Fernando Branco Barletta

Apical Transportation: A Comparative Evaluation of Three Root Canal Instrumentation Techniques with Three Different Apical Diameters

This study conducted an in vitro analysis of the level of apical transportation in mesiobuccal roots of upper molars after manual instrumentation with stainless steel files, preparation with the K3 system, and with a reciprocating NSK handpiece. Sixty roots were mounted in muffles and then longitudinally sectioned. A digital image was acquired of the inner surface of one root half. After instrumentation, the inner surfaces of the same root halves were digitized with file sizes #30, #35, and #40. Each image obtained was superimposed over the corresponding preoperative image, and the apical transportation was measured. The Friedman and Wilcoxon tests were used to compare results for the file sizes, and comparison of the groups was made with the Kruskal-Wallis test, demonstrating statistically significant differences (P = .000). The stainless steel file sizes #35 and #40 caused significant apical transportation, and K3 system proved safe for apical preparation, with little deviation.

Analysis of apical root transportation associated with ProTaper Universal F3 and F4 instruments by using digital subtraction radiography.

INTRODUCTION The aim of this study was to assess the occurrence of apical root transportation after the use of ProTaper Universal rotary files sizes 3 (F3) and 4 (F4). METHODS Instruments were worked to the apex of the original canal, always by the same operator. Digital subtraction radiography images were produced in buccolingual and mesiodistal projections. A total of 25 radiographs were taken from root canals of human maxillary first molars with curvatures varying from 23-31 degrees. Quantitative data were analyzed by intraclass correlation coefficient and Wilcoxon nonparametric test (P = .05). RESULTS Buccolingual images revealed a significantly higher degree of apical transportation associated with F4 instruments when compared with F3 instruments in relation to the original canal (Wilcoxon test, P = .007). No significant difference was observed in mesiodistal images (P = .492). CONCLUSIONS F3 instruments should be used with care in curved canals, and F4 instruments should be avoided in apical third preparation of curved canals.

Computed tomography assessment of three techniques for removal of filling material

In this study, computed tomography (CT) was used to assess three techniques for root canal filling removal. Seventy-five roots of extracted human lower incisors were filled with zinc oxide-eugenol sealer and gutta-percha and separated into three groups before gutta-percha removal (group 1, Gates Glidden burs + K-type hand instrumentation; group 2, K-type reciprocating instrumentation + NSK TEP E16R; group 3, ProTaper rotary instrumentation + NSK NAC E16R). Specimens were CT-scanned before and after filling removal. The mean rate of filling removal was 94.88%. Reciprocating instrumentation was the most effective and manual instrumentation associated with Gates Glidden burs was the least effective technique. Removal rate was significantly different for the three groups according to one-way anova (P = 0.049). The Tukey test showed a significant difference between groups 1 and 2 (P = 0.039) only. CT proved to be a reliable method for assessing root filling removal techniques.

Cyclic Fatigue Resistance of Rotary Nickel-Titanium Instruments Submitted to Nitrogen Ion Implantation

INTRODUCTION The aim of this study was to assess cyclic fatigue resistance in rotary nickel-titanium instruments submitted to nitrogen ion implantation by using a custom-made cyclic fatigue testing apparatus. METHODS Thirty K3 files, size #25, taper 0.04, were divided into 3 experimental groups as follows: group A, 12 files exposed to nitrogen ion implantation at a dose of 2.5 x 10(17) ions/cm(2), accelerating voltage of 200 kV, currents of 1 microA/cm(2), 130 degrees C temperature, and vacuum conditions of 10 x 10(-6) torr for 6 hours; group B, 12 nonimplanted files; and group C, 6 files submitted to thermal annealing for 6 hours at 130 degrees C. One extra file was used for process control. All files were submitted to a cyclic fatigue test that was performed with an apparatus that allowed the instruments to rotate freely, simulating rotary instrumentation of a curved canal (40-degree, 5-mm radius curve). An electric motor handpiece was used with a contra-angle of 16:1 at an operating speed of 300 rpm and a torque of 2 N-cm. Time to failure was recorded with a stopwatch in seconds and subsequently converted to number of cycles to fracture. Data were analyzed with the Student t test (P < .05). RESULTS Ion-implanted instruments reached significantly higher cycle numbers before fracture (mean, 510 cycles) when compared with annealed (mean, 428 cycles) and nonimplanted files (mean, 381 cycles). CONCLUSIONS Our results showed that nitrogen ion implantation improves cyclic fatigue resistance in rotary nickel-titanium instruments. Industrial implementation of this surface modification technique would produce rotary nickel-titanium instruments with a longer working life.

Accuracy of working length determination using 3 electronic apex locators and direct digital radiography.

OBJECTIVES The objectives of this study were to assess the accuracy of working length determination using 3 electronic apex locators and direct digital radiography and to compare the results with those obtained using the visual method (control measurement). STUDY DESIGN Twenty extracted human maxillary premolars were selected: 17 two-rooted and 3 single-rooted (total of 37 canals). Working length was measured using electronic apex locators Elements Diagnostic, Root ZX, and Just II. Subsequently, teeth were positioned in the alveolar bone of a dry skull and submitted to direct digital radiography. A variation of ±1 mm was considered as acceptable. Results were analyzed using the Wilcoxon and the χ(2) tests. RESULTS Results presented an accuracy of 94.6% for Elements Diagnostic, 91.9% for Root ZX, 73.0% for Just II, and 64.9% for direct digital radiography when considering the margin of ±1 mm in relation to the control measurement. Comparisons with the actual control measurements resulted in accuracy results of 13.51%, 13.51%, 10.10%, and 2.70%, respectively. CONCLUSIONS Root ZX and Elements Diagnostic are more accurate in determining working length when compared with Just II and Schick direct digital radiography.

Apical Root Canal Transportation and Remaining Dentin Thickness Associated with ProTaper Universal with and without PathFile

INTRODUCTION This study aimed to compare, using digital subtraction radiography, apical transportation in mesiobuccal root canals of extracted human maxillary molars instrumented with ProTaper Universal F3 and F4 files (Dentsply Maillefer, Ballaigues, Switzerland) with and without the prior creation of glide paths using the PathFile system and to compare, using cone-beam computed tomographic imaging, remaining dentin thickness (RDT) after complete preparation. METHODS Forty mesiobuccal roots with curvatures of 20°-35° were used. In group A, glide paths were created with PathFile #1, #2, and #3 to the working length; in group B, no glide paths were used. All canals were instrumented up to F4 to the working length. Digital subtraction radiographic images were obtained in buccolingual and mesiodistal directions. Apical transportation associated with F3 or F4 was calculated based on the difference between the tip of the first and the last instrument analyzed in each group. RDT was calculated based on cone-beam computed tomographic images. RESULTS Apical transportation was higher after F4 regardless of the use of the PathFile system. No statistically significant differences between groups A and B were observed in apical transportation after instrumentation with F3 or F4 (P > .05). Group A showed greater RDT values at 2 (buccal and mesial walls, P < .05) and 3 mm (buccal and distal walls, P < .05) from the apex but not at 1 mm. CONCLUSIONS The use of the PathFile system before root canal preparation with ProTaper Universal F3 and F4 did not influence apical transportation but was associated with greater RDTs at 2 and 3 mm from the apex.

In Vitro analysis of effect of heat used in dental bleaching on human dental enamel

From a cosmetic point-of-view, white teeth are important for integration of an individual into society. Thus, dental bleaching may be used to reach this objective. When analyzing several proposed techniques, it was observed that heat is frequently involved either in direct application or as a result of a chemical reaction. Taking into account the importance of preserving dental structures, the present study analyzed possible injuries to enamel when heat is used in the bleaching procedure. A colorimetric method was used and the results showed that there was no difference when heat was used. In only one case did the non-communicating tufts become communicating.

Computed tomography assessment of the efficiency of different techniques for removal of root canal filling material

This study evaluated the efficiency of different techniques for removal of filling material from root canals, using computed tomography (CT). Sixty mesial roots from extracted human mandibular molars were used. Root canals were filled and, after 6 months, the teeth were randomly assigned to 3 groups, according to the root-filling removal technique: Group A - hand instrumentation with K-type files; Group B - reciprocating instrumentation with engine-driven K-type files; and Group C rotary instrumentation with engine-driven ProTaper system. CT scans were used to assess the volume of filling material inside the root canals before and after the removal procedure. In both moments, the area of filling material was outlined by an experienced radiologist and the volume of filling material was automatically calculated by the CT software program. Based on the volume of initial and residual filling material of each specimen, the percentage of filling material removed from the root canals by the different techniques was calculated. Data were analyzed statistically by ANOVA and chi-square test for linear trend (?=0.05). No statistically significant difference (p=0.36) was found among the groups regarding the percent means of removed filling material. The analysis of the association between the percentage of filling material removal (high or low) and the proposed techniques by chi-square test showed statistically significant difference (p=0.015), as most cases in group B (reciprocating technique) presented less than 50% of filling material removed (low percent removal). In conclusion, none of the techniques evaluated in this study was effective in providing complete removal of filling material from the root canals.

In vitro comparison of different reciprocating systems used during endodontic retreatment

The present study evaluated the effectiveness of two reciprocating systems for the removal of root-filling material during endodontic retreatment. One hundred extracted mandibular premolars were prepared and root-filled with gutta-percha and sealer. Root fillings were removed with K-files according to the following techniques: Group A--hand instrumentation; Group B--Endo-Gripper system driven by compressed air; Group C--INTRAmatic 29CH + INTRA-LUX 3LD driven by compressed air; Group D--Endo-Gripper system driven by electric engine; Group E--INTRAmatic 29CH + INTRA-LUX 3LD driven by electric engine. The amount of filling debris on root canal walls was assessed radiographically and analysed using Auto CAD 2000 software. One-way anova and Duncans test revealed statistically significant differences only in the middle third (P = 0.01); the best results being reached in group D. The apical third displayed the greatest amount of filling material debris, regardless of the technique used.

The Effect of Argon and Nitrogen Ion Implantation on Nickel-Titanium Rotary Instruments

INTRODUCTION This qualitative study investigated the effect of N(2)(+) and Ar(+) ion implantation on morphologic alterations and fatigue resistance in Pro Taper S1 NiTi (Dentsply-Maillefer, Ballaigues, Switzerland) rotary instruments. METHODS Instruments were divided into three groups: N(2)(+) implanted, Ar(+) implanted, and unmodified control group. All instruments were used to prepare five curved canals in epoxy resin blocks with brushing motion. The instruments were examined in a scanning electron microscope (SEM) before use, after first use, and after the fifth use. A more demanding cyclic fatigue test was undertaken, submitting the instruments to 15-second periods of continuous rotation inside the curved canals without a brushing motion. Crack formation was analyzed with the SEM, and the number of 15-second periods required to fracture each instrument was recorded. RESULTS No significant morphologic alterations were observed in the instruments after the preparation of five canals. Crack density was similar in all groups. In the subsequent cyclic fatigue test, instruments implanted with nitrogen performed worse than those implanted with argon and the control group. Fracture faces show differences in the fracture modes. CONCLUSIONS Ar(+) implantation improved the performance of S1 files moderately, whereas nitrogen ion-implanted files performed worse in the fatigue test. A reduction in file performance seems to be caused by nitrogen diffusion in the grain boundaries, instead of the desired improvement caused by titanium nitride formation.