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ORIGINAL ARTICLE
Year : 2015  |  Volume : 3  |  Issue : 3  |  Page : 80-82

Influence of abutment-configuration on fracture strength of CAD/CAM-fabricated ceramic crowns


Department of Prosthetic Dentistry, University Medical Center, Mainz, Germany

Date of Web Publication30-Oct-2015

Correspondence Address:
Dr. Michael Weyhrauch
Department of Prosthetic Dentistry, University Medical Center of the Johannes-Gutenberg University, Augustusplatz 2, 55131 Mainz
Germany
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Source of Support: None, Conflict of Interest: This study was self-founded by the authors and their institution. The authors want to thank the Vita Zahnfabrik GmbH and Co. KG for technical support by the fracture load tests.


DOI: 10.4103/2321-4619.168735

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  Abstract 

Aims: This in vitro study assessed the fracture strength of computer-aided designing (CAD)/computer-aided manufacturing (CAM)-fabricated crowns on implant-abutments with different configurations. Subjects and Methods: Out of 30, 15 implant-abutments were shortened to 2 mm and a ball-headin metal-alloy was fixed on each abutment. Single crowns (Vita Mark II, Empress CAD, e. max CAD, Lava Ultimate, artBloc Temp Merz Dental, Telio CAD, and Vita CAD Temp) were designed. After cementation of the crowns using RelyX Unicem, a Zwick universal testing machine was used to aplicate occlusal force until the ceramic material was destroyed. Statistical Analysis Used: Statistical analysis were performed using analysis of variance (α =0.05) and Bonferroni correction. Results: This study has confirmed significant increases in fracture strength of crowns made of ceramic materials using the ball-head abutmentc on figuration. Conclusion: Within the limitations of this in vitro study, the following conclusions can be drawn: (1) The fracture strength of CAD/CAM-fabricated all-ceramic crowns could be increased using a rounded abutment up to 1.6 times. (2) The fracture strength of CAD/CAM-fabricated polymers could not be enhanced using a ball-head abutment. The increase of the fracture strength of all-ceramic crowns using the rounded abutment, could give reasons for the producers of implant abutments to improve their abutment design.

Keywords: Abutment design, all-ceramics, computer-aided designing/computer-aided manufacturing, fracture strength, polymers


How to cite this article:
Weyhrauch M, Wentaschack S, Igiel C, Scheller H, Lehmann KM. Influence of abutment-configuration on fracture strength of CAD/CAM-fabricated ceramic crowns. J Res Dent 2015;3:80-2

How to cite this URL:
Weyhrauch M, Wentaschack S, Igiel C, Scheller H, Lehmann KM. Influence of abutment-configuration on fracture strength of CAD/CAM-fabricated ceramic crowns. J Res Dent [serial online] 2015 [cited 2019 Sep 21];3:80-2. Available from: http://www.jresdent.org/text.asp?2015/3/3/80/168735


  Introduction Top


In recent years, all-ceramic systems have become increasingly important in dentistry. Every day in modern dental practices, patient requests for cost-effective and high-value dental prosthesis. Beyond that, the excellent biocompatibility and outstanding low thermal conductivity properties of dental ceramic systems have proven their value, so that ceramic materials represent an alternative to conventional materials in dentistry.[1] Concerning long-term consistency, various studies have shown that all-ceramic systems are excellently suitable for the manufacture of dental prosthesis. In addition, these materials provide outstanding esthetic results with regard to color reproduction and translucency. Even the most pretentious patient's request for a fixed restoration with qualities closely resembling those of natural teeth can be satisfied. The advantages of an implant-supported restoration are evident, and preparation of the healthy tooth structure can be avoided. Especially computer-aided manufacturing (CAM) of all-ceramic dental prosthesis significantly reduces the manufacturing costs, because computer-aided designing (CAD)/CAM technology allows quick and cost-effective production of frameworks and all-ceramic restorations.[2] This is a tremendous advantage with regard to the increase in price of noble-based alloys. However, there is low evidence of stability of restorations fixed on implants regarding the abutment configuration, which is the interface between the prosthetic restoration and the implant. Especially in the posterior region, prefabricated abutments are used to fix the crowns on the implants. Such abutments are mostly available prefabricated from the manufacturers. Up to now, prefabricated abutments mostly exhibit sharp edges and no information is available regarding the influence of these edged design abutments on the stability of the crowns. Thus the null hypothesis was that edged and rounded abutment designs result in no significant differences with regard to the stability of the implant crowns.


  Subjects and Methods Top


The implant abutments (No. 57120; Bego Implant Systems, Bremen, Germany) were screwed onto implant laboratory analogs (No. 56696; Bego Implant Systems) using a torque handle (No. 55799; Bego Implant Systems) with 30 Ncm.

Fifteen prefabricated abutments were used without any modification regarding their form for this study (Configuration A). Fifteen abutments were shortened 2 mm and a ball-headwax-up was made and casted using base metal alloy. This component was fixed on the shortened abutment using RelyX Unicem, thus distributing the load across broad surfaces rather than confining it to the edge of the abutment (Configuration B) [Figure 1]a and [Figure 1]b.
Figure 1 a,b: Different type of abutment configurations

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A total of 240 mandibular right first premolar crowns were made of each CAD/CAM material (Vita Mark II, Ivoclar Empress CAD, Ivoclar e. max CAD, Lava Ultimate, artBloc Temp Merz Dental, Telio CAD, and Vita CAD Temp) using a CAD/CAM system (Cerec inLab ver. 4.1; MCXL, Sirona, Bensheim, Germany, 30-µm cement space, 0-µm spacer). The exterior surfaces of the implant abutments were sandblasted (50 µm, ~10 mm distance, 2 bar) degreased, and silanized with MonobondPfor 1 60s (Ivoclar Vivadent Clinical). The inner surfaces of the crowns were etched with hydrofluoric acid or sandblasted and silanized with Monobond S as defined by the manufacturer. After fixation of the crowns on the two different abutment configurations using RelyX Unicem, the crowns were mounted in distilled water until the ceramic and the polymer microstructure was fractured using a Zwick universal testing machine.


  Results Top


The results of the two different abutment configurations [Figure 1] are shown in [Figure 2] as box-and-whisker plots and in [Table 1]. There are significant differences between the abutment configurations in fracture strength using the all-ceramic crown materials. However, no significant differences were found using the CAD/CAM-fabricated crowns made of polymers [Table 2].
Figure 2: Box-and-whisker plot diagram of the fracture strength yielded by the distraction trial

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Table 1: P values for comparison (ANOVA and Bonferroni adjustment) of the mean fracture strength of the different configurations

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Table 2: Mean fracture load (N) of the CAD/CAM materials with different abutment configurations

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  Discussion Top


This study has evaluated the influence of the abutment design on the fracture strength of CAD/CAM-fabricated monolithic all-ceramic and polymer crowns. The fracture strength showed significant higher values for the all-ceramic crowns using a rounded top on the abutment. Thus it is obvious, that fracture strength of all-ceramics is significant influenced by the design of the abutment in occlusal part. Especially the edges and rims are failure indication of all-ceramic crowns regarding occlusal force. This is in concordance with Zhang et al., who showed that ceramic materials are often broke over sharp edges.[3]

The mechanical characterization of the ceramics could be an explanation, why the rounded surface of the abutment absorbs more force than the edged abutments.[4] The edge of the abutment ensures tensile stress in the all-ceramic crown surface, which induces a crack into the crown. The CAD/CAM-fabricated polymers absorb this tensile stress more than the ceramics, so the abutment design did not have the effect as indicated with the all-ceramic crowns. These findings are confirmed to the observance of Stawarczyk et al., that CAD/CAM-fabricated polymers were not as strongly affected as all-ceramics of the abutment design, because they are more resilient.[5]

Within the limitations of this in vitro study, the following conclusions can be drawn:

  1. The fracture strength of CAD/CAM-fabricated all-ceramic crowns could be increased using a rounded abutment up to 1.6 times.
  2. The fracture strength of CAD/CAM-fabricated polymers could not be enhanced using a ball-head abutment.


 
  References Top

1.
Fischer H, Marx R. Fracture toughness of dental ceramics: Comparison of bending and indentation method. Dent Mater 2002;18:12-9.  Back to cited text no. 1
    
2.
Poss S. CAD/CAM restorations: Aesthetic all-ceramics, predictable fit. Dent Today 2007;26:86, 88.  Back to cited text no. 2
    
3.
Zhang Y, Lee JJ, Srikanth R, Lawn BR. Edge chipping and flexural resistance of monolithic ceramics. Dent Mater 2013;29:1201-8.  Back to cited text no. 3
    
4.
Quinn GD. On edge chipping testing and some personal perspectives on the state of the art of mechanical testing. Dent Mater 2015;31:26-36.  Back to cited text no. 4
    
5.
Stawarczyk B, Ender A, Trottmann A, Ozcan M, Fischer J, Hammerle CH. Load-bearing capacity of CAD/CAM milled polymeric three-unit fixed dental prostheses: Effect of aging regimens. Clin Oral Investig 2012;16:1669-77.  Back to cited text no. 5
    


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2]



 

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Abstract
Introduction
Subjects and Methods
Results
Discussion
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