Morphometric Video Analysis of the Engine-Driven Nickel-Titanium Lightspeed Instrument System
arsicovetere, Clement, and del Rio
Influence of Particle Size of Hydroxyapatite as a Capping Agent on Cell Proliferation of Cultured Fibroblasts
Higashi and Okamoto
Interleukin-1
Stimulates Interstitial Collagenase Gene Expression in Human Dental Pulp Fibroblast
Tamura, Nagaoka, and Kawagoe
In Vitro Cytotoxicity and Dentin Permeability of HEMA
Bouillaguet, Wataha, Hanks, Ciucchi, and Holz
A Commercially Available Cell Culture Device Modified for Dentin Barrier Tests
Schmalz, Garhammer, and Schweiki
Tensile and Tear Properties of Dental Dam
Svec, Powers, Ladd, and Meyer
The Antimicrobial Effect within Dentinal Tubules of Four Root Canal Sealers
Heling and Chandler
Morphometric Video Analysis of the Engine-Driven Nickel-Titanium Lightspeed Instrument System
Ennio S. Marsicovetere, DDS, David J. Clement, DDS, and Carlos E. del Rio, DDS
Two hundred and sixteen Lightspeed instruments were evaluated microscopically for the presence of corrosion, surface debris, and alloy defects. The instruments were assessed morphometrically for consistency of physical design and dimensions by measuring and analyzing eight parameters of the instrument pilot tips, heads, and shafts. Results from visual inspection showed that none of the instruments were corroded; 23 presented surface porosities, and 17 had sharp strips of alloy. Data obtained by morphometric analysis indicated the mean diameter of the head of only 7 of 18 sizes met the ±0.02 mm allowable tolerance set forth by the American Dental Association (ADA) Specification No. 28.
Observation and video analysis indicated that instruments of the same size adhere to the same basic design, but that morphometric variations do exist. The visual and intersize analysis indicated that the Lightspeed is not an instrument of any one determined shape that changes only in diameter. Rather, it is a series of instruments that show gradual shifts in both size and shape as the instrument size increases. Lightspeed instruments are a new type of nickel-titanium endodontic instrument that cannot be evaluated using the standards proposed by the American National Standards Institute/ADA Specification No. 28 for files and reamers.
Influence of Particle Size of Hydroxyapatite as a Capping Agent on Cell Proliferation of Cultured Fibroblasts
Tomie Higashi, DDS, PhD and Hiroshi Okamoto, DDS, PhD
The influence of particle size of biomaterials on cell reaction and cell proliferation was studied by means of coculturing fibroblasts with calcium phosphate ceramics. Both dense and porous hydroxyapatite ceramics obtained under different sintering conditions were selected, and two particle sizes of 300 and 40 µm were used to examine cell reaction. The four materials were each cocultured with dental pulp-derived fibroblasts for 7 days. Cell reaction was observed by phase-contrast microscopy and scanning electron microscopy. Cell proliferation was measured by counting the number of trypsinized cells in 7-day-old culture. On the seventh day, the dense 300-µm particles of hydroxyapatite were completely covered by cultured cells that had proliferated on the dish surface. On the other hand, the porous and dense 40-µm particles were captured or gathered by the cultured cells, which seemed not to proliferate. The porous 300-µm particles were accompanied by numerous small broken pieces on the dish surface, and the cells proliferated only around the large particles. From these results, the dense 300-µm particles of hydroxyapatite can be considered the most appropriate biomaterial.
Interleukin-1 Stimulates Interstitial Collagenase Gene Expression in Human Dental Pulp Fibroblast
asato Tamura, DDS, PhD, Shigetaka Nagaoka, DDS, PhD, and Masataka Kawagoe, DDS, PhD
Interstitial collagenase (matrix metalloprotease-1) is a member of a family of matrix metalloproteases and is thought to play a role in degradation of the extracellular components, such as collagens in normal extracellular matrix remodeling and in many disease processes. We examined interstitial collagenase mRNA expression in human dental pulp fibroblast cultures by Northern blot analysis. These cells did not express interstitial collagenase mRNA in an unstimulated condition. Inflammatory cytokines, such as interleukin-1, induced interstitial collagenase mRNA expression in these cells. The interstitial collagenase mRNA levels began to increase after 2-h exposure, reaching a maximum after 8 h, then dropping to the unstimulated level at 48 h. These effects were observed in a dose-dependent manner in a dose range of 0.1 to 10 ng/ml. Transforming growth factor-
reduced the levels of interstitial collagenase mRNA expression that were induced by interleukin-1. These observations suggest that interstitial collagenase mRNA expression in human dental pulp fibroblasts is regulated by the inflammatory cytokines and that interstitial collagenase may play a role in tissue degradation in inflamed dental pulp.
In Vitro Cytotoxicity and Dentin Permeability of HEMA
Serge Bouillaguet, DMD, DCD, John C. Wataha, DMD, PhD, Carl T. Hanks, DDS, PhD, Bernard Ciucchi, DMD, and Jacques Holz, DMD, PhD
An in vitro diffusion chamber was used to measure the diffusion of 2-hydroxyethyl methacrylate (HEMA) through etched human dentin disks. Concentrations of HEMA, which diffused through dentin, were measured by ultraviolet spectroscopy, and the effect of initial HEMA concentration, dentin thickness, and back pressure on diffusion were assessed. The cytotoxicity of HEMA was determined using BALB/c 3T3 mouse fibroblasts in direct contact with HEMA for 12 or 24 h. HEMA diffused rapidly through dentin under all conditions, but increased thickness, back pressure, or decreased initial concentration all reduced diffusion. The permeability coefficient of HEMA was ~0.0003 cm/min, and diffusion through 0.5 mm of dentin reduced the HEMA concentration by a factor of ~6,000 (with 10 cm of H2O back pressure). It was concluded that the risk of acute cytotoxicity to HEMA through dentin was probably low, but that decreased dentin thickness, lack of polymerization, or extended exposure times might increase the risk significantly.
A Commercially Available Cell Culture Device Modified for Dentin Barrier Tests
Gottfried Schmalz, DMD, PhD, DDS, Pauline Garhammer, DMD, DDS, and Helmut Schweiki, PhD
The suitability of a dentin barrier test based on a commercially available cell culture chamber was evaluated by testing the cytotoxicity of dental cements. The two chambers of the culture device as produced are separated by a membrane. This was replaced by a bovine dentin disk (500 µm thick). Mouse fibroblasts were grown on the "pulpal" side of the dentin for 24 h; test materials were then placed into the "cavity" side of the upper chamber. The number of viable cells was determined after 24 h. After exposure to zinc phosphate cement at a powder/liquid ratio of 2:1, ~100% of cells survived. A ratio of 1:1 yielded 81% survival. Only 24% and 28% of the cells survived after exposure to Ketac Fil and Ketac Silver, respectively. The light-curing glass ionomer cement (Vitrebond) and zinc oxide-eugenol killed all cells. These results agree with those obtained from a previous study, wherein the dentin barrier test device was constructed in our laboratory.
Tensile and Tear Properties of Dental Dam
Timothy A. Svec, DDS, MS, John M. Powers, PhD, G. David Ladd, and Trenholm N. Meyer
The tensile and tear properties of highly extensible latex are sensitive to specimen shape. Three specimen shapes (ASTM D412 Die C dumbbell tensile specimen, rectangular tensile specimen with 1.74 mm hole, and ASTM D624 Die C tear specimen) were evaluated for proposed ANSI/ADA specification #90 for dental dams. Fresh and aged dental dams from two manufacturers (Aseptico and Hygenic) in three weights (thin, medium, and heavy) and from two other manufacturers (Ivory and Ivoclar) in one weight (medium) were tested. Means and standard deviations of 10 specimens for tensile strength (MPa), elongation (%), and tear strength (kN/m) are included herein. Data were analyzed by analysis of variance. Means were compared by a Tukey-Kramer interval calculated at the 0.05 significance level. The use of the dumbbell and tear specimens for the evaluation of dental dam should be reconsidered. The rectangular specimen with a hole is recommended for use in the proposed specification because of its sensitivity to condition (fresh versus aged) and manufacturer.
The Antimicrobial Effect within Dentinal Tubules of Four Root Canal Sealers
Ilana Heling, DMD, MS and Nicholas Paul Chandler, BDS, MSc, FFDRCSI, FDS(Glas and Edin)
The aim of this study was to investigate four root canal sealers-Pulp Canal Sealer EWT, Sealapex, AH26, and Ketac-Endo-for their antibacterial effects within dentinal tubules. Sterile saline served as a control. Sixty-six standardized bovine root specimens were infected with Enterococcus faecalis following smear layer removal. The materials were placed in the lumina, and six specimens from each group were stored for 24 h (48 h for AH26) and 7 days, after which dentin samples were taken from within the lumina using ISO 023 to 035 burs. Powder samples were incubated and the quantity of bacteria present assessed using spectrophotometry.
All sealers showed antibacterial activity at 24 h, except Ketac-Endo. The activity of Pulp Canal Sealer EWT was similar at 24 h and 7 days. Sealapex had greater antibacterial effect at 7 days than it did at 24 h. The strongest effects were demonstrated by AH26.