[The effect of new generation materials used in reconstructive dentistry on the oral cavity environment]

Loss of teeth impairs the functioning of the stomatognathic system, complicates chewing, interferes with speech, and alters the patient's appearance. Reconstruction of the defects with implants or fixed dentures often proves impossible and removable dentures remain the sole option in such cases. Continuous progress in materials science, as well as growing demands and expectations from both dentists and patients drive the efforts of manufacturers of dental materials towards improved and innovative products. The requirements for prosthetic materials are the same as for medications. The main goal is biological neutrality or, at least, biological tolerance. Polymers and metal alloys are being constantly modified to better suit these demands. T.S.M. Acetal Dental in one of the monomer-free polymers that have recently been introduced to prosthodontics. This product has not yet been the object of extensive clinical and laboratory studies in Poland. Wironit extrahart chromium-cobalt alloy and Vertex R.S. Acrylic have been certified by the Polish Ministry of Health for use in Poland. Therefore, these products were selected for reference purposes in the present study. As the certificate for T.S.M. Acetal Dental is lacking, the product was subjected to experiments in animals and to physicochemical tests.

The following physicochemical properties were examined: mechanical strength, fatigue limit, abrasiveness, and contact angle. Histopathology of animal material was directed at the reaction of tissues to the prosthetic materials. Adhesion of bacteria and fungi to the materials was examined. The usefulness of acetal resin in prosthetic practice and the biofunctionality of dentures made of the resin were assessed as well.

Mechanical properties of acetal resin seen in the static bending test were clearly inferior to metal alloys. However, the results of dynamic tests were in favor of acetal resin compared with metal alloy. Abrasiveness of acetal resin exceeded that of the metal alloy. The values of contact angle were distinctly lower for resin than for metal which demonstrated values characteristic for hydrophobic materials. Histopathology showed a moderate inflammatory reaction after six weeks of the animal experiment. The reaction was least intense with T.S.M Acetal Dental. However, the inflammatory reaction contained eosinophils, just like in the case of Wironit extrahart, suggesting that both materials have allergic properties. Both materials produced morphological changes in the parotid glands of the animals. The adhesion of bacteria to the materials varied and depended on the bacterial strain. Staphylococcus aureus and Enterococcus hirae strains demonstrated the strongest adhesion to the mechanically polished chromium-cobalt alloy. On the other hand, Escherichia coli adhered strongest to the acrylic resin (10 times the value for acetal resin). Pseudomonas aeruginosa revealed four-fold weaker adhesion to T.S.M. Acetal Dental than to other materials. The adhesion of Candida albicans to acetal resin was three times weaker than to acrylic resin.