No abstract

Dipeptidyl aminopeptidase activity was found in the culture medium of Bacteroides gingivalis 381. The enzyme, hydrolyzing glycylprolyl-4-methylcoumaryl-7-amide, was purified 750-fold from culture medium by ammonium sulfate precipitation, Sephadex G-200 gel filtration, and DEAE Bio Gel A column chromatography. The molecular weight, determined by gel filtration, was approximately 160,000. The isoelectric point of the enzyme, estimated by isoelectric focusing using polyacrylamide disk gel electrophoresis, was about pH 6.2. The optimum pH of the enzyme was about 8.0, and the Km value was 0.05 mM. The enzyme activity was strongly inhibited by phenylmethylsulfonylfluoride and diisopropylfluorophosphate. The purified enzyme specifically cleaved glycylprolyl dipeptide from partially digested type I collagen.

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A scanning electron microscopy (SEM) study was conducted to evaluate the effects of Nd:YAG laser radiation on removal of a root surface smear layer after root planing in comparison with citric acid treatment. The experimental materials were 15 human teeth affected by severe periodontal disease, which were extracted because of a hopeless prognosis. The teeth had at least 5 mm of attachment loss on the proximal surface tested. After removing all visible calculus using an ultrasonic scaler, each proximal surface was vigorously scaled and root planed with a Gracey curet. Thirty specimens were cut from the root-planed proximal surfaces and assigned randomly to one of two groups: Group A (25 specimens) was divided into 5 subgroups and irradiated with a Nd:YAG laser, using non-contact delivery (3 mm beam diameter, distance from the tip to the specimen 5 cm), at a measured power of 20 W for 0.3, 0.5, 1.0, 2.0, or 3.0 seconds corresponding to energy densities of 84.93, 141.54, 283.09, 566.17, or 849.26 J/cm2; Group B (5 specimens) was not irradiated, but treated for 3 minutes with saturated citric acid (pH 1). The center of each specimen in Group A was used as the experimental area (Exp A) treated by laser irradiation and the peripheral area of the specimen served as a control (Cont A). In Group B, one half of the specimen was used as the experimental area (Exp B) treated by citric acid and the other half served as a control (Cont B). The specimens were then fixed and examined by SEM. The surface of the root-planed specimens (Cont A and B) was irregular, corresponding to the presence of a smear layer, and had an amorphous appearance. Both root surfaces of Exp A and B exhibited clear orifices of dentinal tubules and intertubular dentin without a smear layer. Although the root surface of Exp A showed clear orifices of dentinal tubules with a flat morphology, the root surface of Exp B showed widened funnel-shaped dentinal tubule orifices with a fibrillar, mat-like morphology. The present results indicate that Nd:YAG radiation effectively removes the smear layer, uncovers dentinal tubules, and exposes collagen fibers on the root surface without widening the orifices of dentinal tubules after root planing.

The aim of this study was to compare the effects of bioabsorbable and non-resorbable membranes on experimental guided bone augmentation in 8 Japanese white rabbits. A cutaneous flap was demarcated and raised from the forehead of each animal, the periosteum was lifted, and the calvarial bone on both sides of the midline was exposed. A titanium screw was inserted into the bone on each side of the midline and one screw was covered with a bioabsorbable (polylactic acid) membrane and the other with a non-resorbable (expanded polytetrafluoroethylene) membrane. The implanted screws and membranes were then covered with the periosteum and cutaneous flap. After healing for 6 months, the animals were euthanized and the experimental area was prepared for histological investigation. New bone had formed under both membranes with no sign of infection or membrane exposure. The amount of newly generated bone (89.0 +/- 17.3% versus 54.7 +/- 14.0%, P <0.05) and the percentage of newly generated bone height (81.5 +/- 6.3% versus 58.9 +/- 7.8%, P <0.05) in the space beneath the non-resorbable membrane was greater than that beneath the bioabsorbable membrane. However, there were no statistically significant differences between the bioabsorbable and non-resorbable membranes with respect to the percentage areas of mineralized bone (52.3 +/- 11.3% versus 47.1 +/- 6.7%, P = 0.8658) and bone marrow (47.7 +/- 11.3% versus 52.9 +/- 6.7%, P = 0.4838) and bone contact with the screw (88.3 +/- 6.9% versus 89.2 +/- 7.3%, P = 0.9999). In conclusion, at least within the limitations of this rabbit model, we suggest that non-resorbable membranes with sufficient stiffness should be used to obtain greater bone volume and height instead of bioabsorbable membranes for the GBR procedure, and that this will facilitate predictable bone augmentation in spaces beyond the bone surface. Therefore, the bioabsorbable membrane could not replace the non-resorbable membrane used in this model.