How to create accurate crown and bridge impressions with Aquasil Ultra [VIDEO]

Despite advancements in almost every facet of impression-making, from materials to hemostatic agents to cords and retraction paste, achieving accurate impressions of crown and bridge preparations can be frustrating for practicing dentists.

A recent study found that 89% of impressions taken had one or more observable errors; the most common error was voids or tears at the finish line (likely because of difficulty obtaining intimate contact of material around the tooth and gingiva, faulty manipulation of the materials while placing it around the tooth, or premature removal from the mouth).1

Three major challenges facing dentists when recording conventional crown and bridge impressions are: correctly managing the soft tissue, placing material precisely around the properly prepared tooth, and dispensing both injection and tray materials into the mouth within allowable intraoral working times.

Prior to capturing a final impression, practitioners have historically used mechanical retraction through the placement of cord, alone or in combination with a chemical agent to promote hemostasis, drying, and retraction of tissue (e.g., aluminum chloride, ferric sulfate, racemic epinephrine). In one study of North American dentists, it was found that 95% of respondents routinely used gingival retraction cord during crown and bridge impressions.2

To allow enough material to create an undistorted impression, a 0.2 mm space must be created between tooth and gingiva. This minimum space requirement is intended to allow the impression material to flow into the sulcus and not exceed its tear-strength capability, preventing the chance for remnants to be left behind that could cause gingival irritation and inflammation.3-6

Recently, product manufacturers have introduced retraction paste as a less traumatic means of achieving hemostasis and local retraction (e.g., Epasyl© from Kerr and Traxodent© from Premier).

Even though retraction paste has been shown to create temporary gingival inflammation, it is considered less traumatic when compared to placing retraction cord and is as effective in promoting hemostasis.8,9

There are several ways that conventional crown and bridge impressions are taken: the single-step technique using only one material (e.g., monophase technique), the single-step technique involving impression materials of two viscosities (e.g., light body and heavy body), and the double-step technique which also includes two materials with different viscosities, however, one is allowed to set followed by placement of the second material as a second step.

All of the options for placement of impression material around the prepared tooth require the dentist to perform two tasks simultaneously: expressing the material by pushing down on the plunger or squeezing the impression gun and, placing the material around the tooth.

A new delivery method

DENTSPLY Caulk has developed Aquasil Ultra Cordless Tissue Managing Impression Material and digit power™ Dispenser as a means for dentists to precisely place material for improved crown and bridge impressions without the need for retraction cord or retraction paste in most cases.

The digit power™ Dispenser is a pneumatic impression device that is compatible with most dental units. It connects to an air line at the dental chair via commonly available connectors and uses digit power™ unit-dose impression cartridges. Instead of loading a backfill syringe or squeezing the 50 mL impression gun, dentists are now able to simply step on the rheostat to express material while holding the impression device in a pen-grip.

The small diameter intraoral tip on the impression cartridge allows placement directly into the sulcus or around a dental implant. Different sized impression cartridges are available for either single- or multiple-unit cases.

Aquasil Ultra Cordless Tissue Managing Impression Material is designed for use with a single-step dual-viscosity impression technique.

[RELATED: A behind the scenes look at DENTSPLY Caulk's new Aquasil Ultra Cordless Tissue Managing Impression System]

Both the tray material and the wash material for this system have been formulated to provide several advantages compared to Aquasil Ultra. First, because the wash material is intended to be placed around the prepared tooth without the use of cord or retraction paste, it is designed for flow into sulcus widths of less than 0.2 mm without distortion or tearing.

Compared to Aquasil Ultra the tear strength of Aquasil Ultra Cordless impression material has been improved to prevent rips or tears at the impression margin.

Additionally, to meet the needs of dentists adopting newer technologies, the materials have been optimized for digital scanners. Figures 4 and 5 show the digit power™ Dispenser device being used to capture a final impression for tooth No. 19.

An important feature of the Aquasil Ultra Cordless impression material is the minimizing of errors due to working time/setting time violations. Exceeding the working time and/or setting time of an impression material can result in many different errors. Some examples include: incomplete or inaccurate marginal reproduction, tearing, pulls/drags, lack of coadaptation, and others.10

The digit power™ cartridges are designed so the entire impression cartridge can be expressed within the material’s intraoral working time and practitioners still have enough time to seat the tray properly. The intraoral working time of the single-unit cartridge is 35 seconds while the intraoral working time for the multi-unit cartridge is one minute; the working time of the tray material is approximately one minute and 15 seconds.

Mouth removal times for the single- and multiunit cartridges are three minutes and four minutes and 30 seconds from the start of mixing, respectively.11

Clinical Case at a Glance with Corresponding Technique Video

1. Aquasil Ultra Cordless digit power™ Dispenser, with installed intraoral tip, is shown in the blue plastic adaptor. To its right is the regulator attached to the dental air line. Note at the top of the regulator is a silver knob with settings for flow rate of the impression material.

2. The digit power™ adaptor sits in the tool holder and permits the air switch on the dental unit to be activated.

3. Comparison of conventional plastic intraoral mixing tip (back, right), and digit power™ Aquasil Ultra Cordless plastic intraoral mixing tip, (front, left) with depth markers of 3 mm and 5 mm.

4. digit power™ Dispenser and Aquasil Ultra Cordless single-unit wash material being used to capture a final impression for tooth No. 19. Buccal retracted view.

5. Final impression captured with the Aquasil Ultra Cordless system.

6. Pre-op view of patient. Buccal retracted view.

7. Finished preparations on patient for full-coverage lithium disilicate restorations on tooth Nos. 8 and 9. Buccal retracted view.

8. Final impression of tooth Nos. 8 and 9 on 25-year-old male patient. Note the extension of the material on the mesial aspect of tooth No. 8. No cord was used.

9. After final cementation of lithium disilicate crowns on tooth Nos. 8 and 9.

Closing thought

The Aquasil Ultra Cordless Tissue Managing Impression System is intended to make conventional crown and bridge impression-making easier and more predictable.

The factors that make the Aquasil Ultra Cordless system unique are:

1) Precision placement through a fine cannula allows for delivery of impression material directly into the sulcus.

2) Aquasil Ultra Cordless impression material has been optimized for placement without cord or retraction paste to capture a thin, readable sulcus and prep margins. Increased tear strength minimizes the chance of tearing.

3) The working time of Aquasil Ultra Cordless Tissue Managing Impression Material is designed to coordinate with the amount of material in the unit-dose cartridge for single or multiple preps to eliminate impression errors because of violation of working time and setting time. Dentists can now concentrate on one thing-precisely placing the material-rather than squeezing the gun or depressing the impression syringe during the placement step.

4) The ergonomically designed digit power™ Dispenser uses the pen-grip (the same grip dentists use when using handpiece).

Read the references on the next page ...

REFERENCES

1.Samet N, Shohat M, Livny A, et al. A clinical evaluation of fixed partial denture impressions. J Prosthet Dent 2005;94:112-7.

2.Donovan TE, Gandara BK, Nemetz H. Review and survey of medicaments used with gingival retraction cords. J Prosthet Dent 1985;53(4):525-31.

3.Laufer BZ, Baharav H, Yehuda G, et al. The effect of marginal thickness on the distortion of different impression materials. J Prosthet Dent 1996;76:466-71.

4.Laufer BZ, Baharav H, Cardash HS. The linear accuracy of impressions and stone dies as affected by the thickness of the impression margin. Int J Prosthodont 1994;7:247-52.

5.Shah MJ, Mathur S, Shah A, et al. Gingival retraction methods in fixed prosthodontics: A systematic review. J Dent Sci 2008;3(1):4-10.

6.Shiozawa M, Takahashi H, Finger WJ, et al. Effects of the space for wash materials on sulcus depth reproduction with addition-curing silicone using two-step putty-wash technique. Dent Mater J 2013;32(1):150-5.

7.Feng J, Aboyoussef H, Weiner S, et al. The effect of gingival retraction procedures on periodontal indices and crevicular fluid cytokine levels: a pilot study. J Prosthodont 2006;15(2):108-12.

8.Kazemi M, Memarian MA, Loran V. Comparing the effectiveness of two gingival retraction procedures on gingival recession and tissue displacement: a clinical study. Res J Biol Sci 2009;4(3):335-9.

9.Smeltzer M. An alternative way to use gingival retraction paste. JADA 2003;134(11):1485.

10.Impression-taking Guide. DENTSPLY Caulk. Available at: http://www.caulk.com/assets/pdfs/Techguide.pdf. Accessed June 17, 2013.

11.Aquasil Ultra Cordless Directions for Use. DENTSPLY Caulk.