Preliminary Edentulous Impressions

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Preliminary Edentulous Impressions
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Preliminary Edentulous Impressions

• Preliminary impressions needed for diagnostic
  casts for making custom trays

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Custom Tray

• Required to accurately register moveable mucosa
• Create seal for retention

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Stock Trays

• Stock trays can result in distortion and
  shortening of the final denture flange

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Alginate Syringe Technique

• Irreversible hydrocolloid
• Ensures capture of critical anatomy - sometimes
  missed with just a tray

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Border Molding

• Minimizes distortion of the movable vestibular
  tissues
• Displacement could lead to dislodgment during
  function

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Irreversible Hydrocolloid Storage

• Pre-weighed pouches
• Easier dispensing
• Minimizes contamination
• Bulk material
• Store in cool dry airtight containers

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Irreversible Hydrocolloid Storage

• Deteriorates if
• Stored above 54C
• Repeated openings
• Deterioration results in
• Thin mixtures
• Reduced strength
• Permanent deformation

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Tray Selection

• 5 mm of clearance with soft tissues
• Hydrocolloid requires bulk for accuracy, strength
  and stability

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Tray Selection

• Maxillary trays should extend slightly beyond
  vibrating line
• Mandibular trays should cover the retromolar pads

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Tray Selection

• Sto-K edentulous trays
• Short flanges, so dont distort vestibule

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Tray Modification

• Trays can be modified with compound to extend the
  tray if desired

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Irreversible Hydrocolloid Syringe Technique

• Critical anatomy registration
• Retromylohyoid area
• Hamular notches
• Retrozygomal area

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Patient Preparation

• Practice placing tray
• Rotate into place

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Patient Preparation

• Dry the mucosa
• Dry the maxilla with folded gauze
• Pack 3 gauze in mandible
• Dont let patient close

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Mark Vibrating Line

• Prior to making preliminary final impressions
• Fovea should not be used

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Vibrating Line

• If denture terminates anteriorly, poor seal
• If terminates posteriorly, soft palate movement
  may cause it to dislodge
• Denture may be unretentive and/or uncomfortable

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Locate Mark the Hamular Notch

• Posterior border of a complete denture
• Between the bony tuberosity hamulus

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Locate Mark Hamular Notch

• Denture border must terminate on soft
  displaceable tissue
• Provides comfort and retention
• Notch may be posterior to depression in soft
  tissue

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Locate Mark the Hamular Notch

• Use the head of a mirror, to palpate the notch
• Mark with an indelible marker

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Locate Posterior Border of Hard Palate

• Ensure the denture terminates posteriorly by
  palpating

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Indelible Marks Prior to Impression

• Transfer to the impression and cast when it is
  poured
• Eliminates error
• Tissue should be relatively dry to be most
  effective

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Syringe Preparation

• 12 cc disposable syringe
• Cut off the tip where it begins to curve
• 5 mm orifice

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Plunger Preparation

• Vaseline plunger
• Ease of extruding material
• Use
• Uncontaminated bowl, spatula
• Regular set alginate

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Measuring Powder

• Fluff (shake) the powder, measure, tap and
  flatten the scoop with powder
• Use three scoops for syringe impressions

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Mixing

• Assistant mixes for at least 45 seconds
• Smooth creamy homologous mixture that glistens
• Not granular or lumpy

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Syringe Loading

• The assistant loads the syringe nearly full from
  the back and inserts plunger

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Syringe Technique

• Syringe a broad rope into the vestibule
• Begin at the posterior
• Move quickly toward anterior
• Fill the vestibule to labial frenum

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Cheek Retraction

• Use a mirror, instead of a finger
• Provides better visibility, more maneuverability

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Maxillary Impressions

• Begin opposite the tuberosity
• Inject until alginate is seen in the hamular
  notch before moving forward

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Mandibular Impressions

• Start with the buccal vestibule adjacent
  retromolar pad
• Move forward to the labial frenum
• Repeat on the opposite side

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Lingual Vestibule

• Roll syringe tip under tongue
• Inject into retromylohyoid space until alginate
  appears between tongue ridge
• Move anteriorly, filling to lingual frenum
• Repeat on the opposite side

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Deep Palatal Vaults

• Material can be syringed into the palate
• Smooth with a finger, or voids may occur

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Partially Edentulous

• Syringe a small amount of hydrocolloid on the
  occlusal surfaces
• Force into the occlusal surfaces with finger

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Cleaning the Syringe
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Preliminary Impressions

• The assistant loads the tray while the clinician
  is syringing
• Place the anterior portion of the tray first,
  then seat the posterior of the tray

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Preliminary Impressions

• Less gagging if the patient is lying down
• Tongue position avoids gagging
• Mold the vestibular area
• Pull on the cheeks and lips to activate muscles
  and frena

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Preliminary Impressions

• Support the tray during setting - do not leave
  the patient
• Movement causes distortion

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Preliminary Impressions

• Use water to break peripheral seal
• Remove quickly (to avoid permanent deformation)
• Evaluate impression
• Pour within 12 minutes

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Preliminary Impressions

• Rinse thoroughly with water
• Gently shake to remove excess water

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Preliminary Impressions

• Spray with disinfectant to coat all surfaces, and
  seal in a bag for ten minutes

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Sample Impressions
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Sample Impressions
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Syringe Technique Problems

• Vestibular material may not join the tray
  material
• Saliva contamination
• Insufficient material

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Syringe Technique Problems

• Omitting plunger lubrication may make it
  difficult to express the alginate
• Trapping tongue under the tray will result in
  underextension of the lingual vestibule

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Problems with Syringe Technique

• Severe gaggers poor tolerance for intraoral
  motion
• Use traditional technique

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Diagnostic Casts
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Pouring a Model

• Weighing powder, measure water
• Vacuum mix (less time, stronger cast)
• Use a two pour technique

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Two Pour Technique
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Pouring a Model

• Modulate speed of pouring by tilting back and
  forth or pressing the tray more firmly onto
  vibrator

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Pouring a Model

• Model moist during trimming
• Soak in slurry water, or soak with base of cast
  in water

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Pouring a Model

• Casts should be a minimum of 12 mm (.5 inch) in
  thinnest part
• Separate the alginate impression from the stone
  cast after 45 minutes

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Trimming Casts

• Trim the base on the model trimmer parallel to
  the residual ridges
• Leave the vestibular reflection intact for making
  a custom tray

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Trimming Casts

• All anatomical surfaces should be included with
  minimum voids