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Dr. Barbara Kispélyi
Associate ProfessorSemmelweis University, Faculty of Dentistry
Department of Prosthodontics
PRIMARY IMPRESSION AND PRIMARY CAST
Completely edentoulous elderly
patient
Prof. Fejérdy és mtsai: A felnőtt lakosság fogelevesztési dinamiikája Magyarországon Fogorvosi Szemle 1998
THE COMPLETE EDENTULOUSNESS CAUSES:
1. Biological changes - mastiction2. Social changes3. Changes in appearance4. Phonation5. Psychic
From web
MEDICAL AND DENTAL HISTORY
• Main complaint
• Medical history
• Dental History
• Clinical examination
- extraoral
- intraoral (stomato-oncologic
examination!)
Dr. Károlyházy
Diagnosis Treatment plan Prognosis
SPECIALITIES:
• In medical history
• In dental history
• Psychological changes
• Social changes
From web
IMPRESSION (IN GENERAL):An imprint of the teeth an adjacent surfaces, structures
PRIMARY IMPRESSION:negative likeness of the denture bearing tissues
From web
Material:
-Metallic (aluminum, stainless steel)
-Non metallic:
- Plastic tray (can be sterilized)
- Plastic tray (disposable)
TYPES I.: STOCK TRAY
From web
TRAY SELECTION II.:
• 3-5 mm of clearance with soft tissues
• Differencies in impression materials
From: Basker et al.: Prosthetic treatment of the edentulous patient and from web
TRAY SELECTION III.:
• Maxillary trays should extend slightly beyond vibrating line
• Mandibular trays should cover the retromolar pads
From web
TRAY MODIFICATION:
• Trays can be modified with wax or compound to extend the tray if desired
From web
IMPRESSION MATERIALS FOR PRIMARY IMPRESSION:
• Alginate – irreversible hydrocolloid
• Impression compound
• Elastomer impression materials
• Impression plaster
From web
ALGINATE
• Inexpensive
• Easy to manipulate and secure
• Requires no special equipment
• Good viscosity – high viscosity type is the best
• Dimension stability between circumstances
Usually found in a box or In a bag basically presented as powder & we mix it with water witha measure cup
WORKING TIME AND SETTING TIME
• Working time:
Regular set: 2-3 minutes
Fast-set: 1.25-2 minutes• Setting time:
Regular set: 2-5 minutes
Fast set (by adding materials by the factory): 1-2 minutes
From web
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)
From web
PREPARATION OF THE MOUTH:1. Before dentures are made
Conditions involving the oral mucosa:
- denture stomatitis
- inflammatory papillary hyperplasia of the palate
- angular cheilitis
Conditions involving the bone:
-Sharp and irregular bone
-Undercat ridges
-Tori
-Pathology within the bone
2. Immediately before the impression
From: Basker et al.: Prosthetic treatment of the edentulous patient and web
PATIENT PREPARATION BEFORE THE IMPRESSION:
• Correct position of the dental chair and patient
• Dry the mucosa
• Don’t let patient close
Prof. Fábián és mtsai: A fogpótlástan alapjai
MEASURING POWDER
• Fluff (shake) the powder, measure, tap and flatten the scoop with powder
• Use three scoops for syringe impressions
From web
PRIMARY IMPRESSION:• Find the correct position of the dental chair and patient
• Support the tray during setting - do not leave the patient
• Movement causes distortion
Prof. Fábián és mtsai: A fogpótlástan alapjai
IMPORTANT CONSIDERATIONS TO ENSURE ACCURATE IMPRESSION
• 2-4 mm bulk material in tray
• Snap action removal from mouth
• Allow extra 1-2 minutes after setting to improve tear strength
• Stored in a moist environment to avoid loss of water evaporation and deformation
• Disinfect in less than 10 minutes to avoid dimensional instability
• Alginate syringe technique
From web
PRIMARY IMPRESSIONS – FINAL STEPS:
Evaluate impression - Criteria for acceptable alginate impression:
- All anatomical landmarks and relevant soft tissue recorded
- No large voids
- Free of debris
- No distortion
Rinse thoroughly with water and spray with disinfectant to coat all surfaces,
Hold in water
From web
CAST:
The cast is a positive likeness of the denture bearing tissues
PRIMARY CAST:Made according to a primary impression. Special tray is constructed onto it (after
outlining the borders of the special tray at the dental office)
Dr. Károlyházy
POURING A CAST
• Casts should be a minimum of 12 mm in thinnest part
• Separate the alginate impression from the stone cast after 45 minutes
From web
TRIMMING CASTS
• Trim the base on the model trimmer parallel to the residual ridges
• Leave the vestibular reflection intact for making a special/custom tray