Salivary Streptococcus Mutans and Lactobacillus spp. levels in patients during rapid palatal expansion

To assess the microbial level of Streptococcus Mutans and Lactobacillus spp. during rapid palatal expansion, and compare the data with untreated control patients.

Thirty patients aged between 6-9 years were enrolled in this study (15 males and 15 females). The patients were divided into three groups: 10 patients were treated with rapid palatal expander (RPE) (Test Group 1), 10 patients were treated with Mc Namara expander, and 10 patients were enrolled in the control untreated group. Whole stimulated saliva was collected from each patient at three time points: before initiation of expansion therapy (baseline at T0), after 3 months (T1), after initiation of treatment, and after 6 months from T0 (T2). The protocol of rapid palatal expansion for the two groups was as follows: at placement of the expander 4 activations were performed by the orthodontist (1 mm expansion), followed by 4 activations per day by the parents (two in the morning and two in the evening, 1 mm per day total) to be repeated for 7 days.

Statistics: In this study a different trend in the microbial colonisation for the two treated groups was observed. In the Test Group 1, in which patients were treated with the RPE, there was a significant difference between Strp T0 T1 and between Strp T0 and T2 (p< 0.05). There was also a significant difference between LAC T1 T0 and LAC T2 and T0 (p<0.05). In the Test Group 2, treated with McNamara expanders, it was found was a significant difference between LAC T2 T0 and LAC T1 T0. In the same group it was also found a significant difference between Strp T2 T0; T1 T0; T1 T2 (p<0.05).

The level of the various species of bacteria changes during rapid palatal expansion, and this seems to depend on the type of orthodontic expander. During rapid palatal expansion treatment it is also advisable a periodical microbial monitoring using in-office bacteria tests.