Lecture 1 - Denture Base Resins Flashcards
When completing a checklist for a wax trial denture appointment, what should the checklist consider?
▪ CO = CR
▪ OVD
▪ Midline
▪ Horizontal & vertical overlap ▪ Lip support
▪ Occlusal plane ▪ Buccal corridor ▪ Esthetics
▪ Phonetics
▪ Maxillary posterior limit ▪ Protrusive record
Resin =
A broad term used to describe natural or synthetic substances that form plastic materials after polymerization
What is the main way in which dentures are processed?
Heat activated resins
Acrylic =
Means designating a colorless, pungent acid
We talked a lot about the history of dentures in this lecture. Give a brief synopsis of what was touched on.
▪ Skillfully designed dentures were made as early as 700 BC
▪ Teeth were made of gold, silver, wood
▪ The first dental prosthesis was believed to have
been constructed in Egypt
What were some of the materials that dentures were made of in history?
- Gold
- Wood
- Bone
- Ivory
- Ceramics
- Metals/ alloys
- polymers
What are some known denture base polymers?
▪ Polymethyl methacrylate
▪ Urethane dimethacrylate (light activated)
Vulcanite Rubber =
→ Used with porcelain teeth
important improvement compared to previous materials at this time. Became not ideal because of color, taste, and odor
Which denture base polymer proved to be a much satisfactory material?
Polymethyl methacrylate (light activated)
What was the most significant drawback to using ceramics and porcelain for dentures back then?
The brittleness… they tended to fracture
Would ceramics bond to denture bases back then?
NO! This was another drawback
What are the different types of acrylic resins you should know?
▪ Polymethyl methacrylate
▪ Pure PMMA (colorless, transparent)
▪ Liquid- non polymerized methyl methacrylate
▪ Liquid and powder mixed in proper proportions
What is one advantage to using PMMA as a denture base material?
There is relative ease with which it can be processed
What are the 3 types of denture bases?
- Heat cure
- Chemical cure
- Light cure
- Used in fabrication of all denture bases
- PMMA (powder & liquid)
-Initiator: Benzoyl peroxide
Heat Cure
- Induce the denture base polymerization, does not require thermal energy
- Auto-polymerized and heat activated
Chemical Cure
- Activator –> visible light
- Initiator –> camphorquione
Light Cure
What is the resin base that we use now?
Polymethyl methacrylate (PMMA… veronite)
What are the characteristics of polymethyl methacrylate?
▪ Esthetics
▪ Low solubility, low water absorption
▪ Non-toxic, low allergenicity
▪ Easily repaired, adequate strength
▪ Reproduces detail accurately
▪ Simple molding and processing techniques
Polymethyl methacrylate is a two-component system. What are these two components?
- Liquid
- Powder
What are the 5 PMMA resin ingredients that you should know?
- Liquid monomer – methyl methacrylate
- Powdered polymer – polymethyl methacrylate
- Plasticizer- dibutyl phthalate
- Initiator – benzoyl peroxide
- Pigments
What are the three types of PMMA liquids?
- methyl methacrylate
- glycol dimethacrylate (a cross linking agent)
- hydroquinone (inhibitor for increased shelf life)
What are the four types of PMMA powders?
- PMMA beads
- Pigments
- Plasticizer (dibutyl phthalate)
- Benzoyl peroxide (initiator of polymerization)
What is used in the fabrication of all denture bases?
Heat activated resin
What is required for the polymerization of heat activated resin?
Thermal energy (water bath or microwave oven)
What are the PMMA powders?
Prepolymerized spheres of PMMA and small amount of benzoyl peroxide
What are the PMMA liquids?
Predominantly non polymerized methyl methacrylate with small amount of hydroquinone (inhibitor)
What ingredient is added to the PMMA liquids?
Cross linking agent
What technique is used to process denture resins?
Compression molding (with a pressure vacuum machine)
Besides compression molding, what is another technique that is used to process dentures?
Ejection molding
What is the time and temperature for a bench cure of a denture base resin?
Time = 1 hour
Temperature = room temp
What is the time and temperature for a slow heat cure of a denture base resin?
Time = 9 hours
Temperature = begin in cold water and bring up to 165 degrees Fahrenheit… the exothermic heat of reaction occurs when the resin reaches 150 degrees Fahrenheit
What is the time and temperature for a fast heat cure of a denture base resin?
Time = 2 hours
Temperature = begin in cold water and bring up to 165 degrees Fahrenheit… then 30 minutes at 212 degrees Fahrenheit
What is the time and temperature for a deflasking of a denture base resin?
Time = 30 minutes (1), 30 minutes (2)
Temperature = bench cooling at room temperature (1),
immersed in tap water (2)
** remove the investing plaster but leave the stone casts intact. All the plaster must be cleaned off, and dentures must NOT be removed from casts **
Should you boil the acrylic monomer?
NO→ Do NOT boil the acrylic monomer… this is because it causes POROSITY
At what temperature does acrylic monomer boil at?
It boils @ 100.3 degrees Celsius (212 degrees Fahrenheit)
** avoid increasing the temperature too quickly to prevent porosity **
Internal porosity =
The heat at the surface of the resin is conducted away into an investing medium… there is no porosity on the surface of the resin
What does the vaporization of the monomer affect in internal porosity?
It affects the thick areas of the denture base
What temperature does the monomer boil at in internal porosity? What does it cause?
Temperature = 100.8 degrees Celsius / 213.4 degrees Fahrenheit
** it causes spherical bubbles inside the resin **
Other porosities cause irregular shapes and they located throughout the base. What are the 3 main causes of developing other porosities?
- Inadequate pressure
- Not enough resin in mold 3. Improperly mixed resin
What is the main difference of resin denture teeth in comparison with denture base resin?
Resin denture teeth are basically the SAME composition as the denture base resin, EXCEPT for pigmentation to produce tooth shades
Are resin denture teeth highly cross-linked resins?
YES! → The TEETH and BASE chemically bond to each other
What is the difference between heat activated and auto polymerized?
The fundamental difference is the method of activation of the interior benzoyl peroxide
In autopolymerized = an amine in the liquid reacts with the benzoyl peroxide in the powder to promote polymerization @ room temperature
Is there a greater degree of polymerization with heat activated or autopolymerized?
Heat-activated
What has better color stability: heat activated or autopolymerized?
Heat-activated
In the color stability of the autopolymerized process, what color does the tertiary amine activator in the liquid oxidize and turn to after a few months?
Turns orange
What are the 4 types of denture base resins?
- Light activated
- Heat cure
- Chemically activated
- Autopolymerizing
What is light activated denture base resin made of?
▪ Composite matrix of urethane dimethacrylate ▪ microfine silica
▪ high molecular weight acrylic resin monomer
What is the ACTIVATOR of a light activated denture base resin?
Visible light
What is the INITIATOR of a light activated denture base resin?
Camphorquinone
What form is light activated denture base resin supplied in?
Sheet & rope form packed in light proof pouches
Can light activated denture base resin be flasked in a conventional manner?
NO!
What does opaque investing media provide?
It provides the passage of light
In dentures, teeth are arranged, and the denture bases are sculpted using what?
Light activated resin …
The denture base is then placed into a light chamber & polymerized
What are the two types of CAD/CAM technology?
- Subtractive
- Additive (printing)
CAD/CAM Technology =
It is the 3D processing of dentures. Dentures are cut out from a puck of material.
