Based on Exam 1 Review Doc Flashcards
(159 cards)
1
Q
Why should you place composite incrementally vs bulk filling?
A
-Incrementally placing composite minimizes stresses placed on the material and on the tooth due to polymerization shrinkage (this may be a factor in postoperative sensitivity)
-Resin is bonded to LESS walls → relieves stress in the resin-adhesive surface
incrementally placed has a lower C factor
2
Q
Basic components of Tofflemire matrix system
A
- Retainer: slot faces gingiva
placed on BUCCAL side
band comes out of SIDE channel
slit down so it is easier to remove - Matrix band: burnish adjacent tooth IN CONTACT AREA
- Wooden wedges: wedge properly- through the more open of the embrasures (typically the lingual)
3
Q
Basic components of sectional matrix system (Palodent)
A
- Use provided tweezers to place wedge
- place sectional matrix band using provided tweezers
- place ring on top of wedge
can use on MOD
4
Q
What are the advantages to using a rubber dam?
A
- better visualization
- better access
- prep walls dry and clean
- materials work better
- improved properties- direct contacts of varnish/liner/base with cavity walls
- moisture affects bond as well as materials ability to set up
- prevents injury to patient soft tissues
- prevents aspiration and swallowing of debris
- fewer aerosols
-shiny part of rubber dam on tongue side, matte side faces operator
5
Q
Basic order of operations for preparing Class II
A
- establish initial outline form and depth
- extend proximal box
- once ideal outline form is achieved, remove caries (spoon excavator or round bur on slow speed handpiece)
- refine prep (with steps below)
- plane axiopulpal line angle (reduces stress)
- plane gingival margin (removes loose enamel rods)
- bevel gingival margin (ONLY with ideal preps)
*do not place gingival bevel on dentin or cementum
6
Q
Basic order of operations for composite restoration
A
- place matrix
- etch, bond
- begin by placing material in box
- place composite incrementally
- cure each increment for 20 seconds
- form final anatomy BEFORE final cure
- finishing carbides for minor adjustments after curing
- polishing
7
Q
Basic order of operations for amalgam restoration
A
- Tofflemire matrix in place
- fill box first, then occlusal
- begin carving
- marginal ridge- use explorer
- try a pre-carve burnish to remind you of your outline
- begin with HOLLENBACK carver to recreate anatomy (before set)
- remove band (from side)
- carve interproximal before sets up fully
- refine anatomy
- smooth restoration with wet cotton pellet
- dull, matte finish
8
Q
Why bevel?
A
to reduce microleakage at cervical and ascending walls in class II preps
9
Q
Where should you bevel in Class IIs?
A
Bevel gingival floor of prep
only if on enamel
10
Q
When to bevel?
A
-NECESSARY when in enamel
-DO NOT bevel in deep preps (So little enamel remains that a bevel would remove it all OR Gingival floor is on cementum or dentin)
11
Q
How to bevel?
A
Enamel prepared with a bur (beveled) etches better; exposes ends of enamel rods; reveals prismatic enamel
12
Q
What walls in a class II are a flare recommended?
A
slight flare occlusal of prep
13
Q
Type I enamel etching
A
- “honeycomb”; from dissolution of prism (enamel rod) CORES
- found in occlusal and middle thirds of teeth
- best bonds achieved to type I (and II)
14
Q
Type II enamel etching
A
- “cobblestone”; from dissolution of prism (enamel rod) PERIPHERIES
- found in occlusal and middle thirds of teeth
- best bonds achieved to type II (and I)
15
Q
Type III enamel etching
A
- combination of I and II
- not stuck very deep
16
Q
Type IV enamel etching
A
- “pitted”
- not stuck very deep
17
Q
Type V enamel etching
A
- “aprismatic”
- flat and smooth
- not stuck very deep
18
Q
Acid etching enamel
A
- Chemical “drilling”
- Removes about 10 microns enamel
- Place for 15 seconds prior to rinsing
- Creates porous layer 5-50 microns deep
- RINSE with water 10 seconds after etching
- To remove acid and leave enamel surface clean for bonding
- 25mL minimum water is necessary
- Visualize a FROSTY surface after gentle air dry
19
Q
Which acid is used to etch enamel?
A
30-40% phosphoric acid
20
Q
What are the other types of acid used to etch different materials?
A
Nitric –> metal
Hydrofluoric –> feldspathic porcelain
21
Q
What is the purpose of etching?
A
- Etching transforms smooth enamel into an IRREGULAR surface
- Etching increases wettability and surface area of the enamel
- Etching raises the surface free energy to EXCEED the surface tension of bonding material
22
Q
What is surface wetting?
A
the ability of a liquid to maintain intermolecular contact with a solid surface
23
Q
What type of bond are we trying to achieve with etch/bond?
A
MICROMECHANICAL BOND
24
Q
What is etchant?
A
interacts with superficial dentin and there is no pulpal damage
25
After etching, what does bond agent resin do?
- low viscosity
- flows into mircoporosities
- polymerizes to MICROMECHANICAL BOND
26
What does resin interlock with in enamel?
enamel rods
27
What does resin interlock with in dentin?
dentin collagen
28
What are the types of bonding systems?
- Etch-and-Rinse (FKA Total etch)
- Self-etch
29
What are the basic elements of the Etch-and-Rinse (FKA Total etch) system?
- Etch separately
- Prime (3-step)
- Bond (3-step)
- or Prime + Bond combined (2-step)
30
What are the advantages to Etch-and-Rinse system?
- More predictable, stronger bond
- Enamel adequately prepared
31
What are the disadvantages to Etch-and-Rinse system?
- Collagen collapse is possible (result of user error)
- Etched zone is often deeper than hybrid layer (exposed demineralized, collagen fibrils; post-operative sensitivity)
- Too many steps (more chances for operator error)
32
What are the basic elements of the self-etch system?
- No phosphoric acid-etch step
- Acid part of the primer or primer/bond agent (acidic primer partially dissolves smear layer, allows penetration of bond resin)
33
What are the types of self-etch systems?
- 2 step: acidic primer & bonding agent
- 1-step: most variable/least predictable (acidic primer and bond resin, one solution)
34
What are the advantages of the self-etch system?
- No separate etch: overdried, collapsed demineralized collagen not a problem
- Etched zone and hybrid layer comparable width; however, some exposed collagen
- Low postoperative sensitivity
- Time efficiency
35
What are the disadvantages of the self-etch system?
- Not compatible with self-cure, dual-cure composite (acidic monomers, low pH, “kills” the basic amine activator)
- Will not etch unprepared enamel
- Self-etch primer systems have long-term bond strength?
- Self-etch adhesives (all-in-one) have lower bond strength, long-term breakdown (collagen degradation over time)
- Insufficient penetration of smear layer
36
What effects longevity in bonds?
- Bond to dentin collagen is influenced by Matrix metalloproteinases (MMPs)
- MMPs are present on collagen fibrils and can be seen at 100,000X on SEM
- Chlorhexidine inhibits MMP activation --> leading to longer lasting bonds
37
What are MMPs?
collagen enzymes that metabolize unhybridized collagen
38
What is Consepsis?
2% Chlorhexidine Antibacterial solution applied after etching ---> leads to longer lasting bonds
39
What are the clinical success requirements of bonding?
- Knowledge of substrate
- Good cavity preparation and margins
- Rubber dam and matrix/wedge
- Correct use of the bonding agent (follow directions; Wet/Moist bonding, total etch, self-etch)
- Bond agent compatible with resin composite
40
What are the bond system components?
- Etchant (Phosphoric acid gel (30-40%))
- Primer
- Adhesive Bonding Resin/Agent
- Filler (Mostly unfilled resins, some 0.5-40% by weight)
41
What does the primer do in bonding systems?
- HYDROPHILIC (draws the bond agent in) monomers in HEMA solvent
- Acetone, ethanol/water, water
42
What does the adhesive bonding resin/agent do in bonding system?
- HYDROPHOBIC dimethacrylate monomers (BisGMA)
- Initiators and Activators (Camphorquinone in light activated systems
Benzoyl Peroxide (BPO) tertiary amine in chemical and dual cure systems)
43
When can Universal adhesives be used?
Can be used in total etch, self-etch or selective-etch mode (etch enamel only with phosphoric acid)
44
What adhesive do we use at UMKC?
Universal adhesive
45
What is the chemistry game changer of universal adhesives?
10-MDP
Mechanism of action: a monomer that chemically interacts via ionic bonding to calcium in hydroxyapatite
46
Would you ever directly etch the pulp?
NO
47
What is dentin adhesive?
- Well tolerated by dentin
- Do NOT want to apply it directly to the pulp
- Adverse pulp reaction comes primarily from bacteria remaining in or penetrating the preparation
48
What location for adhesive is predictable and strong?
Incisal ⅓ and middle ⅓ enamel
49
What is makes cervical enamel less favorable for adhesive?
- Shorter and fewer enamel tags (compared to middle ⅓ and incisal ⅓)
- Less prism delineation (due to presence of prismless enamel)
- Bad news: this is where deep class II preps usually end
50
What is the Makeup of enamel?
95-98% inorganic matter by weight
90-92% hydroxyapatite by volume
1-2% organic matter by weight
4% water weight
51
What is the bond strength to perpendicular enamel (ENDS of rods)?
25MPa
52
What is the bond strength to parallel enamel (SIDES of rods)?
7-10MPa
53
Examples of perpendicular oriented enamel
- Cavosurface margins of class I preps
- Bevels of class II preps
- ENDS of enamel rods
54
Examples of parallel enamel
- Internal walls of occlusal preps
- Gingival floor of box of class II preps (see beveling)
- SIDES of enamel rods
55
Summary of enamel bonding
- Etch surface
- Resin tags interlock (macro and micro tags into surface irregularities)
- Micromechanical bonding
- Enamel-adhesive-composite bond
56
What is the makeup
of dentin?
55% mineral by volume
30% collagen
15% water
57
Basic dentin anatomy
- Tubules (fluid filled)
- Peritubular dentin (very INorganic)
- Intertubular dentin (very ORGANIC, collagen rich, where you want to bond)
58
What is the top arrow pointing to?
peritubular dentin
59
What is the bottom arrow pointing to?
intertubular dentin
60
How does the diameter of the dentin tubules change as they get closer to the pulp?
larger
- 0.5 micrometers near DEJ
- 2.5 micrometers near pulp
61
How does the distribution of the dentin tubules change as they get closer to the pulp?
more near pulp
- 20,000/mm2 near DEJ
- 45,000/mm2 near pulp
62
How does deeper dentin differ from less deep dentin?
- more & wider tubules (=more fluid)
- less tubular dentin
63
What is the basic dentin bonding mechanism?
- Acid-etched, demineralized collagen fibrils (2-5 micrometers deep)
- Water supports collagen network
- Dentin bond agent applied, polymerized
64
What factors can affect bonding to dentin?
- Cavity depth (better bond strength in superficial dentin)
- Caries (lower bond strength in carious dentin)
- Moist vs Dry dentin (Moist is better!; Overwet resin does not penetrate well --> decreased bond strength)
- Collagen fibers collapse in dry dentin (resin cannot penetrate; poor hybrid layer; decreased bond strength)
65
What can you do to improve bond to dentin?
- Use extreme caution when using air/water syringe to dry dentin
- Use rubber dam
66
What is the smear layer?
Mixture of tooth debris, often contaminated with saliva, blood cells, and bacteria
- DO NOT bond to smear layer
- removed with acid etch
67
What is the hybrid layer?
- Intermingled layer of collagen and resin
- What we WANT to form when bonding to dentin
- Forms upon light curing, the unfilled resin sets within the collagen fibril network
68
What should you avoid when forming the hybrid layer?
- Avoid OVERetching
- Avoid OVERdrying
- Avoid UNDERdrying
69
What are methods to ensure you restore a patient’s occlusion properly?
- evaluate occlusion BEFORE preparing and then try to recreate that
- visually evaluate CONTRALATERAL side
- check occlusion again with patient sitting up
- Use articulating paper
- Evaluate in MIP
- Evaluate in excursions, protrusives
70
What are potential outcomes if occlusion is not considered when placing a restoration?
- Pain on biting
- Fractured cusp
- Fractured restoration
- Premature wear on tooth
- Trauma to periodontal ligament
- Trauma to temporomandibular joint
- Angry patient
- Frustrated dentist
71
Challenges in trying to restore occlusion?
- Many patients do not have ideal occlusion
- Patient often numb when asked to bite down and feel restoration
- Fatigue
72
What is occlusion?
the way the maxillary teeth contact the mandibular teeth
- or vice versa
- static
73
What is articulation?
the static dynamic relationship b/w occlusal surfaces during function
74
Ideal occlusion =
teeth occlude with each other along their LONG AXES
75
Nonfunctional cusps:
- Buccal on maxillary
- Lingual on mandibular
76
Functional cusps:
- Lingual on maxillary
- Buccal on mandibular
77
What is Cusp-Fossa occlusion?
- Each functional cusp occludes in fossa of opposing tooth
- One to One tooth arrangement
78
What is Cusp-Marginal Ridge occlusion?
- Each functional cusp contacts the MR or fossa of the opposing pair of teeth
- One to Two teeth arrangement
- Most natural dentitions
79
How are maxillary teeth inclined?
facially
80
How are mandibular teeth inlcined?
lingually
81
What are the components of dental composite resins?
- Silane coupling agent
- Resin matrix (organic phase)
- Fillers (inorganic phase)
- Activators & Initiators
82
What does the silane coupling agent do?
- Interfacial bridge
- Strongly binds the filler to the resin matrix
83
What are the benefits of the silane coupling agent?
- Better stress distribution b/w resin matrix and filler particles
- Improves the mechanical properties
- Decreased water sorption along filler-resin interface
84
What does the resin matrix do?
*organic phase*
- 2 reactive ends to allow cross-linking
85
What are the benefits of fillers?
*inorganic phase*
- Reinforcement of resin matrix (increase the mechanical and physical properties)
- DECREASED polymerization shrinkage (proportional to the filler volume)
- DECREASED thermal expansion and contraction (higher filler amount reduces the thermal expansion and contraction coefficients )
- Viscosity control (improved workability, handling)
- DECREASED water sorption
- INCREASED radiopacity (Barium, Strontium, Zirconium)
86
What is the chemical or self-cure activator?
tertiary amine
87
What is the chemical or self-cure initiator?
Benzoyl peroxide
88
What is the light-cured activator?
blue light (465nm)
89
What is the light-cured initiator?
Camphoquorine
90
What are the characteristics of bulk fill?
- Developed to enable restoration in single increment built up to 4-5mm
- Increased depth of cure (polymerization)
- Reduced polymerization shrinkage stress
- Improved adaptation to the surface of the cavity
- Simplified placement technique compared to regular composites
91
How does bulk fill relieve shrinkage stress?
- Altered filler particles (low elastic modulus)
- Presence of stress-relieving monomer
92
How does bulk fill increase the depth of cure?
- Reduced filler amount
- Increased filler particle size
- Alternative photoinitiators
93
How does bulk fill improve adaptation to the surface cavity?
- Rheology modifiers (some manufacturer’s)
94
What is sonic activated bulk fill?
- Rheology modifiers react to the sonic energy applied during placement
95
What is phase 1 of sonic activated bulk fill?
Sonic application: to reduce viscosity = increase flowability to all cavity surfaces
96
What is phase 2 of sonic activated bulk fill?
Sonic energy removed: the composite reverts to viscous, pliable state ideal for contouring and polishing
97
What is the basic composition of bulk fill?
- Filler Particles
- Monomers
- Alternative photoinitiator
- Reinforcing fibers
98
What are the characteristics of filler particles in bulk fill?
- Lower amount of filler particles
- Pre-polymerized filler particles (similarly to microparticules comp)
- Low-elastic modulus = help to absorb stresses
- Added larger filler size particles
99
Which monomers are used in bulk fill?
- UDMA
- Modified UDMA
- Fragmentation dimethacrylate monomers (less shrinkage than typical methacrylate)
100
What are the two types of bulk fill?
- Flowable bulk fill
- Full body bulk fill
101
What is flowable bulk fill?
- Flowable consistency
- Lower elastic modulus and reduced wear resistance (mechanical properties)
- Base for regular composites as the occlusal increment
- Dentin replacement only
- Better adaptation on the surfaces of the cavity
102
What is full body bulk fill?
- Suitable wear resistance (better mechanical properties)
- Replace dentin and enamel
- Possibility of sculpture
- Single increment (up to 4-5 mm)
103
What are clinical applications of bulk fill?
- Posterior restorations (Class I and II)
- Some specific Class III’s
104
What does this represent?
Incremental fill
105
What does this represent?
Bulk-fill flow
(2mm of flowable bulk fill, then add layer of regular composite)
106
What does this represent?
Bulk and body
107
What is dual cure bulk fill?
- Dual cure system: chemical (two pastes- automix) and light-cure
- Single increment (class I and II)
108
What does finishing and polishing do for bulk fill?
- Esthetic appearance and functionality
- Decrease the coefficient of friction = reduced rate of wear
- Improve the clinical parameters and quality of the restoration
- Less bacterial adhesion = less marginal leakage = less possibility of secondary caries
- Color stability = reduce staining
109
What are the advantages to bulk fill composites?
- Simplification of the restorative technique
- Reduced chair time (less stress for the dentist and patients)
- Better flowability = cavity surface adaptation
- Suitable mechanical properties
- Reduced polymerization shrinkage stress
110
What are the disadvantages to bulk fill composite?
- More translucent than regular composites
- Indicated for posterior restorations
- Cannot mimic the natural layering of the tooth
- Need high-output lights
- Place in combination with properly performed bonding technique
111
Would you do a sealant or PRR on teeth that have initial caries present?
PRR
*caries cannot extend into dentin*
112
Would you do a sealant or PRR on teeth that are noncavitated?
Sealant
113
Which is meant to last longer? PRR or sealant?
PRR
114
Who can place sealants?
- hygienist
- assistant
- dentist
115
Who can place PRRs?
- dentist
116
What is different about the PRR technique compared to sealants?
PRR technique similar to sealants but:
- Caries must be removed prior to placement
- Bonding agent and flowable resin composite are used
117
What are resin-based sealants?
- UDMA or bisGMA monomers polymerized by either chemical activator and initiator or light or specific wavelength and intensity
- Can be unfilled, colorless, or tinted transparent materials, or opaque tooth-colored or white materials
118
What are the pros of resin-based sealants?
- Good retention
- Can control working time (light-cured)
- Wear-resistant
119
What are the cons to resin-based sealants?
- Moisture-sensitive
- Require cleaning/etching of tooth surface prior to placement
120
What is the most common type of sealant used?
Resin-based
121
What are glass ionomer sealants?
- Cements with an acid-base reaction b/w fluoroaluminosilicate glass powder and polyacrylic acid solution
- Developed and used for fluoride releasing properties
122
What are the pros to glass ionomer sealants?
- Moisture-friendly
- No need for pretreatment of tooth surface due to chemical bonding to tooth surface
- Continuous release of fluoride
123
What are the cons to glass ionomer sealants?
- Poor retention
- Cannot control working time (chemical reaction)
124
What are polyacid-modified resin sealants?
Combine resin-based material with fluoride releasing and adhesive properties of glass ionomer
125
What are the pros to polyacid-modified resin sealants?
- Continuous release of fluoride
- Controlled working time
126
What are the cons to polyacid-modified resin sealants?
- Lower amounts of fluoride release vs GI
- Retention lower than resin
- Moisture-sensitive
- Require etching prior to placement
127
What are resin-modified glass ionomer sealants?
Glass ionomer sealants with resin components
128
What are the pros to resin-modified glass ionomer sealants?
- Similar fluoride release properties as GI
- Longer working time than GI
- Less water sensitivity than GI
- Does not require etching prior to placement
129
What are the cons to to resin-modified glass ionomer sealants?
- Lower retention than resin
- Lower wear-resistance than resin
130
What are the steps involved in placing sealants?
- Always recommend dry environment (especially important for resin-based)
- Clean pits & fissures with pumice and prophy brush, air abrasion, hydrogen peroxide, or enameloplasty (usually used for deeper grooves)
- Place acid etch (35% phosphoric acid) for 15-20 seconds, rinse, and dry (enamel should appear “chalky” white (for resin-based sealants ONLY)
- Place sealant material of choice and light cure if necessary (resin sealant materials)
- Check occlusion and adjust if necessary
131
Should you use prophy paste to clean a tooth prior to sealant placement?
DO NOT use prophy paste to clean a tooth b/c fluoride and oil interferes with etching process
132
What does research show if you place bonding agent prior to sealant placement?
Research shows an increased bond strength if bonding agent placed prior to sealant placement
133
What are the steps involved in placing PRRs?
- Remove caries
- Etch for 15-20 seconds, rinse, and dry
- Place bonding agent, air dry, and light cure
- Place flowable resin composite, and light cure
- Check occlusion and adjust if necessary
134
Do you need to numb the patient prior to placing a PRR?
NO- due to enamel layer caries only
135
What are some examples of non-surgical caries management techniques?
- Behavioral modification
- Topical fluoride application
- Pit & fissure sealants
136
What is involved with behavior modification?
- Limiting sugary foods and drinks
- Chewing sugar-free gum with xylitol
- Brushing with fluoride toothpaste 2x/day
- Cleaning between teeth 1x/day
137
What is involved with topical fluoride application?
- Placement of fluoride varnish (2.26%)
- Placement of fluoride gel (1.23% acidulated phosphate) (age 6 & up)
- Daily use of 0.09% fluoride mouthrinse (age 6 & up)
- Silver Diamine Fluoride (38%) for arrest of dental caries
138
When is SDF used?
used mainly in pediatric dentistry for patients that would otherwise be difficult to work on
139
What is involved with put & fissure sealants?
- Anatomical grooves of teeth trap food particles and promote presence of bacterial biofilm, increasing the risk of caries
- Effectively penetrating and sealing these surfaces with dental material (sealants) has been proven effective in preventing and arresting caries in permanent molars of children and adolescents
- Placed on pit and fissure areas only on noncavitated teeth (caries risk assessment for patient should be taken into consideration)
140
Should you prepare the smaller or larger lesion first?
larger
141
Should you restore the smaller or larger lesion first?
smaller
142
Can you etch more than one prep at a time?
No- only etch one prep at a time
143
What material was mined from Mammoth Cave in Mammoth Cave National Park in Kentucky/ the active ingredient in sensitivity toothpastes?
Potassium Nitrate (KNO- gunpowder)
144
What is the ideal inciso-gingival height of class III preps?
- 1.5mm on maxillary lateral
- 2.0mm on maxillary central
145
What is the ideal mesial distal height of class III preps?
- 1.0mm on maxillary lateral
- 1.5mm on maxillary central
146
What is the state of the gingival contact in ideal class III preps?
broken
147
What is the state of the incisal contact in ideal class III preps?
intact
148
What is the state of the facial contact in ideal class III preps?
broken MINIMALLY
149
What is the retention in class III preps?
- Retention not always required (do not place in deeper than normal preps)
- If placed, place in dentin
- Incisal point (placed with ¼ or ½ round bur)
- Gingival groove (placed with ¼ or ½ round bur)
150
Where should you bevel in ideal class III?
- Place 1mm bevel lingual
- 45 degrees
(all lingual Cavosurfaces)
151
What are the different non-carious cases of Class V lesions?
- Abrasion- wear
- Erosion- caused by acid
- Abfraction- mechanical loss of tooth structure
152
What is abrasion?
- Toothbrush, pen chewing, occlusal wear from grinding
- Discuss habits with pt
153
What is erosion?
- Bulimia, GERD, alcoholics, extreme diet
- Discuss diet & medical history
154
What is abfraction?
- Loading forces aren’t where they’re supposed to be
- = flexure of tooth and failure of enamel and dentin
155
Causes of dental sensitivity?
- Caries or leaky restoration
Void
- Fluid flows into void (Ex: from CaOH liner having washed away)
- Premature occlusion
- Exposed dentin
- Recession or incomplete formation of CEJ
- Exposed cementum
- Post-perio surgery
- Abrasion and erosion (includes iatrogenic from polishing instruments)
156
How to use clear mylar strip for class IIIs:
- Wedge the matrix at the gingival to hold it against the tooth
- Wedge aids in separating the tooth for good contact and control seepage and moisture contamination
- Minimizes finishing time
- Wedge is required to prevent gingival overhangs & to stop gingival bleeding or moisture seepage
- SPEND TIME ON THIS STEP
- Let excess material extrude toward the incisal (easier to finish incisally vs gingivally)
- For FINAL INCREMENT: tighten mylar strip around restoration and cure
157
Why do you tighten mylar strip around restoration and cure after final increment?
- Results in smooth finish
- Eliminates oxygen interference
- Not necessary to polish this surface if it does not need contouring
158
What is the Cure-Thru matrix?
Compresses the material with a matrix into the Class V prep while giving a great contour
159
What biomaterials should you consider when restoring Class V lesions?
Use nanofill or microfill
- Lower modulus of elasticity (less stiff) than hybrids
- Won’t flex as readily
- Less likely to debond
