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Various engine-driven NiTi endodontic files have been indispensable and efficient tools in cleaning and shaping of root canals for practitioners. In this review, we introduce the relative terms and conceptions of NiTi file, including crystal phase composition, the design of the cutting part, types of separation. This review also analysis the main improvement and evolution of different generations of engine-driven nickel-titanium instruments in the past 20 years in the geometric design, manufacturing surface treatment such as electropolishing, thermal treatment, metallurgy. And the variety of motion modes of NiTi files to improve resistance to torsional failure were also discussed. Continuous advancements by the designers, provide better balance between shaping efficiency and resistance to of NiTi systems. In clinical practice an appropriate system should be selected based on the anatomy of the root canal, instrument characteristics, and operators' experience.
Assuntos
Ligas Dentárias/química , Instrumentos Odontológicos , Desenho de Equipamento , Níquel/química , Preparo de Canal Radicular , Titânio/químicaRESUMO
Cone-beam CT (CBCT) is a relatively novel digital imaging technology to provide undistorted, three-dimensional information of teeth and surrounding tissues for aiding the diagnosis procedure and improving clinical decision-making. The use of CBCT in endodontics is widely and rapidly increasing. The aim of this review article is to introduce not only the current endodontic applications but also the limitations of CBCT such as artefacts and concerns on radiation dose. Furthermore, the evidenced-based guidelines on the reasonable application of CBCT in endodontics is also presented and re-considered. Clinicians should be more conscious neither to take CBCT as a substitute for two-dimensional radiography nor as a routine examination. With the continuous improvement of equipment and technology, it is urgent to establish and update guidelines in clinical practice. Endodontists should strengthen training, update knowledge, familiarize with CBCT technology and cooperate with radiologists to fulfill their diagnostic responsibilities.
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Objective:To compare the fracture resistance of roots of mandibular premolar with different apical preparation diameters.Methods:Sixty single-rooted single canal permanent mandibular premolar teeth extracted newly for orthodontic reason without immatureness,fracture or cracks were selected,with a curvature less than 10°,and internal length:short diameter of less than 2 at a level 5 mm from the apex.All the teeth were decoronated,leaving roots 13 mm in length.The initial apical file size for the teeth was ≤ 15#.The roots were assigned to 6 groups based on weights with random block design.Group A:blank control group,no instrumentation was performed.Groups B-F:the master apical file (MAF) was 40#,45#,50#,55# and 60#,respectively.In the five experimental groups the roots were instrumented using hand files with step-back technique at 1 mm increments,resulting in a taper of 0.05.The irrigant used was distilled water.After mounted in acrylic resin,all the teeth were subject to vertical loading using an Instron testing machine until fractured.The occurrence of fractures was detected when the applied load suddenly decreased.The fracture load values and fracture modes were recorded.Oneway ANOVA and post-hoc Tukey test were used to determine the difference of fracture load values between the groups (P ＜ 0.05).Chi-square tests were used to compare the modes of root fracture.Results:Five experimental groups exhibited lower fracture load values than that of control group [(1 444 ± 155) N].The mean fracture load values for roots instrumented to an apical diameter of 50# [(1 027 ± 128) N],55# [(994 ± 150) N] and 60# [(983 ± 166) N] were significantly lower than that of control group and 40# group [(1 339 ± 131) N] and 45# [(1 287 ± 144) N] (P ＜0.05).Buccal-lingual fracture,mesio-distal fracture and compound fracture occurred 55％,13％ and 32％,respectively.No difference of fracture mode was detected in the six groups.Conclusion:The fracture resistance reduced significantly when the roots were instrumented to an apical diameter of 50# or larger.
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Objective:To evaluate the influence of sodium hypochlorite (NaOCl) solution used during root canal therapy on dentin bond strength.Methods:In the study,15 freshly extracted human third molars with complete dental crowns,caries and filling-free were selected.The occlusal enamel was removed perpendicular to the long axis of the tooth to expose middle flat surfaces of sound dentin.The occlusal dentin surfaces were then polished using 600-grit silicon papers for 1 min and rinsed with deionized water for 1 min.The teeth were randomly divided into three groups according to the treatment received:group A (negative control group),the samples were immersed in deionized water for 20 min;group B,the dentin surfaces were immersed in 2.50％ NaOCl solution for 20 min,with the solution being renewed every 5 min;group C,the dentin surfaces were immersed in 5.25％ NaOCl solution for 20 min,with the solution being renewed every 5 min.All the treated dentin surfaces were bonded using a self-etching adhesive system (SE bond) with a 5 mm in height resin composite (AP-X).After storage in deionized water at 37 ℃ for 24 h,the adhesive samples were sectioned longitudinally to produce 1.0 mm ± 1.0 mm stick specimens (n =45) for micro-tensile bond strength testing (MPa).Failure modes (adhesive failure,cohesive failure or mixed failure) at the dentin-resin interface were observed using a stereomicroscope.The micro-tensile bond strength data among the three groups were analyzed by a one-way ANOVA,then the Post-hoc test(LSD) was employed for pairwise comparison.The distribution of failure modes among the groups were analyzed by chi square test.Results:Significant decreased bond strength values were found for the 2.50％ NaOCl-treated group (26.04 ± 5.74) MPa and 5.25％ NaOCl-treated group (24.46 ± 3.77) MPa when compared with the strength of negative control group (48.71 ± 7.77) MPa,P =0.000.Compared with the negative control group,themicro-tensile bond strength of the 2.50％ NaOCl-treated group and 5.25％ NaOCl-treated grouphad dropped by 46.5％ and 50.2％.However,there was no significant difference of bond strength between the 2 NaOCl-treated groups (P =0.214).The distribution of failure modes showed significant difference in all the three groups (2 =56.324,P =0.000).The mixed failure (68.9％) was the most mode of fracture in the negative control group,followed by adhesive failure (24.4％),and the cohesive failure was leas t (6.7％).The proportion of adhesive failure mode was higher in NaOCl-treated groups than in negative control group (P =0.000).There was no significant difference of the distribution of failure modes between the 2.50％ NaOCl-treated group and 5.25％ NaOCl-treated group(P =0.197),and there was no cohesive failure mode detected in the two groups.Conclusion:The micro-tensile bond strength of dentin to composite resin was lower after exposure to NaOCl solution.
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Objective:To compare the assessments of the presence or absence and the changes of post-treatment periapical lesions using periapical radiographs versus cone-beam computed tomography (CBCT).Methods:Imaging records were selected from a sample of 233 radiographic examinations (in-cluding periapical radiographs and CBCT)of patients with chronic apical periododontitis who received treatment and review in Department of Cariology and Endodontology of Peking University School of Stoma-tology.After testing the inter-observer and intra-observer agreement,two observers determined the pre-sence or absence of a periapical lesion and classified the changes of lesions in 4 categories:absence,re-duction or enlargement of lesion,or uncertain.The differences between CBCT and periapical radiographs in detecting the presence or absence and the changes of periapical lesions were compared using McNemar test and Fisher’s exact test respectively.Results:In the study,233 teeth were assessed with both periapi-cal radiographs and CBCT images.Periapical lesions were detected in 178 teeth on CBCT scans and in 146 teeth on periapical radiographs.CBCT images revealed a significantly larger number of lesions than were revealed by periapical radiographs (P <0.01 ).There was disagreement on the changes of lesions between the two radiological technologies in 25% teeth,and the difference was statistically significant (P <0.01 ). Conclusion:Significant differences were observed between periapical radiographs and CBCT in detection of post-treatment periapical lesions and assessment of the changes of periapical lesions.
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Objective:To evaluate the efficacy and security of two type of rotary nickel titanium system (Twisted File and ProTaper Universal)for root canal preparation based on micro-computed tomography (micro-CT).Methods:Twenty extracted molars (including 62 canals)were divided into two experimen-tal groups and were respectively instrumented using Twisted File rotary nickel titanium system (TF)and ProTaper Universal rotary nickel titanium system (PU)to #25/0.08 following recommended protocol. Time for root canal instrumentation (accumulation of time for every single file)was recorded.The 0-3 mm root surface from apex was observed under an optical stereomicroscope at 25 ×magnification.The presence of crack line was noted.The root canals were scanned with micro-CT before and after root canal preparation.Three-dimensional shape images of canals were reconstructed,calculated and evaluated. The amount of canal central transportation of the two groups was calculated and compared.Results:The shorter preparation time [(0.53 ±0.1 4)min]was observed in TF group,while the preparation time of PU group was (2.06 ±0.39)min (P<0.05).In mid-root level,TF group shaping resulted in less ca-nal center transportation than PU group [(0.070 ±0.056)mm vs.(0.097 ±0.084)mm,P<0.05]. No instrument separation was observed in both the groups.Cracks were not found in both the groups ei-ther based in micro-CT images or observation under an optical stereomicroscope at 25 × magnification. Conclusion:Compared with ProTaper Universal,Twisted File took less time in root canal preparation and exhibited better shaping ability,and less canal transportation.
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Objective:To measure the real temperatures on the pluggers of three continuous-wave de-vices, and to provide theoretical reference to evaluate thermal damage and heat ’s influence on the filling materials.Methods:The dual channel K type thermocouple was contacted to various sizes ’ pluggers in three different continuous-wave devices (BeeFill, Elements, B&L), and the highest temperatures at dif-ferent points ( tip, and 2 mm, 5 mm, 10 mm from the tip) of the pluggers ( preset temperature was 200℃) were recorded.The measurements were performed 5 times.T-test was used to compare the real tem-peratures at the tips with that set on the display and one-way ANOVA was used to compare the tempera-tures of the pluggers in different devices , sizes and points .Results:The highest temperature was at the tip of BeeFill 40/0.03 plugger (198.7 ±7.7) ℃, but there was on statistical differences between that and the preset temperature 200℃.The temperatures of the remaining pluggers were obviously lower than 200 ℃(P<0.05).The lowest temperature of the pluggers was detected at 10 mm from the tip of BeeFill 60/0.06 plugger (69.9 ±4.0) ℃.The highest temperature of each plugger was detected at the tip or 2 mm from the tip (112.1 to 198.7℃,and the median was 140.8℃).Conclusion:The real temperature of most continuous-wave pluggers included in this study is below the set temperature 200 ℃.
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Objective: To compare the incidences of root cracks after canal instrumentation with HyFlex CM system and the ProTaper Universal system .Methods:Sixty mandibular incisors were mounted in resin blocks with simulated periodontal ligaments , and the apex was exposed .The control group of 20 teeth was not prepared , and the other 40 teeth were divided into 2 experimental groups ( n=20 ) .The 40 root canals of the experimental groups were instrumented using HyFlex CM and ProTaper Universal to the major apical foramen ( AF).The horizontal sections 1 mm, 2 mm, and 3 mm from the apex were observed under an optical stereomicroscope at 25 ×magnification .The presence of cracks was noted . Results:No cracks were found in the control teeth .Cracks were found in 1 of 20 ( 5%) teeth in HyFlex CM group , and 17 of 20 ( 85%) teeth in ProTaper Universal group .The difference between the two experimental groups was statistically significant (P<0.01).Conclusion: The HyFlex CM files caused fewer root cracks than the ProTaper Universal files during the root canal instrumentation .