Abstract : Aim : The purpose of this study was to evaluate causes of vertical root fracture (VRF). Methodology : Extracted human maxillary incisors and single-rooted premolars, twenty of each, were divided into 4 groups of 10 teeth each. The apical 1 mm of each tooth was ground perpendicular to the tooth’s axis. The apical cutting surface was polished and then recorded with a digital microscope (×150-175) as a baseline image. Group A : The canals of central incisors were instrumented up to a ＃ 40 K-file and filled by the lateral condensation method. A digital image was recorded after each step. Group B : The same as group A except that the instrument size was a ＃ 80 K-file. Group C : The same as group A except that premolars were used. Group D : The same as group B except that premolars were used. The presence of a fracture line determined by comparison between the baseline and the previous step image was statistically analyzed at a significance level of 5%. Results : The size of the master apical file (MAF) and the maxillary premolar were significantly correlated with VRF generation (p<0.05). Conclusion : We conclude that tooth type and MAF are factors that have a significant effect on VRF generation during root canal preparation.

Abstract : The purpose of this study was to examine the anti-bacterial conditions of the dental chair area and dental gloves, and to compare the disinfecting effects of an ethanol-based disinfectant (Rinapass disinfectant solution) with BV4 containing mainly fatty acids. After an endodontic clinic was closed, samples were obtained from twelve locations around dental chairs with sterile cotton balls. Each cotton ball was immediately used to inoculate an SCD agar plate. Moreover, dental gloves both before and after disinfection were used to inoculate SCD agar plates (Palm-check). Bacteria detected were identified to the genus. Many bacteria were detected from the dental chair area, in spite of disinfection being performed. Bacteria were predominantly detected from the handles of the dental chairs. Staphylococcus spp. were predominant in the bacterial species. The results suggested that bacteria might remain on dental gloves after disinfection, and that the bacteria are predominantly Staphylococcus spp. There was no significant difference between the disinfecting effects of Rinapass disinfectant solution and BV4. After touching the dental chair area during treatment, it may be necessary to carefully disinfect dental gloves.