Year : 2010 | Volume
: 21 | Issue : 1 | Page : 68--71
In vitro comparative analysis of resistance to compression of laboratory resin composites and a ceramic system
Alexandre Campos Montenegro1, Cintia Fernandes do Couto2, Paulo Roberto Rezende Ventura3, Cresus Vinicius Depes Gouvea4, Aldir Nascimento Machado5,
1 Professor of Prosthodontics of Brazilian Navy, Niterói, Brazil
2 Universidade Federal Fluminense (UFF), Niterói, Brazil
3 Universidade Federal Fluminense (UFF), Especialist in Prosthodontics-Associação Brasileira de Odontologia, Rio de Janeiro, Brazil
4 Department of Prosthodontics, Universidade Federal Fluminense (UFF), Niterói, Brazil
5 Department of Implantology, Associação Brasileira de Odontologia, Niterói, Brazil
Alexandre Campos Montenegro
Professor of Prosthodontics of Brazilian Navy, Niterói
Background: Restorative materials must be capable not only of restoring the patient«SQ»s masticatory function, but also to rescue the self-esteem of those maculated by a disharmonious smile. Among the esthetic materials available on the market, the choice frequently lies between ceramic or indirect laboratory resin restorations.
Aim: This study assessed the resistance to compression of two laboratory resins found on the market, namely Artglass® and Targis® , considering Omega 900® ceramic from Vita as control.
Materials and Methods: With the aid of stainless steel matrices, with internal dimensions of 8.0 mm diameter at the base, 9.0 mm in the top portion and 4.0 mm height, 15 test specimens were made, being 5 of each material to be tested. The test specimens were kept in distilled water for 72 hours and submitted to an axial load by the action of a point with a rounded tip 2 mm in diameter, adapted to an EMIC 500 universal test machine. The compression speed was 0.5 mm/min, with a load cell capacity of 200 Kgf.
Results: The means of the results were calculated in kilogram-force (Kgf). The results found were treated by analysis of variance (ANOVA) and the differences found among the groups were identified by the Tukey test (5%).
Conclusion: It was observed that the material Omega 900® offered significantly greater resistance to compression than the other two materials, which did not present statistically significant difference between them.
|How to cite this article:|
Montenegro AC, do Couto CF, Ventura PR, Gouvea CV, Machado AN. In vitro comparative analysis of resistance to compression of laboratory resin composites and a ceramic system.Indian J Dent Res 2010;21:68-71
|How to cite this URL:|
Montenegro AC, do Couto CF, Ventura PR, Gouvea CV, Machado AN. In vitro comparative analysis of resistance to compression of laboratory resin composites and a ceramic system. Indian J Dent Res [serial online] 2010 [cited 2021 Mar 7 ];21:68-71
Available from: https://www.ijdr.in/text.asp?2010/21/1/68/62811
The search for an esthetic material, which could be used as dental restorative material, goes back a long way. Before the advent of restorative materials, artificial teeth were made from extracted human teeth, animal teeth, and ivory. 
The use of ceramics in dentistry for making complete dentures began in the 18 th century. Throughout the passage of time, this material has deserved attention and occupied an outstanding place, since hardly any other material was able to reproduce the beauty and naturalness of teeth, as ceramics did. 
Recently introduced to the market, laboratory resin composites appeared to minimize the problems inherent to resin composites for direct use, such as polymerization shrinkage and technical sensitivity.  In his work, Lacy  affirmed that in spite of the excellent mechanical and optical properties, the application of this system for reconstructing posterior teeth was limited to small cavities.
With the incorporation of multifunctional glass and methacrylate particles into resin composites, there was an improvement in the physical and mechanical properties of these materials.  Denominated by manufacturers as glass polymers or ceromers,  these materials compete with dental ceramics today.
Restorative material must have optic characteristics that enable ideal esthetic reproduction, high flexural and fracture strength, low heat and electrical conductivity, biocompatibility, good wear resistance, minimal abrasiveness to antagonist teeth, and be easy to fabricate and repair. 
Thus, for restorative procedures without metal support structures, one now has the option of two basic systems for indirect use: Laboratory composite resins and ceramics.
Therefore, investigative analyses in vitro of the mechanical properties of restorative materials are opportune, to aid the choice of the type of restoration to be used in each clinical case. This research was designed with the object of assessing and comparing the resistance to compression between a feldspathic ceramic and two laboratory resin composites available in the market.
Materials and Methods
To conduct this research, two different commercial brands of laboratory resin composites available in the market were used, namely Artglass® (Heraeus-Kulzer) and Targis® (Ivoclar). As control group, the feldspathic ceramic system Vita Omega 900® (Wilcos do Brasil, Industria e Comercio Ltda) was used. With the aid of five segmented cone-shaped stainless steel moulds, with internal dimensions of 8.0 mm diameter at the base, 9.0 mm in the top portion and 4.0 mm height, 15 test specimens were made, five of each material was tested. With the smallest mould diameter supported on a smooth and polished glass slide of 4 mm thickness, the indirect resin was placed inside the mould, taking care to avoid trapped bubbles. After the resins were inserted, a second glass slide of the same thickness was used to cover the moulds. On the mould/material set, interposed between the two glass slides, a force of 0.5 Kgf was applied for 60 seconds to accommodate the material and promote the standardized surface smoothness of all the samples.
The glass slab was removed for initial composite polymerization (Demetron LC Curing Light, Kerr's) for 30 seconds, in both surfaces, with light intensity of 600 mW/ cm 2 . After this step, the specimen received additional polymerization according to the composite system. Targis® specimens were coated with glycerin gel (Targis Gel) to prevent formation of oxygen-inhibited surface layer and were placed in the curing unit Targis Power (Ivoclar Vivadent). Artglass® specimens were placed inside the stroboscopic light unit UniXs (Heraeus-Kulzer) for 180 seconds. After that, the indirect composite resin disks were removed from their respective moulds.
To fabricate the porcelain test specimens, an addition silicone mould was used, which also had a segmented cone-shape and the same dimensions as those used to fabricate the resin test specimens. After being made, the ceramic samples were placed in a Vita® oven to undergo pre-drying at an initial temperature of 6008C for 6 minutes, and a final temperature of 910°C for 1 minute. It is important to emphasize that the casting process generates ceramic material shrinkage. It was, therefore, necessary to rebase the ceramic test specimens until they reached the proposed standardized dimensions. The test specimens were stored in deionized water, in dry heat, at a constant temperature of 37°C, for 72 hours. All the test specimens were submitted to the fracture test with an axial load in an EMIC DLMF500 universal mechanical test machine [Figure 1]. To perform the tests, a point with a rounded tip 2 mm in diameter-an accessory of the above-mentioned machine-was used.
On the samples of each material, a label was placed on the face with the biggest diameter, to identify the samples by numbering them from 1 to 15, and marking them with the initial of each tested resin. The identifications were as follows: NO 1A to 5A, for the samples obtained with Artglass® , No. 1T to 5T for the samples of Targis® , and 1O to 5O for the Omega 900 ceramic samples.
The speed was 0.5 mm/min, with a load cell capacity of 200 Kgf. The load and the fracture point were recorded in the software of the machine.
After the experiments, the results found in the maximum compression tests were recorded in Kgf and are represented in mean values in [Table 1].
The results obtained were submitted to ANOVA that showed significant difference among the experimental groups (P , Nevertheless, there are still limitations, such as technique sensitivity, high cost, and when compared with laboratory resin composites, they are not as effectively repaired. 
The development of new esthetic restorative materials, such as laboratory resin composites, favored other viable treatment options. According to Koczarski,  these materials are microhybrid resins with a large quantity of ceramic particles, which have a positive influence on their mechanical properties. The laboratory resins existent on the market had a larger quantity of inorganic components incorporated into their composition, improving their mechanical properties, allowing them to be used as an alternative to aesthetic dental prosthetic treatments, in which a larger masticatory load could be required.  The manufacturers of these new materials emphasize their esthetic characteristics and their physical-chemical properties similar to those of the dental structure. Morena et al.  pointed out the following advantages in comparison with ceramics: Easy fabrication, elasticity, and the capacity to absorb loads. Phillips,  however, related that fractures, abrasions and discoloring are significant problems in the clinical use of these materials.
It is relevant to mention that the indications for ceramic and laboratory resin restorations are similar. When selecting the type of restorative material, one must consider not only the patient's esthetic expectations, but also the biomechanical aspects of the restoration.
Fracture resistance is probably one of the most important characteristics, capable of influencing the durability of these restorations. The wide diversity existent among the different types of restorative materials indicates that the mechanical properties must be assessed before they are clinically applied. Although fracture strength by maximum compression is only one of the criteria for this selection, it is fundamental for clinical success.
Laboratory studies have allowed certain experimental conditions to be standardized and to obtain long-term results in a shorter period of time. Da Fonte et al.  studied the effect of restorative material storage in distilled water and concluded that there was no alteration in the resistance to compression.
Attia et al.  concluded that the mechanical load cycles are capable of compromising the resistance of pure ceramic and composite resin restorations.
In this experiment, the test specimens were not submitted to any type of treatment before the maximum compression tests. These tests were performed in an EMIC DLMF500 universal mechanical test machine. The test consisted of application of an axial load (in Kgf) in the center of the test specimen until the point of fracture. The ceramic material Omega 900® presented the highest fracture resistance values (312.9 Kgf), whereas the laboratory resins Artglass® and Targis® recorded the lowest fracture resistance capacity (223.5 and 204.1 Kgf respectively).
The laboratory resin fracture strength values did not differ statistically between them, as was shown by the Tukey test (P # 0.05). It was possible to observe that the fracture strength value of the Omega 900® ceramic was statistically higher than those of the other materials.
Laboratory resins are correctly indicated for single crowns.  Loose et al.,  however, observed that these polymers can be used in fixed partial dentures of three elements, and that after thermal and mechanical cycles, they presented a higher fracture strength than similar dentures made of In-ceram. It has been stated that fiber reinforcement could improve the performance of these polymers,  but Behr  found that for single crowns, these fibers are incapable of increasing resistance to fracture. Ceramic restorations present high resistance to compression,  but laboratory resins are also capable of resisting masticatory forces. 
The success of new materials is determined only by their clinical longevity. Ku et al.  added that the long-term performance of these materials cannot be determined only by in vitro fracture strength tests.
As modern technologies and continuous research make available new and better materials for dental restorations, the possibilities of combinations among these materials and restorative techniques multiply, as a result of an increasingly demanding market. In this context, it is always opportune to conduct further scientific investigations, with a view to complementing existent knowledge about their biomechanical behaviors, familiarizing professionals with experiments, pointing out alternatives, and reducing clinical failures.
Based on the literature consulted and results obtained with the methodology applied, it was possible to conclude that:
The material Ceramico Omega 900® ceramic produced a statistically higher resistance to fracture value than the other two materials, when submitted to the maximum compression test;The laboratory resins Artglass® and Targis® presented statistically similar values of resistance to maximum compression.
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