Wear Resistance of Different Composite Materials Used with Bonded Orthodontic Retainers: A Laboratory Study

Abstract

Background: The attritional wear of orthodontic retainer bonding materials limits the service time of the fixed orthodontic retainers.

Aim: To investigate wear resistance of different types of bonded retainer composites.

Materials and Methods: Four different composite resins (Filtek Z350, Filtek Supreme Ultra, Transbond XT and Ketac Nano;3MEspe, Seefeld, Germany) were subjected to three-body abrasion test. Twenty specimens of each composite type were prepared by bonding a segment of twist flex wire (size 0.0195”) into blastic upper right and left central incisors. Each specimen was tested under dual axis chewing simulator (Willytec, Munich, Germany) with 49N for 200,000 loading cycles with addition of abrasive media that was used to submerge each specimen to simulate abrasion caused by food particles. The abrasive was media prepared by grinding 30 g of millet-seed and 120 g of white rice and mixed with 275 ml of distilled water. Computer-aided 3D scanner (Ceramill Map 200+, Amanngirrbach, Koblach, Austria) was used to 3D scan each specimen before and after chewing simulator three-body abrasion test. The 3D scans were analyzed by Blender.app PC software, 2.81a version (Blender Foundation, Amsterdam, The Netherlands) to evaluate the volume loss of each composite by calculating the volume difference in mm³ before and after the chewing test. Finally, data were statistically analyzed using ANOVA and the post-hoc Tukey test.

Results: Statistical difference in wear resistance was found between all the groups. The highest wear resistance was found with Filtek Z350 followed by Transbond XT. Lower values corresponded to Filtek Supreme Ultra while the lowest values were related to Ketac Nano.

Conclusion: Wear resistance values were significantly higher with higher composite filler content. The lowest wear resistance value was found with the least filler content composite.