Dental Tribune Israel Edition

3 Dental Tribune Israel | 11/2016 Revisiting the channeled - putty/wash technique for predictable, flawless perfect impressions Dr. Mirela Feraru Dr. Galit Talmor Prof. Nitzan Bichacho Abstract A prerequisite for any long-lasting indirect restoration is a perfect marginal fit, which requires a precise impression. This article describes a technique of polyvinyl siloxanes impression making, originally implemented with condensation-type silicones known also as the “correcting impression technique” (1). The technique provides a predictable perfect impression and minimizes drastically the need for remakes. This article describes the channeled-putty/wash technique highlighting its advantages and pitfalls. Introduction A perfect impression should capture, in an un-deformed manner, the entire configuration of the prepared tooth as well as some of the pristine tooth structure peripherally to the finishing line. Even though digital scanning popularity is increasing, traditional impressions utilizing elastomeric materials still dominate the market (2, 3). The advantages of digital scans over physical elastomeric material impressions are obvious for dentists and laboratory communication purposes, yet current digital scans have limitations and also due to the pricing of the technology, traditional impressions still dominate the dental market, nonetheless the tendency towards digital intra-oral scanning is clear. One can reasonably assume that once the necessary physical tissue retraction will be digitally resolved - their popularity will drastically increase. The accuracy of elastomeric material impressions is influenced by the properties of the materials used, as well as the implemented technique. The elastomeric impression materials most commonly used in the last decades for accurate impression are polyvinyl siloxanes (PVS) and polyethers (PE). Due to their optimal resistance to deformation, accuracy, good dimensional stability, tear resistance, the option for a putty- wash technique and their pricing, PVS are still the material of choice for most dentists (4) and putty/wash is the most popular technique. This article addresses a different PVS impression technique for the two-step putty/wash method. A common problem in elastomeric materials impressions is air entrapment at the interface of the preparation margins and the impression material, which results in an incomplete and deficient impression. Several techniques have been described to deal with this phenomenon (injection pattern of the light body, simultaneous cord removal with the light body injection, utilizing air spray, etc.) but the step of injecting the light body material surrounding the teeth into their sulci has been a challenge for the majority of clinicians. Hence the more abutments to be captured - the more stressed the clinician becomes, due to unpredictable results caused by the risk of air entrapment. This problem occurs irrespective of whether the clinician employs a single medium-body impression, a double mix (putty+light or heavy+light) technique or a traditional two-step putty/wash technique. The following described technique eliminates the need for the intra-oral light body injection and utilizes instead the set putty as a perfect vehicle/matrix to transfer the light body into all the subgingival abutments areas with no voids. Another prerequisite of the two- step impression technique is the need to eliminate (or minimize) the stress that occurs in the set putty during its reinsertion. To do so, one should create enough space in the putty for the light body material. There are several ways (5, 6) to obtain sufficient space, including using a 2 mm controlled relief (which usually is achieved by the use of the provisional crowns) or the use of a polyethylene spacer. Here we describe a step-by-step, two-step impression technique utilizing PVS and venting channels in the set putty, with no preliminary spacer, resulting in consistent, accurate, flawless and predictable perfect impressions. Gingival management Regardless of the technique or material used, a major factor for the success of impression making is the gingival manipulation. The intra-sulcular finishing line, which corresponds to the majority of clinical situations, requires proper gingival deflection in order to provide space for the impression material to embrace its whole circular profile and some pristine tooth structure beyond it. During this procedure, one must avoid an irreversible damage to the connective tissue attachment. A careful inspection of the tissues should be first conducted. The tissue should show no signs of inflammation and care should be taken not to damage it during tooth preparation, provisional restorations fabrication and during the impression procedure. The waiting period between the teeth preparation and the impression timing is site specific dependent and is left up to the clinician’s discretion. Whenever an injury occurs to the periodontal tissues during preparation, it should be left to heal completely before the impression procedure. Positioning a cord in a traumatized tissue might cause further damage and bleeding, hindering impression making. Furthermore, an aggressive insertion of a cord might also cause irreversible damage to the periodontal tissues, especially of the thin and highly scalloped biotype. The same injury might also occur when oversized retraction cords are brutally inserted into the sulcus, which might induce indeed an impressive tissue retraction, but at the price of irreversible detrimental changes of the gingival margin’s position (i.e., iatrogenic gingival recession). Therefore, a preliminary routine mapping of the sulcus and the resultant proper selection of cords size and their positioning is mandatory. According to the position of the preparation margins, a decision regarding the use of a single, or a double-cord technique should be taken, keeping in mind that for a juxtagingival preparation - a single cord is usually sufficient to ensure the slight apicalization of the gingival margins needed for sufficient exposure of the finishing line to the impression material. Pic. 1a-d: Preoperative view of the anterior dentition prior to interdisciplinary ortho-perio-pros full mouth rehabilitation treatment. Defective restorations, crooked teeth and a traumatized soft tissue are evident. Pic. 2: Incisal mirror view - Tooth #11 (8) was prepared for a full crown. #21(9) was prepared for a circumferential veneer. A first cord was inserted a-traumatically. Pic. 3: Facial view of the prepared teeth when the first cord is placed intra-crevicularly. Pic. 4: A P.V.S. Putty impression was taken over the teeth with no separation medium, while the first cord is in place; Pic. 5, 6: Insertion of the second superficial wider diameter cords was performed with gentle rolling movements strokes; Pic. 7: Incisal mirror view - The second cords in place deflecting the free gingiva laterally; Pic. 8: The interdental ‘papillae’ were cut away and removed from the set putty to eliminate all undercuts; Pic. 9:This carving is performed using a Putty Cut (Zhermack clinical) or Deta-Cut core removal knife (Detax Dental GmbH &CO.KG) (pic. 10;11). Pic. 1a Pic. 1b Pic. 1c Pic. 1d Pic. 2 Pic. 3 Pic. 4 Pic. 5 Pic. 6 Pic. 7 Pic. 8 Pic. 9

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