Making the Impression of edentulous patient and possible problems
Making the Impression
1. Select a 12 cc. disposable syringe, cut off the tip to provide at least a 5 mm orifice (Syringes can be sterilized and reused several times)
2. Vaseline the syringe plunger – this is particularly important if syringes have been sterilized
3. Use an uncontaminated bowl and spatula, use regular set alginate
4. Fluff (shake) the powder, measure, tap and flatten the scoop with powder
5. Use three scoops for syringe impressions
6. Have an assistant mix the material for at least 45 seconds, until there is a smooth creamy homologous consistency that glistens. The material should not appear granular or lumpy.
7. The assistant loads the syringe nearly full, from the back and inserts plunger.
8. The clinician syringes a broad rope into the vestibule, beginning at the posterior, moving quickly toward the anterior, and filling the vestibule until the labial frenum is reached.(do not cross the midline – this traps air bubbles). The cheek should be retracted with a mirror, instead of a finger, to provide more room for visibility. In the maxilla, begin opposite the region of the tuberosity and inject until alginate is seen in the hamular notch area, before moving forward. In the mandible, start with the buccal vestibule adjacent the retromolar pad, and move forward until the labial frenum is reached. Repeat on the opposite side. For the lingual vestibule, roll the tip of syringe under the tongue, inject into retromylohyoid space until alginate is seen coming upward between the tongue and the residual ridge, then move anteriorly, filling vestibule until the lingual frenum is reached. Repeat on the opposite side. Do not scrape the mucosa – this is a bloodless procedure!
9. If there is a steep palate, some material can be syringed into the palate, but it should be smoothed with a finger, or voids may occur around the syringed material
10. If the patient is partially edentulous, syringe a small amount of hydrocolloid on the occlusal surfaces (or use some of the vestibular material) and push it forcefully into the occlusal surfaces.
11. The assistant loads the tray while the clinician is syringing
12. Place the posterior portion of the tray first, then seat the anterior of the tray
13. Less gagging will occur, if the patient is lying down (tongue position avoids gagging)
14. The clinician molds the vestibular areas by pulling on the cheeks and lips to activate the muscles and frena
15. Support the tray during setting – do not leave the patient, or allow the patient to support the impression – if the tray moves during gelation, distortion will occur
16. Remove with a sudden jerk (to avoid permanent deformation)
17. Evaluate impression and, if it is acceptable, pour within 12 minutes
18. Rinse the impression thoroughly with water, gently shake to remove excess water. Spray with disinfectant to coat all surfaces, and seal in a bag for ten minutes
Possible Problems with Syringe Technique:
1. Saliva contamination – vestibular material will appear separate from the tray material
2. Insufficient material – lack of integrity between the syringed and tray material
3. Omitting lubrication of the plunger may make it difficult to express the alginate
4. Trapping tongue under the tray will result in underextension of the lingual vestibule
5. Severe gaggers – the syringe technique involves a slight increase in intraoral manipulations which may be counter productive for these patients