Cutting efficiency and corrosion resistance of heat-treated endodontic files after various disinfection protocols.

The aim of this study is to evaluate the effect of various disinfection protocols on the cutting efficiency and chemical composition of ProTaper, Twisted File, Twisted File Adaptive, and Hedström files. Four experimental groups (n = 10) were presoaked in either enzymatic solution or 1% sodium hypochlorite for 30 min, followed by either 5 or 15 min of ultrasonic cleaning and then autoclaved. Resin-simulated canals with a single curvature of 38-40° were prepared by each instrument system. Cutting efficiency of each instrument was analyzed by subtracting the final weight from the initial weight of the resin blocks. Chemical compositions were studied by field emission scanning electron microscopy and X-ray energy-dispersive spectrometry. The cutting efficiency of Hedström, ProTaper, and Twisted File instruments decreased compared to their control groups (p < 0.05) whereas it did not change for Twisted File Adaptive. More corrosion was detected with longer ultrasonication time. No difference was observed regarding the pre-soaking media. Disinfection protocols exerted a significant overall effect on the performance of Hedström, ProTaper, and Twisted File instruments. Corrosion, microcracks, and crevices were evident on all tested instruments after disinfection protocols applied. All disinfection protocols, regardless of the pre-soaking media used or the ultrasonic cleaning time applied, have some effect on the cutting efficiency and the surface characteristics of the files.

Long-term effect of acidic pH on the surface microhardness of ProRoot mineral trioxide aggregate, Biodentine, and total fill root repair material putty.

BACKGROUND: The purpose of this study was to compare the microhardness values of ProRoot mineral trioxide aggregate (MTA), Biodentine, and total fill root repair material (TF-RRM) Putty at varying pH and times. MATERIALS AND METHODS: In this laboratory experiment, materials were mixed and placed in cylinder blocks with internal dimensions of 6 mm × 4 mm. Ten samples of each material were soaked in buffered solutions of butyric acid with 4.4, 5.4, 6.4, and 7.4 pH values and stored at 37°C in 100% humidity. The samples were submitted to the microhardness test at the end of 1 week and then 1 month. Multivariate analysis of variance and Tukey honestly significant difference tests were carried out to compare the mean values at a significance level of P < 0.05. RESULTS: Low pH caused a significant decrease in the microhardness values of all samples. Surface microhardness increased with time (P < 0.0001). The microhardness values of Biodentine were significantly greater than those of ProRoot MTA and TF-RRM putty (P < 0.0001). The lowest microhardness values were recorded for TF-RRM putty groups regardless of the pH of the environment and the evaluation time. CONCLUSION: An acidic environment impaired the surface microhardness of all root repair materials tested. Overall, the mean surface microhardness of TF-RRM Putty was lower than those of ProRoot MTA and Biodentine. Biodentine showed the greatest microhardness values at all pH values, regardless of the evaluation time.

Effect of varying water-to-powder ratios and ultrasonic placement on the compressive strength of mineral trioxide aggregate.

INTRODUCTION: The purpose of this study was to compare the compressive strength of mineral trioxide aggregate (MTA) when mixed with 2 different water-to-powder (WP) proportions using either hand or ultrasonic placement. METHODS: Tooth-colored ProRoot MTA (Dentsply Maillefer, Ballaigues, Switzerland) and white MTA Angelus (Angelus Soluçoes Odontologicas, Londrina, Brazil) were investigated. One gram of each MTA powder was mixed with either 0.34 or 0.40 g distilled water. The 4 groups were further divided into 2 groups of 5 specimens for each of the following techniques: conventional (ie, hand placement) and placement using indirect ultrasonic activation for 30 seconds. All specimens were subjected to compressive strength testing after 4 days. The results were statistically analyzed with multivariate analysis of variance and Tukey Honestly Significant Difference tests at a significance level of P < .05. RESULTS: The mean compressive strength values of ProRoot MTA (84.17 ± 22.68) were significantly greater than those of MTA Angelus (47.71 ± 14.29) (P < .01). Specimens mixed with the 0.34 WP ratio had higher compressive strength values (72.85 ± 25.77) than those mixed with the 0.40 WP ratio (56.69 ± 24.85) (P < .05). The highest compressive strength values were recorded for ProRoot MTA specimens that were mixed in the 0.34 WP ratio, and then the samples were placed with ultrasonic activation (mean = 91.35 MPa). The lowest values were recorded for MTA Angelus samples that were mixed in the 0.40 WP ratio, and the specimens were placed without ultrasonic activation (mean = 36.36 MPa). Ultrasonic activation had no significant difference in terms of compressive strength. CONCLUSIONS: When using ProRoot MTA and MTA Angelus, higher WP ratios resulted in lower compressive strength values. Ultrasonication had no significant effect on the compressive strength of the material regardless of the WP ratio that was used. Therefore, adherence to the manufacturer's recommended WP ratio when preparing MTA for use in dental applications is advised.

Effect of various mixing and placement techniques on the flexural strength and porosity of mineral trioxide aggregate.

INTRODUCTION: The aim of this study was to evaluate the effect of mechanical and manual mixing as well as the effect of ultrasonic agitation during placement on the flexural strength and porosity of mineral trioxide aggregate (MTA). METHODS: White ProRoot MTA and white MTA Angelus were used. One gram of each powder was mixed with a 0.34-g aliquot of distilled water. Specimens were mixed either by mechanical mixing of capsules for 30 seconds at 4500 rpm or by a saturation technique and application of a condensation pressure of 3.22 MPa for 1 minute. The mixed slurries of all materials were loaded into 2 × 2 × 25 mm molds for testing flexural strength and 3 × 4 mm molds for evaluation of porosity. Half of the specimens were placed in the stainless steel molds by using indirect ultrasonic activation. All specimens were incubated for 4 days. Micro-computed tomography was used to determine the porosity of each specimen, and a 3-point bending test was used to evaluate flexural strength. Tukey honestly significant difference and independent t tests were carried out to compare the means at a significance level of P < .05. RESULTS: Irrespective of mixing and placement techniques applied, the flexural strength values of ProRoot MTA were significantly greater than those of MTA Angelus (P < .05). A medium negative correlation was found between flexural strength values and total porosity percentage. CONCLUSIONS: Although mechanical mixing of encapsulated cements was quicker and provided more consistent mixes, this technique along with ultrasonic agitation was not associated with a significant advantage in terms of flexural strength and total porosity over manual mixing.

Direct composite laminate veneers: three case reports.

Re-establishing a patient's lost dental esthetic appearance is one of the most important topics for contemporary dentistry. New treatment materials and methods have been coming on the scene, day by day, in order to achieve such an aim. Most dentists prefer more conservative and aesthetic approaches, such as direct and indirect laminate veneer restorations, instead of full-ceramic crowns for anteriors where aesthetics is really important. Laminate veneers are restorations which are envisioned to correct existing abnormalities, esthetic deficiencies and discolo-rations. Laminate veneer restorations may be processed in two different ways: direct or indirect. Direct laminate veneers have no need to be prepared in the laboratory and are based on the principle of application of a composite material directly to the prepared tooth surface in the dental clinic. Indirect laminate veneers may be produced from composite materials or ceramics, which are cemented to the tooth with an adhesive resin. In this case report, direct composite laminate veneer technique used for three patients with esthetic problems related to fractures, discolorations and an old prolapsed restoration, is described and six-month follow-ups are discussed. As a conclusion, direct laminate veneer restorations may be a treatment option for patients with the esthetic problems of anterior teeth in cases similar to those reported here.

The effect of various mixing and placement techniques on the compressive strength of mineral trioxide aggregate.

INTRODUCTION: The aim of this study was to evaluate the effect of various mixing techniques including mechanical and manual mixing as well as the effect of ultrasonic agitation during placement on the compressive strength of mineral trioxide aggregate (MTA). METHODS: Tooth-colored ProRoot MTA (Dentsply Maillefer, Ballaigues, Switzerland) and white MTA Angelus (Angelus Soluções Odontologicas, Londrina, Brazil) were used. One gram of each powder was mixed with a 0.34-g aliquot of distilled water. Specimens were mixed either by mechanical mixing of capsules for 30 seconds at 4,500 rpm or by a saturation technique and the application of a condensation pressure of 3.22 MPa for 1 minute. Half of the specimens were placed in stainless steel molds and agitated using indirect ultrasonic activation. All specimens were subjected to compressive strength testing after 4 days. RESULTS: The compressive strength values of ProRoot MTA were significantly greater than those of MTA Angelus (P < .05). The highest compressive strength values were recorded from ProRoot MTA samples that were mixed mechanically and placed using ultrasonic activation (mean = 101.71 MPa), whereas the lowest values were recorded for MTA Angelus samples that were mixed manually and placed without ultrasonic activation (mean = 53.47 MPa). Ultrasonically agitated groups had higher compressive strength values (P < .001). The specimens mixed mechanically had higher compressive strength values than those mixed manually (P < .05). CONCLUSIONS: The compressive strength values of ProRoot MTA were significantly greater than those of MTA Angelus. Mechanical mixing enhanced the compressive strength of the material. Regardless of the mixing techniques applied, ultrasonic agitation improved the compressive strength of the material.

Evaluation of smear layer removal after use of a canal brush: an SEM study.

OBJECTIVE: The objective of this study was to evaluate smear layer removal after using the new CanalBrush (Coltene/Whaledent GmbH+Co. KG, Germany). STUDY DESIGN: Twenty extracted maxillary anterior teeth were randomly divided into 2 equal groups. The canals of the teeth in each group were instrumented with ProTaper Universal rotary files (Dentsply Maillefer, Switzerland). Following each file use, the root canals in both groups were irrigated with 5.25% NaOCl and 15% EDTA. At the end of instrumentation, the canals in group 2 were flushed with 15% EDTA, then a CanalBrush was used for 30 seconds, and a final irrigation was conducted with 5.25% NaOCl. All teeth were processed for scanning electron microscopy (SEM), and the removal of the smear layer was examined in the apical, middle, and coronal thirds. Analyses of SEM images were performed by 2 independent evaluators in a blinded manner and using a 4-point scoring system. RESULTS: The middle and apical thirds of the root canals in group 2 showed lower average scores than those in group 1, but the difference was not statistically significant. There was no significant difference in the coronal score between the groups (P > .05). CONCLUSIONS: Irrigating with brushing tended to produce cleaner canal walls, but irrigating brushing was not significantly better than irrigation alone in removing the smear layer on the canal walls.

Shear bond strength of composite bonded with three adhesives to Er,Cr:YSGG laser-prepared enamel.

OBJECTIVE: To assess in vitro the shear bond strength of a nanohybrid composite resin bonded with three adhesive systems to enamel surfaces prepared with acid and Er,Cr:YSGG laser etching. METHOD AND MATERIALS: Sixty extracted caries- and restoration-free human maxillary central incisors were used. The teeth were sectioned 2 mm below the cementoenamel junction. The crowns were embedded in autopolymerizing acrylic resin with the labial surfaces facing up. The labial surfaces were prepared with 0.5-mm reduction to receive composite veneers. Thirty specimens were etched with Er,Cr:YSGG laser. This group was also divided into three subgroups, and the following three bonding systems were then applied on the laser groups and the other three unlased groups: (1) 37% phosphoric acid etch + Bond 1 primer/adhesive (Pentron); (2) Nano-bond self-etch primer (Pentron) + Nano-bond adhesive (Pentron); and (3) all-in-one adhesive-single dose (Futurabond NR, Voco). All of the groups were restored with a nanohybrid composite resin (Smile, Pentron). Shear bond strength was measured with a Zwick universal test device with a knife-edge loading head. The data were analyzed with two-factor ANOVA. RESULTS: There were no significant differences in shear bond strength between self-etch primer + adhesive and all-in-one adhesive systems for nonetched and laser-etched enamel groups (P > .05). However, bond strength values for the laser-etched + Bond 1 primer/adhesive group (48.00 +/- 13.86 MPa) were significantly higher than the 37% phosphoric acid + Bond 1 primer/adhesive group (38.95 +/- 20.07 MPa) (P < .05). CONCLUSION: The Er,Cr:YSGG laser-powered hydrokinetic system etched the enamel surface more effectively than 37% phosphoric acid for subsequent attachment of composite material.

Tensile bond strength of dentin adhesives on acid- and laser-etched dentin surfaces.

OBJECTIVE: To evaluate tensile bond strengths of 2 dentin bonding agents containing solvents on Nd:YAG and Er,Cr:YSGG laser-etched dentin surface. METHOD AND MATERIALS: Occlusal enamel of 146 molars was removed, and exposed surfaces were ground with a diamond bur to produce bur-cut dentin surfaces. Of those teeth, 120 were assigned to 3 groups of 40 samples in which dentin was conditioned with Er,Cr:YSGG laser, Nd:YAG laser, and 37% orthophosphoric acid (control). Each group was further divided into 2 subgroups, acetone- and ethanol-containing bonding agents, and 4-mm-long x 4-mm-wide composite rods were bonded to all specimens using a Plexiglas mold. Tensile bond strength testing of 120 samples was performed at a crosshead speed of 0.5 mm/min using a 50-kgf load cell. The remaining 26 samples were examined under SEM to evaluate the adaptation/penetration of the bonding materials and the alterations in mineral content. Data were analyzed using 1-way ANOVA and Kruskal-Wallis tests; P < .05 was considered statistically significant. RESULTS: The difference between the mean tensile bond strength values obtained with bonding agents was statistically significant in the control group. The bond strength values of the acetone-containing agent in this group were found to be higher than the ethanol-containing agent (P < .001). When compared with Nd:YAG laser, bond strength values obtained with Er,Cr:YSGG laser were higher (P < .001). The bond strength values obtained in the acid-etched group were highest for both bonding agents and demonstrated statistical significance (P < .001). CONCLUSION: Although in this study laser etching is more influential than the solvent type on bond strengths of dentin bonding agents, it cannot be considered as an alternative to conventional acid etching.

The study of the age of becoming edentulous in the last 20 years in Turkey.

The aim of this study was to determine the age of becoming edentulous and make a comparison between the patients examined in 1987 and in 2007 at the Dental School, University of Marmara in Istanbul, Turkey. A total of 680 patients (336 in 1987 and 344 in 2007) visiting the Dental School were examined. Some of the patients had just their teeth drawn, or had already became edentulous before, and were sent to the Department of Prosthodontics, for prosthodontic treatment of their edentulous mandible or maxilla. Some of the patients have few teeth and they were extracted at the Department of Oral and Maxillofacial Surgery, they became edentulous. The age of the patients that they first become edentulous and begin to use complete denture was determined. The patients grouped according to their age, sex and being completely edentulous or edentulous in one jaw. Fisher's exact test was performed during the evaluation of quantitative data. Statistical significance level was established at p<0.05. Between 1987 and 2007, a more than 50% decrease was observed in the number of the patients who were completely edentulous or edentulous only in one jaw. This observation is one of the indications of development of patients' care and improvement in the state of mouth health in Turkey during the last 20 years.

A comparative study of three different root canal curvature measurement techniques and measuring the canal access angle in curved canals.

In the first part of this study the Schneider (S), Weine (W), and Long-Axis (LA) techniques are used for comparing the measurement of canal curvature. One hundred mandibular first and second molar teeth were selected. Radiographs were taken after inserting size 10 K-files into the mesiobuccal root canals. The radiographic findings were digitized on a computer, and the three different curvature angles were measured from drawings of the same root canal and compared statistically. ANOVA showed that there were significant differences between the curvature angle values determined using each technique (p < 0.001). In the second part of this study the term "canal access angle" (CAA) was introduced and it was defined by examining the morphology of canal curvature. Canal length, curvature distance (y), curvature height (x), Schneider angle, and the newly defined CAA were evaluated statistically. Using a multiple regression analysis, the CAA was significantly related to x (p < 0.001) and y (p < 0.005). There was a positive correlation (r = 0.74) between the CAA and curvature height (x). The results indicated that the CAA is a more effective way of evaluating the root canal curvature.

Early tensile bond strength between dentin and composite resin mediated by bonding agents / Forças iniciais de resistência a tração entre a dentina e a resina composta mediada por agentes de adesão

The aim of this study was to evaluate, in vitro, the early tensile bond strength values of three dentin bonding agents (Scotchbond, Tenure and Gluma) to dentin. Fifteen non-carious, extracted, human third molars were used in this study. The bond strengths were calculated in an Instron test machine and expressed in MN/m². The results were evaluated statistically using the Syudentt-test. The in vitro tensile bond strengths of the three bonding agents to dentin showed higher values than the tensile bond strength of composite resin alone and differences among the bond strengths were significant (P<0.05). Greater bond strength values were obtained with the Gluma bonding system than with Scotchbond or Tenure systems