Revision Flashcards
2 implant mandibular overdenture:
Is not the gold standard implant therapy but it is the minimum standard that should be sufficient for most people
Contraindications for implant placement:
Anatomical limitations Medical contraindications Poor OH Non compliant patients Expensive !!!!! Non acceptance of surgical treatment !!!!! Poor communication
Irreversible bone loss is associated with:
denture use because it relies on the bone for support so it is problematic bc of bone having load
-complete dentures cause bone loss
Changes occurring following tooth loss are irreversible
The further bone loss progresses, the more difficult functional rehabilitation becomes
Use of complete dentures results in accelerated rate of bone resorption (compared to no dentures or having implants)
Use of poorly fitting complete dentures results in accelerated rate of bone resorption (compared to use of well fitting dentures)
SOS
Where are the occlusal forces transferred for CD?
What is the result of that?
To reduced surface area
Through the mucosa (not the teeth)
To supporting bone (damaging it)
Result:
Propriorecoetive mechanism of periodontal ligaments is lost
SA of supporting bone and mucosa is diminishing
Number 1 PRIORITY:
Screening for oral/head and neck cancer
When dentures require little/no modification consider doing the:
Copy denture technique = new denture production very similar to the old one but with improved fit
(refers to duplication of an existing denture)
They are a faster alternative to remake acrylic CD
Previous successful Vs unsuccessful dentures - treatment options:
Do nothing
Repair/modify existing denture
New CD
successful:
Copy denture
unsuccessful:
Implants
Psychological support
Irritated denture bearing tissues
- What causes it
- Localized or generalized
- Clinical symptoms
- Treatment
- Poorly fitting denture or poor OH or excessive use of denture adhesive
- Both
- Inflammation, redness, swelling, pressure spots, often no symptoms
- avoid use of dentures for several days; soft tissues rebound to normal morphology
-Alternatively: soft liners or tissue conditioners, Oral and denture hygiene
-in severe cases: permanent relining of existing dentures to allow sufficient time for healing
Occlusal adjustments may also be required
Denture related stomatitis:
- What causes it
- Factors
- Most commonly in
- Conservative approach
- If condition persists
- Aim
=chronic inflammation of mucosa
- Unknown etiology
- mucosal trauma, poor OH and denture hygiene, night time denture wear, bacterial/yeast infections (C albicans)
- maxilla
- avoid use of dentures as much as possible, oral and denture hygiene, drying of dentures overnight
- antifungals, antimicrobials, disinfection agents, antiseptic mouthwashes, microwave disinfection and photodynamic therapy have been used
- HOWEVER: there’s no significant difference between antifungals and disinfection treatment - to improve clinical appearance prior to secondary impressions
Treatment timing and patient compliance are critical to avoid condition relapsing with new dentures
Denture hyperplasia:
- Also known as
- Localised or generalised
- Clinical symptoms
- Treatment
- Cause
- ‘denture irritation hyperplasia’ or ‘epulis fissuratum’
- Localised hyperplasia of soft tissues
- The hyperplastic tissue forms single or multiple folds
- If small, recent and localised, may only require denture border relief +/- soft liner or tissue conditioner, more often requires surgical excision, care must be taken not to reduce the sulcus depth
- due to ill fitting, overextended, thin and sharp denture borders
Fibrous tissue proliferation =
- Also known as
- Most common
- Clinical symptoms
- Prosthodontic management
- Surgical management
- flabby ridge/fibrous tissue replacement
- Anterior maxilla - Often seen in complete dentures opposing natural teeth
- Accelerated residual ridge resorption results in excessive soft tissues over the ridge which is movable, poor foundation for new CD b/c of limited support offer
- modified impression procedure
-record secondary impression with selective compression of the main load bearing areas and a muco-static impression of the flabby ridge region
Can be achieved with a ‘windowed’ custom impression tray and recording the impression in 2
stages using different materials
Border moulding is carried out first; the main load bearing areas and sulci are recorded in ZOE paste and after any excess material is removed the flabby ridge area is recorded in thin mix of alginate syringed in the area, in light bodied silicone or impression gypsum - alternatively, excess soft tissue may be surgically removed
Care must be taken as the height of the residual ridge decreases significantly
Further bone loss should be anticipated due to the surgical intervention
Many complete denture wearers not very keen on surgical procedures!
Our duty for the risk management in CD is:
Prevent total tooth loss or any loss
Avoid use of CD
If CD will be used need to be made well done
Ensure CD will be maintained and re-adapted in time
Convinse them to have implants
What is the priority when patients want to change their existing denture?
To diagnose correctly what is wrong with that (the existing one)
SOS
Overextended borders:
- What does it cause?
- Localised or Generalised?
- Examples
- Causes pain/discomfort and/or displacement of denture in function
- Both
- Labial border -> loss of retention in speech and facial expressions
Maxillary posterior buccal border ->»_space; when mouth opens
Mandibular lingual border ->»_space; with tongue movements
Location of overextention determines clinical presentation - OPPOSITE FOR UNDEREXTENTION
-can result in hyperplasia
What determines whether there will be pain/ulceration or displacement of the denture?
Degree of overextension Amount of retention at rest Border morphology Patient persistence Mucosa tolerance Location of the problem
SOS Underextended borders problems:
- What does it cause?
- Localised or Generalised?
- Causes lack of RETENTION of the denture in function and at rest
- Both
Lack of retention clinically is the same regardless of problem’s location
Thin borders problem:
- What cause?
- What can result in?
- Localised or Generalized?
- Overextended or Underextended?
- Causes pain/discomfort and ulceration in function
- Can result in HYPERPLASIA in the long term if patient persists using the denture and the problem is not rectified
- Both
- Both
Likely to also be sharp ended (hyperplasia)
Thick borders problem:
- Overextended or underextended
- What cause?
- underextended
due to:
incorrect stock impression tray size
no modification of the stock tray
excessive amount of impression material
use of high viscosity impression material
no border moulding (helps to record an accurate impression of the trays) during impression procedure
and due to: - retention loss in function due to muscle activity or even at rest
SOS
Non anatomical morphology problem:
- What does it cause?
- What happens if too bulky?
- Causes lack of retention at rest and in function
- If too bulky, muscular action distabilises denture
Incorrect border thickness and/or extension
Effective border seal cant be achieved
Problem with a poorly adapted base through the whole tissue surface:
Lack of retention and poor support
Overextended denture base problems:
- What does it cause?
- Mainly where?
- Causes difficulty and pain in swallowing, speech, problems and gagging
- Mainly in posterior maxillary region
May manifest immediately at placement through the day as soon as the food bolus enters the mouth cavity
Underextended denture base problems:
- What does it cause?
- Mainly where?
- Patient’s or Dentist’s fault?
- Causes generalized pain throughout the denture supporting area due to insufficient SUPPORT
- Most common in maxilla posterior palatal border
- Dentist’s fault
-training denture
The further the tissues/cheeks out -> sulcus goes up so underextended (unless you correct it in secondary impression)
SOS
Excessively thick denture bases problems
- What does it cause?
Cause discomfort, gagging, speech problems, difficulty in swallowing, pain
Common at posterior borders heel clush or b/w maxillary denture base and coronoid process of mandible - hamular notch
Also no retention
-causes dislodgement of the maxillary denture
during function
Excessively thin denture bases problems
- What does it cause?
Prone to cracks and fractures
-Especially if opposing natural teeth
Insufficient relief in areas of deep soft tissue undercuts:
- What does it cause?
- Symptoms?
- Causes pain during denture placement and removal
- Localised redness and ulceration on the slopes of residual ridge
Good retention
Pressure areas problems:
- What does it cause?
- Causes pain along large areas of fitting surface of the denture base, particularly in function
Poor support - rocking of the denture
May also be in relation to tori
Lack of relief along “knife edge” ridge:
- What does it cause?
- Causes pain across mandibular ridge crest, particularly in function
Thin mucosa crushes b/w rigid denture base and sharp ridge crest
Problems with JRR:
Increased OVD:
What does it cause?
Causes gagging, SPEECH problems and difficulty in SWALLOWING and mastication
Facial pain, pain along the denture borders and across the residual ridge
Destabilization of dentures in function, especially mandibular
Typically deteriorates the longer dentures are in situ until the patient has to remove them
-Teeth in occlusion with the mandible at rest position
- lack of free way space (measure it again with the formula)
- Lips unable to seal (struggle to close the lips)
- Stretched muscles of the lips and chin
- Patients may report the dentures feel too big = MEANS NO FREE WAY SPACE
- May also report the teeth look too big – meaning there is too much teeth showing
-reduced stability, loss of retention in function
Problems with JRR:
Decreased OVD symptoms:
Difficulty in mastication and tiredness, muscular pain, tongue biting
support, stability and retention are not directly affected…but other problems are caused (difficulty in eating, tongue and cheek biting, muscular tiredness, etc) - not a problem
-by decreased OVD the mandible is more protruded
- Excessive freeway space!
- Insufficient lip support
- Vermilion border of the lip turned inwards and thin
- Deep crease over the chin
- Patient may report cheek or lip biting
- BEWARE: possible that the patient reports they feel very comfortable, especially if they have been used to reduced OVD in previous set of dentures!
-we cannot allow it for too long since it will create future problems
Dietary selection & nutritional status of complete denture wearers - 4 factors:
Masticatory function & oral health
General health
Socioeconomic status
Dietary habits
Causes of malnutrition:
Poor general health Poor absorption of protein Intestinal, metabolic and catabolic disturbances Anorexia REDUCED SALIVARY FUNCTION
In order to improve the nutritional status, often necessary to modify dietary habits
Natural dentition > implant supported overdenture > conventional complete denture
✔️
How to establish the patient’s head to establish occlusion?
natural head position:
back - straight up
no neck support
mirror to look straight into eyes
Frankfurt Horizontal Plane:
=connects lowest left orbital and upper tragus
- important to find the correct position of the head
- Asians have lower occlusal plane and higher Frankfurt plane
Curve of Spee:
= connects tip of canine, all buccal cusps of premolars and molars and condyle center of TMJ
- important to find the cuspal ridge
- longitudinal plane of occlusion
Curve of Wilson:
= connects lateral teeth of the same size
- ex: M1
- important for inclination checking
SOS
Antero-posterior position of maxillary anteriors:
Lip support
Nasolabial angle
Amount of teeth ‘showing’
Smile line
-we aim almost 90angle b/w the nose
Balance in CD:
Balance in protrusion:
Very steep occlusal plane, or Exaggerated compensating curve, or Very high cusps
OR Reduced incisal guidance angle
=> possible speech & swallowing problems
-to correct this: set the posteriors, especially second molar higher up. but this will cause problems
-we don’t want balanced occlusion or canine guidance, we go for group function -> even contacts on C, P1, P2, M
balanced occlusion = bilateral even contact b/w upper and lower denture in the intercuspal position
Regarding the occlusion of complete denture it is desirable to create dentures with:
Group function:
- Even contacts on the working side (2 or more teeth other than the canine, preferably all!)
- Smooth path of movement between centric and eccentric positions
- No contacts on the non-working side (but a near miss is welcome!) or anteriors
-NOT canine guidance
Lingualised occlusion:
Monoplane occlusion:
Same principle as in balanced occlusion
Main contacts between upper lingual cusps
Buccal cusps have little or no function
Does not look nice! - everything looks flat
Increased forces transferred to supporting structures
-acrylic on last lower molar
Temporary/record Vs Permanent bases:
what material used?
when are they used:
after what?
Temporary/record bases:
-made of baseplate wax, autopolymerising or light polymerized custom tray resin or polymethyl methacrylate (PMMA)
Uses:
-carry the wax occlusion rims for jaw relationship registration
-used to articulate the working casts
-used to set up the teeth and carry out the trial insertion
-used until the trial insertion stage
-replaced with a permanent denture base material only during the final processing
-Must be well supported, stable and retentive!
Permanent bases: -can be done after secondary impression -made of heat polymerized or auto polymerised PMMA, or other permanent denture base material -can be fabricated early on -good retention and stability with it Uses: -articulation -teeth set up -trial insertion -jaw relationship registration -incorporated in the finished prostheses: these are secured in the mould and only the waxed up polished surfaces are replaced with PMMA during the final processing
Using a permanent base for jaw relationship registration ADV Vs DISADV:
Advantages:
Jaw relationship registration: easier and more accurate
Retention, support and stability can be assessed early on
Adjustments at the borders and/or fitting surface can be done early on
Only need to worry about the occlusion at placement
Disadvantages:
More work for the dental technician
Small extra cost
Risk of permanent deformation of the denture base during the 2nd processing/finishing if mishandled
What is ‘acrylic resin’?
= Any of numerous thermoplastic or thermosetting polymers or co-polymers of acrylic acid, methacrylic acid, esters of these acids or acrylonitrile
-no good properties so not ideal to use it to replace someones teeth
-Properties:
Hardness: soft
Strength: low
Toughness: low
Elastic modulus: low
Thermal conductivity: low
Thermal expansion: high
Density: low
Translucency: high
-Biocompatibility: ok-ish
-Cheap
SOS
What is a polymer?
= A molecule made up of many units
SOS
Oligomer =
a short polymer (2-10 units)
SOS
Monomer =
the molecules that unite to form a polymer with a chemical rxn termed polymerization
-can cause allergic rxns
SOS
Co-polymers:
= when 2 or more different types of monomers are joined
Degree of polymerization:
the total number of units in a polymer molecule
Molecular weight of a polymer molecule:
the sum of the molecular weights of the units it is made from
What is a polymerization reaction and what are its 2 types?
= a rxn of 2 molecules combined to form a larger molecule (ex: monomers to polymers)
- Addition polymerization: no by-product
- Condensation polymerization: low molecular weight by-products (such as water, alcohol)
-the more monomer, the greater the polymerization shrinkage
SOS
PMMA polymerization steps:
how to get PMMA
- Initiation:
- benzoyl peroxide is divided into two identical parts and each is binded to an MMA creating the initiation molecule to start the propagation
- generation of free radicals
- free radical addition polymerization chain reaction
- initiator: benzoyl peroxide (not a catalyst! - it doesn’t get consumed) – readily dissociated on heating to produce radicals
- opening of a double bond in the vinyl group of MMA results in formation of another free radical, which “attacks” another double bond…
- PMMA is prepared by addition polymerisation of MMA - Propagation:
- repeated rxn of same type
- two MMAs bond together
- free radicals react with unsaturation centers leading to chain lengthening
- growing (live) chains = chain lengthening
- for cross linking to occur - Termination:
- by self-limitation; rxn stops
- free radicals are consumed by a rxn with other two radicals by not producing any more radicals, thus terminating the process
- when two radicals come together
- growing chain interacts and then stops, so that another shorter chain starts propagating - Inhibition:
- hydroquinone used to increase storage life
SOS
What is a Cross-linking Polymer and why it is important?
- has the best mechanical properties so if needed to improve properties, we prefer this polymer
- does not soften on heating (we don’t want it to get soft anyway) = thermoset
- results in the formation of a network structure; primary linkages occur between chains, and the polymer becomes a GIANT MACROMOLECULE
SOS
Linear and branched molecules:
-are discrete but held together through weak physical bonds
- On heating, the mobility of the chains increases, the weak bonds break and the chains slide past one another, resulting in a softened material
- On cooling the chain mobility decreases, the physical bonds reform and hardening occurs
-they are termed thermoplastic !!!!!
PMMA properties affected by:
chemical composition
degree of polymerization
number of branches and/or cross-links
Generally, longer chains and higher molecular weight result in increased: strength hardness stiffness creep resistance brittleness
- heat accelerated
- herd base due to hard mechanical properties
Stiffness: Strength: Creep: Hardness: Glass transition temperature: Toughness:
Strength: ability to withstand applied load without failure or permanent deformation
Hardness: resistance to abrasion, indentation, penetration
Stiffness: resistance to elastic deformation
Toughness: ability to absorb energy and plastically deform without fracturing
Creep: slowly occurring plastic deformation under persistent mechanical stress
Glass transition temperature: the temperature at which a polymer ceases to be glassy and brittle and becomes rubberlike !!!
Plasticizers:
molecules which reduce a polymer’s rigidity by lowering the glass transition temperature
-these are small molecules which facilitate movement by surrounding larger ones
Fillers:
particles added to polymers to improve specific properties and lower the cost
Polymerization shrinkage:
up to 21% vol for unfilled resins
6% vol for denture resins
3% vol for resin composites
High impact PMMA:
Incorporation of a rubber phase in the polymer beads for improved impact strength and reduced stiffness
SOS
Advantages Vs Disadvantages of PMMA as a denture base material:
Advantages: Biocompatibility Aesthetics Dimensional stability (in use) Good adaptation Strength Bond with acrylic teeth - no need to worry about mechanical properties Ease of modifications Long shelf life Widespread availability No need for complex equipment Easy handling Cheap
Disadvantages: Residual monomer - toxic for patient (change water now and then and it will disappear) Low thermal conductivity Creep Water resorption - easier for bacteria to colonize Processing shrinkage (?) Fatigue Radiolucent
SOS
What do you think is the clinical significance of the polished surfaces?
Patient comfort Speech Deglutition (=swallowing) Retention & stability (helps to keep muscles and denture in place when polished - if not polished, when muscles contract then it will move the denture outwards thus distabilise it) Aesthetics Hygiene
Components of speech:
Respiration (=the movement of air in inspiration and expiration) Phonation Resonations !!!! Articulations !!!! Neurologic integrations Audition
SOS
Resonance:
The sounds produced by the vocal chords are modified in:
The pharynx
The oral cavity
The nasal cavity
The paranasal sinuses
-anything interfering with these 4 modifications will change the speech
SOS
Articulation:
The sounds are formed in meaningful words
The tongue, lips, palate and teeth play a crucial role
-anything interfering with those will interfere with speech
Speech considerations:
Anatomical classifications:
To check the position of anterior maxillary rim - which sound?
For free way space and medium space - which sound?
For the correct rest position of the mandible - which sound?
a) Which of those may be affected by the contouring polished surfaces?
Vowels are voiced sounds: a, e, i, o, u
-said with open mouth so not a problem; no need to worry about
Consonants may be either voiced or produced without vocal chord vibration in which case they are called breathed sounds: p, b, m, s, t, r, z etc…
Consonants are most important from Prosthodontic point of view
Various classification methods
Clinically significant:
according to anatomical parts involved in their production:
Bilabial: lips (m, p, b)
Labiodental: lips and teeth (f, v)
Linguodental: tongue and teeth (th)
a)LINGUOALVEOLAR: tongue and anterior palate (t, d, r) !!!!!
LINGUOPALATAL and LINGUOVELAR: tongue and palate (k, j, g) !!!!!
-affected more by the contouring of the polished surfaces: lingualveolar and linguopalatal and linguovelar
For free way space and medium space to say ‘s’
To check the position of anterior maxillary rim: the ‘f’ and ‘v’ sounds
For the correct rest position of the mandible: is the ‘m’ sound
When is polishing done?
after tooth positions
- First: establish occlusal plane level and orientation, anteroposterior tooth positions and OVD
- All the above also affect speech!
SOS
Cawood and Howell classification:
=
classes:
= classification of alveolar ridges
Class I: dentate
Class II: immediately post-extraction
-soft tissue / bony undercuts
Class III: well-rounded ridge form, adequate width and height
-favorable for complete dentures
Class IV: knife-edge ridge form, adequate height, inadequate width
-easily traumatized mucosa, painful
Class V: flat ridge form, inadequate in height and width
-reduced stability and support
Class VI: depressed ridge form
-reduced stability, support and retention
Border extension & shape:
Buccal sulcus:
Buccal frenum
Buccal shelf
Buccinator m.
Buccal frenum
Buccal shelf
- is NOT a relief area
- ONLY IN THE MANDIBLE
- important in the fabrication and wearing of mandibular CD
- primary stress bearing area in mandibular edentulous ridge (= areas that withstand functional forces applied to a denture)
- you cannot extend the border further back from the external oblique ridge -> place for buccal shelf
- area between the buccal frenum and the anterior border of the masseter
- The greater the access to the buccal shelf the more support is available for the denture. Access is determined by the attachment of the buccinator m
Buccinator m. !!!!!!!!!
- the way it attaches to maxilla (up, down and out)
- its action will determine the border of the extension
- border extension is limited by this muscle
- determines access to the buccal shelf space
Anatomy of the edentulous mouth:
maxilla:
mandible:
Palatal gingival remnant Incisive papilla Buccal sulcus Residual alveolar ridge Rugae Mental foramen Labial sulcus Lingual sulcus (posterior) Buccal Shelf Vibrating line Retromylohyoid fossa Hamular notch Retromolar pad Buccal sulcus Labial sulcus Maxillary tuberosity Fovea palatini
maxilla: Palatal gingival remnant Incisive papilla Buccal sulcus Labial sulcus Vibrating line Hamular notch Residual alveolar ridge Maxillary tuberosity Rugae Fovea palatini
mandible: Residual alveolar ridge Mental foramen Retromolar pad Buccal sulcus Labial sulcus Lingual sulcus (anterior) Lingual sulcus (posterior) Buccal Shelf Retromylohyoid fossa
SOS
Vibrating line:
- posterior palatal border
- not straight, not extended and very posterior
- imaginary line on soft palate dividing mobile and immobile parts from each other
- extend where the hard palate finishes
- do not extend up to vibrating line because no retention !!!!!!!!
- fovea palatini are in front of it !!!!!
Border extension & thickness:
Hamular notch:
- hamular process is a bony projection of the medial plate of the pterygoid bone and is located distal to the maxillary tuberosity
- lying between the maxillary tuberosity and the hamulus is the hamular notch, which is a key clinical landmark in maxillary denture construction because the maximum posterior extent of the denture is the vibrating line, which runs bilaterally through the hamular notches
Tensor veli palatini m.
Coronoid process !!!!!!!!
-should be avoided
Masseter m.
SOS
Border extension & shape:
Labial sulcus:
Orbicularis oris m.
Labial frenum
Mentalis m.
-determines the border extension of the denture
Orbicularis oris m.
-has an indirect effect on the extend of the
denture
Labial frenum -> needed to provide relief
- relevant to border extension
- big frenum Vs getting rid of it
Mentalis m. !!!!!!!!!
- affects the borders of the mandibular denture
- when people talk it can distabilise their denture
Border extension & shape:
Retromolar pad:
- limits the most posterior position of a mandibular molar
- it is located distal to the last mandibular molar
- it is extremely important in denture construction from both a denture extension and plane of occlusion standpoint
- the plane of occlusion is located at the level of the middle to upper 1/3 of this pad
- most compressible tissue in the lower arch
- Masseter m.
- should be covered by the mandibular denture for retention !!!!
Mental foramen:
- nerves passing from it: inferior alv n and mental n
- your denture can press on this and cause pain
- it determines the border
SOS
Border extension & shape: Lingual sulcus (posterior):
Mylohyoid m.
Retromylohyoid fossa
Lingual sulcus (anterior): Lingual frenum Genioglossus m.
Mylohyoid m.
-mylohyoid ridge !!!!!!!! -> sharp and has an undercut; it is painful if there’s increase in OVD
Retromylohyoid fossa
-area that determines the most distal lingual extent of a mandibular CD (most distal extension of the mandibular denture)
-the opposing areas are usually undercut in relation to each other
-1 difficulty encountered when fabricating the mandibular denture is that these bilateral undercuts may greatly complicate the process of making the preliminary and final impressions. the dentures may also require significant adjustments
in these areas at the time of insertion
What is a denture border?
= the margin of denture base at junction of the polishing surface and the impression surface
Retention =
Stability =
How to check if the denture lacks support?
retention = the ability of the denture to withstand dislodgement against its path of insertion / = the resistance to vertical forces of mastication, occlusal forces and other forces applied in a direction towards the denture bearing area / the ability to resist vertical dislodging forces
-to check it: pull AWAY from the tissues
stability = the ability of the denture to withstand horizontal forces / the ability to resist horizontal rotational displacing forces
support: if it moves TOWARDS the tissues, it lacks support
Which zone should the occlusal rims be designed within to be?
neutral zone
-zone where buccal and lingual forces are balanced
Where should the occlusal plane of occlusal rim be parallel to?
plane of the maxilla
While recording the rest position of the mandible, the patient ‘s head should be:
upright and unsupported
The correct buccolingual placement of teeth plays an important role in phonation. What should the relationship of the teeth and tongue be in pronouncing ‘t’ and ‘d’ sounds?
contact of the tip of the tongue with the anterior palate and lingual surfaces of the maxillary anterior teeth
A patient comes with a complaint of a newly made denture which is loose and causes soreness even after repeated adjustments. What is the most important protocol to follow in such a casa?
check the occlusion
SOS
What are the treatment aims for complete dentures?
- Aesthetics: retention, stability and support
- Speech: retention, stability and support
- Mastication: support, retention and stability!
What does the patient’s denture lack if every time they talk their denture drops?
retention
Which steps can guarantee that the denture will have all 3 qualities (aesthetics, speech and mastication)?
Primary impressions Custom impression trays Secondary impressions Temporary bases - how we record Jaw relationship registration Tooth setup Wax up - how we wax up the polish surfaces
Aim of primary impressions:
Record all the anatomy (full extent of denture bearing tissues) and the correct depth and width of the sulci
Underextended primary impression problem could result to underextended:
custom impression tray
secondary impression
record base
permanent denture base
Retention, support and stability may be compromised
Before the secondary impressions, the custom trays should have some of the desired qualities of the finished denture base when placed in the mouth:
Close adaptation throughout the entire denture bearing area
Anatomic border morphology (not too thick/thin)
Support and stability
What is the clinical significance of positioning, size and orientation of the custom tray handles?
for no lip displacement
Border moulding:
=
when is it done?
process:
= technique of properly extending the flange length
of an impression tray prior to making the final impression
- done BEFORE secondary impression
- ensures correct border extension
-green stick compound heated in flame and dropped in the place where needed for framing to ensure the frenulum is impressed by these sticks
-INCREMENTALLY add this softened thermoplastic impression material on the tray along the border
-activate the relevant muscles
-after this, the custom tray should demonstrate good retention
-then the impression is completed using Zinc Oxide Eugenol impression paste (already close-fitting so no need to add more material)
-then place it in the mouth
-deficiencies can be corrected by addition of more material (no need to add from scratch)
-once complete: rinse and place again in mouth to assess retention (tell patient to relax and pull away from tissues to check it), support and stability
=> if one of these qualities is lacking: the finished denture will also be lacking!
- if border moulding is insufficient repeat if needed
- border molding for mandibular denture should not extend over external oblique ridge
- if underextended borders then it is corrected by border moulding
- Mandible moved side to side to avoid clash with coronoid process
- If it is shiny and smooth the material has either set before or it was a bit inadequate – it didn’t reach the tissues as we wanted that
- We keep applying modelling compound until we capture all the anatomical structures mentioned and have a border seal
- We want to remove some material b/c we don’t want to build up excess as it will interfere with our impression
- The patient should be straight facing the dentist – maxilla is hard
- The line he made on the soft palate is it for the sole purpose of defining the posterior border
Trial Insertion:
=
when are errors detected?
why is it done?
= teeth set up and trying in mouth
- teeth are set in wax and small errors may easily go undetected
- they only become apparent after the dentures are finished (or not at all…)
- in occlusion the wax will be removed even if patient is in ICP, so even then you can identify errors
- it is done to make assessments of the aesthetic position of denture teeth, facial support, phonetics, OVD, occlusal scheme and the centric occlusal position
- gives the patient an opportunity to see the aesthetic results from the previous deliberations during the maxillomandibular records appointment and the tooth selection process
SOS
Jaw relationship registration:
importance:
when is it done?
- after V dimension determination
- important b/c it mounts the cast on the articulator (transfers the exact relationship of maxilla and mandible to the articulator)
- records the retruded position of the mandible at the selected vertical dimension of occlusion
- for a different vertical occlusion the antero-posterior position of the mandible will be also different !!!!!!!!!!
Tooth setup importance:
-3 things we need to include:
- to restore the natural occlusion
- helps you in JRR and diagnosis
-3 things we need to include:
Level and orientation of the occlusal plane
Antero-posterior position of maxillary incisors
Bucco-lingual (bucco-palatal) position of posteriors
SOS
Level and orientation of the occlusal plane (OP):
If OP too superiorly:
If OP too inferiorly:
OP too superiorly (high): (when the tongue moves in function it will hit the teeth and destabilize the lower denture) mandibular denture unstable, loses retention in function
-lower teeth will be too high
(the opposite will happen) OP too inferiorly (low): maxillary denture unstable, loses retention in function!
-upper teeth will be too low
-because horizontal relation changes
SOS
Antero-posterior (AP) position of maxillary incisors:
If set too anteriorly:
If set too posteriorly/palatally/back:
Set too anteriorly: lip pushes denture inferiorly, loss of stability and retention
-m of upper lip pushes the denture outwards
Set too posteriorly: tongue pushes denture labially (outwards), loss of stability and retention!
-will break the peripheral border seal
- Placing the maxillary anteriors too far palatally also usually results to increased OVD!
- set them in correct positions
Bucco-lingual / palatal position of posteriors:
If set too buccally:
If set too lingually:
Set too buccally: cheeks destabilize the dentures, loss of retention
Set too lingually: tongue destabilizes the dentures, loss of retention!
Wax up:
Wax up too bulky:
Wax up lacking in bulk:
-to restore the natural soft tissue contours
Wax up too bulky: cheeks destabilize the dentures, indirect loss of retention
Wax up lacking in bulk: incomplete peripheral seal, lack of retention!
-we need to have correct anatomy of the polished surfaces, that’s why it is important to have a correct anteroposterior position
- When considering the arrangement of the maxillary anterior teeth, what determines esthetics?
- What determines the fullness of the lips (lip support)?
- the position of their incisal edge
2. the cervical portion of teeth and the fullness of maxillary denture base
Most patients desire symmetrical arrangement of the anterior teeth with minimal variations that might provide a more natural look. Which 2 groups of patients might be an exception to this statement?
The patients with existing dentures, who would like the arrangement of the teeth of the new denture to mimic those of the existing denture.
AND
The patients receiving immediate CD also desire that the arrangement of the denture teeth match the arrangement of the natural teeth
In what direction do the crests of the residual ridges resorb following extractions, and what might these resorptive patterns result in?
when the natural teeth are lost:
the mandibular residual ridge resorbs Downward and Outward
the maxillary residual ridge resorbs Upward and Inward (lingually)
Because of these resorptive patterns, it is necessary to create a reverse articulation (cross bite) for the posterior teeth
If an adjustment is necessary to the vertical position of the plane of occlusion, which arch should be favored and why?
the position of the plane of occlusion may be adjusted either superiorly or inferiorly to a small degree
When making adjustments to the height of the occlusal plane, the MANDIBULAR arch should be favored because of its decreased stability
