 4 Gypsum
Dental Stone
* High Strength/Low Porosity
* Low expansion
Best abrasion resistance
Least expansion & Gauging water
fabricate dies
204
Type 5 Gypsum
Dental Stone
* High Strength
* High Expansion
Fabricate dies
205
Gauging Water
extra water needed to to get a workable mix f material
does not chemically react with gypsum
206
Gypsum setting time & Mixing time
20 second vacuum mix or 30 sec hand spatual
Setting time=45-60 mins
207
Noble Metals
Gold
Platinum
Palladium
SILVER is not
208
Silver
Not Noble Metal
* causes greening of porcelain
209
Gold
Noble Metal
Tarnish corrosion resistance
210
Platinum
Noble Metal
Strength
* increases melting temp
211
Palladium
Noble Metal
Strength
212
Metal Alloy
Combine 2+ metals
* greater strength or corrosion resistance
213
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
214
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
215
How to decrease setting time in Gypsum?
HOt water
Less water
Use slurry water
Increased spatula time
216
Compressive Strength
Resist fracture during compression
Ex: Occlusal forces
217
Tensile strength
Reesist fracture during pulling
218
Flexural Strength
Resist fracture during bending
219
Fracture Toughness
resist crack propagation
220
What material has the best fracture toughness?
**Zirconia**
Undergoes **fracture toughening**
* normal tetragonal particles-->monoclinic particles=resist crack propagation
221
Modulus Of elasticity
aka Elastic MOdulus
Measures stiffness or rigidity
SLope=Stress/Strain
**Steeper the sloper the stiffer the material**
222
Brittle
Fractures easily w/o substantial dimensional changes
ex: Porcelain
223
What material is brittle?
Porcelain
fractures easily w/o substantial dimensional changes
224
Ductility
Deforms easily under tensile strength
ex; Wire
225
What dental material is a good example of Ductility
wire
226
Malleability
Deforms easily under compressive stress
ex: gold
227
What dental material is a good example of malleablity
Gold
deforms easily under compressive stress
228
Percentage Elongation
Can be burnished
* contact stress > Yield strength
* ex: Gold
229
What material is a good example of percentage elongation?
Gold
Can be burnished
* contact stress > Yield strength
230
Coefficient of Thermal Expansion
change in size per temp change
* Higher CTE=more tendency to change
**C**omopsite> Met**O**l> **T**ooth> C**e**ramic
231
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
232
Provisional Crown Fabrication
3 M's
1. Method:
2. Mold:
3. Material:
233
Provisional Crown Fabrication: Method
Direct:
* made **in patients mouth**
Indirect:
* **on a cast**
* prefabricated
234
Provisional Crown Fabrication: Mold
Prefabricated Crown: Different materials:
* polycarbonate
* aluminum
* Stainless steel
Cellulose acetate crown form
* transparent plastic material
Putty or shim
235
Provisional Crown Fabrication: Material
PMMA:
* indirect method
* exothermic
PEMA:
* not common
Bis-Acryl Composite
* Direct method
236
Provisional Cements
Contain Eugenol:
* inhibits polymerization of resin
REMOVE as much as possible
237
When making a PFM crown, what must be present for the porcelain to bond to the alloy/metal?
Monomolecular oxidative layer
238
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
239
PFM Crown: Porcelain-Metal Junction
Anterior teeth: Lingual
* only metal present
* conserve tooth structure
**occlusal contacts >/= 1.5 mm away from porcealin-metal junction**
240
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
241
All Ceramic Crowns: Types
Glass-infiltrated Ceramics
Ceramics w/no glass content
242
All Ceramic Crowns: Glass-infiltrated ceramics
etched w/**hydrofluoric acid**
* treated w/**silane**coupling agent
* bonded to tooth
243
All Ceramic Crowns: Ceramics w/No Glass content
Zirconia or alumina
* luted to tooth with cement
244
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
245
Maryland Bridge
Aka Resin-bonded bridge
* minimal prep
* PFM or porcelain
* bopnd to adjacent teeth
can experience **Debonding**
246
Munsell Color System
* **Hue**
* **Chroma**
* **Value**
247
Hue
Color Family
* red, blue, grreen etc
248
Chroma
color saturation or intensity
* dull graying blue or more vibrant pure blue
249
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
250
Metamerism
color appears different under different lighting
251
Fluorescence
Object emits visible light when in UV light
252
Opalescence
Translucent material
* Reflected light=appears blue
* transmitted light=red/orange
253
How to select proper shade and color for crowns?
1. Chroma=Cervical 1/3 of crown
2. Value=middle 1/3 of crown (most important)
3. Hue=incisal 1/3 of crown
254
Characterization of a restoratoin
Reproduce natural defects
* can add more color and make darker but not reverse
Types:
* Staining
* Glazing
255
Staining vs Glazing
Staining:
* Lose Fluorescence
* Increase Metamerism
* **Decreases VALUE**=make darker
Glazing:
* surface porcelain fill in defects
256
Crown Delivery Steps
1. **Shade (esthetics)**=confirm the sahde is what you selected
2. Proximal Contacts: Open-send back; Heavy-adjust
3. Margins
4. Fit
5. R&R Form
6. Occlusion
7. Contour (anatomical)
8. Cement
257
Luting Agents
Aka Cements
6 types:
* Zinc Oxide Eugenol
* Zinc Phosphate
* ZInc Polycarboxylate
* Glass Ionomer
* RMGI
* Resin
258
Luting Agent: Zinc Oxide Eugenol
Temp cement
* soothes pulp
* Eugenol=inhibits polymerixation of resin
259
Luting Agent: Zinc Phosphate
Gold Standard
* Phosphoric acid=**irritates pulp**
* exothermic rxn: mix on child glass slab
260
Luting Agent: Zinc Polycarboxylate
Calcium Chelation
* minimal pulp irritation
261
Luting Agent: Glass Ionomer
Adheres to enamel and dentin
* **releases Fl**
262
Luting Agent: RMGI
most commmon used today
* Higher strength and lower solubility than GI
Do NOT use with all ceramic crowns
* except zirconia
263
Resin Cement
Most compressive strength
* bonds to dentin
Light cure, chemical cure or dual cure
* **light cure=more color stable than dual cure**
264
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)
265
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)
266
Ditching a die
expose margin of prep
267
Die spacer
room for cement
268
Why do long span PFM bridges fail?
Fracture
* due to porcelains low ductility
