Mário Sérgio Soares

Nonlinear normal modes of planar frames discretised by the finite element method

Abstract This article describes the implementation of a computer program to calculate nonlinear normal modes of structural systems. The procedure follows the invariant manifold approach, adapted to handle equations of motion of systems discretised by finite element techniques. In its current version, it generates individual modes of planar framed structures exhibiting geometrically nonlinear behaviour. The program was tested in simple examples available in the literature, and showed very good results. Because finite element discretisations are not restrictive to the geometry of the structural system, it was also possible to generate, for the first time, nonlinear modes of framed structures.

Clinical and surgical evaluation of the indication of postoperative antibiotic prescription in third molar surgery.

OBJECTIVE The aim of this study was to evaluate the need for antibiotic prescription in third molar surgery. STUDY DESIGN A double-blind randomized study was carried out with 71 patients from CODONT (Dentistry Center of the Police of São Paulo). Amoxicillin, clindamycin, or no medication was administered for 7 days immediately after surgery. The participants evaluated the presence of pain, edema, interincisal distance (ID), presence of infection, Pell and Gregory classification, rescue analgesia, osteotomy, and odontosection. RESULTS There was no difference (P < .05) between antibiotics and control over the surgery duration, dose, visual analog scale (VAS), ID, and edema, yet significant differences were seen over time for VAS, edema, and ID. CONCLUSIONS Antibiotic prescription should not be indicated in all clinical conditions, yet it is necessary to correctly evaluate factors such as systemic condition of the patient, skill of the operator, and contamination of the surgical environment.

Comparison of the fracture torque of different Brazilian mini-implants

This study evaluated fracture torque by torsion, in relation to the length and diameter of orthodontic mini-implants, to demonstrate their viability for clinical and experimental use based on the torque recommended by the manufacturers. The fractures at the moment of insertion, whose incidence in the literature is around 4%, are principally due to excessive force and the inability of the implant to resist rotational forces. Thirty orthodontic mini-implants of three commercial brands available in Brazil (Neodent 1.6 x 9 mm, Dentoflex 1.6 x 9 mm and Kopp 1.6 x 9 mm) were attached to a device made specifically for this research, leaving the mini-implants with sufficient stability. The miniimplants were submitted to torsion torque, using a digital torque wrench, until their breaking point. The values obtained with the test were submitted to analysis of variance and the Tukey test. The mean values of mini-implant ruptures were 26 N.cm for group A (Dentoflex), 25.4 N. cm for group B (Kopp) and 32.8 N.cm for group C (Neodent). From the Tukey test we could observe that the relationships between the means of the Dentoflex and Neodent groups, and between the Kopp and Neodent groups, were significant. Between the Dentoflex and Kopp groups, significance was nonexistent. All the values found in our research for fracture torque were higher than the limits recommended by the manufacturers for clinical use in orthodontics. The highest values were found in the Neodent group.

Reduction of finite-element models of planar frames using non-linear normal modes

Abstract This paper is an extended version of Mazzilli et al. (Mazzilli, C.E.N., Soares, M.E.S., Baracho Neto, O.G.P., 1999. Proceedings of the American Congress of Applied Mechanics, PACAM VI, vol. 8, pp. 1589–1592, Rio de Janeiro, Brazil) which presents a powerful reduction technique in non-linear dynamics based on the combination of finite element procedures with a “non-linear” Galerkin method (Zemann, J., Steindl, A., 1996. Proceedings of the 19th International Congress of Theoretical and Applied Mechanics, Kyoto, Japan) and non-linear normal modes (Shaw, S.W., Pierre, C., 1993. Journal of Sound and Vibration 164 (1), 85–124). Its implementation, in the form of a symbolic computation code, was carried out for planar framed structures under assumptions of linear elasticity and geometrical non-linearity, according to the Bernoulli–Euler rod theory (Brasil, R.M.L.R.F., Mazzilli, C.E.N., 1993. Applied Mechanics Reviews 46 (11), S110–S117). To obtain the desired drastic reduction of degrees of freedom and the corresponding set of differential equations of motion in explicit form, it is necessary to supply as input data the displacement components of the pre-selected non-linear normal modes. Validation tests for non-linear free-vibration problems are shown, considering reduced models of higher hierarchy and their ability to supply accurate regenerated non-linear normal modes. For non-linear forced vibration problems, a brief outlook of what is intended to be done is presented.

A study of effectiveness of midazolam sedation for prevention of myocardial arrhythmias in endosseous implant placement

PURPOSE The study aimed to assess electrocardiographic alterations during oral implant placement surgeries under local anesthesia (lidocaine chlorhydrate with epinephrine), using 15 mg of midazolam as an anxiolytic premedication. MATERIAL AND METHODS The study randomly selected 20 patients, aged 21-50 years old, requiring bilateral mandibular dental implants. Each patient was assessed using placebo on one side and midazolam on the contralateral side, with random, double-blinded distribution. The electrocardiogram recorded 12 static leads every 2 min, while D2 derivations were recorded continuously. RESULTS No statistically significant differences were observed between the placebo and midazolam when analyzing the morphological behavior of the electrocardiographic wave and the presence of arrhythmias during the experiment. However, under sedation, assessment of the behavior of electrocardiographic parameters during different stages of the procedure revealed statistically significant differences (P<0.05) for heart rate, P-wave amplitude and duration of the RR and QTc intervals. The arrhythmias detected were considered low risk for patients without systemic alterations and were observed in 53.3% of patients. The most frequently occurring alterations were tachycardia, bradycardia, supraventricular and ventricular extrasystoles and blocked atrial extrasystole, which were similar for both placebo and midazolam, with the greatest incidence during the initial, incision and bone drilling stages. CONCLUSION The use of 15 mg of midazolam made no difference compared with the placebo. The use of 15 mg of midazolam did not show an advantage in the incidence of arrhythmias The anxiolytic premedication does not prevent myocardial arrhythmias in endosseous implant placement. The clinical significance of the arrhythmias may not represent serious risks.

Histological and Radiological Analyses of a Maxillary Sinus Lift with Extensive Drilling of the Schneider Membrane Using Xenogeneic Bone

The objective of this study is to report a clinical case of maxillary sinus with lyophilized, xenogeneic graft, in which, despite a large perforation of the sinus membrane, the surgery was not aborted and the results of histological examinations indicate bone neoformation in the surgical area. Results. This case showed that the biomaterials evaluated in this study and the procedure used to place them proved to be biocompatible and presented high osteogenic potential, leading to a successful surgery and osseointegration implant. Conclusion. Positioning Schneiders membrane and filling it with the graft biomaterial helped to achieve the desired osteoconduction and proliferation of bone cells even though the patient had a large perforation of the sinus membrane.

Simplifying the implant treatment plan for an elderly patient.

I n the search for a better lifestyle and increased life expectancy, more and more elderly are seeking dental treatment. However, many of these patients present systemic compromise that could affect the success and maintenance of the proposed therapy. In such cases, simple proposals, such as partial removable prostheses (PRPs), must be used. PRPs are widely used, especially when conditions for rehabilitation with a fixed prosthesis attached to implants are not favorable. In one study, 10 patients were rehabilitated with inferior PRPs supported by implants in the posterior region; results show increased satisfaction in all patients, minimal wear of the component, absence of excessive bone loss, and periodontal health after 1 year of rehabilitation. Literature describing the combination of PPRs and implants is scarce and is based mainly on clinical reports of posterior implants for distal extension with PRPs. In this case, rehabilitation with fixed prostheses and implants was proposed to the patient, who required surgically guided bone regeneration through subantral graft or PRPs, but the patient declined both proposals. Following this, rehabilitation with implants in conjunction with PRP was planned and proposed to avoid subjecting the patient to sinus lifting surgery and to preserve the remaining tooth and the residual ridge; however, the team explained that greater load would be generated on these if they received only PRPs.