Dual Arch Impressions

Question 1

what are single tray records

Answer 1

• impression of prepared tooth
• adjacent and opposing teeth
• relationship in maximum intercuspation

Question 2

what are the advantages of the dual arch impression

Answer 2

• average occlusal error for articulated casts in 5 microns
• less impression material is necessary (ideally)
• quick procedure for a single tooth restoration bounded by natural occlusal stops
• best used for an intact, mutually protected angle class I occlusion
• overimpression technique (made before tooth preparation) aids in provisional fabrication

Question 3

what are the disadvantages of the dual arch impressions

Answer 3

• the tray is generic, not a custom fit to the dentition/arch form
• most tray types are flexibile
• the tray can interfere with correct jaw closure
• the patient is anesthetized when biting into the impression - must check accuracy
• cast preparation/ mounting are technique sensitive
• no contralateral occlusion reference as in full arch - accurate mounting?
• potential occlusal interferences in lateral movement - must eliminate beforehand
• consider thielmann’s diagonal law of occlusion
• compromised prosthetic occlusal anatomy
• technique sensitive
• not for Bridges or RPD abutment crowns

Question 4

what is the clinical technique for dual arch impressions

Answer 4

• visually inspect the interocclusal relationship in MI before anesthesia
• try in the impression tray and visually verify the same occlusal relationship on both sides of the mouth
• impressions must include the opposing canines for anterior guidance
• perform preparation isolation and gingival retraction
• apply tray adhesive to the internal vertical tray walls- not on the interocclusal insert/mesh
• apply low viscosity impression material around the impression
• fill both sides of the tray with high viscosity material
• insert the tray immediately and verify the originally observed interocclusal relationship
• impression should have translucent areas on the mesh where adjacent teeth occlude completely
• verify no tray interferences in the final impression
• remove any materials that cant be disinfected (cotton rolls, isolation aids)

Question 5

what is the lab technique

Answer 5

• pour the arch with the preparation in die stone, place dowel pins, and allow the stone to set
• pour the opposing arch in regular stone and let it set
• with both arches not separated from the impression, mount the casts on a small metal hinge articulator
• trim all excess overlapping stone that might prevent closure to the proper occlusion
• open the articulator
• separate the arches
• saw the dies from the master cast
• trim the dies and mark the margins