Preliminary Edentulous Impressions

Preliminary Edentulous Impressions Preliminary impressions needed for diagnostic casts for making custom trays

Custom Tray Required to accurately register moveable mucosa Create seal for retention

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

Alginate Syringe Technique Irreversible hydrocolloid Ensures capture of critical anatomy - sometimes missed with just a tray

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

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

Irreversible Hydrocolloid Storage Deteriorates if: Stored above 54°C Repeated openings Deterioration results in: Thin mixtures Reduced strength Permanent deformation

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

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

Tray Selection Sto-K edentulous trays Short flanges, so don’t distort vestibule

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

Irreversible Hydrocolloid Syringe Technique Critical anatomy registration Retromylohyoid area Hamular notches Retrozygomal area

Patient Preparation Practice placing tray Rotate into place

Patient Preparation Dry the mucosa Dry the maxilla with folded gauze Pack 3 gauze in mandible Don’t let patient close

Mark Vibrating Line Prior to making preliminary & final impressions Fovea should not be used

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

Locate & Mark the Hamular Notch Posterior border of a complete denture Between the bony tuberosity & hamulus

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

Locate & Mark the Hamular Notch Use the head of a mirror, to palpate the notch Mark with an indelible marker

Locate Posterior Border of Hard Palate Ensure the denture terminates posteriorly by palpating

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

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

Plunger Preparation Vaseline plunger Ease of extruding material Use: Uncontaminated bowl, spatula Regular set alginate

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

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

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

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

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

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

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

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

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

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

Cleaning the Syringe

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

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

Finger Sweep at Posterior If excess material at border Use finger or cotton swab

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

Preliminary Impressions Break peripheral seal Drops of water Pull up cheek and let air in Wiggle tray until hear seal break

Preliminary Impressions Once seal broken, remove quickly (to avoid permanent deformation) Evaluate impression Pour within 12 minutes

Preliminary Impressions Rinse thoroughly with water Gently shake to remove excess water

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

Sample Impressions

Sample Impressions

Syringe Technique Problems Vestibular material may not join the tray material Saliva contamination Insufficient material

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

Problems with Syringe Technique Severe gaggers poor tolerance for intraoral motion Use traditional technique

Diagnostic Casts

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

Two Pour Technique In Removable Prosthodontics: Preliminary Impressions Only

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

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

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

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

Trimming Casts All anatomical surfaces should be included with minimum voids