Bacterial Colonization of Orthodontic Devices (Molar Bands, Nance Buttons, and Acrylic Plates) and Its Impact on the Marginal Periodontium and Palatal Fibromucosa in Teenagers: A Cross-Sectional Clinical–Microbiological Study

Background: Orthodontic auxiliaries can create plaque-retentive niches that inflame adjacent soft tissues. We compared bacterial colonization on molar bands, Nance buttons, and acrylic plates and assessed associated periodontal and palatal tissue responses in adolescents. Methods: In a cross-sectional study (n = 128; 10–17 years), clinical indices (Plaque Index, Gingival Index, bleeding on probing, probing depth) were recorded at device-influenced teeth. Palatal fibromucosa under palate-contacting devices was graded 0–3 (0 = none, 1 = mild/diffuse, 2 = moderate/confluent, 3 = marked with papillary hyperemia). Swabs from device surfaces, adjacent enamel, and palatal mucosa were cultured for total aerobic counts (log10 CFU/cm2); Streptococcus mutans burden was quantified by qPCR (log10 copies/mL). Group differences and adjusted associations were analyzed. Results: Palate-contacting devices harbored greater palatal biofilm and presented higher soft-tissue inflammation than bands. In adjusted models, device type (Nance, acrylic) remained associated with higher Gingival Index independent of measured behaviors and wear duration. Palatal colonization tracked closely with palatal erythema, supporting a local dose–response at the palatal interface. Conclusions: Appliance design is associated with distinct colonization patterns and soft-tissue responses; palate-covering acrylic components warrant device-specific hygiene and routine palatal inspection. Selecting designs with better cleansability and reinforcing plate-specific cleaning may mitigate palatal inflammation during treatment.