Scanning electron microscopy, a useful tool in forensic dental work.

In selected cases there is a need for microscopic information found on the surface of tooth specimens. Scanning electron microscopy is the method of choice. Based on the knowledge of the structural organization of the mineralized dental tissues differential diagnoses of physical and chemical changes can be made. It is suggested that the forensic dental profession cooperates in establishing a collection of reference material illustrating different traumas to enamel and dentin, deposits on teeth and the structure of restorative dental materials as they will appear after some years in position on a tooth. Four different cases are presented.

Scanning electron microscopic observations of early plaque formation in vivo on enamel specimens treated with delmopinol.

The aim of this double blind, cross-over, scanning electron microscopic (SEM) study was to compare the effect of topical application of 0.5% delmopinol HCl (aqueous solution) with placebo on early supragingival plaque formation on enamel specimens attached to a maxillary premolar. 3 subjects underwent 2x (placebo and delmopinol treatment, respectively) 7 treatment periods (1/2, 1, 2, 8, 24 hours; 3, 7 days) of undisturbed dental plaque accumulation, during which 2 ml of placebo and delmopinol HCl 0.5%, respectively, were applied topically to all teeth 2x daily. At the end of each period, the specimen was retrieved and processed for SEM. For the specimens obtained after 24 h or less, the number of visible micro-organisms was estimated. For the 3- and 7-day specimens, the area covered by plaque was calculated planimetrically. Large inter-individual differences were observed in the number of bacteria attaching during the first 24 h, with apparently no major differences between delmopinol and placebo. 1 subject showed a bacterial colonization predominated by curved rods throughout the first 8 h. Compared to placebo, the area of the specimens covered by plaque was reduced after 3 and 7 days of delmopinol use, with coccoid cells as the predominant morphotype. Plaque maturity, characterized by the appearance of corncob formations and high numbers of different morphotypes, was not observed on the delmopinol specimens, in contrast to the placebo specimens. The study shows that topical application of 0.5% delmopinol HCl delays and interferes with dental plaque maturation.

Periodontal tissue regeneration including cementogenesis adjacent to dentin-bonded retrograde composite fillings in humans.

The roots of two incisors were treated by apicoectomy and a retrograde dentin-bonded composite filling. Periapical healing was observed a few months later by radiography. Later, due to root fracture and marginal bone resorption, the apical parts were removed including adjacent periapical bone. A histological and scanning electron microscopic examination of the tissue showed reformation of periodontium adjacent to the composite, including reformation of a lamina dura, inserting Sharpey's fibers and cementum deposited in intimate contact with the composite. This finding is in agreement with previous observations of tissue surrounding retrograde dentin-bonded composite fillings placed in monkeys, indicating that tissue regeneration including cementogenesis may occur on composite material and consequently form a biological closure of the root canal.

The production of antibodies to cell membranes of squamous epithelium by the use of aldehyde-induced membrane vesicles.

A new method for the isolation of plasma membrane residues which can be used to raise antibodies to oral epithelial cell membranes is described. Plasma membrane vesicles were formed on the cell surfaces of confluent rat oral epithelial cell cultures by exposing the cells in situ to 100 mM freshly prepared formaldehyde. The vesicles formed 10--15 min. after exposure and were released into the medium. The vesicles, 1--10 micrometers in diameter, were sedimented by centrifugation at 30,000 g for 20 min. Antibodies to vesicles were raised in rabbits and used in an indirect immunofluorescence and immunoperoxidase staining technique. In rat and human oral epithelium they stained cell membranes in the basal and spinous cell layers. No cytoplasmic staining was seen in the epithelium. Staining of squamous epithelium from the human uterine cervix, rat and human skin and guinea pig lip was negative.