This study aimed to assess the influence of different cross-sectional area on the cyclic fatigue fracture of Ni-Ti rotary files using a fatigue tester incorporating cyclical axial movement. Six brands of Ni-Ti rotary files (ISO 30 size with .04 taper) of 10 each were tested: Alpha system (KOMET), HeroShaper (MicroMega), K3 (SybronEndo), Mtwo (VDW), NRT (Mani), and ProFile (Dentsply). A fatigue-tester (Denbotix) was designed to allow cyclic tension and compressive stress on the tip of the instrument. Each file was mounted on a torque controlled motor (Aseptico) using a 1:20 reduction contra-angle and was rotated at 300 rpm with a continuous, 6 mm axial oscillating motion inside an artificial steel canal. The canal had a 60° angle and a 5 mm radius of curvature. Instrument fracture was visually detected and the time until fracture was recorded by a digital stop watch. The data were analyzed statistically. Fractographic analysis of all fractured surfaces was performed to determine the fracture modes using a scanning electron microscope. Cross-sectional area at 3 mm from the tip of 3 unused Ni-Ti instruments for each group was calculated using Image-Pro Plus (Imagej 1.34n, NIH). Results showed that NRT and ProFile had significantly longer time to fracture compared to the other groups (p < .05). The cross-sectional area was not significantly associated with fatigue resistance. Fractographycally, all fractured surfaces demonstrated a combination of ductile and brittle fracture. In conclusion, there was no significant relationship between fatigue resistance and the cross-sectional area of Ni-Ti instruments under experimental conditions.

The treatment of esthetic areas with single-tooth implants represents a new challenge for the clinician. In 1993, a modification of the forced eruption technique, called "orthodontic extrusive remodelling," was proposed as a way to augment both soft- and hard-tissue profiles at potential implant sites. This case report describes augmentation of the coronal soft and hard tissues around a fractured maxillary lateral incisor associated with alveolar bone loss, which was achieved by forced orthodontic extrusion before implant placement. Through these procedures we could reconstruct esthetics and function in a hopeless tooth diagnosed with subgingival root fracture by trauma.

This study evaluated the effectiveness and safety of an experimental bleaching strip (Medison dental whitening strip, Samsung medical Co., Anyang, Korea) containing 2.9% hydrogen peroxide. Twenty-three volunteers used the bleaching strips for one and a half hour daily for 2 weeks. As control group, the same strips in which hydrogen peroxide was not included were used by 24 volunteers with the same protocol. The shade change (ΔE*, color difference) of twelve anterior teeth was measured using Shade Vision (X-Rite Inc., S.W. Grandville, MI, USA), Chroma Meter (Minolta Co., Ltd. Osaka, Japan) and Vitapan classical shade guide (Vita Zahnfabrik, Germany). The shade change of overall teeth in the experimental group was significantly greater than that in the control group (p < 0.05) and was easily perceivable. The change resulted from the increase of lightness (CIE L* value) and the decrease of redness (CIE a* value) and yellowness (CIE b* value). The shade change of individual tooth was greatest in canine, and smallest in central incisor. The safety of the bleaching strip was also confirmed.

Citations

Citations to this article as recorded by  

• Effects of Citrus limon Extract on Oxidative Stress-Induced Nitric Oxide Generation and Bovine Teeth Bleaching
  Soon-Jeong Jeong
  Journal of Dental Hygiene Science.2021; 21(2): 96.     CrossRef
• Efficacy of a self - applied paint - on whitening gel combined with wrap
  Soo-Yeon Kim, Jae-Hyun Ahn, Ji-Young Kim, Jin-Woo Kim, Se-Hee Park, Kyung-Mo Cho
  Journal of Dental Rehabilitation and Applied Science.2018; 34(3): 175.     CrossRef
• Effects of a whitening strip combined with a desensitizing primer on tooth color
  Hae-Eun Shin, Sang-Uk Im, Eun-Kyung Kim, Jong-Hun Kim, Jae-Hyun Ahn, Youn-Hee Choi, Keun-Bae Song
  Journal of Korean Academy of Oral Health.2016; 40(1): 31.     CrossRef
• A clinical evaluation of efficacy of an office bleaching gel containing 30% hydrogen peroxide
  Sin-Young Kim, Je-Uk Park, Chang-Hyen Kim, Sung-Eun Yang
  Journal of Korean Academy of Conservative Dentistry.2010; 35(1): 40.     CrossRef
• The evaluation of clinical efficacy and longevity of home bleaching without combined application of In-office bleaching
  Byunk-Gyu Shin, Sung-Eun Yang
  Journal of Korean Academy of Conservative Dentistry.2010; 35(5): 387.     CrossRef
• Effect of the bleaching light on whitening efficacy
  Jong-Hyun Park, Hye-Jin Shin, Deok-Young Park, Se-Hee Park, Jin-Woo Kim, Kyung-Mo Cho
  Journal of Korean Academy of Conservative Dentistry.2009; 34(2): 95.     CrossRef
• Clinical study of shade improvement and safety of polymer-based pen type BlancTic Forte whitening agent containing 8.3% Carbamide peroxide
  Jin-Kyung Lee, Sun-Hong Min, Sung-Tae Hong, So-Ram Oh, Shin-Hye Chung, Young-Hye Hwang, Sung-Yeop You, Kwang-Shik Bae, Seung-Ho Baek, Woo-Cheol Lee, Won-Jun Son, Kee-Yeon Kum
  Journal of Korean Academy of Conservative Dentistry.2009; 34(2): 154.     CrossRef