Retreatment efficacy of hand versus automated instrumentation in oval-shaped root canals: an ex vivo study.

AIM: To compare the efficacy of hand versus automated instrumentation when retreating oval-shaped root canals. METHODOLOGY: Sixty human premolars with single oval canals were instrumented and filled with gutta-percha and sealer and divided into three groups (n = 20)--group 1: ProFile .04 taper rotary instruments; group 2: Anatomic Endodontic Technology (AET), and group 3: manual instrumentation with Hedström files. The teeth were split longitudinally and gutta-percha/sealer remnants in the coronal, middle and apical thirds were assessed with light microscopy. The mean percentage of gutta-percha/sealer remnants for each group was calculated and statistically analysed for significance using an ANOVA repeated measures (P < 0.001) and Tukey's multiple comparison test. The time required for retreatment was analysed using a one-way ANOVA and Tukey's test (P < 0.001). RESULTS: Overall, 10-18% of the canal walls were covered with gutta-percha/sealer remnants after preparation using any technique. Statistical analysis demonstrated that the mean values for remnants of filling material in the ProFile group were significantly higher than for the other groups (P < 0.001), except in the apical third where no significant difference occurred. In all groups, the mean values in the middle third were higher than the coronal and apical thirds. The retreatment time for ProFile and AET was significantly shorter compared to manual instrumentation with Hedström files (P < 0.001). CONCLUSIONS: Under the experimental conditions, AET instruments and manual instrumentation with Hedström files resulted in cleaner canals. However, completely clean root canal walls were not produced with any of the techniques investigated.

Effectiveness in cleaning oval-shaped root canals using Anatomic Endodontic Technology, ProFile and manual instrumentation: a scanning electron microscopic study.

AIM: To compare in vitro the cleanliness of root canal walls in oval-shaped root canals following automated or manual instrumentation. METHODOLOGY: Forty-five oval-shaped single-rooted maxillary and mandibular premolars with straight canals were divided into three groups of 15. Automated canal preparation was performed using Anatomic Endodontic Technology (AET, group 1) and the ProFile system (group 2). Manual instrumentation (group 3) was performed with K-Flexofiles. Irrigation was performed using alternately 5.25% NaOCl and 17% EDTA, followed by rinsing with saline. The roots were split longitudinally into halves and the canals examined at x200 and x400 in a scanning electron microscope. The presence of debris and smear layer was recorded at distances of 1, 5 and 10 mm from the working length using a three-step scoring scale and a 300 mum square grid. Mean scores for debris and smear layer were calculated and statistically analysed for significance (P < 0.05) between and within groups, using the Kruskal-Wallis nonparametric anova and Dunn's tests. RESULTS: At 1, 5 and 10-mm levels the root canals prepared with AET had significantly less surface debris and smear layer on the canal walls compared with canals prepared with ProFile or manual instrumentation. For all three groups significantly lower mean smear layer scores (P < 0.05) were recorded at 5 and 10-mm levels compared with the 1 mm level. Significantly lower mean debris scores (P < 0.05) were also recorded at 5 and 10-mm levels for the AET group whereas no significant differences were found between the three levels for the ProFile and manual instrumentation groups. CONCLUSIONS: Although better instrumentation scores were obtained in canals prepared with AET, complete cleanliness was not achieved by any of the techniques and instruments investigated.

In vivo determination of root canal length: a preliminary report using the Tri Auto ZX apex-locating handpiece.

AIM: The aim of this study was to assess the clinical perfomance of a cordless handpiece with a built-in apex locator - the Tri Auto ZX - designed for root canal preparation with nickel-titanium rotary files. METHODOLOGY: Twenty-five human maxillary incisor and canine teeth scheduled for extraction with mature apices were selected for the study. Informed written consent was obtained from each patient before treatment. After administration of local anaesthesia, the teeth were isolated and the pulp cavities accessed. The Tri Auto ZX along with a size 15 K-file was used in its electronic apex locating function based on the manufacturer's recommendations. A periapical radiograph with the file at the electronically determined constriction was taken, the file removed and the measurement registered as the electronic length (EL). To test the auto reverse function, a size 20 ProFile.04 taper NiTi rotary instrument was mounted in the handpiece. The point for the auto apical reverse function was preset on the panel at the 0.5 mm level. After the file was introduced into the canal and reached the predetermined level, the file automatically stopped and rotated in the opposite direction. A reference point was marked and this measurement was registered as the auto reverse length (ARL). All measurements were made twice by two different investigators. Teeth were then extracted and immersed in a 20% formalin solution for 48 h. After fixation, a size 15 file was inserted into the canal to measure the actual root canal length from the same reference point obtained with the Tri Auto ZX to the apical foramen, as seen in the stereo microscope. When the file tip was visible at the anatomical end of the canal it was withdrawn 0.5 mm and this measurement was registered as the actual length (AL). All measurements were expressed in mm and the measuring accuracy was set to 0.5 mm. The significance of the mean differences between EL and ARL and between EL and AL measurements at the 5% confidence level was evaluated. RESULTS: EL measurements were coincident to ARL in all instances. EL and ARL were coincident to AL in 10 (40%) canals, in the remaining 15 canals (60%) the AL measurements were longer than EL and ARL (+0.5 mm) in 14 instances and shorter (-0.5 mm) in one case. Overall, the AL was longer than the EL or ARL, the mean difference being -0.23 mm +/- 0.32 (P < 0.05). CONCLUSIONS: It was concluded that the Tri Auto ZX was useful and reliable. The Tri Auto ZX measurements protected against overpreparation.

Five canals in a mandibular second premolar.

A case of conservative endodontic therapy for a mandibular second premolar with five root canals is described. A thorough knowledge of the root canal anatomy, careful interpretation of the radiographs, and access cavity modifications are essentials for enhancing intracanal procedures.

Endodontic management of a mandibular third molar fused with a fourth molar.

CASE REPORT: Developmental anomalies in permanent molars frequently require surgical intervention. A case of a mandibular third molar fused with a fourth molar which was successfully treated with conservative endodontic therapy is reported.

Endodontic therapy in a fused mandibular molar.

This case report describes the endodontic management of fusion involving a mandibular third molar and a fourth molar (distomolar).

Endodontic therapy in a maxillary second molar with three buccal roots.

In this study, we report a case of a four-rooted maxillary second molar in which three well-separated buccal roots were located. This case demonstrated that even though it is not common, an extra root containing an independent root canal may occur.

A case of severe vestibular root angulation.

In this article, we describe the appearance and management of an impacted permanent tooth with severe vestibular root angulation. In addition, the possible origin of this type of root malformation as well as some of their epidemiologic aspects are discussed.

Compatibility between standardized endodontic finger spreaders and accessory gutta-percha cones.

Twenty samples of each size designation of finger spreaders and accessory gutta-percha cones were randomly selected from a proprietary standardized system currently used for lateral condensation procedures. Their diameters were measured with a calliper and their morphological variations at the areas of their apical thirds were analyzed with the scanning electron microscope. Results of the measurements indicated that there were high degrees of variation between all spreaders and their corresponding accessory gutta-percha cones (p < 0.001). SEM examination showed the presence of many morphologic irregularities and lack of uniformity between spreaders and cones of the same size. Our results emphasize the need for more precise criteria to fulfill the requirements of standardization by the manufacturer to provide an accurate method for root canal obturation.

Comparison of three instrumentation techniques in the preparation of simulated curved root canals.

Forty-five acrylic blocks with simulated curved canals were divided into three groups of 15 blocks each. In group 1 the canals were instrumented with ultrasonically energized K-files (UEF) using a piezoelectric ultrasonic device. In group 2 the canals were prepared with ProFile 0.04 Taper Series 29 Rotary Instruments (PRI) in conjunction with a low-speed high torque handpiece. In group 3 (control) the canals were hand instrumented (HI) with conventional K-type files using a standard push-pull circumferential technique. The efficiency of these techniques for preparing the simulated canals were compared by measuring the amount of transportation of the prepared canals at different levels from the working length using a double exposure photographic technique. A statistical analysis was used to indicate any significant difference among groups. The results showed that the use of PRI provided well-centred and more tapered preparations. Conversely, the use of UEF and HI resulted in frequent alteration of the original curvature, showing transportation at different levels from the working length.

Endodontic management of mandibular lateral incisor fused with supernumerary tooth.

In this article we report a case of a mandibular lateral incisor in which 3 separate root canals were located. Clinical and radiographic examinations suggested that fusion had occurred between the mandibular incisor and a supernumerary tooth. The endodontic management of the tooth is described, and repair of an apical periodontitis had occurred after 9 months.

Effectiveness of nickel-titanium files for preparing curved root canals.

In this study, the effect of 2 different endodontic files on the final shape of curved root canals of extracted single rooted teeth were examined in the scanning electron microscope. The instruments tested were a newly designed nickel-titanium endodontic file and a conventional K-type file. The files were used with in and out linear movements with a circumferential motion starting with a size 15 file. Final preparation of the apical thirds of the canals was performed with a size 35 file. Shaping effectiveness of the tested instruments was evaluated in terms of respect for conservation of the apical constriction and the presence or absence of ledging. Our observations revealed that more centered and tapered preparations were obtained with the use of the nickel-titanium files than with the conventional K-type files.

Cleaning of endodontic instruments before use.

In this study, 120 new K-files and Hedström files from 3 different manufacturers were examined for surface debris with the scanning electron microscope. The instruments were examined immediately upon removal from their original packages. A second examination of the instruments was performed after they were cleansed in an ultrasonic bath. None of the studied instruments were free of metallic spurs or foreign particles as received from the manufacturers. The ultrasonic bath used together with a cleanser solution appeared to be an effective method to minimize the surface impurities from the manufacturing process prior to use in patients.

Effectiveness of two different methods for preparing curved root canals.

In this study, the effect of using two different methods for preparing curved root canals of extracted, single-rooted teeth were analyzed with the scanning electron microscope. The instrumentation systems tested were the Canal Master and a standard circumferential filing technique in which conventional K-files were used. Shaping effectiveness was qualitatively evaluated in terms of respect for conservation of the apical constriction and the presence or absence of ledging, specially in the apical third of the root canals. As a result of our observations, it appeared that the Canal Master instrumentation technique provided well-centered and tapered preparations. Conversely, the use of conventional K-files with a standard circumferential filing technique resulted in frequent alterations of the initial pattern of the root canals, showing transportation of the apical foramen and ledge formation.

Effectiveness of different endodontic files for preparing curved root canals: a scanning electron microscopic study.

In this study, the effect of using four endodontic files from different manufacturers on the final shape of 80 prepared curved root canals of extracted single-rooted teeth were comparatively analyzed with scanning electron microscopy. The instruments tested were Tri-files, Flex-R files, Flexofiles and conventional K-type files. All files were used with in and out linear movements with a circumferential motion starting with a size 15 file. Final preparation of the apical thirds was performed with a size 30 file. Shaping effectiveness of the tested files was qualitatively evaluated in terms of respect for conservation of the apical constriction and the presence or absence of ledging, specially in the apical third of the root canals. A well-centered and tapered preparation without apical transportation or ledging was detected when Tri-file or Flex-R files were used. Conversely, the use of Flexofile or conventional K-type files resulted in frequent alteration of the initial pattern of the root canals, showing an hour-glass preparation with alteration of the apical constriction and ledge formations.

A case of progressive external root resorption.

This case report describes a radiographical, histological and histochemical study of an extracted mandibular tooth with progressive external root resorption. The cells which appeared to be responsible for the hard tissue resorption showed an intense acid phosphatase activity, similar to that of bone-resorbing cells. Some aspects on the etiology and pathogenesis of resorptive process that occurred in the present case are discussed.

Thermomechanical compaction of gutta-percha: a scanning electron microscope study.

The root canals of 20 freshly extracted maxillary central incisors and canines were prepared and filled by thermo-mechanical or lateral condensation of gutta-percha cones without sealer. The adaptation of the filling material to the root canal walls was then examined with a scanning electron microscope. A more homogenized mass of gutta-percha could be detected in teeth filled by thermomechanical compaction of gutta-percha cones. The morphology of the prepared root canal system was well reproduced by the use of both techniques.

Surface architecture of a low-temperature thermoplasticized gutta-percha.

The surface characteristics of two Ultrafil materials, Regular set (RS) and Firm set (FS) were analyzed by scanning electron microscopy (SEM). The samples of Ultrafil were obtained from both RS and FS cannules which were pre-heated to 70 degrees C. Another RS and FS samples were obtained at room temperature from un-heated cannules. Samples of standard gutta-percha points obtained from the same manufacturer were studied for comparative purposes. RS samples obtained from pre-heated and un-heated cannules exhibited rough surfaces containing randomly distributed crystal-like structures. Heated and un-heated FS samples featured smoother surfaces with fewer crystal-like structures. The gutta-percha points also exhibited smooth surfaces and absence of crystal-like structures. The consequence of the possible release of these structures from Ultrafil in a biological system is discussed.

Silver accumulations in periapical granulomas: report of five cases using the scanning electron microscope, the electron microprobe, and other complementary methods.

A series of cytologic imprints obtained from periapical granulomas were studied with the conventional light microscope, the scanning electron microscope, and the electron microprobe to analyze the chemical composition of several black deposits that were randomly observed near or in the cytoplasm of macrophages and multinucleated giant cells. These granulomas had been removed from endodontically treated human teeth in which the root canals had been obturated with silver cones and Grossman's sealer 3 to 5 years previously. To investigate whether corrosion had occurred on the silver cones, the cones were also examined with the scanning electron microscope and the electron microprobe. Our observations revealed that all the examined silver cones showed different degrees of corrosion on their surfaces, whereas different concentrations of silver, sulfur, and chlorine were detected at the same sites in the cytologic imprints. However, it is impossible to determine from this study whether the presence of corrosive by-products in the periapical tissues is responsible for the development of a pathologic reaction at these sites.