Chiara Pirani

Effectiveness of three different retreatment techniques in canals filled with compacted gutta-percha or Thermafil: a scanning electron microscope study.

INTRODUCTION This study evaluated the root canal wall morphology under scanning electron microscopy magnification after removal of 2 types of root canal fillings by using ultrasonic tips, nickel-titanium (NiTi) rotary instruments, and hand K-files. METHODS Thirty-six extracted roots were filled by using AH Plus (DeTrey-Dentsply, Konstanz, Germany) as a sealer with Thermafil (Tulsa Dental Products, Tulsa, OK) (18 roots) or warm vertically condensed gutta-percha (18 roots). All fillings were removed up to the middle third by using Gates Glidden drills. The retreatment was completed by using K-files (group 1), M-Two NiTi rotary instruments (group 2), or ESI ultrasonic tips (group 3) in 12 roots each. Root canals were irrigated by using 10% ethylenediaminetetraacetic acid and 2.5% NaOCl. The samples were split longitudinally and observed by scanning electron microscopy (100-2000x). The presence of smear layer, filling debris, and the surface profile was evaluated in each picture. Kruskal-Wallis (analysis of variance) and Mann-Whitney tests were used to evaluate the differences between the obturation techniques, the 3 retreatment methods, and the canal thirds (P < .05). RESULTS Resin sealer tags were observed inside dentinal tubules. No statistical differences (P > .05) were found among the 3 retreatment methods. No statistical differences were observed between Thermafil and vertically compacted warm gutta-percha for each group or between the coronal third used as control, middle, and apical thirds. CONCLUSIONS All retreatment techniques showed similar performances in terms of smear layer morphology, debris, and surface profile. None of them completely removed filling debris from dentinal tubules of apical third.

HyFlex EDM: superficial features, metallurgical analysis and fatigue resistance of innovative electro discharge machined NiTi rotary instruments

AIM To evaluate the surface and microstructural alterations of new and used HyFlex EDM prototypes and to test their fatigue resistance. METHODOLOGY Fifteen HyFlex EDM prototypes were used for in vitro instrumentation of severely curved root canals. Surface and microstructural characteristics of new and used files were compared by ESEM analysis equipped with energy dispersive X-ray spectrophotometry (EDS) and optical metallographic imaging. Usage-induced degradation was assessed. Thirty additional HyFlex EDM prototypes and 20 standard manufactured HyFlex CM files were subjected to cyclic fatigue tests. Time to fracture was recorded, and results were validated using the Kruskal-Wallis test (α-level 0.05). Fatigued files were analysed by ESEM for fractographic evaluation. RESULTS Surface and microstructural characterization of EDM prototypes revealed the typical spark-machined surface of a NiTi EDM alloy. No fractures were registered during root canal instrumentation. No evident surface alterations and minor degradation were observed between new and used instruments. The metallographic analysis of new and used files disclosed a homogeneous structure, mostly composed of lenticular martensite grains, and some residual austenite. The cyclic fatigue test showed an increase of fatigue resistance up to 700% on the EDM compared to CM files. CONCLUSIONS Spark-machined peculiar surface is the main feature of HyFlex EDM. Low degradation was observed after multiple canal instrumentations. Prototypes exhibited surprising high values of cyclic fatigue resistance and a safe in vitro use in severely curved canals.

Cyclic Fatigue Testing and Metallographic Analysis of Nickel-Titanium Rotary Instruments

INTRODUCTION The aim of this study was to compare cyclic fatigue resistance of four nickel-titanium rotary systems and to evaluate their surface, fractographic, and matrix morphology. METHODS Four models of endodontic rotary files (EasyShape [Komet/Gebr. Brasseler, Lemgo, Germany], ProTaper [Dentsply Maillefer, Ballaigues, Switzerland], NRT [MANI Inc, Toshigi-Ken, Japan], and AlphaKite [Komet/Gebr. Brasseler]) were subjected to fatigue testing in artificial canals with angle of curvature of 45° and 60° and a radius of curvature of 5 mm until fracture occurred. Nickel-titanium (NiTi) alloy properties were investigated by light microscopy, environmental scanning electron microscopy (ESEM), and energy dispersive x-ray spectrophotometry (EDS). ESEM analysis was conducted on new files to examine surface characteristics and on fractured samples to identify the crack origin and the fractographic features. RESULTS Analysis of variance testing revealed significant differences (P < .001) among the groups. NRT files had the highest fatigue resistance followed by AlphaKite, EasyShape, and ProTaper. All the new files presented surface imperfections. Fractographic analysis found the crack initiation to originate at the level of surface irregularities. Optical microscope inspection of the NiTi alloy matrix disclosed different-sized nonmetallic inclusions among models. EDS analysis of these inclusions showed that they were composed of carbon and oxygen in addition to nickel and titanium. Under light microscopy, austenitic grains appeared larger near the handle and smaller near the tip in all instruments. CONCLUSIONS NRT files presented the longest fatigue life. All samples showed surface irregularities and nonmetallic inclusions. Austenitic grains were smaller near the tip than near the handle. The angle of curvature was confirmed to influence the fatigue life of NiTi instruments.

The use of calcium-silicate cements to reduce dentine permeability

OBJECTIVE To evaluate in vitro the effectiveness of different calcium-silicate (CS) cements specifically designed for dentine permeability reduction. DESIGN Fifty dentine discs were prepared from caries free human molars extracted for surgical reasons. The treatment consisted in applying two different experimental CS cements on dentine surface. Dentine discs treated only with EDTA served as negative control group. Treatment with D-Sense Crystal and Clearfil S(3)-Bond served as positive control groups. After treatment samples were immersed in artificial saliva. The quantitative changes in the hydraulic conductance (i.e. permeability) through dentinal tubules were quantified using a hydrostatic device working at 6.9 kPa. Dentine permeability was measured immediately after EDTA treatment, 10 min and 1 week after treatment application and immersion of dentine samples in artificial saliva. SEM/EDX analyses were performed to obtain qualitative information on dentine morphology and surface deposits. RESULTS The experimental CS cements reduced dentine permeability immediately after application and also 10 min and 1 week after the immersion of the specimens in artificial saliva. D-Sense Crystal and Clearfil S(3)-Bond showed higher levels of dentine permeability after 1 week of immersion in artificial saliva. CONCLUSIONS CS cements reduced dentine permeability in vitro even after immersion in artificial saliva, which makes them new valuable candidates for treatment of dentine hypersensitivity in vivo.

Symptomatic and asymptomatic apical periodontitis associated with red complex bacteria: clinical and microbiological evaluation

In this study, the association of red complex (RC) bacteria that include Treponema denticola,Tannerella forsythia and Porphyromonas gingivalis with acute, exacerbated or chronic apical periodontitis was evaluated. Seventy-one patients with periapical disease were evaluated by clinical examination and microbiological samples obtained from the root canals were analyzed by a polymerase chain reaction assay. Twenty-one (29.6%) samples were positive for RC bacteria, with T.denticola, T. forsythia and P. gingivalis being detected in 14 (19.7%), 10 (14.1%) and 6 (8.5%) samples, respectively. RC bacteria were mainly associated with acute apical periodontitis (29.2%) and phoenix abscess (63.2%), while they were only sporadically detected (7.1%) in patients with chronic apical periodontitis. Generally, RC bacteria were associated with pain and a higher frequency of intracanalar/intrasulcular pus drainage. Involvement of RC bacteria in symptomatic periapical disease should be suspected in the presence of particularly severe clinical pain and pus drainage.

Wear and metallographic analysis of WaveOne and reciproc NiTi instruments before and after three uses in root canals

Reciprocating instruments made from M-wire alloy have been proposed to reduce the risk of fracture. No information is available on the surface alteration after single and multiple uses in root canals. Two reciprocating NiTi instruments were used on extracted teeth up to three times. ESEM/EDS analysis was conducted to determine defects, alterations, and wear features of the apical third of instruments and metallographic analysis was performed on the cross-section of new and used instruments to compare alloy properties. Topography of apical portion was evaluated by AFM before and after uses. Extracted single-rooted teeth were divided into two groups and instrumented according to the manufacturers recommendations with: (A) WaveOne Primary and (B) Reciproc R25. Each group was divided into three subgroups according to the number of canals instrumented: 1, 2, and 3, respectively. Chi square test was performed to verify homogeneity of defects distribution and GLM to evaluate the differences of RMS at baseline and after use for both groups (α level 0.05). No instrument fractured and no spiral distortions were observed under optical microscope even when the number of uses increased. Not significant differences were found for WaveOne and Reciproc. Blades presented a wrapped portion in WaveOne group and a more symmetrical feature in Reciproc group. Metallographic analysis revealed in both groups the presence of twinned martensitic grains with isolated flat austenitic areas. Both instruments demonstrated limited alteration, such as tip deformation and wear. This study confirmed the safe clinical use of both instruments for shaping multi-rooted teeth.

The effect of ultrasonic removal of various root-end filling materials

AIM To compare residual root-end filling material in apical root-end cavities following their removal with ultrasonic retrotips. METHODOLOGY Thirty single-rooted teeth were filled with Thermafil and AH Plus sealer. Root-ends were resected at 90 degrees, 3 mm from the apex. Root-end cavities were prepared with diamond burs and ultrasonic retrotips and filled with one of three filling materials: group I: Retro-TC (calcium silicate-based cement), group II: IRM (Dentsply, Germany), group III: Vitrebond (3M ESPE, USA). After 30 days of storage, ultrasonic retrotips were used to remove materials from the root-end cavities. The ultrasonic application time was fixed at 60 s. Polyether impressions and replicas of the root-ends were made. Root apices and replicas were examined by one operator under a scanning electron microscope. Remnants of residual materials were evaluated using a four-level scoring system; fractures, smear layer and exposed dentinal tubules were also examined. RESULTS Forty per cent of the specimens filled with Retro-TC revealed complete removal of the material with exposure of dentinal tubules, whilst 60% contained residual cement. Twenty per cent of specimens filled with IRM were completely devoid of material, whereas 80% had retained material. Ten per cent of specimens filled with Vitrebond retained a moderate amount of material whilst 90% had substantial retention of the material. Statistically significant differences were found (P < 0.05) amongst the three groups of materials. CONCLUSIONS Retro-TC was successfully removed in 40% of cases using ultrasonics retrotips for 60 s, whereas IRM and Vitrebond specimens had evidence of retained material in 80% and 90% of all specimens respectively.

SEM evaluation of root canal dentin morphology after Ni-Ti instrumentation.

PURPOSE The aim of this study was to compare, through scanning electron microscope (SEM), the ability of four Ni-Ti rotary instrument systems in shaping root canal walls and their ability in removing smear layer and dentin debris. METHODS Forty-six extracted single-rooted human teeth were divided into four groups and prepared to size 35 (Alpha System, FlexMaster, MFile) or 30 (NRT files). Irrigation was carried out with NaOCl and EDTA. Three parameters were evaluated in the coronal, middle, and apical thirds of the root canals: smear layer morphology, pulpal-inorganic debris presence and surface profile morphology. Data were statistically analyzed using the Kruskal-Wallis test (ANOVA). RESULTS None of the Ni-Ti rotary instrument systems resulted in being able to obtain constantly regular shaped surfaces in apical thirds, where smear layer, pulpal and inorganic debris were often present. CONCLUSIONS NRT file specimens resulted in being relatively free from debris and smear layer and gained better results and scores at any canal level.

The effect of the NRT files instrumentation on the quality of the surface of the root canal wall

Purpose To analyze in vitro, trough scanning electron microscope (SEM), the shaping ability of NRT NiTi rotary system (Mani, Inc, Toshigi-Ken, Japan). Methods Ten extracted human teeth were cut at the level of the CEJ and prepared with Gates-Glidden burs 4-3-2 and NRT rotary files up to size #35. Irrigation was performed with 7.5 mL of 5% NaOCl and 7.5 mL of 10% EDTA during each canal instrumentation. Following the shaping sequence, a final irrigation was performed with EDTA followed by NaOCl, each left in situ for three minutes. Teeth were then fractured longitudinally, and the coronal, middle, and apical thirds of the canals were inspected with SEM. Three parameters, divided into four different levels (Alfa and Bravo, considered clinically acceptable; Charlie and Delta, considered clinically unacceptable), were used to score the canal morphology: presence and amount of smear layer; presence of organic and inorganic debris; surface profile. Results SEM assessment revealed that in the coronal and middle third the majority of canals shaped with NRT rotary system presented a clinically acceptable surface. The apical third presented a higher amount of smear layer and dentinal debris instead, compared to the coronal and middle third. Conclusions NRT files demonstrated that they provided good instrumentation of the coronal and middle third, while being unable to obtain a defects-free surface in the apical third.

Immediate Early and Delayed Implants: A 2-Year Prospective Cohort Study of 131 Transmucosal Flapless Implants Placed in Sites With Different Pre-extractive Endodontic Infections

Introduction: To evaluate clinical outcome of early, immediate, and delayed transmucosal implants placed in patients affected by acute/chronic endodontic lesions. Materials and Methods: Eighty-five consecutive patients received 131 titanium implants with zirconium-oxide blasted surface. Pre-extractive diagnosis represented the main criteria for implant placement timing, following “best treatment” criteria. Implants were placed with flapless transmucosal technique. Hopeless teeth with chronic periapical lesions received atraumatic extraction, and an implant was immediately placed (Immediate Group, n = 29). Teeth with acute periapical lesion/abscess were extracted and implants placed after 8 to 12 weeks (Early Group, n = 29). Implants placed 10- to 12-month after extraction constituted the control group (delayed group, n = 73). Implants were loaded 3 months after insertion with provisional resin crowns and after approximately 15 days with definitive ceramic crowns. Marginal bone loss (MBL) was measured in a single-blind manner on periapical radiographs at 1, 3, 6, 12, and 24 months. Results: Multilevel analysis described exploring factors associated with MBL. Survival rate was 100%. MBL after 24 months was 0.78 ± 0.70 (95% confidence interval [CI]: 0.20 to −1.37) at immediate, 0.48 ± 0.70 at early (95% CI: −0.006 to −0.961), and 1.02 ± 1.01 (95% CI: 0.61 to −1.43) at delayed groups. Implant groups (immediate/early/delayed) and location (maxillary/mandibular) showed statistically significant results. Early group showed the lowest MBL values. The immediate group demonstrated less MBL than the delayed group. Conclusion: Early implant placement technique preserves periimplant marginal bone level more than immediate and delayed techniques.