Oral surgery in paediatric dentistry: type of surgical treatment and age distribution in a Public Dental Service in Northern Italy.

AIM: To describe the organisation of the oral dental surgery service of the Department of Pediatric Odontostomatology and Orthodontics, "G. Gaslini" Hospital of Genoa (Italy), as well as type and frequency of the interventions carried out in the considered period of time. MATERIALS AND METHODS: Study design: Descriptive retrospective aepidemiological study about the access and surgery interventions in the years 2015-2018 and the first semester of 2019. This study was conducted at the Department of Pediatric Odontostomatology and Orthodontics of the "G. Gaslini" Hospital of Genoa, Italy, in which treatment is offered to children and adolescents aged between 0-14 years, to whom continuity of care is ensured also after this age range, and to special needs patients, even older that 18 years. The clinical data were extracted from the Hospital database and then statistically analysed with the SPSS programme. RESULTS: Out of a total of 27,663 subjects, the patients who required oral surgery were 1,928 corresponding to 6.96%, for a total of 2,499 surgical interventions of which 1,667 were performed as outpatient surgery (dental chair) and 832 in the operating theatre. All the surgeries were performed by the same three doctors. In the group of patients under 18 years (1,773 subjects) the average age is 9.22 years; it should be underscored that over 70% of oral surgeries are performed on subjects between 7 and 13 years. CONCLUSIONS: Given the low frequency of paediatric oral surgery, this type of intervention should be entrusted to operators and structures that have a wider experience in such cases in order to ensure the highest levels ofsafety.

Size-scaling behaviour of the electronic polarizability of one-dimensional interacting systems.

Electronic polarizability of finite chains is accurately calculated from the total energy variation of the system produced by small but finite static electric fields applied along the chain direction. Normalized polarizability, that is, polarizability divided by chain length, diverges as the second power of length for metallic systems but approaches a constant value for insulating systems. This behaviour provides a very convenient way to characterize the wave-function malleability of finite systems as it avoids the need of attaching infinite contacts to the chain ends. Hubbard model calculations at half filling show that the method works for a small U = 1 interaction value that corresponds to a really small spectral gap of 0.005 (hopping t = -1 is assumed). Once successfully checked, the method has been applied to the long-range hopping model of Gebhard and Ruckenstein showing 1/r hopping decay (Gebhard and Ruckenstein 1992 Phys. Rev. Lett. 68 244; Gebhard et al 1994 Phys. Rev. B 49 10926). Metallicity for U values below the reported metal-insulator transition is obtained but the surprise comes for U values larger than the critical one (when a gap appears in the spectral density of states) because a steady increase of the normalized polarizability with size is obtained. This critical size-scaling behaviour can be understood as corresponding to a molecule which polarizability is unbounded. We have checked that a real transfer of charge from one chain end to the opposite occurs as a response to very small electric fields in spite of the existence of a large gap of the order of U for one-particle excitations. Finally, ab initio quantum chemistry calculations of realistic poly-acetylene chains prove that the occurrence of such critical behaviour in real systems is unlikely.

Can model Hamiltonians describe the electron-electron interaction in π-conjugated systems? PAH and graphene.

Model Hamiltonians have been, and still are, a valuable tool for investigating the electronic structure of systems for which mean field theories work poorly. This review will concentrate on the application of Pariser-Parr-Pople (PPP) and Hubbard Hamiltonians to investigate some relevant properties of polycyclic aromatic hydrocarbons (PAH) and graphene. When presenting these two Hamiltonians we will resort to second quantisation which, although not the way chosen in its original proposal of the former, is much clearer. We will not attempt to be comprehensive, but rather our objective will be to try to provide the reader with information on what kinds of problems they will encounter and what tools they will need to solve them. One of the key issues concerning model Hamiltonians that will be treated in detail is the choice of model parameters. Although model Hamiltonians reduce the complexity of the original Hamiltonian, they cannot be solved in most cases exactly. So, we shall first consider the Hartree-Fock approximation, still the only tool for handling large systems, besides density functional theory (DFT) approaches. We proceed by discussing to what extent one may exactly solve model Hamiltonians and the Lanczos approach. We shall describe the configuration interaction (CI) method, a common technology in quantum chemistry but one rarely used to solve model Hamiltonians. In particular, we propose a variant of the Lanczos method, inspired by CI, that has the novelty of using as the seed of the Lanczos process a mean field (Hartree-Fock) determinant (the method will be named LCI). Two questions of interest related to model Hamiltonians will be discussed: (i) when including long-range interactions, how crucial is including in the Hamiltonian the electronic charge that compensates ion charges? (ii) Is it possible to reduce a Hamiltonian incorporating Coulomb interactions (PPP) to an 'effective' Hamiltonian including only on-site interactions (Hubbard)? The performance of CI will be checked on small molecules. The electronic structure of azulene and fused azulene will be used to illustrate several aspects of the method. As regards graphene, several questions will be considered: (i) paramagnetic versus antiferromagnetic solutions, (ii) forbidden gap versus dot size, (iii) graphene nano-ribbons, and (iv) optical properties.

Non-Gaussian tails in the probability distribution function of heat exchanged during isothermal stretching of aluminum and gold nanowires.

The heat exchanged upon isothermal (0.5-200 K) stretching of aluminum and gold nanowires has been calculated by means of molecular dynamics. Atoms at fixed positions with velocities randomly distributed according to Maxwell distribution were taken as initial conditions. The results clearly reveal the presence of non-Gaussian (exponential) tails in the heat probability distribution function at low temperatures, both in gold and aluminum. As temperature is raised, tails rapidly disappear.

Clinical value of 12 occlusal features for the prediction of disc displacement with reduction (RDC/TMD Axis I group IIa).

The purpose of this study is to quantify the clinical value of 12 occlusal variables for the prediction of disc displacement with reduction diagnosed according to research diagnostic criteria (RDC)/temporomandibular disorder (TMD). Twelve occlusal features were clinically assessed by the same three operators. The sample consisted of 165 TMD patients (65 males, 100 females; mean age: 32.55 +/-11.685 years) with only disc displacement with reduction (RDC/TMD Axis I group IIa) and a control sample of 145 healthy subjects (65 males, 80 females; mean age:31.24+/-12.436 years) diagnosed with RDC/TMD Axis I group 0. A stepwise multiple logistic regression model was used to identify the significant correlation between occlusal features and disease. The odds ratio for disc displacement was 2.84 for absence of canine guidance, 2.14 for mediotrusive interference and 1.75 for retruded contact position (RCP)/maximum intercuspation (MI) slide >or=2 mm. Other occlusal variables did not reveal to be statistically significant. The percentage of the total log likelihood for disc displacement explained by the significant occlusal factors was acceptable with a Nagelkerke's R(2) = 0.124. The final model including the significant occlusal features revealed an optimal discriminant capacity to predict patients with disc displacement with a sensitivity of 63.6% or with a specificity of 64.8% for healthy subjects and an accuracy of 64.2%. Occlusal features showed a low predictive value for detecting disc displacement. Multifactorial complex pathologies such as TMD should be investigated using a multivariate statistical analysis; moreover,the future of aetiopathogenic research in this matter requires a multifactorial approach.

Quasicrystalline and rational approximant wave patterns in hydrodynamic and quantum nested wells.

The eigenfunctions of nested wells with an incommensurate boundary geometry, in both the hydrodynamic shallow water regime and quantum cases, are systematically and exhaustively studied in this Letter. The boundary arrangement of the nested wells consists of polygonal ones, square or hexagonal, with a concentric immersed, similar but rotated, well or plateau. A rich taxonomy of wave patterns, such as quasicrystalline states, their crystalline rational approximants, and some other exotic but well known tilings, is found in these mimicked experiments. To the best of our knowledge, these hydrodynamic rational approximants are presented here for the first time in a hydrodynamic-quantum framework. The corresponding statistical nature of the energy level spacing distribution reflects this taxonomy by changing the spectral types.

Kondo effect of an adsorbed cobalt phthalocyanine (CoPc) molecule: the role of quantum interference.

It has been shown that by distorting a CoPc molecule adsorbed on a Au(111) surface a Kondo effect is induced with a temperature higher than 200 K. We examine a model in which an atom with strong Coulomb repulsion (Co) is surrounded by four atoms on a square (molecule lobes), with two atoms above and below it representing the apex of the STM tip and an atom on the gold surface (all with a single atomic orbital). The Hamiltonian is solved exactly for the isolated cluster, and, after connecting the leads, the conductance is calculated by standard techniques. Quantum interference prevents the existence of the Kondo effect when the orbitals on the square do not interact (undistorted molecule); the Kondo resonance shows up after switching on that interaction. The weight of the Kondo resonance is controlled by the interplay of couplings to the STM tip and the gold surface and between the molecule lobes.

Research diagnostic criteria for temporomandibular disorders (RDC/TMD) axis I diagnoses in an Italian patient population.

The aim of this work was twofold: to evaluate the prevalence of different Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) diagnosis in an Italian population of subjects seeking TMD treatment in a tertiary clinic; and to compare data with those from similar studies in the literature. Participants in this study were 433 consecutive patients seeking TMD treatment at the Section of Prosthetic Dentistry, Department of Neuroscience, University of Pisa, Italy; mean age of patients was 38.8 years, with a female:male ratio of 2.6:1 (276 females, 73.2%; 101 males, 26.8%). RDC/TMD guidelines for examination were adopted to assign axis I diagnosis. The prevalence of RDC/TMD diagnoses was 38.2% (144/377) for group I disorders (muscle disorders), 52.3% (197/377) for group II disorders (disc displacements), and 52.6% (198/377) for group III disorders (arthralgia, osteoarthritis, osteoarthrosis). The present investigation provided findings that, compared and integrated with literature data, can be useful to create a world-wide database, in accordance with the nature of the RDC/TMD classification system.

Enhancement of persistent currents due to confinement in metallic samples.

Confinement and surface roughness (SR) effects on the magnitude of the persistent current are analyzed for ballistic bidimensional metallic samples. Depending on the particular geometry, localized border states can show up at half-filling. These border states contribute coherently to the persistent current and its magnitude is enhanced with respect to their value in the absence of confinement. A linear scaling of the typical current I(typ) with the number of conduction channels M is obtained. This result is robust with respect to changes in the relevant lengths of the samples and to the SR. Possible links of our results to experiments are also discussed.