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1.
Mariko Kubo Wataru Komada Shiho Otake Tasuku Inagaki Satoshi Omori Hiroyuki Miura 《Journal of prosthodontic research》2018,62(1):97-103
Purpose
This study evaluated the fracture strength and mode of failure of structurally compromised teeth with flared root canals restored using composite resin with four different systems.Methods
Sixty endodontically treated bovine teeth were uniformly shaped to simulate human mandibular premolars with flared root canals. The roots were divided into four groups of 15 specimens each based on the type of restoration: composite resin core only (control), glass fiber post, cylindroid glass fiber ribbons, and glass fiber post and ribbons. All specimens were loaded until fracture occurred using a universal testing machine. Average fracture loads were compared with a one-way ANOVA and Tukey HSD test (α = .05). The modes of failure were observed and the Fisher exact test and Bonferroni correction were used for statistical analysis.Results
The fiber post and ribbon group (1035.70 N) and the fiber ribbon group (881.77 N) showed significantly higher fracture strength than the controls (567.97 N) (p < .05). The fiber post and ribbon group also showed significantly higher fracture strength than the fiber post group (769.40 N). Almost all specimens showed unrestorable root fractures (p < .008). The control group had a significantly higher ratio of core sectional fractures (p < .017).Conclusions
Cylindroid glass fiber ribbons significantly increased the fracture strength of the composite resin post and cores in the case of the dentin within the thin root canal wall. Based on the results, this study recommends the combined use of glass fiber post and ribbons. 相似文献2.
Antonio Gloria Saverio Maietta Massimo Martorelli Antonio Lanzotti David C. Watts Pietro Ausiello 《Dental materials》2018,34(7):1063-1071
Objectives
To assess conceptual designs of dental posts consisting of polyetherimide (PEI) reinforced with carbon (C) and glass (G) glass fibers in endodontically treated anterior teeth.Methods
3D tessellated CAD and geometric models of endodontically treated anterior teeth were generated from Micro-CT scan images. Model C-G/PEI composite posts with different Young’s moduli were analyzed by Finite Element (FE) methods post A (57.7 GPa), post B (31.6 GPa), post C (from 57.7 to 9.0 GPa in the coronal–apical direction). A load of 50 N was applied at 45° to the longitudinal axis of the tooth, acting on the palatal surface of the crown. The maximum principal stress distribution was determined along the post and at the interface between the post and the surrounding structure.Results
Post C, with Young’s modulus decreasing from 57.7 to 9.0 GPa in the coronal–apical direction, reduced the maximum principal stress distribution in the restored tooth. Post C gave reduced stress and the most uniform stress distribution with no stress concentration, compared to the other C-G/PEI composite posts.Significance
The FE analysis confirmed the ability of the functionally graded post to dissipate stress from the coronal to the apical end. Hence actual (physical) C-G/PEI posts could permit optimization of stress distributions in endodontically treated anterior teeth. 相似文献3.
Adriana Lemos Mori Ubaldini Ana Raquel Benetti Francielle Sato Renata Corrêa Pascotto Antonio Medina Neto Mauro Luciano Baesso Anne Peutzfeldt 《Dental materials》2018,34(7):1054-1062
Objective
To investigate the relationship between physicochemical interactions of resin luting cements with dentine and retention of fibre posts in root canals.Methods
Retention of fibre posts (RelyX Fiber Post) was assessed by the pull-out method. The diffusion zone of the cements and their chemical interaction with dentine were estimated by micro-Raman spectroscopy. Resin luting cements employing etch-and-rinse (Rely X Ultimate and Variolink II), self-etch (Rely X Ultimate and Panavia F2.0), or self-adhesive (RelyX Unicem 2) modes were investigated. Data were analyzed by analysis of variance followed by Tukey HSD tests.Results
The retention of the fibre posts decreased in the following order: RelyX Ultimate, etch-and-rinse mode > RelyX Unicem 2 ≥ RelyX Ultimate, self-etch mode ≥ Panavia F2.0 ≥ Variolink II (p < 0.05). One of the etch-and-rinse mode cements presented the deepest diffusion zone, while the other, along with the self-adhesive cement, produced the shallowest zone. Cements used in the self-etch mode showed intermediary diffusion into dentine (p < 0.05). All resin luting cements showed some degree of chemical interaction with dentine, the highest recorded for RelyX Ultimate used in the etch-and-rinse mode and the lowest for Panavia F2.0 (p < 0.05). The retention of fibre posts in the root canal could be attributed neither to the mode of interaction of the luting cements with dentine nor to their ability to diffuse into dentine.Significance
Chemical interaction between the resin luting cement and the dentine paired with adequate post pretreatment contribute positively to the retention of fibre posts. 相似文献4.
Daniele Angerame Matteo De Biasi Massimiliano Lenhardt Lorenzo Bevilacqua Vittorio Franco 《Giornale Italiano di Endodonzia》2018,32(2):63-69
Aim
To assess the influence of the crown height, root length, crown-to-root ratio, and tooth type on the survival of teeth subjected to surgical endodontic retreatment and classified as periapically healed.Methodology
A single operator performed endodontic microsurgery interventions between 2008 and 2018 on teeth with refractory apical periodontitis. The present analysis selected the teeth classified as “complete periapical healing” according to the scale suggested by Molven. The postoperative periapical radiographs and those taken at the last recall visit were analysed by two independent calibrated examiners, who measured crown height and root length in a blind manner. The crown-to-root ratio was calculated as the ratio of the two variables. The level of inter- and intra-operator agreement was tested with Bland–Altman plots with 95% limits of agreement. An independent statistician conducted a survival analysis using Kaplan–Meier plots and a log-rank test (α = 0.05) to assess the significance of the differences among the subgroups defined by the following criteria: (a) crown height <median vs. >median; (b) root length <median vs. >median; (c) crown-to-root ratio <1 vs. >1; (d) crown-to-root ratio <median vs. >median; (e) single-rooted teeth vs. multi-rooted teeth.Results
At the end of the analysis, 42 patients were evaluated, each one contributing to the study with a single tooth. The mean follow-up period was 4.2 ± 2.4 years. Survival estimates were significantly improved for the teeth with roots longer than 8 mm, in comparison with that with shorter roots (p < 0.05). There were no statistically significant differences among the remaining considered subgroups.Conclusions
Under the conditions of this retrospective study, teeth with longer residual roots after apical surgery exhibited better chances of survival when compared to teeth with roots shorter than 8 mm. The other considered variables did not seem to affect the survival of apically resected teeth. 相似文献5.
Objective
This study utilizes micro-CT image combined with finite element (FE) analysis and in vitro fatigue testing to investigate the mechanical behavior associating with early resin luting cement damage induced by voids around a circular fiber post in a root canal treated premolar.Methods
Six similar mandibular first premolars with root canal treatment were scanned with high resolution micro-CT before and after fatigue testing. Micro-CT images of all teeth were processed to identify various materials (dentin, luting cement and void) to evaluate the volume/position of the void in each reconstructed tooth root canal model. Six corresponding mesh models from CT images were generated to perform FE simulations under receiving oblique concentrated loads (200 N) to evaluate the luting cement layer mechanical behavior. All teeth were subjected to the fatigue test with 240,000 load cycles simulating chewing for one year to compare results with those in FE simulations.Results
The result showed that most voids occurred adjacent to the apical third of the fiber post. Voids induced the fiber post to pull out, creating a stress concentration at the void boundary. Fatigue life in the experimental testing was found decreased with the stress value/micro-motion increasing in FE analysis.Significance
This study establishes that micro-CT, FE simulation and fatigue testing can be integrated to understand the early de-bonding mechanism at the luting cement layer in a root canal treated premolar, suggesting that attention must be paid to resin luting cement dissolving/debonding easier when voids occur in the apical and peri-apical areas of fiber posts. 相似文献6.
Yasuhiro Tanimoto Manamu Nagakura Norihiro Nishiyama 《Journal of prosthodontic research》2018,62(3):359-364
Purpose
The purpose of this study was to investigate the combined effects of fiber loading and pigmentation on the color differences and flexural properties of glass fiber-reinforced thermoplastics (GFRTPs), for use in non-metal clasp dentures (NMCDs).Methods
The GFRTPs consisted mainly of E-glass fibers, a polypropylene matrix, and a coloring pigment: the GFRTPs with various fiber loadings (0, 10, and 20 mass%) and pigmentations (0, 1, 2, and 4 mass%) were fabricated by using an injection molding. The color differences of GFRTPs were measured based on the Commission Internationale de l’Eclairage (CIE) Lab color system, by comparing with a commercially available NMCD. The flexural properties of GFRTPs were evaluated by using a three-point bending test, according to International Standards Organization (ISO) specification number 20795-1.Results
The visible colors of GFRTPs with pigment contents of 2 mass% were acceptable for gingival color, and the glass fibers harmonized well with the resins. The ΔE* values of the GFRTPs with pigment contents of 2 mass% obtained by using the CIE Lab system were lowest at all fiber loadings. For GFRTPs with fiber contents of 10 and 20 mass% at 2 mass% pigment content, these GFRTPs surpassed the ISO 20795-1 specification regarding flexural strength (> 60 MPa) and modulus (> 1.5 GPa).Conclusions
A combination of the results of color difference evaluation and mechanical examination indicates that the GFRTPs with fiber contents of 10 or 20 mass%, and with pigment contents of 2 mass% have acceptable esthetic appearance and sufficient rigidity for NMCDs. 相似文献7.
The autotransplantation of teeth after cryopreservation has become an increasingly viable method for whole tooth replacement. While the immediate success rates are quite high, damage introduced by cryopreservation within the dentin or enamel could be detrimental to the durability of these teeth.
Objective
to determine whether cryopreservation alters the microstructure of dentin or causes a reduction of its resistance to mechanical failures.Methods
Third molars were obtained from young donors (18≤ age ≤30 yrs) and subjected to a cryopreservation protocol involving storage for 10 days in cryoprotectant solution at ?196 °C. After treatment, the mid-coronal dentin was characterized in terms of its elastic modulus, strength and fatigue behavior. Scanning electron microscopy and Raman spectroscopy were used to evaluate the microstructure and integrity of collagen after cryopreservation.Results
There was no significant difference in the elastic modulus or flexural strength between dentin from the cryopreserved and non-cryopreserved (control) teeth. However, the cryopreservation treatment caused a significant decrease in the fatigue strength of dentin with respect to the controls, with average reduction of nearly 20%. While there were no differences apparent in the collagen matrix or fracture surfaces between the cryopreserved and control groups, the microstructure of dentin from the cryopreserved teeth exhibited unique features and damage that appear to have caused the decrease in durability.Significance
Autotransplantation of cryopreserved teeth may be a viable option for whole tooth restorations, but hidden damage within the dentin could render these teeth more susceptible to mechanical failures by fatigue and fracture. 相似文献8.
Luiza Helena S. Almeida Rafael R. Moraes Renata D. Morgental Sérgio S. Cava Wellington Luiz O. Rosa Patrícia Rodrigues Anderson S. Ribeiro Marcus Só Fernanda G. Pappen 《Dental materials》2018,34(8):e214-e223
Objective
To synthetize calcium aluminate (C3A) and silver-containing C3A particles (C3A + Ag) testing their effects on the properties of a MTA-based endodontic sealer in comparison to an epoxy resin- and a calcium silicate-based sealer.Methods
Pure C3A and C3A + Ag particles were synthesized by a chemical method and characterized using XRD to identify crystalline phases. SEM/EDS analysis investigated morphology, particle size, and elemental composition of particles. Setting time, flow, radiopacity, water sorption and solubility of commercial and modified sealers were evaluated according to ISO 6876/2012. The pH and ions release were measured using a pHmeter and a microwave induced plasma optical emission spectrometer. The inhibition of biofilm growth was evaluated by confocal laser scanning microscopy (CLSM). Data were rank transformed and analyzed by ANOVA and Tukey test (P < 0.05).Results
The C3A particles showed an irregular grain agglomerated structure with voids and pores. In C3A + Ag particles, Ag modified the material morphology, confirming the deposition of Ag. The physicochemical properties of the modified MTA-based sealer were similar to the commercial material, except for the significant increase in Ca+2 release. However, there was no Ag release. Setting time, flow, radiopacity, water sorption and solubility were adequate for all materials. All the materials showed alkaline pH. Antibiofilm effect was improved in the presence of C3A particles, while the biofilm inhibition was lower in the presence of Ag.Significance
The modified sealer presented improved antibiofilm properties and calcium release, without dramatic effects on the other characteristics. It is expected a positive effect in its antimicrobial behavior. 相似文献9.
Ricardo A. Caldas Atais Bacchi Valentim A.R. Barão Antheunis Versluis 《Dental materials》2018,34(9):1331-1341
Objective
Elucidate the influence of debonding on stress distribution and maximum stresses for intra-radicular restorations.Methods
Five intra-radicular restorations were analyzed by finite element analysis (FEA): MP = metallic cast post core; GP = glass fiber post core; PP = pre-fabricated metallic post core; RE = resin endocrowns; CE = single piece ceramic endocrown. Two cervical preparations were considered: no ferule (f0) and 2 mm ferule (f1). The simulation was conducted in three steps: (1) intact bonds at all contacts; (2) bond failure between crown and tooth; (3) bond failure among tooth, post and crown interfaces. Contact friction and separation between interfaces was modeled where bond failure occurred. Mohr–Coulomb stress ratios (σMC ratio) and fatigue safety factors (SF) for dentin structure were compared with published strength values, fatigue life, and fracture patterns of teeth with intra-radicular restorations.Results
The σMC ratio showed no differences among models at first step. The second step increased σMC ratio at the ferule compared to step 1. At the third step, the σMC ratio and SF for f0 models were highly influenced by post material. CE and RE models had the highest values for σMC ratio and lower SF. MP had the lowest σMC ratio and higher SF. The f1 models showed no relevant differences among them at the third step.Significance
FEA most closely predicted failure performance of intra-radicular posts when frictional contact was modeled. Results of analyses where all interfaces are assumed to be perfectly bonded should be considered with caution. 相似文献10.
Doaa Taha Sebastian Spintzyk Christine Schille Ahmed Sabet Marwa Wahsh Tarek Salah Jürgen Geis-Gerstorfer 《Journal of prosthodontic research》2018,62(3):293-297
Purpose
The purpose of this in vitro study was to assess the effect of varying the margin designs and the occlusal thicknesses on the fracture resistance and mode of failures of endodontically treated teeth restored with polymer infiltrated ceramic endocrown restorations.Methods
Root canal treated mandibular molars were divided into four groups (n = 8) and were prepared to receive Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) fabricated polymer infiltrated ceramic endocrowns (ENAMIC blocks). Group B2 represents teeth prepared with a butt joint design receiving endocrowns with 2 mm occlusal thickness and the same for group B3.5 but with 3.5 mm occlusal thickness. Group S2 represents teeth prepared with 1 mm shoulder finish line receiving endocrowns with 2 mm occlusal thickness and the same for group S3.5 but with 3.5 mm occlusal thickness. After cementation and thermal aging, fracture resistance test was performed and failure modes were observed.Results
Group S3.5 showed the highest mean fracture load value (1.27 ± 0.31 kN). Endocrowns with shoulder finish line had significantly higher mean fracture resistance values than endocrowns with butt margin (p < 0.05). However, the results were not statistically significant regarding the restoration thickness. Evaluation of the fracture modes revealed no statistically significant difference between the modes of failure of tested groups.Conclusions
For the restoration of endodontically treated teeth, adding a short axial wall and shoulder finish line can increase the fracture resistance. However, further investigations, especially the fatigue behavior, are needed to ensure this effect applies with small increases of restoration thickness. 相似文献11.
Tousif Iqbal Nathani Aatif Iqbal Nathani Ankur Mahesh Banode Moez Ismail Khakiani Juan Gonzalo Olivieri Fernandez Fernando Durán-Sindreu Terol Francesc Abella Sans 《Giornale Italiano di Endodonzia》2018,32(2):80-85
Aim
The purpose of this study was to determine and evaluate the apical preparation size resulting from different pecking times to the working length (WL) with five different file systems.Materials and methods
Fifty standard simulated endodontic J-shaped blocks were instrumented using ProTaper NEXT (PTN), WaveOne (WO), WaveOne Gold (WOG), OneShape (OS) and the Self-Adjusting File (SAF) (n = 10) with different pecking times (1, 2 and 4) to the WL. For the SAF group, instrumentation was done till WL according to the time, i.e. 1, 3 and 4 min. On completion of each stage, silicone impression material was used to take canal impressions for comparison and evaluation of the apical size preparation, using a stereomicroscope. Two-way analysis of variance was applied to determine differences between groups and pecking times.Results
After four pecking times, a significant increase was observed in the apical diameter of four test groups compared to SAF (P < 0.05), which was not associated with increased apical preparation at all times.Conclusion
A greater apical enlargement occurs with increasing pecking times; however, SAF instrumentation exhibits the minimum changes in the apical preparation after 1, 3 and 4 min. WO, WOG and OS are able to prepare the apical size similar to their tip at a single peck to the WL. 相似文献12.
Eshagh Ali Saberi Narges Farhad Mollashahi Forugh Farahi 《Giornale Italiano di Endodonzia》2018,32(2):57-62
Aim
This ex-vivo study aimed to compare canal transportation in mesio-buccal canal of mandibular first molars prepared with Mtwo and Revo-S multi-file and Neoniti single-file nickel–titanium (Ni–Ti) rotary systems using cone-beam computed tomography (CBCT).Methodology
CBCT scans were obtained from 60 extracted mandibular first molars and the teeth were randomly divided into three groups. Mesio-buccal canal of mesial root was prepared with Revo-S, Neoniti or Mtwo rotary systems according to the instructions of the manufacturers. Post-operative CBCT scans were also obtained. A single operator performed canal preparations while another operator blinded to the group allocation of teeth did the measurements. Data were analyzed using SPSS 20. The mean and standard deviation (SD) of the amount of canal transportation were calculated and compared between the groups using the Friedman test (P ≤ 0.05).Results
No significant difference was noted in canal transportation among the groups in the middle and apical third (P > 0.05). The rotary single-file instrument caused significantly greater canal transportation in the coronal third.Conclusion
No significant difference exists among different rotary systems in the amount of canal transportation caused in the middle and apical third of the mesio-buccal canal in mandibular first molars. Although all rotary files caused some degrees of canal transportation, the rotary single-file instrument caused significantly greater canal transportation than the multiple-file sequences in the coronal third. 相似文献13.
Xin Li Mariano Simón Pedano Bernardo Camargo Esther Hauben Stéphanie De Vleeschauwer Zhi Chen Jan De Munck Katleen Vandamme Kirsten Van Landuyt Bart Van Meerbeek 《Dental materials》2018,34(9):1410-1423
Objectives
To overcome shortcomings of hydraulic calcium-silicate cements (hCSCs), an experimental tricalcium silicate (TCS) cement, named ‘TCS 50’, was developed. In vitro research showed that TCS 50 played no negative effect on the viability and proliferation of human dental pulp cells, and it induced cell odontogenic differentiation. The objective was to evaluate the pulpal repair potential of TCS 50 applied onto exposed minipig pulps.Methods
Twenty permanent teeth from three minipigs were mechanically exposed and capped using TCS 50; half of the teeth were scheduled for 7-day and the other half for 70-day examination (n = 10). Commercial hCSCs ProRoot MTA and TheraCal LC were tested as references (n = 8). Tooth discoloration was examined visually. After animal sacrifice, the teeth were scanned using micro-computed tomography; inflammatory response at day 7 and day 70, mineralized tissue formation at day 70 were assessed histologically.Results
Up to 70 days, TCS 50 induced no discoloration, ProRoot MTA generated gray/black discoloration in all teeth. For TCS 50, 40.0% pulps exhibited a mild/moderate inflammation at day 7. No inflammation was detected and complete reparative dentin with tubular structures was formed in all pulps after 70 days. ProRoot MTA induced a similar response, TheraCal LC generated a less favorable response in terms of initial inflammation and reparative dentin formation; however, these differences were not significant (Chi-square test of independence: p > 0.05).Significance
TCS 50 induced reparative dentinogenesis in minipig pulps. It can be considered as a promising pulp-capping agent, also for aesthetic areas. 相似文献14.
Taylor Enochs Anne E. Hill Cassandra E. Worley Crisnicaw Veríssimo Daranee Tantbirojn Antheunis Versluis 《Dental materials》2018,34(1):152-160
Objective
The relationship between post-gel shrinkage, total shrinkage, and cuspal flexure was examined. Cuspal flexure was measured on restored typodont teeth, which offered a standardized tooth shape for comparison of shrinkage stress effects among restorative composites.Methods
Six restorative composites were compared (Filtek LS, Venus Flowable, Tetric EvoCeram, Filtek Flowable, Esthet-X, and Filtek Supreme). Total shrinkage was determined from changes in projected surface area before and after polymerization (n = 10). Post-gel shrinkage was determined with a biaxial strain gauge that measured strain development during polymerization (n = 10). Cuspal flexure was determined using typodont maxillary second premolars with standard MOD slot preparation (n = 10). Flexure was determined by comparing the three-dimensionally scanned cuspal surfaces before and after restoration. Restoration bonding to the typodont cavity was achieved by sandblasting and adhesive application. Bond integrity was verified by measuring dye penetration. Results were analyzed using ANOVA and Student–Newman–Keuls post hoc test (significance level 0.05). Pearson was used for correlations.Results
Total and post-gel shrinkage were significant different for all composites (t-test; P < 0.001). Depending on the composite, only 9–41% of the total shrinkage was recorded as post-gel shrinkage. Bond integrity of restored typodont teeth was 96–99%. Cuspal flexure correlated strongly with post-gel shrinkage, but there was no correlation with total shrinkage.Significance
Cuspal flexure of restored typodont teeth showed the effect of shrinkage stress caused by polymerizing composite restorations, ensuring standardization while maintaining the effects of tooth/cavity geometry. Post-gel shrinkage gave a good indication to screen composites for the stress they may generate; total shrinkage had no direct correlation with stress. 相似文献15.
Objective
To modify the resin-based composite (RBC) restoration protocol for standardised Class II cavities in third molar teeth restored using conventional RBCs or their bulk fill restorative counterparts. Employing cuspal deflection using a twin channel deflection measuring gauge (during) and microleakage to determine marginal integrity (following) RBC restoration, the modified restoration protocol results were compared with traditional (oblique) restoration of Class II cavities.Methods
Thirty-two sound third molar teeth, standardised by size and morphology, were subjected to standardised Class II cavity preparations and randomly allocated to four groups. Restorations were placed in conjunction with a universal bonding system and resin restorative materials were irradiated with a light-emitting-diode light-curing-unit. The cumulative buccal and palatal cuspal movements from a twin channel deflection measuring gauge were summed, the restored teeth fatigued thermally prior to immersion in 0.2% basic fuchsin dye for 24 h, before sectioning and examination for microleakage.Results
Teeth restored using conventional RBC materials had significantly higher mean total cuspal movement values compared with bulk fill resin restorative restoration (all p < 0.0001). Teeth restored with Admira Fusion and Admira Fusion x-tra had significantly the lowest microleakage scores (all p < 0.001) compared with Tetric EvoCeram and Tetric EvoCeram Bulk Fill restored teeth. The microleakage scores for the range of RBC materials tested were significantly reduced (all p < 0.001) when the modified RBC restoration protocol was employed compared with the traditional Class II restoration technique.Significance
Modification of the RBC restoration protocol of some conventional RBCs and bulk fill resin restoratives significantly improve bond integrity and could be translated as a validation of the limited clinical studies available on bulk fill materials in the dental literature where Class II cavities perform less well than Class I cavities following extended follow-up.Clinical significance
The results of the current study add further weight to experimental protocols employing cuspal movement (during) and cervical microleakage (following) RBC restoration of standardised cavities in natural dentition to provide an indication of polymerization shrinkage stress at the tooth/RBC restoration interface in a ‘clinically meaningful context’. 相似文献16.
Keita Taguchi Keiichi Hosaka Masaomi Ikeda Ryuzo Kishikawa Richard Foxton Masatoshi Nakajima Junji Tagami 《Journal of prosthodontic research》2018,62(3):330-336
Purpose
The use of warm air-blowing to evaporate solvents of one-step self-etch adhesive systems (1-SEAs) has been reported to be a useful method. The purpose of this study was to evaluate the effect of warm air-blowing on root canal dentin.Methods
Four 1-SEAs (Clearfil Bond SE ONE, Unifil Core EM self-etch bond, Estelink, BeautiDualbond EX) were used. Each 1-SEA was applied to root canal dentin according to the manufacturers’ instructions. After the adhesives were applied, solvent was evaporated using either normal air (23 ± 1 °C) or warm air (80 ± 1 °C) for 20 s, and resin composite was placed in the post spaces. The air from the dryer, which could be used in normal- or hot-air-mode, was applied at a distance of 5 cm above the root canal cavity in the direction of tooth axis. The temperature of the stream of air from the dryer in the hot-air-mode was 80 ± 1 °C, and in the normal mode, 23 ± 1 °C. After water storage of the specimens for 24 h, the μTBS were evaluated at the coronal and apical regions. The μTBSs were statistically analyzed using three-way ANOVA and Student’s t-test with Bonferroni correction (α = 0.05).Results
The warm air-blowing significantly increased the μTBS of all 1-SEAs at the apical regions, and also significantly increased the μTBS of two adhesives (Estelink and BeautiDualBond EX) at coronal regions.Conclusions
The μTBS of 1-SEAs to root canal dentin was improved by using warm air-blowing. 相似文献17.
Simone Staffoli Taha Özyürek Avi Hadad Alex Lvovsky Michael Solomonov Hadas Azizi Joe Ben Itzhak Maurizo Bossù Nicola M. Grande Gianluca Plotino Antonella Polimeni 《Giornale Italiano di Endodonzia》2018,32(2):52-56
Aim
To evaluate the centering ability of ProTaper Next (PTN) and 2Shape (TS) nickel–titanium (NiTi) instruments in terms of maintaining the original root canal configuration in a simulated tooth with severe curvature.Methodology
Twenty standardized simulated curved root canals were prepared to an apical size of 0.25 mm using PTN and TS (n = 10 canal/group) nickel-titanium files. A gig was constructed to enable reproducible image acquisition using a photographic camera. Pre- and post-instrumented images were recorded and superimposed using a computer software. The ability of the instruments to remain centered in the canal was determined by calculating a centering ratio at three independent points of the simulated canal: coronal, middle and apical third of the curvature, using a computer software. Statistical analysis was performed using one-way analysis of variance (ANOVA) followed by independent sample t-test at 5% significance level.Results
No significant difference was found between the two systems (p > 0.05). At the apical third, the mean centering ratio was significantly higher than the centering ratio of the coronal and the middle thirds in both TS and PTN (p < 0.05).Conclusions
There were no significant differences in the centering ability of the ProTaper Next and 2Shape systems in simulated severe curved canals. Both systems exhibited some degree of transportation, especially in the apical third. 相似文献18.
Ryota Okada Masaki Asakura Akihiro Ando Hirokazu Kumano Seiji Ban Tatsushi Kawai Jun Takebe 《Journal of prosthodontic research》2018,62(3):287-292
Purpose
The purpose of this study was to ascertain whether computer aided design/computer aided manufacturing (CAD/CAM) composite resin crowns have sufficient strength to withstand the bite force of the molar teeth. The null hypothesis was that the fracture strength of CAD/CAM composite resin crowns is lower than the average maximum bite force of the molar tooth.Methods
The crowns, which shape is the right maxillary first molar, were fabricated using four CAD/CAM blanks made of composite resins (Block HC: HC, KZR-CAD HR: HR, KZR-CAD HR2: HR2, Avencia Block: AVE) and one CAD/CAM blank made of lithium disilicate glass-ceramic (IPS e.max CAD: IPS), which was used as a control. Fracture strength of fabricated crowns bonded to metal abutment and biaxial flexural strength of the materials were evaluated.Results
The results of fracture strength test and biaxial flexural strength test showed different tendencies. The fracture strength of CAD/CAM composite resin crowns except HC ranged from 3.3 kN to 3.9 kN, and was similar to that of IPS (3.3 kN). In contrast, biaxial flexural strength of CAD/CAM composite resins ranged from 175 MPa to 247 MPa, and was significantly lower than that of IPS (360 MPa).Conclusions
All CAD/CAM composite resin crowns studied presented about 3–4 times higher fracture strength than the average maximum bite force of the molar tooth (700–900 N), which result leads to the conclusion that CAD/CAM composite resin crowns would have sufficient strength to withstand the bite force of the molar teeth. 相似文献19.
Luciano Praça Fabrice Chuembou Pekam Rodrigo Otavio Rego Klaus Radermacher Stefan Wolfart Juliana Marotti 《Dental materials》2018,34(11):e280-e288
Objective
This in vitro study aimed to evaluate marginal and internal fit of single crowns produced from high-frequency ultrasound based digital impressions of teeth prepared with finish lines covered by porcine gingiva, in comparison with those obtained by optical scanners with uncovered finish lines.Methods
Ten human teeth were prepared and forty zirconia crowns were fabricated from STL-datasets obtained from four dental scanners (n = 10): extraoral CS2 (Straumann), intraoral Lava COS (3M), intraoral Trios (3Shape) and extraoral ultrasound scanner. The accuracy of the crowns was compared evaluating marginal and internal fit by means of the replica technique with measurements in four areas; P1: occlusal surface; P2: transition between occlusal and axial surfaces; P3: middle of axial wall; and P4: marginal gap. Restoration margins were classified according to their mismatch as regular, underextended or overextended. Kruskal–Wallis one-way ANOVA and Mann–Whitney U test were used to evaluate the differences between groups at p < 0.05.Results
The median value of marginal gap (P4) for Ultrasound (113.87 μm) differed statistically from that of CS2 (39.74 μm), Lava COS (41.98 μm) and Trios (42.07 μm). There were no statistical differences between ultrasound and Lava COS for internal misfit (P1–P3), however there were statistical differences when compared with the other two scanners (Trios and CS2) at P1 and P2.Significance
The ultrasound scanner was able to make digital impressions of prepared teeth through porcine gingiva (P4), however with less accuracy of fit than that of conventional optical scanners without coverage of the finish lines. Where no gingiva was available (P1–P3), the ultrasound accuracy of fit was similar to that of at least one optical scanner (Lava COS). 相似文献20.
Taichi Iwashita Atsushi Mine Mariko Matsumoto Hayaki Nakatani Mami Higashi Asuka Kawaguchi-Uemura Tomoshige Kabetani Yuko Tajiri Dai Imai Ryosuke Hagino Jiro Miura Takuya Minamino Hirofumi Yatani 《Journal of prosthodontic research》2018,62(4):449-455