Use of mini dental implants in ectodermal dysplasia children: follow-up of three cases.

BACKGROUND: Ectodermal dysplasia is a hereditary genodermatosis characterised by a congenital defect of ectodermal structures, causing tooth malformations and anomalies. Implantology has become accepted in these subjects. However cases are often complicated by a reduction in the size of the alveolar process, making the insertion of conventional implants difficult without bone grafting. The reduced diameter of mini-implants and their ease of insertion provide an interesting solution in supporting removable or fixed prosthesis. The purpose of this paper is to report the follow-up of three cases of children (11-12 year- old) with ectodermal dysplasia in which mini-implants were used to support the prostheses. CASE REPORTS: In the first case, two mini-implants were inserted into the anterior part of the mandible for stabilising a removable denture (2 years follow-up). In the other two cases, mini- implants were inserted in the maxilla and mandible to replace missing front teeth with fixed prostheses. Patients were called for follow- up every 6 months: in the sencod case follow-up lasted 4 years in the mandible and 2 years in the maxilla; in the third case, 2 years in the maxilla and 1 year in the mandible. CONCLUSION: The use of mini-implants in children with ectodermal dysplasia can enhance aesthetics, and functional and psychosocial development.

Shortest paths on systems with power-law distributed long-range connections.

We discuss shortest-path lengths l(r) on periodic rings of size L supplemented with an average of pL randomly located long-range links whose lengths are distributed according to P(l) approximately l(-mu). Using rescaling arguments and numerical simulation on systems of up to 10(7) sites, we show that a characteristic length xi exists such that l(r) approximately r for r>xi. For small p we find that the shortest-path length satisfies the scaling relation l(r,mu,p)/xi=f(mu,r/xi). Three regions with different asymptotic behaviors are found, respectively: (a) mu>2 where theta(s)=1, (b) 1

Directed rigidity and bootstrap percolation in 1+1 dimensions.

We study directed rigidity percolation (equivalent to directed bootstrap percolation) on three different lattices: square, triangular, and augmented triangular. The first two of these display a first-order transition at p=1, while the augmented triangular lattice shows a continuous transition at a nontrivial p(c). On the augmented triangular lattice we find, by extensive numerical simulation, that the the directed rigidity percolation transition belongs to the same universality class as the directed percolation. The same conclusion is reached by studying its surface critical behavior, i.e., the spreading of rigidity from finite clusters close to a nonrigid wall. Near the discontinuous transition at p=1 on the triangular lattice, we are able to calculate the finite-size behavior of the density of rigid sites analytically. Our results are confirmed by numerical simulation.

Spreading and shortest paths in systems with sparse long-range connections.

Spreading according to simple rules (e.g., of fire or diseases) and shortest-path distances are studied on d-dimensional systems with a small density p per site of long-range connections ("small-world" lattices). The volume V(t) covered by the spreading quantity on an infinite system is exactly calculated in all dimensions as a function of time t. From this, the average shortest-path distance l(r) can be calculated as a function of Euclidean distance r. It is found that l(r) approximately r for rr(c). The characteristic length r(c), which governs the behavior of shortest-path lengths, diverges logarithmically with L for all p>0.