30-Month randomised clinical trial to evaluate the clinical performance of a nanofill and a nanohybrid composite
Introduction
Aesthetic considerations are playing a greater role in the treatment planning of dental care, even in the restoration of posterior teeth, stimulated by the popularity of aesthetics, patient demands for nonmetallic restorations and the controversy about the systemic and environmental effects of dental amalgam.1, 2 In addition, the minimally invasive approach is increasingly being emphasised in the dental literature.3 Those facts have stimulated the development of adhesive techniques.4 Adhesive dentistry became possible after the introduction of etching enamel with acid,5 the advent of resin composites,6 and the formation of the hybrid layer with adhesive systems first described by Nakabayashi et al.7
However, many changes have taken place in adhesive systems and restorative materials. One significant change was the introduction of the first restorative nanocomposite resin for dentistry. Nanotechnology, also known as molecular nanotechnology or molecular engineering, is the production of functional materials and structures in the range of 0.1–100 nm (the nanoscale) by various physical or chemical methods.8 Nanocomposites contain a unique combination of two types of nanofillers (5–75 nm) and nanoclusters. Nanoparticles are discrete non-agglomerated and non-aggregated particles, 20–75 nm in size. Nanocluster fillers are loosely bound agglomerates of nano-sized particles. The agglomerates act as a single unit enabling high-filler loading and high strength. As a result of the reduced dimensions of the particles and wide size distribution, increased filler load can be achieved, leading to reduction polymerisation shrinkage and increase in the mechanical properties such as tensile strength and compressive strength to fracture. These properties of nanocomposites seem to be equivalent or sometimes even higher than hybrid composites and significantly higher than microfilled composites. As a consequence, manufacturers now recommend the use of nanocomposites for both anterior and posterior restorations.9, 10, 11, 12
In addition, there are composites on the market that combine nanoparticles with other micrometric particles, and these provide even better performance. These materials are considered the precursors of nanoparticle composites and are sometimes referred to as nanohybrids.9
Clinical trials are important to verify the performance of these composites under real conditions of use. This study evaluated the clinical performance of a nanofill, a nanohybrid, and as a control, a conventional microhybrid composite, in restorations in occlusal cavities of posterior teeth over 30 months. The null hypotheses to be tested were (1) there was no difference in the clinical performance amongst the 3 composites after 30 months, and (2) there was no difference in the clinical performance of the composites with the passage of time.
Section snippets
Materials and methods
This was a clinical study, under a controlled and randomised design and followed the guidelines published by Consolidated Standards of Reporting Trials (CONSORT).13, 14
This research was approved by the Research Ethics Committee of the Health Science Center (CEP: #1252) of the Federal University of Paraíba (Brazil). The volunteers and their guardians were consulted to obtain authorisation for their participation in the research, and for the researchers to use the results, by means of signing a
Results
The characteristics of the samples are shown in Table 3. After performing the statistical tests to verify the homogeneity of the sample, it was found that the distribution of the variables was homogeneous in the three groups (p > 0.05). There was no association amongst the variables; that is, the groups were in the same conditions as they were before the restorations were made.
After 30 months, 37 patients were re-evaluated. The results are shown in Table 4. When the four time periods (baseline, 6
Discussion
A nanofill (Filtek Z350) and a nanohybrid composite (Esthet-X) were used in this study; a microhybrid composite (Filtek Z250) was used as the control. These composites are currently available on the market, and their manufacturers present them for restoring anterior and posterior teeth.
Filtek Supreme (3 M ESPE, St. Paul, MN, USA) was the first nanocomposite on the market that contains nanometric particles (nanomers) and nanoclusters (NCs). Nanomers are monodispersed, non-agglomerated, and
Conclusions
The materials investigated showed acceptable clinical performance in Class I restorations after 30 months. Long-term re-evaluations are necessary for a more detailed analysis of these composites. Further long-term clinical trials are necessary to confirm our results.
Acknowledgements
The authors thank 3M ESPE and Dentsply/Calk for the kind donation of materials for this investigation. The authors do not have any financial interests in the companies whose materials are included in this article.
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Nanofilled/nanohybrid and hybrid resin-based composite in patients with direct restorations in posterior teeth: A systematic review and meta-analysis
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