Clinically Relevant Impression Making Tools
Improved delivery system allows for a controlled application of wash material
Paul Bylis, DDS
Impression making can only be predictable if all of the criteria for achieving consistent results are met. Some of these criteria include isolation1, impression material selection, and technique. Although the first is a prerequisite for ensuring quality results and the third plays heavily into everything we do as clinicians, the second cannot be underestimated.
Isolation matters most when it is needed most: when treating first and second molars. Rubber dams can be uncomfortable for the patient, and cotton rolls do not do enough to secure the field against humidity. Whatever method is used to ensure successful isolation, it is important to do so while allowing for the procedure to occur with the least amount of obstructions and potential failures as possible. Some newer alternative systems keep the tongue and cheeks away while suctioning and illuminating. This frees up the assistant to perform other tasks and reduces overall chair time.
Integral to isolation is proper tissue management and hemostasis. As a preventive measure, hemostasis should be performed as soon as possible and quickly managed. Using electrosurgery, any tissue that could potentially get in the way of the diamond bur can be remodeled. In this way, no bleeding occurs related to subgingival reduction procedures. Preparations located at or above the gingiva do not require any tissue augmentation and are typically free from hemostasis considerations.
At the time of the actual impression-making procedural step, both the impression material and the impression technique chosen for a specific case are relevant to achieving successful results.2 A clinician's technique and skill can only do so much to compensate for a material's limitations. And a material's attributes can only do so much to compensate for a clinician's technique. For my cases, I select a material that is both hydrophilic and high in tear strength.3
Equally important to the material selection is the delivery device used to get the material into the patient's mouth. Historically, only a few options have been available, including machine or hand mixed for tray materials and hand mixed or single-unit for wash materials. Fortunately, more ergonomic, user-friendly alternative delivery systems are becoming available that can improve the practice's workflow, greatly reduce stress, and make for a better patient experience.
Case Report
A patient presented to the office with a broken distobuccal cusp on tooth No. 18 (Figure 1). In addition, the distolabial cusp had a stained craze line where it met the floor of the existing amalgam restoration. After a local anesthetic was administered, isolation was achieved using a mouthpiece system (Isolite 3, Zyris). With the patient resting on the prop, all vital areas safely retracted, and the field kept clear through continuous evacuation of oral fluids, the difficult area can be treated in a controlled fashion.
At this time, the assistant also placed wedgeguards (Palodent Plus Sectional Matrix System Wedgeguards, Dentsply Sirona) between the adjacent teeth (Figure 2). With the wedgeguards in place, the remaining amalgam restoration could be very comfortably removed and the tooth could be efficiently prepared. Creating this environment allows the clinician to focus his or her concentration on the task at hand. The mesial and distal tooth structure can be quickly reduced to create a consistently well-formed margin. The bonus is a faster, more accurate preparation with no damage to the adjacent teeth.
After the wedgeguards were removed and the core build-up placed, the need for electrosurgery to control proper hemostasis in the operating field was assessed. If the potential to inadvertently cut the gingiva due to subgingival marginal placement exists, the tissue should be modified to avoid creating a bloody field. A straight needle electrode was used very gently around the areas of the tooth that would benefit from the placement of traditional cord, including the mesial, distal, and lingual aspects of the preparation. Due to the efficiency of this step,4 packing cord or placing a hemostatic agent was not necessary, reducing the time delay and enabling an immediate impression.
To acquire the impression, a hydrophilic impression material with high tear strength and dimensional stability was selected (Aquasil® Ultra+, Dentsply Sirona) along with a battery powered precision delivery system (digit Power® Dispenser, Dentsply Sirona) to improve the results. The digit Power Dispenser was loaded with an Aquasil Ultra+ LV (low viscosity) cartridge and the timer mode was set to accommodate the needs of the case. The timer on the screen counts down the exact time necessary for applying the wash material and positioning the tray and indicates the mouth removal time, so one never has to worry about taking the tray out too early or losing time from letting the tray set a little longer "just to be sure." The foot control, which offers variable dispensing speeds, eliminates any undue hand pressure on the device and facilitates an even more comfortable hand position closer to the dispensing tip (Figure 3). The digit Power Dispenser was taken to the mouth and the wash material was dispensed (Figure 4). The unit fits in the hand similar to holding a handpiece. This allows for more precise control of the delivery system and more intimate proximity to the preparation when compared with traditional 50 ml cartridge guns and smaller dispensing syringes. It is important to keep the syringe tip fully immersed in the material the entire time to avoid bubbles. Next, a triple tray loaded with Aquasil Ultra+ heavy body was placed, and the patient is instructed to bite down until the timer indicated that the impression could be removed (Figure 5). Monolithic zirconium was chosen as the material for the definitive restoration, and the patient was pleased with the final result (Figure 6).
About the Author
Paul Bylis, DDS
Innovative Dental Design
Glen Burnie, Maryland
References
1. Johnson GH, Lepe X, Aw TC. The effect of surface moisture on detail reproduction of elastomeric impressions. J Prosthet Dent. 2003;90(4):354-364.
2. Naumovski B, Kapushevska B. Dimensional stability and acuracy of silicone - based impression materials using different impression techniques - a literature review. Pril (Makedon Akad Nauk Umet Odd Med Nauki). 2017;38(2):131-138.
3. Aquasil® Ultra+ Smart Wetting Material. Denstply Sirona Website. Key Benefits. https://www.aquasilultraplus.com/en-us#Key%20Benefits. Accessed June 14, 2018.
4. Hasar ZB, Ozmeric N, Ozdemir B, et al. Comparison of radiofrequency and electrocautery with conventional scalpel incisions. J Oral Maxillofac Surg. 2016;74(11):2136-2141.
