Bone growth factors in maxillofacial skeletal reconstruction

The development of guided bone regeneration (GBR) has substantially influenced the possibilities for using implants. The use of bone augmentation procedures has extended the use of endosseous implants to jaw bone areas with insufficient bone volume. Lack of bone volume may be due to congenital, post-traumatic, or post-surgical defects or the result of disease processes. The recently achieved predictability and success of this procedure can change the treatment of a compromised patient into a nearly normal challenge. Based on pioneer experiments investigating healing of periodontal tissues following surgical therapy, a principle of tissue healing was discovered by Nyman & Karring in the early 1980’s (60, 62, 87, 88). It was found that cells which have access to and migrate into a given wound space determine the type of tissue regenerating in that space. Both the exclusion of undesired cells from the wound area and the formation of a wound space into which desired cells are allowed to migrate were initially achieved by the placement of barrier membranes (61). The present understanding of the mechanisms leading to regeneration of desired tissues is still in accordance with these initial concepts. The aim of the present chapter was to review the techniques and membrane materials applied for GBR in conjunction with implant based oral rehabilitation.

Bone augmentation by means of barrier membranes.

The goal of periodontal therapy is to protect and maintain the patient's natural dentition for his or her lifetime. More specifically, after periodontal regenerative surgery, the aim is to achieve complete wound healing and regeneration of the periodontal unit. A recent innovation in dentistry is the preparation and use of platelet-rich plasma (PRP), a concentrated suspension of the growth factors found in platelets. These growth factors are involved in wound healing and are postulated as promoters of tissue regeneration. This clinical update outlines the specific effects of these growth factors, both in vitro and in vivo, on periodontal wound healing. The review focuses on current animal and human trials using PRP to promote tissue regeneration and alveolar bone repair. The article goes on to describe the clinical benefits of PRP and the step-by-step preparation of PRP in the dental office.

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Platelet-rich Plasma: A Promising Innovation in Dentistry

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Pile Foundation Analysis And Design

SynOptics Communications Inc.

Optimal pile arrangement for minimizing differential settlements in piled raft foundations

Geologic site conditions and site coefficients for estimating earthquake ground motions in the inland areas of Korea

This paper presents an optimal pile placement scheme to minimize the differential settlements of piled raft systems. A raft is modelled as a plate based on the Mindlin theory, and soils and piles are modelled as the Winkler springs and single springs, respectively. Interactions between piles are neglected. The pile spring constant is obtained by the method proposed by Randolph and Wroth, and the frmula is adopted to obtain the Winkler spring constant. The raft is discretized by isoparameteric finite element. The object function for the optimization is derived from the area of the deflected surface of a raft, and the locations of piles are selected as design variables. Inequality constraints are imposed to keep all piles completely inside of the raft. The recursive quadratic programming is adopted to minimize the nonlinear object function with respect to the design variables. The direct differentiation method is used to obtain the sensitivity of displacement. The validity and effectiveness of the proposed method are demonstrated by three numerical examples.

Optimal Pile Placement for Minimizing Differential Settlements in Piled Raft Foundations

The interactions among closely located piles and a cap in a pile group are complex. The current design practice for vertically loaded pile groups roughly estimates their overall behavior and generally yields conservative estimations of the group capacity. For a proper pile group design, factors such as the interaction among piles, the interaction between cap and piles, and the influence of pile installation method all need to be considered. This paper presents the results of the model test, which can be used to better understand the interactions of vertically loaded pile groups in granular soil. Load tests were carried out on the following: an isolated single pile, single-loaded center piles in groups, a footing without any piling, free standing pile groups, and piled footings. The influences of pile driving and the interactions among bearing components on loadsettlement and load transfer characteristics of piles and on the bearing behavior of a cap in a group are investigated separately by comparing the...

An experimental study of the interaction of vertically loaded pile groups in sand

The biological effects of drug-loaded biodegradable novel membrane for guided bone regeneration (GBR) was evaluated. The membranes were polyglycolic acid mesh coated with poly-L-lactic acid containing flurbiprofen, tetracycline or PDGF-BB. Porous structure was generated in the membranes by using a phase inversion method. The membrane was less toxic, nicely biodegradable and biocompatible for 8 wk after implantation in the dorsal skin of the rat. The drugs released from the membranes were shown to be effective for new bone formation. Tetracycline, flurbiprofen or PDGF-BB loaded membrane was markedly effective for osteoid tissue and new bone formation in the bony defect prepared in rat calvaria to compare with that by unloaded membrane. These results suggested that drug-loaded biodegradable barrier membrane might be a potential tool for GBR in periodontal therapy.

Choong-Ki Chung

Papers

Optimal pile arrangement for minimizing differential settlements in piled raft foundations

Geologic site conditions and site coefficients for estimating earthquake ground motions in the inland areas of Korea

Optimal Pile Placement for Minimizing Differential Settlements in Piled Raft Foundations

An experimental study of the interaction of vertically loaded pile groups in sand

Biological effects of drug-loaded biodegradable membranes for guided bone regeneration.