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Extracted third molars were used to study the effect of Nd:YAG laser irradiation combined with CO2 laser beam on dental hard tissues. The specimens were studied with SEM after lasing and the size of the impact areas and beam penetration into enamel and dentin were planimetrically analyzed. High-energy CO2 laser (e.g. 10 s irradiation with 10 W output energy) penetrated all enamel and dentin. The simultaneous addition of Nd:YAG irradiation to the CO2 beam was found to increase the effect of CO2 laser, while Nd:YAG irradiation alone, used with equivalent energy densities, did not cause any effect on enamel surface. Thus, Nd:YAG laser was found to potentiate statistically significantly the effect of CO2 irradiation, but the morphologic alterations on dental hard tissues, such as crater formation at the beam focus site, appeared to be due to CO2 irradiation alone.

— The fluoride release of varnish-coated silicates and liners and sealants was studied by measuring the uptake of the released fluoride by synthetic hydroxyapatite. Silicate specimens were made and coated with cavity varnish. The specimens were shaken in solution with the apatite for 7 weeks. The apatite was analyzed for fluoride each week and the specimens were then transferred to a fresh solution with new apatite. The varnish reduced the fluoride release during the first three weeks, but after that time the release from the varnish-coated specimens was the same as that from the uncoated specimens. The release from the liners and sealants was studied by coating composite resin specimens with the material. The resin contained no fluoride. The specimens were shaken in solution with apatite and the fluoride uptake was measured each week in the same manner as for the silicate specimens. The liners showed an initial release of fluoride. When the two different sealants were applied as two layers, only one of the brands showed initial release of fluoride. Five layers of sealant resulted in an initial release from both brands.

(1970). The Stability of Extracted Collagen Molecules from Human Periodontal Membrane. Acta Odontologica Scandinavica: Vol. 28, No. 6, pp. 959-966.

— A comparative investigation was performed on glycosaminoglycan-like fractions obtained from calculus, parotid saliva, and dental plaque. The calculus (sub-gingival and supragingival) was obtained from extracted teeth. Human parotid saliva was collected with an acrylic cup and the dental plaque was gathered from different individuals. The samples were hydrolyzed with papain and the glycosaminoglycan-like compounds were precipitated with the conventional methods. The analyses were made from the material precipitated with cetylpyridinium chloride (CPC). The results showed that the CPC-precipitate of the plaque material contained less uronic acids, sulphate. hexoses. sialic acid, and proteins than did calculus and saliva. The results revealed further that the CPC-precipitate derived from calculus contained phosphate and some calcium. Both saliva and plaque were devoid of these components. The plaque sample lacked the fractions existing in pherograms of both calculus preparation and preparation of parotid saliva (alcian'blue positive). A part of the fractions in the pherograms of calculus and saliva could be stained with lissamine green.

(1969). Enzymatic Release of Phosphorus from Human Dental Enamel by Enzyme Preparations of E. coli. Acta Odontologica Scandinavica: Vol. 27, No. 5, pp. 477-480.

Enzymes of human dental plaque that are capable of hydrolyzing α-naphthyl phosphate were fractioned by means of Sephadex G-100 gel filtration and DEAE-ion exchange chromatography. The results demonstrated the existence of several enzymes in human dental plaque that possessed this hydrolyzing activity.

A representative sample of Finnish denture wearers (n = 3875) aged 30 or over were examined clinically and interviewed about their oral hygiene habits, use of dental services and possible prosthetic treatment during last visit to a dentist. Of these denture wearers, over 80% brushed their dentures at least once a day, and 16% visited a dentist at least once in 2 yr. For denture stomatitis the age-standardized risk ratio decreased with brushing frequency in women and increased in men. For frequency of dental visits the prevalence of denture stomatitis increased in both men and women when visits were made over 2-yr intervals. The prevalence of denture stomatitis was higher in the group with dentures over 1 yr old. It seems that the oral hygiene measures as they are generally carried out and regular dental visits are not effective enough methods in preventing denture stomatitis.

(1970). The Effect of F- Ions on the Rate of Some Hydrolytic Enzyme Reactions. Acta Odontologica Scandinavica: Vol. 28, No. 6, pp. 947-958.

– The purpose of the study was to determine the fluoride content of acrylic and composite resins and to study the release of fluoride from these materials in comparison to the release from silicates. The analytical results showed that one composite contained approximately the same amount of fluoride as is generally reported for silicates. The other resins contained none or only minimal amounts of fluoride. The release of fluoride was studied by measuring the uptake of fluoride by synthetic hydroxylapatite. Rectangular test specimens, 2 × 2 × 12 mm, made of the fluoride-containing resin were shaken in a neutral (pH 6.8) and an acidic (pH 5.8) solution with the hydroxylapatite for 7 weeks. The apatite was analyzed for fluoride each week and the test specimens were then transferred to a fresh solution with new apatite. As a control, a composite without fluoride was studied in the same way. For comparison two silicate cements were also included in the study. The results show that, during the first week, the uptake of fluoride by the apatite was greater from the silicates than it was from the composite. After that period the uptake continued at a lower level and did not show any marked decrease during the observation period. This continued uptake was about the same from both the silicates and the composite.

A spectrophotometric method for the determination of dextranase activity with the use of Blue Dextran is described. Due to its rapidity the new method is especially recommended for the determination of the dextranase activity in column chromatography.

The effect of ammonium sulfate on the rate of dissolution of human enamel, dentin, and synthetic hydroxylapatite at different pH values was studied. Ammonium sulfate enhanced the dissolution of all the tested materials. The sulfate ion was responsible for the increase in the solubility of powdered dentin at all tested pH values between 4.2 and 7.4.

The substrate specificity of alkaline phosphatases derived from different types of tissue is still open to investigation. In this laboratory investigations have been carried out on the human foetal alkaline phosphatase activity in order to elucidate, above all, the substrate specificity of the enzymes obtained from cartilaginous epiphysis, parietal bone and liver. A preliminary report on the results obtained has been given earlier [ 1 ] . Various chromatographic experiments revealed that parietal bone contains an alkaline phosphatase which is not very active or is present only in small amounts in the other tissues. In spite of the location of the different enzymes, the alkaline phosphatases found were considered to be similar in many respects, displaying perhaps only one main type of enzyme. This was evidenced in this paper by 1) essentially similar kinetic behaviour of most of the enzymes identified under the test conditions employed, and 2) similar activating effect of various divalent metal cations tested.

– Human dental plaque was collected into iced water. The starting crude enzyme preparation — obtained by sonication and ultracenfrifugation - was tested for its keto acid-forming activity using different amino acids as substrate. It could be shown that only L-cystine and L-cysteine were converted to keto acid by this enzyme preparation. The partly purified enzyme preparation, after BioGel P-300 gel permeation chromatography, was capable of forming keto acid only from L-cysteine. The affector studies conducted revealed that cations, such as Al2+, Cr3+, Ca2+, Fe2+, and Cut+, reduced the reaction velocity, and the same could be noted when Na-cyanide, dithiotreitol, and mercapto-ethanol were tested. NaF, MgCl2, iodoacetate, Na-citrate, and Na2-EDTA exerted no effect on this enzymic reaction. The tested coenzymes, flavin mononucleotide (FMN), flavin dinucleotide (FAD), riboflavin phosphate, and pyridoxal-5-phosphate, were innocuous to the keto acid-forming activity. This study confirms earlier studies that human dental plaque contains an enzyme disulfide reductase, an enzyme known to convert L-cystine to L-cysteine, and suggests the existence of a desulfhydrase enzyme in the plaque which converts L-cysteine to pyruvic acid, ammonia, and hydrogen sulfide.