Parkell introduces a new scannable polyvinyl impression material.
In most case scenarios, once isolation of the prepared tooth is achieved, the digital data-capturing step is accomplished with the acquisition camera. There are certain situations where the clinician finds it difficult to obtain the required data intraorally. Whether it is in achieving sufficient isolation for powdering or inaccessibility of the acquisition camera due to limited opening of the mouth, there are times that taking an impression is just easier for the patient and the clinician. Some techniques use a combination of reversible and irreversible hydrocolloid impression materials to impress the prepared tooth and then pour immediately with a scannable die material (Mach-Scannable™, Parkell). Another technique includes the use of a polyvinyl impression material that is poured with a scannable gypsum die material. This technique requires a certain amount of time to elapse prior to pouring to allow for the polyvinyl impression material to de-gas. However, this technique substantially lengthens the appointment time or even creates a two-appointment scenario. Both of these systems have the software capability to scan an impression, invert the data, and create a digital model of the impression.
According to the manufacturer, the E4D system (D4D Technologies, www.e4dsky.com) is capable of scanning all types of impressions (including alginate), bite registrations, and models without any powder or contrast agent due to the laser-based scanning technology. Presently, there are bite registration materials that the CEREC system (Sirona Dental Systems, www.sirona.com), which uses Blu-ray technology, can scan that do not require powdering or a contrast agent to be applied. However, that is not the case for polyvinyl tray and wash impression materials. Until now, a polyvinyl impression still must be powdered or sprayed with a contrast agent before the CEREC system could scan it. Parkell is introducing a scannable polyvinyl impression material that allows the CEREC system to scan the impression without having to use a powder or contrasting agent. This impression material joins Parkell's other scannable products that include bite registration material (Blu-Mousse®) and die material (Mach-2® Scannable).
The scannable impression technique can be used in a number of different treatment scenarios. For example, when the clinician chooses to use the correlation mode, a preoperative impression can be taken of the tooth and then immediately scanned into the occlusion window. The tooth is then prepared. Tissue retraction is implemented at the clinician's discretion with either retraction cord or a diode laser. The dental assistant would then load a quad impression tray or a dual-arch tray with the scannable impression tray material while the clinician injects the scannable wash material around the tooth preparation. Using an air–water syringe, the clinician would then blow the impression material off the preparation to reduce the surface tension of the prepared tooth surface. The wash material is then again injected around the tooth preparation followed by the insertion of the loaded impression tray. After the material sets, the tray is removed and the impression is dried thoroughly. It now can be scanned (Figure 1). On the monitor, the cursor is set to the preparation window and the appropriate number of images is taken. In each of the windows (preparation and occlusion) the "invert" icon is checked prior to advancing the program. The virtual model will be displayed, and the clinician can complete the restoration in the normal fashion (Figure 2).
The introduction of a scannable impression material allows the clinician to eliminate the powdering step and possibly increase the use of extraoral scanning in their CAD/CAM armamentarium. Patients who present difficulties in intraoral scanning can now easily be treated with a scannable impression.
Case presented courtesy of Dr. Gregg Helvey, Middleburg, Virginia.
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