Determining cutting efficiency of nickel-titanium coronal flaring instruments used in lateral action.

AIM: To develop a method to evaluate the cutting behaviour of nickel-titanium (NiTi) coronal flaring instruments. METHODOLOGY: BioRaCe BR0 (BR), HyFlex CM 1 (HY), ProFile OS No. 2 (PF) and ProTaper Sx (PT) instruments were used in simulated coronal flaring using a lateral action against bovine dentine blocks, at 250 and 500 rpm. Cutting efficiency was assessed by three methods: first, areas of notches produced by instruments were directly measured under a stereomicroscope. Second, dentine specimens were then analysed by surface profilometry to determine the maximum cutting depth and finally by microcomputed tomography to assess the volume of removed dentine. Data were compared using parametric tests with the significance level set at 0.05. RESULTS: For all three methods, HY and PF were the most and the least cutting-efficient instruments, respectively (P < 0.05). Significant differences were detected between 250 and 500 rpm for HY and PT (area); for BR, HY and PT (depth); and for BR and HY (volume). There were strong positive correlations between the results obtained with those three different methods with r-values ranging from 0.81 to 0.92. CONCLUSION: Measuring the amount of material removed in a specific time under stereomicroscopy is a simple and rational way to assess the cutting behaviour of NiTi rotary instruments in lateral action. HyFlex, manufactured with thermomechanically treated NiTi wire, was the most efficient instrument, and increased rotational speed was associated with increased cutting efficiency.

Use of cone beam computed tomography in the diagnosis, planning and follow up of a type III dens invaginatus case.

AIM: To present the case of a maxillary left lateral incisor with Oehlers' type III dens invaginatus in which cone beam computed tomography (CBCT) was used as an adjunctive resource in the diagnosis as well as in the planning and 2-year follow-up of the nonsurgical/surgical treatment. SUMMARY: The tooth had two root canals: a primary (main) canal with vital pulp that appeared to be closed apically and an invaginated canal that was necrotic, wide-open at the portal of exit and associated with a large chronic periapical lesion extending to the apex of the maxillary left central incisor. Radiographic tracking of a sinus tract in the labial gingiva of the affected tooth with a gutta-percha point revealed its origin to be the invagination. The CBCT scans revealed that the periapical radiolucency was significantly larger than seen radiographically as well as an increased thickness of the buccal cortical plate. Conventional root canal treatment of the primary canal was undertaken. As nonsurgical access to the invaginated canal was not possible, endodontic surgery was performed for curettage of the lesion, root-end cavity preparation using ultrasonic tips and root canal filling with white mineral trioxide aggregate (MTA). CBCT scanning after 17 months and clinical and radiographic follow-up after 24 months revealed complete periapical repair and absence of symptoms. KEY LEARNING POINTS: The combination of nonsurgical and surgical treatments produced periapical repair in a tooth with type III dens invaginatus with two root canals. CBCT may aid the diagnosis as well as the management plan and follow-up of teeth with this developmental anomaly.

Antibacterial activity of two MTA-based root canal sealers.

AIM: To evaluate the pH and antibacterial activity of Endo CPM Sealer and MTA Fillapex by two different methods, using white MTA and Endofill as references for comparison. METHODOLOGY: Antibacterial activity was evaluated against Enterococcus faecalis (ATCC 29212). The agar diffusion test (ADT) was performed to evaluate the effect before setting. The materials were placed in four equidistant wells made in ten agar plates. After incubation at 37 °C for 48 h, the inhibition zones were measured using a digital paquimeter. The direct contact test (DCT) was performed to assess the antibacterial effect after setting. Suspensions of crushed materials were prepared and mixed with E. faecalis. After different periods of time (1, 6, 15 and 60 min), the survival of bacteria was assessed by using 10-fold serial dilution and cultivated on agar plates in triplicate. Colony-forming units (CFU) mL(-1) were calculated after incubation. pH values were also measured in triplicate. Comparison between sealers in the ADT and DCT was performed by the Kruskal-Wallis test. RESULTS: In the ADT, inhibition zones were found with MTA Fillapex and Endofill. They were similar to each other and greater than the other sealers (P < 0.05). None of the tested sealers demonstrated antibacterial activity in the DCT, and thus, all sealers had similar bacterial counts compared with the negative control group (P > 0.05). White MTA and Endo CPM Sealer suspensions had pH values >11, whilst MTA Fillapex and Endofill had lower values. CONCLUSIONS: MTA Fillapex and Endofill had an antibacterial effect against E. faecalis before setting, but none of the sealers maintained antibacterial activity after setting, despite the high pH of the MTA-based materials.

The anatomy of the root canal system of three-rooted maxillary premolars analysed using high-resolution computed tomography.

AIM: To analyse the anatomy of the root canal system of maxillary premolars with three distinct roots using high-resolution computed tomography (µCT). METHODOLOGY: Ten three-rooted human maxillary premolars were scanned transversally from crown to apex at 42µm intervals using a high-resolution desktop µTC system (Skyscan 1072). The images were processed and analysed for the following features: cross section of the roots and canals in the apical, middle and coronal thirds; location of the apical foramen; distance from the pulp chamber roof to the bifurcation and trifurcation of the canals and anatomic variations of the root canal system. The results were expressed descriptively. RESULTS: The cross-sectional shape of canals was heterogeneous along the length of the roots. The location of the apical foramen varied, tending to lie palatally or distally. The buccal pulp horn was larger than the palatal. The mean distance from the most cervical region of the pulp chamber roof to the bifurcation and trifurcation of the canals was 3.13 and 5.08mm, respectively. CONCLUSIONS: Features of the internal anatomy of the pulp cavity of three-rooted maxillary premolars were identified with the use of µCT. The results revealed the heterogeneity of three-rooted maxillary premolars.

The effect of head-fractioned teletherapy on pulp tissue.

AIM: To evaluate the early and delayed effects of fractioned teletherapy (radiotherapy) on the dental pulps of rats using Co(60). METHODOLOGY: In group 1 - rats (n = 15) were subjected to fractioned teletherapy by 30 daily sessions fractioned in doses of 200 cGy day(-1), totaling 60 Gy and the rats were killed immediately after the final dose of irradiation; group 2 - same protocol but killed 30 days following the final irradiation dose; groups 3 (n = 7) and 4 (n = 8) - formed controls without irradiation. Following perfusion, the left mandible of each rat was dissected and processed for histopathology. Serial sections (5 microm) were obtained and stained with HE or picrosirius. Observations were recorded for the coronal pulp tissue. A blinded observer evaluated HE sections using pre-defined indices of inflammation, nuclear alterations and extracellular matrix (ECM) hyalinization. Images of sections stained with picrosirius were converted to black and white for analysis by image-pro plus; areas in black (collagen) were measured as percentage area. The pulps of mandibular incisors of the specimens prepared for transmission electron microscopy (TEM) were subjected to descriptive analysis. Magnifications of 6300 and 10000 x were used to observe 10 pulp fibroblasts from each group. RESULTS: No inflammatory reactions or modification of the ECM status were found (P = 0.428) in any specimens. The collagen content also displayed no significant changes (P = 0.067) as a result of treatment. Groups 1 and 2 displayed significantly more nuclear alterations than the control groups (P < 0.05). The bubble-like aspect was more pronounced in group 1, and the bubbles looked smaller in group 2. The ECM showed no differences in the hyalinization status and there were no differences in the collagen area within the pulps. Under TEM, the pulp fibroblasts in group 1 displayed nuclear alterations that resembled circular, oval or elongated perforations; perforations also appeared in the cytoplasm. CONCLUSION: Fractioned teletherapy is capable of producing nuclear alterations in the dental pulp tissue of rats.