Dental Materials Flashcards
What is the role of copper in dental amalgams?
Copper is added to:
- Improve mechanical properties
- Resistance to corrosion
- Marginal integrity
Copper-enriched amalgams contain little or no γ2 phase.The copper–tin phase, which replaces γ2 in these materials, is still the most corrosion-prone phase in the amalgam. The corrosion however is still much lower than conventional amalgam.
In spite of that, it is thought that corrosion actually offers a clinical advantage. The corrosion products will gather at the tooth-amalgam interface and fill the microgap (marginal gap) which helps to decrease microleakage.
What dental materials have an effect on an MRI?
What dental materials do NOT have an effect?
Dental materials may be classified in many ways. Here it is classified based on magnetic susceptibility as:
FERROMAGNETIC
These are those types of materials which are strongly ATTRACTED to a MAGNET. Their PERMEABILITY is very HIGE in the range of hundreds and thousands.
Examples include chromium oxide, cobalt, ferrite (iron), cadolinium, nickel, rare earth magnet, magnetite, yttrium, etc.
STAINLESS STEEL
The powerful magnetic field of MR system will attract iron containing (or ferromagnetic) objects and may cause them to move suddenly and with a great force like a “missile”. This can cause possible risk to patient or anyone in an objects “flight path”. It can pull any ferromagnetic object in the body too.
Tissue injury can be caused due to HEATING of prosthesis
PARAMAGNETIC
These are those materials which are not very strongly attracted to the magnet. They are slightly magnetized when placed in a strong magnetic field and act in the direction of the magnetic field. Their relative permeability is slightly more than one. Examples of such materials are magnesium, tin, platinum, lithium, tantalum, aluminum, molybdenum, etc.
TITANIUM is a paramagnetic material that is not affected by the magnetic field of MRI. The risk of implant-based complications is very low, and MRI can be safely used in patients with implants.
DIAMAGNETIC
These are those materials which are repelled by a magnet. They are slightly magnetized when placed in a strong magnetic field and act in the direction opposite to that of the magnetic field. Their permeability is slightly less than one. For example wood, zinc, copper, bismuth, silver, gold, etc., are diamagnetic materials.
Crowns made of porcelain, composite resin, or gold pose no risks from MRI. If a patient has a crown made with metal, or of porcelain fused to metal, they should consult their dentist before getting an MRI.
Resin Infiltration.
For what purpose?
mm of depth reached?
Resin infiltration is a minimally invasive restorative treatment for post-ortho white-spot lesions (WSL) and certain congenital hypocalcified enamel lesions (“hypo” spots). …
HYPO SPOTS, or enamel bruising, are congenital enamel defects often caused by trauma or infection involving the primary teeth.
- Lesions etched 3×2 minutes – this removes the outer remineralized layer of enamel that had previously been blocking calcium and other ions from entering the tooth
- Finishing bur on any surfaces that do not indicate an improved appearance
- Application of drying agent (ethanol)
- Application of the resin infiltrant
- Material soaks in for 3 minutes (allowing for capillary action)
- Remove excess material with cotton rolls, micro-brushes & floss
- Light cure the material
- Material added again for 1 minute, excess removed, and cured
- Finish with polishing discs or burs
- Temporary blanching of gums can occur in lesions close to the gumline
Infiltrate, via capillary action over several minutes and 2 applications, an unfilled “fluid” resin to the extent of the dentino-enamel DEJ
junction or slightly beyond.
The MAXIMUM DEPTH of penetration of the resin material was 6.06 ± 3.32 μm. Caries infiltration can be used as a painless and effective option for treating white spot lesions.
BLEACHING
Carbamide Peroxide vs Hydrogen Peroxide
Both have equally effective results
The main difference between hydrogen peroxide and carbamide peroxide is that hydrogen peroxide is an effective whitening agent by itself.
Carbamide peroxide contains hydrogen peroxide in it.
For every 30% of carbamide peroxide, there is also 10% of hydrogen peroxide. (3 to 1 ratio)
The concentration approved as safe and effective by the FDA and ADA for tooth whitening (10 percent Carbamide Peroxide) is similar to 3.6 percent hydrogen peroxide.
Hydrogen peroxide breaks down faster than carbamide peroxide and releases most of its whitening agent within 30-60 minutes. Carbamide peroxide releases about 50% of its whitening agent in the first two hours and it remains active for up to six additional hours.
Hydrogen peroxide should only be used in a controlled environment under dental supervision due to extreme gum irritation and hyper tooth sensitivity.
Carbamide peroxide can be used at home without dental supervision.
No more than 22% carbamide peroxide is recommended for at home use.
What is Bond Strength?
BOND STRENGTH
Defined as the load needed to break a bond divided by the cross-sectional area of the bonding interface.
values in MEGAPASCALS (MPa)
Glass Ionomer Cements (GIC)
Ingredients?
Glass-ionomer cements are based on the reaction of:
- SILICATE GLASS POWDER(calciumaluminofluorosilicate glass)
- POLY-ACRYLIC ACID, an ionomer.
Polymerization Shrinkage from least to greatest amount?
. ➡️⚫️
GI - RMGI - PACK - FLOW
LEAST .
GI ⬇️ RGMI ⬇️ Pack Comp ⬇️ Flowable Comp
GREATEST ⚫️
Total Etch vs Selective Etch
TOTAL ETCH:
Classic technique of utilizing a 30% to 40% phosphoric acid gel to prepare both the ENAMEL and the DENTIN for adhesive procedures. One of the greatest advantages of this technique is its ability to prepare enamel, dentin, and sclerotic dentin for bonding, resulting in HIGH BOND strengths.
Dentin etching has been shown to frequently produce postoperative TOOTH SENSITIVITY 🤕 if not used properly
⬇️
Place a desensitizing agent. One of the most successful steps is use of GLUTARALDEHYDE containing liquids.
-They COAGULATE the DENTIN, thereby obturating the dentinal canals and REDUCING the dentin
PERMIABILITY to the subsequently placed resin.
SELECTIVE ETCH:
Technique where enamel margin surfaces are etched with 35 % phosphoric acid etch to ensure a strong bond to the enamel surface.
Unfilled vs Filled Sealants
UNFILLED:
Have a HIGHER RATIO of RESIN to filler material, and DO NOT need to be adjusted with a dental handpiece.
They are in essence SELF-OCCLUDING.
Due to LOW VISCOSITY (rate of flow) of unfilled sealants, they readily flow into the pits and fissures.
FILLED:
Does require checking of the occlusion and possible adjustment with a stone bur.
Addition of filler particles LOWERS the sealant’s ability to PENETRATION into fissures and microporosities of etched enamel.
RETENTION RATES:
The retention rates of resin-based unfilled pit and fissure sealant was slightly higher and clinically shown better performance than resin-based filled pit and fissure sealant.
What is the difference between a Sealant and a PRR?
SEALANTS:
NO tooth structure is removed
PRR: (Preventative Resin Restorations)
A very small portion of ENAMEL is REMOVED, which cleans out the cavity as well, and a COMPOSITE restoration is placed.
T/F
Studies have shown Sealant retention is better on MAXILLARY Molars over mandibular molars.
FALSE
The retention of sealant on MANDIBULAR teeth was seen to be SUPERIOR to that on maxillary teeth in both resin-based filled pit and fissure sealant.
What can over-drying after rinsing off etchant do?
Collapse the Collagen Network
What is Polymerization?
A process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks.
What material in a SSC adds tensile strength?
CHROMIUM
Most stainless steel contains about 18 percent chromium; it is what hardens and toughens steel and increases its resistance to corrosion, especially at high temperatures.
What is the Hybrid layer
Hybrid layer = demin dentin and polymerized resin
Adhesive resin should create the so-called hybrid layer (consisting of a collagen network exposed by etching and embedded in adhesive resin). This layer is an interface between dentin and adhesive resin and the final quality of dental restoration depends greatly on its properties.
