Dental materials Exam 4

Describe the effects of polymer size , structure and properties on strength , stiffness , and dimensional stability

- Strength , Stiffness , Stability of a given polymer is generally increased the longer the individual polymer chains are - Unreacted monomers in a polymer can be a source of irritation for the patient . Then can alter and affect the stability of the final polymer

Condensation Polymerization

-Also known as step growth polymerization -Water or alcohol release as a by product , the reaction . of two monomer units -Reaction is slow & do not produce polymers of suitable length

Applications in dentistry

-Denture bases -Teeth -Liners composites -Sealants -Temporaries -Custom trays -Impression materials -Adhesives -Cements -Ortho appliances -Mouthguards & nightguards

Describe the general procedure for the production of a heat - cured denture

-Heat activated systems are supplied as powder / liquid systems similar to those of cold - cure resins . -When the powder and liquid are mixed , they go through the same initial stages of the setting process . -Because no chemical activator is present , the mixed material stays in the dough stage for an extended period of time . -After the material is formed into the desired shape , the material is heated in a water bath . -The heat breaks down the benzoyl peroxide , forming free radicals . -Polymerization proceeds by changing the dough into a rigid material These products are a bit stronger & tougher than cold - cure acrylic resins

Discuss patient indications and contraindications for use of bleaching agents

-Inform the patient that aesthetic anterior restorations will not change with whitening procedure . Need to replace restorations -Cracked or hypoplastic enamel -Carious lesions -Amalgam stains - no nonvital tooth whitening -Nonvital whitening on a tooth extensively restored -Cervical abrasion or tooth sensitivity -Receiving radiation or chemotherapy ( no light system ) -Patient with melanoma do not use light system -Patient using photosensitive drugs or herbal remedies do not use light system

Cobalt Chromium Alloys Uses :

1. Orthodontic wires 2. Frameworks Do not use any denture cleansers containing chlorine products such as sodium hypochlorite ( bleach ) on partials or any prosthetic with a base metal

Describe the uses of base metals ( non - noble ) in orthodontics , prosthodontics and pedodontics

1. Tooth restorations . 2. Frameworks for bridges , partials 3. Wires & brackets 4. Implants

Surgical procedure for placing implants must not injure the bone . Killing the bone prevents Osseointegration of the implant . Recommended temperatures are not to exceed :

117F

Orthodontic wire

55 % Nickel and 45 % Titanium

Beta - titanium alloy

79 % ( Ti ) , 11 % ( Mo ) Are highly elastic , ideal for ortho

Which of the following takes place during the second and endosseous implant surgery ?

A healing cap is attached to the body of the implant

Describe concerns over the biocompatibility of certain types of alloys used in dentistry

All alloys used in dentistry are considered compatible in that they do not cause a toxic reaction Although every alloy releases ions into solution to some extent , the corrosion process is very slow and considered a negligible hazard

Plasticizers effect

Are large bulky side groups that tend to push the polymer chains apart & reduce the number & effectiveness of the ( cross - linking ) which makes the polymer more flexible & rubber - like

Heat activated acrylic resins

Are similar to chemically activated systems . The major exception is that no chemical activator is present in the liquid . A minor difference is that less inhibitors are present in the liquid . The inhibitor is not needed to provide working time ; it functions as a preservative , reacting with free radicals to prevent polymerization during storage .

Entanglements ( Cross - linking )

Between polymer chains creating frictional forces keeping them from slipping past one another thus giving strength & stability

Explain what is meant by a " bioactive " ceramic

Bioactive - reacts directly with bone and forms hydroxyapatite or some other calcium phosphate compound on their surface , producing a direct chemical bond . Ex . , Synthetic hydroxyapatite ( works best as a coating on metallic implants )

The patient's home care regimen of implant maintenance may consist only of a toothbrush and floss . Without proper maintenance , the possibility of implant failure greatly increases :

Both statements are true

Composition of cobalt - chromium alloys :

Cobalt ( Co ) -60 %

List the components in powder and liquid of both heat - cured and cold - cured acrylics for dentures , appliances , and custom trays

Cold ( Chemical ) -Cure Heat - Cure Liquid Methyl methacrylate Methyl methacrylate Hydroquinone Hydroquinone Ethylene glycol Ethylene glycol Tertiary amine Powder Acrylic resin powder Acrylic resin powder Benzoyl peroxide Benzoyl peroxide Fibers and colorants Fibers and colorants

Over the counter

Crest whitestrips Only over - the - counter product with demonstrated safety and efficacy . Whitening agent is 5.3 % hydrogen peroxide Colgate Simply White and Simply White Night Gel is painted on teeth Gel contains 18 % carbamide peroxide Over the counter • Whitening dentifrices - whitening is achieved through mechanical removal of extrinsic stain o Abrasives are : hydrated silica , precipitated calcium carbonate , and dicalcium phosphate dihydrate Peroxides are : calcium peroxide and sodium percarbonate Additional products - chewing gum , floss , mouth rinses , flexible waxlike strips

The type of implant that involves cutting a hole into the alveolar bone and then pressing her screen and the implant is called :

Endosseous

The prosthodontic phase of implant treatment involves a placement of several parts or attachments . A patient who has completed the surgeries and restorative care would receive in order :

Implant , abutment cylinder , crown

Stainless steel composed of :

Iron ( Fe ) -69 % Chromium ( Cr ) -18 % passivation Nickel ( Ni ) -8 % stabilizes alloy Molybdenum ( Mo ) -5 % hardness Carbon ( C ) -0.2 % hardness

Denture Base

Is made in the dental laboratory following the dentist's prescription ( final impression ) ; it is made on the master cast , which is a positive reproduction of the patient's alveolar ridge . The base is the pink part of the denture that sits on the alveolar ridge .

Compare the composition and properties of the various types of metals and ceramics used in dental implants

Metals : 1. Surgical stainless steel ( lower carbon content ) 2. Titanium - used either in pure form or as an alloy . Is lightweight , high strength , relatively flexible , and highly reactive with O₂ producing an oxide layer very compatible with body tissues Ceramic Coated metals provide two benefits : 1. Structural component of the implant is rigid , high strength metal with superior fracture resistance 2. Accelerates the rate of bone formation at the bone implant interface and enhances its strength and stability Concern with interface between metal and ceramic which creates another potential site for failure ( Disadvantage ) Ceramic is like bone but has no protein , it is brittle and so it can not support the same forces as bone .

Acrylic resin systems & porosity

Methyl methacrylate & other monomers . evaporate easily at room temperature . If a monomer evaporates during handling or processing , the resulting material is porous . Porosity weakens the material . Pressure & temperature controls are used to minimize porosity .

Chromium ( Cr ) -25 % corrosion resistance

Nickel ( Ni ) -10 % enhances ductility Molybdenum ( Mo ) -5 % hardens / strengthens Carbon ( C ) -0.3 % greater amounts make alloy more brittle

in office whitening

O power whitening ( bleaching ) 0 High concentration of hydrogen peroxide 15 % -35 % May use bleaching light , resin curing lights , or laser

Explain osseointegration as it relates to success of dental implants

Osseointegration is the process by which new bone forms at the surface of an endosseous implant creating a strong adhesion to stabilize it within the tissue . Formation of this interface depends on : 1. Chemical composition of the implant 2. Surface characteristics 3. Care with which surgical procedure performed 4. Design of prosthesis 5. Follow - up hygiene care

Identify factors that can affect the success of dental implant therapy

Patient Selection - critical to success 1. Must be motivated 2. Healthy and free from systemic disease 3. Maintain healthy oral environment 4. Sufficient healthy bone present Contraindications are smoking , parafunctional habits , poor home care , and progressing periodontitis

Explain pitting corrosion and identify susceptible alloys

Pitting corrosion - protective layer does not form as easily in a solution containing chloride ions and bodily fluids contain high levels of chloride ions ( sodium chloride ) When a surface is scratched , pitting corrosion can occur , but is usually not a problem in orthodontics or pedodontics because the service life is short Base alloys

To ensure longevity and function of the implant , the patient is responsible for :

Plaque control

All of the following should be included and post care maintenance of a patient with an implant except which one ?

Putting the start of material for the adjacent restoration

The following conditions are contraindications for implant placement except :

Recurrent caries

Composition of Ni - Ti alloys

Specific formulations of Ni - Ti alloys have a special shape memory effect Can be bent into a specific shape above its critical temp , then reshaped at a temp below On reheating above its critical temp , the wire will remember its original shape and try to recover it Concept has not been commercialized

State the responsible metal for corrosion resistance of each alloy used in orthodontics and prosthodontics

Stainless steel - is a base metal alloy with small amount of carbon ( gives hardness ) & chromium ( stainless effect ) which makes it corrosion / tarnish resistant

List the benefits and potential side effects of bleaching treatment

Tooth sensitivity - comes from to tight of tray or from the whitening agent itself Tooth sensitivity and gingival irritation are the most frequently reported side effects of whitening . Light may result in reversible pulpitis Both side effects are transient lasting no more than a few days after treatment is discontinued . During the bleaching process . Any bleaching product using peroxides will produce free radicals . Free radicals have been linked with cancers . With time and abusive usage of bleaching products side effects can be discovered . Patients with risk factors or oral cancer , tobacco and excessive alcohol use should avoid abusing whitening products .

Light - activated & dual - cure acrylic resins

Used for temporary crowns , custom trays , and other acrylic resin uses have been introduced . Because these composite materials are stronger they are gaining acceptance , and cheaper .

Thermoplastic

ability to be reversibly transformed from a brittle , glassy solid to a softened , moldable plastic by heating beyond a certain temperature

a patient who has very small or essentially no mandibular ridge is said to have a :

atrophic edentulous mandible

Cross linkages

attach two polymer chains together & create more stability

titanium is very difficult to cast . It is not very strong but is acceptable for implant uses :

both statements are true

Transosseous or Staple

bottom plate protrudes from the underside of the mandible and attachments for the prosthesis reside above the alveolar ridge

Composition of Titanium alloys

essentially pure form of titanium used in implants , titanium alloy has 6 % Aluminum and 4 % Vanadium

Nickel - Chromium Alloys

excellent corrosion resistance due to chromium content and characteristics are similar to stainless steel and Co - Cr alloys Nickel - 80 % Chromium - 15 % Beryllium added to enhance casting and bond to porcelain

Polymers

long chains of organic molecules produced by the reaction of many smaller identical molecules

Subperiosteal

metal framework that rests on alveolar ridge with abutments or attachments for the prosthesis protruding from holes in the gingiva

Cold - cure or chemically activated acrylic resins

o liquid O Powder o Physical changes during setting o Polymerization reaction o Residual monomer o cross - linking

Endosseous

placed into bone by first drilling a hole , then tapping a screw - thread into which the implant is fitted

Denture liners

plasticizers that simply reside in the folds of the polymer and do not actually chemically react

Explain the rationale for applying a surface coating to a metallic dental implant

reacts directly with bone and forms hydroxyapatite or some other calcium phosphate compound on their surface , produces a direct chemical bond .

Tissue Conditioner : " chairside reline "

temporary liner is made from a tissue conditioner that cushions the tissue . This adds a small amount of new material to the denture so that it fits properly . Can be done chairside or in lab .

Glass transition temperature

the critical temperature determined by structure of monomers and presence of plasticizers

Addition Polymerization

• Monomers added on after another to form long chain polymer • Involve reactions containing carbon carbon double bonds ( C = C ) • Heat is given off each time a C = C bond splits which accelerate the reaction . Each monomer reacts the entire mass of polymer shrinks • Benzoyl peroxide for self - curing ( initiators ) -Camphoroquinon e for light - cured ( initiators )