Level of residual monomer released from orthodontic acrylic materials.

Objective: To quantify, with high-pressure liquid chromatography (HPLC), the amount of residual monomer leached from different orthodontic acrylic materials prepared with two different manipulation methods. Materials and Methods: Eighty cylindrical specimens (5 x 25 mm) were divided into eight groups (n = 10). The specimens were prepared with four acrylic materials Orthocryl Neon Blue (Dentaurum), Orthocryl EQ (Dentaurum), Orthoplast (Vertex), and 0-80 (Imicryl) and with two different manipulation methods: doughing and spray-on. HPLC measurements were made at intervals of 2 hours, 6 hours, 1 day, 1 week, and 3 months. One-way analysis of variance (ANOVA) and Tukey's honestly significant difference multiple-comparison test were used to assess the amount of monomer eluted from the various groups. To assess the differences within each group over the various periods, repeated-measures ANOVA and paired t-tests were used. Results: Statistically significant differences were found within the groups in the amount of residual monomer in the specimens at different time intervals (P < .001). HPLC showed statistically significant differences among the groups (P < .05) in the amount of eluted monomer. Evaluation of the manipulation techniques showed that the monomer release rate was higher in the specimens prepared with the doughing method. When the four acrylic materials were compared, the specimens made from Orthoplast (Vertex) showed the highest rate of monomer release with both manipulation techniques. Conclusion: The spray-on method can be recommended to clinicians for the preparation of orthodontic appliances.