Relationship between body size and habitat complexity preference in age-0 and -1 year winter flounder Pseudopleuronectes americanus.

The interaction between body size, habitat complexity and interstice width on habitat preference of age-0 and -1 year Pseudopleuronectes americanus was examined using continuous remote video observation. The habitat choices of juvenile P. americanus were recorded over a 6 h period in tanks with four treatments: bare sand, sand with low complexity cobble, sand with intermediate complexity cobble and sand with high complexity cobble. Both age-0 and -1 year fish preferred cobble to bare sand. Within cobble treatments, age-0 year fish preferred intermediate complexity cobble, with a 1.59 ratio of interstitial space to body width. The largest age-1 year fish (123-130 mm standard length, L(S) ) preferred low complexity cobble. While a significant preference was not detected, medium age-1 year fish (83-88 mm L(S) ) tended to select low complexity cobble, whereas small age-1 year fish (73-82 mm L(S) ) tended to select low and intermediate cobble, with an interstitial space to body width ratio of 1.05. For medium and large age-1 year fish, there was an increased selection of low complexity cobble, corresponding to larger interstitial space to body size ratios. This study indicates that juvenile P. americanus prefer complex habitat to unstructured habitat and that this preference is mediated by a relationship between fish body size and the size of structure interstices. These results contribute to the growing body of knowledge of complex habitat selection and drivers of habitat choice in flatfishes.

Assessment of the pathogenicity of bacterial species isolated from acute dentoalveolar abscesses.

The pathogenicity of 20 strains belonging to nine bacterial species isolated from acute dentoalveolar abscesses was assessed individually and in two species combinations by subcutaneous inoculation of mice. Infections were produced by all the bacteria although variations were seen both in the type of lesion produced and the subsequent recovery of viable bacteria. Anaerobic gram-negative bacilli were recovered more often (p less than 0.05) at high concentrations (10(6)-10(9) cfu/ml) and produced a localised abscess with peripheral necrosis more frequently (p less than 0.001) than either Streptococcus milleri or anaerobic gram-positive cocci. Lesions induced by a combination of bacteria comprising anaerobic gram-negative bacillus and any other species yielded both strains at high concentration more often (p less than 0.001) than a combination comprising anaerobic gram-positive cocci and S. milleri. It is concluded that anaerobic gram-negative bacilli are major pathogens in acute dentoalveolar abscesses.

The role of iron deficiency in experimentally-induced oral candidosis in the rat.

In comparison with normal rats, those with iron deficiency anaemia showed no significant difference in susceptibility to experimental infection with Candida albicans although anaemic rats had a significantly greater incidence of persistent infection. These findings support the suggestion that patients with chronic candidosis should be investigated for iron deficiency.

Spread of squamous cell carcinoma to the nonirradiated edentulous mandible--a preliminary report.

The changes in the mandible and in its relationship to surrounding soft tissue structures after loss of the teeth are described; the regular presence of deficiencies in the cortical bone along the line of the occlusal ridge is emphasized. Resection specimens of squamous carcinoma of the oral cavity not treated by radiotherapy were examined where there was mandibular involvement by tumor, and showed that the main route of tumor entry into the bone was through the occlusal ridge. Subsequent perineural spread along the inferior alveolar nerve has been found to be a regular occurrence.

Routes of entry of squamous cell carcinoma to the mandible.

A recent preliminary report of a study to determine the patterns of invasion of squamous cell carcinoma to the nonirradiated edentulous mandible indicated that tumor entered mainly through the residual alveolar occlusal ridge. This study has now been extended and includes both nonirradiated and irradiated mandibles. Of a total of 46 nonirradiated mandibles (10 partially dentate and 36 edentulous) invaded by tumor, 41 were invaded through the occlusal surface. This confirms the findings of the preliminary report. These findings indicate that there is a rational basis on pathologic grounds for adopting a conservative approach to the nonirradiated mandible. In 16 irradiated mandibles, the routes of tumor entry were found to be much more variable than in the nonirradiated mandible. In 16 irradiated mandibles, the routes of tumor entry were found to be much more variable than in the nonirradiated mandible, and multiple foci of tumor invasion of the bone were often present wherever tumor in adjacent soft tissues approached the bone. This variability of tumor entry means that a conservative approach to mandibular excision cannot be pursued in the previously irradiated mandible and full-thickness segmental resection is necessary if bone involvement appears likely.

Reactive changes in the mandible in the presence of squamous cell carcinoma.

A series of 80 mandibles, which were removed as part of composite resections for primary intraoral squamous cell carcinoma, was examined. Of these, 58 were nonirradiated and 22 were previously irradiated. Several changes were observed in the nonirradiated mandible in response to invading tumor. Deposition of new bone was obvious on the periosteal and endosteal surfaces. Osteoclastic resorption of bone was prominent and there was replacement of hemopoietic marrow by fibrous tissue. By contrast, it was found in the irradiated specimens that osteoblastic activity was absent but that osteoclastic activity persisted. The hemopoietic marrow was replaced by fibrous tissue. The lack of osteoblastic activity was interpreted as being due to irradiation. The extent of these changes and their relationship to the invading tumor have implications for both surgeon and pathologist.

Mandibular osteotomy in the surgical approach to the oral cavity.

The improved stability that results from the combination of K-wire transfixion of a mandibular osteotomy with direct wiring has made it possible to use a straight, as opposed to a stepped, bone cut and to avoid the invariable need for dental extractions. It has also made possible an alternative osteotomy site, immediately anterior to the mental foramen. The use of this site allows mandibular swing to take place after division only of mucous membrane and mylohyoid. It is best combined with a modified lip-splitting incision which has been found to improve ultimate cosmesis.

Production of a nonwettable enamel surface.

A water-repellent enamel surface was achieved using a new material that is a combination of fumed silicon dioxide and a silane. The effects of this coating on enamel were studied. In vitro studies suggest that the material produces good water and saliva repellency. However, no reduction in bacterial colonization between treated and control enamel occurred. results of in vivo investigations of coated and control Styroflex strips showed a reduction in deposits on the former. Retention with or without previous acid etching of the enamel was poor.

Investigations into black extrinsic tooth stain.

An investigation has been carried out into the nature of the black pigment in black extrinsic tooth stain. The results suggest that the black material is a ferric salt, probably ferric sulfide, formed by the reaction between hydrogen sulfide produced by bacterial action and iron in the saliva or gingival exudate.

The ability of lymphoscintigraphy to direct sentinel node biopsy in the clinically N0 neck for patients with head and neck squamous cell carcinoma.

This study aimed to evaluate the ability of lymphoscintigraphy (LSG) to direct sentinel node biopsy (SNB) in the identification of occult metastases in the clinically N0 neck for patients with head and neck squamous cell carcinoma (HNSCC). 57 clinically N0 neck sides in 48 patients were assessed using the triple diagnostic approach of pre-operative LSG, intra-operative use of a gamma probe and blue dye. SNB was performed after radiocolloid and blue dye injection. Pre-operative LSG and the intra-operative use of a gamma probe identified radioactive sentinel nodes, and visualization of blue stained lymphatics identified blue sentinel nodes. 104 sentinel nodes were harvested from 43 patients. The identification rate was 90% (43 of 48). Of the 104 nodes harvested, 17 of 62 (27%) nodes identified as both radioactive and blue were positive for occult metastases compared with 5 of 42 (12%) nodes identified as hot or blue only (p<0.05). Sentinel nodes were identified in 39 of 48 (81%) patients using LSG. Of 39 patients in whom sentinel nodes were identified using LSG, 37 of 39 (95%) had radioactive sentinel nodes harvested intra-operatively. In patients who had no sentinel nodes identified on LSG, 4 of 9 (44%) had radioactive sentinel nodes harvested intra-operatively. This difference was statistically significant using the t-test (p<0.05). LSG directs SNB and is essential in the identification of occult metastases within the clinically N0 neck for patients with HNSCC.

Diurnal variation in labelling index in human buccal epithelium.

Diurnal variations in the number of DNA-synthesizing cells (labelling index) in human buccal epithelium were studied by in vitro pulse labelling with tritiated deoxythymidine. Eleven male volunteers provided 33 biopsy specimens at six time periods. The results showed a 24-h periodicity in the labelling index in this tissue. The mean peak labelling index obtained at 22:00 h (3.20 +/- 0.18) was significantly different from the means obtained at the rest of the times. The 24-h mean labelling index (labelled cells/100 cells) was 2.48 +/- 0.47 for three subjects who volunteered samples at all six time periods. The labelling index obtained around the middle part of the day for all subjects (2.44-2.59) appears to be representative of a 24-h basal or reference value.

Quantitative histological analysis of the epithelium of the ventral surface of hamster tongue in experimental iron deficiency.

Quantitative analysis of the ventral tongue epithelium of iron-deficient hamsters revealed significant progressive alterations in epithelial compartment thickness. As iron deficiency developed there was an initial increase in the proportion of the epithelium made up by progenitor cells and a decrease in the proportion formed by maturing cells. With increasing degree of deficiency, the maturation compartment formed less, and the keratinized compartment more, of the epithelium until, at the stage of anaemia, there was a significant reduction in the maturation compartment and a significant increase in the keratin thickness.

The influence of rate of cell entry to S phase on the labelling index of human buccal epithelium.

The physiological basis of the circadian rhythm in cell kinetics in human epithelia remains unclear. A 24-h periodicity in the labelling index (LI) of human buccal epithelium has been demonstrated previously. A double-labelling technique in vitro using tritiated deoxythymidine was used here to examine fluctuations in the time spent in S phase (Ts) and the rate of cell entry to S phase (S influx). While the range in Ts values was limited (5.1-6.9 h), influx to S phase ranged from 0 to 1.26% per hour at six different time periods. An increase in the S influx was apparent around 18:00 h leading to a peak LI 4 h later. These preliminary data indicate that the most likely kinetic mechanism related to circadian variations in LI is a variable G1-S influx at this site.

Cell kinetics of hamster ventral tongue epithelium in iron deficiency.

The cell-kinetic parameters of labelling index and duration of the S phase of the cell cycle (Ts) were investigated in the ventral tongue epithelium of hamsters with experimentally-induced iron deficiency. The labelling indices in animals with iron-deficiency anaemia and iron deficiency without anaemia did not differ from normal, but the Ts values were significantly shorter indicating an increased cell-production rate. The epithelial cell-kinetic parameters of iron-depleted animals did not differ from normal, but the labelling index was greater than in animals with the more severe stages of iron deficiency.

Effect of prolonged iron deficiency on enamel pigmentation and tooth structure in rat incisors.

The effect of iron deficiency maintained for over 6 months on the pigmentation and structure of incisors was investigated in female white rats. Gross loss of pigmentation was observed. Sections revealed enamel hypoplasia and aplasia. Dentinogenesis was much less affected, but there were areas of altered dentine with abnormal tubules and increased thickness of predentine with cellular and vascular inclusions.

A forensic classification of distortion in human bite marks.

The occurrence of distortion in human bite marks is well recognised. A forensic classification of distortion is suggested which is based upon the causative factors and their inter-relationships. The terms primary distortion and secondary distortion are introduced and described. The objective of this classification is to emphasise the need for a scientific approach to the recognition and interpretation of the types of distortion found in human bite marks. The relationships between distortion, distinctive features and superimposition techniques in bite mark analysis are discussed.

Histological, microbiological and haematological investigations in denture-induced stomatitis.

Biopsy specimens of palatal mucosa from 10 edentulous female subjects exhibiting the signs of chronic atrophic denture-induced stomatitis were fixed and processed to produce sections which were quantitatively analysed by light microscopy. The type and degree of surface keratinization, the epithelial thickness and basement membrane morphology were assessed. Microbiological and haematological evaluations were related to the histological findings. It was found that within this clinical entity of palatal inflammation there was considerable variation in tissue response at a cellular level, and that the numbers of organisms associated with the inflammatory reaction appeared to be fewer in patients with abnormal haematological status.

Rat palatal histology related to denture-like appliances.

Two designs of palatal denture-like appliance were fitted to rats. Tooth- and tissue-borne appliances caused changes in epithelial thickness and keratin thickness, but these varied with anatomical site and type of appliance. A single inoculation of Candida albicans at the time of insertion of the appliance failed to establish infection consistently. Debris accumulation under the appliances was a problem which will restrict long-term studies with this model.

The effect of chairside relining materials on rat palatal mucosa.

OBJECTIVES: To investigate the effects of denture relining materials on oral mucosa in vivo in a rat model. METHODS: Denture-like appliances covering the palate in Wistar rats were relined with a resilient soft linting material and a hard 'chairside' relining material. The effects on the palatal epithelium were studied by quantitative analysis using computerized planimetry. RESULTS: The relining materials caused an increase in the thickness of the keratinized layer, while not increasing the total epithelial thickness. CONCLUSIONS: Relining materials are not totally without effect on oral mucosa. Further in vivo research is indicated.

The effect of diet on palatal prosthetic coverage in rats.

UNLABELLED: Previous studies have used a rate model for examination of the histopathology of oral candidiasis or mucosal coverage with dental prostheses. These studies have been complicated by the presence of accumulated debris between mucosa and prostheses. OBJECTIVES: The present study was undertaken to develop further the Wistar rat as a suitable animal model on which to study the effects of dental prostheses on oral mucosa. METHODS: The effects of three dietary regimes, used for 7 and 14 days, upon debris accumulation under denture-like appliances and measurable epithelial parameters were analysed by computerised planimetry. RESULTS: Individual variation in animal weights during the study was noted, with some appliance-wearing animals exhibiting a weight gain while others lost weight. A powdered diet used in a paste form gave the least accumulation of debris under appliances and the least differences between appliance wearers and controls. CONCLUSION: The use of the Wistar rat model utilising the past diet described is indicated for future investigation of the effect of prostheses on oral mucosa.