In vivo evaluation of operative torque generated by two Nickel-Titanium rotary instruments during root canal preparation

Objectives This in vivo study evaluated the operative torque and preparation time of ProTaper NEXT (Dentsply Maillefer; Ballaigues, Switzerland) and EdgeFile X7 (EdgeEndo; Albuquerque, New Mexico, United States) rotary systems during root canal preparation of maxillary premolars. Materials and Methods Ten double-rooted maxillary premolars with independent canals were selected. Each canal in each tooth was prepared with one of the rotary systems (n = 10), ProTaper NEXT or EdgeFile X7. The instruments were rotated at 300 rpm with maximum torque set at 2 N.cm using an electric motor (KaVo; Biberach, Germany) that automatically recorded torque values at every 1/10th of a second (ds). Statistical Analysis Operative torque (N.cm) and preparation time (s) of the first shaping instrument (size 17/.04) of both rotary systems were recorded and statistically compared using the Mann-Whiney U test with a significance level set at 5%. Results No instrument exhibited flute deformation or underwent intracanal failure. No differences were found between the instruments regarding the maximum (peak) torque values (p > 0.05). EdgeFile X7 17/.04 required significantly less preparation time (3.75 seconds interquartile range [IQR]: 3.2-9.0) than ProTaper NEXT X1 (15.45 seconds IQR: 8.35-21.1) (p < 0.05). The median operative torque values of ProTaper NEXT X1 (0.26 N.cm; IQR: 0.18-0.49) were significantly higher compared with EdgeFile X7 17/.04 (0.09 N.cm; IQR: 0.05-0.17) (p < 0.05). Conclusions Although no difference was found between the median peak torque values of ProTaper NEXT X1 and EdgeFile X7 17/.04 instruments, the operative torque and instrumentation time results were impacted by their different designs and alloys during clinical preparation of root canals

Role of the flat-designed surface in improving the cyclic fatigue resistance of endodontic NiTi rotary instruments

The aim of this study was to investigate the role of the flat-designed surface in improving the resistance to cyclic fatigue by comparing heat-treated F-One (Fanta Dental, Shanghai, China) nickel-titanium (NiTi) rotary instruments and similar prototypes, differing only by the absence of the flat side. The null hypothesis was that there were no differences between the two tested instruments in terms of cyclic fatigue lifespan. A total of 40 new NiTi instruments (20 F-One and 20 prototypes) were tested in the present study. The instruments were rotated with the same speed (500 rpm) and torque (2 N) using an endodontic motor (Elements Motor, Kerr, Orange, CA, USA) in the same stainless steel, artificial canal (90° angle of curvature and 5 mm radius). A Wilcoxon-Mann-Whitney test was performed to assess the differences in terms of time to fracture and the length of the fractured segment between the flat- and non-flat-sided instruments. Significance was set at p = 0.05. The differences in terms of time to fracture between non-flat and flat were statistically significant (p < 0.001). In addition, the differences in terms of fractured segment length were statistically significant (p = 0.034). The results of this study highlight the importance of flat-sided design in increasing the cyclic fatigue lifespan of NiTi rotary instruments

Fatigue resistance of new and used nickel-titanium rotary instruments: a comparative study

Aim of the present study was twofold. First, to evaluate in vitro, the performance of two different NiTi rotary instruments in one molar case; then, to evaluate their resistance to cyclic fatigue, compared to new ones

Changes of radiographic trabecular bone density and peri-implant marginal bone vertical dimensions around non-submerged dental implants with a laser-microtextured collar after 5 years of functional loading

Objectives: The progressive peri-implant bone remodeling caused by dynamic cycles of microdamage may change peri-implant bone characteristics and volume after the functional loading. This prospective study was designed to evaluate the radiographic trabecular bone density and peri-implant vertical dimensional changes around the non submerged dental implant with a laser-microtextured collar (NSLI)s after 5 years of functional loading. Methods: Digital periapical radiographs of 58 NSLIs supported fixed single crowns and fixed partial dentures in 26 patients (14 men, mean age of 52 ± 3.8 years) were used for comparative evaluation between the implant placement [Baseline (BSL)], the definitive Crowns Delivery (CD) and the 5 years post-functional loading examination (T5). Regions of interest (ROI) were taken into consideration for the measurement of mean gray levels, standard deviation, and variation coefficient. The texture parameters, such as contrast, correlation, angular second moment and entropy, were investigated by using the software ImageJ (v.1.50i), by means of the Gray-level Co-occurrence Matrix (GLCM) Texture Tool plugin. Vertical Periimplant Marginal Bone Level (VPMBL) was assessed at the mesial and the distal sides of each implant by subtracting the measure at BSL from the measure at T5 by means of dedicate software (VixWin Platinum Imaging Software). Mixed regression models were adopted to analyze data. The possible effects of some variables, such as the use of provisional denture, location, crown/implant ratio, type of prosthetic design (single or splinted), on radiographic dimensional vertical changes, gray levels and texture analysis variables were also evaluated. Results: From BSL to T5, mesial and distal VPMBL showed a statistically significant gain of 0.9 ±0.5, and 0.10 mm ±0.6, respectively (P<0.05). From CD to T5, mean gray levels increased from 94.4±26.8) to 111.8±27.1 (P<0.05), while the coefficient of variation decreased from 0.08±0,03 to 0.05±0.04) (P<0.05). Variables showed no statistically significant correlation with texture parameters (P > 0.05). Conclusion: NSLIs showed an increase in radiographic vertical peri-implant marginal bone levels and bone density up to 5 years of loading

Harnessing the power of biologic agents on the oral microbiota: a way to promote oral and systemic health?

During the long history of their evolution, higher organisms, including mammals, have learnt to take great advantage from living in close contact with selected populations of microbes.1 By living in close contact, animals and microbes underwent a progressive and mutual co-evolutive process that is believed to be a major driving force in the development of adaptive immunity of vertebrates.2 As a result of this co-evolutive process, humans and other animals are characterized by their own unique microbiomes, each consisting of many hundred species of viruses, bacteria, archaea, fungi, and protozoa, unevenly distributed to colonize the different accessible regions of the body.3 The human microbiome is believed to account for 1-3% of body weight and to comprise more than 100 trillion cells.4 The microbiota is involved in complex host-microbe and microbe-microbe interactions, thus modulating nutrient acquisition, adjusting immune system development and general homeostasis (via epigenetic modifications of host genes5), and playing the role of protective barrier to pathogens.4 When a microbiota undergoes qualitative and quantitative changes with regard to distribution in a site and metabolic activity, this condition is defined dysbiosis and is expected to be associated with local and/ or distant pathologic signs.6 Bacterial products released by a dysbiotic microbiota interact with homeostatic mechanisms of the human host and cooperate to the pathogenesis of major human diseases, including diabetes mellitus, inflammatory bowel syndrome, atherosclerosis, obesity, liver disease, and cancer.4,7 he oral microbiota is the second more abundant and one of the most diverse and unique microbial communities in the human body.8 Although many of the most relevant oral and dental diseases, including caries, periodontal and peri-implant diseases, have been long recognized as of microbial origin, only recently the application of culture independent molecular methods using 16S rRNA gene comparative analyzes enabled us to understand that they are caused by dysbiosis rather than by the action of specific pathogens.9-11 The effects of oral dysbiosis are not limited to oral tissues: periodontal diseases, for example, are among the most common human diseases and their associations with diabetes, cardiovascular disease, metabolic disease and obesity, rheumatoid arthritis, certain cancers, respiratory diseases, and cognitive disorders is now supported by increasing evidence.12 Recent molecular investigations showed that some potentially pathogenic oral bacteria (named pathobionts), as for example Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and Fusobacterium nucleatum, colonize in low numbers the oral cavity of healthy individuals, without alerting sentinel systems of mucosal defences.13,14 Conditions able to disrupt the eubiotic equilibrium promote the overgrowth of pathobionts, which suddenly become pathogens (with support from commensal

Peri-implant marginal bone changes and soft tissue conditions around single implants with laser-microgrooved collar placed in regenerated extraction sockets and in native bone: 2-year results of RCT

The aim of present study was to compare peri-implant marginal bone changes and soft tissues conditions around single implants placed in alveolar sockets regenerated with porcine xenograft and collagen membrane or non-regenerated native bone. Forty patients who required single tooth extraction and single implant placement in premolar/molar area, were enrolled in this study. Subjects were randomly assigned to the control group (S; extraction sockets spontaneously healed) or to the test group (R; extraction sockets grafted with porcine-derived bone and covered with collagen membrane). Six months after extractions, single tapered implants with laser-microgrooved collars were inserted. For each implant, radiographic MBL and clinical parameters were evaluated during 2 years of function. At the 24-month follow-up, a survival rate of 100% was reported for all implants. For the S group, the mean marginal bone loss (MBL) was 0.118 ± 0.07 mm while for the R group the mean MBL was 0.131± 0.03 mm. No statistically significant differences were reported among groups (P >0.05). Between the two groups, no statistically significant differences were found also for plaque index, bleeding on probing, probing depth and gingival recession. At the 24-month follow-up, results showed that implants with laser-microgrooved collar surface placed in regenerated extraction sockets and in native bone did not performed differently with respect to implant survival, MBL and peri-implant soft tissue parameters

Torque range, a new parameter to evaluate new and used instrument safety

The aim of the present study is to evaluate operative torque, torque at failure and the difference between these two values-the "torque range"-of two different NiTi files. We also sought to evaluate and compare these parameters for new and used files. Forty S-One 20.06 and forty M-Two 20.06 were tested, divided in four equal groups (n = 10) for each brand. Ten instruments from each brand performed three root canal treatments each on standardized extracted single-rooted teeth. Afterwards, each group was subjected to the following two tests: operative torque and torsional resistance. Mean values for all the tested groups were calculated. The results for new instruments showed that S-One developed significantly higher operative torque, but higher torsional resistance. The results for used instruments showed that the S-One 20.06 developed less operative torque and higher mean torsional resistance value compared to the M-Two. Moreover, the percentage reduction of both values was significantly higher for M-Two. The results of the present study showed a safer torsional behavior of the S-One. These results could be related to the heat treatment and the manufacturing process

Fatigue resistance of two Nickel-Titanium rotary instruments before and after ex vivo root canal treatment

Aim: The aim of the present study is twofold: to evaluate cyclic fatigue resistance differences of two different nickel-titanium rotary instruments, brand new and after an ex vivo instrumentation of single root extracted teeth. Materials and methods: Twenty new S One 20.06 were randomly divided into two groups. The first group (n = 10) was immediately subjected to a cyclic fatigue test (S One Group I). The second group (n = 10) (S one Group II) performed a cyclic fatigue test after three ex vivo root canal treatment with a single-file technique. The same process has been carried out for 20 M-Two 20.06 instruments. Results: Mean time to fracture (TtF) for Group I was 51.14 ± 1.28 for S One and 32.62 ± 0.17 for M-Two 20.06 and for Group II was 46.00 ± 0.99 for S One and 27.75 ± 1.58 for M-Two 20.06. The reduction in TtF values from Group I to Group II was 11% for S One and 15% for M-Two. Statistical analysis found significant differences in all the groups examined (p value < 0.05). Mean fragment length (FL) for Group I was 3.07 ± 0.17 for S One and 3.05 ± 0.14 for M-Two 20.06 and for Group II was 3.05 ± 0.07 for S One and 3.05 ± 0.14 for M-Two 20.06. Statistical analysis was pursued, and no significant difference was found (p value > 0.05). Conclusion: The S-One showed significantly more resistance to cyclic fatigue stress than M-Two for both new and used instruments. This validates the hypothesis that the AF H wire enables the S One files to endure more the cyclic fatigue stresses. Clinical significance: This study demonstrates the cyclic fatigue resistance of a new endodontic instrument after repetitive usage

Torsional resistance of two new heat treated nickel titanium rotary instruments: an in vitro evaluation

Objective: To evaluate the difference in torsional resistance, angular deflection and fragment length between two new rotary instruments: AF Blue S4 and S-One. These files share all features except cross-sectional design. Material and Methods: A total of 40 new Nickel-Titanium instruments of 25 mm in length were tested in this study and divided in two groups: 20 AF Blue S4, tip 25 and constant 6% taper and 20 AF-Blue S4 tip 25 and constant 6% taper. The torsional test was performed by the use of a torque recording endodontic motor (KaVo, Biberac, Germany). Torque to Fracture (TtF), Angular Deflection (AD) and Fragment Length (FL) was recorded for each instrument. To ensure an immovable block at 3mm of the instrument tip, an auto-polymerizing resin (DuraLay; Reliance Dental Mfg Co, Worth, IL) was used. Each file was rotated clockwise at a speed of 300 rpm until fracture occurred. Results: Group A (AF Blue S4) showed higher TtF and AD than Group B (S-One), and statistical analysis found significant differences between the two instruments (p<0.05). The mean values for FL showed no significant differences (p>0.05) between the two instruments. Conclusion: The AF Blue S4 seems to have a higher resistance to torsional stress in vitro. Clinically, the use of AF Blue S4 could be safer in narrow canals