José González Bahillo

The effect of rotational speed and the curvature of root canals on the breakage of rotary endodontic instruments.

One of the biggest concerns when working with rotary endodontic instruments is that the instrument might break in the root canal thus compromising the treatment. This study evaluated the effect of rotational speed and the curvature of root canals on the breakage of ProFile rotary instruments to determine whether either causes an increase in instrument breakage. One hundred twenty root canals of extracted molars were divided into two groups according to whether the curvature of the canal was greater or lesser than 30 degrees. Three different rotational speeds (150, 250, and 350 rpm) were then used to carry out the instrumentation of the canals. The curvature of the canals would seem to be the most important factor that increases the risk of instrument breakage.

In vitro comparison of passive and continuous ultrasonic irrigation in simulated lateral canals of extracted teeth

INTRODUCTION Complete endodontic system disinfection requires the removal of vital and necrotic pulp tissue, microorganisms, and toxins. The purpose of this study was to compare the effects of 2 ultrasonic irrigation techniques on the penetration of sodium hypochlorite into the main canal and simulated lateral canals of extracted teeth. METHODS Two simulated lateral canals each were created 2, 4, and 6 mm from the working length in 60 single-rooted teeth (6 canals/tooth, n = 360). To resemble the clinical situation, a closed system was created in each tooth. The teeth were randomly assigned to 3 experimental irrigation groups: group 1 (n = 20), positive pressure irrigation (PPI); group 2 (n = 20), passive ultrasonic irrigation (PUI); and group 3 (n = 20), continuous ultrasonic irrigation (CUI). Samples were evaluated by direct observation of still images recorded under a dental operating microscope. To examine irrigating solution penetration, 20% Chinese ink (Sanford Rotring GmbH, Hamburg, Germany) was added to a 5% sodium hypochlorite solution and delivered into the root canals. RESULTS The results showed a significantly higher (P < .05) penetration of irrigant into the lateral canals in the CUI group. PUI and CUI did not differ significantly in solution penetration into the apical thirds of the main canals. The PPI group showed a significantly lower penetration of sodium hypochlorite into the main and lateral canals compared with the CUI and PUI groups. CONCLUSIONS CUI as a final rinse significantly increased the penetration of irrigating solution into simulated lateral canals.

A Comparative Study of Microleakage through Enamel and Cementum after Laser Er:YAG Instrumentation in Class V Cavity Obturations, Using Scanning Electron Microscopy

Objective: The purpose of this study was to use scanning electron microscopy (SEM) in order to compare the surfaces of cavities prepared using laser with those prepared conventionally, and to measure the degree of leakage through both enamel and cementum. Materials and Methods: We prepared 135 class V cavities and divided them randomly into three groups: laser-treated (group A), laser-treated, and acid-etched (group B) and rotary instrumented (group C). Results: On analyzing the tooth enamel, the amount of leakage was found to be similar in groups A and B, whilst the samples in the group C were more prone to leakage. On analyzing the cementum, the group C samples appeared to display surfaces that were more conducive to the adhesion of the materials used in obturation (although this difference was not strictly significant), and this might have provoked the relatively low levels of leakage. Conclusion: The use of acid etching in conjunction with both conventional and laser cavity preparation improves the ad...

Colorimeter and scanning electron microscopy analysis of teeth submitted to internal bleaching.

INTRODUCTION This in vitro study compared the tooth color and the ultrastructure of internal dental tissues before and after internal bleaching. METHODS Sodium perborate was placed in the pulp chamber of endodontically treated molars and sealed with intermediate restorative material. The test samples were stored in a physiologic solution, and the bleaching agent was replaced every 7 days. A control group was used. After 1 month, the colors of the test and control samples were measured with a colorimeter, and the internal surfaces were observed under field emission scanning electron microscopy (FESEM). RESULTS Statistically significant differences were found between the test and control sample colors. The FESEM ultrastructure analysis of the internal enamel and dentin surfaces did not show any changes after the internal bleaching. CONCLUSIONS The results of the present study show that sodium perborate is effective in bleaching nonvital teeth and does not produce ultrastructural changes in the dental tissues.