Guidelines for conducting epidemiological studies of blast injury

Blast injuries are often caused by more than one mechanism, do not occur in isolation, and typically elicit a secondary multi-system response. Research efforts often do not separate blast injuries caused by blast waves from those caused by blunt force trauma and other mechanisms. 15 experts from nine different NATO nations developed in the HFM Research Task Group (RTG; HFM-234 (RTG)) 'Environmental Toxicology of Blast Exposures: Injury Metrics, Modelling, Methods and Standards' Guidelines for Conducting Epidemiological Studies of Blast Injury. This paper describes these guidelines, which are intended to provide blast injury researchers and clinicians with a basic set of recommendations for blast injury epidemiological study design and data collection that need to be considered and described when conducting prospective longitudinal studies of blast injury.

Guidelines for using animal models in blast injury research

Blast injury is a very complex phenomenon and frequently results in multiple injuries. One method to investigate the consequences of blast injuries is with the use of living systems (animal models). The use of animals allows the examination and evaluation of injury mechanisms in a more controlled manner, allowing variables such as primary or secondary blast injury for example, to be isolated and manipulated as required. To ensure a degree of standardisation across the blast research community a set of guidelines which helps researchers navigate challenges of modelling blast injuries in animals is required. This paper describes the guidelines for Using Animal Models in Blast Injury Research developed by the NATO Health Factors and Medicine (HFM) Research Task Group 234.

Comparison of selected skin decontaminant products and regimens against VX in domestic swine

An anesthetized domestic swine model was used to compare the efficacy and cross-contamination potential of selected skin decontaminant products and regimens against the chemical warfare agent, VX. Animals topically exposed to 2×, 3× or 5× LD50 VX showed typical signs of organophosphate nerve agent poisoning, including miosis, salivation, mastication, dysrhythmias, and respiratory distress prior to death. Animals were exposed to 5× LD50 VX and then decontaminated 45 min later with the reactive skin decontamination lotion (RSDL®), Fuller’s earth (FE), 0.5% hypochlorite, or soapy water. Survival was 100% when the reactive skin decontamination lotion or FE was utilized, although 50% of Fuller’s earth-decontaminated animals exhibited serious signs of VX poisoning. Decontamination of VX-treated animals with 0.5% hypochlorite was less effective but also increased survival. Soapy water was ineffective in preventing lethality. Blood cholinesterase levels were not predictive of clinical outcome in decontaminated animals. The potential of “decontaminated” VX in open wounds to cause poisoning was assessed by vigorously mixing 5× LD50 VX with the test decontaminants for 5 min and then placing the mixture onto a full-thickness skin wound. Soapy water was ineffective in preventing lethality. Although treatment with dry Fuller’s earth prevented death and all signs of organophosphate poisoning, a significant proportion of treated animals decontaminated with Fuller’s earth in aqueous suspension exhibited serious signs of organophosphate poisoning, suggesting that live agent may be desorbed from Fuller’s earth when it is exposed to a liquid environment. Animals treated with reactive skin decontamination lotion or 0.5% hypochlorite-VX mixtures showed no signs of organophosphate poisoning during the 6- h test period.

Adaptive and non-adaptive responses in rats exposed to ozone, alone and in mixtures, with acidic aerosols

Healthy young adult (300 g) Sprague-Dawley rats were exposed for 1-day or 5-day periods, nose only, to purified air (CA) or four different pollutant atmospheres. Pollutant atmospheres included (a) 0.2 ppm ozone; (b) 0.4 ppm O3; (c) a low concentration mixture of ozone and sulfuric acid-coated carbon particles (0.2 ppm, 100 microg/m(3) and 50 microg/m(3), respectively); and (d) a high-concentration O3 and sulfuric acid-coated carbon particle mixture (0.4 ppm, 500 microg/m(3) and 250 microg/m(3), respectively). Following 1-day exposures to the high O3 concentration, significant (p< or =.05) decreases were observed in respiratory tidal volumes and significant increases were observed in lung inflammatory response. Following 5-day exposures to 0.4 ppm ozone, tidal volumes and lung inflammation were not significantly different from those seen in CA controls. In contrast, following 5-day exposures to the high-concentration O3-particle mixture, lung inflammation was increased significantly relative to that seen after 1-day high concentration mixture exposure or after CA exposure. Macrophage Fc-receptor binding, an important immunological function of macrophages, was significantly depressed after 5-day exposures to either the high- or low-concentration O3-particle mixtures compared to 1-day exposures or to CA. Thus, at the concentrations tested, repeated exposures to O3 produced diminished responses in breathing pattern changes and lung parenchymal injuries compared to acute, single exposures. This diminution was not observed after exposures to mixtures of acidic particles plus ozone. We conclude that mixtures of ozone and acidic particles may alter adaptive mechanisms that have been reported by us and others after repeated exposures to ozone alone.

Evidence for the lack of base-change and small-deletion mutation induction by trichloroethylene in lacZ transgenic mice

Trichloroethylene (TCE) is a widely used industrial solvent employed mainly for degreasing and cold-cleaning metal parts. It is also used for dry cleaning, and in the production of a number of chemical products. It has been shown to induce liver and lung tumors in rodents, and have a variety of positive and negative results using in vitro and in vivo mutagenicity tests. In order to assist in the interpretation of the mechanism of carcinogenicity, TCE was tested for the ability to induce gene mutations and small deletions using the lacZ transgenic mouse model (MutaMouse). Male and female animals were exposed by inhalation to 0, 203, 1153, and 3141 ppm TCE, 6 h per day for 12 days. 14 and 60 days following the last exposure, animals were sacrificed and the mutation frequency in bone marrow, kidney, spleen, liver, lung, and testicular germ cells determined. The results of this study indicate that TCE did not induce base-change or small-deletion mutations as detected in this assay in any of the tissues examined. Environ. Mol. Mutagen. 34: 190-194, 1999. Published 1999 Wiley-Liss, Inc.

Acute effects of inhaled urban particles and ozone: lung morphology, macrophage activity, and plasma endothelin-1

We studied acute responses of rat lungs to inhalation of urban particulate matter and ozone. Exposure to particles (40 mg/m3 for 4 hours; mass median aerodynamic diameter, 4 to 5 microm; Ottawa urban dust, EHC-93), followed by 20 hours in clean air, did not result in acute lung injury. Nevertheless, inhalation of particles resulted in decreased production of nitric oxide (nitrite) and elevated secretion of macrophage inflammatory protein-2 from lung lavage cells. Inhalation of ozone (0.8 parts per million for 4 hours) resulted in increased neutrophils and protein in lung lavage fluid. Ozone alone also decreased phagocytosis and nitric oxide production and stimulated endothelin-1 secretion by lung lavage cells but did not modify secretion of macrophage inflammatory protein-2. Co-exposure to particles potentiated the ozone-induced septal cellularity in the central acinus but without measurable exacerbation of the ozone-related alveolar neutrophilia and permeability to protein detected by lung lavage. The enhanced septal thickening was associated with elevated production of both macrophage inflammatory protein-2 and endothelin-1 by lung lavage cells. Interestingly, inhalation of urban particulate matter increased the plasma levels of endothelin-1, but this response was not influenced by the synergistic effects of ozone and particles on centriacinar septal tissue changes. This suggests an impact of the distally distributed particulate dose on capillary endothelial production or filtration of the vasoconstrictor. Overall, equivalent patterns of effects were observed after a single exposure or three consecutive daily exposures to the pollutants. The experimental data are consistent with epidemiological evidence for acute pulmonary effects of ozone and respirable particulate matter and suggest a possible mechanism whereby cardiovascular effects may be induced by particle exposure. In a broad sense, acute biological effects of respirable particulate matter from ambient air appear related to paracrine/endocrine disruption mechanisms.

High caries levels: problems still to be tackled

According to the World Health Organization more than 60% of European countries have achieved the goal of no more than 3 DMFT at the age of 12 years. The others, including the newly independent Baltic states, still have high caries levels. Data from recent studies show that mean caries prevalence among 12-year-olds in Latvia, Lithuania, and Estonia was 5.8, 4.9, and 4.6, respectively. Absence of caries was recorded in 5% of Latvian and Estonian and 12% of Lithuanian 12-year-olds. Fifteen-year-old Latvians and Lithuanians averaged 8.1 and 7.0 DMFT, which, owing to the absence of radiographic examination, may be a substantial underestimation of real caries levels. The possible adverse effects of the privatization of dental care and the benefits of increased access to fluoride dentifrice in these countries have not yet been evaluated. The extremely poor oral hygiene seen in epidemiologic surveys indicates that fluoride dentifrices may not be widely used. The caries levels in the Baltic states resemble those commonly encountered a couple of decades ago in the Nordic countries. Data from two follow-up studies in Iceland show 66% and 52% decline in caries prevalence for 12- and 15-year-old children, respectively, over a period of 7 years. However, the caries experience of the 15-year-olds in the latter study was similar to that of 12-year-olds 10 years earlier, both in mean caries score (DMFS 11.3 and 12.1) and frequency distribution. Nor has the proportion of occlusal and approximal DF values changed in spite of frequent use of fissure sealants. While caries has become mainly a pit and fissure phenomenon in 12-year-olds, 44.3% of Swedish 19-year-olds reportedly have approximal lesions, and, when enamel lesions are recorded, approximal caries dominates the DFS scores. Analyses of trends in Nordic countries show that, despite a substantial decline in caries prevalence, vigilance is required to prevent a delayed caries development in the future adult population.

Trends in dental health among Icelandic urban children

Caries experience, oral hygiene and caries-related salivary parameters were recorded in a 20% representative sample of 12-year-old schoolchildren in Reykjavik, Iceland in 1991. The majority of the children was re-examined 3 years later in 1994. Trends in prevalence of caries and salivary bacteria were assessed by comparison with an analogous earlier longitudinal study (1984-87). Mean DFS values for 12-year-olds were 12.1 and 4.1, for 15-year-olds 23.3 and 11.3 in the earlier and later study, respectively. Reduction in DFS was 66% and 52% for the respective age groups. The decline was most pronounced in the group with low caries prevalence. Trends in caries experience were paralleled by salivary bacteria. The mean caries scores and frequency distributions of 15-year-olds in 1994 closely resembled those of 12-year-olds a decade earlier, suggesting a delay rather than a true fall in caries prevalence.

Caries risk assessment in adolescents

Detailed caries records and salivary microbiological tests were utilized to predict caries development in a group of 15-16-year-old Swedish adolescents. Both, caries experience and salivary microorganisms, correlated significantly with a subsequent 3-year increment of DFS. The strongest associations were recorded between the prevalence of baseline incipient lesions and the development of manifest caries (r = 0.51). Incipient lesions accounted for 27% of the 31% variability in the DFS increment explained by joined caries and salivary data. All predictors analysed showed insufficient sensitivity for identifying true caries active individuals. However, the combined sensitivity and specificity for incipient lesions and comprehensive caries record (incipient + manifest lesions) attained values allowing to predict caries development in the majority of individuals. Using precavity lesions as a sole predictor, 79-81% of the individuals were correctly classified with regard to their future caries levels. The addition of manifest caries increased the accuracy of classification to 86-89% depending on the stringency of screening and validation criteria.

Sensitivity of lungs of aging Fischer 344 rats to ozone: assessment by bronchoalveolar lavage

Biological effects indicators in bronchoalveolar lavage fluid were studied in Fischer 344 rats of different ages after exposure to 0.4-0.8 ppm ozone for periods of 2-6 h on a single day or on 4 consecutive days. The magnitude of alveolar protein transudation induced by ozone was not different between age groups, but the interindividual variability of protein changes was higher in senescent (24-mo-old) rats. By comparison to juvenile (2-mo-old) and adult (9-mo-old) rats, senescent animals had higher increases of interleukin-6 (up to 10-fold higher) and N-acetyl-beta-D-glucosaminidase (NAGA; 2-fold higher) in lung lavage after ozone. Ascorbic acid was lower in lungs of senescent rats (one-half of juvenile values), and acute ozone exposure brought a further decrease in lung ascorbate. Whereas alveolar protein transudation was attenuated after ozone exposure on 4 days, persistent elevation of NAGA in senescent rats suggested only partial adaptation. Injection of endotoxin did not modify the patterns of effects. Incorporation of 18O-ozone into macrophages and surfactant was not different between age groups, indicating that the magnified biological responses in senescent rats were not dominated by differences in internal dose of ozone. The results indicate that senescent rats respond differently than juvenile and adult rats to lung injury.

Temporary tooth separation in the treatment of approximal carious lesions

The tunnel preparation is among the techniques proposed for restoration of approximal carious lesions. The preparations minimizes the sacrifice of sound tooth structure. The diagnostic and management problems associated with the restricted access to the approximal area, however, have limited use of this treatment modality. The difficulty of ascertaining the possible loss of enamel surface integrity is overcome by temporary tooth separation, which permits direct visual and tactile examination of approximal sites. Additionally, the increased access facilitates both preparation of the cavity and placement of the restorative material.

Relationships between free smooth surface and proximal caries in the young permanent dentition

Cross-sectional relationships between free smooth surface and proximal caries were assessed in 3 age groups, comprising 252 subjects aged 12 yr, 301 aged 15-16 yr and 102 aged 18-19 yr. Caries diagnosis was clinically on white spot and radiographically on enamel lesion level. Fair correlation between buccal-lingual and proximal caries observed among 12-yr-olds (r=0.47) declined in the older subjects (r=0.24). While statistically significant the variability in proximal caries, explained by buccal-lingual lesions, was low (range 6-22%). Sensitivity and specificity for buccal-lingual lesions as an indicator for proximal caries in the same tooth ranged from 0.37-0.44 and 0.84-0.91, respectively, with associated Pv+ and Pv- ranging from 0.41-0.44 and 0.84-0.91, respectively. Sensitivity and specificity for buccal-lingual caries in identifying subjects with proximal caries ranged from 0.33-0.44 and 0.67-0.98, respectively. Pv+ ranged from 0.94-0.99 and Pv- from 0.06-0.35. ROC curve analysis yielded A(z)-values of about 0.76 in the two younger age groups and 0.57 in the oldest. The results imply that information obtained from visual examination should be applied with caution when inferences about current caries status on proximal surfaces are made from the presence of buccal-lingual caries.

Effects of acid aerosol exposure on the surface properties of airway mucus

It was hypothesized that the mucous layer lining the tracheas of rats and guinea pigs contains surfactant material capable of lowering the air/mucus surface tension, gamma, and that exposure to an irritant aerosol would raise the gamma. The gamma of the surface film was measured directly by a spreading droplet technique and indirectly by displacement of polymethyl methacrylate particles into the aqueous layer. The morphology of the mucous film was examined by electron microscopy after nonaqueous fixation. gamma was 33.3 +/- 0.70 (SE) mN/m and 32.3 +/- 0.68 (SE) mN/m for the normal rat and guinea pig trachea, respectively. Exposure for 4 h to aerosols of sulfuric acid (94.1 +/- 18.68 (SD) and 43.3 +/- 4.57 (SD) mg/m3) caused a several-fold increase in thickness of the mucous layer with exudation of protein-like material. The osmiophilic surfactant film at the air/mucus interface became irregularly thickened and multilayered. Despite these morphological changes gamma remained low, 33.2 +/- 0.43 (SE) mN/m and 32.6 +/- 0.60 (SE) mN/m for rats and guinea pigs, respectively, and displacement of particles into the subphase was not compromised. The results indicate that rodent tracheas are able to maintain a low surface tension in the presence of injury.

Oral health in Latvian 15-year-olds

Oral hygiene, caries and periodontal conditions were assessed in a representative sample of 15-year-old Latvian schoolchildren, comprising 506 subjects. Caries, diagnosed on the cavity level, was detected in 97.6% of the population. The mean DMFT and DMFS were 8.1 and 14.1, respectively. Although 91% of the children had had restorative treatment, the D component accounted on average for 33% of the DMFS score. Visible dental plaque was found in 98.4% of the children; in a majority (88%) abundant plaque deposits were recorded. Community Periodontal Index of Treatment Needs (CPITN) was assessed by standard WHO methods. Deviation from periodontal health was observed in 90.7% of the children. Calculus was recorded in 26.1% and gingival pockets in 25.9% of the sample. Additionally, 38.7% of the children had gingival bleeding. The mean number of sextants with healthy periodontal conditions was 2.5. Calculus and pocketing averaged 0.6 and 0.4 sextants, respectively. Attachment loss, recorded in 11.7% of the subjects, did not exceed 3 mm. The results showed high caries prevalence, considerable need for treatment and virtual absence of oral hygiene.

Mutans streptococci and dental caries prevalence in a group of Latvian preschool children

Paraffin-stimulated saliva samples were collected from 140 children 3- and 4-yr old attending nine nursery schools in Latvia. The salivary levels of mutans streptococci were rated from zero to 3 after being cultured on a commercially available strip selective for these microorganisms. Of the children, 29.3% were rated at zero (approximately < 10(4) cfu per ml saliva). This group of children demonstrated the lowest mean caries prevalence dmfstot = 1.5 (SD 1.9). The highest dmfstot was found among children in class 2 (38.6%; approximately > 10(5)-10(6) cfu/ml) and class 3 (12.1%; approximately > 10(6) cfu/ml) with a mean caries prevalence of 6.5 (SD 5.8) and 6.4 (SD 6.0), respectively. The study demonstrates the association between high caries prevalence and high salivary levels of mutans streptococci in the young child. It is suggested that early identi-fication of mutans streptococci-colonized children might be of value in selecting at caries risk children for preventive measures.

Caries experience in Latvian nursery school children

In 1993 the dental health was assessed in 631 Latvian 3--4-yr-old nursery school children. Forty-eight percent of the 3-yr-olds and 26% of the 4-yr-olds were caries free. The mean dmft for the total sample was 3.2 (2.2 and 3.8 in the 3-and 4-yr-olds, respectively). Molar caries, accounting for 66% of the total dmft score, was dominant in both age groups. Sixteen percent of the children had received restorations, 38% of which manifested recurrent caries. Recurrent caries was relatively more frequent in the younger children. Concomitant with a general increase in caries level, the polarization of the disease was less pronounced in the older children. The upper 25% of the distribution for 3- and 4-yr-olds contained 74% and 40% of the dmft, respectively. Daily toothbrushing was reported for 60% of the children. Of those, 38% used fluoride-containing dentifrice. No significant associations were found between caries experience and toothbrushing frequency, use of fluoride dentifrice or parents' education.

Short-term inhalation toxicity of methanol, gasoline, and methanol/gasoline in the rat

Four- to five-week-old male and female Sprague Dawley rats were exposed to vapors of methanol (2500 ppm), gasoline (3200 ppm), and methanol/gasoline (2500/3200 ppm, 570/3200 ppm) six hours per day, five days per week for four weeks. Control animals were exposed to filtered room air only. Depression in body weight gain and reduced food consumption were observed in male rats, and increased relative liver weight was detected in rats of both sexes exposed to gasoline or methanol/gasoline mixtures. Rats of both sexes exposed to methanol/gasoline mixtures had increased relative kidney weight and females exposed to gasoline and methanol/gasoline mixtures had increased kidney weight. Decreased serum glucose and cholesterol were detected in male rats exposed to gasoline and methanol/gasoline mixtures. Decreased hemoglobin was observed in females inhaling vapors of gasoline and methanol/gasoline at 570/3200 ppm. Urine from rats inhaling gasoline or methanol/gasoline mixtures had up to a fourfold increase in hippuric acid, a biomarker of exposure to the toluene constituent of gasoline, and up to a sixfold elevation in ascorbic acid, a noninvasive biomarker of hepatic response. Hepatic mixed-function oxidase (aniline hydroxylase, aminopyrine N-demethylase and ethoxyresorufin O-deethylase) activities and UDP-glucuronosyltransferase activity were elevated in rats exposed to gasoline and methanol/gasoline mixtures. Histopathological changes were confined to very mild changes in the nasal passages and in the uterus, where decreased incidence or absence of mucosal and myometrial eosinophilia was observed in females inhaling gasoline and methanol/gasoline at 570/3200 ppm. It was concluded that gasoline was largely responsible for the adverse effects, the most significant of which included depression in weight gain in the males, increased liver weight and hepatic microsomal enzyme activities in both sexes, and suppression of uterine eosinophilia. No apparent interactive effects between methanol and gasoline were observed.

Mutans streptococci, lactobacilli and caries experience in 12-year-old Icelandic urban children, 1984 and 1991

In order to evaluate changes in salivary counts of cariogenic bacteria and relate these to trends in caries experience, stimulated saliva was collected from a 20% random sample of 12-yr-old residents of Reykjavik, Iceland (252 children) in 1991 under conditions consistent with those of a survey conducted in 1984. The mean and median counts of salivary mutans streptococci and lactobacilli remained similar in the two studies. However, the frequency distribution at lower levels of mutans streptococci differed significantly between 1991 and 1984, e.g. in the present study 25.8% of the children had < 10(5) compared with 13.8% in the study 1984. The mean caries prevalence in the permanent dentition (DFStot) was 11.0, which is significantly lower than in 1984 (mean DFStot 28.8). A significant difference in caries prevalence was found at various levels of salivary mutans streptococci. Strep. mutans (serotype c/e/f) was carried by all mutans streptococci-positive children, save one child, who carried only Strep. sobrinus. The proportion of 12-yr-olds who carried Strep. sobrinus had decreased significantly to 15.7% from 34.0% in 1984. Significantly more children with Strep. sobrinus showed high levels of total mutans streptococci than children with only Strep. mutans. As the case was in 1984 significantly more Strep. sobrinus carriers had a high level of salivary lactobacilli as well as higher caries prevalence than the children who did not carry this species.

Dental behavior management problems in Swedish children

4505 Swedish children aged 4-11 yr were surveyed regarding dental behavior management problems (BMP) and dental health. Dental charts were retrieved from clinics in the Public Dental Service in Göteborg, and data were then compiled regarding BMP, action against BMP, caries, fillings, use of local anesthetics, and number of missed appointments. Behavior management problems were found in 10.5% of the children, and were more common in the younger children, among children who missed appointments, and in children who received restorative treatment without local anesthetics. The BMP children had more carious and fewer filled surfaces. In 43.4% of the cases with BMP the strategy chosen was postponement of dental treatment or no measure taken.

Inhalation toxicity study of methanol, toluene, and methanol/toluene mixtures in rats: effects of 28-day exposure

The inhalation toxicity of methanol and toluene was investigated in rats. Young Sprague Dawley rats of both sexes were exposed to vapors of methanol (300 ppm, 3000 ppm), toluene (30 ppm, 300 ppm) or methanol/toluene (300/30 ppm, 300/300 ppm, 3000/30 ppm, and 3000/300 ppm) six hrs per day, five days/week for four weeks. Control animals inhaled air only. Increased serum alkaline phosphatase activity was observed in males exposed to high-dose toluene, and decreased creatinine was noted in the group exposed to high-dose methanol/toluene. The thyroid gland in females appeared to be a target organ for inhaled methanol, toluene, and methanol/toluene, although the changes were confined to a mild, and occasionally moderate, reduction in follicle size. Histopathological changes of the nasal passages, consisting of subepithelial nonsuppurative inflammation, occurred in higher incidences in rats exposed to methanol/toluene than in those exposed to the individual vapors. Inhalation of methanol, toluene, or methanol/toluene produced no changes in liver weights, hepatic mixed-function oxidases, or serum aspartate transaminase activities, and onlly minimal changes in liver histopathology. The only liver changes were decreased liver weight and increased cytoplasmic density of the periportal areas in females exposed to high-dose methanol/toluene. These data indicated that exposure to methanol, toluene, or a mixture of both produced mild biochemical effects and histological changes in the thyroid and nasal passage. No apparent interactive effects were observed.

Reactivity of young and old human enamel to demineralization

The aim of this study was to determine the susceptibility of newly erupted and old permanent teeth to artificial, caries-like attacks. Two groups of caries-free teeth were used. Group 1 consisted of 38 teeth extracted for orthodontic reasons (9-12-yr-old children); group 2, of 40 teeth extracted for periodontal reasons (45-65-yr-old patients). After thorough cleaning, a test window was isolated on the incisal two-thirds of the buccal surface. After demineralization with 6% HEC gel at pH 4.9 for 8 days, longitudinal ground sections were prepared for imbibition studies in polarized light and for secondary ion mass spectrometry (SIMS). In the young teeth, the lesions appeared to be uniform in their extension in the enamel, whereas the old teeth showed less marked and thinner surface zones and greater depth of the positively birefringent body of the lesion. Polarized light microscopy and SIMS data support the hypothesis that there are different enamel pathways in the initiation of the natural carious process.

Caries experience in Icelandic 12-year-old urban children between 1984 and 1991

In order to evaluate trends in caries experience, a 20% random sample of 12-yr-old residents of Reykjavik, Iceland (252 children) was examined clinically and radiographically in 1991 under conditions consistent with those of the survey conducted in 1984. In addition to caries data, frequency of toothbrushing and use of fluoride dentifrice were recorded. The mean DFT and DFS were 3.0 and 4.1, respectively. The decrease in caries experience reached 60% with an annual fall in DFS of nearly 10%. During the 7-yr period between examinations the decline in DFT and DFS scores averaged 5.2 and 8, respectively, the annual reduction amounting to 0.7 DF teeth or 1.1 DF surfaces per child. The ratio of approximal/occlusal caries and the proportion of approximal caries were similar in both surveys. Fourteen percent of the children were free from manifest caries in 1991, but only 2% in 1984. Polarization between low and high prevalence individuals had intensified. Ninety-five percent of the children brushed their teeth regularly and 97% reported using a fluoride dentifrice.

Effect of luxation injuries on permanent teeth

Trauma to the supporting tissues of the teeth are among the most common dental injuries, leading to such complications as pulp canal obliteration, necrosis and root resorption. The aim of this investigation was to study the outcome for young permanent teeth subjected to luxation injuries. From 108 dental records 171 teeth with injuries to the supporting tissue were selected. The material comprised 130 subluxated, 15 extruded, 9 intruded, 15 exarticulated and 6 laterally luxated teeth in children aged 6-19 years. Apart from luxation, 59 teeth (35%) had additional crown and root fractures. 65% of the teeth recovered without complications. 78% of the subluxated teeth and 24% of the luxated teeth showed uneventful posttraumatic healing. Concomitant uncomplicated crown fractures or root fractures without displacement of the coronal fragment did not interfere with the healing. Of 60 teeth with healing complications, 52 (87%) were subsequently recorded as healed, the remaining 8 were extracted or had progressive root resorption. Loss of pulp vitality and external root resorptions were the most often recorded complications (28% and 17% of the total material respectively). Pulp canal obliteration was noted in 3% of the cases. Extent of injury and degree of tooth maturity were found to be related to healing complications.

Effect of different fluoride levels in dentifrice on the development of approximal caries

The development of approximal carious lesions was monitored on annual bite-wing radiographs obtained from 315 children, participating in a controlled dentifrice trial; 157 of these children had used a dentifrice containing 250 ppm F and 158 a dentifrice containing 1,000 ppm F (both as NaF) during a 3-year period as the sole fluoride supplement. The total number of surfaces recorded was 6,099 at the baseline and 7,358 at the final examination. In the 250-ppm F group 393 approximal lesions (297 in the outer half, 96 in the inner half of the enamel) and in the 1,000-ppm F group 399 lesions (319 and 80, respectively) were diagnosed at the baseline examination. After 3 years the fraction of sound surfaces had decreased from 79% at baseline in both groups to 54% in the low-F group and to 58% in the high-F group. Concurrently, the relative number of enamel lesions had increased from 13% in both groups to 26% in the low-F group and 24% in the high-F group. 66% of the surfaces in the low-F group and 60% in the high-F group remained sound, and the relative proportion of static enamel lesions was 26 and 28%, respectively. The differences did not reach statistical significance. The results imply that higher fluoride levels in the dentifrice are more effective in retarding the initiation of caries, while they do not differ with respect to the progression of radiographically detectable approximal carious lesions.

Caries-preventive effect of fluoride dentifrices with and without anticalculus agents: a 3-year controlled clinical trial

A 3-year, double-blind, randomized caries trial was conducted to evaluate the relative anticaries efficacy of four sodium fluoride dentifrices containing 250 ppm fluoride, 1,000 ppm fluoride in combination with 1% disodium 1-hydroxyethylidene-1.1-bisphosphonate (HEBP), and 1,000 ppm fluoride in combination with 1% disodium azacycloheptylidene-2.2-bisphosphonate (AHBP). As a positive control, a monofluorophosphate dentifrice (1,000 ppm fluoride) was used. At outset 1,161 Icelandic children, 11 and 12 years of age, were randomly assigned to one of the five treatment groups and 1,035 subjects completed the trial. After 3 years of unsupervised brushing, the dentifrice containing 250 ppm fluoride was significantly less effective in controlling the caries increment. The combination of sodium fluoride and AHBP was significantly more effective than the positive control.

Sugar consumption and caries experience in 12- and 13-year-old Icelandic children

Dietary habits with regard to sugar consumption and caries experience were studied in a group of 275 Icelandic children aged 12 and 13 years. The pattern of meals and sugar-containing food intake frequency were assessed by means of a dietary questionnaire. All dental examinations were performed by one examiner, using standardized methods and diagnostic criteria. Only 75% of the children had three regular meals daily. Breakfast and lunch were the most frequently omitted meals. Sweet buns were consumed by 32% of the children with meals and by 58% between meals, whereas soft drinks were consumed by 42% and 46%, respectively. Eighty-three per cent of the children reported eating sweets daily. The most popular products included confectionery, buns, cakes, and soft drinks, which constituted 53% of the intake with meals and 68% of that between meals. A higher caries incidence was associated with frequent intake of buns and cakes with meals and confectionery.

Enamel fluoride and caries in Icelandic children and a comparison of enamel fluoride in Swedish and Icelandic children

The fluoride content in surface enamel and its relationship to caries experience was studied in a group of Icelandic schoolchildren living in a low-fluoride area. Fluoride content was assessed by means of in vivo enamel biopsies sampled from 248 subjects aged 11 and 12 years. Dental examinations were performed in conjunction with the biopsy sampling and by the same examiner 1 year later. The prevalence and incidence of initial (DSI) and manifest (DFS) caries lesions were recorded separately. A median fluoride concentration of 610 ppm at a median biopsy depth of 4.2 microns was observed. A significant positive correlation was found between DSI and enamel fluoride content in girls and all older children. Additionally, surface enamel fluoride was measured in 72 Swedish children from a low-fluoride area but exposed to regular topical fluoride treatments. The difference in mean fluoride concentrations between the Icelandic and Swedish study populations was highly significant. From the measured fluoride concentrations the enamel fluoride profiles for both study populations were constructed. The differences in fluoride content were most pronounced in the outermost layer, apparently reflecting the higher exposure to and acquisition of topical fluoride in the Swedish children.

Mutans streptococci, lactobacilli and caries prevalence in 11- and 12-year-old Icelandic children

Since the caries prevalence has not declined in Iceland as it has in other European countries, it was of interest to study the presence of cariogenic bacteria in Icelandic children. The prevalence of salivary mutans streptococci and lactobacilli was examined in 217 11- and 12-yr-old Icelandic children and was related to their caries prevalence. In 2% of the children mutans streptococci were not found whereas 31% and 35% of the 11-yr-olds and 12-yr-olds respectively carried more than 10(6) CFU per ml saliva. Lactobacilli were not detected in 8% of the children whereas 28% of the 11-yr-olds and 23% of the 12-yr-olds had more than 10(5) CFU per ml saliva. The mean caries prevalence (DFS), initial caries included, for 11-yr-olds was 21.6 and for 12-yr-olds 28.8. Both mutans streptococci and lactobacilli were significantly correlated to each other as well as to caries prevalence. An increased number of these microorganisms, especially the mutans streptococci, were associated with an increased DFS. Children with high salivary counts of mutans streptococci and lactobacilli showed four times higher DFS than children with low numbers. The magnitude of salivary cariogenic bacteria as well as caries prevalence was found to resemble the situation in Sweden 10 yr ago. S. mutans (serotype c/e/f) was carried by all mutans streptococci positive children. S. sobrinus (serotype d/g) was found in 60 children (30.2%). Children with both S. mutans and S. sobrinus had significantly higher salivary counts of mutans streptococci and lactobacilli as well as caries prevalence than children with only S. mutans.

Dental health in Icelandic urban children aged 11 and 12 years

A total of 1370 children were examined for caries, gingivitis, periodontal pocketing, calculus and loss of marginal alveolar bone. The mean DFT and DFS scores were 6.2 and 8.7 for 11-yr-old children and 8.2 and 12.1 for 12-yr-olds. The average number of initial caries lesions was 12.4 among 11-yr-olds and 15.7 among 12-yr-olds. The proximal and smooth surfaces accounted for 37% of the total DFS score in the 11-yr-old children and 43% in the 12-yr-olds. The median DFS score for the 11-yr-old boys and girls was 7, while for the 12-yr-old boys it was 9 and for the girls 11. Only 1.8% of the children were free from caries. The occurrence of gingivitis, expressed by GBI, was 20 in both age groups. 8% of the children showed no advanced gingival inflammation, while less than 1% had bleeding gingivitis at all examined surfaces. Supragingival calculus was found in 10% of the children. Neither periodontal pocketing nor loss of marginal alveolar bone was observed.