Cutting efficiency of different diamond burs after repeated cuts and sterilization cycles in autoclave.

CONTEXT: The aim was to evaluate the cutting efficiency of different diamond burs after successive cuts and repeated sterilization in an autoclave. The morphology and grit sizes were analyzed and correlated to cutting efficiency. MATERIALS AND METHODS: Ten medium-grit diamond burs of five different manufacturers were investigated (KG, KG Sorensen; TH, Tri-Hawk; KM, Komet; HC, Heico; and FD, Frank Dental). Changes in the cutting efficiency of diamond burs on composite resin blocks were measured after five repeated cuts and after five sterilization cycles. Grit sizes were analyzed by scanning electron microscopy (SEM) and correlated to cutting efficiency. The data were statistically analyzed using 3-way ANOVA and Tukey's test (α = 0.05). RESULTS: Significant differences were observed for diamond burs (P < 0.0001) and condition (P < 0.0001). FD presented the lowest mean cut time (21.88s), followed by KM (36.08s). TH (40.18s), HC (41.65s), and KG (42.23s) had the highest cut times. The number of cuts was not statistically significant. New burs had a significantly shorter cutting time (33.38s) when compared with the ones after sterilization cycles (39.55s). A moderate to strong positive correlation was found between diamond size and cutting time (Pearson's coefficient of 0.77). CONCLUSION: All diamond burs demonstrated lower cutting efficiency after repeated autoclaving. Cutting efficiency did not decrease as the number of cuts increased.

Scanning of root canal impression for the fabrication of a resin CAD-CAM-customized post-and-core.

Customization of post-and-cores using computer-aided design and computer-aided manufacturing (CAD-CAM) requires the scanning of a pattern and the subsequent digital design. This technique describes a method of fabricating a CAD-CAM-customized post-and-core designed from a scanned polyvinyl siloxane impression and milled from a nanoparticle/nanocluster-filled resin block. The polyvinyl siloxane impression allowed a faster and more efficient customization of the CAD-CAM post-and-core than a conventional acrylic resin pattern. The properties of the nanoparticle/nanocluster filled resin block make the material suitable for chairside CAD-CAM post-and-core fabrication.

CAD/CAM post-and-core using different esthetic materials: Fracture resistance and bond strengths.

PURPOSE: To evaluate the fracture resistance (FR), and push-out bond strengths (BS) of custom-made CAD/CAM post-and-cores manufactured with different esthetic materials. METHODS: 90 single-rooted extracted teeth were selected, endodontically treated and prepared to receive the posts. The specimens were randomly divided into three equal groups according to the material: hybrid ceramic Vita Enamic (HC); nano-ceramic resin composite Lava Ultimate (RC); and experimental epoxy-resin reinforced by glass-fiber (FG). The post-and-cores were manufactured using CAD/CAM and cemented using a self-adhesive resin cement (Rely X Unicem2). A subgroup of 30 specimens (n=10) was subjected to fatigue (1,000,000 cycles at 5 Hz) and then to the FR test. Another subgroup with 60 specimens was submitted to the BS test, with and without fatigue. Data were submitted to analysis of variance (FR - one-way ANOVA; BS - two-way ANOVA) and Tukey's test (α= 0.05). RESULTS: The FR values (mean±SD, in Newtons) were 414.5±83.9 (HC), 621.3±100.3 (RC), and 407.6±109.0 (FG), with RC showing significantly higher FR values (P< 0.05). For BS, there was no statistically significant difference among the materials, with and without fatigue (P> 0.05). The type of material used to obtain the CAD/CAM-customized post-and-cores had a significant effect on the FR, but not on the BS of the specimens. Fatigue did not influence the BS for the tested materials. CLINICAL SIGNIFICANCE: CAD/CAM custom-made esthetic post-and-cores showed good performance relative to fracture resistance and bond strength to root canal dentin walls. The CAD/CAM materials tested could be used as an alternative to restore wide flared root canals in esthetically compromised teeth.