Modulation of class II (DR and DQ) antigen expression on gingival Langerhans cells in vitro by gamma interferon and prostaglandin E2

The effect of human and murine gamma interferon (IFN-gamma) on Class II (DR and DQ) expression by human gingival Langerhans cells (LC) was examined using an organ culture system. Human and murine IFN-gamma increased the expression of both DR and DQ antigens during a 72-h period. Maximal levels of DR expression (100% of T6+ cells) were produced within 6 h of IFN-gamma treatment and were maintained during culture. DQ expression was maximal (100% of T6+ cells) at 18 h and was more labile than DR. The effect of IFN-gamma on DR and DQ was abrogated by prostaglandin E2 (PGE) while indomethacin, and inhibitor of PGE synthesis, mimicked the effect of IFN-gamma on DR and DQ expression. Gingival keratinocytes maintained their expression of DR for 72 h in the presence of gamma-IFN, but did not express DQ under any of the culture conditions used in this study. These results demonstrate that gamma-IFN induces differential expression of Class II antigens in the oral mucosa in vitro, and suggest that gamma-IFN and PGE may be involved in the control of DR and DQ antigen expression in vivo.     

Denture base acrylic reinforced with high modulus fibre

Dentures are frequently fractured owing to the poor fracture resistance of Denture Base Acrylic. This experiment was designed to compare the transverse strength of samples of conventional and cross-linked acrylic with samples containing various proportions of one of two high modulus fibres. The stiffest and strongest specimens were those of the conventional acrylic and all the reinforced specimens were significantly weaker. The reason for this appears to be failure to achieve true adhesion between the fibre and the matrix resulting in the layers of fibre separating the matrix into layers of narrow cross-section.     

A comparison of the sealing properties of different retrograde techniques: an autoradiographic study

Single-rooted teeth were instrumented and filled in vitro with a lateral condensation of gutta-percha with sealer. Following obturation, the tooth apices were treated by various retrograde procedures. The teeth were then coated with ethyl acetate, immersed in 45Ca solution, washed, and sectioned, and autoradiographs were used to compare the leakage of the various techniques. Statistical analysis indicated that lateral condensation produced a significantly better seal than any retrograde technique tested except retrofilling with Super EBA cement and that a significantly worse seal was obtained with amalgam retrofill when compared to all retrograde techniques except cold-burnished gutta-percha following apicoectomy. No significant difference existed between other group combinations.     

Cure performance of light-activated composites by differential thermal analysis (DTA)

A technique which utilizes differential thermal analysis and a divided fibre optic system is a valuable aid to the study of the curing behaviour of lightactivated composites. Degree of cure and temperature rise can readily be evaluated as a function of irradiation time. Shade of material, thickness, sample temperature and the presence of porosity all have a significant effect on cure behaviour. The temperature rise for a 60 mm³ sample of material varies between 20°C and 40°C for the materials tested.     

Salivary concentrations of steroid hormones in males and in cycling and postmenopausal females with and without periodontitis

Concentrations of testosterone, dehydroepiandrosterone, eslradiol, progesterone, 17α-hydroxyprogesterone, and cortisol were measured in the saliva by radioimmunoassay. Saliva from male and cycling and postmenopausal female patients with and without periodontitis was studied.
It was found that salivary concentration of progesterone was increased in all patients with periodontitis. While testosterone was significantly increased in the female diabetic and non-diabetic patients with periodontitis, no difference in its concentration was found in the saliva of non-diabetic males with and without periodontitis. Salivary dehydroepiandrosterone was also increased in postmenopausal females with periodontitis. In contrast, estradiol was significantly decreased or not measurable in all patient groups with periodontitis. The concentration of cortisol and 17α-hydroxyprogesterone showed no significant differences in postmenopausal patients with and without periodontitis. In addition, the salivary concentration of all hormones in postmenopausal females showed circadian variation. Moreover, results obtained in postmenopausal and ovariectomized females provided evidence for extragonadal production of sex steroid hormones in postmenopausal females.
The present results suggest that there is a relationship between the altered production of sex steroid hormones and the incidence of periodontal pathology.     

Perturbation of cobalt 60 radiation doses by metal objects implanted during oral and maxillofacial surgery

The influence on cobalt 60 dose distributions of typical metal parts used in oral and maxillofacial surgery was studied. Relative doses were determined by exposing x-ray films in a polystyrene phantom set-up containing samples of Vitallium, titanium, and stainless steel. Optical densities were converted to doses with the aid of sensitometric curves. The results show that for normal incidence there is a 25% to 40% increase in dose at the entrance side of the metal and a 20% to 25% decrease in dose at the exit side. The enhancement effect falls off rapidly and becomes negligible at about 1 mm from the interface. The reduction effect decreases more gradually and is still evident at distances of a few centimeters. These dose perturbations should be taken into account in the planning of radiation therapy for patients in whom metal objects have been implanted.