Microleakage and Resin-to-Dentin Interface Morphology of Pre-Etching versus Self-Etching Adhesive Systems

The purpose of this study was to compare the microleakage and tissue-adhesive interface morphology from Class V restorations using different systems of dentin adhesives. Class V cavities were prepared on buccal surfaces of 27 extracted caries-free molars and premolars. Teeth were randomly assigned to one of three groups: (1) Prime & Bond NT, a 5th generation system using an initial step of total etch followed by a second step of application of a self bonding primer (2) Clearfil SE Bond, a 5th generation adhesive system employing two separate steps of self-etch priming and subsequent bonding (3) One-up Bond F, a 6th generation one step self-etching, self-priming and self-bonding adhesive. Microleakage and interface morphology of teeth restored with these adhesives and a composite resin were evaluated. Kruskal-Wallis Test (p = 0.05) was used to analyze the results. SEM analysis was used to relate interface morphology to microleakage. The mean and (SD) values of microleakage were: Prime and Bond NT: 0.15 (0.33), Clearfil SE Bond: 0.06 (0.17) and One-up Bond F: 2.96 (0.63). The mean microleakage for One-up Bond was significantly higher than for the other groups (p<0.05). Protruding tags in dentin channels were observed in Prime and Bond and Clearfil systems, but not in One-up Bond. The single step adhesive system, although more convenient for the clinician, uses a low viscosity formulation difficult to keep in place on cavity walls. It also tends to be too aggressive and hydrophilic to create an impermeable hybridized tissue-adhesive interfacial layer resistant to microleakage. Two-step adhesive systems, on the other hand, were retained on all segments of the cavosurface during application, and formed a hybridized interfacial layer resistant to microleakage

Hard-Object Feeding in Sooty Mangabeys (Cercocebus atys) and Interpretation of Early Hominin Feeding Ecology

Morphology of the dentofacial complex of early hominins has figured prominently in the inference of their dietary adaptations. Recent theoretical analysis of craniofacial morphology of Australopithecus africanus proposes that skull form in this taxon represents adaptation to feeding on large, hard objects. A modern analog for this specific dietary specialization is provided by the West African sooty mangabey, Cercocebus atys. This species habitually feeds on the large, exceptionally hard nuts of Sacoglottis gabonensis, stereotypically crushing the seed casings using their premolars and molars. This type of behavior has been inferred for A. africanus based on mathematical stress analysis and aspects of dental wear and morphology. While postcanine megadontia, premolar enlargement and thick molar enamel characterize both A. africanus and C. atys, these features are not universally associated with durophagy among living anthropoids. Occlusal microwear analysis reveals complex microwear textures in C. atys unlike those observed in A. africanus, but more closely resembling textures observed in Paranthropus robustus. Since sooty mangabeys process hard objects in a manner similar to that proposed for A. africanus, yet do so without the craniofacial buttressing characteristic of this hominin, it follows that derived features of the australopith skull are sufficient but not necessary for the consumption of large, hard objects. The adaptive significance of australopith craniofacial morphology may instead be related to the toughness, rather than the hardness, of ingested foods

Influence of method and period of storage on the microtensile bond strength of indirect composite resin restorations to dentine

This study evaluated the influence of the method and period of storage on the adhesive bond strength of indirect composite resin to bovine dentin. Ninety bovine incisors were stored in three different solutions: 0.2% thymol, 10% formalin, and 0.2% sodium azide, during 3 periods of storage: 7 days, 30 days and 6 months, resulting in 9 groups (n = 10). The roots were cut off and the buccal surface was ground with #600-grit silicon carbide paper. The surface was conditioned with 37% phosphoric acid for 15 s and a composite resin restoration (TPH Spectrum) was fixed using a one-bottle adhesive system (Adper Single Bond) and a dual-cured resinous cement (Rely X ARC) under a load of 500 g for 5 minutes. The samples were serially cut perpendicular to the bonded interface to obtain slices of 1.2 mm in thickness. Each slab was trimmed with a cylindrical diamond bur resulting in an hourglass shape with a cross-sectional area of approximately 1 mm². The microtensile bond strength (&#956;TBS) testing was performed in a testing machine (EMIC 2000 DL) at a 0.5 mm/minute crosshead-speed until failure. After fracture, the specimens were examined under SEM to analyze the mode of fracture. &#956;TBS Means were expressed in MPa and the data were analyzed by two-way ANOVA (3X3) and the Tukey test (&#945; = 0.05). The storage times of 7 and 30 days produced no significant difference irrespective of the solution type. The formalin and thymol solutions, however, did have a negative influence on bond strength when the teeth were stored for 6 months