Research and Education|Articles in Press

Digital versus conventional veneering of zirconia and cobalt chromium crowns: Fracture load before and after thermomechanical aging


      Statement of problem

      To complement the digital workflow for manufacturing fixed dental prostheses, both high-strength frameworks and esthetic veneers should be designed and fabricated digitally. However, how the fracture load of digitally veneered restorations compares with conventionally fabricated restorations is unclear.


      The purpose of this in vitro study was to examine the fracture load of digitally and conventionally veneered zirconia and cobalt chromium crowns initially and after thermomechanical aging.

      Material and methods

      Milled zirconia and cobalt chromium copings for a maxillary canine were fabricated (N=96). Digital veneers were milled and connected to the copings with a sintered ceramic slurry. The conventional veneers were fabricated by using a master mold, and the crowns were bonded to the cobalt chromium abutments. Half the specimens were subjected to 6000 thermal (5 °C to 55 °C, 60 seconds) and 1 200 000 mechanical (50 N, 1.5 Hz, 0.7 mm lateral movement) cycles opposed by steatite antagonists, and the fracture load was determined. Fracture types were categorized, and scanning electron microscopy performed. The data were analyzed with a 3-way global univariate analysis of variance, t test, the Pearson chi-squared test, and the Weibull modulus (α=.05).


      Unlike the framework material (P=.316) and artificial aging (P=.064), the veneering protocol affected the fracture load (P=.007). Digital veneers (range: 2242 to 2929 N) led to lower values than conventional veneers (range: 2825 to 3166 N), which was significant for aged cobalt chromium copings (P=.024; 2242 versus 3107 N). Conventionally veneered crowns showed lower Weibull moduli after thermomechanical aging (range: 3.2 to 3.5) than initially (range: 7.8 to 11.4). The copings of all the zirconia specimens fractured, while chipping occurred with the cobalt chromium specimens.


      The high fracture load values of the veneered crowns, even after simulated 5-year aging, indicated sufficient mechanical properties (nearly 4-fold the average occlusal force of 600 N) for the successful clinical application of digitally veneered zirconia and cobalt chromium copings.
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        • Mazza L.C.
        • Lemos C.A.A.
        • Pesqueira A.A.
        • Pellizzer E.P.
        Survival and complications of monolithic ceramic for tooth-supported fixed dental prostheses: a systematic review and meta-analysis.
        J Prosthet Dent. 2021; 128: 566-574
        • Pjetursson B.E.
        • Valente N.A.
        • Strasding M.
        • Zwahlen M.
        • Liu S.
        • Sailer I.
        A systematic review of the survival and complication rates of zirconia-ceramic and metal-ceramic single crowns.
        Clin Oral Implants Res. 2018; 16: 199-214
        • Vahnstrom M.
        • Johansson P.H.
        • Svanborg P.
        • Stenport V.F.
        Comparison of porcelain veneer fracture in implant-supported fixed full-arch prostheses with a framework of either titanium, cobalt-chromium, or zirconia: an in vitro study.
        Clin Exp Dent Res. 2022; 8: 544-551
        • Edelhoff D.
        • Sorensen J.
        Tooth structure removal associated with various preparation designs for anterior teeth.
        J Prosthet Dent. 2002; 87: 503-509
        • Edelhoff D.
        • Sorensen J.
        Tooth structure removal associated with various preparation designs for posterior teeth.
        Int J Periodontics Restorative Dent. 2002; 22: 241-249
        • Juntavee N.
        • Dangsuwan C.
        Role of coefficient of thermal expansion on bond strength of ceramic veneered yttrium-stabilized zirconia.
        J Clin Exp Dent. 2018; 10: e279-e286
        • Benetti P.
        • Kelly J.R.
        • Sanchez M.
        • Della Bona A.
        Influence of thermal gradients on stress state of veneered restorations.
        Dent Mater. 2014; 30: 554-563
        • Tholey M.J.
        • Swain M.V.
        • Thiel N.
        Thermal gradients and residual stresses in veneered Y-TZP frameworks.
        Dent Mater. 2011; 27: 1102-1110
        • Mainjot A.K.
        • Schajer G.S.
        • Vanheusden A.J.
        • Sadoun M.J.
        Influence of cooling rate on residual stress profile in veneering ceramic: measurement by hole-drilling.
        Dent Mater. 2011; 27: 906-914
        • Özcan M.
        How to repair ceramic chipping or fracture in metal-ceramic fixed dental prostheses intraorally: step-by-step procedures.
        J Adhes Dent. 2014; 16: 491-492
        • Özcan M.
        Intraoral repair protocol for chipping or fracture of veneering ceramic in zirconia fixed dental prostheses.
        J Adhes Dent. 2015; 17: 189-190
        • Beuer F.
        • Schweiger J.
        • Eichberger M.
        • Kappert H.F.
        • Gernet W.
        • Edelhoff D.
        High-strength CAD/CAM-fabricated veneering material sintered to zirconia copings--a new fabrication mode for all-ceramic restorations.
        Dent Mater. 2009; 25: 121-128
        • Cantner F.
        • Cacaci C.
        • Mucke T.
        • Randelzhofer P.
        • Hajto J.
        • Beuer F.
        Clinical performance of tooth- or implant-supported veneered zirconia single crowns: 42-month results.
        Clin Oral Investig. 2019; 23: 4301-4309
        • Choi Y.S.
        • Kim S.H.
        • Lee J.B.
        • Han J.S.
        • Yeo I.S.
        In vitro evaluation of fracture strength of zirconia restoration veneered with various ceramic materials.
        J Adv Prosthodont. 2012; 4: 162-169
        • Kanat B.
        • Comlekoglu E.M.
        • Dundar-Comlekoglu M.
        • Hakan Sen B.
        • Ozcan M.
        • Ali Gungor M.
        Effect of various veneering techniques on mechanical strength of computer-controlled zirconia framework designs.
        J Prosthodont. 2014; 23: 445-455
        • Torabi K.
        • Vojdani M.
        • Giti R.
        • Taghva M.
        • Pardis S.
        The effect of various veneering techniques on the marginal fit of zirconia copings.
        J Adv Prosthodont. 2015; 7: 233-239
        • van der Bilt A.
        • Tekamp A.
        • van der Glas H.
        • Abbink J.
        Bite force and electromyograpy during maximum unilateral and bilateral clenching.
        Eur J Oral Sci. 2008; 116: 217-222
        • Rosentritt M.
        • Plein T.
        • Kolbeck C.
        • Behr M.
        • Handel G.
        In vitro fracture force and marginal adaptation of ceramic crowns fixed on natural and artificial teeth.
        Int J Prosthodont. 2000; 13: 387-391
        • Wimmer T.
        • Erdelt K.J.
        • Eichberger M.
        • Roos M.
        • Edelhoff D.
        • Stawarczyk B.
        Influence of abutment model materials on the fracture loads of three-unit fixed dental prostheses.
        Dent Mater J. 2014; 33: 717-724
        • Stawarczyk B.
        • Beuer F.
        • Ender A.
        • Roos M.
        • Edelhoff D.
        • Wimmer T.
        Influence of cementation and cement type on the fracture load testing methodology of anterior crowns made of different materials.
        Dent Mater J. 2013; 32: 888-895
        • Stawarczyk B.
        • Ozcan M.
        • Roos M.
        • Trottmann A.
        • Hammerle C.H.
        Fracture load and failure analysis of zirconia single crowns veneered with pressed and layered ceramics after chewing simulation.
        Dent Mater J. 2011; 30: 554-562
        • Fischer J.
        • Stawarczyk B.
        • Tomic M.
        • Strub J.R.
        • Hammerle C.H.
        Effect of thermal misfit between different veneering ceramics and zirconia frameworks on in vitro fracture load of single crowns.
        Dent Mater J. 2007; 26: 766-772
        • Emslander A.
        • Reise M.
        • Eichberger M.
        • Uhrenbacher J.
        • Edelhoff D.
        • Stawarczyk B.
        Impact of surface treatment of different reinforced glass-ceramic anterior crowns on load bearing capacity.
        Dent Mater J. 2015; 34: 595-604
        • Stawarczyk B.
        • Hristova E.
        • Sener B.
        • Roos M.
        • Edelhoff D.
        • Keul C.
        Effect of hydrofluoric acid etching duration on fracture load and surface properties of three CAD/CAM glass-ceramics.
        Oral Health and Dental Mangement. 2014; 13: 742-751
        • Krejci I.
        • Lutz F.
        In-Vitro-Testverfahren zur Evaluation dentaler Restaurationssysteme.
        Schweiz Monatschr Zahnmed. 1990; 100: 1445-1449
        • Rosentritt M.
        • Behr M.
        • van der Zel J.M.
        • Feilzer A.J.
        Approach for valuating the influence of laboratory simulation.
        Dent Mater. 2009; 25: 348-352
        • Butikofer L.
        • Stawarczyk B.
        • Roos M.
        Two regression methods for estimation of a two- parameter Weibull distribution for reliability of dental materials.
        Dent Mater. 2015; 31: e33-e50