A clinical trial was conducted to investigate the development of caries lesions associated with fixed orthodontic appliance therapy. To introduce a cariogenic challenge on Sound buccal enamel surface in vivo, specially designed orthodontic bands were attached to premolars scheduled for extraction for orthodontic reasons. The bands were modified by having two metal wires (0·8 mm in diameter) welded to the inner surface of the band to produce a space for plaque accumulation similar to that occurring under loose orthodontic bands. The bands were cemented with a zinc phosphate cement (Tenet®) an left in situ for 4 weeks. Of 22 premolar teeth banded in eight different patients, eight showed definite white spot lesions, eight showed definite faint enamel opacities, and six showed no discernable lesions. Examination of definite white spot lesions by scanning electron microscopy revealed characteristic patterns of initial tissue destruction. Focal holes and an accentuation of the perikymata were observed affecting the enamel surface zone, an area previously considered to remain relatively intact during the development of a caries lesion. The superficial nature of the caries lesions observed and the rapidly of their formation is significant in the clinical management of decalcified areas forming beneath orthodontics bands.
A strain of Alcaligenes paradoxus, unable to degrade phenoxyacetic acid, was shown to degrade two synthetic derivatives of this molecule, the herbicides 2,4dichlorophenoxyacetic acid and 2-methyl-4-chlorophenoxyacetic acid. The ability to degrade these pesticides is encoded by a 58-megadalton conjugal plasmid, pJPl.
This cross-sectional study investigated performances of two consecutive cohorts of second year dental students on completion of a conventional didactic course and two succeeding cohorts of second year dental students on a recently introduced problem-based learning (PBL) course at The University of Liverpool School of Dentistry. A 40 part true/false questionnaire tested recall of factual knowledge in anatomy, biochemistry, oral biology and physiology. The results showed no significant difference in the total scores when negatively marked between the conventional and PBL course groups but higher total scores in the PBL groups when positively marked. Performances in anatomy, oral biology and physiology did not differ between the groups when negatively marked but the scores of the conventional course groups in biochemistry were significantly lower than the others. With positive marking biochemistry scores were not significantly different but all other subjects were significantly higher in the PBL course groups. The PBL course groups offered fewer blank responses than the conventional course groups but the ratio of correct to incorrect responses, for both definite and intelligent guess responses, were similar in these groups. The compositional profile of the study groups was similar with respect to educational background but the PBL course groups included more females and more older students. The results of this study show that the overall knowledge recall in the basic sciences by dental students on PBL or conventional didactic courses does not differ and may be helpful to those considering the introduction of PBL into the curriculum.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.