Background: Space maintainers are used to preserve created space caused by the premature loss of primary teeth but they may
also upset the oral environment and play a role in caries formation. The current research aimed to assess the impact of removable
and fixed space maintainers on salivary pH, flow rate, and the oral microflora.
Methods: Thirty-eight patients aged between 4 and 10 years, each of whom required a fixed (n = 19) or removable space
maintainer (n = 19), were enrolled in this research. The salivary pH, saliva flow rate, salivary Streptococcus mutans, and
Lactobacillus counts were measured immediately prior to the placement of the space maintainers (baseline-T0) and during the
follow-up period, at the 1st (T1), 3rd (T3), and 6th (T6) month. The Wilcoxon, Mann–Whitney U test and Friedman tests were
applied for statistical analyses.
Results: Streptococcus mutans and Lactobacillus counts were significantly higher at the 6th month time period in comparison with
the baseline scores for both groups (P < 0.001). The salivary pH and flow rates did not change significantly at any measurement
period (P > 0.05).
Conclusions: Space maintainers can favour caries formation by changing the oral microflora. It is advisable to warn patients and
their parents of the risks and provide motivation to perform meticulous oral hygiene.