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SHORT COMMUNICATION  
Year : 2019  |  Volume : 30  |  Issue : 1  |  Page : 127-129
CAD/CAM system influence marginal fit of different ceramic types?


1 School of Dentistry, Graduate Program of Dentistry, University of Western São Paulo, Presidente Prudente, Brazil
2 School of Dentistry, Postgraduate Program of Dentistry, University of Western São Paulo, Presidente Prudente, Brazil
3 School of Dentistry, Graduate Program of Dentistry; School of Dentistry, Postgraduate Program of Dentistry, University of Western São Paulo, Presidente Prudente, Brazil

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Date of Web Publication20-Mar-2019
 

   Abstract 

Objective: This study aimed to evaluate the marginal fit of zirconia and lithium disilicate ceramic restorations processed by computer-aided design (CAD)/computer-aided manufacturing (CAM) system. Materials and Methods: Ten models were prepared from a metal die, on which scanning was carried out to obtain the virtual model for the processing of zirconia and lithium disilicate ceramics using the CAD/CAM technique. Gypsum models were fabricated and used for scanning the restorations. The infrastructures were designed using software, and CAD/CAM was used to fabricate the restorations (n = 10). The analysis of the marginal discrepancy was measured at 12 points of the margin using the original metallic die. For each crown, an arithmetic average of the discrepancy values was obtained. Results: The marginal fit of the copings of lithium disilicate was 133.10 ± 26.87 μm and zirconia was 127.34 ± 47.97 μm. There was no statistically significant difference (P = 0.7709) between the materials. Conclusion: The marginal fit is similar between lithium disilicate and zirconia ceramics milled in the CAD/CAM system used.

Keywords: Ceramics, dental crown, dental materials

How to cite this article:
de Almeida IG, Antunes DB, Braun NX, Restani A, Straioto FG, Galhano GA. CAD/CAM system influence marginal fit of different ceramic types?. Indian J Dent Res 2019;30:127-9

How to cite this URL:
de Almeida IG, Antunes DB, Braun NX, Restani A, Straioto FG, Galhano GA. CAD/CAM system influence marginal fit of different ceramic types?. Indian J Dent Res [serial online] 2019 [cited 2019 Oct 22];30:127-9. Available from: http://www.ijdr.in/text.asp?2019/30/1/127/254530

   Introduction Top


Ceramics were developed to eliminate metallic infrastructures to improve distribution of light reflection, for better aesthetics.[1] These systems can be manufactured in layers, composed of a ceramic infrastructure and cover ceramic or in a single layer (monolithic crowns).[2],[3]

The second generation of lithium disilicate (IPS e.max/Ivoclar Vivadent, Schaan, Liechtenstein) ceramics comprised smaller and homogeneous crystals. These characteristics improve properties such as fracture toughness and flexural strength, which allowed the preparation of posterior monolithic fixed prostheses.[4] Another advantage of this system was the introduction of these types of ceramics in computerized processing [computer-aided design (CAD)/computer-aided manufacturing (CAM)] technology.[5]

CAD/CAM technology manages the design of a prosthetic structure in a computer (CAD) followed by its creation using a computer machine (CAM). The main objectives of this technology are to automate a manual process to obtain a high-quality restoration, standardize manufacturing processes, and reduce production costs.[6]

The zirconia ceramics are only manufactured using CAD/CAM technology,[7] notable for their physical, mechanical, biological, and chemical properties.[6] This material comes in two forms: (1) completely synthesized (hard) zirconia, which takes a long time to work and quickly depletes the milling burs, and (2) partially synthesized zirconia (soft zirconia), which allows for easier and faster processing.

Since zirconia must be baked in a kiln after being milled by the CAD/CAM system, the contraction from baking must be compensated for at the time of milling.[8] Alternatively, lithium disilicate does not contract when submitted to crystallization after milling. Thus, it is important to determine whether the marginal adaptation of single prostheses made using these two materials is similar, even considering the contraction of zirconia after sintering. This study aimed to evaluate the marginal fit of zirconia and lithium disilicate ceramic restorations processed by a CAD/CAM system.


   Materials and Methods Top


Fabrication and reproduction of metal die

A standard metallic die was machined from a stainless steel metal bar, simulating a single unit crown with smooth axial walls, having 3° of convergence on each axial side [Figure 1], as described by Souza.[9]
Figure 1: Standard metallic die used to simulate a single unit crown preparation

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The molds (n = 10) were used to obtain 10 plaster casts of Type IV gypsum (Elite Rock Thixotropic; Zhermack SpA, Rovigo, Italy), which were used to obtain the virtual casts to process 10 lithium disilicate (e.max; Ivoclar) and 10 zirconia crowns using the CAD/CAM technique.

Scanning and copying

The dimensions of the models were scanned using inEos optical system (CEREC, Sirona Dental Systems GmbH, Bensheim, Germany). The margins were delimited in the software, and the infrastructure was designed [Figure 2]. After data acquisition, the scans were transferred to the software (CEREC, Sirona).
Figure 2: Image result of the scanned process using the inEos optical system with delimitation of the preparation margins

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The infrastructures were designed on 10 restorations that were customized with a thickness of 0.6 mm. The prototypes were transferred to the CEREC mill (Sirona) [Figure 3] and the structures were milled using specific drills of each ceramic system. After milling, the lithium disilicate and zirconia specimens were baked/sintered (Programat; Ivoclar) following the manufacturer's recommendations.
Figure 3: Image of infrastructure design obtained that milled in lithium disilicate and zirconia

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Analysis of the vertical marginal fit

All measurements were performed by a single operator. The vertical marginal fit analysis was performed with the copings positioned on the metallic restoration under a constant force throughout the measurement process. The device allowed the rotation of the coping by 360° for reading the margin at the 12 previously marked points, and an arithmetic average was calculated using these values to obtain a single average value for each crown.

The data were submitted to statistical analysis, at a significance level of 5%. The experimental variable analyzed was the marginal adaptation of the lithium disilicate and zirconia ceramic crowns fabricated using the CAD/CAM technique. The statistical analysis was performed using Student's T-test.


   Results Top


There was no statistically significant difference in the marginal adaptation of the lithium disilicate (133.10 ± 26.87 μm) and zirconia (127.34 ± 47.97 μm) copings [Table 1]. The value of P for comparison of the type of packing material X adaptation (P = 0.7709).
Table 1: Result of (medium±standard deviations) analysis of marginal fit (μm) (n=10) of lithium disilicate and zirconia ceramics

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   Discussion Top


The null hypothesis was accepted, because there was no statistical difference in the marginal fit of lithium disilicate and zirconia crowns. There were no studies in the literature that evaluated these materials in vitro using the CEREC system.

The study evaluated in vitro zirconia crowns manufactured using CAD/CAM with the Zirkonzahn system, and disilicate crowns were made using the injection technique. The results were lithium disilicate showed lower values of marginal adaptation.[10]

Two materials analyzed were manufactured using the CAD/CAM system and the marginal adaptation values varied between 113 μm for lithium disilicate and 68.5 μm for zirconia. However, the restorations were milled using different systems, the lithium disilicate was milled using the ED4 system, and the zirconia was fabricated in a milling plant.[11]

The marginal fit of lithium disilicate was 133.10 μm and zirconia was 127.34 μm, which was considered clinically acceptable. Studies have suggested that a marginal fit less than 120 μm is clinically acceptable, and a scientifically significant marginal fit value for a crown has not yet been established.[12]

The marginal misfit of the ceramics causes retention of dental biofilm, caries, and bone resorption.[13] This limitation of CAD/CAM system ceramics could compensate with resin cements. Resin cements will promote a unique seal between ceramics, enamel, and dentin, thus increasing the ceramic strength and their superior mechanical and aesthetic properties.[13]

The present results indicate that the CAD/CAM system still does not present standardized values of marginal discrepancy. They are dependent on the quality of the preparation, the type of scan and system used, and operator dexterity. Although manufacturing a prosthetic device using a computerized system can minimize the number of errors, the final quality still depends on the preparation of the restoration.


   Conclusion Top


The marginal fit is similar between lithium disilicate and zirconia ceramics milled in the CAD/CAM system used.

Financial support and sponsorship

This work was funded by FAPESP through scientific initiation grants by the process 2014/18721-9.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
Brunot-Gohin C, Duval JL, Verbeke S, Belanger K, Pezron I, Kugel G, et al. Biocompatibility study of lithium disilicate and zirconium oxide ceramics for esthetic dental abutments. J Periodontal Implant Sci 2016;46:362-71.  Back to cited text no. 1
    
2.
Zhang Y, Lee JJW, Srikanth R, Lawn BR. Edge chipping and flexural resistance of monolithic ceramics. Dent Mater [Internet] 2013;29:1201-8.  Back to cited text no. 2
    
3.
Kocaaǧaoǧlu HH, Gürbulak A. An assessment of shear bond strength between ceramic repair systems and different ceramic infrastructures. Scanning [Internet] 2015;37:300-5.  Back to cited text no. 3
    
4.
Kern M, Sasse M, Wolfart S. Ten-year outcome of three-unit fixed dental prostheses made from monolithic lithium disilicate ceramic. J Am Dent Assoc [Internet] 2012;143:234-40.  Back to cited text no. 4
    
5.
Chaar MS, Passia N, Kern M. Ten-year clinical outcome of three-unit posterior FDPs made from a glass-infiltrated zirconia reinforced alumina ceramic (In-Ceram Zirconia). J Dent [Internet] 2015;43:512-7.  Back to cited text no. 5
    
6.
Guess PC, Att W, Strub JR. Zirconia in fixed implant prosthodontics. Clin Implant Dent Relat Res 2012;14:633-45.  Back to cited text no. 6
    
7.
Zaher AM, Hochstedler JL, Rueggeberg FA, Kee EL. Shear bond strength of zirconia-based ceramics veneered with 2 different techniques. J Prosthet Dent [Internet] 2017;1-7.  Back to cited text no. 7
    
8.
Sadaqah NR. Ceramic laminate veneers: Materials advances and selection. Open J Stomatol 2014;4:268-79.  Back to cited text no. 8
    
9.
Souza ROA. Evaluation of the vertical and internal marginal discrepancies of total ceramic crowns made by a CAD/CAM system, varying the cervical term [dissertation]. São José dos Campos; 2007.  Back to cited text no. 9
    
10.
Ji MK, Park JH, Park SW, Yun KD, Oh GJ, Lim HP. Evaluation of marginal fit of 2 CAD-CAM anatomic contour zirconia crown systems and lithium disilicate glass-ceramic crown. J Adv Prosthodont [Internet] 2015;7:271-7.  Back to cited text no. 10
    
11.
Batson ER, Cooper LF, Duqum I, Mendonça G. Clinical outcomes of three different crown systems with CAD/CAM technology. J Prosthet Dent [Internet] 2014;112:770-7.  Back to cited text no. 11
    
12.
Sakornwimon N, Leevailoj C. Clinical marginal fit of zirconia crowns and patients' preferences for impression techniques using intraoral digital scanner versus polyvinyl siloxane material. J Prosthet Dent [Internet] 2017;1-6.  Back to cited text no. 12
    
13.
Ribeiro ILA, Campos F, Sousa RS, Alves MLL, Rodrigues DM, Souza ROA, et al. Marginal and internal discrepancies of zirconia copings: Effects of milling system and finish line design. Indian J Dent Res 2015;26:15-20.  Back to cited text no. 13
    

Top
Correspondence Address:
Dr. Andressa Restani
Rua Dr. Arthur Falcone, 796 – Centro, Presidente Bernardes/São Paulo 19300-000
Brazil
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijdr.IJDR_77_18

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