Prosthodontics Flashcards
What 5 factors are associated with retention?
Gravity
Mastication
Tongue
Active
Speech
What features should be taken in a maxillary impression?
Maxillary tuberosity
Hamular notch
External anterior vibrating line
Functional depth and width of sulcus
What is the primary support of a maxillary denture?
Hard palate
What features should be taken in a mandibular impression?
Pear shaped pads
Buccal shelf
Retromolar pads
Extension into lingual pouch
What is the primary support in a mandibular denture?
Buccal shelf
Pear shaped pad
What is the posterior border of the maxillary denture?
1-2mm anterior to the vibrating line and palatine fovea
What materials can be used for a primary impression?
Impression compound
Alginate
What materials can be used for secondary impressions?
ZOE
Silicone
Alginate
What is balanced occlusion?
Simultaneous bilateral contacts when static
What is balanced articulation?
Continuous simultaneous contacts during excursive movements
What is the neutral zone?
Stable position
Equilibrium between soft tissues and tongue
What is Christensens phenomenon?
Dissocclusion of posterior rim when mandible protrudes
What are the Cawood and Howell Classification (1-6)?
1; pre-extraction
2; post-extraction
3; rounded
4; knife edge
5; flattened
What is occlusion? (Academy of Prosthodontics)
The static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues.
What is intercuspal position (ICP)?
The complete intercuspation of the opposing teeth independent of the condylar position.
May be referred to as the best fit of the teeth regardless of condylar position.
What is retruded contact position?
Guided occlusal relationship occurring at the most retruded position of the condyles in the joint cavities
What are index teeth?
Contacting facets of teeth in the intercuspal position
What are the features of intercuspal position?
Needs sufficient index teeth
Stable occlusion
May vary through life
Depends on tooth relationship
Sometimes more anterior than RCP
What are the features of retruded contact position?
Insufficient index teeth
Unstable occlusion
Most reproducible position
Is a condylar position
Sometimes more posterior than ICP
What occlusion is usually used when conforming the occlusion?
ICP
What occlusion is usually used when changing the occlusion?
RCP
When would you conform the occlusion?
Stable condition with sufficient index teeth
When would you change the occlusion?
Unstable occlusion with lack of sufficient index teeth
What can be used to articulate study casts?
Inter-occlusal record
What are three ways of recording an interocclusal record?
Bite registration paste
Wax wafer
Modified wax wafer (alminax)
What can be used to articulate study casts when there is insufficient teeth?
Record blocks
What are four types of record block?
Wax
Wire strengthened
CoCr Base
Shellac base
What is used to modify a record block?
Hot plate/ Bunsen Burner and Wax knife
Bite registration paste
What are options that can be used to solve denture design problems?
Modification of survey lines
Precision attachments
Two part denture
Swinglock denture
Connector for lingually tilted teeth
How can we modify survey lines?
Using composite
Why would we modify survey lines using composite?
To give more favourable clasping and improve denture retention
Where can you find the different types of precision attachments?
Cendres et Metauc catalogue
What are precision attachments made uo out of?
Socket in denture for ball
Lock for the tube
When would a two part denture be used?
Gross tissue loss and different paths of insertion
What is a two part denture formed of?
Split pins on cobalt chrome denture
Acrylic slots into pins on different path of insertion
What does a swinglock denture consist of?
A lock and a hinge
What are the benefits and drawbacks of a swinglock denture?
Engages bone and tissue undercuts for retention
Good oral hygiene is essential
Technically demanding
What are the options for a connector for lingually tilted teeth?
Lingual tilt
Buccal bar
What alterations can be made for dentures in bruxism patients?
Metal backing to teeth
Cobalt chrome to reduce fracture
Metal occlusal surfaves
Use of cross-linked teeth for better wear resistance
Acrylic post dam to increase retention
What is retching?
Physiological mechanism
Involuntary contraction of the muscles of the soft palate or pharynx
What part of the brain is associated with retching?
Higher centres in the medulla oblongata
What are the two types of retching?
Psychogenic
Somatic
What is psychogenic retching?
Occurs by sight, smell, sound or thought
What is somatic retching?
Occurs by touching trigger zones
What are examples of trigger zones in retching?
Palatoglossal fold
Palatopharyngeal fold
Base of tongue
Palate
Uvula
Posterior pharyngeal wall
When can retching lead to difficulties in prosthetics?
Impression taking
Jaw registration
Toleration of dentures
Denture retention (palate may be reduced)
How can you manage a retching patient?
Identification of problem
Identify trigger zones
Anxiety reduction
Patience and empathy
What are passive relaxation techniques?
Dim lighting
Music
Avoid sight of dental instruments
What are active relaxation techniques?
Controlled rhythmic or relaxed abdominal breathing
What are examples of desensitisation techniques for retching patients?
Repeated brushing or stroking anterior palate or tongue with finger/toothbrush
‘Homework’ of brushing/stroking for patient pre-treatment
Swallowing with mouth open
What are examples of distraction techniques for retching patients?
Talking to patient
Getting patient to concentrate on keeping their leg raised/wiggling toes
Get patient to press or tap their temple
Put salt on the tongue
Ask patient to close eyes
Rinse mouth with very cold water just before treatment
What are examples of additional complementary treatments to accompany desensitisation?
Hypnosis
Acupressure
Cognitive Behaviour Therapy
What does the MAGIC technique stand for?
Main Amelioration of Gagging Indoctrination by Communication
Explain the process of the MAGIC technique:
Patient fills their lungs completely with air
Sends a strong message from lung stretch receptors to the medulla oblongata that there is plenty of air and no risk of choking or aspiration
Psychogenic gage reflex is subverted
What modifications can be made during impression taking for retching patients?
Modify stock trays
Lower trays in upper arch
Modify special trays: palatal reduction
Use of rapid setting impression materials: dental composition, alginate mixed with warmer water
What modifications can be made during denture design for retching patients?
Shortened dental arch
Horseshoe palate
Use of buccal bar connector
Use of CoCr rather than acrylic
Use of ‘essix’ retainer denture
Use of a training plate
Multiple post dams
Denture well adapted to tissues
Why opt for multiple post dams in a retching patient?
Postdams provide pressure to palatal tissue that is helpful in reducing retching
How can you provide a denture well adapted to tissues for a retching patient?
Palate not too thick
Cusps of posterior teeth may need to be rounded so they do not stimulate dorsum of the tongue
Consider no 2nd molars on prosthesis
According to Carlsson, what proportion of patients are dissatisfied with their dentures?
10-30%
What factors lead to patient’s dissatisfaction with their dentures?
Lack of retention and stability
Disconnect between patient and clinician expectations
Reduced self esteem due to wearing a denture and negative impact on socialisation
Facial aesthetics changed due to tooth loss
Decreased chewing efficiency
What factors contribute to effective communication with pros patients?
Listen to patient ]
Know your subject
Avoid jargon
Be attentive
Answer questions
Respect confidentiality
Be empathetic
What are key questions to ask a patient in the initial assessment for dentures?
How long ago were your teeth removed?
How many dentures have you had since you lost your teeth?
How old is the last denture you had made?
Are you wearing the last denture you had made?
What features should you pay attention to when examining and palpating the denture bearing area?
Severely resorbed ridges
Flabby ridges
Tori
Prominent mentalis muscles, mylohyoid ridges, genial tubercles
High muscle attachments
Pain on ridge palpation
What are some key statements that can be used to manage pros patient expectations?
I’m sorry to say that you may never be able to wear a denture that meets all your expectations to your complete satisfaction
Unfortunately, it is highly unlikely that you will ever feel that your denture is as firm as your natural teeth
You are going to need much perseverance in trying to cope with your dentures and it is likely that it will be a very difficult time for you
What is a dental implant?
An artificial tooth root that is surgically anchored into the jaw to hold a replacement tooth or teeth in a denture in place.
What is the benefit of implants?
They do not rely on the neighbouring teeth for support
What can an implant restore?
A single tooth
Multiple teeth
Can secure a denture firmly
What are the four stages for placement of an implant?
Raise flap
Place implant
Place cover screw
Suture
What are the 6 stages for placement of an single tooth implant?
Uncover implant
Place abutment
Take impression with coping
Choose colour
Place temp
Cast impression with lab dummy
What are the two methods of retention for multiple teeth implants?
Cement retained
Screw retained
What type of abutments can be used in securing implant retained dentures?
Locator abutments
Ball adjustments
Gold bar
CAD-CAM titanium bar
Novaloc abutment
Magnetive retention
What are common post implant treatment complications?
Peri-implant mucositis
Peri-implantitis
Loose/fractured components
Late implant failure
What is the role od the GDP in implant patients?
Oral health advice
Triage and diagnosis (if possible) of a complication
Referral of the complication to an appropriately trained, indemnified and competent implant dentist
Manage taking account of SDCEP guidelines
What are the SDCEP guidelines in regard to maintenance of dental implants?
Ensure the patient is able to perform optimal plaque removal around the dental implants
Examine the peri-implant tissues for signs of inflammation and bleeding on probing and/or suppuration and remove supra- and submucosal plaque and calculus deposits and excess residual cement
Perform radiographic examination only where clinically indicated
What is peri-implant mucositis?
Inflammation of the peri-implant mucosa with no evidence of crestal bone loss. The tissues will appear red and swollen and may bleed on gentle probing
How can you tell whether a patient has peri implant mucositis or peri-implantitis?
Radiographic examination to assess peri-implant bone levels compared with baseline radiograph
What is peri-implantitis?
Infection with suppuration and inflammation of the soft tissues surrounding an implant, with clinically significant loss of peri-implant crystal bone after the adaptive phase.
The tissues will appear red and swollen, may bleed on gentle probing and there will be suppuration
How is peri-implantitis managed?
Refer patient back to the clinician who placed the implant
Arrange a follow up appointment 1-2 months after, if no improvement seek advice from secondary care
If the inflammation has settled and stabilised, arrange radiographic follow up in 6-12 months
What is the effect of the presence of natural lower teeth and a complete upper denture?
High forces can be developed against the upper maxillary edentulous ridge leading to trauma and instability of the dentures
What is the effect of abuse of the soft tissue in the denture bearing area?
Mucous membrane damage
Ulceration and discomfort
What is the effect of trauma to the maxillary denture bearing area?
Abuse of soft tissues
Alveolar resorption and fibrous tissue replacement
What is the effect of alveolar resorption and fibrous tissue replacement?
Fibrous or flabby ridge
What does combination syndrome consist of?
Bone loss from the anterior part of the maxillary ridge
Hypertrophy of the tuberosities
Papillary hyperplasia in the hard palate
Extrusion of the mandibular anterior teeth
Bone loss under the denture base
How can you reduce trauma to the maxillary denture bearing area?
Maximise coverage of the denture bearing area by the prosthesis
Ensure prosthesis covers the primary load bearing sites
How can we optimise stability of the maxillary denture?
Optimum border seal
Effective post dam
How can we optimise loading of the denture bearing area?
Use of over denture abutments
What factor can lead to instability of the maxillary denture?
Absence of lower posterior teeth
Incisor overbite
Irregular occlusal plane
How can we manage an incisor overbite in patients with a complete upper denture?
Reduction of the incisor edges of natural teeth
Siting of the denture teeth
How can you manage irregular occlusal planes of natural lower teeth with a complete upper denture?
No adjustments
Minimal localised occlusal grinding
Radical occlusal adjustment
Extraction of teeth
Overlay appliances
What alteration can be made for complete lower denture and upper natural teeth?
Soft linings
Implants
What does a face bow do?
Transfers the relationship between the maxillary teeth and the axis of mandibular rotation
What is the sagital condyle guidance angle?
Condyle during protrusion to horizontal plane
What is the aim of a jaw registration?
Determines inteemaxillary relationship in RCP
What is the aim of boxing in?
Preserving the functional width and depth of the sulcus
What does LIMBO stand for?
Lip support
Incisal level
Midline
Buccal corridor
Occlusal plane
What are the limiting structures in the maxillary arch?
Labial frenum
Labial sulcus
Hamular notch
Buccal frenum
Buccal sulcus
Vibrating line
What is the primary supporting structure in the maxillary arch?
Hard palate
What are the secondary supporting structures in the maxillary arch?
Rugae
Maxillary tuberosity
What are the relief areas of the maxillary arch?
Incisive papilla
Crest of alveolar ridge
Palatine raphe
Palatine fovea
What are the limiting structure of the mandibular arch?
Labial frenum
Labial sulcus
Retromolar pads
Lingual frenum
Buccal frenum
Buccal sulcus
Alveololingual sulcus
What are the supporting structure of the mandibular arch?
Buccal shelf
Residual ridge
What are the relief areas of the mandibular arch?
Mylohyoid ridge
Mandibular tori
Genial tubercle
What is the aim of a complete denture?
Adequate masticatory function
Restore natural appearance
Restore normal speech
Comfort and preservation of supporting structures
What are the parts of a complete denture?
Denture base
Flange and border
Teeth
What are the surfaces of a complete denture?
Fitting surface
Polished surface
Occlusal surface
What are the factors affecting retention of a complete denture?
Physical
Anatomical
Physiological
Mechanical
What are the physical factors of retention?
Adhesions
Cohesion
Atmospheric pressure
Gravity
What is adhesion?
Forces of attraction between different molecules
Saliva and base
What is cohesion?
Forces of attraction between same molecules
Saliva and saliva
What is atmospheric pressure in regard to denture retention?
Hydrostatic pressure due to weight of world
What is the role of gravity in denture retention?
Works against the upper
Works for the lower
What are the anatomical factors of denture retention?
Shape of edentulous area
Undercuts
Anatomy of border areas
What are the physiological factors of denture retention?
Neuromuscular control
Viscosity and volume of saliva
What are the mechanical factors of denture retention?
Balanced occlusion
Contour of polished surface
Position of occlusal plane
Position of teeth in respect to ridge
What is balanced occlusion?
Bilateral simultaneous anterior and posterior occlusal contacts in centric and eccentric position
What features of the contour of the polished surface improve retention?
Contoured and harmonious with oral surface
Where should lower posterior teeth be positioned in respect to the ridge?
Lower posteriors directly above lower ridge and in neutral zone
What materials should a primary impression be taken with?
Alginate
Impression compound
What materials should a master impression be taken with and what is the spacer width?
Alginate (3mm)
Silicone elastomers (3mm/0mm)
Zinc oxide Eugenol (0mm)
What materials should a master impression be taken with and what is the spacer width?
Alginate (3mm)
Silicone elastomers (3mm/0mm)
Zinc oxide Eugenol (0mm)
What are the four features of RPD design?
Support
Retention
Reciprocation
Indirect Retention
What is the definition of support?
Resistance to occlusal directed forces
What is the definition of retention?
Resistance to vertical displacement
What is the definition of reciprocation?
Resistance to retentive (lateral movement)
What is the definition of indirect retention?
Resistance to rotational displacement
What are examples of common denture fractures?
Midline
Tooth detaches from denture base
Loss of flange
Acrylic saddle detaches from Co/Cr baseplate
Clasp fracture/bent
What are the causes of denture fracture?
Impact
Acrylic thin in section
Work hardening of metal
Parafunctional habits
Occlusion- deep overbite
Soft linings
Denture processing problem- porosity
Bonding between tooth and base or acrylic and CoCr
How can a simple repair of a denture be carried out?
If fractured pieces can be located together, disinfect and send to lab (no impression needed), cast poured, fractured area removed, new acrylic processed
How is a denture repaired when a part is missing?
Impression taken with fractured denture in mouth
Disinfected
Cast poured and new acrylic processed into defect
How is the loss of an acrylic tooth managed?
Rebonded if tooth is there
If repeat failure, determine why,, may need to redesign denture
What are examples of other repair methods?
May need to add retentive tags
Solder on tags and/or use 4-META or silicone CoCr to retain acrylic on Co/Cr
What are examples of materials that can be used for temporary denture repair?
Self-cure acrylic
Cyanoacrylate glue
Usually chairside
What are examples of strengtheners that can be used in denture repairs?
Wire mesh
Glass fibre mesh
Stainless steel
What are the types of denture additions?
Immediate addition
Post immediate addition
Retention
What is an immediate addition?
When a tooth is lost after denture construction and a tooth is added on the day of tooth extraction
What is a post immediate denture addition?
When a tooth is lost after denture construction and at a later date a tooth is added
What is a retention addition?
When denture retention is inadequate a clasp is added to try and improve retention
What are the clinical issues with denture additions?
Usually requires an impression of the arch with the denture in the mouth during the impression
Can sometimes do chairside addition in self-cure acrylic (often temporary)
When is an addition to a Co/Cr denture more difficult?
Lingual bar connector
What is the issue with addition to a flexible denture?
Virtually impossible due to weak bonding between tooth and nylon and has short term longevity
What is the powder component of acrylic?
Polymer: PMMA beads
Initiator: benzoyl peroxide (0.5%)
Pigments; salts of Cd/Fe or organic dyes
What is the liquid component of acrylic?
Monomer; MMA
Cross linking agent; ethyleneglycoldimethacrylate (10%)
Inhibitor; hydroquinone
Activator- only in self cure - N,N’ dimethyl-p-toluidine
How much does the monomer shrink when processing acrylic?
21%
What is the ratio of powder to liquid in acrylic and what does it reduce shrinkage by?
P:L 2.5:1
Reduces shrinkage by 5-6%
What are the stages of processing acrylic?
Sandy
Stringy
Dough
Rubbery
Hard
What are the advantages of acrylic?
Cheap
Easy to add or reline or repair
Technically easier to make
Aesthetic
What disadvantages of acrylic?
Low impact resistance
Poor resistance to fracture fatigue- needs to be thick
Poor impact strength- needs to be thick
Water absorption and candida growth
Allergy to residual monomer
Denture whitening (alterations in microstructure)
Risk to technician
When can dentures be hand articulated?
Lots of remaining teeth
No open ended saddles
When can dentures not be hand articulated?
Few remaining teeth
Bilateral open ended saddles
What are the stages in making chrome dentures that can be hand articulated?
Primary impressions
Master impressions
Framework trial
Tooth trial
Finish
What are the stages in making chrome dentures that can’t be hand articulated?
Primary impressions
Primary jaw registration
Master impressions
Framework trial
Record blocks on framework
Tooth trial
Finish
What are the stages in making acrylic dentures that can be hand articulated?
Primary impressions
Master impressions
Tooth trial
Finish
What are the stages in making acrylic dentures that can’t be hand articulated?
Primary impressions
Master impressions
Jaw registration
Tooth trial
Finish
What are the stages in making an immediate acrylic denture?
Primary impressions
Finish
How do inlays and crowns work?
Preserve tooth by protecting from fracture and wear
Controls loads on teeth, provides stable occlusal contacts
Protects axial walls from stress
Protects teeth in tooth wear cases
What are the basic principles of onlays and posterior crowns?
Caries removal
Keep as much sound tooth tissue
Maintain pulpal and periodontal health
Restore form and function
Longevity
Aesthetics
Occlusal stability
Must be cleanable
Thorough case assessment
What are the material options for a posterior crown?
Precious metal
Non-precious metal
Zirconia
Metal ceramic
Lithium dislocate
What are the material options for a posterior only?
Precious metal
Non-precious metal
Zirconia
Composite
Lithium disilicate
Describe the benefits of an onlay?
Indirect restoration
Less destructive than a crown
Cuspal coverage
Height of cusps need reduced
Supragingival margins
Access for sensibility testing
Describe the drawbacks of an onlay?
Retention/resistance issues
Technical challenges
Aesthetic challenges
When is an onlay indicated?
Toothwear
Restoration of some RCT teeth
Failure of direct restorations
Fractured cusps
What are the guidelines for onlay prepararation?
Even width shoulder irrespective of material
Follow the slopes of visible cusps
What are the benefits of a posterior crown?
Indirect retention
Retention/resistance often better
Easier technically
Aesthetically sound (if tooth coloured)
Covers all cusps
What are the disadvantages of posterior crowns?
More destructive than an only
Often suubgingival margins
Cannot access for sensibility testing
Need a sound crown core
When is a posterior crown indicated?
Toothwear
Restoration of heavily restored RCTd teeth
Failure of large direct restorations
Fractured cusps
Aesthetic- if tooth coloured
What factors are needed when treatment planning for a posterior crown?
Up to date acceptable radiograph
Tooth history
Dental disease status- tooth and mouth
Importance of tooth to dentition
Tooth restorability
Relationship to other teeth
Occlusal factors
Patient expectations
Human factors- anxiety, mobility, costs
Medical/social history
What is the impact of retention grooves in a tooth wear case needing crowns?
Enhances crown retention with high loads
What does a metal margin in a MCC do?
Conserves tooth
Why may anterior teeth require crowns?
Extent of caries and restoration
Trauma
Following RCT
Failure of direct restorations and/or veneers
Aesthetics
Why may you need to exercise caution with anterior crowns?
Uncontrolled caries and periodontal disease
Tooth wear
Smilorexia/unrealistic expectations
Previous failure
Heavily restored mouths
Age (old and young)
Cost
What are examples of types of anterior crowns?
Metal ceramic
Lithium disilicate
Zirconia
Feldspathic porcelain
What is the strength of zirconia like?
Very strong
Good for posteriors
What are the aesthetics of zirconia?
Good
Less translucent
What is the preparation of a zirconia crown like?
Least reduction
What is the durability of zirconia?
Very durable
Highly resistant to wear
When is zirconia most suitable?
Higher forces
Posterior teeth
What is the strength of lithium disilicate?
Strong
Not as strong as zirconia
What are the aesthetics of lithium disilicate like?
Excellent
Close to natural teeth
What is the preparation of lithium disilicate like?
More reduction than zirconia
What is the durability of lithium disilicate?
Less durable than zirconia
When is a lithium disilicate crown most suitable?
Optimal aesthetics
Anterior teeth
What is the strength of metal ceramic?
Very strong
Anterior palatal metal
What is the aesthetics of metal ceramic crowns like?
Excellent
Less translucent than LiDiSi
What is the preparation for a metal ceramic crown in comparison to other anterior crown options?
Most reduction
What is the durability of a metal ceramic crown?
Very durable; issues with porcelain fracture
When would a metal ceramic crown be most suitable anteriorly?
Higher forces- tooth wear in anteriors and posteriors
What are the principles of tooth preparation in crown preparation?
Preservation of tooth structure
Retention and resistance
Structural durability
Marginal integrity
Preservation of the periodontium
Aesthetic considerations
What should be considered in regard to tooth substance removal in anterior crowns?
Appropriate but not excessive
Follow anatomical form
Take account of closeness of pulp to incisal (look at radiographs), parafunction, occluso-gingival height and aesthetics
Material dependent
What is the impact of under preparation of crowns?
Aesthetic problems- opacity
Periodontal problems- emergence and inflammation
Result- biological and aesthetic failure
What is the preparation for an anterior metal ceramic crown?
Shoulder labially
Chamfer lingually
1.5mm labially
2mm incisally
How can you maintain consistency in tooth preparation?
Correct visualisation
Silicone index
VFR stent or similar
Depth gauge bur
Post cementation critical reflection for learning
What may an inter-occlusal record be made of?
Wax
Reinforced wax
PVS jaw registration paste
Record blocks
What issues can occur when shade taking?
Colour washout
Illuminate metameric failure
Observer metameric fails
