Effects of the penetration of a root canal filling material into the mandibular canal. 1. Tissue reaction to the material

The root canal filling paste Vitapex (Neo Dental Chemical Products Co., Tokyo), made of calcium hydroxide and iodoform with the addition of silicone oil, was experimentally introduced into the mandibular canals of 29 dogs. Tissue reactions to the paste were examined by radiography, histopathology, and electron microscopy. These examinations revealed that the paste was phagocytosed by macrophages and, in general, was gradually resorbed over time. The paste was also found to cause heterotopic calcification and/or ossification within the area of original penetration.     

In vitro resistance to fracture of porcelain inlays bonded to tooth

To assess the resistance to fracture of ceramic inlays, extracted sound human molars were restored with different ceramic materials and glass-ionomer or composite resin luting cement. Compression forces were applied to the specimens until they fractured, and maximal force developed, extent and location of fractures, and the micromorphology of the fractured surfaces were studied. Inlays made of Vitadur N with aluminum oxide profile and bonded with composite resin demonstrated the highest resistance among the restorative combinations, but their resistance was still lower than that of intact (control) teeth. The extent of fracture increased proportionally to the fracture resistance of the specimens. Scanning electron microscopic observation confirmed the effectiveness of the adhesion between composite resin and etched ceramic and the absence of sufficient micromechanical anchoring between glass-ionomer cement and etched ceramic.     

Humoral immune response to selected subgingival plaque microorganisms in insulin-dependent diabetic children

Juvenile diabetics have been shown to have an increased susceptibility to gingivitis and periodontitis following puberty. However, little data are available on changes in the microbial flora that occur at the onset of puberty. This study was performed to determine if antibacterial antibody titers to selected periodontal disease-associated microorganisms might be helpful in revealing changes in plaque flora at the onset and conclusion of puberty. Sera was obtained from 35 subjects (ages 7 to 18 years) selected from a population of insulin-dependent diabetics. The subjects were given a thorough medical examination which included an assessment of sexual maturation and a dental examination which included the recording of onset and magnitude of bleeding according to the papillary bleeding score. Antibody titers to A. naeslundii (AN), B. intermedius (BI), B. gingivalis (BG), F. nucleatum (FN), A. actinomycetemcomitans (AA), C. ochracea (CO) and T. denticola (TD) were determined using the microELISA. Stratification of antibody titers by age groups (less than or equal to 12 years, 12 to 15 years, greater than 15 years) revealed that titers to AN increased significantly (P less than 0.025, ANOVA) and progressively (P less than 0.05, regression analysis) with increasing age. In contrast, the titers to FN were maximal in the under 12 year group and decreased with age (ANOVA, P less than 0.05; regression analysis, P less than 0.05). There were no significant variations in titers observed for the other microorganisms. Stratification by sexual maturity revealed a similar progressive decrease of the titer to FN (ANOVA, P less than 0.05; regression analysis, P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)     

Cell proliferation after flap surgery, root conditioning and fibronectin application

This study evaluated the effects of citric acid demineralization and autologous fibronectin application on cell proliferation after mucoperiosteal flap surgery. Three adult rhesus monkeys were used. After flaps were raised, the roots were surgically exposed and planed. Surfaces on the experimental sides were decalcified with citric acid, and after thorough rinsing, the inner aspect of the flaps and the roots were bathed with 1 ml of autologous plasma fibronectin in normal saline (400 micrograms m/ml) and the flaps sutured. Contralateral teeth, acting as controls, were treated only with the surgical procedure. One hour prior to sacrifice, the animals were injected with an intravenous injection of tritiated thymidine (1 microCi/gm body weight). Surgeries were staggered to produce the following time periods: 3, 7, 15, 21 and 28 days. After processing, autoradiographs were obtained for evaluation, and labeled cells were counted in five compartments at 400 x: (1) oral epithelium, (2) crevicular area, (3) supracrestal connective tissue, (4) coronal periodontal membrane and (5) coronal bone marrow. Forty tissue sections per procedure (20 slides per tooth) were counted and means obtained for the three monkeys. Differences between experimental and control values were statistically evaluated for each component, at each time interval, using pairwise t tests. Fibronectin-treated areas showed significantly increased cellular proliferation (P less than 0.01) during the first 2 weeks, affecting mainly all the supracrestal tissues. Histologically, the establishment of a well-organized fibrinous clot at 3 days was noted in these areas. Results show a faster healing after surgery with the use of citric acid and fibronectin. It was concluded that citric acid followed by fibronectin enhanced cellular proliferation.