Effect of Orthodontic Brackets on the Accuracy of Apex Locators: A Pilot Study.

The purpose of this study was to evaluate the effect of metal orthodontic brackets on the accuracy of electronic apex locator (EAL). The actual canal lengths (ACL) of 40 mandibular incisor teeth were determined. Then, the teeth were randomly divided into two groups (n = 20). Orthodontic metal brackets were applied in the first group, and no brackets, in the second group. The working length of each tooth was measured with an EAL under 3 test conditions according to the distance between the lip clip and sample tooth. Data were analyzed using one-way repeated measures analysis of variance and Tukey's post hoc tests (p = 0.05). In the bracketed samples, when the lip clip was located at 1 cm and 2 cm from the samples. The mean differences between the EAL measurements and ACLs were statistically higher than those when the samples were located 3 cm from the lip clip (p < 0.05). There were also statistically significant differences between EAL measurements and ACLs in the bracketed samples located 1 and 2 cm from the lip clip (p < 0.05). In the nonbracketed group, the differences between EAL measurements and ACLs were not statistically significant in the samples located 1, 2, and 3 cm from the lip clip (p > 0.05). Use of orthodontic metal brackets can negatively influence the accuracy of the electronic apex locator when the distance between the lip clip and bracket was short. A minimum of 3 cm distance should be kept between the lip clip and tooth in order to make consistent electronic measurements.

Effect of final irrigation protocols on the fracture resistance of roots with varying dentine thickness.

This study evaluated the effects of 9% etidronic acid (HEBP) and 17% ethylenediaminetetraacetic acid (EDTA) used either with conventional syringe irrigation (CSI) or passive ultrasonic irrigation (PUI) on the fracture resistance of roots with different dentine thickness. The root canals of 120 extracted teeth were widened, leaving dentinal walls with different thicknesses of either 0.75 mm, 1.50 mm, or 2.25 mm with 40 teeth in each group. Within each of these groups, four subgroups (n = 10) were formed according to the final irrigation regimens applied: 2.5% NaOCl-17% EDTA with CSI; 2.5% NaOCl-17% EDTA with PUI; 2.5% NaOCl + 9% HEBP with CSI; 2.5% NaOCl + 9% HEBP with PUI. The irrigated root canals were obturated with AH Plus sealer and gutta-percha cones. A compressive vertical loading was applied to the samples and the force at fracture was recorded. Data were statistically analysed using a multiple linear regression analysis. The most influencing factor for the fracture strength of roots was the remaining dentine thickness, followed by the irrigation method, and then the irrigation solution. The samples irrigated using PUI were statistically significantly more resistant to fracture than those using CSI (mean difference = 116.3 N; 95% CI = [53.9, 178.6] N). The application of HEBP was associated with higher resistance to fracture than the application of EDTA (mean difference = 71.0 N; 95% CI = [8.6, 133.3] N).

Fracture resistance of roots with simulated internal resorption defects and obturated using different hybrid techniques.

BACKGROUND/PURPOSE: Teeth with internal resorption are susceptible to fracture because of the remaining thin dentinal walls. The aim of this study was to investigate the fracture resistance of roots with simulated internal resorption cavities and obturated with different hybrid techniques. MATERIALS AND METHODS: Seventy single root canals were instrumented. On the coronal half of the roots, standardized internal cavities with a length of 8 mm were created. The apical 6 mm of the 60 root canals were filled with AH Plus sealer and gutta-percha cones. Then, 80 roots were divided into four experimental groups and two control groups according to the internal cavity obturation: Group 1, AHPlus sealer + high-temperature thermoplasticized injectable gutta-percha; Group 2, DiaRoot Bioaggregate; Group 3, Biodentine; Group 4, MTA Fillapex; Group 5, instrumented, but not obturated roots; Group 6, intact roots. A compressive vertical loading at a speed of 1 mm/min was applied to the roots. The forces when the fracture occurred were statistically analyzed with one-way analysis of variance and post hoc Tukey test. RESULTS: Biodentine group showed statistically higher resistance to fracture than the other experimental groups (P < 0.05). CONCLUSION: Filling the internal resorption cavities with thin dentinal walls using Biodentine may provide strength to the tooth structure more than the other calcium silicate-based materials.