Non-Metal Primary Crowns in Telescopic and Double-Crown Systems Involving Natural Teeth: A Scoping Review

Background/Objectives: This scoping review mapped clinical, in vitro, and in silico evidence on non-metal primary crowns in telescopic and double-crown systems involving natural teeth, including retention, wear, mechanical behavior, clinical outcomes, and auxiliary retention-control elements. Methods: PubMed/MEDLINE, Scopus, Dentistry & Oral Sciences Source through EBSCO, and Web of Science were searched for English-language reports published from 2015 onward. These limits and the exclusion of case reports were predefined in a written, unregistered protocol. Elicit provided supplementary citation discovery, and a targeted backward reference-list check was performed using the same eligibility criteria. Findings and extractable numerical retention outcomes were charted descriptively without formal critical appraisal or quantitative pooling. Results: Forty-eight reports were included, 40 in vitro, one in silico, and seven clinical reports, representing six identifiable cohorts. Two clinical reports arose from the same randomized cohort. The backward reference-list check identified nine additional eligible reports. Clinical evidence was concentrated on zirconia primary crowns with electroformed or electroplated gold secondaries, although two additional short-term trials evaluated zirconia with polymeric secondary structures. Retention varied with the complete material and design combination. Four laboratory reports examined auxiliary retention-control concepts; no clinical study isolated their effects. Conclusions: Clinical evidence remains very limited. Polymeric primary crowns and auxiliary retention-control elements were represented mainly by laboratory evidence. Retention should be interpreted as a system-level outcome. Mixed-support outcomes require support-specific interpretation, and this review does not establish comparative clinical superiority.