Biomedical subjects
Publications and source records attributed to K M Pang.
The literature on age estimation from the structure of adult human teeth is reviewed. Several anatomic changes of teeth have been shown to be valuable in age determination, but there is still controversy concerning the accuracy of cemental annulation. It is believed that improvements in age estimation can be made using direct measurement rather than scoring systems.
The microvasculature of human tongue papillae originating from 9 males and 6 females, aged 0.5 to 2 years was studied by scanning electron microscopy (SEM) of vascular corrosion casts and by light microscopy (LM) of India ink injected specimens. All papillae showed a microvasculature characterized by primary, secondary and tertiary capillary loops. In the filiform papillae the loops were generally arranged in a corolla-like pattern with the tertiary loops demonstrating a hair-pin shape. The fungiform papillae showed basically a similar architectural pattern although the loops were somewhat more compact and complex in structure. A small, shallow depression of the tertiary loops at the top of these papillae was found to be occupied by a prominent rete ridge of the surface epithelium. There was a gradual transition from filiform to foliate papillae, the latter appearing as rows of coalesced filiform papillae. The circumvallate papillae easily identified by the surrounding furrow showed a rather complex and compact pattern of capillary loops of which typical hair-pin shaped tertiary loops dominated the periphery of the papilla. Small grooves or depressions in the vascular network were found to be occupied by rete ridges of the overlying mucosal epithelium.
The various nuclei of the trigeminal complex were studied by immunohistochemical (enkephalin localization) and ultrastructural means in the brainstems of eight newborn human babies that died within 24 h after birth. Positive enkephalin neurons were detected in the chief sensory and spinal trigeminal nuclei as well as in some fibers of the trigeminal nerve. Ultrastructurally, two morphologically distinct types of neuron were observed, respectively, in the motor nucleus, the spinal nucleus and the mesencephalic nucleus of the trigeminal complex, whereas three morphologically distinct types of neuron were observed in the chief sensory nucleus. "Glomerulus" formation was a frequently observed feature in the chief sensory nucleus. In the spinal nucleus, rolls of synaptic terminals stacking up one on top of another and synapsing onto the final synaptic element were very much in evidence. Axosomatic, axodendritic, dendrodendritic and dendroaxonic synapses were demonstrated in all the different nuclear areas of the trigeminal complex but axoaxonic synapses were absent in the mesencephalic nucleus. Some of the findings in the present human study were similar to those reported in the rats and cats.
A total of 317 upper and lower third molars were randomly divided into working and control samples and used to estimate chronological age employing a method which combined multiple regression analysis of data from Gustafson's and Maples's scoring system, direct morphological measurements obtained with a Kontron image analysis system and logarithmic data transformation. The standard errors of estimate were 2.4-6.8 years in the working sample and 1.9-7.5 years when the derived formulae were tested on the control sample, respectively. Compared to previous studies, this method provides a smaller standard error of estimate from a single molar tooth. The method is presently being tested on other tooth categories, like premolars, canines and other types of molars.
The effect of low dose He-Ne laser on the healing of intestinal anastomosis was studied in the albino rat. A small piece of jejunum was removed from each rat and the ends sutured back with a simple interrupted pattern. In the experimental animal, the anastomosis was irradiated through an optic fiber with a He-Ne laser (1 mW) for 15 minutes whereas in the control animal, the anastomosis was not irradiated. The differences between the two groups were compared by histology, transmission electron microscopy, scanning electron microscopy and autoradiography 3 and 7 days after operation. The laser treated experimental animals demonstrated thicker collagen fibers and an increased quantity of collagen at the junction of the anastomosis compared to control animals. Increased uptake of labelled proline was also evident in the laser treated animals. These observations all point to a possible enhancement of collagen synthesis triggered by laser irradiation.
The effects of low dose CW laser were studied by in vivo and in vitro systems. The experimental tissues that were used included bladders, tracheas and tongues as experimental tissues. Buddings (round surface projections) from the transitional epithelium of bladder were frequently observed 3 days after laser treatment in both in vivo and in vitro systems. The trachea and tongue were less affected. In both the in vivo and in vitro systems, some epithelial cells of the trachea showed decreased microvilli and cilia 3 days after treatment whereas the epithelial cells of the tongue revealed no response to laser treatment in both systems. Low dose laser, however, appeared to promote the rate of healing of experimental tongue ulcer: healing was about 1 day earlier in the laser treated than non-treated animals and vessel infiltration and epithelialization were detected earlier in the treated.
Black stain may develop on the coronal surfaces of human teeth, and this type of stain is common in the Hong Kong Chinese population. The present study was undertaken to ascertain if the deposit conforms in composition to the black stain found elsewhere, and to describe its ultrastructure using the scanning electron microscope. Gram-stained smears were made from black stain on the teeth of 11 adult Hong Kong Chinese and studied microscopically. From another 15 persons extracted teeth exhibiting black stain were obtained and fixed. Two ground sections were made from each tooth, one was stained with toluidine blue, the other was dried and prepared for scanning electron microscopy. The gram-stained smears demonstrated predominantly gram-positive filamentous microorganisms with an admixture of gram-positive cocci and rods. The ground sections revealed a deposit on the outer surface of the enamel, which was clearly divided into two distinctly different layers: an inner yellow opaque layer, and an outer layer of microorganisms. Scanning electron microscopy demonstrated that the deposit consisted entirely of microorganisms, and that in portions close to the enamel they were often obscured by a substance indicative of calcification. Thus the black stain found on the teeth of Hong Kong Chinese is similar in composition and structure to that reported to occur in other populations. The black stain is a special type of dental plaque characterized by its simple flora and its tendency to calcify.
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A teenage boy with mixed-cellularity Hodgkin disease presented with severe anemia secondary to pure red cell aplasia of marrow without evidence of lymphomatous infiltration or hemolysis. In vitro studies of the patient's serum demonstrated an inhibitor of erythropoietin activity which appeared to be an IgG but which did not directly bind erythropoietin. The patient's anemia resolved and the inhibitor disappeared following chemotherapy for Hodgkin disease. Presumably, the inhibitor was directed at a very early stage of red blood cell production. This phenomenon may be related to other autoimmune manifestations occasionally seen in patients with lymphomas. The case is presented to bring attention to the unusual occurrence of red cell aplasia in Hodgkin disease. Several hypotheses concerning significance and etiology of the anemia are detailed.
The remineralization effect of chewing gum containing fluoride (F) was studied on natural carious lesions. Maxillary acrylic appliances carrying the carious enamel sections were worn by three subjects. After 3 days of chewing 15 sticks of fluoride gum (Fluogum, containing 0.113 mg F/stick sweetened with xylitol/sorbitol), there was a significant reduction in both lesion depth and in the size of the body of the lesion (p less than 0.001). Exposure of carious lesions to 3 days in an oral environment without fluoride supplement reduced the size of the body of the lesions by an average of 5% (p less than 0.05). Chewing one or two sticks of the gum for 15 minutes raised the salivary-fluoride concentration to a peak of 1.13 ppm 5 minutes after chewing one stick, and raised the concentration to 2.73 ppm 10 minutes after chewing two sticks. The area under the curve of salivary-fluoride concentration versus time obtained following chewing one and two sticks were 0.78 h.microgram/ml and 1.89 h.micrograms/ml, respectively. There was a high positive correlation (r = 0.78) between the saliva flow and elimination of fluoride. Plaque fluoride level increased 1.7 fold following chewing two sticks of gum (p less than 0.05). The effect of chewing two sticks (a dose of 0.226 mg F) on plasma fluoride level was negligible, an indication of the safety of chewing gum regimen. More work is needed to document the cariostatic efficacy of a fluoride-containing chewing gum.