Dental Impression Materials Research Paper

The medical field is characterized by various equipment and materials that are used to enhance the provision of medical services. Each of these materials is designed in a manner that meets a specific need or medical purpose. In restorative dentistry, dental impression materials have been used to fulfill various needs among patients (Anusavice & Phillips, 2012). Some scholars have argued that the use of such materials is a means to an end in that, they enhance the services provided to patients, hence facilitating recovery. Dental impression materials are basically used to perform activities that entail recording the shape of a patient’s teeth as well as the alveolar ridges for purposes of medical analysis. There are various types of dental impression materials; they are characterized by varying properties and uses and are usually associated with certain benefits and challenges (Anusavice & Phillips, 2012). Medics, have classified dental impression materials in accordance to their level of use i.e. some materials are usually regarded as elastic while others are classified as non-elastic considering their capacities to be withdrawn over undercuts (Anusavice & Phillips, 2012). Dental Impression Materials Research Paper .This research will focus on certain issues ascribed to dental impression; it will involve an exploration of dental material impression trays, their classification, bite registration and the available types of materials used to make impressions.

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Dental Impression Trays

In the context of restorative dentistry, a dental impression tray is basically a container that the dental impression material; it is usually applied to set and support the impression. There are three main types of dental impression trays; one of these trays is the stock tray. Stock trays play an imperative role in the process of taking primary impressions (Terry & Geller, 2013). These trays are manufactured in a variety of sizes and shapes; the procedure for selecting an appropriate stock tray is based on a determination of whether or not is matches the measurements and dimensions of a patient’s dental arches. Stock trays are also manufactured in two main dimensions edentulous and dentulous, which are also made in varying shapes and sizes, considering the fact that many clients have different dental dimensions. Some stock trays are manufactured using metallic materials and are usually considered re-usable. There are also stock trays, manufactured by the use of plastic materials, specifically polystyrene and nylon and are usually disposed after use. Medical research indicates that the current dental impression stock trays were manufactured approximately three decades ago and scientists have embarked on a research geared towards the creation of new dental trays to meet the needs of dentate mouths and edentulous mouths (Terry & Geller, 2013).
Another dimension of dental impression trays is the special tray; basically they are a set of dental impression trays that are custom made to meet the need or fit the dental arches of specific individuals. The process of customizing such trays is usually guided by a dentist, after taking an analysis of the dental characteristics of his/her patient. That is, they are made on a cast after performing a preliminary impression, by using stock trays.Dental Impression Materials Research Paper .  Acrylic and shellac materials are preferred in the use of special trays. The acrylic materials used to manufacture special trays may be cold cured or light, while the shellac materials used to manufacture special trays are usually thermoplastic materials. The construction of special trays as aforementioned is primarily performed on a cast, which assists in adaptation of the dental impression materials and enhances efficient use of the material. The resultant special tray/ master cast is properly detailed and refined in an accurate manner to fit the specific denture characteristics. There are two main varieties of special tray; the first variety involves those that are referred as “closed special tray”. This type of special tray is manufactured in a manner that there is no space between the special tray and the cast material. It is usually manufactured using impression wax as well as zinc oxide. There is also “the spaced tray”; this type of tray occurs in three main dimensions: Alginate, where a 2mm space is left for the alginate impression material; the impression plasters, where a 1.5mm is left for the impression material and an impression tray with a spacing of 3mm between the tray and the impression material, usually elastomeric impression materials (Terry & Geller, 2013).
Alginate trays are the third dimension of dental impression trays; their name is based on the fact that they are manufactured using alginate impression material, which is an irreversible hydrocolloid and elastic material. The inseparable part of an indirect restoration is made of an irreversible hydrocolloid. It is apparent that alginate is one of the most commonly used dental impression material. This is based on its simplicity of application and the fact that it is an indispensable part of dental services service provision as well as its cost-effective nature. For many years the use of alginate materials has formed the bulk of dental practices and has been extended to the manufacture of sports mouth guards and the manufacture of orthodontic impression models.Dental Impression Materials Research Paper .  Research has also indicated that alginate impression materials can be applied in the final impressions, for purposes of indirect restoration when one experiences chamfer preparation margins (Terry & Geller, 2013). Similarly, alginate trays are manufactured in various shapes and sizes i.e. extra large, large, medium and small or even extra small. Some manufacturers have designed alginate trays labeled with certain numbers i.e. 21, 20, 22, 7, 1, 4, 7 et cetera. Alginate trays with labels 1, 4, 5 and 7 means that they are for maxillary, while alginate trays with labels between 20 and 22 are for mandibular. These labels are designed in a manner that the larger the number, the smaller the tray and vice-versa (Terry & Geller, 2013).

The use of adhesives and perforations on dental impression trays

Medical research places emphasis on the importance of firm adherence of the impression materials to the impression trays (Bensel et al, 2013). However, this can only be achieved by following dental guidelines asserting that medics should apply adhesives or perforations. Adhesives solutions are recommended when a dentist decides to use alginate impression materials or when one decides to use silicon or polysulphide impression materials (Bensel, 2013). The most common adhesive materials used for alginate impression materials are solutions of resins soaked in alcohol. These are usually supplied in special bottles and users are also provided with a brush or at times, an aerosol spray. In the case of polyshulphide impression materials, rubber solution adhesives soaked in acetone are recommended while in silicon material impression, amylacetone or isopropylalcohol are recommended. Dental Impression Materials Research Paper .

Classification of Dental Impression Materials

Classification of impression materials is based on six major characteristics: To begin with, there are impression materials classified in accordance to mode of elasticity and setting. There are three main types of impression material within this category: Rigid impression materials such as reversible thermoplastic and irreversible thermosest; elastic impression materials i.e. agar, which is reversible, and alginate, which is irreversible; and elastomeric impression, which includes polysulphides, polyesther et cetera.
The second category of impression materials is based on area of use and type of impression; it is also sub-divided into two main categories; dentulous, (Primary: Alginate and Secondary: Agar and elastomers) and edentulous, characterized by impression plasters and alginate for primary uses and ZOE impression pasts for secondary uses.
In regard to the third category of impression materials, they are classified according to their uses in the industry. This category is also sub-divided into two main dimensions, the dentulous and the edentulous. The edentulous in this category is majorly applicable for purposes of complete denture prosthesis, characterized by the use of alginates, impression pastes, ZOE impressions et cetera. There is also the dentulous in this category, characterized by the use of RPD and FPD.
Classification of the fourth category is based on the level/amount of pressure applied; which may involve mucostatic used with an impression plaster and mucocompressive used with an impression compound. The fifth category is based on the technique of manipulation for instance: Hand-mixing, which may occur in three main ways, kneading, vigorous mixing and circular motion by use of a glass slab.Dental Impression Materials Research Paper .  Consequently, impression materials are classified in accordance to the tray applied for impression for example: Stock tray impression that may involve the use of plastic i.e. in the case of orthodontic trays and special trays i.e. when using resin as an adhesive material.

Types of Materials used to make Impressions

There two main types of materials used to make impressions; one of the most common types involves the use of hydrocolloid impression materials (Anusavice & Phillips, 2012). The main two types of hydrocolloid impression materials are alginate and agar. Chemically, agar is a reversible form of hydrocolloid owing to the fact that it has a characteristic feature that allows it to pass repeatedly between low viscous sol and high viscous gel by a process of cooling and heating (Anusavice & Phillips, 2012). On the other hand, alginate as a materials used to make impressions is chemically irreversible owing to the fact that once it is converted from gel to sol, it cannot be reversed to the original form. Alginate and agar can be used in an independent basis or when combined to make records for crown impressions. Their use was introduced in the late 1903’s by Sears for purposes of recording crown impressions. However, agar is not a common material used among dentists as a result of the fact that its use involves the application of expensive water cooled tray as well as expensive baths (Anusavice & Phillips, 2012).
The second type of materials used to make impressions is made from synthetic elastomers; their use was introduced in the late 1950’s and are currently highly popular among dentists owing to the fact that they have facilitated the reduction of challenges associated with the use of hydrocolloids, which are: Inadequate tear resistance and poor dimensional stability (Terry & Geller, 2013).Dental Impression Materials Research Paper .  There are three main impression materials made from synthetic elastomers, they include: Silicon impression materials i.e. silicon rubbers; polyethers, which are associated with a fast setting time compared to other materials and; polysulphides, which are available in a variety of viscosities (Terry & Geller, 2013).

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Bite Registration

Bite registration basically involves noting a patient’s impressions of the lower and the upper teeth in accordance to the position that has been bitten (Frank & Frank, 2012). It is an important process as it facilitates efficiency in relation to manufacturing or making of mouth-guards and making of dentures as well as the making of crown fittings (Frank & Frank, 2012). One of the simplest techniques of bite registration involves creating a three-dimensional bite impression by biting a polysiloxane or in some cases biting a wax (Frank & Frank, 2012). Dental Impression Materials Research Paper .

References

Anusavice, K. J., & Phillips, R. W. (2012). Phillips’ science of dental materials. Elsevier Health Sciences.
Frank, E., & Frank, S. (2012). Bite registration in Cerec and in lab. International journal of computerized dentistry, 15(2), 149.
Terry, D. A., & Geller, W. (2013). Esthetic & Restorative Dentistry: Material Selection & Technique. N. Bichacho, A. James, M. B. Blatz, M. L. Stankewitz, O. Tric, P. Adar, & J. M. Powers (Eds.). Quintessence Publishing Company.
Bensel, T., et al. (2013). Disinfection effect of dental impression tray adhesives. Clinical oral investigations, 17(2), 497-502. Dental Impression Materials Research Paper.