ENDO, 04/2016

Aim: To assess, using the principle of three-dimensional (3D) coordinate metrology, the location and degree of surface damage or wear of two commercially available engine-driven nickel-titanium (NiTi) files after clinical use. Methodology: A total of 24 engine-driven NiTi endodontic files, 12 rotary (ProTaper, Dentsply Maillefer, Ballaigues, Switzerland) and 12 reciprocating (Reciproc, VDW, Munich, Germany), were collected after clinical use. A coordinate measurement dental scanner was used to capture the 3D coordinate data of each endodontic file surface. The surface data were subjected to 3D analysis using a 3D free-form surface analysis software package, which involved the surface interpolation, registration and subtraction of each image of the scanned surface to a baseline 3D image of a new, unused file. Three representative points at the coronal, middle and apical third of each sample were selected to assess any differences in surface damage or wear between the two file types. The reproducibility of the methodology, the measurement of new, unused and used engine-driven NiTi files, was tested. Results: The reproducibility of the methodology was excellent, with a depth difference of 0.002 mm for the new, unused files and 0.005 mm for used files of both types. Reciprocating files generally showed greater surface damage in comparison with rotary files. Furthermore, reciprocating files showed greater wear in the apical third and less wear in the coronal third. In contrast, rotary files had greater surface damage in the coronal third, decreasing towards the apical third. Conclusions: 3D coordinate metrology provided an objective, reproducible, more economical and non-destructive method for assessing the surface damage or wear of engine-driven NiTi files after clinical use. There was more damage seen with files operated in reciprocation compared with those operated in continuous rotary motion. The file operating motion and surface contact at different stages of root canal preparation may account for the differences in the degree and location of surface damage. Keywords: NiTi files, ProTaper, Reciproc, surface damage, 3D dental scanner

Root canal treatment may present a considerable number of different challenges of widely differing severity. Problems occurring during root canal treatment frequently require modifications of treatment and the use of specific materials and instruments. Some of these problems can be prevented by thorough case selection and proper treatment planning. Others can be managed more easily and successfully if their possible occurrence is anticipated; and strategies, instruments and materials for immediate management are available. Thus, diagnosis-related and problem-oriented treatment planning (and preparation) is recommended. The following case report presents an example for problembased endodontic treatment planning and treatment. Keywords: management, prevention, problems, root canal treatment, systemic diseases

Aim: To investigate the preferences and experiences of general dental practitioners (GDPs) and endodontists in using nickel-titanium rotary instruments (NiTi-RIs) for root canal retreatment (RCR) and to explore the influencing factors. Materials and Methods: Following a pilot study, the final questionnaire comprised 43 questions. The sample size was calculated considering 90% power calculation, dentists' population (n = 7050), and worst accepted response rate of 48%. The electronic questionnaire was emailed to 600 GDPs and all endodontists in Saudi Arabia (n = 175). A reminder email was sent after 8 weeks. Responses were collected, and data were analysed using the chi-square test at P = 0.05. Results: The overall response rate was 53.2%. The highest proportion of respondents (74.4%) used NiTi-RIs for RCR; with a greater proportion of endodontists (88.2%) compared to GDPs (66.2%) [P 0.001]. The most common reason for not using NiTi-RIs was unavailability (52.4%). The proportion who used conventional NiTi-RIs for RCR (61.3%) was greater than those who use specially designed NiTi-RIs (38.7%) [P 0.001]. More endodontists (52.2%) used specially designed NiTi-RIs compared to GDPs (33.3%) [P = 0.016]. 68.6% and 53.9% of participants experienced complications when using conventional and specially designed NiTi-RIs, respectively. While fracture of conventional NiTi-RIs was the most common complication (44.6%), ledge formation was the most common one while using specially designed NiTi-RIs (47.9%). Conclusions: Results indicate common incorporation of NiTi-RIs into RCR procedures among GDPs and endodontists. Unavailability is the main limitation, whereas instrument fracture and ledge formation are the most common complications while using conventional and specially designed NiTi-RIs, respectively. Keywords: complications, endodontists, general dental practitioners, nickel-titanium rotary files, retreatment, survey

Newer NiTi rotary and reciprocating instruments have enabled the management of unusual and challenging root canal anatomies. While the use of these instruments has somewhat negated the plethora of problems encountered with hand instruments only, problems may still occur with the newer engine-driven instruments. This case report discusses the potential problem areas, highlights the integrated application of both hand and rotary instruments and details the benefits of this approach to achieve successful root canal procedures. Keywords: dilacerated root canal, integrated root canal procedure, problem solving, S-shaped root canal

Aim: The presence of a furcation groove on the palatal aspect of bifurcated maxillary first premolars (MFPs) leaves the dentine cementum wall (DCW) thickness critically thin in this region of the root. The purpose of this study was to evaluate the morphology of the furcation groove and the DCW thickness along the groove before and after root canal instrumentation, utilising cone beam computed tomography (CBCT). Materials and methods: Twenty-five human MFPs with bifurcated roots and furcation groove were divided into three groups according to one of three file systems: Hyflex CM, ProTaper Next (PTN) and Self-Adjusting File (SAF). Pre-instrumentation CBCT analysis was performed for the location, length, beginning and end of groove, and measurement of the minimum DCW thickness along the length of the groove. Post-instrumentation CBCT scans were analysed again for residual DCW thickness. The amount and percentage of cut dentine were calculated. Results: The groove began at a mean distance of 1.88 ± 0.13 mm above the bifurcation in 16 out of 25 samples, with a mean length of 5.61 ± 0.38 mm and a mean maximum depth of 0.7 ± 0.15 mm, located at a mean distance of 4.92 ± 0.15 mm above the apex. Preoperatively, the mean DCW thickness was 0.73 ± 0.07 mm. Post-instrumentation, statistically significant reductions in DCW thickness were observed with Hyflex 40/4% (P value = 0.0002), PTN X3 and X4 (P = 0.0002 and 0.0001) and SAF (P = 0.0002). Conclusions: Instrumentation of buccal canals of MFPs with furcation grooves should be performed using files with smaller tip sizes and minimum taper. Keywords: cone beam computed tomography, furcation groove, maxillary first premolar, residual dentine cementum wall thickness