Preliminary Edentulous Impressions

1. Preliminary Edentulous Impressions

2. Preliminary Edentulous Impressions • Preliminary impressions needed for diagnostic casts for making custom trays

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

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

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

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

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

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

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

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

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

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

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

14. Patient Preparation • Practice placing tray • Rotate into place

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

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

17. 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

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

19. 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

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

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

22. 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

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

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

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

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

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

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

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

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

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

32. 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

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

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

35. Cleaning the Syringe

36. 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

37. 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

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

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

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

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

42. Preliminary Impressions • Rinse thoroughly with water • Gently shake to remove excess water

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

44. Sample Impressions

45. Sample Impressions

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

47. 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

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

49. Diagnostic Casts

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