Abstract
As part of orthodontic treatment, air polishing is routinely used for professional tooth cleaning. Thus, we investigated the effects of static powder polishing on sliding behaviour and surface quality of three different bracket materials (polymer, ceramic, metal), including a3D-printed bracket. Two bracket types of each material group were polished with an air-polishing device using sodium bicarbonate. Exposure times were set at 10, 20, and 60 s; the application distance was 5 mm. The force loss due to sliding resistance was tested with an orthodontic measurement and simulation system (OMSS) using a0.016 inch × 0.022 inch stainless steel archwire. Untreated brackets served as control. Polishing effects and slot precision were evaluated using an optical digital and scanning electron microscope. Sliding behaviour and slot precision differed significantly between and within the groups. Prior to polishing, polymer brackets showed the least force loss, ceramic brackets the highest. With progressive polishing time, the resistance increased significantly with titanium brackets (26 to 37%) and decreased significantly with steel brackets (36 to 25%). Polymer brackets showed the smallest changes in force loss with respect to polishing duration. Slot precision showed the largest differences between material groups and was primarily manufacturer-dependent with hardly any changes due to the polishing time. Powder polishing can positively or negatively affect the sliding properties of the bracket-archwire complex but is more dependent on the bracket-archwire material combination (i.e., manufacture-dependent slot precision). For titanium brackets, resistance only increased after 60 s of polishing. For ceramic brackets, effective reduction was observed after 10 s of polishing. Polymer brackets, including the 3D-printed brackets, showed better sliding properties than ceramic or metal brackets even after polishing for 60 s. Removal of plaque and dental calculus should lead to anoticeable improvement of the sliding properties and outweighs structural defects that may develop.
Highlights
Orthodontic patients are subject to difficult oral hygiene when wearing fixed appliances
When using air-polishing devices, glycine or sodium bicarbonate appliances are used to remove plaque, staining or dental calculus, whereby a different field of application is recommended for both types of powder
It was found that the presence of plaque and dental calculus in the bracket–archwire complex affects the efficiency of an orthodontic treatment by increasing the sliding resistance [10]
Summary
Orthodontic patients are subject to difficult oral hygiene when wearing fixed appliances. When using air-polishing devices, glycine or sodium bicarbonate appliances are used to remove plaque, staining or dental calculus, whereby a different field of application is recommended for both types of powder. Due to the relatively long duration of orthodontic treatment, professional tooth cleaning should be carried out regularly to prevent the development of white spot lesions. For this reason, knowledge of possible disadvantages of this cleaning process on orthodontic treatment is important. Earlier studies have dealt with this topic [19, 37] It was the intention of the study presented here to analyse polished brackets in combination with unpolished archwires. Smooth surfaces of brackets and archwires allow low friction sliding behaviour and result in better im-
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