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PATIENT
VISIT 2– FINAL IMPRESSIONS
Clinical
Procedures
Final Impressions
1. Definitions
Final Impression: A final impression of an edentulous mouth is the
negative registration of an area over which the complete denture will be
worn.
After border molding is completed, the next clinical procedure is
making final impressions. The patient should have left the current
dentures out of the mouth 24-48 hours prior to this visit.
2. Material
The material most commonly used are
rubber base (polysulfide),
zinc
oxide and eugenol and Elastomeric impression material.
Zinc oxide and eugenol impression
material is hard setting, free
flowing impression paste. It is used when the oral tissues are very
yielding, flabby and are not firmly attached to the underlying bone. It
has a comparatively short mixing and setting time. Displacement of the
basal seat tissues is easily detected when using this material for final
impressions. Among the disadvantages are the difficulty in removing the
material from severe undercuts and from the final impression tray if the
impression must be repeated( Zinc oxide and eugenol can not be
disinfected) .
Rubber base impression material may be more easily removed from the
impression tray. They are elastic and can be removed from undercut areas
without damage to the impression or the patient. The setting time is
considerably longer than with zinc oxide and eugenol materials unless fast
setting materials are used. Rubber based impression materials can mask
displacement of the basal seat tissues. Rubber base and Polyether
are used if the
tissues are more firmly attached to the underlying bone, non-yielding and
less moveable. It can also be used if there are slight bony and/or tissue
undercuts.
Maxillary Final Impression
using ZOE or Rubber base impression material
click here for video 1. Place Vaseline over and around the patient's mouth and lips.
2. Dry the tray. If rubber base impression material is to be used, paint
the tissue surface and borders of the tray with an adhesive taking care
not to block the holes in the palate with the adhesive.
3. Instruct the patient to rinse with mouthwash. Dry the palate and basal
seat tissues with gauze. Have the patient close and retain the gauze in
the mouth. Remember, overdrying the mouth will stimulate salivary flow.
4. If using zinc oxide and eugenol (Opotow), place one 4-inch strip of
tube 1B and 2 4-inch strips of the material in tube 2A on the mixing pad.
Mix until a homogeneous color. If using rubber base impression material,
place equal 4-inch lengths of light body base and catalyst
on the
mixing pad. Mix until homogeneous.
5. Distribute the material uniformly in the tray using a small
cement spatula. Cover the borders 2-3 mm onto the labial and buccal
surface of the tray. Place only enough impression material in the
posterior of the tray to record the tissues. Excess material will flow
out the posterior of the tray and cause the patient to gag.
6. Remove the gauze from the patient's mouth. Standing to the
right of the patient, rotate the tray into the patient's mouth. Place the
index fingers on the posterior rim and fully seat the tray. The
vestibular tissues may be briefly and lightly border molded for about 30
seconds after the tray has been seated. Retain the tray in position with
finger pressure at all times.
7. Allow the material to set. Generally, this is 3-4 minutes for fast set
rubber base and 7-8 minutes for regular set rubber base.
8. Remove the maxillary final impression using the techniques described
previously for preliminary impression.
9. Inspect the impression to determine if it is acceptable.
10. Disinfect the impression by rinsing excess saliva with water. Place
the impression in a ziplock bag and spray into the bag with the current
approved disinfectant. Wait 10 minutes before unsealing
bag and pouring impression.
Checklist for the Maxillary Final
Impression
A. Labial and buccal vestibular reflection fully recorded.
B. Pterygomaxillary notch recorded.
C. Palate and vibrating line recorded without voids or distortion.
D. No tray showing through the impression material.
E. Labial and buccal frenae recorded.
F. Uniform color of impression material indicating proper mixing.
G. No large voids or wrinkles in the impression surface.
Evaluate your impression with your clinical faculty
member. Large voids or other deficiencies may necessitate remaking the
final impression. Small air bubbles may be acceptable.
Use a warm, sharp Bard-Parker blade to trim the excess impression material
from the impression tray. Begin in the right buccal pouch area and
trim 4 mm below the border of the impression. Trim the posterior
material flush with the posterior surface of the tray.
Maxillary Rubber Base Impression
Mandibular Final Impression using Rubber base
impression material
click here for video 1. Place Vaseline around the patient's mouth and lips.
2. Dry the tray.
3. Paint the tissue surface and borders of the tray with rubber base
adhesive.
4. Instruct the patient to rinse with mouthwash. Dry the patient's mouth
with gauze. Excess saliva will prevent registering fine tissue detail.
Gauze packs are placed over the submaxillary and sublingual gland ducts
while the impression material is being prepared. Do not dry the mouth
excessively.
5. Place equal 4-inch lengths of light-body rubber base catalyst and base
on the mixing pad. Mix until homogeneous.
6. Distribute the material uniformly in the tray using a small
cement spatula. Cover the borders 2-3 mm onto the labial and buccal
surface of the the tray.
7. Remove the gauze from the patient's mouth. Standing to the
right of and if front of the patient, reflect the patient's cheek with a
mouth mirror and rotate the tray into the patient's mouth. Hold it in
position with the index and forefinger with enough pressure to keep the
tray seated. The vestibular tissues may be briefly and lightly border
molded for about 30 seconds after the tray has been seated.
Instruct the patient to open his or her mouth widely and lightly
protrude the tongue and lick the upper lip from one corner to the other.
Also, ask the patient to lick between the upper ridge and lip. Now have
the patient rest the tongue. This will determine the depth and width of
the lingual sulcus.
8. Allow the material to set.
9. Remove the final impression using the technique described previously
for the preliminary impression.
10. Inspect the impression to determine if it is acceptable.
Checklist for the Mandibular Final Impression
A. Labial and buccal borders fully recorded
B. Retromolar pad covered.
C. Retromylohyoid area recorded.
D. No tray showing through the impression material
E. Lingual, labial and buccal frenae correctly recorded.
Using a sharp scissors, trim the excess
impression material 4 mm short of the lingual, buccal and labial border as
before. Remove any unsupported impression material which would distort
when the impression is poured (especially likely in the lingual flange
area) with scissors.
Mandibular Rubber Base Impression
Border molding and final
impression using Elastomeric impression material
click here for video 1. Place Vaseline around the patient's mouth and lips.
2. Dry the tray.
3. Paint the borders of the tray with Elastomeric impression material
adhesive, wait until it set.
4. Place heavy body Elastomeric impression
material along the periphery of the tray.
5. Place the tray in the patient mouth and
instruct him to perform movements such as sucking a finger or pursing the
lips. The vestibular tissues may be briefly and lightly border
molded for about 30 seconds after the tray has been seated. Retain
the tray in position with finger pressure at all times.
6. Allow the material to set according to manufacturer recommendations.
7. Remove the maxillary final
impression. Inspect the impression to determine if it is acceptable.
8. Remove all excess material from the tissue
surface of the tray using sharp knife. Paint the tray with polyether
adhesive.The final impression is completed with light body Polyether
impression material ( follow same steps as
Rubber base) .
Maxillary Elastomeric Final
Impression
The ends the clinical procedures for visit 2. |