Advertisement
Journal of Prosthetic Dentistry

Effect of layer thickness on the flexural strength of multiple-unit laser-sintered metal frameworks

Published:February 24, 2021DOI:https://doi.org/10.1016/j.prosdent.2020.10.006

      Abstract

      Statement of problem

      Laser sintering devices have been increasingly used to fabricate the metal frameworks of metal–ceramic restorations. In the fabrication process, the sintering layer thickness is an important parameter; however, information on how it may affect the flexural strength of metal frameworks remains limited.

      Purpose

      The purpose of this in vitro study was to evaluate the flexural strength of 3-unit and 4-unit cobalt-chromium (Co-Cr) metal frameworks laser sintered with 20-μm, 30-μm, and 40-μm layer thicknesses.

      Material and methods

      Three-unit and 4-unit master metal die models with premolar and molar abutments were prepared through direct metal laser sintering (DMLS). A total of 40 metal frameworks (n=10 for each metal die model) were fabricated by the lost-wax technique (group C, served as the control group) and through DMLS with 20-μm, 30-μm, and 40-μm layer thickness (experimental groups LS20, LS30, and LS40, respectively). Each metal framework was cemented to a master die with a polyvinyl siloxane impression material and then subjected to a 3-point bend test at a crosshead speed of 1 mm/min. The yield force of each metal framework was used to calculate the flexural strength. Data were statistically analyzed by using 1-way ANOVA followed by a Tukey honestly significant difference (HSD) test and an independent-samples t test (α=.05) The microstructure of the fracture surface was evaluated by scanning electron microscopy.

      Results

      Group C reported the lowest mean flexural strength (P<.05), whereas group LS20 reported the highest mean flexural strength, although no significant difference (P>.05) in flexural strength was observed among the DMLS groups. The 3-unit metal frameworks exhibited a statistically significant higher mean flexural strength than the 4-unit metal frameworks (P<.05).

      Conclusions

      The sintering layer thickness did not significantly affect the flexural strength of the laser-sintered metal frameworks. However, the DMLS groups reported a higher mean flexural strength than the cast group.
      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'

      Subscribe:

      Subscribe to Journal of Prosthetic Dentistry
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect

      References

        • Eliasson A.
        • Arnelund C.F.
        • Johansson A.
        A clinical evaluation of cobalt-chromium metal-ceramic fixed partial dentures and crowns: a three-to seven-year retrospective study.
        J Prosthet Dent. 2007; 98: 6-16
        • Krug K.P.
        • Knauber A.W.
        • Nothdurft F.P.
        Fracture behavior of metal-ceramic fixed dental prostheses with frameworks from cast or a newly developed sintered cobalt-chromium alloy.
        Clin Oral Investig. 2015; 19: 401-411
        • Denry I.
        • Holloway J.A.
        Ceramics for dental applications: a review.
        Materials. 2010; 3: 351-368
        • Roberts H.W.
        • Berzins D.W.
        • Moore B.K.
        • Charlton D.G.
        Metal-ceramic alloys in dentistry: a review.
        J Prosthodont. 2009; 18: 188-194
        • Wataha J.C.
        Alloys for prosthodontic restorations.
        J Prosthet Dent. 2002; 87: 351-363
        • Swain M.V.
        Unstable cracking (chipping) of veneering porcelain on all-ceramic dental crowns and fixed partial dentures.
        Acta Biomater. 2009; 5: 1668-1677
        • Kaleli N.
        • Saraç D.
        Influence of porcelain firing and cementation on the marginal adaptation of metal-ceramic restorations prepared by different methods.
        J Prosthet Dent. 2017; 117: 656-661
        • Kaleli N.
        • Saraç D.
        Comparison of porcelain bond strength of different metal frameworks prepared by using conventional and recently introduced fabrication methods.
        J Prosthet Dent. 2017; 118: 76-82
        • Strub J.R.
        • Rekow E.D.
        • Witkowski S.
        Computer-aided design and fabrication of dental restorations: current systems and future possibilities.
        J Am Dent Assoc. 2006; 137: 1289-1296
        • Miyazaki T.
        • Hotta Y.
        CAD/CAM systems available for the fabrication of crown and bridge restorations.
        Aust Dent J. 2011; 56 Suppl 1: 97-106
        • Van Noort R.
        The future of dental devices is digital.
        Dent Mater. 2012; 28: 3-12
        • Sun J.
        • Zhang F.Q.
        The application of rapid prototyping in prosthodontics.
        J Prosthodont. 2012; 21: 641-644
        • Tara M.A.
        • Eschbach S.
        • Bohlsen F.
        • Kern M.
        Clinical outcome of metal-ceramic crowns fabricated with laser-sintering technology.
        Int J Prosthodont. 2011; 24: 46-48
        • Santos E.C.
        • Shiomi M.
        • Osakada K.
        • Laoui T.
        Rapid manufacturing of metal components by laser forming.
        Int J Mach Tools Manuf. 2006; 46: 1459-1468
        • Ekren O.
        • Ozkomur A.
        • Ucar Y.
        Effect of layered manufacturing techniques, alloy powders, and layer thickness on metal-ceramic bond strength.
        J Prosthet Dent. 2018; 119: 481-487
        • Ucar Y.
        • Ekren O.
        Effect of layered manufacturing techniques, alloy powders, and layer thickness on mechanical properties of Co-Cr dental alloys.
        J Prosthet Dent. 2018; 120: 762-770
        • Gu D.
        • Shen Y.
        Balling phenomena in direct laser sintering of stainless steel powder: metallurgical mechanisms and control methods.
        Mater Des. 2009; 30: 2903-2910
        • Koutsoukis T.
        • Zinelis S.
        • Eliades G.
        • Al-Wazzan K.
        • Rifaiy M.A.
        • Al Jabbari Y.S.
        Selective laser melting technique of Co-Cr dental alloys: a review of structure and properties and comparative analysis with other available techniques.
        J Prosthodont. 2015; 24: 303-312
        • Mazzoli A.
        Selective laser sintering in biomedical engineering.
        Med Biol Eng Comput. 2013; 51: 245-256
        • Sames W.J.
        • List F.
        • Pannala S.
        • Dehoff R.R.
        • Babu S.S.
        The metallurgy and processing science of metal additive manufacturing.
        Int Mater Rev. 2016; 61: 315-360
        • Chockalingam K.
        • Jawahar N.
        • Chandrasekhar U.
        Influence of layer thickness on mechanical properties in stereolithography.
        Rapid Prototyp J. 2006; 12: 106-113
        • Mercelis P.
        • Kruth J.P.
        Residual stresses in selective laser sintering and selective laser melting.
        Rapid Prototyp J. 2006; 12: 254-265
        • Schaub D.A.
        • Chu K.R.
        • Montgomery D.C.
        Optimizing stereolithography throughput.
        J Manuf Syst. 1997; 16: 290-303
        • Simchi A.
        Direct laser sintering of metal powders: mechanism, kinetics and microstructural features.
        Mater Sci Eng. 2006; 428: 148-158
        • Withers P.J.
        • Bhadeshia H.
        Residual stress. Part 2–nature and origins.
        Mater Sci Technol. 2001; 17: 366-375
        • Bae E.J.
        • Kim J.H.
        • Kim W.C.
        • Kim H.Y.
        Bond and fracture strength of metal-ceramic restorations formed by selective laser sintering.
        J Adv Prosthodont. 2014; 6: 266-271
        • Kaleli N.
        • Ural Ç.
        • Özköylü G.
        • Duran İ.
        Effect of layer thickness on the marginal and internal adaptation of laser-sintered metal frameworks.
        J Prosthet Dent. 2019; 121: 922-928
        • Kaleli N.
        • Ural Ç.
        • Küçükekenci A.S.
        The effect of layer thickness on the porcelain bond strength of laser-sintered metal frameworks.
        J Prosthet Dent. 2019; 122: 76-81
        • Sakaguchi R.L.
        • Ferracane J.L.
        • Powers J.M.
        Craig's restorative dental materials.
        14th ed. Elsevier, St. Louis, MO2019: 69-70
        • Vander Voort G.F.
        • Lampman S.R.
        • Sanders B.R.
        • Anton G.J.
        • Polakowski C.
        • Kinson J.
        • et al.
        ASM handbook volume 9: metallography and microstructures.
        ASM International, Materials Park, OH2004: 22
        • Kim H.R.
        • Jang S.H.
        • Kim Y.K.
        • Son J.S.
        • Min B.K.
        • Kim K.H.
        • et al.
        Microstructures and mechanical properties of Co-Cr dental alloys fabricated by three CAD/CAM-based processing techniques.
        Materials (Basel). 2016; 9: 596