39. Impressions and models. Impression trays.

whats in it

what is an impression

objective for impression making

types of impressions

types of impression trays

maxilla list of areas of landmarks

mandible list of areas of landmarks

Impression

- - -

a negative likeness or a copy in reverse of the surface of an object
An imprint of the teeth and adjacent structures for use in dentistry
The replicas are prepared in 2 steps:

1) making a negative (impression),

2) prepare a replica – an accurate positive model of teeth and adjacent oral tissue

Objective for impression making:

• -  Preservation of the alveolar ridges

• -  Retention

• -  Aesthetics

• -  Stability

• -  Support

• -  Maximal precision in terms of accuracy, deformation, resilience

0. Types of impressions:

0. Complete denture impression:

1. - A negative registration of the entire edentulous arch, stabilizing and boarder seal areas present in the edentulous arch

   Preliminary impression:
   - An impression made for the diagnostics purposed or for construction of a custom tray

   Final impression:
   - An impression that is turned into a “master cast”

types of impression TRAYS

C – Custom trays

• Made on the patient’s model (edentulous or dentate)

• Highly accurate

• Single use

U – Universal sectional trays

• Used for specific sections of the mouth

• Especially in edentulous cases

• Single use

T – Triple trays

• Records upper, lower, and occlusion all at once

• Useful in crown & bridge for small areas

• Single-use

E – Edentulous/dentate stock trays (metal or plastic, perforated or not)

• Metal: autoclavable

• Plastic: single-use

• Not easily adjustable

• Available in multiple sizes

• Perforated versions improve impression material retention

maxilla list of areas of landmarks:

Limiting structures:
Supporting Structures:

0. Primary stress bearing areas:

(and secondary)

0. Relief areas:

mandible list of areas of landmarks:

Limiting structures:
Supporting Structures:

relief areas

maxilla

Limiting structures:
- Labial and buccal frenum

68

• -  Labial and buccal vestibule

• -  Hamular notch

• -  Posterior palatal seal area

  Supporting Structures: Primary stress bearing areas:

• -  Hard palate

• -  Postero-lateral slopes of residual alveolar ridge Secondary stress bearing areas

• -  Rugae

• -  Maxillary tuberosity

• -  Alveolar tubercle

  Relief areas:

• -  Incisive papilla

• -  Cuspid eminence

• -  Mid- palatine raphe

• -  Fovea Palatina

mandible

0. Mandible

   Limiting structures:

   • -  Labial and buccal frenum

   • -  Labial and buccal vestibule

   • -  Lingual frenum

   • -  Alveololingual sulcus

   • -  Retromolar pad

   • -  Pterygomandibular raphe

   • LLLARP

     Supporting Structures:

   • -  Buccal shelf area

   • -  Residual alveolar ridge

     Relief areas:

   • -  Crest of the residual alveolar ridge

   • -  Mental foramen

   • -  Genial tubercle

   • -  Torus mandibularis -