Comparison of Residual Monomer Loss from Cold-Cure Orthodontic Acrylic Resins Processed by Different Polymerization Techniques

Abstract

Introduction

This investigation aimed to assess and compare the amount of residual monomer (RM) released from removable orthodontic appliances constructed by sprinkle-on and dough techniques.

Materials and methods

One hundred and twenty acrylic samples were prepared from orthodontic autopolymerized acrylic resins and divided into three groups, according to the processing method: sprinkle-on with polyclave, sprinkle-on without polyclave and dough technique. After polymerization, the specimens of each group were immersed in distilled water for 24 h, 48 h, 72 h and 1 week. High-performances liquid chromatography (HPLC) was utilized to measure residual monomer content.

Results

Maximum observed RM was 1284·91±129·07 ppm measured for sprinkle-on technique without polyclave after 24 h of water immersion. At this time, the level of RM was significantly different among the three applied techniques (P<0·05). In all soaking time groups, sprinkle-on technique with polyclave released the least amount of RM. Within each group, the maximum monomer releasing was observed after the first 24 h and decreases were observed in subsequent time groups. The reduction over the time was not significant in the polyclave groups (P>0·05).

Conclusion

The sprinkle-on technique with polyclave and longer water immersion reduced residual monomer released from acrylic orthodontic appliances.