Accuracy of thermal microsensors embedded in orthodontic retainers of different material composition and thickness: An in vitro study

Objectives: The present research aimed to assess the accuracy and precision of the TheraMon^® microsensor embedded in different thicknesses of Hawley retainers (HR) for comparison with vacuum formed retainers (VFR).

Methods: Thirty microsensors contained within different thicknesses and composition of retainers were divided into three equal groups: Group A thick coverage HR (3 mm), Group B thin coverage HR (1 mm), and Group C VFR (1 mm). The microsensors were immersed in thermostatic water at a controlled temperature of 35°C, which corresponds to the average intra-oral temperature. After 1 week, data were gathered using the TheraMon^® client software and analysed using ANOVA and Turkey’s HSD tests.

Results: All TheraMon® microsensors were functional and produced uninterrupted recordings during the 1-week test period. Thermal detection differed between the three removable retainer groups. A near accurate thermostatic water detection was noticed with the thin HR with a mean temperature of 34.81 ± 0.04°C, followed by VFR 34.77 ± 0.09°C, and finally the thick HR 34.73 ± 0.05°C (ANOVA p-value = 0.025). A between-group comparison showed a significant mean difference (MD) between the thin and thick HR groups (MD: 0.08, p-value = 0.01). However, there were no significant differences between VFR and neither the thick Hawley (MD: 0.04, p-value = 0.27) nor the thin Hawley group (MD: -0.03, p-value = 0.39).

Conclusion: A removable retainer’s variation in material thickness and composition could induce small but detectable changes in the precision of thermal detection by TheraMon^® microsensors.