Dental radiographic exposure normalization program (DENT). The experience in Nassau County, NY

A Federally sponsored program for reducing unnecessary exposures from dental radiographic procedures is monitored over four years. The results are encouraging.     

Ecological and genetic analysis of copper and streptomycin resistance in Pseudomonas syringae pv. syringae

Strains of Pseudomonas syringae pv. syringae resistant to copper, streptomycin, or both compounds were recovered from symptomless and diseased tissue of four woody hosts in three nurseries in Oklahoma. In strains resistant to copper and streptomycin (Cur Smr), resistance to both compounds was cotransferred with a single plasmid which was either 68, 190, or 220 kilobase pairs (kb). All Cus Smr strains contained a 68-kb conjugative plasmid. Cur Sms strains contained one plasmid which varied in size from 60 to 73 kb. All conjugative plasmids which transferred streptomycin resistance contained sequences homologous to the strA and strB Smr genes from the broad-host-range plasmid RSF1010. The Smr determinant was subsequently cloned from a 68-kb Cur Smr plasmid designated pPSR1. A restriction map detailing the organization of the homologous Smr genes from pPSR1 and RSF1010 and cloned Smr genes from P. syringae pv. papulans and Xanthomonas campestris pv. vesicatoria revealed the conservation of all sites studied. The Cur genes cloned from P. syringae pv. tomato PT23 and X. campestris pv. vesicatoria XV10 did not hybridize to the Cur plasmids identified in the present study, indicating that copper resistance in these P. syringae pv. syringae strains may be conferred by a distinct genetic determinant.     

Bond strength, interfacial characterization, and fracture surface analysis for a new stress-breaking bonding agent

Three commercial dentin bonding systems were analyzed by tensile bond testing, area analysis of fractured surfaces, and SEM analysis of the tooth-resin interfaces. Tensile bond strengths in megapascals(SD) were Tenure-Marathon V ([T-M]; 8.86[3.02]), new system with low-viscosity resin ([K-LVR-P]; 6.50[2.01]), and new system without low-viscosity resin ([K-P] = 7.28[1.75]), which were significantly greater than Scotch-bond 2-P50 ([SB-P50]; 3.96[1.02]). Gaps that ranged up to 5.6 microns (mean for the group) were observed around most of the restorations at dentin surfaces and less so at enamel surfaces, where some of the restorations remained free of gaps. The gaps near the dentin margin were significantly smaller for K-LVR-P than for SB-P50. The tensile test revealed mixed failure modes in all systems, and in the cross sections of class V restorations, the gaps were confined to the dentin-resin junction.     

Apolipoprotein E type 4 allele and cerebral glucose metabolism in relatives at risk for familial Alzheimer disease

OBJECTIVE: Cerebral parietal hypometabolism and left-right asymmetry occur early in the course of Alzheimer disease (AD), and the apolipoprotein E type 4 allele (APOE epsilon 4) is a risk factor for familial AD. To determine if APOE epsilon 4 is associated with lowered brain function in nondemented relatives at risk for familial AD, we studied 12 relatives with APOE epsilon 4 and 19 relatives without APOE epsilon 4. We also compared them with seven patients with probable AD. DESIGN: After grouping subjects according to diagnosis and genotype, brain function measures were compared among groups. SETTING: University medical center. PATIENTS: At risk subjects had mild memory complaints, normal cognitive performance, and at least two relatives with AD. Subjects with APOE epsilon 4 did not differ from those without APOE epsilon 4 in mean age at examination (56.4 vs 55.5 years) or in neuropsychological performance (mean Mini-Mental State Examination score, 28.8 vs 29.3). MAIN OUTCOME MEASURES: Cerebral glucose metabolism was measured using positron emission tomography and fludeoxyglucose F 18. RESULTS: Parietal metabolism was significantly lower and left-right parietal asymmetry was significantly higher in at-risk subjects with APOE epsilon 4 compared with those without APOE epsilon 4. Patients with dementia had significantly lower parietal metabolism than did at-risk subjects with APOE epsilon 4. CONCLUSIONS: These results suggest that the inheritance of APOE epsilon 4 is associated with reduced cerebral parietal metabolism and increased asymmetry in non-demented relatives at risk for probable AD. Longitudinal study will determine if glucose metabolic measures provide a means to monitor experimental treatment responses during the early phases of the disorder.     

Extraction site healing complicated by neoplasia

Malignant melanoma arises from melanocytes, dendritic cells of neural crest origin. Melanocytes occur within the basal layers of the epidermis, mucous membranes, retina and uveal structures of the eye and the meninges. Rarely, they may also occur in the bladder, adrenal medulla and ovaries. These melanomas metastasise widely and metastases in the oral mucosa have been seen in about 3% of patients with cutaneous melanoma, and can complicate the healing of extraction sites. This paper presents a case of malignant melanoma of the mandible.