Don M. Ranly

The effects of calcium hydroxide on bovine pulp tissue: variations in pH and calcium concentration

Two properties of Ca(OH) 2 , high pH and calcium ion concentration, may contribute to its success in stimulating reparative dentin formation. Bovine pulp was treated with Ca(OH) 2 solutions of varying pH and concentration or with saturated Ba(OH) 2 and examined for enzymatic activity and protein denaturation. Treated pulps were homogenized and centrifuged and the supernatants were analyzed for alkaline phosphatase and lactic dehydrogenase activity. Both enzymatic activities were slightly depressed by the Ca solutions of lower pH and completely destroyed by saturated Ca(OH) 2 and saturated Ba(OH) 2 . Slab gel electrophoresis of treated pulp protein disclosed that saturated Ca(OH) 2 did not alter the pattern when compared with controls, whereas saturated Ba(OH) 2 significantly modified the banding. When the Ba(OH) 2 concentration was reduced to the molarity of saturated Ca(OH) 2 , the electrophoretic patterns of treated pulp protein were similar. These results suggest that the effects of Ca(OH) 2 are mainly pH dependent. Its efficacy may result from lower solubility and, therefore, toxicity when compared with alkaline salts of divalent cations such as Ba(OH) 2 .

An autoradiographic study of formocresol pulpotomies in rat molars using 3H-formaldehyde

Pulpotomies were performed on rat molars with use of formocresol containing 3 H-formaldehyde. Autoradiographs showed that a nonspecific distribution of isotope occurred initially. After a week, part of the labeling became specific, appearing principally in the nuclei of odontoblasts. After two weeks, numerous pulpal cell types were labeled within the nuclei, as were osteoclasts in the periodontal space and adjacent bone marrow cells.

Osteocalcin expression in young and aged dental pulps as determined by RT-PCR

Dental pulps were obtained from third molars of young adults (17-25 yr) or from molar teeth of individuals > 50 yr of age and examined for the expression of osteocalcin (OC) mRNA by RT-PCR. OC was selected as a determinant of pulp vitality, because it has long been associated with the production of hard tissue matrix in teeth and bone. For comparative purposes, the expression of OC in each pulp was normalized relative to its housekeeping gene-product GAPDH by the establishment of a OC/GAPDH ratio. This study demonstrated that OC expression, presumably by cells of odontoblast lineage, does not diminish relative to the extant cell population. Our findings suggest, despite a reduction in volume and cell numbers, that the pulps of aging teeth retain a capacity for dentin deposition and a potential for caries and trauma resistance.

Biochemical Effects of Tissue Fixatives on Bovine Pulp

The effects of formocresol, formaldehyde, cresol, glycerine, and glutaraldehyde on bovine pulp tissue were evaluated on the basis of their influence on the solubility of aqueous protein and on enzymatic digestibility using trypsin and collagenase. The results indicate that formaldehyde is the component of formocresol that interacts with the protein portion of bovine pulp tissue. Cresol and glycerine have little effect on protein, whereas glutaraldehyde has an equal or greater effect in comparison with formaldehyde or formocresol. The addition of cresol to formaldehyde appears to potentiate the effect of formaldehyde on protein. Glutaraldehyde mimics many of the fixative properties of formaldehyde and improves on others, thereby justifying future testing of glutaraldehyde as a pulpotomy agent.

The effect of formocresol on lipids of bovine pulp

Bovine pulp was incubated in either formocresol, cresol, saline, or chloroform:methanol, a standard lipid solvent. Lipids extracted by the incubation media were separated and visualized by thin-layer chromatography; phospholipids were quantified by chemical analysis. Cresol (100%) extracted 4 times as much phospholipid as did chloroform:methanol and 15 times as much as saline. Formocresol, which contains 35% cresol, did not extract phospholipids to the same degree as pure cresol, but did significantly more than chloroform:methanol. Histological studies revealed considerable destruction by the solutions containing cresol. Our findings suggest that the caustic effects of formocresol results from the dissolution of cell membranes by cresol.

The Effects of Formocresol on Rat Sponge Implant Tissue: A Biochemical Study

An investigation was conducted on the effect of formocresol treatment on the aqueous extractability and enzymatic susceptibility of excised implant tissue. The treated tissue demonstrated a decreased solubility and a diminished digestibility by trypsin, pepsin and collagenase. However, its reactivity toward hyaluronidase showed little alteration.

Reaction of rat connective tissue to unfixed and formaldehyde-fixed autogenous implants enclosed in tubes

Fixed and unfixed samples of rat connective tissue were enclosed in polyethylene tubes and reimplanted subcutaneously in the animal from which they originated. Histologic studies of the implants indicated that sterile necrotic autogenous tissue elicited a milder response, characterized by less infiltration of polymorphonuclear neutrophil leukocytes (PMN cells), than autogenous tissue fixed in formaldehyde, and was resorbed and replaced by granulation tissue at about the same rate as fixed autogenous tissue that had been washed to remove formaldehyde. Unwashed fixed autogenous tissue fixed in formaldehyde caused necrosis of surrounding tissue and was resorbed at a slower rate than the other implants. The fixation in formaldehyde of autogenous connective tissue was reversible and resulted in complete degeneration and necrosis of the fixed tissue by 15 weeks.

Distribution, metabolism, and excretion of [14C] glutaraldehyde

Radiolabeled glutaraldehyde (GA) was infused into rats in order to determine its distribution between cellular and humoral fractions of the blood, its potential metabolism by RBCs, its rate of excretion, and the nature of its urinary products. This study demonstrated that [14C]GA was distributed between the RBCs and plasma at a ratio greater than 1. Although the absolute counts of both fractions dropped 80% over 3 days, the percentage bound or incorporated increased over time. Despite the extensive uptake by RBCs these cells were unable to metabolize GA to CO2. Urinary excretion of the radiolabel was rapid; the predominant form in the urine was less than 1 kDa in size. All evidence suggested that it was not native GA. We conclude that the RBCs can incorporate GA, but can not metabolize it completely to CO2. Nevertheless, much of the infused GA was rapidly converted to nonreactive metabolites and eliminated by the kidney.