Fixation of indirect constructions restoration with permanent cement is the final clinical stage of orthopedic treatment. It should be noted that the result of the treatment with the using of unremovable dentures essentially depends on the correct choice of cement for fixation.
The comparative analysis conducted to improve the quality of fixing method of unremovable dentures was carried out on the base of the Research laboratory of dental materials and products of JSC «STOMA», Ukraine.
We used the following materials: glassionomer cements “KetakCem”, Germany; “Riva”, Australia. The study of physico-mechanical properties of materials was carried out according to the following parameters: determination of the strength of the diametrical stretching (T, MPa), bending strength (σ, MPa), determination of the water absorption index (W, μg / mm³), free linear shrinkage (L,%), solubility index (D,%), and compressive strength (C, MPa).
At the determination of the strength the diametrical stretching index (T, MPa) according to the results of laboratory tests "Ketac Cem", "Riva" and the new glass ionomer cement developed by us for permanent fixing of unremovable dentures.We have received that the indices of all selected cements are within 8.8 - 9.9 MPa which are close to international standards ISO 4104.
Also we found out that the boundary value at the diametral stretched "Riva", which is (8.9 ± 0.3) MPa, is not greater than Ketac Cem (9.9 ± 0.6) and is reliably non-existent significant differences (p> 0.05). The glass ionomer cement developed by us with an index of 8.8 ± 0.5% (T, MPa) with a certainty (p> 0.05) has no difference between the indicators of «Ketac Cem» and «Riva» materials.
Consequently, the strength limit at the diametrical extension of a new glass ionomer cement for permanent fixation has no significant difference compared with its foreign analogues (p> 0,05). The strength of the curtain (σ, MPa) of the materials under investigation for fixing unremovable dentures varies within (55.9 ± 70.2). It was found out that the durability of a new glass ionomer dental cement is (58.3 ± 0.4%). It is significantly lower (p <0,001) than the ‘Ketac Cem’ material - 70,2 ± 0,7%, while the "Riva" (55,9 ± 0,8%) has the least value.
We indicate that the strength of the material @Riva "is significantly lower (p <0.001). In determining the rate water absorption, we obtained the following results: the glass ionomer cement developed by us has the limits of water absorption which is 42.7 ± 0.4 μg / mm3 compared with the analogues Ketac Cem and Riva - 36.3 ± 0.6 and 39 , 7 ± 0.3 μg / mm 3, respectively. The data of statistical processing showed that the water absorption of glass ionomeric cements is significantly lower (p <0,001). Free linear shrinkage of new glass ionomer cement has limits of 0,44 ± 0,03%, which exceeds the value of "Ketac Cem" (0,33 ± 0,02) by 0,11±0,01%, and is significant (p <0, 05) is less in comparison with "Riva", the index of which is 0,66±0,09%. The solubility index of the cement we developed is 1.30 ± 0.16%, which is 0.07 ± 0.03% higher than Ketac Cem - 1.23 ± 0.17%, but not significantly different from the material "Riva ", which index is 1.32±0.14%, which corresponds to ISO, but these data do not have statistically significant differences (p> 0.05).
The results of the compression strength index are characterized not by a significant difference between them: the cement developed is 76.2 ± 0.4% MPa, which is significantly (p <0.001) 2.4 ± 0.1% less than Ketac Cem - 78.6 ± 0,5%, but does not have a significant difference (p> 0,05) between the developed material and the «Riva» index which is 76,0 ± 0,8%, respectively.
Mechanical resistance of restored teeth with extensive crown damage
