Unit 308 Flashcards
Prosthodontics is…
the restoration or replacement of damanged or missing teeth by the use of artificially constructed devices.
When teeth have been damaged and cannot be restored by fillings they are restored by..
inlays, crowns, veeners
when teeth have been extracted they are usually replaced with…
dentures, bridges, implants
who contructs the artificial devices?
Dental Technician
Why is getting the occlusion correct so important with prosthodontics?
The musculature surrounding the temporomandibular joint especially the lateral pterygloid muscles will become strained if patient does not bite in their correct occlusion.
What materials are used to record an accurate copy of the patients mouth?
Impressions
What properties should impression materials have?
- easy to mix
- cost-effective
- adequate working time before setting
- relatively short setting time
-record tooth details accurately - stable and elastic
What kind of patients can we use non-elastic impression materials on?
edentulous
Alginate is what type of impression material?
irreversible hydrocolloid
What are the 2 main reasons alginate is commonly used?
easy to mix and relatively cheap
Can alginate impressions be used to make the working model for a crown, bridge, veener or inlay construction?
NO
What is the reason alginate cannot be used to make the working model?
it is not accurate enough
What is alginate powder made of?
calcium salt, alginate salt and filler
what temperature should the water be when mixing alginate?
room temperature
what is spatulating?
folding the powder into the water and vigorously spreading it against the bowl side.
The working time of alginate is determined by?
the temperature of the mixing water used
What does chromogenic materials mean?
materials that change colour in response to some stimulus e.g. mixing and setting stages.
Dimensional changes of alginate in the presence/absence of water.
Left in water - impression expands
Left out of water - impression shrinks
Addition silicone impression material is what type of material?
Elastomer
Why is addiction silicone impression material used?
Highly accurate when set
How is the impression material produced in regards to the tubs of heavy bodied putty with liquid or paste activator?
chemical reaction
What can cause addition silicone impression material to be affected (setting times and mixing)?
Some types of rubber PPE gloves
What types of gloves are advised to be worn when mixing addition silicone impression materials by hand?
vinyl gloves
Are silicone impressions affected by temperature?
NO
What material is light bodied material used with?
Addition silicone impression
What technqiue is best to use for a very accurate impression - adition silicone imp?
two stage technique
- condensation cured silicones
What is the average setting time for silicone impressions?
4 minutes or more
Advantages of silicone impressions:
- dimensionally stable in the presence of moisture
- mixing techniques prevent the formation of air bubbles
- excellent elasticity, strength and accuracy
- suitable for all types of prosthodontics
Disadvanatges of silicone impressions:
- more complicated n time consuming
- expensive materials
-uncomfortable for patient
-paste materials are sticky prior to setting
Do polyethers materials create very accurate impressions?
YES
An example of polyethers impression material:
impregum
What is the impression material polyethers presented as?
2 pastes in different colours
How is polyethers material mixed?
waxed paper pad and collected into special syringes for administration to the prepared tooth.
remaining material is loaded onto an impression tray
What type of material is polyethers?
elastomer
Polyethers impression material has a similar setting time to silicones but set more stiffly how are they usually removed from the mouth?
sharp displacing action from the mouth
Main disadvantage of polyethers material:
slightly less dimensionally stable when moist compared to silicones.
How is a disinfectant bath made for impressions?
10% sodium hypochlorite with water
products such as proforma
How long should an impression be left in a disinfectant bath?
10 minutes
Alginate impressions are packaged how?
covered with a wet gauze and sealed in an air tight bag
Elastomer impressions are packaged how?
Blown dry using the tripe syringe and sealed in an air tight bag.
Wash imps before placing in disinfectant and after.
Impressions must be stored at what temperature?
room temperature
Alginate impressions must remain…
moist at all times
What shape is an impression tray?
horse shoe shape
edentulous patients would need what type of tray?
edentulous tray
dentate patients would need what type of tray?
boxed tray
What is the reason behind impression trays having holes in them?
impression materials are not adhesive to plastic or metal
so the holes enable the material to lock itself into the tray.
The impression trays that are made in numerous sizes for adults and children are called?
stock trays
The trays made in acrylic by the technician are called?
special trays
What are the trays called that record a partial section of both dental arches and occlusion in one impression?
triple trays
fixed prosthodontics means…
tooth restorations or replacements that are cemented within or onto a tooth.
The 4 fixed prosthodontics are:
- crown
-bridge
-veener
-inlay
The material used for each prosthodontics is decided on:
- the tooth involved
- aesthetics
- is the material temporary or permanent
- occlusion does the patient bite in an unusual way
Temporary crowns and bridges can be constructed at the chairside using :
stock crown forms
preoperative impressions to construct them
How much of a tooths surface does a crown cover?
3/4
The usual method of making crowns is sending them of to the lab to construct however this can take up to 2 weeks, what are the quicker alternatives of a constructing a permanent crown?
- 3 dimensional imaging techniques - scan n construct on the same day
- new comp materials e.g. luxacrown construct crowns at the chairside
What materials are used to take impressions for a crown?
- alginate impression of the opposing arch
- occlusal registration - bite registation putty + catalyst
- elastomer impression
When is the face bow technique carried out?
when several crowns are being constructed on the same arch
What burs are used when preparing a tooth for a crown?
(friction grip)Long tapered diamond bur
Why is gingival retraction cord used?
To allow the impression material to flow into the crevice and accurately record the prepared tooth margins.
What is retraction cord soaked in?
astringent solution - adrenaline or alum
What are Beebee crown shears used for?
short beaked shears used for cutting and shaping the margins of temporary crowns.
What are crown formers used to do?
plastic or polycarbonate tooth shaped formers - variety of sizes and available for each tooth shape
Luting cement - self cure resin
chemical bonding between tooth and prosthesis
double syringe mix
Luting cement - light cure resin
light cure bonding between tooth and prosthesis
double syringe mix
Luting cement - dual cure resin
combination of self cure and light cure bonding between tooth and prosthesis
double syringe mix
Luting cement - polyester resin
chemically adhesive and inert in saliva
waxed pad and spatula
Luting cement - glass ionomer
chemically adhesive to tooth and inner surface of prosthesis
waxed pad and spatula
Luting cement - zinc polycarboxylate
chemically adhesive to tooth and inner surface of prosthesis
glass slab and spatula
Luting cement - zinc phosphate
mechanically adhesive to rough inner surface of prosthesis and surface of tooth
glass slab and spatula
A fixed prosthesis is permanently cemented onto the tooth using a…
luting cement
Porcelain jacket crown
anterior teeth only
good aesthetics
All ceramic crown
modern version of PJC
constructed of stronger ceramic materials e.g. zirconia
posterior n anterior
require less tooth preparation than a conventional bonded crown e.g emax
Porcelain bonded crown
consist of substructure of metal for strength with a buccal or labial face of porcelain for better aesthetics
They appear less opalescent than the all ceramic crowns
Full gold crown
made of yellow gold or mixture of precious or non precious metals
STRONGEST of all crowns
ideal for posterior teeth and patients with a heavy bite
Over time a tooth that has a root filling can become brittle and fracture, the tooth will need additional support, this is achieved by..
Post crown
A post crown consists of..
a metallic post and core structure that is then shaped to hold a conventional crown.
In a post crown what are the metallic posts constructed from?
preformed posts e.g. paraposts or dentatus posts
The post and core are handmade by the technician + crown
What instrument is the root filling removed with when preparing for a post crown?
gates glidden drill
A suitable material for core construction is:
hardened glass ionomer cements such as Vitremer.
Glass fibre posts are cemented into the post hole using self adhesive resin cements before a core is constructed using bulk fill composite material e.g filpost and relyx fibre post.
Why are temporary crowns placed whilst the permanent crown is being constructed?
maintain appearance
prevent sensitivity
maintain the correct space between adjacent teeth
maintain the correct occlusion between opposing teeth
Temporary crowns placed using a prefabricated product are made by…
fitting a crown form over the prepared tooth
Is it true handmade and prefabricated temp crowns can be successfully used for posterior teeth?
YES
Trimmed prefabricated crowns are cemented using..
temp bond
Hall crowns are made out of…
stainless steel crown forms
What is the reason behind hall crowns?
to manage caries in deciduous molars instead of convential fillings.
No drilling is needed.
By isolating the tooth it prevents any further bacteria being able to attack the tooth, so the cavity will not progress further.
What is a bridge?
artificial device which is composed of two or more units, one of which will replace a missing tooth.
Where do the units lie in regards to bridges?
one or more units will lie over the dental ridge where a tooth is missing.
The other units sit over the prepared teeth that will hold the bridge in place.
Bridge - what are the units called that replace the missing tooth?
pontic
Bridge - what are the units called that hold the bridge in place?
retainers
Bridge - what are the teeth that bridges are cemented onto called?
abutments
Advantages of bridges:
- more aesthetically pleasing than dentures
- no embarrassment of a prosthesis falling out
- more hygienic than dentures
- help patients who have a strong gag reflex
Good oral hygiene is important for patients with bridges why?
produce stagnation areas - under the pontics
Do bridges require special effective cleaning techniques?
Yes
What is a fixed - fixed bridge?
where retaining teeth are involved to either side of the missing teeth as one solid design.
What is a fixed - moveable bridge?
where a joint is incorporated in the design to allow some degree of flexibility to the bridge.
What is a cantilever bridge?
where the retaining tooth or teeth are to one side of the pontic only.
what is a simple cantilever bridge?
design where retaining teeth are those immediately to one side of the pontic only.
what is a spring cantilever bridge?
design where the retaining teeth are to one side but several teeth away from the pontic.
what is an adhesive bridge?
where the retaining teeth undergo minimal tooth preparation and retention is provided by lingual or palatal metal wings only.
what bridge is usually required for anterior or posterior missing teeth?
full crown retainers are generally required.
why are fixed fixed bridges not used much nowadays?
inflexibility can cause damage to retaining teeth
what is the main bridge that is usually used?
Adhesive bridge
With bridges is the health of the abutment tooth important?
Yes
All types of bridges except for adhesive rely on the retaining teeth being of full crown coverage.
why are radiographs taken when deciding if a patient is suitable for a bridge?
determine the health of the teeth
What are adhesive bridges primarily used for?
replacing one of two front teeth
When preparing the tooth for a maryland type bridge how much preparation is needed?
not much
only preparation that is required is to roughen the palatal/lingual enamel where the flanges will adhere.
What is the purpose of a maryland bridge (adhesive)?
to conserve tooth tissue
Who are adhesive bridges ideal for?
younger patients who have fewer restorations + minimal overbite
will adhesive bridges withstand heavy occlusal forces?
NO
ideal cases for posterior adhesive bridges would be?
patients with no opposing teeth to the bridge or a denture is present as the opposing teeth so that occlusal forces are lower than if natural teeth were present.
what materials do we need to cement an adhesive bridge?
dual cure resin cements with primers - strong chemical bond
panavia - luting cement
why is a temporary bridge necessary between stages?
prevent sensitivity, space closure and tipping or overeruption of the abutment teeth.
temporary bridges can be used as replacements for up to how long?
6 months after the extraction of the tooth
what material is used to make a temp bridge?
composite type resin e.g temphase or protemp
Oral hygiene instructions to patients with a bridge:
- 2 x daily brushing
- careful regular flossing or interdental brushing
- sensible diet – lower sugars
- attend check ups
what is the best floss for patients with bridges to use?
Superfloss
What are veeners?
composite or porcelain material made to cover the labial surface of an anterior teeth.
what are veeners usually used for?
- discoloured tooth e.g. root filled tooth
- close diastemas
-change the shape of a tooth - cosmetic procedure
Composite veeners are completed by who?
dentist - chairside
Porcelain veeners are completed by who?
Lab technician
Is it true porcelain veeners are fragile?
YES
What surface of the tooth is prepared for veeners?
Labial surface
For veeners what is the tooth temporarily covered in whilst the veener is being constructed?
composite
When fitting a permanent veener what material is used to cement the veener?
special light cure or dual cure luting cements are used e.g. RelyX
What is the constructed veener coated with prior to placing?
silane agent - allows the luting cement to chemically bond to it
What are inlays used to do?
restore a cavity in a tooth.
produce a restoration of higher strength
What materials can inlays be made out of?
gold, porcelain, or a special type of composite (contains more filler than normal).
What teeth do dentists usually recommened inlays for?
lost cusps, undergo heavy occlusal forces, too weak for normal restorations.
Is less tooth preparation needed for inlays compared to crowns?
yes
What does a tooth preparation for an inlay include?
same as a conventional filling
the sides must not be undercut they should be parallel.
what is the tooth restored with whilst waiting for the inlay to be constructed?
temporary filling
what is the correct word for cement being dissolved out of a prosthesis?
dissolution.
what are removeable prostheses?
all types of dentures
made in a lab in various stages to replace missing teeth.
the correct word for no teeth left in the jaw:
edentulous
what is the denture replacement for an edentulous patient?
full or complete denture
if some teeth are still present in a patients mouth what denture would be recommended?
partial denture
what are the majority of dentures made out of?
acrylic
reasons why a patient would not be suitable for replacement by dentures:
- any previous denture experience
- is the shape of the patients mouth naturally retentive for dentures
- medical contraindictions
what does acrylic consist of?
polymer (powder) and monomer (liquid)
what is the process of setting acrylic called?
curing
Two common methods of curing?
- heat curing - dentures n ortho appliances by technician
- cold curing - chairside by dentist to make temporary restorations
what are the two main reasons dentures must be retentive?
-speech
-chewing
examples of what the level of retention relies on:
- suction film
-post dam
-accurate design and fit
-natural undercuts e.g. alveolar ridges or roots
-stainless steel clasps
With edentulous patients the alveolar ridge can be adjusted to improve retention and comfort. what are the surgical procedures that do this?
- alveoplasty
- alveolectomy
How many stages are acrylic dentures made in?
4 to 5
what are the 5 stages of dentures?
- first imps
- second imps special trays
- bite registration
- try in
- fit
what are wax bite rims used for?
are adjusted in height so that correct face height of the patient can be recorded.
what are pink wax sheets used for?
addition to the rims if necessary
What is a willis bite gauge used to do?
to record the desired occlusal face height in edentulous patients, where no natural teeth remain as a guide.
Instructions given to a patient when they are provided with dentures:
- demonstration of how to remove
- do not wear overnight - to avoid oral thrush
- store overnight in a pot containing water or soaking agent
- clean after food with denture brush and denture toothpaste
- avoid soaking in bleach based cleansers
Why should dentures not be brushed with normal toothpaste?
too abrasive on acrylic teeth
examples of denture soaking agents:
steradent or dentural
what is a le cron carver used for?
to make fine adjustments to the try in if necessary
How often should an edentulous patient return to the practice for a checkup?
every 2 years
Overtime the alveolar bone changes shape due to loss of teeth, therefore the dentures will not fit forever.
Adhesive denture products:
polygrip
fixodent
Overtime if the patients denture is not fitting correctly what can the dentist recommened?
denture reline
What is denture stomatitis treated with?
antifungal drugs e.g. nystatin, fluconazole and good oral hygiene instructions
Patients who tend to suffer with staining on there dentures are recommended to soak there dentures at night in hypochlorite for 20 mins. however patients who have dentures with metallic components should soak there dentures in what?
non-hypochlorite disinfectants such as dentural
bleach based products will cause metal corrosion
are metal based dentures more difficult than acrylic and why ?
yes
the metal is rigid and provides no room for adjustment once made
advantages of chrome cobalt dentures:
- thinner palatal covering
- overcomes any tissue reaction
- denture base is a lot stronger
what is a skeleton design in chrome cobalt dentures?
partial dentures, giving minimal tissue coverage and making the denture more tolerable for the patient
for chrome cobalt dentures what material should be used?
elastomer with a special tray as it gives a highly accurate impression
what is an immediate denture?
a denture that is fitted straight after an XLA
IMPRESSIONS are took prior xla
with an immediate denture is the patient recommended to wear this for 24 hours after XLA?
yes
Immediate dentures are only constructed from acrylic.
What is the reasoning behind the “spoon shape” technique with 1 tooth anterior dentures?
the gingival margins of other teeth are not covered by the denture, making it less likely to retain food debris around the teeth = more hygienic.
After an immediate denture is fitting how soon should the patient be back for the dentist to check the denture fitting?
next day after xla
How long does it usually take for significant loss of retention after an immediate denture?
3-6 months
Why would relines and rebases be required?
as alevolar bone resorption occurs beneath the denture with time, and the retentive fit is lost = becomes loose
imp and denture sent to the lab
When would a denture addition be necessary?
If a patient has naturally lost a tooth or had an xla and needs the tooth placing as an addition on the denture
imp and denture will be sent to the lab
Tissue conditioners - soft lining:
when the soft tissue beneath the denture are continually sore, so the denture cant be worn routinely without causing great discomfort.
requires a regular replacement every 12-18 months
“BOUNCE”
Tissue conditioners - functional impression:
Material which sets over several hours and therefore records the soft tissues and denture extremities more accurately than conventional impression techniques.
Slow curing acrylic resion e.g. viscogel and core comfort
powder and liquid are mixed together and placed onto the denture, the denture must be worn for 6 hours and the patient must not drink or eat in this time.
Once comfortable an impression of the denture will be sent to the lab and will be replaced with heat cured acrylic.
what are obturators?
specialist removable prostheses provided in the dental hospital
used to seal off an abnormal cavity in the maxilla e.g. due to a cleft palate or space left after significant oral surgery, tumour/cyst removal.
elastomer is used to take an impression
what are overdentures?
full denture that is fitted ontop of standing teeth or retained roots in the dental arch
they reduce the absorption and shrinkage of alevolar ridges that normally occurs after xla.
patients who arent suitable for full dentures, cleft palate or undergone surgical removal of part of their jaw.
dental implants can be used to support an overdenture.
What is a fixed appliance?
composed of individual metal or ceramic components bonded onto each tooth n connected by an archwire.
What is a removeable appliance?
acrylic base with stainless steel clasps, and springs.
remove for cleaning
What are the stainless steel/ceramic components called for fixed appliances?
Brackets
How are brackets bonded to the tooth?
light cure resin material
What is an orthodontic band?
circular metal device on molar teeth
What are orthodontic bands cemented on with?
luting cement
What are ortho archwires made out of?
nickel titanium
stainless steel
Oral health advice for patients with fixed appliances?
- electric toothbrush
-interdental brushes
-fluoride mouthwash
-disclosing tablets
-avoid sticky foods, cariogenic/acidic food/drink
What materials are used in the construction of removeable appliances?
alginate imps
wax bite registration
What 2 models are made from the impressions took in relation to removeable appliances?
study models
working models
What is an Adams cribs used to do?
retain the appliance in the mouth
What are retractors used to do in ortho?
push teeth backwards
What are expansion screws used to do in ortho?
move several teeth outwards
How should removeable appliances be cleaned?
after each meal
toothbrush and toothpaste
What are functional appliances?
specialised type of removable orthodontic appliance, both arches
E.g. twin block
What is the main aim of functional appliances?
correct skeletal class II discrepancies
When are functional appliances suggested?
before the age of 14, after the pre molars have erupted n the mandible is still growing.
What are conventional fixed orthodontics used to treat?
whole dentition
What are short term cosmetic fixed appliances used to treat?
anterior malocclusion
What does interproximal reduction IPR do?
trim and adjust individual tooth widths
What will the dentist carry out for short term cosmetic fixed appliances?
oral, photographic and radiographic assessment
For short term cosmetic fixed appliances what material is used to make the study models?
alginate
For short term cosmetic fixed appliances what material is used to make the second set of imps?
silicone - elastomer
What is the patient provided with/advised to have after short term cosmetic fixed appliances is complete?
fixed retainer
removable soft gum shield - essix retainer
What are retainer like appliances called?
aligners
The working models for aligners are scanned into what program to show what the teeth will eventually look like?
scanned three dimensional into a specialised computer program
What is an implant made out of?
titanium double screw cylinder
Where is the implant inserted?
a hole drilled into the alveolar bone of either jaw to replace missing teeth.
What does osseointegration mean?
alveolar bone gradually grows around the screw, so that it becomes locked in the bone.
How long does osseointegration take to occur?
several months
The crown can only be placed on top of the implant once the implant is firm in the bone.
What surgical procedure may need to be completed before insertion of an implant, when the floor of the antrum is close?
Sinus lift
What medical conditions may prevent a patient from having implants?
diabetes, osteoporosis, haemophilia
What is peri-implantitis?
inflammation of the gingival soft tissues due to the Prescence of plaque around the implant
What can happen if a patient has peri-implantitis?
the implant will become loose and fall out
