primary impression and primary cast - semmelweis egyetem

Dr. Barbara Kispélyi

Associate ProfessorSemmelweis University, Faculty of Dentistry

Department of Prosthodontics

PRIMARY IMPRESSION AND PRIMARY CAST

SEMMELWEIS UNIVERSITY FACULTY OF DENTISTRYDEPARTMENT OF PROSTHODONTICS

CURRICULUM:Prosthetic treatment of the edentulos patient

- Chairside steps

- Labside steps

From web

Completely edentoulous elderly

patient

Prof. Fejérdy és mtsai: A felnőtt lakosság fogelevesztési dinamiikája Magyarországon Fogorvosi Szemle 1998

From: Basker et al.: Prosthetic treatment of the edentulous patient

THE COMPLETE EDENTULOUSNESS CAUSES:

1. Biological changes - mastiction2. Social changes3. Changes in appearance4. Phonation5. Psychic

From web

• GERONTOLOGY

• GEROSTOMATOLOGY

• GEROPROSTHETIC

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

- overextended- static- taken by a stock-tray

STOCK TRAY

Requirements:

- rigid

- size and shape

- border extension

- retain its shape

PARTS OF THE TRAY

handle

flangesfloor

From A. Abusallamah

Material:

-Metallic (aluminum, stainless steel)

-Non metallic:

- Plastic tray (can be sterilized)

- Plastic tray (disposable)

TYPES I.: STOCK TRAY

From web

• Perforated

• Non-perforated

TYPES II.: STOCK TRAY

From web

• size

• form

• edentulous

TYPES III.: STOCK TRAY

From web

TRAY SELECTION

TRAY SELECTION I.:

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

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

INFLUENCE THE WORKING AND SETTING TIME:

• water temperature

• Powder : Liquid

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

TAKING THE IMPRESSION

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

ALGINATE SYRINGE TECHNIQUE:• Retromylohyoid area

• Hamular notches

• Retrozygomal area

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

THE RESULT:

From web

LABORATORY STEPS

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

• Weighing powder, measure water

• Vacuum mix (less time, stronger cast)

From web

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

THANK YOU FOR YOUR ATTENTION!