A. C. Karim

Adriamycin alters the alkaline phosphatase activity in hamster molars during development in vitro

The effect of a 2 hour exposure to adriamycin (1 mg/litre) on alkaline phosphatase (ALPase) activity of the golden hamster 4-5 day old second maxillary molars (M2) was investigated in vitro. The molars were grown in BGJb medium containing 15% fetal bovine serum, glutamine (200 micrograms/ml), vitamin C (250 micrograms/ml), penicillin G (50 micrograms/ml), and streptomycin sulphate (30 micrograms/ml). The gas phase contained 50% O2 + 5% CO2 + 45% N2. The molars were supported on cellulosic membrane filters and grown for 3, 5, and 7 days at the medium-gas interface in a closed humidified chamber. Biochemical analysis indicated a steady increase in ALPase activity throughout this study in the control samples. However, after adriamycin treatment no increase in ALPase activity could be observed. The histochemical data showed that the increased activity in the control was confined to the peripheral pulp, sub-odontoblastic layer, stratum intermedium, ameloblasts and odontoblasts. Although these layers showed a decreased activity after adriamycin treatment, the ameloblasts showed an increase in activity over the control. The data has shown that adriamycin caused a reduction in total ALPase activity in developing molars in vitro; osteodentin production by pulp cells; and appeared to produce an acceleration in the differentiation of ameloblasts.

The effects of adriamycin on dental proteins formation and mineralization in vitro

Second maxillary molars of 4-5 days old golden hamsters were exposed for 2 h in vitro to 1 mg/L adriamycin, rinsed and subsequently cultured up to 7 days without the drug. At days 3, 5 or 7 of culture the synthesis of extracellular tooth matrices and their mineralization were examined by measuring the incorporation of 3H-proline and the uptake of 45Ca and 32PO4 by the explants during a 24 h pulse labeling. Compared with unexposed control explants, exposure to adriamycin for the first 2 h of culture had no effect on total biosynthesis of proline-containing matrix proteins. However, at days 3 and 5 of culture it increased the quantity of water-soluble enamel matrix proteins (amelogenins). Adriamycin also strongly reduced the amount of organically-bound 32P-activity in a fraction extractable with guanidine-HC1-EDTA only, allegedly containing a mixture of mineral-associated proteins from both enamel and dentin. Since this decrease of 32P-activity coincided with the formation of osteodentin in the pulp as shown previously in histological and electron microscopical studies, it was speculated that osteodentin matrix may not contain the highly phosphorylated, dentin-specific phosphoproteins (DPP). Adriamycin also affected the uptake of 45Ca and 32PO4. At day 3 these values were slightly higher than control values but lower at days 5 and 7. It therefore appears that a 2 h exposure to adriamycin in concentrations as low as 1 mg/L causes an acceleration of secretory amelogenesis by tooth germs in vitro. It also induces pulp cells to form osteodentin.

A surgical technique for administering laser irradiation to rat incisor dentin

With the advent of lasers in the field of dentistry, various methods have been used to expose dentin to laser irradiation. This was done indirectly through the alveolar bone, as well as directly on dentin wafers and on extracted human teeth. However, dentin is a vital tissue and the only way to show the ramifications of laser irradiation is by directly exposing the dentin to this energy source under in vivo conditions. In the present study we describe a highly reproducible method for accomplishing this. Male Sprague Dawley rats were anesthetized and an incision was made at the junction of the attached palatal mucosa and the unattached buccal mucosa parallel to the maxillary bones on both sides. This procedure exposed the underlying bone where a 2 mm square window, at a point 3 mm caudal and parallel to the gingival attachment, was cut out to the depth of the periodontal ligament. The site was flushed with a 0.9% sterile sodium chloride solution and gently dried with gauze. The beam of the laser was focused in the middle of the 2 mm square window and a pre‐determined energy level and pulse duration (2 W 50 ms or 10 W 50 ms) were selected. The focal length guide was held at right angles to the dentin surface and in contact with the maxilla at all times. The energy densities of either 52.6 or 263.2 J/cm2 were delivered to the ‘root’ dentin by a single pulse. The survival rate was 92%. The animals that died did so while under anesthesia and not after exposure to laser irradiation. The animals that survived tolerated the surgery and the laser irradition very well, regaining (and eventually surpassing) their initial weight 3 days after the procedures were performed. The thickness of the dentin that was exposed to laser irradiation was not completely penetrated by the energy levels used. At both energy levels some dentinal tubules appeared blocked and evidence of melted dentin was apparent. However, at the higher energy level two distinct zones were observed in the funnel‐shaped lesion. In the inner zone distinct dentinal tubules were not readily visible, while in the outer zone the tubules were opened and completely free of debris. This technique is highly reproducible and yields consistent results with little or no stress to the animals. Although the energy levels used did not penetrate the entire thickness of the dentin, the depth of penetration of the laser beam appears to be related to the energy level used and the thickness of the dentin layer present. Anat Rec 260:359–365, 2000.