1. Primary impression, primary cast Flashcards
What are the 5 complete edentulousness causes?
- Biological changes - mastiction
- Social changes
- Changes in appearance
- Phonation
- Physchic
A thorough and systematic history and examination of the patient will ensure that all relevant details are recorded so that the dentist can determine the ___ (3 things)
- diagnosis
- treatment plan
- prognosis.
4 main steps of Assessment of the Patient
- Main complaint
- Medical History
- Dental history
- Clinical examination
5 pieces of info that you need to obtain from dental history of a patient
- When the natural teeth were extracted
- The reason for extractions
- The occurence of any surgical complications
- How many dentures have been worn subsequently
- The degree of success or failure with the dentures
Dental history of a patient can provide important information on __ (3 things)
- The rate of bone resorption
- Retained roots
- The adaptive capability of the patient
2 types of clinical examination of patient teeth
- Extra oral examination
- Intra-oral examination (stomato-oncologic examination)
What is an extra-oral examination?
Extra oral examination of the head and neck for abnormalities in size, shape and symmetry of the head, lymph nodes, eyes, ears, nose, lips and mouth.
6 pieces of information that a dentist can obtain from extra-oral examination of the patient
- Discrepancy between actual and biological ages
- Skeletal relationship
- Occlusal vertical dimension
- Dental appearance (especially during smiling and speaking)
- Extra-oral lesions
- Intolerance or other difficulties with the dentures
What are the 2 objectives of intra-oral examination?
- Whether there is any pathology in the mouth;
- What the prospects are for the new dentures providing a satisfactory level of comfort
and function.
What is a primary impression?
A negative likeness of the denture bearing tissue
3 characteristics of primary impression
- Overextended
- Static
- Taken by a stock tray
What are the 4 requirements of stock tray?
- Rigid
- Size and shape
- Border extension
- Retain its shape
Identify parts of the stock tray
How many types of stock tray are there?
3 types
Classify stock tray based on material (type 1)
- Metallic (aluminium, stainless steel)
- Non metallic (resterilized or disposable tray)
Type 2: Stock tray
-> We only have perforated trays
-> True or false?
False
-> We have perforated and non-perforated stock tray
What do we need to know when using non-perforated stock tray?
We need to use it with an adhesion material
Classify stock trays baed on outer appearance and type of teeth loss treatment (type 3)
- Size
- Form
- Edentulous
What is the The ideal relationship of a stock tray to the sulci and denture-bearing mucosa?
a stock tray should cover the entire denture-bearing area and allow a uniform space of a few millimetres in between it and the underlying mucosa
What is the size of clearance with soft tissues when using stock tray?
3 - 5 mm
What is the requirment for maxillary tray?
Maxillary trays should extend slightly beyond vibrating line (the line that indicates the normal posterior extension of the upper denture)
What is the requirement for mandibular trays?
Mandibular trays should cover the retromolar pads
How can we modify the stock tray?
- Trays can be modified with wax or compound to extend the tray if desired
4 types of impression materials for primary impression
- Alginate - irreversible hydrocolloid
- Impression compound
- Elastomer impression materials
- Impression plaster
Is alginate impression material expenisve?
No, it is inexpensive
Is alginate material difficult to manipulate and secure? If yes, how?
No, it is quite easy to manipulate and secure
Which special equipment is required to use for alginate impression material?
No special equipment is needed
How does viscosity of alginate impression material affect primary impression?
Good and high viscosity type is the best
Working time of alginate primary impression
Regular set: 2 - 3 minutes
Fast-set: 1.25 - 2 mins
Setting time of alginate impression material
Regular set: 2 - 5 mins
Fast set (by adding materials by the factory): 1 -2 mins
2 factors that influence the working and setting time
- Water temperature
- Powder: liquid
Troubleshooting alginate impression
- Premature set (hot water)
- Slow set (cold water)
- Voids (air bubbles with the mixing)
- Distortion (not accurate as may be we remove the impression while it still liquid)
- Excess alginate at back of tray (may be more alginate is placed)
Before the detures are made, what does a dentist need to do?
The dentist need to take dental conditions involving the oral mucosa and bone into account.
-> Why? to improve the condition of the mouth so that it is in the optimum state to receive the new prostheses
3 steps in patient preparatiion before the impression
- Correct position of the dental chair and patient
- Dry the mucosa
- Don’t let patient close
How to mesure powder of impression material?
- Shake the powder
- Use 3 scoops of syringe impressions
2 steps when taking primary impression
- Find the correct position of the dental chair and patient
- Support the tray during setting - do not leave patient move (otherwise, it will cause distortion)
Things to consider when storing primary impression
Stored in a moist environment to avoid loss of water evaporation and deformation
Why do we need to disinfect primary impression in order to obatin accurate impression?
To avoid dimensional instability
3 areas needed to be applied alginate syringe technique
- Retromylohyoid area
- Hamular notches
- Retrozygomal area
3 final steps for primary impression
- Evaluate impresion
- Rinse thoroughly with water and spray with disinfectan to coat all surfaces
- Hold in water
When evaluating alginate impresison, what is the criteria for an acceptable one?
- All anatomical landmars and relavant soft tissue recoreded
- No large voids
- Free of debris
- No distortion
What is a cast?
a positive likeness of the denture bearing tissues
How is the primary cast made? What is the function?
- Made according to a primary impression
- Function: special tray is constructed onto primary cast after outlining
How do we pour a cast?
- Weigh powder
- measure water
- Vacuum mix
- Separate alginate impression from the stone cast after 45 minutes
How do we trim casts?
- Trim the base on model trimmer parallel to the residual ridges
- Leave the vestibular reflection intact for making a special/custom tray.
