Observational study on the non-linear response of dolphins to the presence of vessels

With the large increase in human marine activity, our seas have become populated with vessels that can be overheard from distances of even 20 km. Prior investigations showed that such a dense presence of vessels impacts the behaviour of marine animals, and in particular dolphins. While previous explorations were based on a linear observation for changes in the features of dolphin whistles, in this work we examine non-linear responses of bottlenose dolphins (Tursiops Truncatus) to the presence of vessels. We explored the response of dolphins to vessels by continuously recording acoustic data using two long-term acoustic recorders deployed near a shipping lane and a dolphin habitat in Eilat, Israel. Using deep learning methods we detected a large number of 50,000 whistles, which were clustered to associate whistle traces and to characterize their features to discriminate vocalizations of dolphins: both structure and quantities. Using a non-linear classifier, the whistles were categorized into two classes representing the presence or absence of a nearby vessel. Although our database does not show linear observable change in the features of the whistles, we obtained true positive and true negative rates exceeding 90% accuracy on separate, left-out test sets. We argue that this success in classification serves as a statistical proof for a non-linear response of dolphins to the presence of vessels.

First report on the serum chemistry and haematology of free-ranging dusky (Carcharhinus obscurus) and sandbar (Carcharhinus plumbeus) sharks in the eastern Mediterranean Sea

Shark assessments in the Mediterranean Sea are still scarce, and serum chemistry and haematological data have yet to be reported for wild dusky (Carcharhinus obscurus) or sandbar (Carcharhinus plumbeus) shark populations in the Mediterranean Sea. Herein, blood samples were obtained from adult dusky (n = 23) and sandbar (n = 14) sharks from an aggregation site near the Hadera power and desalination plants in Israel in the winters of 2016-20. Several serum chemistry analytes were characterized with relation to stress, body size and environmental conditions. Glucose concentrations were higher, while total cholesterol concentrations were lower in dusky sharks than in sandbar sharks, potentially due to distinct metabolic pathways utilized during the capture-related activity by both species. However, differences in sex and size are noted and should be considered. The blood cell morphology of both species was consistent with previous findings for sandbar sharks. Atypical monocytes were noted in one dusky shark. Preliminary and exploratory reference intervals for female dusky sharks were calculated for glucose, triglycerides, total cholesterol, total protein and creatine kinase. These data must be viewed with caution due to the potential influence of capture-related stress on analyte concentrations and activities and the fact that only females were employed in the calculations. Moreover, the sampling site is adjacent to coastal power and desalination plants, which may significantly affect shark physiology. Although limited, this novel database on dusky and sandbar shark serum chemistry and haematology aspects is essential as a first attempt to obtain data on these species in the eastern Mediterranean Sea and for future conservation and long-term biomonitoring efforts.

Preliminary study of shark microbiota at a unique mix-species shark aggregation site, in the Eastern Mediterranean Sea

Sharks, as apex predators, play an essential ecological role in shaping the marine food web and maintaining healthy and balanced marine ecosystems. Sharks are sensitive to environmental changes and anthropogenic pressure and demonstrate a clear and rapid response. This designates them a "keystone" or "sentinel" group that may describe the structure and function of the ecosystem. As a meta-organism, sharks offer selective niches (organs) for microorganisms that can provide benefits for their hosts. However, changes in the microbiota (due to physiological or environmental changes) can turn the symbiosis into a dysbiosis and may affect the physiology, immunity and ecology of the host. Although the importance of sharks within the ecosystem is well known, relatively few studies have focused on the microbiome aspect, especially with long-term sampling. Our study was conducted at a site of coastal development in Israel where a mixed-species shark aggregation (November-May) is observed. The aggregation includes two shark species, the dusky (Carcharhinus obscurus) and sandbar (Carcharhinus plumbeus) which segregate by sex (females and males, respectively). In order to characterize the bacterial profile and examine the physiological and ecological aspects, microbiome samples were collected from different organs (gills, skin, and cloaca) from both shark species over 3 years (sampling seasons: 2019, 2020, and 2021). The bacterial composition was significantly different between the shark individuals and the surrounding seawater and between the shark species. Additionally, differences were apparent between all the organs and the seawater, and between the skin and gills. The most dominant groups for both shark species were Flavobacteriaceae, Moraxellaceae, and Rhodobacteraceae. However, specific microbial biomarkers were also identified for each shark. An unexpected difference in the microbiome profile and diversity between the 2019-2020 and 2021 sampling seasons, revealed an increase in the potential pathogen Streptococcus. The fluctuations in the relative abundance of Streptococcus between the months of the third sampling season were also reflected in the seawater. Our study provides initial information on shark microbiome in the Eastern Mediterranean Sea. In addition, we demonstrated that these methods were also able to describe environmental episodes and the microbiome is a robust measure for long-term ecological research.

A survey of arsenic, mercury, cadmium, and lead residues in seafood (fish, crustaceans, and cephalopods) from the south-eastern Mediterranean Sea

Seafood is capable of bioaccumulating heavy metals (HM), making it a potentially major dietary source of HM for humans. Presently, little data exists on seafood from the eastern-most boundary of the Mediterranean Sea. This study aims to provide exposure insight of the Israeli population to HM through the consumption of locally caught seafood by assessing the levels of arsenic, mercury, cadmium, and lead in raw tissues of seafood. A wide survey of local fisheries was conducted providing 296 samples from 11 different species, including seven fish, two crustacean, and two cephalopod species. Total arsenic, cadmium, and lead were analyzed by graphite-furnace atomic absorption. Total mercury was measured by cold-vapor mercury analyzer. Arsenic speciation was performed by anion chromatography-inductively coupled plasma sector field mass spectrometry. Results suggested that the total arsenic concentrations were significantly higher in crustaceans and cephalopods than fish. Arsenic speciation revealed two samples that exceed 1 mg/kg of inorganic arsenic, whereas methylated arsenic was below the detection limit. Elevated mercury levels were detected in the commercial benthic species Mullus barbatus (red mullet), cadmium was detected in one-third of the samples, and lead detected in eight samples. Comparing the results to health guidelines, 99.4% of seafood tested in this study abide with acceptable levels of heavy metals in seafood, as defined by both Israeli and European Union guidelines.

Specific pathogens and microbial abundance within liver and kidney tissues of wild marine fish from the Eastern Mediterranean Sea

This study is an initial description and discussion of the kidney and liver microbial communities of five common fish species sampled from four sites along the Eastern Mediterranean Sea shoreline. The goals of the present study were to establish a baseline dataset of microbial communities associated with the tissues of wild marine fish, in order to examine species-specific microbial characteristics and to screen for candidate pathogens. This issue is especially relevant due to the development of mariculture farms and the possible transmission of pathogens from wild to farmed fish and vice versa. Although fish were apparently healthy, 16S rRNA NGS screening identified three potential fish bacterial pathogens: Photobacterium damselae, Vibrio harveyi and Streptococcus iniae. Based on the distribution patterns and relative abundance, 16 samples were classified as potential pathogenic bacteria-infected samples (PPBIS). Hence, PPBIS prevalence was significantly higher in kidneys than in liver samples and variation was found between the fish species. Significant differences were observed between fish species, organs and sites, indicating the importance of the environmental conditions on the fish microbiome. We applied a consistent sampling and analytical method for monitoring in long-term surveys which may be incorporated within other marine fish pathogens surveys around the world.

Prevalence of nervous necrosis virus (NNV) and Streptococcus species in wild marine fish and crustaceans from the Levantine Basin, Mediterranean Sea

Infectious diseases in marine animals have ecological, socio-economic and environmental impacts. Nervous necrosis virus (NNV) and Streptococcus iniae have become major threats to marine aquaculture and have been detected in morbid marine organisms worldwide. However, despite their importance, there is a lack of knowledge regarding the prevalence of these pathogens in wild fish species. Here we sampled indigenous and Lessepsian species from different trophic levels and different biological niches in the eastern Mediterranean. A total of 174 fish and 32 crustaceans were tested for S. iniae and a total of 195 fish and 33 crustaceans were tested for NNV. We found an overall prevalence of 9.71% Streptococcus spp. and 21.49% NNV in selected marine fish and crustaceans by PCR and qPCR. In fish, the zoonotic agent S. iniae was detected at a higher prevalence in kidney compared to liver tissue. Co-infection by both pathogens was detected only in 5 specimens. We also examined gilthead sea bream Sparus aurata from an Israeli offshore marine farm during the grow-out period, in order to assess the possibility of horizontal pathogen transmission from wild to maricultured fish. Three out of 15 (20%) fish were found to be NNV positive after 120 d in the sea, suggesting spontaneous transmission from wild to farmed fish. Our findings suggest that more surveys should be conducted, especially in areas were mariculture farms are planned to be established.

Comparative effects of dexmedetomidine, propofol, sevoflurane, and S-ketamine on regional cerebral glucose metabolism in humans: a positron emission tomography study

INTRODUCTION

The highly selective α₂-agonist dexmedetomidine has become a popular sedative for neurointensive care patients. However, earlier studies have raised concern that dexmedetomidine might reduce cerebral blood flow without a concomitant decrease in metabolism. Here, we compared the effects of dexmedetomidine on the regional cerebral metabolic rate of glucose (CMR_glu) with three commonly used anaesthetic drugs at equi-sedative doses.

METHODS

One hundred and sixty healthy male subjects were randomised to EC₅₀ for verbal command of dexmedetomidine (1.5 ng ml^-1; n=40), propofol (1.7 μg ml^-1; n=40), sevoflurane (0.9% end-tidal; n=40) or S-ketamine (0.75 μg ml^-1; n=20) or placebo (n=20). Anaesthetics were administered using target-controlled infusion or vapouriser with end-tidal monitoring. ¹⁸F-labelled fluorodeoxyglucose was administered 20 min after commencement of anaesthetic administration, and high-resolution positron emission tomography with arterial blood activity samples was used to quantify absolute CMR_glu for whole brain and 15 brain regions.

RESULTS

At the time of [F¹⁸]fluorodeoxyglucose injection, 55% of dexmedetomidine, 45% of propofol, 85% of sevoflurane, 45% of S-ketamine, and 0% of placebo subjects were unresponsive. Whole brain CMR_glu was 63%, 71%, 71%, and 96% of placebo in the dexmedetomidine, propofol, sevoflurane, and S-ketamine groups, respectively (P<0.001 between the groups). The lowest CMR_glu was observed in nearly all brain regions with dexmedetomidine (P<0.05 compared with all other groups). With S-ketamine, CMR_glu did not differ from placebo.

CONCLUSIONS

At equi-sedative doses in humans, potency in reducing CMR_glu was dexmedetomidine>propofol>ketamine=placebo. These findings alleviate concerns for dexmedetomidine-induced vasoconstriction and cerebral ischaemia.

CLINICAL TRIAL REGISTRATION

NCT02624401.

Assessing cetacean surveys throughout the Mediterranean Sea: a gap analysis in environmental space

Heterogeneous data collection in the marine environment has led to large gaps in our knowledge of marine species distributions. To fill these gaps, models calibrated on existing data may be used to predict species distributions in unsampled areas, given that available data are sufficiently representative. Our objective was to evaluate the feasibility of mapping cetacean densities across the entire Mediterranean Sea using models calibrated on available survey data and various environmental covariates. We aggregated 302,481 km of line transect survey effort conducted in the Mediterranean Sea within the past 20 years by many organisations. Survey coverage was highly heterogeneous geographically and seasonally: large data gaps were present in the eastern and southern Mediterranean and in non-summer months. We mapped the extent of interpolation versus extrapolation and the proportion of data nearby in environmental space when models calibrated on existing survey data were used for prediction across the entire Mediterranean Sea. Using model predictions to map cetacean densities in the eastern and southern Mediterranean, characterised by warmer, less productive waters, and more intense eddy activity, would lead to potentially unreliable extrapolations. We stress the need for systematic surveys of cetaceans in these environmentally unique Mediterranean waters, particularly in non-summer months.

The Rough-Toothed Dolphin, Steno bredanensis, in the Eastern Mediterranean Sea: A Relict Population?

Only recently included among the cetacean species thought to regularly occur in the Mediterranean, the rough-toothed dolphin (Steno bredanensis) is an obscure and enigmatic member of this ensemble. Preliminary genetic evidence strongly indicates an Atlantic origin, yet the Mediterranean distribution for this species is conspicuously detached from the Atlantic, with all authenticated records during the last three decades being east of the Sicilian Channel and most within the bounds of the Levantine Basin. These dolphins are apparently a small, relict population, probably the remnant of a larger one, contiguous with that in the Atlantic and nowadays entrapped in the easternmost and warmest province. Abundance data are lacking for the species in the Mediterranean. Configuring acoustic detection software to recognise the apparently idiosyncratic vocalisations of rough-toothed dolphins in past and future acoustic recordings may prove useful for potential acoustic monitoring. Evidence accumulated so far, though scant, points to seasonal occupation of shallow coastal waters. Vulnerability to entanglement in gill-nets, contaminants in the region, and the occurrence of mass strandings (possibly in response to anthropogenic noise), are major conservation concerns for the population in the Mediterranean Sea.

Early physical maturation of female common bottlenose dolphin Tursiops truncatus in the eastern Levantine Basin

Regional resource limitation in the eastern Levantine Basin was predicted to protract the growth of members of the Israeli sub-population of the common bottlenose dolphin (CBD), compared to CBD sub-populations of similar adult size. Growth curves were fitted to length-at-age data available for 24 male and 26 female CBD stranded or incidentally caught along the Israeli coastline between 2000 and 2009. The obtained model growth constants were compared to those of other CBD sub-populations from the southeastern coast of the United States and a correlation to regional seawater primary productivity was sought. As in other sub-populations, local CBD females initially grow faster than males for approximately 3–4 years and remain longer until around eight years old, after which males surpass them in length. Yet the steep early growth of females as well as its high rate of decay was found to be extreme compared to other CBD sub-populations, with 99% of the asymptotic length being reached at the age of six years. A positive correlation between seawater primary productivity and early growth rate as well as growth decay constants could be demonstrated for CBD males from Texas, Florida and Israeli coasts. Females of the same sub-population presented a non-monotonic relationship to primary productivity. Early female attainment of physical maturity in an ultra-oligotrophic region was unpredicted and is not readily explained. It may accompany early reproductive maturation, selected for as partial compensation for lower lifelong reproductive success.

Persistent organochlorine pollutants and heavy metals in tissues of common bottlenose dolphin (Tursiops truncatus) from the Levantine Basin of the Eastern Mediterranean

DDT's, PCBs and heavy metals (HM) were measured in tissues of common bottlenose dolphins, collected along the Israeli Mediterranean coast during 2004-2006. SigmaDDT and PCBs concentrations were highest in the blubber, with a wide concentration range of 0.92-142 and 0.05-7.9 mg kg(-1) wet weight, respectively. Blubber PCBs values were an order of magnitude lower than in tissues of this and other delphinid species in the Western Mediterranea. We found relatively high DDE/SigmaDDT percentage (85-96%); a common indicator of DDT degradation, which fitted the general trend of increase in the last 20 years in the Mediterranean Sea, indicating the progressive degradation of the remnant DDT and the absence of new inputs. Concentrations of HM ranged as follows: 0.01-123 mg kg(-1) wet weight for Hg, <0.04-1.3 for Cd, 1-30 for Cu, 0.3-4 for Mn, 19-517 for Fe, 4.3-68 for Zn and 2.4-48 for Ni. These concentrations were similar to those found in specimens collected during previous years in the region, suggesting stability over time in the HM levels of the basin's food-web.

Multifactorial modeling for prediction of caries increment in adolescents

The purpose of the study was to develop a multifactorial model for the prediction of 11-month caries increment in adolescents. The mean age of the subjects (n = 181) at the base-line examination was 13 years and 3 months. The risk indicators consisted of past caries experience, white spot lesions, visible plaque, gingivitis, salivary secretion rate, buffer effect, sucrase, mutans streptococci, lactobacilli, and Candida. The multifactorial modeling included all the above risk indicators, age, and gender and resulted in different models in boys and girls, indicating the difficulty of caries prediction in adolescents. When boys and girls were combined, the final model included past caries experience, Candida, and salivary sucrase. Although the accuracy of the model was slightly below the 80% level recommended for screening purposes, the results provide clinically valuable information. The risk of caries increases with an increasing number of positive tests within the model.

Assessment of single risk indicators in relation to caries increment in adolescents

Base-line data on a series of risk indicators were related to 11-month caries increment in 181 subjects with a mean age of 13 years and 3 months. A caries increment equalling or exceeding one tooth surface was recorded in 21% of the subjects. The risk indicators consisted of past caries experience, white spot lesions, visible plaque and gingivitis, and six salivary tests: secretion rate, buffer effect, sucrase, mutans streptococci, lactobacilli, and Candida. Significant associations between caries increment and past caries experience (p = 0.002), white spot lesions (p = 0.01), lactobacilli (p = 0.02), Candida (p = 0.006), and sucrase (p = 0.02) were observed. The ensuing odds ratios were thus recorded: past caries experience, 3.6; white spot lesions, 2.9; salivary sucrase activity, 2.9; lactobacilli, 2.5; and Candida, 2.8.

Multifactorial modeling for root caries prediction: 3-year follow-up results

The study was part of a series aiming at the development of caries tests. The initial material (n = 104, age range 47-79 yr, mean 62 yr) was reduced to 96, who were observed for 3 yr. During the follow-up four subjects died, all due to myocardial infarction, and four refused to participate. Thorough oral examinations were conducted at the baseline, 1- and 3-yr registrations; coronal and root surface caries were registered separately according to WHO classification. The tests included salivary mutans streptococci, lactobacilli, candida/yeasts, secretion rate, buffer effect and sucrase activity, and quantitation of visible plaque. The association between prospective root caries increment and several tests was significant. Multifactorial modeling resulted in the combination of Past Root Caries Experience (OR 12.8), Lactobacilli (OR 8.6) and Candida (OR 2.8). At screening, the criterion "two or three positive tests" of these yielded acceptable accuracy (77.1) and a relative risk of 3.3.

Xylitol-induced changes of enamel microhardness paralleled by microradiographic observations

The study, aimed to analyze the feasibility of a prospective field study, was carried out in Polynesian children with rampant untreated caries. Slabs of bovine enamel were inserted for 8-12 days in cavities and subsequently replaced by permanent fillings. Before use, the surface of the slab was polished, and one half predemineralized and tested for microhardness. The follow-up in 30 subjects involved 54 slabs, 30 from negative controls with no added sweets and 24 from subjects receiving 20 g/day of xylitol in candy. The microhardness of the slabs was reassessed, and the difference between measurements calculated and tested for significance. The differences between the groups were highly significant, the predemineralized halves showing pronounced rehardening at exposure to xylitol. Parallel microradiographic observations conformed with the above findings. The results indicate that the use of a noncariogenic sweetener might be of value in high caries risk subjects.

Multifactorial modeling for root caries prediction

The study was part of a series of investigations aiming at the development of diagnostic caries tests for screening of risk subjects. The material consisted of 100 adult subjects (mean 62 yr, range 47-79 yr), 50 of these under chronic medication. The series of tests included two chairside registrations, i.e. incipient demineralization of exposed root surfaces without cavitation (RD 1) and quantitation of visible plaque (VPT%), three microbiological tests for mutans streptococci, lactobacilli, and candida/yeasts and three tests on stimulated saliva, i.e. secretion rate, buffering capacity and sucrase activity. A thorough clinical examination was conducted at the baseline and 1-yr registration phases, caries being registered at a tooth surface level according to WHO recommendations separately for coronal and root caries. Considerably more root caries than coronal caries developed during the observation period. For coronal caries increment, the predictive value of any of the tests was not significant. For root caries, however, the association between several tests and prospective caries increment was significant. Subsequent multifactorial modeling yielded the highest predictive value to the combination of Past Root Caries Experience (OR 25.0, Visible Plaque (OR 4.2), Candida (OR 8.0) and Lactobacilli (OR 5.8). A positive finding of Past Root Caries (RDFS) or the combination of the other three tests (Can, LB, VPT%) as criteria for selection in screening for root caries produced good accuracy (84.0) and a relative risk of 5.5.

Sucrose consumption and salivary sucrase activity in a 2-year longitudinal study

Sucrose consumption data of the sucrose group (n = 33) of a 2-yr longitudinal study was plotted against salivary sucrase activity values obtained during this 2-yr period. The correlation coefficients varied between 0.194 and 0.551. The subjects were divided into high (greater than or equal to 10 mumol x min-1 x (10(-3)) and low (less than 10) sucrase activity subgroups. There were significant differences in the sucrose consumption and in intake frequency between these two subgroups. These findings give further support for the possibility of using sucrase activity for the estimation of the level of individual sugar consumption.

Screening of caries in children through salivary lactobacilli and yeasts

The caries predictive value of salivary counts of lactobacilli and yeasts was evaluated in 298 children (from 6 to 11 yr of age) concurrently to a 3-yr xylitol field study in Hungary. On a group level the salivary yeasts and the combined information of lactobacilli and yeasts predicted the 3-yr caries increment acceptably. On an individual basis salivary yeasts had more power than salivary lactobacilli. At best the sensitivity and specificity of yeasts were 74% and 75%, and the combined information of lactobacilli and yeasts, 69% and 83%, respectively. Although the results were not that good in all subgroups of the study, they indicate the value of salivary yeasts in caries prediction either as a sole test or together with salivary lactobacilli.

Collaborative WHO xylitol field studies in Hungary. VII. Two-year caries incidence in 976 institutionalized children

The aim was to assess caries increment as influenced by partial substitution of sucrose by xylitol (X group) over a 2-year period in comparison with systemic fluoride (F group) and restorative treatment only (C group). The study differed from the 3-year field study of the same series primarily in that existing base-line differences were eliminated because the protocol required that all the new subjects entering the institutions in the 1st year were to be included for a 2-year trial. During this period the number of dropouts was 243 (19.9% of all subjects), the final material consisting of 976 children (6-12 years old). The 2-year DMFS increment was 3.8 in the X group, 4.8 in the F group, and 6.0 in the C group. The corresponding ratio (RS) between caries incidence and the tooth surface population at risk was RSX, 4.5; RSF, 5.5; and RSC, 7.5. The xylitol regimen resulted in a lower increment of caries than measured in the F and C groups (p less than 0.001; convariance analysis, with base-line prevalence, number of permanent teeth, and visible plaque index as covariants.

Collaborative WHO xylitol field studies in Hungary. VI. Changes in the carbohydrate to protein ratio of dental plaque

The carbohydrate to protein ratio of dental plaque was analyzed in a field study assessing the effect of partial substitution of dietary sucrose by xylitol (X group) in comparison with systemic fluoride (F group) and restorative treatment solely (C group). The biochemical analysis was supplemented by quantitative assessment of plaque through the visible plaque index (VPI). The present substudy was carried out cross-sectionally and longitudinally (n = 83) in initially 6- to 11-year-old children. Missing base-line values for the carbohydrate to protein ratio were partly compensated for through reexamination of the carbohydrate to protein ratio 15 months after termination of the trial. The latter series served as reference to indicate the base-line situation. A lower carbohydrate to protein ratio was measured in the X and F groups than in the C group. Improvement of the VPI values was obtained only in the X group. Our results suggest the potential value of parallel quantitative and qualitative assessment of plaque.

Collaborative WHO xylitol field studies in Hungary. V. Three-year development of oral hygiene

The oral hygiene conditions were evaluated within a 3-year field study aimed at assessing the cariostatic value of partial substitution of sucrose by xylitol (X group) in comparison with systemic fluoride (F group) and restorative treatment only (C group). Parallel to caries and further associated studies the visible plaque index, based on the total number of permanent and deciduous teeth, was determined longitudinally at annual examinations in 688 institutionalized children, initially 6 to 11 years old. The observations were analyzed with regard to sex, age, experimental grouping, and total development. The oral hygiene conditions were generally poor. At the base-line examination only 26% of the children had acceptable oral hygiene; at the end this level was reached by 42%. A definite improvement was measured only in the X group, in which the final values differed significantly (p less than 0.001) from the base-line values and also from the end situation in the F and C groups. It is concluded that the development was influenced by several factors, such as different snacking habits and access to sweets, the study per se, and xylitol-induced effects.

Collaborative WHO xylitol field studies in Hungary. II. General background and control of the dietary regimen

The consumption of sucrose and xylitol and the exposure to fluoride (F) were analyzed in a field study aimed at assessing the value of peroral xylitol as a caries-preventive measure. The coverage of the general background referred to the conditions of 689 institutionalized children observed for a 3-year-period. The material in the dietary substudy consisted of 286 subjects aged 8-13 years. The intake and excretion of F was monitored at all institutions in a total of 380 children. The frequency of the consumption of sucrose was high, its intake increasing over the weekend in comparison with weekdays. The consumption of the xylitol-containing products did not reduce the frequency of sucrose intake. Varying and fluctuating levels of exposure to systemic F was registered, as also reflected in the urinary F/creatinine quotient.

Collaborative WHO xylitol field studies in Hungary. III. Longitudinal counts of lactobacilli and yeasts in saliva

The levels of salivary lactobacilli and yeasts were determined annually in half of the subjects of the xylitol (X) and fluoride (F) groups of a 3-year caries study. These measurements were carried out with Dentocult (DC) and Oricult (OC) dip-slide methods. A high level of lactobacilli prevailed throughout the study in these subjects. Significant changes were registered in some subgroups--that is, improvement in one of the X institutions and worsening in one of the F and one of the X institutions. At base line the counts of OC were worse in the X than in the F group. In the total material some improvement occurred during the course of the study, mainly in the X group. The changes associated with the preventive program should also be considered as related to the improvement in oral hygiene, restorative treatment, and the mere study effect.

Collaborative WHO xylitol field studies in Hungary. IV. Saliva levels of Streptococcus mutans

Salivary Streptococcus mutans was quantified to detect possible age-, sex-, and group-dependent differences at the end of a 3-year field study assessing the value of partial substitution of sucrose with xylitol (X group) in comparison with systemic administration of fluoride (F group) and restorative treatment solely (C group). The material of this substudy consisted of 390 institutionalized children aged 9-14 years. S. mutans was determined through the spatula technique and grouped into categories 0, less than 10(5), 10(5)-10(6), and and greater than 10(6) CFU/ml saliva. Zero to less than 10(5) values included more than 80% of the subjects of the X group. The cross-sectional comparison between groups showed lower S. mutans values in the X group than in the F and C groups. These differences between groups were highly significant. S. mutans was not dependent on age or sex.

Collaborative WHO xylitol field studies in Hungary. I. Three-year caries activity in institutionalized children

The aim of this 3-year field study was to assess the value of partial substitution of sucrose with peroral xylitol (14-20 g/day) as a caries-preventive measure (X group) in comparison with systemic administration of fluoride (F group) and restorative treatment procedures solely (C group). An F dentifrice was used unsupervised in the X and F groups, the former containing 10% xylitol. The C group used customary, predominantly F-free dentifrices distributed by the local health authorities. The final material consisted of 689 institutionalized children (6-11 years). Caries was scored yearly in duplicate by two continuously calibrated teams. At base line the X group had a significantly higher caries prevalence than the F and C groups. The 3-year DMFS increment was 4.2 in the X group, 6.5 in the F group, and 7.7 in the C group. The corresponding ratio (RS) between caries incidence and the tooth surface population at risk was RSx, 4.9; RSF, 6.6; and RSC, 8.6. It is concluded that dietary xylitol in solid sweets resulted in a lower increment of caries than obtained in the F and C groups (p less than 0.001, covariance analysis, with base-line prevalence, number of permanent teeth, and visible plaque index as covariants).

Field studies on sugar substitutes

Four field studies assessing the caries preventive value of partial substitution of sucrose by xylitol or a mixture of xylitol and sorbitol were recently conducted. The trials (in Thailand, Hungary and two in French Polynesia) had certain common features, i.e. protocols approved by the WHO; low intake of polyol(s); non-randomized young study populations, differing baseline caries prevalences between groups; and planned duration of 32-36 months. Analysis of the findings was facilitated through the use of rates to measure caries increments expressed as DMF teeth and surface counts in relation to the numbers of teeth at risk. Irrespective of baseline differences, all studies revealed, in comparison to known methods, that partial substitution of sucrose was associated with a preventive effect.

Xylitol and caries: the collaborative WHO oral disease preventive programme in Hungary

The aim of this study was to assess the practical value of peroral xylitol at low to moderate dosage as a caries preventive measure. The trial was planned as a field study to test the feasibility of partial sucrose substitution in the relatively uniform conditions expected to occur in institutionalized children. The caries increment in the experimental group (X-group) was compared with the increments in other groups following the systemic administration of fluoride in milk or drinking water (F-group), and conventional dental treatment procedures alone (C-group). Conventional treatment was also provided for children in the X- and F-groups who used in an unsupervised manner a fluoride-containing dentifrice. The dentifrice used by the X-group also contained 10 per cent xylitol. The C-group used predominantly fluoride-free dentifrices. At baseline there were 990 children in the study. At the end of the 3-year study period there were 689 subjects. The caries scoring into four main categories was carried out yearly according to WHO criteria. The analysis of the data showed highly significant differences between the X-, F- and C-groups when measuring caries activity as the increment of DMF teeth and tooth surfaces, and also as the increment rate assessing the true caries incidence in a biostatistical sense. These results were obtained in conditions where caries prevalence and incidence continued to be high. The observations indicate that peroral xylitol has a cariostatic effect.

Quantification of dental plaque through planimetric analysis

The aim of this study was to develop a planimetric, automatic method for evaluation of the extension and volume of plaque. Series of color macrophotographs of stained plaque were analyzed with a digitizer entering Cartesian coordinate data from the graphic records in a calculator. Estimations were carried out on the reproducibility, discriminatory power, and time required for the planimetric analysis. In addition, the ratios between values obtained before and after reproducible cleansing were interpreted as measurement of the adhesion of plaque in vivo.