Antonio Batista

The radiographic platform: A new method to evaluate root canal preparation in vitro

An in vitro method for evaluating root canal preparation in curved canals is presented. Based on Schneiders method, this technique makes it possible to obtain the position of the instrument before and after instrumentation in the same X-ray film. The use of the radiographic platform is a valuable research and teaching aid.

Lyapunov exponents of a lattice of chaotic maps with a power-law coupling

Abstract We consider a lattice of coupled chaotic logistic maps in which the coupling strength between sites decreases with the lattice distance in a power-law fashion, making possible to pass continuously from a local to a global coupling. The corresponding Lyapunov spectra are described by means of the maximal exponent and the average of the positive exponents, which are analyzed in terms of the coupling properties. Our results are compared with spatio-temporal patterns known for global and local couplings.

Synchronization of Coupled Kicked Limit Cycle Systems

Abstract A class of kicked nonlinear limit cycle oscillators is described by a prototype circle map. We consider a spatially extended system in which these maps are coupled in a unidimensional lattice, according to a coupling scheme that includes the global (mean-field) and local (nearest-neighbor) prescriptions as limiting cases. We analyze frequency synchronization in the system, investigating its behavior under variations of the coupling parameters.

Kolmogorov-Sinai entropy for locally coupled piecewise linear maps

We present analytical results for the Kolmogorov–Sinai entropy of a one-dimensional lattice of locally coupled piecewise linear maps, for some particular values of the coupling strength. Our results explain the numerically observed fact that the entropy of a lattice of chaotic maps increases for strong coupling.

Influence of apical patency and cleaning of the apical foramen on periapical extrusion in retreatment.

This study evaluated the influence of apical patency, root filling removal technique and cleaning of the apical foramen, concerning the amount of debris extruded during root canal retreatment. Forty mandibular incisors were randomly assigned to 4 groups - GIM (n=10), GIIM (n=10), GIPT (n=10) and GIIPT (n=10), which were named according to leaving (I) or not (II) apical patency during canal preparation and filling removal technique (manual - M or ProTaper system - PT). After filling material removal, each specimen of each group had the apical foramen cleaned by sizes 15, 20 and 25 instruments, generating 12 subgroups: GIM15, GIM20, GIM25, GIIM15, GIIM20, GIIM25, GIPT15, GIPT20, GIPT25, GIIPT15, GIIPT20 and GIIPT25. Extruded filling debris was collected by a Milipore filtration system, an HV-durapore, 0.45 µm pore filter with a 25 mm diameter. The filters were weighed before and after the collection on an analytical scale (10-5 g), and the difference was calculated. The mean weight of extruded filling debris was analyzed statistically by Kruskal-Wallis and Friedman ANOVA tests (α=0.05). The mean values found in the groups (in mg) were: GIM (0.95 ± 0.94), GIIM (0.47 ± 0.62), GIPT (0.30 ± 0.31) and GIIPT (0.32 ± 0.44). There was no statistically significant difference among any of the groups or subgroups (p>0.05). ProTaper provided the smallest amount of extruded filling material, regardless of presence or absence of apical patency, followed by manual technique, without and with apical patency. Additional amounts of debris were collected during cleaning of the apical foramen, regardless of the instrument, presence/absence of patency or root filling removal technique.