Three-Dimensionally Printed Polymethyl Methacrylate Denture Base Resins: A Critical Narrative Review of Physicomechanical Properties, Biological Behaviour and Clinical Performance

Abstract

Additive manufacturing has become an increasingly common alternative to conventional heat polymerisation and subtractive milling for the fabrication of complete denture bases from polymethyl methacrylate-based photopolymer resins. Despite rapid clinical uptake, published evidence on the physicomechanical, biological and clinical behaviour of these materials remains fragmented across in vitro, ex vivo and clinical study designs, and existing reviews have tended to focus narrowly on either material innovation or dimensional accuracy rather than integrating the full evidence base. This critical narrative review synthesises the available literature on three-dimensionally printed polymethyl methacrylate denture base resins, examining mechanical performance, physicochemical stability, biocompatibility, surface behaviour, microbial colonisation, dimensional accuracy, reinforcement strategies, repairability and patient-reported clinical outcomes. Literature was identified through structured searching of multidisciplinary and dentistry-specific bibliographic databases, supplemented by citation tracking, up to a defined cut-off date. The evidence indicates that additively manufactured resins generally show lower flexural strength, fracture toughness and degree of conversion than milled or conventionally processed polymethyl methacrylate, with performance strongly moderated by printing orientation, layer thickness and post-curing protocol. Water sorption and solubility of unmodified printed resins frequently diverge from values obtained for heat-cured material and, in several studies, exceed relevant international standard thresholds. Biocompatibility depends heavily on residual monomer elimination through post-processing, while surface free energy rather than roughness alone appears to govern Candida albicans colonisation in several comparative analyses. Nanoparticulate reinforcement and resin modification can partially offset mechanical deficits, and randomised clinical trials suggest patient satisfaction broadly comparable with, though not consistently superior to, conventional dentures. Confidence in these conclusions remains limited by heterogeneous testing protocols, short observation periods and a near-total reliance on in vitro designs. The review identifies material and protocol standardisation, longitudinal clinical evaluation and mechanistic biocompatibility research as priority areas requiring further investigation before three-dimensionally printed polymethyl methacrylate resins can be regarded as an unqualified substitute for established denture base materials.