High frequency ultrasound imaging of a single-species biofilm

OBJECTIVE: This study evaluated the feasibility of a high frequency ultrasound scan to examine the 3D morphology of Streptococcus mutans biofilms grown in vitro. METHODS: Six 2-day S. mutans biofilms and six 7-day biofilms were grown on tissue culture membranes and on bovine dentine discs. A sterile growth medium on the membrane and disc were used as controls. Surfaces were rinsed and then immersed in sterile saline. High-frequency ultrasound imaging system was used to scan these surfaces at 55MHz, and a computer program calculated the average thickness of the biofilm layer from the 3D images. RESULTS: 3D pictures of the biofilm layers were obtained. Different cross-sections and plains are easily demonstrated. The average thickness of the 7-day biofilm was significantly bigger than the 2-day on both the membranes and dentinal discs. No structures were observed on the sterile membrane or disc. CONCLUSION: Three-dimensional structural imaging in situ is possible without damaging the biofilm layer in a quick and easy manner and can therefore be used to evaluate biofilms longitudinally as a function of time.     

Autofluorescence of bulk sound and in vitro demineralized human root dentin

The aim of this paper is to report on the demineralization-induced changes in dentin autofluorescence. Confocal laser scanning microscopy (CLSM) images and fluorescence excitation and emission spectra of in vitro demineralized root surfaces and sound controls on the same tooth roots were compared. When observed in CLSM images, demineralized dentin, excited at 488 nm. gave an increased emission at 529 nm compared to sound dentin. The difference in fluorescence decreased deeper into the root, as the sound dentin underneath the lesion was reached. In contrast, when using fluorescence spectrophotometry, excitation around 460 and 488 nm yielded a lower emission around 520 nm for demineralized dentin than for sound dentin, but in a more pronounced peak. From excitation spectra for emission around 520 nm. it could be seen that in demineralized dentin the contribution of excitation between 480 and 520 nm was more important than in sound dentin. The recorded fluorescence in CLSM images was not affected by demineralization-caused changes in scattering and absorption properties, due to the small measurement volume. Thus, the increased fluorescence for demineralized dentin implies an increased quantum yield. In fluorescence spectrophotometry. where the measurement volume is large, changes in scattering and absorption do have an influence on the fluorescence signal. Then, increased absorption by non-fluorescing chromophores and increased re-absorption around the emission wavelength may compensate for the increase in quantum yield and absorption around the excitation wavelength by fluorophores.     

Non-contact removal of coadhering and non-coadhering bacterial pairs from pellicle surfaces by sonic brushing and de novo adhesion

Coadhesion between oral microbial pairs is an established factor in the spatiotemporal development and prevalence of mixed-species communities in early dental plaque in vivo. This study compares removal and de novo adhesion of pairs of coadhering and non-coadhering oral actinomyces and streptococci by sonic brushing on salivary pellicles in a non-contact mode as a function of the distance between the brush and the pellicle surface in vitro. First, actinomycetes were adhered to a pellicle surface, after which streptococci suspended in saliva were allowed to adhere. Removal was examined by non-contact, sonic brushing with a wetted brush on a either a wetted or a substratum immersed to a depth of 7 mm. After brushing, de novo adhesion of streptococci to brushed pellicles was studied. For coadhering and non-coadhering pairs, 34% and 9%, respectively, of the adhering bacteria were involved in aggregates comprising more than 10 organisms. Non-contact, sonic brushing removed up to 99% of the adhering bacteria, regardless of the state of immersion of the substratum. Bacterial removal decreased with increasing distance of up to 6 mm between brush and pellicle surface. For the non-coadhering pair, subsequent exposure of pellicles to a streptococcal suspension yielded about 6% of bacteria involved in large aggregates. Alternatively, de novo adhesion of the coadhering streptococcal strain to pellicles brushed on the wetted substratum yielded 31% of bacteria involved in large aggregates, but after brushing the immersed substratum only 12% of the adhering bacteria were found in large aggregates. It is concluded that non-contact sonic brushing, under immersion, removes high percentage of adhering bacterial pairs up to a distance of 6 mm between the brush and the pellicle surface. However, non-contact, sonic brushing with only a thin wet film on the substratum may leave footprints to which streptococci preferentially adhere.     

A giant osteoma of the mandible: case report.

A 53-year-old patient with a giant osteoma of the right mandible is presented. The clinicopathological features of osteoma of the mandible are discussed and Gardner's syndrome was excluded.     

Granulocyte elastase in gingival crevicular fluid: improved monitoring of the site-specific response to treatment in patients with destructive periodontitis

Abstract In 13 patients with severe destructive periodontitis. the response to periodontal therapy was estimated by granulocyte elastase level in gingival crevicular fluid (GCF). 62 sites were classified according to changes of probing depths (PD) and quantitative bone height (BH%) before and after 5–year regular maintenance treatment: (i) 17 consistently healthy sites with no changes of PD and BH%; (ii) 6 initially healthy sites with deterioration in PD and BH%; (iii) 14 diseased sites with improvement in PD and BH%; (iv) 25 diseased sites with no improvement in PD and BH%. GCF was collected by an intracrevicular washing system. The released elastase in the supernatants (EA-S) and the cell-bound elastase in the pellets (EA-P) were determined with a low molecular weight substrate specific for granulocyte elastase. The ratio of EA-S and EA-P (S/P-ratio) was used as a relative measure of elastase released by the granulocytes present. The sites classified as diseased with no improvement or initially healthy but deteriorating, had significantly higher EA-S, EA-P and S/P-ratios than the consistently healthy sites or diseased but improving sites (p < 0.01). Both EA-S and S/P-ratio showed strongly positive correlations with the current levels of gingival inflammation and periodontal destruction (p < 0.001). The present study suggests that increased elastase level is associated with disease progression, and may be used to monitor the response to longitudinal maintenance therapy.     

Tobacco and alcohol related to the anatomical site of oral squamous cell carcinoma

The aim of the present study was to evaluate the possible relationship between tobacco smoking and alcohol drinking and the anatomical sites of squamous cell carcinoma (SCC) of the lip and oral cavity. For this purpose, a case-case study has been performed in 690 patients. The study was focused on the relative risk (RR) or developing SCC at various (sub)sites, for smokers and drinkers of alcohol (divided into moderate and heavy users) relative to non-smokers and non-drinkers. Estimates of ratios of these relative risks were obtained. The relative risk associated with tobacco smoking, adjusted for the use of alcohol, appeared to be highest for SCC in the retromolar area, followed by the floor of mouth, whereas the lowest RR was found in the cheek mucosa. For alcohol drinking, adjusted for tobacco smoking, RR of SCC of the floor of mouth was significantly higher than for the tongue, whereas the RR of SCC of the cheek appeared to be lowest. Furthermore, this study suggests that the contrasts between relative risks, observed by anatomical site of oral SCC, are more pronounced for tobacco smoking than for the use of alcohol. The possible local and systemic factors responsible for these variations of susceptibility for tobacco and alcohol within the oral cavity are discussed.     

Swallowing thresholds of mandibular implant-retained overdentures with variable portion sizes

We analysed the effect of three portion sizes Optocal Plus (small, medium and large) on swallowing thresholds in subjects with either conventional complete dentures or mandibular implant-retained overdentures (transmandibular and permucosal cylindric implants). Tests were carried out in 52 women and 15 men (mean age 59 years) 4 years after treatment in a randomised controlled clinical trial. The results indicated that the degree of mucosal support for the mandibular denture did not affect the number of chewing strokes, time till swallowing or swallowed particle size. Only the chewing rate differed: subjects wearing mandibular implant-retained overdentures chewed the food at a higher rate than complete-denture wearers. With larger portion sizes, subjects needed significantly more chewing strokes and time until swallowing and they would have swallowed larger particles. Men chewed their food more efficiently than women, as they used the same number of chewing strokes and time, but achieved a greater particle size reduction at the swallowing moment.     

Salivary secretion and chewing: stimulatory effects from artificial and natural foods

The aim of the present study was to determine the relationship between the flow rate of saliva and characteristics of the food. Therefore, we determined the rate of saliva secretion in 16 healthy subjects in rest and while chewing natural and artificial foods (toast with and without margarine, three sizes of breakfast cake, and Parafilm). We also determined the chewing rate, number of chewing cycles until swallowing, and time until swallowing. The physical characteristics of the foods were quantified from force-deformation experiments. The results showed that the average at which mechanical failure occurred (yield force) was 1.86 ± 0.24 N for the breakfast cake and 16.3 ± 1.3 N for the melba toast. The flow rates obtained without stimulation and with Parafilm were significantly lower (P < 0.001) than the flow rates obtained from chewing food. No differences in flow rate occurred between the natural foods. The flow rates of the saliva as obtained without stimulation, with Parafilm stimulation, and with chewing on the various foods were significantly correlated (P < 0.05). There were no significant differences in chewing rate among the foods. The number of chewing cycles and the time until swallowing significantly depended on the type or volume of the food.