Antibacterial Effects of Some Root End Filling Materials
Torabinejad, Hong, Ford, and Kettering
Mutagenicity of AH26 in an In Vitro Mammalian Cell Mutation Assay
Schweikl, Schmalz, Stimmelmayr, and Bey
Properties of Hand-Held Spreaders after Simulated Use
Svec and Powers
Comparative Evaluation of the Antibacterial Effects of Intracanal Nd:YAG Laser Irradiation: An In Vitro Study
Fegan and Steiman
Properties of Endodontic Hand Instruments Used in Rotary Motion. Part I. Cutting Efficiency
Tepel, Schäfer, and Hoppe
Antibacterial Effects of Some Root End Filling Materials
Mahmoud.Torabinejad, DMD, MSD, PhD, C. U. Hong, DDS, MS, T. R. Pitt Ford, BDS, PhD, and J. D. Kettering, PhD
In addition to having good sealing ability, root end filling materials should "ideally" have some antibacterial activity to prevent bacterial growth. This investigation compared the antibacterial effects of amalgam, zinc oxide-eugenol, Super EBA and a mineral trioxide aggregate on nine facultative bacteria Streptococcus fecalis, Streptococcus mitis, Streptococcus mutans, Streptococcus salivarius, Lactobacillus species, Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, and Escherichia coli B and seven strict anaerobic bacteria, Prevotella (Bacteroides) buccae, Bacteroides fragilis, Prevotella (Bacteroides) intermedia, Prevotella (Bacteroides) melaninogenica, Fusobacterium necrophorum, Fusobacterium nucleatum, and Peptostreptococcus anaerobius. After growing these bacteria on solid media, freshly mixed and 24-h set test materials were placed on the surface of these inoculated media and incubated in the appropriate atmosphere for 24 to 48 h at 37° C. Impregnated discs with the Super EBA liquid were used as positive controls. The antibacterial effects of each material were measured in millimeters and the data were analyzed using one-way and two-way analysis of variance and Scheffé tests to determine the statistical differences between the antibacterial effects of the test materials. Impregnated discs with Super EBA liquid caused varying degrees of growth inhibition for both facultative and strict anaerobic bacteria. Both types of amalgam had no antibacterial effect against any of the bacteria tested in this study. Mineral trioxide aggregate had an antibacterial effect on some of the facultative bacteria and no effect on any of the strict anaerobic bacteria. Zinc oxide-eugenol and Super EBA pastes had some antibacterial effects on both types of bacteria tested. Based on the results of this study, it appears that none of the test materials had the complete antibacterial effects desired for root end filling materials.
Mutagenicity of AH26 in an In Vitro Mammalian Cell Mutation Assay
Helmut Schweikl, PhD, Gottfried Schmalz, DMD, PhD, DDS, Horst Stimmelmayr, PhD, and Brigitte Bey
The mutagenic activity of the root canal sealer AH26 was tested in the V79/hprt mammalian cell mutation assay. AH26 was mixed and eluted immediately after mixing or after setting times of 24 h or 7 days. Different amounts of dimethyl sulfoxide or physiological saline eluates were then tested for mutagenicity. Eluates of mixed AH26 were toxic and mutagenic, and both effects strongly depended on the setting time. The number of mutants after exposure to eluates of unset AH26 was enhanced ~7- to 10-fold. However, the mutagenic activity of the mixed material was clearly reduced after a setting time of 1 wk. Physiological saline eluates of the mixed AH26 were toxic at higher doses, but were not found to be mutagenic. Dimethyl sulfoxide eluates of the liquid component of AH26 elicited mutagenic effects similar to the freshly mixed material; eluates made in physiological saline were barely mutagenic at a 10-fold higher concentration. In accordance with recommendations of international guidelines, the V79/hprt mammalian cell mutation assay will be routinely used for the evaluation of the mutagenicity of dental materials in further investigations.
Properties of Hand-Held Spreaders after Simulated Use
Timothy A. Svec, DDS, MS and John M. Powers, PhD
Root canal spreaders are available in a wide variety of diameters, lengths, and tapers. Proposed ANSI/ADA Specification no. 71 standardizes certain properties of these instruments; however, none of these testing procedures subjects the instruments to conditions of clinical usage. Diameters (D3 and D16) and taper of 40 D11T root canal spreaders from each of three companies [Endeco (EN), Hu-Friedy (HF), and Premier (PR)] were measured. Permanent angular deformation of the instrument tip was measured by a bend test apparatus for four conditions: (group A) as-supplied control, (group B) spreader sterilized in an autoclave for 10 cycles, (group C) spreader inserted 50 times at a rate of 200 mm/min into plastic blocks with a canal curvature of 30 degrees, and (group D) spreader sterilized for 10 cycles and then inserted in blocks as described. All instruments passed the bend test in proposed specifications under all conditions. The EN spreader was more susceptible to permanent deformation than HF or PR. There were no statistical differences among the control and the three simulated clinical conditions.
Comparative Evaluation of the Antibacterial Effects of Intracanal Nd:YAG Laser Irradiation: An In Vitro Study
Steven E. Fegan, DDS and H. Robert Steiman, PhD, DDS, MSD
The purpose of this study was to determine if the Nd:YAG laser was capable of disinfecting contaminated root canals in vitro. Eighty canals of extracted single-rooted teeth were prepared to size 35 K-file. The teeth were sterilized with ethylene oxide gas and then inoculated with Bacillus stearothermophilus. Eight groups were treated as follows: 1, sterility control; 2, positive control, no treatment; 3, hand instrumentation with sterile water filling chamber; 4, hand instrumentation with NaOCl (5.25%) filling chamber; 5, ultrasonic instrumentation with sterile water; 6, ultrasonic instrumentation with NaOCl; 7, laser exposure with sterile water; and 8, laser exposure with NaOCl. All instrumentation times were 1 min. Teeth were then flushed with 1.0 ml of sterile water onto blood agar plates, and the number of colony forming units were determined. Results indicate that: (i) all groups treated with NaOCl effectively inhibited the growth of B. stearothermophilus; (ii) hand and ultrasonic instrumentation with sterile water did not effectively disinfect root canals; and (iii) the Nd:YAG laser was effective in inhibiting the growth of B. stearothermophilus. The effects of the Nd:YAG laser on other bacteria more commonly found in root canal systems should be evaluated.
Properties of Endodontic Hand Instruments Used in Rotary Motion. Part 1. Cutting Efficiency
Joachim Tepel, Dr. med. dent., Edgar Schäfer, Dr. med. dent., and Wolfgang Hoppe, Prof. Dr. med. dent.
Cutting efficiency of 24 different types of endodontic hand instruments, which are primarily designed for a rotary (reaming) working action, was investigated under standardized conditions. With a computer-driven testing device, resin specimens with simulated cylindrical canals were instrumented using a defined working motion simulating the clinical use of the instruments. Maximum penetration depth was the criterion for cutting efficiency. Sample size was 12 instruments for each type and size (#25 and #35).
Nitinol K-files showed the least cutting efficiency. Stainless steel reamers and especially K-files showed better cutting efficiency than Nitinol K-files. Flexible stainless steel instruments displayed the best results.
With regard to cutting efficiency, flexible stainless steel instruments were clearly superior to stainless steel reamers and K-files, and especially to Nitinol K-files.