Surveyed data for structural shielding calculations of radiographic x-ray installations in Taiwan

The use of surveyed data on the x-ray tube workloads and clinical exposure parameters was suggested in NCRP Report No. 147 for the structural shielding design of medical x-ray installations. To guide the shielding design of radiographic x-ray rooms in Taiwan, a large-scale survey was conducted to collect information required for the computations of the transmissions from broad x-ray beams through shielding materials. Surveyed data were collected during one week from 10,750 projections of 6,657 examinations in 13 radiographic rooms from nine hospitals. This survey was the first time that this type of clinical data has been collected in Taiwan on a large scale. The surveyed total workload was divided into separate contributions from x-ray projections directed at the floor, the wall bucky, and all barriers (used for secondary barriers). Based on the surveyed workload distributions, the unshielded air kerma per patient at 1 m from the source was calculated by the PCXMC program using surveyed x-ray tube parameters on the generator waveform, anode material, target angle, and filtration. Subsequently, the transmissions of x-rays through different barrier materials were computed by considering the average workloads and the average workloads plus one standard deviations. The latter computations were for a sensitivity study to find the influence of workload variations in different hospitals on the shielding requirements. All surveyed data and calculated results were compared with corresponding values given in NCRP 147 to analyze the radiographic imaging differences between Taiwan and U.S.

Caries management with fluoride agents

Dental caries is the single most common, chronic oral disease of childhood. It is progressive and cumulative, and becomes more complex over time. The Surgeon General's Report on Oral Health revealed that more than 51 million school hours are lost each year as a result of dental problems. Contemporary caries management philosophy has changed from the traditional surgical approach to a medical model that emphasizes prevention. Among various strategies for caries prevention or reduction, fluoride therapy has been highly promoted. Various in-office and over-the-counter fluoride products are available for caries prevention. Dental professionals should identify and assess the caries risk level of patients and optimize the use of fluorides in caries management. Since multiple sources of fluoride exposure exist, a coordinated approach to fluoride delivery is essential.

Randomized trial on fluorides and sealants for fissure caries prevention

To investigate the effectiveness of topical fluorides in preventing fissure caries, we conducted a randomized controlled trial with parallel groups. In total, 501 children (1,539 molars, 3,078 sites), mean age 9.1 years, who had at least one sound permanent first molar with deep fissures or fissures with signs of early caries were recruited. They were randomly allocated among four groups: (1) resin sealant, single placement; (2) 5% NaF varnish, semi-annual application; (3) 38% silver diamine fluoride (SDF) solution, annual application; and (4) placebo control. Follow-up examinations were conducted every 6 months by a masked examiner. After 24 months, 485 children (97%) were examined. Proportions of pit/fissure sites with dentin caries in the sealant, NaF, SDF, and control groups were 1.6%, 2.4%, 2.2%, and 4.6%, respectively. A multi-level logistic regression analysis accounting for the effects of data clustering and confounding factors showed that fissures in any of the three treatment groups had significantly lower risks of carious cavity development into dentin than did controls (p < 0.05). We concluded that placement of resin sealant, semi-annual application of NaF varnish, and annual application of SDF solution are all effective in preventing pit and fissure caries in permanent molars (ClinicalTrials.gov number CT01446107).

Planning and implementation of community oral health programs for caries management in children

Tooth decay or cavities (dental caries) can have a significant impact on children's quality of life, causing pain, infection, and other problems in the oral environment. Good oral health is a fundamental element of good general health for children, yet dental caries is still prevalent among children in many countries. Dental caries is well-understood, and effective prevention is an attainable goal. Dental professionals should actively engage with communities--in particular, the underprivileged--to identify dental caries problems and implement appropriate and effective community oral health programs (COHPs) to improve oral health and reduce oral health inequalities. This paper discusses COHPs as well as the steps involved in caries prevention for children. These steps cannot ensure the success of every COHP, but they are helpful for developing, integrating, expanding, and enhancing them. The effectiveness of COHPs for the prevention of caries in children varies from country to country, according to cultural, social, economic, and health care settings. Careful consideration of the local situation is required when selecting the elements of COHPs.

Suberoylanilide hydroxamic acid, a histone deacetylase inhibitor, protects dopaminergic neurons from neurotoxin-induced damage

BACKGROUND AND PURPOSE

Prevention or disease-modifying therapies are critical for the treatment of neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and Huntington's disease. However, no such intervention is currently available. Growing evidence has demonstrated that administration of histone deacetylase (HDAC) inhibitors ameliorates a wide range of neurologic and psychiatric disorders in experimental models. Suberoylanilide hydroxamic acid (SAHA) was the first HDAC inhibitor approved by the Food and Drug Administration for the sole use of cancer therapy. The purpose of this study was to explore the potential new indications of SAHA for therapy of neurodegenerative diseases in in vitro Parkinson's disease models.

EXPERIMENTAL APPROACH

Mesencephalic neuron-glia cultures and reconstituted cultures were used to investigate neurotrophic and neuroprotective effects of SAHA. We measured toxicity in dopaminergic neurons, using dopamine uptake assay and morphological analysis and expression of neurotrophic substances by enzyme-linked immunosorbent assay and real-time RT PCR.

KEY RESULTS

In mesencephalic neuron-glia cultures, SAHA displayed dose- and time-dependent prolongation of the survival and protection against neurotoxin-induced neuronal death of dopaminergic neurons. Mechanistic studies revealed that the neuroprotective effects of SAHA were mediated in part by promoting release of neurotrophic factors from astroglia through inhibition of histone deacetylation.

CONCLUSION AND IMPLICATIONS

The novel neurotrophic and neuroprotective effects of SAHA demonstrated in this study suggest that further study of this HDAC inhibitor could provide a new therapeutic approach to the treatment of neurodegenerative diseases.

Fracture resistance of root filled premolar teeth restored with direct composite resin with or without cusp coverage

AIM

To evaluate the fracture resistance and fracture patterns of root filled maxillary first premolar teeth (with mesio-occlusal cavity preparation) restored with several composite restoration designs.

METHODOLOGY

One hundred extracted sound human maxillary first premolars were randomly divided into five groups. Group 1 remained untreated (negative control). Conventional root canal treatment with additional mesial-occlusal cavity preparation was carried out on teeth in groups 2-5. In group 2, the teeth were restored intra-coronally with direct composite resin (positive control). In group 3, the palatal cusps of the teeth were reduced, and the cavities were restored with composite resin covering the palatal cusp (partial coverage). In group 4, the buccal and palatal cusps along with the distal marginal ridges were reduced; the cavities and cusps were restored with composite resin (conventional full coverage). In group 5, the buccal and palatal cusps were reduced but the distal marginal ridges were conserved. The cavities and the cusps were restored with composite resin (modified full coverage). All teeth were subjected to a progressive compressive loading parallel to their longitudinal axis until fracture. Fracture resistance was analysed using the one-way ANOVA and Fisher's LSD test. Fracture patterns were analyzed with chi-square test. The significance level was set at 0.05.

RESULTS

The fracture resistance (mean ± SD) of groups 1-5 was 1131 ± 207N, 904 ± 184N, 927 ± 224N, 1095 ± 289N and 1085 ± 243N, respectively (groups 1, 4, 5 > groups 2, 3; P = 0.004). Cusp fractures were recorded as the fracture pattern in 20 (100%), 19 (95%), 16 (80%), 8 (40%) and 12 (60%) premolars in groups 1-5, respectively (groups 1, 2 > groups 4, 5; group 3 > group 4; P < 0.001).

CONCLUSIONS

When direct composite resin was used to restore root filled maxillary first premolar teeth involving a proximal surface, those restored with full-coverage designs had greater fracture resistance.

Oral health of Chinese people with systemic sclerosis

The aim was to study oral health status, salivary function, and oral features of Chinese people with Systemic Sclerosis (SSc). Chinese people with SSc attending a university specialist clinic were invited for a questionnaire survey and a clinical examination. Ethics approval was sought (UW 08-305). Gender- and age-matched individuals without SSc who attended a university dental hospital were recruited for comparison. Forty-two SSc patients with a mean age of 54.0 ± 12.2 were examined. This study found no Chinese people with systemic sclerosis were periodontally healthy and many (76%) had periodontal pockets despite most of them (93%) practiced daily tooth-brushing. They all had caries experience (DMFT = 10.5) and many (65%) had untreated decay. Mucosal telangiectasia was a common oral feature (80%). They had lower resting salivary flow rates (0.18 ± 0.17 ml/min vs. 0.31 ± 0.21 ml/min; p = 0.003) and pH values (6.90 ± 0.40 vs. 7.28 ± 0.31; p < 0.001) and reduced maximal mouth opening (40.1 ± 6.5 mm vs. 43.6 ± 7.0 mm) than people without SSc.

Caries management with fluoride varnish of children in U.S

Fluoride varnish prolongs the contact time between fluoride and tooth surface to reduce caries. Its active ingredient is usually 5% sodium fluoride, or 22,600 ppm fluoride. Its use as an "off-label" approved drug for caries control in the United States has been on the rise, along with increasing evidence of its efficacy in case-based studies. It sets rapidly on teeth, and it is simple, quick and easy to apply. Side effects or complications of its use are rare. Gagging and swallowing are unusual. The risk of dental fluorosis is minimal. And it can be safely used in young children.

Dentin hypersensitivity and its management

Dentin hypersensitivity is a common patient complaint that is more prevalent than the profession realizes. It is important for dentists to diagnose dentin hypersensitivity by exclusion and provide appropriate treatment recommendations for patients. Various treatment methods have been proposed but no universally accepted desensitizing agent or treatment has been identified. When a patient has symptoms that can be attributed to dentin hypersensitivity, a thorough clinical examination should be carried out to rule out other likely causes prior to diagnosis and treatment. Depending on the identified cause, a combination of individualized instructions on proper oral health behaviors, use of at-home products, and professional treatment may be required to manage the problem.

Oral health status of Chinese teenagers with cerebral palsy

OBJECTIVES

To examine caries experience, periodontal status, and oral hygiene practices of Chinese teenagers with cerebral palsy in Hong Kong.

PARTICIPANTS

Chinese students aged 12 years or older studying in the three special schools of the Spastics Association of Hong Kong were invited to participate. CLINICAL SETTING MEASURES: Caries experience and periodontal status were assessed by a clinical oral examination using World Health Organization criteria. Information on oral hygiene and snacking habits were obtained by a questionnaire. Information on medical history and mental status was obtained from school records.

RESULTS

Of 65 students with a mean (+/- SD) age of 15.0 +/- 2.0 years, the majority (74%) had spastic cerebral palsy. About half of the participants (49%) had mild mental retardation and 31% had moderate mental retardation. Caries experience as the mean DMFT score (+/- SD) was 1.2 +/- 1.9 and 43% of caries remained untreated; however, 62% of participants had no caries experience. None of the participants had healthy gums, 57% had calculus, and 66% snacked between meals. They all practised daily tooth brushing, with or without caregiver assistance. About one third (33%) also used mouthrinse. There were no significant differences in caries experience between the participants who brushed their teeth with and those who brushed without caregiver assistance.

CONCLUSIONS

The mean DMFT score of this sample of Chinese teenagers with cerebral palsy was 1.2. Despite daily tooth brushing, the periodontal status of all participants was poor. Providing oral hygiene instructions and scaling are essential to improve their oral health.

Transgenic expression of haem oxygenase-1 in pancreatic beta cells protects non-obese mice used as a model of diabetes from autoimmune destruction and prolongs graft survival following islet transplantation

AIMS/HYPOTHESIS

Haem oxygenase 1 (HO-1) has strong anti-apoptotic, anti-inflammatory and antioxidative effects that help protect cells against various forms of immune attack. We investigated whether transgenic expression of Ho-1 (also known as Hmox1) in pancreatic beta cells would protect NOD mice from autoimmune damage and prolong graft survival following islet transplantation.

METHODS

To evaluate the protective effect of beta cell-specific HO-1 in autoimmune diabetes, we used an insulin promoter-driven murine Ho-1 construct (pIns-mHo-1) to generate a transgenic NOD mouse. Transgene expression, insulitis and the incidence of diabetes in mice were characterised. Lymphocyte composition, the development of T helper (Th)1, Th2 and T regulatory (Treg) cells, T cell proliferation and lymphocyte-mediated disease transfer were analysed. The potential effects of transgenic islets and islet transplantation on apoptosis, inflammation and the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) were evaluated.

RESULTS

Transgenic mice showed less severe insulitis and a lower incidence of diabetes than non-transgenic control littermates. Lymphocyte composition and functions were not affected. Islets from transgenic mice expressed lower levels of proinflammatory cytokines/chemokines, proapoptotic gene expression and amounts of ROS/RNS, and were more resistant to TNF-α- and IFN-γ-induced apoptosis. Islet grafts from transgenic mice also survived longer in diabetic recipients than control islets.

CONCLUSIONS/INTERPRETATION

Transgenic overexpression of Ho-1 in beta cells protected NOD mice from diabetes and delayed the autoimmune destruction of islet grafts, providing valuable insight into the development of better strategies for clinical islet transplantation in patients with type 1 diabetes.

The relationship between acid-suppressing drugs and phytobezoar formation: a retrospective analysis and discussion of phytobezoar formation

OBJECTIVES

Although phytobezoars are a rare cause of gastrointestinal obstruction, they are most commonly found in patients with previous gastric surgery. It is well known that predisposing factors of phytobezoar formation are ingestion of fruits containing soluble tannin, presence of dilute hydrochloric acid in the stomach, and gastric stasis or delayed emptying. We investigated whether intake of acid-suppressing drugs that neutralize gastric acidity or inhibit gastric acid secretion to constitute a hypo-acidic condition, increases the risk of phytobezoar formation.

MATERIALS AND METHODS

Between September 1992 and October 2008, 32 patients (24 male and 8 female) with gastrointestinal phytobezoars were diagnosed either surgically or endoscopically at the Tri-Service General Hospital, Taipei, Republic of China. The data were collected from hospital records and analyzed retrospectively.

RESULTS

Eighteen (56.25%) of all patients had previous gastric surgery and 6 (42.9%) of the 14 patients who had not undergone surgery had diabetes mellitus. The majority of admissions were during winter and spring (between October and March) (P < 0.01) and none of the patients had taken acid-suppressing drugs during the 6 months before detection of gastrointestinal phytobezoars.

CONCLUSIONS

In our study, intake of acid-suppressing drugs did not increase the risk of phytobezoar formation in patients with normal gastric motility. Moreover, we believe that the major factor in phytobezoar formation is gastric stasis or delayed emptying, which sufficiently prolongs the retention period of materials in the stomach, while dilute hydrochloric acid is a minor factor.

Dietary behavior and knowledge of dental erosion among Chinese adults

Objectives

To study the dietary behavior and knowledge about dental erosion and self-reported symptoms that can be related to dental erosion among Chinese adults in Hong Kong.

Methods

Chinese adults aged 25-45 years were randomly selected from a list of registered telephone numbers generated by computer. A telephone survey was administered to obtain information on demographic characteristics, dietary habits, dental visits, and knowledge of and presence of self-reported symptoms that can be related to dental erosion.

Results

A total of 520 participants were interviewed (response rate, 75%; sampling error, ± 4.4%) and their mean age was 37. Most respondents (79%) had ever had caries, and about two thirds (64%) attended dental check-ups at least once a year. Respondents had a mean of 5.4 meals per day and 36% had at least 6 meals per day. Fruit (89%) and lemon tea/water (41%) were the most commonly consumed acidic food and beverage. When asked if they ever noticed changes in their teeth, most respondents (92%) said they had experienced change that can be related to erosion. However, many (71%) had never heard about dental erosion and 53% mixed up dental erosion with dental caries.

Conclusion

Hong Kong Chinese adults have frequent intake of food and many have experienced symptoms that can be related to dental erosion. Their level of awareness of and knowledge about dental erosion is generally low, despite most of them have regular dental check-ups. Dental health education is essential to help the public understand dental erosion and its damaging effects.

Development of improved free-air ionisation chamber as absolute dosimetry standard for low-energy X rays in INER

The National Radiation Standard Laboratory of the Institute of Nuclear Energy Research (INER) designed and constructed an improved Attix style free-air ionisation chamber (FAC) for low-energy X-ray measurements. Clinically, X rays in this energy range are used in mammography radiology. This chamber is also used to perform air-kerma measurements. The original Attix two-sectional design was redesigned by INER using the piston design. The correction factors were determined experimentally for volume estimation, ion recombination and air attenuation. The aperture transmission, wall transmission, electron loss and photon scatter correction factors were determined using Monte Carlo calculations. INER established the Bureau International des Poids et Mesures (BIPM) X-ray beam code and performed a comparison of secondary standard air-kerma calibration factors for 10-50 kV low- energy X rays to verify the experimental accuracy and measurement consistency of the improved chamber. The INER-NMIJ/National Institute of Advanced Industrial Science and Technology (AIST) experimental results comparison using a transfer chamber yielded a difference <1.0% at the 95% confidence level in calibration factors. The overall uncertainty for the X-ray measurement in terms of air kerma was <0.6% at the 95% confidence level. These results indicated that the improved FAC is capable of serving as a primary standard as well as a trace standard in low-energy X-ray calibration services in Taiwan and even forming a basis for the future mammography X-ray air-kerma primary standard.

Use of fluorides in dental caries management

Fluoride is commonly and widely used to prevent and even arrest caries. The clinical effects of fluorides depend on the chemical compounds utilized and the methods used to apply the fluoride ion to the surface of the tooth. Fluorosis has been reported in conjunction with increased doses of fluoride. A coordinated approach to fluoride delivery is essential to avoid the risk of fluorosis.

Clinical diagnosis of fissure caries with conventional and laser-induced fluorescence techniques

We studied the in vivo validity of dentinal fissure caries diagnosis by visual examination, bitewing radiography, and use of a laser-induced fluorescence device (DIAGNOdent). A total of 144 and second molars with macroscopically intact occlusal surfaces in 41 Chinese young adults were examined visually, by bitewing radiography, and by DIAGNOdent. Visual examination after pit and fissure opening was used as the reference standard. The sensitivity and specificity of detecting caries that had extended into the dentin were, respectively, 0.89 and 0.44 by visual detection of opacity or discoloration after air drying, 0.13 and 1.00 by bitewing radiography to detect radiolucency extending into the dentin, and 0.70 and 0.84 by DIAGNOdent testing with a cut-off score of 40. Caries detection by a combination of visual examination and DIAGNOdent had a sensitivity of 0.67 and specificity of 0.94. Receiver operating characteristic analysis showed that this combined approach was superior to the other methods.

Dosimetry study for beta-radiation treatment of in-stent restenosis

Intravascular brachytherapy (IVBT) has been recognised as a treatment modality for reducing coronary restenosis after angioplasty and stent-implantation procedures. For the treatment of in-stent restenosis using beta-emitter (188)Re, delivering adequate doses to the entire vessel wall is not possible without the potential of overdosing tissues. A method to measure the dose distribution, perturbation and percentage depth dose using plane-parallel and cylindrical tissue-equivalent phantoms has been developed. Good agreement was found between experimental results and Monte Carlo simulation performed using MCNP4C code. The dose given to the affected area in the vascular region for intravascular radiation treatment was 15-30 Gy. Dose inhomogeneity beyond the stent surface decreased significantly with increasing radial distance. In the region close to the stent outer surface (>0.5-mm radial distance), a dose reduction of 11-17% due to the stent was observed. However, the dose perturbations due to the physical properties of metallic stents were found to be significant in IVBT for in-stent restenosis by using measured dose profiles in phantoms. The method can provide accuracy in beta isotope in vivo dosimetry results for treatments involving short-range dose distributions and provide a relatively high-level spatial resolution for detection.

Occlusion and orthodontic treatment demand among Chinese young adults in Hong Kong

PURPOSE

The aim of this study was to investigate the occlusion, the demand for orthodontic treatment and the reasons for this among Chinese young adults in Hong Kong.

MATERIALS AND METHODS

A questionnaire was used to study previous orthodontic experience and to evaluate the orthodontic treatment demand and the reasons for this in Chinese university students. Among those who had no orthodontic treatment, 120 participants were invited for an occlusal assessment. Their treatment need was graded using the index of orthodontic treatment need.

RESULTS

A total of 240 students, aged 18 to 27 years, completed the questionnaire survey. Thirty-one students (13%) had orthodontic treatment. Sixty-seven (28%) students had orthodontic treatment demand, and their common reasons were to improve appearance (78%), self-image (36%), self-confidence (34%) as well as to follow parental advice (24%). The reasons for those students who would not consider having orthodontic treatment included no perceived need (64%), long treatment time (18%) and high treatment fee (14%). All 120 invited participants who had no orthodontic treatment attended the occlusal assessment. One-fifth had a normal occlusion. Most malocclusions were manifested as Angle Class I (48%) followed by Class III (21%) malocclusion. Fifty-six students (47%) had moderate and 40 students (33%) had 'great' or 'extremely great' treatment need.

CONCLUSIONS

The most prevalent malocclusion among this group of Chinese young adults was Angle Class I malocclusion. Although the majority of the Chinese young adults had malocclusion with a high treatment need, their demand for orthodontic treatment was relatively low. Apart from consideration of dental health needs, the common reasons for orthodontic treatment demand were influenced by the desire for improvement in appearance.

Uses of sodium fluoride varnish in dental practice

Fluoride varnish is developed to prolong the contact time between fluoride and tooth surface, so that the tooth becomes more resistant to caries attack. The active ingredient of fluoride varnish is usually 5% sodium fluoride, (22,600 ppm fluoride). Studies have found that fairly insoluble globules of calcium fluoride-like material formed on the tooth surface after topical fluoride application. These globules act as a reservoir of fluoride in the mouth for a prolonged period of time. Systematic reviews corroborate evidence for the efficacy of fluoride varnish in the prevention of dental caries. Sodium fluoride varnish is used to prevent caries development, arrest early enamel and even soft dentine caries through promotion of remineralization of carious tooth substance. It is also used to treat tooth hypersensitivity. Some use it as a provisional luting agent by itself or combined with other provisional luting agents for cementing provisional crowns. Fluoride varnish has recently gained much attention in dentistry because it is quick and easy to apply. It sets rapidly on teeth, and gagging and swallowing is unusual. Side-effects or complications of its use are rare. Studies show that fluoride varnish is safe for young children and the risk of dental fluorosis is minimal. The simplicity of its application makes it very suitable and practical for use in dental clinics and outreach dental services, especially in young children and in other special needs groups.

Promoting caries arrest in children with silver diamine fluoride: a review

Although there has been a decrease in the prevalence and the severity of dental caries in children over the past few decades, the benefits have not been equally shared by many low-income or underserved children in many industrialised countries, or children in developing countries. Dental caries is still the most common and challenging dental disease in children for a clinician to treat. Silver diamine fluoride (SDF) has been in use to arrest dental caries in many countries. A 38% (44,800 ppm fluoride ions) SDF solution is commonly used to arrest caries in primary teeth of children, especially those children who are young and difficult to manage. Application of SDF to arrest dental caries is a non-invasive procedure that is quick and simple to use. However, it stains the carious teeth and turns the arrested caries black. It also has an unpleasant metallic taste that is not liked by patients, especially children. The low cost of SDF and its simplicity in application suggest that SDF is an appropriate therapeutic agent for use in community dental health projects. Reports of available studies found no severe pulpal damage after SDF application. The current literature suggests that SDF can be an effective agent in preventing new caries and in arresting dental caries in the primary teeth of the children. It can be used to arrest caries progression in very young children who are less cooperative, and it allows definitive restoration to be performed when they grow older and become more receptive to dental procedures.

Are the local blood oxygen level-dependent (BOLD) signals caused by neural stimulation response dependent on global BOLD signals induced by hypercapnia in the functional MR imaging experiment? Experiments of long-duration hypercapnia and multilevel carbon dioxide concentration

BACKGROUND AND PURPOSE

The relationship between the local blood oxygen level-dependent (BOLD) signals caused by neural stimulation (fBOLD) and the global BOLD signals induced by hypercapnia (hBOLD) has not been fully investigated. In this study, we examine whether fBOLD is modulated by hBOLD signals, by means of experiments using a relatively wide range of inhaled carbon dioxide (CO(2)) for a long duration of 5 minutes.

MATERIALS AND METHODS

Ten healthy volunteers were recruited, each undergoing 6 separate experiments by inhaling gas mixtures with different fractions of CO(2) (room air, 3%-7%). Each experiment contained 3 phases, prehypercapnic, hypercapnic, and posthypercapnic, during which boxcar visual stimulus was given. The local fBOLD signals were measured from areas showing activation patterns highly correlated with the visual stimulus paradigm, whereas the global hBOLD signals were measured from areas showing no visual activations. Percentage changes in fBOLD during transient-state hypercapnia and steady-state hypercapnia were both investigated in response to varying degrees of hypercapnic perturbations.

RESULTS

The hBOLD signals increased with increase of inhaled CO(2) fractions. The duration for the hBOLD signals to reach steady state prolonged with increase of inhaled CO(2) fractions. Normalized fBOLD ratio was inversely related to the inhaled CO(2) during steady-state hypercapnia but showed positive association with hBOLD during transient-state hypercapnia.

CONCLUSION

Our study concludes that the steady-state fBOLD signal intensity is dependent on and inversely related to the hBOLD signals. Previous reports documenting independent and additive relationships between hBOLD and fBOLD may likely be due to transient-state observations.

A review of sodium fluoride varnish

Fluoride varnish was incorporated into clinical dentistry to reduce caries; its use in the U.S. has increased progressively since it was approved by the FDA in 1994. This paper reviewed clinical studies and found that fluoride varnish's effectiveness in caries prevention, ease of application, and safety give it an advantage over other types of topical fluoride treatments (such as gels and rinses) or other caries management methods. As a result, it is regarded as one of the superior topical fluoride agents for young children.