SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Dental composite

27

SUMMARY Aim: To determine the volumetric polymerization shrinkage of four different types of composite resin and to evaluate microleakage of these materials in class II (MOD) cavities with and without a resin-modified glass ionomer cement (RMGIC) liner, in vitro. Materials and Methods: One hundred twenty-eight extracted human upper premolar teeth were used. After the teeth were divided into eight groups (n=16), standardized MOD cavities were prepared. Then the teeth were restored with different resin composites (Filtek Supreme XT, Filtek P 60, Filtek Silorane, Filtek Z 250) with and without a RMGIC liner (Vitrebond). The restorations were finished and polished after 24 hours. Following thermocycling, the teeth were immersed in 0.5% basic fuchsin for 24 hours, then midsagitally sectioned in a mesiodistal plane and examined for microleakage using a stereomicroscope. The volumetric polymerization shrinkage of materials was measured using a video imaging device (Acuvol, Bisco, Inc). Data were statistically analyzed with Kruskal-Wallis and Mann-Whitney U-tests. Results: All teeth showed microleakage, but placement of RMGIC liner reduced microleakage. No statistically significant differences were found in microleakage between the teeth restored without RMGIC liner (p>0.05). Filtek Silorane showed significantly less volumetric polymerization shrinkage than the methacrylate-based composite resins (p<0.05). Conclusion: The use of RMGIC liner with both silorane- and methacrylate-based composite resin restorations resulted in reduced microleakage. The volumetric polymerization shrinkage was least with the silorane-based composite.

Concepts: Statistics, Statistical significance, Composite material, Teeth, Premolar, Dental composite, Glass ionomer cement, Resin

26

SUMMARY This clinical report describes a restorative technique used to replace two Class II resin composite restorations on the upper premolars. A sectional matrix band was used in conjunction with an elastic ring (Composi-Tight) to obtain tight proximal contact. A nanofilled resin composite (Filtek Supreme Ultra) was incrementally applied using oblique layers to reduce the C-factor, each layer being no more than 2 mm thick, and then light cured for 20 seconds with a light-emitting diode lamp (EliparFreeLight 2 LED Curing Light) with a power density of 660 mW/cm(2). A centripetal technique was used to restore the lost tooth structure from the periphery toward the center of the cavity in order to achieve a better contour and anatomy with less excess, thereby minimizing the use of rotary instruments during the finishing procedures. Finally, the resin composite restorations were finished and polished, and a surface sealer (Perma Seal) was applied to fill small gaps and defects that may have been present on the surfaces and margins of the restorations after the finishing and polishing procedures.

Concepts: Layer, Light-emitting diode, Lighting, Surface, Diode, LEd, Class II railroad, Dental composite

26

SUMMARY The purpose of this in vitro study was to compare the two-body wear resistance of human enamel, a pressable glass-ceramic (Imagine PressX), a type 3 gold alloy (Aurocast8), three resins composites currently available on the market (Enamel Plus HRi, Filtek Supreme XTE, Ceram.X duo), and one recently introduced resin composite (Enamel Plus HRi-Function). Resin composites were tested after simple light curing and after a further heat polymerization cycle. Ten cylindrical specimens (7 mm in diameter) were manufactured with each dental material according to standard laboratory procedures. Ten flat enamel specimens were obtained from freshly extracted human molars and included in the control group. All samples were subjected to a two-body wear test in a dual-axis chewing simulator over up to 120,000 loading cycles, against yttria stabilized tetragonal zirconia polycrystal cusps. Wear resistance was analyzed by measuring the vertical substance loss (mm) and the volume loss (mm(3)). Antagonist wear (mm) was also recorded. Data were statistically analyzed using one-way analysis of variance (ANOVA) (wear depth and volume loss) and Kruskal-Wallis one-way ANOVA on ranks (antagonist wear). Heat-cured HRi function and Aurocast8 showed similar mean values for wear depth and volumetric loss, and their results did not statistically differ in comparison with the human enamel.

Concepts: Statistical tests, Statistics, Variance, In vitro, Mean, Analysis of variance, Dental composite, One-way ANOVA

26

This study evaluated the mechanical, thermal, and morphological characteristics of different classifications of dental composites as a function of the material condition (new, aged and expired). Specimens were obtained according to these factors: Composites: Filtek P60, Filtek Z250, Filtek Z350XT, and Filtek Silorane; and Material conditions: new, aged, and expired. The syringe composites underwent an accelerated aging protocol (Arrhenius model). The flexural strength (FS) and flexural modulus (E) were obtained. The thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were also performed and the glass transition temperature (Tg) and the weight loss calculated. Topographic analysis of the composites was performed under SEM. The material conditions influenced the mechanical properties of the composites. The silorane composite exhibited a characteristic thermal behavior different from that of the methacrylates. In general, the Tg increased after the accelerated aging protocol and decreased for expired ones, compared to the new composites. A significant increase in FS of Filtek Z350XT after aging was accompanied by an increase in the Tg. The filler packings were in accordance with the manufacture׳s information. The topographic aspects of the composites were modified as a function of the material condition. The mechanical properties of the composites following a simplified protocol of accelerated aging varied as a function of the expiration date. The silorane composite presented a characteristic thermal behavior. Although the dental manufacturers may not be able to control variables as storage temperature and transportation conditions, these effects on the composite clinical performance can be minimized if properly considered.

Concepts: Thermodynamics, Materials science, Composite material, Differential scanning calorimetry, Glass, Glass transition, Dental composite, Thermal analysis

26

In this study, new dimethacrylate monomer SiMA without Bisphenol A (BPA) structure was synthesized and used as base resin of dental composite materials with the aim of reducing human exposure to BPA derivatives.

Concepts: Bisphenol A, Chemical synthesis, Materials science, Synthesis, Composite material, Epoxy, Dental composite, Composite materials

26

The ester linkages contained within dental resin monomers (such as Bisphenol A-glycidylmethacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA)) are susceptible to hydrolytic degradation by salivary esterases, however very little is known about the specific esterase activities implicated in this process. The objective of this work was to isolate and identify the dominant proteins from saliva that are associated with the esterase activities shown to be involved in the degradation of BisGMA.

Concepts: Protein, Saliva, Enzyme, Ester, Hydrolysis, Lipase, Dental composite, Hydrolase

26

The restoration of endodontically treated teeth involves a difficult decision-making process, especially when it comes to more complex prosthetic rehabilitations. Regarding singletooth restoration, there are high-level requirements for the restorative components and the application of all necessary treatment steps to achieve the final restoration. So when is there a need for a single-crown restoration or when might a composite resin restoration also be sufficient? For the assessment of endodontically treated teeth as abutment teeth for prosthetic restorations, there are no clear guidelines beyond single-tooth restorations. The aim of this article is to compile important aspects of the restoration of endodontically treated single teeth, including more complex prosthetic reconstructions, based on the scientific literature.

Concepts: Composite material, Crown, Dental composite, Composite materials

25

A concept is proposed for an approach to the learning of dental morphology and occlusion. Dental morphology, function, and esthetics should reflect a fundamental driving force, that is, the faithful emulation of the natural dentition’s structural (functional, mechanical) and esthetic properties. The innovative part of the proposed approach is the emphasis on visual arts and the 2D-3D-4D aspect that starts with drawing (2D/3D) and continues with partial wax-up exercises that are followed by labial waxups and, finally, full wax-ups using innovative technical aids (electric waxers, prefabricated wax patterns, etc). Finally, the concept of layers (4D) and the histoanatomy of enamel/dentin and optical depth are taught through the realization of layering exercises (advanced acrylic mock-ups and composite resin restorations). All these techniques and materials are not only used to teach morphology and occlusion, but also constitute essential tools that will be of significant use for the student dentists and dental technologists in their future daily practice. The clinical significance of the presented methodology should allow not only students but also practicing dentists and dental technologists to help their youngest collaborators to develop a deep sense of morphology, function, and esthetics.

Concepts: Education, Teeth, Tooth development, Art, Aesthetics, Dental composite, Fine art, Conceptual art

25

The use of composite restorations for patients with tooth wear is considered as a more conservative treatment option. The aim of this study was to systematically review the literature investigating the survival rates of anterior composite restorations when used in managing tooth wear in patients. PubMed and MEDLINE (Ovid) databases were screened for studies from 1995 to 2015. Cross-referencing was used to further identify articles. Article selection and data extraction were performed in duplication. Languages were restricted to English. A quality appraisal of included studies was carried out using the Strength of Recommendation Taxonomy system. Six hundred and sixty-six articles were initially identified from which eight articles were full-text reviewed. Six articles involving five studies were selected for inclusion. Three studies were prospective and two retrospective. Included studies involved placement of 772 direct and indirect anterior composite restorations in 100 patients with follow-up periods between 5 months and 10 years. The survival rates of anterior composites were >90% and 50% at 2¬∑5 and 5 years, respectively. Posterior occlusion was re-established in 91% of patients within 18 months. Meta-analysis could not be performed due to the heterogeneity of included studies. The systematic review’s overall strength of recommendation was graded B. There is evidence to support the use of anterior composite restorations at an increased vertical dimension of occlusion in the short/medium-term management of tooth wear. Long-term reporting of outcomes remains limited. Further research is needed with standardised study design, detailed reporting of outcomes and long-term review.

Concepts: Evidence-based medicine, Systematic review, Taxonomy, Composite material, Meta-analysis, PubMed, Dental composite, Composite video

22

Tooth wear in bruxing patients often results in a need for treatment with composite restorations. In some cases, bruxing patients receive an occlusal splint as a protective means as well. However, the wear between these opposing materials has not been investigated yet. The aim of this in-vitro study was to assess the wear of different splint materials against resin composite materials. A two-body wear test was conducted using the ACTA wear machine. The materials selected for this study were three composites used for direct restorations (Filtek Z250, CLEARFIL AP-X, and Filtek Supreme XT) and four occlusal splints materials, viz., a polyamide resin (ThermoSens) an conventional (hand-processed), milled, and printed polymethylmethacrylate (PMMA). As antagonistic materials, stainless steel, Filtek Supreme XT, and CLEARFIL AP-X were used. The wear rate of the seven materials was determined after 200,000 cycles, using a profilometry. The rates were analyzed using two-way ANOVA and post-hoc Tukey tests. The wear rates were significantly higher for the conventional and milled PMMA materials than for all other materials (p < 0.001). The wear rates of printed PMMA and the polyamide resin were comparable to composite wear rates. The antagonist materials have minor or no influence on the amount of wear of the various splint materials (p < 0.001). In conclusion, different splint materials yielded different wear rates for all antagonist materials tested. Keeping in mind that the present study is an experimental in vitro study, this finding enables practitioners to choose the splint material necessary according to their patients' needs. This article is protected by copyright. All rights reserved.

Concepts: In vitro, Composite material, All rights reserved, Boeing 787, Copyright, Dental composite, Aramid, Splints