The objective of this laboratory study was to compare root-end cavities prepared with sonic Retro-prep tips in a MM1500 Sonic Air handpiece with those created by burs in a conventional handpiece. A total of 80 single-rooted extracted human teeth with mature apices and straight canals were included in the study. Four groups of 20 extracted teeth were prepared as follows: I, a 3-4 mm root-end resection perpendicular to the long axis of the root, with a size 40 sonic Retro-prep tip creating an apical cavity 3 mm into root canal system; II, a 45 degrees bevel of the root-face removing a 3-4 mm root segment and root-end preparation as per group I; III, root-end resection as per group I, with an apical cavity prepared using a size 010 inverted cone bur 3 mm down the long axis of the root; IV, resection as per group II, followed by an apical cavity preparation with a size 010 inverted cone bur 3 mm into the root canal system. The apical root portion and root-end cavities were replicated and prepared for SEM analysis at x 20 and x 80 magnification. The degree of chipping associated with the margin of the root-end cavities, as evaluated with a standard grading system, and the incidence of root-face cracks were noted. Marginal chipping of root-end cavities prepared using sonic instrumentation was significantly worse than that produced by burs (P < 0.001). Perpendicular root-end resections showed significantly better scores than bevelled root-end resections (P < 0.005). The incidence of root-face cracking was low with no significant difference between the experimental groups.
The aim of this study was to assess the shaping ability of the M4 reciprocating handpiece and Safety Hedstrom files in simulated canals. A total of 40 simulated canals of various angles and positions of curvature were prepared with an M4 handpiece using Safety Hedstrom files oriented with the ground, flattened surface towards the inner aspect of the curve. A standard regimen was adopted throughout. Pre- and post-operative longitudinal images of the canals were taken with a video camera and stored and manipulated in a computer with image analysis software. The presence of canal aberrations and the amount and location of resin material removed as a result of preparation were determined from composite images of superimposed pre- and post-operative views. Preparation time varied significantly (P < 0.001) between the canal types; overall, 20 degrees canals were prepared more quickly than 40 degrees canals. Zips and elbows were observed in 16 out of the 40 canals with most (11) being created in 40 degrees specimens. Ledges were found in 19 canals and perforations in only 1. There were no significant differences between canal shapes for these aberrations. Excessive removal of material from the inner aspect of the canal at the curve to create a danger zone was found in 20 canals, but only in those with 40 degrees curves. Significant differences in total canal width between the canal types were seen at the zips (P < 0.05), elbows (P < 0.05) and danger zones (P < 0.001). Transportation at the danger zones varied significantly (P < 0.001) between canal types. Under the conditions of this study, the M4 handpiece and Safety Hedstrom files created hour-glass preparations in a substantial proportion of canals. In reality, the Safety Hedstrom file with its one flattened surface was ineffective at reducing removal of material along the inner aspect of canal curves in severely curved specimens and clearly has the potential to create strip perforations in teeth.
Exogenous TGF-beta 1 has an autocrine effect on cell cultures of osteoblasts. Administration of TGF-beta 1 alone or in combination with Ca(OH)2 increases the synthesis of TGF-beta 1 in osteoblast cultures. Ca(OH)2 and TGF-beta 1 are compatible when placed in a culture of osteoblasts. Ca(OH)2 provides a favourable environment for the anabolic effects of TGF-beta 1.
Collagen protein synthesis by osteoblasts is influenced by transforming growth factor-beta (TGF-beta 1) and is essential to bone formation. The effectiveness of TGF-beta 1 depends on efficient delivery of the growth factor to target cells, adequate binding to cell surface receptors, and an optimum environment for promotion of collagen synthesis. The effects of calcium hydroxide (Ca(OH)2), TGF-beta 1, and Ca(OH)2/TGF-beta 1 co-administration on total protein, collagen protein, and noncollagen protein synthesis by early (subculture I) and late (subculture V) osteoblast cultures were tested. TGF-beta 1 significantly increased all protein synthesis in subculture I osteoblasts (p = 0.001; p < 0.001; p = 0.019). Ca(OH)2/TGF-beta 1 co-administration significantly increased total protein and collagen protein levels in subculture I osteoblasts as well (p = 0.048; p = 0.012). TGF-beta 1 increased total protein and collagen protein synthesis significantly in subculture V cells (p = 0.025; p = 0.01). These data indicate that co-administration of Ca(OH)2 and TGF-beta 1 enhances collagen synthesis by osteoblasts and may have implications for the clinical setting.
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