Salivary concentrations of Streptococcus mutans and Lactobacilli during an orthodontic treatment. An observational study comparing fixed and removable orthodontic appliances

Aim: This study aimed to investigate salivary concentrations of Streptococcus mutans (S. mutans) and some Lactobacilli, and plaque index (PI) in patients wearing fixed versus removable orthodontic appliances. Methods: A sample of 90 orthodontic patients (56 males and 34 females) was included in the study: 30 subjects (aged 21.5±1.5 years) were treated with removable clear aligners (CA), while for other 30 cases (aged 23.3±1.6 years) a fixed multibrackets appliance (MB) were utilized, and 30 patients (aged 18.2 ±1.5 years) wearied a removable positioner (RP). Salivary concentrations of S. mutans and Lactobacilli and PI were evaluated prior to start of the orthodontic treatment, after 3 months and 6 months. Results: After 6 months, 40% of MB patients (12 subjects over 30) showed a concentration of S. mutans associated to high risk of developing tooth decay (CFU/ml>105), differently from participants wearing removable appliances (odds ratio = 5.05; 95% C.I. = 1.72-14.78; chi-square = 9.64; p = 0.0019). The same trens was observed for the concentration of Lactobacilli (odds ratio = 4.33; 95% C.I. = 1.53-12.3; chi-square = 8.229; p = 0.004). In addition, over the duration of the study, CA patients maintained PI at 0 level, while MB patients experienced a statistically significant increasing trend of PI over time, and their PI became clinically/statistically relevant after 6 months, respect to CA and RP patients. Conclusions: Comparing all the data, while, after 6 months, only about 10% of CA patients and 13.3% of RP patients achieved a microbial colonization which may lead to high risk of caries development, about 40% of MB patients - and 20% after 3 months - showed a high level of vulnerability to developing caries, which require additional strategies for plaque control and microbial colonization to be employed.