Dentinal defects induced by 6 different endodontic files when used for oval root canals: an in vitro comparative study

OBJECTIVES: To compare the formation of dentinal defects using stainless-steel hand K-files (HFs), rotary files, reciprocating files, and Self-Adjusting File (SAF), when used for oval root canals. MATERIALS AND METHODS: One hundred and forty extracted human mandibular premolar with single root and oval canal were selected for this study. Oval canals were confirmed by exposing to mesio-distal and bucco-lingual radiographs. Teeth with open apices or anatomic irregularities were excluded. All selected teeth were de-coronated perpendicular to the long axis of the tooth, leaving roots segments approximately of 16 mm in length. Twenty teeth were left unprepared (control), and the remaining 120 teeth were divided into 6 groups (n = 20) and instrumented using HF (size 40/0.02), Revo-S (RS; size 40/0.06), ProTaper NEXT (PTN; size 40/0.06), WaveOne (WO; size 40/0.09), RECIPROC (RC; size 40/0.06), and the SAF (2 mm). Roots were then sectioned 3, 6, and 9 mm from the apex, and observed under stereomicroscope, for presence of dentinal defects. “No defect” was defined as root dentin that presented with no visible microcracks or fractures. “Defect” was defined by microcracks or fractures in the root dentin. RESULTS: The control, HF, and SAF did not exhibit any dentinal defects. In roots instrumented by RS, PTN, WO, and RC files exhibited microcracks (incomplete or complete) in 40%, 30%, 55%, and 50%, respectively. CONCLUSIONS: The motor-driven root canal instrumentation with rotary and reciprocating files may create microcracks in radicular dentine, whereas the stainless-steel hand file instrumentation, and the SAF produce minimal or less cracks.

Refinement influence in the cleaning efficacy of rotary nickel-titanium Mtwo ® instruments in oval-shaped canals by means of optical microscopy.

Objective: This study evaluated the cleaning efficacy of the rotary nickel–titanium Mtwo® by means of optical microscopy in oval‑shaped root canals and compared refinement influence using ultrasonic files or Hedströem files. Materials and Methods: Twenty mandibular incisors were accessed, included in epoxy resin blocks, and cut transversely at 3, 6, and 9 mm from the apex. Teeth were instrumented using rotary nickel–titanium Mtwo. Digital images of the root cross sections were obtained before and after instrumentation with a digital camera attached to an optical microscope. Subsequently, samples were randomly divided into two groups for refinement. Group I was refined using ultrasonic files #30 and group II with Hedströem files #30. Final digital images of cross sections after refinement were captured and analyzed. The boundaries for the uninstrumented perimeter were measured by the software ImageTool 3.0. The data obtained were statistically analyzed by analysis of variance (ANOVA) and t‑test. Results: Mtwo instrumentation produced 41.48% of the uninstrumented perimeter. The final refinement using Hedströem and ultrasonic files decreased the uninstrumented perimeter. Significant differences (t‑test, P = 0.00) were found at the three thirds after the final refinement, except for the apical third that was enhanced by Hedströem file. However, there was no statistical difference between the two refinement techniques used (P > 0.05). Mtwo instrumentation was not capable of cleaning and shaping the entire perimeter of the root canals walls. Conclusions: The final refinement, either with ultrasonic files or with Hedströem files, resulted in significantly less uninstrumented perimeter.

Avaliação da adaptação de cones de guta-percha no segmento apical de canais ovais / Evaluation the adaptation of guta-percha in apical segment of long oval canals

O presente estudo teve por finalidade avaliar, in vitro, o grau de adaptação de cones de guta-percha no segmento apical de canais ovais longos de 40 primeiros pré-molares inferiores, obturados pela técnica de compactação lateral da guta-percha (TCL) e de Schilder (TS). Cortes a 1, 3 e 5 mm aquém do ápice radicular perpendiculares, ao longo eixo do dente, revelaram superfícies que foram analisadas com auxílio de estereomicroscópio e as imagens avaliadas através de um software. A média da área do terço apical não preenchida por guta-percha a 1 mm grupo 1 = 38,72% e grupo 2 = 22,64%; a 3 mm grupo 1 = 30,32% e grupo 2 =15,80%; a 5 mm grupo 1 = 57,38% e grupo 2 = 26,42%. A técnica de Schilder foi mais eficaz.

The present study aimed to evaluate in vitro the degree of adaptation of gutta-percha in the apical segment of the long oval canals first 40 premolars, filled by lateral compaction technique of gutta-percha (TCL) and Schilder (TS). Cuts at 1, 3 and 5 mm below the apex perpendicular to the long axis of the tooth surfaces revealed that analyzed with stereomicroscope and images evaluated through software. The average area of the apical third not filled with gutta-percha to the 1 mm group 1 = 3 8.72% and G roup 2 = 2 2.64%, the 3 m m g roup 1 = 3 0.32% a nd G roup 2 = 15.80% , the 5 mm group 1 = 57.38% and group 2 = 26.42%. Schilder's technique was more effective.

A sem observation on the efficiency preparation of oval canals using hand and engine-driven instruments / 대한치과보존학회지

The purpose of this study was to evaluate the efficiency of the preparation of oval canals using hand and engine-driven instruments with SEM observation. Thirty single-rooted teeth with oval canal were used in this study. The teeth were divided into 3 groups. In group A, the teeth were instrumented up to a size 35 K-file using RC-prep and irrigated with 5% NaOCl between each file size. In group B, the teeth were instrumented with Profile according to the manufacture's instructions using RC-Prep and irrigated with 5% NaOCl between each file size. In group C, the teeth were instrumented with GT file according to the manufacture's instructions using RC-prep and irrigated with 5% NaOCl between each file size. Then, in all teeth, a final flush of 5ml of distilled water delivered for 30s. Canals were dried with sterile standardized paper points. After preparing the canals, the teeth were sectioned along their mesial and diatal surfaces by using low-speed diamond disc, chisel and mallet. Each root section was then dehydrated in graded concentration of alcohol (70, 80, 90, 100%), mounted on an aluminum stub, sputter-coated with gold-palladium and observed with scanning electron microscope (HITACHI S-4200) in middle and apical area. The results of this study were as follows: 1. In the middle area, group B and group C showed less smear layer than group A, and it was statistically significant (p 0.05). 3. In the apical area, group C showed less smear layer than group A, and it was statistically significant (p 0.05). 5. In the apical area, group B showed greater smear layer than group C, but it was not statistically significant (p > 0.05). 6. In all groups, the middle area was less smear layer than the apical area, and it was statistically significant (p < 0.05).