Comparison of physical-mechanical properties between conventional resins and CAD/CAM polymers used on temporary restorations fabrication before and after thermal cycling

Abstract

In treatments that require a long phase of use of temporary restorations, the resistance and stability are impaired, due to continuous fatigue caused by chewing and aging of the material. In view of this, it has stimulated the development of materials and techniques that allow the improvement of its mechanical properties, being CAD/CAM polymers the most recent material developed for confection of temporary restorations. However, its physical-mechanical behavior, compared to other materials for the same purpose, is scarce in the literature. Thus, this study will evaluate flexural strength (FS), elastic modulus (EM), surface roughness (Ra and Rz) and Knoop microhardness (KM) of different types of resins used for confection of temporary restorations, before and after several cycles of thermal cycling. 160 specimens will be made with 25×2×2 (±0,005) mm, divided into 16 groups (n=10), according to the material and cycles of thermal fatigue. Four different dental resins will be evaluated: (HAR) heat-polymerized acrylic resin (Clássico), (AAR) - auto-polymerized acrylic resin (Alike), (BR) bis-acryl resin (Protemp4) and (RCAD) CAD/CAM polymers (Telio CAD); submitted to the cycles of thermal fatigue by means of different tests: (Control (C): in distilled water at 98,6°F for 24 hours; (TC1): 2,500 cycles thermal cycling, from 41 to 131°F for 30 seconds; (TC2): 5,000 cycles thermal cycling and (TC3) 10,000 cycles of thermal cycling. The analysis of the FR, ME, Ra, Rz and MK will be performed before and after each period of thermal cycles. The analysis of FR and ME will be performed on a universal testing machine (EMIC) through three-point bending test. The values of Ra and Rz will be measured through perfilometer. In the MK analysis, the specimens will be subjected to readings in microdurometer equipment. The data will be analyzed in the adherence testing curve, applying the appropriate statistical test to compare the specimens' average values. (AU)