Evaluation of Dental Students' Skills Acquisition in Endodontics Using a 3D Printed Tooth Model.

OBJECTIVE: The purpose of this prospective quantitative study was to assess the improvement of skills among pre-clinical dental students who practiced root canal obturation on a 3D-printed tooth model. METHODS: Preclinical students at the dental school (n=145) enrolled in the 2-week endodontic rotation course were invited to participate in the study. Four alphabetically distributed intact groups of first-year students were randomly allocated to either the control or the experimental group that obturated canals of a 3D-printed tooth. The plastic model was obtained from a microCT scan and based on an STL data set. The model was an identical replica of a natural mandibular molar that had been instrumented, ready for obturation. The control group did not obturate the tooth model but received identical instruction. Later in the course all students obturated an extracted human mandibular molar tooth. Technical obturation quality was assessed by two blinded evaluators. Radiographs were used to evaluate obturation length and density. Inter-observer reliability of average performance scores was calculated with the intra-class correlation coefficient for both consistency and absolute agreement. Obturation skills of those who practiced with the model were statistically compared to students who did not use the model with the Mann-Whitney U-test. RESULTS: Inter-observer reliability was very high for both consistency and absolute agreement. No significant differences were found in obturation skills between the experimental and control group (P>0.05). CONCLUSION: Under the condition of this study, dental students' obturation skills did not significantly improve by further practicing obturation using a 3D-printed model.

Root Canal Morphology of 116 Maxillary Second Premolars by Micro-Computed Tomography in a Mixed Swiss-German Population with Systematic Review.

INTRODUCTION: The aim of this investigation was to examine the root canal system morphology of maxillary second premolars (Mx2Ps) of a Swiss-German population by means of micro-computed tomography and provide systematic review of the root canal configuration (RCC) literature of Mx2Ps. METHODS: The RCC, main foramina as well as accessory canals and foramina frequency of 116 Mx2Ps, were investigated by means of micro-computed tomography and 3-dimensional software imaging. The RCC from the coronal to apical thirds of the root as well as the main foramina number were described by using a four-digit system code. The literature review follows the PRISMA guideline analyzing randomized controlled trials and cross-sectional, cohort, comparative, validation, and evaluation studies on RCC in Embase, grey literature, PubMed, and Scopus. RESULTS: Most frequently observed RCCs of Mx2Ps were 1-1-1/1 (35.3%), 1-1-1/2 (21.6%), and 2-1-1/1 (14.7%). Another 11 less frequent RCCs were observed. All Mx2Ps had 1 root. One main foramen was observed in 59.5% and two in 37.9%. Accessory foramina were observed in 46.6%. Thirty-one percent of the Mx2Ps showed accessory canals. One connecting canal between the buccal and palatal was observed in 12.1%. CONCLUSIONS: Detailed RCC information of Mx2Ps in a Swiss-German population and the results of a systematic literature review of different populations and research methods used to investigate root canal morphology and configuration of Mx2Ps are given. Within the limitations of the study, a high RCC, connecting and accessory canals variability occur in maxillary second premolars.

An Ex Vivo Study of Root Canal System Configuration and Morphology of 115 Maxillary First Premolars.

INTRODUCTION: The aim of this study was to investigate the root canal system morphology of maxillary first premolars by means of micro-computed tomographic imaging in a Swiss-German population. METHODS: The root canal configuration (RCC) of 115 maxillary first premolars (Mx1Ps) were investigated by means of micro-computed tomographic imaging and 3-dimensional imaging. The RCC and the physiological foramina results are described by a 4-digit system code. RESULTS: Twelve different RCCs were observed in 30 single-rooted Mx1Ps; 2-2-2/2 (30.0%), 1-2-2/2 (13.3%), 1-2-1/2 (10%), and 2-2-1/2 (10.0%) were the most frequent ones. Seven different RCCs were observed in 2-rooted Mx1Ps (n = 81) in which the 1-1-1/1 (56.8%), 1-1-1/2 (29.6%), and 1-1-2/2 (8.6%) in the buccal root and 1-1-1/1 (92.6%) and 1-1-1/2 (6.2%) in the palatal root RCCs appeared most frequently. Three-rooted Mx1Ps (n = 4) showed a 1-1-1/1 (100.0%) RCC in all roots. The buccal root canal in 2-rooted Mx1Ps had 1 physiological foramen in 59.3% and 2 in 40.7% and 1 to 6 accessory foramina in 38.2%. The palatal root canal showed 1 physiological foramen in 93.8% and 2 in 6.2% and 1 to 2 accessory foramina in 14.8%. Single-rooted Mx1Ps showed 1 physiological foramen in 10.0%, 2 in 70.0%, 3 in 13.3%, and 4 in 6.7% and 1 to 3 accessory foramina in 46.7%. CONCLUSIONS: The results of this study provide detailed morphologic RCC information of Mx1Ps in a Swiss-German population. Single-rooted Mx1Ps showed morphologic diversifications more frequently than 2- or 3-rooted Mx1Ps. Within 2-rooted Mx1Ps, the buccal root had higher RCC variety, accessory canals, and foramina number than the palatal root.

3-dimensional Analysis and Literature Review of the Root Canal Morphology and Physiological Foramen Geometry of 125 Mandibular Incisors by Means of Micro-Computed Tomography in a German Population.

INTRODUCTION: The aim of this study was to examine the root canal system morphology of mandibular incisors by means of micro-computed tomographic imaging. METHODS: The root canal configuration, physiological foramina, frequency of accessory and connecting canals, and the size and shape of the physiological foramina of 125 mandibular incisors were investigated by means of micro-CT and 3-dimensional imaging software. Root canal configuration of the coronal, middle, and apical thirds and the physiological foramina number are described by a 4-digit system code. RESULTS: The most frequent root canal configurations were 1-1-1/1 (56%), 1-2-1/1 (17.6%), and 1-1-1/2 (10.4%); 9 additional different root canal configurations were observed. Single-rooted incisors showed in 80% 1, in 16% 2, and in 4% 3 physiological foramina, respectively. Accessory canals were found in only 13.6% of the investigated teeth. Connecting canals were observed in 36% of the sample, most often in root canal configurations 1-2-1/1 (12.8%) and 2-2-1/1 (7.2%). The morphologic dimensions of a total of 146 physiological foramina were measured. Their mean wide and narrow diameters were 0.24 mm (standard deviation = 0.1 mm) and 0.23 mm (standard deviation = 0.08 mm) when only 1 physiological foramen was present. The physiological foramen shapes observed were oval (56%), round (28.8%), and irregular (15.2%). CONCLUSIONS: The study provides detailed information about the root canal morphology of anterior teeth in a German population. Within the limitations of the study, the authors recommend according to results obtained in this investigation a final physiological foramen preparation size of ISO 30-35; yet, such a decision should be carefully considered on an individual basis.

Remineralization of Artificial Dentin Caries Using Dentin and Enamel Matrix Proteins.

To assess the remineralizing potential of dentin matrix proteins and enamel matrix derivatives (DMPs and EMDs) after application on artificially induced dentin lesions, given the hypothesis that these materials increase the mineral uptake, binding, and mineralization. Forty-eight caries-free human premolars were used. Teeth were cut, polished, and embedded, leaving an open window on the root surface, of which one-third was covered with a flowable composite to preserve the healthy untreated dentin. Then, samples were demineralized in Buskes solution for 33 days. A micro-CT scan prior to treatment was performed. Next, the samples were randomly allocated into four groups: (A) An untreated negative control (CON), (B) application of porcine dentin matrix proteins (DMP), (C) treatment with enamel matrix derivatives (EMD, Emdogain, Straumann), and (D) amine fluoride application (AMF, Elmex fluid, GABA). All samples were placed in artificial saliva for 21 days. A second micro-CT scan was performed, after which the change in gray scaling within a defined region of interest (0.25 mm3) was analyzed. ANCOVA was applied to discover statistical differences between the different treatments. Both, treatment with AMF; (P = 0.011 versus CON) as well as with DMP (P = 0.043 versus CON) yielded a statistically significant difference compared to the control treatment. EMD treatment was not found to differ (P > 0.05). Mainly the top layer of the defects showed clear signs of remineralization, which was also evident in CON. This study was able to visually confirm the remineralization potential of demineralized dentin especially after DMP application, which, however, did not outperform AMF. Based on this, additional studies combining proteins and fluorides are now warranted and ongoing.

Effect of canal preparation with TRUShape and Vortex rotary instruments on three-dimensional geometry of oval root canals.

The purpose of this study was to assess the geometry of non-round root canals after preparation with TRUShape (a novel instrument with s-shaped longitudinal design) in comparison to conventional rotary instrumentation using micro-computed tomography. Twenty distal root canals of mandibular molars were randomly distributed in two groups to be shaped with either TRUShape or Vortex rotaries. Percentages of unprepared surface and volume of dentin removal for the entire canal and for the apical 4 mm were calculated. Canal transportation and the structure model index (SMI) were assessed. Data were compared with Student t-tests. Shaping with both techniques resulted in similar prepared surface and volume of dentin removed, as well as the extent of canal transportation. The SMI shape factor was significantly lower for TRUShape preparations (P = 0.04) suggesting less rounding during rotary preparation. Although both instruments were suitable for the preparation of oval canals, TRUShape appeared to better conform to the original ribbon-shaped anatomy.

Three-dimensional analysis of the physiological foramen geometry of maxillary and mandibular molars by means of micro-CT.

The aim of this study was to investigate the physiological foramen diameter, shape and distance between physiological and anatomical apex of maxillary and mandibular first and second molars. Accurate knowledge of the physiological foramina morphology; thus, inherent mechanical shaping technical hindrances, is decisive when taking the corresponding root canal final preparation decision. The morphological dimensions of a total of 1727 physiological foramina were investigated by means of micro-computed tomography. Mean narrow and wide (to a high number, oval) diameters of the physiological foramen were 0.24, 0.22 and 0.33 mm and 0.33, 0.31 and 0.42 mm in mesiobuccal (MB), distobuccal (DB) and palatal (P) roots in maxillary first molars; 0.24, 0.22 and 0.33 mm and 0.41, 0.33 and 0.44 in MB, DB, and P roots in maxillary second molars. Mandibular first molars showed mean narrow and wide diameters of 0.24 and 0.30 mm and of 0.39 and 0.46 mm in mesial (M) and distal (D) roots; second mandibular molars showed 0.25 and 0.31 mm and 0.47 mm in M and D roots. The mean distance between the physiological foramina and anatomical apex was 0.82, 0.81 and 1.02 mm and 0.54, 0.43 and 0.63 mm in MB, DB and P roots of the maxillary first and second molars, respectively. A mean distance of 0.95 mm (M) and 1.05 mm (D) in the first and 0.78 mm (M) and 0.81 mm (D) in the second mandibular molars was observed. Based on the results obtained, assumable recommendations for final preparation size of the physiological foramen were calculated. However, when taking into consideration, the resulting standard deviations of marginal errors must be cautiously considered when taking a final decision in clinical endodontic treatment.

Root canal morphology and configuration of 123 maxillary second molars by means of micro-CT.

The aim of this study was to investigate the root canal configuration, accessory canals and number of main foramina of 123 maxillary second molars by means of micro-computed tomography. The teeth were scanned and reproduced with 3D software imaging. The root canal configuration and number of main foramina were evaluated by means of a four-digit system. The morphological complexity of human maxillary second molars is depicted by the number of accessory and connecting canals. The most frequently observed root canal configurations in the mesiobuccal root were 2-2-2/2 (19.5%), 2-2-1/1 (14.6%) and 2-1-1/1 (13.0%). A 1-1-1/1 configuration was observed in 93.5% and in 96.7% in the distobuccal and palatal roots, respectively. The MB1 root canal had one accessory canal (18.7%), and 8.9% of the MB2 root canal had one or two accessory canals. The distobuccal (11.3%) and palatal (14.6%) root canals had at least one accessory canal, and connecting canals were observed in 16.3% of mesiobuccal roots. The MB1, MB2, distobuccal and palatal root canals had one main foramen in 99.2%, 43.1%, 98.4% and 99.2% of samples, respectively. In the mesiobuccal root, one accessory foramen was detected in 14.6%, two were detected in 7.3%, and three were detected in 5.7%. The distobuccal root showed one or two accessory foramina in 9.1% of samples. The root canal configuration of maxillary second molars is quite heterogeneous; the mesiobuccal root has predominantly two root canal entrances (58.4%, 1 in 41.1%) with one main foramen (54.4%). Two main foramina were observed in 43.0%. Morphological variations, connecting and accessory canals were observed in all apical thirds.

Micro-CT assessment of internal morphology and root canal configuration of non C-shaped mandibular second molars

The root canal system morphology of the mandibular second molar was investigated by means of micro-computed tomography (µCT). The root canal configuration (RCC), foramina and accessory canals frequency of 93 mandibular second molars of an Egyptian sample were investigated by µCT scans. The RCC and main foramina number (MFN) are described by means of a four-digit system from coronal to apical. The most frequently observed RCCs in the mesial root were 2-2-1/1 (32.3%), 2-2-2/2 (28.0%), 1-1-1/1 (6.5%) and 2-1-1/1 (6.5%); an additional twelve different RCCs were also found here. In the distal root, the RCC 1-1-1/1 was observed in 81.7%; another ten different RCCs with a frequency of less than 5% were also observed in this root. Anastomoses be-tween the mesiobuccal and mesiolingual canals in the mesial root were witnessed in the coronal (20.5%), middle (19.4%) and apical (10.8%) thirds. Accessory canals were found in the coronal (mesiobuccal 15.0%, mesiolingual 12.9%, distobuccal 1.1%), middle (mesiobuccal 7.5%, mesiolingual 10.8%, distolingual 3.3%) and apical (mesiobuccal 19.3%, mesiolingual 16.2%, distolingual 10.8%, distobuccal 2.2%) thirds. The RCC of mandibular second molars showed a great variety. When compared with the first mandibular molar in a historical control from the same sample, the mandibular second molar presented less morphological diversifications. Yet, the mesial root canalsystem of the mandibular second molar showed more RCC variations, connecting and accessory canals than the distal root.

Root Canal Morphology and Configuration of 118 Mandibular First Molars by Means of Micro-Computed Tomography: An Ex Vivo Study.

INTRODUCTION: The aim of this study was to investigate the root canal system morphology of the mandibular first molar by means of micro-computed tomography. METHODS: The root canal configuration, foramina, and accessory canals frequency of 118 mandibular first molars were investigated by means of micro-computed tomography and 3-dimensional software imaging. A 4-digit system describes the root canal configuration from the coronal to apical thirds and the main foramina number. RESULTS: The most frequent root canal configurations in mesial root were 2-2-2/2 (31.4%), 2-2-1/1 (15.3%), and 2-2-2/3 (11.9%); another 24 different root canal configurations were observed in this root. A 1-1-1/1 (58.5%), 1-1-1/2 (10.2%), and 16 other root canal configurations were observed in the distal root. The mesiobuccal root canal showed 1-4 foramina in 24.6%, and the mesiolingual showed 1-3 foramina in 28.0%. One connecting canal between the mesial root canals was observed in 30.5% and 2 in 3.4%. The distolingual root canal showed 1-4 foramina in 23.7%, whereas a foramen in the distobuccal root canal was rarely detected (3.4%). The mesiobuccal, mesiolingual, and distolingual root canals showed at least 1 accessory canal (14.3, 10.2, and 4.2%, respectively), but the distobuccal had none. CONCLUSIONS: The root canal configuration of mandibular first molars varies strongly. According to our expectations, both the mesial and distal roots showed a high number of morphologic diversifications. The root canal system of the mesial root showed more root canal configuration variations, connecting and accessory canals than the distal root.

Root Canal Morphology and Configuration of 179 Maxillary First Molars by Means of Micro-computed Tomography: An Ex Vivo Study.

INTRODUCTION: The objective of this study was to propose a root canal configuration description method and to investigate the root canal system morphology of the maxillary first molar by means of micro-computed tomographic imaging. METHODS: The root canal configuration, foramina, and accessory canal frequency of 179 maxillary first molars were investigated by means of micro-computed tomographic imaging and 3-dimensional software imaging. The root canal configuration and main foramina number are described from coronal to apical with a 4-digit system. RESULTS: The most frequent root canal configurations were 1-1-1/1 (45.8%), 2-2-2/2 (25.1%) and 2-2-1/1 (10.1%) in mesiobuccal roots and 1-1-1/1 in distobuccal (97.2%) and palatal (98.9%) roots. The first mesiobuccal (MB1) root canal had 1 accessory canal in 26.3% of the teeth, the distobuccal root canal had 12.3%, and the palatal root canal had 9.5%; in the second mesiobuccal root canal, there was rarely 1 accessory canal. There was 1 accessory canal in 26.3%, 12.3%, and 9.5% in the MB1, distobuccal, and palatal root canals, respectively. The MB1, distobuccal, and palatal root canals had 1 main foramen. The MB2 had 1 main foramen in 39.0% of the teeth and no main foramen in 61.0%. CONCLUSIONS: The root canal configuration of maxillary first molars is quite diversified. Contrary to our expectations in this research, the mesiobuccal root has predominantly 1 root canal entrance and only 1 main foramen. Anatomic variations including connecting and accessory canals occur in any third of root.

A Micro-computed Tomographic Assessment of Root Canal Preparation with a Novel Instrument, TRUShape, in Mesial Roots of Mandibular Molars.

INTRODUCTION: A novel S-shaped rotary file was developed to conform to nonround canal cross sections. However, the instrument should also perform well in small curved canals. This study used micro-computed tomographic scans to test the effects of TRUShape (Dentsply Tulsa Dental Specialties, Tulsa, OK) and a conventional rotary on canal geometry. METHODS: Twenty mandibular molars with independent mesial canals were submitted to preoperative micro-computed tomographic scans (20-µm resolution). Canals were randomly allocated to 2 groups using Vortex (Dentsply Tulsa Dental Specialties) and TRUShape for shaping according to the directions for use. Scans were obtained after size 20/.06 and 30/.06; the following outcome variables were calculated: dentin volume, smallest radicular wall thickness, treated canal surface, canal transportation, and accumulated hard tissue debris. The number of preparation errors was tabulated; data were statistically contrasted using repeated measures and factorial analyses of variance. RESULTS: The initial canal sizes were similar in both groups. Both instruments promoted preparation with no overt procedural errors. Vortex removed significantly more dentin both at size #20 and #30 (P < .02). Significantly (P < .02) more radicular wall dentin remained toward the furcation in the TRUShape group (1.02 ± 0.25 mm vs 0.94 ± 0.22 mm). The untreated surface at size #20 was 28.5 ± 13.9 and 19.4 ± 8.9 (P < .05), and it was 15.1 ± 8.5 and 11.3 ± 4.9 (P > .05) at size #30 for TRUShape and Vortex, respectively. Canal transportation at size #30 varied between 85 ± 57 µm and 179 ± 65 µm; the overall transportation scores were significantly lower for TRUShape (P < .05). CONCLUSIONS: TRUShape provided conservation of dentin by limiting dentin removal and in the absence of substantial canal transportation. In the present study, the use of TRUShape in the mesial canals of mandibular molars did not result in decreased amounts of unprepared canal surface.

Impacts of conservative endodontic cavity on root canal instrumentation efficacy and resistance to fracture assessed in incisors, premolars, and molars.

INTRODUCTION: Conservative endodontic cavity (CEC) may improve fracture resistance of teeth but compromise the instrumentation of canals. This study assessed the impacts of CEC on both variables in 3 tooth types. METHODS: Extracted human intact maxillary incisors, mandibular premolars, and molars (n = 20/type) were imaged with micro-computed tomographic imaging (20-µm resolution) and assigned to CEC or traditional endodontic cavity (TEC) groups (n = 10/group/type). Minimal CECs were plotted on scanned images. Canals were prepared with WaveOne instruments (Dentsply Maillefer, Ballaigues, Switzerland) using 1.25% sodium hypochlorite and post-treatment micro-computed tomographic images obtained. The proportion of the untouched canal wall (UCW) and the dentin volume removed (DVR) for each tooth type was analyzed with the independent-samples t test. The 60 instrumented and 30 intact teeth (negative control, n = 10/type) were loaded to fracture in the Instron Universal Testing machine (Instron, Canton, MA) (1 mm/min), and the data were analyzed with 1-way analysis of variance and the Tukey test. RESULTS: The mean proportion of UCW was significantly higher (P < .04) only in the distal canals of molars with CEC (57.2% ± 21.7%) compared with TEC (36.7% ± 17.2%). The mean DVR was significantly smaller (P < .003) for CEC than for TEC in incisors (16.09 ± 4.66 vs 23.24 ± 3.38 mm(3)), premolars (8.24 ± 1.64 vs 14.59 ± 4.85 mm(3)), and molars (33.37 ± 67.71 mm(3)). The mean load at fracture for CEC was significantly higher (P < .05) than for TEC in premolars (586.8 ± 116.9 vs 328.4 ± 56.7 N) and molars (1586.9 ± 196.8 vs 641.7 ± 62.0 N). In both tooth types, CEC did not differ significantly from the negative controls. CONCLUSIONS: Although CEC was associated with the risk of compromised canal instrumentation only in the molar distal canals, it conserved coronal dentin in the 3 tooth types and conveyed a benefit of increased fracture resistance in mandibular molars and premolars.

Three-dimensional defect evaluation of air polishing on extracted human roots.

BACKGROUND: Root surfaces experience continuous abrasive instrumentation during lifelong periodontal maintenance. Periodontists need both effective and minimally abrasive debridement techniques. Air polishing devices might, therefore, constitute a good alternative to mechanical instrumentation. Because little is known of the three-dimensional shape and volume of the abrasion caused by different powders, it is the aim of the study to investigate the three-dimensional extent of these defects. METHODS: Cementum-covered roots of 20 extracted human premolars were coated with resin caps, leaving four areas with identical diameter open for instrumentation using bicarbonate powder and glycine powder. Treatment times were 5 and 10 seconds in a first interval and 10 seconds in a second interval. Maximum settings were chosen for power and lavage. The teeth were scanned using microcomputed tomography initially and after every treatment interval. Differences in volume and defect depths were calculated by superimposition of the scans and tested for significance (Wilcoxon test, P <0.001). RESULTS: Defect volumes (in mm(3)) presented in medians (interquartile ranges) for the bicarbonate powder after 5, 10, 15, and 20 seconds, respectively, were 0.16 (0.11), 0.28 (0.16), 0.32 (0.18), and 0.41 (0.28), and for glycine powder, 0.00 (0.02), 0.01 (0.05), 0.03 (0.11), and 0.06 (0.1). For each time period, abrasion caused by glycine was significantly lower (five- to 20-fold) compared to defects caused by bicarbonate. CONCLUSIONS: In patients with exposed root surfaces, cleaning with bicarbonate powder cannot be recommended. Less abrasive glycine powder, however, demonstrated non-critical substance loss.

Self-adjusting files in retreatment: a high-resolution micro-computed tomography study.

INTRODUCTION: Rotary instruments that are used for retreatment are very effective, but most of them leave root filling residue in the canal. The aim of this study was to evaluate the efficacy of removing gutta-percha-based root fillings with ProTaper retreatment files (Dentsply Maillefer, Ballaigues, Switzerland) followed by F1 and F2 ProTaper instruments and to compare these results with those obtained with a #25 .06 ProFile instrument (Dentsply Maillefer) followed by the Self- Adjusting File (SAF; ReDent, Ra'anana, Israel) using high resolution micro-computed tomography (CT) scanning. METHODS: Twenty-eight mandibular molar teeth with oval distal root canals were divided into 2 equal groups of 14 teeth each. The distal root canals were instrumented with ProTaper files up to an F2 instrument, the roots were subsequently filled, and the root filling was allowed to set fully. Removal of the root canal filling was performed with D1-D3 ProTaper retreatment files followed by F1 and F2 ProTaper instruments or with a #25 .06 ProFile followed by SAFs. Chloroform was used in both groups to assist in the removal of the root filling material. High-resolution micro-CT scans were used to measure the residual quantities of the root filling material after completion of the procedures. Statistical analysis was performed using the Wilcoxon test and the Student t test. RESULTS: The median root filling residue in the ProTaper group was 5.39% (interquartile range [IQR] = 4.71) of the original volume of the root canal filling. In the ProFile and SAF group, the median residue was 0.41% (IQR = 1.64, P < .001). An arbitrarily selected threshold of less than 0.5% residue was defined as "effectively cleaned," and 57% of the teeth treated with the ProFile and the SAF met this threshold, whereas none of the cases in the ProTaper group did. The ProFile and SAF procedure required less time than the ProTaper protocol. CONCLUSIONS: None of the retreatment methods rendered all of the canals completely free of all root filling residue. Under the conditions of this study, the ProFile and SAF procedure was more effective than the ProTaper procedure and left significantly less root filling residue in the root canal.

Reduction of hard-tissue debris accumulation during rotary root canal instrumentation by etidronic acid in a sodium hypochlorite irrigant.

INTRODUCTION: Hard-tissue debris is accumulated during rotary instrumentation. This study investigated to what extent a calcium-complexing agent that has good short-term compatibility with sodium hypochlorite (NaOCl) could reduce debris accumulation when applied in an all-in-one irrigant during root canal instrumentation. METHODS: Sixty extracted mandibular molars with isthmuses in the mesial root canal system were selected based on prescans using a micro-computed tomography system. Thirty teeth each were randomly assigned to be instrumented with a rotary system and irrigated with either 2.5% NaOCl or 2.5% NaOCl containing 9% (wt/vol) etidronic acid (HEBP). Using a side-vented irrigating tip, 2 mL of irrigant was applied by 1 blinded investigator to the mesial canals after each instrument. Five milliliters of irrigant was applied per canal as the final rinse. Mesial root canal systems were scanned at high resolution before and after treatment, and accumulated hard-tissue debris was calculated as vol% of the original canal anatomy. Values between groups were compared using the Student's t test (α < .05). RESULTS: Irrigation with 2.5% NaOCl resulted in 5.5 ± 3.6 vol% accumulated hard-tissue debris compared with 3.8 ± 1.8 vol% when HEBP was contained in the irrigant (P < .05). CONCLUSIONS: A hypochlorite-compatible chelator can reduce but not completely prevent hard-tissue debris accumulation during rotary root canal instrumentation.

The challenge of C-shaped canal systems: a comparative study of the self-adjusting file and ProTaper.

INTRODUCTION: C-shaped canals are anatomic features that present the clinician with both diagnostic and operational challenges. The aim of this study was to compare the efficacy of the Self-Adjusting File (SAF; ReDent, Ra'anana, Israel) in shaping C-shaped canals with that of the rotary ProTaper file system (Dentsply-Maillefer, Ballaigues, Switzerland). METHODS: Sixteen mandibular second molars and 4 maxillary second molars with C-shaped canals were obtained, originating from native Chinese population. They were divided into 2 equal groups of 10 teeth each, based on similar canal morphology as presented in preliminary micro-computed tomography-derived images. One group was shaped using the SAF, whereas the other was shaped using the ProTaper file system. Reconstructed micro-computed tomographic images before and after treatment were superimposed over each other, and the percentage of the canal wall unaffected by the procedure was calculated. Comparison of the 2 groups for this parameter was performed using the Student t test. RESULTS: When treated with the SAF, 41% ± 14% of the canal walls remained unaffected by the procedure, whereas 66% ± 6% of the wall area was unaffected when using ProTaper, which was significantly higher than that of the SAF-treated group (P < .001). CONCLUSIONS: The SAF was more effective than the ProTaper file system in shaping the walls of C-shaped root canals.

Microtomography-based comparison of reciprocating single-file F2 ProTaper technique versus rotary full sequence.

INTRODUCTION: A preparation technique with only 1 single instrument was proposed on the basis of the reciprocating movement of the F2 ProTaper instrument. The present study was designed to quantitatively assess canal preparation outcomes achieved by this technique. METHODS: Twenty-five extracted human mandibular first molars with 2 separate mesial root canals were selected. Canals were randomly assigned to 1 of the 2 experimental groups: group 1, rotary conventional preparation by using ProTaper, and group 2, reciprocate instrumentation with 1 single ProTaper F2 instrument. Specimens were scanned initially and after root canal preparation with an isotropic resolution of 20 µm by using a micro-computed tomography system. The following parameters were assessed: changes in dentin volume, percentage of shaped canal walls, and degree of canal transportation. In addition, the time required to reach working length with the F2 instrument was recorded. RESULTS: Preoperatively, there were no differences regarding root canal curvature and volume between experimental groups. Overall, instrumentation led to enlarged canal shapes with no evidence of preparation errors. There were no statistical differences between the 2 preparation techniques in the anatomical parameters assessed (P > .01), except for a significantly higher canal transportation caused by the reciprocating file in the coronal canal third. On the other hand, preparation was faster by using the single-file technique (P < .01). CONCLUSIONS: Shaping outcomes with the single-file F2 ProTaper technique and conventional ProTaper full-sequence rotary approach were similar. However, the single-file F2 ProTaper technique was markedly faster in reaching working length.

Micro-computed tomography evaluation of the preparation of long oval root canals in mandibular molars with the self-adjusting file.

INTRODUCTION: The aim of this study was to assess the shaping potential of a novel nickel-titanium instrument, the self-adjusting file (SAF), in long oval root canals in distal roots in mandibular molars. METHODS: Twenty mandibular molars with long oval distal root canals were selected and scanned preoperatively and postoperatively by using micro-computed tomography at an original resolution of 20 µm. Canals were shaped with the SAF, three-dimensionally reconstructed, and evaluated for volume, surface area, canal transportation, and prepared surface. Data were statistically contrasted by using paired t tests and regression analysis. RESULTS: Preoperatively, canal volume was 7.73 ± 2.13 mm(3), and canal area was 42.83 ± 8.14 mm(2). Volumes and surface areas increased significantly (P < .001) by 4.84 ± 1.73 mm(3) and 3.34 ± 1.73 mm(2), respectively, and no gross preparation errors were detected. Unprepared canal surface varied between individual canals, and mean unprepared surface was 23.5% ± 8.9%. Prepared areas were significantly larger compared with rotary canal preparation done in a previous study. Canal transportation scores were higher in the coronal root canal third (106 ± 50 µm) compared with the apical third (81 ± 49 µm). CONCLUSIONS: In vitro, preparation of long oval-shaped root canals in mandibular molars with the SAF was effective and safe. Moreover, shapes generated with the SAF were more complete compared with rotary canal preparation.