Year 4 Flashcards
Describe the physiologic rest position
The mandibular position assumed when the head is in an upright unsupported position and the involved muscles are inequilibrium in tonic contraction, and the condyles are in a neutral, unstrained position
Describe the rest vertical dimension
The vertical dimension of the lower face with the mandible in the rest position
Describe the occlusal vertical dimension
The vertical dimension of the lower face with the teeth in centric occlusion
Describe the free way space
Difference between RVD and OVD, usually 2-4mm at the incisors
Describe the retruded arc of closure
The arc described by any point on the mandible during a closing movement made with the condyles in their most posteriorpositions
Describe the retruded contact position
The relation of the mandible to the maxilla with the mandible in its most retruded position at a prescribed occlusal vertical dimension
Describe intercuspal position
The mandibular position that gives maximum tooth contact
Define balanced occlusion
A static relationship
The simultaneous even occlusal contact between maxillary and mandibular teeth
Define balanced articulation
A dynamic relationship
The simultaneous bilateral occlusal contacts between maxillary and mandibular teeth during the movement
5 factors of balanced articulation (Hanau’s Quintet)
Condylar guidance
Incisal guidance
Cuspal angles
Plane of occlusion
Compensating curves
Describe the trends in population levels of edentulousness in high and low income countries
In high‐income countries the trend has been a drop in edentulism
In low income countries the rate of edentulism continues to be high
2 physical effects of tooth loss
Impacts appearance
Impacts function of speech and mastication
1 emotional effect of tooth loss
Decreased self confidence
4 things to assess when assessing the edentulous patient
Soft tissues
Alveolar ridges
Salvia
Hard tissues
6 stages in the provision of complete denture
Patient history and assessment
Preliminary impressions
Master impressions
Wax registration
Wax try-in
Insertion
Review
3 features of alveolar ridges to assess
Shape
Firm or flabby
Sensitive or comfortable
What modification does sensitive or mobile ridges require
Modified impression technique
What modification do sharp ridges/ prominent mylohyoid ridges require
Provision of relief
Define denture stability
Quality of a denture to be firm, steady, constant and resist displacement by functional forces
Define denture retention
Resistance of a denture to removal from the denture bearing tissues in a vertical direction
Define denture support
Resistance of a denture to occlusally-directed forces, determined by the form and consistency of the denture-bearing tissues
3 factors that contribute to loose dentures
Lack of stability
Lack of retention
Lack of support
2 features likely to give good denture stability
Adequate firm, bony support
Well-formed ridges
Describe the ideal relationship between retentive and displacing forces for denture stability
Retentive forces should be greater than displacing forces
2 factors retentive forces depend on
Acquired muscular control
Physical forces of retention
Describe acquired muscular control
Control with lips, cheeks and tongue and by
the muscles of mastication
5 features of dentures that improve acquired muscular control
Correct extension
Correctly contoured polished surfaces
Lower teeth placed on top of alveolar ridge in the neutral zone
Level of lower occlusal plane below level of resting tongue
Correct occlusal relationships
Describe the physical forces of retention
Adhesion and cohesion of saliva between mucosa and acrylic producing a negative pressure to cause retention
2 features of denture design/construction that improve physical forces of retention
Good peripheral border seal
Correctly extended and accurate impression
4 displacing forces for dentures
Lip and cheek muscles
Tongue
Occlusal interferences
Viscous and sticky foods
Define the neutral zone
That area where the forces between the tongue and cheeks or lips are equal
Describe how muscular balance is achieved
Setting the lower teeth on top of the lower ridge
Size of the average upper denture bearing area
24cm2
Size of the average lower denture bearing area
14cm2
2 features of good complete denture impressions
Cover the maximum possible denture-supporting area
Close contact with the underlying mucosa
Describe the 3 features a correctly extended complete upper denture should include
Tuberosities into hamular notch
Full functional depth and width of buccal and labial sulci
Non-moving junction of hard and soft palate
Describe the 2 features a correctly extended complete lower denture should include
At least 2/3 of the retromolar pad
Full functional depth and width of buccal, labial and lingual sulci
Ideal impression material for complete preliminary impressions
Impression compound
4 impression compound properties
Mucocompressive
Supports itself beyond the tray
Poor surface detail
Shrinkage
3 complete preliminary impression materials
Impression compound
Silicone putty
Alginate
Describe special impression trays
Custom made impression trays by the lab in light or chemically cured acrylic
Describe why special trays are extending 2mm short of maximum denture bearing area
Allow space for impression material and border moulding
3 features of special impression trays
Rigid and dimensionally stable
Incorporated handle to avoid interference with lip
Incorporated finger rests for lowers to avoid displacing cheeks
Correct wax spacer for ZnO/Eugenol master impressions
0.5 mm
Correct wax spacer for PVS master impressions
1.5 mm
Correct wax spacer for alginate master impressions
3 mm
2 reasons why is greenstick used
Obtain correct functionally border moulded extension Correct any area of under extension
4 areas greenstick should be added
Post dam
Hamular notches
Lingual pouches of lower
Posterior buccal sulci
3 complete master impression materials
Zinc-oxide eugenol
Polyvinylsiloxane if undercuts
5 properties of zinc-oxide eugenol
Gradual set, few minutes to allow border moulding
Good surface detail
Rigid
Dimensionally stable
Potentially causes burning sensation
Describe the gag reflex
Muscular contraction of the back of the throat, evoked by either touching the roof of the mouth or psychogenic stimuli, mediated by the autonomic nervous system
4 management strategies for the gag reflex
Calm confident approach
Good communication
Minimise presence of physical stimulus
Divert patient’s attention
3 denture faults causing gagging
A loose upper denture
Overextension at post dam
Excess occlusal vertical dimension
2 functional differences between artificial and natural dentition
Natural dentition greater biting force x5
Artificial dentition does less efficient chewing x6 number of chewing strokes
Why is RCP used when designing complete denture occlusion
ICP is non-existent
Occlusal scheme of choice for complete dentures
Bilateral balanced articulation occlusal set up
Define bilateral balanced articulation occlusal set up
Bilateral simultaneous contact of teeth in RCP and during excursions
4 reasons why balanced articulation is important
Increases stability
Distributes the occlusal load over the whole denture bearing area
Enhances masticatory function
Enhances aesthetics
3 advantages of using RCP
It is reproducible
Patients easily accommodate to it
Allows a set up in balanced articulation occlusion
Describe why compensating curves are necessary
Introduction of a curve to the occlusal plane antero-posteriorly maintains cuspal contact during excursions
How is the correct lip support of a denture achieved
Correct anterior placement of incisors
Describe the correct anterior placement of incisors
Positioned up to 1cm ahead of incisal papilla and inclined to give 90° columella-philtrum angle
How much of incisor height should be shown
1 or 2 mms below lip at rest
Nearly all the crown when smiling
Describe where the lower occlusal plane should be positioned
Below the resting level of the tongue, runs into the retromolar pad about half way up
Why is it important to have correct lower occlusal plane
Allows the occlusal forces applied to the dentures to be perpendicular to the alveolar ridges which improves stability
What should the anterior occlusal plane be parallel to
Interpupillary plane
What should the posterior occlusal plane be parallel to
Ala-tragal line through tragus of the ear to lower border of ala of nose
4 methods to used to help record retruded position
Tongue retrusion and gentle guiding through bimanual mandibular manipulation
Swallowing
Fatigue muscles that protrude mandible
Gothic arch tracing
Describe the problem associated with an decreased OVD
Poor appearance as patient is overclosed
Describe problems associated with an increased OVD
Patient is overopen
Discomfort in facial musculature as no rest from tooth contact
Trauma and pain in denture bearing tissue
Clicking of teeth during speech
5 things to be checked when examining trial dentures on an articulator
Waxed up to full extension and well adapted
Polished surfaces correctly shaped
Tooth position satisfactory
Centric occlusion
Balanced articulation
5 things to be checked when examining trial dentures in the mouth
Upper anterior tooth position
Jaw relationship
3 things to assess jaw relationship of trial dentures
Check even contact into ICP at RCP
Antero-posterior component
Vertical component
Describe how to correct errors in upper anterior tooth position
Move 1-2 teeth as guide chair-side
Mark new centre line
Choose new mould / shade
3 causes of antero-posterior jaw relationship errors
Registration rims not in correct RCP at recording time
Error in mounting rims on articulator
Warpage / distortion of base plates of rims
Describe how to correct errors in jaw relationship
Minor error can be accepted and modify occlusion at insertion
Obvious errors require re-registeration to rearticulate casts on articulator and reset teeth for re-try
Describe how errors in A-P are corrected
Corrected at the re-registration by trimming the wax on the lower to the appropriate OVD and A-P
Describe how errors in OVD are corrected
Over-open: articulator pin raised by appropriate amount and teeth reset
Over-closed: articulator pin dropped by appropriate amount and teeth reset
Define the posterior palatal seal
Raised portion of the denture base at the posterior extent of the upper denture located on its fitting surface
What is the importance of the posterior palatal seal
Maximises the peripheral seal and retention of the upper denture
Describe the process of indicating placement of posterior palatal seal
Palpated with round ended burnisher after accepting trial denture
Marked by scoring with round-ended instrument
3 design features of posterior palatal seal
Broad rounded dam better tolerated than sharp V-shape
Anterior limit depends on soft palate flexion
Broader laterally
Describe the method of creating a functional post-dam when posterior seal inadequate at insertion
Use chemically activated acrylic (BMA + PEMA) chairside
Request post-dam replaced in laboratory
Define an articulator
A mechanical device that represents the temporomandibular joint and jaw members
4 requirements of an articulator
Maintain centric contact
Hinge opening
Can accept face bow transfer
Reproduce eccentric movements
4 advantages of using articulated dental casts
Better visibility
Allows lingual view
Time saving at chairside
Allows refinement of occlusion
4 classifications of articulators
Class I: simple hinge
Class II: average value
Class III: semi-adjustable
Class IV: fully adjustable
2 features of a plane line articulator
Not capable of eccentric movement
Can only relate casts in one static position
4 features of average value articulators
Based on average facial measurements
Allows a balanced articulation set up
Do not usually accept a facebow
Limits in replicating mandibular movement
Describe the factors influencing the arrangement of teeth to produce balance
To ensure balance when the incisal guidance or condylar slope is increased, then plane of occlusion, cusp angle or compensation curve must also be increased
2 features of semi-adjustable articulators
Face bow record required
Allows customisation of condylar and incisal guidance
3 features of adjustable articulators
Allows balanced articulation
Functional movements can be individually tailored
Requires clinician to record accurate records
Describe the 2 types of semi-adjustable articulator
Arcon: condylar element on lower member
Non-arcon: condyle on upper member
4 disadvantages of using articulated dental casts
Potential inaccuracy in casts
Error in mounting of casts
Error in record of occlusal / jaw relationships
Limited ability of rigid articulator tracks to reproduce patients mandibular movements
Describe a single complete denture
Complete denture that occludes against some or all of the natural teeth
3 complications when providing a single complete denture
High occlusal forces on the underlying edentulous tissues from the opposing natural teeth
Unharmonious occlusal plane due to position of natural teeth
Why is a single denture more likely to fracture at the midline
Combination of occlusal stress and position of opposing teeth
Describe the cause of an anterior flabby ridge
Repeated occlusal trauma causing rapid, gross bone resorption due to a complete denture opposed by natural anterior teeth
Problem with maxillary complete denture opposing natural teeth
Require lower posterior teeth to contact upper complete denture to help keep it in place
Problem with mandibular complete denture opposing natural teeth
Relatively small denture supporting tissue and thin mucosa and submucosa overlying the bone of the lower residual ridge means that underlying bone is extremely prone to resorption
3 methods of overcoming problems associated with the single complete denture
Replace opposing missing posterior teeth
Ensure all fundamental steps in denture construction must be followed and completed correctly
Improve the occlusal plane of the natural teeth in the opposing arch by extracting teeth, reducing the height of enamel with burs or crowning teeth
3 stages in the insertion of complete dentures
Adjustment of fit surface
Occlusal adjustment
Instructions and aftercare
2 potential adjustments of fit surface at insertion
Smoothing of processing defects
Reduction of areas of pressure
Reasons for occlusal errors at insertion
Changes in tooth position during processing of acrylic
Errors not detected at trial
3 methods of correcting of occlusal errors
Split cast remount technique to correct processing / flasking errors
Occlusal adjustment at chairside
Occlusal adjustment in laboratory following completion of a new pre-centric check record of RCP
Define a pre-centric check record and why it is completed
Record of RCP on the terminal hinge axis
Reduces post-insertion discomfort and patient visits
Describe the method of conducting a pre-centric check record
Place two thicknesses of wax onto lower posteriors, soften wax evenly
Have mandible close in RCP until teeth indent the wax
Describe occlusal correction of complete dentures by selective grinding
Use articulating paper
Reduce cuspal inclines and deepen fossae rather than shorten cusps where possible
Describe upper and lower reductions necessary to prevent premature contact in RCP
Reduce palatal upper
Reduce buccal lower
Describe upper and lower reductions necessary to prevent premature contact in lateral excursions
Reduce buccal upper
Reduce lingual lower
Describe upper and lower reductions necessary to prevent premature contact on anterior teeth in protrusive excursion
Reduce palatal incisal edge upper
Reduce labial incisal edge lower
3 requirements of denture cleansers
Non-toxic, easy to remove, leave no trace of irritant material
Ability to attack or dissolve organic and inorganic portions of denture deposits
Harmless to all materials used in denture construction
Describe 4 methods of rehabilitating of soft tissues when providing new dentures
Correct fit surface faults
Ease pressure spots
Reduce overextension
Instruct patient on denture hygiene
Describe 1 method of rehabilitating patients with overclosure and protrusion associated with worn dentures when providing new dentures
Use occlusal pivots to allow smooth adaptation to changes in OVD
Describe when duplication of dentures is indicated
For patients requiring replacement complete dentures which have been well designed and previously successful to allow for good neuromuscular continuity
4 requirements to facilitate duplicate dentures to be constructed
Satisfactory aesthetics or easily modified
Satisfactory occlusion or easily modified
Adequate extension or easily modified
Adequate OVD or easily modified
4 pathologies associated with complete dentures
Direct mechanical trauma
Denture-induced hyperplasia
Denture-induced stomatitis
Angular cheilitis
2 denture related causes of traumatic ulcers
Overextended borders
Unbalanced occlusion
2 managements of denture related traumatic ulcers
Managed using pressure relief cream
Denture reduction and correction
Denture related causes of hyperplasia
Trauma caused by over-extension or occlusal errors of poorly fitting denture
Define denture-induced hyperplasia
Raised areas composed of dense fibrous tissue and related to the periphery or fitting surface
Describe the locations where denture-induced hyperplasia lesions are usually found
Anterior labial or buccal sulci
Incidence of denture-induced hyperplasia in the denture wearing population
2-13%
Management of denture-induced hyperplasia
Grind periphery to relieve
Improve fit, use tissue conditioner
Leave denture out as much as possible whilst healing occurs
Define denture-induced stomatitis
Chronic inflammatory response of the denture- bearingmucosa to harmful stimuli
Describe the location where denture-induced stomatitis lesions are usually found
Beneath an upper complete denture
Incidence of denture-induced stomatitis in the denture wearing population
11 - 67%
Describe Newtons classification of denture-induced stomatitis
Type I: pinpoint hyperaemia
Type II: diffuse erythema of denture bearing area
Type III: papillary hyperplasia, can be drug induced
5 causes of denture induced stomatitis
Continuous denture wear
Poor denture hygiene
Direct trauma from fit surface
Candida albicans infection
Poor salivary secretions
3 problems untreated denture induced stomatitis can cause
Poor fit of dentures
Tissue hyperplasia
Systemic candidal involvement
Management of denture induced stomatitis
Leave denture out at night
Tissue conditioners
Reduce denture areas causing trauma
Antifungals
Define angular cheilitis
Infection of commissures of mouth, broken skin and erythema by Candida albicans and Staphylococcus aureus
3 causes of angular cheilitis
Fe / vitamin B12 / folate deficiency
Adjunctive antibiotic therapy
Immunological deficiency
Management of angular cheilitis
Antifungals
4 conditions complicating complete denture prosthodontics
Enlarged tuberosities
Prominent mylohyoid ridges
Tori
Prominent frenal attachments
Describe improvements that can be made by denture reline and rebase
Improve the fit of the dentures and a moderate amount of extension
Define denture rebase
Laboratory replacement of the majority of the denture base following clinical impressions of the fit surface
3 indications for denture rebase
Residual ridges have resorbed and adaption of bases poor
Gross alveolar resorption has occurred 3-6 months after insertion
Construction of new dentures may cause physical or mental stress
5 requirements for denture rebase
Denture base extension adequate
Aesthetics satisfactory
Occlusion correct
OVD satisfactory
Speech satisfactory
Method for rebasing dentures
Remove undercut areas from dentures
Make relief holes in anterior palate of upper
Take closed mouth impression with zinc-oxide eugenol or polyvinylsiloxane
Define denture reline
Temporary solution to improve denture fit using hard or soft materials
3 indications for denture reline
Improves denture fit
Treat pathology: denture-induced trauma, denture-induced stomatitis / denture-induced hyperplasia
Aid to diagnosis
Describe the material and indication for a soft reline
Soft elastic material which absorbs occlusal load and reduces pressure on the tissues may relieve persistent pain
Describe the material and indication for a hard reline
PBMA monomer to improve looseness before a rebase is performed
Describe the material and indication for a tissue conditioner
Soft seudo-elastic material that flows under pressure, applied a denture to allow a more even distribution of forces and improved fit
5 causes of denture base fractures
Trauma: dropped, high occlusal forces
Alveolar resorption due to poor fit
Inaccurate impression due to poor fit
Inadequate relief that rocks on bony palatal torus
Warping due to reccuring during repairs, rebase
Describe the process for repairing a denture
Denture temporarily fixed in position with wax
Technician pours a temporary model and cut key to add repair acrylic
Technician mixes PMMA and applies it into the key to repair denture
Process for adding of teeth to existing denture
Take impression with denture in mouth for model fabrication
New acrylic tooth placed and held in place with plaster index
Laboratory uses chemically- cured acrylic to fix tooth in place to existing denture
Define immediate dentures
Denture constructed before the extraction of the teeth which it replaces and inserted immediately after the teeth are extracted
4 advantages of immediate dentures
No edentulous period
Duplicate tooth position closely for good aesthetic and functional result
Tongue change prevented
Sockets protected
3 disadvantages of immediate dentures
Can’t duplicate extreme tooth position or malocclusion
Additional time and expense as lose fit quickly, rebase/remake required sooner
Not possible for multiple extractions
Define overdentures
Removable prosthesis that completely encloses one or more teeth (or roots) or implants beneath its fitting surface
6 benefits of retaining teeth for overdentures
Preservation of alveolar bone
Greater surface area to transmit forces to bone
Improved retention directly from remaining tooth substance or use of precision attachments
Improved stability
Improved masticatory function
Increased patient acceptance
4 disadvantages of overdentures
Periodontal risk factor
Caries risk factor
Greater bulk, patient tolerance compromised
Risk of denture fracture where space lacking or heavy occlusal load
3 features to examine when providing overdentures
Periodontal disease status
Inter-ridge space on articulated study casts
Potential abutment teeth
3 potential abutment preparations when providing overdentures
Coronal reduction to dome shape
Coronal reduction and restoration with endodontics and plastic restoration / indirect coverage
Coronal reduction and restoration with endodontics and indirect coverage with precision attachment
Advantage of precision attachments for overdentures
Aid retention from the root
4 disadvantages of precision attachments for overdentures
Increased cost
Difficult maintenance
Higher loading of teeth
Caries around attachment
2 methods of preventing of problems with overdentures
OHI / dietary advice
Topical fluorides
Define dental implants
A small titanium screw surgically placed into the jaw bone which acts as a root to support crowns, bridges or dentures to replace one or more missing teeth
3 indications for dental implants
Hypodontia
Severe trauma
Post-oral malignancy
3 components of a dental implant
Abutment
Titanium screw
Crown
5 contraindications to dental implants
Smoker
Diabetic
Osteoporosis
Radiotherapy
Immunodeficiency diseases
4 advantages of dental implants
Avoids dentures
Maintains alveolar bone
Avoids conventional bridgework and conserves adjacent tooth tissue
Improves chewing ability
4 disadvantages of dental implants
Requires surgery
Lengthy treatment
Requires some level of bone quality and quantity
Expensive
Define osseo-intergration
Direct mechanical and functional contact between living bone and implant
