Flexural strength of rebased denture polymers

Abstract

The properties of denture base and reline resins may be affected by daily changes between room temperature and mouth temperature. The purpose of the study was to evaluate the effect of thermocycling on the flexural strength of the relined denture base polymer with reline resin. Three denture base resins, three hard reline resins and their combinations were tested. Fourteen specimens, 65x10x2.5 mm, were fabricated for each material. Polymer combination specimens were made using 1.5 mm hard reline resin on 1.0 mm cured denture base resins. Half of the specimens were stored for 50+/-2 h in distilled water at 37 degrees C, while the other half were thermocycled for 20 000 cycles between 4 and 60 degrees C. Three point bending tests were conducted on a universal testing machine at a cross-head speed of 0.5 cm/s. The flexural strengths were measured and a statistical analysis was performed on the data using three-way ANOVA (P<0.05). The results showed that the flexural strength of relined denture base polymer was significantly higher than that of hard reline polymer. Thermocycling did not affect the flexural strength of the relined denture base polymers, whereas the denture base polymer and reline polymer alone showed a decrease in strength after thermocycling.

Correlation in the mechanical properties of acrylic denture base resins

“…Since flexural strength of polymers is very sensitive to the testing procedure, such as amount of deflection or specimen dimensions, direct comparison between the results of this study and those of previous reports should be cautious 10) . However, in general the flexural strength and modulus results of the present study are similar with those of previous reports that tested in water bath 10,[33][34][35] , whereas, particularly for IVO and LUC, they are slightly lower than those of other previous reports tested in air or unknown condition 13,20,36,37) . Our results support findings from the earlier report showing that the breaking load and deflection of acrylic resins tested in 37°C water medium were lower than those tested in air 8) .…”

Effect of thermocycling in a hard denture liner and acrylic resin after different chemical and mechanical polishing

“…By the other hand, these materials have different chemical compositions, and the final structure of the polymer may differ considerably, resulting in different clinical results 6 . In relation to the properties, some studies show that the direct relining have lower results compared to the conventional acrylic resins 7 . When the prostheses are submitted for intermittent or continuous exposure to chemical agents (food and beverages and chemical cleaning agents) and forces of chewing, can occur the degradation of these materials 8 .…”

“…When the prostheses are submitted for intermittent or continuous exposure to chemical agents (food and beverages and chemical cleaning agents) and forces of chewing, can occur the degradation of these materials 8 . This degradation can cause microcracks on acrylic resins surface and can change their surface characteristics 7 . It is known that polishing for denture base acrylic resins can be performed mechanically or chemically 9 .…”

Akri̇li̇k Rezi̇nler, Yumuşak Astar Materyalleri̇ Ve Doku Düzenleyi̇ci̇leri̇n Çözünürlük Özelli̇kleri̇

“…Bazı araştır-macılar su moleküllerinin polimer matriks içerisine penetre olarak plastizer gibi görev yaptığını ve akrilik kaidelerin ve yumuşak astar materyallerinin mekanik özelliklerini olumsuz olarak etkilediği belirtmektedirler. [5][6][7] Tam tersine bazı araştırmacılar ise su gibi küçük plastizer moleküllerin ortamda bulunmasının enerjiyi dağıtan moleküler harekete yardımcı olduğunu bildirmektedirler. 8 Akrilik rezin suya batırıldığında 2 fenomen doğal olarak gerçekleşir; su emilimi ve residüel monomer salınımı.…”

“…Bundan dola-yı kaide polimerindeki moleküllerin miktarı zaman içerisinde değişir. [5][6][7]9 Çözünürlük ise polimerden çözünen maddelerin salınması olarak tanımlanır. 10 Rezinlerin ağız içinde temas ettikleri birçok sıvıda çözünmemesi istenir.…”