Year 3 Flashcards
What is Kennedy class I saddle
Bilateral distal extension saddle
What is Kennedy class II saddle
Unilateral distal extension saddle
What is Kennedy class III saddle
Unilateral bounded saddle
What is Kennedy class IV saddle
One saddle which crosses mid-line anterior to remaining teeth
What is Craddock class I saddle
Tooth supported
What is Craddock class II saddle
Mucosal supported
What is Craddock class III saddle
Tooth and mucosal supported
What are 6 ideal features of indirect retainers
- Be rigid
- Prevent rotation of the denture
- Not interfere with the occlusion of the patient
- Be readily tolerated by the patient
- Prevent food packing
- Be placed as far as possible from the rotation point
What are 4 features influencing a clasps resistance to deformation
- Length of the clasp arm
- Diameter of the clasp arm
- Cross-sectional form of the clasp
- Type of alloy of the clasp
Where should a indirect retainer be placed
Anterior to the axis of rotation
2 types of occlusally approaching clasps
Circumferential clasps
3-arm clasps
3 types of gingival approaching clasps
T-bar
Reverse L-bar
I-bar
5 ideal features for connectors
- Cover the minimum area compatible with strength
- Be rigid enough to prevent flexure
- Prevent food packing
- Be readily tolerated by the patient
- Not cover the gingival margins
How much free space is required from the gingival margins for lower connectors
Minimum of 2 mm from gingival margins
How much free space is required from the gingival margins for upper connectors
Minimum of 5 mm from gingival margins
Name 4 upper connectors
Palatal plate
Palatal strap
Skeletal
Horseshoe
Name 5 lower connectors
Lingual bar
Sub-lingual bar
Lingual plate
Dental bar
Labial bar
5 benefits of replacing teeth
Aesthetics
Speech
Mastication
Maintenance of dental health
Physiological benefits
4 means of replacing teeth
Removable prostheses
Fixed prostheses
Implants
Orthodontics
4 benefits to oral health by replacing teeth
Maintain stability of the remaining dentition to prevent over-eruption and drifting
Reduce risk of tooth wear
Provide adequate masticatory function
Reduce risk of TMD or TMJ pathology
4 structures to record in preliminary impressions
All surfaces of all teeth
All of the palate back to junction of hard and soft palate
Bounded saddle areas: alveolar ridge, full depth of buccal, labial, lingual sulci
Distal extension saddle areas: hamular notch (upper), 2/3 retromolar pad (lower), full functional depth and width of buccal, labial, lingual sulci
How to record a preliminary impression
Select an impression tray with sufficient extension
Customise tray with compound to record palatal surface and distal extension
Add adhesive to tray and allow to dry
Add handle to tray
Load tray with aliginate
Take impression
Disinfect impression
Describe the jaw relationship to which you would restore a patient requiring a partial denture when using the conformative approach to occlusal rehabilitation
Intercuspal position (ICP) /centric occlusion
3 benefits from changing the path of insertion
- Improve aesthetics
- Improve retention
- Avoids interferences from large undercuts
Describe the jaw relationship to which you would restore a patient requiring a partial denture when using the reorganised approach to occlusal rehabilitation
Retruded contact position (RCP)
What is path of insertion
Path followed by denture from first contact with teeth until fully seated
What is path of displacement
Direction in which the denture tends to be displaced in function which is assumed to be at right angles to the occlusal plane
7 functions of guide planes
Horizontal stability
Increased retention
Reciprocation
Prevention of clasp deformation
Prevent food packing
Definitive path of insertion
Improved aesthetics
Describe 2 reasons for rest seat preparations
Provide more suitably inclined bearing surface for the occlusal rest
Provide space between the occlusal surface of the upper and lower teeth to allow a rest of adequate thickness and strength to be used
6 functions of occulsal rests
- Transmits vertical load along the long axis of the tooth
- Prevents horizontal movements
- Maintains saddle/clasps components in correct position so that they don’t sink toward the mucosa
- Deflects food impaction
- Prevents tooth over eruption
- Improves occlusion by restoring occlusal tooth contacts and avoid premature occlusion
2 materials used for master impressions
- Polyvinylsiloxane type II medium viscosity
- Alginate
4 common faults that may occur in an impression
- Tray not in correct position: not seated fully or tray offset
- Impression material already set before seat or removed too early
- Tray extension errors: under/over
- Voids /defects due to air, debris, saliva, blood, drags, insufficient
Dimensions required for mid-palatal strap
0.5mm thick x 15 mm wide
Dimensions required for acrylic plate connector
2mm thick
Dimensions required for palatal plate
0.5-0.6mm thick
Dimensions required for skeletal connector
0.75mm thick
Dimensions required for lingual bar
> 8mm: 2mm clear of gingival margin, 2mm clear of floor of mouth, 4mm bar width
Dimensions required for sub-lingual bar
5mm: 2mm clear of gingival margin, 3mm bar width
Dimensions required for lingual plate
< 4mm
Undercut dimensions required for colbalt-chrome clasp
0.25mm
Undercut dimensions required for gold alloy clasp
0.5mm
Undercut dimensions required for wrought clasp
0.75mm
Suggest 10 possible oral health risks associated with RPD wear
Caries
Abrasion of teeth with clasp
Fracture of restorations
Inflammation of periodontal ligament
Tooth mobility
Gingival inflammation
Denture-induced stomatitis
Denture-induced hyperplasia
Possible increase of resorption of alveolar bone
Muscles of mastication dysfunction
Describe how wax occlusal registration rims are modified
Try in wax occlusal registration rims and ensure no overextension of borders and reduce as necessary with wax knife
Ask patient close into maximum intercuspation with the wax rims in position and trim wax rim with hot plate and wax knife until no contacts remain and there is 2 mm space apparent between wax and opposing teeth
Outline the 3 different physical processes that produce gypsum product and give each product their common name
Heated in open oven 115 - 120c forms b-hemihydrate plaster of Paris
Heated in autoclave under steam pressure 120 - 130c forms hydrocal
Boiled in 30% calcium chloride forms improved dental stone (densite)
What are the 3 pieces of advice should be given with new RPD’s
Oral and denture hygiene instruction
RPD care and maintenance instruction
New dentures nearly always cause some discomfort and that they will feel awkward to start
What are the oral/denture hygiene instructions given to patients after receiving RPD
No night wear
Regular cleaning
Soaking dentures in a suitable cleaner - never use sodium hypochlorite on metal dentures
What 4 ways can you optimise support when designing RPD’s
- Occlusal rests
- Occlusal onlays
- Embrasure hooks
- Denture base
What is support
Resistance to the vertical load applied to prosthesis during function
Describe how to prepare a mesial rest seat on a lower molar tooth
Use round diamond bur to cut occlusal rest of about one half of the bucco-lingual cusp-cusp width and one third of the mesiodistal width of the tooth
Describe how and where you would prepare a guide plane on a premolar tooth when using a vertical POI
Use straight bur about to cut guide plane of about 2mm surface area at survey line to create parallelism
5 things to do when assessing a newly produced denture framework
Ask patient if it feels comfortable
Check that the partial denture seats completely
Check retention and stability and ensure that clasp tips are activated
Check denture appearance at rest and smiling
Check occlusion
How to respond when patient believes denture is loose
Check that clasp tips touch the tooth surfaces as designed and adjust as necessary
Reassure that dentures with distal extension saddles may feel especially loose until muscular control is gained and an improvement occurs
Advantages of lingual bar
Covers minimum surface area of teeth and tissue
Relatively small, minimally interferes with functions
Disadvantages of lingual bar
Not as rigid as the lingual plate or sublingual bar
Requires minimum 8mm space
What is the preferred choice of impression material for master impressions and 4 reasons why
Polyvinylsiloxane type II medium viscosity
1. Allows for highly accurate impression
2. Good dimensional stability
3. Good tear resistance
4. Impressions may be repoured
4 differences between tooth and mucosal supported
Directed down long axis to PDL rather than directly to alveolar bone
Via occlusal rests placed on natural teeth rather than via saddles and mucosa
Craddock classification I rather than II
Different casting technique as altered cast technique can be used for mucosal supported dentures
4 ways in which clasp retainers can be attached to a denture base
Laser welded
Embedded
Soldered
Incorporated
Which lower distal extension saddle denture design feature dictates using a vertical POI
RPI system
4 situations where it is most appropriate to use alginate for master impressions
Gross undercuts (tilted teeth)
Large interdental spaces between contiguous teeth
Periodontally involved teeth: gross recession, mobile teeth
Patients with poor tolerance/compliance of impressions in general
Which Kennedy class has no modifications and why
Kennedy IV because when classifying dentures always start at most posterior missing tooth
Requirement for a shortened dental arch
At least 2 posterior occluding units either side
5 requirements for an impression tray
Be rigid in use
Have sufficient extension to support an impression of all structures
Incorporate occlusal stops
Have a robust, preferably integral handle
Be capable of withstanding autoclave or be single use
What 3 features of dentures are likely to cause premature contact
Occlusal rests
Clasp shoulders
Major / minor connectors
What material are master casts poured in
Improved dental stone (densite) high strength type 4
4 benefits of occlusal rather than gingival clasps
Provides bracing
Reduced caries risk especially if root cementum exposed
Better for gingival health
Better tolerated
A benefit of of gingival rather than occlusal clasps
Better aesthetics as can tuck into an anterior distal u/c
What is reciprocation
Resistance to displacing forces in the lateral direction on abutment teeth when clasps move up and over the maximum bulbosity
What is bracing
Resistance to displacing forces in the horizontal direction when the denture is fully seated
3 reasons RPD’s must be designed on articulated casts
Allows visualisation of space available between the dental arches
Prevention of premature occlusion with: clasps, rests, connectors
Ensure tooth-tooth centric occlusal stops are maintained
Give 3 examples of dental application of different curing (activation) methods
Visible light activation: light 470 nm releases free radicals e.g. composite resin, triad tray material
Heat activation: > 650C benzoyl peroxide decomposes to release free radicals e.g. heat-cured methylmethacrylate denture base material
Chemical activation: chemical activating agent acts on benzoyl peroxide to release free radicals e.g. auto-polymerisation acrylic for orthodontic plate or denture repair materials
Advantages of sub-lingual bar
Rigid
Well toleranced
Good aesthetics
Requires only 5mm
Disadvantages of sub-lingual bar
Requires border molded impression of floor of the mouth
Not compatible with prominent lingual frenal attachments
What is direct retention
Components used to prevent displacement
What is indirect retention
Components that change the axis of rotational displacement and make clasps operate as intended
7 clinical stages in RPD construction
Preliminary impressions for production of study casts
Recording occlusal/jaw relationships for articulation of study cats
Master impressions for working casts
Castings trial, occlusal/jaw relationship records
Trial prosthesis
Insertion
Review
3 functions of preliminary impressions
Allow study cast production
Assess the occlusion
Enable custom tray construction
4 tooth modifications required prior to taking master impressions
Rest seat preparation
Guide planes
Survey line reduction
Undercut augmentation
2 ways to provide undercut augmentation
Composite: added to tooth to augment and create an undercut which would allow correct positioning of a clasp
Indirect restorations: design restoration with augmented undercuts
What 4 things are assessed at castings trial
Prescription was followed and is correct
Denture fit
Position of components
Occlusion
4 reasons study casts are surveyed
Identifies optimum path of insertion: for appearance, retention
Identifies guide planes
Allows design, material selection and positioning of clasps
Allows blocking out of unwanted undercuts
4 surveyor tools
Analysing rod
Carbon marker
Trimmer
Undercut gauge
3 components of the RPI system
Mesial rest
Distal proximal plate
GAC I-bar to mid-buccal convexity
7 things to check in trial dentures
Aesthetics
Tooth position
Occlusion
Polished surfaces
Mould
Shade
Flange
