Predictable Impressions Using the New Gripper “Sideless Posterior” Tray
The single posterior crown or onlay is one of the most common indirect clinical procedures in dentistry. The ability to take definitive impressions of single restorations with a dual-arch quadrant posterior tray is due in large part to its benefits: ease of use, convenience, patient comfort, the need for less impression material, and time savings. Some of the historical challenges with this type of tray have been patient discomfort, poor impression quality, operator errors, the patient biting on the tray, and the patient biting through the tray.
Discus Dental’s (Culver City, CA) new Sideless Gripper Tray is a more streamlined version of its predecessor, the Posterior Gripper Tray (Figure 1). The Posterior Gripper Tray was innovative in its design and construction, and the new version offers modifications that make the tray even more desirable.
This article will outline the steps for preparing and placing a single posterior IPS e.max® (Ivoclar/Vivadent®, Inc, Amherst, NY) CAD all-ceramic crown. The focus will be on taking a successful impression with the new Sideless Gripper Tray.
The new sideless tray's super-rigid design makes it ideal for all vinyl polysiloxane (VPS) impression applications. For added accuracy, the Sideless Gripper Tray features a unique patent-pending polymer resin/metal hybrid design for the ultimate in rigidity and patient comfort. Each tray features a large handle for superior placement and a soft-lined mesh for exceptional impression accuracy. Each handle grip is made with a matte finish that can be written on for easy patient identification and date recording. This is helpful not only in the practice but also in the laboratory.
The main enhancements to the Posterior Gripper Tray include a stainless-steel wire with half the thickness as the previous tray in the retro molar pad region and an overall decrease in size and weight (Figure 2). In addition, the handle has been offset to the side for easier placement.
HISTORY AND TREATMENT
A patient in her mid-40s presented with a large gold crown on tooth No. 19. Although the margins of the crown exhibited microleakage and minor recurrent caries, the radiographs showed no significant findings. The treatment plan was conservative; tooth No. 19 would be built up with composite and prepared for an IPS e.max CAD crown.
A preoperative impression of the existing restorations was taken with a light-body VPS impression material (Precision, Discus Dental) and a Sideless Gripper Tray lined with a clear bite-registration material (Peppermint Snap Clear Bite, Discus Dental). The tooth was prepared for a crown using a super-coarse and a fine, round-end taper diamond. The old amalgam build-up was removed and the tooth was etched and bonded with a dual-cure bonding agent (Cabrio® CQ, Discus Dental) and built up with a flowable microhybrid composite (Matrixx Flowable, Discus Dental). Finishing was completed using finishing discs. The finished preparation was checked for adequate occlusal clearance, smooth tapering walls, and visible margins.
The Sideless Gripper Tray was used to take the impression using Precision Extra Lite body and Medium body VPS (Discus Dental). The Extra Lite was injected around the dried crown preparation while the assistant loaded the tray with the Medium. When the tray was loaded, the lower-viscosity Extra Lite body was injected into the center of the higher-viscosity Medium body on both sides of the dual-arch tray (Figure 3). This can minimize the pulls and drags that often occur when using a higher-viscosity VPS material in the heavy-body or putty/wash technique.
The tray was then positioned over the teeth to be impressed using self-retracting lip retractors for isolation and visibility. The patient gently closed over the tray and bit into the VPS without biting the sides of the tray (Figure 4). The impression was checked for accurate detail and absence of bubbles, pulls, and drags. The preparation shade of ST8 was recorded and photographed. A bite registration was taken with a VPS material (Vanilla Bite, Discus Dental) to help ensure the accuracy of the mounting.
A self-curing acrylic resin in shade A3 (PERFECtemp II, Discus Dental) was added to a preoperative impression of the existing restorations and placed on the preparation. After a 2-minute setting time, the provisional was gently teased off the tooth and finished outside the mouth with finishing discs and polishers. It was cemented on the clean and dried tooth preparation with a dual-cured provisional cement. The occlusion was adjusted and the patient was dismissed. The impressions, bite records, a detailed laboratory prescription, digital photos, and prescribed shade were sent to the laboratory.
The new IPS e.max CAD porcelain crown was inspected for marginal fit, color, and defects. The temporary restoration was removed with a set of hemostats and the crown was tried in to ensure a proper fit and marginal integrity.
The internal aspect of the crown was re-etched with 37% phosphoric acid for 15 to 20 seconds, rinsed with water, and dried. Silane was applied to the internal surface for 1 minute and lightly air-dried.
The preparation was cleaned using a chlorhexidine solution and the composite build-up was microabraded with a microetcher. The entire crown preparation was coated with a thin layer of MultiLink® (Ivoclar Vivadent) adhesive primer for 15 seconds.
The yellow shade of MultiLink dual-cure posterior resin cement was applied to the inside of the restoration. The restoration was held down using a ball burnisher and spot-tacked in place for 2 seconds using a 2-mm tacking tip. The excess cement was removed using a rubber tip and floss. The crown was light-cured for 20 seconds from each aspect. The occlusion was checked and the crown was polished. The finished restorative result was both functional and esthetic.
This article has outlined the use of a new sideless, dual-arch posterior tray for impression taking and model preparation of a posterior pressed porcelain crown.
The VPS capture of multiple restorations using a dual-arch tray must always be approached with caution. The technique is ideal for a single-unit restoration where the prepared tooth is surrounded by teeth in stable occlusion in mesial and distal positions to the preparation. The accuracy of replicating the intra-arch occlusal relationship decreases as the number of restorations attempted with one dual-arch tray increases.
This article was written by Edward Lowe, BSc, DMD. He is a clinical faculty member at the Pacific Implant Institute in Vancouver, BC, and maintains a full time private practice devoted to comprehensive functional esthetic and reconstructive dentistry in Vancouver, BC.
For more information, contact:
Discus Dental, Inc
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|Figure 1 The Posterior Gripper Tray (top) vs the Sideless Posterior Gripper Tray (bottom).||Figure 2 View of the thinner metal wire and the decreased tray height.|
|Figure 3 A layer of light-body material is injected into the medium-body material.||Figure 4 The impression is placed with retractors in place.|