DENTAL-2368; No. of Pages 7
ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.intl.elsevierhealth.com/journals/dema
Full-arch prostheses from translucent zirconia: Accuracy of fit Caroline Sachs a , Julian Groesser a , Markus Stadelmann b , Josef Schweiger a , Kurt Erdelt a , Florian Beuer a,∗ a b
Department of Prosthodontics, Ludwig-Maximilians University, Munich, Germany Master Dental Technician, Stadelmann Dental, Munich, Germany
a r t i c l e
i n f o
a b s t r a c t
Article history:
Objectives. The aim of this study was to evaluate the marginal and internal fit of single
Received 14 May 2013
crowns, compared to 14-unit frameworks made of translucent yttria-stabilized zirconia.
Received in revised form
We hypothesized that there is an influence of the type of restoration on the marginal and
17 December 2013
internal fit.
Accepted 8 May 2014
Methods. Eight teeth (FDI locations 17, 15, 13, 11, 21, 23, 25 and 27) of a typodont maxillary
Available online xxx
model were provided with a chamfer preparation to accommodate a 14-unit prosthesis or four single crowns (SCs). Ten 14-unit fixed dental prostheses (FDPs) and 40 single
Keywords:
crowns were fabricated using a computer aided design (CAD)/computer aided manufac-
Translucent zirconia
turing (CAM) system with pre-sintered translucent yttria-stabilized zirconia blanks. The
CAD/CAM
restorations were cemented onto twenty master dies, which were sectioned into four pieces
Fixed dental prosthesis
each. Then, the marginal and internal fits were examined using a binocular microscope. In
14-Unit framework
order to detect the differences between the two types of restorations a non-parameteric test
Marginal fit
(Mann–Whitney-U) was carried out; to detect differences between the abutment teeth and
Internal fit
the abutment surfaces non-parametric tests (Kruskal–Wallis) and pairwise post hoc analy-
In vitro
ses (Mann–Whitney-U) were performed after testing data for normal distribution (method according to Shapiro–Wilk). Level of significance was set at 5%. Results. The mean (SD) marginal opening gap dimensions were 18 m (14) for the single crowns and 29 m (27) for the 14-unit FDPs (p < 0.001). Abutment 21 of the FDPs showed statistical differences concerning the location of the teeth in both marginal and internal fit (p < 0.001). The measured gaps (types I–IV) revealed statistical differences between all types, when comparing SCs to the FDPs (p < 0.001). Significance. Single crowns showed significantly better accuracy of fit, compared to the 14unit FDPs. However, both restorations showed clinically acceptable marginal and internal fit. © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
∗ Corresponding author at: Department of Prosthodontics, Ludwig-Maximilians-University, Goethestraße 70, 80336 Munich, Germany. Tel.: +49 89 4400 59558; fax: +49 89 4400 59502. E-mail address: fl[email protected] (F. Beuer). http://dx.doi.org/10.1016/j.dental.2014.05.001 0109-5641/© 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Sachs C, et al. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.05.001
DENTAL-2368; No. of Pages 7
2
ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
1.
Introduction
All-ceramic restorations are becoming increasingly popular because of their high esthetic potential and outstanding biocompatibility. Zirconia unites all of the positive characteristics of ceramics, although it has limited esthetics, due to its high opacity. Recent research by Stawarczyk et al. reveals that varying the sintering temperature can influence the translucency of yttria-stabilized zirconia. When using higher sintering temperatures, the material showed higher translucency, which led to better esthetic results. In a pre-sintered state, yttria-stabilized zirconia—which showed a flexural strength from 31 to 50 MPa—can be processed in a time-saving manner and with little wear on tools using most computer-aided design (CAD)/computer aided manufacturing (CAM) machines [1–7]. Predictable sinter shrinkage and avoiding sintering distortion are of paramount importance and depend on the uniform density of the blank. Uniaxial, isostatic and biaxial molding procedures are commonly used to manufacture yttria-stabilized zirconia blanks [6]. The uniaxial pressed blanks showed high differences in density between the central and peripheral zones, which limits their application to single crowns and fixed dental prostheses (FDPs) of up to four units [8]. In the biaxial molding procedure, pressure is applied on the zirconia powder by an upper and lower rigid punch, which also rotate around their own axes [9]. The benefits of both biaxial pressing and isostatic pressing include minimum sintering distortion, achieving high flexural strength after sintering (over 1300 MPa), and better accuracy of fit [6,7]. The mechanical behavior of all-ceramic crowns, in terms of strength, resistance, and retention, is essentially influenced by the accuracy of a framework [10–12]. In clinical practice, the marginal and internal fit determines the durability of a restoration. There is a consensus between various authors that marginal openings below 120 m are clinically acceptable [13–16]. Although gaps of less than 80 m are difficult to detect in clinical practice, some authors postulate marginal gaps of 50–75 m [17] and 70 m (10) [18] as clinically acceptable limits. However, poor marginal adaptation of restorations increases plaque retention and changes the composition of the microflora, which can lead to the onset of periodontal disease [19,20]. Furthermore, the risk of secondary caries increases with the marginal gap width [21,22]. Concerning the influence of the internal fit on the durability of the restorations, cement layers above 70 m tend to reduce the fracture strength significantly [23]. Due to the growing demand for long-span FDPs, more scientific studies concerning the fit of full arch restorations compared to single crowns are needed. Therefore, the aim of this study was to examine the marginal and internal fit of single crowns, compared to 14-unit frameworks made of yttria-stabilized zirconia (ICE Zirkon Translucent, Zirkonzahn S.r.l., Gais, Italy). The working hypothesis of this approach is that the type of restoration (single crowns or 14-unit FDPs) will show an influence on the internal and marginal fit.
2.
Materials and methods
A maxillary typodont model (standard working model AG3, Frasaco GmbH, Tettnang, Germany) with eight abutment teeth was used. Therefore, the maxillary central incisors, canines, second pre-molars and second molars were provided with a 360◦ 1.0 mm chamfer preparation. The occlusal and incisal reductions were 1.5–2.0 mm. Twenty polyether impressions (Impregum, 3 M ESPE, Seefeld, Germany) of the typodont model were made with metal impression trays (U3, Orbilock, Orbis Dental Handelsgesellschaft mbH, Münster, Germany). Subsequently, twenty models of a class IV special scan die stone (Rocky Mountain orange label, Klasse 4 Dental GmbH, Augsburg, Germany) were fabricated. The models were digitized (Fig. 1) with a white light projector scanner (S 600, Zirkonzahn S.r.l.) showing details of less than 10 m (unpublished data Zirkonzahn S.r.l.). The single crowns and 14-unit zirconia FDPs were designed with a CAD software (Zirkonzahn.Modellier, Zirkonzahn S.r.l.): the full-contour design was reduced by 0.8 mm for the veneering porcelain, with a minimum thickness of 0.5 mm for the framework. For the 14-unit zirconia framework design, distances between the pontics and the gingiva of 0.1 mm and a connector with a round cross-section and a minimum area of 9 mm2 were used. Further milling parameters for the crown foundation were the following: cement-gap thickness of 0.035 mm starting 0.3 mm of the preparation margin. At the transition from the axial wall to the occlusal surface 0.45 mm cement gap thickness were used while 0.4 mm were used for the occlusal surface. All parameters were chosen according to the manufacturer’s recommendations [10]. The design was sent to CAM software (Zirkonzahn.Nesting, Zirkonzahn S.r.l.) to position it in a virtual zirconia blank. In this case, the software automatically shrank the volume of the sintering foot, to fit the 14-unit framework. The aim was to avoid deformation of the curved arch in the anterior during the following sintering process. All restorations were milled with a 5 + 1 axes milling unit (M5, Zirkonzahn S.r.l.), using three different burr diameters
Fig. 1 – Screen-shot of the digitalization of a maxillary model with eight abutment teeth (FDI locations 17, 15, 13, 11, 21, 23, 25 and 27).
Please cite this article in press as: Sachs C, et al. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.05.001
DENTAL-2368; No. of Pages 7
ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
(2.0 mm, 1.0 mm and 0.5 mm) and pre-sintered zirconia blanks (Ice Zirkon Translucent 95H18, Zirkonzahn S.r.l.) that were characterized by a Weibull modulus of 17.1, a flexural strength of 1198.53 MPa (81.84) and a Vickers hardness of 1368 (28) [24]. Both the single crowns and the 14-unit frameworks were sintered to full density in a special furnace (600 V−2 , Zirkonzahn S.r.l.) at 1500 ◦ C for 12 h. Next, the single crowns and 14-unit FDPs were checked for fit using a standardized protocol from the literature [25,26]. Color (Bite-X Articulating Paste, Asami Tanaka Dental Enterprises Europe GmbH, Friedrichsdorf, Germany) was applied onto the abutment teeth, and both the single crowns and 14-unit frameworks were set back onto the model without force. If red spots occurred on the inner surfaces, they were removed using a red ring diamond burr (Diamond bur 201 Round end taper, Zirkonzahn S.r.l.) with water-cooling spray. This procedure was repeated until the restoration had a good clinical seat on the model, without imperfections, and provided a correct marginal closure. The time needed for adaptation was recorded. Concerning the full-arch prostheses in the upper jaw, a slight distortion between the central incisors and second molars became obvious during the adaption process. The next step was to cement the single crowns and the 14-unit FDPs onto the models with glass ionomer cement (Ketac Cem Maxicap, 3M ESPE) according to the manufacturer’s instructions. After applying the glass ionomer cement into the crowns with microbrushes, the single crowns and the 14-unit frameworks were placed onto the models with finger pressure, and the excess was removed with foam pellets. For the remaining setting time, which was 7 min, starting from the activation of the capsule, the copings and FDPs were loaded evenly with 50 N in a cementation device [27]. The four dies on the left side of the arch were chosen for measurement, which led to a total number of 80 specimens (40 of the single crowns and 40 of the FDPs). The sectioning lines (mesial–distal, facial–lingual) were marked centrally on the die, in order to have comparable crosssections. To avoid fracture of the cemented specimens during sectioning, the substructures were embedded into gypsum (Resin Rock, Whip Mix, Louisville, USA). Twenty-four hours later, they were segmented into smaller units, and each die was sectioned into four pieces by a cutting machine (Secotom50, Struers GmbH, Willich, Germany), according to the marked lines. Due to the brittleness and Vickers hardness of yttriumstabilized zirconia, a cut-off wheel (M1D13, Struers GmbH) was used under permanent water-cooling with a speed of 0.1 mm/s. After cleaning, the frameworks were examined at original magnification 50× (Axioskop 2 MAT, Carl-Zeiss AG, Oberkochen, Germany). One image of a calibration slide was made at the same magnification and used as a reference for calibration at each imaging session. In detail, three to eight digital images of each aspect of the die (mesial, facial, distal, lingual) were made with a digital single-lens reflex camera (Nikon D 100, Nikon Corporation, Tokyo, Japan), mounted on the microscope (Axioskop 2 MAT). An imaging program (Adobe Photoshop CS5, Adobe Systems Incorporation, San Jose, USA) was used to combine the single photos to a complete crosssection of the die. The images were transferred to an imaging data program (Optimas 6.5, Media Cybernetics Incorporation,
3
Fig. 2 – Marginal gap measurement: example of a microscopic picture (magnification 50×). The marginal opening (MO) was defined as the closest convergence of the zirconia framework (F) and the plaster die (D).
Rockville, USA) and measured according to the protocols of prior studies (Fig. 2) [10]. The marginal opening (type IV) was defined as the closest convergence of the zirconia framework and the plaster die. Furthermore, the values were measured of the cement gaps for the chamfer preparation (type I), the axial wall (type II), and the occlusal space (type III). Concerning the marginal opening, the smallest value was chosen, while for all other types of cement gaps, a mean value was generated. The obtained data were imported into a statistical program (SPSS 20.0, SPSS Incorporation, Chicago, USA) and evaluated. Mean values were calculated. In order to detect the differences between the two types of restorations a non-parameteric test (Mann–Whitney-U) was carried out; to detect differences between the abutment teeth, the measurement locations (types I–IV) and the different abutment surfaces (mesial, lingual, distal, buccal) non-parametric tests (Kruskal–Wallis) and a pairwise post hoc analyses (Mann–Whitney-U) were performed after data failed the testing for normal distribution (method according to Shapiro–Wilk). Level of significance was set at 5%.
3.
Results
The adaption process required a mean of 7 min (0.5) for the single crowns and 63 min (6.2) for the 14-unit frameworks. The gap dimensions of the marginal openings (type IV) were 18 m (14) for the single crowns (SCs) and 29 m (27) for the 14-unit frameworks (FDPs), which exhibited statistical difference (p = 0.005). The means of the complete cement gaps (type I–IV) were 90 m (58) for the SCs and 124 m (86) for the FDPs, which also showed statistical difference (p < 0.001).
Please cite this article in press as: Sachs C, et al. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.05.001
DENTAL-2368; No. of Pages 7
4
ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
Fig. 3 – (a) Mean values and standard deviations of both restoration types at the chamfer preparation, the axial wall, the occlusal aspect and the marginal opening in m. (b) Detailed analysis of the central incisor: mean values and standard deviations of both restoration types at the chamfer preparation, the axial wall, the occlusal aspect and the marginal opening in m.
Please cite this article in press as: Sachs C, et al. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.05.001
DENTAL-2368; No. of Pages 7
ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
5
Fig. 4 – Mean marginal opening values and standard deviations of both restoration types at the central incisor (21), canine (23), second premolar (25) and second molar (27) in m.
3.1.
Results for the SCs
For all types (I–IV) taken together, a statistical difference between the central incisor and the second molar could be detected (p = 0.019). The measurement location showed statistical influence at the lingual side of the central incisor (p < 0.001). Concerning the SC‘s marginal opening (type IV), the location of the abutment teeth showed no statistical influence (p = 0.555).
3.2.
Results for the FDPs
For all types (I–IV) taken together, the central incisor showed significantly larger cement gaps (p < 0.001). Concerning the measurement location, the central incisor showed statistical differences to all of the other dies at the mesial, distal and lingual sides (p < 0.001). For the facial side, only a statistical difference between the central incisor and the canine could be detected (p = 0.004). For the marginal opening, only the central incisor showed statistical differences (p < 0.001) to all other dies (FDI locations 23, 25 and 27).
3.3.
Comparison of SCs and FDPs
The measured gaps revealed statistical differences between all types (types I–IV), when comparing the SCs to the FDPs (p < 0.001). The gap differences between SCs and FDPs in the occlusal area (type III) exceeded the gap differences in the marginal opening (type IV), with values of 64 m (24) and
11 m (12), respectively (Fig. 3a). When comparing the SCs to the FDPs, significant differences (p < 0.001) for type III at each die (FDI locations 21, 23, 25 and 27) and at the central incisor (FDI location 21) in all other types (p < 0.001) became obvious (Fig. 3b). Furthermore, statistical differences in the marginal fit (type IV) between the dies were detected at the central incisor (p < 0.001) (Fig. 4). Regarding the measurement location within the abutment teeth, there were significant differences between the SCs and FDPs in all locations (mesial, facial, distal and lingual) for the central incisor. The other abutments showed no significant differences between the SCs and FDPs in the different measurement locations (0.072 < p < 0.57).
4.
Discussion
Fourteen-unit fixed dental prostheses showed statistically significant wider marginal openings and internal cement layers than single crowns fabricated using the same conditions supporting the working hypothesis. Multiple parameters like scanning, designing, milling, sintering and adaptation can influence the accuracy of zirconia substructures. Concerning the scanning procedure the inner curve of the chamfer preparation was considered the most critical area. However, both experimental groups (SCs and FDPs) were fabricated on the same preparations under identical conditions, so it might be supposed that the sintering process caused the distortion that appeared. The slight distortion between the central incisor and the second molar in the
Please cite this article in press as: Sachs C, et al. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.05.001
DENTAL-2368; No. of Pages 7
6
ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
Table 1 – Mean marginal openings, standard deviations, 95% confidence interval and minimum gaps of experimental groups. Restoration
Measured tooth
Mean (SD) gap in m
95% confidence interval Upper
Single crowns Single crowns Single crowns Single crowns 14-Unit FDPs 14-Unit FDPs 14-Unit FDPs 14-Unit FDPs
Incisor Canine Premolar Molar Incisor Canine Premolar Molar
a
18 (11) 22 (20)a 15 (11)a 17 (14)a 55 (31)b 25 (21)a 18 (18)a 16 (13)a
Minimum gap in m
Lower
15 16 12 13 45 19 13 12
21 29 19 22 65 31 24 20
5 2 0 0 4 2 2 2
Different superscript letters indicate statistically different groups.
FDPs and the poor marginal fit of the central incisor (FDPs) support the assumption that sintering does not just cause linear shrinkage, but also a distortion of the restoration. According to the manufacturer‘s recommendations, the framework was designed with a sintering foot, which supported the milled restoration during the sintering process. The sintering foot was reduced to the volume of the restoration and had connecting pins to the restoration on each second unit with the exception of the anterior units (FDI locations 12–22). A different design of the sintering foot and the supporting pins might influence the sinter shrinkage and the accuracy. The highest misfit occurred at the central incisor and canine of the FDPs. Different densities in the semi-sintered blanks, as well as the curved geometry of the anterior arch might be possible explanations for this problem. Basically inaccuracies in the fit of one abutment might lead to a failure of the whole 14-unit restoration or at least show an impact of the accuracy on the other abutments. Furthermore, the complicated adaption process of long-span FDPs stands in contrast to the advantages of CAD/CAM, which are to raise productivity and reduce costs [28]. The cementation process on eight dies might also influence the precision negatively. This effect might be even higher in clinical reality compared to in vitro conditions. Due to the increasing demand for 14unit frameworks, the study examined whether the marginal and internal gaps of such restorations are clinically acceptable. The values, especially for the marginal fit of the FDPs, were in the range of clinical acceptance, whereas the results for the SC‘s gap dimensions were considerably lower [13–18]. The 14-unit FDPs in this study showed lower mean marginal openings than restorations with fewer units (SCs and 3-unit FDPs) fabricated with other all-ceramic systems [11,26,29–33]. Furthermore, they showed similar values for the marginal openings as those found in a study on the marginal fit of 14-unit FDPs by Beuer et al. using a different blank material and CAD/CAM system [10]. Concerning the internal fit, the 14unit FDPs in this study showed mean gaps of 123 m (63) for the axial wall and 214 m (72) for the occlusal surface. These results are higher than reported by comparable studies (SCs and 3-unit FDPs) in the literature [26,29,32,34]. The following limitations apply to this study: (a) the typodont maxillary model was prepared ideally, which does not represent clinical practice; (b) the measurement does not display the inaccuracies caused by clinical impressioning; (c) only one width of cement spacer was examined; (d) the
adaption process may have influenced the accuracy of the marginal and internal fit; and (e) only one cementation technique and material was used. It can be concluded that 14-unit substructures form translucent zirconia showed an inferior overall fit compared to single crowns from the same material fabricated under the same conditions. However, both types of restorations showed marginal gaps under in vitro conditions that would be clinically acceptable (Table 1).
Acknowledgements The authors wish to thank Enrico Steger (Zirkonzahn S.r.l.) for supporting the study with the milling unit M5 and all necessary materials. The authors would like to sincerely thank Josef Schweiger and Markus Stadelmann for their advice in technical questions and Christine Keul for her assistance with the measuring procedure. The authors are very grateful to Dr. Kurt Erdelt for his assistance with the statistics.
references
[1] Stawarczyk B, Ozcan M, Hallmann L, Ender A, Mehl A, Hammerle CH. The effect of zirconia sintering temperature on flexural strength, grain size, and contrast ratio. Clin Oral Investig 2013;17:269–74. [2] Triwatana P, Nagaviroj N, Tulapornchai C. Clinical performance and failures of zirconia-based fixed partial dentures: a review literature. J Adv Prosthodont 2012;4:76–83. [3] Beuer F, Schweiger J, Edelhoff D. Digital dentistry: an overview of recent developments for CAD/CAM generated restorations. Br Dent J 2008;204:505–11. [4] Kohorst P, Herzog TJ, Borchers L, Stiesch-Scholz M. Load-bearing capacity of all-ceramic posterior four-unit fixed partial dentures with different zirconia frameworks. Eur J Oral Sci 2007;115:161–6. [5] Tinschert J, Natt G, Mohrbotter N, Spiekermann H, Schulze KA. Lifetime of alumina- and zirconia ceramics used for crown and bridge restorations. J Biomed Med Res B: Appl Biomater 2007;80:317–21. [6] Holzner, S, Weber, G. Material and blank for dentures. EP Patent No 2034947; 2011. [7] Frank, SHH, Moscheler, S, Schnagl, R, Suttor, D. Method of producing a dental prosthesis. US Patent No 0119180; 2004.
Please cite this article in press as: Sachs C, et al. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.05.001
DENTAL-2368; No. of Pages 7
ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
[8] Oh GJ, Yun KD, Lee KM, Lim HP, Park SW. Sintering behavior and mechanical properties of zirconia compacts fabricated by uniaxial press forming. J Adv Prosthodont 2010;2:81–7. [9] Young-Jung, K. Biaxial press molding system. US Patent No 6890168; 2005. [10] Beuer F, Neumeier P, Naumann M. Marginal fit of 14-unit zirconia fixed dental prosthesis retainers. J Oral Rehabil 2009;36:142–9. [11] Bindl A, Mormann WH. Marginal and internal fit of all-ceramic CAD/CAM crown-copings on chamfer preparations. J Oral Rehabil 2005;32:441–7. [12] Reich S, Kappe K, Teschner H, Schmitt J. Clinical fit of four-unit zirconia posterior fixed dental prostheses. Eur J Oral Sci 2008;116:579–84. [13] Belser UC, MacEntee MI, Richter WA. Fit of three porcelain-fused-to-metal marginal designs in vivo: a scanning electron microscope study. J Prosthet Dent 1985;53:24–9. [14] Karlsson S. The fit of Procera titanium crowns. An in vitro and clinical study. Acta Odontol Scand 1993;51:129–34. [15] McLean JW, von Fraunhofer JA. The estimation of cement film thickness by an in vivo technique. Br Dent J 1971;131:107–11. [16] Sulaiman F, Chai J, Jameson LM, Wozniak WT. A comparison of the marginal fit of In-Ceram, IPS Empress, and Procera crowns. Int J Prosthodont 1997;10:478–84. [17] Hung SH, Hung KS, Eick JD, Chappell RP. Marginal fit of porcelain-fused-to-metal and two types of ceramic crown. J Prosthet Dent 1990;63:26–31. [18] Weaver JD, Johnson GH, Bales DJ. Marginal adaptation of castable ceramic crowns. J Prosthet Dent 1991;66:747–53. [19] Felton DA, Kanoy BE, Bayne SC, Wirthman GP. Effect of in vivo crown margin discrepancies on periodontal health. J Prosthet Dent 1991;65:357–64. [20] Lang NP, Kiel RA, Anderhalden K. Clinical and microbiological effects of subgingival restorations with overhanging or clinically perfect margins. J Clin Periodontol 1983;10:563–78. [21] Walton JN, Gardner FM, Agar JR. A survey of crown and fixed partial denture failures: length of service and reasons for replacement. J Prosthet Dent 1986;56:416–21. [22] Bronson MR, Lindquist TJ, Dawson DV. Clinical acceptability of crown margins versus marginal gaps as determined by
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
7
pre-doctoral students and prosthodontists. J Prosthodont 2005;14:226–32. Tuntiprawon M, Wilson PR. The effect of cement thickness on the fracture strength of all-ceramic crowns. Aust Dent J 1995;40:17–21. Turp V, Tuncelli B, Sen D, Goller G. Evaluation of hardness and fracture toughness, coupled with microstructural analysis, of zirconia ceramics stored in environments with different pH values. Dent Mater J 2012;31:891–902. Beuer F, Aggstaller H, Edelhoff D, Gernet W. Effect of preparation design on the fracture resistance of zirconia crown copings. Dent Mater J 2008;27:362–7. Beuer F, Aggstaller H, Edelhoff D, Gernet W, Sorensen J. Marginal and internal fits of fixed dental prostheses zirconia retainers. Dent Mater 2009;25:94–102. Proussaefs P. Crowns cemented on crown preparations lacking geometric resistance form. Part II: effect of cement. J Prosthodont 2004;13:36–41. Encke BS, Heydecke G, Wolkewitz M, Strub JR. Results of a prospective randomized controlled trial of posterior ZrSiO(4)-ceramic crowns. J Oral Rehabil 2009;36:226–35. Dittmer MP, Borchers L, Stiesch M, Kohorst P. Stresses and distortions within zirconia-fixed dental prostheses due to the veneering process. Acta Biomater 2009;5:3231–9. Kohorst P, Brinkmann H, Li J, Borchers L, Stiesch M. Marginal accuracy of four-unit zirconia fixed dental prostheses fabricated using different computer-aided design/computer-aided manufacturing systems. Eur J Oral Sci 2009;117:319–25. Att W, Komine F, Gerds T, Strub JR. Marginal adaptation of three different zirconium dioxide three-unit fixed dental prostheses. J Prosthet Dent 2009;101:239–47. Kohorst P, Brinkmann H, Dittmer MP, Borchers L, Stiesch M. Influence of the veneering process on the marginal fit of zirconia fixed dental prostheses. J Oral Rehabil 2010;37:283–91. Reich S, Wichmann M, Nkenke E, Proeschel P. Clinical fit of all-ceramic three-unit fixed partial dentures, generated with three different CAD/CAM systems. Eur J Oral Sci 2005;113:174–9. Beuer F, Naumann M, Gernet W, Sorensen JA. Precision of fit: zirconia three-unit fixed dental prostheses. Clin Oral Investig 2009;13:343–9.
Please cite this article in press as: Sachs C, et al. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.05.001
ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.intl.elsevierhealth.com/journals/dema
Full-arch prostheses from translucent zirconia: Accuracy of fit Caroline Sachs a , Julian Groesser a , Markus Stadelmann b , Josef Schweiger a , Kurt Erdelt a , Florian Beuer a,∗ a b
Department of Prosthodontics, Ludwig-Maximilians University, Munich, Germany Master Dental Technician, Stadelmann Dental, Munich, Germany
a r t i c l e
i n f o
a b s t r a c t
Article history:
Objectives. The aim of this study was to evaluate the marginal and internal fit of single
Received 14 May 2013
crowns, compared to 14-unit frameworks made of translucent yttria-stabilized zirconia.
Received in revised form
We hypothesized that there is an influence of the type of restoration on the marginal and
17 December 2013
internal fit.
Accepted 8 May 2014
Methods. Eight teeth (FDI locations 17, 15, 13, 11, 21, 23, 25 and 27) of a typodont maxillary
Available online xxx
model were provided with a chamfer preparation to accommodate a 14-unit prosthesis or four single crowns (SCs). Ten 14-unit fixed dental prostheses (FDPs) and 40 single
Keywords:
crowns were fabricated using a computer aided design (CAD)/computer aided manufac-
Translucent zirconia
turing (CAM) system with pre-sintered translucent yttria-stabilized zirconia blanks. The
CAD/CAM
restorations were cemented onto twenty master dies, which were sectioned into four pieces
Fixed dental prosthesis
each. Then, the marginal and internal fits were examined using a binocular microscope. In
14-Unit framework
order to detect the differences between the two types of restorations a non-parameteric test
Marginal fit
(Mann–Whitney-U) was carried out; to detect differences between the abutment teeth and
Internal fit
the abutment surfaces non-parametric tests (Kruskal–Wallis) and pairwise post hoc analy-
In vitro
ses (Mann–Whitney-U) were performed after testing data for normal distribution (method according to Shapiro–Wilk). Level of significance was set at 5%. Results. The mean (SD) marginal opening gap dimensions were 18 m (14) for the single crowns and 29 m (27) for the 14-unit FDPs (p < 0.001). Abutment 21 of the FDPs showed statistical differences concerning the location of the teeth in both marginal and internal fit (p < 0.001). The measured gaps (types I–IV) revealed statistical differences between all types, when comparing SCs to the FDPs (p < 0.001). Significance. Single crowns showed significantly better accuracy of fit, compared to the 14unit FDPs. However, both restorations showed clinically acceptable marginal and internal fit. © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
∗ Corresponding author at: Department of Prosthodontics, Ludwig-Maximilians-University, Goethestraße 70, 80336 Munich, Germany. Tel.: +49 89 4400 59558; fax: +49 89 4400 59502. E-mail address: fl[email protected] (F. Beuer). http://dx.doi.org/10.1016/j.dental.2014.05.001 0109-5641/© 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Sachs C, et al. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.05.001
DENTAL-2368; No. of Pages 7
2
ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
1.
Introduction
All-ceramic restorations are becoming increasingly popular because of their high esthetic potential and outstanding biocompatibility. Zirconia unites all of the positive characteristics of ceramics, although it has limited esthetics, due to its high opacity. Recent research by Stawarczyk et al. reveals that varying the sintering temperature can influence the translucency of yttria-stabilized zirconia. When using higher sintering temperatures, the material showed higher translucency, which led to better esthetic results. In a pre-sintered state, yttria-stabilized zirconia—which showed a flexural strength from 31 to 50 MPa—can be processed in a time-saving manner and with little wear on tools using most computer-aided design (CAD)/computer aided manufacturing (CAM) machines [1–7]. Predictable sinter shrinkage and avoiding sintering distortion are of paramount importance and depend on the uniform density of the blank. Uniaxial, isostatic and biaxial molding procedures are commonly used to manufacture yttria-stabilized zirconia blanks [6]. The uniaxial pressed blanks showed high differences in density between the central and peripheral zones, which limits their application to single crowns and fixed dental prostheses (FDPs) of up to four units [8]. In the biaxial molding procedure, pressure is applied on the zirconia powder by an upper and lower rigid punch, which also rotate around their own axes [9]. The benefits of both biaxial pressing and isostatic pressing include minimum sintering distortion, achieving high flexural strength after sintering (over 1300 MPa), and better accuracy of fit [6,7]. The mechanical behavior of all-ceramic crowns, in terms of strength, resistance, and retention, is essentially influenced by the accuracy of a framework [10–12]. In clinical practice, the marginal and internal fit determines the durability of a restoration. There is a consensus between various authors that marginal openings below 120 m are clinically acceptable [13–16]. Although gaps of less than 80 m are difficult to detect in clinical practice, some authors postulate marginal gaps of 50–75 m [17] and 70 m (10) [18] as clinically acceptable limits. However, poor marginal adaptation of restorations increases plaque retention and changes the composition of the microflora, which can lead to the onset of periodontal disease [19,20]. Furthermore, the risk of secondary caries increases with the marginal gap width [21,22]. Concerning the influence of the internal fit on the durability of the restorations, cement layers above 70 m tend to reduce the fracture strength significantly [23]. Due to the growing demand for long-span FDPs, more scientific studies concerning the fit of full arch restorations compared to single crowns are needed. Therefore, the aim of this study was to examine the marginal and internal fit of single crowns, compared to 14-unit frameworks made of yttria-stabilized zirconia (ICE Zirkon Translucent, Zirkonzahn S.r.l., Gais, Italy). The working hypothesis of this approach is that the type of restoration (single crowns or 14-unit FDPs) will show an influence on the internal and marginal fit.
2.
Materials and methods
A maxillary typodont model (standard working model AG3, Frasaco GmbH, Tettnang, Germany) with eight abutment teeth was used. Therefore, the maxillary central incisors, canines, second pre-molars and second molars were provided with a 360◦ 1.0 mm chamfer preparation. The occlusal and incisal reductions were 1.5–2.0 mm. Twenty polyether impressions (Impregum, 3 M ESPE, Seefeld, Germany) of the typodont model were made with metal impression trays (U3, Orbilock, Orbis Dental Handelsgesellschaft mbH, Münster, Germany). Subsequently, twenty models of a class IV special scan die stone (Rocky Mountain orange label, Klasse 4 Dental GmbH, Augsburg, Germany) were fabricated. The models were digitized (Fig. 1) with a white light projector scanner (S 600, Zirkonzahn S.r.l.) showing details of less than 10 m (unpublished data Zirkonzahn S.r.l.). The single crowns and 14-unit zirconia FDPs were designed with a CAD software (Zirkonzahn.Modellier, Zirkonzahn S.r.l.): the full-contour design was reduced by 0.8 mm for the veneering porcelain, with a minimum thickness of 0.5 mm for the framework. For the 14-unit zirconia framework design, distances between the pontics and the gingiva of 0.1 mm and a connector with a round cross-section and a minimum area of 9 mm2 were used. Further milling parameters for the crown foundation were the following: cement-gap thickness of 0.035 mm starting 0.3 mm of the preparation margin. At the transition from the axial wall to the occlusal surface 0.45 mm cement gap thickness were used while 0.4 mm were used for the occlusal surface. All parameters were chosen according to the manufacturer’s recommendations [10]. The design was sent to CAM software (Zirkonzahn.Nesting, Zirkonzahn S.r.l.) to position it in a virtual zirconia blank. In this case, the software automatically shrank the volume of the sintering foot, to fit the 14-unit framework. The aim was to avoid deformation of the curved arch in the anterior during the following sintering process. All restorations were milled with a 5 + 1 axes milling unit (M5, Zirkonzahn S.r.l.), using three different burr diameters
Fig. 1 – Screen-shot of the digitalization of a maxillary model with eight abutment teeth (FDI locations 17, 15, 13, 11, 21, 23, 25 and 27).
Please cite this article in press as: Sachs C, et al. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.05.001
DENTAL-2368; No. of Pages 7
ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
(2.0 mm, 1.0 mm and 0.5 mm) and pre-sintered zirconia blanks (Ice Zirkon Translucent 95H18, Zirkonzahn S.r.l.) that were characterized by a Weibull modulus of 17.1, a flexural strength of 1198.53 MPa (81.84) and a Vickers hardness of 1368 (28) [24]. Both the single crowns and the 14-unit frameworks were sintered to full density in a special furnace (600 V−2 , Zirkonzahn S.r.l.) at 1500 ◦ C for 12 h. Next, the single crowns and 14-unit FDPs were checked for fit using a standardized protocol from the literature [25,26]. Color (Bite-X Articulating Paste, Asami Tanaka Dental Enterprises Europe GmbH, Friedrichsdorf, Germany) was applied onto the abutment teeth, and both the single crowns and 14-unit frameworks were set back onto the model without force. If red spots occurred on the inner surfaces, they were removed using a red ring diamond burr (Diamond bur 201 Round end taper, Zirkonzahn S.r.l.) with water-cooling spray. This procedure was repeated until the restoration had a good clinical seat on the model, without imperfections, and provided a correct marginal closure. The time needed for adaptation was recorded. Concerning the full-arch prostheses in the upper jaw, a slight distortion between the central incisors and second molars became obvious during the adaption process. The next step was to cement the single crowns and the 14-unit FDPs onto the models with glass ionomer cement (Ketac Cem Maxicap, 3M ESPE) according to the manufacturer’s instructions. After applying the glass ionomer cement into the crowns with microbrushes, the single crowns and the 14-unit frameworks were placed onto the models with finger pressure, and the excess was removed with foam pellets. For the remaining setting time, which was 7 min, starting from the activation of the capsule, the copings and FDPs were loaded evenly with 50 N in a cementation device [27]. The four dies on the left side of the arch were chosen for measurement, which led to a total number of 80 specimens (40 of the single crowns and 40 of the FDPs). The sectioning lines (mesial–distal, facial–lingual) were marked centrally on the die, in order to have comparable crosssections. To avoid fracture of the cemented specimens during sectioning, the substructures were embedded into gypsum (Resin Rock, Whip Mix, Louisville, USA). Twenty-four hours later, they were segmented into smaller units, and each die was sectioned into four pieces by a cutting machine (Secotom50, Struers GmbH, Willich, Germany), according to the marked lines. Due to the brittleness and Vickers hardness of yttriumstabilized zirconia, a cut-off wheel (M1D13, Struers GmbH) was used under permanent water-cooling with a speed of 0.1 mm/s. After cleaning, the frameworks were examined at original magnification 50× (Axioskop 2 MAT, Carl-Zeiss AG, Oberkochen, Germany). One image of a calibration slide was made at the same magnification and used as a reference for calibration at each imaging session. In detail, three to eight digital images of each aspect of the die (mesial, facial, distal, lingual) were made with a digital single-lens reflex camera (Nikon D 100, Nikon Corporation, Tokyo, Japan), mounted on the microscope (Axioskop 2 MAT). An imaging program (Adobe Photoshop CS5, Adobe Systems Incorporation, San Jose, USA) was used to combine the single photos to a complete crosssection of the die. The images were transferred to an imaging data program (Optimas 6.5, Media Cybernetics Incorporation,
3
Fig. 2 – Marginal gap measurement: example of a microscopic picture (magnification 50×). The marginal opening (MO) was defined as the closest convergence of the zirconia framework (F) and the plaster die (D).
Rockville, USA) and measured according to the protocols of prior studies (Fig. 2) [10]. The marginal opening (type IV) was defined as the closest convergence of the zirconia framework and the plaster die. Furthermore, the values were measured of the cement gaps for the chamfer preparation (type I), the axial wall (type II), and the occlusal space (type III). Concerning the marginal opening, the smallest value was chosen, while for all other types of cement gaps, a mean value was generated. The obtained data were imported into a statistical program (SPSS 20.0, SPSS Incorporation, Chicago, USA) and evaluated. Mean values were calculated. In order to detect the differences between the two types of restorations a non-parameteric test (Mann–Whitney-U) was carried out; to detect differences between the abutment teeth, the measurement locations (types I–IV) and the different abutment surfaces (mesial, lingual, distal, buccal) non-parametric tests (Kruskal–Wallis) and a pairwise post hoc analyses (Mann–Whitney-U) were performed after data failed the testing for normal distribution (method according to Shapiro–Wilk). Level of significance was set at 5%.
3.
Results
The adaption process required a mean of 7 min (0.5) for the single crowns and 63 min (6.2) for the 14-unit frameworks. The gap dimensions of the marginal openings (type IV) were 18 m (14) for the single crowns (SCs) and 29 m (27) for the 14-unit frameworks (FDPs), which exhibited statistical difference (p = 0.005). The means of the complete cement gaps (type I–IV) were 90 m (58) for the SCs and 124 m (86) for the FDPs, which also showed statistical difference (p < 0.001).
Please cite this article in press as: Sachs C, et al. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.05.001
DENTAL-2368; No. of Pages 7
4
ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
Fig. 3 – (a) Mean values and standard deviations of both restoration types at the chamfer preparation, the axial wall, the occlusal aspect and the marginal opening in m. (b) Detailed analysis of the central incisor: mean values and standard deviations of both restoration types at the chamfer preparation, the axial wall, the occlusal aspect and the marginal opening in m.
Please cite this article in press as: Sachs C, et al. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.05.001
DENTAL-2368; No. of Pages 7
ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
5
Fig. 4 – Mean marginal opening values and standard deviations of both restoration types at the central incisor (21), canine (23), second premolar (25) and second molar (27) in m.
3.1.
Results for the SCs
For all types (I–IV) taken together, a statistical difference between the central incisor and the second molar could be detected (p = 0.019). The measurement location showed statistical influence at the lingual side of the central incisor (p < 0.001). Concerning the SC‘s marginal opening (type IV), the location of the abutment teeth showed no statistical influence (p = 0.555).
3.2.
Results for the FDPs
For all types (I–IV) taken together, the central incisor showed significantly larger cement gaps (p < 0.001). Concerning the measurement location, the central incisor showed statistical differences to all of the other dies at the mesial, distal and lingual sides (p < 0.001). For the facial side, only a statistical difference between the central incisor and the canine could be detected (p = 0.004). For the marginal opening, only the central incisor showed statistical differences (p < 0.001) to all other dies (FDI locations 23, 25 and 27).
3.3.
Comparison of SCs and FDPs
The measured gaps revealed statistical differences between all types (types I–IV), when comparing the SCs to the FDPs (p < 0.001). The gap differences between SCs and FDPs in the occlusal area (type III) exceeded the gap differences in the marginal opening (type IV), with values of 64 m (24) and
11 m (12), respectively (Fig. 3a). When comparing the SCs to the FDPs, significant differences (p < 0.001) for type III at each die (FDI locations 21, 23, 25 and 27) and at the central incisor (FDI location 21) in all other types (p < 0.001) became obvious (Fig. 3b). Furthermore, statistical differences in the marginal fit (type IV) between the dies were detected at the central incisor (p < 0.001) (Fig. 4). Regarding the measurement location within the abutment teeth, there were significant differences between the SCs and FDPs in all locations (mesial, facial, distal and lingual) for the central incisor. The other abutments showed no significant differences between the SCs and FDPs in the different measurement locations (0.072 < p < 0.57).
4.
Discussion
Fourteen-unit fixed dental prostheses showed statistically significant wider marginal openings and internal cement layers than single crowns fabricated using the same conditions supporting the working hypothesis. Multiple parameters like scanning, designing, milling, sintering and adaptation can influence the accuracy of zirconia substructures. Concerning the scanning procedure the inner curve of the chamfer preparation was considered the most critical area. However, both experimental groups (SCs and FDPs) were fabricated on the same preparations under identical conditions, so it might be supposed that the sintering process caused the distortion that appeared. The slight distortion between the central incisor and the second molar in the
Please cite this article in press as: Sachs C, et al. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.05.001
DENTAL-2368; No. of Pages 7
6
ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
Table 1 – Mean marginal openings, standard deviations, 95% confidence interval and minimum gaps of experimental groups. Restoration
Measured tooth
Mean (SD) gap in m
95% confidence interval Upper
Single crowns Single crowns Single crowns Single crowns 14-Unit FDPs 14-Unit FDPs 14-Unit FDPs 14-Unit FDPs
Incisor Canine Premolar Molar Incisor Canine Premolar Molar
a
18 (11) 22 (20)a 15 (11)a 17 (14)a 55 (31)b 25 (21)a 18 (18)a 16 (13)a
Minimum gap in m
Lower
15 16 12 13 45 19 13 12
21 29 19 22 65 31 24 20
5 2 0 0 4 2 2 2
Different superscript letters indicate statistically different groups.
FDPs and the poor marginal fit of the central incisor (FDPs) support the assumption that sintering does not just cause linear shrinkage, but also a distortion of the restoration. According to the manufacturer‘s recommendations, the framework was designed with a sintering foot, which supported the milled restoration during the sintering process. The sintering foot was reduced to the volume of the restoration and had connecting pins to the restoration on each second unit with the exception of the anterior units (FDI locations 12–22). A different design of the sintering foot and the supporting pins might influence the sinter shrinkage and the accuracy. The highest misfit occurred at the central incisor and canine of the FDPs. Different densities in the semi-sintered blanks, as well as the curved geometry of the anterior arch might be possible explanations for this problem. Basically inaccuracies in the fit of one abutment might lead to a failure of the whole 14-unit restoration or at least show an impact of the accuracy on the other abutments. Furthermore, the complicated adaption process of long-span FDPs stands in contrast to the advantages of CAD/CAM, which are to raise productivity and reduce costs [28]. The cementation process on eight dies might also influence the precision negatively. This effect might be even higher in clinical reality compared to in vitro conditions. Due to the increasing demand for 14unit frameworks, the study examined whether the marginal and internal gaps of such restorations are clinically acceptable. The values, especially for the marginal fit of the FDPs, were in the range of clinical acceptance, whereas the results for the SC‘s gap dimensions were considerably lower [13–18]. The 14-unit FDPs in this study showed lower mean marginal openings than restorations with fewer units (SCs and 3-unit FDPs) fabricated with other all-ceramic systems [11,26,29–33]. Furthermore, they showed similar values for the marginal openings as those found in a study on the marginal fit of 14-unit FDPs by Beuer et al. using a different blank material and CAD/CAM system [10]. Concerning the internal fit, the 14unit FDPs in this study showed mean gaps of 123 m (63) for the axial wall and 214 m (72) for the occlusal surface. These results are higher than reported by comparable studies (SCs and 3-unit FDPs) in the literature [26,29,32,34]. The following limitations apply to this study: (a) the typodont maxillary model was prepared ideally, which does not represent clinical practice; (b) the measurement does not display the inaccuracies caused by clinical impressioning; (c) only one width of cement spacer was examined; (d) the
adaption process may have influenced the accuracy of the marginal and internal fit; and (e) only one cementation technique and material was used. It can be concluded that 14-unit substructures form translucent zirconia showed an inferior overall fit compared to single crowns from the same material fabricated under the same conditions. However, both types of restorations showed marginal gaps under in vitro conditions that would be clinically acceptable (Table 1).
Acknowledgements The authors wish to thank Enrico Steger (Zirkonzahn S.r.l.) for supporting the study with the milling unit M5 and all necessary materials. The authors would like to sincerely thank Josef Schweiger and Markus Stadelmann for their advice in technical questions and Christine Keul for her assistance with the measuring procedure. The authors are very grateful to Dr. Kurt Erdelt for his assistance with the statistics.
references
[1] Stawarczyk B, Ozcan M, Hallmann L, Ender A, Mehl A, Hammerle CH. The effect of zirconia sintering temperature on flexural strength, grain size, and contrast ratio. Clin Oral Investig 2013;17:269–74. [2] Triwatana P, Nagaviroj N, Tulapornchai C. Clinical performance and failures of zirconia-based fixed partial dentures: a review literature. J Adv Prosthodont 2012;4:76–83. [3] Beuer F, Schweiger J, Edelhoff D. Digital dentistry: an overview of recent developments for CAD/CAM generated restorations. Br Dent J 2008;204:505–11. [4] Kohorst P, Herzog TJ, Borchers L, Stiesch-Scholz M. Load-bearing capacity of all-ceramic posterior four-unit fixed partial dentures with different zirconia frameworks. Eur J Oral Sci 2007;115:161–6. [5] Tinschert J, Natt G, Mohrbotter N, Spiekermann H, Schulze KA. Lifetime of alumina- and zirconia ceramics used for crown and bridge restorations. J Biomed Med Res B: Appl Biomater 2007;80:317–21. [6] Holzner, S, Weber, G. Material and blank for dentures. EP Patent No 2034947; 2011. [7] Frank, SHH, Moscheler, S, Schnagl, R, Suttor, D. Method of producing a dental prosthesis. US Patent No 0119180; 2004.
Please cite this article in press as: Sachs C, et al. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.05.001
DENTAL-2368; No. of Pages 7
ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
[8] Oh GJ, Yun KD, Lee KM, Lim HP, Park SW. Sintering behavior and mechanical properties of zirconia compacts fabricated by uniaxial press forming. J Adv Prosthodont 2010;2:81–7. [9] Young-Jung, K. Biaxial press molding system. US Patent No 6890168; 2005. [10] Beuer F, Neumeier P, Naumann M. Marginal fit of 14-unit zirconia fixed dental prosthesis retainers. J Oral Rehabil 2009;36:142–9. [11] Bindl A, Mormann WH. Marginal and internal fit of all-ceramic CAD/CAM crown-copings on chamfer preparations. J Oral Rehabil 2005;32:441–7. [12] Reich S, Kappe K, Teschner H, Schmitt J. Clinical fit of four-unit zirconia posterior fixed dental prostheses. Eur J Oral Sci 2008;116:579–84. [13] Belser UC, MacEntee MI, Richter WA. Fit of three porcelain-fused-to-metal marginal designs in vivo: a scanning electron microscope study. J Prosthet Dent 1985;53:24–9. [14] Karlsson S. The fit of Procera titanium crowns. An in vitro and clinical study. Acta Odontol Scand 1993;51:129–34. [15] McLean JW, von Fraunhofer JA. The estimation of cement film thickness by an in vivo technique. Br Dent J 1971;131:107–11. [16] Sulaiman F, Chai J, Jameson LM, Wozniak WT. A comparison of the marginal fit of In-Ceram, IPS Empress, and Procera crowns. Int J Prosthodont 1997;10:478–84. [17] Hung SH, Hung KS, Eick JD, Chappell RP. Marginal fit of porcelain-fused-to-metal and two types of ceramic crown. J Prosthet Dent 1990;63:26–31. [18] Weaver JD, Johnson GH, Bales DJ. Marginal adaptation of castable ceramic crowns. J Prosthet Dent 1991;66:747–53. [19] Felton DA, Kanoy BE, Bayne SC, Wirthman GP. Effect of in vivo crown margin discrepancies on periodontal health. J Prosthet Dent 1991;65:357–64. [20] Lang NP, Kiel RA, Anderhalden K. Clinical and microbiological effects of subgingival restorations with overhanging or clinically perfect margins. J Clin Periodontol 1983;10:563–78. [21] Walton JN, Gardner FM, Agar JR. A survey of crown and fixed partial denture failures: length of service and reasons for replacement. J Prosthet Dent 1986;56:416–21. [22] Bronson MR, Lindquist TJ, Dawson DV. Clinical acceptability of crown margins versus marginal gaps as determined by
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
7
pre-doctoral students and prosthodontists. J Prosthodont 2005;14:226–32. Tuntiprawon M, Wilson PR. The effect of cement thickness on the fracture strength of all-ceramic crowns. Aust Dent J 1995;40:17–21. Turp V, Tuncelli B, Sen D, Goller G. Evaluation of hardness and fracture toughness, coupled with microstructural analysis, of zirconia ceramics stored in environments with different pH values. Dent Mater J 2012;31:891–902. Beuer F, Aggstaller H, Edelhoff D, Gernet W. Effect of preparation design on the fracture resistance of zirconia crown copings. Dent Mater J 2008;27:362–7. Beuer F, Aggstaller H, Edelhoff D, Gernet W, Sorensen J. Marginal and internal fits of fixed dental prostheses zirconia retainers. Dent Mater 2009;25:94–102. Proussaefs P. Crowns cemented on crown preparations lacking geometric resistance form. Part II: effect of cement. J Prosthodont 2004;13:36–41. Encke BS, Heydecke G, Wolkewitz M, Strub JR. Results of a prospective randomized controlled trial of posterior ZrSiO(4)-ceramic crowns. J Oral Rehabil 2009;36:226–35. Dittmer MP, Borchers L, Stiesch M, Kohorst P. Stresses and distortions within zirconia-fixed dental prostheses due to the veneering process. Acta Biomater 2009;5:3231–9. Kohorst P, Brinkmann H, Li J, Borchers L, Stiesch M. Marginal accuracy of four-unit zirconia fixed dental prostheses fabricated using different computer-aided design/computer-aided manufacturing systems. Eur J Oral Sci 2009;117:319–25. Att W, Komine F, Gerds T, Strub JR. Marginal adaptation of three different zirconium dioxide three-unit fixed dental prostheses. J Prosthet Dent 2009;101:239–47. Kohorst P, Brinkmann H, Dittmer MP, Borchers L, Stiesch M. Influence of the veneering process on the marginal fit of zirconia fixed dental prostheses. J Oral Rehabil 2010;37:283–91. Reich S, Wichmann M, Nkenke E, Proeschel P. Clinical fit of all-ceramic three-unit fixed partial dentures, generated with three different CAD/CAM systems. Eur J Oral Sci 2005;113:174–9. Beuer F, Naumann M, Gernet W, Sorensen JA. Precision of fit: zirconia three-unit fixed dental prostheses. Clin Oral Investig 2009;13:343–9.
Please cite this article in press as: Sachs C, et al. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.05.001
