PAGE 1

Asist. Prof. Dr. Fulya GÜLENER Biruni University, Faculty of Dentistry, Department of Prosthetic Dentistry

PAGE 2

Purpose of Functional Impression

• Goal:

  • Reduce the stretching difference between natural teeth and mucosa.

  • Minimize denture base movements that create a leverage effect on supporting teeth.

  • Prevent exposure of support tissues to traumatic pressures.

  • Provide maximum support to the denture base.

  • Distribute occlusal loads evenly between natural and artificial dentition to reduce specific chewing pressures.

PAGE 3

Functional Impression Criteria

• The borders of the denture should remain within the functional area.

• Extending the borders beyond the functional area can restrict functional movements, irritate inflamed oral mucosa, and lead to hyperplastic tissue development over time.

PAGE 4

Impression Materials for Functional Impressions in Edentulous Arches

• Types of Materials:

  • Zinc Oxide-Eugenol (ZnO2-Eugenol)

  • Elastomeric materials

  • Temporary tissue liners (Soft tissue conditioners)

• Characteristics: Use low viscosity and high fluidity materials for final impressions.

PAGE 5

Zinc-Oxide Eugenol (ZOE)

• Characteristics:

  • Non-elastic and rigid, providing accurate impressions.

  • Cannot be applied in deep undercut areas as it tends to break.

  • Ideal for mucostatic impression techniques, minimizing tissue displacement.

  • Can be repaired if parts of the impression are missing.

PAGE 6

Zinc-Oxide Eugenol (ZOE) Continued

• Application:

  • Used with an individual impression tray.

  • It adheres to instruments and hands, making removal difficult.

  • Hydrophilic nature can lead to air bubbles in moist environments.

  • Mix equal parts of base and activator paste until homogeneous, apply in thin layers for impressions.

  • Adequate working time available for border molding.

PAGE 8

Elastomeric Impression Materials

• Increased use for functional measurements of complete dentures.

• Types:

  • Polysulfides

  • Silicones (both condensation and addition types)

  • Polyether

• Mucostatic impression technique is commonly used.

PAGE 9

Elastomeric Impression Materials: Silicone

• Characteristics:

  • Not affected by moisture during the impression process.

  • High precision and can be poured multiple times.

  • Extended working time.

PAGE 11

Elastomeric Impression Materials: Polyether

• Characteristics:

  • High precision with short setting time.

  • Great physical properties but more expensive.

PAGE 12

Impression of Flabby Ridges

• Both mucocompressive and mucostatic techniques are used together.

• Used when alveolar ridges are partially or completely covered by labile mucosa, typically observed in the anterior maxilla with compromised upper denture support from lower teeth occlusion.

PAGE 13

Impression of Flabby Ridges Continued

• Force Transmission:

  • If patients bite down on anterior teeth and lower anterior teeth contact opposing upper teeth, excess force can occur.

  • No contact should be made with anterior teeth during tooth alignment to prevent this.

PAGE 14

Combination (Kelly's) Syndrome

• Symptoms:

  • Loss of bone from maxillary anterior edentulous ridge.

  • Down growth of maxillary tuberosities.

  • Development of papillary hyperplasia in hard palate.

  • Extruded lower anterior teeth.

  • Mandibular bone resorption results from the construction of a mandibular distal extension partial denture against a maxillary complete denture.

PAGE 15

Changes Associated with Combination Syndrome

• 1. Loss of vertical dimension of occlusion.

  • 2. Occlusal plane discrepancy.

  • 3. Anterior spatial resumption of the mandible.

  • 4. Development of epulis fissuratum.

  • 5. Poor adaptation of the prosthesis.

  • 6. Periodontal changes.

• Cause: Result of excessive force, inadequate denture foundation, and unfavorable occlusal relationships.

PAGE 16

Impression of Flabby Ridges Technique

• Initial impressions made to create a cast model.

• Individual impression trays are fabricated from traditional techniques:

  • Use alginate for preliminary impressions and PMMA for individual trays.

• Minimum force (mucostatic) applied while recording mobile mucosa, traditional methods used elsewhere.

PAGE 17

Mucostatic Impression Technique

• Utilize impression plaster for non-pressure techniques on fibrous areas.

• For completely labile ridges, use impression plaster with minimal pressure applied.

PAGE 18

Plaster Impression Method

• Procedure:

  • Start with a diagnostic impression using hydrocolloid material (alginate).

  • Create individual trays based on the obtained model.

  • Fibrous areas marked on the model and left exposed in the tray.

  • Non-pressure techniques used to record fibrous areas with ZOE employed elsewhere.

PAGE 22

Herbst Tests

• Used to adapt the flanges of impression trays and denture bases to match functional movements of surrounding tissues.

• Conducted before functional impressions or during prosthesis delivery.

• Tests Count: 5 for maxilla and 7 for mandible.

PAGE 23

Herbst Tests: Maxilla Test 1

• Procedure:

  • Patient’s mouth half opened; buccinator muscle active.

  • If the tray moves, edges should be shortened (typically at the 1st and 2nd premolars and 1st molars).

  • Contour adjustments are made in these areas during shaping.

PAGE 24

Herbst Tests: Maxilla Test 1 1

• Patient opens mouth wide similar to yawning.

• Involves contraction of pterygomaxillary raphe, buccinator, and masseter muscles.

PAGE 25

Herbst Tests: Maxilla Test 1 1

• If tray moves during trials behind tubercles, adjustment made at the second molars.

PAGE 26

Herbst Tests: Maxilla Test 1 1 1

• Patient instructed to whistle/suck.

• Movement indicates inadequate labial frenulum and vestibular shelf fit; corrections needed in these areas.

PAGE 27

Herbst Tests: Maxilla Test 1 1 1: Labial Border

• Heating labial flange area and asking patient for lip movements helps note frenum prominence.

PAGE 30

Herbst Tests: Maxilla Test IV

• Important aspects of maxillary impression procedures focus on posterior palatal seal design; includes:

  • Recessed denture border minimizes patient discomfort during swallowing.

  • Border seal reduces risk of denture dislodgment.

  • Compensates for polymerization shrinkage during processing.

PAGE 42

Herbst Tests: Mandible Test V1

• Patient instructed to swallow; contraction of upper constrictor muscle noted.

• If tray moves during adjustments, it indicates areas needing tray length corrections.

PAGE 44

Mandibular Herbst Tests Summary

• A combination of specific patient instructions corresponding to functional movements ensures accurate adaptation in varied dental regions, enhancing the proper fitting of impression trays during border molding.

PAGE 45

Boxing Overview

• ZOE impression can be cast using the wax boxing technique.

  • This allows for stable and quality model casting.

PAGE 49

Advantages of Boxing

• Preserves impression periphery width, reduces bubbles, minimizes trimming time, avoids fracture, allows for model base shaping, and simplifies articulator connections.

PAGE 50

Conclusion

• Thank you for your attention.

• Contact: fgulener@biruni.edu.tr