Impression techniques in fixed prosthesis
Introduction
The impressions represent the link between the prosthetic therapy developed by the practitioner in the oral cavity and the production of the prosthetic part in the laboratory, through optimum recording of the elements of the preparation and the surrounding elements.
II/Definition of the footprint
1/According to E. BATAREC:
An impression is a negative cast of all or part of the arch and surrounding tissues to obtain a positive model, a faithful replica of the recorded tissues.
III/Qualities required for fingerprints:
- Dimensional accuracy.
- Precision with detail defining power.
- Recording all the elements necessary to relate the model to the antagonist.
- Made with a material compatible with the replica material and the impression processing method.
- Dimensional stability (dragging-braking).
Choosing the impression tray
- The impression tray must be rigid, retentive and perforated.
- Perfectly sized to fit the patient’s mouth
allowing brief and axial disinsertion.
- The space between the impression tray and the area to be recorded must be regular.
GLOBAL FOOTPRINT WITHOUT GUIDANCE
The impression is obtained, using a standard impression tray or a PEI, either in one go or relined with clearance of the cervical limit either by deflection or by gingival eviction, thus allowing the impression material to pass beyond the cervical limit.
- WASH-TECHNIQUE
The wash technique involves taking impressions in two stages and with two materials of different viscosities used one after the other.
- For clinical situations adjacent to regions of low clearance inducing very little dragging at the time of disinsertion (exclude poorly positioned teeth, exposed roots, unfilled caries cavities, etc.)
- For coronal-radicular preparations.
Problems raised:
Essentially, they will result in the subsequent deformations that the print may undergo ,
They are practically linked to the very compression that the fluid elastomer will undergo.
These deformations, which reflect the elastic behavior of materials under tension , will immediately result, upon withdrawal, in a relaxation effect.
2) Injected elastomer technique / double mixture
PRINCIPLE
01 time 02 viscosity
The impression is made in a single step using a PEI , 02 elastomers of the same family but of different viscosity (low and medium) and presenting the same state of plasticity at the time of taking the impression; polymerizing together and at the same time.
The major interest of the process, apart from its simplicity, lies above all in its intentions: to avoid the marked effect of secondary relaxation linked to and induced by the Wash Technique.
TECHNICAL
- The impression tray is coated with adhesive.
- A double cord or spacer material achieves the gingival separation.
- The impression tray is filled with medium viscosity.
- The self-mixing gun or syringe is loaded with low viscosity.
- The second retractor cord or spacer material is deposited.
- absence of bubbles The preparations are covered with low viscosity material.
- Excess low viscosity material is distributed over the impression tray.
- The impression tray is inserted and held until the material sets.
- Uninsert and check the record, verify .
Indications
- Simple coronal preparation with supra cervical or juxta gingival margin.
- Coronal-radicular preparation
Disadvantages
However, it presents certain dangers because
of fairly low compression.
limited subgingival penetration.
the impression tray material may force out the injected material.
Conclusion
- Case resolution involves different approaches, techniques, materials, and generally different designs, but all have the same goal: to obtain the best possible results.
Good oral hygiene Regular scaling at the dentist Dental implant placement Dental x-rays Teeth whitening A visit to the dentist The dentist uses local anesthesia to minimize pain