Effect of filler particle size and nanoparticle addition on deformation rate dependence of experimental resin-based composites

The aim of this study was to determine the effect of filler particle size and nanoparticle addition on the bi-axial flexure strength [BFS] of the experimental resin-based composites [RBC] at varying deformation rates. In total, 9 RBC with different filler particle size and nanoparticle addition were investigated and for each RBC, 90 disc-shaped specimens [12 mm diameter, 1 mm thickness] were fabricated. All specimens were stored in distilled water at 37 +/- 1°C for one week prior to testing. The BFS of each RBC was determined at 0.1, 1.0, and 10.0 mm/min deformation rates [n = 30] in a universal testing machine. A general linear model [GLM] ANOVA highlighted a significant effect of deformation rate, filler particle size and nanoparticle addition on the BFS [P<0.001]. A general increase in BFS was identified with increasing deformation rate whereas a high volume percentage of nanoparticles and an increase in filler particle size led to a reduction in BFS. Two-way ANOVA revealed a significant effect of deformation rate [P<0.001] and nanoparticle addition [P<0.001] for BFS data sets for each RBC series with similar filler particle size. The deformation rate dependence of experimental RBC was not significantly affected by various combinations of filler particle size and nanoparticle addition

In vitro comparison of the apical microleakage of mineral trioxide aggregate [MTA] with amalgam as a retrograde filling material

The objective of this study was to compare apical microleakage of MTA with Amalgam following retrograde root filling. Experimental study. This study was conducted at the Department of Operative Dentistry, Fatima Jinnah Dental College and Hospital, Karachi March 2006-March 2007. One hundred twenty extracted human single rooted teeth were randomly assigned into four groups of 30 teeth each. The root canal filling carried out and retropreparations were cut in each root using round bur to a depth of 2-3 mm. Cavity varnish applied prior to retrofillings. Group I retrofilled with amalgam. In group II MTA was used, Group III served as negative control and group IV as a positive control. Roots were suspended in 2% methylene blue and placed into incubator at 37°C for 7 days. Teeth were split and chosen halve evaluated using a dissecting microscope at 10[x] magnification. The roots were evaluated and scored as either acceptable or unacceptable. The results showed that MTA displayed significantly less dye leakage than Amalgam. 24 samples [83%] out of 29 samples of MTA scored as acceptable, where as 4 specimens [16%] out of 28 samples of Amalgam showed acceptable score. MTA was found to be superior to Amalgam in providing apical seal when used as a root-end filling material. Favorable results were obtained with MTA in leakage study and it was concluded that MTA provided a better apical seal than Amalgam

Dental resin-based composites: a transition from macrofilled to nanofilled

The invention of dental resin based-composites [RBCs] has provided a broad range of materials for the restoration of load-bearing posterior teeth with excellent clinical results and adequate longevity. A variety of RBCs, namely "microhybrid", "nanohybrid" and "nanofilled" have been marketed with bold claims of a technological advancement. Although "microhybrid", "nanohybrid" and "nanofilled" RBCs have exhibited a degree of clinical and experimental success compared with their predecessors, however, it is difficult to justify which RBC is superior as a result of slight variations in filler size and associated interchangeable mechanical and physical properties of RBCs. The objective of the current review article is to highlight the development of various filler particles of dental RBCs and resultant variation in mechanical and physical properties which may ultimately provide directions for future research on the RBCs

Incidence of three canals in maxillary first premolar-a case report

This paper reports successful endodontic treatment of a maxillary first premolar with three canals. Maxillary premolars have highly variable root canal morphology, but it is rare, especially in the first premolar, to find three canals. However, in everyday endodontic practice, clinicians have to treat teeth with atypical configurations. Extra roots or root canals if not detected are a major reason for failure. Systematic examination of preoperative X-rays and correct access. Ni-Ti rotary instrumentation technique was chosen for root canal preparation, and Canals were obturated with gutta percha cones [Sure-Endo, Seoul, Korea] and Sealapex [Ken, Sybron, USA] root canal sealer using cold lateral condensation filling technique This methology led to efficient preparation and suitable definitive root canal obturation