No abstract

A previous study by our group found nickel-titanium (NiTi) 0.02 hand files maintained the original canal shape better than similar stainless-steel K-files (SS-K). Inexperienced dental students used both file types on molar teeth. The purpose of this study was to compare the 1-yr success rate of endodontic treatment of the same teeth used in our previous study. Twelve-month follow-up radiographs were compared with the immediate follow-up radiographs. Both sets of radiographs were taken with the same customized stent. Quantification of osseous changes using digital imaging was used. Thus, a reliable numerical estimation (densitometric ratio) of disease and healing processes could be established. Sixty-seven percent of the patients returned for the 12-month radiographs (19 NiTi vs. 21 SS-K). Immediate postoperative periapical status was found to be similar (p > 0.05). Teeth instrumented with the NiTi files demonstrated a higher mean change in densitometric ratio, compared with SS-K files (p < 0.05). Further tests of success (values: > or =0) and failure (value: < or =0) with the Fisher exact test showed more success (decreasing radiographic density) with NiTi files and more failures (increasing radiographic density) with SS-K type files (p < or = 0.03). This study indicates that maintaining the original canal shape after instrumentation leads to a better prognosis of endodontic treatment.

No abstract

The aim of this study was to determine the periodontal healing of replanted dogs' teeth which, after extended extra-oral dry times, had been soaked in various media before replantation. Incisors and premolars of beagle dogs were root canal treated, extracted and bench dried. The teeth were grouped according to dry times of 30, 45 and 60 minutes. Each group of teeth was soaked in one of three media, Hank's balanced salt solution, ViaSpan (Belzer UW-CSS, Dupont Pharmaceuticals), or Conditioned Medium (supernatant of confluent culture of human gingival fibroblasts) for 30 minutes before replantation. Controls consisted of teeth extracted and replanted without drying on soaking (negative control), and bench-dried teeth replanted without soaking in the media (positive control). The dogs were killed 6 months after replantation of the teeth, which were prepared for histologic evaluation. Five microns cross-sections (every 70 microns) of the root and surrounding tissue were evaluated for healing/resorption according to Andreasen's criteria. The best healing occurred for the roots which had been immediately replanted. Healing in the positive control groups decreased with increased dry time. For the 30-minute dry time groups, soaking in media had no beneficial effect on periodontal healing compared with the controls. Soaking in ViaSpan resulted in an increased healing incidence for both the 45- and 60-minute bench-dried groups while soaking in the other media had no consistent beneficial effect. It appears from this study that an avulsed tooth that has been left dry for 30 minutes should be replanted immediately without soaking. However, teeth that have been dry for 45 or 60 minutes would benefit from soaking for 30 minutes in ViaSpan.

The purpose of this study was to assess the efficacy of Nd:YAG laser irradiation in disinfecting the root canal system. Seventy-five teeth were uniformly instrumented and sterilized, and their root canals were infected for 60 min with an overnight culture of Enterococcus faecalis in Tryptic Soy Broth. The teeth were divided into 6 groups: 1--non-infected controls; 2--infected controls; 3--infected, laser treated; 4--infected, laser dummy (dye only); 5--infected, laser dummy (dye and air-water spray); 6--infected, NaOCl-treated (reference group). After treatment, the root canals were dried and dentinal shavings removed for a post-treatment culture. Quantitative analysis of bacteria surviving the various treatments were performed and the bacterial counts for each group were compared. SEM analysis of teeth split longitudinally was used to illustrate the effect of treatment on the smear layer and on surface bacteria. Nd:YAG laser irradiation (group 3) significantly reduced the number of bacteria while NaOCl irrigation (group 6) effectively disinfected the canals.