OBJECTIVES: Dental wear is considered one of the reasons for composite restorations failure. Several clinical problems may arise as result of uncontrolled wear process, including compromising masticatory function, poor aesthetics, loss of interocclusal space, teeth pain and sensitivity, and tempromandibular problems. Newly released flowable composites have been introduced to the market, that are indicated for occlusal class I and II cavity restorations. The purposes of this study are (1) to evaluate the wear resistance of newly released flowable composites against two antagonists, and compare them to universal packable composite, (2) to compare the wear properties of the two different types of antagonists, (3) to evaluate mechanical and esthetic properties, including microhardness, gloss, and surface roughness, of all resin composites and correlate it to wear characteristics of the materials. MATERIALS AND METHODS: (1) Five flowable composites were used in this study: 1. Filtek Supreme Ultra Flow (3M ESPE), 2. NovaPro Flow (Nanova Biomaterials), 3. SureFil SDR Flow (Dentsply), 4. Clearfil Majesty Flow (Kuraray), and 5. G-aenial Universal Flo (GC). One universal resin composite (Filtek Supreme Ultra Universal) was used as control group. 16 Specimens were prepared from each composite by injecting into aluminum molds, then divided into two groups for two types of antagonists (n=8). The first antagonist from natural enamel cusps, the other type was from feldspar ceramic block, Vitabloc Mark II. Both were standardized and polished. After mounting the antagonists in the wear-testing machine, a uniform sliding abrasion was applied up to 200k sliding cycles. Then the measurement of dry weight, wear depth and surface roughness of the specimens and the antagonist cusps were conducted at 3 different intervals, baseline, 100k, and 200k cycles. The amount of wear was determined by measuring the weight loss and calculating volume loss. One representative sample was randomly selected from each group for scanning electron microscope examination of the surface morphology. (2) 3 samples were prepared from each resin composite material for the microhardness and gloss test. The composite specimens were finishing and polishing by Buehler grinding-polishing system for four minutes each, then rinsed and ultrasonically cleaned in distilled water for 4 minutes. The surface gloss test was performed by using Novo Curve glossmeter. Five gloss readings were taken from each specimen at different locations, and the mean value was calculated and recorded as the GU reading of each specimen. The Knoop’s microhardness was measured on a MICROMET 2003 microhardness tester. Five indentations at different locations with at least 100 μm apart were performed on each specimen. The five readings were averaged to produce a single hardness value for each specimen. RESULTS: (1) In general, statistical analysis revealed a significantly higher surface roughness and higher weight loss of all resin composites when opposed by ceramic antagonists compared to the samples opposed by enamel antagonists. Among the tested resin composites, there were significant differences in regards to specimen wear depth, weight loss, volume loss, and surface roughness, regardless of the antagonist type used. Both Filtek supreme universal and Filtek supreme ultra flow groups showed significantly deeper wear compared to the other flowable materials, regardless of the antagonist type used. Moreover, there were statistically significant differences in antagonist’s weight and height loss between the groups. The control group universal composite caused significantly higher weight and height loss of both antagonists. (2) The microhardness and gloss results demonstrated statistical significant differences between all the composite materials. Clearfil Majesty Flow and Filtek Supreme Universal groups exhibited a significantly higher surface gloss compared to the other materials with the exception of the Filtek Supreme Ultra Flow group. Filtek Supreme Universal group exhibited a significantly higher Knoop’s hardness compared to the other materials. CONCLUSIONS: Despite the limitation of this study, less weight loss and surface roughness of the flowable composites were shown when opposed by dental enamel antagonists. A significantly deeper wear was noticed on both Filtek supreme universal and flowable composites when opposed by ceramic antagonists, indicating the detrimental effect of the Feldspathic ceramic on the nanohybrid composites compared to the other nanofilled flowable composites used in the study.

L’odontologie conservatrice a connu une véritable révolution avec l’avènement de la dentisterie adhésive et le développement des résines composites associé au collage aux tissus dentaires. L’apparition il y a 20 ans des résines composites fluides a élargi encore les possibilités thérapeutiques des praticiens. La mise sur le marché d’un grand nombre de résines composites qui diffèrent par leur nature matricielle et par le type, la taille et la proportion des charges incorporées associée au manque d’informations des fabricants sur les compositions exactes de leurs produits empêchent les praticiens de réellement connaitre les caractéristiques des matériaux qu’ils utilisent. L’hyper-caractérisation in vitro desdits matériaux est une voie importante pour avancer dans la compréhension de leur comportement. Afin de juger de l’impact de la variation du taux de charges dans le comportement mécanique et physico-chimique des résines composites fluides, nous avons étudié deux groupes de matériaux : un premier groupe constitué de résines composites fluides expérimentales à matrice commune et à taux de charges variable et un deuxième groupe composé de résines composites fluides disponibles dans le commerce. Pour chacun de ces matériaux après la détermination du taux de charges par la méthode de la calcination, l’évaluation des caractéristiques rhéologiques (viscosité complexe et module de conservation), la mesure de la micro-dureté (micro-dureté Vickers), la contraction volumétrique de prise selon la méthode de la déflexion d’une lame de verre, l’analyse thermo-mécanique dynamique en flexion (module de conservation, module de perte, facteur d’amortissement) ainsi que les capacités d’absorption d’eau et de solubilisation (détermination par différentiel de gravimétrie après immersion dans différents milieux) sont autant de facteurs potentiellement influencés par ledit taux de charges qui ont été étudiés. Si le taux de charges devrait clairement faire partie des critères de choix du praticien tant il apparait influant sur les plans mécaniques et physico-chimiques, il apparait qu’un taux de charges élevé ne représente pas une garantie suffisante pour répondre de façon optimale au cahier des charges du matériau d’obturation idéal. L’emploi de résines composites fluides déformulées à taux de charges variable permet d’évaluer le rôle de la phase dispersée, pour autant, l’étude en parallèle de matériaux commerciaux met en lumière l’influence de la nature matricielle et des différentes entités monomériques entrant dans la structure polymère. / Conservative dentistry has undergone a genuine revolution, with the advent of adhesive dentistry and the development of resin composites combined with dental bonding. The emergence of flowable resin composites 20 years ago further expanded the treatment options open to dental practitioners. The appearance on the market of a large number of resin composites that differ in terms of their matrix type, along with the size and the proportion of the fillers incorporated, combined with a lack of information from manufacturers concerning the exact compositions of their products, means that practitioners do not really know all the characteristics of the materials they are using. In vitro hypercharacterization of these materials is an important approach to help us gain a better understanding of their properties. In order to assess the impact of variation of filler contents on the mechanical and physicochemical properties of flowable resin composites, we studied two groups of materials: a first group, composed of experimental flowable resin composites with the same matrix and a variable filler content, and a second group, composed of commercially available flowable resin composites. For each of these materials, after determination of the filler content using the calcination method, assessment of their rheological properties (complex viscosity and storage modulus), measurement of microhardness (Vickers microhardness), volumetric setting shrinkage using the glass slide deflection technique, dynamic thermo-mechanical analysis in flexure (storage modulus, loss modulus, damping factor), along with the water absorption and dissolution capacities (determination by thermal gravimetry differential following immersion in different media) are all factors potentially influenced by the said filler contents studied. While the filler content should clearly be one of the decision-making criteria used by practitioners given the influence it seems to have on both mechanical and physicochemical properties, it nonetheless appears that a high filler content is not, in itself, a sufficient guarantee that the material meets the optimum specifications for an ideal filling material. The use of deformulated flowable composite resins with a variable filler content makes it possible to assess the role of the dispersed phase. However, a parallel study of commercially available materials highlights the influence of the matrix type and the various monomeric entities included in the polymer structure.