Research and Education| Volume 129, ISSUE 5, P796.e1-796.e7, May 2023

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Effect of adding a hard-reline material on the flexural strength of conventional, 3D-printed, and milled denture base materials


      Statement of problem

      Novel 3-dimensionally printed resin and milled polymethyl methacrylate materials have been marketed for computer-aided design and computer-aided manufacturing (CAD-CAM) denture base fabrication. However, information on the flexural strength of digitally fabricated denture base material is limited, and little is known about how they are affected by a hard-reline procedure.


      The purpose of this in vitro study was to assess the flexural strength of 6 digitally manufactured denture base materials and to assess the effect of a hard-reline procedure on their flexural strength.

      Material and methods

      A total of 140 strips of denture base material were fabricated from a conventional heat-polymerized polymethyl methacrylate (L199), 3 brands of milled polymethyl methacrylate (IBC, DSL, and ADH), and 3 brands of 3D-printed resin (DFD, ADB, and DrFD) (n=20). Ten specimens in each group did not receive any treatment, and 10 were relined with a hard-reline material (ProBase Cold Trial Kit). Specimens were then subjected to a 3-point flexural strength test using a universal testing machine at a crosshead speed of 5.0 mm/min. A 1-way ANOVA test followed by the Tukey multiple comparison test was used to detect the difference in flexural strength and the strain at fracture of the different types of denture base materials (α=.05). The comparison of flexural strength between with and without hard-reline was analyzed using an unpaired t test (α=.05).


      All materials, with or without the hard-reline, met the International Organization for Standardization (ISO) 20 795-1:2013 standard for flexural strength (65 MPa). The milled materials (DSL>IBC≈ADH) showed higher flexural strength than the 3D-printed or conventional materials (DrFD>DFD≈ADB≈L199) without a hard-reline. No statistical difference in flexural strength was found among the hard-relined denture base materials (P=.164). All 3 milled materials showed reduced flexural strength after relining, while the relined conventional (L199) and 3D-printed materials (DFD and ADB) showed notably higher flexural strength; printed DrFD showed no significant difference (P=.066). In terms of strain at fracture, the milled materials displayed higher values than those of the conventional or 3D-printed materials (P<.05).


      All digitally fabricated denture base materials were within acceptable limits for clinical use, even after hard relining. Flexural strength was highly dependent on the type of material. Hard relining affected the flexural strength of most of the digitally fabricated denture base materials.
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        • Kattadiyil M.T.
        • AlHelal A.
        • Goodacre B.J.
        Clinical complications and quality assessments with computer-engineered complete dentures: a systematic review.
        J Prosthet Dent. 2017; 117: 721-728
        • Murray M.D.
        • Darvell B.W.
        The evolution of the complete denture base. Theories of complete denture retention—a review. Part 1.
        Aust Dent J. 1993; 38: 216-219
        • Douglass C.W.
        • Shih A.
        • Ostry L.
        Will there be a need for complete dentures in the United States in 2020?.
        J Prosthet Dent. 2002; 87: 5-8
        • Janeva N.M.
        • Kovacevska G.
        • Elencevski S.
        • et al.
        Advantages of CAD-CAM versus conventional complete dentures - A Review.
        Open Access Maced J Med Sci. 2018; 6: 1498-1502
        • van Noort R.
        The future of dental devices is digital.
        Dent Mater. 2012; 28: 3-12
        • Baba N.Z.
        • Goodacre B.J.
        • Goodacre C.J.
        • Müller F.
        • Wagner S.
        CAD-CAM complete denture systems and physical properties: a review of the literature.
        J Prosthodont. 2021; 30: 113-124
        • Bilgin M.S.
        • Erdem A.
        • Aglarci O.S.
        • Dilber E.
        Fabricating complete dentures with CAD-CAM and RP technologies.
        J Prosthodont. 2015; 24: 576-579
        • Alghazzawi T.F.
        Advancements in CAD-CAM technology: options for practical implementation.
        J Prosthodont Res. 2016; 60: 72-84
        • Wimmer T.
        • Gallus K.
        • Eichberger M.
        • Stawarczyk B.
        Complete denture fabrication supported by CAD-CAM.
        J Prosthet Dent. 2016; 115: 541-546
        • Steinmassl P.A.
        • Wiedemair V.
        • Huck C.
        • et al.
        Do CAD-CAM dentures really release less monomer than conventional dentures?.
        Clin Oral Investig. 2017; 21: 1697-1705
        • Tallgren A.
        The continuing reduction of the residual alveolar ridges in complete denture wearers: a mixed-longitudinal study covering 25 years.
        J Prosthet Dent. 2003; 89: 427-435
        • Awad A.N.
        • Cho S.H.
        • Kesterke M.J.
        • Chen J.H.
        Comparison of tensile bond strength of denture reline materials on denture bases fabricated with CAD-CAM technology.
        J Prosthet Dent. 2023; 129: 616-622
        • Hout D.
        • Wonglamsam A.
        • Kanchanavasita W.
        Flexural strength of relined denture base using different thickness of self-cured relining material.
        M Dent J. 2017; 37: 223-232
        • Vergani C.E.
        • Seo R.S.
        • Pavarina A.C.
        • dos Santos Nunes Reis J.M.
        Flexural strength of autopolymerizing denture reline resins with microwave postpolymerization treatment.
        J Prosthet Dent. 2005; 93: 577-583
        • Chai J.
        • Takahashi Y.
        • Kawaguchi M.
        The flexural strengths of denture base acrylic resins after relining with a visible-light-activated material.
        Int J Prosthodont. 1998; 11: 121-124
        • Takahashi Y.
        • Chai J.
        • Kawaguchi M.
        Effect of water sorption on the resistance to plastic deformation of a denture base material relined with four different reline materials.
        Int J Prosthodont. 1998; 11: 49-54
        • de Oliveira Limírio J.P.J.
        • Gomes J.M.L.
        • Alves Rezende M.C.R.
        • et al.
        Mechanical properties of polymethyl methacrylate as a denture base: conventional versus CAD-CAM resin - A systematic review and meta-analysis of in vitro studies.
        J Prosthet Dent. 2022; 128: 1221-1229
        • Aguirre B.C.
        • Chen J.H.
        • Kontogiorgos E.D.
        • et al.
        Flexural strength of denture base acrylic resins processed by conventional and CAD-CAM methods.
        J Prosthet Dent. 2020; 123: 641-646
        • International Organization for Standardization (ISO)
        Dentistry– base polymers – Part 1: denture base polymers.
        ISO. 2013; (20795–1)
        • Prpić V.
        • Schauperl Z.
        • Ćatić A.
        • et al.
        comparison of mechanical properties of 3D-printed, CAD-CAM, and conventional denture base materials.
        J Prosthodont. 2020; 29: 524-528
        • Vojdani M.
        • Giti R.
        Polyamide as a denture base material: a literature review.
        J Dent (Shiraz). 2015; 16: 1-9
        • Gharechahi J.
        • Asadzadeh N.
        • Shahabian F.
        • Gharechahi M.
        Flexural strength of acrylic resin denture bases processed by two different methods.
        J Dent Res Dent Clin Dent Prospects. 2014; 8: 148-152
        • Abualsaud R.
        • Gad M.M.
        Flexural strength of CAD-CAM dental base materials: systematic review and meta-analysis of in vitro studies.
        J Int Soc Prev Community Dent. 2022; 12: 160-170
        • Jaikumar R.A.
        • Karthigeyan S.
        • Ali S.A.
        • Naidu N.M.
        • et al.
        Comparison of flexural strength in three types of denture base resins: an in vitro study.
        J Pharm Bioallied Sci. 2015; 7: S461-S464
        • Zafar M.S.
        Prosthodontic applications of polymethyl methacrylate (PMMA): an update.
        Polymers (Basel). 2020; 12: 2299
        • Fouda S.M.
        • Gad M.M.
        • Abualsaud R.
        • et al.
        Flexural properties and hardness of CAD-CAM denture base materials.
        J Prosthodont. 2023; 32: 318-324
        • Anadioti E.
        • Musharbash L.
        • Blatz M.B.
        • et al.
        3D printed complete removable dental prostheses: a narrative review.
        BMC Oral Health. 2020; 20: 343
        • Sun Y.
        • Song S.Y.
        • Lee K.S.
        • et al.
        Effects of relining materials on the flexural strength of relined thermoplastic denture base resins.
        J Adv Prosthodont. 2018; 10: 361-366
        • Perea-Lowery L.
        • Minja I.K.
        • Lassila L.
        • Ramakrishnaiah R.
        • Vallittu P.K.
        Assessment of CAD-CAM polymers for digitally fabricated complete dentures.
        J Prosthet Dent. 2021; 125: 175-181
        • Hayes M.D.
        • Edwards D.B.
        • Shah A.R.
        Fractography in failure analysis of polymers.
        Plastics Design Library, 2015: 48-92