Cyclic fatigue resistances of Hyflex EDM, WaveOne gold, Reciproc blue and 2shape NiTi rotary files in different artificial canals

The aim of the present study was to compare the cyclic fatigue resistances of HyFlex EDM (HEDM), WaveOne Gold (WOG), Reciproc Blue (RB), and 2Shape (TS) NiTi systems having different metallurgic properties. HEDM, WOG, RB, and TS instruments were rotated in artificial canals which were made of stainless steel with an inner diameter of 1.5 mm, 45°, and 90° angles of curvatures and a radius of curvature of 5 mm until fracture occurred, and the time to fracture (TTF) was recorded in seconds. Also, number of cycles to fracture was calculated (NCF). Data were statistically analyzed using Kruskal-Wallis and t test. The statistical significance level was set at P < 0.05. When comparing the TTF of all the instruments tested in the artificial canal with 45° curvature, RB had statistically the highest cyclic fatigue resistance followed by HEDM and TS (P < 0.05), while the WOG showed the lowest cyclic fatigue resistance (P < 0.05). In artificial canal with 90° curvature, RB showed a significantly higher cyclic fatigue resistance than the other tested files (P < 0.05), while there was no significant difference among the TS, WOG and HEDM groups (P > 0.05). When the NCF values were taken into consideration, HEDM reported a significantly higher cyclic fatigue resistance than TS in both canal curvatures analyzed (P < 0.05). Within the limitations of the present study, RB NiTi files showed statistically higher cyclic fatigue resistance in artificial canals with 45° and 90° than the other NiTi files tested.

Regenerative endodontic procedures: a review of the literature and a case report of an immature central incisor

Background: Trauma of developing teeth may lead to pulpal necrosis with subsequent arrestment of root development, making them more susceptible to fracture. Regenerative endodontic procedures induce maturogenesis in necrotic immature permanent teeth in order to promote continuation of root growth. Mineral trioxide aggregate (MTA) is widely used as a blood clot protecting material, although it presents a potential drawback of discoloration. Biodentine is a tricalcium silicate cement with adequate bioactive properties that solve the problem of discoloration. Case report: The current case report demonstrates a maturogenesis of an upper central incisor with chronic apical abscess. Calcium hydroxide was used as intracanal medicament for a week. After a blood clot was formed, Biodentine was placed over it. Periapical healing and root growth were evident at 6 months follow-up. Cone Beam Computed Tomography (CBCT) confirmed apical closure and complete healing at 1 year. Key-learning points: Apical closure of necrotic immature permanent teeth is possible by means of regenerative endodontic procedure.Regenerative endodontic procedure with Biodentine has some advantages over that performed with MTA: No tooth discoloration, hort setting time, asy manipulation. CBCT is the best technique to evaluate root canal growth (length and wide).

Cyclic fatigue comparison among endodontic instruments with similar cross section and different surface coating

BACKGROUND

The aim of this study was to analyze the influence of rotary instruments' geometry and surface titanium-nitride (TiN) treatment on the fatigue fracture, through the comparison of cyclic fatigue resistance of two endodontic systems that have similar cross-sectional design and different surface coating.

METHODS

In this study 130 Mtwo (10/.04; 15/.05; 20/.06; 25/.06; 30/.05; 35/.04; 40/.04) and Easy Shape (15/.04; 20/.05; 25/.06; 30/.05; 35/.04; 40/.04) were tested for cyclic fatigue resistance. Time to fracture (TtF) was determined by counting the seconds of continuous rotation until final fracture in an artificial canal with 60° angle and a 5 mm radius of curve. The fracture surface of each fragment was examined with a scanning electron microscope (SEM). Data were subjected to one-way analysis of variance (ANOVA) and Tukey post-hoc tests.

RESULTS

Mtwo perform a significantly (P<0.001) higher number of cycles to fracture (NCF) compared with Easy Shape of the same size and taper. The comparison between Mtwo and Easy Shape instruments with the same taper showed higher TtF values of Mtwo files than the Easy Shape ones (P<0.001) while there were no differences among Mtwo and Easy Shape instruments with the same tip, (P>0.05).

CONCLUSIONS

Mtwo exhibit a higher NCF thanks to the smaller metal volume contained in their core. Titanium-nitride coating does not influence the performance of Easy Shape instruments on static test of cyclic fatigue.

New Technologies to Improve Root Canal Disinfection

Abstract Effective irrigant delivery and agitation are prerequisites to promote root canal disinfection and debris removal and improve successful endodontic treatment. This paper presents an overview of the currently available technologies to improve the cleaning of the endodontic space and their debridement efficacy. A PubMed electronic search was conducted with appropriate key words to identify the relevant literature on this topic. After retrieving the full-text articles, all the articles were reviewed and the most appropriate were included in this review. Several different systems of mechanical activation of irrigants to improve endodontic disinfection were analysed: manual agitation with gutta-percha cones, endodontic instruments or special brushes, vibrating systems activated by low-speed hand-pieces or by sonic or subsonic energy, use of ultrasonic or laser energy to mechanically activate the irrigants and apical negative pressure irrigation systems. Furthermore, this review aims to describe systems designed to improve the intracanal bacterial decontamination by a specific chemical action, such as ozone, direct laser action or light-activated disinfection. The ultrasonic activation of root canal irrigants and of sodium hypochlorite in particular still remains the gold standard to which all other systems of mechanical agitation analyzed in this article were compared. From this overview, it is evident that the use of different irrigation systems can provide several advantages in the clinical endodontic outcome and that integration of new technologies, coupled with enhanced techniques and materials, may help everyday clinical practice.

Fracture resistance of endodontically treated teeth restored with a bulkfill flowable material and a resin composite

AIM

To determine and compare the fracture resistance of endodontically treated teeth restored with a bulk fill flowable material (SDR) and a traditional resin composite.

METHODS

Thirty maxillary and 30 mandibular first molars were selected based on similar dimensions. After cleaning, shaping and filling of the root canals and adhesive procedures, specimens were assigned to 3 subgroups for each tooth type (n=10): Group A: control group, including intact teeth; Group B: access cavities were restored with a traditional resin composite (EsthetX; Dentsply-Italy, Rome, Italy); Group C: access cavities were restored with a bulk fill flowable composite (SDR; Dentsply-Italy), except 1.5 mm layer of the occlusal surface that was restored with the same resin composite as Group B. The specimens were subjected to compressive force in a material static-testing machine until fracture occurred, the maximum fracture load of the specimens was measured (N) and the type of fracture was recorded as favorable or unfavorable. Data were statistically analyzed with one-way analysis of variance (ANOVA) and Bonferroni tests (P<0.05).

RESULTS

No statistically significant differences were found among groups (P<0.05). Fracture resistance of endodontically treated teeth restored with a traditional resin composite and with a bulk fill flowable composite (SDR) was similar in both maxillary and mandibular molars and showed no significant decrease in fracture resistance compared to intact specimens.

CONCLUSIONS

No significant difference was observed in the mechanical fracture resistance of endodontically treated molars restored with traditional resin composite restorations compared to bulk fill flowable composite restorations.

Efficacy of Reciproc(®) and Profile(®) Instruments in the Removal of Gutta-Percha from Straight and Curved Root Canals ex Vivo

Objectives

To compare the efficacy of Reciproc^® (VDW GmbH) and ProFile^® (Dentsply Maillefer) instruments at removing gutta-percha from straight and curved root canals ex vivo filled using the cold lateral condensation and GuttaMaster^® (VDW GmbH) techniques.

Material and Methods

Forty mesial roots of mandibular molars with two curved canals and 80 single-rooted teeth with straight root canals, a total of 160 root canals, were randomly assigned to eight groups (canals per group = 20) according to filling technique, retreatment instrument and root canal curvature as follows: Group I, cold lateral condensation/ProFile^®/straight; Group II, cold lateral condensation/ProFile^®/curved; Group III, cold lateral condensation/Reciproc^®/straight; Group IV, cold lateral condensation/Reciproc^®/curved; Group V, GuttaMaster^®/ProFile^®/straight; Group VI, GuttaMaster^®/ProFile^®/curved; Group VII, GuttaMaster^®/Reciproc^®/straight; and Group VIII, GuttaMaster^®/Reciproc^®/curved. The following data were recorded: procedural errors, retreatment duration and canal wall cleanliness. Means and standard deviations were calculated and analysed using the Kruskal-Wallis test, one-way analysis of variance and Tukey’s test (P < 0.05).

Results

Reciproc^® instruments were significantly faster than ProFile^® instruments at removing GuttaMaster^® from both straight (P = 0.0001) and curved (P = 0.0003) root canals. Reciproc^® were statistically more effective than ProFile^® instruments in removing GuttaMaster^® from straight root canals (P = 0.021). Regardless of filling technique or retreatment instrument, gutta-percha was removed more rapidly from curved than from straight root canals (P = 0.0001).

Conclusions

Neither system completely removed filling material from the root canals. Compared with ProFile^® instruments, Reciproc^® instruments removed GuttaMaster^® filling material from straight and curved root canals more rapidly.

Deformations and cyclic fatigue resistance of nickel-titanium instruments inside a sequence

AIM

To compare the effect of brushing motion on torsional and cyclic fatigue resistance of TF Adaptive instruments after clinical use.

METHODS

20 packs of TFA small sequence (SybronEndo, Orange, CA, USA) were used for this study and divided into two groups. Each instrument prepared one resin tooth, consisting in 4 canals with a complex anatomy. In group A, no brushing motion was performed. In group B, after the green instrument reached the working length, brushing motion with circumferential filing was performed for 15 seconds in each canal (overall 1 minute). All the instruments were then subjected to cyclic fatigue test and mean values and standard deviation for time to fracture were evaluated. Data were subjected to one-way analysis of variance and Bonferroni t-test procedure with a significance set at P < 0.05.

RESULTS

No instruments were broken during preparation of root canals. Two TF Adaptive green and 5 yellow showed unwinding after intracanal clinical use. No statistically significant differences were found between green instruments of both groups (P > 0.05), while a statistically significant difference was found between the yellow instruments (P < 0.05), with group B showing an higher resistance to cyclic fatigue.

CONCLUSIONS

A prolonged passive brushing motion did not adversely affected mechanical resistance of the instrument used for this purpose. Resistance to both deformations and cyclic fatigue of the second instrument within the TFA small sequence was enhanced by the coronal flaring provided by the brushing action of the first instrument used.

Cutting efficiency of instruments with different movements: a comparative study

OBJECTIVES

The aim of the present study was to evaluate the cutting efficiency of two new reciprocating instruments, Twisted File Adaptive and WaveOne Primary.

MATERIAL AND METHODS

10 new Twisted File Adaptive (TF Adaptive) (SybronEndo, Glendora, CA, USA) and 10 new WaveOne Primary files (Dentsply Maillefer, Ballaigues, Switzerland) were activated using a torque-controlled motor, respectively TFA motor (SybronEndo, Glendora, CA, USA) and Silver motor (VDW, Munich, Germany). The device used for the cutting test consisted on a mainframe to which a mobile plastic support for the hand-piece is connected and a stainless-steel block containing a Plexiglas block against which the cutting efficiency of the instruments was tested. The length of the block cut in 1 minute was measured in a computerized program with a precision of 0.1 mm. Mean and standard deviations of each group were calculated and data were statistically analyzed with one-way ANOVA and Bonferroni t test (P < 0.05).

RESULTS

TF Adaptive displayed significantly greater maximum penetration depth than WaveOne Primary (P < 0.05). In fact, TF Adaptive instruments (Group 1) cut the Plexiglas block to a mean depth of 8.7 (SD 0.5) mm, while WaveOne Primary instruments cut the Plexiglas block to a mean depth of 6.4 (SD 0.3) mm.

CONCLUSIONS

Twisted File Adaptive instruments demonstrated statistically higher cutting efficiency than WaveOne instruments.