Using the wrong sized mixing tip would also be problematic. The initial mix of the material should be discarded because it is possible that one side of the mixing tip was filled before the other side at the start of mixing. When extruding impression material through a mixing tip, the base and catalysts are pushed through a spiral to mix both components. To ensure the preparation is entirely clean prior to impression, some clinicians prefer to clean the preparation with pumice/alcohol and use nitrile gloves instead of latex.Īnother issue may be that the impression material did not mix properly. Also, the residue of some build-up materials or bis-acryl provisional material may inhibit the set of impression material. Such contact could be the source of the problem. Often the clinician may swipe a gloved finger across a tooth preparation prior to impression or roll a retraction cord between two gloved fingers. The sulfur coating on latex gloves, for example, may inhibit the set of impression materials. One possible cause of unset impression material is the material contacting a substance that inhibits its setting. Potential Impressioning Mistakes Unset Material Within the Impression This article reviews some common errors that are present in final impressions and suggests possible causes for and solutions to these mistakes. However, if the dentist is unable to identify the cause of the error in the original impression, the mistake may very well be duplicated in the retake. Various factors such as time, cost, patient comfort, and soft-tissue health may prevent a dentist from retaking an impression. A recent evaluation conducted within a commercial dental laboratory determined that 86% of crown-and-bridge impressions contained at least one detectable error and 55% contained a critical error related to the finish line. Making an accurate impression requires understanding the anatomy surrounding the finish line, the material being used both for impressions and gingival displacement, and the correct use of impression trays. Perhaps one of the most challenging procedures in dentistry is obtaining an ideal impression for a fixed dental prosthesis. For unilateral impression taking, however, trays can be used or a "free-hand" (trayless) technique can be used.Diagnosing a Failed Impression: Common Errors and How to Overcome Them For bilateral impression taking, trays are always used. We also emphasize these two techniques since they provide an opportunity to demonstrate two alternative impression taking procedures: taking impressions with and without impression trays. Consequently, the impression material of choice is left to the preference of the individual.įor purposes of this presentation, we will cover compound impression taking techniques for impression taking for both fixed bilateral and fixed unilateral appliances. The most critical feature for an impression taking material for space maintainers is accuracy in obtaining the band registration around the tooth.Īlthough we like compound when taking impressions for space maintainers, we are fully aware that many clinicians prefer alginate because of their familiarity with this material. If you use other materials successfully and/or if your office routine is set up for other materials, by all means continue to use them. ![]() ![]() Of course, alternative materials can be used. In particular, it is accurate and stable, and you will see how these qualities make it highly suitable for taking impressions for space maintainers as we proceed through the chapter. Compound is an excellent impression material, especially for fixed appliances. We will focus on impression taking with compound. And as you know very well by now, removable space maintainers are rarely indicated and seldom used in pediatric dentistry. The two impression materials most commonly used in pediatric dentistry for space maintainers are alginate and compound.Īlginate is indicated primarily when removable appliances are being made. Once the bands have been fitted to the teeth, an impression is taken. Our purpose in this subsection is to cover impression taking techniques involved with space maintainer appliances. Appliance Construction: Impression Taking
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