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PATIENT VISIT I – DIAGNOSIS AND PRELIMINARY IMPRESSIONS
PRELIMINARY IMPRESSIONS (1-1&1/2 HOURS)
Objective
Instruments & Materials
Preparation
b. Heat the water bath to 140 degrees F (60 degrees C) c. Seat the patient in the upright position and protect the patient's clothing with a napkin Selection of Impression Trays
Mandibular tray
selection b. When you insert the tray into the mouth, lift the handle superiorly and position the tray so that the posterior portion covers the retromolar pads. c. Lower the tray anteriorly and observe the adaptation of the tray to the anterior alveolar ridge. 3-5 mm of clearance should exist between the tray and ridge to allow space for the impression material.
Maxillary tray
selection b. Move the tray handle inferiorly and place the posterior edge of the tray in the pterygomaxillary notches. c. move the anterior edge of the tray toward the ridge. you should observe 3-5 mm of clearance between the tray and anterior ridge.
Impression Materials Used for the Preliminary Impression 1. Impression compound (Modeling compound) 2. Irreversible hydrocolloid (Alginate) Modeling compound: Impression compound is relatively simple to use, has a minimal danger of aspiration, and can be stored for a longer period of time without distortion than alginate. Most importantly, compound impressions can be corrected by additions of small amounts of compound. Alginate cannot be corrected. This allows you to fix small errors in the impression avoiding subjecting your patient to multiple impressions. The material used for edentulous preliminary impressions in the prescribed procedures is red impression compound supplied in cake form. The softening temperature is 132 degrees F. The water bath is maintained at 140 degrees F. The material should not stay in the water at this temperature any longer than is necessary to make the impression. Irreversible hydrocolloid. Alginate is used by many dentists for making preliminary impressions. It has greater accuracy of surface detail than impression compound. Edentulous impression trays are available which are designed specifically for use with alginate. The major advantages of alginate are related to its flow properties when easily displaceable tissues are present. It is the material of choice when extreme undercuts exist. Making the Preliminary Impression After data collection and treatment plan presentation to your clinical instructor, you will be making preliminary impressions. This impression will then be used to form a preliminary (diagnostic) cast upon which a final impression tray is made. Definitions
Anatomic Landmarks Recorded by the Preliminary Impressions
The dentist must be able to identify the anatomic landmarks recorded in the impression. Either the maxillary or mandibular impression may be made first. The mandibular impression is made first if the patient has a tendency to gag. Steps in Making the Maxillary Preliminary Impression using impression compound 1. Place 1& 1/2 cakes of red impression compound wrapped in a paper towel in the water bath set at 140 degrees F, 5 to 10 minutes prior to impression making. 2. Seat the patient and be sure the patient's clothing is protected with a napkin. 3. Remove the softened impression compound from the water bath, kneed it, and roll it into a rounded triangular shape. Place it in the previously selected tray and mold the compound with your fingers to the approximate size and shape of the patient's mouth. Create a grove fro the maxillary residual ridge with your fingers. Be certain to cover the borders of the tray with compound to retain the impression in the tray once the material hardens. 4. Flame the compound surface by passing over it quickly with a torch several times until it is glossy and smooth. this softens the surface layer of the compound and will ensure the accurate reproduction of the tissue surface. Temper the compound in the water bath after flaming to avoid burning the patient. This is accomplished by briefly about 10 seconds) immersing the tray in the 140 degree F water bath. 5. Stand slightly in front of and to the right of the patient. Rotate the tray against the right corner of the mouth. The left corner is reflected with a mouth mirror. 6. Center the tray over the residual ridge so that the tray handle is in alignment with the median line of the face. 7. Apply pressure, using the index finger of one hand, in an upward and backward motion to the middle of the palatal portion of the tray. 8. Discontinue the seating pressure when the impression material has reached the vestibular border. 9. Hold the impression in position with the index finger of one hand in the palate and grasp the cheek with the index finger and base of the thumb of the other hand. Gently pull the cheek outward and downward. 10. Change hands and manipulate the other cheek in a similar manner. 11. Lift the lip outward and downward. Gently massage the outside of the lips with both thumbs to shape the impression in this area. The impression is held until firm (about 30 seconds). 12. raise the cheeks to break the seal and gently push downward on the flange of the impression in the first molar region. It might be necessary to apply a downward and forward pull on the handle of the tray simultaneously. If unsuccessful, ask the patient to close his or her lips and blow air to inflate the cheeks. This will also break the border seal and cause the impression to dislodge. 13. Inspect the impression to determine if it is acceptable. Correct any deficiencies present with the green or brown stick compound. 14. Chill in ice water. Oral tissue must be in an optimal state of health prior to impression making. To prevent any distortion of the oral tissue by the patient's dentures, tell the patient to leave the dentures out of the mouth for 24-48 hours prior to the next appointment. 15. Disinfect the impression by placing it into a plastic bag and spraying into the bag with the current surface disinfectant in use in the clinic. Seal the bag for 10 minutes prior to pouring the impression Checklist for the Maxillary Impression
Steps in Making the Mandibular Preliminary Impression using Impression Compound Generally, the mandibular impression procedure is more easily tolerated by the patient. It is often accomplished first to gain the patient's confidence, especially if the mandibular ridge is parallel to the floor when the mouth is open. 1. Place 1 & 1/2 cakes of red impression compound wrapped in a paper towel in the water bath heated to 140 degrees F, 5 to 10 minutes prior to impression making. 2. Have the patient seated upright. 3. Remove the softened impression compound from the water bath, kneed it, and roll it into a sausage shape. Mold the compound with your fingers to the approximate shape and size of the previously selected tray. make a grove in it with your finger s approximately where the crest of the alveolar ridge will be located. Allow a small amount of compound to cover the tray borders to retain the impression in the tray when the compound hardens. 4. Flame the compound surface by passing over it quickly with a torch several times until it is smooth and glossy. Temper the compound by immersing it in the 140 degree F water bath to avoid burning the patient. 5. Stand in front of the patient and place the tray at the left corner of the mouth. The right corner of the mouth is reflected with a mouth mirror. 6. Rotate the tray into the mouth and carefully center it over the residual ridge. 7. Apply pressure to seat the tray by placing your index fingers over the premolar areas on both sides. Place the thumbs outside the mouth under the mandible for support. 8. As you seat the tray, distend the cheeks in the molar area to make certain they are not trapped beneath the impression material. Use an even downward pressure until the compound has reached the depth of the vestibule. 9. Hold the tray firmly in position and border mold on the right in the area of the buccal frenum by pulling the cheeks upward, inward, anteriorly and posteriorly while the compound is still soft. 10. Change hands and manipulate the left cheek in a similar manner. 11. Now have the patient lick the upper lip from one corner of the mouth to the other corner of the mouth. The impression is held until firm. 12. Loosen the impression after the compound has set by placing the index fingers along the border in the buccal shelf area and gently lift by rotating the fingers along the border. 13. Inspect the impression to determine if it is acceptable. If minor defects or small voids are present, they can be corrected using stick compound. 14. Chill in ice water. 15. Disinfect the impression using current recommended surface disinfectant for 10 minutes in a sealed bag prior to proceeding to the labs. Oral tissues must be in their optimal state of health prior to impression making. To prevent any distortion of the oral tissues by the patient's dentures, tell the patient to leave the dentures out of the mouth for 24-48 hours prior to the next appointment. Checklist for the Mandibular Impression
Steps in Making the
Maxillary Preliminary Impression using 1. Seat the patient and be sure the patient's clothing is protected with a napkin. 2. Select stock try that will cover all the landmarks indicating the denture bearing area. Also check the impression try and make sure it covers the hamular notches posteriorly. 3. The tray should be lifted in the front. You should observe 3-5 mm of clearance between the tray and anterior ridge. 4. Deficient tray borders should be corrected by adding utility wax. 5. Utility wax can be added to the central portion of the try to act as a guiding stop to seat the tray in place without displacing the mucosa. 6. Mark the hamular notches and the vibrating line (AH line) using the indelible sticks. 7. The alginate is mixed following the manufacturer instructions then loaded into the stock tray. Stand in front of the patient and place the tray at the left corner of the mouth. The right corner of the mouth is reflected with a mouth mirror. 8.The loaded tray should be seated posteriorly first then pushed slowly to the front so that the alginate flows anteriorly. Center the tray over the residual ridge so that the tray handle is in alignment with the median line of the face. At this time the upper lip is elevated so that the alginate flows into the labial sulcus. 9. The seating pressure is stopped and border molding is performed so that the impression is not overextended. The tray is held in place until the alginate has completely set. 10. Remove the impression from the mouth. Inspect the impression to determine if it is acceptable. 11.Disinfect the impression using current recommended surface disinfectant for 10 minutes in a sealed bag prior to proceeding to the labs. 12. Alginate impressions tend to be overextended so the denture outline should be drawn on the impression with an indelible stick. This outline will be transferred onto the cast and will be helpful to fabricate the custom tray.
Checklist for the Maxillary Impression
Steps in Making the
Mandibular Preliminary Impression using 1. Select stock try that will cover all the landmarks indicating the denture bearing area. Also check the impression try and make sure it covers the retromolar pads, external oblique ridge and Mylohyoid ridge. 2. The retromolar pad area should be marked using indelible stick before making the impression. 3. Any deficient area should be corrected by utility wax. The wax should be used on the entire lingual border and retromolar pad to carry the alginate into the lingual sulcus. 4. The alginate is mixed following the manufacturer instructions then loaded into the stock tray. Stand in front of the patient and place the tray at the left corner of the mouth. The right corner of the mouth is reflected with a mouth mirror. 5.Center the tray over the residual ridge so that the tray handle is in alignment with the median line of the face. At this time the upper lip is elevated so that the alginate flows into the labial sulcus. 6.The seating pressure is stopped and border molding is performed so that the impression is not overextended. The tray is held in place until the alginate has completely set. 7. Remove the impression from the mouth. Inspect the impression to determine if it is acceptable. 8. Disinfect the impression using current recommended surface disinfectant for 10 minutes in a sealed bag prior to proceeding to the labs. 9. Alginate impressions tend to be overextended so the denture outline should be drawn on the impression with an indelible stick. This outline will be transferred onto the cast and will be helpful to fabricate the custom tray.
Mark Retromolar Pad |
