# Retrospective Assessment of Palatal Biofilm and Mucosal Inflammation Under Orthodontic Appliances in Young Adults (2022–2025): A Single-Center Cohort with Microbiologic Sub-Sampling

## TL;DR

This study found that orthodontic devices like acrylic plates cause more plaque and inflammation on the palate compared to other types, suggesting the need for better hygiene practices.

## Contribution

The study provides real-world evidence on how different orthodontic appliances affect palatal biofilm and inflammation over time.

## Key findings

- Acrylic appliances caused the highest palatal biomass and erythema compared to bands and Nance buttons.
- Palatal CFU levels correlated with inflammation and gingival changes.
- Recent dental prophylaxis reduced the odds of severe palatal erythema.

## Abstract

Background and Objectives: Orthodontic auxiliaries create plaque-retentive niches that may amplify biofilm accumulation and inflame adjacent soft tissues. While cross-sectional comparisons suggest higher palatal burden beneath acrylic elements, less is known about real-world patterns accumulated across years of routine care. We retrospectively evaluated periodontal and palatal outcomes, and, in a microbiology sub-sample, site-specific colonization, across three device types: molar bands, Nance buttons, and removable acrylic plates. Methods: We reviewed 2022–2025 records from a university orthodontic service, including consecutive patients aged 18–30 years with documented pre-placement and 6-month follow-up indices. Groups were bands (n = 92), Nance (n = 78), acrylic (n = 76). Standardized charted measures were abstracted: Plaque Index (PI), Gingival Index (GI), bleeding on probing (BOP%), probing depth (PD), and palatal erythema grade (0–3). A laboratory sub-sample (n = 174 visits) had archived swabs cultured for total aerobic counts (log10 CFU/cm2) at the device, adjacent enamel, and palatal mucosa; Streptococcus mutans burden was available from qPCR (log10 copies/mL). Results: Baseline characteristics were similar, except for longer wear at follow-up in Nance (10.1 ± 4.0 months) vs. bands (8.7 ± 3.2) and acrylic (6.9 ± 3.0; p < 0.001). At 6 months, device type was associated with greater worsening of PI and GI (both p < 0.001) and with higher palatal erythema (bands 0.7 ± 0.5; Nance 1.6 ± 0.8; acrylic 1.9 ± 0.7; p < 0.001). Microbiologically, palatal mucosal colonization was lowest with bands (3.3 ± 0.5), higher with Nance (4.9 ± 0.6), and highest with acrylic (5.0 ± 0.7; p < 0.001); S. mutans mirrored this gradient (p < 0.001). Palatal CFU correlated with erythema (ρ = 0.6, p < 0.001) and ΔGI (ρ = 0.5, p < 0.001). In adjusted models, acrylic (OR 6.7, 95% CI 3.5–12.8) and Nance (OR 4.9, 2.5–9.3) independently predicted erythema ≥2; recent prophylaxis reduced odds (OR 0.6, 0.3–0.9). Conclusions: In this single-center cohort, palate-contacting designs were associated with higher palatal biomass and erythema than bands. These associations support device-tailored hygiene considerations and proactive palatal surveillance, particularly for acrylic components.