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PubMed1999

[Comparative analysis of tissue reaction to acrylic resin materials in studies on Wistar strain rats].

The study takes up the issue of assessing rat tissue reaction to operatively inserted implants of different acrylic resin materials used in prosthetic dentistry. The materials subjected to analysis were polyacrylics: Vertex Soft, Vertex R.S., Vertex S.C., Superacryl and silicone material Molloplast B. The prolongation of life and the dynamic development of prosthetic treatment have caused removable dentures to be used longer and among more people. Polymerised acrylic resin material of these dentures is a potential pathogenic factor to the oral cavity mucosa which is in contact with it. As many as 20 to 70% of patients using removable acrylic dentures suffer from prosthetic stomatopathy. It is considered that the mucosa irritation may be caused by denture trauma, a mycotic infection or toxic action of some components of acrylic materials. Therefore the use of new generation acrylic materials in producing prosthetic dentures needs a precise assessment of undesirable local and systemic effects. A comparative analysis of the effect of correctly polymerised acrylic material on rat mucosa, parotid glands and lymphatic nodes was carried out. Systemic toxicity of these materials was assessed. Acrylic plates were prepared from the most often used acrylic resin materials in the Department of Prosthetic Dentistry PAM and a silicone material (these materials were polymerised precisely according to the producers instruction). Before implantation the plates underwent a thermodynamic analysis in order to ensure that the polymerisation process was carried out correctly and to determine thermal resistance of particular materials. Next sterile acrylic plates were implanted in rats under general anaesthesia. The animals were divided into 6 groups, 10 rats each. In four groups acrylic plates were implanted, in one group silicone material plates were implanted and it represented the comparative group, in one control group an incision of the buccal mucosa was made. The rats were observed during a period of 6 weeks, they were weighed every two weeks and no loss in body mass was noted (Tab. 1). After 6 weeks the rats were anaesthetised with ether and dissectioned. Biopsy specimens were taken from the buccal mucosa, porotid gland and lymphatic cervical nodes around the plates in order to make histological specimens. Blood samples were also taken to carry out blood cell counts and liver tests to determine eventual systemic toxicity of the studied acrylics. Histological specimens were stained with hematoxylin and eosin. In borne cases in order to precisely assess the intercellular substance other staining methods were used such as van Gieson, PAS and silvering of precollagen fibres on reticulum. Prepared specimens were assessed in a light microscope in magnification of 80 to 400. Basing on specimens of the control group an analysis of tissue reaction to the particular tested acrylic resin material was carried out. It was ascertained that the most irritative properties to the rat buccal mucosa were caused by self-cure acrylic material--Vertex S.C. This polymer caused in all rats in the tested group a reactive hypertrophy of cervical lymphatic nodes (Tab. 2 and Fig. 3). The least damaging effect on the surrounding tissues was caused by heat-cured acrylic resin material Superacryl (Fig. 4). The tested materials had no damaging effect on the rat parotid gland and did not have a toxic action on the internal organs.

Acrylic Resins↗
PubMedDate not supplied

Trends in elastomeric impression materials.

In the past three years more addition silicones have been supplied as hydrophilic materials and heavier viscosities have been provided in automatic mixing cartridges. Also, a polyether is now supplied in an automatic mixing system. There has been an increase in the number of products available as monophase or single viscosity systems. Both addition silicones and polyethers are available as bite registration materials.

Dental Impression Materials↗
PubMed1993

Effect of plasma treatment on the wettability of elastomeric impression materials.

This study investigated the effect of "plasma treatment" on the wettability of impression materials and void formation in die stone casts. Four addition reaction silicones, one condensation reaction silicone, and one polyether impression material were used. Wettability was determined before and after plasma treatment by contact angle registration of a saturated aqueous solution of calcium sulfate (CaSO4) on flat surfaces made from the tested impression materials. Two groups of surfaces were used for each material. The surfaces in one of the groups were exposed to saliva for 5 minutes. The same impression materials were used to produce four groups of die stone casts from a master die. Two groups were produced from impressions that had been exposed to milk. One group from the exposed and one from the bare surfaces were plasma-treated before pouring. Voids in the stone casts were counted under a stereoscopic microscope. The results indicated that after plasma treatment, the drop of CaSO4 solution completely spread over the addition type silicone surfaces. The corresponding die stone casts were found to be void free. It was concluded that plasma treatment produced high-energy impression surfaces that result in void-free die stone casts from the addition type silicone materials.

Adult↗
PubMed2004

A three-visit, complete-denture technique utilizing visible light-cured resin for tray and base plate construction.

This article describes a technique of constructing a set of maxillary and mandibular complete dentures in three visits instead of the usual five clinical appointments. This system of complete-denture construction is made possible because of the combined use of visible light-cured material as an impression tray and record base material, as well as the use of new biometric wax occlusion rims. Unlike some earlier techniques that use light-cured resin composites as the denture base materials, this method retains the use of heat-cured polymethylmethacrylate as the denture base material.

Acrylic Resins↗
PubMed1978

A review of modern impression materials.

A number of new elastic impression materials have been developed over the past few years. The working time, setting time, elasticity at set, permanent deformation, dimensional change on setting and long-term stability were determined for several of these impression materials. The new addition type silicone impression materials proved superior to the other materials tested, but all materials were capable of giving good clinical results.

Dental Impression Materials↗
PubMed2005

Universal paradigms for predictable final impressions.

The master blueprint for indirect restorations is the final impression. The challenge for the clinician is to establish a protocol that ensures a predictably excellent final impression. The purpose of this article is to provide a protocol that integrates the many detailed steps of impression making, from patient comfort to dental laboratory communication. Understanding the biology of the dentogingival junction, dental materials and their interactions, and proper technique all contribute to the final results.

Dental Impression Materials↗
PubMed1992

Effect of tray space on the accuracy of monophasic polyvinylsiloxane impressions.

The effect of tray space on the dimensional accuracy and stability of impressions made from four brands of monophasic polyvinyl siloxane material was assessed on the recovered stone casts by quantitative and qualitative methods. In general, both evaluation methods agreed that tray space and repeat pour did not affect the accuracy of the dies for individual castings. But disagreement was observed in the findings for fixed partial dentures (FPDs). Quantitative measurement of the interpreparation (IP) dimensions did suggest the possibility of a potential problem when a FPD is cast in one piece because of a significantly reduced distance between the two abutments. However, from the findings of this study it can be concluded that a rigid stock tray can be used with a monophasic polyvinyl siloxane impression material.

Analysis of Variance↗
PubMed1979

A study of the reproducibility of the functional denture space with a dynamic impression technique.

A study was made on four patients to determine the reproducibility of the outer form of the buccal and lingual flanges of a complete lower denture as developed by functional movements of the surrounding tissues. 1. Two dentists participated in the study to find out the operator effect when making impressions for the functional form of the flanges. 2. Two tissue-conditioning impression materials were used to determine if the characteristics of the impression material had any effect on the final form. 3. The impression materials were applied to the denture flanges by two different methods. 4. The impressions were placed in a mitre box, stabilized with plaster, and sectioned in the molar, premolar, and incisor regions. This provided five cut surfaces for measuring. 5. Each section was measured at five to six representative distances. 6. The differences in the flange form measurement and the distances among the impressions made with the same technique and material were small, and the reproducibility can be considered clinically acceptable. 7. There were statistically significant differences in the flange form measurement distances among the different materials and method of application of the material.

Alveolar Process↗