**6. Debonding of ceramic brackets**

Almost three decades ago, Ghafari and Chen [33] compared the performance of chemical retention ceramic brackets to silane-treated grooved base ceramic brackets (a combination of chemical and mechanical retention). They [33] concluded that mechanical retention might reduce the negative side effects of debracketing by favoring failure within the adhesive, thus protecting the integrity of the enamel surface, i.e., the health of the tooth, as well as the integ-

The reports about iatrogenic tooth damage during debracketing impelled manufacturers to make changes in the base designs of ceramic brackets, relying more on mechanical retention for bond strength. In fact, the majority of ceramic brackets available today are purely mechanically retained brackets [4, 30, 34]. Mechanical retention is achieved by creating undercuts or grooves in the base of the bracket. These undercuts make a mechanical interlock with the

Currently, many different mechanical base designs are available, such as microcrystalline base design with a stress concentrator, button-structured base design, ball-base design with gingival ball reduction, dovetail base design, laser-structured base design, and "portal" bond-

An additional, interesting base design is the application of a thin layer of polymer onto the ceramic bracket base [19]. Thus, bonding takes place between the enamel and the flexible polymer mesh base. Encouraging in vitro results concerning the enamel surface after debrack-

At this point, only two published clinical studies [14, 39] with a purely mechanical retention mechanism were encountered. There is a need for clinical studies, particularly randomized

Although some major orthodontic supply companies explicitly state in their instruction sheets that their ceramic brackets are for single use only, several laboratory studies suggested various techniques for the reuse, i.e., the rebonding, of ceramic brackets [40–44]. For reuse, the

It has been pointed out that the appropriate term is "reuse" or "recondition" instead of "recycle," since the term "recycled" implies the manufacturing of new brackets from the raw material of the original, failed brackets [12]. Nevertheless, the literature usually refers to these

An in vitro study [43], carried out in 2016, investigated the "recycling" of polycrystalline ceramic brackets with a microcrystalline base via the following three methods: first is the erbium-doped yttrium aluminum garnet (Er:YAG) laser, and the other two are traditional

delicate bracket base structure and demonstrated significantly less bond strength than new

O3

particles) damaged the

clinical studies, i.e., the gold standard for evaluating clinical procedures.

methods, i.e., flaming and sandblasting. Sandblasting (50 μm Al<sup>2</sup>

rity of the ceramic bracket.

12 Current Approaches in Orthodontics

adhesive bonding agent possible [28].

ing base design [4, 15, 35, 36].

eting were obtained [30, 37, 38].

**5. Rebonding of ceramic brackets**

bracket has to be intact in the first place.

brackets as "recycled."

Debonding usually refers to the removal of orthodontic brackets and the residual adhesives from the tooth enamel at the end of fixed appliance treatment [45].

Ceramic brackets lack flexibility. In other words, the rigid ceramic and the rigid enamel have little ability to dissipate stress when exposed to debracketing forces at the end of treatment. Thus, bracket fracture and/or enamel damage may occur during debracketing [2, 11].

Several approaches aiming to minimize the side effects associated with the debracketing of ceramic brackets exist. These are the conventional (mechanical), ultrasonic, electrothermal, and laser techniques [11, 21].
