Accuracy of trial restorations from virtual planning: A comparison of two fabrication techniques.

STATEMENT OF PROBLEM: Different technologies have been used to fabricate trial restorations. However, studies investigating the accuracy of trial restorations fabricated with different techniques in comparison with the initial 3-dimensional virtual design are lacking. PURPOSE: The purpose of this clinical study was to evaluate completely digital workflows for managing the esthetic outcome through the production of trial restorations with 2 different technologies: stereolithography apparatus (SLA 3D) and computer-aided design and computer-aided manufacturing (CAD-CAM). The aim was to determine which of them provided trial restorations more similar to those of the 3D virtual design. MATERIAL AND METHODS: Thirty participants who did not meet ideal esthetic proportions for the anterior maxillary teeth were enrolled. For each, 2 intraoral and extraoral frontal photographs and intraoral digital scans were made. The digital images were processed by using the Digital Smile System (DSS) software program to have a smile preview after the treatment. Virtual designs were matched with the surface tessellation language (STL) files from the intraoral scans and edited by exocad DentalCAD to create custom trial restorations using SLA 3D and CAD-CAM technologies. Two independent examiners measured the virtual restorations by using virtual calipers in the software program and then the trial restorations by using digital calipers. The measurements were carried out from the incisal edge to the gingival margin, mesial-distal widths of the central incisors, and the distance from the distal margins of maxillary right and left canines. The trial restorations were evaluated intraorally for fit. The participants approved the definitive treatment outcome after the evaluation. The normality of data was verified with the Shapiro-Wilk test, and the Friedman test for matched groups with the Bonferroni and Dunn tests for multiple comparisons were used (α=.05). RESULTS: Comparing the 3D designs with the printed trial restorations, a significant increase was only found in the mesial-distal width of central incisors (P<.05), while the milled trial restorations showed a significant increase (P<.05) of all measurements except for the maxillary right and left canines. Comparing printed trial restorations with the milled ones, the only significant difference was found in height measures of maxillary right central incisor, with the milled trial restorations exhibiting higher values than the printed ones (P<.05). The printed trial restorations showed good clinical fit, and the milled restorations had poor clinical adaptation. CONCLUSIONS: The accuracy of printed trial restorations was higher than that of milled trial restorations, except for the canine to canine width of maxillary anterior teeth. However, this difference did not compromise the fit of the printed trial restorations. The milled trial restorations had increased dimensions in comparison with the measurements made in 3D designs, and consequently, their clinical fit was compromised. SLA 3D- printing technology provided the best fit.

Cutting efficiency of heat-treated nickel-titanium single-file systems at different incidence angles.

Cutting efficiency of Reciproc R25 (REC) and Reciproc blue R25 (REB) at different inclinations was evaluated. Sixty new files were tested at 90°, 70° and 45° of inclination in relation to the sample (n = 10), using a customised machine. All files were activated in reciprocation against standardised gypsum blocks for 120 s. Cutting efficiency was determined by measuring the block weight loss with an analytical balance and measuring the length of the block surface cut using a digital calliper. Data were statistically analysed (two-way ANOVA, Bonferroni t-test) with the significance level set at P < 0.05. There was no difference for REC among the tested angles. REB had no statistical difference between 90° and 70°; however, its cutting efficiency significantly increased at 45°. There was a significant difference between REC and REB at 45° only. Under these conditions, increased file inclination to 45° and blue heat treatment improved cutting efficiency of reciprocating files.

Root fillings with a matched-taper single cone and two calcium silicate-based sealers: an analysis of voids using micro-computed tomography.

OBJECTIVES: To compare the percentage of voids in matched-taper single-cone fillings with GuttaFlow Bioseal or BioRoot RCS root canal sealers, using micro-computed tomography. MATERIALS AND METHODS: Forty-eight single-rooted mandibular premolars were prepared using rotary files and randomly allocated into 2 groups (n = 24), wherein the canals were filled with a matched-taper single gutta-percha cone and one of the two sealers: Group 1, GuttaFlow Bioseal and Group 2, BioRoot RCS. The specimens were scanned with micro-CT before and after root canal filling. A specialized software was used to calculate the voids volume percentage (V%) in the filling for the whole root canal, root canal thirds, and the last millimeter from the apex. Data were statistically analyzed by ANOVA and Tukey tests (p < 0.05). RESULTS: Root canals filled with GuttaFlow Bioseal had significantly less V% than those filled with BioRoot RCS in all the root-thirds (p < 0.05) except at the apical 1 mm (p > 0.05). Comparing the root-thirds, GuttaFlow Bioseal showed similar V% in all regions (p > 0.05), while BioRoot RCS group had significantly greater V% in the coronal third compared with the other thirds (p < 0.05). CONCLUSIONS: Root canals filled with a matched-taper single cone and GuttaFlow Bioseal had significant less voids than those with BioRoot RCS, except at the apical 1 mm. CLINICAL RELEVANCE: Voids in root fillings have been reported to have a negative impact on root canal treatment. This study highlights the percentage of voids in root fillings composed of a single cone of gutta-percha with two types of calcium silicate-based bioceramic sealers.

Association of oral dysbiosis with oral cancer development.

Oral squamous cell carcinoma (OSCC) is the leading cause of mortality for oral cancer. Numerous risk factors mainly related to unhealthy habits and responsible for chronic inflammation and infections have been recognized as predisposing factors for oral carcinogenesis. Recently, even microbiota alterations have been associated with the development of human cancers. In particular, some specific bacterial strains have been recognized and strongly associated with oral cancer development (Capnocytophaga gingivalis, Fusobacterium spp., Streptococcus spp., Peptostreptococcus spp., Porphyromonas gingivalis and Prevotella spp.). Several hypotheses have been proposed to explain how the oral microbiota could be involved in cancer pathogenesis by mainly paying attention to chronic inflammation, microbial synthesis of cancerogenic substances, and alteration of epithelial barrier integrity. Based on knowledge of the carcinogenic effects of dysbiosis, it was recently suggested that probiotics may have anti-tumoral activity. Nevertheless, few data exist with regard to probiotic effects on oral cancer. On this basis, the association between the development of oral cancer and oral dysbiosis is discussed focusing attention on the potential benefits of probiotics administration in cancer prevention.

Association of vitamin D in patients with periodontitis: A cross-sectional study.

BACKGROUND AND OBJECTIVE: Vitamin D has been considered to possess anti-inflammatory and antimicrobial activity, which may be a link for the known interaction of periodontitis (CP) and coronary heart disease (CHD). This study investigated the association between serum vitamin D levels and periodontitis in patients with CP and with CHD. Furthermore, the objective was to determine whether periodontitis and CHD had an impact on serum vitamin D levels. MATERIAL AND METHODS: Using a cross-sectional design, a total of 46 patients with CP, 45 patients with CHD, 45 patients with both CP and CHD, and 43 healthy patients were enrolled in the present study. RESULTS: Patients in the CP (17.4 ± 5.2 ng/mL) and in the CP + CHD (16.5 ± 5.6 ng/mL) group presented a significantly lower mean serum level of 25(OH)vitamin D compared to patients in the CHD (24.6 ± 3.7 ng/mL) and healthy control groups (29.9 ± 5.4 ng/mL) (P < .001). 25(OH)vitamin D levels were positively correlated with the number of teeth and negatively with C-reactive protein (CRP) and all periodontal parameters (P < .001). In all patients, there was a proportional increase of 25(OH)vitamin D levels with a progressive increase in number of teeth (P-trend <.001) while there were a proportional decrease in 25(OH)vitamin D levels with a progressive increase in clinical attachment level (CAL, P-trend = .001), probing depth (PD, P-trend = .006), and bleeding sites (BOP, P-trend <.001) levels. CONCLUSION: Patients with CP and CP + CHD presented significantly lower serum levels of vitamin D compared to CHD and healthy controls. Moreover, the presence of CP negatively influenced serum vitamin D levels.

Cyclic Fatigue Resistance of Nickel-titanium Rotary Instruments according to the Angle of File Access and Radius of Root Canal.

INTRODUCTION: The aim of this study was to compare the influences from different access angles and curvature radii on cyclic fatigue resistance of nickel-titanium rotary files. METHODS: Two file systems (2Shape [TS; MicroMega, Besançon, France] and HyFlex CM [HCM; Coltène/Whaledent, Allstätten, Switzerland]) were used. A total of 192 instruments of TS #25/.04 (TS1), TS #25/.06 (TS2), HCM #25/.04, and HCM #25/.06 were evaluated at 3 insertion angles (0°, 10°, and 20°) and 2 radii (5 mm and 3 mm) in 16-mm stainless steel artificial canals with a 60° curvature. Cyclic fatigue resistance was determined by the number of cycles to failure (NCF) using a customized testing device. Data were analyzed statistically with the significance level established at 95%. RESULTS: In the 3-mm radius canal, the instruments showed lower cyclic fatigue resistance than in the 5-mm radius canal (P < .05). HCM #25/.06 and all .04 taper instruments had a significant NCF reduction at 20° and 10° in the 3-mm radius canal (P < .05), whereas TS2 showed no significant differences. In the 5-mm radius of curvature, although .06 taper instruments had no significant NCF reduction for each angle tested, .04 taper files exhibited significant NCF reduction when tested at 20° (P < .05). Comparing the same size instruments, HCM had higher NCF than TS (P < .05). Instruments with a .04 taper exhibited higher NCF than the .06 ones with the same heat treatment (P < .05). CONCLUSIONS: An inclined insertion into the canals decreased cyclic fatigue resistance of thermal-treated instruments with a .04 taper at all radii of curvature tested. The synergistic effect of a small radius of curvature and access angulation of heat-treated instruments decreases their fatigue resistance.

Association between periodontitis and glycosylated haemoglobin before diabetes onset: a cross-sectional study.

OBJECTIVES: The aim of the present cross-sectional study was to investigate the association between serum glycosylated haemoglobin (HbA1c) levels and periodontal status in patients with periodontitis (CP) and periodontally healthy controls. Furthermore, the objectives were to determine if the periodontitis influenced the serum HbA1c levels. MATERIALS AND METHODS: A total of 93 patients with CP and 95 periodontally healthy subjects were enrolled in the present study using a cross-sectional design. At baseline, patients were examined and characterized on a regular basis for blood serum parameters and non-fasting blood samples levels. In all patients, a full periodontal examination was performed and clinical attachment loss (CAL) was the primary outcome variable chosen. The spearman correlation, a stepwise multivariable linear regression, and Jonckheere-Terpstra tests were applied in order to assess the relationship between HbA1c levels and periodontitis. RESULTS: Patients in the CP group presented a significantly higher median serum level of HbA1c [40.9 (31.2; 45.6) mmol/mol)] compared to patients in the healthy control group [35.3 (29.6; 38.6) mmol/mol)] (p < 0.001). HbA1c levels were negatively correlated with the number of teeth and positively correlated with C-reactive protein levels and all periodontal parameters (p < 0.001). Moreover, there was a significant decrease in the number of teeth when HbA1c levels increased (P-trend < 0.001), while there was a significant increase in periodontal parameters (CAL, p = 0.002); PD, p = 0.008; BOP, p < 0.001) when levels of HbA1c increased. CONCLUSIONS: Patients with CP and undiagnosed diabetes presented significantly higher serum levels of HbA1c compared to periodontally healthy controls. Moreover, the presence of periodontitis was positively correlated with serum HbA1c levels before diabetes onset. CLINICAL RELEVANCE: HbA1c levels were positively correlated with the severity of periodontitis before diabetes onset.

Comparison of Effectiveness of Etoricoxib and Diclofenac on Pain and Perioperative Sequelae After Surgical Avulsion of Mandibular Third Molars: A Randomized, Controlled, Clinical Trial.

OBJECTIVE: The objective of this analysis was to compare the efficacy of etoricoxib and diclofenac in the management of perioperative sequelae following impacted mandibular third molar surgery. MATERIALS AND METHODS: Ninety-seven patients who needed surgical avulsion of an impacted mandibular third molar were chosen for the study. All patients were randomly allocated to receive one of the following treatments, twice a day for 5 days after surgery: placebo (n=33), diclofenac (n=32), or etoricoxib (n=32). The primary outcome evaluated was postoperative pain, recorded by each patient and evaluated using the Visual Analogue Scale score. The secondary outcomes chosen were, compared with preoperative ones, changes in postoperative swelling and maximum mouth opening. RESULTS: Compared with placebo, treatment with etoricoxib and diclofenac demonstrated an enhancement in the primary outcome. Furthermore, when compared with the other groups, patients who had undergone etoricoxib presented a significant median reduction in postoperative pain at 2 hours (P<0.001), 12 hours (P=0.025), and at 48 hours (P=0.018) after surgery. Moreover, the linear regression analysis showed that diclofenac and etoricoxib determined a significant influence on Visual Analogue Scale at 2, 6, 12, 24, 48 hours and at 10 days after surgery. There were no differences in swelling and maximum mouth opening values between groups. DISCUSSION: This study demonstrated that both treatments were effective. However, treatment with etoricoxib showed a greater reduction in the incidence and severity of postoperative pain following third molar surgery compared with diclofenac and placebo.

Identification of Novel MicroRNAs and Their Diagnostic and Prognostic Significance in Oral Cancer.

Background: Oral cancer is one of the most prevalent cancers worldwide. Despite that the oral cavity is easily accessible for clinical examinations, oral cancers are often not promptly diagnosed. Furthermore, to date no effective biomarkers are available for oral cancer. Therefore, there is an urgent need to identify novel biomarkers able to improve both diagnostic and prognostic strategies. In this context, the development of innovative high-throughput technologies for molecular and epigenetics analyses has generated a huge amount of data that may be used for the identification of new cancer biomarkers. Methods: In the present study, GEO DataSets and TCGA miRNA profiling datasets were analyzed in order to identify miRNAs with diagnostic and prognostic significance. Furthermore, several computational approaches were adopted to establish the functional roles of these miRNAs. Results: The analysis of datasets allowed for the identification of 11 miRNAs with a potential diagnostic role for oral cancer. Additionally, eight miRNAs associated with patients' prognosis were also identified; six miRNAs predictive of patients' overall survival (OS) and one, hsa-miR-let.7i-3p, associated with tumor recurrence. Conclusion: The integrated analysis of different miRNA expression datasets allows for the identification of a set of miRNAs that, after validation, may be used for the early detection of oral cancers.

Analysis of the Effectiveness of Lornoxicam and Flurbiprofen on Management of Pain and Sequelae Following Third Molar Surgery: A Randomized, Controlled, Clinical Trial.

The aim of this study was to analyze the effectiveness of Lornoxicam and Flurbiprofen in reducing perioperative sequelae after impacted mandibular third molar surgery. Ninety-one patients who needed surgical extraction of an impacted mandibular third molar were selected for the study. All subjects were randomly allocated to receive one of the following treatments twice a day for 5 days after surgery: placebo (n = 29), Flurbiprofen (n = 31), or Lornoxicam (n = 31). The primary outcome was postoperative pain, evaluated using the visual analogue scale (VAS) score at 30 min, 2, 6, 12, 24, 48 h, 7 and 10 days following surgery. The secondary outcomes chosen were changes in postoperative swelling and maximum mouth opening values compared to preoperative ones. Compared to placebo, treatment with Flurbiprofen and Lornoxicam was characterised by an improvement in the primary outcome. Moreover, the treatment with Lornoxicam presented significantly lower median pain scores at 2 h (p < 0.001) and at 6 h (p = 0.016) compared to Flurbiprofen and at 2 h (p < 0.001), 6 h (p = 0.01), and at 24 h (p = 0.018) after surgery compared with placebo. Swelling and maximum mouth opening values were not significantly different between the groups at each follow-up session. This trial demonstrated that treatment with Lornoxicam showed a decrease in the incidence and severity of pain in the first postoperative phase following third molar surgery compared to Flurbiprofen and placebo.

Cyclic fatigue resistance, torsional resistance, and metallurgical characteristics of M3 Rotary and M3 Pro Gold NiTi files.

OBJECTIVES: To evaluate the mechanical properties and metallurgical characteristics of the M3 Rotary and M3 Pro Gold files (United Dental). MATERIALS AND METHODS: One hundred and sixty new M3 Rotary and M3 Pro Gold files (sizes 20/0.04 and 25/0.04) were used. Torque and angle of rotation at failure (n = 20) were measured according to ISO 3630-1. Cyclic fatigue resistance was tested by measuring the number of cycles to failure in an artificial stainless steel canal (60° angle of curvature and a 5-mm radius). The metallurgical characteristics were investigated by differential scanning calorimetry. Data were analyzed using analysis of variance and the Student-Newman-Keuls test. RESULTS: Comparing the same size of the 2 different instruments, cyclic fatigue resistance was significantly higher in the M3 Pro Gold files than in the M3 Rotary files (p < 0.001). No significant difference was observed between the files in the maximum torque load, while a significantly higher angular rotation to fracture was observed for M3 Pro Gold (p < 0.05). In the DSC analysis, the M3 Pro Gold files showed one prominent peak on the heating curve and 2 prominent peaks on the cooling curve. In contrast, the M3 Rotary files showed 1 small peak on the heating curve and 1 small peak on the cooling curve. CONCLUSIONS: The M3 Pro Gold files showed greater flexibility and angular rotation than the M3 Rotary files, without decrement of their torque resistance. The superior flexibility of M3 Pro Gold files can be attributed to their martensite phase.

Cyclic Fatigue Resistance of Heat-treated Nickel-titanium Instruments after Immersion in Sodium Hypochlorite and/or Sterilization.

INTRODUCTION: The purpose of this study was to assess the effects of sodium hypochlorite (NaOCl) immersion and sterilization on the cyclic fatigue resistance of heat-treated nickel-titanium (NiTi) rotary instruments. METHODS: Two hundred ten new 25/.06 Twisted Files (TFs; SybronEndo, Orange, CA) and Hyflex CM (Coltene Whaledent, Cuyahoga Falls, OH) files were divided into 7 groups (n = 15) for each brand. Group 1 (control group) included new instruments that were not immersed in NaOCl or subjected to autoclave sterilization. Groups 2 and 3 were composed of instruments dynamically immersed for 3 minutes in 5% NaOCl solution 1 and 3 times, respectively. Groups 4 and 5 consisted of instruments only autoclaved 1 and 3 times, respectively. Groups 6 and 7 recruited instruments that received a cycle of both immersion in NaOCl and sterilization 1 and 3 times, respectively. Instruments were subsequently subjected to a fatigue test. The surface morphology of fractured instruments was studied by field-emission scanning electron microscopy and x-ray energy-dispersive spectrometric (EDS) analyses. The means and standard deviations of the number of cycles to failure (NCF) were calculated and statistically analyzed using 2-way analysis of variance (P < .05). RESULTS: Comparison among groups indicated no significant difference of NCF (P > .05) except for the groups of TFs sterilized 3 times without and with immersion in NaOCl (P < .05). HyFlex CM files exhibited higher cyclic fatigue resistance than TFs when files were sterilized 3 times, independently from immersion in NaOCl (P < .05). EDS analysis showed the presence of an oxide-rich layer on the Hyflex CM files' external surface. No morphologic or chemical differences were found between files of the same brand subjected to different treatments. CONCLUSIONS: Repeated cycles of sterilization did not influence the cyclic fatigue of NiTi files except for TFs, which showed a significant decrease of flexural resistance after 3 cycles of sterilization. Immersion in NaOCl did not reduce significantly the cyclic fatigue resistance of all heat-treated NiTi files tested.

Influence of Continuous or Reciprocating Optimum Torque Reverse Motion on Cyclic Fatigue Resistance of Two Single-File Nickel-Titanium Rotary Instruments.

OBJECTIVE: Different single-file instruments and kinematics have been introduced on the market. It is important to know the cyclic fatigue performance of these instruments in these new kinematics such as reciprocation of Optimum Torque Reverse (OTR) motion. The aim of this study was to evaluate the resistance to cyclic fatigue of F6 SkyTaper and OneShape used in continuous rotation (proper rotation) or in reciprocating OTR motion. METHODS: A total of forty-eight nickel-titanium files were tested. Twenty-four instruments of both brands were divided into two groups (n=12) on the basis of the motion tested: continuous rotation (group 1) or reciprocating OTR motion (group 2). Resistance to cyclic fatigue was determined by recording time to fracture (TtF) in a stainless steel artificial canal with a 60° angle of curvature and 5 mm radius of curvature. Data were analysed by two-way analysis of variance and post-hoc Bonferroni tests for multiple comparisons with P<0.05 as the level of significance. RESULTS: F6 SkyTaper showed higher TtF compared with OneShape, both in continuous and in OTR motion (P<0.0001). The two tested instruments showed higher cyclic fatigue resistance in reciprocating OTR motion than continuous rotation (P<0.0001). CONCLUSION: OTR motion significantly improves cyclic fatigue resistance of the tested instruments. In addition, F6 SkyTaper showed higher cyclic fatigue resistance than OneShape in both motions.

Torsional and Cyclic Fatigue Resistance of a New Nickel-Titanium Instrument Manufactured by Electrical Discharge Machining.

INTRODUCTION: The purpose of this study was to evaluate the torsional and cyclic fatigue resistance of the new Hyflex EDM OneFile (Coltene/Whaledent AG, Altstatten, Switzerland) manufactured by electrical discharge machining and compare the findings with the ones of Reciproc R25 (VDW, Munich, Germany) and WaveOne Primary (Dentsply Maillefer, Ballaigues, Switzerland). METHODS: One hundred-twenty new Hyflex EDM OneFile (#25/0.08), Reciproc R25, and WaveOne Primary files were used. Torque and angle of rotation at failure of new instruments (n = 20) were measured according to ISO 3630-1 for each brand. Cyclic fatigue resistance was tested measuring the number of cycles to failure in an artificial stainless steel canal with a 60° angle and a 3-mm radius of curvature. Data were analyzed using the analysis of variance test and the Student-Newman-Keuls test for multiple comparisons. The fracture surface of each fragment was examined with a scanning electron microscope. RESULTS: The cyclic fatigue of Hyflex EDM was significantly higher than the one of Reciproc R25 and WaveOne Primary (P < .05 and P < .001, respectively). Hyflex EDM showed a lower maximum torque load (P < .05) but a significantly higher angular rotation (P < .0001) to fracture than Reciproc R25 and WaveOne Primary. No significant difference was found comparing the maximum torque load, angular rotation, and cyclic fatigue of Reciproc R25 and WaveOne Primary (P > .05). CONCLUSIONS: The new Hyflex EDM instruments (controlled memory wire) have higher cyclic fatigue resistance and angle of rotation to fracture but lower torque to failure than Reciproc R25 and WaveOne Primary files (M-wire for both files).

Cyclic fatigue resistance of nickel-titanium instruments after immersion in irrigant solutions with or without surfactants.

INTRODUCTION: The aim of the study was to assess cyclic fatigue resistance of reciprocating (Reciproc and WaveOne) and continuous rotating (ProTaper) nickel-titanium files after immersion in different irrigation solutions with or without surfactants during several short time periods. METHODS: A total of 270 new Reciproc R25, WaveOne Primary, and ProTaper F2 files were tested. Instruments of each brand were divided into 1 control group (n = 10) formed by new files and 4 test groups (n = 20) formed by instruments dynamically immersed at 37°C for 16 mm in 5.25% sodium hypochlorite (NaOCl), Hypoclean (5.25% NaOCl with surfactant), 17% EDTA, or EDTA Plus (17% EDTA with surfactant). Each test group was subdivided into 2 subgroups (n = 10) on the basis of the time of dynamic immersion in the endodontic irrigant solution (45 seconds or 3 minutes). Resistance to cyclic fatigue was determined by recording time to fracture in a stainless steel artificial canal with a 60° angle of curvature and 5-mm radius of curvature. The fracture surface was examined by using scanning electron microscopy. RESULTS: Immersion in NaOCl did not reduce the cyclic fatigue of reciprocating or continuous nickel-titanium files. The 17% EDTA reduced the fatigue resistance of all instruments after 3 minutes. The immersion in irrigants with surfactants did not influence the cyclic fatigue of instruments except for Reciproc immersed in Hypoclean solution. CONCLUSIONS: EDTA immersion reduced the cyclic fatigue resistance of all instruments after 3 minutes. Addition of surfactants did not influence the cyclic fatigue of files except when added to NaOCl when it contacts Reciproc instruments.

Long-term sealing ability of 3 endodontic obturation techniques.

This in vitro study sought to evaluate the sealing ability of 3 root canal obturator systems after immersion in simulated body fluid for 1 year. The coronal sections of 30 single-rooted teeth were removed at the cementoenamel junction at 12 mm (±1 mm), and roots were instrumented with nickel titanium instruments. Specimens were divided into 3 groups (n = 10) according to the obturation manufacturer-specified system and immersed in simulated body fluid. A digital fluid flow-meter was used to detect the flow rate at 1 week, 1 month, and 12 months after immersion. This study demonstrated that the tested endodontic obturation systems were unable to keep their sealing ability stable during the first year. At 12 months, all root filling systems showed increased flow rates (P < 0.0001).

Influence of continuous or reciprocating motion on cyclic fatigue resistance of 4 different nickel-titanium rotary instruments.

INTRODUCTION: The aim of this study was to evaluate the resistance to flexural fatigue of Reciproc R25 (VDW, Munich, Germany), WaveOne Primary (VDW, Munich, Germany), Mtwo (Sweden & Martina, Padova, Italy), and Twisted File (TF; SybronEndo, Orange, CA) instruments used in continuous rotation or in 2 different reciprocating motions. METHODS: A total of 180 nickel-titanium files from 4 brands marketed, 2 for use in reciprocating motion (ie, Reciproc R25 and WaveOne Primary) and 2 for use in continuous rotation (ie, Mtwo and TF both taper .06/0.25 tip diameter), were tested. Forty-five instruments for each brand were divided into 3 groups (n = 15) on the basis of the motion tested: continuous rotation (group 1: 300 rpm) and reciprocal motion (group 2: "RECIPROC ALL" mode and group 3: "WAVEONE ALL" mode). The resistance to cyclic fatigue was determined by counting the number of cycles to failure in a 60° curve with a 5-mm radius. Data were analyzed through 2-way analyses of variance. RESULTS: The cyclic fatigue resistance of the 2 reciprocating motion instruments (ie, "RECIPROC ALL" and "WAVEONE ALL") was significantly higher than the continuous rotation in each brand (P < .001). No significant difference was observed in cyclic fatigue between the 2 different reciprocal motions tested in each brand (P > .05). When considering the appropriate clinical motion for each brand, no significant difference in cyclic fatigue was found between TF, Mtwo, and Reciproc R25 instruments, whereas the cyclic fatigue resistance of WaveOne files was less than the other 3 brands (P < .05). CONCLUSIONS: Reciprocal motion showed a significantly higher cyclic fatigue resistance in all brands compared with continuous rotation. No differences were found between the 2 reciprocating motions.

Cyclic fatigue resistance of four nickel-titanium rotary instruments: a comparative study.

AIMS: The aim of this study is to investigate cyclic fatigue resistance of four nickel - titanium rotary (NTR) instruments produced by a new method or traditional grinding processes. METHODS: FOUR NTR INSTRUMENTS FROM DIFFERENT BRANDS WERE SELECTED: group 1. Twisted File produced by a new thermal treatment of nickel - titanium alloy; group 2. Revo S SU; group 3. Mtwo and group 4. BioRaCe BR3 produced by traditional grinding processes. A total of 80 instruments (20 for each group) were tested for cyclic fatigue resistance inside a curved artificial canal with a 60 degree angle of curvature and 5 mm radius of curvature. Time to fracture (TtF) from the start of the test until the moment of file breakage and the length of the fractured tip was recorded for each instrument. Means and standard deviations (SD) of TtF and fragment length were calculated. Data were subjected to one-way analysis of variance (ANOVA). RESULTS: Group 1 (Twisted File) showed the highest value of TtF means. Cyclic fatigue resistance of Twisted File and Mtwo was significantly higher than group 2 (Revo S SU) and 4 (BioRace BR3), while no significant differences were found between group 1 (Twisted File) and 3 (Mtwo) or group 2 (Revo S SU) and 4 (BioRaCe BR3). CONCLUSIONS: The cyclic fatigue resistance of Twisted File was significantly frigher than instruments produced with traditional grinding process except of Mtwo files.

Cyclic fatigue resistance of three different nickel-titanium instruments after immersion in sodium hypochlorite.

INTRODUCTION: The purpose of this study was to assess the resistance to cyclic fatigue of three nickel-titanium (NiTi) files after the immersion in sodium hypochlorite (NaOCl) solution in conditions similar to those used in clinical practice. METHODS: A total of 150 new Twisted Files (SybronEndo, Orange, CA), Revo S SU files (Micro Mega, Besancon, France), and Mtwo files (Sweden and Martina, Padova, Italy), size 25.06, were tested. Fifty files of the same brand were randomly assigned to five groups (n = 10) and submitted to the following immersion protocol in 5% NaOCl at 37°C for 16 mm: no immersion (control), 5 minutes statically, 1 minute statically, 5 minutes dynamically (300 rpm/min), and 1 minute dynamically. Resistance to cyclic fatigue was determined by counting the numbers of cycles to failure in a 60° curve with a 5-mm radius. Data were analyzed by two-way analyses of variance. RESULTS: Resistance to cyclic fatigue of the same NiTi file was not significantly affected by immersion in NaOCl (P > .05). The Twisted File showed a higher resistance in all groups than Revo S SU (P < .001). The comparison between the same groups of Twisted Files and Mtwo files or between Mtwo and Revo S files did not show significant differences (P > .05) except for two cases: group 2 of the Twisted Files and Mtwo files and group 5 of the Mtwo and Revo S SU files (P < .05). CONCLUSIONS: Static or dynamic immersion in NaOCl for 1 minute or 5 minutes did not reduce the cyclic fatigue resistance of NiTi significantly. However, the type of instrument influences cyclic fatigue resistance. In our study, Twisted Files were more resistant followed by Mtwo and Revo S SU files.