Impression trays and corresponding casts Lecturer: Hatem Dousouky Ahmad

Types of impressions and corresponding casts Primary cast. (Study cast-Diagnostic cast) Primary impression Secondary impression. (Final impression) Final cast (Master cast-Working cast)

Lecture out line: Important definitions. Types of impressions and comparison. Types of trays. Stock trays:(types-uses-requirements). Special trays:(types-uses-requirements). Cats: Primary casts. Final casts. Boxing of impressions.

1- important definitions. Complete denture impression: Negative record of the limiting and supporting oral tissues used to: 1ry impression 2ry impression pour master cast and construct all other steps of denture. pour primary cast and construct a special tray.

Important definitions. Types of impressions and comparison. Types of trays. Stock trays:(types-uses-requirements). Special trays:(types-uses-requirements). Cats: Primary casts. Final casts. Boxing of impressions.

2-Types of impressions and comparison. Primary impression Secondary impression purpose To record the dimensions of the edentulous arch To record the fine details of the edentulous arch Tray used Stock tray Special tray uses Pouring primary cast. Construction of special. Pouring master cast. Construction of occlusion blocks. Completion of the denture. Material used Impression compound. Alginate. Impression plaster material. Zinc oxyde /eugenole impression material. Rubber base impression material.

Important definitions. Types of impressions and comparison. Types of trays. Stock trays:(types-uses-requirements). Special trays:(types-uses-requirements). Cats: Primary casts. Final casts. Boxing of impressions.

Types of trays. Stock trays:(types-uses-requirements). Trays are instruments used to carry the impression material in the patients mouth until its complete setting. Components : flanges floor handle

Stock trays. Non metallic Metallic Plastic: Made of metal: Hygienic (one use). Others are autoclavable. Difficult to trim. Made of metal: St.st. or aluminum. Strong. Autoclavable. Nb: Aluminum trays allow adaptation and cutting with scissors

Stock trays: Dentulous trays Edentulous trays Flat floor. Square in cross section. Longer flanges. Straight handle. (why?) Rounded floor. Rounded cross section. Shorter flanges L shaped handle.

Partially edentulous stock trays Having flat floor in one area. And rounded floor in other areas. Usually made for patients with remaining anterior natural teeth and posterior edentulous ridge.

Type of impression material to be used: Stock trays Type of impression material to be used: Impression material without adhesive properties uses : Perforated trays. Examples of non sticking impression materials: Alginate Rubber base impression material. Impression material with good adhesive properties uses : NON perforated trays. Examples of sticking impression materials: Impression compound. Zinc oxide / Eugenol impression.

3-Requirements of a stock tray Reasonable fit. Cover maximum possible area. With sufficient space to allow for the impression material thickness. Accepts modification. Easy to be cleaned. Autoclavable.

عَنْ أَنَسِ بْنِ مَالِكٍ قَالَ: نَزَلَتْ هَذِهِ الْآيَةُ فِي أَنَسِ بْنِ النَّضْرِ: {مِنَ الْمُؤْمِنِينَ رِجَالٌ صَدَقُوا مَا عَاهَدُوا اللَّهَ عَلَيْهِ} رَوَاهُ الْبُخَارِيُّ، عَنْ بُنْدَارٍ. هناك فرق بين أن تنصر عزيزا ظاهرا.. وبين أن تنصر ضعيفا منهزما......من المؤمنين رجال....الأية

Important definitions. Types of impressions and comparison. Types of trays. Stock trays:(types-uses-requirements). Special trays:(types-uses-requirements). Cats: Primary casts. Final casts. Boxing of impressions.

II- Special trays. Special trays are trays constructed specially for each patient, there for they fit the seat tissues better than the stock trays. Advantages of special trays: They fit accurately the dental arch. Requires less impression material  less dimensional inaccuracy. More comfortable to the patient.

Materials used for special trays: Shellac base plate. Chemical cure acrylic resin Supplied in sheets. Thermoplastic material. Less rigidity. Strengthened by wires. Easley constructed and adjusted. Does not accept border tracing. Supplied in powder and liquid. Thermo-stable material. More rigidity. Sufficient strength. Easley constructed and adjusted. Accepts border tracing.

Important definitions. Types of impressions and comparison. Types of trays. Stock trays:(types-uses-requirements). Special trays:(types-uses-requirements). Casts: Primary casts. Final casts. Wax spacer. Boxing of impressions. Post dam (definition-techniques).

4- casts Primary cast (diagnostic cast) Master cast origin (final or working cast) origin Primary impression Final impression Material of construction Dental plaster Dental stone uses Diagnosis.(?) Construction of special trays. Construction of occlusion blocks. Construction of the denture.

Diagnostic (primary )casts. Ridge shape. Inter arch relation. Relief areas. Vault of the palate. Depth of vestibules. Presence of tori and their sizes. Sharp bony edges. Posterior palatal seal area.

Important definitions. Types of impressions and comparison. Types of trays. Stock trays:(types-uses-requirements). Special trays:(types-uses-requirements). Cats: Primary casts. Final casts. Wax spacer. Boxing of impressions.

Wax spacer Special trays are constructed directly on the study casts or over a layer of wax called the wax spacer. Spacer gives equal space for the impression material. The wax spacer is adapted over all the cast or over specific areas according to the dentist needs. 3-4 holes are cut in it to give stoppers for the tray. Spacers allow: relief, stress distribution, stability and increases the accuracy of impression.

Wax spacer.

Important definitions. Types of impressions and comparison. Types of trays. Stock trays:(types-uses-requirements). Special trays:(types-uses-requirements). Cats: Primary casts. Final casts. Wax spacer. Boxing of impressions. Post dam (definition-techniques).

5- Boxing of the impression. A procedure made to develop a base for the cast and to protect the borders of the impression.

A-Wax boxing method Used for zinc oxide and eugenol impressions Adding beading wax Adding boxing wax Used for zinc oxide and eugenol impressions Not suitable for alginate or rubber base impressions.

5 mm 15 mm

Advantages: Boxing the impression allow vibration of the dental plaster to avoid bubbles in the cast. Protection of the borders. Providing the cast with a base to give sufficient strength for the cast. Save time and material. Standardization of the master cast.

B-Plaster and pumice boxing Used for alginate impression and rubber base impressions.

Important definitions. Types of impressions and comparison. Types of trays. Stock trays:(types-uses-requirements). Special trays:(types-uses-requirements). Cats: Primary casts. Final casts. Wax spacer. Boxing of impressions. Post dam (definition-techniques).

Thank you