Secondary impression in complete denture CD

secondary impression / final impression in complete denture.
#prosthodontics
#prostho

BDS 4th year
Nischala Chaulagain
Nobel Medical College , Biratnagar

1. SECONDARY IMPRESSIONS IN COMPLETE DENTURE Guided by Submitted by Dr Shanti Chhetri Nischala Chaulagain Department of Prosthodontics BDS 5 th batch

2. Contents : 1. Lab procedures prior to Secondary impression making. 2. Making a secondary impression using a special tray (a) Secondary impressions in maxilla. (b) Secondary impressions in mandible. 3. Inspection of the impression. 4. Disinfecting the impression 5. Remaking the impression . 6. Conclusion

3. Lab procedures prior to Secondary impression making. Finishing the Primary Cast. Fabrication Of Special Tray.

4. A. Finishing the Primary Cast Primary cast – poured immediately u sing dental plaster - the impression compound tends to distort according to the environmental changes. The cast should be separated from the impression about an hour after the initial set. The poured impression is placed in a warm, slurry water bath till the impression compound softens. (over-softened : the material leaches from the cast)

5. Fabrication Of Special Tray:- Definition : Special tray is defined as, “A custom made device prepared for a particular patient which is used to carry, confine and control an impression material while making an impression.” when a primary impression is made using a rigid-high fusing material like impression compound the soft tissues in the palate and in the sulcus usually get displaced.(over extended impression) Green stick compound (type 1 impression compound) is used to record the sulcus in function.

6. Ideal Requirements of special tray:- Conditioning the Primary Cast before Special Tray Fabrication Soaked in slurry water. The special tray should be 2-4 mm short of the sulcus .(over extended borders of primary impression) Severe undercuts should be blocked out using wax. (may result in the breakage of the cast at the time of removal. )

7. Steps In Fabrication Of Special Tray

8. The relief areas should also be marked in the cast. Some areas which should be relieved: incisive papilla , mid-palatine raphe in the maxilla and lingual to the crest of the ridge in the mandible Relief may also be required for abnormal clinical situations (e.g. flabby ridge , sharp mylohyoid ridges, sharp glenoid tubercles, areas with the mucosal covering, bony specules , etc).

9. Adapting the Relief Wax:- Relief is given to prevent the tray from exerting excessive pressure on these areas during impression making. In the maxillary cast :- incisive papilla and the mid-palatine raphe. In the mandibular cast:- over the crest of the alveolar ridge.

10. Also, holes can be drilled through the tray in these areas( rugae and midpalatine suture) to allow the impression material to escape and reduce pressure on the tissues.

11. Adapting the Spacer In addition to relief wax, a spacer is adapted through out the extent of the special tray. The spacer should be adapted throughout the extent of special tray except posterior palatal seal area in maxilla and buccal shelf area in mandible. --2 mm thick. #Spacer functions- Allow the tray to be properly positioned during border moulding. even thickness of impression material. Prevents distortion of material at the final stage.

12. Placement of Stoppers:- The part of the special tray that extends into the cut out of the spacer is called stopper. -The stoppers provide vertical stop during impression making.

13. Application Of separating Medium:- A surface tension reducing agent can be applied over the spacer to increase the wettability of the separating medium. Cold mould seal is the most commonly used separating medium. It is basically an aqueous solution of sodium alginate. (tin foil, starch, vaseline ) Composition:-

14. Soluble sodium alginate reacts with calcium present in the cast to form insoluble calcium alginate. Applied with a brush using single-sided strokes.

15. Fabrication Of Special tray:- Most commonly used materials for making special tray are:- -Cold cure acrylic -Shellac -vacuum formed thermoplastic resin Cold cure acrylic : It is also known as the auto-polymerizing resin. This material sets by polymerization reaction . * Composition:- * Advantages & disadvantages:- Note:-Self Cure acrylic trays should be fabricated 24hrs before impression procedure to ensure adequate degree of polymerization

16. Two major techniques are commonly used in the fabrication of an acrylic special tray:- Sprinkle-on Technique Dough Technique. After mixing the monomer and polymer the mix undergoes six different stages:- wet sandy stage stringy stage(early and late ) dough stage rubbery stage and stiff stage

17. Procedure:-

18. Fabrication of the handle:- It should be 3—4 mm thick, 8 mm long, and 8mm high. Vertical distance from sulcus to handle = 2 cm. Deficiencies at the junction should be filled by sprinkle-on technique

19. Secondary impression procedures for Maxilla Includes following procedures : Border molding. Tray preparation after border molding. Making the wash impression Recording the posterior palatal seal Checking for errors in the posterior palatal seal

20. 1. Border molding or peripheral tracing: Border molding is defined as “ the shaping of an impression material by the manipulation or actions of the tissues adjacent to the borders of the impression”- GPT Two techniques : a. Single step or simultaneous border molding b. Incremental or sectional border molding

21. Single step or simultaneous border molding : It is a procedure by which the entire periphery of the tray is refined using a single step . Polyether impression material is the material of choice.

22. Clinical procedure for single step border molding..

23. Incremental or sectional border molding : It is a procedure in which portions of the periphery of the tray are refined individually. The material of choice is green stick compound. ( low fusing compound) In this case , the spacer is generally removed just before impression making.

24. Clinical procedure for Incremental border molding…

25. 2. Tray preparation after Border molding: The tray should be prepared before making the master impression. Wax spacer is removed to provide space for impression material. 0.5-1mm of tracing compound is removed from the outer, inner and top surfaces of the border , using a scalpel or a bur .

26. Material over PPSA is not removed.(enhances the PPS, serves as a guide for tray, prevents aspiration of material) Thickness of the flanges and border should be 2.5-3mm . The holes prevent the tissue displacement during impression making .

27. 3. Making the master or wash impression The impression material should be of low viscosity to record the structures accurately. The amount of material loaded onto the tray should be able to form a uniform, thin layer. The material of choice for a secondary impressions are Zinc oxide eugenol (ZnOE) impression paste, medium bodied (if spacer is used) or light bodied elastomeric impression materials.

28. Clinical procedure for secondary impression …

29. 4. Recording the POSTERIOR PALATAL SEAL: The posterior palatal seal is defined as , “The soft tissues along the junction of the hard and soft palate on which pressure within the physiological limits of the tissues can be applied by a denture to aid in the retention of the denture “ –GPT . *Classification of the posterior palatal seal (PPS) - Class I: Butterfly shaped :it is narrow in the mid palatine raphe.

30. -Class II: Arch shaped. : It is widest in the mid palatine raphe. - Class III: Narrow band. : Here it is a thin narrow band (2-3mm) extending from one hamular notch to other

31. *Displacement /compressibility : major advantage of PPS – can be compressed within physiological limit to improve retention. - PPS is least compressible at mid palatine raphe -maximum at the lateral parts of the cupids bow #Recording PPS is very important for the retention of denture # A good PPS is essential to provide a peripheral seal.

32. Methods used to mark the postdam are : *conventional approach *fluid wax technique *arbitary scraping of the master cast *extended palatal technique (Silverman proposed that the posterior border of the denture can be extended by 8 mm for patients with class I soft palate. But, this is not accepted now).

33. A.Conventional approach This procedure is done after master cast is poured. Trail base is fabricated using well adapted self cure resin or a shellac base plate. Patient is asked to rinse the mouth with some astringent mouth wash then PPA is wiped with gauze. The “T” burnisher is used to locate hamular notch by palpating posteriorly to the maxillary tuberosity on both sides

34. The full extent of hamular notch is marked with an indelible pencil. The posterior vibrating line is marked.(imaginary line located at the junction of soft palate that shows limited movement and soft palate that show marked movement .)

35. The trial base is inserted to the patient’s mouth to transfer the indelible markings to the trial base. Then the trial base is seated on the master cast to transfer the markings to the cast. Trail base is trimmed till posterior border forms the posterior border of the denture.

36. The anterior vibrating line is marked.(is an imaginary line lying at the junction between the immovable tissue over hard palate and slightly movable tissue of soft palate .) *The patient should perform the VALSALVA MANEUVER The anterior vibrating line is cupid bow shaped because it follows the posterior nasal spine and posterior part of hard palate. Pterygomaxillary seal PPS

37. The area between anterior and posterior vibrating line is scraped in the master cast to a depth of 1-1.5mm on either side of mid palatine raphe. In the region of mid palatine raphe , it should be only 0.5-1mm in depth .

38. Checking the postdam (PPSA) After scrapping the master cast, the postdam is checked. The tray is modified (painted with cold mould seal and resin is added to the scrapped areas) and inserted into patients mouth. A mouth mirror is kept at the distal end of trail base and used to check either there is presence of space.

39. Advantages Disadvantages Trail base has increased retention ,and easier for retention during jaw relation. patient can experience retentive qualities of denture at an earlier stage. patient has idea of the posterior extent of the denture base. final adjustments during insertion are minimized. It is not a physiological technique hence, it is technique-sensitive. Excessive scrapping of the cast can frequently lead to tissue compression.

40. B.Fluid wax technique This technique is done immediately after making the wash impression and before pouring the master cast. ZnOE and impression plaster are suitable impression materials as fluid wax adheres well to them. The anterior and posterior vibrating lines are marked as described in the conventional technique. These lines are marked in the patients mouth immediately after making the wash impression.

41. The markings are transferred to the secondary or wash impression by reseating the impression in the mouth. The wash impression is painted with fluid wax. Commonly used waxes are:- Lowa wax (white) by Dr Smith, Korecta wax no:4 (orange) by Dr OC Applegate, Adaptol wax (green) by Nathan G Kaye, H-L physiologic paste (yellow—white) by CS Harkins.‘

42. The wax should be painted only within the margins of the palatal seal marked on the impression. Usually, it is applied in excess and cooled below mouth temperature so that it gains resistance to flow. These waxes soften at mouth temperature and flow intra orally during impression making.

43. The patient’s head should be positioned such that the Frankfort's horizontal plane is 30° below the horizontal plane. It is only at this position that the soft palate is at its maximal downward and forward functional position. Flexion of the head also helps to prevent aspiration of the impression material and saliva.

44. The patient's tongue should be positioned at the level of the mandibular anteriors .(Helps to pull the palatoglossus muscle anteriorly .) The impression tray is inserted into mouth and patient is asked to make rotational movements of his head without altering the plane ( to record the functional movements of the palate . ) The impression is removed after 4-6 minutes and examined

45. In contrast to green stick compound, glossy areas show tissue contact. Dull areas show areas which were not in contact with the tissues. (they are added with more wax and the procedure is repeated.) With every reinsertion , the impression should be held for 3-5 minutes under gentle pressure and 2-3 minutes under firm pressure applied in the mid-palatine area. After achieving even tissue contact, the impression is removed and re-examined.

46. The wax in the region of the anterior vibrating line should have a knife edge margin . (Blunt margins indicate improper flow and the impression should be repeated.) Fluid wax extending beyond the posterior vibrating line should be cut with a hot knife. *The impression is refined again till feather-edge margins are produced.*

47. Advantages Disadvantages It is a physiological technique. Chances of over compression of tissues are less, Increased retention of the trial base and convenience in jaw relation. There is no need for scrapping the master cast arbitrarily. Handling of the material is very difficult. Increased chair-side time during patient appointment.

48. C. Arbitary scrapping of the master cast In this technique, the anterior and posterior vibrating lines are visualized by examining the patient’s mouth and approximately marked on the master cast. 0.5 to 1 mm of stone in the posterior palatal seal area of the master cast is scrapped. The technique is inaccurate and not physiological and is Iess preferred. *There are some techniques for arbitrary scrapping of master cast*

49. Winkler's Technique:- Arbitrarily mark the anterior and posterior vibrating line and scrape 1 to 1.5 mm. It is the least accurate method for recording PPS. It has a high potential for over post-damming because it is a non-physiological technique. Light body elastomers have also been used to record PPS using putty impression procedures.

50. Boucher's technique:- Width of PPS is limited to a bead on the denture that is 1.5 mm deep and 1.5 mm broad at its base with a sharp apex. Resulting design is beaded PPS. The narrow and sharp bead will sink easily into soft tissue to provide Seal against air entering under the denture.

51. Errors in Recording the Posterior Palatal Seal Underextension Overextension Underpostdamming Overpostdamming

52. Underextension This is the most common cause for poor PPS. It may be produced due to one of the following reasons:- When the denture does not cover the fovea palatine , the tissue coverage is reduced and the posterior border of the denture will not be in contact with the soft resilient tissue during functional movements. The dentist may intentionally leave the posterior borders underextended in order to reduce the patient's anxiety to gagging. Improper marking of the anterior and posterior vibrating lines. Excessive trimming of the posterior border of the cast.

53. Overextension Overextension of the denture base can lead to ulceration of the soft palate and painful deglutition. Covering of the hamular process can lead to sharp pain in that region. In order to relieve these areas, indelible pencil markings are made on them (hamular process, ulcers, etc.) and transferred to the denture. These regions are trimmed and polished.

54. Underpostdamming This can occur due to improper head and mouth positioning, e.g. when the mouth is wide open while recording the PPS the mucosa over the hamular notch becomes taut; which produces space between the denture base and the tissues. Inserting a wet denture into a patient's mouth and inspecting the posterior border with the help of a mouth mirror can identify underdamming. If air bubbles are seen to escape under the posterior border, it indicates underdamming. To correct : the master cast can be scrapped in the PPA or fluid wax impression can be repeated.

55. Overpostdamming This commonly occurs due to excess scraping of the master cast. It occurs more commonly in the hamular notch region. Mild overpostdamming in the hamular notch region can lead to tissue irritation of the mucosa and excessive postdamming produces downward displacement of the denture posteriorly.

56. Secondary impression procedures for Mandible Border molding Tray preparation after border molding. Making the wash or master impression.

57. 1. Border molding or peripheral tracing: 1. Single step or simultaneous border molding. 2. Incremental or sectional border molding. Recording the labial and buccal flange The labial flange :

58. The buccal flange :- cheek : outward, upward, backward and forward To record the distobuccal sulcus, the cheek should be well retracted and moved upward and inward.

59. To record the action of masseter muscle :

60. Recording the lingual flange The anterior lingual border is molded by a)asking the patient to protrude his tongue out which helps to record the length of the lingual flange and b) then later to touch the anterior part of the palate which helps in establishing the width of the flange.

61. Protrusion of the tongue helps to record the movements of the mylohyoid muscle also raises the floor of the mouth. The lingual flange thus recorded will be lingually sloping and parallel to the direction of the mylohyoid muscle fibers. While border molding the distal end of the lingual flange, the action of the retromylohyoid curtain should be recorded.

62. The superior constrictor and the medial pterygoid muscles determine the position of the retromylohyoid curtains . The action of the superior constrictor is recorded while protruding the tongue. The action of the medial pterygoid is recorded by asking the patient to close forcefully against resistance.

63. Recording the Retromolar pad To record the distal end of the tray, the patient is asked to open his mouth wide. After recording the distal end, the impression is verified . If a notch is produced in the postero - medial end of the tray tray is overextended up to the pterygomandibular raphe. Finally, after border molding is complete, the patient should be able to touch the entire upper lip with the tongue without displacement of the tray.

64. Summary Of Mandibular Border Molding:-

65. 2. Tray preparation after border molding : Similar to the procedure done for maxillary impression. The escape holes should be placed 10 mm apart in the alveolar ridge region and over the retromolar pad.

66. 3.Making the Final or Wash impression (Similar steps as in maxilla ) The tray is rotated in a horizontal plane and inserted into the mouth using the anterior handle. The tray is seated completely by applying alternating pressure over the posterior handles.

67. The patient should be asked to touch his upper lip with his tongue while making the impression. Passive movements performed. After the material is set, the impression is removed & examined for any defects.

68. 3)Inspecting The Impression:- The impression made is inspected for air inclusions and voids. The surface is inspected to make sure, that all the landmarks are recorded accurately. Small voids can be rectified by filling them with wax. 4)Disinfecting The Impression:- The impression is disinfected using iodophor or 2% glutaraldehyde . It should be left undisturbed for 10 minutes.

69. 5) Remaking The Impression:- Mostly due to improper positioning of the impression trays. the flange which lies on the side of deviation will be excessively thick, and the flange opposite to the deviation will be thin. Other reasons :- Large voids Improper consistency of impression material Movement of the tray during the setting of the impression materials Inadequate scrapping of the border molding material. Using too much or too little impression material.

70. Reference Textbook of Prosthodontics , Deepak Nallaswamy 2 nd edition

71. Conclusion Secondary impression is the most important step in fabrication of a retentive CD prosthesis. So the proper use of techniques will help in making a good secondary impresion in which the further procedures of a CD fabrications can be done.

72. Thank you all