Heat Release, Time Required, and Cleaning Ability of Mtwo R and ProTaper Universal Retreatment Systems in the Removal of Filling Material

Introduction: This ex vivo study evaluated the heat release, time required, and cleaning efficacy of MTwo (VDW, Munich, Germany) and ProTaper Universal Retreatment systems (Dentsply/Maillefer, Ballaigues, Switzerland) and hand instrumentation in the removal of filling material. Methods: Sixty single-rooted human teeth with a single straight canal were obturated with gutta-percha and zinc oxide and eugenol-based cement and randomly allocated to 3 groups (n = 20). After 30-day storage at 37 degrees C and 100% humidity, the root fillings were removed using ProTaper UR, MTwo R, or hand files. Heat release, time required, and cleaning efficacy data were analyzed statistically (analysis of variance and the Tukey test, alpha = 0.05). Results: None of the techniques removed the root fillings completely. Filling material removal with ProTaper UR was faster but caused more heat release. Mtwo R produced less heat release than the other techniques but was the least efficient in removing gutta-percha/sealer. Conclusions: ProTaper UR and MTwo R caused the greatest and lowest temperature increase on root surface, respectively; regardless of the type of instrument, more heat was released in the cervical third. Pro Taper UR needed less time to remove fillings than MTwo R. All techniques left filling debris in the root canals. (I Endod 2010;36:1870-1873)

Short-term in situ/ex vivo study of the anticariogenic potential of a resin-modified glass-ionomer cement associated with adhesive systems

Objective: As resin-modified glass-ionomer cement (RMGIC) is an adhesive material, its association to dentin bonding agents (DBAs) was previously proposed. This study investigated the adjunctive behavior of an RMGIC with etch-and-rinse bonding systems under in situ/ex vivo cariogenic challenge. Method and Materials: Bovine enamel blocks (3 3 2 mm) were randomly assigned to group VP, Vitremer + its own primer (3M ESPE); group VSB, Vitremer + Single Bond (3M ESPE); and group VPB, Vitremer + Prime & Bond 2.1 (Dentsply). Two blocks of each group were randomly placed in an acrylic palatal appliance, so each appliance included six blocks. Volunteers (n = 10) wore these appliances according to given instructions to promote a sucrose challenge eight times/day for 15 days. After this period, the blocks were removed from the devices and cleaned, and demineralization was assessed through longitudinal microhardness analysis (Knoop indenter, 25 g/5 s). Data were submitted to three-way ANOVA and Tukey test (P < .05). Results: No treatment was able to completely avoid demineralization. All materials showed a statistically significant difference in mineral loss when the microhardness on the outer enamel was compared with deeper regions (P < .05). Conclusion: Association of the tested RMGICs with etch-and-rinse DBAs did not seem to be more beneficial against caries than the conventional treatment with RMGIC. (Quintessence Int 2010; 41: e192-e199)

Root Canal Area Increase Promoted by the EndoSequence and ProTaper Systems: Comparison by Computed Tomography

Introduction: The aim of this study was to compare the increase of the root canal area after instrumentation with EndoSequence or ProTaper rotary systems. Methods: Twenty-two mesial root canals from mandibular molars were instrumented. Teeth were mounted on a base, numbered, and divided into 2 groups; teeth from 1-11 (PT group) were instrumented by using the ProTaper system, and teeth from 12-22 (ES group) were instrumented by using the EndoSequence system. Cone beam computed tomography was performed on all teeth before and after instrumentation. Measurements at 3,5, and 7 mm as well as differences in instrument performance were statistically compared by the Student t test at 5% significance level. Results: Both systems increased significantly the root canal area (P < .05) at all levels. Comparison between the rotary systems showed significantly greater increase (P < .05) for EndoSequence at 3 mm, with no statistically significant difference (P < .05) at the other levels. Conclusions: Both rotary systems increased significantly the root canal area. (J Endod 2010;36:1179-1182)

Enamel Wetness Effects on Bond Strength Using Different Adhesive Systems

Objective: To evaluate, through the application of different dentin bonding systems, the influence of wetness on shear bond strength in enamel. Methods: This study evaluated three etch-and-rinse adhesive systems (Scotchbond MP [used with and without primer]; Singlebond; and Prime&Bond 2.1) and two self-etching adhesive systems (Clearfil SE Bond; and Xeno IV). Flat bovine enamel surfaces were either air-dried for 30 seconds or blotted with absorbent paper after acid-etching for the conventional bonding agents or before the application of self-etching bonding agents. The resin composite EsthetX was bonded to flat surfaces that had been treated with one of the adhesives, following the manufacturer`s instructions. After being stored in water at 37 degrees C for one week, bonded specimens were broken in shear. Data were evaluated with two-way analysis of variance (ANOVA) and Student-Newman-Keuls tests (alpha=0.05). For comparing each condition individually, regardless of the adhesive or wetness condition, a one-way ANOVA and a Student-Newman-Keuls test (alpha=0.05) were applied. Results: The two-way ANOVA showed significant differences among adhesive systems. An interaction effect was also observed (p < 0.05), but wetness did not influence shear bond strength (p=0.98). The one-way ANOVA showed that the all-in-one adhesive was the only material influenced by the presence of water at the enamel`s surface. Conclusion: The all-in-one adhesive behaved differently depending on whether the enamel surface was dry or wet.

Evaluation of proximal caries in images resulting from different modes of radiographic digitalization

Objective: The aim of this study was to evaluate the performances of observers in diagnosing proximal caries in digital images obtained from digital bitewing radiographs using two scanners and four digital cameras in Joint Photographic Experts Group (JPEG) and tagged image file format (TIFF) files, and comparing them with the original conventional radiographs. Method: In total, 56 extracted teeth were radiographed with Kodak Insight film (Eastman Kodak, Rochester, NY) in a Kaycor Yoshida X-ray device (Kaycor X-707;Yoshida Dental Manufacturing Co., Tokyo, Japan) operating at 70 kV and 7 mA with an exposure time of 0.40 s. The radiographs were obtained and scanned by CanonScan D646U (Canon USA Inc., Newport News, VA) and Genius ColorPage HR7X (KYE Systems Corp. America, Doral, FL) scanners, and by Canon Powershot G2 (Canon USA Inc.), Canon RebelXT (Canon USA Inc.), Nikon Coolpix 8700 (Nikon Inc., Melville, NY), and Nikon D70s (Nikon Inc.) digital cameras in JPEG and TIFF formats. Three observers evaluated the images. The teeth were then observed under the microscope in polarized light for the verification of the presence and depth of the carious lesions. Results: The probability of no diagnosis ranged from 1.34% (Insight film) to 52.83% (CanonScan/JPEG). The sensitivity ranged from 0.24 (Canon RebelXT/JPEG) to 0.53 (Insight film), the specificity ranged from 0.93 (Nikon Coolpix/JPEG, Canon Powershot/TIFF, Canon RebelXT/JPEG and TIFF) to 0.97 (CanonScan/TIFF and JPEG) and the accuracy ranged from 0.82 (Canon RebelXT/JPEG) to 0.91 (CanonScan/JPEG). Conclusion: The carious lesion diagnosis did not change in either of the file formats (JPEG and TIFF) in which the images were saved for any of the equipment used. Only the CanonScan scanner did not have adequate performance in radiography digitalization for caries diagnosis and it is not recommended for this purpose. Dentomaxillofacial Radiology (2011) 40, 338-343. doi: 10.1259/dmfr/67185962

The mu-way intersection problem for m-cycle systems

An m-cycle system of order upsilon is a partition of the edge-set of a complete graph of order upsilon into m-cycles. The mu -way intersection problem for m-cycle systems involves taking mu systems, based on the same vertex set, and determining the possible number of cycles which can be common to all mu systems. General results for arbitrary m are obtained, and detailed intersection values for (mu, m) = (3, 4), (4, 5),(4, 6), (4, 7), (8, 8), (8, 9). (For the case (mu, m)= (2, m), see Billington (J. Combin. Des. 1 (1993) 435); for the case (Cc,m)=(3,3), see Milici and Quattrochi (Ars Combin. A 24 (1987) 175. (C) 2001 Elsevier Science B.V. All rights reserved.

The metamorphosis of lambda-fold 4-wheel systems into lambda-fold 4-cycle systems

A 4-wheel is a simple graph on 5 vertices with 8 edges, formed by taking a 4-cycle and joining a fifth vertex (the centre of the 4-wheel) to each of the other four vertices. A lambda -fold 4-wheel system of order n is an edge-disjoint decomposition of the complete multigraph lambdaK(n) into 4-wheels. Here, with five isolated possible exceptions when lambda = 2, we give necessary and sufficient conditions for a lambda -fold 4-wheel system of order n to be transformed into a lambda -fold Ccyde system of order n by removing the centre vertex from each 4-wheel, and its four adjacent edges (retaining the 4-cycle wheel rim), and reassembling these edges adjacent to wheel centres into 4-cycles.

Anisotropy-based performance analysis of linear discrete time invariant control systems

The anisotropic norm of a linear discrete-time-invariant system measures system output sensitivity to stationary Gaussian input disturbances of bounded mean anisotropy. Mean anisotropy characterizes the degree of predictability (or colouredness) and spatial non-roundness of the noise. The anisotropic norm falls between the H-2 and H-infinity norms and accommodates their loss of performance when the probability structure of input disturbances is not exactly known. This paper develops a method for numerical computation of the anisotropic norm which involves linked Riccati and Lyapunov equations and an associated special type equation.

On single laws for varieties of quasigroups associated with extended cycle systems

It has been previously shown by Lindner and Rodger that quasigroups associated with 2-perfect extended m-cycle systems can be equationally defined if and only if m is an element of {3, 5, 7}. In this paper we present a single identity for each such m which is equivalent to the identities given for these varieties.

Robust parameter settings of evolutionary algorithms for the optimisation of agricultural systems models

Numerical optimisation methods are being more commonly applied to agricultural systems models, to identify the most profitable management strategies. The available optimisation algorithms are reviewed and compared, with literature and our studies identifying evolutionary algorithms (including genetic algorithms) as superior in this regard to simulated annealing, tabu search, hill-climbing, and direct-search methods. Results of a complex beef property optimisation, using a real-value genetic algorithm, are presented. The relative contributions of the range of operational options and parameters of this method are discussed, and general recommendations listed to assist practitioners applying evolutionary algorithms to the solution of agricultural systems. (C) 2001 Elsevier Science Ltd. All rights reserved.

Quantum nonlinear dynamics of continuously measured systems

Classical dynamics is formulated as a Hamiltonian flow in phase space, while quantum mechanics is formulated as unitary dynamics in Hilbert space. These different formulations have made it difficult to directly compare quantum and classical nonlinear dynamics. Previous solutions have focused on computing quantities associated with a statistical ensemble such as variance or entropy. However a more diner comparison would compare classical predictions to the quantum predictions for continuous simultaneous measurement of position and momentum of a single system, in this paper we give a theory of such measurement and show that chaotic behavior in classical systems fan be reproduced by continuously measured quantum systems.

Fatigue life and failure modes of crowns systems with a modified framework design

Objectives: To evaluate the effect of framework design on the fatigue life and failure modes of metal ceramic (MC, Ni-Cr alloy core, VMK 95 porcelain veneer), glass-infiltrated alumina (ICA, In-Ceram Alumina/VM7), and veneered yttria-stabilized tetragonal zirconia polycrystals (Y-TZP, IPSe.max ZirCAD/IPS e.max,) crowns. Methods: Sixty composite resin tooth replicas of a prepared maxillary first molar were produced to receive crowns systems of a standard (MCs, ICAs, and Y-TZPs, n = 10 each) or a modified framework design (MCm, ICAm, and Y-TZPm, n = 10 each). Fatigue loading was delivered with a spherical steel indenter (3.18 mm radius) on the center of the occlusal surface using r-ratio fatigue (30-300 N) until completion of 10(6) cycles or failure. Fatigue was interrupted every 125,000 cycles for damage evaluation. Weibull distribution fits and contour plots were used for examining differences between groups. Failure mode was evaluated by light polarized and SEM microscopy. Results: Weibull analysis showed the highest fatigue life for MC crowns regardless of framework design. No significant difference (confidence bound overlaps) was observed between ICA and Y-TZP with or without framework design modification. Y-TZPm crowns presented fatigue life in the range of MC crowns. No porcelain veneer fracture was observed in the MC groups, whereas ICAs presented bulk fracture and ICAm failed mainly through the veneer. Y-TZP crowns failed through chipping within the veneer, without core fractures. Conclusions: Framework design modification did not improve the fatigue life of the crown systems investigated. Y-TZPm crowns showed comparable fatigue life to MC groups. Failure mode varied according to crown system. (C) 2010 Elsevier Ltd. All rights reserved.

Image quality assessment and medical physics evaluation of different portable dental X-ray units

Introduction: Recently developed portable dental X-ray units increase the mobility of the forensic odontologists and allow more efficient X-ray work in a disaster field, especially when used in combination with digital sensors. This type of machines might also have potential for application in remote areas, military and humanitarian missions, dental care of patients with mobility limitation, as well as imaging in operating rooms. Objective: To evaluate radiographic image quality acquired by three portable X-ray devices in combination with four image receptors and to evaluate their medical physics parameters. Materials and methods: Images of five samples consisting of four teeth and one formalin-fixed mandible were acquired by one conventional wall-mounted X-ray unit, MinRay (R) 60/70 kVp, used as a clinical standard, and three portable dental X-ray devices: AnyRay (R) 60 kVp, Nomad (R) 60 kVp and Rextar (R) 70 kVp, in combination with a phosphor image plate (PSP), a CCD, or a CMOS sensor. Three observers evaluated images for standard image quality besides forensic diagnostic quality on a 4-point rating scale. Furthermore, all machines underwent tests for occupational as well as patient dosimetry. Results: Statistical analysis showed good quality imaging for all system, with the combination of Nomad (R) and PSP yielding the best score. A significant difference in image quality between the combination of the four X-ray devices and four sensors was established (p < 0.05). For patient safety, the exposure rate was determined and exit dose rates for MinRay (R) at 60 kVp, MinRay (R) at 70 kVp, AnyRay (R), Nomad (R) and Rextar (R) were 3.4 mGy/s, 4.5 mGy/s, 13.5 mGy/s, 3.8 mGy/s and 2.6 mGy/s respectively. The kVp of the AnyRay (R) system was the most stable, with a ripple of 3.7%. Short-term variations in the tube output of all the devices were less than 10%. AnyRay (R) presented higher estimated effective dose than other machines. Occupational dosimetry showed doses at the operator`s hand being lowest with protective shielding (Nomad (R): 0.1 mu Gy). It was also low while using remote control (distance > 1 m: Rextar (R) < 0.2 mu Gy, MinRay (R) < 0.1 mu Gy). Conclusions: The present study demonstrated the feasibility of three portable X-ray systems to be used for specific indications, based on acceptable image quality and sufficient accuracy of the machines and following the standard guidelines for radiation hygiene. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

On the Hopf bifurcation in control systems with a bounded nonlinearity asymptotically homogeneous at infinity

The paper studies existence, uniqueness, and stability of large-amplitude periodic cycles arising in Hopf bifurcation at infinity of autonomous control systems with bounded nonlinear feedback. We consider systems with functional nonlinearities of Landesman-Lazer type and a class of systems with hysteresis nonlinearities. The method is based on the technique of parameter functionalization and methods of monotone concave and convex operators. (C) 2001 Academic Press.