UCLA

Background: The oral microbiome is host to a diverse set of microbes and is extremely dynamic depending on the environment that it is placed in. Microbial profile changes are associated with a patient’s ability to practice proper oral hygiene, the diet they maintain, adequate salivary flow and composition, and a myriad of other contributing factors. Orthodontic appliances pose as an obstacle as they act as plaque retentive surfaces on the teeth and hinder the patient’s ability to perform oral hygiene successfully. The inability to remove plaque allows it to develop into a mature biofilm, capable of causing dental diseases such as caries and periodontal disease.Objective: Our study aims to investigate how patients microbial profiles and gingival/plaque indices change over time comparing patients undergoing orthodontic therapy through fixed appliances with those receiving clear aligner therapy with a focus on early time points. Methods: The study was performed on a total of nine patients, five of which received fixed appliances and four received clear aligner therapy. Both supragingival and subgingival bacterial samples were collected at six different timepoints: T0 (baseline directly before orthodontic treatment commences), T1 (one-week after orthodontic treatment commences), T2 (two- weeks), T3 (three-weeks), T4 (four-week) and T5 (three-months). Additionally, at each visit the gingival and plaque indices were recorded. The indices were compared within each group at successive time points as well as between both treatment groups. The composition of the plaque samples was elucidated by extracting the DNA and performing next generation sequencing of the 16S rRNA. Changes in plaque profiles, diversity, and overall composition were compared between timepoints and between both treatment groups. Results: The results of the study showed that there was a general trend for higher gingival indices in patients undergoing FA when compared to CA therapy, which was statistically significant at T5 (p< 0.01). Similarly, patients undergoing treatment with FA showed statistically significantly higher plaque scores at timepoints T3-T5 than patients in the CA group (p< 0.01). The microbiological analysis revealed that the bacteria associated with the clear aligner tray had a unique microbial flora when compared to both the supragingival and subgingival flora. This flora exhibited significantly lower levels of Actinomyces, and higher levels of Porphyromonas and Streptococcus. The FA group showed significantly higher levels of various genera of bacteria known to be involved in the progression of periodontal disease such as, Porphyromonas, Tannerella, Fusobacterium, Leptotrichia, and Lachnospiraceae. Alpha – and beta-diversity showed no significant differences in composition of supragingival versus subgingival microbial communities but did confirm the unique microbiota associated with the tray bacteria. Conclusions: The results of the study correlate with previous studies that discussed a higher gingival and plaque index associated with patients undergoing orthodontic treatment with fixed appliances when compared to clear aligners. The microbiological analysis confirmed a unique biofilm community associated with the tray and not the supragingival nor the subgingival microbiota. More importantly than quantity of the bacterial load, the type of the bacteria is an important player in the progression of periodontal disease, specifically the red complex. Our analysis showed that the patients undergoing FA therapy showed significantly higher levels of periodontal pathogens compared to CA, which is consistent with the observation of significant differences in gingival indices between treatments.