Ultrastructural changes in cultured human periodontal ligament cells exposed to dental materials

Apoptosis: an introduction for the endodontist

Apoptosis plays an important role in many aspects of endodontics, yet there is a paucity of information in this regard in the endodontic literature. Apoptosis is a single deletion of scattered cells by fragmentation into membrane-bound particles that are phagocytosed by other cells. It is a key process in the embryological development of the tooth, periodontal ligament and supporting oral tissue in the progression of oral disease, bone resorption, immunological response and inflammation, and in wound healing and certain pharmacological effects. The understanding of the ability of clinical materials to induce or inhibit apoptosis and the investigation of apoptosis as it relates to the pathogenesis of pulpal and periradicular pathology may eventually lead to new treatment approaches for the endodontist. The purpose of this review is to familiarize the clinical endodontist with current knowledge on apoptosis as it relates to the pulp and periradicular tissues.

Adhesion between poly(ethylene-co-vinyl alcohol) (EVA) and titanium

Lap shear adhesive strength between titanium and various kinds of commercial polymers was evaluated. Among them, poly(ethylene-co-vinyl alcohol) (EVA) showed the highest strength. The results of electron spectroscopy for chemical analysis and the contact angle to water indicated that the high adhesive strength of EVA might be due to its high hydrophilicity. Water resistance of adhesion by water immersing at 37 degrees C was investigated. In the case of polyurethane-titanium, the adhesive strength decreased immediately. In contrast, EVA-titanium kept its initial adhesive strength for at least up to 1 month. It was confirmed that surface modification of titanium by hydrogen peroxide enhanced the adhesive and peeling strength. It was based on not only an increase in surface adhesive area but also an increase in the hydrophilicity of titanium by the production of Ti-OH.

Cellulose phosphates as biomaterials. In vivo biocompatibility studies

Femoral implantation of regenerated cellulose hydrogels revealed their biocompatibility, but a complete osseointegration could not be observed. Phosphorylation was therefore envisaged as the means to enhance cellulose bioactivity. In vitro studies showed that regenerated cellulose hydrogels promote bone cells attachment and proliferation but do not mineralize in acellular simulated physiological conditions. On the contrary, phosphorylated cellulose has shown an opposite behavior, by inducing the formation of a calcium phosphate layer in simulated physiological conditions, but behaving as a poor substrate for bone cells attachment and proliferation. In order to investigate the in vivo behavior of these materials, and assess the influence of mineralization induction ability vs. bone cells compatibility, unmodified and phosphorylated cellulose hydrogels were implanted in rabbits for a maximum period of 6 months and bone regeneration was investigated. Despite the difficulties arising from the retraction of cellulose hydrogels upon dehydration during the preparation of retrieved implants, histological observations showed no inflammatory response after implantation, with bone intra-spongious regeneration of cells and the integration of the unmodified as well as the phosphorylated cellulose implants. After a maximum implantation period of 6 months, histological observations, histomorphometry and the measurement of the amount of 45Ca incorporated in the surrounding tissue indicated a slightly better osseointegration of phosphorylated cellulose, although no significant differences between the two materials were found.

The effect of endodontic materials on periodontal ligament cell proliferation, alkaline phosphatase activity, and extracellular matrix protein synthesis in vitro

Recent studies have demonstrated that periodontal ligament-derived (PDL) cells have the potential to regenerate a complete periodontal connective tissue attachment apparatus on both root and artificial substrates. To study the characteristics of endodontic materials conducive to periodontal regeneration, we have established an experimental model using PDL cell cultures that express a 42 kDa protein (CP42) associated with cementum extracellular matrix. In this report, the effect of gutta percha, dental amalgam, composite and calcium hydroxide on PDL cell proliferation, collagen and noncollagen protein synthesis, alkaline phosphatase activity, and CP42 expression are presented. While all substrates supported PDL cell attachment and proliferation, highest levels of alkaline phosphatase activity, collagen and noncollagen protein synthesis were observed in control cultures. Lowest levels of the above parameters were observed with gutta percha while amalgam, composite and calcium hydroxide had intermediate levels. Only control PDL cultures demonstrated CP42 expression. These data suggest that culture substrate can markedly influence periodontal extracellular matrix gene expression in vitro and provide an experimental model to select and develop endodontic materials compatible with periodontal regeneration in vivo.

Review of dental materials citations: Part B, July to December 1995

OBJECTIVE

A lag of many months occurs between journal issue publication and updates to electronic databases. The objective of this literature analysis was to identify and categorize all of the dental materials citations in biomedical journals that were published from July 1995 through December 1995.

METHODS

Seventeen primary and 51 secondary journals were searched using their tables of contents to detect and record dental materials publications from July to December of 1995. Those journals that were typically rich in dental materials articles were classified as primary ones. Citations were categorized into 17 topics and divided into subsections. The review excluded case reports, most literature related primarily to dental implants, and most articles on biomedical materials used outside of the field of general dentistry.

RESULTS

The greatest number of citations was related to topics of dentin bonding and resin-based restorative filling materials (composites and glass ionomers). There was no major change in the number of dental materials publications per year reported from 1993 (n = 786) to 1995 (n = 751).

SIGNIFICANCE

This citation list provides a comprehensive resource for use by academicians and researchers to bridge the gap between initial publication and access to electronic searching methods for major databases.