Influence of Powder/Liquid Proportioning Technique and of Pressing Stage in the Properties of an Acrylic Resin Activated by Microwaves

Juliana Rottini, Manuela de Borges Henriques, Fernando Freitas Portella, Carmen Beatriz Borges Fortes


Aim: To evaluate the influence of powder/liquid proportioning method and stage of packing into a gypsum mould in Knoop microhardness, glass transition temperature, resistance to Izod impact, specific gravity and swelling degree of a microwave-cured resin. Methods: A type 5 resin was prepared using two powder/liquid proportioning methods (recommended by manufacturer and saturation technique), and packed in different stages (stricky and dough). Manufacturer stated a powder/liquid of 3:1. On saturation technique the liquid was dripped on powder until the complete wetting. Polymerized resins was characterized regard Knoop microhardness, glass transition temperature, resistance to Izod impact, specific gravity and swelling degree. Results: The pressing stage did not influence none of evaluated properties (p>0.05), however the resins obtained by saturation technique presented Knoop microhardness, glass transition temperature, resistance to Izod impact and specific gravity higher and swelling degree lower than those obtained as stated by manufacturer (p<0.05). Conclusion: Powder/liquid proportioning method influence the physical, chemical and mechanical properties of a microwavecured resin. The saturation technique produces a polymer presenting better properties in comparison to those obtained by manufacturer instructions. Pressing stage (on stricky or dough phase) did not influence none of evaluated properties.


Acrylic resins; Dentistry; Hardness; Transition temperature


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