The Impact of Orthodontic Adhesives on the Subgingival Microbiota During Early Fixed Appliance Therapy: A Pilot Study

<i>Background and Objectives</i>: The most common method for treating malocclusions today is fixed orthodontic therapy, during which brackets and tubes are bonded to the surface of the teeth, which makes oral hygiene difficult to maintain. Increased plaque retention, gingival bleeding, and gingivitis can be diagnosed in the early phases of treatment. The periodontal response to plaque accumulation can be explained by quantitative and qualitative changes in the subgingival microbiota. The aim of our research was to investigate the changes in the subgingival microbiota that occurred within 6-8 weeks after bonding when two different orthodontic adhesives were used. <i>Materials and Methods</i>: Thirty patients were followed; molar tubes were bonded with a composite (C) in fifteen cases, and in the other fifteen cases, they were bonded with glass ionomer cementum (GIC). A microbiological sample was taken from the gingival sulcus of the maxillary first molars at the time of appliance placement (T1) and 6-8 weeks (T2) after bonding. Bacterial DNA detection was performed using the micro-IDent^®plus11 (Hain Lifescience GmbH, Germany) PCR (polymerase chain reaction) method. The statistical analysis included McNemar's test to analyze the paired binary data and Fisher's Exact Test to compare the prevalence of each of the 11 bacteria at T1 and, ultimately, T2 between the two studied groups. The Bonferroni correction was also applied. <i>Results</i>: When analyzing GIC vs. C at T1 and T2, none of the studied pathogens showed significant differences. <i>Conclusions</i>: Given the lack of statistical significance, these trends do not confirm a definitive impact of the procedure on bacterial presence. The increased presence of periodontal pathogens might suggest that bonding does not reduce the bacterial loading of subgingival microbiota. Less protective effects of the GIC intervention against <i>Tannerella forsythia</i> and <i>Eubacterium nodatum</i> bacteria were detected.