The endodontic file is a disposable instrument.

Most cutting and machining tools wear when properly operated on intended substrates. Little is known about endodontic files when machining on human dentin. It was shown earlier that the efficiency of files was very variable when evaluated on Plexiglas substrates. The present study of seven different brands and types of files was undertaken to understand their wear better when machining human dentin. It was shown that all files evaluated rapidly deteriorated when machining dentin. This decline in efficiency was significant but different within, as well as, among brands. It was suggested that endodontic files be disposable.

Permeability changes of dentine treated with titanium tetrafluoride.

OBJECTIVES: The aim of this research was to evaluate the effect of titanium tetrafluoride on dentine permeability in comparison with sodium fluoride and acidulated phosphate fluoride to determine their contribution to acid resistance of dentine. METHODS: Thirty-two dentine discs were prepared from extracted mandibular molars. The hydraulic conductance of all discs was measured before and after the formation of smear layer. The discs were then randomly divided into five experimental and one-control groups. Coronal surfaces of dentine discs were treated with either fluoride solutions of NaF, APF, 1% TiF4, 0.5% TiF4 and 0.1% TiF4 or de-ionised water. Following the measurement of hydraulic conductance, treated surfaces were subjected to 25% citric acid application. Then, final permeability measurements were made. The data were statistically analysed using ANOVA and Tukey's HSD multiple comparisons. RESULTS: While smear layer formation considerably reduced dentinal permeability of dentine discs, fluoride or de-ionised water application to smeared surfaces did not cause any significant change in hydraulic conductance (p > 0.05). After citric acid application, control and NaF groups showed higher permeability values than 1%, 0.5% and 0.1% TiF4 and APF groups (p < 0.01). CONCLUSION: Clinical use of acidic solutions of titanium tetrafluoride in dentine cavities may be considered since smeared dentine surfaces are modified to a stabile and acid-resistant state.

Effect of reduced air pressure on dye penetration in standardized voids.

OBJECTIVE: This study determined the correlation between the degree of dye penetration in standardized voids to various reduced pressures. STUDY DESIGN: Standardized voids of 0.50 and 0.22 mm in diameter were created in 60 human roots; specimens were divided into five groups. Four groups were subjected to a 2% filtered aqueous methylene blue dye solution under different conditions of atmospheric pressure for 7 days and reduced pressures of a 10 torr, a 260 torr, and a 510 torr for 30 minutes. The conditions for the fifth group were similar to the last group except that ethyl alcohol was substituted for water in the dye. RESULTS: All positive control specimens showed complete dye penetration. The least linear dye penetration was observed in passively immersed specimens. The results were significantly different from those when reduced pressure had been used (p < 0.001). There were no significant differences among the groups with reduced pressure. No significant difference was found at any pressure level between the means of dye diffusion in the 0.50 and the 0.22 mm voids. The smallest standard deviations were observed for the most reduced air pressure of 10 torr, followed by the group of the least reduced pressure of 510 torr, with the use of the tincture dye solution. CONCLUSIONS: A 10-torr reduced pressure and an application of the tincture dye solution would provide an improved method for microleakage studies.

A comparison of stainless steel and nickel-titanium H-type instruments of identical design: torsional and bending tests.

OBJECTIVE: For a true comparison of clinically relevant qualities of instruments manufactured from different alloys, the instrument must be identical in design. The purpose of this study was to perform mechanical tests on stainless steel and nickel-titanium instruments of identical design. STUDY DESIGN: Identical experimental endodontic files of H-type with double helix were fabricated from stainless steel and nickel-titanium alloys. Torsional and bending tests were carried out according to American National Standards Institute/American Dental Association specification No. 58 and International Standards Organization No. 3630/1. Changes in instruments during the testing were also analyzed with scanning electron microscope technique. RESULTS: The results indicated that the torsional moment of the stainless steel files was significantly higher than for the nickel-titanium files (P <.001), whereas the mean angular deflection for the nickel-titanium files was significantly higher. The mean bending moment for the nickel-titanium files was significantly lower (P <.001) than the mean value for the stainless steel files. The scanning electron microscope demonstrated that the fracture surfaces of the stainless steel files were brittle, whereas the nickel-titanium files had a ductile fracture. CONCLUSIONS: When the design of endodontic instruments of different alloys is identical, the nickel-titanium files are more flexible in bending. However, nickel-titanium files require less force to deform to fracture.

Machining efficiency and wear resistance of nickel-titanium endodontic files.

OBJECTIVE: Nickel-titanium endodontic files are more flexible than stainless steel. Little information is reported concerning machining efficiency and wear resistance of nickel titanium. This study assessed the dentin-machining ability and wear resistance of nickel titanium endodontic files in vitro. STUDY DESIGN: The method described earlier to assess machining efficiency and wear resistance of stainless steel files was used. Eight different types and brands of nickel titanium files were studied: Ultra-Flex Hedström, Ultra-Flex K, Mity Hedstrom, Mity K, Mity Turbo, Hedstrom Naviflex NT, NiTiFlex, and Hyflex X-file. Thirty files of each brand were evaluated. One-way ANOVA and t tests were performed to analyze the data. RESULTS: Considerable variation was found in matching efficiency and wear. The best initial machining ability of all nickel titanium instruments was recorded for the Hyflex-X file (0.60 +/- 0.16 mm2); the poorest performance was for the Mity Turbo file, which machined less than one third of the best performing instrument (0.19 +/- 0.12 mm2). CONCLUSIONS: We compared our results with results of a previous study of stainless steel endodontic files and concluded that nickel titanium instruments are as aggressive as or better than stainless steel instruments in removing dentin. They are also more durable than their stainless steel counterparts.

Morphologic effects on L929 fibroblasts of titanium tetrafluoride application.

OBJECTIVE: The aim of this study was to investigate the effect of titanium tetrafluoride solution on L929 fibroblasts by scanning electron microscopy. Titanium tetrafluoride was then compared with sodium fluoride and acidulated phosphate fluoride. STUDY DESIGN: Cells were treated with fluoride solutions for 1 minute either directly, through a filter membrane with a pore size of 0.4-micron, or indirectly, through dentin disks; they were then investigated at an electron microscopic level. RESULTS: Fluoride application on smeared dentin disks showed fewer cytotoxic effects on fibroblasts than application on nonsmeared dentin disks. Acidulated phosphate fluoride and titanium tetrafluoride appeared to be more cytotoxic than sodium fluoride. Because all fluoride solutions used in this study contained the same fluoride concentration, pH was considered to be the main factor causing the higher toxicity. CONCLUSION: Because these solutions demonstrated toxicity in vitro, they must be further evaluated under in vivo conditions to ascertain their clinical safety.

Rx for caries prevention: time line for home care. A software aid for communication of patient instructions for management of dental caries.

Treatment of a caries active patient requires the clinician to be knowledgeable in the restorative and risk management issues with which these patients often present. Modifications of risk factors that promote dental caries play an important part in the long-term restorative success in these patients. Patient compliance to recommendations addressing modifiable caries risk factors for maintenance of oral health is important to long-term caries risk management. Effective dentist-patient or hygienist-patient communication is a first step to encouraging a proactive role by the patient. Others have reported verbal communication accompanied by written communication to result in better compliance compared to verbal communication, alone (Tagliacozzo & Ima, 1970; MacDonald, MacDonald & Phoenix, 1977; Baker & others, 1991; Harvey & Plumridge, 1991; Vukmir & others, 1993; Makoul, Arntson & Schofield, 1995). Further evidence shows that medical patients who misunderstand their treatment plans and associated instructions usually exhibit poor compliance to following directions (Cargil, 1992; Counsell, Geddis & Smith, 1993; Vukmir & others, 1993; Makoul & others, 1995; Mayeaux & others, 1996). Computer-generated (printed) instructions were shown to significantly increase compliance to emergency room instructions when compared to verbal or verbal + hand-written instructions (Vukmir & others, 1993). Written instructions for use in management of dental caries have not been widely addressed in the literature (Fuller & Harding, 1991; Benn & others, 1997). This report presents a novel computer-generated, graphic approach to written communication that recognizes the patient's need to be reminded that home care consists of daily cyclic events. The objective of this approach is to promote communication with and comprehension by a wider population range than what might be affected by text-only instructions. The software for this method is pre-loaded with recommendations that can be modified by the dentist or hygienist and can be easily adapted as part of a comprehensive disease management program used in the office.

Polypeptide-catalyzed biosilicification of dentin surfaces.

In situ formation of mineral particles by biocatalysis would be advantageous for occluding dentin tubules to reduce permeability or for sealing of material-tooth interfaces. One approach would require that the peptide-catalyst remain functional on the dentin surface. Based on recent observations of retained activity on other surfaces, we hypothesized that poly(L-lysine) (PLL), an analog of the protein catalyst responsible for silica formation in primitive marine species, would remain functional on dentin. PLL was applied to dentin discs along with a pre-hydrolyzed silica precursor, tetramethyl orthosilicate (TMOS). Discs were analyzed microscopically (scanning electron microscopy, SEM) and chemically (x-ray photoelectron spectroscopy, XPS). The treated discs, but not the negative controls, exhibited partial distinct coating whose XPS survey was consistent with that of silica, demonstrating that the polypeptide was required and retained its mediating activity. Peptide-catalysts that mediate mineral formation can retain functionality on dentin, suggesting a wide range of preventive and treatment strategies.

Dimensional changes of endodontic sealers.

The purpose of this study was a long-term comparison of the dimensional changes of endodontic sealers of diverse properties. The sealers were injected as thin layers on the internal walls of glass pipettes 1 mm in diameter. The pipettes were filled with deionized water, and the water meniscus levels were recorded periodically up to 180 days. The water was removed from the pipettes, samples were allowed to dry, and the mass and the volume of the sealers were measured. AH26 and Endo-Fill had an initial expansion followed by a volumetric loss. The two zinc oxide eugenol-based sealers studied started to shrink within hours after mixing; the first volumetric loss for AH26 was recorded during the first 30 days and for Endo-Fill after 30 days. The least dimensional change at any time was observed for Endo-Fill. It was concluded that a significant dimensional change and continued volume loss can occur in some endodontic sealers.

Assessment of marginal stability and permeability of an interim restorative endodontic material.

The purpose of this study was to assess the marginal stability and permeability of a new interim restorative endodontic material, Tempit (Centrix Inc., Milford, Conn.), and to compare the findings with the results of two commonly used restorative endodontic materials, Cavit (Premier Dental Products Co., Philadelphia, Pa.) and IRM (Intermediate Restorative Material Capsules, The Caulk Co., Division of Dentsply International Inc., Milford, Del.) This study was performed in several steps. First, the endodontic access cavities were prepared and restored on 80 extracted mandibular molars. The samples were exposed to methylene blue dye solution for 6 days, thermocycled, and sectioned; the dye penetration and diffusion were measured along the margins and into the body of the materials. The second experiment was a special study performed in standardized glass tubes to better evaluate the marginal and body dye penetration into the materials by increasing the length of the fillings. To eliminate the possibility of hygroscopic setting mechanisms of materials, samples were first allowed to set under water before dye was introduced. Cavit and Tempit showed a substantial amount of dye diffusion into the body of the materials. Cavit exhibited the best sealing ability at all times. The marginal and body dye penetration were significantly different for the Tempit material in all experiments than Cavit (p < 0.001). IRM demonstrated the least body penetration of all three materials (p < 0.001) but had a substantial marginal leakage not significantly different from the results of the Tempit material (p = 0.6 and p = 0.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Orientation of retentive matrices on spherical attachments independent of implant parallelism.

Traditionally, it has been advocated that implants planned for use as overdenture abutments be placed parallel to each other to obtain predictable attachment retention and complete seating of the restoration and to prevent premature wear of components. However, it is often difficult or impossible to place implants parallel to each other, and patients with implants that have already been placed in a variety of positions frequently are referred to restorative dentists. This article describes a technique for the fabrication of a matrix-paralleling device as well as 2 of its uses. The device allows proper orientation of the retentive matrices to establish a common path of withdrawal for the prosthesis and all attachments. Provided that the matrices are parallel to each other, spherical overdenture attachments can be used even when the implants are not parallel.