Post on 16-Apr-2017
INDIAN DENTAL ACADEMY
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SPECIAL IMPRESSION TECHNIQUES
IMPRESSION PROCEDURE FOR THE SEVERELY IMPRESSION PROCEDURE FOR THE SEVERELY ATROPHIED MANDIBLEATROPHIED MANDIBLE
WAX BASE DEVELOPMENT FOR COMPLETE DENTUREWAX BASE DEVELOPMENT FOR COMPLETE DENTURE IMPRESSIONSIMPRESSIONS
IMPRESSIONS OF UNSUPPORTED MOVABLE TISSUESIMPRESSIONS OF UNSUPPORTED MOVABLE TISSUES
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Severely resorbed mandibular ridge• Lack of ideal amount of supporting structures decreases support and
encroachment of the surrounding mobile tissues onto the denture border reduces both stability and retention. The main aim is to gain maximum area of coverage.
• Flange technique by Lott & Levin(1966) involves making impressions of the soft structures of the mouth adjacent to the buccal, lingual and palatal surfaces and incorporating the resulting extension or flange into the denture.
• Tryde(1965) used the dynamic impression method. – Dynamic impression methods.JPD 1965;VOL-16
• Krammeck used modelling compound to record the extensions.
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Hypermobile or hyperplastic ridges
• These ridges should be recorded without distortion. Zafrulla Khan technique( 1981). Hobkirk technique – rubber base materialFiller technique- two tray technique.
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WINDOW TECHNIQUE
• Jaggers, Shay and Zafrulla Khan : Impressions of unsupported movable tissues; JADA october 1981, 103; 590-592
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• In conditions where patients have worn maxillary complete denture opposed only by mandibular anterior teeth.
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COMBINATION SYNDROME
• KELLY (1972) introduced the term
“Combination Syndrome”
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• The remaining soft tissues in the anterior maxillary region are easily distorted by routine impression procedures, resulting in an unstable denture base.
• Surgical reduction of the pliable tissues often results in the loss of the anterior mucobuccal fold area.
this may cause retention problems
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• To avoid these problems, a technique that minimises distortion when impressions of edentulous arches with unsupported, moveable tissues are made is used.
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PROCEDURE
• A primary impression is made and a cast is poured.
• An indelible pencil is used to outline the unsupported movable tissue.
• A single custom tray is made, and an opening is cut in the tray as indicated by the transfer of indelible pencil line.
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• Modelling plastic is adapted bilaterally on the posterior aspect of the tray to act as handles.
• The tray is adjusted in the mouth, and a routine border molding is formed.
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• The tray is painted with an adhesive and a regular body impression is made.
• The excess material is trimmed to the outline of the aperture
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• The completed base impression is returned to the mouth.
• This impression does not touch the unsupported tissues.
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• Then a highly mucostatic impression material, impression plaster is brushed on the unsupported movable tissue.
• The initial layer precludes entrapment of air and enables visualisation of the unsupported tissue.
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• A separating media is applied to the impression plaster and the master cast is made
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AN IMPRESSION PROCEDURE FOR THE SEVERELY ATROPHIED MANDIBLE : JPD 1995 ; 73(6); 574-577
DeFranco and SallustioJPD; june 1995; 73(6); 574-577
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• The objective is to maximize the supportive aspect of the available denture foundation by two approaches
- Functional
- Anatomic
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• Peripheral borders are developed functionally with the mouth closed
• The final phase of impression is made with the mouth open to satisfy the anatomic approach
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PROCEDURE
• A maxillary final impression is made and cast is poured
• Construct a record base for the maxillary cast and develop a flat wax occlusal rim.
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• Make a preliminary impression of the mandible and make a lower tray to be used initially as a record base with a flat wax occlusion rim.
• Make a jaw registration at a selected vertical dimension of occlusion.
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• Develop the border extensions with tissue conditioning material.
• Develop the lingual borders with the mouth open and have the patient make essential tongue movements.
• Also instruct the patient to border mold the material physiologically by producing “ooo” and “eee” sounds while biting on the occlusal rim.
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• Repeat the step as often as necessary to develop proper extension.
• Relieve the tray wherever it shows through the conditioning material before each subsequent addition.
• Remove overextensions with a hot knife blade.
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• Leave each application of conditioning material in the mouth approx. 10 minutes to allow it to stabilize.
• After the desired extensions are formed with the conditioning material, make the final second impression with a polysulfide rubber impression material with the mouth open and use standard border molding procedures.
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• Pour the cast immediately to avoid distortion of the material.
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• This procedure will provide the patient with a denture that has function with maximum support and stability.
• The greatest disadvantage of this procedure is the amount of the time necessary to develop the final impression. The average appointment time needed is 45-60 mins.
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• Appelbaum and Rivetti : WAX BASE DEVELOPMENT FOR COMPLETE DENTURE IMPRESSIONS; JPD; may 1985; 53(5); 663-666
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Developing the base with mouth temperature wax
• A preliminary functional impression tray with wax occlusion rims is made with an opposing occlusion rim or denture.
• The tray trimmed to relieve functioning muscle impingements.
• A closed mouth impression with mouth temperature wax is made to establish maximum coverage within tissue tolerance.
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• The IOWA wax is prepared in a container in a hot water bath and is applied to the tray with a soft brush. (firm contact produces glossy surface)
• After full ridge tissue contact is made, wax is applied to the borders and is adapted to the functioning musculature to develop the border and flanges of impression tray.
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• Essential actions :
- Protrusion and retrusion of the lips for the facial musculature (“proo-wiss”)
- Moving the mandible laterally and protrusively to record coronoid process of mandible
- Placing the tongue alternatively into the cheeks and by wiping the lips by the tongue to develop lingual and retromylohyoid flange of mandibular tray
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• The impression is allowed to remain in the mouth and allowed to remain for 8 to 12 minutes to permit as close adaptation of the wax to all surfaces as possible.
• During this period, the patient periodically performs the approppriate muscle functions. And then ice-cold water is poured into the mouth to chill the wax, and the impression is carefully removed.
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• Impression is boxed by plaster and pumice and cast is poured.
• Separating media is applied on the cast and after the separating media has dried, an autopolymerising soft resilient liner is applied to the undercuts.
• Spacer is applied and a resin tray is fabricated
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• When the tray resin has set, the bottom side of the cast is reduced on a cast trimmer just short of contact with the tray material.
• The cast with tray is placed in hot water to soften the wax shim and the cast is fractured with a hammer to permit recovery of the tray without damage
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• Wax spacer is removed, and excess resin is removed from the tray.
• The final impression material, metallic oxide paste is mixed according to manufacturer’s directions and loaded into the tray.
• Impression material is wiped along all the flanges of the impression tray in contact with functioning musculature.
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• The patient is instructed to perform the previously described muscular movements while the impression material is developing its body.
• The tray is removed from the mouth after the material has set and the impression is inspected.
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• This technique permits the harnessing and stabilizing effects of an active musculature to operate on the ultimate denture base.
• The musculature imparts properties of retention and stability to the base that will tend to provide the greatest longevity for the residual alveolar ridge.
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