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

MMP-7 and MMP-9 Are Overexpressed in The Synovial Tissue from Severe Temporomandibular Joint Dysfunction

Matrix metalloproteinases (MMPs) are tissue-enzymes that play a key role during the remodeling process, such as in inflammatory diseases. MMP-7 and MMP-9 have been shown to be implicated in extracellular matrix homeostasis and in joint disc remodeling. The objective of this study was to determine the relation of MMP-7 and MMP-9 expression with severe temporomandibular joint dysfunction, in particular with anterior disk displacement without reduction (ADDwoR), using an immunohistochemical approach. Therefore, twenty human temporomandibular synovia in the test group and ten in the control group were collected. The results showed there was a statistically significant difference (P\u3c0.001) for morphometric and densitometric analysis of both detected MMPs in control and test groups. In conclusion, MMP-7 and MMP-9 were overexpressed in the synovial tissue of patients with ADDwoR

Root-end resection with or without retrograde obturation after orthograde filling with two techniques: A micro-CT study

To evaluate the filling ability of two orthograde obturation techniques followed by the apical resection with or without retrograde obturation through micro-computed tomography (CT). Thirty-two single-rooted permanent teeth were prepared and randomised into four groups (n = 8) according to the orthograde obturation technique (single cone technique [SCT] and mineral trioxide aggregate placement) combined or not with retrograde obturation. The volume of voids (VoV) within the entire endodontic space, the apical 3 mm, and 1 mm after root resection was calculated by micro-CT. Statistical analysis showed no significant difference among the groups regarding the total VoV in all root canals, as well as within the apical 1 mm after root resection. The SCT and apical resection without retrograde filling showed significantly better results in terms of VoV at the apical 3 mm after root resection. Within the study limitations, SCT associated with apical resection without retrograde preparation exhibited a similar or less amount of voids than the other groups

Identifying spin bias of nonsignificant findings in biomedical studies

Abstract Objective The purpose of this research note is to share a technique for the identification of spin bias that we developed as part of a living systematic review on the cardiovascular testing of e-cigarette substitution for cigarette smoking. While some researchers have remarked on the subjective nature of ascertaining spin bias, our technique objectively documents forms of spin bias arising from the misrepresentation of nonsignificant findings and from the omission of data. Results We offer a two-step process for the identification of spin bias consisting of tracking data and findings and recording of data discrepancies by describing how the spin bias was produced in the text. In this research note, we give an example of the documentation of spin bias from our systematic review. Our experience was that nonsignificant results were presented as causal or even as significant in the Discussion of studies. Spin bias distorts scientific research and misleads readers; therefore it behooves peer reviewers and journal editors to make the effort to detect and correct it

A scoping review of new technologies for dental plaque quantitation: Benefits and limitations

&lt;h3&gt;Objectives&lt;/h3&gt;&lt;p&gt;To determine the validity and reliability of novel digitalized tools for &lt;a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/tooth-plaque"&gt;dental plaque&lt;/a&gt; detection and explore the benefits and limitations connected to their use.&lt;/p&gt;&lt;h3&gt;Data&lt;/h3&gt;&lt;p&gt;Reporting followed the Preferred Reporting Items for &lt;a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/systematic-review"&gt;Systematic Reviews&lt;/a&gt; and Meta-Analyses (PRISMA) Extension for Scoping Reviews. All human clinical studies comparing dental plaque detection using digitalized systems against a standard reference were included.&lt;/p&gt;&lt;h3&gt;Sources&lt;/h3&gt;&lt;p&gt;PubMed and Scopus were screened from 01 January 2013 to 28 September 2023. Bibliographies of primary studies and principal peer-reviewed scientific journals were manually searched.&lt;/p&gt;&lt;h3&gt;Study selection&lt;/h3&gt;&lt;p&gt;The initial search identified 576 articles, with a total of 13 included in the review, published between 2015 and 2023. Most of the studies included (77&nbsp;%) were cross-sectional with three being prospective. Digital devices captured 2D and 3D images via cameras and intra-oral scanners, respectively. The Turesky's modified &lt;a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/plaque-index"&gt;plaque index&lt;/a&gt; was the most frequent clinical index. Correlation with clinical examination was moderate to strong, with good to excellent intra- and inter-system agreement.&lt;/p&gt;&lt;h3&gt;Conclusions&lt;/h3&gt;&lt;p&gt;Within the limitations of this scoping review, image analysis-based plaque detection systems demonstrated good correlations with clinical plaque indices, using both 2D and &lt;a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/3d-imaging"&gt;3D imaging&lt;/a&gt; systems. Whilst digital plaque detection devices offer advantages in terms of procedural standardization and reproducibility, they also have limitations, therefore currently, their application should be underpinned by a comprehensive clinical examination.&lt;/p&gt;&lt;h3&gt;Clinical significance&lt;/h3&gt;&lt;p&gt;Digital plaque detection tools, that provide standardized measurements and store acquired images, facilitate more informed feedback to patients. This objective analysis may enhance clinician confidence in their utility for &lt;a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/clinical-trial"&gt;clinical trials&lt;/a&gt; and other applications.&lt;/p&gt;&lt;h2&gt;Funding&lt;/h2&gt;&lt;p&gt;This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.&lt;/p&gt

Evaluation of the Cyclic Fatigue of Two Single Files at Body and Room Temperature with Different Radii of Curvature

Background: To compare the influence of different temperatures and curvature radii on the cyclic fatigue resistance of F6 SkyTaper (F6ST) and One Curve (OC) single file nickel-titanium rotary instruments. Methods: A total of 120 instruments of F6ST and OC #25.06 were evaluated in 5 mm and 3 mm curvature radii at two temperatures (20 °C ± 1 °C and 37 °C ± 1 °C) in 16 mm stainless steel artificial canals associated with a curvature of 60°. The cyclic fatigue of tested files was assessed by employing a customized testing apparatus and expressed as times to fracture (TtF). A statistical analysis was performed with the significance level set at 95%. Results: All instruments decreased their TtF at 37 °C except for OC in the 3 mm radius, in which no significant difference was detected between 20 °C and 37 °C. A 3 mm curvature radius negatively affected TtF of all tested instruments, except for F6ST at 20 °C. F6ST had higher TtF than OC in the 3 mm radius at 20 °C, with no significant difference between them in the other tested conditions. Conclusions: Under the limits of the present in vitro study, body temperature impaired cyclic fatigue resistance of all files, except for OC in the 3 mm curvature radius. All instruments exhibited lower times to fracture in the 3 mm radius, excluding F6ST at 20 °C

Influence of Coronal Flaring on the Shaping Ability of Two Heat-Treated Nickel-Titanium Endodontic Files: A Micro-Computed Tomographic Study

Nickel-titanium (NiTi) usage is associated in endodontics with some complications including canal transportation. Centering ability of a NiTi file is the ability to stay centered in the root canal system during instrumentation. Any undesirable deviation from the natural canal path is indicated as canal transportation. A possible strategy to improve the centering ability of NiTi instruments is the pre-enlargement of the coronal third of the root canal to minimize coronal interferences. This procedure is known as coronal flaring. The aim of this study was to perform a micro-computed tomographic (micro-CT) evaluation of the effect of coronal flaring on canal transportation and centering ability of two heat treated nickel-titanium rotary instruments, 2Shape (Micro Mega, Besançon, France) and HyFlex CM (Coltène Whaledent, Altstätten, Switzerland). Thirty extracted mandibular molars with two independent mesial canals were selected and randomly instrumented (n = 15 canals) with One Flare (Micro Mega, Besançon, France) before HyFlex CM, HyFlex CM (without coronal flaring), One Flare before 2Shape and 2Shape (without coronal flaring). One Flare (Micro Mega, Besançon, France) was introduced 4 mm below the canal entrance for canals prepared with coronal flaring. HyFlex CM and 2Shape were used accordingly to manufacturers’ instructions. New files were used for each canal. During and after instrumentation, irrigation procedures were performed. Micro-CT images were obtained pre- and post-preparation to measure and record root canal transportation and centralization. They were reconstructed from root apex to canal orifices, generating approximately 1000 sections per specimen. The anatomical thirds were determined by dividing the number of cross-sectional slices by three. Root canal transportation and centralization were determined by Gambil method, and the mean values were analyzed by repeated measures analysis of variance followed by multiple comparisons of Bonferroni to compare the different instrumentations procedures and the root thirds (p < 0.05). As for root canal transportation, 2Shape reported significantly higher values compared to HyFlex CM in the cervical region independently from the coronal flaring. In the apical region, 2Shape caused significantly minor canal transportation when used with coronal flaring with compared with the absence of coronal flaring. Regarding the centralization, HyFlex CM showed higher values than 2Shape in the cervical, independently from coronal flaring. In the apical region, 2Shape with coronal flaring exhibited significant major centering ratio, compared with not. Within the limitations of this study, coronal flaring reduced canal transportation and improved centralization of the 2Shape files in the apical section while it had no significant influence on shaping ability of the HyFlex CM instruments. Coronal flaring could represent a valid strategy to improve the shaping ability of NiTi files knowing that its benefit could be influenced by the shaping file used

In Vitro Evaluation of Different Irrigation Protocols on Intracanal Smear Layer Removal in Teeth with or without Pre-Endodontic Proximal Wall Restoration

International audienc

Torsional, Static, and Dynamic Cyclic Fatigue Resistance of Reciprocating and Continuous Rotating Nickel-Titanium Instruments

Introduction: The aim of this study was to evaluate torsional, dynamic, and static cyclic fatigue resistance of the reciprocating One RECI (OR; Micromega, Besançon, France), WaveOne Gold (WOG; Dentsply Maillefer, Ballaigues, Switzerland), rotary One Curve (OC, MicroMega), and ProTaper Next X2 (PTN X2; Dentsply Sirona, Charlotte, NC) instruments. Methods: A total of 120 OR (n = 30), WOG (n = 30), OC (n = 30), and PTN X2 (n = 30) nickel-titanium instruments were used. Torque and rotation angle until failure under static torsion loading were measured according to ISO 3630-1. Static and dynamic fatigue resistance was measured as the time to fracture in an artificial stainless steel canal with a 60° angle and 5-mm radius of curvature at intracanal temperature. The results were analyzed with 1-way analysis of variance and the post hoc Tukey test. The alpha-type error was set at 5%. Fracture instruments from torsion and fatigue tests were examined with a scanning electron microscope. Results: OR showed higher static fatigue resistance and rotation angle at fracture than WOG, OC, and PTN X2 (P < .05). WOG exhibited higher torsional resistance than the others (P < .05). The cyclic fatigue tests in dynamic mode had higher TTF than static for the PTN X2 and WOG groups (P < .05). In the dynamic tests, OR and WOG showed higher TTF than OC and PTN X2 (P < .05). Conclusions: Under these experimental conditions, One RECI exhibited suitable mechanical properties with the highest cyclic fatigue resistance and angle of rotation among the tested instruments. Keywords: Continuous rotation; One RECI; cyclic fatigue resistance; reciprocating motion; torsional resistance