Introducing
Your new presentation assistant.
Refine, enhance, and tailor your content, source relevant images, and edit visuals quicker than ever before.
Trending searches
impression materials
9
The impression Road
Impression
materials
what is impression materials
& uses
what is impression
material
A negative likeness or copy in reverse of the surface or object(an imprint of the teeth and adjacent structures for use in dentistry)
positive cast
+ve and
-ve
negaive
impression
why is it?
1-copy the teeth and surrounding oral
2-Dental models enable dentists to perform a better diagnosis and treatment
3-Particular treatment, such as removable and fixed prostheses, can be executed thanks to dental casts
Imp definisions
Imp.
definition
1- primary impression
2- seconadry impression
3- cast
4- tray
primary impression
primary
- taken for patient for 1st time ,doesn’t record
the fine details of oral structures
- An impression made for the purpose of construction of a special tray
secondary imp.
(final impression)
secondary
Over wash impression: final impression made of two layers
1.The first is made of primary impression material
2.The primary impression act as special tray for secondary impression (2nd layer)
record all fine details of the oral
structure
Cast
positive replica of hard,, soft oral structure formed by pouring the impression by one of the model materials
Cast
Tray
is a container that caries the impression material into patient
Tray
History
Timeline
- With the advancement in technology, digital dentistry is also making its way into the field
intra oral scanner
Thus, there was always a need for an impression material that could remain elastic even after setting
That is when agar, manufactured from algae, was introduced in dentistry. Although this jelly-like material was elastic, it required a complicated procedure to be used as an impression material
Wax was the only impression material used in dentistry until the mid-19th century when gutta-percha material first appeared
History
When the algae used to manufacture agar was unavailable during the second world war, Americans used local algae to manufacture another elastic impression material known as alginate, which has gained popularity since then.
Alginate and agar have disadvantages, like dimensional instability and low tear strength, which led to the manufacture of elastomeric impression materials
Then in 1857, Charles Stent created a thermoplastic
modeling compound similar to today's impression compound.
Still, the problem with this material was that it was rigid and could not reproduce undercut areas
classification
based on
Based on use
use
1.For primary impressions, e.g., alginate, impression compound, elastomeric putty
-For secondary impressions, e.g., light body elastomers and zinc oxide eugenol
Based on setting reaction
setting
reaction
1.Reversible: impression compound, impression waxes, agar.
2.Irreversible: alginate, impression plaster, elastomeric impression materials
Based on the State of the Impression Material After Setting in the Oral Cavity
state after setting
1.Rigid: impression compound, zinc oxide eugenol, impression plaster, impression waxes.
2.Elastic: alginate, agar, polysulfides, addition and condensation silicones, polyether
Impresion matrials
types of
impression
mareials
1- Non elastic materials
Impression compound Zinc-oxide eugenol
2- Hydrocolloids
agar alginate
3- synthetic elastomers
polysulphides polyethers addition silicon
Non elastic materials
Non elastic
materials
These materials are rigid when set and therefore exhibit very little elasticity. Due to the rigidity of the materials any significant deformation to the impressions results in permanent deformation
Compound for complete denture impressions requires heating to soften the compound before use
Impression compound
- Consists of a base paste (zinc oxide, inert oils, resins) and a catalyst paste (eugenol, accelerator, filler).
- Clinical use: secondary impressions for complete dentures
Zinc-oxide eugenol
Recent advances in alginates
- Siliconized alginates: silicon are added to strengthen the material
Aliginate
Alginate is a hydrocolloid widely used as an impression material in dentistry. It is derived from alginic acid, present in brown algae. It is an irreversible and elastic impression material
Hydrocolloids
Agar
Agar is a reversible hydrocolloid. It has the ability to repeatedly pass between different viscosities simply by heating and cooling.
Elastomeric
material
They can undergo deformation, yet rapidly recover to their original dimensions when the stress is released
There are three distinct groups of synthetic elastomers. These include: polysulphides, polyethers and silicones (addition and condensation)
Addition silicone
It is the most widely used impression material in dentistry. Also called PVS or VPS. Can use it as a one or two-stage impression
Advantages: excellent dimensional stability (no shrinkage on setting), fast setting, high patient acceptance, better dimensional stability than condensation silicone
Disadvantages: expensive, platinum catalyst reacts with powdered gloves/new composites, temperature sensitive
Supplied as a base and catalyst paste.
With the release of newer impression materials, polysulphides have become increasingly unpopular due to their list of disadvantages.
Clinical use: long working time required
Disadvantages: unpleasant taste and smell, long setting time
Polysulphides
Polyethers
These are the most hydrophilic of the synthetic elastomer impression materials. Therefore we often use them when moisture control is difficult.
However, because of this they possess the tendency to swell in conditions of high humidity. Therefore they need storing dry
Advantages: dimensionally stable
Disadvantages: rigid absorbs water low tear strength
1-Impressions must be thoroughly disinfected to prevent cross infections. After washing the impression to remove residues of saliva and blood, the chosen disinfectant is applied, either by spraying on the impression or immersing it in the disinfectant solution for a specified time.
2- Hydrocolloids (agar and alginate) and polyether possess hydrophilic features. Therefore, if disinfection guidelines are not followed, it may lead to swelling of the impressions, but when done properly, it does not affect the dimensional stability and accuracy of the impression
Issues with impression materials
Digitization in dentistry provides more restoration options, better esthetics, greater efficiency, and accuracy.
New ways for effective and efficient inter-professional and clinician-patient interactions have evolved.
Data can be more efficiently used for forensic and purposes.This digital dentistry technology (such as intraoral scanners and in-office CAD/CAM) proves helpful for patients and reduces contamination risks
Intraoral Digital Impression Scanner
Digital intraoral scanners have become an ongoing trend in the dental industry and the popularity is only getting bigger.
But what exactly is an intraoral scanner?
How do intraoral scanners work?
An intraoral scanner consists of a handheld camera wand, a computer, and software.
The small, smooth wand is connected to a computer that runs custom software that processes the digital data sensed by the camera.
In the beginning, dentists will insert the scanning wand into the patient's mouth and gently move it over the surface area of the teeth.
The wand automatically captures the size and shape of each tooth.
It only takes a minute or two to scan, and the system will be able to produce a detailed digital impression.
What are the advantages?
Enhanced patient scanning experience.
Time-saving and fast results
Increased Accuracy
What are the disadvantages?
There are very few disadvantages to intraoral scanners.
In fact, the primary drawback may be that they are not yet available for use at every dental practice.
As it is still a somewhat new technology, the cost of the equipment is high