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Background The aim of this systematic review is to determine microRNAs (miRs) that are differently expressed between diseased pulpal and periapical tissues. Design This systematic review used PubMed, Scopus, EBSCO, ProQuest, Cochrane database as well as manual searching to extract studies from January 2012 up to February 2022. Results A total of 12 studies met the eligibility criteria were included. All selected studies were of case-control type. Twenty-four miRNAs associated with apical periodontitis, 11 were found to be upregulatedand 13 were downregulated. Four out of the 44 miRs associated with pulpal inflammation were upregulated, whereas forty were downregulated. Six miRs, namely hsa-miR-181b, hsa-miR-181c,hsa-miR-455-3p,hsa-miR-128-3p, hsa-miR199a-5p, and hsa-miR-95, exhibited considerable downregulation in both periapical and pulp tissues. Conclusion MiRs have been investigated for their role in pulpal and periapical biology and may be utilised in diagnostic and therapeutic purposes. Further investigations are required to determine why certain irreversible pulpitis situations progress to apical periodontitis and others do not, based on the various miR expressions. Moreover, clinical and laboratory trials are needed to support this theory.

Background: The aim of this systematic review was to address the clinical effectiveness of space maintainers and space regainers in the prevention and correction of dental arch decrease in the mixed dentition. Methods: An electronic search was conducted using five databases and 6 relevant journals. Inclusion criteria were: Randomized Controlled Clinical Trials (RCTs), Controlled Clinical Trials (CCTs), cohort studies and case-control studies of children in the mixed dentition requiring a space maintainer or a space regainer, children with mild to moderate crowding, and with Class I and mild Class II or Class III skeletal pattern. Results: Following the three phases of a systematic search, 11 were included for the final analysis, of which 1 article was found to be of critical risk, 2 articles of serious risk and 8 articles of moderate risk of bias. Conclusions: Space maintainers may preserve arch length and prevent crowding in mildly to moderately crowded cases, but at the cost of proclination of the lower incisors. Space regainers were somehow effective in distalizing the maxillary and mandibular first permanent molars and thus contributing to the resolution of mild to moderate crowding in the mixed dentition. However, considering the low evidence provided by this systematic review, high-quality studies are needed.Registration: PROSPERO (CRD42020170035).