Complete dentures Flashcards
When a denture has a close fit to the tissues what is stronger?
The retentive force because of surface tension
What is the Cawood and Howell classification?
Class 1 = dentate
2= immediate post XTN
3= well rounded ridge, adequate height and width
4= knife-edge, adequate height, inadequate width
5 = flat ridge
6 = depressed ridge
What is retention? What are the influencing factors?
The capacity of the denture to resist displacement away from the tissues.
- Adhesion
- Cohesion
- Tissue contact
- Peripheral seal
- Neuromuscular control
What is stability? What are the influencing factors?
Capacity of the denture to resist movement whilst in contact with the tissues i.e. horizontal/rotational forces
- Maxillary and mandibular ridges
- Adaptation of denture base
- Occlusion
- Neuromuscular control
What is support?
Resistance of vertical movement towards the ridge
How do you measure the freeway space?
Resting face height - occlusal vertical dimension
Willis height gauge
What do you use a Foxs bite plane to assess?
- Interpupillary line
- Alar-tragal line
How should you assess periodontal health around implants?
6 point pocket chart
What can traumatic ulcers be caused by in a denture patient?
- Overextension of flange
- Sequestration of bony spicule (loose or sharp bone following extraction and mucosa on top affected)
- Rough fitting surface
- Foreign body beneath denture
What is
a) Denture granuloma
b) Leaf fibroma
a) If over a long period of time - tissue becomes hyperplastic
b) Leaf-like structure attached by thin stalk and lifts away, squashed and flattened by denture
What are the 3 features of combination syndrome in EAA?
- Extremely alveolar atrophy anteriorly in maxilla
- Mandibular teeth remain only
- Bulbous tuberosities
When a mandible is 2-3mm wide what is it also known as? What bony prominence is palatable within the mouth because of this?
Pencil thin mandible
Genial tubercle - bump of tissue lingual to ridge and can cause pain when wearing the dentures
If the patient is complaining of a sharp stabbing neuralgic pain in two areas of the mandibular ridge when you run your fingers along it what could it be?
Bone resorbed so that the mental foramen are repositioned to the crest of mandible so the mental nerve is exposed
What is
a) Acute pseudomembranous candidosis
b) Acute atrophic candidosis
c) Chronic hyperplastic candidosis
d) Chronic atrophic candidosis
a) Associated with immune deficiency = thrush
b) Prolonged steroid or broad spectrum antibiotic use
c) Candida leukoplakia - whiteness of tissue can’t be wiped off
d) Denture stomatitis
For denture stomatitis, what is
a) Type 1
b) Type 2
c) Type 3
a) Pinpoint hyperaemia and diffuse inflammation (limited area) associated with posterior of maxillary denture
b) Diffuse erythema of most of denture bearing area
c) Granular inflammation or inflammatory papillary hyperplasia
What poor host defences are an aetiological factor for denture stomatitis?
- Defects in cellular immune system
- Malnutrition in association with high carb diets, iron, folate, B12 deficiency
- Hypo endocrine states, diabetes, blood disorders
What are the aetiological factors for denture stomatitis?
- Poor host defences
- Denture trauma
- Xerostomia (saliva reduces adherence of C.albicans, and less IgA which can prevent infection)
- Continuous denture wear
- Denture plaque
- Low pH (favours Candida)
- Malnutrition
- Oral antibiotics
- Hormonal impalance
What is to be recommended for the management of denture stomatitis?
- Denture hygiene advice (clean thoroughly with nailbrush and soap, soak in CHX mouthwash or sodium hypochlorite if acrylic for 15 mins twice daily)
- Leave dentures out at night
- Tissue conditioners
- Correction of denture faults
- Diet advice
- Antifungals (fluconazole DIFLUCAN 50mg/day 7-14days systemically or miconazole 2% gel DAKTARIN TDS 14 days or nystatin)
- Brush palate daily
What is the treatment for angular cheilitis?
Miconazole2% cream or sodium fusidate 2% ointment
What are overdentures?
Prosthesis that derives support from one or more abutment teeth (implant) by completely enclosing them beneath its impression surface
What are the advantages for retaining teeth as abutments?
- Improved stability as maintained alveolar ridge
- Improved retention as increases denture bearing area
- Roots can be used for precision attachments to further improve retention
- Improved sensory feedback: maintaining PDL ligament as has proprioceptive fibres
- Decreased psychological trauma as not fully edentate
What are the problems with overdentures?
- Difficulty with undercuts as canines have canine buttresses which makes it harder to make dentures and find a path of insertion
- Caries or periodontal disease around remaining roots
- Fracture of acrylic as reduced amount
- High degree of maintenance
What are the indications for an overdenture?
- Single complete denture where you are trying to avoid rapid resorption
- Cleft palate/surgical defect
- Hypodontia (lack of development of ridge)
- Severe toothwear to gum level
What are the contra indications for an overdenture?
- Extremes of age
- Severe debilitation
- Poor cooperation
- Mental handicap
- Any condition that precludes RCT
- Previous treatment
What is the selection criteria for abutments?
- Canines good crown:root ratio as roots long. Canines>premolars>molars>incisors
- Symmetrically distributed in arch
- No subgingival caries
- RCT possible
- Cleansable
- At least 2 require
What is the simplest abutment preparation?
Doming
What are the disadvantages of precision attachments?
- Cost
- More complicated maintenance
- Weakened denture base
- OH requirements
- Increased load to abutments (perio)
In a stud attachment, what is the patrix and what is the matrix?
Patrix = ball part/male that sits on the root face Matrix = female that is embedded within fitting surface of denture
What are locator attachments?
Locator attachments sit within denture and the locator is attached to the tooth surface with coping or adhesive cement, but more often used with implants
What is the precision attachment that is called a keeper?
A ‘soft’ magnet attached to the root surface either by use of coping or with composite
What is the positioning of the locator implants in the mandible for implant supported overdentures?
- Intra-foraminal = medial aspect of inferior dental nerve foramen/ mental foramen medial to positioning of 4 or the 3 so it doesn’t encroach on inferior dental canal
- Parallel = surfaces of locators are straight - if not they create undercuts
- 2 implants
What is the positioning of the locator implants in the maxilla for implant supported overdentures?
- 4 implants at least as maxillary bone isn’t as robust and doesn’t support implants as well
What do the following colours mean for the inserts used in implant supported overdentures?
a) Blue
b) Clear
c) Red, orange and green
d) Black
a) Weakest strength
b) Strongest
c) No central bulbosity so help if locators have not been truly parallel in their insertion
d) Lab attachment
What are the indications for a copy denture?
- Previous satisfaction with dentures i.e. only minor issues
- Immediate dentures after all dentition removed (fit will be poorer due to first 6 months bone resorption)
- Multiple repairs but pt happy with appearance and fit of denture
- Elderly pts with reduced adaptive capacity
What are the stages of simple copy technique?
1) Pt assessment
2) Copy box impressions (mod with greenstick then alginate imp)
3) Technician pours replicas and casts. Articulates and set up teeth
4) Try in and wash impression with ZnOE or silicone close mouth technique
5) Flask, pack, process and finish
6) Insert
7) Review
What can be done if the anatomy is unfavourable before osseointegrated implants?
- Pre-prosthetic surgery e.g. sulcoplasty for when sulcus shallow
- Ridge augmentation - calcium hydroxyapatite insert
- Subosseous implants
What are sub periosteal implants (blades)?
Lower part fits under periosteum and inserted into bone, comes through the tissues at the neck. Denture clips onto bar
Why can you have a healthy implant with pocketing but no bleeding?
Where we would have a gingival crevice on a normal tooth we have long junctional epithelium and no PDL
What factors affect integration of an implant to bone?
- Biocompatibility
- Implant design
- Implant surface
- State of host bed
- Surgical technique
- Loading conditions
What are the issues with a Kennedy class 1 removable partial denture and an implant supported mandibular over denture?
- Tendency to rock where area at back lifts up
- Food packing under saddles posteriorly
What different types of elastic impression materials are
a) Hydrocolloids
b) Elastomers?
a) Alginate (irreversible), Agar (reversible)
b) Polysulphide, silicones (addition or condensation), Polyether (Impregum)
If you are taking an impression of someone with a flabby anterior ridge, what modifications would you make?
A special tray with a window
Liquid impression plaster in the flabby area
What are the a) Advantages and b) Disadvantages of Compound as an impression material?
a) - Mucocompressive to record depth of sulcus (very viscous material)
- Can be used in combination with other materials
- Compatible with cast material
- Can be trimmed easily, added to and readapted
- Can be used in stock tray to produce special tray
b) - Have to warm with water
- Can’t be used to record undercuts as rigid and brittle– High viscosity so doesn’t record surface setail
- Need technique to soften material so no internal strains due to low thermal conductivity
What are the a) Advantages and b) Disadvantages of Zinc Oxide Eugenol paste as an impression material?
a) - Mucostatic for fine detail
- Dimensionally stable
- Can be added and readapted to if faulty
- Doesn’t lose surface detail in wet mouth
- Adheres well to dry surface and to impression compound
b) - Allergies to eugenol
- Can’t be used with undercuts
- Only sets rapidly in thin layer
- Presence of water and increase in temperature reduce the setting time
What are the a) Advantages and b) Disadvantages of Alginate as an impression material?
a) - Cheap and easy to use
- Well controlled setting time
- Non toxic or irritant
- Can be used in stock or special trays
- Records fine details and undercutes
b) - Not dimensionally stable (imbibition and syneresis)
- Must be cast asap and wrap in damp towel/plastic bag
- Poor tear resistance and strength
- Surface reproducibility not as good as agars or elastomers
What are the main causes of impression inaccuracy?
- Operator technique
- Stock tray incorrect size
- Porous cast = incomplete initial reaction so cast has been poured before completely set
- Tray showing through due to mixing error or not enough material
- Polymerisation shrinkage
- Thermal contraction from oral to room temp
- Absorption of water or disinfectant over a period of time
- Loss of a condensation reaction product (water or alcohol)
- Impression away from tray (dried out or no adhesive)
For what material should a special tray be perforated?
Alginate
How are close fitting trays made for fibrous ridges?
Zinc oxide eugenol paste then impression plaster carefully painted around flabby part
What materials are used to construct special trays?
- Light cure acrylic resin (easily adaptable, uniform thickness, long working time, needs light curing equipment)
- Self cure acrylic resin (slight distortion on curing but they are then stable)
- Heat cure acrylic resin
- Compound Type II
What types of model/cast materials are used?
- Plaster = white. Heat to 120 in open vessel, beta-hemihydrate. Large, irregular, porous
- Stone = pigmented. Heat to 120-130 under pressure, alpha- hemihydrate. Smaller, regular, dense, less porous
- Special stone = heat in boiling solution of CaCl2, alpha hemihydrate
What is the purpose of the following features of an implant?
a) Parallel sided
b) External thread
c) Apical taper
d) Vents
e) Internal notches
f) Internal thread
a) Retention
b) Primary fixation and increased SA for optimum osseointegration
c) Minimise damage to surrounding structures
d) Allows collection of blood and debris without causing hydrostatic pressure build-up
e) To rotate fixture during placement
f) For attachment of abutments
How long are healing abutments left in?
2-3 weeks
What implant systems are there at the hospital?
Nobel Biocare, branemark or straumann
What space should there be between gingiva and surface of abutmetn?
2mm
When should radiographs be taken for implants?
Baseline, after 2 years then every 5 years
When should the neutral zone impression technique be used? At what stage is it used?
For lower denture cases where soft tissue displacement in function makes a significant contribution to the instability of the denture
Request lower neutral zone tray after registration and impression taken at try-in
What material should be used for neutral zone impressions?
Medium body silicone, impregum, visco gel, coe soft
What technique should be used for neutral zone impressions?
- Seat in mouth with upper trial denture in situ
- Functional movements such as days of week, swallowing
- Allow to set then reseat to see if functional stability improved
How many bricks of compound are required for
a) Maxillary imp
b) Mandibular imp?
a) 1.5-2 bricks
b) 1 brick
How are special trays made?
1) Mark posterior border extension (behind maxillary tuberosities and distal to palatal fovae/ vibrating line) and depth of sulcus
2) Wax placed 0.6mm thick for ZnOE
3) Light cured resin placed over spacer and excess for handle
4) Cure for 5 mins
5) Rinse wax from inner surface then cure under side of 30 s
6) Trim with handpiece where overextended and smooth edges
What dimensions are the record blocks made to in the lab?
Upper = 22mm height, 10 degree anterior inclincation, occlusal width 5-6mm anterior, 7-8 premolar, 9-10 molar Lower = 18mm height, vertical
On an average value articulator what is the condylar angle set as? The incisal guidance table?
30 degrees
10 degrees
