Eugenio Pedullà

The piezoelectric and rotatory osteotomy technique in impacted third molar surgery: comparison of postoperative recovery.

PURPOSE The aim of this study was the comparison of postoperative outcome in mandibular impacted third molars treated by piezoelectric surgery or by rotatory osteotomy technique. PATIENTS AND METHODS One hundred patients with impacted mandibular third molars were included in the study. Fifty patients were treated by rotatory osteotomy technique (group A) and 50 patients were treated by piezoelectric osteotomy technique (group B). Therapeutic protocol was the same for both groups. Twenty-four hours after surgery, 2 different parameters, facial swelling and trismus, were evaluated in both groups. A pair of compasses were used for the evaluation of facial swelling and trismus was evaluated. RESULTS The average surgery time was 17 minutes in group A, 23 minutes in group B; the mean facial swelling was 7.04 mm in group A, 4.22 mm in group B; trismus was 16.76 mm in group A, 12.52 mm in group B. Statistical analysis showed a significant reduction (P < .05) of postoperative facial swelling and trismus in group B; however, in this group, a statistically significant increased (P < .05 vs group A) surgery time was required. CONCLUSION The piezoelectric osteotomy technique produced a reduced amount of facial swelling and trismus 24 hours after surgery, but a longer surgery time was required when compared with the rotatory osteotomy technique.

Influence of cyclic torsional preloading on cyclic fatigue resistance of nickel - titanium instruments

AIM To evaluate the effect of different torsional preloads on cyclic fatigue resistance of endodontic rotary instruments constructed from conventional nickel-titanium (NiTi), M-Wire or CM-Wire. METHODOLOGY Eighty new size 25, 0.06 taper Mtwo instruments (Sweden & Martina), size 25, 0.06 taper HyFlex CM (Coltene/Whaledent, Inc) and X2 ProTaper Next (Dentsply Maillefer) were used. The Torque and distortion angles at failure of new instruments (n = 10) were measured, and 0% (n = 10), 25%, 50% and 75% (n = 20) of the mean ultimate torsional strength as preloading condition were applied according to ISO 3630-1 for each brand. The twenty files tested for every extent of preload were subjected to 20 or 40 torsional cycles (n = 10). After torsional preloading, the number of cycles to failure was evaluated in a simulated canal with 60° angle of curvature and 5 mm of radius of curvature. Data were analysed using two-way analysis of variance. The fracture surface of each fragment was examined with a scanning electron microscope (SEM). Data were analysed by two-way analyses of variance. RESULTS Preload repetitions did not influence the cyclic fatigue of the three brands; however, the 25%, 50% and 75% torsional preloading significantly reduced the fatigue resistance of all instruments tested (P < 0.01, P < 0.001 and P < 0.0001, respectively) except for the HyFlex CM preloaded with 25% of the maximum torsional strength (P > 0.05). CONCLUSIONS Torsional preloads reduced the cyclic fatigue resistance of conventional and treated (M-wire and CM-wire) NiTi rotary instruments except for size 25, 0.06 taper HyFlex CM instruments with a 25% of torsional preloading.

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.

Fracture Strength of Endodontically Treated Teeth with Different Access Cavity Designs

Introduction The purpose of this study was to compare in vitro the fracture strength of root‐filled and restored teeth with traditional endodontic cavity (TEC), conservative endodontic cavity (CEC), or ultraconservative “ninja” endodontic cavity (NEC) access. Methods Extracted human intact maxillary and mandibular premolars and molars were selected and assigned to control (intact teeth), TEC, CEC, or NEC groups (n = 10/group/type). Teeth in the TEC group were prepared following the principles of traditional endodontic cavities. Minimal CECs and NECs were plotted on cone‐beam computed tomographic images. Then, teeth were endodontically treated and restored. The 160 specimens were then loaded to fracture in a mechanical material testing machine (LR30 K; Lloyd Instruments Ltd, Fareham, UK). The maximum load at fracture and fracture pattern (restorable or unrestorable) were recorded. Fracture loads were compared statistically, and the data were examined with analysis of variance and the Student‐Newman‐Keuls test for multiple comparisons. Results The mean load at fracture for TEC was significantly lower than the one for the CEC, NEC, and control groups for all types of teeth (P < .05), whereas no difference was observed among CEC, NEC, and intact teeth (P > .05). Unrestorable fractures were significantly more frequent in the TEC, CEC, and NEC groups than in the control group in each tooth type (P < .05). Conclusions Teeth with TEC access showed lower fracture strength than the ones prepared with CEC or NEC. Ultraconservative “ninja” endodontic cavity access did not increase the fracture strength of teeth compared with the ones prepared with CEC. Intact teeth showed more restorable fractures than all the prepared ones. HighlightsThe effects of 3 access cavities on the fracture strength of teeth were evaluated.Teeth with traditional endodontic cavity showed lower strength than other groups.No difference was observed between conservative and “ninja” access cavity designs.All prepared teeth showed more unrestorable fracture patterns than intact ones.

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.

Environmental Temperature Drastically Affects Flexural Fatigue Resistance of Nickel-titanium Rotary Files

Introduction: The aim of the present study was to analyze how a low environmental temperature can affect the fatigue life of instruments made by different types of heat‐treated nickel‐titanium alloys. Methods: The flexural cyclic fatigue of 40 new specimens for each of the following systems was tested for cyclic fatigue resistance: ProTaper Universal F2 (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper Gold F2 (Dentsply Tulsa Dental Specialties, Tulsa, OK), Twisted Files SM2 (SybronEndo, Orange, CA), Mtwo #25.06 (VDW, Munich, Germany), and Vortex Blue #30.04 and #40.06 (Dentsply Tulsa Dental Specialties). Instruments were tested at 2 different environmental temperatures: 20°C (±2°C) for room temperature (RT) group and −20°C (±2°C) for the cooled environment (CE) group (n = 20). The number of cycles to failure (NCF) and the length of the fractured fragment (FL) were recorded. The means and standard deviations of NCF and FL were then calculated; NCF data were statistically analyzed using a paired t test between groups RT and CE for each instrument tested (P < .05), whereas FL data were analyzed using analysis of variance (P < .05). Results: The mean NCF values measured were significantly higher for the CE groups than the RT groups in all the systems tested (P < .05). The increase in cyclic fatigue resistance varied from 274%–854%. No differences in FL were registered among the different groups (P < .05). Conclusions: A low environmental temperature determines a drastic increase in the flexural fatigue resistance of NiTi endodontic instruments manufactured with traditional alloy and different heat treatments. HighlightsThe effect of a reduced environmental temperature (−20°C ± 2°C) on flexural fatigue resistance of NiTi instruments was tested and compared with room temperature (20°C ± 2°C).Fatigue resistance tested at a low environmental temperature was significantly higher for all the groups tested.No difference was observed between fragment length among the groups with the geometry of the curve maintained constant for all instruments tested.Environmental temperature is an important variable in determining the fatigue resistance of nickel‐titanium rotary files.

Effects of 6 Single-File Systems on Dentinal Crack Formation

Introduction: The purpose of this study was to compare the formation of microcracks after canal preparation performed with different single‐file systems as One Shape (Micro‐Mega, Besancon, Cedex, France), F6 SkyTaper (Komet Italia Srl, Milan, Italy), HyFlex EDM (Coltene/Whaledent AG, Altstatten, Switzerland), WaveOne (Dentsply Maillefer, Ballaigues, Switzerland), Reciproc (VDW, Munich, Germany), and WaveOne Gold (Dentsply Maillefer). Methods: Eighty‐four human extracted mandibular central incisors (40–60 y) were selected and divided into 6 experimental groups (n = 12 teeth) and a control group (unprepared teeth): One Shape (group 1), F6 SkyTaper (group 2), HyFlex EDM (group 3), WaveOne (group 4), Reciproc (group 5), and WaveOne Gold (group 6). Roots were then sectioned at 3, 6, and 9 mm from the apex, and the surface was observed under a stereomicroscope. Data were analyzed using logistic regression (P < .05). Results: No cracks were observed in the control group. All the systems tested caused cracks, mainly in the apical section (3 mm). HyFlex EDM (33.3%) and WaveOne Gold (58.3%) showed fewer microcracks than other experimental groups (P < .01); however, no significant difference was found between them in crack formation (P > .05). There was no difference among the other experimental groups (P > .05). Conclusions: All the instruments tested created dentinal cracks. Within the limitations of this study, the flexibility of nickel‐titanium instruments because of heat treatment seems to have a significant influence on dentinal crack formation. HyFlex EDM and WaveOne Gold caused less microcracks than the other instruments tested. HighlightsThe effects of 6 single‐file systems on crack formation were evaluated.HyFlex EDM and WaveOne Gold produced less microcracks than other files.There was no difference among One Shape, F6 SkyTaper, Wave One, and Reciproc files.The apical section showed the major number of cracks for all instruments.The flexibility of nickel‐titanium alloy seems to have a great influence on crack formation.

Mechanical Properties of Various Heat-treated Nickel-titanium Rotary Instruments

Aim The purpose of this study was to compare the bending stiffness, cyclic fatigue, and torsional fracture resistances of heat‐treated and conventional nickel‐titanium rotary instruments. Methods V‐Taper 2 (VT2; #25/.08), V‐Taper 2H (V2H; #25/.06), Hyflex CM (HCM; #25/.06), HyFlex EDM (HDM; #25/variable taper), and ProTaper Next X2 (PTN; #25/variable taper) were tested. The bending stiffness was measured with the customized device (AEndoS), and the files (n = 15) were fixed at 3 mm from the tip and bent at 45° with respect to their long axis. Cyclic fatigue resistance was tested by pecking and rotating instruments (n = 15) in artificial canal with a 7.8‐mm radius and 35° angle of curvature until fracture. The ultimate torsional strength and toughness were estimated by using AEndoS. The file tip of 5 mm was fixed between resin blocks and driven clockwise at 20 rpm until fracture. The results were analyzed by using one‐way analysis of variance and Duncan post hoc comparison. The fracture surfaces and longitudinal aspect of each group were examined under the scanning electron microscope. Results CM‐wire instruments had lower bending stiffness than others. HDM showed the highest cyclic fatigue resistance, followed by VTH and HCM (P < .05). VT2 showed the highest ultimate strength, followed by HDM, VTH‐PTN, and HCM. HDM and VT2 showed significantly higher toughness than VTH, HCM, and PTN (P < .05). Scanning electron microscope analysis showed typical fractographic features of cyclic fatigue and torsional fractures. Conclusions CM‐wire instruments showed higher flexibility and cyclic fatigue resistance than M‐wire and conventional nickel‐titanium instruments. Large cross‐sectional area and conventional nickel‐titanium showed high torsional resistance. HighlightsCM‐wire instruments showed higher residual angles than M‐wire and conventional NiTi.CM‐wire exhibited lower bending stiffness than M‐wire and conventional NiTi.Hyflex EDM had significantly higher fatigue resistance than M‐wire and conventional NiTi.Hyflex EDM and V‐Taper2 exhibited higher torsional resistance than other files.SEM examinations showed typical features of cyclic fatigue and torsional fracture.

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.

Influence of Different Angles of File Access on Cyclic Fatigue Resistance of Reciproc and Reciproc Blue Instruments

Introduction: The purpose of this study was to compare the cyclic fatigue of Reciproc (REC; VDW, Munich, Germany) and Reciproc blue (REB, VDW) with different angles of file access. Methods: The cyclic fatigue resistance of 120 new REC R25 and REB R25 (REB) files was tested. Instruments were divided into 8 groups on the basis of the access angle inside the artificial canal tested (n = 15): groups 1, 2, 3, and 4 included REC tested at 0°, 10°, 20°, and 30°, respectively, and groups 5, 6, 7, and 8 consisted of REB tested at 0°, 10°, 20°, and 30°, respectively. Resistance to cyclic fatigue was determined by recording the time to fracture in a stainless steel artificial canal with a 60° curvature and a 5‐mm radius using a customized testing device. Data were analyzed using 2‐way analysis of variance followed by the post hoc Tukey test with a significance level of 5%. The fracture surface of fragments was examined with a scanning electron microscope. Results: The cyclic fatigue of REC was reduced from each angle of insertion, whereas REB reduced its fatigue resistance when 20° or 30°access inclination was tested. REB exhibited higher cyclic fatigue than REC when the angle of file access was 0° and 10° (P < .05), whereas there was no difference between the instruments tested at 20°. REC had higher cyclic fatigue resistance than REB at 30° (P < .05). Conclusions: REB files exhibited higher cyclic fatigue resistance than REC when the access to the canal was straight or with a limited inclination. HighlightsCyclic fatigue of NiTi files with different access angles was evaluated.Reciproc blue had higher cyclic fatigue resistance than Reciproc at 0° and 10°.No difference was observed between Reciproc and Reciproc blue at 20°.All tested files exhibited a decreased cyclic fatigue at a 30° access angle.High file inclination reduces the cyclic fatigue resistance of Reciproc blue.