[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.