Prosthodontics Flashcards
What are the general statistical trends for tooth loss, in Scotland?
More teeth are lost with age
More teeth are lost in more deprived areas, than less deprived areas
What are the 4 main impacts of tooth loss for the individual?
Mastication and speech
Pain/discomfort
Appearance/self-esteem
Social interactions
What are the 6 main reasons for tooth loss?
Congenitally missing Trauma Periodontal disease Caries Pulpal disease Other pathology
What is the typical pattern for tooth loss?
Lost either singly or in small groups
A partially dentate state may last many years and never progress to edentulism
What are examples of congenital disease that can lead to tooth loss?
Hypodontia
Ectodermal dysplasia
Cleft lip and palate
Why can periodontal disease lead to tooth loss?
Loss of periodontal ligament support, and so loss of anchor into the gomphosis
How does pulpal disease cause tooth loss?
Originates from infection
Dendritic cells differentiate into osteoclastic-like cells that resorb the dentine
What other examples can cause tooth loss?
Cancer treatment
Ameloblastoma in the mandible
What is the definition of a shortened dental arch?
A reduced dentition primarily resulting from the loss of mailar teeth with the aim of preserving a functional dentition for long-term use
What are the prerequisites for a shortened dental arch?
20 or more functional opposing teeth
Including anterior teeth
At least 4 occlusal units
Name different types of occlusal units and there values?
1 unit = occluding premolar
2 units = occluding molars
What are the pros and cons for a shortened dental arch?
Pros:
- adequate chewing
- aesthetics not significantly compromised
- tooth migration may occur but stability is maintained
- TMJ healthy
- no change in wear
- avoid use of potentially damaging partial dentures
What are the 3 main factors for damage to the oral cavity with a partial denture?
Biological
Direct trauma
Mechanical effects
Explain how biological damage can a partial denture cause?
Dental plaque:
- increase caries and perio as they are plaque traps
Explain how direct trauma can a partial denture cause?
Acrylic engages into the embrasure spaces for stability, resistance and retention
Can lead to accelerated alveolar bone loss and recession
Otherwise known as ‘gum stripping’
What is the definition of an extra-coronal restoration?
One that which is outside or external to the crown portion of a natural tooth
(sits over remaining tooth structure)
Name 3 types of extra-coronal restorations?
Full coverage gold shell crown
Ceramic crowns
Gold inlay onlay
Name the 4 different types of indirect extra-coronal restorations?
Veneer
Onlay
Partial coverage crown
Full coverage crown
What is the definition of a veneer?
A thin sheet of material used to finish or protect an ornamental facing. It is a superficial or attractive display with many layers
What is the definition of a onlay?
Partial coverage restoration that restores one or more, cusps and the adjoining occlusal surface, and is retained by mechanical or adhesives means.
What is the definition of a partial coverage crown?
An artificial replacement that restores missing tooth structure, surrounding the remaining structure with a dental material. Retained by mechanical or adhesive means
What is the definition of a full coverage crown?
An artificial replacement that restores missing tooth structure, covering the full coronal surface of with tooth with a dental material. Mechanical or adhesive means
What are the main reasons for the use of a indirect extra-coronal restoration?
Support for remaining tooth tissue in broken down teeth
To prevent microleakage (infection spread)
Aesthetics
In what order should treatment be planned?
- relieve pain
- cause related therapy
- initial reassessment
- basic operative care
- reassessment
- reconstructive therapy
- recall and maintenance
What are the risks of a extra-coronal restoration?
Pulpal inflammation Periapical periodontitis Poor plaque control Resto failure with poor occlusal management Loss of occlusal stability
What are the 4 golden rules to abide by when planning an extra-coronal restoration?
- Plan restoration that maintain structural integrity of the remaining sound tooth tissue
- Consider the least invasive and destructive option
- Always consider the effect on the pulp
- For endodontically treated teeth, provide the best coronal seal possible and support weakened tooth structure
What is a good alternative to ECR for prevention of microleakage?
Modern bonding systems
Gives excellent marginal adaptation and reliable bonding system
What is a good alternative to ECR for aestehtics?
Internal bleaching for non-vital teeth
Microabrasion for fluorosis
What are the advantages of good communication skills when trying to gauge what a patient is asking for?
Better diagnosis of patient’s problems
Increased adherence of patients to your recommendations and advice
Greater patient satisfaction
Reduce patient complaints and litigation
What to aim for when communicating to a patient needing a complete denture?
Keep expectations very low
Changes to their bone and co-morbidities may help this
Name 2 QoL questionnaries?
OHIP-14
GOHIA
What does OHIP-14 stand for?
Oral health impact profile
What does GOHAI stand for?
General oral health assessment index
NAme the 4 main features of assessment for QoL questionnaries?
Function
Pain
Psychosocial
Discomfort
Name 6 groups of people that have a reduced self-perception when assessing QoL for complete dentures?
Current users of removable prosthodontics Having less teeth Edentulous Women Nutritional deficit Cognitive impairment
How are nutrition and complete dentures related?
A poorly adjusted denture will lead to changes in mastication and food selection increasing soft diet which is usually highly fermentable carbohydrates leading to infection/caries
This can cause isolation of the patient (not leaving)
Identify what the patient wants and identify the changes that have occured orally such as?
Reasons for tooth loss and when
Resorption of residual alveolar bone
Systemic disease
Xerostomia
Name the 7 clinical stages of complete denture construction?
Patient assessment, treatment plan and informed consent Primary impressions Secondary impressions Recoding the jaw relationship Wax denture try-in Fit of complete dentures Complete denture review
What information must be gathered during the patient assessment stage?
General history
Extra-oral examination
Intraoral examination
Examine existing denture
What to identify in the extraoral examination?
Smile line Angular cheilitis Lower facial height Labial and buccal support tissue If teeth show on smile
What to identify in the intraoral examination?
Extent of ridge resorption Flabby ridge Mylohyoid ridge Frenal attachments Tuberosity Soft tissue overgrowths
What information must be gathered from the treatment planning and consent stage?
Formulate treatment plan:
- new denture or copy
- copy follow copy protocol (also note in notes)
Plan clinical and lab stages and appointments (follow NHSG lab protocol)
Discuss availability with patient
Approval from clinical supervisor
Gain informed consent
What to prepare for primary impressions for a complete denture?
Modify maxillary and mandibular disposable trays with putty or greenstick to correct extensions
If trimming needed, trim with acrylic trimming or tri-cutter bur
If single complete denture is being made use dentate poly tray or metal tray
Make impressions with alginate (can change but need explanation)
Once disinfected, mark required extensions of special tray (2mm above muco-buccal fold)
What document must you fill in when requesting a primary impression to be completed?
A complete student clinical prescription card for a non perforated 3mm spaced with tissue stops, custom special tray using a light cured resin extending to the marked border with a rim handle.
If flabby ridge eother space with another layer of wax or perforate tray
Alternatively construct tray with open window and lid
What to prepare for secondary impressions for a complete denture?
Assess special tray before insertion
Check extensions in mouth
Use greenstick or silicone putty to border mould the peripheral extension
Ensure good peripheral seal
A non-perforated tray will enable to confirm this peripheral seal at early stage
Make impression with alginate
For flabby or undercut ridge use spaced or perforated tray
Tray with a window and lid over flabby tissue can be used
If a flabby ridge is present, what should you change about the secondary impression?
If open tray with a lid is used, medium body silicone should be used over firm tissues and light body silicone applied through window over the flabby ridge
Place lid to close tray window
Consider a Piezograph for mandibular arch to record neutral space prior to occlusal rim wax
What document must you fill in when requesting a secondary impression to be completed?
Fill in a complete student clinic prescription card for working cats
Request for clear heat-cured acrylic denture bases to support maxillary and mandibular wax occlusal reg rims
If piezograph requested, use mandibular heat cured acrylic denture base for this
Piezograph and neutral zone can be made after maxillary occlusal rim if modified
Adjusted maxillary time useful during reg of neutral zone
Prescrie to convert the piezograph to mandibular wax occlusal rim on the heat cured mandibular acrylic denture base
Explain how to record the jaw relationship?
- Mand and Max?
- Check for what?
- Ensure that?
Check both max and mand base plates for extensions, stability and retention
Shape the labial and buccal surfaces of the max rim to provide correct soft tissue support and teeth-show
Adjust palatal slopes of max occlusal rim to ensure tongue space
Adjust max rim using a Fox’s occlusal plane indicator
Check the vertical dimension at rest with the adjusted max occlusal rim in place
Adjust the mand ri to fit max rim to provide free way space
Use willis gauge to establish adequate free way space (nose to chin)
Ensure the heel of the mand rim is not interfering with the heel of the max rim and base
Ensure the occlusal plane of mand rim is below dorsum of tongue and in level with retromolar pad at post ends
Ensure adequate tongue space
What is the equation for free way space?
FWS = VDR - OVD
must be a minimum of 2mm
What to measure after the vertical dimension of the occlusal rims have been adjusted and FWS dimension established?
The correct retruded jaw relationship
What are the 5 basic points to check before recording the retruded jaw relation?
FWS Stability Consistent horizontal jaw relationship Adequate freeway space Even occlusal rim contact Soft tissue support
What to mark on the maxillary rim after recording the retruded jaw relation?
Centre line
Symmetric canine lines
High smile line
Incisal edge level
What to mark on the mandibular and maxillary time after recoding the jaw relation?
Locating cones on both wax rims
How to explain to the patient to place jaw in RCP?
Ask the patient to curl the tongue towards the soft palate and close the mouth.
What material is used to record the RCP?
Silicone bite reg material
What can be helpful to complete if copying a denture?
Alginate impression of current denture
What to ask the patient about the aesthetics of their denture?
Prosthetic teeth shape, size and shade and engage dental nurse in discussion
Which document to fill in after recording the jaw relationship
mark the prosthetic teeth shade and mould choice on the Student Clinical Prescription Card. Enter patients gender, date of birth, race, relevant set up information and any characteristics that may be useful for the laboratory
Pick up red articulator from teaching lab and take to NHSG lab
Explain the process of the wax denture try-in stage?
Use average value articulator
Assess the seet in both occlusions
Ensure denture has smooth borders
Assess each trial denture separately in mouth to determine stability, retention, base extensions and neutral zone
Don’t leave wax trial denture in for too long will melt
Try ax and mand trial denture together to check occlusion, OVD, FWS, appearance and speech
Check shade, mould, tooth size, position, lip support and centre line
Check occlusal plane in relation to reference planes
Ensure mand occlusal plane is below dorsum of tongue and post line with retromolar pads
Adjust if necessary
What to do if there are occlusal interferences destabilising the denture?
adjust individual teeth by trimming the base of the prosthetic tooth and replacing it on the wax rim
remove involved teeth, add wax and re-record the jaw relationship using silicone bite registration material.
Ask the laboratory to rearticulate and re-set teeth for a re-try ensuring that you have given them as much information as possible about the required changes
When to proceed to the fit stage?
Only when the patient, yourself and clinical supervisor are happy
Encourage patient to bring friend to try-in appointment for their opinion
What document to fill in after the wax denture try-in stage?
Complete student clinical prescription card:
- flask pack and finish denture for fit
- label dentures with patient name
- return completed denture with the articulation and allocated articulator
Explain the fitting denture stage?
Check dentures of articulation and ensure occlusion
Check fitting surface of max and mand denture for irregularities
Sterilise before placing
Try each denture in separately
Use pressure indicating paste to identify any need for adjustment
Assess retention, stability, base extension and neutral zone
Check shade, mould, tooth size and position, level and angle of occlusal lane, lip support and centre line
Ensure denture fitting surfaces and borders are smooth
Insert dentures individually and confirm occlusal stability
COnfirm patient satisfaction
Denture advice on use, care and hygiene
Importance of annual checks
Replacement every 5 years
Periodic reline
What to do if the occlusion is not correct after minor adjustments?
If occlusion is not correct after minor adjustments, re-reg relationship using silicone bite reg
Prescribe lab remount new bite reg
Check the denture occlusion on this new articulation and make the required occlusal adjustments under supervision
What to assess at a complete denture review?
Review patient after 1 week Check denture bearing areas Carry out any refinements necessary Arrange further reviews Return to GDP for routine checks
How can the denture become destabilised?
If the muscle are encroached upon during contraction
Name the 12 muscles which play a part in denture stabilisation?
Frontalis Orbicularis oculi Zygomaticus Buccinator Orbicularis oris Platysma Cranial aponeurosis Temporalis Occipitalis Masseter SCM Trapezius
Name the 3 intraoral structures which a lower denture must form a good relationship with?
Pterygomandibular raphe Labial and buccal frenum Glandular tissues (retromolar pad)
What part of the denture can interact with the retromolar pad?
Posterior extension of denture base
How does the coronoid process and the buccal flange of the denture interact?
The buccal flange lies laterally to the maxillary tuberosity. It may impinge on the tuberosity and cause pain or instability
How far should the denture be extended?
Should be extended through the hamular notch via the area of the fovea palatinae
What is the definition of the hamular notch?
Junction of the maxillary tuberosity and the hamular process
What provides a guide to the position of the posterior palatal border for a denture?
Fovea palatinae
What is the definition of fovea palatinae?
Air of mucous gland duct orifices near the midline at the junction of the hard and soft palate
What guide can the incisive papilla give for a denture?
Where the incisors and canines should be set
What is the definition of the incisive papilla?
Mass of fibrous tissue
What is the definition of the palatal rugae?
Irregular mucosal transverse ridges found in anterior hard palate
Where is the vibrating line found?
Junction of moveable and immoveable part of the soft palate
2mm anterior to the fovea palatinae
What is the function of the vibrating line in terms of dentures?
Aids to establish the post palatal seal
Distal end of denture at least to the vibrating line
Where is the postal palatal seal?
From hamular notch to hamular notch
Anterior to vibrating line
Aids retention
Where is the posterior palatal seal?
From hamular notch to hamular notch
Anterior to vibrating line
Aids retention
What guides the saddle extension?
Where the hamular notch lies
Name 5 characteristics of the residual ridge that you must consider?
Height Width Form Thickness Consistency
Name the 2 types of maxilla vault shape?
U
V
How can the palatal vault shape affect the denture?
Retention
Resistance to lateral displacement
Tongue space
What is the definition of torus palatinus?
A bony enlargement occuring the the midline of the hard palate
Covered by thin incompressible mucoperiosteum
How can torus palatinus cause denture construction complication?
Bulk
Consistency
What is the definition of the buccal sulcus?
Extends from buccal frenum to hamular notch
Name 3 factors that change the size of the vestibule?
Contraction of buccinator muscle
Position of the mandible
Amount of bone loss
What can change the size and shape of the distal end of the buccal flange?
Movement of the ramus of the mandible at the distal end of the buccal vestibule
What is the definition of the labial sulcus?
Runs from one side of the buccal frenum to the other side, divided by the labial frenum to left and right
Outer surface is the orbicularis oris runs horizontally
Reflection of mm superioloy marks the height, no muscle attachment at reflection and moveable tissues here leads to overextension
How does the palatal mucosa change between people?
Differential compressibility
Where is the buccal shelf located?
Lies between the alveolar ridge and the external oblique ridge
Extend from buccal frenum to retromolar pad
How does the buccal shelf interact with the denture?
It is a flat horizontal shelf of bone, covered by mucosa that supports the distal part of the lower denture
How can the buccal shelf size and position vary?
From the degree of alveolar ridge resorption
What is the definition of the retromolar pad?
Pear shaped area containing glandular tissues, loose areolar CT, lower margin of pterygomandibular raphe, fibres of buccinator and superior constrictor, along with the fibres of the temporal tendon
Name 5 anatomical features of the mandibular arch?
Mylohyoid ridge Lingual tuberosity Mental foramen Genial tubercles Torus mandibularis
What happens to the mental foramen after severe residual ridge resorption?
It occupies a more superior position and the denture base must be relieved to prevent verne compression and pain
What is the definition of torus mandibularis?
A bony enlargement appearing unilaterally or bilaterally on the lingual aspect of the mandible in the canine-premolar region
What are the direct and indirect effects of the mylohyoid ridge?
Has an indirect effect on anterior lingual border up to second premolar & direct effect on
posterior lingual border in molar region
Where is the sublingual gland region located and how can it affect the denture?
In premolar region, when the floor of the mouth is raised, the gland comes close to the crest of the ridge & reduces the vertical space available for the extension of the flange in this region.
Why is the retromylohyoid space important?
For denture stability and retention
How is the retromylohyoid space formed?
Post: - superior constrictor Lat: - mandible and pterygomandibular raphe Ant: - lingual tuberosity Inf: - mylohyoid
Name the 5 muscles of the FoM?
Genioglossus Mylohyoid Hyoglossus Styloglossus Genioglossus
Name the 3 muscle in the facial curtain?
Buccinator
Orbicularis oris
How does the facial curtain change for edentulous patient?
Characteristic toothless look
Collapses
What is the definition of the modiolus and how it can affect the denture
Area where extrinsic perioral muscle decussate to join intrinsic fibres of the orbicularis oris muscle
Very forceful which can influence the labial flange thickness of a denture
What to do when there are limiting structures along the periphery?
Captured with a border moulded special tray
Allows muscles to trim impression material to their functional levels
How do the dentures stay stable during rest and function?
If the retentive forces acting on the dentures exceed the displacing forces
How is the support determined for a complete denture?
By the form and consistency of the denture-bearing tissues and the accuracy of the fit of the denture
Name the 3 surfaces of the the denture?
Occlusal
Polished
Impression
What do the 3 surfaces help to form?
The suction effect from the negative pressure formed
What can a patient learn to aid the stability and seal of their denture?
Patient acquired skills
What are the patient acquired skills?
Use of lips, cheeks and tongue to stabilise denture
Chewing on both sides at same time
Smaller portions and softer food
Name the 5 physical forces for a complete denture?
Adhesion Cohesion Surface tension Capillary action Atmospheric pressure & Peripheral seal
What is the definition of adhesion and what factors does it depend on?
Force of attraction between dissimilar molecules such as saliva, acrylic resin and mucosa Factors: - good adaption to oral cavity - size of denture bearing area - saliva best to be serous
What is adhesion directly proportional with?
SA of the denture base
Which denture arch has better retentive force?
Maxillary
What is the definition of cohesion and an example within a denture?
Forces of attraction between similar molecules
Maintains the integrity of the film of saliva
What is the definition of interfacial surface tension?
Is the resistance to separation of 2 parallel surfaces with a fluid medium in between
How is surface tension formed?
Results of the cohesive forces acting on the surface of the fluid
What factors affect surface tension and how it enhances retentive force?
Ability of the fluid to wet the rigid surrounding material
By promoting contact of saliva to both mucosa and denture base, surface tension works to enhance further retentive force
Explain why the interfacial surface tension plays more a role for the maxillary denture than the mandibular denture?
Most patients produce enough saliva to keep the external borders of the mandibular denture awash in saliva, therefore eliminating the effect of interfacial surface tension
What forms from surface tension and increased cohesive forces in a denture?
Cohesive forces result in the formation of a concave meniscus at the surface of the saliva in the border region of the denture
What relationship forms with the concave meniscus?
Between the width of the buccal channel and resistance to flow of saliva
A drop in pressure of the saliva film would cause what?
Cause impaction of the buccal mucosa and greatly increase retention
What effect occurs due to the fluid film bound by a concave meniscus having a lower pressure than the supporting medium?
A pressure differential exists between saliva film and air, therefore aids retention
What relationship does the size of the pressure differential have?
Inversely related to the diameter of the meniscus
Closer the fit to the tissues the stronger the retentive forces attributable to surface tension
What is the definition of capillary action and a denture example?
The quality or state because of surface tension causes elevation or depression of the surface of a liquids is in contact with a solid
Close adaption of the denture base to the mucosa cause the saliva in between to improve the contact between them
How is saliva important to physical forces to retention?
Presence of a continuous thin film of saliva between denture and mucosa, which wets both surfaces
What changes to retention if the viscosity of saliva increases?
Decreased retention due to the excessive viscosity resulting in a thick and discontinuous film between denture and mucosa
What mechanism is used to resist large displacing forces of a denure over a short duration?
Retentive mechanism from the viscosity of the saliva and the valve like action of the soft tissues
What mechanism is used to resist small forces acting over a long period of time (e.g. gravity)
Occlusal forces
Explain why the capillary action is more effective on the maxillary denture than the mandibular denture
Capillary attraction ceases to be effective is the tube is submerged under the surface of the liquid
Mandibular dentures saliva accumulates along the periphery and reduces the capillary effect
Explain why muscular forces play more of a role in mandibular dentures rather than maxillary?
Due to reduced denture bearing area
Difficulty in obtaining and maintaining a border seal
Name the 5 factors that are necessary to obtain an optimal physical retention?
Border seal Denture bearing area (largest( Accuracy of fit Bony undercuts Retention aids
What are the 5 main limitations for a denture?
Poor retention with the mandibular denture
Alveolar resorption reduces retention (but can be overcome by increase muscular control)
Patient dissatisfaction (after skills learnt)
Denture movement in function that are not detectable clinically
Varied tolerance
What are the 3 displacing forces acting through the occlusal surface?
Occlusal imbalance
Mastication
Forces related to the anterior teeth (lose seal)
Name 3 factors which reduce support and create instability?
Resorption in alveolar ridges and palate remain stable but can cause tipping during mastication
Ridges resorbed and are small resistance to lateral displacing forces will be poor
Flabby ridges
What is the definition of biomechanics?
Study of the mechanical nature of biological processes
What ae the effects of ageing on the oral cavity in relation to dentures?
Reduced functional capacity and precision control
Reduced ability for oral gymnastics
Restricted mouth opening
Describe the natural change of dentition?
Characterised by adaptive responses to constant dynamic changes, continuous reparative changes of the basal bone and alveolar process
What are the effects of tooth loss?
Periodontium involved with support and positional adjustment of the tooth as well as sensory perception are lost with tooth loss
Edentulous state has few adaptive mechanisms
Tissue changes are progress and mainly regressive
Name the 5 consequences of loss of periodontal ligament (with denture stability in mind)?
Viscoelasticity of PL missing
Sensory feedback mechanism missing
Osteogenic potential that responds to the forces applied missing
SUpport and sensory perception are therefore altered with complete denture
Mucous membranes serve the functions of PL with its attendant deficiencies
What is the periodontal ligament area?
45 cm2
What is the denture bearing area of the maxilla and mandible?
Maxilla:
- 22.96 cm2
Mand:
- 12.25 cm2
Cawood and Howell Classification: - class I tooth loss?
Dentate
Cawood and Howell Classification: - class II tooth loss?
Immediately post extraction
Cawood and Howell Classification: - class III tooth loss related to alveolar ridge?
well-rounded ridge form, adequate in height and width
Cawood and Howell Classification: - class IV tooth loss?
Knife edge ridge form, adequate in height and inadequate in width
Cawood and Howell Classification: - class V tooth loss?
Flat ridge form, inadequate height and width
Cawood and Howell Classification: - class VI tooth loss?
Depressed ridge form, with some basalar loss evident
Where is the greatest amount of bone loss seen on the maxilla and mandible?
Labial and buccal aspects of the maxillary alveolar ridges
Lingual aspect of the mandibular ridge
What reduces proportional to residual ridge resorb in relation to dentures?
Denture bearing area
Name 3 systemic conditions that affect the tolerance of tissues and increases inflammation?
Anaemia
Diabetes
Nutritional deficiencies
Supporting tissues have little or adaptability to functional forces applied
Name the 7 changes a patient will undergo in an edentulous state in relation to the maxilla and mandible?
Altered facial appearance due to changing maxillomandibular relationship
Altered and reduced support system
Compromised reflex adaptability
Decreased oral tissue tolerance
increases risk of pathological changes
Increases risk of maladaptive denture wearing experience
Increased functional and parafunctional movements
Name the 6 changes a patient will undergo in an edentulous state in relation to the oral cavity?
Reduced denture support area Reduced or altered neuromuscular control Reduced chewing forces Reduced salivary flow Reduced healing potential Resulting in compromised denture beating tissues
Name the 5 changes to forces of mastication in an edentulous patient?
20kg forces applied with natural dentition
6-8 kg forces applied with complete denture
5-6 times less maximum bite force with denture
Chewing efficiency reduced by 80%
Changes in food choices
Name the psychosocial effects of complete denture?
QoL
Emotional
Name the aesthetic effects of complete denture?
Lower facial height
Collapse of commisure
Cheeks
Lips
Name the functional effects of complete denture?
Mastication
Speech
Food choices
Name the systemic effect of complete denture?
Metabolic
CV
Cancer
Local tissue changes
What factors affect movement of dentures?
Stability of denture
Resiliency of mucosa
What can movement of the complete denture manifest as?
Displacement Lifting Sliding Tilting Rotating
Name the 3 muscles affecting retention and stability?
Orbicularis oris
Buccinator
Risorius
(Intrinsic and extrinsic tongue muscles)
What are the 2 main objectives for the construction of a complete denture?
Minimise the forces transmitted to the supporting tissues
Reduce the movement of the prosthesis
What are the factors under the clinicians control for complete denture?
Appropriate optimal extension of the denture base
Maximum intimate contact of the denture base with basal seat
Designing the smooth surfaces of the denture to utilise and balance perioral and tongue muscles activity to maximise retention and stability
Arrangement of the prosthetic teeth in the neutral zone
What is the definition of the neutral zone?
The potential space between the lips and cheeks on one side and the tongue on the other side; that area or position where the forces between the tongue and cheeks or lips are equal
What is the first stage of denture assessment?
Measuring the rest face height
This can be carried out with the Willis gauge:
- position of the fixed arm under the nose
- position of the sliding arm under the shin
- vertical orientation of the gauge
What is the second stage of denture assessment?
Record rims should be placed on well-fitting rigid bases
Try in record blocks and check adaptation and extensions starting with the upper
Modify where required but can only reduce any overextensions
Make adjustments to upper record block first
Blocks are bulky
Explain how to measure the maxillary jaw relationship?
Add or remove wax to modify occlusal surface of upper record block to change occlusal plane orientation: - should be parallel to Ala-Tragus line Fox's plane guide Add or remove wax to modify tooth position: - lip support - incisal level - incisal tooth position - buccal or palatal surfaces
Explain how to measure the mandibular jaw relationship? Part 2
Remove upper block and insert lower wax record block
Add or remove wax to modify tooth position:
- essential to place lower block (and future denture) in neutral zone:
- lip support, buccal and lingual surfaces (tongue space)
Again always check by replacing back in oral cavity
Decisions regarding occlusal plane should have previously been made as to
where modifications are to occur:
- care with position of occlusal surfaces in relation to tongue.
Add or remove wax to modify occlusal surfaces to achieve appropriate
occlusal vertical dimension (OVD).
Check that there is an appropriate amount of Freeway Space (FWS)
(usually 2-4mm)
Explain the replica technique for jaw relationship?
Modify extensions where required (should have been
done before taking primary impressions) and take light
bodied silicone elastomer impression (base will always be close fitting if this option chosen).
Carry out modifications to wax rims to prescribe for
‘try in’ stage.
These modification stages are exactly the same whichever process is followed.
If light bodied impressions are damaged during
modification process, retake impressions.
Use ‘closed mouth’ technique to retake impressions:
- maintains OVD
Explain the process of recording the jaw relationship?
Patient needs to be in a supine position.
Check relationship with both blocks in patient’s mouth
Ensure that it is as reproducible as possible.
Record ligamentous (or retruded contact position) if patient has moved to habitual
path of closure.
Ligamentous position is considered the most reproducible.
Recheck that there is an identifiable FWS.
Ensure center line is appropriate and marked if removed during modifications
What to do after measuring jaw relationship on wax blocks?
Cut two notches in posterior occlusal surface of upper block
Place upper record block in patient’s mouth.
Apply appropriate adhesive to lower block for bite
recording paste being used.
Apply sufficient bite recording paste to occlusal surfaces
of lower block
(NOT on to anterior segment, need to be able to observe anterior tooth relationship)
Insert block and guide patient into correct jaw
relationship.
Allow sufficient time for material to set before
removing from mouth.
What information to send to the dental technician, after bite block registration?
Remove both blocks carefully.
Separate blocks carefully so that dental technician can cast impressions in
upper and lower blocks where required.
Select appropriate anterior and posterior teeth.
This includes shade (DEPLHIC V or VITA), mould, arrangement and posterior cusp
form.
Prescribe for correct articulator:
Depends on posterior tooth prescription.
What is important to create a conventional bilateral balanced occlusion?
Inter-cuspal position = Retruded contact
position
ICP on posterior teeth
Working side and balancing side contacts in
lateral excursions
Anterior and posterior contact in protrusive
excursions
What is important to create a lingualised bilaterally balanced occlusion?
Maxillary palatal cusps contacting mandibular
central fossae.
Differs from Conventional bilateral balanced
occlusion by eliminating the contacts between
the mandibular buccal cusps and maxillary
central fossae.
Achieved by:
- modifying anatomical mandibular posterior teeth or
- by applying anatomical maxillary posterior teeth
against flat mandibular posterior teeth.
What is important to create monoplane occlusion?
Can establish balanced or non balanced
occlusion
Occlusal contact comprise surfaces rather
than point
When would you use LBBO teeth?
Severe ridge resorption
What are the 7 influencing factors for selection of teeth?
Previous dentures (if any). Age of patient. Size and shape of facial skeleton. Colour of complexion. Patient choice. Patient’s friend. Old photos
Name the 3 types of denture teeth materials?
Acrylic
Composite
Porcelain
What are the pros and cons for acrylic denture teeth?
Highly cross-linked acrylic (improves wear resistance and colour
stability).
Good appearance and adhesion to denture base.
Wears easily
What are the pros and cons for composite denture teeth?
Harder and longer lasting than acrylic.
Good aesthetic properties.
Reduced bond strength to underlying acrylic.
Can be modified/added
What are the pros and cons for porcelain denture teeth?
Retention to denture based through mechanical features called diatoric
holes (pins) designed into the teeth (can be dislodged).
Good appearance but can be noisy, chip with high occlusal forces
Name a denture shade guide?
Vita
DEPLHIC V
Explain how to position the denture teeth?
Using a straight edge aligned with the inner
canthus of the eye and the ala of the nose to
find the position of the canine (marked on the
wax rim).
Width of the 2 central incisors:
- using the philtrum width.
- the height of the central incisor should be equal
to or greater than the height of the smile line
above the incisal edge.
High smile should be marked on the wax rim.
When should larger central incisors be used?
High lip line.
Large stature.
Large face.
Explain the process of shape selection of denture teeth?
Use patient’s old denture (if happy with
previous one).
Inverted shape of the patient’s face.
Shape of the patient’s upper palate.
What face shape do square teeth fit?
Complement a square set face and strong features
What face shape do ovoid teeth fit?
Create a softer appearance and complement, delicate and rounded features
What face shape do tapering teeth fit?
Tapering face shape
What face shape do rectangular teeth fit?
Long square shaped faces
What are the changes of the oral cavity due to age?
Attrition of natural teeth:
- incisal edges will tend to be flattened.
Loss of muscular tone in lips and face:
- flanges and teeth will need to attempt to restore ‘appearance’ (can be difficult).
Need to place anterior teeth in correct position:
- lip support BUT if too far anterior causes denture displacement.
Amount of tooth showing:
- at rest and when smiling.
Name the antero-posterior, lateral and mediolateral posterior compensating curves?
AP: - curve of spee Lat: - Curve of monson ML: - Curve of wilson
What are the 5 main factors for prosthesis stability?
Occlusal relationship Base shape Fitting surface adaptation Tooth position Polished surface shapes
Name the 3 things that give optimal physical retention?
Border seal
Area of impression surface
Denture bearing area
Accuracy of fit
How far can the buccal surface of the denture be extended in the incisal, canine, premolar and molar area?
Incisal 6mm
Canine 8mm
Premolar 10mm
Molar 12mm
Name 3 types of impression materials to create a primary impression?
Impression compound Polyvinyl siloxane (elastomer) putty or irreversible hydrocolloid (alginate)
What is the process of border moulding?
Dry the tray then add compound to section A, then B and finally C
A is at the posterior ridges of the denture
B is at the middle part of the periphery of the denture
C is at the front and incisor area of the denture
Where should the posterior upper denture be extended to?
Between the junction between the hard and soft palate and the vibrating line
Describe the process of a closed mouth CD process?
Primary
Secondary:
- functional
- neutral zone
Describe the process of a open mouth 2 step CD process?
Primary Secondary Step one: border moulding - operator manipulated - functional moulded Step two: final impressions - mucostatic tech - selective pressure tech - functional tech - neutral zone tech
Describe the process of a open mouth 1 step CD process?
Border moulding and final impression:
- operator manipulated
- functional moulded
What materials can be used for border moulding?
Greenstick
Elastomers
What materials can be used for final impressions?
Impression plaster Elastomers Fluid wax Alginate ZOE impression paste
Explain the mucocompressive/mucodisplacive/definitive pressure impression technique?
Denture becomes unstable at rest, because the denture bearing tissues were captured in the impression in a compressed state on to which the denture base had a good fit.
But the denture base didn’t adapt well to the relaxed state
Made with a closed mouth so that the patient can bite together
Explain the mucostatic/minimal pressure impression technique?
Suitable for flabby ridges
Denture stable at rest
Flabby tissues distort in function, when the denture base does not fit this tissue state well
A pure mucostatic impression may not provide adequate border seal for retention
Explain the selective pressure technique?
Combines pressure over some areas and minimal pressures over other areas
Pressure applied over primary stress bearing area so that the denture base is well adapted to the tissues overlying these areas, allowing denture to be supported well in function
The non load bearing areas are captured with minimal support. Achieved by providing relief over aera with special trays, those areas with pressure will have no relief.
Idea is that if no relief more force is transmitted to the tissues which get derform as in function, so the resultant impresion is mucodisplacive over these areas. Whereas, where the relief provided minimal pressure applied on tissues
Explain the functional impression technique?
Impression that is made while the tissues are in function, using viscogel as a material, within the tissue surface of the denture base and sending the patient away. After a week patient is recalled, the viscogel would be moulded in a routine function and captured the denture bearing tissues in a functional state
How do faulty impression occur?
Usually due to clinicians lack of knowledge of anatomy of denture bearing tissues and structures along the periphery of the dentures
Adequate attention to detail is required
Primary impressions must be good (good foundation needed)
Clinician can imagine the impression surface
Name the 14 anatomical landmarks of the maxilla?
Incisive papilla Labial frenum Labial sulcus Rugae area Palatine raphe Buccal frenum Buccal sulcus Crest of alveolar ridge Posterolateral of residual alveolar ridge Posterior palate Tuberosity Hamular notch Vibrating line Fovea palatinae
Name the 13 anatomical landmarks of the mandible?
Labial frenum Labial sulcus Genial tubercle Lingual frenum Torus mandibularis Mental foramen Buccal frenum Buccal sulcus Alveololingual sulcus Mylohyoid ridge Buccal shelf Residual alveolar ridge Retromolar pads
Name the 6 maxillary denture bearing areas?
Valve seal area Primary stress bearing area Secondary stress bearing area Relief area Pterygomaxillary area Posterior palatal seal area
Name the 5 mandibular denture bearing areas?
Secondary stress bearing area (sliped of the ridges) Primary stress bearing area (buccal shelf area) Secondary relief area (ridge crest) Secondary stress bearing area Valve seal area (sulcus area)
Comparison between edentulous jaws?
Maxilla has more supporting areas
Limiting structures are less in number and have a less stronger influence over the denture border
The opposite is correct for the mandible
What should the preliminary impression aim to reproduce?
Sulcus depth
Sulcus width along the entire periphery
Certain anatomical landmarks which indicates the correct extensions of the customised tray such as
maxillary tuberosity and retromolar pads
What makes a good impression material for a primary impression?
High viscosity material which compensates for the poor fit of the stock tray
Such as impression compound or high viscosity alginate
What should the master impressions aim to reproduce?
Record the maximum denture bearing area and develop an effective border seal
Modified by reducing any over extension and the peripheries adapted by the addition of gree stick or impression compound
Why do we need to use impression materials?
Take an accurate impression of the patient’s anatomy
Control the contraction of the impression material during setting
Be more comfortable for the patient
Name 4 types of materials to be used for a special tray?
Light cure acrylic resin
Autopolymersing acrylic resin
Vacuum form thermoplastic materials
Shellac
What to mark and block out on the maxillary cast?
Mark: - a red line at the depth of the vestibule - a blue line 2mm above the red line, which determines the tray extension Block: undercut areas; - frenum - buccal surface of the tuberosity - rugae - flabby portions of the alveolar ridges
What to mark and block out on the mandibular cast?
Mark:
- a red line at the depth of the vestibule
- a blue line 2mm above the red line, which determines the tray extension
Block: undercut areas;
- mylohyoid ridge
- frenum
- lingual side of the mandible opposite the retromylohyoid space
What is the space required for ZOE paste?
0.5-1mm
What is the space required for silicone (medium)
1.5-2mm (1 layer of wax)
What is the space required for alginate?
3mm (2 layers of wax)
What is the space required for Silicone (heavy)
3-4.5mm (3 layers of wax)
What is the space required for impression plaster?
4.5m (3 layers of wax)
What is the average thickness of a sheet of baseplate wax?
1.5mm
What is the definition of tissue stops?
Help position the tray correctly in the mouth and ensure an even layer of impression material (better control of setting expansion and less likely to displace tissue)
Cut 2-4 mm square or round holes through the spacer wax in 4 area - highest/most bony points at the canine and molar regions
Don’t place over compressible or flabby tissues/incisive papilla area
Explain the process of making the tray for light cure resin?
Tray material adapted to the cast and excess removed with knife
Add tray stop gaps with some off-cuts of the tray material
Adapt a sheet of tray material to cover the wax, avoid thinning at the periphery
A handle can then be made from the excess material and added to the tray, the handle must be placed in line with the middle of the palate
Light cure on top side for 3-5 mins
Remove wax spacer and set inside 3 mins
Remember to set our tissue stops for 1 min before removing the wax
Smooth edges with an acrylic burr
At what height should the handle be stepped up by?
10mm, if no teeth in anterior
What are the functions of finger rests for denture construction?
Stabilise tray in mouth
Equal distribution of pressure
Reduces pressure applied to tissues
Where should to rest your fingers for the finger rest for denture construction?
Not impinge upon the tongue space and not extend above the occlusal plane and are placed near the 2nd premolar/1st molar teeth
What to do to create space for the frena?
Draw a pencil line along the trat at the same angle as the frena
Trim away a rounded noth to allow space around it
Notch out relief for muscle attachments and make sure there is a 2mm clearance for border moulding before smoothing off the edges
What are the necessary requirements of the completed maxillary special tray?
Tray periphery should be 2-3 mm thick
Edges should be rounded
Rest of tray should be about 1-2 mm in thickness
periphery should be flush with the blue line
Tray handle must extend vertically from the crest of the ridge and approx 10mm high and 15 mm wide
Finger rest not impinging
What are the clinical presentations and histology for a flabby ridge?
Alveolar ridge mobile, extremely resilient
Anterior part of maxilla, when remaining anterior in mandible
Marked fibrosis, inflammation and bone resorption
What are the causes for a flabby ridge?
Replacement of bone by fibrous tissue
Excessive load of the residual ridge
Unstable occlusal conditions
What are the problems and suggested solutions for flabby ridge?
Provides poor support of the dentures
Removed surgically to provide the stability required by dentures
Extreme cases, total removal not done, leads to elimination of vestibular sulcus
Resilient ridges provide support for retention
What questions should be answered when requesting creation of a special tray?
Which arch?
What material?
What thickness of spacer (and any border relief)?
Whether you need perforations?
Whether you require tissue stops + finger rests?
Extensions of any window area required?
Handle type/style?
What are the 11 ideal properties of an impression material?
Non toxic or irritant Cheap Long shelf life Taste Setting time Compatibility with other materials Surface reproducibility Dimensional stability Working time Ease of mixing Handling of material
What are the surface reproducibility, dimensional stability of ease of casting gypsum abilities of alginate?
Surface reproducibility: - good Dimensional stability: - poor Ease of casting gypsum: - good
What are the surface reproducibility, dimensional stability of ease of casting gypsum abilities of Medium bodied silicone?
Surface reproducibility: - excellent Dimensional stability: - excellent Ease of casting gypsum: - fair
What is the thicknesses necessary for the land area of a denture and what is used to create it?
4mm maxillary and mandibular
Beading wax
Where must a complete denture sit to have good stability?
In the neutral zone, for most CD construction techniques
Indications for the NZ technique of CD construction?
Proven instability problems which has not been possible to rectify with conventional techniques or implants
Name the 8 indications for use of NZ tech for a CD?
Resorbed ridges Enlarged tongue Migration of mentalis Facial reconstructive surgery Poor neuromuscular control Poor facial tonicity through age related degeneration Parkinson's Stroke
Why does alveolar ridge resorption cause denture instability?
As it flattens it has reduced ability to resist the lateral displacing forces
The distance from the occlusal surface to ridge increases in atrophic mandible therefore greater leverage applied causing denture instability
How to adjust a CD to accommodate alveolar ridge resorption?
These surfaces should be so contoured such that the horizontally directed forces applied by the peri -denture muscles to seat the denture
What does lateral spread of the tongue cause in relation to CD?
Reduces the width of the NZ
Managed by timely provision of RPD as teeth are lost
Name 5 degenerative changes following tooth loss that can affect CD construction?
Alveolar ridge resorption Lateral spread of tongue Migration of the mentalis muscle Loss of facial tonicity Diminished capacity for successful neuromuscular adaptation
Name 3 problems are caused with patients being older when they become edentulous?
Poor denture bearing tissues
Poor capacity for adaptation
Poor tolerance of complete dentures impacts on quality of life indices and nutrition
