ABSTRACT
Objective:To investigate the patterns of microbial infection on the apical external root surfaces of treated and untreated teeth associated with chronic apical periodontitis and to study bacteria in the biofilm in order to find out the species,constitution and origination of bacteria in periapical biofilm.Methods: Ten teeth with chronic apical periodontitis from patients of the Department of Stomatology of People's Hospital,Peking University: 5 untreated teeth with a radiographically visible chronic periradi-cular lesions and 5 teeth with extensive carious lesions,radiolucent lesions of varying sizes and attached periradicular tissues were selected for study.Using aseptic techniques and sterile instruments,bacterial samples of the root canals were taken,inoculated and separated according to usual practice.After extraction,ten teeth were fixed and the apical 5 mm portion of one root was sectioned.Root tips were dehydrated,sputter coated with gold,and then examined for the occurrence of bacteria on the apical root surfaces using scanning electron microscope.Five healthy teeth with vital pulp were used as controls.Results: Microbial study showed that ten specimens yielded bacterial growth.The most prevalent bacteria were P.micros and F.nueleatum.In the 5 untreated teeth,bacterial cells were usually observed close to the apical foramen in only 1 specimen.Morphologically,these bacteria consisted of cocci.In the 5 treated teeth,a dense bacterial aggregation composed mainly of cocci and rods was observed surrounding the apical foramen of all specimens.Besides rods,other bacterial morphological types were recognized,including coaggregations of cocci and filaments,characterizing a fully developed "corn-cob".No microorga-nisms were found in the healthy controls.Conclusion:Bacterial biofilm was always present in teeth with post-treatment endodontic disease.The presence of apical bacterial biofilm is clinically important,and it may cause failure of endodontic treatment as a consequence of persistent infection.
ABSTRACT
Objective To determine the reliability of the tooth wear index in representing the profile of tooth cervical defect. Methods One hundred and ninety-three teeth with wedge-shaped defects were selected in 69 plaster casts. The sizes of every wedge-shaped defect were measured by using vernire caliper and the volumes of those were calculated. Otherwise, by weighting the restoration of defects, the real volumes of the 9 teeth defects were calculated by formulating. Results The formulation for calculatin of the real volume of the defects was presented as: volume = 0.4735 + 2.5948 X (deep of profile X height X broad of defects)/6. The profile of the defect was strongly related to the volume. Conclusions The value of one dimension measure of the wedge-shaped defects may present the tooth wear index.
ABSTRACT
<p><b>OBJECTIVE</b>To clinically investigate and identify the occlusal force as one of factors relative to formation of wedge-shaped defects.</p><p><b>METHODS</b>123 subjects, selected from a group of middle-aged and elderly people in an urban area were divided into four groups: control, light, middle and severe group according to the severity of wedge-shaped defects. Cuspid, first and second premolars, and first molar in maxilla were examined for occlusal force by occlusometer, and the peak value of occlusal contact strain on every maxillary tooth was studied by photocclusion.</p><p><b>RESULTS</b>Significant reduce of occlusive force in the defected teeth was found than that of in the control teeth. The occlusal contact strain of first premolars with defects by photocclusion was statistically increased. The relative occlusal contact strain of first premolars and first molar of defects was higher than that of their proximate teeth.</p><p><b>CONCLUSION</b>Occlusal force could have relation to the formation of wedge-shaped defects.</p>