Biomaterials and Tissue Engineering Strategies for Mastoid Obliteration: A Systematic Review of the Clinical and Preclinical Evidence.

Background/Objectives: Mastoid obliteration is being increasingly used to reduce cavity-related morbidity after mastoidectomy. Alongside autologous grafts, synthetic biomaterials and tissue-engineering approaches have emerged as potential alternatives. This systematic review synthesized the clinical and preclinical evidence on biomaterials for mastoid obliteration, focusing on efficacy, safety, biological integration, and translational potential. Methods: A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-compliant search of PubMed, Scopus, and Web of Science identified studies published between January 2010 and May 2026. Eligible studies evaluated biomaterials for mastoid obliteration in clinical settings or experimental models. Data on study design, biomaterial type, intervention, outcomes, complications, and biological endpoints were extracted. Risk of bias was assessed using the Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I), Revised Cochrane Risk of Bias Tool for Randomized Trials (RoB 2), and the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) risk-of-bias tool. Results: Twenty-eight studies were included (19 clinical, 9 preclinical). Clinical evidence supported mastoid obliteration as an effective strategy for improving cavity stability, reducing chronic otorrhea, promoting epithelialization, and aiding cholesteatoma control. Outcomes appeared to depend more on successful cavity elimination than on the superiority of a specific biomaterial. Autologous materials showed reliable and reproducible results, while S53P4 bioactive glass demonstrated comparable effectiveness with additional antibacterial properties. Hydroxyapatite-based materials and allografts showed more variable outcomes. Biologically enhanced approaches, including concentrated growth factors and composite constructs, yielded promising but limited clinical evidence. Preclinical studies indicated that conventional biomaterials are primarily osteoconductive, whereas composite scaffolds, bone morphogenetic protein-2 (BMP-2) delivery systems, and stem cell-based strategies may enhance osteogenesis and tissue integration. However, clinical translation remains limited. Conclusions: Mastoid obliteration is an effective reconstructive strategy whose success depends mainly on stable cavity reduction and adequate epithelial coverage. Autologous materials and S53P4 bioactive glass currently have the strongest clinical support, whereas advanced tissue-engineering approaches require further validation through prospective comparative studies, standardized outcomes, long-term follow-up, and translational research.