1. Field of the Invention
Embodiments of the invention described herein pertain to the field of viscous, thixotropic impression materials. More particularly, but not by way of limitation, one or more embodiments of the invention enable an apparatus, system and method for mixing and dispensing dental impression materials.
2. Description of the Related Art
During the practice of dentistry or orthodontics, it becomes necessary from time to time to take an impression of a patient's teeth in order to provide treatment or to complete a required procedure, such as filling a cavity or fitting a retainer. Conventionally, creating an oral impression is a two step process, which occurs in a dentist or orthodontist's office. First, an impression or negative mold of the patient's teeth is created. To create the mold, a viscous, thixotropic impression material, typically sodium alginate, is prepared by measuring a powder (e.g., alginate powder), and then mixing the powder with a precise quantity of water in an open container or bowl using a paddle or spatula. The impression material is mixed until smooth and even in consistency, forming a paste, after which it is put into a dental impression tray and placed in the patient's mouth. After a short period of time, the impression compound sets and becomes firm. Upon removal from the patient's mouth, an impression of the patient's dental arrangement is left in the tray.
The next step is to create a cast from the mold. A plaster derivative, such as dental stone, is prepared, again by measuring out and mixing a dry powder with a precise quantity of water to form a paste. The paste is mixed with a spatula in a bowl, and is then scooped into the dental impression mold to cast a mock-up of the patient's dental arrangement (teeth) once the paste dries. From this model, the dentist or orthodontist may plan treatment procedures, or make dental appliances suitable for the specific patient's dental arrangement.
Currently, the measuring and mixing required to prepare the impression materials is a tedious, messy and cumbersome manual process. Quantities of dry powder and water must be carefully measured, the wetted powders must be thoroughly and evenly mixed by hand, and once mixed, scooped and transferred into the impression tray. In a typical alginate impression, 1-2 ounces of water and about 2 ounces of powder must be carefully combined and then spatulated aggressively to reach a creamy consistency. The whole process must be completed quickly and with considerable force. For example, if the process is not completed quickly enough, the compound may prematurely set. If enough force is not used, the mixture may not reach the necessary smooth and creamy consistency.
There are a number of difficulties with this common method of dental impression preparation. One problem is the consistency and uniformity required of the impression compound mixtures. The ratio of water to powder is required to be precise, and this precision is dependent on the complete incorporation of water into the powder. If some of the powder is un-wetted and unmixed due to being in inaccessible places in the mixing cup or poor mixing technique, the ratio of water to powder is effectively too high, and the compound will not perform properly. Areas of unmixed powder may also clump and not flow properly.
The impression compound is also sensitive to the formation and entrapment of bubbles, which bubbles negatively affect the smoothness of the resulting molds and casts. In addition, the impression powder is prone to “slumping”. This causes a disparity between the required amount and the actual dispensed amount, which discrepancy can be as high as 30%.
Another problem is that the impression and dental stone compounds consist of a fine powder before being mixed with water. This powder becomes air-borne during the preparation process, and can be irritating if inhaled. Additionally, the powder can get into instruments and equipment in the dental office, some of which are quite expensive and intolerant to this type of contamination.
A further problem is the sterility and cleanliness of the equipment used to mix the compounds. Every item going into the patient's mouth during dental and orthodontic procedures must be sterilized, usually by use of an autoclave, a type of oven that applies heat, which kills any harmful micro-organisms that may reside on the instruments or appliances being sterilized. The paddles, bowls and other equipment currently used to prepare impression compound are not able to withstand the heat of the autoclave procedure, and are therefore difficult to sterilize.
Yet another problem arises once the impression material or plaster derivative is mixed and must be transferred to the impression tray. It is difficult to efficiently transfer the compound without leaving much of it behind in the mixing cup. Once the impression process is complete, a sticky mess is left behind with many bowls, spatulas and/or spoons to disinfect.
Currently, polyvinyl siloxane is sometimes used as a mold material, rather than sodium alginate, in an attempt to address some of the problems associated with the preparation of dental impression materials. Polyvinyl siloxane is an elastomeric epoxy that results from combining two viscous liquids, rather than mixing dry powder with water. These viscous liquids are sometimes dispensed with a squeeze gun. However, polyvinyl siloxane is between ten and twenty times the cost of sodium alginate, and is therefore often cost prohibitive. In addition, even if polyvinyl siloxane is used as the impression compound, the dental stone for the cast must still be mixed with water from a dry powder in the aforementioned manner.
Thus, mixing and dispensing dental impression materials using conventional systems and methods suffers from a large number of shortcomings. Therefore, there is a need for an apparatus, system and method for mixing and dispensing dental impression materials.