Radiat. Res. 46, 229-235 (1971).The low-temperature esr spectra of y-irradiated calcium phosphate samples, that are similar in structure and composition to the principal inorganic components of bone and tooth, are interpreted in terms of the radicals P04-2, 0, and H. There are indications in the low-temperature esr spectra of some 7-irradiated collagenous materials that most of the damage is concentrated randomly along the main peptide chains and that relatively few radicals are formed in the side chains of the amino acid residues.

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E PITHELIAL hyperplasia and diminished keratinization, usually associated with inflammation, are the principal microscopic changes reported in the gingiva in pregnancy.1-3 It has not been established whether pregnancy itself produces these changes or whether it simply modifies the gingival response to local irritation so that the epithelial changes are exaggerated.3 4 Increased amounts of water-soluble, alcohol-insoluble glycoproteins observed in gingivitis in pregnancy have been attributed to hormonal origin.5' 6 On the other hand, comparable findings have been associated with gingival inflammation in nonpregnant individuals.7 8 It would appear that, in order to determine the effect of pregnancy upon the gingiva, the problem should be studied without the complicating factor of inflammation. Study of the attached gingiva provides such an opportunity. PROCEDURE Sixty gingival specimens with and without clinical signs of marginal gingivitis were obtained from 30 patients aged 16 to 32 years, in the second and third trimester of pregnancy. Forty-two specimens, with and without clinical signs of marginal gingivitis, obtained from 21 nonpregnant females in a comparable age group served as controls. Two contiguous rectangularshaped specimens were taken from each patient on the buccal surface of the maxillary or mandibular premolar and molar areas so as to include the marginal and attached gingivae and, in most cases, the alveolar mucosa (Figs. 1, A, and 1, B). One specimen was fixed in a solution of 1 per cent trichloracetic acid in 80 per cent alcohol and the other in a solution of 10 per cent formalin in 95 per cent alcohol, buffered to pH 7.0 ± 0.3. Slides in serial sections were prepared from each of these specimens, employing the following staining technics: hematoxylin and eosin; the Barrnett-Seligman technic9 for protein-bound sulfhydryl and disulfide groups; the Weiss, Tsou, Seligman'0 technic for protein-bound amino groups; and the periodic acid-Schiff technic" for glycogen and other water-insoluble, alcohol-insoluble polysaccharides.

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