Binary impression dental1/5/2024 The tray can also support the material impression and improve accuracy. Impression trays are used to carry the impression material into the mouth, and the handle of the tray is used to remove the impression. Unacceptable restorations made on casts from cheap impression materials can make dentistry a nonprofit enterprise. An accurate cost analysis needs to include the percentage of first impressions that are acceptable and the number of restorations that need to be remade. The cost of impression materials varies greatly, from pennies per impression to as much as several dollars. Note that the lengths dispensed, but not the volumes, are equal. Polysulfide ( lower) and polyether ( upper) impression materials. It is interesting to note that dental impression materials are also used to make impressions for medical prostheses (such as artificial eyes) and forensic investigations (bite marks).įIGURE 8.3. Several impression trays are shown in Figure 8.2. The tray functions as a carrier and can stabilize the set impression material. They are then loaded into an impression tray, placed in the mouth, and seated onto the tissues of interest. Regardless of their form, impression materials are mixed (or heated) to make a thick paste or liquid. Several materials are softened or melted by heating. Some are powders that are mixed with water others are paste–paste systems. Impression materials are supplied in a variety of forms. A replica of a single tooth is called a die. Other uses require very exact (within 0.1%) replication of the size and shape of a preparation for the construction of a restoration or appliance. Study models are used in diagnosis and treatment planning. Some uses are simply to produce a physical model of the oral tissues for study, called a study model. Because impression materials are used for many purposes, a wide variety of products are available to make impressions of oral tissues. Not all impression materials are compatible with all model materials. The impression must be an accurate duplication of the hard and soft tissues of interest and be stable enough to allow disinfection and production of an accurate model.įIGURE 8.1. The impression is a negative reproduction, whereas the replica (model or cast) is a positive reproduction, as illustrated in Figure 8.1. The replicas are used to construct restorations and other appliances. These supporting structures include gingiva, alveolar bone or residual ridge, hard and soft palate, and frenums, which are muscle attachments. In dentistry, we take impressions of teeth and their supporting structures. Impression materials are used to make replicas (models or casts) of teeth and other oral tissues. Taking impressions can be a welcome change from the typical daily routine of the hygienist. And it is not unlikely that you may be asked to assist with a “final impression” appointment should the dental assistant not be present that day. Should you make athletic mouth guard or whitening trays, an impression will be a part of the appliance fabrication process. It is important to have an understanding of the various types of impression materials, their specific use, and their handling characteristics. Taking impressions may be one of the responsibilities of the dental hygienist in a busy practice.
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