![]() ![]() Nonetheless, disposable plastic impression trays have been introduced to the market and are very attractive in countries with high personnel costs since time for cleaning and sterilization can be saved. As processing steps are omitted, significantly more waste is produced. In times of aggravated hygiene guidelines and centralized sterilization, single-use products grow in importance. On the other hand, cleaning and processing for re-use are expensive and time-consuming. The border-lock design combined with the use of tray adhesives hinders detachment of the cured impression. For final impressions, metal trays with flanged margins (border-lock) are recommended as they offer torsional rigidity and inherent stability. A major impact is also attributed to the type and design of the impression trays used. With respect to procedural aspects, in digital impression-taking, for instance, powdering which is often necessary when glossy surfaces are positioned next to relevant structures can affect the accuracy.īack to conventional impression-taking, the technique (one-step/two-step and monophase/dual-phase) can impact the outcome as well as disinfection measures applied to cured impressions. Oral hygiene and periodontal health and therefore bleeding tendency, the location of the preparation margin, saliva, and the angulation of the abutment tooth, among others, all affect the accuracy of impressions. ![]() īeyond this, conventional and digital impression-taking are influenced by various clinical parameters and procedures. ![]() It should be also acknowledged that laboratory adjustment of restorations including refinement of fit and occlusal contacts is more challenging without having plaster casts. For the sake of completeness, digital impressions by use of intraorally three-dimensional scanners should also be mentioned which seem to be-regarding accuracy-comparable if used for the fabrication of single crowns, but are still disadvantageous to conventional impression-taking when it comes to long-span or full-arch restorations. To date, some hybrid materials such as silicones with hydrophilic properties are available on the market, which aim to combine the various advantages. Hereby, each of the advantages of one material is the disadvantages of the other. Both enable excellent dimensional accuracy and the detail reproduction needed but the material classes also include advantages/disadvantages just to mention a few, PE materials are designed to show initially hydrophilic behavior which should enable a better flow onto moist tooth structures, while VPS materials are rather neutral in taste and can be stored over longer time periods. Nowadays, there are largely two established elastomeric material classes for impression-taking of abutment teeth prepared for fixed and removal dental prostheses: polyether (PE) and vinyl polysiloxane (VPS). In restorative treatment, the reliable communication of the clinical situation to the dental technician is a complex but key process. ![]()
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