Miltiadis Mitsias Spiridon-Oumvertos Koutayas Stefan Wolfart Matthias Kern Inﬂuence of zirconia abutment preparation on the fracture strength of single implant lithium disilicate crowns after chewing simulation Authors’ afﬁliations: Miltiadis Mitsias, Matthias Kern, Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry Christian-Albrechts University at Kiel, Kiel, Germany Spiridon-Oumvertos Koutayas, Department of Prosthodontics, School of Dentistry, Albert-Ludwig University, Freiburg, Germany Stefan Wolfart, Department of Prosthodontics and Dental Materials, Medical Faculty, RWTH Aachen University, Aachen, Germany Miltiadis Mitsias, Private Practice, Athens, Greece Spiridon-Oumvertos Koutayas, Private Practice, Corfu, Greece Corresponding author: Dr. Miltiadis Mitsias, DDS, MSc, Dr Med Dent 29 Marasli Str. Athens 10676 Greece Tel.: +30 210 72 19 000 Fax: +30 210 72 19 010 E-mail: mmitsias@msn.com Key words: fracture mode, fracture strength, implant abutment, internal connection, lithium disilicate, preparation, zirconia Abstract Objective: The use of all-ceramic crowns over zirconia abutments is a well-established esthetic treatment option in implant dentistry; however, the effect of the mechanical processing due to abutment preparation has not been investigated under functional loading. The purpose of the study was to evaluate the inﬂuence of the zirconia abutment preparation depth and preparation mode on the fracture strength and fracture mode of lithium disilicate crowns after chewing simulation. Material and methods: Seventy single implant-supported lithium disilicate glass-ceramic crowns (IPS e.max Press, Ivoclar Vivadent) were adhesively cemented (Multilink Automix, Ivoclar Vivadent) onto zirconia abutments (ZirDesign, Astra Tech) using implants with a diameter of 4.5 mm and a length of 15.0 mm (Osseospeed, Astra Tech). Study design concerned the replacement of a maxillary central incisor (11.0 mm in height and 8.0 mm in width). Subgroups (n = 7) were subjected to dynamic loading (C) up to 1.2 9 10 6 loading cycles at 135° with 98N in a thermomechanical chewing simulator (Kausimulator, Willytech); followed by quasi-static loading at a cross-head speed of 0.5 mm/min until fracture in a universal testing machine (Z010/TN2S, Zwick). Additional subgroups were also subjected to quasi-static loading (S) at 135°. Lithium disilicate implant crowns were divided into ﬁve study groups (n = 14) according to the abutment preparation depth [A (control): 0.5 mm, B: 0.7 mm, C: 0.9 mm, and preparation mode [(No label): milling by the manufacturer, (P): copy-milling by the Celay System (Mikrona)]. Results: All specimens survived dynamic loading and mean fracture strengths (N) after quasi-static loading were as follows: Group SA: 384 ± 84; Group CA: 403 ± 67; Group SB: 294 ± 95; Group CB: 374 ± 75; Group SC: 332 ± 52; Group CC: 373 ± 105; Group SPB: 332 ± 80; Group CPB: 499 ± 91; Group SPC: 380 ± 101; and Group CPC: 358 ± 54. Conclusions: Statistical analysis using multiple linear regression showed that both the preparation depth and mode had no inﬂuence on the fracture strength of the implant crowns (P > 0.05); however, fracture strength increased statistically signiﬁcantly after 5 years chewing simulation (P = 0.01). Introduction Implant zirconia ceramic abutments have been very well adopted by dentists and dental technicians especially for the management of areas presenting high esthetic demands (Blatz et al. 2009; Koutayas et al. 2009). The whit- ish color shade of the zirconia abutments offer a favorable addition regarding grayish appearance, a known shortcoming of tita- nium abutments in clinical situations of thin peri-implant mucosa (<2 mm) or all-ceramic crowns with increased translucency (Jung et al. 2007; Sailer et al. 2007; Watkin & Ker- stein 2008). Zirconia also exhibits a series of outstanding properties such as improved frac- ture strength (Yildirim et al. 2003; Vagkopou- lou et al. 2009), high radioopacity, reduced plaque accumulation, and inﬂammation risk (Rimondini et al. 2002; Warashina et al. 2003; Scarano et al. 2004; Manicone et al. 2007; Welander et al. 2008) that make certain a clinically accepted biomechanical behavior as abutment (Ekfeldt et al. 2011). Different prefabricated zirconia abutments, particularly for internal connection implant Date: Accepted 8 September 2012 To cite this article: Mitsias M, Koutayas S-O, Wolfart S, Kern M. Inﬂuence of zirconia abutment preparation on the fracture strength of single implant lithium disilicate crowns after chewing simulation. Clin. Oral Impl. Res. 00, 2012, 000–000 doi: 10.1111/clr.12058 © 2012 John Wiley & Sons A/S 1