Passive and Active Self-Ligating Brackets: An Analysis of the Clinical Evidence

Self-ligating brackets (SLB) — commercially introduced on a large scale in the early 2000s with Ormco's Damon system and quickly followed by dozens of competing systems — have sparked one of the most heated and prolonged debates in contemporary orthodontic literature. The marketing claims accompanying their launch — faster treatments, less pain, greater arch expansion, less need for extractions — fueled both clinical enthusiasm and critical pushback from the scientific community, producing a series of systematic reviews and meta-analyses in the 2010s and 2020s that have systematically scaled back initial expectations.

The fundamental distinction between passive and active self-ligating brackets is clinically relevant. Passive brackets (e.g., Damon Q, 3M SmartClip) use a sliding-door mechanism that creates an open slot when no wire is inserted: when the wire is inserted, the door's closing force doesn't actively press on the wire. Theoretically, this produces low friction during alignment phases with small-diameter wires, allowing the so-called "light wire technique" with forces intrinsic to the wire that theoretically maximize physiological movement. Active brackets (e.g., DENTSPLY's In-Ovation R, Strite Industries' Speed) instead use a spring clip that actively presses on the wire, generating controlled preload.

Atack et al.'s systematic review (EJOF, 2020) — which analyzed 23 RCTs and quasi-randomized studies comparing SLB with conventional elastomeric-ligated brackets — reached clear conclusions: there's no evidence of a statistically significant difference in overall treatment duration, number of appointments, extent of transverse expansion, or extraction prevalence between the two systems. The friction difference — real under laboratory conditions with mechanical simulators — appears clinically irrelevant under intraoral conditions of use, where biological friction (resistance from soft tissue and alveolar bone) dominates over bracket-wire mechanical friction.

Post-appointment pain has been one of the most used arguments in favor of SLB. Fleming et al.'s RCT study (AJODO, 2009) — frequently cited in the literature — found no significant differences in pain over the 5 days following activation appointments between patients treated with Damon3MX and conventional brackets ligated with metal elastomeric ties. A later meta-analysis (Lim et al., 2023, including 12 RCTs) confirmed this finding, with one exception: pain in the first 6 hours after placing the initial wire is statistically lower with passive SLB (average difference of 5 mm on a 100 mm VAS scale) — a statistical difference of dubious clinical relevance.

The "low-force low-friction" paradigm underlying the Damon philosophy — which posits the possibility of expanding dental arches beyond skeletal limits by reducing friction — has been critically examined by several research groups. Cattaneo et al.'s CBCT study (2011) documented that patients treated with Damon showed significantly greater buccal tipping of lower incisors and upper molars compared to controls treated with traditional technique, with reduced supporting alveolar bone in the chin region: not skeletal expansion, but dental tipping with a risk of gingival recession.

The pragmatic clinical takeaway is that self-ligating brackets — both passive and active — are well-built systems that simplify the ligation procedure (documented clinical time savings of 5-7 minutes per appointment) and potentially reduce frictional forces during alignment phases with light wire. However, an experienced orthodontist using conventional edgewise technique can achieve equivalent results in quality, treatment duration and extraction rate. Bracket system choice should be guided by the orthodontist's treatment philosophy, their familiarity with the mechanics, and the specifics of the clinical case, not by expectations of documented superiority.