Is Routine Placement of Space Maintainers Justified After Premature Loss of Primary Molars? A Narrative Review and Proposed Decision Flowchart

Space maintainers (SpMs) are widely recommended after premature loss of a primary molar. This recommendation based largely on mid-twentieth-century case series rather than comparative trials. This narrative review examines whether the evidence supports routine placement of SpMs, considering their effectiveness, space changes without treatment, and the factors associated with clinically significant space loss. PubMed/MEDLINE, Scopus, Web of Science, and the Cochrane Library were searched. SpMs reduce measurable space loss, but its clinical relevance varies. Premature loss of a mandibular primary second molar produces substantial space loss and warrants intervention, whereas a single long-term cohort reported minimal or even favorable arch changes after loss of a maxillary primary first molar. Arch, tooth, successor development, facial pattern, and time since tooth loss are associated with space loss, although none has been prospectively validated. Fixed appliances frequently require recementation or replacement and increase gingival inflammation, and no cost-effectiveness analysis against observation exists. The literature does not support automatic SpM placement and indicates that it is not justified in defined low-risk scenarios, particularly loss of a maxillary primary first molar. A selective, risk-based approach is therefore favored, supported by a proposed decision flowchart. Prospective validation and randomized comparisons of SpM versus observation are needed.